Zoology

General Introduction

Zoology is a systematic exposition of animals according to their external and internal structure, and the functions of their organs.

The internal structure can be frequently inferred from the external characters; we may, for example, determine the aliment of an animal, and the structure of the digestive organs, by examining the teeth. This is, however, not sufficient in all cases, so that it becomes necessary also to examine the internal parts, because the relation between animals depends upon the entire organization; and this being well ascertained, the functions of the various organs can generally be determined without much difficulty.

From the earliest period it was found necessary to group those animals together which were observed to have certain natural characters in common. We find, upon inquiry, that the endeavors to arrange animals systematically have taken two principal directions, which have been named natural and artificial classification. The former has in view the classification of animals upon the greater or less perfection of the various organs, among which those connected with the circulation and oxygenation of the blood, locomotion, and digestion, hold a prominent place; the latter depends upon a character or habit arbitrarily chosen, and independent of others. A character, however, which may be regarded as unessential by one observer, will be considered as of the greatest importance by another. In the earlier stages of science, when the number of known species was comparatively small, artificial methods were popular, because they were considered easy of acquisition: now, however, it is found that they are calculated to give superficial ideas; and that to present the condition of zoological science in its true light, a more philosophical system must be made use of.

Aristotle, whose great mind was master of many sciences, both moral and physical, and whose works had an authority in Europe for many centuries, second only to that of the sacred Scriptures, takes precedence, in point of time, as the first systematic zoological observer. Born at Stagira, in the year 383 before Christ, he became the instructor of Alexander the Great, who formed a large collection of animals to enable him to pursue his investigations. As a history of zoological systems forms no part of the plan of this work, only a short outline of the most important periods will be given.

Aristotle divides animals into such as have blood, and such as are without it. The former comprehends the (A) Vertebrata, and the latter the (B) Evertebrata of later authors. These are subdivided as follows:

A.

• Animals which are Viviparous, Mammalia.
• Animals which are Oviparous,
• Animals which are with four feet, Reptiles.
• Animals which are with two feet and wings, Birds.
• Animals which are without feet, Serpents.
• Animals which are with fins, Fishes.

B.

• Animals without shells, Worms.
• Animals with a soft shell, Crabs.
• Animals with a calcareous shell, Snails.
• Animals with an articulate body, Insects.

Pliny the elder, nearly four hundred years later, compiled an extensive work on natural history, but without offering a system, or adding any original matter of scientific value, although the large collections of living animals in Rome must have afforded him many facilities for study.

Galen paid more attention to the internal structure than to the formation of a system; and from his time, A.D. 200, to the fifteenth century nothing was done of any account.

Belon, the reviver of natural history in modern times, was born in 1517, and after travelling three years in Europe, Egypt, Greece, and Asia Minor, at the expense of the bishop of Mans and Clermont, and the cardinals of Tournon and Lorraine, he returned to Paris in 1550 with a large collection, when he published his works.

Rondeletius, a medical professor at Montpellier, published a work in 1554, on Ichthyology; and another appeared in the same year, upon the same subject, by Salviani, a Roman physician.

Conrad Gesner, a physician born at Zurich, in 1516, published an extensive history of animals in 1585.

Aldrovandi, a professor of Bologna, born in 1525, was the author of fourteen folio volumes, published between 1599 and 1640.

Mouffet’s Theatrum insectorum the earliest English zoological work, was published in 1634. Most of the authors of this period repeated the fables of Pliny, or were deceived by those who sold factitious curiosities, a remnant of which still remains in the occasional appearance of a stuffed mermaid or impossible fossil. It was not until the appearance of Linnæus that natural science was placed upon a permanent basis. Born in Sweden, in 1707, he was at first intended for the Church, but subsequently studied medicine, suffering much from destitution during the period of his studies. In 1732 the University of Upsal sent him upon his celebrated Lapland tour. After this he taught mineralogy, and in 1735 took his medical degree.

Linnæus, whose great mind embraced the three kingdoms of nature, established the artificial method; since he indicated and arranged animals, plants, and minerals, by means of a few characteristics, enabling every naturalist to find a special name for each animal—a method which should as much as possible serve as a complete catalogue, convenient for ascertaining the names of known species, or of intercalating such as might be unknown. His classification is briefly as follows:

1. Animals whose heart has two ventricles and two auricles; blood warm and red.
   1. Viviparous. Mammalia. Oviparous. Aves (Birds).
2. Animals whose heart has one ventricle and one auricle; blood cold and red.
   1. With lungs. Amphibia (Reptiles). With gills. Pisces (Fishes).
3. Animals with one ventricle and no auricle; blood cold and yellowish.
   1. With antennæ. Insecta (Insects). With tentacles. Vermes (Worms).

The Linnæan Yermes included Intestina, Mollusca (not those of later authors), Testacea, Zoophyta, and Infusoria.

The impulse which Linnæus gave to the study of nature resulted in large collections formed in exotic regions chiefly by his disciples, among whom were Thunberg, Forskol, Spaarman, Hasselquist, and Osbeck; and as these collections contained many species which could not be properly arranged according to his system, the want of a more natural one was soon felt, and this was finally supplied by the immortal Cuvier, who laid the foundation of a natural classification in a deep study of the entire structure of the animal frame; showing, for example, how the characters of an unknown fossil animal might be determined from a few bones.

Cuvier was born in 1769, at Montbéillard, on the Alaine, in France, then belonging to the house of Wiirtemberg; and died in 1832, aged sixty-three. The national museum at Paris, the first in Europe, was the chief scene of his triumphs. He divides animals into Vertebrata and Invertebeata, separating the first into Mammalia or beasts; Aves or birds; Reptilia or reptiles; and Pisces or fishes. The Invertebrata he separates into Mollusca or shellfish; Articulata or insects, &c.; and Radiata, including starfish and some heterogeneous materials.

The most recent mode of determining the relative station of animals, is that employed by Agassiz, founded upon the development of the young from the ovum; a mode which, in the hands of this distinguished professor, has in some cases furnished more certain results than the consideration even of the nervous system.

Zoology is distinguished as general and special. The former compares the internal and external structure of animals, not only to understand the, phenomena of animal growth and life, but also to unravel the laws according to which the organs are developed from the lowest to the highest classes which associates it with comparative anatomy and physiology; the latter compares individual animals with each other to determine the peculiarities of individual species, treating of their character and habits.

The attempt has been frequently made to arrange animals in a regular scale from the lowest to the highest, under the impression that each animal must have an equal, a higher, or a lower organization when compared with others. This might be the case if there were only one set of organs; but as there are many, an animal may have a simple organization in one, and a complicated one in another. Thus by their organs of locomotion and general economy, insects would be placed above mollusca, whilst the latter are allied to the higher orders by their circulation. One proposes to arrange animals in a series of parallel lines, whilst another thinks that their affinities will be best shown by arranging them in a circle. The entire organism being moved through the nervous system, this has more recently received a great share of attention; and although it has proved satisfactory to a certain extent, it is at times difficult to make safe deductions from variations in the details. Under these circumstances, there are to be found those who, like Duméril and Swainson, think that external characters are sufficient for the classification of animals, as it is through these that they are placed in communication with external nature. Blainville makes the external organs the basis of his twenty-five divisions; considering their position, the skin and its appendages, and the structure and uses of the limbs.

There are many important affinities between plants and animals, as we have already mentioned in the introduction to Botany. One of the most important of these has been discovered in modern times, by means of the improved microscope. Thus it has been shown that the structure and growth, as well in animals as in plants, is due to cells. There are, besides, other points of similarity, which will be stated further on.

It is still doubtful whether certain organisms belong to plants or animals, there being grounds upon each side of the question. Some animal productions, as corals, were at an early day regarded as plants; whilst certain vegetable productions have, until a recent period, been considered animals, and indeed some are still considered such. These doubtful organisms are to be found chiefly among the low and minute forms which require a microscope for their investigation. In the case of sponges, strong arguments have been brought forward upon both sides, by acute observers who have examined them in a living state, for the sponge of commerce is a mere skeleton.

At first view, animals and plants would seem to be sufficiently separated by the respiration; as the former breathe and assimilate oxygen and expel carbonic acid gas, whilst in the latter this operation is reversed. This view of a contrary action is, however, not strictly correct, because in animals respiration must continue without intermission, whilst plants breathe inwards by day and outwards by night. Leaves and spiral vessels are the breathing organs of plants; gills, tracheæ, and lungs, those of animals. With regard to nutrition, animals and plants are nourished by extraneous materials suitable to their organization, which are taken up and distributed by vessels, which do not correspond, however, except that those of plants may be considered similar to the alimentary canal of animals. In certain plants, as in Chelidonium and Vallisneria, a kind of circulation has been observed.

A still greater relation appears in the propagation of animals and plants, which frequently takes place in both kingdoms by means of spontaneous division, and the growth of the separating shoots or buds, as in the case of the creeping roots, and the shoots of many plants; and also in some animals, where numerous stems united by a common base, give rise to others which become separated and commence an independent existence, as in the polypi. The spontaneous division of the infusoria belongs to this mode of reproduction. Plant and animal eggs can also be brought into comparison with each other, if the lower orders of both be taken for this purpose. The phenomena of vegetable life which are also present in the animal kingdom, may be stated as follows:

1. The ability of individual portions when detached to grow and live independently, and even to originate others. Many plants can be increased by cuttings, and it is well known that pieces cut from fresh water polypi will grow and form perfect individuals.
2. As plants always produce new shoots, so in the corals are similar parts produced; and as a tree placed with its top in the ground may produce leaves and blossoms from the upturned roots, so the base of a sertularia may become the head by producing young polyps.
3. The formation of buds happens in both kingdoms, of which the polypi again afford examples.
4. In plants we also find traces of irritability, like the movements of the mustard plant when touched. Animals and plants are both subject to sleeping and waking.
5. Plants and animals undergo metamorphosis, and sustain malformation and disease, which sooner or later result in death, after which both are subject to fermentation and putrefaction.
6. Plants and animals, and their organs, are developed gradually according to a certain plan. As the root and stem are formed out of the seed, and the leaves from the cotyledons, until at length the flower and its component parts are produced, so we find the several organs of the animal body to be formed from the membrane of the yolk.
7. As there are plants which live but a few days, are even hours, like many fungi, so there are animals, as the ephemera. Most plants, like most insects, live but a single summer. On the other hand, plants as well as animals may attain a very great age, and examples are not rare of trees a thousand years old. Animals also become very old, although it is difficult to arrive at any certain conclusion upon this point. There is reason to believe that the crevish or river crab (Astacus) lives about twenty years; the honey bee ten years; the pike several centuries; carps and eels a century; crocodiles and tortoises, whose growth continues during a long period, probably attain a very great age; a toad was watched in a house for thirty-six years; chickens live from twenty to thirty years; parrots, ravens, and swans, from eighty to one hundred; a goose lived to near one hundred; an ass thirty-six; and a horse sixty. The colossal mammalia may live several centuries.
8. Plants and animals are subject to hybernation, a phenomenon which we find especially in the polar and temperate zones, partly on account of the absence of the necessary heat, the deficiency of the means of subsistence, but also on account of a peculiar organization. In this condition plants lose their leaves and animals fall into a continued death-like sleep, concealed in holes and caves. All the functions are limited to their minimum. In hot regions we find a corresponding summer repose in animals and plants, connected with the great heat and aridity of the season. Then many tropical plants shed their leaves; crocodiles lie in the mud apparently dead, land shells close their aperture by a diaphragm; and certain freshwater species bury themselves at the bottom of ponds which become desiccated, until the return of the rainy season calls them to renewed life.
9. Plants, like animals, exhibit, under certain circumstances, great tenacity of life. Seeds of plants can preserve their germinating power for a long time, that of beans lasting one hundred years or more. An onion found in the hand of an Egyptian mummy germinated after an interval of not less than two thousand years, and the same thing happened with some cereal grains. The eggs of infusoria seem to afford a parallel in the animal kingdom. The examples cited of living toads found embedded in solid stone have not been sufficiently well authenticated to be admitted as facts, nor have the species thus said to be found ever been described or named.
10. Plants and animals become degenerate, as in the case of cultivated vegetables, which are sometimes quite unlike their original species.
11. There are living plants and animals which are capable of giving light in the dark, as some of the former which grow in subterranean passages, certain roots, and the blossoms of certain orange-flowered plants. Many animals, as the Medusas and fire-flies, emit a phosphorescent light; and it is well known that decaying animal and vegetable matter is luminous under certain circumstances.

But notwithstanding the various relations between plants and animals, there are still essential differences which it is sufficient merely to allude to here. The most essential distinction lies in the free will of the animal, and the power to make use of it in voluntary motion; and the presence of nervous matter to convey sensation. A mouth, muscles, bones, and organs of sense, are not present in any plant. Animal heat, electricity, and art, have no parallel among vegetables.

Instinct is peculiar to animals, like that of migration, defence, the constructions of bees and wasps, the expeditions of war and to make slaves which ants undertake, &c. Instinctive actions are not taught, although a permanent habit may become an instinct. The young duck swims at once, the young snapping turtle bites when taken from the egg and a harmless serpent without fang or rattle will vibrate its tail like a rattlesnake, producing a similar sound among dry leaves. The brain of the young is modelled upon that of the adult, and where the scale of ideas is limited, they must be as essentially hereditary as the external form.¹ An English writer endeavors to found a distinction between instinct and reason, by citing the case of a young animal, as a monkey, being terrified by one of its natural enemies, as a large serpent, when seen for the first time, which would not be the case with a young human being. Nevertheless, if man were for ages subject to be devoured by a large reptile, watching and caution would at length become habitual, and be transmitted as an instinct. The brain of the young is not necessarily that of the adult, but that of the adult at an earlier stage. So a quality or habit is not always transmissible from a parent to its immediate offspring, but it may appear in a more distant descendant, by a kind of “alternation of generations.” Colonel Hamilton Smith considers the spotted horse as an original Asiatic race with which the ordinary breeds were sometimes crossed, and he thus accounts for the occasional appearance of examples of it. The original race is mild and intelligent, which is one reason for its frequent use in equestrian exhibitions.

One of the most important inquiries in the history of animals and plants, is that which relates to their distribution. That of the latter has been treated of under Botany; and as regards animals, our contracted space limits us to the following general view.

There are both aquatic and terrestrial animals, the number of which may perhaps be equal; but there are also species which can live both in water and on land, as many of the amphibia, and some other vertebrata. Some aquatic animals live partly in fresh, and some in salt water; but there are others which leave the sea to spawn in the fresh water, as the salmon. In the sea itself there are several regions depending upon the depth. Some marine animals live near or at the surface, others upon the bottom, in some cases within certain limits as to depth. Many land and sea animals live only as parasites upon or within others. Some species have a peculiar parasite, while others support several kinds.

Zoogeography, or the geographical distribution of animals, teaches the circumstances and positions under which animals occur, both as regards individual species, genera, or larger groups. The chief circumstances which seem to control animal distribution, are temperature, elevation, and natural barriers; whence it results that not only the continents, but much smaller regions, have their peculiar fauna. In proceeding from the tropics, species will be found to diminish rapidly. Some animals are circumscribed within very narrow limits, being confined to a single locality, as the curious reptile genus Amblyrhynchus to the Galapagos islands, or the Aurochs (Bison priscus) to a single forest in Russia. The genus Bradypus (sloth) and Dasypus (armadillo), Auchenia (llama), are confined to South America; the Marsupialia (possum, &c.) to America and Australia, and the Zebras to Africa. Others are more widely spread, as the dogs, bats, mice, &c. Libellula (pl. 74, fig. 44) ferruginea occurs from Spain to Java. Peltis pusilla, a coleopterous insect, inhabits China, Madagascar, and Brazil.

The brightest colored and the larger forms of animal life are generally found in the warmer zones, as the large crocodiles and gigantic serpents among reptiles, and the lions and tigers among cats. There are, however, some exceptions, as some of the largest whales inhabit cold climates, whilst the American mastodon was larger than any recent elephant.

Man exercises considerable influence upon the distribution of animals. Cultivation, and the removal of forests, together with hunting and fishing upon a large scale, drive them to other localities, and reduce their numbers; whilst steam navigation causes certain species of fish to leave rivers in other respects well adapted to them. For his own use, man transports various domestic animals, some of which, like the horse and ox in South America, have formed large wild herds. Goats and dogs occur similarly in certain islands. Some animals have been so long domesticated, that the original stock is unknown, if it still exists, as in the case of the cat and camel.

The animal kingdom is usually separated into two large sections by the presence or absence of an internal skeleton; a separation, however, which is not natural, as the two sections are not of equal value, as will appear when we speak of the divisions. The essential part of such a skeleton is the spine, composed of a series of vertebræ, whence the animals provided with it are named Vertebrata; and those without it Evertebrata or Invertebrate animals. The latter section is much the richest in genera and species; it is separated into three great divisions (the Vertebrata forming another) and many minor groups; and, from the difficulty which they present, there still remains a good deal of uncertainty in the classification of certain portions. The following sketch, together with pl. 74, represents the orders according to the classification of Cuvier somewhat modified, and generally in inverse order.

Instead of an internal skeleton, many of the evertebrate animals are provided with a kind of external skeleton for the protection of the inner soft parts. The chief distinction between them and the Vertebrata lies in the, nervous system, which is not developed as a brain and spinal marrow, but as a nervous ring round the œsophagus, or as a double chord, with bead-like swellings at various intervals, as if the brain were divided into different centres of vitality, giving rise to various nerves. Hence, in dividing an insect into several parts, each seems to have nearly the same amount of vitality. Cuvier divides this section into three divisions, which are named Radiata, Mollusca, and Articulata.

The Radiata are named from the arrangement of the parts around an axis somewhat as in plants, whence they are also called Zoophyta. The Mollusca or soft animals, which include the shellfish, are characterized by the soft pulpy and slimy nature of the body, which is inclosed in a kind of mantle; they are generally without regular limbs, and some are without a head. Their power of locomotion is generally limited, and some are altogether sedentary. The Articulata are distinguished by a ringed or jointed body and limbs, the external part being the hardest, and partaking of the nature of an external skeleton. They are generally provided with well developed limbs, and are able to fly, run, and swim, with great facility. A few are without limbs. This division includes insects; Crustacea, or crabs; Arachnida, or spiders; and Annelida, or ringed worms.

Division I. Radiata

Class 1. Infusoria

This class includes animals so minute that many of them cannot be seen with the naked eye. They are named from being found in infusions of organic matter. They are generally provided with vibrillæ or vibratile organs, also named cilia, which resemble a minute fringe of hairs, which are constantly in motion, causing either locomotion of the animalcula, or currents of water, which bring their food within their reach.

Order 1. Polygastrica (Homogenea, Cuvier), to which has been attributed a compound stomach, resembling a bunch of grapes, whence the name applied by Ehrenberg, who made the supposed discovery. The genus Monas (pl. 74, fig. 1) is an organized globule which moves by rotation. Some authors think they are not animals, but the seeds of Algæ. The smaller kinds are only from one to two thousandths of a line in length, so that a drop of water may contain half as many individuals as there are human beings upon the earth, or five hundred millions of them.

Order 2. Rotifera, in which the action of the vibrillæ is supposed to resemble a wheel in motion. They are now removed to the lowest position among the Crustacea. Pl. 74., fig. 2, Monocerca.

Class 2. Zoophyta

This includes the abundant order of the coral animals, the naked Polypi (fig. 4), of which the freshwater species are the best known. The sponges (pl. 74, fig. 3) have also been placed here. The classification given here (that of pl. 74) is not followed in the subsequent pages.

1. Order 1. Corallina. Pl. 75, figs. 58, &c.
2. Order 2. Gelatinosa. Pl. 74, fig. 4, Hydra.
3. Order 3. Actinia. Pl. 77, figs. 5, 6.

Class 3. Acalephæ

This class includes the Medusae, Sea Jellies, Sea Nettles, &c. Pl. 76, fig. 74, Aurelia.

1. Order 1. Hydrostatica. Pl. 74, fig. 5, Diphies.
2. Order 2. Acalephia. Medusa. Pl. 74, fig. 6, Velella.

Class 4. Echinodermata

Radiated animals with a hard integument, like those on pl. 76, figs. 60 to 71. Some have and some are without locomotive organs.

1. Order 1. Epedicellata. Pl. 74, fig. 7, Sipunculus.
2. Order 2. Pedicellata. Pl. 74, fig. 8, Holothuria, Asterias, Echinus, &c.

Class 5. Intestina

In this class (excluding the Annelida) Cuvier placed the intestinal worms, and others which bear some resemblance to them, but which are not confined to the internal parts of animals.

1. Order 1. Entozoa (Cavitaria, Cuvier). Pl. 74, fig. 9, Ligula.
2. Order 2. Sterelmintha (Parenchymata, Cuvier). Fig. 10, Nemertes.

Division II. Mollusca

Class 1. Acephala

This class has no proper head, the mouth opening immediately into the anterior part of the body. The gills are suspended upon each side of the body. The Tunicata are without an external shell; the Conchifera have a bivalve shell.

1. Order 1. Tunicata. Pl. 74, fig. 11, Botryllus. Pl. 77, fig. 3, Salpa.
2. Order 2. Conchifera. Pl. 74, fig. 12, Ostrea. See also pl. 76, figs. 25–50.

Class 2. Gastropoda

In this class locomotion is effected by means of a fleshy disk, called a foot, upon the lower surface of the body. The orders are distributed according to the structure of the branchiæ. This class is abundant in species, and includes the greater part of the univalve shells.

1. Order 1. Cyclobranchiata. Pl. 74, fig. 13, Chiton.
2. Order 2. Scutibranchiata. Pl. 74, fig. 14, Fissurella.
3. Order 3. Tubulibranchiata. Pl. 74, fig. 15, Vermetus.
4. Order 4. Ctenobranchiata. Pl. 74, fig. 16, Strombus.
5. Order 5. Heteropoda. Pl. 74, fig. 17, Carinaria.
6. Order 6. Tectibranchiata. Pl. 74, fig. 18, Bulla.
7. Order 7. Inferobranchiata. Pl. 74, fig. 19, Phyllidium.
8. Order 8. Nudibranchiata. Pl. 74, fig. 20, Tritonium.
9. Order 9. Pulmonata. Pl. 74, fig. 21, Limnea.

Class 3. Pteropoda

In this class the organs of locomotion are a pair of fleshy, wing-like fins at the sides of the neck. It includes but one order. Pl. 74, fig. 22, Clio.

Class 4. Cephalopoda

The body is formed like a sack, the head is surrounded with long arms, used for prehension and locomotion; the eyes are large, and the mouth armed with a strong beak. There is but one order in the class. Pl. 74, fig. 23, Octopus. Pl. 76, figs. 16, 17, 75, 76, 77.

Division III. Articulata

Class 1. Annelida

Worms with cold red blood, the body lengthened and divided into rings, of which the first forms the head. Articulated feet are never present, but many of the genera are provided with stiff movable bristles. Nearly all live in water; the Lumbricus (earth-worm) is, however, an exception. Some live in tubes which they form in the bottom, some form them out of agglutinated particles of sand, and others secrete a kind of shell. Some of these, on account of the shell, have been thoughtlessly classified with the Mollusca.

1. Order 1. Abranchiata. Pl. 74, fig. 24, Hirudo (leech).
2. Order 2. Dorsibranchiata. Pl. 74, fig. 25, Aphrodite.
3. Order 3. Tubicola. Pl. 74, fig. 26, Amphitrite.

Class 2. Cirrhopoda

This class was formerly included in the Mollusca, on account of the shell; its affinities are, however, with the Crustacea. They are attached to stones, corals, crabs, shells, the bottoms of ships, whales, and marine tortoises. Pl. 74, fig. 27, and pl. 76, fig. 52, Anatifa. Pl. 76, fig. 54, Balanus.

Class 3. Crustacea

This class includes the articulata with articulate feet, which breathe by means of gills. Their circulation is double. There are two pair of antennæ, and never less than five pair of feet, and there are frequently more. The integument is more or less hard, the eyes are either sessile or elevated upon movable pedicles, as in the two highest orders. The situation and form of the gills, the position of the head and tail, the structure and number of the feet and parts of the mouth, afford characters for their classification.

1. Order 1. Trilobita.
2. Order 2. Pœcilopoda. Pl. 74, fig. 34, Caligus (parasitic).
3. Order 3. Branchiopoda. Pl. 74, fig. 33, Cyclops (waterflea).
4. Order 4. Isopoda. Pl. 74, fig. 32, Oniscus.
5. Order 5. Læmodipoda. Pl. 74, fig. 31, Gyamus (whalelouse).
6. Order 6. Amphipoda. Pl. 74, fig. 30, Talitrus.
7. Order 7. Stomatopoda. Pl. 74, fig. 29, Squilla.
8. Order 8. Decapoda. Pl. 74, fig. 28, Cancer.

Class 4. Arachnida

This class is provided with articulate limbs, and includes spiders, mites, and scorpions. They differ from insects in wanting antennæ, in having simple eyes, and in having the head coalescing with the thorax, and forming the cephalothorax. The feet are generally eight in number, being but six in insects; they are not subject to a metamorphosis, but moult the skin instead. The Pulmonaria (spiders and scorpions) breathe by a kind of lungs, or pulmonobranchiæ; the Trachearia (including the mites and some small aquatic species) by tracheæ, as in insects. Most of the Arachnida are predaceous in their habits.

1. Order 1. Pulmonaria. Pl. 74, fig. 35, Aranea.
2. Order 2. Trachearia. Pl. 74, fig. 36, Chelifer.

Class 5. Insecta

Insects have articulated feet, a dorsal vessel instead of a heart, and they breathe through lateral spiracles, connected with two principal tracheæ. Some insects are apterous and some winged, the number of wings being either two or four. The four wings are of a similar texture in some, and of a different texture in others. In the Coleoptera the posterior pair alone are used in flight, the anterior pair being converted into covers for their protection whilst at rest. The number of feet is six, except in the vermiform centipedes and millipedes (Myriapoda), which have characters intermediate to the true insects and the annelida; and, indeed, they are regarded by some as a distinct class. Insects undergo a more or less complete metamorphosis, which, in the Myriapoda, is confined to an increase of the number of segments and feet. Insects do not grow in this perfect state, having attained their full volume previous to their final transformation.

1. Order 1. Myriapoda. Pl. 74, fig. 37, Scolopendra.
2. Order 2. Thysanura. Pl. 74, fig. 38, Lepisma.
3. Order 3. Parasita. Pl. 74, fig. 39, Pediculiis.
4. Order 4. Suctoria. Pl. 74, fig. 40, Pulex.
5. Order 5. Coleoptera. Pl. 74, fig. 41, Carabus.
6. Order 6. Orthoptera. Pl. 74, fig. 42, Forficula.
7. Order 7. Hemiptera. Pl. 74, fig. 43, Cimex.
8. Order 8. Neuroptera. Pl. 74, fig. 44, Libellula.
9. Order 9. Hymenoptera. Pl. 74, fig. 45, Tenthredo.
10. Order 10. Lepidoptera. Pl. 74, fig. 46, Vanessa.
11. Order 11. Diptera. Pl. 74, fig. 47, Stomoxys.

Vertebrata

The Vertebrate Division of the animal kingdom, as has been already remarked, includes animals with an internal articulated skeleton or framework, capable of growth, supplied with blood-vessels and nerves, and serving for the support of the soft parts; and it is here that animals of the greatest size are found. The body is divided into head, trunk, and organs of locomotion, and the nervous system has attained its greatest concentration in a single brain or nervous centre. The group of Vertebrata having the same value as the previous Divisions, it is unnatural to consider it as balancing the Evertebrata conjointly, and on this account it will be here considered as a division including the following classes.

Class 1. Pisces

In all fishes the blood is oxygenated by means of gills, which are supported by a bony framework, named the branchial arches, which generally amount to four. The external structure is adapted for inhabiting and moving through the water. The air-bladder, although not concerned in breathing, is really the homologue of the lungs in the higher classes. It is not present in all fishes.

Fishes are divided into two series, according as the skeleton is cartilaginous or osseous. In the former the organization is low, the ribs are rudimentary, and in the lowest form the spine is a continuous line of cartilage not yet divided into vertebrae. The orders of cartilaginous or chondropterygeous fishes are as follows:

1. Order 1. Cyclostomata. Pl. 74, fig. 48, Petromyzon, lampereel.
2. Order 2. Selachii. Pl. 74, fig. 49, Squalus, shark.
3. Order 3. Sturiones. Pl. 74, fig. 51, Acipenser, sturgeon.

The osseous fishes, which are much the most numerous, are distributed in the following orders:

1. Order 1. Plectognathi. Pl. 74, fig. 52, Orthagoriscus.
2. Order 2. Lophobranchii. Pl. 74, fig. 53, Hippocampus.
3. Order 3. Apodes. Pl. 74, fig. 54, Anguilla, eel.
4. Order 4. Subbrachiata. Pl. 74, fig. 55, Pleuronectes; 56, Merlangus.
5. Order 5. Abdominales. Pl. 74, fig. 57, Cyprinus, chub.
6. Order 6. Acanthopterygii. Pl. 74, fig. 58, Xiphias, swordfish.

Class 2. Reptilia

Reptiles are cold-blooded vertebrata, which breathe by means of lungs, or lungs and gills. The heart is composed of a large ventricle with which the two auricles communicate. The ventricle receives venous blood from the system through the right am-icle, and oxygenated blood from the lungs through the left one, so that both pure and impure blood are mixed in the ventricle, previous to being sent through the system, a portion passing through the lungs. This peculiarity of the circulation accounts for these animals being cold-blooded, since in the animals with warm blood, one of the two ventricles transmits unmixed oxygenated blood to the system.

The brain of reptiles is small, and exercises less influence upon the system than in the higher classes, since they can live a considerable time when it is removed. The body is naked or covered with scales, but these are unlike those of fishes. The first order is named Batrachia by Cuvier, and Amphibia by other authors, on account of their adaptation to breathing both air and water at the same time, or at different periods of their life. In some of the amphibia the gills are permanent (Gnesiobranchiata), and in others they disappear (Agnesiobranchiata).

1. Order 1. Batrachia. Pl. 74, figs. 59, Salamondra; 60, Rana.
2. Order 2. Ophidia. Pl. 74, figs. 61, Vipera; 62, Boa.
3. Order 3. Sauria. Pl. 74, figs. 63, Anguis; 64, Ophisaurus; 65, Chirotes; 66, 67, Chalcides; 68, Bipes; 69, Anolis; 70, Scincus; 71, Tilicua; 72, Chamæleo; 73, Ptyodactylus; 74, Basiliscus; 75, Iguana; 76, Draco; 77, Agama; 78, Stellio; 79, Lacerta; 80, Tejus; 81, Crocodilus; 82, Plesiosaurus; 83, Ichthyosaurus.
4. Order 4. Chelonidea. Pl. 74, figs. 84, Chelonia; 85, Testudo.

Class 3. Aves

Birds are oviparous vertebrata, with warm blood and a double circulation, clothed with feathers, and provided with two feet and two wings. The air has access to various parts of the body, which diminishes their specific gravity, and assists them in flight. Of all the classes of animals this is the most strictly defined; and its characters are more uniform, and have fewer exceptions, on which account the classification presents some difficulties. The chief characters used for this purpose are furnished by the bill and feet.

1. Order 1. Palmipedes. Pl. 74, figs. 86, Anas; 87, Sula; 88, Pelecanus; 89, Procellaria; 90, Podiceps.
2. Order 2. Grallæ. Pl. 74, figs. 91, Phœnicopteytis; 92, Rallus; 93, Scolopax; 94, Ardea; 95, Grus; 96, Otis; 97, Struthio.
3. Order 3. Gallinaceæ. Pl. 74, figs. 98, Galius; 99, Crax; 100, Columba.
4. Order 4. Scansores. Pl. 74, figs. 101, Psittacus; 102, Picus.
5. Order 5. Passeres. Pl. 74, figs. 103, Buceros; 104, Merops; 105, Sitta; 106, Alauda; 107, Cypselus; 108, Pica.O
6. Order 6. Accipitres. Pl. 74, figs. 109, Otus; 110, Vultur; 111, Milvus.

Class 4. Mammalia

The young are produced alive in this class, which differs from all others in nourishing the young with milk secreted by the mammary glands. The thorax and abdomen are separated by a diaphragm composed of muscles, which is used in respiration. Man, by his physical characters, stands at the head of this class; although from his moral attributes some naturalists have denied him a place in the animal kingdom.

1. Order 1. Cetacea. Pl. 74, fig. 112, Balæna.
2. Order 2. Ruminantia.
   1. a, Cervidæ; fig. 113, Cervus.
   2. b, Bovidæ; fig. 114, Bos.
   3. c, Camelidæ; fig. 115, Camelus.
3. Order 3. Pachydermata.
   1. a, Solipeda; fig. 116, Equus.
   2. b, Suidæ; fig. 117, Sus.
   3. c, Proboscidea; fig. 118, Elephas.
4. Order 4. Monotremata. Fig. 119, Ornithorhynchus.
5. Order 5. Edentata. Fig. 120, Manis. Fig. 121, Bradypus.
6. Order 6. Rodentia. Fig. 122, Lepus. Fig. 123, Sciurus. Fig. 124, Castor. Fig. 125, Mus.
7. Order 7. Carnivora. Fig. 126, Didelphis (possum), Fig. 127, Phoca (seal), Fig. 128, Mustela (weasel). Fig. 129, Viverra (ferret). Fig. 130, Felis (cat). Fig. 131, Hyæna. Fig. 132, Canis (dog), Fig. 133, Ursus (bear).
8. Order 8. Insectivora. Fig. 134, Erinaceus.
9. Order 9. Chirofiera. Fig. 135, Vespertilio (bat), Fig. 136, Pteropus.
10. Order 10. Quadrumana. Fig. 137, Lemur. Fig. 138, Hapale. Fig. 139, Simia.
11. Order 11. Bimana. Fig. 140, Homo.

The order and classification which we propose to adopt, will be found to differ somewhat from the system given above, which is essentially that of Cuvier.

Descriptive Zoology

Evertebrata

Class Porifera

If sponges belong to the animal kingdom, they stand at the lowest point, where they will constitute a class to which Grant’s name Porifera may be applied. In the living sponges the water is imbibed through the smaller pores, and flows out of the larger ones in a regular stream. They exhibit no sensation when pierced, torn, burnt, or acted upon by acids, so that they are exceeded in sensitiveness by many plants.

Dujardin considers that he has proved them to be groups of animals. In placing a fragment of living sponge under the microscope, it was found to shape itself into rounded masses, the edges of which changed their form continually; and small bits moved by contracting and expanding.

Johnston, in his History of British Zoophytes, classes sponges with plants, on the ground that they are permanently fixed, not irritable, their movements involuntary, a stomach wanting, and from their resembling the cryptogamia in taking their form from the object to which they are attached.

Mr. Hogg states that sponges have no tentacles, vibrillæ, mouth, œsophagus, stomach, gizzard, alimentary canal, intestine, anus, ovaria, ova, muscles, nerves, ganglia, irritability, palpitation, or sensation. “Surely, then, we cannot any longer esteem these natural substances to be individual animals, or even groups of animals, in which not one organ or a single function or property peculiar to an animal can be detected.”

Sponges are usually marine, although there are a few species which are found in streams and stagnant water. They have a loose texture, covered and penetrated by a jelly-like substance; and they are perforated with numerous passages. The gelatinous substance seems alone to be present in the young, the fibrous substance appearing at a later period.

The species of spongia are numerous, about 150 kinds being described by Lamarck. The best known is Spongia officinalis (pl. 75, fig. 45). It is found attached to rocks and stones in the Mediterranean, particularly about the Greek islands, where they are collected by divers. Its reproduction is so rapid, that it may be collected in the same place after an interval of two years. The younger specimens are the most sought after, on account of their greater delicacy. Formerly burnt sponge was used in domestic medical practice for goitre, its action depending upon the presence of iodine.

The form of sponges is subject to an endless variety, and even the same species varies to a great degree, apparently with the locality; so that it is difficult to classify their properly. They are principally made up of irregular, globular, fan-shaped, palmate, branched, cup-shaped, funnel-shaped (often of great size), tubular, leaf-shaped, or ragged forms, which either surround other objects, or rise upon a short pedicle. The cup-shaped S. usitatissima, and the trumpet-shaped S. tubæformis, are from the American seas. The former is an article of commerce. S. fistularis (pl. 75, fig. 44) is a large brown species, with fine and very flexible fibres, from the American seas.

Notwithstanding the investigations of zealous inquirers, polyps have not been found in sponges. A number of observers who have watched their growth from the commencement, first observed the gelatinous substance, and afterwards the filamentous matter in it, which may be regarded as a skeleton. The growth of sponges is quite different from that of corals, as might be expected from the absence of polyps. Some regard the circulation of water through sponges as a kind of breathing process, a view which is inadmissible. With respect to their propagation, but little is satisfactorily known. According to Olivi, small oval bodies are found in the jelly-like mass, especially in autumn, which have been too hastily named eggs.

Sponges contain calcareous or silicious spicula, in which they resemble certain plants. They may be detected by burning a piece of sponge and placing some of the ashes beneath a microscope. These spicula are uniform in each species; so that they are useful in affording specific characters.

The chief peculiarities of marine sponges are also found in the fresh water species, as Spongillæ lacustris; S. fluviatilis; and S. friabilis, which inhabit swamps and running streams. The three named species, however, constitute probably but one, at different stages of growth.

The following genera are placed here, because, according to Milne Edwards, they have no polyps (new edition of Lamarck, vol. 2, p. 208, 520, 522). Some of the best authorities place them among plants.

Penecillus penecillus, Linn. (pl. 75, fig. 37), resembles a hair pencil, and the stem has a whitish calcareous crust (American seas). Flabellaria opuntia, Linn. (fig. 36) (American seas). Acetabulum mediterraneum (fig. 41). Corallina officinalis, Linn. (pl. 75, fig. 38), white, reddish, or green, four inches long. C. rubens (fig. 35) (Mediterranean). These delicate bodies were long supposed to partake of the animal nature of the true corals; but the structure is now considered to be nearer that of the algæ.

Pedicellaria, Müller (pl. 75, fig. 4), is a portion of an Echinus.

Class Infusoria

These minute animals have been observed and studied only since the discovery and improvement of the microscope. Several species were known in ancient times, because they occurred in such numbers as to discolor the water green or red, in the latter case giving it the appearance of blood; but no one anticipated this discoloration (which was regarded as a mark of divine displeasure) to be due to animals.

Leeuwenhoek, in 1675, first observed the infusoria, in standing rain water, without being fully convinced of their animal nature. Subsequently, in pursuing some medical inquiries into the nature of the material which gives its pungency to pepper, he made an infusion of this substance, which he was afterwards astonished to find swarming with animals. They were subsequently found in infusions of other vegetables, and in those of animal and metallic substances; and although it has been found that infusions are not essential to their production, they still retain the name of Infusoria. They are also called Protozoa, because they were supposed to constitute the first appearance of animal life. In the year 1701, Leeuwenhoek discovered that Rotifera, from the sediment which had been dried for a year in the gutter of a roof, could be revived. From this date, notwithstanding the number of observers, no one seemed disposed to investigate the internal structure of these minute objects, until the researches of Ehrenberg showed that they are provided with at least a mouth and a digestive cavity.

The larger species of Infusoria attain the size of a tenth of a line or more. The body is gelatinous and naked, but some are protected by a coriaceous, calcareous, or silicious defence; and as these mineral materials remain after the death of the animal, they are sometimes so abundant as to form entire geological formations. Some Infusoria have the body covered with minute sandy particles; others have only a shield upon the back; others again have the entire body inclosed in a case with one or more openings. When a defence is present, it is usually in a single piece, although there are some composed of more.

The Infusoria are usually colorless and translucent, but some are green, some yellow, and a few red; and when these colored species are very abundant, they give the water a discolored appearance. The shape is globular, oval, fusiform, cylindrical, vermiform, or irregular; and some are continually varying their form, so that the same individual might be mistaken for several distinct species. This is especially the case in the genus Proteus, which has derived its name from the sudden and great variation of form the same individual assumes under the eye of the observer. A head, neck, and tail, are usually distinguishable, and in some one end is very long, giving the animal a fanciful resemblance to a swan. The tail is sometimes used as a foot, and in some species is capable of being extended like the tube of a telescope. There are various external appendages like spines or bristles, but the most usual of these are the vibrillæ, which are used in locomotion, and to draw the food within reach by forming a kind of minute whirlpool in the water. In the Rotifera (which are really Crustacea) the vibrillæ are arranged in two circles at the anterior extremity; and when they are in action, some observers fancy that they resemble wheels in a state of rotation, whence the name of rotifera.

The Baccilariæ (now regarded as plants) are united together side by side in ribbon-like bands. B.paradoxa is a very interesting species, which may be compared to a ruler; but as many individuals rest side by side like rulers upon a table, they may form a square or parallelogram. The motion is peculiar, each single body (the edges remaining in a line) being capable of sliding rapidly along the one with which it is in contact; so that when those upon one side have extended themselves, the whole may resemble a flag attached to a pole, as in the diagram.

The Gaillonellæ (plants) are united end to end, forming a chain. In the genus Meridion the individual parts or frustules are wedge-shaped, so that when placed edge to edge they form an arch, or even a circle or spiral. In Micrasterias the interior is divided into many cells. Isthmia has an end fixed, and forms rows, the parts being in contact at different angles by a small isthmus.

All the animal Infusoria seem to be provided with a mouth, which is generally terminal, but sometimes placed near the middle of the body. The vent is not always present, or at least has not been discovered in all, so that it is possible that the undigested portion of the food may be rejected from the mouth, as in the Polypi. Where it has been observed, the vent was near the mouth; or upon the abdomen; or at the posterior extremity, above or below. The breathing organs, where they have been observed, appear as simple openings. The organs of motion are the tail, foot, bristles, vibrillæ, &c.

The organs of sense, as far as known, are those of feeling (of which the snout, and perhaps the bristles, are the organs), and perhaps vision, although Dujardin doubts the existence of the latter. The organs supposed to be eyes are dark red or black stigmas situated anteriorly upon the upper side, and Ehrenberg thinks that a glandular body beneath them performs the function of an optic nerve. Most of the polygastrica have a single stigma. Distigma has two; some of the Rotifera (crustacea) two, three, four, or more, arranged in two clusters, as in Theorus; in a semicircle, as in Cyclogena; or upon pedicles (like those of land snails) as in Otoglena. It is uncertain whether the structure of these eye-like spots resembles that of any of the animals above them; or whether their vision, if they possess this sense, is more than sufficient to distinguish light from darkness. Indeed, a perfect vision would scarcely be of much use to them, as they are said not to sleep, but to be as active in darkness as in light.

The internal organization of these singular animals is not less interesting than their exterior form; and indeed it may be considered the more surprising, when their size, in comparison with that of the larger animals, is taken into consideration. Their movements are extremely multifarious, and for all these there is an appropriate system of muscles. These may be observed running in various directions, the most interesting being those which keep up the unceasing play of the vibrillæ. But these organs are not confined to this class, vibrillæ being found externally and internally in many of the higher animals.

In the Polygastrica Ehrenberg represents a long curved intestine with immerous globular bodies suspended to it somewhat like grapes, from the mouth to the vent, which he regards as so many stomachs. This view passed midisputed for a considerable time; for although other observers failed to detect the connexion between the supposed stomachs and intestine, the failure was attributed to want of skill in microscopic manipulation. Ultimately this structure was doubted, although Pouchet reaffirmed it in 1848, and among others. Professor Rymer Jones expresses his doubts as follows:

“In carnivorous animalcules which devour other species, we might expect, were these the stomachs, that the prey would at once be conveyed into one or other of these cavities; yet, setting aside the difficulty which must manifestly occur in lodging large animalcules in these microscopic sacs, and having recourse to the result of actual experience, we have never in a single instance seen an animalcule, when swallowed, placed in such a position, but have repeatedly traced the prey into what seemed a cavity excavated in the general parenchyma of the body.

“In the second place, the sacculi have no appearance of being pedunculated, and consequently in a certain degree fixed in definite positions . . . So far from their having any appearance of connexion with a central canal, they are in continual circulation, moving slowly upwards along one side of the body, and in the opposite direction down the other, changing, moreover, their relative positions with each other, and resembling in every respect the colored granules visible in the gelatinous parenchyma of the hydra.

“With respect to the central canal, we have not in any instance been able to detect it . . . much less the branches represented as leading from it to the vesicles or stomachs, as they are called. Even the circumstances attending the prehension of food would lead us to imagine a different structure; witness, for example, the changes of form which Enchelis pupa undergoes when taking prey almost equal to itself in bulk. Such a capability of taking in and digesting a prey so disproportionate, would, in itself, go far to prove that the minute sacculi were not stomachs; as it. evidently cannot be in one of these that digestion is accomplished.” —General Outline of the Animal Kingdom. 1841.

The observations of Dujardin (Hist. nat. des Zooph. Infusoires, 1841) confirm those of Jones. He thinks that they do not lay eggs.

Many of Ehrenberg’s discoveries were made by infusing indigo or carmine in the water in which he kept Infusoria, and this being swallowed, marked the limits of the internal cavity. He did not detect the liver, spleen, or organs of circulation and respiration; but there are two organs in the gullet supposed to be analogous to salivary glands.

All Infusoria live in the water, some being confined to fresh, and others to salt water; but there are others which inhabit both. Some swim about almost continually, some attach themselves at will to plants or animals, and others are attached to particular animals, as to the Cyclops or waterflea, the freshwater Polypus; and even upon or within other Infusoria. One species is found in the rectum of frogs, and another (Paramecium compressum) in the intestines of the earthworm. Agassiz has observed the eggs of Planaria producing a species of “Paramecium” which was consequently an immature condition of that animal. All the attempts of Ehrenberg to detect Infusoria as inhabitants of the air have failed.

The modes of locomotion in the Infusoria are various. Some swim by means of the vibrillæ; some, like the monads, revolve like a globe on its axis; others roll upon their transverse axis; others glide along with a regular motion like the snails; and others like the leech.

The reproduction of the Infusoria takes place by means of spontaneous division; by budding, which is the least common; and perhaps by the ordinary mode of generation, although this is denied by Dujardin, who affirms that there are no males; and indeed, no indications of sexual instinct have been observed among them. The first mode of reproduction occurs in the so-called Polygastrica, and takes place either transversely or longitudinally, each half forming an independent animal. The division is not always complete, and in this case the two parts remain attached to each other. Some present a singular peculiarity, in which the soft part alone of the animal is divided, whilst the harder parts or armor remain undivided, as in Ophrydium versatile, which often divides itself to the extent of millions, whilst the gelatinous exterior remains entire, although it increases in size. In others the protection is completely divided, whilst the animals remain more or less closely united. The division in pedunculated genera does not generally extend beyond the pedicle, which, in case the divisions are numerous, resembles the trunk of a small tree. This remarkable mode of reproduction by division proceeds with such rapidity under favorable circumstances, that a single animal may give rise to a million of descendants in the course of eight or ten days.

The sudden and unaccountable appearance of Infusoria, especially in closed vessels, was once attributed to spontaneous or equivocal generation, a theory which still has its defenders, although it appears to be pretty well ascertained that such a hypothesis is not necessary. We may readily imagine that the inconceivably minute eggs of such creatures (or of those of which these animalcula are the imperfect condition) can be raised into the air with vapor and transported in all directions, penetrating wherever the air itself finds access.

The vital power of some species (and of the crustaceous Rotifera) is so great that they can survive with so little moisture as to be considered dry, exhibiting no signs of vitality until moistened with a drop of water, when they resume their active life. Doyere found that they may be completely dried in sand, in the dry air, or in a vacuum, and be revived by placing them in water. When placed in water at the temperature of 50° Centigrade (=126° F.) they were killed, but would revive if the temperature did nor exceed 45° or 48° Cent. Some species are said to occur naturally in warm springs whose temperature equals 40° or 50° Cent.; whilst some species are not destroyed by being frozen. Ehrenberg found Infusoria in materials taken from floating masses of ice, and in sea water from a depth of 1100 to 1600 feet, brought by Captain Ross from the regions towards the south pole, between the latitude of 63° and 78°, where the temperature must have been very low, and the light much reduced at such a depth.

The extent of certain geological strata made up of the solid parts of the Infusoria is extraordinary, when the minuteness of the aggregated particles is considered; some of the silicious shields being so small, that, according to Ehrenberg, one hundred millions weigh but a grain. They are found in Hint, semiopal, bog iron ore, ochre, tripoli (and other polishing minerals which owe their action to the shields of silicious species), mountain meal, a clay which is eaten in Lapland, and another variety in South America, but which probably merely fills the stomach without aftbrding nourishment. Sometimes these remains form a stone sufficiently light to float in water, and strong enough to be employed in building. In Lüneburg and about Berlin, the infusorial strata are as much as twenty feet deep and twenty miles in extent. Infusorial strata have been discovered by William B. Rogers upon the Kappahannoc river at Stratford cliffs, on the Potomac, and on James River below City Point; and in other parts of Virginia. These deposits belong to the miocene formation.

The extent of the artificial group Infusoria will probably be much reduced as researches are continued. Kützing has separated the Bacillaria and Diatomeæ as Algæ, and he considers Gaillonella ferruginea to be a conferva. He thinks some of these organisms have both a vegetable and an animal nature, and that in such simple forms the distinction between animal and vegetable does not exist.

The observations of Unger, Flotow, Thuret, and C. Th. Siebold, have thrown doubts upon the animal nature of other Infusoria of the genera Enchelys, Chlamidomonas, Chilomonas, Chsetoglena, and others. These researches seem to show that the spores of Algae are locomotive by means of vibrillss, although Unger and Bory would contend that these supposed spores are animal in their nature, but convertible into plants.

Agassiz considers many of the Infusoria to be the larvae of worms, &c., and he seems disposed to suppress the entire class by distributing its members among the other classes of animal and vegetable nature. There is reason to believe that supposed species of Leucophra and Difflugia are immature Alcyonellse. Neverthless, it would be premature to give up the entire class until a greater number of the more distinct forms are ascertained to be large, because, whilst we admit that individual species may have been described under several distinct names, the number of infusorial species seems too great for the comparatively small number of worms, &c., likely to be derived from them.

The name Infusoria is adopted here on account of the heterogeneous contents of the division; but if future observation renders it probable that the removal of portions will still leave a distinct group incapable of union with other classes, these may take the more appropriate name of Protozoa, sometimes applied to the entire group; and its symbol, to extend the views of Agassiz, will be a circle.

Professor J. W. Bayley of the Military Academy, West Point, is the chief American authority upon the Infusoria. Most of his papers may be consulted in the American Journal of Science.

We now proceed to the consideration of the species figured in the atlas.

Anentera (without intestines)

Monas lens, Müller (pl. 75, fig. 1), is about \(\frac{1}{800}\) of a line long. The line used in Natural History is the twelfth part of a French inch.

Vibrio anguillula (pl. 75, fig. 7). This active species, which bears some resemblance to an eel, is found in vinegar and in sour paste, and can be revived after having been desiccated. It is by some placed among the worms, while Dr. Joseph Leidy, a distinguished comparative anatomist of Philadelphia, thinks their nature may be vegetable. His remarks, somewhat condensed, are as follows:

“Even those moving filamentary bodies belonging to the genus Vibrio, I am inclined to think, are of the character of algous vegetation. Their movement is no objection to this opinion, for much higher confervse, as the Oscillatorias, are endowed with inherent power of movement, not very unlike that of the Vibrio. . . In the stomach and small intestine of the toad, Bufo americanus, there exist simple, delicate, filamentary bodies. One is exceedingly minute, forms a single spiral, is endowed with a power of rapid movement, and appears to be the Spirillum imdula of Ehrenberg; the second is an exceedingly minute, straight, and short filament, with a movement actively molecular in character, and is probably the Vibrio lineola of the same author; the third consists of straight, motionless filaments, measuring \(\frac{1}{1125}\) inch long, by \(\frac{1}{15,000}\) broad; some were, however, twice, or even thrice this length, but then I could always detect one or two articulations, and these, in all their characters, excepting want of movement, resemble the Yibrio. In the rectum of the same animal, the same filamentary bodies are found, with myriads of Bodo intestinalis; but the third species, or longest of the filamentary bodies, have increased immensely in number, and now possess the movement peculiar to the Vibrio lineola, which, however, does not appear to be voluntary, but reactionary; they bend and pursue a straight course, until they meet with some obstacle, when they instantly move in the opposite direction, either extremity forward. But it must not be understood that these facts militate against the hypothesis of the production of contagious diseases through the agency of Cryptogamia. It is well established that there are microscopic Cryptogamia capable of producing and transmitting disease, as in the case of the Muscardine, &c.”—Proceed. Acad. Nat. Sci. for October. 1849.

Vibrio tritici, which infests wheat, has been revived by moisture after being in a dry condition for six years.

Gonium pectorale (pl. 75, fig. 11, enlarged) is an interesting species, resembling a table-shaped mass, in which there are about sixteen green auimalcula. When abundant they give a green color to the water.

Volvox globator (fig. 15, enlarged) was discovered by Leeuwenhoek in 1698. and is abundant in stagnant water. It is globular, of a pale-green color, and from one third to a sixth of a line in diameter. The surface is finely reticulated and provided with vibrillæ, by means of which it advances slowly through the water with a revolving motion. The Volvox is sufficiently transparent to allow six or eight smaller bodies of the same nature, but of a darker-green color, to be seen moving freely about the interior, which are the young; and even these, towards the period of their exclusion, contain another set of germs. The rupture of the exterior of the large body sets the small ones free.

Birsaria vesiculosa (fig. 3) lives in the rectum of frogs; it is oval, and the margin is provided with vibrillæ: size one twentieth of a line.

Proteus diffluens (the genus has also been named Amœba) (fig. 2), seldom exceeds one twenty-fourth of a line in size. It resembles a mass of translucent jelly, which is continually changing its form from rounded to linear or cordate, sometimes projecting parts of the margin in various directions, so as to present a most varied outline.

Cyclidium glaucoma (fig. 8) is remarkable for its peculiar motion, which resembles that of the genus Gyrinus, a waterbug, which swims rapidly in circles on the surface of the water.

Trichodina cometa (fig. 14) is one twenty-fourth of a line long, and lives as a parasite upon the fresh-water polyps (fig. 21), of which it gnaws the arms, causing death.

Urocentrum turbo (fig. 13) has an oval-triangular, translucent body, and a stem about one third of its length. Length from one thirty-sixth to one twenty-fourth of a line. Found among duck-weed.

Carchesium polypinum (fig. 20) has a bell-shaped body, mounted upon a slender, spiral, branched stem, formed by incomplete division. Found among aquatic plants.

Enterodela (with the intestines evident)

Opercularia articulata (pl. 75, fig. 17) is composed of a stout-branched stem, two or three lines long, each of which supports a bell-shaped body, which is subject to variations in shape. It attaches itself to water insects, and is sometimes so abundant upon them as to present the appearance of a covering of mould.

Stentor mylleri (fig. 18) inhabits aquatic plants; when extended, it is shaped like a trumpet or funnel, but when contracted, it exhibits the form represented in the plate. Its length varies according to the amount of its contraction, from one tenth to one half a line.

Cryptomonas ovata (fig. 4) is a lengthened green body, one forty-eighth of a line long, provided with a delicate shield.

Bursaria truncatella (fig. 12) is somewhat egg-shaped, with one end deeply excavated: one fourth to one third of a line long.

Chilodon cucullatus (fig. 10) is somewhat lengthened, flat, and rounded, with a small projection in front. Common in stagnant water.

Trachelocerca olor (fig. 5) takes its trivial name from the distant resemblance it bears to a swan. It lives among duck-weed and conferva, and is from one twenty-fourth to one twentieth of a line long.

Traehelocevca virdis (fig. 6) is more rare than the preceding, and inhabits the same places. It takes its trivial name from the green germs within it.

Paramecium compressum, (fig. 9), already alluded to, is from one twentieth to one twenty-fourth of a line long, and is probably an early stage of Planaria.

The structure of the two next species figured among the Infusoria shows that they are Crustacea. The first is Rotifer vulgaris (pl. 75, fig. 16), remarkable for the two circles of vibrillæ already referred to, and for the posterior forceps by which it attaches itself. Melicerta ringens (fig. 19) can withdraw itself into an external case; it lives in society, and has the vibrillæ distributed in four divisions.

Division I. Radiata

The radiated division of the animal kingdom, in the arrangement of Agassiz, and to a certain extent, in that of Milne Edwards, includes all those forms in which the radiated structure is more or less evident, as in the Zoophyta, the Medusae, and the Echinodermata. In Cuvier’s arrangement, the Zoophyta (under which term he includes all the Radiata) are a heterogeneous assemblage of radiated forms, Epizoic Crustacea, Intestinal Worms, and Infusoria.

“In a general point of view, we may, however, compare further, all radiated animals, when we shall find that they really constitute a natural, well circumscribed group in the animal kingdom, agreeing in all important points of their structure, being strictly constructed upon the same plan, although the three classes which we refer to this great department differ in the manner in which the plan is carried out.”—Agassiz’s Lectures on Embryology, Boston, 1849. P. 43.

The Radiata are distributed into three classes, Colenterata, Zoophyta, and Echinodermata. The first includes the Acalephæ or Medusæ, to which the Hydroida are added; the second the Zoophyta, excluding the Hydroida; and the third the Echinodermata.

The Hydroida have been usually placed in the class Zoophyta, although in the development of some of the families in which it has been observed, they present characters indicating a great affinity with the Acalepliffi, which in their turn have been regarded as an individual class. In dismembering the Zoophyta to unite the Hydroida and Acalephæ, we may either apply the name of the latter to the united group, or choose a distinct one. The latter course is preferable, being least likely to cause confusion, and we have accordingly adopted the name proposed by Fry and Leuckart. The necessity of this union is insisted upon by Forbes in his British Naked-eyed Medusæ p. 82; and in Agassiz’s Lectures on Embryology, p. 44.

Class 1. Colenterata

This class contains the orders Hydroida, Pulmonigrada, Ciliograda, Cirrigrada, Physograda, and Diphyida, all of which (excepting the first) constitute the Acalepha of Cuvier. For the sake of uniformity in the nomenclature, we here propose the name Systoligrada, instead of Diphyida, the locomotion being similar to that of the Pulmonigrada.

Order 1. Hydroida. The order Hydroida contains animals, some of which have, and some have not a coralium, or the stony material named coral. This does not constitute an essential distinction here, or among the Zoophyta, because the condition of the hard material is different in different genera, being sometimes merely indicated by the presence of calcareous granules scattered through the body.

In the Hydroida the internal cavity is tubular and simple, and the order includes the four families, Hydridæ, Sertularidæ, Campanularidæ, and Tubularidæ.

The Hydridæ, of which the fresh water polypus is a familiar example, occur in America as well as in Europe. It forms the genus Hydra, and is a soft naked polyp (pl. 75, figs. 21–23) found attached to plants in stagnant water, and increasing by lateral buds, as represented in figs. 22, 23; but unlike some Zoophyta, the young thus produced become detached when they attain a certain size. The internal cavity of the young is for some time continuous with that of the parent, so that the nourishment taken by the latter can be digested by both. Finally the young gets arms of its own, the cavity closes below, and the new animal becomes detached and commences an independent life. This mode of increase takes place in summer. Trembley, by watching an individual, found that it produced forty-five young in two months.

This genus was discovered in Europe by Trembley, in the year 1739, and we have observed it here. It attaches itself by the base to plants, rubbish, or even aquatic insects. These animals move somewhat in the manner of a leech, by stretching out the body and attaching the arms to an object, then drawing up and attaching the base, and so on in succession. When placed in a glass of water, they are said to pass from the shade into the light. The figures represent them about the natural size, so that they can be pretty readily detected with the naked eye. When disturbed, the arms and body are contracted into a small compass. The arms are used to catch their prey, which consists of minute Crustacea, and other animal food. The body is usually sufficiently translucent to allow the contents of the internal cavity to be seen.

The structure of the Hydra is of the simplest kind, being limited to the tubular body and its single aperture for the admission and exclusion of food; and the margin of this opening is fringed with from six to eighteen very elastic, flexible, and thread-like arms.

Under a high magnifying power, the arms of Hydra are seen to be studded with hemispherical projections, which resemble a bunch of grapes when they are drawn together by the contraction of the arms. Most of these projections support a short hair, some are armed with a thorn, and others support a very long hair ending with a spur composed of several thorns around a pear-shaped mass. See the last edition of the Règne Animal, Zoophytes, pl. 64.

It is evident that the Hydræ, like the Medusæ or sea nettles, have a stinging power, judging from the manner in which their prey is paralyzed when seized. Worms which will live and move for some time when cut into fragments, die instantly when seized by a hydra: and if a worm which has been seized is taken from the animal before it is swallowed, it does not revive. When a minute animal comes within reach of one of the arms, it is seized and swallowed, and this sometimes happens to young fishes. They sometimes even swallow each other, but the swallowed individual is cast out again unhurt. The uniformity of structure is proved by the fact that if the animal is turned inside out, the food can be digested by what was once the outside.

The genus Hydra has been named after the fabulous monster of antiquity bearing the same name, because parts cut away will be reproduced; and under favorable circumstances, when an individual is divided into several parts, each part will become a perfect animal. It is probable that Hydra grisea (pl. 75, fig. 21), H. fusca (fig. 22), and H. viridis (fig. 23), are varieties of but a single species.

The order Hydroida, according to Mr. Dana, contains the following families:

1. Hydridæ. Not coralligenous.

2. Sertularidæ. Coralla corneous. Sertularia abietina (pl. 75, fig. 33). S.polyzonalis (fig. 30). S. opercidata (fig. 34). Plamdaria falcata (fig. 31). Thuiaria thuia (fig. 32), all European.

   “In a single specimen of Plumularia angidosa collected by the author in the East Indies, there are about 12,000 polyps to each plumose branch; and, as the whole zoophyte, three feet long, bears these plumes on an average every half inch, on opposite sides, the whole number of polyps is not short of eight millions; all the offspring of a single germ, and produced by successive budding.”—Dana.

3. Campanularidæ. Coralla corneous, calicles pedicillate.
4. Tabularidæ. Coralla tubular and corneous. Tabularia indivisa (pl. 75, fig. 42) (Atlantic and Mediterranean), attached to stones in deep water, T. coronata (pl. 75, fig. 29) (Northern seas). Stem one third of a line in diameter. In this genus the tentacles are not retractile.

The remaining orders of the class Colenterata were called Acalephse by Cuvier, from the Greek word ακαληρη, a nettle, from the stinging quality which many of these animals possess. Blainville gave them the expressive name of Arachnoderma, from αςαχυιου a cobweb, and δερμα the skin, from the extreme tenuity of the tissues. They are also tenned Medusæ, sea-nettles, stang-fishes, sea-jellies, and jelly-fish. They are found floating in all seas, particularly those of the tropics; their size varies from one sixth of a line to two feet, and the weight of large ones reaches fifty or sixty pounds. Yet this great mass is composed almost entirely of water, which pervades the tissues, and these are of such extreme tenuity that the weight of one of these masses is reduced by desiccation to grains instead of pounds.

The more familiar forms belong to the Pulmonigrada, also termed Discophora, which may be compared to an expanded umbrella, or to a mushroom, the alternate contraction and expansion of which enable the body to move through the water with the convex or upper surface foremost; a mode of progression which has afforded a name to the order, from its resemblance to the action of lungs.

The beauty of many of these animals equals anything in organic nature; the colors are prismatic or entirely wanting, and in the latter case, the gelatinous transparent body resembles a mass of colorless liquid gum, which can only be distinguished by its motions from the water which surrounds it.

“When in a jar or basin they are often very difficult to distinguish, but by placing the vessel in the sun, we see their shadows floating over the sides and bottom like the shadows of flitting clouds on a landscape. These soon guide us to the creatures themselves, and before long we distinguish their ocelli and colored reproductive organs.”—Forbes.

The disk forming the greater part of the body varies from hemispherical to flattened discoidal, and is sometimes lengthened into a conical or subcylindrical form. The central portion is thickest, and the inferior surface is concave. The margin is either entire or fringed with tentacles, which vary greatly in length, number, and form. Some of these tentacles have a colored spot at their base called an ocellus, and upon this Forbes has divided the Discophora into two groups; namely, the Steganophthalniata (covered eyes), in which the ocelli are protected by membranous lobes, and the Gymnophthalmata (naked eyes), in which the ocelli are not protected. The former are more highly organized than the latter, and in most of the genera the sexes are not united in the same individual. Agassiz has discovered a nervous ring around the mouth, with branches extending to the ocelli; an arrangement which resembles that in the Echinodermata. Ehrenberg had made a less distinct announcement, and Dr. Grant announced the discovery of a nervous system in Beroe, in the year 1833.

From the centre of the concavity of the disk arises the peduncle, which varies much in size and shape, in some genera forming a considerable portion of the animal, and in others being reduced to a slender extensile and contractile tube, at the extremity of which the mouth is situated. The cavity of the peduncle, or its base, is the stomach, whence branches are sent towards the disk, around the margin of which there is a canal connecting with them. These radiating gastro-vascular branches vary in number from four to twelve or more. In the naked-eyed genera they are seldom branched; and when they are, the branches run to the marginal canal, as in the genus Wilsia² (Forbes, Monog. of the British Kaked-eyed Medusæ London, 1848, pl. 1 fig. 1). The same structure occurs in Berenice (Cuv. Regne An. Zooph., pl. 53, fig. 1^a). In the covered-eyed group, the branches after extending about two thirds the distance towards the edge anastomose around the margin in a broad and close vascular net work (beautifully exhibited in Milne Edwards’ figure of Khizostoma, R. An. pl. 50).

The position of the generative system is variable in this class. In general both sexes seem to be united in the same individual.

When the ocelli are present, the sense of sight is probably sufficient to enable the animal to distinguish between light and darkness, and the sense of hearing may also be present. Their food is furnished by small marine animals, among which the Crustacea fill a prominent place. The sense of feeling is probably most developed in the palpi, the tentacles, and the arms, arising from the centre, and surrounding the mouth or pedicle.

The stinging quality is not universal in the Medusæ, being apparently confined to a few of the higher forms. Bathers sometimes suffer severely by coming in contact with the larger species, whose long tentacles and arms are sometimes entangled around the limbs, and cast off by the animal, leaving the sufferer to disengage himself from these unwelcome appendages at his leisure. The stinging property is supposed to be confined to an external coat of mucus, which the animal can cast off.

The luminousness of the sea is due chiefly to multitudes of acalephæ.

“At one time, the evening serene and delightful, a pleasant breeze just filling the sails, and the bow of the vessel throwing the water to each side, as it gracefully parts the yielding waves, all round the ship, far as the eye can reach, may be seen innumerable bright spots of light rising to the surface, and again disappearing, like a host of small stars dancing and sparkling on the bosom of the sea. At another time, the night dark and lowering, a fresh breeze urging the ship rapidly onwards through her pathless track, upon looking over the stern, in addition to the smaller specks just now mentioned, large globes of living fire may be seen dancing in the smooth water in the wake of the rudder; now, at a great depth, shining through the water, then rising rapidly to the surface, they may be seen, as they reach the top of the wave, flashing a bright spark of light, sufficient almost to dazzle the eyes of the beholder; and now, again, they may be traced floating majestically along, till they gradually disappear in the darkness of the water in the distance. At other times, again, when light rain is falling, or, perhaps, previously to the rain coming on, when a light nimbose cloud is overspreading the sky, upon the water being agitated by the ship passing through it, a beautiful general luminousness is diffused all round, bright enough to illuminate the whole ship’s side, and the lower large sails; and it is no unusual occurrence to have the appearance so bright, that a person with little difficulty, and near the surface of the water, might be enabled to read a book by its aid. . . It is in warmer regions and more southerly latitudes that this phenomenon attains its greatest degree of brilliancy and beauty.”—W. Baird, On the Luminousness of the Sea, with figures. Mag. Nat. Hist. 1830, vol. 3, p. 308; vol. 4, p. 500. See also vol. 6, pp. 314–319.

Luminous acalephss occur upon the coast of the United States, and they may be observed on a night passage in a steamboat in Long Island Sound. The light is usually produced under exciting circumstances, or when the animal is disturbed, and all parts do not produce light. Spallanzani found that in cutting off the margin for about half an inch, the latter remained phosphorescent, which was not the case with the disk.

Order 2. Pulmonigrada. The following species of this order are figured; Thaumantias eymhaloidea (pl. 76, fig. 73), Northern Seas. Aurelia aurita, Linn. (fig. 74), Northern Seas; six to ten or eleven inches in diameter. In this genus the mouth is surrounded with four arms, and the central peduncle is wanting. This species has a bluish disk, fringed with slender tentacles, and having eight marginal ocelli, which are black, with a red point above. Beneath there are four long fringed central arms, with the mouth between them. Sometimes the margin of the arms contains eggs. The ovaries, however, have their openings between the base of each pair of arms; there are four of them shaped like a horse-shoe, and of a purple color, which renders them visible from above, as seen in the figure.

Order 3. Ciliograda. This order (also named Ctenophora by Eschscholtz) is named from its organs of motion, which consist of a series of flat phosphorescent vibrillæ, arranged longitudinally upon the surface of the body, along the eight ribs, and by the action of which progression is effected. These vibrillæ are arranged with their flat surfaces nearly in contact, and they are raised slowly and struck rapidly. Some authors suppose them to subserve the purpose of gills as well as organs of locomotion. The genus Beroe, which is a good example, varies in form from globular to cylindrical, but a little compressed. The cavity beneath is very large, and the animal moves with the mouth foremost. In addition to the mouth there is an excretory orifice. Cestum veneris has a ribbon-shaped body, the two margins of which are fringed with beautifully colored phosphorescent vibrillæ, which at night give the animal the appearance of a band of flame, as it moves through the water. It attains the length of three or four feet.

Order 4. Cirrigrada. The form is discoidal, and there is an internal subcartilaginous discoidal skeleton, which distinguishes them from the Pulmonigrada. In Porpita (pl. 76, fig.83) margin is fringed with stout claviform tentacles, provided with three ranges of pedunculated glands or suckers. The stomachal pedicle is large, and surrounded by numerous tentaculiform cirri, by means of which locomotion is efiected. These bear some resemblance to the tentacles of the Actiniæ, to which Blainville thinks the order has some affinities. In Velella (V. spirans, Forsk., pl. 76, fig. 84), besides an oval cartilaginous skeleton, there is a vertical process arising from it which supports a crest-like membrane.

Order 5. Physograda. This order was called Hydrostatic Acalephæ by Cuvier, a designation which, like the proper name, points to a peculiarity of structure, namely, the support of the body by one or more air-vessels, which cause the animal to float. Physalia pliysalis, Linn. (pl. 77, fig. 1), possesses stinging qualities; it inhabits the Gulf of Mexico and the Atlantic, and is known to sailors as the Portuguese man-of-war. The air-vessel is very large, and has a small aperture at each end, from which the air can be expelled when the animal wishes to sink. It is probable that this may be accomplished to a certain extent by the muscular power of the air-vessel. Blainville thinks that this order (which wants the radiated character), with Beroe and Diphyes, may be allied to the Mollusca, and in the year 1836 he proposed for them the name Malactinozoaria, under the impression that they constitute an intermediate division.

Order 6. Systoligrada. The name Diphyida is derived from that of the genus Diphyes, in allusion to its double nature, each animal being composed of two somewhat conical pieces, the point of one being inserted a short distance into the larger end of the other, and retained by a very slight attachment. See the Penny Cyclopædia for an extended account, illustrated with figures of this and the preceding orders.

Sars, a distinguished naturalist of Norway, discovered in 1836 that some of the Acalephæ resemble the Zoophyta, in having a gemmiparous reproduction. He observed certain projections from the base of the pedicle (or exterior of the stomach), which proved to be budding young, attached by the upper or outside portion of their disk. These young resemble the adult in all essential particulars, and, like the Hydræ, they have an independent action previous to their separation from the parent. This is represented at a, in the annexed figure of Lizia octopunctata of Sars (an animal about one fourth of an inch long), as given by Forbes. The species is named from the eight black ocelli, four of which are large, and towards these the gastric vessels are directed. In Sarsia prolifera, Forbes, the gemmation takes place at the base of the exterior tentacles.

We come now to describe a mode of generation which has no parallel in the higher animal forms, and to which the Medusse and some other animals are subject. This mode is termed Alternation of generations by the Danish naturalist, Steenstrup, who has the credit of generalizing the facts upon which the theory is founded, and of which he is in part the discoverer. An English translation of his work on the subject, by George Busk, was published by the Ray Society in 1845, entitled, “On the Alternation of Generations; or the Propagation and Development of Animals through Alternate Generations: a peculiar form of fostering the young in the lower classes of animals.” Besides this author, the chief observers in this curious branch of science are Chamisso, who published observations on the Salpæ in 1819; Sars, on the Medusae, between 1828 and 1841; Siebold and Loveu in 1837; and Van Beneden in 1844–7. (See the Cyclop. of Anat. and Phys., Art. Polypifera.)

This phenomenon is described by Steenstrup as that of “an animal producing an offspring, which at no time resembles its parent, but which, on the other hand, itself brings forth a progeny, which returns in its form and nature to the parent animal, so that the maternal animal does not meet with its resemblance in its own brood, but in its descendants of the second, third, or fourth degree or generation; and this always takes place in the different animals which exhibit the phenomenon in a determinate generation, or with the intervention of a determinate number of generations. This remarkable precedence of one or more generations, whose function it is, as it were, to prepare the way for the later succeeding generation of animals, destined to attain a higher degree of perfection, and which are developed into the form of the mother, and propagate the species by means of ova, can, I believe, be demonstrated in not a few instances in the animal kingdom.”

When a medusa, as Aurelia aurita (pl. 76, fig. 74), produces an egg, the progeny resembles an animalcule (Diagram, fig. 1), which moves in the direction of the arrow by means of vibrillæ. The anterior extremity has a round sucker (but not a mouth), by means of which, after several changes of form, it attaches itself to some extraneous object (Diagram, fig. 2). The changes still continue, the two projections at the free end are extended, a mouth is formed in the centre, and a second pair of projections arises between the first. About the fifth or sixth day the four tentacles have become longer, and the body quadrate, and the animal now constitutes the supposed perfect genus, Scyphistoma (Diagram, fig. 3), of Sars. In the next place, four additional tentacles arise between the four earlier ones, and this production continues until the number equals twenty-eight or thirty, and by this time the animal resembles a polyp.

In the subsequent changes an entirely new phenomenon is observable. The free extremity of the body begins to show indications of a division into segments, of which one is shown in Diagram, fig. 4; the length and number of segments increase, the body becomes cylindrical, and is now about a line in diameter (its original size being that of a grain of sand), the upper margin of the segments becomes free and divided into lobes (Diagram, fig. 5), capable of independent motion, when the form constitutes the supposed genus, Strobila, of Sars, named from its resemblance to the cones of a pine tree.

Finally, the union between the segments is more and more reduced, until they separate like a pile of hemispherical cups, as in Diagram, fig. 6, when they are seen to be separate animals in an inverted position; in fact, the young or larvæ oi Aurelia (pl. 76, fig. 74). These larvæ (constituting the supposed genus Ephyra) are about a line in width, and continue growing and passing through such a change as to give it the structure of the adult, which it acquires when about an inch in size. It is not precisely known what becomes of the polypiform head of the Strobila (Diagram, fig. 5), but the base is said to produce a new set.

It appears from these facts that the animal (Diagram, fig. 1) hatched from the egg of a medusa, does not become a free medusa, but a kind of polyp, Scaphistoma strobila, which does not produce its like, but from which medusæ are developed. The polypoid nurse, as it has been termed, is uniformly an undeveloped female, whilst of the resulting medusae, some are male and some female. The nurse, like the adult medusa, has the power of increase by budding.

The annexed fig. 1 represents an individual of the presumptive genus Coryne, placed in the family Tubularidæ (p. 27). The head is a six-armed hydroid, beneath which are four quadrate, bell-shaped bodies, which are not organs, but distinct individuals of an entirely different form from the hydroid. In the concavity of each is suspended a quadrate stomach, as shown in fig. 2. These bodies have an independent motion, sucking the water in, and throwing it out like the Medusæ. They finally detach themselves, and swim freely like medusæ, to which they bear a close resemblance. Steenstrup, who observed this species in Iceland, found larger individuals (fig. 3), which he considers the adult medusaform of the former, in which one of the angles bears a lobed organ and two threads, which he regards as female generative organs. Steenstrup regards Coryne as “a previous generation of preparative nurses, which are so far asexual, inasmuch as that their generative organs are not developed.”

Forbes describes two minute British species allied to fig. 3, under the generic name of Steenstrupia, suggesting that they may be a stage in the history of some hydroid form.

Class 2. Zoophyta

The Zoophyta are chiefly marine; some species are sedentary and others free, some live as single independent animals, and others are collected together in large colonies, the base of the stems being united. Some are without a hard support, others secrete a stony skeleton, which is named coral (corallum, coralla in the plural).

The corallum is not usually external like the shell in the Mollusca, as is popularly supposed, but an internal secretion “entirely concealed,” in the words of Dana, “within the polyp, as completely as the skull of an animal beneath its fleshy covering. All corals are more or less cellular, and through these cellules the animal tissues extend.” In some, however, the coral is exposed, as when the increase takes place by a terminal secretion upon a separate stem, when the apex alone is living, and as the stem increases in length the part below dies. This increase above and death below are common in most corals, and to this the great masses of coral are attributable. According to Dana, a solid dome of Astrsea, twelve feet in diameter, has a living exterior of only a half or three fourths of an inch in thickness.

The classification adopted here is chiefly that of James D. Dana, as given in his magnificent work on Zoophytes, the result of his labors in the United States Exploring Expedition. The characters of the families are in most cases condensed from the same work.

The Order Actinoida includes not only the flower-shaped genera, like Actinia (pl. 77, figs. 5, 6), which do not secrete a coral, but also numerous coralligenous genera. The name of this order, from the Greek ακτιυ, a ray, is in allusion to the radiated arrangement of the tentacles, which, when expanded, in many cases resemble the petals of a flower. When contracted this resemblance disappears, and the mass may be compared to a lemon in shape. Lesueur has described a species (A. marginata) from Massachusetts Bay. (Jour. Acad. Nat. Sci. i. 172.)

The Actiniæ are found in the sea, attached to stones, submerged timber, &c. They have the power of detaching themselves and floating, and of creeping slowly upon their flat base, at the rate of about two inches in an hour. The texture of the exterior is either fleshy or coriaceous, the surface slimy, smooth, or tuberculous, and very sensitive. The mouth is simple, and fringed by the tentacles. These organs being tubular, they are expanded by having water forced into them, and when they contract, the water is ejected through a minute terminal perforation. The tentacles of some species resemble the Acalephæ in having a stinging power.

The interior of the Actiniæ is taken up with the stomach, which is a simple sac, of which the mouth is the opening, and extending nearly to the base of the animal, where it communicates with the visceral cavity, occupying the space between the stomach and the exterior wall. The cavity is provided with a series of vertical muscular partitions, more or less perfect, which extend from the exterior wall to the stomach, so that a transverse section of the animal would resemble a wheel, of which the nave would represent the stomach, and the spokes the visceral partitions.

The Actiniæ feed upon fish, crabs, shell-fish, &c., the shells and other indigestible parts being ejected from the mouth after a period of ten or twelve hours. A large individual sometimes accidentally swallows a smaller one, but the latter is usually cast out unharmed, as in the case of the Hydra. The objects swallowed are sometimes as large as the Actinia itself in a state of repose. The following account is given in G. Johnston’s excellent History of British Zoophytes.

“I had once brought me a specimen of Act. gemmacea, that might have been originally two inches in diameter, and that had somehow contrived to swallow a valve of Pecten maximus of the size of an ordinary saucer. The shell, fixed within the stomach, was so placed as to divide it completely into two halves, so that the body, stretched tensely over, had become thin and flattened like a pancake. All communication between the inferior portion of the stomach and the mouth was, of course, prevented; yet, instead of emaciating and dying of an atrophy, the animal had availed itself of what undoubtedly had been a very untoward accident, to increase its enjoyments and its chances of double fare. A new mouth, furnished with two rows of numerous tentacula, was opened upon what had been the base, and led to the under stomach; the individual had, indeed, become a sort of Siamese twin, but with greater intimacy and extent in its unions!”

The Actiniæ are hermaphrodite; the reproduction is both by division and by eggs; and the eggs or young (as the case may be) are ejected through the mouth, or rarely, by a kind of abortion, through the tentacles, according to Contarini. The young do not differ essentially from the adult, the chief difference being in the small number of their tentacles.

The Actiniæ reproduce lost parts, especially the tentacles, with great facility; and when the body is cut into two, three, or even four parts, each may survive and become a complete animal. If the section is horizontal, the lower part acquires a new mouth and tentacles, and the upper part a new base, although in one instance the latter produced a second mouth. so that food was taken at both extremities of the new animal. These experiments indicate that the base has the greatest vital power. (See Contarini, Trat. delle Attinie, &c., Agassiz’s Lectures, and Johnston’s Zooph.)

Actiniæ will survive after being placed in water hot enough to blister the skin, and they may be frozen and thawed with impunity, but immersion for a few minutes in fresh water kills them.

The order Actinoida contains the sub-orders Actinaria and Alcyonaria, and the families, according to Dana, are as follows:

Sub-order 1. Actinaria.

Often coralligenous, cells lamelliradiate.

Tribe 1. Astrcæcea

Many tentacles in imperfect series; coralla calcareous, with multiradiate cells, with the lamellae extending beyond the cells.

Fam. 1. Actinidæ. Not coralligenous, usually attached, but sometimes floating in the sea. Actinia (pl. 77, figs. 5, 8). Lucernaria (pl. 76, fig. 72). (Johnst. Zooph., p. 228. H. An. pl. 63, with anatomical details.)

Fam. 2. Astræidæ. Coralla calcareous, tentacles marginal, coralla with excavate cells, stars circumscribed. Astrea astroites (pl. 75, fig. 62). Meandrina lahyrinthica, Linn. (pl. 75, fig. 64); hemispherical, with long winding lines: American seas.

Fam. 3. Fungidæ. Disks not circumscribed, tentacles scattered, short, or obsolete; simple or aggregate-gemmate; when aggregate the disks are confluent; surface of the coralla stellate, without proper cells. Fungia fungites, Linn. (pl. 75, fig. 65), has a circular coral, with radiating lamellæ, like the imder surface of some mushrooms; beneath granulated.

A common species from the Indian Ocean and Red Sea. In this genus the corallum is formed by a single polyp, which covers it beneath as well as above. The tentacles are scattered, and when touched, are withdrawn between the lamellæ.

Tribe 2. Caryophyllacea

Tentacles numerous, in two series; coralla calcareous, cells multiradiate, interstitial surface not lamello-striate. The fourth family is not coralligenous.

Fam. 1. Cyathophyllidæ. Interior middle of each corallum usually transversely or obliquely cellular.

Fam. 2. Caryophyllidæ. Tentacles crowded and long, mouths far exserted; interior of the corallum not transversely cellular, rays of the cells more than twelve. Oculina virginea, Linn. (pl. 75, fig. 58). White, eighteen inches high. East and West Indies and the Mediterranean. O. gemmascens (pl. 75, fig. 59). White, eight inches high.

Fam. 3. Gemmiporidæ. Tentacles short and marginal, in two or three series; disk broad, somewhat convex; coralla porous, calicles with a thick margin. ? Explanaria ananas (pl. 75, fig. 63).

Fam. 4. Zoanthidæ. Exterior subcoriaceous, tentacles short and marginal, in two or three series.

Tribe 3. Madreporacea

Tentacles in a single series, seldom more than twelve, sometimes obsolete; coralla calcareous, cells small, six-to twelve-rayed, or obsolete; interstitial surface not lamello-striate.

Fam. 1. Madreporidæ. Tentacles twelve; cells deep, extending to the centre of the corallum. Madrepora prolifera (pl. 75, fig. 60).

Fam. 2. Favositidæ. Tentacles twelve; lime secreted periodically at base, so that the interior of the corallum is septate, rarely solid. Pocillopora polymorpha (pl. 75, fig. 55). (Lamarck, 2, 311.) Red Sea.

Fam. 3. Poritidæ. Tentacles rarely more than twelve; base forming porous calcareous secretions beneath; coralla finely porous, cells shallow, rays indistinct. Porites porites, Linn. (P. clavaria, Blainv.) (pl. 75, fig. 61). American and Indian seas.

Tribe 4. Antipathacea

Animals six-tentaculate, base forming corneous secretions.

Fam. 1. Antipathidæ. Animals fleshy, enveloping a corneous spinulous axis. Antipathes spiralis (pl. 75, fig. 51); stem entire, long, and spiral, about as thick as a quill, and attaining a length of sixteen feet. Indian Ocean.

Sub-order 2. Alcyonaria

Eight-tentaculate; tentacles papillose, apex of the papillæ perforate; often coralligenous.

Tribe 1. Alcyonacea

Fam. 1. Pennatulidæ. Free, or with the base sunk in the mud. Pennatula phosphorea, Linn. (pl. 75, fig. 26). Bears some resemblance to a quill. It is found in the European seas, and emits a pale-blue phosphorescent light when disturbed. P. granulosa, Lam. (fig. 25), and P. grisea, Esper (fig. 27), inhabit the Mediterranean; Virgularia juncea, Esper (fig. 24), Europe.

Fam. 2. Alcyonidæ. Fleshy, with calcareous granules. Alcyonium ficiforme (pl. 75, fig. 46), size and shape of a fig, and of a yellowish-brown color: and A. palmatum (fig. 47), stem divided irregularly, somewhat like a hand; pale-red. Mediterranean.

Fam. 3. Cornularidæ. With corneous tubular coralla.

Fam. 4. Tubiporidæ. With calcareous tubular coralla. Tubipora musica (pl. 75, fig. 66) is of a fine red color, the body green. Indian seas.

Fam. 5. Gorgonidæ. With basal epidermic secretions. Gorgonia flabellum (pl. 75, fig. 48). Reticulate, branches inwardly compressed; three feet long. Warm seas of India and America. G. verrucosa, Linn. (pl. 75, fig. 49). Atlantic, six to twelve inches. G. ceratophyta (fig. 50), Mediterranean. Isis hippuris, Linn. (fig. 53); stem jointed and strong, branches dichotomous. East Indies. Coralium nobile, Linn. (pl. 75, fig. 52), is branched, one foot high, varies from a fine deep-red to a rose color, or white with a reddish tinge. It admits of a fine polish, and is much used for light ornamental work. When fresh, the exterior is fleshy and polypiferous, which, in drying, forms a crust with scattered cellules.

The forms of the corals which most of the zoophyta secrete, are extremely varied; representing various plants and mosses, variously shaped vessels, domes, obelisks, radiated disks, leaves, &c.; and the size of the coral mass varies from a few lines to twelve or even twenty feet. The large masses have commenced in a single animal, from the successive budding of which, the whole has resulted.

“Calculating the number of polyps that are united in a single Astrsea dome of twelve feet diameter, each covering a square half inch, we find it exceeding 100,000; and in a Porites of the same dimensions, in which the animals are under a line in breadth, the number exceeds five and a half millions. There are here, consequently, five and a half millions of mouths and stomachs to a single zoophyte, contributing together to the growth of the mass, by eating, and growing, and budding, and connected with one another by their lateral tissues and an imperfect cellular or lacunal communication.”—Dana, p. 60.

In those cases where single polyps occupy the extremity of dead branching-stems, there is no union of the soft parts of different individuals.

Class 3. Echinodermata

The Echinodermata, which are all marine, and include what are popularly termed star-fish, sea eggs, &c., are the most highly organized class in the radiated division of the animal kingdom. The bodies of some are raised upon a pedicle, the base of which is fixed to a single place; others are without a pedicle, and move freely and slowly along the bottom. Some of the latter are provided with a multitude of sucker-like feet, which, in Asterias aurantiaca, amount to 840, according to Tiedemann. Some are provided with eye dots, which, in Asterias, &c., are situated at the extremity of the rays; and where the nervous system has been detected, it forms a circle around the œsophagus, with branches to the rays, &c. The mouth is armed with hard bony teeth, enabling the animal to live upon crustacea and shell fish. Some live at the bottom of the sea on the surface of the rock, and others burrow in the sand.

The integument of some of the members of this class is sustained by a calcareous skeleton, which incloses the viscera and supports movable spines varying much in size and shape. The skeleton is composed of pieces which are often joined together like polygonal stones in a pavement. These plates, the spines, and the entire skeletons, are very abundant in various geological formations, in which they are preserved in great perfection.

The class contains the orders Crinoidea, Asteridea, Ecbinidea, Holothuridea, to which some add another for the reception of Siponculus, Echiurus, &c., constituting the apodous Echinodermata of Cuvier.

Order 1. Crinoidea. This order is almost extinct, but is found plentifully in a fossil state in the older rocks. These remains consist of the solid calcareous skeleton, of which the chief parts are the stem, the body, and the arms. The body is oval or cup-shaped, protecting the internal softparts, and made up of numerous plates, of which the variations in number and form afford generic characters. The arms are five or more in number, simple or branched, fringed with lateral articulated appendages, and placed around the upper margin of the body, the mouth being situated between them. When the arms are closed, some species resemble a lily, whence the trivial name of Encrinus liliiformis. The vent is distinct and lateral.

The central solid part of the stem has been compared to the bones in a lizard’s tail, being made up of a column of disks, which are either circular, polygonal, or star-shaped. The stem is often provided with articulated simple lateral branches, which, like the arais, are filled with calcareous joints, many thousand of which are contained in the remains of a single animal. The disks of the stem have a perforation through them, which admits of their being strung like beads; and, according to Dr. Buckland, they were used for rosaries in ancient times. In northern England they are called St. Cuthbert’s beads; and before their nature was known, they were named Entrochites in books.

Pentacrimts asteria, Linn. (P. caputmedusæ, Miller) (pl. 76, fig. 58), is a recent species from the West Indies, of which a specimen is in the British Museum, the Paris Museum, that of the Geological Society of London, and that of the London College of Surgeons. (This and other species of the order are figured in the Penny Cyc. ix. 390, and in the new edition of the Règne Animal.) Encrinus radiatus (fig. 57).

Pentaerinits europæus, Thompson, a minute animal found on the coast of Ireland, is now considered by this author to be the pedunculated young of Comatula, a starfish somewhat like pl. 76, fig. 62. This confirms one of the views of Agassiz (Lectures, p. 13), that the earlier fossil animals often resemble the embryonic or immature forms of the more recent periods. Holopus rangii, Orbigny (pl. 76, fig. 56) (Mag. de Zool. 1S37, pl. 3) is a recent genus from Martinique.

Order 2. Asteridea, In this order the supporting stem is wanting, and the animal has the power of locomotion, sometimes by means of the arms, and sometimes with the aid of the sucker-like feet. The arms in some genera are provided with numerous lateral filaments, and in some cases they divide into branches. The genus Astrophyton (named also Euryale and Gorgonocephalus) (pl. 76, fig. 63), is remarkable for its five dichotomizing arms sending off branches, and terminating in a multitude of curled filaments, which, it is said, may amount to eight thousand in a single individual.

The genus Ophiura (pl. 76, fig. 64) is named from the resemblance which its long and slender arms bear to the tail of a serpent, not only in form, but in the numerous bony pieces of which they are composed, and which are not unlike the scales of a serpent. The arms are very flexible; and by giving them an undulating motion, the animal can swim to a certain degree. On each side of the base of the arms is an opening which is the outlet of the ovaries, of which there are ten. Several species inhabit the coast of the United States. In Ophiolepis (fig. 62), a genus allied to Ophiura, the disk is entire, with smooth plates. In both genera the arms have movable spines, which in some species are appressed, and in others projecting. The species figured, O. scolopendrina, is found near the Isle of France. In these genera the mouth is in the centre of the ventral surface, and from it are continued five grooves, through which a few sucker-like feet are projected. The mouth is armed with a strong osseous apparatus for masticating food. The arms, when broken off, can be reproduced. Pl. 76, fig. 61, represents Astrogonium granulare of the seas of northern Europe. In this genus the rays are not so well developed as in Asterias (fig. 60), which gives it a pentagonal figure.

Oreaster turritus (pl. 76, fig. 59) attains a length of ten inches, and inhabits the Indian Ocean.

Solaster is distinguished by an increased number of rays; S. papposus (pl. 76, fig. 66) is a foot in diameter.

Stellonia rubens (fig. 65) attains a foot in size, and is so abundant in the seas of Europe as to be spread over the soil as a manure.

Asterias (fig. 60) has the rays so much enlarged that there is room in the concavity of each for two extensions or appendages of the stomach, with an ovary between them, and a liver; which is not the case in the slender rayed genera like Ophiurus. Moreover, the size of the rays renders them less flexible, and badly fitted for locomotion; but as a compensation, they are pierced along their inferior surface (between short transverse bones arranged in series on each side of a deep central groove) with a multitude of ambulacral perforations, through which the feet already mentioned project, and which enable the animal to crawl up a surface as smooth as glass, and also assist in holding its prey. The sucker-like feet are connected within the aperture through which they project, with a globular vesicle filled with water, by the hydrostatic action of which the suckers are extended or withdrawn. Each vesicle is connected by a small tube with a canal which traverses each ray, starting from a circular canal around the œsophagus.

“This apparatus communicates with another tube which penetrates from the dorsal surface downwards, having its opening shut by a perforated plate called the madreporic body, which in starfishes is always seen in the angle between two of the rays; so that we have here an hydraulic apparatus of a very complicated nature.” (Agassiz.) Through this series of vessels the water flows in both directions, either downwards through the upper aperture, or upwards through the tubular feet; subserving in its course the functions of locomotion and respiration. The water which fills the general cavity is admitted through the numerous minute perforations of the exterior. “The heart is placed along the calcareous tube which arises from the madreporic body, and the blood-vessels form circular rings around the entrance of the stomach, from which and to which the radiating arteries and veins move.” (Agassiz’s Lectures, and his Letter to Humboldt in 1847.) There are also movable spines upon the lower surface which assist in locomotion.

When food is taken, the animal bends its rays towards the mouth, so as to form a cup-shaped cavity, when the food is gradually moved to the mouth. There is no vent distinct from the mouth. The rays, when lost by accident, can be reproduced, and it is asserted that if a ray with part of the mouth be detached, it will form a new animal. The stomach is central and sends off two branching divisions or caeca in each ray. There is an English law which imposes a fine upon fishermen who do not kill a species of Asterias which is said to destroy oysters.

Agassiz has discovered that starfish, after their eggs are laid, take them up and retain them below the mouth between their suckers; and when they are forcibly removed to some distance, the animal will approach and take them up again, showing a remarkable instinct in so low an animal.

We pass from Asterias (pl. 76, fig. 60), through the pentagonal form Astrogonium (fig. 61) to Agassiz’ genus Culcita, which resembles the last somewhat in shape, except that the five sides are convex instead of concave, so that the outline is more nearly circular, approximating the circular and oval forms of the next family.

Order 3. Echinidea. This order includes the oval or circular bodies known as sea-eggs, sea-urchins pottrsin in French), the skeleton of which is a calcareous crust composed of twenty equal or unequal rows of polygonal plates pierced by various pores. The mouth is beneath, and armed or unarmed, central or sub-terminal; the vent is distinct, and varies in position, being formed beneath and above, and when beneath, marginal or towards the centre. The generative pores are four or five, placed around the summit.

When the animal dies, the integument (including the spines with which it is covered, and which present much variety in form and size) is soon lost, leaving the calcareous shell which protects the interior soft parts. The integument of the calcareous portion not only secretes the shell, but extends in a thin layer over the solid spines, which are thus formed layer by layer as the animal increases in size.

The circular form of these animals might at first induce an observer to doubt their affinity with the more star-shaped Asteridea, but if the rays of the latter are supposed to be shortened, and the concavity between them filled up, the approximation will appear when the correspondence of the organs is considered.

The plates of an Echinus (pl. 76, fig. 69) run in vertical rows, two of which are wide and two narrow alternately; the wide pair have tubercles which support the larger spines; and the narrow ones have vertical rows of minute perforations which form the ambulacra, and allow the passage of the sucker-like feet which, in addition to the spines, are concerned in locomotion, and perhaps in passing water to the respiratory organs which lie beneath.

The mouth of the Echini is armed with five jaws working together by means of a complicated piece of mechanism, and which have been compared by Aristotle to a lantern, hence called the lantern of Aristotle.

Among the chief authorities upon this department are Lamarck, Blainville, Delle Chiaje, Goldfuss, Desmoulins, J. Miiller, Sars, Milne Edwards, Dufossé, Duvernoy, Klein, Gray, and especially Agassiz.

The forms in this order are very various, from the flat and discoidal Scutella, which is flat beneath and but slightly convex above, to the sub-globular Echinus and elevated Galerites, which is considerably higher than wide. Some have the ambulacra disposed in oval or elliptic lines upon the upper surface, resembling the four or five petals of a spreading flower. According to Duvernoy, in the Echinidas in which the rosette is formed, a series of branchiæ (instead of feet) are passed through these perforations, in addition to the internal branchiæ; and in consonance with this view, he divides the Echinidae into two sections: the Exobranchia, with external branchiæ (including forms like Clypeaster, Cassidulus, and Spatangus); and the Homopoda for the remainder (including forms like Cidaris and Galerites).

Echinus, and other genera with large spines, are found on the bottom of the sea, whilst the Scutellæ, which have short bristly spines, burrow in sand.

Spatangus (pl. 76, fig. 67) and its allies have the mouth armed and placed towards the anterior end; the vent posterior, and placed upon the upper or lower surface; the shell thin in texture, lengthened, and gibbous; ovarian pores four.

Clypeaster (fig. 68), and the allied genera, have the mouth central, or nearly so, and the vent near the posterior margin, and upon the upper or lower surface, according to the genus.

Echinus (pl. 76, fig. 69), and Cidaris (figs. 70, 71), have a subglobular shell and two kinds of spines, the larger of which are supported upon large tubercles. The mouth is central beneath, and the vent in the apex.

The tendency to take an oblong form in Spatangus and Ananchytes, and the mouth being placed near the opposite extremities of the body, indicate an approach to the next order.

Order 4. Holothuridea. The animals composing this order have an elongated worm-like form, and the shell has disappeared, although some earthy matter is deposited around the mouth. In Holothuria and the allied genera the body is very contractile; the skin is irritable and has numerous mucous-secreting pores, and perforations for the passage of the sucker-like feet, which are either generally distributed, or arranged in five rows representing the ambulacra, or confined to the middle portion of the ventral surface. The mouth is fringed with branching tentacles capable of being withdrawn; the vent is at the opposite extremity of the body; and the entire animal bears a striking resemblance to a cucumber, whence it is called by sailors the sea-cowcmnber, and one of the genera bears the name of Cucumaria (C. frondosa, pl. 76, fig. 85). They are extensively collected about the islands and reefs of the Eastern oceans as a culinary delicacy for the Chinese markets.

Captain Flinders mentions a Malay fleet of sixty vessels and one thousand men, as forming an expedition to fish for these animals.

“The object was a certain marine animal called trepang; of this they gave me two dried specimens, and it proved to be the beche-de-mer or sea-cucumber, which we had first seen on the reefs of the east coast, and had afterwards hauled on shore so plentifully with the seine, especially in Caledon Bay. They got the trepang by diving, in from three to eight fathoms water; and where it is abundant, a man will bring up eight or ten at a time. The animal is split down one side, boiled, and pressed with a weight of stones; then stretched open with slips of bamboo, dried in the sun, and afterwards in smoke, when it is fit to be put away in bags, but requires frequent exposure to the sun. A thousand trepangs make picol, of about 125 Dutch pounds; and one hundred picols is a cargo for a prow.”

Order 5. Sipunculidea. These are sometimes included in the order Holothuridea, with which they agree in the tentacles, the intestinal canal, and circulatory system, although they want the tubular feet. Sipunculus (pl. 74, fig. 7, and pl. 77, figs. 27, 28). According to Quatrefages the anatomy of Echiurus indicates an affinity both to the chsetopodous annelida and to Holothuria, giving it characteristics of distinct types. Some authors, as Blainville and Gervais, place these animals among the Annelida.

Class Helminthes

The classification of the various forms of worms has been attended with difficulties, some of which still remain, notwithstanding the efforts of distinguished naturalists to ascertain their characteristics. The worms, whose body is composed of a series of rings, as in the leech and earth-worm, and whose nervous system is composed of a line of ganglia, united by a double nervous cord, as in insects, form with these the division Articulata, of which they constitute the class Annelida.

After excluding the Annelida from the class of worms, there still remain many forms, both aquatic, and living in the interior of other animals, to which the term Helminthes is restricted. Here the annulate structure has disappeared, and the median nervous system has been separated into two distinct branches, usually arising from a large ganglion anteriorly, or two ganglia united by a transverse branch. From the characteristics which these animals aflbrd, it is difficult to decide whether they belong to the radiate or articulate division of the animal scale, or, as is probable, form an inter-class with characters common to both. Milne Edwards, Gervais, and Agassiz, think the form a common type with the Articulata, thus uniting all the worms in one division. The latter disposes of the differences in the nervous system, by considering them essentially the same, the two distinct or bilateral threads (and sets of ganglia, where they exist) being approximated to form a single series. The genus Malacobdella has certain intermediate characters, which render it difficult to place, the nerves being separated, the intestine simple, and the sexes separate. It is about an inch long, white, translucent like Planaria, and has a posterior sucker. It is marine, and lives as a parasite in the mantle of the molluscous genera My a and Venua. Blanchard thinks it forms a distinct type of worms, as the generative organs alone have an affinity with those of the Annelida; and Duvernoy places it among the Trematoda.

On the other hand, the Helminthes may be regarded as a two-rayed animal (a view taken in part by Duvernoy), allied to the Radiata by this very nervous system, which, in Tristoma (R. An. pl. 36), forms a complete circle, which may be compared with that of the Radiata. The digestive system of this animal and of Planaria, bears an analogy to that of the Radiata, even the more typical forms, for in the Echinidea it has already departed from the radiated type. In some Planariæ (R. An. pl. 37, fig. 1^c) the gastro-vascular ramification forms a complete net-work, which has its counterpart in Rhizostoma (R. An. pl. 50).

We lay no stress upon the absence of the articulate structure in most Helminthes, because it is wanting in some of the Epizoa, which, although sometimes arranged with the Radiata, belong to the Crustacea. The articulate appearance of Tænia arises from the fact, that each joint is to a certain extent a single individual, affording an analogy with the Radiata, which is strengthened by the transverse nutrient tubes.

Cuvier, Duvernoy, and others, place the Helminthes among the Radiata. The classification of the latter, in 1848, is as follows, the vernacular names (which have no authority in science) being replaced by systematic ones.

Class Helminthes, comprising the three sub-classes, Helminthophyta, Parenchymata, and Cavitaria.

Sub-class I. Helminthophyta

Animals simple or compound; form ribbon-shaped, a double alimentary canal, no vent. Including the two orders Cystica (from Kystis, a bladder) and Cestoidea (from Kestos, a band).

1. Cystica, with one family:
   1. Hydatidsæ.
2. Cestoidea, with three families:
   1. Cysticercidæ.
   2. Ligulidæ.
   3. Tæniidæ.

Sub-class II. Parenchymata

Form flattened, rarely cylindrical, nervous system bi-radiate; a bifurcated or branched alimentary sac. It includes the two orders and families:

1. Trematoda.
2. Planariidæ.

Sub-class III. Cavitaria

Having a visceral cavity, the nervous system bi-radiated. Composed of four orders, the first having a visceral cavity instead of an intestine, the remaining three with two openings at the alimentary canal, at opposite extremities.

1. Enterodela,³ with one family:
   1. Acanthocephala.
2. Enterodela cylindrica [Nematoidea, Rudolphi], two families:
   1. Ascaridæ.
   2. Gordiidæ.
3. Enterodela plicata [Acanthotheca, Diesing], a single family and parasitic genus:
   1. Linguatulidæ.
4. Enterodela tænioida, one family:
   1. Nemertidæ.

The greater part of the Helminthes live in various parts of other animals, deprived of light, with little occasion for locomotive powers, and governed by circumstances of great uniformity, so that we need not be surprised at the simplicity of structure in individual genera, although they present a considerable amount of variation in the aggregate. From the mode of their occurrence within other animals, they have been termed Entozoa. in which certain external species are included. In some cases the same species is found in waters as well as in the interior of animals. There is scarcely an animal, whether terrestrial or aquatic, which does not nourish some of these parasites, and but few of the latter infest several distinct species. They have been found in beasts, birds, reptiles, fishes, insects, mollusca, and even in the acalephæ.

These entozoa are found, according to the species, in various parts of the bodies they infest, as the intestines, brain, bronchiæ, liver, kidneys, muscles, blood, and bones.

I. Helminthophyta

a. Cystica

These are named from the resemblance of the posterior part of the body to a bladder, a part which is filled with fluid (pl. 77, fig. 29). This is fibrous and sensitive, at times as large as an egg, and it sometimes forms part of several individuals. In Cœnurus the head or heads are each attached to a short neck; they are sub-globular, crowned with hooks, and have suckers arranged around the convexity, to enable it to attach itself to the substance whence it derives its nourishment. It lives in the brain and spinal nerve of sheep, and more rarely in the brain of oxen, destroying parts of it, and giving rise to a fatal disease, called by the expressive name of  “staggers,” from its chief symptom.

In Echinococcus (called Acephalocyste by the French) there is no head outside of the kyst, the animals being restricted to its inside. It occurs in the liver, spleen, and other parts, and is not exclusively confined to man.

b. Cestoidea

Cysticercus is found in man as well as in animals, between the tissues of the muscles, sometimes penetrating to the eye-ball, the heart, and the brain. The form is that of the Cystica (with which it is usually and perhaps correctly placed), whilst in some other respects it approaches the Cestoidea.

What is called “measles” in hogs arises from an abundance of enkysted worms (Cysticercus cellulosæ, pl. 77, fig. 30), which have been found occupying as much space as the brain in these animals, and causing convulsions and death.

The intestinal worms of the genus Ligula (L. cingulum, pl. 77, fig. 34) are flat, ribbon-shaped, without articulations, marked with a longitudinal stria, and also transversely striate. They live in birds, and especially in fishes. The species figured is from one to five feet long, and is found in the Cyprinus brama of Europe. This worm is said to be eaten in some parts of Italy. Bothrimonus sturionis infests the American Acipenser oxyrhynehus. It is not articulated, it has a longitudinal impressed line above and below, with numerous raised points along it, these beneath having a pore. The head is sub-globular, with a double sucker.

The genus Bothriocephalus (named from bothros, a groove, and kephale, the head) is a long, flat, jointed worm, with a longitudinal groove upon each side of the sub-quadrate head, distinguishing it from Tænia, or the true tape-worm. It is also distinguished by having the segments much wider than long, and the openings from the ovaries are beneath, and not lateral. The genus infests birds, fishes, and reptiles; and one species, B. latus (pl. 77, fig. 32), infests man in Russia, Switzerland, and some other parts of Europe.

The common tape-worm. Tænia solium, (pl. 77, fig. 33), is composed of flat, sub-quadrate articulations, which are very small and fragile for some distance from the head, so much so that this part is rarely obtained perfect, and the small head was for a long period unknown. The head is globular and provided with four terminal suckers, arranged in a square around the mouth. The alimentary canal is double, being composed of an intestine running along each side of the body, with a transverse canal connecting the opposite sides at the beginning of each segment, giving the interstices the appearance of a ladder. The centre of each segment is occupied by distinct generative organs of both sexes, which have their outlet in a lateral pore, alternately upon the right and left side of the segments. As each segment is capable of producing a large number of eggs, it is difficult to conceive why the animals should be comparatively so few in number. This species attains a length of twenty feet or more, and a single one is usually confined to a single individual, although as many as twenty have been found together. Tænia cateniformis (fig. 31) is about an inch long, and infests the cat.

II. Parenchymata

These are soft contractile bodies, without any appearance of division into rings, and bearing some resemblance to a leech, but sometimes so short as to be circular.

1. The Trematoda are internal monoicous parasites, having an anterior, suctorial opening, and one or more suctorial disks of attachment, which afford generic characters. Distoma (or Fasciola) hepatioum (pl. 77, fig. 36), which is a good example, is about an inch long, infests the gall-bladder, liver, and rarely the neighboring veins in man, sheep, oxen, deer, gazelles, camels, goats, horses, and hares. In sheep it is the cause of the fatal disease named rot. The severe winter of 1841–2 in Germany, was followed by the death of many deer, which were found to be much infested with Distoma.

Fresh-water snails of the genera Planorbis and Limnea are infested by a minute animal, with a globular body and slender tail, resembling a tadpole, and forming the supposed genus Cercaria, of which two American species were published in 1840, the motions of which are similar to those of their European analogues, the tail being rapidly thrown into the shape of an S, and easily detached.⁴ Steenstrup has in some measure cleared up the history of the Cercariæ, which are the larvæ of Trematoda. After swimming about freely for some time, they attach themselves to the outside of the snail, and settle in the mucus of the exterior, maintaining themselves by an abdominal sucker, and in the course of their movements losing the tail, a loss which gives them somewhat the appearance of a Distoma. They now enter the pupa state, in which they remain for some months without apparent change. They afterwards acquire spines anteriorly, and such individuals were found within the snail. C. Th. Siebold thinks the Distoma is finally developed in the water-fowls which swallow the snails, an analogous fact having been observed by Creplin, who found a species in a stickleback fish, and also in water-fowls.

2. The Planariidæ contain a number of small leech-like animals, found both in fresh and salt water, which glide along like a snail over solid objects, or, passing up an object to the surface, they creep along this with the back downwards, and the belly attached to a thin film of water. The single opening to the ramifications of the stomach is usually about the centre of the inferior surface; and whatever is taken through this that is indigestible, is subsequently rejected by sucking in a quantity of water, and ejecting the whole together.

Planaria (Planocera) cornuta (pl. 77, fig. 35) has two horn-like extensions anteriorly. P. (Dendrocælum) gracilis, Hald. 1840, is three fourths of an inch long, and one tenth broad, fuliginous, veined with black; oblong, suddenly tapering to a point posteriorly; sides nearly parallel; head truncate in front; neck narrowed, eye dots two, on the narrow part, oblong and white, with a black dot upon the internal margin; ventral opening less than one third the entire length from the posterior extremity. It inhabits springs in eastern Pennsylvania, and feeds upon animal matter. When cut in two, each part becomes an entire animal.

III. Cavitaria

a. Enterodela

1. The Acanthocephala, which are placed with the Parenchymata by Cuvier, are composed of round worms represented by the genus Echinorhynchus, the chief character of which is a straight, round, retractile trunk, armed with rows of recurved tooth-like hooks, which retain it in place when thrust into the intestines. A small pore is sometimes observable at the end of this trunk, but it is probable that nourishment is absorbed by its entire surface. A vascular tube runs longitudinally on each side, and is lost towards the posterior extremity. These noxious animals seem not to have been found in man, although numerous species infest vertebrate animals. They sometimes bore through the intestines, and pass into the cavity of the abdomen, and into other parts of the body. Echinorhynchus gigas (pl. 77, fig. 39) is from three to fifteen inches long, and infests hogs, especially such as are confined to be fattened.

b. Enterodela cylindrica

1. The Ascaridæ include various genera of internal parasites, of which the genus Ascaris is among the best known, and contains slender, round worms, tapering towards both ends. The head is provided with three little valves, between which the mouth is placed. The intestine is straight, the vent terminal, and the nervous system bilateral. Ascaris lumhricoides (pl. 77, fig. 41) takes its trivial name from its general resemblance to a lumbricus, or earth-worm. It is white, from six to twelve or fifteen inches long, and the female is larger and more abundant than the male. It infests the small intestines of man, and is frequently fatal to children, in which it sometimes penetrates to the stomach, and even to the mouth. As many as five hundred have been ejected by a child in the course of eight days. It is sometimes discharged from abscesses in the abdomen, and it has rarely been passed from the bladder. This species infests the hog and the ox, and an allied one (once considered the same) is found in the horse.

Owen, some years ago, calculated the number of eggs in a female of this species to exceed sixty millions. Gluge and Mandl found eggs of an Ascaris, without the animal, in the lungs of frogs, supposed to be introduced with the air.

Oxyuris vermicularis, Linn. (pl. 77, fig. 42), is half an inch long, cylindrical, with the posterior portion subulate. It infests the large intestines of children.

Tricliocephalus dispar (fig. 40) is found with the preceding species, and differs in having the anterior extremity attenuated like a thread, and resembling the lash of a whip, of which the posterior end would be the stock. It is one or two inches long, of which the thick part occupies about a third.

2. Gordiidæ. The genus Filaria is long, slender, thread-like, and smooth, with a somewhat rigid texture, and many species are found in various animals, including insects and mollusca. Filaria medinensis (pl. 77, fig. 43), the guinea worm, infests the muscles and subcutaneous tissues, chiefly of the lower limbs, in Arabia, Upper Egypt, West Africa, and the West Indies. It is sometimes located about the eye, and beneath the tongue; and occasionally it makes its way to the surface of the body, causing a sore, from which it may be extracted if a little is withdrawn daily, care being taken not to break it, as in that case the inclosed part remains and causes inflammation, which may render amputation necessary. A sailor, who frequently met Africans on shipboard with sores caused by the worm, had been on shore in West Africa for three hours barefoot, having himself a small sore on the thigh at the time. He arrived in England in October, 1843; and in the middle of the subsequent May a sore appeared on the left instep, which finally opened and disclosed part of a white worm, about the size of a violin string, of which five inches were cut off. This was succeeded by violent inflammation and suppuration upon the foot and leg, until the remaining two feet and a half of the worm came away. On the 23d of May another sore appeared upon the left fore-arm, disclosing a second filaria, which was gradually and carefully removed in fourteen days, and found to be thirty-two inches long. A third could then be felt under the integument of the right foot. This species attains a length of six feet, and is said to be sometimes seen swimming in the water of the countries it inhabits.

Filaria papillosa (fig. 45) is found in the abdomen, chest, and eyes of the horse. Dr. Charles A. Lee gives a figure of it in the Am. J. Sci., 1840, vol. xxxiv. p. 279. He states that it is from one to seven inches long, and one third of a line in diameter. The specimen seen by him seems to have grown from half an inch to about four inches in four months.

Filaria phalangii (pl. 77, fig. 62) has been found in Phalangium cornutum.

Filaria lycosæ, Hald. Pale-reddish when recent; flavous when dried by heat; rigid, smooth, and shining, slightly tapering towards one end; about five inches long, and one millimetre in diameter at the largest end. Found in Eastern Pennsylvania, in a specimen apparently of Lycosa scutulata, Hentz, ten lines long, and, when the size of the spider is considered, a remarkably large species. The specimen being much contorted, and one end still within the spider, the precise length could not be determined. Fig. 43 might pass for a representation of it, and the spider is a little larger than fig. 37^a in pl. 78.

The genus Gordius is found free in water, or as an internal parasite. Gordius aquaticus is found under all these circumstances, as it has been ascertained to infest insects. These worms resemble a thin thread or stout hair, and being seen in running water, or in puddles along roads, particularly after rain (see Mag. Nat. Hist., 1836, pp. 9, 241–2, 355), they are popularly supposed to be metamorphosed horse-hairs. They are male and female, oviparous, and have a more complicated organization than their external simplicity might be supposed to indicate.

c. Enterodela plicata

1. The Linguiatulidæ are internal parasites infesting various organs; they are flattened and tapering posteriorly, and rugose transversely. In Linguatula the interior extremity is armed with a few recurved spines.

d. Enterodela tænioida

1. Nemertidæ. The principal genus is Nemertes, Cuvier (pl. 74, fig. 10), an extremely long and soft marine worm, of a flattened form, the anterior extremity slender, and the posterior one ending with a broad attaching disk. It approaches Hirudo in its mouth and vascular system. It lives buried in the sand, and is said to feed on shell-fish.

Division II. Mollusca

The Mollusca, or Malacozoa (soft animals), constitute one of the great Divisions of the animal kingdom. Except the shell, which is not always present, these animals have nothing in the nature of bones; and they want the ringed structure and jointed members of the Articulata. The body is soft, the integument slimy, and generally without epidermis, and in the testaceous species capable of secreting a shell. The alimentary canal has an opening at each end, and the circulating system is more or less complete. The eyes of univalve mollusca are generally situated upon or near the tentacles; those of bivalves upon the edge of the mantle, as in Pecten (pl. 76, figs. 27, 29); or on the posterior portion which forms the siphons, as in Unio (pl. 76, fig. 47).

From the great number, variety, and beauty of the shells of so large a portion of the Mollusca, the study of these, under the name of Conchology, attracted attention at an early period, when a cabinet of shells was often regarded in the same light as a casket of jewels, and great sums were paid for rare and handsome species; and, indeed, this interest still maintains its ground, there being shells, the price of which is one or two hundred dollars at the present day.

It was at length discovered that little of natural classification and the habits of this class could be known, without a study of the entire animal; so that Conchology finally became merged into Malacology. There is, however, no impropriety in the use of the former term in an enlarged sense, if it be considered to include the study of those animals which are usually provided with a calcareous shell.

Some of the older conchologists, guided by the shell alone, included radiated forms, like Echinus, in this division; and even at the present day, the cirrhopoda (pl. 76, figs. 51–54) and some of the annelida, which have a hard exterior tube, are sometimes described in books avowedly devoted to mollusca. On the other hand, whilst all “shells,” whether secreted by the mollusca or the articulata, were classed together, true mollusca, when unprovided with a shell, were often placed among worms and annelida.

The term (Vermes) Mollusca was used by Linnaeus in 1758, in a wide sense, as it included radiata, like Actinia, Medusa, and Echinus; Crustacea like Lernæa, as well as Ascidia, Limax, and the Cephalopoda, and even some annelida; whilst his order (Vermes) Testacea included most of the univalve and bivalve shell-fish. The “class Mollusca” of Lamarck, follows his class Conchifera, and includes the five “orders,” as he terms them, of Pteropoda, Gastropoda (excluding the spiral univalves), Trachelipoda (including the spiral univalves. Cephalopoda, and Heteropoda. Pallas and Cuvier were the first to use the term Mollusca in its modern sense; and the latter, in 1798, recognised three sections, subsequently provided with the systematic names of Cephalopoda, Gastropoda, and Acephala. The term Mollusca having by these means acquired a somewhat indefinite meaning, Blainville proposed that of Malacozoa, which is the preferable term, if the term Malacology supersedes that of Conchology.

The shell of the Malacozoa can have one, two, or more pieces; it may be external or internal, and it varies much in size, being in some cases capable of containing all the soft parts, with room to spare, and in others a mere excrescence upon some part of the animal. It is secreted by the mantle, a fold of the integument which appears as a flap, lining the shell in bivalves, and a continuation of it appears as a collar around the neck, and lining the aperture of the shell in the spiral univalves. In the order Tunicata the body is inclosed in a kind of coriaceous purse instead of a shell.

The mantle usually secretes two kinds of material, the nacre, or pearly portion of the shell, and the epidermis, or periostraca; but in some genera the latter is absent, as in Oliva (pl. 75, figs. 122, 125, 126) and Cypræa (pl. 76, figs. 5–7), in which the wide mantle is turned up on each side, so as to inclose the shell. When the shell is broken by accident, the crevice is closed by layers of nacre; and if a pebble gets into the shell by accident, and cannot be got rid of, it is covered in like manner. When the nacre or “mother-of-pearl” is of a fine quality, the tubercular masses which arise from injuries have a peculiar lustre, which causes them to be admired under the name of pearls. Shells are often found repaired, which had been crushed and distorted to such an extent as to lead one to believe it scarcely possible for an animal to survive after so much mutilation.

The varied spots and lines which ornament so many marine shells, are distributed by the periodical action and inaction of the secreting process. The species of the genus Conus, although co veered by a thick epidermis, are usually marked with bands, spots, and reticulations of brilliant colors, which make them a favorite ornament to collections. The epidermis, however, should not be removed, or it should at least be preserved upon a specimen of each species, as it varies considerably according to the species. The former unscientific custom of polishing such shells as have a homely exterior is now discontinued.

The microscopic structure of shells presents many curious features, which have been thoroughly studied by Carpenter, who has illustrated the subject with figures. In some shells the structure resembles that of minerals, and seems to be formed of minute crystals of carbonate of lime, or of fibres resembling arragonite.

In the genus Argonauta (pl. 76, fig. 17) the ends of two of the arms are greatly dilated, and these dilations clasp the shell upon each side, which seems to be formed by a secretion from their inner surface.

In some of the naked land-snails, like pl. 77, fig. 21, a small thin shell may be taken out of the back, and the cuttle-fish has a corresponding internal shell, known as cuttle-bone, which is more complex, having a hard, rough surface above, and a series of close-set, thin, parallel plates beneath. The lower end terminates in a point which corresponds to those fossil organic remains of cephalopoda, named Belemnites.

In bivalve shells the mantle is slightly attached to the shell, in some degree parallel with its margin, and at a little distance from it; but this line of attachment, which is named the pallial impression, varies considerably in its course in different families, and through this variation affords distinctive characters. The mantle, or projections from it, secretes the spines, rugosities, and other appendages, by which the shell is varied. Sometimes the deposition of the shell goes on smoothly, when a thickening of the margin, a varix, or a row of spines will be secreted, to be followed by a smooth space, and this alternation takes place as long as the animal grows. See pl. 75, figs. 101–104, 111, 119. Univalve shells are usually strengthened by having the margin of the aperture thickened, and as this is added from time to time, the shell may acquire a ribbed appearance, as in figs. 101, 102. In other cases, as in fig. 91, the old lip is absorbed before a new growth is started, so that the shell remains smooth. Sometimes the margin is not formed until the animal attains its full growth.

The oblique deposition of calcareous matter in spiral univalves gives them an elongated form, as in pl. 75, fig. 117, and when less oblique, the shell is more robust (fig. 98). In forms like Patella (fig. 77) the calcareous deposit extends in equal degrees; but if the increase is more abundant upon one side, the spine is curved, as in fig. 81. When the aperture is lateral, and the shell has little or no obliquity, the forms seen in pl. 76, figs. 2, 4, 7, 11, are the result.

In spirivalve shells the solid axis is named the columella, and a muscle is attached to it which connects the animal with the shell, and enables it to retire within it. The columella is often marked with prominent folds and tooth-like projections, which afford generic characters. The anterior extremity of the mantle is elongated in some genera, and the edges brought in contact, so as to form a slender tube, through which water passes to the gills; and as this siphon secretes calcareous matter, the shell takes the rostrated form, as in pl. 75, figs. 109–112.

Spiral shells are usually dextral, increasing towards the right, in which they resemble an ordinary screw; but there are a few genera, exceptional species, and varieties of dextral species, which are sinistral (pl. 75, fig. 100). A bivalve shell is considered sinistral when the projecting points at the hinge, named teeth (which present a certain degree of uniformity in each species), are changed so that the modification which belongs to the one side normally is found upon the other.

Some of the spirivalves, when the animal retires into the shell, as in fig. 88, close the aperture by an operculum attached to the posterior and upper part of the foot. It is sometimes smaller than the aperture, and can be drawn in some distance; in other cases it fits the aperture exactly. In texture it is either thin and horny, or thick and shelly, sometimes increasing obliquely or spirally, by deposition upon one side, and at other times enlarging concentrically, but always taking the shape of the aperture. In the genus Hipponyx the anomaly is presented of the operculum being attached to the rocks upon which the animal is found. In dry seasons the land-snails protect themselves by a temporary operculum, formed by a slimy secretion, which hardens, and thus closes the aperture.

Most bivalves, as the name implies, are composed of two valves (pl. 76, figs. 32–34), united by a ligament upon the back; but some, of these have accessory pieces (fig. 49), which are not of sufficient importance to remove them from their class. Even the anomalous form, Aspergillim (pl. 75. fig. 71), belongs to the Bivalves or Conchifera; for, although it is a shelly tube, pierced at the anterior extremity like a pepper-box, an examination will disclose a small open bivalve shell, solidly imbedded in the shelly material of the tube. This is roughly represented near the upper end of the figure, although the artist probably did not recognise its true character.

The nervous system of the Malacozoa is not symmetrical, as in the Articulata, nor radiated, as in the Hadiata, but the ganglia are distributed unsymmetrically from the brain, or chief ganglion, situated above the œsophagus.

The Malacozoa are divisible into three sub-divisions or classes, the lowest containing the Acephala (pl. 76, fig. 34, &c.), named Acephalophora by Blainville; the next the Gastropoda (fig. 1, &c.), named Paracephalophora by Blainville, and including the Pteropoda, according to this author; and the highest the Cephalopoda (pl. 76, figs. 16, 17, 75–77).

Class 1. Acephala

This class contains the four orders Bryozoa, Tunicata, Brachiopoda, and Conchifera. The sections, here named orders, are by some naturalists considered to be classes, which they sub-divide into orders of a different value. Indeed, it is extremely difficult to construct groups which shall have the same value under the same name, in different departments of Zoology; and there is no special rule which can be followed in all cases.

Milne Edwards, observing that the Bryozoa, which had previously been confounded with the Zoophyta, bear certain near relations to the Tunicata, united the two in a sub-division of the true mollusca, and Cuvier had previously shown that the Tunicata are related to the Conchifera. Dujardin gives to the group of Bryozoa the same value among the Mollusca that he assigns to the Conchifera and Brachiopoda. Agassiz also unites them to the Acephala, of which he considers them to be the lowest order, corresponding to the Foraminifera, to which he assigns the lowest place among the Gastropoda. In fact, the Bryozoa have much resemblance to the Mollusca in their alimentary canal, which is quite different from that of the Zoophyta.

Order 1. Bryozoa. This name was imposed by Ehrenberg, who was one of the first to demonstrate the true nature of them. They are small animals, aggregated in great numbers, like coralligenous zoophytes, having a distinct stomach and an intestine curved upon itself, with an outlet near the mouth. An analogy with the Ceph.alopoda is apparent in the tentacles which surround the mouth, and which are covered with vibrillæ. These vibrillæ cause currents of water which bring the animalcula within reach, which serve as food. The tube into which the animal withdraws varies in texture, being membranous, horny, fibro-gelatinous, or calcareous. This tube corresponds to the outer tunic of the Tunicata, in being in organic connexion with the interior parts, even the calcareous matter of the harder kinds being deposited throughout the membranous tissues. Each tube is in contact with its neighbors, sometimes to the number of many thousands.

Dr. Farre thus describes the tube or cell in the Vesicularidæ: “The transparent horny cell which closely embraces the body of the animal, is nearly unyielding in its lower two thirds, but terminates above by a flexible portion, which serves to protect the upper part of the body when the whole is expanded, in which state it is of the same diameter as the rest of the cell, but, when the animal retracts, is folded up, and drawn in after it, and completely closes the mouth of the cell. The flexible part consists of two portions, the lower half being a simple continuation of the rest of the cell, the upper consisting of a row of delicate bristle-shaped processes or setæ, which are arranged parallel with each other around the top of the cell, and are prevented separating beyond a certain distance by a membrane of excessive tenuity, which surrounds and connects the whole. This mode of termination of the cell is one of constant occurrence, as will be described in other species, and is evidently a provision for allowing of the freest possible motion of the upper part of the body in its expanded state, to which it affords at the same time support and protection.”—Phil. Trans., 1837, p. 393.

Johnston thus describes the habits of some of these animals: “Let us now suppose that the polypes are in a state of extrusion, and fully expanded, all the cilia in play, and the water whirling in rapid streams up and down the opposite sides of the tentacula, carrying with them nutriment and the breath of life. All is quietness and security around, and the little creatures are evidently in a state of happiness and enjoyment; no one who has witnessed the microscope scene (the myriads of the little flosculous heads that pullulate and blossom over the entire polypidom, as thickly peopled as the swarming hive) can have any doubt of this, especially when he remarks the acuteness and vivacities of their sensibilities and actions; for, under his eye, one will ever and anon suddenly sink out of view, hide itself within the cell, again on a sudden emerge and expand, or, it may be, lay itself down in repose and concealment, until digestion has freed it from a state of repletion, or forgetfulness has removed the alarm of an enemy. These positions are assumed with such rapidity, that the eye cannot trace the steps of the process, and large glasses and minute skill are required to reveal to us its mechanism.”—Brit. Zooph., p. 241.

Excellent figures of this group are given by Milne Edwards, in the illustrated edition of the Règne Animal, and by Johnston. The following genera of Escharidæ are figured on pl. 75: Flustra (fig. 54), Retepora (fig. 56), and Eschara (fig. 57). The following classification is that of Johnston:

*Natives of the Sea. Tentacula forming a perfect circle. Polypiaria infundibulati, P. Gervais. Fams. 1 to 6.

**Lacustrine. Tentacula in the form of a horse-shoe. Polypiaria hippocrepia, P. Gervais. Fam. 7.

Fam. 1. Vesicularidæ. Corneous, fistular, confervoid; cells vesicular, deciduous, not operculate. Vesicularia, Serialaria, Yalkeria, Baverbancia.

Fam. 2. Crisiadce. Calcareous, branched, confervoid, jointed; cells linked together in series, distinct, tubular, or elliptical, with a terminal or subterminal aperture; no operculum. Crisia, Notamia, Hippothoa, Anguinaria.

Fam. 3. Tubidiporidæ. Calcareous, variable in shape, never confervoid; cells tubular, round, rising from a base and projecting, aperture terminal and non-operculate. Tubulipora, Discopora.

Fam. 4. Celleporidw. Calcareous, lobed, ramous, or crustaceous; cells in quincunx, utricular, in juxtaposition, with a contracted terminal aperture. Cellepora, Lepralia, Membranipora.

Fam. 5. Escharidæ. Calcareous or membranous, variable; cells usually in quincunx, oblong, pentagonal, or hexagonal, conjunct, immersed, or horizontal to the plane of axis, with a subterminal or lateral, and commonly operculate aperture. Flustra, Cellularia, Acamarchis, Farcimia, Ketepora, Eschara.

Fam. 6. Alcyonidulæ. Polypidoms sponge-like, polymorphous; cells irregular in disposition, immersed and concealed, with a contractile non-operculate aperture. Alcyonidium, Cliona.

Fam. 7. Limniades. Polypidoms fleshy, spongy or corneous, polymorphous; animals in tubes with angular or round orifices, closed when they recede. Cristatella, Plumatella.

Order 2. Tunicata. These animals, especially Ascidia (pl. 77, figs. 7, 8) and its allied forms, may be compared to bivalve mollusca or conchifera, in which the margins of the mantle are united so as to form a sac, in which two openings are left, one for alimentation and respiration, and the other for excretion. The mantle is of a tough coriaceous or cartilaginous texture, and is endowed with contractility. Cellulose, which is almost exclusively found in plants, has been ascertained to enter into the composition of the Tunicata. A current is made to flow over the branchiæ by the action of the vibrillæ, and the contractions and expansions of the body remove the water.

The Tunicata have no external organs of locomotion, so that they float about at random, or are fixed to rocks, sea-weed, or other extraneous bodies. Some species are agglutinated together in masses, or in long chains, but there is no organic connexion between them.

This order includes three families represented by the genera Salpa, Ascidia, and Pyrosoma. Salpa (pl. 77, fig. 3) forms long lines of aggregated individuals. These animals were first distinctly noticed in 1756, and named Thalia in Brown’s History of Jamaica, and in 1775 Forskal applied the name of Salpa. The mantle is transparent, and is provided with tubercular suckers, by means of which the bodies adhere together. The aggregated individuals produce young which are free, and which are unlike the parent; and these free individuals produce a brood of aggregated individuals, thus presenting an example of alternate generation. This discovery was published by Chamisso in 1830. These animals abound in the warm seas, swimming at various depths, commoidy with the back downwards, and coming to the surface in calm weather. Their power of locomotion is slight, the only means being the ejection of water which has been used in respiration. (See Agassiz’s Lect. Einbryol., p. 91.) Pyrosoma includes compound, gelatinous, and nearly transparent animals, remarkable for their brilliant phosphorescence.

Order 3. Brachiopoda. “The Brachiopoda ought to be combined with Lamellibranchia, having the same structure, and differing only in secondary modifications.” (Agassiz.) This order includes bivalve mollusca, named from having a long, spiral, fleshy, arm-like, fringed organ on each side of the mouth, used in securing food, and generally capable of being extended and withdrawn into the shell, and when large it is rolled into a spiral. In the genus Spirifer, which is scarcely more than a Productus, these organs are preserved in a mineralized state. The mouth is provided with fleshy lips, and is situated between the arms. The mantle itself subserves the purposes of respiration, a peculiarity which is recorded in the name Palliobranchiata, given to them by Blainville.

The shell is often adhering, either directly, as in Crania (pl. 76, fig. 24), or by means of muscles, as in Terebratula (fig. 23), in which the muscles pass through a perforation in the beak of the left valve. This genus has a curious framework within the shell. The species figured, T. caputseipentis, Linn., and T. psittacea, Gmelin, are found upon both sides of the North Atlantic. (See Gould, Invertebrata of Massachusetts, pp. 141, 142.)

It has been maintained that in this order, the valves, instead of being right and left, are dorsal and ventral, the large or perforated one being dorsal. Professor Agassiz (Monies de Mollusques, p. 14) thinks this view is founded upon a false interpretation of the anatomy, and that the Brachiopoda do not present this anomaly. lie considers the larger valve as that of the left side, as in Ostrea and Anomia, but whilst the left valve is perforated in Terebratyla, Anomia has the perforation in the right. The descriptions of some conchologists being founded upon the opinion that there is an absence of orientation in the valves of this order, must be read with care or they will not be understood.

In the genus Lingula the two valves are so much alike that it is difficult to decide upon their mutual relations. In this genus there is a long pedicle, but probably not for attachment to extraneous bodies, as the species live buried in the sand.

Order 4. Conchifera. This order contains most of the bivalve shells, including some with accessory pieces. From the laminated form of the gills, two of which usually hang like a curtain on each side, between the mantle and the body, they are named Lamellibrancbia by Blainville.

In the Conchifera the back of the animal is under the hinge of the shell; and when the shell is removed, the heart may be observed in some families beating at the anterior part of the back. Beneath this, at the anterior extremity, is a simple opening constituting the appendages named labial palpi, the vibrillæ of which cause currents, which bring nourishment within reach.

Upon comparing the shell of an oyster with that of a freshwater mussel, a discolored impression will be found near the centre of the former, and two impressions in the latter, situated towards each end. These are the muscular impressions, serving for the attachment of the adductor muscles, which draw the valves together; and when they are relaxed the shell is opened by the elasticity of the dorsal ligament, which may be either external or internal.

Some conchifera remain permanently fixed, like the oyster, which is attached by its left valve. Others, as Pinna (pl. 76, fig. 18), are attached by a bunch of fibres, named the byssus, which is secreted by the foot. Some can swim by alternately opening and closing the valves, of which Pecten (figs. 27–9) affords an example; whilst others move by means of a foot, which enables them to burrow in the mud, or move along in the sand. The foot is situated below the mouth; and when present, the mantle must be open to allow it to pass. See pl. 76., fig. 50, left-hand end.

Posteriorly the mantle has two openings, one above the other, forming siphons for respiration and excretion. These are sometimes made merely by the partial contact of the ends of the mantle, which may project but little, although at other times it extends and forms long perfect tubes (fig. 50). The inferior tube is named the branchial siphon, and is used in breathing; the upper one is the anal siphon, and serves for the excretions. The curve in the pallial impression is caused by the displacement of the mantle, to afford room for the retracted siphons when their size is considerable.

The hinge is usually provided with projections of calcareous matter, named teeth from their shape; and those of one valve are fitted into corresponding vacancies or depressions in the other. These present so many modifications that they have been made a principal character in the construction of genera. Those situated under the beak of the shell are termed cardinal teeth; and those anterior and posterior to these the lateral teeth, a badly selected term, all the teeth being equally lateral. Indeed, the hump of a dromedary, or the dorsal fin of a fish, might as well be termed “lateral.” This misapplication arose when the length of a bivalve mollusc from the mouth towards the vent was named its breadth, and Lamarck, Say, and others, named that end “posterior” at which the mouth is situated, and which precedes in locomotion. A few minutes devoted to observation and dissection of the animal would have prevented this error, which must be borne in mind in reading the descriptions of these authors, or they cannot be understood. In some genera, as Arca (pl. 76, fig. 32), the teeth are alike, and form a cremilated line along the dorsal margin of the shell.

In the seventh volume of the Nouv. Mém. de la Soc. Helvét. des Sc. Nat., Professor Agassiz has proposed an improved nomenclature for the armature of the hinge in Venus and the allied forms, but which nuiy be extended to other families. The annexed diagram represents the relative positions and names of the teeth, the upper part representing the anterior part of the shell, its back being towards the observer, and the right valve upon the right hand. The presence of the accessory tooth in the left valve distinguishes the genus Cytherea from Venus. The same name is applied to a tooth and its corresponding cavity in the opposite valve.

Most of the Conchifera are marine, living attached, half buried, or entirely buried in the sand or mud, some at the bottom of a perforation from a few inches to several feet deep. Others perforate wood, and some rocks; and as they increase in size, enlarge the prison which they are never to quit, receiving their nourishment through the opening by which they entered.

The Conchifera may be divided into several tribes, named Rudista, Inclusa, and Elatobranchia. The first of these, Rudista, is doubtful as a separate section, being composed of bivalve shells, the lower one of which is adherent, and the upper raised in a conical form; but their true nature and position in the animal scale have not been determined, and they occur only in a fossil state. Some authors place them near Chama in the Elatobranchia; others think them Brachiopoda, and even Tunicata; and others elevate them to the rank of a distinct order. Some of these bivalves were at one time believed to present the chambered structure of Orthoceras, and they have on this account been incorrectly referred to the Cephalopoda by some authors. This was the case with Hippurites, one of the principal genera, which was placed near Belemnites. In Hippurites there is, indeed, an imitation of a chambered structure, but it has an analogy to that observed in certain species of Ostrea, when the shell is sawed in two across the foliated layers, the siphon of the Cephalopoda having no existence.

Tribe Inclusa

The members of this tribe, although inclosed in bivalve shells, resemble the Tunicata in having the margins of the mantle closed for about three fourths of its circumference. The more typical forms have the shell gaping, and a long double siphon posteriorly, which cannot be entirely withdrawn.

Fam. 1. Mactridæ. Hinge with an erect V-shaped tooth, ligament internal. The genns Mactra, Linn. (pl. 76, fig. 40), includes sub-trigonal shells which are slightly gaping; hinge with a concave tooth to receive the ligament; two additional striated teeth near the hinge. This genus contains shells which sometimes attain a considerable size. M. solidisshna, Cliemnitz (Gould, Invertebrata of Massachusetts, p. 51), of the United States coast, is sometimes found six inches long and four in height. In this family the foot passes through an opening in the mantle, and the two siphons, although distinct, are inclosed in a common integument. Some authors place this family among the Elatobranchia. Lutraria lineata, Say, American Conchology (pl. 9). L. plicatella, Lamarck, vol. vi. p. 93.

Fam. 2. Myidæ. This family is differently divided by different authors, some including the two groups of which Osteodesma and Solemya are the types, whilst others believe that these should form distinct families. In Mya the shell is gaping, and there is a broad spoon-shaped tooth projecting from the hinge to the opposite valve, where there is a cavity to receive it. The labial palpi are long, stout, and pointed. The mantle is closed, except a small anterior opening for the passage of a slender foot, and the ordinary openings for the siphons, which are very long, and inclosed in a common envelope. This genus buries itself in the sand, with the exception of the end of the siphons. Mya arenaria, which has a shell three or four inches long, inhabits both sides of the Atlantic, between high and low water-mark. It is extensively used in New England as food, under the name of clam, a name which is applied to Venus mercenaria in the middle States. The genus Corbula forms part of the restricted family of Myadæ.

In the opinion of some authors, Osteodesma and the allied genera Lyonsia, Periploma, Thracia, and Anatina, form a family, although the aggregate of these genera seems to have no higher rank than that of a sub-family. Some of the shells are of an extremely delicate texture; these have no cardinal teeth, and there is an ossiculum or accessory bone forming part of the mechanism of the hinge, upon which Deshayes has founded the family name Osteodesmacea. Mya norvegica was at first the type both of Lyonsia, Turton, 1822, and Osteodesma, Deshayes, 1835, but the latter author subsequently admitted Lyonsia, and applied his own term to a different group. Couthouy’s paper in the third volume of the Boston Journal of Natural History, and Gould’s Invertebrata of Massachusetts, may be consulted upon these genera.

Fam. 3. Solemyidæ. The genus Solemya is by some considered as forming a distinct family, whilst by others it is placed in the family of the Solenidæ. Some of its characters are very distinct; the branchiæ are thick, and single upon each side, and they are divided so as to resemble those of Crustacea. The foot is truncated and shaped like a sucking disk; the posterior half of the mantle is closed, the siphons are short, and the periostraca of the shell projects in a flap, far beyond the calcareous portion.

Fam. 4. Saxicavidæ. This family includes Saxicava and Byssomia. The first contains small species and secretes a byssus. The cardinal teeth are obsolete, the ligament is external, and the shell gaping. The shell present. many distorted varieties, and some species excavate cavities in rocks. Some authors unite this family to the Lithophaga, among the Elatobranchia.

Fam. 5. Pandoridæ. A small family formed of the single genus Pandora, which has only a single branchia on each side. The shells are small, pearly within, the valves unequal, the ligament interior, the siphons short, the hinge with two diverging teeth in the right or flat valve, and two corresponding impressions in the left, which is convex. P. trilineata, Say (American Conchology, pl. 2), inhabits the American coast from Maine to Florida. This genus is by some placed with the Solenidæ, and by others with the Myidæ.

Fam. 6. Solenidæ. This family is composed of the genera Solen (pl. 76, figs. 45–6), Solecurtus, Glycimeris, Panopaea, and Pholadomya. The ligament is external, the shell gaping at both ends, and the foot is long and fleshy, and is passed out of the anterior extremity. The genus Solen lives in holes several feet deep, in which it passes up and down by means of its foot, and with such rapidity that it is difficult to take. Fishermen take them for bait by suddenly thrusting a barbed spear into their retreat, but if they are not struck at once they descend beyond reach. The genus Glycimeris is remarkable for having the body so large in proportion to the shell, that the latter is unable to inclose it. G. siliqua, the only species of the genus, as now restricted, inhabits the banks of Newfoundland, and the shell is usually got from the stomachs of cod-fish. Panopæa is a genus including species mostly of a large size, few in number, and occurring recent and fossil. P. arctica inhabits the banks of Newfoundland, and about eight fossil species have been named from the tertiary formations of the United States.

Fam. 7. Pholadidæ. This family contains various genera, which live in perforations which they make in rocks, wood, or clay, each being a prisoner for life in a cell of its own construction. In Pholas (pl. 76, figs. 49, 50) the shell is widely gaping, and provided with accessory pieces at the hinge (fig. 49), and the foot is shaped like a sucker. Pholas dadylus (fig. 50) is used as food. A few fossil species are found in the tertiary formations of Europe and America. The genus Teredo is placed by some authors in the next family, Tubicola, on account of its form; but Deshayes thinks the characters of the animal require that it should be placed here. Teredo navalis (pl. 75, fig. 67), which is so destructive to timber and shipping when not protected, appears as a long, sinuous, calcareous tube, lining perforations in wood, and if one of these be followed to its lower end, the valves of the shell will be found. The shell is thick, and so short as to be annular, having a single adductor muscle, and the posterior extremity of the tube is open. According to Laurent, when the young Teredo escapes from the egg, it swims about by means of vibrillas. At first the body is inclosed in the shell proper, and the little animal can move about with the aid of a long linguiform foot. After spending about twenty-four hours in swimming and moving about upon submarine objects, it attaches itself to wood, making a depression in which it locates itself, and excretes a mucous mass which covers it, but allowing a passage for the siphons. The young animal is soon after able to commence perforating. The transparent shell of the embryo soon disappears, and is replaced by the permanent one. In boring, the wood is generally entered across the grain, but afterwards the animals turn in the direction of the fibres, though they are subject to be continually turned from their course by each other, the wood being perfectly honey-combed by their number, and often in the course of a year.

Fam. 8. Tubicola. The name indicates the tubular form of the external protection in this family. The tube is secreted by the mantle, and its continuation covering the siphons. In Aspergillum (pl. 75, fig. 71) both valves form part of the tube; in Clavagella the valves are placed within a short tube, one of them being attached; and in Gastrochæna the shell is not attached, but inclosed in a tube. The mantle is open in front for the passage of a little foot, the siphon and branchiæ are usually long, and the palpi are small. These shell-fish inhabit clay, sand, or cavities in stone or wood, pierced by themselves.

The genus Aspergillum was first correctly figured in 1685, by Lister, one of the fathers of conchology; but it was many years before its true approximate place was known, since it required much sagacity to detect a bivalve shell under the form of a tube. We accordingly find it placed at one time among univalve genera, and at another with the Annelida which form tubes, and Linnaeus placed it with Dentalium. The happy idea of Aspergillum being a true bivalve is due to De Roissy, and is a remarkable example of the detection of natural affinities. A parallel example appears in the Planorbis cornuarietis which, to all appearance, was referred to its proper genus, but which Sowerby referred to Ampullaria, with none of which did it seem to be allied; but the subsequent discovery of the animal proved his reasoning to be correct, although strongly opposed at the time. The structure of Clavagella is quite anomalous, the valve of the right side forming part of the inside of the tube, and the left valve being free. The anatomy is essentially that of a bivalve mollusc, and shows an affinity with Aspergillum. It is provided with a small foot.

The genus Gastrochæna, Spengler, 1783 (or Fistulana, Lam., 1801), is a boring shell, sometimes found in calcareous rocks, and sometimes in sand, secreting, besides its proper shell, a separate exterior tube; and, as the shell may be accidentally found without the tube, after the death of the animal, an error was committed in describing the shell alone as one genus, and the tube and shell together as another, namely, Fistulana; an error which Deshayes was the first to correct, and he accordingly suppresses the latter name. Shell symmetrical, and widely gaping anteriorly, without cardinal teeth, a ligament posteriorly, pallial impression deeply sinuated, foot small, and secreting a byssus. The following species are found in the tertiary strata of the United States. Gastrochæna ligula, H. C. Lea, Am. Phil. Trans., vol. ix. G. larva, Conrad (Fistulana), Am. J. Sci., 1846, p. 213. G. elongata, Desh., Conrad, Nat. Inst. Washington.

Tribe Elatobranchia

This tribe includes the great mass of Conchifera, after separating the preceding one. With very few exceptions, the Inclusa have two adductor muscles, and although the same character is possessed by most of the Elatobranchia, a large portion of them have but one, so that the whole are divided by this character into two sections, thus:

• § Monomyaria, with one adductor muscle.
• §§ Dhmjaria, with two adductor muscles.

This character, although of much importance, is not applicable in every case, because a classification that would adhere to it strictly, would sometimes unite dissimilar groups and separate allied ones, as far as the other characters are concerned. The first section includes the five families: 1. Anomiidæ; 2. Placunidæ; 3. Ostreidæ; 4. Pectinidæ; 5. Aviculidæ.

Fam. 1. Anomiidæ. The genus Anomia has a principal central adductor muscle, but besides this it has two approximate, one passing towards the perforation at the apex of the smaller (and in position the lower) valve, where it is attached to a shelly plug, shaped like a short, flat-headed rivet, and inserted in the aperture, its exterior flattened surface being attached to extraneous bodies. The ovary terminates between the membranes of the mantle upon the right side, where the eggs are stored before they are ejected, an anomaly presented by no other conchifer, but which, with some other characters, indicates an affinity with Brachiopoda. On this account Deshayes thinks that this family forms a distinct group, which should stand between the Brachiopoda and the Conchifera. In Anomia the margins of the mantle are entirely disunited; the shell is very irregular, orbicular, the free or larger valve convex, and the lower one concave or flat, and taking the form of extraneous bodies, to which it is attached. This causes the shell to offer many varieties, and the species to be of difficult determination. The aperture in the perforated valve is only a deep sinus, narrowed at the margin, with the shell projecting upon one side, and forming an ossiculum with a flattened surface of articulation, which enters and is attached to the concavity of the opposite valve by an internal ligament. This family is allied to the next by Broderip’s genus, Placunanomia, which has a notch in the side of the lower valve, presenting an analogy with that in Pedum, a genus of Pectinidse.

Fam. 2. Placunidæ. This family is represented by the genus Placuna, the shell of which (the only part known) is allied to Anomia and Ostrea. It is imperforate, free, inclined to circular, thin, and foliaceous in texture, translucent, and the valves are so flat that but little room is left for the animal, which must consequently be very thin. In one valve there is a V-shaped tooth, and in the other a corresponding depression; ligament marginal. This and the preceding family are by some included in the Ostreidæ.

Fam. 3. Ostreidæ. The genus Ostrea (pl. 76, fig. 25, O. cristigalli), well known as an article of food, is widely distributed in various parts of the world, and has been in request from a remote period. The shell is inequivalve and irregular, the ligament partly internal and partly external, and the left and larger valve is usually attached to extraneous bodies. On the western coast of Africa, where the branches of certain aquatic trees hang in the water at high tide, the oysters affix themselves to these branches, where they may be seen suspended at low tide. There are four lanceolate labial palpi; and the branchiæ, two upon each side, are conspicuous objects when the shell is opened. The very large liver is recognised by its dark color, which causes it to be indistinctly seen through the translucent integuments. There is no appearance of a rudimentary foot, but eyes have been detected.

The ancient Romans were very fond of oysters, and soon discovered those of Britain to be superior to their own, and imported them in winter 23acked in snow, and in such a manner as to prevent the valves from opening, a mode still practised when oysters are to be transported a considerable distance. Previous to this period Sergius Aurata had invented and practised the art of breeding oysters in artificial beds, turning his art to great profit. This is still practised in the Mediterranean, where ponds are used, into which the sea enters at high tide. About Naples oysters attach themselves to sticks, and here numerous poles are stuck into the bottom, and when the oysters which become affixed to them have acquired a sufficient size to be taken, they are collected by withdrawing the poles. Oysters attain a marketable size in four or five years, although not yet fully grown, large individuals being considered less delicate than those of a medium size. Those are most highly esteemed which have grown in the mouths of rivers, where the water is less saline, and it is probable that their food varies according to the locality. Oysters feed upon infusoria; and when certain green kinds are abundant, they impart a green color to the animal, a color which is often incorrectly attributed to some mineral substance. The extent to which oysters are consumed would exterminate them in accessible localities were they not prolific. A single oyster may eject 50,000 or 60,000 eggs in a year, commencing in the spring and continuino; through the summer.

Deshayes does not think the genera Grypliæa, Lamarck, and Exogyra, Say, are sufficiently distinct from Ostrea; whilst Yon Buch, the celebrated geologist, insists that they are founded upon good characters. The former author is inclined to look for variations in the soft parts of allied genera, although in such the shell usually presents the more prominent generic and specific characters. Yariations in the shell are as important among the Mollusca as in the teeth and horns of the Mammalia, or the bill and feathers of birds; and, although a species may be found which associates it with two genera, this is not sufficient evidence that the two should be united. According to Deshayes, Ostrea passes by insensible gradations into Exogyra, and this, by equally gradual steps, returns to Ostrea, so that in his opinion the species of the three form but one natural genus.

Fam. 4. Pectinidæ. In Pecten (pl. 76, figs. 27 to 29), the chief genus of the family, the shell is regular, toothless, inequivalve, eared at the hinge margin; ligament entirely internal, and placed in a triangular depression; surface often covered with ribs. Mouth with deeply cut lips and a pair of palpi on each side; mantle disunited, margin with numerous cilia, having eyes between them; branchiæ sub-divided into separate parallel filaments; foot small and dilated, a byssus sometimes present. The genus Pecten is widely distributed in a recent and fossil state, and is not confined to any particular country or climate.

These shells are free, and live upon a surface of mud or sand, from a trifling depth to twenty fathoms, and they are fished up as an article of food. They present several distinct forms, and many of them possess great beauty. Pecten pleuronectes is named after the generic name of the flounder, because one side is dark colored, and the other white. P. jacobaeus was formerly worn by pilgrims who had visited the Holy Land. P. quinquecostatus occurs fossil in the cretaceous deposits of Europe and America, and there are numerous species belonging to the tertiary formations of the United States. Lima, a genus of free shells, is allied to Pecten.

Spondylus (pl. 76, fig. 35) is a genus of attached, rough or spiny, and usually heavy and finely colored shells, allied to Pecten and Ostrea. There are two strong teeth in each valve, and a depression for the ligament. Hinnites is allied to Pecten and Spondylus, and possesses the peculiarity of being free until it attains a certain size, when it becomes permanently affixed.

Fam. 5. Aviculidæ. This family includes the shells from which most of the pearls of commerce are obtained. They are allied to the two preceding families, and most of the genera are byssiferous, with pearly shells. The large well known shell (pl. 76, fig. 20), which sometimes attains a size of ten inches, produces the finest oriental pearls, as well as most of the mother-of-pearl which is used in the arts. It forms the genus Meleagrina, Lamarck, although it is now considered not to be distinct from Avicula, and it is therefore named Avicula margaritifera, Linn. It inhabits the Indian seas. Avicula, according to the celebrated anatomist Poll, has the mantle unclosed, and fringed with tentacular appendages. The foot is small and secretes a byssus.

The genus Malleus (M. malleus, Linn., pl. 76, fig. 26) is remarkable for having the hinge margin extended in some species in the antero-posterior direction. The shell is very irregular, the foot secretes a byssus, and the mantle has a fringe of small tentacles. Perna (fig. 30) has an irregular shell, hinge straight, with a row of transverse furrows for the insertion of the ligament. The byssus passes through a gaping vacancy in the front of the shell. The genera Malleus, Perna, Vulsella, Crenatula, Catillus Inoceramus, and some others, are placed by some authors in a distinct family, Malleidæ.

Pearls are secreted upon the inside of the shell, or in folds of the mantle, the latter being the most regular; and as their quality depends upon that of the nacre, those shells which have this of a fine quality produce the best pearls. The pearls of common oysters are rough concretions of no commercial value, and similar concretions are sometimes formed by univalve species, the mantle of which has, of course, the power of secreting the calcareous matter of the shell. Although pearls are formed out of the same material as the shell, a bead turned out of the latter has not their peculiar lustre, because the arrangement of the material is different, the successive layers being plane in the shell and spherical in the pearl. On this account shaping an irregular pearl does not alter its lustre. Irregular pearls are sometimes worn without being shaped, when the form is agreeable. Pear-shaped ones have a proper form for ear-jewels, and are highly esteemed. Being composed of carbonate of lime and albumen, pearls are subject to be soiled by the acid in sweat.

Artificial pearls, with a perfect lustre, are made by lining bubbles of very thin glass with the silvery material which lines the scales of freshwater fish, of the genus Leuciscus. This is introduced in suspension, in a liquid, and when dry, wax is introduced to give strength and solidity.

Pearl fisheries are conducted at many places in various parts of the world, but the chief are in the east. Among the most important are those of the Persian Gulf, and the coasts of Coromandel, Ceylon, and Japan. The Persian Gulf has been a favorite locality from a remote period. Panama and the coast of Columbia were good localities formerly. A round and perfect pearl, as large as a pigeon’s egg, belonging to Philip II. of Spain, and worth $150,000, was taken at the Island of St. Margarita, on the north coast of South America; and Tavernier bought one from Catifa, in Arabia (an ancient locality), for £110,000.

About $450,000 are annually produced by the fisheries at the Bahrein Islands in the Persian Gulf, which are fished in June and July. At Ceylon the fishing extends from February to the beginning of April, but the fishing days rarely exceed thirty, from many causes. There are various holidays kept by the members of different castes and religions among the divers. A black race from the coast of India profess the Catholic faith, and do not fish on Sunday; and other days are kept as holidays by the heterogeneous population. Storms also interfere with the fishing.

The beds of pearl shells lie at a depth of six or eight fathoms, and the fishing is done by divers who are able to remain under water from a minute to a minute and a half, or even longer. Indeed, the earlier writers upon the subject assert that a diver might remain submerged one fourth or half an hour, but this is an exaggeration.

Pearls from freshwater mussels were sent from Perth to London between the years 1761 and 1764, to the amount of £10,000, but the fisheries were soon exhausted. A pearl weighing thirty-three grains was taken at this locality. The price of these pearls varied from ten to thirty-six shillings an ounce.

The pearl fisheries of Ceylon formerly employed 50,000 or 60,000 men at sea or on shore. Captain Percival, in his account of the island, describes the mode of proceeding. The shore, deserted at other times, presents during the fishing season a busy scene made up of people of various colors and countries; fishers, merchants, brokers, jewellers, speculators in shells before they are opened, and conjurors who are well paid to perform incantations to prevent the sharks from attacking the divers. The chief locality is off the coast of Condatchy, twenty miles at sea. The right of fishing is sold every season by the government to the highest bidder for each of the localities into which the bank is divided, and the purchaser is generally a black merchant. The same spot is not allowed to be fished again for three or four years, and the shell is supposed to arrive at maturity in seven years.

At the firing of a signal gun at ten o’clock at night, the fleet of boats sets out with the land-breeze, reaching the banks in time to commence fishing at sunrise, and starting on its return with the sea-breeze about noon. A gun is fired when the fleet is seen from the shore, to acquaint the owners with the fact. The shells are placed upon mats in pits, and buried until the animal is rotted and become dry, when the shells are easily opened and the pearls readily found.

Each boat has twenty men and a pilot. Of these ten are divers and ten boatmen, who row and assist the divers. Five dive at a time, and when these come up the other five go down, which gives them time to recover for each successive dive. The boat has five stones, of which each diver takes one to accelerate his descent, and this is attached to a distinct rope, to be drawn up at leisure. These men use their toes with great facility in picking up small objects from the ground, and when one of them is ready to descend he catches the rope which holds the stone with the toes of the right foot, his network bag with those of the left, and the rope which is to draw him up with his right hand, the other hand being employed to close his nostrils. When he reaches the bottom the bag is hung round his neck, and he commences filling it as rapidly as possible, returning in the course of about two minutes, first making a signal with the rope in his right hand. A diver may make forty or fifty plunges in a day, and bring up one hundred shells each time. This takes place in water from thirty to fifty feet deep; and as the pressure must diminish the volume of air in the lungs, the water must enter the nostrils to a greater or less distance. In consequence of this, when the diver emerges, water, and often blood, are discharged from the mouth, nostrils, and ears. Captain Percival states further, that there are divers who can remain under water four or five, and in one case six minutes. Some oiled their bodies and stuffed their ears and nostrils before descending, but this practice was not general.

The Greek divers were celebrated in ancient times, and they seem to have preserved their skill up to the present day. Like those of the Indian seas, they are taught to dive from childhood. Dr. Lefèvre, a French navy surgeon, gives an interesting account of them, having been present when they were employed in recovering property from the vessels sunk at the battle of Isavarino. The water was from one hundred to one hundred and twenty feet deep, and yet the divers not only reached the outside of the vessels, tearing off the copper, &c., but they entered the hold and brought out small objects, such as pistols, Turkish pipes, &c. When ready to descend, the Greeks seat themselves upon the edge of the boat, with their elbows upon their knees, and breathe rapidly with short inspirations, making the sign of the cross at intervals. Finally, they take a deep inspiration, and plunge headforemost, having a small rope attached to the thumb of the right hand, by which they may be drawn up when they dive deep.

Dr. Lefèvre, at three different times, carefully noted the time that the divers remained under water, and with the following result: Out of fourteen divers, the shortest period of submersion was fifty seconds; two remained sixty-five; among the longest, two remained under ninety, one ninety-four, one ninety-five, and one ninety-eight, the average being seventy-six seconds. When the divers emerge, the face is strongly injected, and they often bleed freely from the nose, and sometimes from the ears and eyes. They dive three or four times in an hour, and upon emerging, they put on thick woollen cloaks. The sea is sufficiently clear to enable divers to see objects at the depth to which they go.

The Phocidæ (seals) remain fifteen minutes under water, having not only large lungs, but an adapting peculiarity in the circulation. In a state of inaction they can remain much longer, and when on land as much as two minutes sometimes elapses between each inspiration. According to Frederic Cuvier, the seals in the Paris collection sometimes slept with the head under water for an hour at a time, a period which exceeds that of a harpooned whale. In the case of the whale, however, there is great muscular action, which requires more oxygen than a state of repose demands.

§§ Dimyaria

The second section, Dimyaria, of the tribe Elatobranchia, includes the two sub-sections, *Mytilacea and **Cardiacea, the first of which includes the four families, 1. Mytilidæ; 2. Arcidæ; 3. Unionidæ; 4. Carditidæ.

Fam. 1. Mytilidæ. This family includes the genera Mytilus (pl. 76, fig. 22) and several allied genera, and Pinna (figs. 18, 19). These animals have a linguiform foot, which secretes a byssus by which they are attached to rocks, the byssus being at first applied by the foot. The shell is equivalve, but very inequilateral, so that the umbones or beaks, which are usually situated about the middle of the back, are here placed at or near the anterior extremity of the shell. In Mytilus the lobes of the mantle are disunited, except at a single point posteriorly, which separates the anal siphon. The anterior adductor muscle is much smaller than the posterior one. Lithodomus is a sub-cylindrical bivalve, which, in its young state, is suspended to rocks by a byssus; but it subsequently perforates the rocks, and lives in a cavity but little larger than the shell, and then the byssus disappears.

The genus Mytilus is used for food, under the name of mussel. Mytilus choros, which is found at Chiloe and other parts of the western coast of South America, attains a length of seven or eight inches; and as the animal is as large as the egg of a goose, and of a fine flavor, it is much esteemed. The favorite mode of cooking it is to make a fire upon flat stones in a pit, and when these are sufficiently heated, the fire and ashes are removed and the shell-fish deposited, and covered, first with leaves, &c., and then with clay. This mode of cooking is practised on the coast of Australia, and in the islands of the Pacific.

The common mussel, Mytilus edulis, is easily taken, as it lives in shallow water, and even between high and low water, upon both sides of the north Atlantic. The shell is smooth, and of a blue or violet color. This species is poisonous to some constitutions, perhaps one in a hundred, and it is possible that this quality depends somewhat upon the season. An emetic, followed by castor oil, is recommended when bad symptoms arise from eating this shell-fish. The symptoms appear in one or two hours, and they are either internal inflammation, eruption, or resembling a catarrh or asthma, sometimes terminating fatally.

The genus Pinna has a somewhat triangular shell, pointed anteriorly, and it includes several species which attain to a great size, as P. radis (pl. 76, fig. 19), which is a foot and a half long. The byssus of several species is line and silky, and six inches or more in length. It is manufactured at Palermo and parts of Italy into gloves, stockings, and other small articles of dress, which are expensive, and kept as curiosities. The mollusc is eaten, and it produces small amber colored pearls.

From a remote period various fables have been current about the pinna and certain small crabs which are found in the shell, as in mussels, oysters, and other shell-fish. When the pinna opens its shell, the cuttlefish, it is said, “rushes upon her like a lion, and would always devour her but for another animal whom she protects in her shell, and from whom in return she receives very important services.” When the crab goes out and sees the cuttle-fish approaching, it “returns with the utmost speed and anxiety” to the pinna, “who, being thus warned of the danger, shuts her doors and keeps out the enemy.” Pliny’s story has been often repeated, according to which small fishes enter the shell to feast upon the animal, which does not regard their nibbles until the pinnoteres or pinnophylax gives it a bite, which causes it to close the shell, and thus to kill the fish, some of which is given to the crab as a reward for its watchfulness. Even in the present day similar fables are still recorded by careless compilers.

Fam. 2. Arcidæ. The genus Arca (pl. 76, figs. 31, 32) has a byssus in some species; the foot is split, the mantle is open, and the anomaly of two hearts is presented. The hinge margin has a row of numerous teeth, which fit between those of the opposite valve. The shell is rather thick, elongated, oblique, and has the beaks distant. Some species, as A. tortuosa, are curiously curved. In Pectunculus the shell is more nearly circular in outline, and the line of the teeth partakes of the curvature of the shell. In Nucula the lines of the teeth before and behind the beaks form an angle with each other.

The tertiary beds of the United States contain about thirty described species of Area, and about the same number of Pectunculus. The genus Trigonia is by some authors made the representative of a distinct family, which is objected to by Deshayes and Agassiz. A single living species, T. pectinata, inhabits the seas of Australia. The fossil species are numerous, and extend from the Lias to the Cretaceous group. A single tertiary species occurs in Bolivia. The genus has been illustrated in a masterly manner by Agassiz in his Etudes critiques sur les Mollusques fossiles: Neuchatel, 1840. Trigonia thoracica (Morton’s Synopsis, &c. p. 65, pl. 15, fig. 13) is from the cretaceous formation of the United States.

Fam. 3. Unionidæ. To this family the name of Nayades was given by Lamarck, but it is now usually restricted to an order of plants. It includes the greater part of the freshwater bivalve shells, which are so abundant in the waters of the United States, where they surpass, in number and variety of species, those of any other country. They usually live in sand or mud, ploughing furrows in their course, the ventral half of the shell being generally sunk in the bottom, which gives it a vertical position. Some inhabit gravel bars; and as it is difficult for them to progress through such an unyielding material, these species seldom change their place. A few species, as the genus Mycetopus, live in perforations made apparently with the foot, which has a peculiar development. These species of Unio, when left dry by the fall of the rivers, bury themselves in the moist sand. Unio (Truncilla) triqueter, a shell much like pl. 76, fig. 38, where we have observed it in the Ohio, does not take the more or less horizontal position of those like pl. 76, figs. 21, 47, but the anterior extremity is sunk diagonally into the mud or gravel, so as to bring the posterior truncation level with the bottom.

The shell is composed of nacre, and varies from little more than the thickness of paper to half an inch, or more, according to the species. It is covered with a periostraca, usually colored with various tints of yellow, green, or brown, sometimes ornamented with markings or radiating lines of a different color, among which green upon a yellowish ground is the most frequent. The surface is plain, as in the species inhabiting the rivers of the Atlantic coast of the United States, or with undulations or knotty projections, as in those of the tributaries of the Mississippi. Two species, Unio spinosus, Lea, from Georgia, and U. collinus, Conrad, from Virginia, have a few spines upon the shell. The beaks, being the oldest part, and the most exposed to the action of abrading agents, are subject to be worn off, and to such an extent that the younger portion in some cases disappears, and is replaced by successive secretions of shelly matter from the mantle. This renders it difficult to refer young and old shells to the same species. On this account no cabinet can be deemed complete without series indicating the gradual changes and variations in size, and other characteristics to which individual species are subject.

The variation in external character is extremely great in this family, where the same species will, in some instances, vary more than distinct species, which present more uniform characteristics. The variations of Unio complanatus (one of which is well represented in pl. 76, fig. 47) are so great that not less than fifty specimens are required to illustrate it properly.

 The Unionidæ inhabit the rivers and ponds in Europe, Asia, Africa, Australia, both Americas, and particularly those of the United States. Their distribution here has not been as thoroughly studied as it deserves to be, but the following facts may be stated. The species inhabiting the rivers of the Atlantic coast (excepting U. viridis, which is found in Kentucky, and U. cariosus, which has been taken in White River, Indiana) do not occur in the tributaries of the Mississippi. A few western species, as U. alatus, siliquoideus, ventricosus, and pressus, have found their way through New York, as far east as Lake Champlain. U. rectus is found on the southern border of Lake Superior, in Lake Champlain, the Ohio and Alabama rivers, presenting a wide range. U. complanatus, although it seems not to be found in the tributaries of the Mississippi, occurs in some of the streams of the southern shore of Lake Superior, and thus belongs to the basin of the St. Lawrence: it is found in Maine, and probably in every river as far south as the Savannah. Species are found in east Tennessee, as U. intermedins and subtentus, which are not found in Kentucky or the States on the south; and Louisiana has species not found beyond its limits. Unio plicatus and siliquoideus (the latter found in Lake Champlain, and the former above Pittsburgh, and in Grand river, Michigan) are found as far towards the southwest as San Antonio in southern Texas. U. lanceolatus has no greater range than from Tar river, in North Carolina, to the James and Kappahannoc in Virginia; and U. collinus, subplanus, and constrictus, seem not to extend beyond James river.

The following table exhibits the distribution of some of the species of the Atlantic rivers, from the Connecticut to the James. Asterisks under the name of a river denote the presence of a species in it, and dots indicate where it has not been found. The three first on the list extend into Maine:

The Unionidæ admit of being divided into three sub-families: Unionincæ, Iridininæ, and Etheriinæ.

Sub-fam. 1. Unioninae. The labial palpi are four: the foot is large and linguiform; the mantle is not united, and the posterior siphons are not tubular, being formed by the mere contact of its posterior margin on each side, but leaving two openings. The extremity scarcely extends beyond the shell; it is papillate, and provided with eyes which have the power of distinguishing light from darkness, as the siphons are suddenly withdrawn when a shadow is cast upon them. Some genera of this sub-family present no distinctive characters by which an Unio or an Anodonta, &c., can be distinguished without the shell, and on this account some authors insist that a character is worthless in the shell if unaccompanied by some distinction of the soft parts; and forgetting that the shell is part of the animal as the bill is part of a bird, they insist upon having two characters instead of one.

In the genus Unio there are two cardinal teeth in each valve anteriorly, and a lamellar tooth posteriorly in the right valve, fitting between two in the left one.

Anodonta has the hinge margin without teeth, and the shell is usually thin in texture.

Alasmodonta has cardinal teeth, but no lamellar teeth. Say founded this genus in 1818, and it was named Margaritana by Schumacher, in a work, the title-page of which bears the date of 1817. “The priority of this date would lead me to adopt the name given by that author, did it not appear that the work was not published for several years after it was printed. It was not known to the naturalists of this country, France, Germany, or England, until the year 1824.” (Say’s Am. Conchology.) Swainson uses both names, restricting Schumacher’s to the Margaritifera (pl. 76, fig. 47) of Europe, and Say’s to the form A. undulata.

Strophilus, Rafinesque, 1820 (Pseudodon, Gould, 1844, Proceed. Bost. Soc. p. 160, with four species), has a small swelling instead of regular cardinal teeth, and the soft parts differ in having the young, after they leave the ovaries, deposited transversely in the exterior branchiæ, instead of being in vertical folds, as in most of the species. In Diplasma of the same author, founded on some shells from Hindostan, there are anterior as well as posterior lamellar teeth, and these are double in the right valve anteriorly, and in the left posteriorly.

Rafinesque, in the “Continuation” of his Monograph of the Bivalve Shells of the river Ohio, institutes a genus, Loncosilla, for a solenoid shell, brought by Dr. Burrough from the river Jellinghy, in Bengal. Rafinesque considered it to be allied to Anodonta, on account of its fluviatile habits, but the characters of the shell are such as to induce us to coincide with Dr. Burrough in believing it to be essentially a solen. The shell is less than an inch long, “somewhat swelled, both ends rounded, and a little gaping, back horizontal; outside and inside smooth and whitish.”

Lamarck considered these mollusca to be hermaphrodite; and the dissections of competent anatomists, such as Neuwyler and Van Beneden, confirm this view.

Dr. J. P. Kirtland of Cleveland, well known as a successful cultivator of natural science, announced, in the twenty-sixth volume of Silliman’s Journal, his ability to distinguish the sexes by the shell alone in this sub-family. It is well known that the shells of many (although not all) species present individuals which are more full at the base posteriorly, and these were assumed to be females, the enlargement of the shell being, as it was thought, required for the gravid branchiæ. Some species, as Unio viridis, may be gravid without exhibiting any change of external form. If some individuals remain barren, and others prolific through a course of years, it is possible that the weight of the gravid branchiæ may cause the soft parts to descend and bring with them the shell secreting mantle, which may account for the enlargement without recourse to the theory of separate sexes, which are not found in the allied families. But this explanation will hardly account for the second form in Unio velum or U. flexuosus, or for the extraordinary transverse diameter (as in Unio siliquoideus) which is sometimes assumed in addition to the more common posterior enlargement.

Dr. Kirtland has discovered the presence of a line which he compares to a byssus (Silliman’s Jour., 1840, vol. xxxix. p. 166), by which the young of various species of Unio attach themselves to extraneous objects, a character which indicates an affinity with the Arcidæ and Mytilidæ, with which they have other affinities.

The genus Castalia, from the rivers of South America, is allied to Area and Trigonia in form, and to the latter by some affinity in the teeth. It was placed next to Trigonia by Lamarck, but an examination of the mollusc shows that it is allied to Unio, and the same remark applies to Hyria. The propriety of making a single genus of all these is doubtful, genera being thus made to depend upon the number of species, because the more numerous these are, the more links will there be between dissimilar forms. If Castalia and Unio were distinct genera when the number of species was small, they are still distinct, and the generic basis established by Deshayes in malacology and Temminck in ornithology untenable. (Desh. in Lam. Animaux sans Vertèbres, 6,523.) Some might extend these views to species, and deny specific distinctions in those genera which have many species, and this has been done by Lamarck in Cerithium, but he is consistent in extending his views to species in general.

Some have gone so far as to assert that the family of Unionidse contains not only a single genus but a single species. Without inquiring how the term species is to be limited, we feel confident that most of the Uniones can be determined specifically, as well as most genera of conchifera. The spines of Unio spinosus and U. collinus are often lost with age, and yet there is no difficulty in distinguishing them. U. trapezoides was confounded by Lamarck with one or two other species, yet no great knowledge is requisite to distinguish it. Deshayes doubts the distinctness of Unio lanceolatus, yet a very slight examination is sufficient to show that it is different from all others. Unio subtentus, viridis, cylindricus, heterodon, and a host besides without prominent characters, can always be distinguished.

Sub-fam. 2. Iridininæ. This sub-family contains some shells which have a great resemblance to Anodonta, and others which have teeth upon the hinge margin much as in Area, and which are represented by the transverse elevations upon the teeth of Castalia. Iridina is generally elongated, and differs from the Unioninse in having the mantle closed posteriorly, the siphons tubular, short, unequal, and without the retractor muscles of the marine genera with long siphons. Iridina blainvilliana, Lea (Anodonta or Columba, Am. Phil. Tr. v. 77, fig. 35), may be an exception, because the unusual curve in the pallial impression indicates a considerable power to retract the siphons.

The genus Iridina was established by Lamarck upon I. exotica (also named nilotica and elongata) in which the hinge is smooth, but acquires granulations with age, when it conforms to Lamarck’s characters. It is also named Spatha, Lea, 1837, and Calliscaplia, Swainson, 1840.

The genus Pleiodon was founded by Conrad, in 1834 (J. Acad. Wat. Sci., vol. vii. p. 178, pl. 13, P. ovata, Swainson), for a shell from Liberia in which the teeth “are alternately inserted, a generic character widely differing from Iridina, which is simply crenulated or tuberculated on the margin of the hinge.” The teeth are further compared with those of Area and Nucula. In a specimen now before us there is a flat internal ligament at the anterior internal extremity of the teeth.

Sub-fam. 3. Etheriinæ. The genus Etheria presents an irregular and very variable shell, without teeth, and somewhat resembling that of Ostrea, and although it is attached (indifferently by either valve), it is provided with a large foot. Before the mollusc was known, it was placed near Chama, but its affinities are with the Unionidæ; it resembles Iridina in having the extremity of the branchiæ united by a small connexion forming the superior siphon. The shell is nacreous, covered with a periostraca, and formed like some species of Ostrea, with laminated cavities, which are so large that the shell is proportionally lighter than that of any other species. They inhabit the Nile from the first cataract upwards, and the Senegal two hundred leagues from its mouth; and Dr. Goheen brought several imperfect specimens from the upper St. Paul’s in Liberia, several hundred miles from the sea. Several species are known.

The genus Mulleria is said to be founded upon young specimens of Etheria.

Fam. 5. Carditidæ. In Cardita the mantle is united for a short space posteriorly, forming a short anal siphon. It has three or four pair of truncated palpi; the shell is suborbicular or transverse, generally ribbed, and the two cardinal teeth are oblique. This genus occurs plentifully in a fossil state.

** Cardiacea

The sub-section Cardiacea of the section Dimyaria contains the families: 1, Chamidæ; 2, Tridacnidæ; 3, Cardiidæ; 4, Cycladidæ; 5, Tellinidæ; 6, Lucinidæ; 7, Veneridæ; 8, Crassatellidæ. In these the mantle is closed posteriorly, and the siphons are united or distinct.

Fam. 1. Chamidæ. This family includes Chama, Diceras (somewhat doubtful as a distinct genus), and Cleidothærus. In Chama the shell is irregular, spinous or rough, and attached, with the valves unequal and the umbones involute. The hinge has an oblique stout tooth fitting into an opposite cavity. The species present many varieties, chiefly from taking the form of the bodies to which they affix themselves. Cleidothærus resembles Chama, but is remarkable for having an internal accessory piece held by a portion of the ligament.

Fam. 2. Tridacnidæ. This family is represented by the genus Tridacna, which includes the largest species of shell known, Tridacna gigas (pl. 76, fig. 33). The position of the animal in the shell differs from that of most bivalves, as the foot passes through an opening in the lunule upon the closed or hinge margin of the shell; to effect which the position of the animal is changed so as to bring the open foot of the mantle above. The mantle is nearly closed, leaving a small anal aperture, a large branchial one, and a third corresponding to the lunule, for the foot, which is large and byssiferous. The anterior adductor muscle is obsolete, or confounded with the large posterior one, the two being very close together, forming a single impression.

The shell of Tridacna gigas is said to attain a length of three or four feet, and a weight of 300 pounds. The French name them benitiers, from the use made of them in the Catholic churches to contain holy water. The significant name of the genus was applied by the ancients to certain oriental oysters, which were so large as to require three bites in eating them. The mollusc of Hippopus resembles that of Tridacna; and although the shell has no opening, this part varies much in size among the species of Tridacna, so that the two genera are now usually united. It may be remarked that the lunule of Hippopus is not entirely closed.

Fam. 3. Cardiidæ. In this family the siphons are very short. In Cardium (C. echinatum, pl. 76, fig. 42) the foot is long, slender, and bent forwards at an angle in the middle, and with the aid of it the mollusc can leap with considerable force. The species live buried in sand and mud. Cardium edule is eaten extensively in Europe. It is so abundant in the North Sea that shiploads are raked up and taken to Holland and other places to be burnt into lime, and a good locality will furnish 200 or 300 cargoes. Hemicardium cardissa (pl. 76, fig. 41).

Isocardia (I. cor., pl. 76, fig. 34) has a subglobular shell, with the prominent umbones curved or contorted. The species figured inhabits the Mediterranean and the coast of Ireland.

Fam. 4. Cycladidæ. This family includes certain freshwater genera which have a general resemblance to marine forms, as Cardium, Tellina, and Venus. They have generally a smooth olivaceous periostraca.

Cyclas (pl. 76, fig. 43) is a genus of small subglobular shells from one eighth to one half an inch or more in size, inhabiting ponds and streams, sometimes upon the bottom and sometimes beneath it. The foot is long and tongue-shaped, the mouth closed posteriorily, and there are two retractile siphons. Besides the small diverging cardinal teeth, there are short anterior and posterior lamellar teeth. When kept in vessels of water, it is said that they can traverse the surface with the aid of the foot, the body being suspended beneath.

Pisidium is allied to Cyclas, but it is more wedge-shaped, and there is but one siphon. P. dubium, Say (Cyclas), Gould, Invert, of Mass. p. 75, fig. 56; P. abditum, Hald., 1841; Proc. Acad. N. S. i. 53, has a strap-shaped foot covered with vibrilæ, and considerably longer than the shell; and it can be extended, attached, and the body drawn up. The animal advances in this manner over the bottom of a smooth dish, being sometimes vertical and sometimes throwing itself upon one or the other side. The longer or wedge-shaped end of the shell goes foremost and is anterior; and although the foot is chiefly extended in this direction, it can be turned backwards, and indeed its flexibility is such as to allow it to be extended in any direction. The shell is one eighth of an inch long, pale yellow, the lines of growth very fine, the cardinal teeth indistinct, and the lamellar teeth robust. Lives in springs beneath the mud. The siphon is scarcely protruded beyond the margin of the shell, as it is in most species of Cyclas. Immature young are found within them, as in Cyclas.

Cyrena is a genus containing much larger and heavier shells than Cyclas, and chiefly confined to the fresh waters of warm climates. Cyrena carolinensis and Rangia cyrenoides (or Gnathodon cuneatus) are found in the southern United States both recent and fossil. The latter has some affinities with Mactra.

Megadesma is represented by a single species (reclusa, Chemnitz; paradoxa, Born; radiata, Lamarck), about three inches long, thick in texture, of a triangular form, green with violet rays, the inside white clouded with violet, and the pallial impression curved. The older authors placed it under Yenus and Tellina. It inhabits Junk river and other rivers of west Africa near the mouth.⁵

Glaucomya of Gray belongs here. Mr. Cuming found it living in the fresh waters of the Philippines, and it occurs fossil in the freshwater formations of Paris. It was at first confounded with Venus.

Fam. 5. Tellinidæ (also named Nymphacea). In this family the cardinal and accessory teeth are well developed, the shells are seldom covered with a periostraca, the mantle is margined with very sensitive tentacular appendages, and closed posteriorly, the siphons areexserted, and the pallial impression has a deep sinus.

Donax (pl. 76, figs. 38, 39) has a wedge-shaped shell, truncated upon the posterior slope, making this extremity unusually short. Some authors, as Swainson, have mistaken the posterior for the anterior extremity, although the short ligament and the curve in the pallial impression should have prevented such an error. Donax is a genus of handsome and usually small shells, abundant in individuals, and living vertically in the mud at a trifling depth of water. A few species are found in tertiary formations. Capsa includes shells allied to Donax, but without accessory teeth.

Tellina (pl. 76, fig. 44) is a genus of handsome and usually elongated shells with a fine nacre, often polished and radiated externally, and in some cases rough. The recent species are numerous, and there are a considerable number of fossil species in the tertiary of Europe and America.

Blainville places Amphidesma as a section of Lucina; Latreille considers it the representative of a family; and Deshayes thinks it has characters intermediate to Mactra and Tellina, to the latter of which he surmises that the unknown animal is allied.

Fam. 6. Lucinidæ. This family is sometimes united to the Tellinidæ. Lucina presents some important distinguishing characters. The shell is suborbicular, white or pale colored; the labial palpi are absent, the branchiæ of each side are united so as to appear single, although separable; the foot is vermiform, and there is a single anal siphon capable of being turned within itself like the finger of a glove. The branchial siphon is reduced to a simple perforation. The genus has numerous species, recent and fossil in the tertiary formations.

Fam. 7. Veneridæ. This family contains the extensive genera Venus (pl. 76, fig. 36) and Cytherea (fig. 37), and also Arthemis of Poll. The species of Venus and Cytherea being numerous, the accessory tooth which distinguishes the latter is found more or less developed, and as it is at times reduced to a mere vestige, Deshayes is inclined to consider the genus as not well founded. It is adopted by most concliologlsts, although rejected by Linnæus, Cuvier, and Blainville.

This family contains some of the most beautiful forms and finely colored species, both in tint and pattern, among bivalve shells. There are upwards of 150 living species, and the fossil species are also numerous, and chiefly found in the tertiary strata. There have been about sixty tertiary species named from the formations of the United States. Venus mercenaria is an inhabitant of both coasts of the North Atlantic, and is used for food. In the markets of Philadelphia it bears the name of clam, and in Boston that of cwahog. The colored margin of the shell was used by the aborigines in the manufacture of their wampum. Cytherea dione (pl. 77, fig. 37) is remarkable for its longitudinal sulcations, and the double rows of long spines posteriorly.

Fam. 8. Crassatellidæ. This family is represented by the genus Crassatella, the mollusc of which being unknown, its affinities are doubtful. There are about twenty recent species known, and a considerable number of fossil ones, chiefly tertiary, but also cretaceous. Some authors place the genus Astarte (also called Crassina) here, but Deshayes thinks the mollusc (which is unknown) has an affinity with Venus.

Class 2. Gastropoda

This class includes most mollusca with univalve shells, whether spiral or not, as well as species without a shell. The head, absent in the Acephala, is here present; and on its presence Blainville’s appellation of Paracephalophora is founded, a character which is of more importance than the foot.

Order 1. Polythalamia. This, the first systematic name applied to these animals, was proposed by Soldani, 1789. More recently they have been studied by D’Orbigny, who is the chief authority upon them, and by Dujardin. The original name is defective, and both these authors have conferred French names upon them, in contempt of those rules which keep nomenclature pure and uniform, names which are of no more account than the German name Bauchfüszler instead of gasteropoda; and should the systematic name be adopted subsequently to such a vernacular one, and be a translation of it, the author of the latter cannot be quoted for the systematic name.

These animals have been also named Foraminifera and Rhizophoda. Their classification is difficult. Their shell bears a distant resemblance to that of certain cephalopoda, and on this account they were for a considerable period referred to this class. D’Orbigny considers them as a distinct class between the Echinodermata and Zoophyta, and Dujardin regards them as acalephæ, and as allied to infusorial forms like Amiba and Difflugia. Agassiz regards them as the lowest form of the gasteropodous mollusca, and we place them provisionally here, although they seem to have neither head nor foot, two important organs in this class. The apparent want of viscera indicates a position below that of the Bryozoa, and although the locomotive organs may be assumed as giving them a higher position, these are probably merely a modification of the tentacles.

These animals are microscopic, glutinous, and translucent, but tinted with bluish, reddish, brown, or yellow, the tints being uniform in each species. The soft parts are inclosed in a calcareous (rarely cartilaginous) shell, fitted to the varied outline of the body, and presenting numerous variations in form, affording characters for genera and higher groups. It has one or more openings, or numerous pores, which allow egress to certain filaments used as organs of locomotion. These can be extended to six times the diameter of the body, and they recall the allied organs in the Echinodermata and Cirrigrada. They are ramified like the branches of a tree, and have the power of secreting calcareous matter upon the outside of the shell, in which they resemble the extensions of the mantle in some orders. The characteristic name Rhizopoda of authors, has been drawn from these filaments.

The Polythalamia inhabit most seas, and they are so abundant that D’Orbigny calculated that an ounce of sand from the Antilles contained 3,840,000 individuals. The same author informs us that these little beings from a sixth to half a millimetre long, are more abundant than the minute Crustacea, or the infusoria whose shields form the tripoli of commerce. Banks are formed by them dangerous to navigation; they obstruct bays and straits, of which the celebrated harbor of Alexandria is an example; and with the coralligenous zoophyta they form reefs and islands.

In a fossil condition they are no less conspicuous. In Russia calcareous beds are formed by a single species of Fusulina, and various species enter largely into the composition of chalk and certain tertiary formations. They are so abundant as in some cases to amount to 3,000,000,000 in a cubic metre; and the city of Paris and the surrounding towns are almost built of them, so abundant are they in the materials used. Dr. Buckland makes the following remarks: “Nummulites are so called from their resemblance to a piece of money; they vary in size from that of a crown piece [!] to microscopic littleness, and occupy an important place in the history of fossil shells, on account of the prodigious extent to which they are accumulated in the later members of the secondary, and in many of the tertiary strata. They are often piled on each other nearly in as close contact as the grains in a heap of corn. In this state they form a considerable portion of the entire bulk of many extensive mountains, e.g. in the tertiary limestones of Verona and Monte Bolca, and in secondary strata of the cretaceous formation in the Alps, Carpathians, and Pyrenees. Some of the pyramids and the sphinx of Egypt are composed of limestone loaded with nummulites. It is impossible to see such mountain masses of the remains of a single family of shells thus added to the solid materials of the globe, without recollecting that each individual shell once held an important place within the body of a living animal; and thus recalling our imagination to those distant epochs when the waters of the ocean which then covered Europe were filled with floating swarms of these extinct molluscs, thick as the countless myriads of Beröe and Clio borealis that now crowd the waters of the polar seas. Lamarck, in his observations on Miliola, remarks that these very minute animals have had much more influence on the masses which compose the surface or exterior crust of our globe than the remains of elephants, hippopotami, and whales.”

Viewing this group as a class, D’Orbigny divides it into six orders, each of which, excepting the first, is subdivided into two families. Of the recent species, 68 genera and 900 species are known, more than half of which belong to the warm seas. D’Orbigny’s opinion of their classification is as follows: Though less complicated in their organization than many zoophyta, they have not a common life, nor are they aggregated like them, whilst their locomotive powers and testaceous envelope place them much higher. On the other hand they are in all respects less complete than the echinodermata; and judging from the radiation of their filaments, the position of the foraminifera is in Cuvier’s radiated division, between the Echinodermata and the Zoophyta, as a distinct class.

Order 2. Pteropoda. This order takes its name from two large expansions, one on each side anteriorly, which are analogous to the wings of a butterfly both in appearance and action, being used in locomotion. This order was considered by Lamarck and Cuvier to form a distinct class, but Blainville and other distinguished naturalists are of opinion that its contents are essentially gasteropoda. Some species, as Clio borealis (pl. 76, fig. 78, one inch long), are naked; others, as Hyalæa are provided with a delicate shell. These molluscs are monoicous, and swim about in the sea without the power of creeping or attaching themselves to solid bodies. This order contains the families Hyalæidæ, Clioïdæ, and Phillirhoïdæ. In Hyalæa the branchiæ are composed of pectiniform transverse laminæ or leaves,⁶ a character which would afford a name for the order in consonance with those of the allied orders, because Cuvier’s name, Heteropoda, appertains to the group as a class.

Fam. 1. Hyalæidæ. The shell of Hyalæa has a delicate texture and curious form, bearing a distant resemblance to that of Terebratula, to which the genus was at one time referred. The shell which covers the abdomen is translucent, subglobular, and has the appearance of a bivalve in which the two valves unite in a single piece without a hinge. The mollusc has two stout tentacles and two lips, and the wing-like expansions are placed near the mouth. They live in the high seas, seldom approaching the shores, flapping themselves along with great facility, and descending when disturbed. Being extremely abundant where they occur, they are devoured in great numbers by whales and other animals. Cleodora and Limacina are other genera.

Fam. 2. Clioïdæ. Clio has six retractile tentacles in two groups, and a rudimentary foot. Clio borealis is abundant in the north polar regions, where it is eaten by whales and fishes.

Fam. 3. Phillirhoïdæ. The head of Phylliroë is lengthened, and bears two tentacles, the snout is retractile, and the body is gelatinous and transparent, very much compressed laterally, and provided with a caudal fin. According to Peron and Lesueur the branchiæ are internal, and in the form of granular cords, but Quoy and Gaimard could not detect these organs. Some authors place this family among the Caryobranchia.

Order 3. Caryobranchia. The body is gelatinous, transparent, and capable of being enlarged by absorbing water. The head is proboscidiform; the foot is long, compressed, or vertical, provided with a little sucker, and used as a fin in swimming. The animal is usually inverted in the water, the foot being above. The branchiæ are pectinated, and arranged around a nucleus, whence the name of the order. Some of the Heteropoda of Lamarck belong here. The order has the additional half Latin and half Greek hybrid name Nucleobranchia, which is inadmissible.

Fam. 1. Atlantidæ. The genus Atlanta has an extremely delicate, vitreous, transparent shell, shaped like planorbis, with the aperture trumpet-shaped, with one side deeply excised, and having a closely fitting operculum, of the same texture as the shell, the spire projecting from one side. The mollusc is spiral and compressed, the foot large, compressed, and provided with a small sucker above. Eyes two, behind the tentacles. This genus is found far at sea, swimming with great facility, and sinking when not in action. Deshayes thinks the fossil genus Bellerophon is allied to this genus in its natural affinities.

Fam. 2. Carinariidæ. The shell of Carinaria is extremely delicate, and much smaller than the animal (pl. 74, fig. 17, on the right hand below). Its resemblance in form, and in having a single chamber, induced some authors formerly to place it near Argonauta (pl. 76, fig. 17), with which the animal has no affinity. The mollusc is gelatinous, transparent, and rough; the eyes two, situated at the base of the tentacles. The heart and branchiæ are contained in the shell, and opposite to this is the compressed foot (or ventral fin), the posterior extremity being provided with another fin. The Carinarise are found at sea, and are supposed to feed upon minute Crustacea. They can attach themselves to floating bodies with the aid of the sucker upon the foot.

Fam. 3. Pterotraclieidæ. This family is allied to the preceding one, but the tentacles and shell are wanting. The former are reduced to tubercles (or entirely absent) with the eyes on the outside of their base. A membrane supplies the place of the shell of Carinaria. Pterotrachea (also named Firola) is the principal genus. The habits are identical with those of Carinaria.

Fam. 4. Pterosomidæ. Composed of the genus Pterosoma, in which the body is cylindrical, surrounded horizontally with a broad marginal membrane used in swimming, Neither tentacles nor branchiæ were observed. P. plana is nine centimetres long, and inhabits the sea between the Moluccas and New Guinea.

Order 4. Gymnobranchia (also known by the hybrid term of Nudilyrcmchia). The members of this family are without a shell or a branchial cavity, the organs of respiration are in the form of external appendages upon the back, and their distribution and shape afford characters for the families. The embryonic young have a shell, and they remind us somewhat of Atlanta. These animals are monoicous; they have a large flat disc or foot to move upon, and their food is either vegetable or animal, some preferring one kind and some another.

Fam. 1. Dorididæ. In this family the branchial plumes surround the vent in the form of a flower, situated upon the upper surface towards the posterior extremity (pl. 77, figs. 16, 17). The upper part is composed of a kind of large mantle, the jaws are corneous, the tentacles four in number, two dorsal and two labial. The dorsal tentacles and the branchiæ are sometimes retractile.

Doris includes many species whose brilliant coloring renders them conspicuous objects. The dorsal tentacles have transverse ridges variously disposed in the different species; the branchiæ are subdivided in a regular manner, but not uniformly in the different species. The eggs are deposited to the number of several thousand in a ribbon-shaped mass attached by its edge to extraneous objects, and wound in a spiral, varying from one to five or more turns. These animals live upon stones and marine plants; they move very slowly, and are not much addicted to locomotion. The length varies from about half an inch to six or seven inches.

Fam. 2. Tritoniidæ. In this family there is a membranous veil or expansion in front, above the mouth (pl. 77, fig. 2); the branchiæ are in two longitudinal rows, and laminated, plumose, or papillate; two dorsal retractile tentacles. Tritonia (pl. 74, fig. 20), Tethys (pl. 77, fig. 2).

Fam. 3. Eolididæ. “Branchiæ papillose or branched, arranged on the sides of the back; stomach simple.” (Alder and Hancock.) These authors divide this family into two sub-tamilies, Malibæinæ and Eolidinæ, to which Glaucincæ may be added. The first contains the genus Dendronotus, of which D. arborescens, Muller, is found upon both sides of the North Atlantic. It is beautifully figured from specimens taken at Boston, by Mr. Couthouy, in the Bost. Jour. Nat. Hist., vol. v. Dr. Gould compares its branchiæ to some fifteen or twenty widely and numerously branched plants. See his Invertebrata of Massachusetts, pp. 4–7, for descriptions of various species in this order.

In Eolis the branchiæ are elongated papillæ resembling short cords arranged in longitudinal rows, and sometimes so numerous as to cover the back entirely. Eolis salmonàcea of Couthouy has about a hundred of them. They are frequently tinted with several bright colors, when they add much to the beauty of the various species.

Glaucus has the branchiæ (which are used in swimming) in symmetrical pairs upon each side, each being a wing-like projection, with the margin fringed with numerous filaments. There are three or four pair, according to the species, the anterior being the largest, and the remaining ones becoming gradually smaller. Deshayes doubts whether these organs are branchiæ, since they are cast off by the animal when disturbed; and indeed Couthouy expresses the same doubt in the case of Eolis, from which they can be cast off, and, when cut off, the animal does not seem to suffer much. He regards them as accessory to the general surface in the operation of oxygenating the system. The papillæ in one species dissected by Alder and Hancock contain a hepatic gland in the middle, and a circulation of blood towards the margin. The surface is covered with vibrillæ, so that they must be used in breathing, although the general surface may be adapted to this function.

Fam. 4. Plachobranchidæ. Founded upon the single genus Plachobranchus of Van Hasselt. The body has broad lateral expansions used as swimming organs, and these, and also the back, are covered with branchial lamellæ. The expansions can be turned upwards, and their margins made to meet over the back. P. ocellatus, two inches long, was found at Java.

Order 5. Crypsibranchia (also known by the inadmissible name of Tectibranchia). The branchiæ are unsymmetrical, composed of leaves more or less divided, and they are covered by the upturned mantle. These animals are monoicous, and are comprised in the two families Aplysiidæ and Bullidæ.

Aplysia (pl. 77, fig. 18) was named lepus marinus by the ancient authors, and many fables entered into its history. The shape is not much unlike that of a naked snail, but the body is larger posteriorly. There are two pair of tentacles, the anterior ones being the largest, and of such a form (in connexion with that of the body) as to suggest the name of sea hare for the animal. The branchiæ are in a cavity protected by an operculum containing a thin corneous body, which is a rudimentary shell, and have their parietes composed of interlaced fibres; they are pierced with numerous small holes through which the blood may escape into the stomach, and the vascular system receive the liquid products of digestion.

The species of Aplysia are found upon the coasts of continents and islands at no great depth, some crawling upon rocks or hiding in their crevices; others hiding in the mud or sand, but with the branchial siphon exposed. Their food is marine plants or animals. The shell in the different species varies in texture, some approaching the solid shell of Dolabella, and the change is so gradual, that Rang, the chief authority upon these genera, considers the latter genus merely a section of Aplysia.

Fam. 2. Bullidæ. The chief genera of this family are the allied Bulla, with the shell external; and Bullæa with the shell internal. In Bulla (B. physis, pl. 76, fig. 3) the tentacles are wanting, the shell is thin in texture, subglobular, more or less completely enrolled, and having the aperture the entire length of the shell.

Order 6. Hypobranchia (also incorrectly named Inferobranchia). This order is named from the position of the branchiæ under the margin of the mantle. It contains three families, represented by the genera Phyllidia, Pleurobranchus, and Umbrella.

Fam. 1. Phyllidiidæ. Diphyllidia (pl. 74, fig. 19) is oblong oval, with a coriaceous rough integument, forming a prominent lateral border. The branchiæ surround the body, and are in the form of transverse lamellæ: there are four tentacles, two of which are superior and retractile.

Fam. 2. Pleurobranchidæ. In Pleurobranchus the branchiæ resemble a fringe formed of laminae, on each side of a medial branch placed in a groove upon the right side between the mantle and foot. The animal is shaped like a slug (Limax) or naked snail; and it has a small internal flat thin shell, and four tentacles.

Fam. 3. Umhrellidæ. This family is monoicous; the branchiæ are foliaceous, and disposed in a long line upon the right side. Umbrella has a discoidal, external, dorsal shell, bearing some resemblance to that of a very flat Patella; a very large foot, and four tentacles. Some authors consider this family as a distinct order under the name of Pomatobranchia.

Order 7. Cyclobranchia. In this order the branchiæ, as the name indicates, are arranged in a circle around the body above the foot. It contains the two families Patellidæ and Chitonidæ, both of which are monoicous, and have a long tongue armed with teeth. Blainville named this order Cervicobranchia, from an erroneous opinion that the organs generally received as branchiæ are merely membranous plaits without the ftmction of branchiæ, which he supposed should be looked for in a sac above the neck.

Fam. 1. Patellidæ. The genus Patella (pl. 75, figs. 76, 77, 79) has a simple conical shell with an oval or circular base; inside with a submarginal cicatrix open in front. The shell covers the animal like an inverted cup. The animal is monoicous, creeping slowly upon a large foot, with which it can adhere with great tenacity to rocks. Some species seem not to move, except perhaps at long intervals, as they are found in depressions which they have formed in the rocks, and which correspond to the outline of the shell.

Fam. 2. Chitonidæ. The shell of Chiton (pl. 76, fig. 55) differs so much from that of Patella, that its position among the Mollusca was for a long time doubtful. An examination of the animals of both genera at length proved them to belong to allied families. The shell is oval, and divided transversely into eight pieces resting upon the back of the animal, with the lateral portions united by a coriaceous border. Thus constructed, the Chitons have the power of bending themselves together. The tentacles and eyes are wanting, but the former are replaced by a veil. Their habits are similar to those of Patella. In Chitonellus the animal is long and narrow, and the border of the shell extends so far upon the back that the dorsal plates are reduced to a small size.

Order 8. Aspidobranchia (also incorrectly named Scutibranchia). In this order the shell is allied to that of Patella in form, but it is emarginate, or perforate. The order is divided into the two families Fisaurellidæ and Calyptræidæ.

Fam. 1. Fissurellidæ. The shell of Fissurella, with the perforation through the apex, bears a distant resemblance to a key-hole scutcheon, and, excepting the perforation, resembles that of a Patella; but it is often too small to cover the animal. The perforation admits water to the branchiæ, and allows the fæcal matter to be excluded. There are two pectinated branchiæ in a cavity at the anterior part of the back; and two tentacles, with the eyes at their external base. Fissurella græca (pl. 75, fig. 80). Emarginula (fig. 82) differs from Fissurella in having the aperture which admits water to the branchiæ removed to the anterior margin of the shell, where it forms a notch; and the apex of the shell is directed backwards, whilst in Fissurella it turns forwards.

Fam. 2. Calyptræidæ. The shell of Calyptræa is patelliform or trochiform, irregular, somewhat conical, with the apex rather posterior. Towards the apex of the inside there is a plate which is sometimes funnel-shaped, and sometimes like the vertical half of a funnel. In other species it forms a spiral, which approximates the shell to that of the spiri valve genera. The animal is not spiral, the two tentacles are large and triangular, having the eyes upon an enlargement of the external side; the branchial cavity is large and oblique, and the branchiæ are pectinated, filamentous, and exsertile. Calyptrcea sinensis (pl. 75, fig. 78).

Crepidula has an ovate or oblong shell, generally convex above, the internal cavity divided some distance by a shelly diaphragm which represents the plate in Calyptrasa, and above which the viscera are placed. The animals of these two genera are alike, and the shells of some species present intermediate characters, so that it is difficult to tell to which of the two genera they should be referred. The Crepidulæ are sedentary, seating themselves upon stones, or upon each other, and adapting the margin of their shells to the irregularities of the object upon which they place themselves.

Order 9. Nematobranchia (or Cirrhobranchia). The genus Dentalium (pl. 75, figs. 73–75) was for a long time believed to belong to the Annellida, until dissection proved it to be a mollusc. The shell is a long, slender, and slightly curved cone, open at both ends, and sometimes ribbed or striate externally, as in D. elephantium (fig. 73). The convex part of the shell corresponds to the back of the mollusc. The branchiæ are composed of numerous extensible filaments forming a bundle upon each side of the neck, and it is probable that the branchiæ can be used to convey food to the mouth. The vent is at the posterior or smaller end of the shell, the lips are scolloped into a number of palpiform projections, and the ordinary tentacles and eyes are absent. The animal lives vertically in the sand with the head downwards. There are some shells which closely resemble those of Dentalium, and which were classed with them until it was ascertained that their animal is an annellid. They form the genus Ditrupa.

Order 10. Ctenobranchia (also named Pectinibranchia). This is an extensive order of dioicous spirivalve mollusca, in which the branchiæ are pectinated, one or two in number, and placed in a large cavity above the neck; the tongue is armed with numerous teeth, the tentacles and eyes are usually two in number, and the aperture is usually closed by an operculum. Most of the families are marine, but some inhabit fresh water. The families are as follows: 1, Melaniidæ; 2, Cerithiidæ; 3, Vermetidæ; 4, Trochidæ; 5, Pyrimidellidæ; 6, Buccinidæ; 7, Purpuridæ; 8, Strombidæ; 9, Conidæ; 10, Cypræidæ; 11, Volutidæ; 12, Sigaretidæ.

Fam. 1. Melaniidæ. Menke’s corresponding family named Turbinea is inapplicable, because in its various modifications it is used for the family to which Turbo belongs, by Lamarck and Deshayes, and by Blainville for a family of Polythalamia. Some of the genera of this family inhabit the sea, and others the fresh waters. The mantle is simple, without fringe or siphon; the head ends in a short trunk, and the food is vegetable, chiefly decaying algæ. The family contains a number of sub-families, the limits of which are not well ascertained. Melania amarula (pl. 75, fig. 90).

Littorina is a genus of small marine shells which inhabit the coasts. L. tenebrosa, which inhabits both sides of the North Atlantic, leaves the water for hours, climbing up the grass of the salt meadows. According to Dr. Gould, it may be found “at a considerable distance from any water.” He remarks, also, that “it lives a week or more after being removed from the water.” The species vary very much in their specific characters. Planaxis and Eulima are placed in this family, as well as Turritella (a shell much like pl. 75, fig. 117, but with the aperture entire), but as the mantle is stated to be scolloped, it seems to be more nearly allied to the Cerithiidæ. The mantle of Scalaria (pl. 75, fig. 101, S. clathrus; fig. 102, S. scalaris) not having been described, its place remains doubtful, although it probably comes near to Turritella.

Paludina is a genus of freshwater shells of a subglobular or conical form, usually covered with a greenish periostraca, and sometimes ornamented with bands, as in pl. 75, fig. 95, which represents the shell of P. vivipara of Europe and the United States, but the animal is incorrectly drawn, so as to resemble a land snail. The foot is a large, flat body, with the sides parallel, truncated in front and rounded behind; the tentacles subulate, not annulated, and bearing the eyes upon an enlargement of their external side. Paludina decisa is about half an inch long, of a fine green color, and is widely distributed in the United States. The animal is figured in the Freshwater Univalve Mollusca of the United States.

Amnicola resembles a minute Paludina in the form of the shell, but the operculum is subspiral, and not concentric as in that genus.

Valvata is a genus of small shells much like Amnieola, but the aperture is circular and the operculum concentric. The branchiæ are exserted, and in the form of a minute plume. An exserted organ like a single thread is supposed to be an accessory branchia.

Paludina, Valvata, imdi Ampullaria, from Lamarck’s Perisotmata; and Cuvier and Swainson placed them under a division of which Turbo is the type.

Melania is the type of the sub-family Melaniinæ, which includes a number of genera, among which are Melania, Melanopsis, Pirena, and Auculosa. In Melania the shell is solid, turreted, with a greenish or blackish periostraca, the aperture elliptical, the external margin sharp, and the operculum corneous and subspiral. The species live upon calcareous rocks, or upon the ordinary bottom of the rivers, especially in those of the United States. The zoological characters or the genus are given in the American Journal of Science, 1841, vol. xli. p. 21.

Leptoxis (or Anculosa) is allied to Melania, but the shell is shorter. The animal attaches itself to rocks where the current is very rapid, and it seldom moves from its position. The history of this genus is given in Chenu’s Illustrations Conchyologiques, where it is illustrated by 170 figures. The genus seems to be confined to the rivers of North America. Kafinesque’s generic name Leptoxis was published two years before Say’s Anculosa. Some authors suppose the former to be a genus of Physidæ, but the question is settled by some manuscript drawings of the former author, which represent the shell, tentacles, and operculum of Anculosa.

Melamopsis is allied to Anculosa, and the species seem to be confined to Europe. It is probable that the few described species of European Melania belong in reality to Melanopsis.

Say’s Melania armigera (and also Lea’s M. duttonana and M. Catenoides), belongs to Kafinesque’s genus Pleurocera, in which there is a short straight canal anteriorly, and when this canal is lengthened as in Fusus, the genus Io of Lea is the result. Strejpoina of Rafinesque (or Ceriphasia of Swainson) are slightly different forms, in which the aperture and the vertical plane formed by the anterior portion of the whirls, bear some resemblance to the same parts in Cerithium telescopium.

Fusus fluvialis of Say is the type of Io, and as it would be an anomaly to find a genus so decidedly marine as Fusus inhabiting fresh waters, it becomes a matter of interest to know the animal of the American shell. This was observed in 1841, in its native waters in Holston, Powel’s, and Clinch rivers, in eastern Tennessee, by Halderman, who made a drawing of the living animal. Its characters and habits are not those of Fesus, but of Melania proper, as distinguished from Leptoxis; for although it inhabits the rapids as well as quiet water, in both cases it avoids the current by seeking shelter beneath shelving rocks, or in hollows or crevices in them. The head is large, and with the tentacles much exposed; the foot is as large as in Melania; the coloration is the same (black lines upon an orange ground); the operculum is subspiral as in Melania, the mantle extends into the canal of the shell, but does not form a closed siphon; the vent is upon the right side; the mouth is a longitudinal slit; the eyes (which are sensitive to the light) are upon a short enlargement of the outer base of the tentacles, which may be a little longer than in Melania, and they are not visibly annulated. It differs from Fusus, and resembles Melania in living upon vegetable food; and it moves along in a sluggish manner, moving the head from side to side upon the bottom. Io spinosa and I. tenebrosa are merely varieties of I. fluvialis. The spinose individuals are much the most abundant, although the species is rare when compared with various species of Melania.

Quoy and Gaimard, to whom the science of Malacology is indebted for a knowledge of the animals of many shells, have figured a number of species as belonging to Melania, the shells of which cannot be distinguished from those of that genus, whilst in the figures the mantle is represented as scolloped. Similar species were drawn in the course of the United States Exploring Expedition. These species must be placed in the family Cerithiidæ.

Fam. 2. Cerithiidæ. The genus Cerithium (pl. 75, figs. 105–109) are remarkable for the great number of species both recent and fossil (tertiary) which it contains. The animal has the general character of Melania, except that the mantle is scolloped.

The number of species and varieties being so great in this genus, Lamarck was led to doubt the permanency of species, and he judged that those which seemed better established in other cases, would present equal uncertainty were their number greatly increased.

Fam. 3. Vermetidæ. The genus Vermetus (V. lumbricalis, pl. 75, fig. 69) has a loosely and irregularly coiled shell affixed by its posterior extremity. As the animal enlarges it increases the size of the shell, and moves forward in it, cutting off the empty posterior portion by a diaphragm from time to time. The animal is much like that of Turbo or Delphinula, the foot (as there is no locomotion) is obsolete, the posterior portion being adapted to support a thin operculum which closes the aperture. There are two tentacles, with the eyes at their base externally. There is a single branchia. Cuvier placed this genus, with Magilus and Siliquaria, in a distinct order named Tubulibranchia. In the genus Magilus the young has an ordinary short ventricose turbinated shell (having a distant resemblance to pl. 75, fig. 91). We have seen, in the case of Aspergillum (p. 60), how a bivalve shell can take the form of a tubular one; and Magilus is an example of the same thing in a spirivalve one. The animal inhabits cavities in living coral, and to prevent being buried by the growth of the surrounding inaterial, it has the power of forming a tube, the margin of which it builds up as the coral increases, so that the aperture retains the level of the general surface. The tube thus attains five or six times the length of the original shell, and it assumes various curves and irregularities, depending upon the growth of the coral.

Fam. 4. Trochidæ. The members of this family are herbivorous, and most of them have the mantle or foot ornamented with tentacular appendages. The shell of Trochus is short and conical, solid, and nacreous. The genera Trochus (T. solaris, pl. 75, fig. 106; T. magus, fig. 107; Turbo, fig. 103) Monodonto and Delphinida (D. delphinus, fig. 104) are nearly allied, and the animals do not differ. In Solarium (S. perspectivum, pl. 75, fig. 108), the shell and animal differ, the head not being proboscidiform.

Janthina ianthina (pl. 75, fig. 96) is the type of a sub-family, distinguished by the possession of an apparatus which enables the animal to float at the surface of the sea. The name is derived from the Greek word for violet, the shells of all the species being of this color. The shell is trochoidal and very fragile, having the right side of the aperture sharp, and often notched. The animal has a large proboscidiform head, two tentacles, and eyes; the mantle with an expansion said to be used in swimming; the foot with an appendage or float formed of a great number of air-vesicles. This appendage can be cast off and renewed. The latter process was observed by Dr. Eeynell Coates, who describes it as being formed by inclosing a bubble of air in a cavity formed by contracting the margin of the foot, which then secretes a covering for it. The eggs are attached to the under surface of the float, and subsequently cast off with it. This animal was first described and figured by Fabius Columna, in 1616.

In Haliotis (H. tuberoulata, pl. 75, fig. 86), the shell is ear-shaped, much depressed, very short and flat, the aperture longer than wide, and as large as the base of the shell, left side with a sub-marginal row of perforations; nacre very brilliant and iridescent. As the animal increases in size a new hole is formed in the shell, and the oldest one is closed. The head is proboscidiform, with two long tentacles, each with an oculiferous peduncle; foot large, provided above with a double membrane scolloped into leaflets of a very ornamental character. The water is admitted to the branchiæ through the holes in the shell, which also allow certain filamentous appendages of the mantle to protrude through them. There are two pectinated branchiæ. The genus Stomatia is allied to Haliotis, but the shell has no perforations. This sub-family was included by Cuvier among the Aspidobranchia, but Deshayes assigns good reasons for placing it among the Ctenobranchia.

Neritina (N. fluviatilis, pl. 75, fig. 87) is a genus of small sub-globular or oval fluviatile shells, with a semi-circular aperture closed by a calcareous operculum. The two tentacles are long, and each is accompanied by a short secondary tentacle, with an eye upon its summit.

Fam. 5. Pyramidellidæ. This is a small family, composed of the genera Pyramidella and Tornatella.

Fam. 6. Buccinidæ. In Buccinum (B. undatum, pl. 75, fig. 120), the foot is narrow, the head small, continued in a proboscis, with two tentacles, each having an exterior oculiferous peduncle; siphon protruding; sexes distinct, the male with a long exterior organ from the right side of the neck; shell oblong-oval, with a notch anteriorly. The species figured inhabits both sides of the North Atlantic. The genus has numerous species, both recent and fossil. Nassa and Eburna belong to this family. Eburna glabrata is an Ancillaria, and Deshayes thinks the remaining species of Eburna should be merged into Buccinum.

Fam. 7. Purpuridæ. This marine family is mostly carnivorous; the water is taken to the branchiæ through a siphon, which passes out of the notch or canal at the anterior part of the shell. The eyes and tentacles are two in number, and the proboscis is well developed. The operculum is thin, and much smaller than the aperture, to allow the animal to withdraw some distance within the shell. Cancellaria is placed in this family, although it has no operculum, and lives upon vegetable food. The animal resembles Purpura.

Purpura lapillus (pl. 75, fig. 118) is about an inch long, and abundant on rocky coasts on both sides of the Atlantic.

Pleurotoma (P. babylonia, pl. 75, fig. 110) is a genus with an elongated spire, a straight canal, and a narrow notch posteriorly in the right lip of the shell, corresponding to a notch in the mantle. The species of this genus are numerous, amounting to over a hundred of recent, and more than this number of fossil tertiary species. There have been nearly fifty species described from the tertiary formations of the United States.

Murex (M. ramma, pl. 75, fig. 111; M. haustellum, fig. 112; M. tribulus, fig. 113). Rondeletius and Aldrovandi have treated of this and some allied g-enera. The genus murex of Linnæus was founded in 1758, but Rondeletius had named several of the species purpura, under the belief of their being the purpuræ of Pliny, which were supposed to furnish the purple of the Tyrians. The shell named Murex by Pliny and Rondeletius, belongs to the modern genus Strombus. Murex is a genus of rough shells, with ridges, spines, or tubercles, which are secreted periodically, in three or four rows around the shell. The right margin of the mantle is divided into lobes, the irregularities of which account for those of the shell in the different species. There are about 170 recent and 130 tertiary fossil species known.

Harpa (H. ventricosa, pl. 75, fig. 119) is a genus of finely formed ribbed shells of brilliant colors, and a polished exterior. The foot is very large, and without an operculum. Ten species are described in Lamarck. The genus occurs fossil in the Paris basin.

Cassidaria (C. echinophora, pl. 75, fig. 121). This genus contains a few recent and fossil species. The animal is like that of Cassis, in which the foot is longer than the shell, the head proboscidiform, with a projecting rostrum and mouth from its extremity.

Fusus is a genus of marine shells, thickest in the middle, and tapering towards both ends; the animal with a small head, ending in two short tentacles, the eyes at their external base, but not upon a peduncle or thickening of the tentacle, thus differing from Murex and Purpura, but allied to Turbinella and Fasciolaria. The head has a terminal slit, whence the rostrum issues, and the nucleus of the operculum is terminal.

Fam. 8. Strombidæ. In this family the right margin of the aperture is dilated, corresponding to the width of the mantle, but this character is not present in the immature shells, so that a young Strombus (pl. 75, fig. 114) might be mistaken for a Conus (pl. 76, fig. 11). The head is proboscidiform, with a vertical slit from which a long rostrum is extended; the tentacles are large, divided at the end, and the truncated extremity of the larger external branch bears the large eyes, which have a variously colored iris and a cornea, which have not been observed in any of the allied families. They live on coral banks at no great depth, and some species attain to a considerable size. The locomotion differs from that of most gastropoda, being effected by leaping, for which purpose the operculum (which has a peculiar shape) is applied to the ground. Strombus lentiginosus (pl. 75, fig. 114). S. gigas of the Antilles is eight or ten inches long, and remarkable for the fine peach blossom tint of the aperture. The shell is used to ornament grottoes and gardens, and by sawing off the apex it is converted into a rude trumpet. Pterocera (P. chiragra, pl. 75, fig. 115) differs from Strombus in having the adult shell digitated, and the structure of the mantle corresponding with it. Rostellaria (R. rectirostris, fig. 116).

Fam. 9. Conidæ. The shell of the germs Conus (pl. 76, figs. 8–12) is obconical, involute, and has a short spire and a narrow aperture as long as the body whirl; and the exterior is covered with a periostraca. The genus includes many beautiful and highly prized species. Linnseus described 35 species, Bruguières 146, Lamarck 181, increased to 219 in the last edition of 1845, exclusive of 23 European fossil species. At present there are probably 300 recent species known. The head is proboscidiform, the eyes are upon the middle of the tentacles, the foot is long and very narrow, having a corneous sub-spiral operculum, so small in comparison with the aperture, that it cannot serve to close the shell. The mantle is scanty (in which it differs from the next family), and prolonged in a siphon, which extends a little beyond the shell. The animal is carnivorous, and the tongue is armed with hooked teeth.

Fam. 10. Cypræidæ (or Involuta). In this family there is neither operculum nor periostraca, the shell is rolled upon itself nearly as in Conus, but some are rolled upon a cylindrical instead of a conical axis, so that there is no spire exposed. The shells are very beautiful and highly polished, the mantle being so wide that its sides can be turned over the back of the shell, where it secretes the ornamental layer of the shell. The point of union of the margins of the mantle is often indicated by a discolored line upon the back of the shell.

Cypræa (C. moneta, pl. 76, fig. 5; C. mauritiana, fig. 6; C. arabica, fig. 7), has the mantle edged with tentacular filaments, and when they are turned over the back, the shell is hidden. The aperture is long and narrow, each side denticulated, and the external margin turned in. C. moneta is used as money in western Africa.

Ovula (O. ovum, pl. 76, fig. 4; O. volva, fig. 2), as the name indicates, is shaped somewhat like an egg, with the ends attenuated, and the inner margin of the aperture without denticulations. The animal resembles that of Cypræa.

Oliva (O. ispidula, pl. 75, fig. 122; O. porphyria, fig. 125; O. maura, fig. 126) has the head very small, and the tentacles united at the base. These resemble somewhat the same organs in Strombus, being divided, and having a terminal eye upon one of the branches. O. porphyria is the largest and handsomest species of the genus, being four or more inches long, of a pale brownish purple, marked with numerous zigzag angular lines, and having the anterior extremity violet. It inhabits the coast of South America.

Fam. 11. Volutidæ. In this carnivorous family there are usually distinct folds upon the columella. Voluta is a genus of large and handsome, generally inoperculate shells, with a wide aperture notched in front, and the apex rounded. A part of the shell has sometimes the appearance of being varnished, which indicates the extent to which it is covered by the mantle. The animal cannot entirely enter the shell, the head is proboscidiform, and the tentacles are short, with the eyes at their external base.

Mitra (M. episcopalis, pl. 75, fig. 123; M. papalis, fig. 124) is a genus of handsome shells extremely rich in species, there being about 250 recent and 100 fossil species known. The animal is very dull in its movements, the head small and V-shaped, on account of the projection of the slender tentacles. These have the eyes upon an external peduncle. In Mitra episcopalis (shell white with red spots), the rostrum is once and a half times the length of the shell, exceeding that of any other genus. This enables it to attack its prey at some distance.

Terebra (T. maculata, pl. 75, fig. 117) has the foot (which bears an operculum) but little longer than the last whirl of the shell, a proboscidiform head, tentacles and eyes in the usual form, and the siphon projecting beyond the shell. There are upwards of a hundred recent species known.

Fam. 12. Sigaretidæ. Sigaretus (S. haliotideus, pl. 75, fig. 89) is a genus in which the shell is somewhat ear-shaped, and the foot very large and thick, nearly hiding the shell, which is sunk into it. The tentacles are flat and triangular, but unaccompanied by eyes. Although the animal is too large to enter the shell, it is provided with an operculum. Natica (N. canrena, pl. 75, fig. 88) is carnivorous like the preceding genus, and like it, has no siphon. It has a large foot (four or five times the length of the shell) bearing an operculum. The head is terminated by a pair of lips from which a rostrum can be protruded.

Order 11. Pneumonobranchia. This order includes all the spirivalve and naked mollsca, whether inhabiting land or water, in which the branchiæ, without being proper lungs, are adapted for breathing air, so that the species which inhabit the water are obliged to come to the surface from time to time to breathe air. They seem all to be phytophagous. The order includes eight families.

Fam. 1. Ampullariidæ. The genus Ampullaria has a globular shell several inches in size, which is generally covered with a green periostraca, and is provided with a closely fitting concentric operculum, which is in some cases corneous, and in others shelly. With Paludina and Valvata it forms one of Lamarck’s families, named Peristomata by Reeve. The North American species is figured with the animal in the monograph already quoted. The head is proboscidiform, the extremity cleft, leaving a conical branch half an inch long on each side, and these are used as palpi. The mouth is purse-shaped, the tentacles slender, tapering, and more than an inch long, the eyes borne upon a secondary tubercle at the base externally. The shell is without a notch, yet there is a siphon an inch long which is formed by an extension of the mantle folded into a tube. This is brought to the surface of the water and air drawn through it, and often expelled from it in bubbles when beneath the surface. Guilding describes a shorter siphon upon the right side. The animal lives in the rice swamps of Georgia, feeding upon living plants. Living mostly in the intertropical regions of both hemispheres, where the waters frequently disappear in the dry season, Ampullaria has the power of becoming torpid beneath the mud until the return of the wet season. Some specimens sent from Egypt to France were thrown into water to clean them, and the next day they were found moving about. Deshayes dissected some of these, and found pectinated branchiæ, which would place the genus near Paludina, and he describes a large cavity, to which he assigns the function of holding a store of water to be supplied to the branchiæ during the period of torpidity. This may be correct; although a further examination will probably show that this cavity is adapted to breathe air, and on this account we place it in the present order. Planorbis bicarinatus (and probably its entire family) hybernates at the bottom of streams with the air cavity filled. The ability to breathe air and water by means of distinct organs is not anomalous, as it appears in certain reptiles. The sexes are separate.

Fam. 2. Amphibolidæ. The genus Amphibola (also named Ampullacera) has a sub-spiral corneous operculum, and is formed upon a New Zealand shell formerly considered to be an Ampullaria. It was found to breathe air by Quoy and Gaimard, who found it abundantly in very shallow brackish water. It has a large head ending in two lobes, is without tentacles, and the eyes are placed flat upon the head. The pulmonary cavity is large, in which it resembles that of Ampullaria. The sexes are united in the same individual. Two species are known, A. avellana and A.fragilis.

Fam. 3. Cydostomidæ. The genus Cyolostoma is monoicous; it has a turbinated shell with a circular aperture, and, unlike most land snails, it has a pancispiral operculum. The head is proboscidiform, the tentacles two, with the eyes at their external base; and the foot is composed of two longitudinal parts which are advanced alternately. Other species have a concentric operculum, and in these the foot has the ordinary construction. Cuvier and Deshayes consider the mode of respiration less important than the general structure, and they are consequently of the opinion that the affinities of this family are with the Trochidse. The species are numerous, amounting to nearly 200.

Helicina may be considered the type of a sub-family. It has an oblique aperture, and a closely fitting operculum which is not sub-spiral, but increases from one of the sides or angles.

Fam. 4. Physidæ. This family is composed of certain genera of inoperculate fragile uniformly colored shells, inhabiting quiet fresh waters, coming to the surface to breathe, and creeping along it with the back downwards by means of the vibrillæ which cover the foot as well as the two tentacles and other parts. Many eggs are deposited together in a glairy mass. The breathing aperture is at the external side, and is opened from time to time to take in a supply of air. In Physa the shell is turbinated, sinistral, the mantle large, with a digitated margin turned npon the shell, and the foot long and pointed posteriorly. The tentacles are filiform, and the eyes are situated upon the head near their internal base. Planorbis (pl. 77, fig. 99) has a discoidal shell, with the turns visible on both sides. The mantle is simple, the foot rather small, and the tentacles and eyes as in Physa. In Limnea (L. stagnalis, pl. 75, fig. 92), the shell is dextral, turbinated, and generally larger than in the allied genera; the tentacles are triangular, and the eyes situated at their anterior base. Ancylus is a genus of little patelliform shells, the position of which in the systems has been a subject of much dispute, some contending that they belong here, and others to the Hypobranchia. The animal is not essentially different from Limnea, and it is possible that some species breathe air, and others water. Some authors have asserted that they come to the surface to breathe air, but this has never been observed in the American species, some of which are found beneath stones, in dead bivalve shells, and under other circumstances, which would render it difficult for them to reach the surface and descend again. But as free air may not be considered necessary to these animals, they may be placed among the Physadse, especially as a species of Physa inhabiting beneath shelving rocks in rapid water is found at the mouth of the Nolachucky river, Tennessee, in such a position that it could not breathe air. It is probable that a small variety of Physa heterostropha inhabiting springs seldom or never breathes air. It has been ascertained that frogs kept under water can oxygenate the system through the skin, and the Physadæ may have the same power. The passage to the next family seems to be through Gray’s genus Chilina, which is a Limnea with folds upon the columella.

Fam. 6. Auriculidæ. In this monoicous family there are two tentacles, and the eyes are at their external and posterior base. Some species inhabit land, and others plants near the sea, and salt water marshes. Auricula midæ (pl. 76, fig. 1) is the largest species of the genus, being four inches long, and of a solid texture.

Fam. 7. Helicidæ. This family includes most of the numerous species of land snails with an external spiri valve shell. All breathe free air, are monoicous and inoperculate, and have two large tentacles, with an eye upon the apex, capable of being retracted by being turned within itself. Besides these, there is an inferior and smaller pair of tentacles present in most cases, although in some of the minute species they have not been detected. Most of the land shells of Europe and North America belong to Helix, a very extensive genus, containing upwards of 500 species from, various parts of the globe, including the islands of the Pacific, all the continents, high mountains, and cold climates, although the larger species are intertropical. They vary in size from about a tenth of an inch to four inches. The shells vary much in form; the aperture is sometimes reduced to a narrow fissure, or armed with teeth, in such a manner as to lead one to think it impossible for the animal to get out or in. They hybernate under ground, closing the aperture with a temporary operculum. Among the genera may be mentioned Bulimus (pl. 75, figs. 93, 94), Clausilia (fig. 100), which has a peculiar operculum attached to the shell within the aperture, Pupa, Streptaxis, &c. Their food is fresh or decaying vegetable matter, and some feed upon fungi. The large European species are cooked and eaten, and the Romans fattened them for the table.

Fam. 8. Limacidæ. This family includes the naked snails without a turbinated shell, but some of them have an internal shell, or a small external one which is little more than an appendage. The head, tentacles, organization, habits, and food, do not differ essentially from those of the preceding family. The genus Limax (pl. 77, figs. 19–21) is destructive to the plants cultivated by the farmer and gardener in Europe, and new modes of destroying them are continually sought after. The species which occur in North America have not yet proved injurious, and the same remark applies to the snails, which are troublesome to gardeners in Europe. The body of Limax is very contractile, but when moving on its lower surface or foot, it is rather slender, thickest in the middle, and tapering towards the extremity. Upon the back is a kind of fleshy shield, beneath which the head can be drawn.

Class 3. Cephalopoda

This class was named Malakia by Aristotle, and Mollia by Pliny. It includes certain dioicous marine mollusca, which have the feet or arms around the mouth at the extremity of the head. The body is soft, the mantle closed beneath according to most authors, but above according to Eang. Most of them have three hearts. The mouth is armed with strong mandibles much like those of a parrot, adapted for crushing the shells of Crustacea and mollusca, and the tongue is armed with pointed horny teeth. The eyes are either pedunculated or level with the surface, and they have the sense of vision fully developed. They have also an organ of hearing. The arms are usually cotyligerous, or studded with suckers like cupping glasses, which enable them to hold fish and other living prey. The Greeks, in naming these sucking cups, made use of the word kotylus (in composition), whence the English name cuttle-fish is derived. The cotyls are sometimes armed within with curved hooks, which assist in holding and destroying the prey. Onychoteuthis has a pair of arms much longer than the rest, the terminal expansion of which is studded with rows of hooks, but the power is increased by a simple sucker on each wrist (as it may be called), which are applied together to keep the extremities of the arms in contact.

There is a fleshy infundibulum or funnel opening before the neck, and serving as an outlet for the fæces and water from the branchiæ. The water ejected from the branchial sac through the funnel is a principal agent in locomotion, by means of which the animal can move backwards with great swiftness. Inspiration and expiration are regular in these animals. “The first is effected,” says Dr. Coldstream, “by a gradual dilatation of the sac in every direction, but particularly at the sides, accompanied by a subsidence of the lateral valves, collapse of the walls of the funnel, and a rush of water through the lateral openings into the sac. Inspiration being completed, the lateral valves are closed, the sac is gradually contracted, the funnel erected and dilated, and the water expelled through it with great force in a continuous stream.” An Octopus with a sac four inches long was found to respire ten times in a minute.

The Cephalopoda are either naked, or provided with an external shell. Some of the former are brilliantly colored, red, purple, or bluish, and they are remarkable for the rapidity and extent to which the colors change. In habits they are rapacious and active, moving continually, and some of them shoot through the water like an arrow.

Agassiz thinks that in this order the Nautilidæ are the lowest, and Sepiadæ the highest. We will here follow the classification of D’Orbigny, according to which the class is divided into two orders, Acetabulifera and Tentaculifera, the former being subdivided into two tribes, Octopoda and Decapoda,⁷ containing seven families conjointly. As the name implies, the Acetabulifera are provided with cotyls, and the head is distinct, characters which do not exist in the Tentaculifera; and the former have two, and the latter four branchiæ, whence Owen’s names of Dibranchiata and Tetrabranchiata.

Tribe Octocera

Fam. 1. Octopidæ. The genus Octopus (O. octopodius, Linn. (Sepia) pl. 76, fig. 75) is the polypus of the ancients, whence the French name poulpe is derived. The body is obtuse posteriorly, with fins (fin-like expansions), and the interior dorsal shell is wanting. As the name implies, it has eight arms. The species figured attains a length of two feet and a half, including the arms, which constitute considerably the longest portion. It creeps upon the ground with the mouth downwards, drawing itself along by means of the circle of arms; or leaving the bottom, it swims backwards by flapping the fleshy disk from which the arms arise. It is provided with an ink bag. The eyes can be covered with the surrounding skin, in the manner of an eyelid. There are two complicated branchijie somewhat like a fern leaf, through which the blood is forced, by a heart at the base of each; a third heart, near the bottom of the cavity, receives the oxygenated blood, and distributes it through the body. It is eaten on the shores of the Mediterranean.

Argonauta (A. argo, Linn., pl. 76, fig. 17), six or seven inches long, has a closely rolled involuted shell without partitions, laterally compressed, tuberculate, very thin, white, translucent, with the last turn including the rest. This is the Nautilus of the ancient authors, who were acquainted with A. argo, the Mediterranean species, about the sailing of which so many fables have been related, as in the following lines from the “Pelican Island.”

“Light as a flake of foam upon the wind,
Keel upwards from the deep emerged a shell,
Shaped like the moon ere half her horn is filled;
Fraught with young life, it righted as it rose,
And moved at will along the yielding water.
The native pilot of this little bark,
Put out a tier of oars on either side,
Spread to the wafting breeze a twofold sail.
And mounted up and glided down the billow
In happy freedom, pleased to feel the air,
And wander in the luxury of light.”

For a long time naturalists considered the maker of the shell of Argonauta to be unknown, believing the inhabitant found in it to be a parasite, like the crabs which take possession of the empty shells of the spirivalve mollusca; and they were led to this belief, by the fact that there is no muscular attachment between the animal and the shell, presenting a peculiarity which is unique among the mollusca. The animal has eight arms, two of which have wide expansions at the extremity, which are applied one to each side of the shell, which is in fact secreted by their internal surface; and should it be intentionally broken, the damage is repaired by the same organs in ten or twelve days, a proof that the shell belongs to no other animal. It creeps upon the bottom with the shell above, or shoots through the water backwards by means of the funnel, with the narrow part of the shell in advance, and the arms extended like a rudder. When it retires within the shell, the expansions of the clasping arms are partly withdrawn, leaving a little of the anterior portion of the shell uncovered; consequently, they are never extended as sails, as many fabulous accounts would lead us to believe. See the Mag. Nat. Hist., 1839, pp. 421 and 521; 1840, pp. 8 and 57.

Tribe Decacera

Fam. 2. Sepiidæ. Sepia (pl. 76, fig. 77) has the body surrounded by a narrow fin; and of the ten arms, two are pedunculated and longer than the rest. A light friable oblong-oval and spongy shell, usually named “cuttle-bone,” is contained within the back. The contents of the ink-bag in this animal are dried and used by painters under the name of sepia.

Fam. 3. Loligidæ. Loligo (L. loligo, Linn., pl. 76, fig. 76) has the body slender, with lateral fins, the shell thin, horny, and translucent two pedunculated arms longer than the rest, and the eyes are without a lid, but covered with a transparent membrane. Its motion backwards through the water by means of its funnel, is extremely rapid, and it sometimes throws itself out of the water, or upon land. The species are much used for food, especially in China.

Fam. 4. Loligopsidæ. Loligopsis has a slow motion, the shell is corneous, the body slender and translucent, and has few muscles.

Fam. 5. Teuthididæ. Onychoteuthis (already referred to) has a corneous internal shell, a slender body, with a triangular fin upon each side posteriorly, uniting upon the back.

Fam. 6. Belemnitidæ. Shell corneous, conical, largest anteriorly, and containing a series of chambers, posteriorly pierced by a siphuncle, and inserted in a hard case or belemnon. which is generally pointed posteriorly. The family is extinct, but its remains are abundant in a fossil state in the oolitic and cretaceous formations.

Fam. 7. Spirulidæ. The genus Spirula (S. spirula, pl. 76, fig. 13) is the only one in the family, and until recently it contained but a single described species. The shell is a thin open spiral (not twisted longitudinally as represented in the figure), with numerous partitions concave externally, through which a small ventral siphuncle runs. The shell is internal, at the posterior extremity of the body. There are ten arms, of which two are larger than the rest. The common species inhabits the Atlantic and Pacific Oceans, and although the shell is common, the animal is very rare, and requires further examination.

The second order, Tentaculifiera, contains two families: Nautilidæ, and Ammonitidæ.

Fam. 1. Nautilidæ. In the genus Nautilus (N. pompilius, Linn., pl. 76, fig. 16), the shell is spiral, many-chambered, the partitions transverse, concave externally, their margins simple; a central siphuncle passing through them; the whirls in contact, the last enveloping the preceding ones. Nautilus pompilius is the best known species; the shell is nacreous, ornamented with irregular reddish bands, the umbilicus closed. It is six or eight inches in diameter, and inhabits the Indian and Pacific Oceans. A second species is known, N. umhilicatus, which is much rarer than the former, and has the centre of each side widely umbilicate, so that the whirls can be counted. The history of the order is taken from N. pompilius. The animal is contained in the last open chamber of the shell; it has a pediform appendage for creeping, and when it walks upon the bottom, the aperture is downwards. The jaws are like a reversed parrot bill, the mouth is surrounded with numerous tentacles retractile into separate sheaths, and disposed in eight groups corresponding to the arms of Octopus. They are surrounded by a kind of hood, which serves to protect the animal when withdrawn into the shell. The two eyes are large and prominent, the heart single, with a ventricle and auricle, and inclosed in a large pericardium which is connected with the siphuncle. The siphon or funnel, which is ventral, corresponds to the part of the shell furthest from the centre, that is, the external lip. The fossils named rhyncholites, are the beaks of various species of Nautilus and Ammonites. Several other genera, with the shell both curved and straight, belong to this family, and among the latter is the fossil genus Orthoceras, of Breyn (not of Lamarck), of the older formations.

Fam. 2. Ammonitidæ (pl. 76, figs. 14, 15). In this family the shell is spiral in the same plane, curved, or straight, with the siphuncle at the dorsal margin. The partitions which divide its chambers are irregular, with the margins digitated or foliated, often in a singular and beautiful manner. All the species are extinct, and they are found from the older fossiliferous formations to the cretaceous strata. This and the preceding family are represented at the present day by the two living species of Nautilus, and four of Spirula, a mere remnant of the profusion of species of chambered shells which lived in the ancient seas. Upwards of 300 species of the genus Ammonites have been described or indicated; and although it is probable that many of these belong to varieties and young individuals, with every allowance, the genus is very extensive.

Division III. Articulata

The Articulata are named from having the various parts of the body and limbs articulated to each other. The nervous system is composed of ganglions united by a double cord, and there is usually a kind of exterior skeleton composed of a series of rings protecting the interior parts, and serving as points of attachment for muscles. In some cases respiration is effected by means of branchiæ, and in others by tracheae or air tubes. When limbs are present, there are never fewer than six.

Authors upon the Articulata are not agreed upon the number and extent of the classes into which they should be distributed, but they will be treated of in detail, nearly as they are given in pages 11, 12, according to which the classes are five, namely 1, Annelida; 2, Cirrhopoda; 3, Crustacea; 4, Arachnida; 5, Insecta. The three last of these formed the Insecta of Linnæus, a term which some modern writers wish to maintain according to its original extent; and when this is done, the restricted class of insects must have a distinct name; as Ptilota (winged insects), applied by Aristotle, and Condyloma, applied by Latreille. The Myriapoda will form the fifth, and the Insecta the sixth class, in the succeeding pages.

Class 1. Annelida

The Annelida or Chætopoda are generally recognisable by a soft body, a lengthened annulated form, red blood, and the nervous system central, ganglionic, and distinct. The rings of the body are of a membranous consistency, and never corneous as in insects, or calcareous as in the Crustacea. They are generally numerous, the length of the animal depending to some extent upon the number of rings, which vary from twenty or thirty to more than five hundred. When very numerous, the number is not uniform in the same species. The head is usually distinct, and often provided with two or four eyes, and in some cases with a variable number of tentacles and cirri, but the last are not confined to the head. The sides are generally furnished with bunches of bristles and fleshy projections arranged in a line and used in locomotion; and although they are called feet, articulate limbs are never present. The lateral bristles in some cases afford a means of defence, and they vary much in character, some being simple, and others barbed in a variety of ways, presenting uniform characters which are useful in classification, and must be studied by those who wish to be well acquainted with the class. Their forms have been classified and named by Savigny. The alimentary canal is complete, extending from end to end. Most of the annelida are marine, some being free, whilst others construct a tube of calcareous matter, and of agglutinated particles of sand, fragments of shells, or other objects. Cuvier divides the class into three orders, named Abranchia, Dorsibranchia, and Tubicolæ; but as the names of orders should be taken from the same part, the last one is here replaced by the term Cephalobranchia.⁸

Order 1. Abranchia. The animals of this order are without branchiæ, respiration being effected by means of the skin. Cuvier supposed certain lateral pores to be respiratory orifices, but these have been ascertained to be the outlets of the organs which supply the mucus. The order includes the four families: Hirudinidæ (leeches); Lumbricidæ (earth-worms); Echiuri; and Maldaniæ.

Fam. 1. Hirudinidæ. This family includes the worms known as leeches, of which there are various genera, both marine and freshwater. The body is slimy and extensible, narrowing towards each end, composed of from 18 to 140 segments. Some species are cylindrical, and others flattened, and the posterior extremity has a disciform sucker to enable the animal to adhere. In some cases the mouth is surrounded with a sucker also, and in these, besides swimming, locomotion is effected by extending the body, fastening the anterior extremity, and then drawing up the posterior one. The eye-like points vary in number from two to ten. The species feed upon blood or the juices of animal matter. Some have teeth to puncture the integument, but others, not being thus armed, attack only the softer kinds of food, as worms, larvae, or mollusca; and some swallow worms entire.

A species of leech finds its way under the eyelids, and into the nasal passages of Ardea virescens, in Martinique. In Algeria, Hæmopis vorax is abundant, and attacks man and animals upon land; and it is found sticking to the inside of the mouth and throat of slaughtered cattle in that country. According to Baron Larrey, the French soldiers were much plagued by a small species which attached itself to the entrance of the throat. The same species was found in the nasal passages of the horse.

As it is difficult for a leech to affix itself to an animal, except at rare intervals, it has been provided with peculiar digestive organs to enable it to undergo a long fast. The stomach is formed of a number of cells, each of which has a lateral sac upon each side. The entrance from the stomach to the intestine has a valve, and at the posterior extremity, of the intestine there is a sphincter to close it, so that the food may be admitted and retained in small portions as it is required, and it is a remarkable fact, that the blood thus kept in store (which may amount to nearly half an ounce) retains its natural properties for many months. Hence the difficulty of employing leeches in medicine when they have been gorged within some months. This difficulty is obyiated in some degree, by forcing them to disgorge a part of the blood by pressure, and a mode has been discovered by piercing them with a lancet one third the length from the head, and placing them in tepid water, when the contents of the stomach will escape, especially if assisted by pressure. The wound heals in a few days, and the leech may be applied again in fifteen or eighteen days.

These animals are monoicous and oviparous, the eggs being deposited in a kind of cocoon, resembling in size and form that of the silkworm, its material resembling fine sponge. A Swedish species deposits its eggs in the earth at some distance from the water.

Among the genera are Hirudo (H. officinalis, pl. 77, fig. 26), Malacobdella (M. grossa, fig. 22), referred to in page 43; Clepsina (fig. 24), Hæmopis (H. vorax, fig. 25). Two species of leech are almost exclusively used in medicine: Hirudo officinalis, the green or Hungarian leech, the belly of which is without spots; and H. medicinalis, the German or brown leech, with a spotted belly.

The mouth of those leeches which are capable of biting, is tri-radiated, each ray having a tooth which resembles a segment of a minute circular saw, the margin of which is armed with a double row of microscopic denticulations. The suction, whilst it draws the skin within the reach of the teeth, renders it tense, so that they act like lancets, and the apparatus answers the double purpose of a small scarificator and cupping-glass. An examination of the wound made by a leech will show the tri-radiated arrangement of the teeth. Artificial leeches are sometimes made use of, the quality of which must greatly depend upon the accuracy with which the natural instrument is imitated.

Three species of Hirudo, and one of Clepsina, have been described from the waters of the United States.

It was at one time believed that changes in the weather might be foretold from the actions of leeches, but the value of these indications was much overrated. They have been made to fast two or three years; they require five years to become large enough for use, and they may live twenty years. They seem not to multiply rapidly when they have not access to blood; and on this account, cows and horses are driven into the breeding ponds, and so frequently, that they become emaciated from the loss of blood. Three millions of leeches are used annually in Paris; and four dealers in London import upwards of seven millions annually. In 1819, five or six millions were used in Paris, at a cost of 120,000 francs; and in 1827, thirty-three millions were required in France. To preserve them in health, they must have clay, sticks, &c., to crawl amongst, to assist them in casting the skin, this part being often renewed; and if the old surface is not removed, respiration is interfered with.

Gervais, who insists upon the identity of the Annelida and Entozoa, places the family which includes Sipunculus (p. 42) next to the Hirudinidæ

Fam. 2. Lumbricidæ. The genus Lumbricus (pl. 77, figs. 38, 44) contains the earth-worms, known by their habits of living in the earth, and coming to the surface in wet weather and at night. The body is reddish or bluish, cylindrical, composed of many rings, the head indistinct, the mouth without teeth, and having neither eyes nor tentacles. The segments are provided beneath with minute bristles, and above with one or two pores. At certain periods, in some of the species, the part of the body containing the reproductive organs has a broad collar named the clitellum.

These worms are monoicous, they feed upon the organic matter contained in the soil, generally ejecting the indigestible portion at the surface of. the ground. Some species live in the soft mud at the bottom of streams, and the ordinary species may be kept in vessels of mud and water. The largest European species is a foot and a half long, but there are several exotic species several feet in length.

Earth-worms are very useful to the soil, as their perforations open it and allow the air and moisture to penetrate. They also assist in ameliorating it, and in increasing its depth; and where they are abundant, it is probable that every inch of soil has passed through their digestive system. In old unploughed pastures the soil formed by their castings is known to have amounted to an inch in depth in live years.

Nais (pl. 77, figs. 9, 10), which belongs to this family, has the segments with lateral spines or fascicles. The old genus thus named by Miiller, has been subdivided by more recent writers. They inhabit the fresh waters.

Tubifex is a genus of microscopic worms found in fresh water, where they form a tube in the mud, whence they project the greater part of the body, waving it about, but instantly withdrawing when disturbed. Several species of the United States have been described.

Fam. 3. Echiuri. These have been alluded to in page 42. The body is short, composed of but few indistinct articulations, cylindrical, sacciform, provided with pairs of retractile bristles upon some of the segments. Thalassema echiurus, of the European seas, is the best known species.

Fam. 4. Maldaniæ. This is one of the families of the distinguished naturalist Savigny, who accompanied the French expedition to Egypt. In the genus Clymene, the body is long and cylindrical, the extremities abrupt, the segments few and dissimilar, the head distinct, the thoracic portion long, and the abdomen short. The thoracic feet have two branches. It forms a tube with small shells and sand.

Order 2. Dorsibranchia. Here the organs of motion, and especially those of respiration, are arranged in linear series, either from end to end, or at the middle portion of the body. The head and eyes are usually distinct, and there are antennæ, jaws, and an extensible rostrum. The families are arranged by Audouin and Milne Edwards as follows: 1, Aphroditidæ; 2, Amphinomidæ; 3, Eunicidæ; 4, Nereidæ; 5. Ariciidæ; 6. Peripatidæ; 7, Chætopteridæ; 8, Arenicolidæ.

Fam. 1. Aphromitidæ. Body generally depressed, and shorter and wider than in the other annelida. Back with two rows of large membranaceous scales or elytra (except in the genus Palmyra), beneath which are the branchiæ, which are not well developed. Two pairs of jaws are generally present, and the elytra and superior cirri are alternately present and absent upon the segments to a certain extent. Aphrodite has thirteen pairs of elytra, three antennæ. The jaws are cartilaginous or rudimentary. Several species rival the humming birds in the brilliancy and play of their colors. A. aculeata (pl. 77, fig. 15), of the European seas, attains a length of six inches, and the dorsal scales are hidden by a hairy covering.

Fam. 2. Amphinomidæ, Segments similar, branchæ ramose, tufted, or plumose, well developed, dorsal, or at the base of the feet; head distinct, mouth unarmed, no aciculi, feet with one or two branches.

Fam. 3. Eunicidæ. The rostrum has from seven to nine corneous jaws; branchiæ wanting or well developed, in the form of pectinated filaments: feet aciculate. Eunice has two eyes, seven strong jaws, four upon the left and three upon the right side; five large tentacles above the mouth, and two smaller ones at the nape; branchiæ pectinated upon one side of the supporting branch. The body is long and sub-cylindrical, the segments sometimes numbering four hundred. This genus contains the largest species of annelida known, E. gigantea of the Antilles, which is four feet or more in length.

Fam. 4. Nereidæ. In this family the jaws are either absent, or amounting to two or four; the rostrum extends considerably beyond the head; antennæ mostly well developed. Nereis is a genus of worms found upon the coast, moving about freely, or hidden in the cavities of rocks, or in dead shells; and sometimes sunk in the mud. Like many other annelida, it is used by fishermen as bait. Some are of a considerable size, and the colors are often agreeable. Phyllodoce (pl. 77, fig. 11) belongs to this family. The place of Spio filicornis (fig. 14), which has two very long antennæ, is not ascertained.

Fam. 5. Ariciidæ. Head and rostrum distinct; antennæ, eyes, and branchiæ wanting, or rudimentary; jaws and tentacular cirri absent; each foot with a single cirrus.

Fam. 6. Peripatidæ. This family contains the single genus Peripatus, of Guilding, who observed it in the West Indies, and described it as a mollusc. The body is somewhat limaciform, both ends obtuse, the annulations not very distinct, each side margined with a row of short, thick, conical and granlilar feet, decreasing in size from the middle of the body towards each end, and having short bristles at their extremity; no cirri, gills, nor similar appendages. The head is distinct, with two stout annulate antennæ, and the mouth has a pair of corneous jaws. Peripatus juliformis of Guilding, from which the characters are taken, is three inches long, dark brown, annulated with yellow, the dorsal line black; and it has thirty feet on each side. Lacordaire found a specimen in Cayenne, sunk in the mud at the margin of a river, and Goudot found another species near Table Mountain in South Africa, under a stone in a shady place. The nervous system differs from that of the other annelida in being bilateral (somewhat as in Malacobdella); and on this account, Gervais is of opinion that it forms the type of a distinct grou23 of worms, whilst Milne Edwards, who discovered this peculiarity, considers it as indicating a passage to Nemertes. See Kirby’s Bridgewater Treatise, p. 259, pl. 8, fig. 1, 2.

Fam. 7. Chætopteridæ. The genus Chætopterus was formed by Cuvier for a worm from the Antilles, eight or ten inches long, inhabiting a tube of a parchment-like consistence, whence its name Ch. pergamentacerus. There are neither rostrum, jaws, nor a proper head. There is a lip with two rudimentary antennæ, followed by a disk with eight or nine pair of feet, succeeded on each side by a wing-like projection, bearing bristles. The branchiæ are medial, and in the form of laminæ; posterior extremity with numerous lateral feet.

Fam. 8. Arenicolidæ. In Arenicola the body is cylindrical, composed of a moderate number of segments subdivided by numerous wrinkles. The head is rudimentary, with a small terminal rostrum; no jaws, eyes, antennæ, nor cirri. The feet have two branches, and are armed with simple and armed bristles; branchiæ in bunches divided like the branches of a tree, and arranged in pairs along the middle portion of the body, numbering from thirteen to twenty pair. They burrow in the sand about low water mark, and are extensively used by fishermen as a favorite bait for marine fish. A. piscatorum is eight or ten inches long.

Order 3. Cephalobranchia (or Tubicola). These sedentary annelida live in calcareous, sandy, or membranaceous tubes; the soft appendages are generally confined to the anterior extremity; the head is indistinct, without eyes, rostrum, or jaws; the branchiæ are plumose, and situated at the anterior extremity (pl. 75, fig. 68). They comprise the two families Serpulidæ and Amphitritidæ. The former is distinguished from the latter by having the branchial plumes separated into two masses by a pedunculated operculum, or covered by a solid one when withdrawn within the shell.

Fam. 1. Serpulidæ. The genus Serpula (pl. 75, fig. 70) has the body tapering posteriorly, the mouth terminal, and surrounded with a crown of long, feathery, and often finely colored branchiæ, which give the animal the appearance of a zoophyte. These are used in taking the small living objects upon which they feed. The feet are lateral, the seven anterior pair attached to a membranous base. The part bearing these feet forms a kind of thorax distinguishable from the remaining part of the body. From the internal base of each of the two masses of branchiæ a filament arises, one of which has its extremity enlarged into an operculum for closing the aperture. The tubes which these animals secrete are calcareous, and twisted in a very irregular manner. They are affixed to submarine bodies, either singly, or a great many in a single mass. The tubes are common in the tertiary and secondary formations.

Fam. 2. Amphitritidæ. In this family the indistinct head is composed of three segments, the thorax of not less than twelve, and the abdomen of a great many. The mouth has numerous prehensile tentacular filaments, and the tube is formed out of a mucous secretion to which extraneous objects, such as fragments of shells, are affixed. They live singly or aggregated. Amphitrite (pl. 77, fig. 13), Sabella (pl. 75, fig. 68), Terebella (pl. 76, fig. 82). The genus Hermella resembles the Dorsibranchia in having the branchiæ dorsal; the cephalic appendages not being branchiæ but tentacles, according to Milne Edwards.

Class 2. Cirrhopoda

The animals of this class are monoicous, inclosed in a hard shell or subgelatinous envelope, deprived of locomotive powers, and affixed to extraneous submarine bodies, some by a peduncle (pl. 76, figs. 51, 52), and others by their base (figs. 53, 54). The earlier authors placed these animals with the Mollusca, and the shells are often retained in conchological cabinets. Their articulated cirrhi and double nervous axis indicate their true nature; and whilst they have been made a distinct class from the Crustacea, partly on account of the supposed absence of an articulate structure, Dr. St. Ange affirms that evident traces of such a structure exist.

These animals undergo a metamorphosis, the young being bivalvular like bivalve mollusca, and capable of swimming about freely for some time before it affixes itself permanently. In this condition the limbs can be protruded from the front of the shell; the anterior pair being large, and provided with a sucker and hooks for attachment to submarine bodies. The six posterior pairs are used in swimming. The animal, at this period, bears considerable resemblance to the small branchiopoda. Mr. Thompson, of Cork, placed some of them in a vessel of sea water, and in a week’s time two of them had mantled and were affixed to the vessels as barnacles. A few days afterwards, another individual was observed to throw off its shell and affix itself. Both the orders of Cirrhopoda undergo these changes.

The jaws are lateral, articulated, and toothed; the cirrhi are articulated, curved, and arranged along the abdomen, resembling somewhat the members along the lower surface of the tail in the Crustacea. The class contains the two orders Campylosomata and Ac[a]mptosomata, both of which are widely distributed by floating wood, ships, sea-weed, mollusca, whales, turtles, &c.

Order 1. Campylosomata. This order contains the pedunculated flattened forms like Mitella (Oken, 1815; Pollicipes, Leach, 1817, pl. 76, fig. 51), and Lepas (Linn., 1748; Anatifa, Brug., 1792, pl. 76, fig. 52), in which the shell is generally composed of two large lateral triangular basal pieces, followed by two smaller pieces with a fifth dorsal piece. Sometimes there are accessory pieces at the base, and the whole are in some cases so much reduced in size as to be rudimentary like the shell in Chitonellus (p. 81). Sowerby’s genus, Lithotrya occupies holes in rocks; but it is not known whether it forms them, or takes possession of those previously made by boring mollusca.

Order 2. Acamptosomata. In this order the animal is short and conical, without a peduncle, the shell solid and conical, sometimes sub-cylindrical, with the base or attached portion open or closed, the aperture provided with a two-valved or four-valved operculum. Those of the order known to the ancients were named Balanus (pl. 76, fig. 54), on account of their resemblance to an acorn, a name which is still retained. They were a favorite article of food with the ancients. The natives of Chili eat a very large species, Balanus psittacus, which is five and a half inches high by three and a half in diameter; it has much the taste of a crab. The young of this species are attached to the adults, and in turn support their desendants, so that they occur in large masses of fifty or a hundred individuals.

Some genera, as Pyrgoma, are buried in coral; Acasta inhabits sponges; Chelonobia is attached to turtles; and Tubicinella and Coronula (pl. 76, fig. 53) are imbedded in the skin of whales.

Class 3. Crustacea

In this class the sexes are separate; the body and limbs are distinctly articulated; the breathing is by means of gills, or more rarely (in some of the lower forms) by the external surface. The larger forms, as the lobsters and crabs, and the great majority of the smaller ones, inhabit the sea, where they take the place of the insects which are so abundant on land. Some species inhabit the fresh waters, and a few the land. The larger species are many times the bulk of the largest insects, from which they decrease to forms of microscopic size. In some of them the characters of the class are so obscure that they have been placed with the parasitic worms, learned from the hard integument, this afibrds a prominent characteristic, being a calcareous exterior skeleton of considerable thickness and strength in the larger species; becoming more delicate, and often transparent in the smaller ones, to disappear, or to escape observation in some of the obscure forms. This covering is periodically cast ofi" and renewed, like the integuments of certain reptiles, and the larvæ of insects.

In comparing various members of this class (pl. 78), the number of segments, and the consequent ability to bend the body, will be found to be very variable, so that whilst the body of some (figs. 1–9) is a solid box incapable of flexure, that of others is composed of a number of loosely connected segments moving freely, and chiefly downwards from the horizontal position. This allows some of the members of the class to roll themselves into a ball by approximating the head and tail.

The normal number of the segments in the body of the Crustacea is twenty-one, of which seven belong to the head, trunk, and tail, respectively, and when a smaller number appears, it is generally to be attributed to the fusion of several into one. In fig. 22, pl. 78, the head is observed to be distinct, whilst in fig. 1 it forms a single piece with the trunk, the tail being articulated and turned beneath, although partly visible in figs. 3 and 8. In Limulus (fig. 34), the segments of the tail are fused into a single shelly plate, as well as those of the head and trunk or cephalo-thorax, the shield or plate of which is called the carapace.

The moulting of the larger Crustacea takes place about once a year, but Mr. Lyell mentions a species of Cancer covered with oysters six years old, so that the shell could not have been renewed during this period. Young and growing animals moult frequently, as in Daphnia, which may change every two days. Previous to moulting, a crustacean becomes sickly and refuses food, the carapace becomes loosened, and the corium beneath secretes a new, soft, and membranous shell, which finally becomes calcareous. When the old shell has become loosened, the animal, after various exertions, extricates itself from it in about half an hour, withdrawing the antennæ, feet, and even the gills, from an external film. The shell of the limbs splits to allow the large extremity to pass, and it sometimes happens that a limb is left in the old shell. Some of this class have the power of throwing off a limb.

The Crustacea feed mostly upon animal food, which is taken sometimes solid and sometimes in a liquid state, and the oral organs are modified accordingly. Some small species are very destructive to the timber of ships and docks.

In forms like the lobster, swimming is efiected by striking downwards and inwards with the tail, which forces the body in a backward direction. In the branchiopoda the feet are used in swimming, not being adapted to walking; and in the entomostraca (figs. 27, 29), the body is impelled through the water by the feet, in a succession of jerks.

The walking feet of the Crustacea generally amount to ten or fourteen. In some (fig. 1, &c.), the anterior pair are robust, the extremity provided with a movable thumb forming pincers. Sometimes the end of a foot can bend, so as to form a hook; and in other cases the last joint closes upon an extension or enlargement of the preceding joint, forming an organ of prehension.

There are two mandibles, four lower jaws, succeeded by six auxiliary or foot-jaws, followed by the feet; and when there are fourteen feet, the four anterior ones are transformed from the four posterior foot-jaws.

Most of the Crustacea see well, and the eyes are either sessile or placed upon pedicles. Some of the parasitic species are without eyes in their perfect and affixed state, although provided with them when young, and capable of swimming about. As in the insects, both compound eyes and stemmata are found in this class, but the former are the most common. In a few cases both are found together.

There are sufficient reasons to believe that the sense of smelling is present in the Crustacea, although its special organ has not been discovered.

There are four antennæ, of which the second pair is supposed to be connected with the sense of hearing, because there is near the base a cavity filled with a liquid, and receiving a special nerve. It has an exterior orifice closed with a membrane, which may be compared to a tympanum.

The Crustacea are oviparous; and when the young leave the egg, some resemble the adult of the species to which they belong, although most of them undergo a metamorphosis. Mr. J. Y. Thompson, of Cork, discovered an individual of Bosc’s supposed genus Zoea, to be only the young of the common crab; and Jurine had observed the change which the small fresh water species undergo. The young of Lernsea and the allied genera are much like those of Cyclops.

There are two sections of the Crustacea: Entomostraca, in which the number of legs varies; and Malacostraca, in which there are ten or fourteen legs.

Entomostraca

Order 1. Rotatoria (or Rotifera). This order has already been alluded to (pp. 9 and 25) in treating of the Infusoria. It is divided into such as are naked and such as have a shield, and each of these series has three sections according to the arrangement of the vibrillæ. According to Ehrenberg, this order contains fifty-five genera, divided into eight families; but Dujardin reduces the families to five, and the genera to twenty-four. The genus Rotifera (pl. 75, fig. 16) includes species less than half a millimetre long, which live in water, or among damp moss. The mouth and tail are capable of holding, so that the animal can move by attaching each end alternately, as in the leeches. They have also the power of swimming through the water by means of the vibrillæ. When at rest they affix themselves by the tail and bring their food within reach in the currents caused by the vibrillæ. Burmeister, in his work on the Organization of Trilobites, 1843, places the Rotatoria as the lowest of the Crustacea, and next to them the Cirrhopoda, under the belief that the latter do not form a distinct class; and in 1842, J. E. Gray placed the Cirrhopoda here. These animals, and the Rotatoria, are monoicous.

Order 2. Cormostomata. Sexes separate, mouth with a suctorial beak, carapace generally in a single piece, feet adapted for holding, walking, or swimming. Parasitic upon fishes, and undergoing metamorphosis. The order, as given here, includes two of Milne Edwards’s orders, which contain five families conjointly. It includes Baird’s legion Pæcilopoda, which is divided into two orders, five tribes, and eleven families, as given in his Natural History of British Entomostraca, 1850. This order has been named Siphonostoma, but as this designation has been otherwise employed, that of Professor J. D. Dana is adopted. This author gives it as a sub-order containing four tribes. (Proceed. Am. Acad. of Arts and Sci. vol. ii. p. 53.)

The Lernæidæ (pl. 76, figs. 80, 81) are without eyes; the head is small and the thorax large, the separation being sometimes obscure, and the thoracic organs are rudimentary. The single pair of antennæ is sometimes absent, and the number of foot-jaws is two or four. The body is curiously shaped, and irregular in the various genera, in some presenting the appearance of a mal-formed worm, and indeed, some authors have placed them among the worms, and others among the zoophytes. Dr. George Johnston remarks, that “of all the curious creatures which the naturalist meets with in his researches, there are none more paradoxical than the Lernææ; none which are more at variance with our notions of animal conformation, and which exhibit less of that decent proportion between a body and its members which constitutes what we choose to call symmetry or beauty. Of its paradoxicalness, no better proof can be given, than the difficulty which the most experienced systematists have found in determining the proper place and rank of the family among organized beings.” Kroyer, as quoted by Baird, says that “the exterior of these animals is often so highly fantastical, that we are disposed to admire the freaks of nature in bringing forth such forms. But it is evident, that when continued observations and investigations have put us in possession of the condition of these forms, we shall see here, as everywhere else, that singularity resolves itself into regularity.”

Suriray threw a light upon the affinities of these animals by discovering that the appendages at the extremity of the body (Lernæa, pl. 78, fig. 30, inverted) are egg pouches, as in the admitted Crustacea like Cyclops (pl. 78, fig. 27). Audouin and Milne Edwards announced the opinion in 1826, that these animals are Crustacea which become monstrous after they have become permanently affixed as parasites. The organization was first satisfactorily ascertained by Nordman; and the knowledge respecting them, although far from complete, has now arrived at such a point, that their station among the Crustacea may be considered to be well ascertained. These results are due chiefly to the labors of Burmeister, Rathke, Kroyer, and Kollar.

Aristotle and Pliny mention several fish which are infested by these parasites, and Conrad Gesner gave an extended history and figure of a species in 1558, Rondeletius having figured it four years previously. These authors state that it infests the tunny and swordfish, in the flesh of which the anterior extremity is buried, and so firmly fixed that it is difficult to remove without breaking it. Some are found sticking in a similar manner in the eyes of fish, and others to their gills, mouth, or under their fins, where they are less firmly attached.

For a long time the female alone of these animals was known, and it was a subject of wonder how they became transferred from one fish to another, being perfectly stationary and incapable of locomotion; and when carefully removed from their position, but few of them show any signs of life, although some move the head and jaws for a short time. The mode of reproduction was also an obscure point in their history. The ovarian sacs, of course, indicated the female sex, unless all the individuals were supposed to be monoicous. But some individuals were at length found without sacs, and these were naturally taken for males, until Kroyer discovered them to be females after the eggs had been cast and the sacs had disappeared. Nordman at length found adhering to some of the females, certain small living bodies unlike the females, but somewhat like the young, and these he considered males, a view in which Kroyer concurs. These males are much smaller than the females, and those of different species resemble each other, even when the females are quite dissimilar.

When the young leave the egg, they bear a remarkable resemblance to those of Cyclops, Apus, and other undoubted Crustacea. They have a large eye, a pair of antennæ, two pair of large swimming feet, by means of which they swim through the water until they find a proper station to which they can attach themselves, as already described in the Cirrhopoda, and other groups of the lower animals. As in the higher forms, they moult frequently during their growth. After affixing themselves, the feet disappear, or are transformed into foot-jaws or other organs adapted to their new mode of life. The eye being now useless, disappears also. In some, two long arms appear (see the inverted figs. 30, 31), which are united at the apex, where they form a sucking cup, with its concavity armed with teeth, forming an organ which is immersed into the flesh of fishes, and is used in maintaining the place of the animal. This metamorphosis, by which an animal is apparently less perfect in the adult state that when a larva, is styled retrogressive by Burmeister.

In the annexed figure, a represents the young, and b the adult female of Leinæocera, a genus named from the horn-like projections upon the head. The body is slender, the feet are entirely absent in the adult, and the thorax includes most of the body, the abdomen being very small. L. cyprinacea (b) is about eight lines long, and was discovered by Linngeus, in 1746. Figure c represents the male, and d the female of Anchorella uncinata. The former is globular, and affixes itself by means of two pairs of hooks. The rudimentary abdomen of the latter is at the base of the egg sacs. It is one fourth of a line long, whilst the female is six or eight lines. The long projection in the figure of the latter represents the arms. This species is found upon the fins and gill covers of the cod and haddock.

Achtheres percarum (pl. 78, fig. 31), the female of which is two lines long, affixes itself to the tongue, inside of the mouth and eyes of Perca fluviatilis. The alimentary canal is straight, without any division between stomach and intestine, and the nervous system is said to consist of a longitudinal cord on each side of it.

The Caligidæ are distinguished from the Lernæidæ by the better developed organs of motion. The foot-jaws are well developed, and the thorax has several distinct rings and pairs of feet. Like the preceding family, this one is divided into several sub-families. Caligus (pl. 74, fig. 34) has a very large depressed circular head, with large frontal plates having a sucking disk laterally beneath. There are eight feet, and the antennæ are small and bi-articulate. They inhabit the sea, and affix themselves, with the aid of their foot-jaws, to the body or branchial cavities of fish. They readily move from one part of the fish to another, going either backwards or forwards; or leaving the lish, they swim freely through the water. In dissecting them, Pickering and Dana found no blood in the stomach at any time, whence they conclude that the food is the mucus upon the surface of the fish. The cylindrical egg tubes of the female are in some species several times the length of the body in this family, the eyes forming a single row. The integument is renewed periodically. The following genera belong to different sub-families.

Ergasilus (pl. 78, fig. 29), which is parasitic in the gills of fishes, bears a considerable resemblance to Cyclops (fig. 27). They are of a minute size, and when they leave the egg, they have three pairs of swimming feet. The male has not yet been detected.

Phyllophora (P. cornuta, pl. 78, fig. 28) is remarkable for certain dorsal scale-like appendages somewhat analogous to those of the Annelides, as Aphrodite. The single species known is found at Tongatabu.

Order 3. Branchiopoda. This order includes a considerable number of marine and freshwater species, generally of small size, the head distinct, the eyes generally close to the median line, and often in contact, and apparently single, giving rise to the names Cyclops and Monoculus. They swim freely through the water, either with a uniform motion or by a series of jerks, the organs of motion being the feet, tail, and more rarely the antennæ. They have a pair of mandibles, one pair of foot-jaws, and an upper and lower lip. Some authors, who consider this group to be of a higher value than an order, divide it into orders and other sub-divisions. The families here given (except the Cyprididæ) admit of a further division into sub-families, groups which are sometimes considered to be families.

Fam. 1. Cyclopidæ. Cyclops (pl. 74, fig. 33) is a freshwater genus in which the body is pyriform, and tapering posteriorly; the head not distinctly separated from the thorax, and having the eye near the anterior extremity. The superior or larger pair of antennæ are used to assist in locomotion, and they vary in the two sexes, being usually shorter in the male, besides differing in other characters. Some of the marine species are phosphorescent. The freshwater species inhabit stagnant water and springs, where they may be seen with the naked eye jerking themselves through the water, if looked for attentively. The females may be distinguished by the large pair of egg sacs (pl. 78, fig. 27) when these are present. The young undergoes a metamorphosis, which lasts about twenty days. Jurine, who has published an elaborate work upon these microscopic creatures, cut off about two thirds of the antennæ of a female Cyclops, but observed no change in the mutilated organ until the animal moulted, when both antennæ appeared alike perfect. Inhabiting ponds which often disappear by desiccation, these animals and those of the neighboring families reappear with the first rain, having doubtless remained in the mud or damp earth. When removed from water and dried fifteen or twenty minutes, but few survive, and none when the interval of dryness reaches twenty-five minutes. They will recover their activity after having been thoroughly frozen. They are carnivorous, and when other food is not at hand, they devour their own young. These animals are extremely prolific, and furnish food to the aquatic larvæ of insects. Cyclops setosa, Hald., Jour. Acad. Nat. Sci. viii. 331, is the American analogue of the European C. quadricornis.

Fam. 2. Cyprididæ (Ostracoda of Latreille). In this family the animal is inclosed in a bivalve shell with a dorsal hinge, and capable of being closed when the antennas and feet are withdrawn. There are four antennæ, those of the second pair being large, elbowed, and adapted to assist in swimming. Most of the species are minute, inhabiting fresh or salt water. The species of the genus Cypris are abundant during the summer in puddles of stagnant water, where they may be seen swimming about or walking upon objects at the bottom. The eye is of a dark color, and the shell sufficiently translucent to allow it to be seen at the upper and anterior part. The eggs are attached to extraneous bodies, and the young are not subject to metamorphosis. Their food is stated to be dead animal matter, and conferva. Many of the species are beautifully marked with variations of color. The following American species are indicated in the Proceed. Acad. Nat. Sci. vol. i. pp. 53 and 184: Cypris agilis, C. simplex, and C. scabra, Hald.

Fam. 3. Daphniidæ (or Cladocera). Here a bivalve shell incloses the body, with the exception of the head, which is distinctly exposed, and bears a large compound eye capable of some motion. The inferior antennas are very large, and generally two-branched. There are four, five, or six pairs of feet, which afford characters for the sub-families; or families, if the Cladocera are considered to constitute an order. Daphnia is abundant in the stagnant pools where Cypris and Cyclops are found, and their locomotion resembles that of the latter. The young are retained between the body and shell posteriorly above, where they may be seen through the latter. The Daphniæ are so abundant as sometimes to discolor the water, the red species giving it somewhat the appearance of blood. Dr. W. Baird, in his Natural History of the British Entomostraca, 1850, p. 78, says he has “frequently seen large patches of water in different ponds assume a ruddy hue, like the red rust of iron, or as if blood had been mixed with it, and ascertained the cause to be an immense number of D. pulex. The myriads necessary to produce this effect are really astonishing, and it is extremely interesting to watch their motions. On a sunshiny day, in a large pond, a streak of red, a foot broad, and ten or twelve yards in length, will suddenly appear in a particular spot, and this belt may be seen rapidly changing its position, and in a very short time wheel completely round the pond. Should the mass come near enough the edge to allow the shadow of the observer to fall upon them, or should a dark cloud suddenly obscure the sun, the whole body immediately disappear, rising to the surface again when they have reached beyond the shadow, or as soon as the cloud has passed over.”

At certain periods Daphnise may be found with a black saddle-shaped appendage (named the ephippium) upon the back of the shell, which Strauss discovered to be a receptacle for two eggs from which to reproduce the species in the spring. At the fifth moult, the ephippium is cast off and floats about at random, protecting its contents until the succeeding spring. Daphnia abrupta and D. fenestrata, Hald., Proceed. Acad. i. 184, 196, are American species. The name of the latter is changed from reticulata, as this has been already applied to a European species.

Fam. 4. Apodidæ. This family includes Latroille’s fifth order, Phyllopoda, in which the body is either naked, inclosed in a bivalve shell, or with the head and thorax covered with a carapace. The body is divided into a great number of segments, most of which have foliaceous feet adapted for breathing, the number of which varies from eleven to sixty pair. Antennæ two or four in number, and not adapted for swimming; eyes two or three.

Apus (pl. 78, fig. 25) has a large carapace covering nearly the entire body; one pair of short antennæ, and sixty pair of branchial feet. Schæffer enumerated the number of pieces which enter into the composition of the body, and found them to amount to 1,802.604. He found that each of the caudal filaments in Apas cancriformis contains 480 articulations. It inhabits fresh water ponds, and swims equally well with the back above or below. It reappears in desiccated ponds in two days after a rain; and it has been found in ponds that have been without water for several years, whence it may be inferred that the eggs retain their vitality for a long time. They feed upon the microscopic Entomostraca, and are in turn devoured by frogs.

The metamorphosis of Apus is much like that of Cyclops, Lernosa, &c. When the young leave the egg the body is narrowed posteriorly, the tail is wanting, the antennæ are large, and the first and only pair of feet are robust, and longer than the body, thus presenting opposite characteristics from the adult. The length of the common European species, A. cancrifonnis, is two and a half, and the breadth one and a half inches. There are but few species known. One has been described from the West Indies, one from the eastern side of the Rocky Mountains, and another from the Sandwich Islands.

Branchipus pisciformis (pl. 78, fig. 26) was described under this name, according to W. Baird, by Schæffier, in 1752, and was subsequently named Chirocephahis diaphanus, by Prévost. It has two pedunculated eyes, four antennæ, eleven pairs of branchial feet, and there is no shield. In the male, the larger pair of antennæ are prehensile, resembling mandibles, their base is large and fleshy, and the outer joint curved and cylindrical. From the base of these antennæ arises a pair of large flexible proboscidiform organs with their appendages, all of which are usually rolled up beneath the head. In the female the large antennæ have a singular structure, being short, compressed, bent downwards, pointed at the end, and unprovided with appendages. The species figured is more than an inch long, and is found in pools swimming upon its back. As in nearly all the Entomostraca, the branchial feet are kept moving continually. These animals swim with the aid of the tail, darting through the water like small fishes. They feed upon dead animal and vegetable matter. The female has an external branchial sac, and the young undergo a metamorphosis.

Limnadia is inclosed in a bivalve shell somewhat as in Cypris, but the animal is larger, being nearly half an inch long. The American species, L. coriacea, Hald., 1842, was found in a puddle a few inches deep, which was subject to desiccation; and although a number of living individuals were transported to a little pond not liable to be dried up, the species has not been seen since, in these or other localities.

Order 4. Trilobites. These animals are known only from their fossil remains, which are limited to the crustaceous covering. In most cases the body is divided into three lobes by two longitudinal impressions, and into transverse segments. The shield of the head is composed of a single piece, followed by the thoracic segments, and these by the shield of the posterior extremity or abdomen, which varies much in size, and is either plane or marked with transverse impressions like those which separate the thoracic segments. The cephalic shield or buckler is large, more or less semicircular in front, truncated or concave behind, and generally divided into three longitudinal lobes corresponding to those of the trunk. When they are present the eyes are situated upon the inner portion of the exterior lobes. They are in the form of a more or less elevated tubercle, which is sometimes semilunar or reniform. In some the surface is smooth, whilst in others it is composed of numerous facets forming a compound eye. In the opinion of Burmeister, the eyes of all the Trilobites are compound, and covered with a smooth cornea; and when this has disappeared, the faceted portion is exposed to view. To effect this, the cornea must have been thinner and more destructible in the genera in which faceted eyes appear.

The thorax is composed of a variable number of distinct segments, which are arched over the back into the longitudinal grooves, whence the lateral flattened portions, or pleurae, project and form the external margin, where they are bent beneath and doubled upon themselves. The thoracic segments are generally composed of a wide and narrow portion, the latter being anterior and covered by the posterior margin of the preceding segment, unless the body is bent, when this portion appears. The number of segments in the thorax varies from six (in one case but two) or eight to twenty.

Feet have never been found with the Trilobites, so that it is probable that they did not exist as solid members, but resembled the corresponding parts in the Branchiopoda.

The remains of these animals are found abundantly in the palaeozoic and carboniferous formations of various parts of the world.

Burmeister, who has written an elaborate and satisfactory work on the organization of the Trilobites, assigns reasons for believing them to be allied to the branchiopoda, with similar habits, swimming by means of their soft gill feet; just beneath the surface of the water, with the back below, having the power of creeping upon the bottom, feeding upon small marine animals, and rolling themselves into a ball (those able to do so) as a defence. They probably lived gregariously in the shallow waters of bays and coasts, with but few species in a single locality.

Milne Edwards places the Trilobites between the Branchiopoda and the Isopoda, to the latter of which they have only a distant external resemblance, and the absence of articulate feet indicates a wide difference.

Order 5. Xiphosura. This order is here restricted to the single genus Limulus (pl. 78, fig. 34), which Burmeister makes a tribe, under the name of Pæcilopoda, a name which has a very different value assigned to it by other authors. On this account we prefer the name given by Gronovius. The terms Epizoa and Parisita are also used in such a manner as to cause confusion, being applied both to the Lernæidæ and to the Anoplura or lice. Limulus is remarkable for the long, hard, and sharp caudal spine, with which spears are pointed in some countries. They are called king-crab on the coast of the United States, where they are collected as food for hogs, although these animals will not attack them until accustomed to such an unusual kind of food. The body is covered by a large anterior carapace, and a smaller posterior one, the gill feet are attached to the abdomen, and six pairs of strong articulated ambulatory feet to the thorax. The latter are present in the fossil species which have been discovered. The caudal stylet is wanting in the embryonic young, which differs from the adult in some other particulars. The species live upon animal food.

Malacostraca

Order 6. Isopoda. In this order the body is depressed and oval, and there are seven pairs of feet attached to the seven movable segments of nearly equal size which form the thorax (pl. 78, figs. 20–22). The young resemble the adult, but they have only six pairs of walking feet. Some of the species are parasitic upon fishes or Crustacea, and these have the organs of motion and the eyes rudimentary. Most of the species are marine, although some inhabit the fresh waters, and others the land, the last requiring damp localities to preserve their gills from desiccation. The four antennæ are of a medium size, and directed in front, the first pair being in some cases rudimentary. The organs of raanducation are well developed, the thorax occupies a great part of the body, the feet are armed with a single nail, and in some cases they are prehensile. The females have a corneous horizontal plate at the base of the feet, which forms a receptacle in which the eggs are hatched. The abdomen is in the form of a terminal plate above, and beneath it supports six pairs of organs, five of which are respiratory false feet, and the sixth takes various forms, according to the family.

Milne Edwards divides the order into three sections, according to their walking, swimming, and sedentary habits. The first includes the Idoteidæ, Asellidæ, and Oniscidæ; the second the Sphæromidæ and Cymothoidæ, under a different mode of division from that of Latreille; and the third the Epicarides or Bopyridæ, under two families.

The walking Isopoda have the terminal false feet in the shape of operculums, or of projecting caudal stylets, which are never flattened into swimming organs; the first pair of antennæ are generally short or rudimentary.

In the swimming Isopoda there is a large caudal fin provided with lateral expansions formed by the modified fourth pair of false feet. All the antennæ have the same form, and the second pair are well developed.

The sedentary Isopoda are parasitic, and whilst the males present the general characters of the order, and have seven thoracic and five or six abdominal segments which are quite distinct, the females are misshapen, with the segments of the body indistinct. The thorax is narrow in the male and wide in the female, and the eves are present in the former and absent in the latter. The antennæ are more or less rudimentary, and the feet very short, submarginal, and formed for holding, but not adapted for walking and swimming. The male is much smaller than the female.

Latreille divides the Isopoda into six families, corresponding to the following names: 1, Bopyridæ; 2, Cymothoidæ; 3, Sphæromidæ; 4, Idoteidæ; 5, Asellidæ; 6, Oniscidæ.

Fam. 1. Bopyridæ. Bopyrus crangorum is found affixed to the gills, and beneath the shell of several large Crustacea, as Palæmon and Hippolyte. The male is only one fifth or one sixth the size of the female, and is found under the abdomen of the latter. When the young leave the egg, they are much like those of Cyclops.

Fam. 2. Cymothoidæ. Most of these are parasitic upon marine fish, to which they affix themselves with the aid of their strongly hooked feet. The body is lengthened oval, narrowing towards each end, the head is small, and the feet are large and operculiform. The young leave the egg with only six pairs of feet, and at this period the abdomen is adapted for swimming. Some are sedentary, and others possess the power of walking. The sub-families are the Serolinæ, Cirolaninæ, and Nerocilinæ.

Fam. 3. Sphæromidæ. The genus Sphæroma (pl. 78, fig. 21) has the thoracic segments nearly alike in form and size, the feet slender, and the false feet (except the last pair) received into a cavity beneath the abdomen. The species live among submarine plants, and they can roll themselves into a ball. Cymadocea (pl. 78, fig. 20) is allied to Sphæroma, but it is less flexible, and therefore not able to roll itself into a ball. It contains the two sub-families, Sphærominæ and Ancininæ.

Fam. 4. Idoteidæ. In this family the four antennæ are placed in the same line, and the first pair are very small. The body is slender, not much thicker in the middle, and truncated or concave posteriorly. The respiratory false feet are concealed in an opercular cavity beneath the abdomen. Sub-families, Arcturinæ and Idoteinæ.

Fam. 5. Asellidæ. Body elongated and flattened above; the two pairs of antennæ are setaceous, and arranged in two lines, the first pair small. The abdomen is composed of one large scutiform segment without lateral swimmerets, and with two terminal stylets. Some of the species are marine, and others fluviatile. A species of Asellus is common in the fresh waters of Europe, and A. communis, Say, Jour. Acad. Nat. Sci. i. 427, is abundant in similar localities in the United States; and as it differs from the European representative of the genus in having the sides rectilinear, entire, and gradually diverging posteriorly, and the posterior segment being the widest as well as the largest, and transversely quadrate; we propose to give it the generic name of Abacura, from αβαξ a table, and ουςα the tail. The antennæ and caudal appendages are as in Asellus. It is half an inch or less in length, and may be found walking upon the bottom of springs.

Fam. 6. Oniscidæ. These animals are either marine or terrestrial, the first pair of antennæ are rudimentary, the second only being fully developed and conspicuous. The feet are slender, and formed for walking. The terrestrial genera (Porcellio, pl. 78, fig. 22) inhabit humid places, as cellars, crevices in walls, beneath stones or loose bark, and similar localities, feeding upon decaying vegetable matter. The female carries the eggs in a sac beneath the body. When the young first make their appearance, they have a segment of the body and a pair of feet fewer than the adult; and the head and antennæ are proportionally larger. The young are retained for a short time between the respiratory laminae. Oniscus affinis, Say, is a common American species.

The singular marine genera, Pycnogonum and Nymphon (pl. 78, figs. 32, 33), with but four pairs of legs, were formerly placed in this, or the preceding or succeeding order, by various authors, but they are by many believed to belong to the Arachnida.

Order 7. Læmodipoda. The animals of this order are small, and present an unusual aspect. The head is small, the thorax has six segments, and the posterior extremity ends in a little tubercle corresponding to the abdomen. There are four antennæ; the mouth has a pair of toothed mandibles, two pairs of lamellar maxillae, and one pair of foot-jaws. There are five or seven pairs of feet, and in the former case the missing ones are generally those of the third and fourth pairs, which are represented by lamellar scales. The feet are prehensile, and the first and second pairs have a kind of hand capable of holding; the foraier are affixed to the head, and the latter to the thorax. Branchial vesicles are attached to the second or third thoracic segments, and sometimes to the first. The order contains two families.

Fam. 1. Caprllidæ. Caprella (pl. 78, fig. 23) is a small and very slender animal with thin feet, a thick head narrowing posteriorly, and the first pair of antennæ larger than the second. The species live among marine plants, along which they walk in the manner of a leech. In swimming, they bend the posterior extremity and straighten it suddenly.

Fam. 2. Cyamidæ. Cyamus (pl. 78, fig. 24) is a genus found in colonies parasitic upon whales.

Order 8. Amphipoda. This order takes its name from bavins: two kinds of feet, cheliform and simple, and because the feet vary in the position of the former. The body is compressed, the back generally arched, the mandibles with a palpus, the eyes immovable, and the posterior extremity generally w4th styliform appendages, and turned beneath. The segment next the head supports the first pair of feet, which correspond to the second pair of foot-jaws. The antennæ are slender and project in front. Most of these little animals swim with great vigor, by curving the tail beneath the body and jerking it back. There are fresh water as well as marine species, and they may be seen in most springs of fresh water. Some are found upon the beach under sea weed, or burrowing in the sand, and as they are too narrow to walk, they jerk themselves along whilst lying upon one side. There are two families, each of which contains several sub-families.

Fam. 1. Gammaridæ. In most of these, the thorax is composed of seven segments, the first pairs of feet are well developed, and used in prehension, and the five succeeding pairs are ambulatory. Orchestia (pl. 78, fig. 18).

Fam. 2. Hyperinidæ. Ancylomera (fig. 19). These are generally parasitic upon fishes and medusæ. They swim well, but walk badly.

Order 9. Stomatopoda. Branchiæ abdominal and free, not affixed to the sides as in the Decapoda; abdominal appendages well developed. The shell is delicate and transparent, the thoracic carapace is large; and the body bears some resemblance to that of a lobster, being semi-cylindric, rounded above, and flat beneath, and the posterior extremity is obtuse and spinose. The large and conspicuous arm-like organs, which resemble the raptorial anterior feet of Mantis (pl. 80, fig. 90), present a remarkable character, and are doubtless used in taking their prey. The last articulation closes upon the previous one like the blade of a knife into the handle, and it is well adapted for holding. These organs correspond to the second pair of foot-jaws in the lobster and crab, and to the first pair of thoracic feet in the Isopoda. The oval laminated organ in front of these is an appendage of the second or external pair of antennæ. The last segment of the abdomen and the appendages of the sixth segment, form a caudal fin used in swimming, assisted by the three posterior pair of thoracic feet. Squilla (pl. 78, fig. 15); Gonodactylus (fig. 16). Gonodactylus chiragra inhabits the Mediterranean, the coasts of the Seychelles, America, Trincomalee, and Tongatabu. The order contains the two families, Erichthiidæ and Squillidæ.

Order 10. Diplopoda. This is usually included with the preceding, though Milne Edwards separates it as a distinct order, but without assigning to it a systematic name. That here chosen is in allusion to the appendages of the feet, which give them the appearance of being double. It is an order of small extent, of which Phyllosoma (pl. 78, fig. 17) is the type. The eyes are placed upon peduncles, the abdominal appendages are rudimentary, the branchiæ wanting, the body broad, thin, and scale-like, composed of a large cephalic shield, and a smaller thoracic one bearing the feet upon extensions of its margin. These animals are translucent, and so thin that it is difficult to perceive how there can be room for the internal organs between the upper and lower surface. In Phyllosoma the mandibles are large; the first and second pairs of mandibles, and first pair of foot-jaws, are small, and the second pair of foot-jaws are not raptorial. The feet are long and slender, and provided with palpiform appendages; and from the ease with which the feet are lost from the point where the appendage is attached, they are seldom seen perfect, so that the latter appears to be the true termination of the foot. The first pair of feet are small, and without a terminal nail, and generally without an appendage. The last pair are often rudimentary. The abdomen is sometimes confounded with the thorax, and at other times rudimentary.

Order 11. Decapoda. The individuals of this order, as the name implies, have ten ambulatory feet; the branchiæ are placed in lateral cavities beneath the sides of the large carapace; the head is immovable; the mouth has numerous organs between the mandibles and first pair of feet; and the eyes are pedunculated. This order contains the largest of the Crustacea, as the lobsters and crabs.

Latreille divides this order into two families, named sub-orders by Westwood and tribes by Burmeister, who includes them with the Stomatopoda in his order Podophthalma, and gives each of these an equal rank with the Stomatopoda, Isopoda, and other orders. Milne Edwards divides the Decapoda into three sections, admitting the Brachyura and Macrura, but separating certain anomalous genera from both, but chiefly from the Macrura, to form the third section Anomura (also written Anomoura, and meaning, the tail anomalous).

In the Anomura the cephalothorax is large, the abdomen is not fully developed, and is mnch like that of the Brachyura. The second pair of external antennæ are well developed, the external foot-jaws are generally like feet; the three or four anterior pairs of feet are generally like those of the Brachyura, and adapted to locomotion, but the remaining ones are rudimentary, and in some cases used only for holding.

Fam. 1. Paguridæ. The genus Pagurus (pl. 78, fig. 10), and several others of the same family, are remarkable for having the abdomen weak and soft, and the two posterior pairs of feet much reduced in size, and not adapted for walking. These animals are protected by the empty spiral shell of a mollusc, and as they increase in size they crawl along the beach hunting a larger shell, and various trials are made until a suitable one is found, the old one being again and again resumed, until the animal has suited itself. The abdomen and small feet enter the shell, and when the animal wishes to be safe, it withdraws itself so far that the head and robust anterior feet close up the aperture like an operculum. The posterior extremity of the body is curved, and with the posterior feet, adapted to maintain the shell in a proper position. One of the anterior pair of feet is larger than the other, and both terminate in a pair of pincers or chelæ. The sub-families are Pagurinæ, Hippinæ, and Porcellaninæ.

Fam. 2. Raninidæ. In Ranina (R. serrata, pl. 78, fig. 9) the carapace is roughly serrated and transversely truncated before and narrowing posteriorly, producing a sub-triangular form. The anterior feet are cheliform, but not of a very large size, and the succeeding feet have the tarsus or last articulation lamellar. The abdomen is narrow, of seven articulations, the last ones bent downwards. The species figured inhabits the East Indies, and is said to crawl up objects, even to the tops of houses. The sub-families are: Dromiinæ, Homolinæ, and Ranininæ.

The Macrura are named from having a large and well developed tail or abdomen, ending in a fan-shaped fin (pl. 78, figs. 11–14). The form is generally elongated, the carapace longer than in the crabs, and generally armed with a frontal spine; and the species, with few exceptions, are marine. The antennæ are in general long, the first pair not received into a cavity as in the crabs; the mandibles are well developed; the walking feet are slender, and the first and second pairs frequently cheliform. The abdomen has seven articulations, of which the five basal ones bear the false feet. The caudal fin is formed of five pieces, the middle being an extension of the seventh or last segment, whilst the lateral ones arise from the sides of the sixth. These Crustacea, although they walk well, must be regarded as chiefly swimmers, shooting backwards through the water by the action of the abdomen and caudal fin.

Fam. 1. Scyllaridæ (cuirassés, M. Edwards). In the genus Palinurus pl. 78, fig. 11, the body has much the shape of that of a lobster, but is more cylindrical, and none of the feet are cheliform, although the anterior ones are rather more robust than the others. The carapace is armed anteriorly with two large spines; the external antennæ are very long, with the base spiny; the basal segment of the abdomen is without false feet, although the four following have them. The species are of a large size; they have a very hard shell, and they live upon rocky coasts. The European species, P. vulgaris, attains a length of fifty centimetres, and a weight of eight kilograms. It is the karabos of Aristotle, and the locusta of Suetonius and Belon. The various species are more or less spinous. Scyllarus (pl. 78, fig. 12) is remarkable for having the peduncle of the exterior antennæ much dilated laterally, and more or less dentated, the terminal filaments being absent. The sub-families are: Galatheinæ, Eryoninæ, Scyllarinæ, and Palinurinæ.

Fam. 2. Astacidæ. This family includes the genus Astacus (lobster) and Potamobia, the analogous fresh water form known under the English names of crawfish, crayfish, crevish, or crevis, the three last of which agree in the first syllable. The latter are caught in Europe for food, by placing decaying meat in nets or bunches of brushwood, from which they cannot readily escape. They are also caught by a bait at the end of a stick, which they will not leave if it is withdrawn slowly, until a net can be passed under them. They are said to live twenty years, and to grow during this period. The genus is well represented in the United States. Callianassa (pl. 78, fig. 14). C. major, of Say, is four inches and a half long, and was found by this author “by digging in the sand of the bay shore of the river St. John, in East Florida, about eighteen inches below the surface, near low-water mark; it had formed a tubular domicil, which penetrated the sand in a perpendicular direction to a considerable depth; the sides were of a more compact consistence than the surrounding sand, projecting above the surface half an inch or more, resembling a small chimney, and rather suddenly contracted at the top into a small orifice.” The second family, fouisseurs of Milne Edwards, is included in the Astaoidæ by Latreille. The sub-families are: Glaucothoinæ, Callianidinæ, and Astacinæ.

Fam. 3. Palæmonidæ. Palæmon, which is much used for food, inhabits sandy bottoms near the coasts, or the mouths of rivers, and like the lobsters, boiling turns them red. Stenopus (pl. 78, fig. 13, exhibiting the false feet under the abdomen). The sub-families are: Crangonince, Alpheinæ, Palæmoninæ, and Penæinæ.

Fam. 4. Mysisidæ.⁹ Some authors place this family with the Stomatopoda. It includes two sub-families: Mysisinæ and Leuciferinæ.

In the Brachyura (pl. 78, figs. 1–9), the carapace is generally transverse, and square, oval, or circular, the abdomen is small, without a caudal fin, it is bent beneath and received into a depression of the thorax, and is not used in locomotion. The eye peduncles are generally longer than in the Macrura; there are two pairs of antennæ one pair of mandibles, two of jaws or maxillæ, three of foot-jaws, succeeded by ten feet, the first pair having a pinching claw, the rest simple, and adapted in most cases for walking, but sometimes for swimming. The abdomen is wider in the female than in the male, and is composed of seven segments; but some of these are sometimes united together in the female, so as to present from four to six. Linnæus included the various genera of Brachyura in his genus Cancer, which corresponds very nearly to the English name crab. They are divisible into four families.

Fam. 1. Leucosiadæ. This family, called Oxystomes by Milne Edwards, includes the four sub-families, Calappinæ Leucosiinæ, Corystiinæ, and Dorippiinæ, in which the shell is more or less orbicular, the eyes generally small, and the external foot-jaws triangular.

The Calappinæ form part of Latreille’s Cryptopodes, named from the feet being partly hidden by the projecting margin of the carapace. The Leucosiinæ are much like the Cancridæ or ordinary crabs. Philyra (pl. 78, fig. 7) is a genus of small Crustacea, with the carapace circular and depressed. In the Corystiinæ, the external antennæ are robust and rather long, and the sternal plate narrow. In Corystes, the anterior feet are much larger in the male than in the female, and the abdomen has five articulations in the former and seven in the latter. The Dorippiinæ (Dorippe, pl. 78, fig. 8), which form part of Latreille’s Notopodes, have the sternal plate circular and bent upwards posteriorly, the cheliform feet short, the two next pairs long, and the one or two last pairs, which are generally much reduced in size, are placed higher than the others, as if upon the posterior part of the back.

Fam. 2. Ocypodidæ. This family of Leach corresponds to the Catamétopes of Milne Edwards, in which the carapace is depressed, rhomboidal or ovoid, and the eye peduncles long and slender. The following are the sub-families: Thelphusinæ, Gecarcininæ, Pinnotherinæ, Ocypodinæ, Gonoplacinæ, and Grapsinæ.

Thelphusa is a genus of crabs which lives along the banks of freshwater streams. The Gecarcininæ (Gecarcinus, pl. 78, fig. 4) are remarkable for having branchiæ adapted to aerial respiration. They live among damp forests in holes which they make, and where they moult. Their food is vegetable, and they generally move about at night, or in wet weather. They visit the sea at certain periods, for the supposed purpose of depositing their eggs. They run with great agility, and like the crabs in general, in either direction. Pinnotheres ostreum is commonly found within the shell of Ostrea virginiana of the United States coast. In this genus the males are much smaller and more rare than the females. They are found within the shell of various bivalve Mollusca, as Pinna and Mytilus, where they are compensated for the weakness of their shell. The Ocypodinæ (Ocypoda, pl. 78, fig. 6; Gelasimus, fig. 5) live upon the coast, digging holes several feet deep, where there is not too much sand to cause them to cave in, and some of the species run so rapidly that a man can scarcely catch them. Ocypoda arenaria inhabits the coast of the United States and the Antilles, digging a hole three or four feet deep, just beyond the limit of the surf, whence it vranders in search of food. According to Say, they hybernate at some distance from the water, in a hole made for the purpose, the mouth of which they close. Gelasimus vocans, known on the United States coast under the name of tiddler, has one of the anterior feet of the male much larger than the other, the large one being indifferently upon the right or left side.

Fam. 3. Cancridæ, including the Portunidæ and Pilumnidæ of Leach, is equivalent to the Cydométopes of Milne Edwards, and includes, under two sub-families, most of the forms known under the name of crab. The sub-families are: the Cancerinæ (Cancer, pl. 78, figs. 1, 2) and the Portuninæ (Thalamita, fig. 3), which includes a great number of species under various genera. They are found near the coasts a considerable number together, and are taken for food. They feed upon living or dead animal food, particularly upon decaying carcases. Some of them attain a large size, Pseudocarcinas gigas being ten inches or more in diameter. The Portuninæ correspond to Latreille’s swimming Brachyura, and are distinguishable from the Cancerinæ by the posterior feet being flattened and adapted for swimming, as represented in figure 3. In Lupa, the carapace is wider than long, and has nine tooth-like projections on each side before. The common edible crab of the Atlantic coast of the United States, has been described as Lupa hastata by Say, Jour. Acad. Nat. Sci. i. 65, 1817. It is abundant in bays and inlets, feeds upon putrefying animal matter, and buries itself in the sand to the eyes and antennæ. The shell is generally cast in the spring, when the animals are sought after under the name of soft crabs.

Fam. 4. Maiidæ. This family includes the thorny and spider-crabs, many of which have long and slender feet. The epistoma, or region between the mouth and antennæ, is large and square; the carapace is narrowed anteriorly, so as to give it a triangular outline, whence Latreille’s names Triangulares and Oxyrhinchi. The front is narrow, and generally extended into a prominent rostrum; the nervous system is more concentrated than in any of the other Crustacea, and on this account it may be considered the highest group among them. They are all marine, living at considerable depths; their motions are tardy, and they do not swim. As American examples, Leptopodia calearata and Libinia comaliculata, Say, may be mentioned. There are two sub-families: Maiinæ and Parthenopiinæ.

Class 4. Arachnida

This class includes the various articulate forms known as spiders, mites, and scorpions, the characters of which place them between the Crustacea and Insecta. In general, the head is not distinct from the thorax, but intimately connected with it, forming a large segment named the cephalothorax, which is followed by the abdomen, and this is either distinct or united in a single piece with the former. These animals are not subject to a perfect metamorphosis, but they have, in some cases, a partial one. They have neither wings, antennæ, nor upper lip; the number of feet is eight, affixed to the sternum or lower side of the cephalothorax; the mouth is provided with a pair of mandibles or chelicera which usually project well in front, a pair of jaws or maxillæ supporting palpi, and a lower lip. The chelicera are considered by Latreille not to be equivalent to the mandibles of the Crustacea and insects, but to correspond to the internal antennæ of the former, and modified into predaceous organs; a view which, if correct, would deny proper mandibles to these animals, although these organs have an important place in the Articulata as a whole. Each of the two maxillæ bears a palpus or articulated organ much like the ordinary feet, but smaller, and like the ordinary feet of the Crustacea. (See pl. 78, figs. 35–40.) In Scorpio (pl. 77, figs. 51, 52), the palpi are cheliform, and much larger and stronger than the feet, resembling the first pair of true feet in the crab and lobster. There is an affinity between Scorpio and the Xiphosura or genus Limulus, in the mandibles, which are cheliform, each ending in a pincer. The feet correspond to those of insects, the round basal portion or coxa being joined to the thigh or femur by means of a short interposed trochanter, the femur being followed by the tibia, and this by the tarsus, which has three articulations in the more typical forms.

The eyes are simple and smooth, and their number varies from two to eight. Their number and relative position are much used as generic characters.

The respiratory organs are of two kinds. The first (which resemble those of the Crustacea) are formed of numerous internal gills or lamina contained in internal pouches, and answering to lungs. The second kind are composed of tracheae or air tubes (as in insects), connected with two spiracles. Those with the former are termed pulmonary, and the latter tracheary arachnidans. Both kinds may occur united, and the Podosomata (Pycnogonum, &c.), like some of the lower Crustacea, have no means of respiration except the skin.

The abdomen is generally soft and more or less globular in form, and it bears the spiracles, anal and generative apertures (the latter being near the base beneath), and the spinnerets in those forms which spin webs. The skin is generally of a tough leathery texture, and the muscles are attached to its internal surface, thus assimilating it to the external skeleton of the Crustacea and insects.

Most of the Arachnida feed upon fresh animal food, as insects, which they take alive, either in their nets, or by running or suddenly leaping upon them. Some, as the ticks, are parasitic upon various animals; whilst others, as some of the mites, feed upon vegetable matter, being found in flour and figs. Some mites infest dried meat and cheese.

The Arachnida are mostly oviparous; the young, upon leaving the egg, are active, and resemble the adult, although some have a pair of feet less, which are finally acquired after several moultings, for, like the Crustacea, the members of this class chausre their integument from time to time.

The nervous system is much concentrated, being principally composed of a large ganglion in the centre of the cephalothorax, before which are two others with branches to the eyes and mouth. The principal ganglion has branches to the abdomen and feet. In the scorpions, instead of the great central ganglion, there are two rows of small ones, each united by a nervous cord.

The class is divisible into the three sections, Aporobranchia, for Pycnogonum, &c., in which there are no special breathing organs; Trachearia, in which breathing is effected by means of tracheæ; and Pulmonaria, in which the gills resemble the leaves of a book, and are adapted to breathing air only. The first section contains one, and each of the others two orders. The orders are named from the characters furnished by the body. The Podosomata, Leach, have the feet and body much alike; the Monomerosomata, Leach, have only one segment apparent; in the Adelarthrosomata, Westwood, the segments are uncertain; in the Polymerosomata, Leach, they are numerous, as in the scorpion; and in the Dimerosomata, Leach, including the common spiders, the body is divided into two portions.

Order 1. Podosomata. These animals are placed among the Crustacea by Milne Edwards, because they have not the organs of respiration of the Arachnida, but respire by means of the skin, like some of the lower Crustacea, a character which some of the Hydrachnidæ have, although no one would pretend to remove them to the Crustacea on this account. In form, the animals of this order approach to the crustacean genus Cyamus (pl. 78, fig. 24), although they have but eight feet like the Arachnida. These are long and slender, and composed of eight articulations, including the claw. The head, or rather the rostrum, is lengthened, and either cylindrical or conical, without appendages, and the mouth is terminal and tri-lobed. The thoracic portion can be distinguished from the snout, which character distinguishes them from the great mass of the Arachnida, and it is composed of four segments, followed by a small abdomen. There are four eyes upon an eminence, situated upon the upper surface of the first segment of the thorax, and as the snout does not, in the opinion of Erichson and Kröyer, comprise the whole head, this must be looked for in the first segment of the thorax, which often bears a pair of cheliform organs, corresponding, in the view of Latreille, to the cheliform mandibles of Scorpio. The female (and in some cases the male also) has attached to the first segment of the thorax a pair of appendages much like the feet (but much smaller in size, and without a terminal claw), used to support the bunches of eggs, and which may be considered maxillæ. As Erichson regards the segment next to the ostrum as the head, he names its feet a third pair of jaws, whilst Kröyer considers them feet, on the ground that the segment to which they are attached is made up of the posterior part of the head (including the eyes) united without a division to the anterior part of the thorax.

The alimentary canal is straight, and it is peculiar in having lateral tubular branches penetrating far into the feet, which dispenses with the necessity of having a regular circulation. In the more typical Arachnida, examples are found of a stomach with branches, but they do not enter the feet.

The order is widely spread, members of it having been found at Spitzbergen, the coasts of Europe and America, and Australia. Their habits are sluggish, and some of the species live together in considerable numbers. Kröyer has found that they have three stages of transformation, the body being in the first roundish or oval, without an abdomeli, but with cheliform mandibles even in Pycnogonum, the adult of which is without them, a fact which indicates the little importance of these organs, and the lower condition of the forms which retain them. The third pair of feet, the segments of the body, and the abdomen, appear in an undeveloped state in the second stage; and in the third, the last pair of feet are acquired, the preceding feet have become more perfect, and the body has become longer and more like that of the adult. Another moult brings the body nearly to its final form, whilst the feet, which had diminished in length from the first to the last pair, become of equal length.

This order is not extensive, but it contains a number of genera comprised in two families.

Fam. 1. Pycnogonidæ, in which the feet are comparatively short, the body rather robust, and the cheliform organs wanting. Pycnogonum (pl. 78, fig. 32) has been erroneously stated to infest whales.

Fam. 2. Nymphonidæ Nymphon (pl. 78, fig. 33, inverted), in which the body and feet are very slender, and having a pair of cheliform mandibles. N. pallida, Say, 1821 (Anaphia), Jour. Acad. Nat. Sci. vol. ii. p. 60, pl. 5, fig. 7, was found on the coast of South Carolina. The expanse of its feet is one and a half, and its length one fourth of an inch.

Order 2. Monomerosomata (pl. 77, figs. 46, 47, 64–71). This order contains the small and generally microscopic spider-like animals known as mites and ticks, and to which an aerial and tracheary respiration is usually attributed, including those which are aquatic. According to Dujardin, Gamasus and other genera with cheliform mandibles, have tracheæ, whilst Acarus and Sarcoptes breathe through the skin. He asserts further, that in Trombidium, inspiration takes place by the latter mode, and expiration by the former; and that in the aquatic genera respiration takes place through spiracles scattered over the surface. The body is not divided by the separation of the abdomen as in the ordinary spiders, nor are various segments apparent as in Chelifer and Scorpio. This being the case, when the anterior portion appears to form a head, it is by the enlargement of the haustellum or parts of the mouth, the eyes being in nearly every case situated upon the anterior part of the cephalothorax. The labium or lower lip supports or incloses the organs of manducation; the palpi are usually free, of five articulations, and they present many varieties of form which are useful in classification. In some they are adapted for seizing their prey, in some for holding, and in others for drawing their food towards the mouth. The feet are usually composed of seven articulations, including the coxa (which is either attached or movable), so that they correspond with those of the Areneidge. The extremity has usually two claws, capable of being thrown back and received into a corresponding cavity. The supposed Acari, with six feet, for which genera have been proposed, are the immature condition of other genera. Duges divides the order into seven families, the succession of which is here followed in reversed order. The genera are numerous.

Fam. 1. Oribatidæ. These have a remarkably hard exterior, the back being formed like a carapace, whence Hermann’s generic name Notaspis. This carapace sometimes has a transverse division, and Duges mentions a species in which the feet can be hidden by its lateral borders. The palpi have five articulations, of which the second is the thickest and longer than the rest conjointly. The mandibles are cheliform or didactyle, and the eyes are usually absent.

Fam. 2. Bdellidæ. Body oblong and tumid posteriorly, contracted behind the eyes; rostrum in the form of a head, and elongated; palpi resembling antenna, mandibles with a claw, or cheliform; feet cursorial.

Fam. 3. Acaridæ. In this family the feet are carunculated, the mandibles cheliform, and the palpi indistinct, on account of their adherence along the inside margin of the labium. These animals increase rapidly, and various species infest provisions and living animals, including man. Others roam at large upon the ground, or on plants and other objects. Acarus siro (pl. 77, fig. 70) is the cheese-mite, which is mentioned by Aristotle. In Sarcoptes, the body is soft and timid, the four posterior feet are rudimentary and provided with long bristles, the collar below and the base of the feet are armed with hooks, and the anterior feet terminate in vesicles. This genus is parasitic under the skin of various animals, including man, causing the disease named itch, and although this fact has been often doubted, it seems now to be established beyond dispute. The species which infests man has been known to the Arabs, and is mentioned by an Arabic author, Abenzoar, of the twelfth centary. It has been known from time immemorial in Southern Europe, where it has been considered to be the cause of the itch, under names which are diminutives of the terms used for lice, with which they were naturally confounded in the absence of microscopic examination. Linnæus confounded this species with Acarus siro, considering the two to be varieties of a single species, a view which has been contended for in later times. It seems probable that Acarus siro is occasionally found about the itch pustules, but the Sarcoptes must be searched for at the bottom of the tortuous galleries which it forms under the skin, extending from one to six lines. The common Sarcoptes scabiei (pl. 77, fig. 68) is marked with curved lines above, the middle has small elevations, and there is a small bristle on each side, and two large ones posteriorly.

The itch, caused probably by different species of Sarcoptes, is spread over a great portion of the earth, and is endemic in some localities, and although it is readily destroyed, there are those who consider the irritation in the light of a luxury, and refuse to have it removed.

Various species of Sarcoptes infest man, monkeys, horses, and dromedaries. That of the last-named animal (S. dromedarii) is larger and better armed than the ordinary species, and in several instances it has been communicated to man.

According to Diijardin, the supposed genus Hypopus of Dugès, which was placed in this family, is the immature condition of Gamasus.

Fam. 4. Ixodidæ, The genus Ixodes (pl. 77, figs. 67, 71) includes the parasitic animals known as ticks. The eyes are wanting, and the body has a tough integument; their form is oval, and flat and scale-like when found among grass and bushes; but when they have affixed themselves to the animals which they infest, they become greatly distended, so that an individual a tenth of an inch long may acquire a length of one third of an inch or more by distension, when it resembles a small bean. Being very slow in their movements, they must wait long before they are afforded an opportunity to affix themselves where they can suck blood, so that the distensibility of the body and the division of the stomach into various large branches, enable them to make amends for a long fast, as in the case of the leech. The position of the animal in its parasitic state is maintained by the rostrum, which is composed of three hard corneous pieces, two above (the mandibles), their extremity armed with a movable piece margined with teeth, and one below, which is the labium. This is obtusely rounded at the end, concave above, and armed upon its lower surface with transverse rows of serrifurm teeth, with their points directed backwards, and recalling the somewhat similar structure in the Acanthocephala (p. 47), and designed for a similar use. In a state of repose, the external margins of the mandibles are clasped by the palpi, the hairs of which cover the labium beneath. The explanation of the parts of the mouth given here, is that of Dugès.

The feet in this family are robust, and have six articulations, and when the animals are among plants, and ready to attack their prey, they suspend themselves by two of their feet, extending the others to affix themselves to any passing animal. Say took Ixodes ammdcitus from a deer, and I. orbiculatus from a squirrel. They torment and even kill cattle when they are abundant; dogs suffer much from them, and in the West Indies they must be removed from horses and asses once a week. They also attack birds, tortoises, lizards, and serpents. They seem to be common in various parts of the world, but their distribution is local, as they are unknown in certain localities and common to others not very distant from the former. Say has described nine species inhabiting the United States, including the small and troublesome seed-tick, which renders an excursion so disagreeable in some parts of the western states. The species attack man, and cause a troublesome sore, the effects of which may continue in an occasional itching, for a period of several years.

Fam. 5. Gamasidæ. Palpi slender, short, free, and incurved, body depressed, eyes wanting; parasitic upon beasts, birds, reptiles, and insects. In Gamasus the body is oval, tough, and scutiform above, the mandibles cheliform, and the first pair of feet are slender, and the second thick. They are often seen running upon the ground, and when they are upon the animals which they infest, they run about from place to place, differing from Ixodes in this respect, and in not gorging themselves to such an extent. Gamasus coleopterorum has the back covered with two pale brown plates divided and surrounded by a light space. It is found in Europe and the United States upon various Coleoptera, particularly those which live in dung. Five species are described by Say.

The genus Argas (A. fischeri, pl. 77, fig. 46; A. savinii, fig. 47) is remarkable for containing the poisonous A. persicus, which lives in old houses about Miana in Persia, and is said occasionally to cause the death of foreigners, although it is not fatal to the natives.

A species has been described by Guerin, which was discovered in Central America by Sallé, who states that he and his companion were awakened from profound sleep by sharp bitings or stingings, and upon getting a light he found his hands covered with blood, and swellings like large fleabites. His companion supposed that they had been stung by wasps, but upon awaking the muleteer, it was found that they had been attacked by an insect called talaje, and upon searching, some of the Argas were found swelled with blood, and others empty, with the skin rugose. They live in the crevices of the walls in old houses, coming out at night and returning before morning.

Fam. 6. Hydrachnidæ. This family includes the small globular and oval forms found in water, in which the coxae are so broad as to form a kind of sternum. The young of Hydrachna are born with six feet. They swim about for some time, and then affix themselves to the bodies of aquatic insects by the anterior extremity, when the palpi and feet seem gradually to be withdrawn, and the exterior of the body becomes a kind of sac or cocoon, but the rostrum still penetrates the smaller extremity to draw nourishment from the insect to which they are affixed. The young animal leaves this skin by moulting, and attaches itself to a plant, where another moult takes place before it resembles the adult. During the period of attachment to aquatic insects, these animals can be transported by flight, and distributed to the various small detached ponds in which they are found.

The genus Unionicola, Hald., 1842, differs from Hydrachna in being unable to swim, in having the palpi conical, the antepenultimate articulation the longest and very thick, and the point simple, whilst in Hydrachna, as represented by Duges, these organs are cylindrical, with a double terminal claw; the penultimate articulation is the largest, and the nails of the feet are not bifid as in Unionicola. This genus is parasitic between the folds of the mantle in the Unionidæ. H. triangularis, Say (oviformis, Hald.), inhabits Unio cariosus; it is black, and has a Y-shaped white mark upon the back. U. reticulatus, Hald., is pale, ochraceous, and infests Unio viridis. The last is a large species, being a line and a half long, the length in general hardly reaching a line. From their mode of life, it is probable that in this genus the system is oxygenated through the skin from the water.

Fam. 7. Tromhidiidæ. This family is composed of the larger land forms, which bear some resemblance to the Phalangiidæ in the next order. The genus Trobidium is usually of a bright red, which extends over the feet and palpi, and the surface is velvety, which characteristics, together with their slow motions, will render them recognisable in the forests. The body is composed of two portions, the trunk, and an anterior and inferior portion, including the rostrum and the four anterior feet. The larvæ have six feet, and resemble small drops of red sealing wax affixed to the legs and other parts of Phalangium (pl. 77, fig. 62) and various insects. These were once considered to be a distinct genus, under the name oi Leptus.

Order 3. Adelarthrosomata. The animals of this order respire by tracheæ, and have cheliform mandibles. They are included in the three families: Phalangiidæ, Cheliferidæ, and Galeodidæ.

Fam. 1. Phalangiidæ (pl. 77, figs. 62, 63). This family includes the slender footed spider-like animals known as harry-long-legs. The mandibles are cheliform and the palpi filiform, the eyes two, central, and near together, and the abdomen annulate and closely united to the cephalothorax. They feed upon small insects, avoid the full glare of the light, and are harmless, except that some of them have the power of exuding a disagreeable scent when disturbed. The slender feet are much like antennæ, the tarsus being in some cases composed of fifty articulations; and when the animal is standing or walking, several of the feet are held up or moved about, as if for the purpose of feeling and ascertaining the presence of objects. Some authors place the Phalangiidæ in one order, and the remaining families (including the Scorpionidæ and Phrynidæ) in another, under the name of Solifugæ.

Fam. 2. Cheliferidæ. The genus (pl. 77, fig. 48 a, natural size, and 61, natural size) is remarkable for the large cheliform palpi resembling arms, which give the species the appearance of minute scorpions, except that they have not the tail of the latter. They feed upon minute animals, living in the woods or in houses, especially among books (as noticed by Aristotle), where they are rather beneficial than hurtful. They run rapidly backwards, forwards, or sideways, like the crabs; they are oviparous, have two or four eyes upon the cephalothorax, an annulate abdomen, and the eight feet are of equal size. Say describes two species inhabiting the United States.

Fam. 3. Galeodidæ. Galeodes (pl. 77, figs. 49, 50). The animals of this family resemble large hairy and fierce looking spiders. The palpi are long and resemble feet, and the abdomen has nine or ten articulations. The generic name Galeodes was proposed by Olivier, in 1791, and Solpuga by Herbst, in 1797, according to Agassiz’ Nomenclator, so that the former has priority. The two terms are, however, used by Koch for different genera. The body is divisible into head, thorax, and abdomen, and the eyes are situated upon the head. The first pair of feet, as well as the palpi, are without nails, although the remaining feet have them. They run with great agility, and when interrupted they stop, raise the head, and place themselves upon their posterior feet in a menacing attitude. Lucas, who was sent by the French Government to investigate the entomology of Algeria, says, that when about to catch one of them, it leaped upon his arm and bit the sleeve, maintaining its hold until it was secured. According to Captain Hutton’s observations, these animals are probably not poisonous, as a lizard bitten by one of them did not die. Another lizard three inches long, exclusive of the tail, was almost entirely devoured by one of them, which gorged it so much that it remained motionless for fourteen days. It was nocturnal, rapacious, and was able to bite hard coleoptera into pieces. Its chief food was insects, which it masticated, and did not suck out, in the manner of spiders. They fight fiercely with each other, the victor eating the vanquished. The female watches her eggs and young with much assiduity. The latter, according to the same author, were hatched in fourteen days, and did not stir for three weeks, when they moulted and became active. Galeodes lives under stones, and digs holes for itself in the earth.

Order 4. Polymerosomata. In this order, which is the first of the section Pulmonaria, the body has distinct segments.

Fam. 1. Scorpionidcæ. Scorpio (pl. 77, fig. 51); Buthus (fig. 52). These animals are remarkable for the articulated tail-like extension of the abdomen in the typical sub-family Scorpioninæ, in which the end of the abdomen is armed with a poisonous sting. The scorpions have another peculiar appendage, being a kind of comb upon each side of the base of the abdomen beneath. The eyes vary in number and position, and thus afford characters for various genera. The mouth is situated at the base of the palpi and the two anterior pairs of feet.

The extent to which the sting of scorpions is mortal, and the existence of a pore. or pores to give egress to the poison, have been matters of dispute both in ancient and modern times. Pliny and Tertullian assert correctly, that it is not the wound of the sting, but the poisonous liquid, which is the cause of the evil. The poison gland opens by a pore on each side of the point of the sting. The sting of the small species seems to occasion no greater injury than that of a hornet or similar insect, whilst that of the larger species is believed to be fatal in certain cases. The Arabs, and the inhabitants generally of countries infested by the larger scorpions, regard them with horror. The sting is used in defence, and in killing the insects which are taken for food. They carry the tail curved upwards in walking. They are solitary, living in dark places, and often entering houses and taking refuge in beds, clothing, boots, &c. The scorpions are found in the warm regions of both continents; in North and South America; and two identical species are found in the Mediterranean region of Europe, Asia, and Africa.

In the sub-family, Theliphoninæ, the sting and abdominal combs are absent, and the abdomen ends in a slender tail.

Fam. 2. Phrynidæ. This family forms a link in the passage to the Dimerosomata, as the general appearance approaches that of a spider, the abdomen being oval and pedunculated, although it is segmented, and without a caudal appendage. Phrynus, the only genus of the family, has but six ambulatory feet, the anterior pair being very long and slender, and having all the articulations following the femur replaced by a multitude of small articulations, giving to these organs a kind of antennal character, which is observable in a less degree in Thelyphonus, where the tarsus alone is thus subdivided.

Order 5. Dimerosomata. In this order, which includes the spiders, the body is divided into cephalothorax and abdomen, the latter being joined to the former by a small peduncle. The mandibles are strong, they move vertically, or to some extent horizontally, and they have a terminal movable curved nail or tooth, which has a pore near the point through which a poisonous fluid escapes. The mandibles of the male are generally larger than in the female, although the individuals of the latter sex are usually the largest. The palpi have we articulations, and are attached to the maxillæ or jaws. They are padiform, simple, and ending with a nail in the female, and variously shaped in the male. The maxillæ vary much in shape, and aSbrd good characters in classification. Between the maxillas is the labium or under lip. The feet are of the same shape, but differ in length and thickness. They are usually terminated by a pair of serrated nails. There are six or eight eyes, but generally the latter number, and they are variously grouped in the different genera. The abdomen is usually soft, and sometimes very large. The generative organs are situated at its base beneath; it contains two or four spiracles, and towards the extremity are the vent, and spinnerets connected with the organs which secrete the silk.

The effect of the poison of spiders has been much exaggerated, although under certain circumstances it may be serious. Walcknaer, a voluminous writer upon these animals, states that he has caused himself to be bitten by various species, but no ill effects resulted.

Each spimferet of a spider contains a multitude of pores which, in some species, amount to more than a thousand, so that the compound thread from four spinnerets may contain four thousand strands. It has been suggested, that as the strength of a rope is increased by being composed of many separate strands, the strength of the cord of a spider is secured in the same manner; but this is an error. The strands of a rope increase its strength because the ends of the separate short fibres are thereby better secured; but the silk of the spider, being a uniform fibre, cannot be compared with a compound rope, and at best it is generally comparatively weak. The silk being in a liquid state within the body, and much being required in a short time (as when the spider descends by its thread), the extreme tenuity of the strands enables them to harden almost instantly by contact with the air. newly born spiders are capable of spinning, and Leuwenhoeck has calculated that it would require four millions of the strands of one of them to form a thread as thick as a hair of his beard.

Some spiders shoot out long lines of silk, which have sufficient buoyancy to serve them as balloons for transporting themselves through the air. In the autumn, these gossamers are abundant in the air and on the ground, and they may be frequently seen floating in the breeze with a spider attached. Thus an individual has been observed coming: across the River Susquehanna upwards of three hundred feet above the water towards a cliff of that height.

The webs of spiders are made according to various patterns. Some are closely woven into a funnel into which the spider retreats, and opening externally into a wide surface. The tube of the funnel sometimes extends into a hole in the earth, or other material. Among the webs stretched to take flies, those formed by the large and handsome species of Epeira (pl. 77, figs. 53, 59) are among the most regular.

The cocoon in which the eggs of spiders are inclosed is carefully guarded. Some species seat themselves over it as if in the act of incubation, some place it in their retreats, some in their webs, and the wandering species affix it to their abdomen. In this case, if it be forcibly removed, it is sought for with great solicitude, and when found, carried off or re-affixed.

Flies and other insects constitute the chief food of spiders, and they must be taken living by the spider itself, or they will be generally rejected. Spiders are capable of fasting several months, and they pass the winter without food, being then torpid. They are eaten by various birds, reptiles, and other animals, and some of the stinging Hymenoptera fill the cells of their young with them for the food of the latter, being endowed with the remarkable instinct of disabling the spiders to such an extent as to render them perfectly helpless, so as to be unable to resist the young Hymenoptera, whilst they have life enough to keep them in a fresh state as long as they are wanted for food.

The spiracles are situated near the base of the abdomen beneath, one or two upon each side of the middle. When there are but two spiracles, they communicate with extremely thin laminated gills which have their extremities directed towards the aperture, so that the air can be readily admitted to them. When there are four spiracles, the two posterior ones communicate with tracheæ. The latter belong to the family Mygalidæ (considered a section or sub-order by some authors, under the name of Tetrapneumones), and containing the sub-families Mygcdinæ, Atypinæ, and Dysderinæ. Those with two spiracles have been named Dipneumones. They constitute the family Areneidæ, with the six sub-families: Areneinæ, Theridioninæ, Epeirinæ, Thomisinæ, Lycosinæ, and Salticinæ.

The species of Mygale (pl. 77, fig. 58) live in holes of their own construction, some of which are closed by a trap-door, which renders them difficult to find, and affords a protection to the ingenious constructor. The trap-door is wider externally than internally, or slightly conical, and the mouth of the aperture is formed so as to receive it with great exactness, whilst the form is such as to prevent it from becoming fastened, as would often be the case were it cylindrical. This door is made of about thirty layers of silk and dirt, the layers being somewhat in the shape of small brass weights, the different sizes of which lie one within the other. Upon leaving or entering its burrow the lid closes after the spider by its own weight, and when the animal is upon the outside it must be raised to allow it to enter. The elasticity of the hinge is sufficient to close the aperture if the lid be raised vertically, or drawn still further back; and it is assisted by the distribution of the earthy material, which is thickest towards the hinge, and on this account less likely to be thrown backwards beyond its centre of gravity. Near the margin of the inner side of the lid, and opposite the hinge, the Mygale forms a series of small holes to enable it to insert its claws and jaws to hold it in place, in case of an attempt to raise the lid from without; and if a knife is inserted so as to run beneath the spider, and the clay be then lifted with it, the deceived animal, circumvented in this unexpected manner, suffers itself to be captured without opposition. Nemesia (pl. 78, fig. 35).

Segestria (S. perfida, pl. 78, fig. 36) forms a tubular web in crevices. It inhabits Europe and North Africa.

Lycosa (L. tarentula, pl. 78, fig. 37 a b c; L. melanogaster, fig. 38) is the genus which contains the poisonous tarantula, the effects of the bite of which were supposed to be cured by music, but denied by competent Italian authority in the last century; and as far back as 1672, Doctor Cornelio, of Naples, asserted the supposed disease tarentismus to be in some cases feigned, and in others a delusion arising from melancholy. This and some allied species live in winding holes a foot or two deep. The genus Lycosa is common in the United States.

Argyroneta (A. aquatica, Linn., pl. 77, fig. 56, and pl. 78, fig. 49) is a genus of spiders with unusual aquatic habits. Breathing air, and with the structure of the land spiders, this animal lives in the water, diving beneath the surface, where it lives among aquatic plants in a kind of diving bell of its own construction, and into which it transports air from the surface. The spider, when about to carry a bubble down, bends its body, draws in its legs, and plunges suddenly, the bubble being retained by some unknown means. This is carried beneath a leaf or fiat surface, and a web passed around it, thus forming a nucleus for the structure, which is gradually enlarged as bubbles are added, until it has attained the required size, when it is as large as a small walnut. It must, of course, be closed above, and the entrance must be below. If a fly is thrown into the water, the spider leaves its retreat to get it, and attaching a thread to it, drags it down. The winter is past, and the eggs laid, in this retreat. Soon after the young leave the egg, they ascend to the surface and commence taking down bubbles and constructing habitations of their own. This spider never leaves the water, but will live several days if removed from it. The single species known inhabits Europe from France to Lapland.

The bite of Latrodectus malmignatus (pl. 78, fig. 44) is said to be very dangerous in Corsica, being compared with that of a viper. This genus was formed from that of Theridion (pl. 77, fig. 55).

The species of Tegenaria (T. domestica, pl. 78, fig. 46) are found in buildings, where they live in holes, cellars, crevices, and angles of walls, in which they spin a tube connected with a broad horizontal web externally, supported by numerous lines in various directions. The web is in popular use for checking the bleeding of slight wounds, and individuals of the genus are said to have been sometimes attracted by music.

The genus Gasteracantha (G. armata, pl. 77, fig. 57 b) is remarkable for having an irregular abdomen armed with spines and tubercles. It is widely distributed, appearing in America, Asia, and Australia. It is allied to Epeira.

Hersilia caudata (pl. 7[8], fig. 39); Chersis savinii (fig. 40); Salticus formicarius (fig. 41); Eripus heterogaster (fig. 42 a b c); Arcys lanceolarius (fig. 43); this and the preceding one are from Brazil; Nyssa timida (pl. 78, fig. 45 a b c d e); Lachesis perversa (pl. 78, fig. 47); Uloborios walcnærius (pl. 77, fig. 57 a, and pl. 78, fig. 48); Tetragnatha argyra (pl. 77, fig. 54).

The papers of Prof. N. M. Hentz, on the spiders of the United States, may be consulted in the Boston Journal of Natural History.

Class 5. Myriapoda

The Articulata of this class bear a close external resemblance to worms, having a lengthened multi-articulate wingless and cylindrical or depressed body, and numerous articulated feet, whence they derive their scientific name as well as their common designation of centipedes and millipedes. In the Chilopoda (centipedes) there are generally one, and in the Chilognatha (millipedes) two pairs of feet to each segment, and they are usually terminated by a simple claw. In the former order they are lateral, and in the latter they are placed more towards the middle of the body beneath. In certain accidental cases, there may be three pairs of feet to an odd segment. The number of feet varies from twelve pairs to upwards of three hundred pairs.

The Myriapoda are terrestrial, living in dark and damp places, among moss, or under bark and stones, some feeding upon animal food, and others upon fungi, fruits, or decaying vegetable matter. They differ from insects in the nature of their metamorphosis, being born without members; but the first moult exposes the head, antennæ, and three pairs of feet, the second moult exposes seven pairs of feet towards the anterior part of the body, and finally, with the sixth moult, the full number of feet and segments is acquired, although the generative organs are not developed for two years subsequently. These facts were ascertained upon the genus Iulus, by Savi, a distinguished naturalist of Bologna.

Some of the species are luminous at night, at certain seasons or under certain circumstances, and some secrete a penetrating, pungent, and disagreeable material with an acid scent, although with neither acid nor alkaline qualities. Gervais ascertained that species of Geophilus will live a day or two in water, and that parts of the body will stir after being separated two weeks. Some species are pretty widely spread, Scutigera coleoptrata being found from the North of Europe to Egypt and Barbary; and it is found in the United States, where it has probably been introduced by shipping, according to a suggestion of Say.

This class is placed between the Arachnida and Insecta, by Latreille, in his last work (Cours d’Entomologie), although his opinion had varied previously. There are certain analogies between the Annelida and the Myriapoda, as in the genus Peripatus of the former and Polyxenus of the latter, the fascicular setæ of which resemble those of some of the Annelida. Their affinity to the Crustacea is observable upon comparing forms like the terrestrial genus Oniscus, and Glomeris, which has a similarly shaped body, the power of rolling itself into a ball, a crustaceous exterior, and similar habits; and although the number of feet is fourteen in Oniscus, and thirty-two in the male and thirty-four in the female of Glomeris, the external resemblance is so striking, that Glomeris marginatus has often been taken for a variety of Armadillo vulgaris. They have also been considered to be Arachnida, and more generally, a subdivision of the true insects. Westwood, following Macleay to a certain extent, places the Ptilota of Aristotle (the winged insects) in one class, and the Ametabola in another, the latter being composed of the four orders, Chilognatha, Chilopoda, Thysanura, and Anoplura. The two first of these constitute the Myriapoda, and the last includes the lice. These heterogeneous materials are thrown together on account of their imperfect metamorphosis, a character which is indicated in the name Ametabola.

The class contains the two orders, Chilognatha (lip formed from the jaws), and Chilopoda (lip formed from feet), of which the former contains twenty-one and the latter sixteen genera, in the classification of Newport published in the Philosophical Transactions. Various species in the United States are described by Say, in the Journal of the Academy of Natural Science, vol. ii., 1821.

Order 1. Chilognatha. The genus Iulus may be taken as the type of this order, in which the body is slender, composed of many segments of a crustaceous consistence externally, often cylindrical, and provided with a multitude of short feet arranged in double pairs, except anteriorly, where they are single. The motion of these animals is slow, and when disturbed they generally roll themselves into a ball or spiral. The antennæ are short and slender, two in number, and have seven articulations. The mandibles are crustaceous, triarticulate, and without palpi; the generative organs are situated behind the seventh pair of feet in the male, and behind the second pair in the female. The spiracles are situated behind each pair of feet, and must not be confounded with the lateral outlets of the odoriferous glands.

The order contains the six families, Glomeridæ, Polyxenidæ, Polydesmidæ, Iulidæ, Polyzonidæ, and Siphonophoridæ.

The body of Iulus is cylindrical, and composed of forty or more segments. The genus is common, and widely distributed in various parts of the earth. When disturbed, some of the species exude a disagreeable scent, which in the large and common species of the United States (I marginatus, Say), resembles muriatic acid. This species is three inches long, blackish, and the segments have a rufous margin.

Order 2. Chilopoda. Here the body is depressed and linear, with a tough exterior, and the segments are proportionally longer, and not so numerous as in the Chilognatha. The feet also are less numerous, and the posterior pair are usually projected backwards in the manner of a tail, and used in drawing the body backwards. The antennæ are slender and tapering, and composed of fourteen or more articulations. The mouth is armed with a strong pair of curved jaws with a palpiform appendage. The eyes are usually simple, four or five on each side, or absent. These animals are nocturnal; they live upon animal food, and run rapidly.

The order includes the families, Scutigeridcæ, Lithobiidæ, Scolopendridæ, and Geophilidæ.

The genus Scolopendra has four pairs of eyes, twenty-one segments, or twenty-two if the head is considered to be composed of two segments. In the latter case the segments may be made to correspond with the thirteen composing the body of insects, if the præscutum, scutum, scutellum, and postscutellum of each of the three thoracic segments, are counted separately. Under this view, the segment preceding the nine abdominal segments in Scolopendra will be the metathoracic postscutellum; and the posterior division of the head will be the prothoracic præscutum. A similar division of the segments appears in Cryptops.

The genus Scolopendra is widely distributed over the globe, the larger species (one of which is a foot in length) being peculiar to warm regions. Their bite is poisonous, and may be compared to that of the scorpions.

Class 6. Insecta

The name of the class of Insects is derived from the insected or articulated structure of the body, and its frequent division into several portions, as in the Hymenoptera. It has been variously applied to portions of the Articulata, but always including the hexapod orders, which are provided with wings in most cases, and to which the term has been more and more restricted.

Insects are dioicous articulate animals, breathing air by means of tracheæ, and having a head and abdomen united by an intermediate thorax bearing the six feet and two or four wings when these are present. They have a free head bearing two antennæ, and they are subject, during their growth, to certain external and internal changes termed metamorphoses. Most insects have wings, a peculiarity which none of the other classes possess. The integument is usually sufficiently hard to serve as a kind of external skeleton, to the inside of which various muscles are attached.

The body of insects is usually considered to be composed of thirteen (sometimes fourteen) segments, which are apparent in the larva, although some of them are frequently so much reduced in size, or so intimately joined together, that they cannot be distinguished in the adult. The head forms a single segment, followed by the thorax, which is composed of three segments, and the remaining ones belong to the abdomen.

In Orismology, or the application of names to organs, it has become a matter of very great importance to apply the same name to the same part in different groups of animals, so far as this can be satisfactorily ascertained. The neglect of the older entomologists to observe a rule the advantages of which are so apparent, has been productive of much confusion, and we accordingly find the term thorax, which is correctly applied to the part between the head and abdomen of a Hymenopter (pl. 79, figs. 11, 14, 18), also employed to signify the segment next to the head in Coleoptera (pl. 81, figs. 18, 23, 43, &c.). The inaccuracy of this will appear, upon reflecting that the thorax in the Hymenoptera bears the wings and all the feet, whilst the segment next to the head in the Coleoptera bears the anterior pair of feet alone, corresponding only to one third the thorax of the former. In the Coleoptera, the elytra or wing-covers, when in a state of repose, generally cover the abdomen and two thirds of the thorax, keeping the latter out of view when the insect is viewed from above. A lateral or ventral view (pl. 81, figs. 105, 106, 130) will exhibit the remaining parts of the thorax bearing the wings and the medial and posterior feet. In some cases the abdomen is entirely exposed, the elytra being so short as not to extend beyond the thorax (pl. 81, figs. 1–7). The three segments which comprise the thorax both of a hymenopter and a coleopter, may be recognised by the three pairs of feet; but whilst that next to the head (named the prothorax) is conspicuous in the latter, it is reduced to a mere collar in the hymenopter, where the next segment or mesothorax is largely developed, to bear the large anterior pair of wings, whilst the corresponding part in the Coleoptera have to bear the elytra, which are not used as organs of flight. Finally, the metathorax, or third segment of the thorax, is reduced in the Hymenoptera, the wings of this segment being small and of but secondary importance in flight, whilst in the Coleoptera the same organs are the only instruments of flight.

Most insects are oviparous; some, as Musca carnaria, are ovo-viviparous, the eggs being hatched within the body, and in the Pupipara the young advances to the pupa state before it is excluded, the apparent egg-shell being the pupa case.

The egg of insects is generally oval, but there are many other forms, as globular, hemispherical, cylindrical, lenticular, conical, pyriform, &c. The eggs of Hemerobius are attached to leaves at the extremity of a long thread. Some are crowned at one extremity, and others have ear-like appendages. In most cases the surface is smooth, but they sometimes occur ribbed or sculptured in various patterns. White, yellow, and green, are almost the only colors observed in them. The eggs of insects are deposited according to the wants of the young to which they are to give birth, either in earthy water, dung, upon dead animals, or in putrid vegetables, beneath the skin of caterpillars, in punctures in Jiving vegetables, where they sometimes cause galls; some are glued to leaves or branches, and others are placed in cells where the young are fed.

The larva appears when the shell of the egg is burst at the period of its maturity. The name larva is applicable to the young of all insects, although those of butterflies are also named caterpillars, and those of certain flies maggots. The larva is in most cases unlike the adult insect, generally appearing as a cylindrical worm, either without feet or with six or more walking organs, of which six only are articulated feet. In this condition nourishment is taken, often in great quantities; the growth is rapid, and a series of moultings is undergone. When the larva has attained its full size, in many cases it becomes an inactive pupa without external organs, and incapable of locomotion or taking food; but when the pupa case is burst, the perfect insect appears. In some cases the larva resembles the adult at all times in most particulars; and when, after successive moultings, it becomes a pupa, this is still much like the adult, and continues to eat and move about, differing from the larva in having incipient wings inclosed in an envelope, and from the adult in not having perfect wings. Insects are thus subject to two principal kinds of metamorphosis, whence the latter have been named Homomorpha, and the former Heteromorpha. The metamorphosis of the Lepidoptera, Coleoptera, Hymenoptera, and Diptera, is heteromorphic; whilst that of the Orthoptera and Hemiptera is homomorphic.

Heteromorphic larvæ are more or less cylindrical, with or without feet, and a distinct head. They have generally thirteen segments, each of which has been provided with a name by Newman, as follows, commencing with the head: 1, caput; 2, prothorax; 3, mesothorax; 4, metathorax; 5, propodeon; 6, podeon; 7, metapodeon; 8, octoon; 9, ennaton; 10, decaton; 11, protelum; 12, paratelum; 13, telum.

The head of larvæ is in some cases not different from the other segments, being equally soft, and without antennæ, eyes, or jaws. A larva of this kind (the feet being also absent) is popularly termed a maggot. The caterpillars, which have a more perfect organization, have a corneous head generally bearing the various organs apparent in the perfect insect or imago. The antennæ of larvae have a simple structure, and but few articulations, even in those cases where the adult has them complicated and very long.

Of the two kinds of eyes found in adult insects, compound and simple, the latter, named stemmata, are alone present in the larvæ, but these are sometimes entirely destitute of visual organs. When present, there are from one to six upon each side. Some caterpillars have the power of secreting a silken thread, out of which their cocoon is made, the secreting organ being a part of the mouth. The larvae of some Coleoptera have an analogous organ at the posterior extremity.

The sides of terrestrial larvæ generally show the spiracles, which usually amount to nine or ten upon each side. All the segments, except the first, or head, third, fourth, and last, are usually supplied with spiracles. In some aquatic larvæ there are lateral gills, and in others breathing is accomplished through the posterior extremity.

The larva state is that in which insects generally live the longest, the life of the imago being often very short; so short, that in some cases they require no nourishment, and are not provided with a mouth. Some species of Melolontha live a few weeks in the adult state, and three years as larvæ. Cicada septendecim (and probably other species) does not survive a single season, although its larva is seventeen years in coming to maturity.

Pupa. In the homomorphous forms the passage from the larva to the pupa state is gradual, and is accompanied by but little external change, especially in the wingless forms, as bed-bugs, and certain grasshoppers. Amongst the latter, the different stages of the genus Phalangopsis can hardly be determined, but we have observed that certain spines upon the legs appear only in the last stage, thus indicating the adult.

When the caterpillar incloses itself in a cocoon to take the helpless condition of a pnpa, various internal changes take place, tending towards the organization of the future insect; and even previous to this, the internal organization of the larva had been gradually undergoing various changes in the nervous and alimentary systems, unaccompanied by any external change except that of size. Some pupse are protected by a cocoon, and some are not thus protected. Of the latter, some are suspended by the posterior extremity, and others, as Papilio, attach themselves with the head above, and a thread around the body to maintain it in its position. Some suspended pupæ are finely marked with bright colors and golden spots, whence the name of Chrysalis, which is seldom used, and aurelia, which is obsolete.

Agassiz has pointed out several curious analogies among the classes of Articulata, composing the larvæ of Lepidoptera (particularly those with bristly tufts) to the Annelida; and the pupæ in which the abdomen alone is capable of motion (the head and thorax being united under a kind of carapace) to the decapodous Crustacea, which are, on account of this affinity with one of the conditions of insects, placed at the head of their class. He places the Insects above the Crustacea, because the former leave the condition in which they are covered by a carapace, and advance a step further. Finally, this philosophical author places the Lepidoptera at the head of the insects (as Swainson had done upon different grounds), because the larva is mandibulate, and the adult insect perfectly haustellate, so that it advances further from the larva condition than any of the orders. See Lectures on Embryology; and Proceed. Am. Assoc. Charleston, 1850.

Imago. The perfect insect or imago appears when the case of the pupa is split, and in the winged species, the wings, which were closely folded, begin to expand and take their final shape. The imago differs from the larva in having the body divided into the three principal divisions of head, thorax, and abdomen.

The integument of insects contains a peculiar principle, named chitine by Odier, which constitutes a third or fourth of its bulk. It resembles bone somewhat in its composition, as it contains phosphate of lime, and a trace of other compounds found in bone. The chitine forms part of the dermis, which is covered by a thin epidermis. Coccine is another chemical constituent, found particularly in the genus Coccus.

The head of insects is usually regarded as a single piece, but as the corresponding part in the Crustacea is considered to be made up of minor parts, it has been proposed to extend the same theory to the class under consideration, either allowing as many theoretical segments as there are kinds of appendages, or allowing two kinds of appendages to some of them. Of these two modes of viewing the question, the former is preferred in studying the Crustacea, and should therefore have the preference in this class.

The organs concerned in manducation (enumerating them from above) are, the upper lip or labrum, the mandibulæ, or upper jaws, the maxillæ or lower jaws, the tongue or ligula, and the lower lip or labium. Brullé divides the ligula into an upper organ or epipharynx, and a lower one or hypopharynx, on the ground that the ligula may be superior or inferior, both portions being sometimes present, although unequally developed. If the lips and ligula be considered to be formed by the union of a right and left hand piece, they will correspond to four pairs of organs like the right and left mandibles and maxillæ, makiug six sets of organs corresponding to as many theoretical segments. Brullé, who proposes this theory, does not take the eyes or antennæ into account in his enumeration.

The various organs composing the mouth of insects have not the same degree of development in all, some being very conspicuous in certain cases, and obscure, modified, or obsolete in others. The distinguished Savigny, the entomologist who accompanied Bonaparte’s celebrated expedition to Egypt, discovered the remarkable fact that the antlia or spiral sucker of a butterfly, and the maxillæ of a coleopter, are modified conditions of the same organs; and he extended this comparison to the mouth of all the orders. The haustellum of a fly is composed chiefly of the labium, and the promuscis of a hemipter of the maxillæ and mandibles.

Without attempting to divide the head of insects into theoretical segments, its various minor parts must be indicated for the purposes of reference and description. Its general form is more or less globular, with many variations, and it has projections like horns, but they are never articulated. The head (caput), exclusive of the attached organs, is named the cranium; the upper part from the front backwards, is the epicranium; the top of the head is the vertex, which is usually the seat of the stemmata or simple eyes; and the posterior part is the occiput. The anterior margin is the clypeus, and back of this is the front. The part between the eyes is sometimes named the sinciput; and the sides of the head genæ or cheeks. The principal part of the head beneath is the gula. The anterior part of the head is often prolonged into a rostrum, as in the Curculionidæ.

The antennæ of insects are situated upon the face near the eyes, by which they are sometimes partly surrounded, and they are attached to the head by a ball and socket connexion. These organs are generally capable of moving at the base, and the various articulations move upon each other. The articulations vary much in form and number, and afford good characters for classification. The antennæ may be shorter than the head, and more than twice the length of the body, and the number of articulations may vary from one to fifty, sixty, or more. Long antennæ are made up either of many short articulations or of a few long ones. The antennæ often difier in the sexes of the same species, in length, and in the number and form of the articulations. Among the various forms of antennæ may be mentioned the setaceous; moniliform, shaped like a string of beads; serrate; pectinate; bipectinate, with a pectination upon each side; geniculate, or bent like an elbow; clavate; flabellate, &c. Some have supposed the antennæ to be organs of feeling, others of hearing, and others of a peculiar sense, but their use is not known, and may vary in different orders.

Eyes. Insects have two kinds of eyes, compound and simple, named respectively eyes and stemmata. The former are situated upon the sides of the head, and are composed of many hexagonal lenses placed in contact. These have been enumerated in various insects, and it has been ascertained that in the eye of an ant there are fifty lenses, in a dragon-fly twelve thousand, and in various butterflies from six to thirty thousand. The form of a compound eye is round, oval, or kidney-shaped, in the last case frequently receiving an antenna in the concavity. The eyes often nearly cover the entire head, extending upwards to bring their inner margins in contact, so that the greater part of the surface of the head has the function of a vast compound eye, as in the dragon-flies (Libellula). In some insects the eyes of the male cover more of the head than those of the female. Although there is usually but one eye upon each side, this is sometimes divided, as in the flat water insect of the genus Gyrinus, in which half of the divided eye is above and half below. In Tetraopes (meaning four eyes) the eyes have been divided by the base of the antennæ; and in some cases where they are kidney-shaped, the emargination is so deep that only a narrow strip connects the two ends of the eye. The stemmata are three (less commonly two, or perhaps even one) lenses or simple eyes, situated upon the vertex or forehead, and generally forming a triangle. The stemmata are also named ocelli, but as this term is also applied to spots resembling eyes (as in the wings of butterflies), the former term is preferable.

The mouth of insects, although composed of the same essential parts, has these modified into two principal types of structure, one of which is adapted to masticate, and the other to suck food. The former is termed mandibulate, and the latter haustellate, and we have the corresponding section of insects, Mandibulata and Haustellata; but in the Hymenoptera we find biting mandibles in conjunction with sucking organs.

In the Mandibulata the mouth organs are as follows: The labrum, or upper lip, is a variously shaped horizontal plate, articulated to the clypeus and covering the mandibles. The mandibles, or upper jaws, move laterally and horizontally, like scissors. The internal margin is sharp, and often toothed, and the apex is generally curved inwards. The maxillæ, or lower jaws, are situated beneath the former, and have a similar motion, but they are less robust. When fully developed, the maxillæ are composed of four or five pieces, namely, 1, the cardo, or hinge; 2, the stipes, or stalk; 3, the squama, or palpifer, closely united with the former, and supporting an articulated palpus, or feeler; 4, the mando, or lacinia, which forms the inside of the maxilla, and is clothed with stiff bristles. In the predatory Coleoptera its apex is curved, and often articulated, as in Cicindela (pl. 81, fig. 26). 5, the galea, or external lobe of the maxilla, which becomes a kind of second or internal bi-articulate palpus in Cicindela. In the Orthoptera the galea is large, and articulated at the base, and its internal side is concave, so that it approximates and protects the mando, whence its name of galea. The mando is often absent, or united to the galea, so as to form a single organ.

The labium, or lower lip, closes the mouth below, and although it corresponds with the upper lip, it is a much more complicated organ. In some points of view it may be compared with a pair of maxillæ united in a single plate, as it has an articulated palpus on each side, much like those of the former organs. The labium is partly covered by and articulated with the mentum, which is articulated to the anterior part of the cranium, beneath named the jugulum. The labial palpi are attached one on each side of the labium near the tongue. The projecting sides of the tongue are named paraglossæ.

Thorax. The thorax supports the organs of motion, and is attached to the head of an insect by a membranous connexion. Its entire upper and lower surfaces are named respectively tergum and pectum. It is composed of three divisions, named prothorax, mesothorax, and metathorax; the upper surfaces of which are termed pronotum, mesonotum, and metanotum, and the inferior surfaces antepectus, medipectus, and postpectus.¹⁰ The prothorax bears the anterior pair of feet, but as it bears no wings it is simpler in its structure, and its theoretical parts are more difficult to discover than those of the two other thoracic segments. It is in the latter, therefore, that we must look for the subdivisions of these segments. These are generally enumerated from the front backwards, when the four subdivisions of the upper part will be the præscutum, scutum, scutellum, and postscutellum, and those below, the paraptera, sternum, episterna, and epimera. The term pleura is applied to the sides in descriptions, but it is not limited to any particular part. The sternum is the chief central part with which the two episterna articulate, and the two epimera are near the insertion of the feet, and the paraptera (or tegulæ, oy patagia) near the wings. Newport thinks it exists in a rudimentary condition in the prothorax, but Straus Dürckheim thinks the part referred to by that author is the rudiment of another segment. The mesothoracic scutellum is often seen wedged between the base of the elytra in the Coleoptera (pl. 81, figs. 23, 124, 131, &c.) The prothorax and mesothorax have usually each a pair of spiracles, but in the Hymenoptera the second pair is upon the metathorax.

The chief appendages of the thorax are the feet, which are never absent. These organs have many modifications to adapt them to their various uses of walking, swimming, grasping, leaping, digging, &c. The thoracic cavities into which the base of the feet is fitted are named acetabula, and the basal part of the limb which enters them is the coxa; but this is sometimes firmly attached, so as to have no independent motion. Next to the coxa follows a small articulation named the trochanter; then follows the principal articulation, the femur, or thigh, to which succeeds the tibia, which is often armed at the end with fixed or movable spines, named calcaria. This part is more generally provided with spines and cilia than the other parts. The tibia is followed by the tarsus, which is made up of several small articulations immed phalanges, of which there are never more than five. The end of the tarsi is usually armed with two claws named ungues.

Insects which have five articulaitions to the tarsus are named pentamerous. Those with four are named tetramerous; but as a fifth immovable and microscopic articulation has been discovered, Burmeister names this form cryptopentamerous, and Westwood, pseudotetramerous, a useless addition of names, for, as Mulsant observes, the terms Tetrainera, &c., refer to the number of free articulations. Sober goes so far as to consider all the Coleoptera pentamerous; but even could the abortive articulations be detected, the relation of the different groups would not be altered, because the tarsi of the Pentamera would still have five, and those of the Tetramera four movable pieces. In the Heteromera the four anterior tarsi have five, and the posterior pair four articulations. Trimerous, dinerous, and monomerous tarsi are also enumerated. The anterior tarsi are sometimes wanting, as in Ateuchus.

The wings, when present, are either two or four, the anterior pair being affixed to the mesothorax, and the posterior ones to the metathorax. Sometimes the two pairs are equal, and when they are of unequal size, sometimes the anterior ones are the largest, as in the Hymenoptera and Lepidoptera; and sometimes the posterior ones, as in the Orthoptera. In the Coleoptera the anterior wings are converted into elytra for the protection of the true wings, not being used as organs of flight. The wings are composed of two usually transparent membranes, between which various hollow nervures are distributed, and filled with air from the body. In the Orthoptera (grasshoppers, &c.) the upper or anterior wings (named tegmina) are thicker and narrower than the inferior ones, and the latter are folded like a fan. In a part of the Hemiptera the base of the upper wings has a leathery texture. All the wings of the Hymenoptera, Lepidoptera, and Neuroptera, are of a uniform texture respectively. Those of the Lepidoptera are covered with minute scales; those of the Neuroptera have numerous reticulating nervures, and in the Hymenoptera the nervures are but few. In the Diptera, or flies, the anterior wings are used in flight, the posterior ones being reduced to a small knobbed thread (halteres). In the Strepsiptera the posterior wings are fully developed, the anterior ones being abortive. In most of the orders of winged insects there are genera and species which have no wings; and some have wings in one sex and not in the other, as in the female coleoptera, known as glowworms. In one genus of Orthoptera the posterior wings are present, without a vestige of the anterior pair.

Abdomen. The abdomen is attached to the metathorax, either by its entire breadth, or by a portion of it only. The upper surface is named the dorsum, and the lower one the venter. Of the nine distinct normal segments some are occasionally absent by a union of several into one. In some cases the segments of the dorsum and venter do not correspond; in Carabus, for example, the former has nine and the latter but five. In many cases the abdomen of the male has one segment more than that of the female, and the dorsum has generally one more than the venter. The connexion between the upper and lower parts of the same segment, and between the segments, is effected by a membrane, and in the latter case the base of each segment slides within the preceding one. The abdomen is more capable of motion than the thorax, and in some insects it is very flexible, as in the coleoptera with short elytra, the wasps, &c. The abdominal spiracles are situated at the junction of the dorsum and venter, or in the lateral margin of the dorsum, and nearly every segment has a pair of spiracles. The abdomen has various appendages, as the forceps in the male of Panorpa, hooks, stylets, ovipositor, sting, &c.

The nervous system of insects corresponds with the articulate type, being composed of a double cord with a line of ganglions. The principal organ of circulation is a dorsal vessel, which is a long muscular pulsating heart. The alimentary canal offers many modifications to adapt it to the various kinds of food upon which insects subsist.

Many insects, particularly the Coleoptera, are luminous at night. Among these are members of the genera Elater and Lampyris. In both sexes of certain species of the former genus, the light is emitted chiefly from a raised oval spot on each side of the pronotum, but the sides of the abdomen are luminons also. The light is sufficient to enable a person to read small print, if the insect be passed along the lines. In Lampyris the light proceeds from the posterior extremity of the body, and it is more bright in the female (which is sometimes apterous) than in the winged male. The larvæ of some of the Lampyrides are luminous, and in the southern United States there is a small flat larva (probably of an Elater) about an inch long, which emits a strong phosphorescence from all the segments, equal to that of Elater noctilucus; and when the head and tail are brought together, a brilliant circle, like a ring of diamonds, is formed. According to Kirby and Spence, the eyes of some nocturnal Lepidoptera are luminous. In several North American species of Sphinx we have observed eyes apparently phosphorescent, by dim candlelight, or when shaded from its direct light; but this false phosphorescence has always disappeared when the light was extinguished, so that in these cases, at least, there was only a peculiar reflection.

Many insects imitate the possum in simulating death when disturbed; some allow themselves to drop from leaves; elaters, when unable to escape by running, either simulate death, or by a click throw themselves out of the way. The genus Brachius, when disturbed, shoots out a vapor accompanied by a slight sound. Some insects defend themselves by biting, some by stinging, some by ejecting acrid matter from the stomach and mouth, and others by exuding a disagreeable scent. The caterpillars of the genus Papilio project, when disturbed, a forked gland from the neck above, which is the seat of a very offensive odor. The spinous tufts of some caterpillars have an irritating quality like that of nettles.

Sounds are emitted by various insects, and by means of various organs, as the rubbing together of the wings in Orthoptera, the end of the abdomen against the inside of the elytra, and the prothorax against the mesothorax. The male Cicada makes a very loud and shrill sound, which is produced by a peculiar apparatus opening at the base of the abdomen. The vibrating apparatus is lateral, and the mirror-like membranes within the external aperture may be destroyed without interrupting the sound. A nocturnal butterfly, Acherontia atropos (pl. 80, fig. 15), produces a plaintive cry, which is said to proceed from the head. We have discovered that a sound is made by an American species of Lithosia (another nocturnal lepidopter) by vibrating the sides of the thorax; and we have heard a very low and dull musical sound from the hemipterous genus Belostoma (pl. 80, fig. 71), produced apparently by a vibration within the thorax, and from the lowness of the note produced, a large portion of the organs must be concerned in producing it.

The relations of insects to man are more numerous and important than those of the other classes of animals excepting the domestic breeds, and they exceed these in the importance of their history. Almost every year new enemies to the various vegetable productions cultivated by the farmer and gardener make their appearance, the history of which must in many cases be known before the proper means can be taken to prevent their increase. Often the noxious insect has a destroyer in some other insect, and the latter, being seen about the infested vegetable, is often mistaken for the real enemy Some insects destroy the leaves and blossoms of plants, as the larvæ of butterflies; the larvæ of some Coleoptera, especially those of some of the beetles (pl. 81, fig. 130), are very destructive to the roots of grass, which they sometimes destroy to such an extent that the sod can be taken up in large flakes. An instance is related of a farmer whose crops were entirely destroyed by the larvæ of Melolontha (pl. 81, fig. 130), of which eighty bushels were collected. At one time the cultivation of the sugar cane had to be abandoned on account of the increase of an ant (Formica saccharivora), which destroyed all the plantations; and on the eastern continent large tracts are sometimes rendered desolate by the ravages of the large grasshopper, Locusta inigratoria. The Curculionidæ (including the weevils) (pl. 81, figs. 67–76) are destructive to various kinds of grain and seed; the Cerambycidæ (pl. 81, fig. 50, &c.) destroy growing and dead wood; Bostrichus, &c., perforate the bark; and the Aphides and other families suck the sap; so that amongst the various orders, all parts of a plant, from the root to the seed, whether living or dead, are subject to destruction.

Insects are frequently useful to plants in bringing the pollen to the pistils, and thus securing the continuance of the species in cases where this could not be effected except by such extraneous means. The insects which feed upon honey and pollen effect this object, not only in cases where the stamens and pistils, although together, present difficulties in the mode of getting the pollen to the latter, but in those cases where the plants are dioicous, when it sometimes happens that the staminate and pistillate flowers are several miles apart. Moreover, the stamens and pistils often arrive at maturity at different periods in the same blossom, so that the ripe pollen is carried upon the hairy body and limbs of the insect to the mature pistils of a different tree.

The predaceous insects are useful in destroying those which feed upon vegetables, and they attack both the perfect insects and their larvæ. The parasitic families destroy an immense number of caterpillars, and the larvæ of flies which destroy vegetables, and their size is so graduated that they are capable of destroying larvae of all sizes, from those several inches in length, to such as do not exceed one twenty-fifth of an inch.

Insects in their various states constitute the food of many beasts, birds, reptiles, and fishes. Some, as the large grasshoppers, are sometimes dried and eaten in the Levant; some savage nations eat the large grubs found in rotten wood; and the cossus, which the ancients esteemed as a great delicacy, was a larva of some kind, and an allied one is now eaten in Brazil. Ants are eaten by the savages of Brazil, the formic acid probably replacing the vinegar used in civilized gastronomy; whilst some of the lowest savage tribes devour their own vermin.

The various species of blistering flies are employed under the name of cantharides; the genus Coccus furnishes the beautiful dyeing material cochineal; the galls formed on oak trees by insects of the genus Cynips, are used in the arts; and insects furnish honey, silk, and manna.

Caprification is an art which has been practised from a remote period. It consists in causing figs to ripen by suspending upon the trees branches of the wild fig tree (named caprificus by the Romans), which is infested by an insect which pierces the fruit and causes it to ripen.

The indigenes of Brazil have made a curious surgical application of ants, many of which, when they attack with their mandibles, will allow themselves to be pulled to pieces rather than let go. When one of these natives has received a cut, the sides of the wound are brought together carefully, and an ant adapted for the purpose is made to bite the conjoined edges, when the body is torn from the head, the process being repeated according to the length of the wound, so that the natives are often seen with rows of ant heads upon various parts of the body.

Although insects are essentially terrestrial, there are families, the members of which swim upon the surface (as Gyrinus), or walk with the body raised above it (as Gerris, or Hydrometra), the tips of their feet touching the surface, and a few which walk upon the bottom (as Nepa). These are almost entirely confined to the fresh waters. West wood, however, describes a genus (Micradymma) which inhabits the coasts of the sea between high and low water mark, under such circumstances that it must remain four hours under water at each tide, and he mentions other instances of Coleoptera remaining beneath salt water for shorter periods. (Mag. Zool. and Bot. ii. 121.) According to Audouin, a small carabideous insect, Aepus fluvescens, passes a great part of the time beneath the sea, holding a small quantity of air among the bristles with which it is in part clothed; but whether it can abstract oxygen from the water when this is exhausted, has not been determined. It is probable, however, that this power exists in the coleopterous genus Elmis, and some allied ones, the species of which are small, tardy in their movements, and unable to swim. They live affixed to stones at the bottom of fresh waters, which are sometimes so rapid that the insects could not reach the surface and return to the position in which they are found.

Among the insects which walk upon the water, the most remarkable is the genus Halobates (allied to Gerris), which is found far at sea in the Southern Atlantic and the intertropical regions of the Pacific. Most of the species have been described from wingless individuals, probably larvæ.

Orders of Insects

The distribution of insects into orders has been one of the chief problems of Entomology, and one about which there is a great want of unanimity. Latreille, the father of modern Entomology, who was born in 1762, and devoted a long life to the science, proposed a system in 1796, which he subsequently modified in various editions of his works, in 1806, 1817, 1825, 1829, and 1832. In these he adopted the following arrangement of the orders, which is still very generally followed:

1. Insects without wings.
   1. Without metamorphosis
      1. Thysanura, *Mouth mandibulate.
      2. Parasita, **Mouth suctorial (lice).
   2. 3. Siphonaptera, A metamorphosis (fleas).
2. Insects with wings.
   1. Elytroptera, (Anterior wing acting as a sheath for the posterior one.)
      1. *Mouth mandibulate
      2. 4. Coleoptera, Wing-covers horny, metam. perfect.
      3. 5. Dermaptera, Wing-covers horny, metam. imperfect.
      4. 6. Orthoptera, Wing-covers coreaceous, metam. imperfect.
      5. 7. Hemiptera, **Mouth suctorial, metam. imperfect.
   2. Gymnoptera (wings alike)
      1. *Wings four.
      2. †Mandibulate, mandibles distinct.
      3. 8. Neuroptera, Wings reticulated.
      4. 9. Hymenoptera, Wings veined.
      5. 10. Lepidoptera, ††Mouth suctorial, mandibles abortive.
      6. **Wings two.
      7. 11. Rhipoptera, †Two twisted halteres before the wings.
      8. 12. Diptera, ††Halteres two, behind the wings.

It must be borne in mind that the same name is in some cases not given to the same group by different authors, and that the same order sometimes has several names. The English authors exhibit a fondness for numerous for orders, separating, for example, the Cicadie from the Hemiptera, under the, name of Homoptera.

After various modifications, Burmeister proposed, in 1839, a very different arrangement, founded principally upon the metamorphosis, of which he admits two grades, one half, the other entire, according to which  he names insects Hemimetabola (Ametabola of Leach) and Holometabola (Metabola of Leach), each of which contains haustellate and mandibulate orders, of which the former contains two: 1, Rhynchota; 2, Gymnognatha; and the latter four: 3, Antliata, Fabr. (Diptera, Linn.); 4, Piezata, Fabr. (Hymenoptera, Linn.); 5, Glossata, Fabr. (Lepidoptera, Linn.); and 6, Eleutherata, Fabr. (Coleoptera, Linn.). For all these, except the second, Burmeister adopts the names of Fabricius. The peculiarity of this arrangement is the reduction of the orders to six, and the distribution of the minor parts of each, as will be observed in the following sketch.

The Rhynchota are made to include the tribe and family Pediculina (the lice), or haustellate Anoplura/ whilst the mandibulate Anoplura, or bird lice, form the second tribe of his order Gymnognatha, under the name of Mallopliaga, the first tribe being the Physopoda, from which Haliday and most English entomologists form their order Thysanoptera. The order Thysanura of preceding authors forms a tribe, next to which succeed the Orthoptera (including Blatta); Dermatoptera (Forficula, pl. 81, figs. 1–3); Corrodentia (Termes, Embia); Subulicornia (Ephemera, Libellula); Plecoptera (Semblis); Trichoptera; and Plannipennia (Sialis, &c.), all as tribes of the same order. It results from this, that the Neuroptera and Orthoptera, as well as other groups usually considered orders, form but one order, in the opinion of Burmeister. Erichson (in Agassiz’s Nomenclator) places the Thysanura as an order, except that the Lepismidæ are withdrawn and placed in the order Orthoptera, which is further enlarged by the addition of the Libellulidæ, which are abstracted from the remaining Neuroptera. Erichson admits the orders Thysanoptera, Epizoa (lice), and Suctoria (fleas).

Burmeister states the principle upon which he establishes his orders as follows: “The more marked the transformation the more heterogeneous is the individual in the several stages of its existence; and as all insects proceed from the same point, those necessarily, whose metamorphosis we call complete, must attain a higher grade than the rest, which transform themselves incompletely. We thus obtain two chief groups among insects, Hemimetabola and Holometabola. Both commence a new development in the organization of the mouth, as they at first exhibit to us abortive, setiform, oral organs, only adapted to suction, but in the higher grades these suctorial organs develope themselves into free mandibles, with a lip covering them. Thus each group has Insecta haustellata and Insecta mandibulata. Each of these groups may then be further subdivided, according to the form of the larva, the structure of the wings, and the entire internal organization, and these divisions constitute their orders. We thus obtain an arrangement, the principles of which are deduced from the idea of the entire insect, and which, as this idea becomes separated according to its several characters and constituents, it consequently necessarily and spontaneously forms itself by the philosophical laws of thought.”

The orders of Latreille will be chiefly followed here, not because they are considered to be correct, but because the accuracy of the modifications proposed by Erichson and Burmeister has not been sufficiently tested. Moreover, the views of these celebrated entomologists do not correspond.

Order 1. Thysanura (pl. 77, figs. 79–84). In this order, established by Latreille in 1796, and considered a tribe of liis order Gymnognatha by Burmeister, the body is apterous, more or less cylindrical, and often covered with minute scales like a silvery dust. The antennæ are longer than the head, and the mouth is provided with mandibles and maxillae. They are of active liabits, living in woods, among moss, or beneath stones and bark. Some of the small species are sometimes found on the surface of the water near the margin, or hopping about on the surface of snow in winter, sometimes in great numbers. The order contains the two families, Poduridæ and Lepismidæ.

Fam. 1 Podioridæ. Here the body is oblong or globular, the antennæ are rarely composed of more than four articulations, but in the genus Macrotoma the three or four articulations are divided into a great many rings or indistinct segments, indicating an affinity with the Lepismidæ. The palpi are indistinct according to some authors, and absent according to others. The mandibles and maxillae are membranaceous, the eyes simple, varying in number, and the abdomen is four or six articulate. The prothorax is sometimes much reduced in size, or wanting above, although a part of it remains below, to which the anterior feet are attached. The posterior extremity is provided with a spring or appendage bent along the abdomen, and used in leaping. This, however, is wanting in the genus Anura, in which the mandibles and maxillæ seem to be absent. They are usually confined to damp places, and die very soon if deprived of moisture. The oral aperture is so minute that it is supposed they subsist upon the juices of decaying vegetable matter.

Podura (pl. 77, fig. 79 a, natural size; b, magnified, exhibiting the caudal spring). Smynthurus (fig. 80) has the abdomen large and globular. The species of this genus are often seen hopping upon the surface of water and snow. The dark-colored species of this family are so abundant at times as to give the snow the appearance of being sprinkled with course gunpowder. J. M. M‘Minn mentions their occurrence in the mountains of Pennsylvania, in the following words (Proceed. Acad. Nat. Sci. iv. 246): “I have frequently noticed them in mid-winter on the snow, but I never saw such a multitude of them together as I witnessed on the 17th of Feb., 1849. The snow was entirely covered for the fourth of a mile along the road, and several rods on either side. The mercury in Fahrenheit was standing about fifteen degrees; the atmosphere was dry and clear. These little animals were quite stupid, and to all appearance had been but a short time there, and as it was about nine o’clock in the morning, I judged that they arrived at night. Their motion was slow, and those on the top were quietly endeavoring to get under. The next day, when I again passed the spot, I could not detect a vestige of them. The wind had been strong from the north for several days, and I have noticed that we had strong north winds whenever I had seen them.” This species is probably the Podura nivicola described by Dr. A. Fitch, who gives a similar history of it in his account of the “Winter Insects of Eastern New York,” published in the Am. Jour, of Agr. and Sci. for May, 1847.

Fam. 2. Lepismidæ. In this family the antennæ are setaceous, and composed of a great number of small articulations; the oral organs are present, the palpi are conspicuous, and each side of the abdomen has a row of movable appendages, which Latreille considers false feet, and Gervais respiratory organs. The abdomen is composed of ten segments, and terminated by a number of multi-articulate threads, which vary in number according to the genera. The genus Machilus (pl. 77, figs. 81, 84) has a leaping spring like Podura, and a large compound eye formed by the fusion of the two which appear in other genera. The genus Lepisma (figs. 82, 83) is found in houses in Europe and America, and from the silvery color of its scales, it is sometimes called sugar-fish. It runs rapidly, and is difficult to take without removing the scales. The common species is supposed to eat sugar, whence its name Lepisma saccharina.

Order 2. Anoplura. The order Anoplura (thus named by Macleay from the absence of locomotive caudal appendages) was also named Parasita by Latreille, on account of its parasitic habits, and Epizoa by Nizsch, from its occurrence upon animals. In this order, which includes the lice, there are six feet, no wings, and two or four stemmata. Burmeister, as we have already seen, places the two families of which it is composed in separate orders, one, the Pediculidæ or lice, among the Hemiptera, and the Nirmidæ or bird lice among the Orthoptera, the former being haustellate and the latter mandibulate. The general structure and habits of the two families are very much alike, and we have seen that the best characters, as those afforded by the organs of respiration, are in certain cases not uniform throughout an order; so that in the present case the difference between the oral organs of the two families may be of no more account than the absence of special respiratory organs in some of the Crustacea. The head and thorax are distinct, the antennæ are short, and composed of but few articulations; the tarsi have but one articulation, terminating in a simple nail, sometimes doubled back, so as to form a claw adapted for holding.

Fam. 1. Pediculidæ. The mouth is a small suctorial retractile rostrum placed beneath the head. The thorax is narrower than the abdomen, which is large, and with the segments (of which there are from seven to nine) distinct. There are six pairs of spiracles. This family contains several genera, of which the best known is Pediculus. P. capitis (pl. 77, fig. 77, a b c) infests the human head. The eyes are a black point on each side, the antennæ have five articulations, and the general color is pale yellowish, with a dark line on each side. The skin is tough, and sufficiently translucent to exhibit the internal organs. Lice multiply rapidly with warmth and moisture. Leeuwenhoek, by keeping a male and female in his stocking, which he wore day and night, ascertained that one of them might increase to five thousand in eight weeks. They are found chiefly on children and dirty persons, more frequently upon the back of the head, and the use of hair powder is favorable to their increase. They are easily destroyed by various mercurial ointments, or an infusion of Coccidus indicus. The louse which infests negroes is a distinct black species with a large flat head. Pediculus vestimenti (the clothes louse) is a second species which is found upon the back and breast, and in the clothing of unclean persons. It is more slender, with a thinner neck than P. capitis, and its eggs are attached to the hair of the breast and arms. It is conunon upon the lower classes in Russia and Spain. P. tabescentium infests the body also. It resembles P. capitis and P. vestimenti, but is a little larger, the head round, the thorax quadrate, the abdomen ending with four bristles, the antennæ rather long, and the color pale yellow. It inhabits the human body in the folds of the skin, and is found in connexion with the disease named Phthiriasis. It forms small scale-like flaps of the skin, beneath which it is found, particularly upon the back, breast, and neck. Among those who have died of this disease were Antiochus Epiphanes, Herod, Plato, the emperor Maximian, and the poets Alemanus and Ennius. Burmeister thinks this species has a spontaneous origin in the corruption of the fluids in old or enervated subjects. He states that it is not contagious, as a woman of seventy who occupied a bed with her husband did not communicate it to him. This case was cured by the application of oil of turpentine. Cleanliness is of no avail, new lice being in some cases produced until the death of the patient. See Burmeister’s Manual of Entomology, English ed., p. 307, § 203; and Kirby’s Bridgewater Treatise, chap. 1. The human race is attacked by still another and smaller species of parasite, which differs so much from the former one, as to constitute a distinct genus named Phthirius (P. pubis, pl. 77, fig. 76). The body of this species is short and wide, and the thorax much wider than the head. It infests the axillary and inguinal regions.

Fam. 2. Nirmidæ. These insects are chiefly found infesting birds, and are familiarly termed bird lice. The head is generally large and triangular, rounded in front, and often with pointed projections; the mouth is beneath; the labrum, labium, mandibles, and maxillae are present, the last being in most cases minute, and either with or without palpi. When the palpi are present, they have four articulations. These insects do not feed upon blood, but the feathers upon which they are usually found seem to supply them with food. A bird may have from one to five species of these lice; and the same species sometimes inhabits several distinct birds, but in general certain forms are confined to certain orders and families of them.

The genus Trichodectes of Nitzsch belongs to this family, and is found upon Mammalia, as the dog, cat, weasel, bear, porcupine, horse, ox, sheep, deer, &c. Gyropus also infests Mammialia. The most useful single work upon this order is Denny’s Monographia Anoplurorum Britanniæ, London, 1842, 8vo., with 20 colored plates.

Order 3. Siphonostoma. This name was proposed for the fleas (Pulex, and several allied genera) by Latreille, in 1825; Kirby and Spence named them Aplianiptera, in 1826; Degeer named them Suctoria, 1778; and some restrict the term Aptera to them. The mouth approaches nearer to that of the higher Diptera, with which order they have the greatest affinity, and in which they would probably be placed by Burmeister. Fleas are parasitic in their perfect state, infesting man, beasts, and birds. The body is compressed, with a tough shining integument, and transverse rows of bristles. There are no wings, but these organs are represented by two scales on each side. There are two stemmata; the mouth is provided with a tongue, two lancet-shaped palpi, and a pair of long slender mandibles with serrulate edges. The maxillary palpi have four articulations, and are so long that they resemble antennæ (the antennæ being inconspicuous), and below these there are two maxillæ, shaped like triangular plates. The antennæ are minute, situated behind the stemmata, and capable of being hidden in a cavity. The feet are long and bristly, and adapted for leaping, and the tarsi are pentamerous. The larva of the flea is a slender white active grub, without feet, but it is provided with antennæ, and a pair of posterior hooks. It attains its full size in about twelve days, when it spins a silken cocoon, and becomes a quiet pupa, in which the limbs of the imago are visible.

Fleas (Pulex irritans, pl. 77, fig. 73 a b) abound where there are dogs and hogs; in camps and barracks, where they often swarm in the quarters of the soldiers. The larva seems not to be parasitic, living upon the litter of stables, &c. They are often produced from eggs laid under the toenails, or in the seams of the drawers of uncleanly persons, where they find nourishment adapted to their wants.

Pulex penetrans (pl. 77, fig. 72 a b c d), the type of Guérin’s genus Dermatophilus, is a small species which lives parasitically beneath the skin of the feet of men and dogs in the warm parts of America, particularly Guiana and Brazil. It is known as the jigger (chegoe, chigo), and by a dozen other names. It is found in sandy places, where it hops about like the other species, until it finds a suitable resting-place, when it penetrates beneath the skin and forms serious sores. In this condition the abdomen of the female enlarges to the size of a small pea (fig. 72 c, enlarged and inverted), and is found to be full of eggs. The male has not been observed, and is probably not parasitic. They frequently lodge in the toes, especially beneath the nails, causing great pain and inflammation, and it sometimes happens that the toes must be amputated, in consequence of the sores to which they give rise. Waterton saw the foot of a negro which was a mass of ulcers from the neglected attacks of this insect. According to this author, “The Indian and Negro wenches perform the operation of extracting chegoes with surprising skill. They take a pin, and by a very slow process, they lay the part bare, and contrive to work quite round the bag which contains the chegoe and its offspring. As soon as this has been effected, they turn the bag out, whole and uninjured; by which means none are left in the hole to form a new colony.” Besides man and dogs, the sand flea attacks sheep, goats, cats, hogs, oxen, horses and asses. According to Azara, it does not extend beyond 29° of south latitude.

Order 4. Coleoptera (pl. 81, figs. 84–148). This order includes all the insects with thin membranous wings on the metathorax, covered by hard coriaceous wing-covers or elytra attached to the mesothorax, their color and texture having more or less resemblance to the general exterior surface of the body. The mouth is mandibulate, and the wings folded transversely to allow them to be withdrawn beneath the elytra. There are, however, exceptions to most of the characters by which groups in the animal kingdom are defined. The wings, and even the elytra, are sometimes wanting. The elytra, which unite in a straight line along the dorsum, lap the one over the other in a few cases; and in others they are connate, or soldered together into a single piece, there being no wings beneath them.

The galea of the maxillæ in the Orthoptera is rarely represented in the Coleoptera, and when it is, the form is entirely different; and the wings are neither formed nor folded as in that order. The head, thorax, abdomen, and feet, are distinct, and the prothorax is a conspicuous part, capable of motion, and allowing the head to move upon it. The eyes are generally two in number, and stemmata are extremely rare. In rare cases the eyes are absent. The mouth is composed of a labrum, mandibles, maxillæ, and labium, with their appendages. The antennæ and parts of the mouth are extremely variable, and afford characters for genera and higher groups.

The abdomen is attached by its entire base; beneath it is more or less hard, but above it is membranous, being protected by the elytra. Coleoptera, with a few exceptions, do not fly with the ease and rapidity of some of the other orders, and they do not take wing so readily, it being necessary first to raise the elytra and extend the wings; but in the Cicindelidæ and some other families, this is done with remarkable quickness.

The head and prothorax are often ornamented by horn-like projections, sometimes resembling jaws, as in (pl. 81, fig. 148) Scarabæus hercules, in which the upper projection is from the pronotum, and the lower one from the head; and Oryctes nasicornis (fig. 145) has a horn arising from its head resembling that of a rhinoceros. The sexes are distinguished in various ways in the different groups, as by the antennæ in some, and the feet in others. In some genera, as Lucanus (fig. 124), the mandibles are much larger in the male than in the female, and of a different form. This order is oviparous, the male dies soon after pairing, and the female after depositing her eggs. In cases where the male has not paired, it has been preserved alive for a period much beyond that of its ordinary life.

The Coleoptera have been studied more than any other order of insects, the causes of which may be stated as follows. With the exception of the Lepidoptera, they contain the handsomest species. The Lepidoptera are difficult to take in a perfect condition, and when taken they require more attention in carrying and handling, and in expanding the wings, besides taking up more room in cabinets, and being more likely to be destroyed by moths and other destructive larvæ. Coleoptera present great variety in their structure; their exterior hardness renders their preservation a simple matter. It requires but little trouble to collect and bring home a great many at a time, and they can be easily caught and collected when insects which are more upon the wing are not seen. There are more books upon the Coleoptera, which facilitates their study and renders it more easy to discover new species.

In forming a collection of Coleoptera (and these remarks will, in most cases, apply to other orders), various localities must be sought. Many frequent the blossoms and leaves of shrubs and trees, various species are found in rotten wood, dung, carrion (Necrophorus prefers dead reptiles), beneath stones, logs, bark, or under the earth. Species which live in fungi may be readily taken by making a pile of this material and looking through it in the course of a day or two. Some species which live in moist places, or beneath the sand along the margins of water courses, can be driven from their retreats by dashing up water with the hand. Hosts of small species are found amongst the grass, from which they may be swept with a canvas net attached to a stout wire ring twelve or thirteen inches in diameter, and fixed in a handle about two feet long. The canvas and fixtures must be sufficiently strong to allow briers and other rough vegetation to be swept without injury to it. A great many species are attracted by a light at night. When captured, Coleoptera (and other insects which are not readily injured) should be put into small short vials in which a little paper has been put to allow them to cling to, but predaceous ones should be put into a bottle with a little ether in it, as they would destroy the others. For the smaller kinds a bottle must be provided with a quill (to be closed with a stopper) inserted through the cork, through which they are to be passed into the bottle, to prevent the inmates from escaping when a new prisoner is to be added. These may be killed by having a little paper in the vial moistened with ether, or by immersing the whole in hot water.

Each specimen should have a pin of a suitable size passed vertically through the right wing cover, to within less than half an inch of the head. When an insect is too small to have a pin passed through it, this must be stuck through the large end of a small triangle or wedge of thin card, about one fourth of an inch long, and one sixteenth of an inch wide at the large end, the opposite end being pointed. Upon the upper surface of the point of this card, small insects must be gummed, and in such a position that the pin being vertical and upon the right, and the point of the card towards the left side, the insect must cross it at right angles, the right elytron being towards the pin, and the abdomen towards the manipulator, and this position must be preserved in the cabinet. The gum used must be gum arable, with a little starch and inspissated ox gall, this being indispensable to prevent the gum from flying with the extremes of temperature, and it is sufficiently adhesive to prevent insects from being jarred loose by touching the pins. The same material is to be used in mending insects. The pins used for the small cards should be small No. 1 of the German manufacturers, and in general thin pins should be preferred. When insect pins cannot be procured, the ordinary kinds may be used, but in this case a great many specimens must be attached to cards. If pins are subsequently procured, the carded insects may be placed for a few hours in a closed vessel of moist sand, when they can be detached, and will be sufficiently relaxed to allow them to be pinned without breaking the antennæ and feet.

Specimens are to be arranged in horizontal rows on the drawers of a cabinet, made with every joint close. The drawers for the Coleoptera of the United States may be from twenty to twenty-four in number, of a size to allow a glazed cover to each, of ten by twelve inch glass, the frame of which should both enter about half an inch within, and project over the edge of the drawer on the four sides, to give double security to the joint. This frame should be carefully fitted before the drawer is put in. The bottom should be smoothly covered with sheet cork, corn-stalk pith, the soft root of the southern tupelo, or the wood of Agave americana. If soft white pine is used, a small hole must be made with an awl before a specimen can be inserted. The depth of the drawers will depend upon the length of the pins used. The German insect pins are 1\(\frac{3}{8}\) inches long, and are preferable on account of their toughness and elasticity, in which they excel the English and French pins. The pin that holds the insect will also pass through the label. A piece of camphor wrapped in gauze or other thin material should be placed in one corner of every drawer, and should it be found from the dust beneath a specimen that there is an enemy at work within it, it should be removed and subjected to a heat nearly equal to that of boiling water. This may be done by placing it in a covered tin vessel, which may be immersed in another containing hot water. A good wash to destroy moths and the various larvae found in collections, is composed of one part of oil of turpentine, and six of camphorated alcohol. A few globules of mercury are sometimes placed in the drawers to prevent the ravages of the minute louse-like Troctes pulsatorius. Constant care is necessary to prevent collections from being destroyed, and new specimens should be introduced with great caution, as they may contain eggs which will produce a destructive larva.

Much of the history of insects remains to be known, and larvae should be drawn and described, and kept until their final change shows what they are. By a system of numbering, valuable observations may be made without a knowledge of the scientific name of an insect. This knowledge comes slowly, and the observer should not relinquish his studies because he meets with difficulties. ISTew discoveries are made every year in Europe, whose entomology has been long studied by numerous active observers, and still more important ones would reward a similar class upon this continent, where so much remains to be made known in the various orders of insects.

Coleoptera are widely spread, the largest species being found between the tropics. They seem not to be as hardy as some of the Neuroptera and Diptera, none being found in Spitsbergen and similar localities. The richest collection of Coleoptera is that of the Royal Museum of Berlin, which contains 40,000 species.

Various classifications of the Coleoptera have been proposed, not one of which has acquired an exclusive popularity. Here we follow that of Westwood, which agrees better with the arrangement of Stephens and Latreille, than with that of Erichson, which will probably supersede them in time.

The order is divided into sections (Westwood Shuckard), according to the joints of the tarsi, which, although they are not uniform in every case, afford a remarkably good general characteristic. This gives the four sections, Pentamera, Heteromera, Tetramera, and Trimera. Macleay divides the Pentamera into two groups (named tribes by Westwood), Chilopodomorpha and Chilognathomorpha, according as the larva resembles Scolopendra and Julus; and he endeavors to divide the remaining sections in an analogous manner according to the forms of the larvæ. There is a discrepancy in Mr. Westwood’s nomenclature of the Tetramera, of which he admits the three ordinary groups, but applies to them the name of sub-sections, which he does not apply in the other sections. The tribes are divided into groups termed sub-tribes by Westwood (sub-division by Shuckard, and section by Stephens), and each division of the sub-tribe is named stirps by Westwood and Stephens (and tribe by Shuckard). These divisions may be tabulated as follows:

The Coleoptera of the section Pentamera have five articulations to each tarsus, and they are the most perfect and the most numerous members of the order. In some of the Hydradephaga and Brachelytra the tarsi are anomalous, and in the latter there are dimerous forms, and such as have four articulations to the anterior and medial feet, and five to the posterior ones. Latreille divides the Pentamera into six families, Carnassiers, Brachelytra, Serricornia, Clavicornia, Palpicornia, and Lamellicornia. The first corresponds to the Adephaga of Clairville, which include the predaceous land and water families, the former being the Geodephaga, containing the two families Cicindelidæ and Carabidæ; and the latter the Hydradephaga, with the two families Dyticidæ and Gyrinidæ.

The Adephaga have slender antennæ and a palpiform bi-articulate galea to the maxillæ in addition to the ordinary maxillary and labial palpi. The maxillæ have a row of stiff bristles along the inner margin, and the apex armed with a hook.

Fam. 1. Cicindelidæ. In this family the antennæ are slender, the apex of the maxillæ is in most cases a movable tooth bent inwards, and in the male the anterior tarsi are usually wider than in the female. These insects are of a moderate size, often of brilliant colors, the head and eyes rather large, the mandibles strong, pointed, curved, and toothed, and all the organs of manducation and locomotion well developed. They inhabit hot and sandy localities and dusty roads, running rapidly, and when disturbed, taking wing with great facility, and alighting again at a little distance. They are very ferocious, and prey upon other insects. Among the genera, Cicindela (pl. 81, figs. 26–29) is the most abundant and the best known. Between forty and fifty species of the United States are known, for descriptions of which. Say’s paper in the Trans. Am. Phil. Soc, vol. i., 1818; and that of Dr. J. L. Le Conte in the Annals of the N. Y. Lyceum of Nat. Hist., may be consulted. The name Cicindela (accented on the third syllable) is sufficiently well known to prevent names like soldier bug, or Spanish fly, from being applied to them.

Fam. 2. Carahidæ (pl. 81, figs. 11–16). This family corresponds very nearly to the genus Carabus, as viewed by Linnæus. It is allied to the preceding, but the terminal tooth of the maxillæ is hardly ever movable, the mandibles have in general the predaceous structure less developed, and the head is generally narrower than the prothorax. These Coleoptera are predaceous, feeding upon insects, but a few feed also upon vegetable food. They are numerous in genera, species, and individuals, and they abound in cold and temperate regions. Many of the species are less than an eighth of an inch in length. They inhabit fields, where they feed upon larvæ and insects, and they constitute a majority of those found under stones and rubbish. They are generally nocturnal, although some, including the subulipalpi, are diurnal, with habits much like those of the Cicindelidæ. Many of the species have a fetid odor, and exude an acrid liquid when disturbed.

The second stirps, Hydradephaga (Hydrocanthari, Latr.), have the posterior and middle feet flattened, and margined with a bristly fringe, adapting them for swimming, and the posterior pair is distant from the medial feet. The body is oval and depressed, sometimes subglobular, the head broad, and the mandibles robust. There is much less variation of form, and fewer genera and species among them than appear in the Geodephaga; and the forms from different countries and climates present but little variety, even in color. Of the two families, the Dyticidæ have long antennæ and short anterior feet, whilst the Gyrinidæ have the antenna short and the anterior feet long. The former swim beneath the surface, coming up occasionally to breathe, and the latter swim in circles upon it. These insects swim with great facility, and prefer lakes, ponds, or standing water. Like the Geodephaga, they are predaceous, both in their larva and perfect state. They seldom leave the water except to find another locality, and then they prefer flying by night.

Fam. 1. Dyticidæ. Dyticus (D. marginalis, pl. 81, fig. 17) includes certain large species which are destructive to young fish, larvæ, and worms. They are very hardy, and may be sometimes seen in small pieces of water, when the surrounding parts are covered with ice. In some of the members of this family the elytra are smooth in the male and sulcate in the female, and in some males the three basal articulations of the anterior tarsi are enlarged and furnished with little organs like suckers.

Fam. 2. Gyrinidæ. Here the antennæ are short, and of eleven articulations, the eye of each side is divided into two parts by the sides of the head, and the posterior and middle feet are flat and very short. They swim in circles upon the surface of the water, sometimes in great numbers, and when disturbed they dive with great facility. Like the preceding family, they are sometimes active in winter; and one species, according to Westwood, has been found upon Mount Etna in the region of perpetual snow.

The second sub-tribe Rypophaga (or cleansers) have the antennæ clavate, or thickening towards the apex, two labial and two maxillary palpi, the galea represented by the exterior maxillary lobe, which is generally dilated, and sometimes jointed, seldom palpiform. There are three stirpes, Philhydria, Necrophaga, and Brachelytra.

The Philhydria partake of the aquatic habits of the Hydradephaga, living along its moist margins. They have the body short, and convex above, the abdomen covered by the elytra, the hind feet formed for swimming or walking, the mandibles small, the maxillary palpi with four articulations, and the outer lobe generally articulated. The Philhydria contain the six families: 1, Heteroceridæ; 2, Parnidæ; 3, Helophoridæ; 4, Hydrophilidæ; 5, Sphæridiidæ; 6, Agathidiidæ. The first are the Acanthopoda, the second the Macrodactyla, and the third, fourth, and fifth, the Palpicornia of Latreille.

In the fourth family, Helophoridæ, the body is ovate or hemispherical, and adapted for swimming or walking upon subaquatic objects. The prothorax is narrowed anteriorly, and the feet are compressed. They are generally of dull tints, they prefer stagnant waters, and some are found in those that are brackish. Some of those which swim have the trasi of the four hinder feet fringed with long hairs. Hydrophilus (pl. 81, fig. 18) is a genus of large Coleoptera, with the sternum ending posteriorly with a long spine, the antennæ of nine articulations, and shorter than the maxillary palpi. In swimming, the feet are moved alternately, giving a less rapid motion than in the predaceous families; and being vegetable feeders in their imago state, they have no need of great locomotive powers. The female has a posterior pair of organs for secreting a cocoon to contain the eggs. This is nearly an inch in diameter, and is composed of fine white silk interiorly, with a gummy coating which hardens, and is impervious to the water. It is affixed to floating aquatic plants. It is formed in about half an hour, and the extremity of the abdomen serves as a mould upon which to form it. The eggs, to the number of fifty or sixty, are inclosed in a regular upright position, and the young escape below where the aperture is very slightly closed.

The second stirps, the Necrophaga of Latreille, have the body depressed, the elytra often abbreviated, the apex of the antennæ thickened, the mandibles generally prominent, the maxillæ with a double membranous extension, the outer lobe slender, rarely articulate, the maxillary palpi with three articulations, or with the basal articulation minute, and the feet ambulatory. These insects feed upon, and thus remove dead carcases; some remove decaying fungi in the same manner, and some feed upon the exuding juices of plants. The families, according to Westwood, are: 1, Scaphidiidæ; 2, Silphidæ (pl. 81. fig. 104); 3, Nitidulidæ (fig. 102); 4, Engidæ; 5, Paussidæ; 6, Mycetopliagidæ; 7, Dermestidæ. Stephens places the Erotylidæ here also, but with the exception of the tarsi, their affinities are with the Trimera. In rare cases in the Mycetophagidæ the tarsi are tetranicrous and heteromerous.

In the Silphidæ the body is depressed, the antennæ clavate, with eleven articulations of which the terminal four or five form the head. The genus Necrophorus (pl. 81, figs. 105, 106) is remarkable for finding the carcases of small animals soon after death, burying them by working the earth from beneath them, and afterwards covering them. The female deposits her eggs in these buried carcases.

The larvæ of the Dermestidæ destroy animal matter, especially dried skins. Dermestes lardarius is well known, from its attacks upon stores of beef and pork; and Anthrenus is very destructive to the various animal objects preserved in museums. In their perfect state, the Anthreni are found upon flowers.

The Brachelytra (pl. 81, figs. 4–6) form the third stirps of the sub-tribe Rypophaga, and are distinguished by the elongated form of the body and the shortness of the elytra (which seldom cover half the abdomen), and beneath which the wings are closely folded. The antennæ are generally slightly thickened towards the apex, the mandibles are robust and seldom exserted, and the abdomen is flexible, and often raised over the back in running. They run and fly with great facility, and in their habits are allied both to the Carabidæ and to the other Rypophaga. They live about dead animal and vegetable matter, or in damp localities, and some of them eat larvæ and other living food. The habits of the adult and larvæ are the same, and they do not differ much from each other, which indicates a low position in the living scale. According to Westwood, this group should be considered a family under the name of Staphylinidæ, although it is usually divided into a number of so-called families. Most of the species are small, and require a good microscope and a good manipulation to study them properly. Westwood states the sub-families to be the six following: 1, Staphylinides; 2, Stenides; 3, Oxytelides; 4, Omaliides; 5, Tachyporides; 6, Pselaphides. In the last group there are only three articulations to the tarsi, one of which is so small as to have been at first overlooked, so that they were considered dimerous, and formed into a primary section named Dimera. They are from two to four millimetres long, and are found under stones, in meadows, and in ants’ nests. Dr. J. L. Le Conte has published an interesting memoir on the North American species.

The Cordylocerata of Westwood constitute the third sub-tribe of the Pentamera, and include the stirpes Clavicornia and Lamellicornia. The stirps Helocera, the name of which is adopted from Duméril by Stephens, is named Clavicornia by Westwood, a term under which Latreille included the Necrophaga.

The Clavicornia have the body short, sub-globular or sub-quadrate, the antennæ clubbed, the basal articulation often forming half the entire length, and the sternum in some cases hiding the mouth below. The feet are compressed, and can be drawn close to the body, which has generally cavities to receive them. This stirps contains the two families Byrrhidæ and Histeridæ. Hister (pl. 81, figs. 119–128) is the chief genus of the latter family, in which the body is sub-quadrate, often widest in the middle, of a hard consistence, mostly black, marked with striæ and punctures, the disposition of which affords good specific characters. The elytra are somewhat shorter than the abdomen, the antennæ are elbowed, and the mandibles strong and projecting. When disturbed, they draw up the feet, withdraw the antennæ into cavities beneath the thorax, and simulate death. They are found in carrion, dung, and decaying fungi. The genus Hololepta is very flat and scale-like, and the species are found beneath moist bark. The American species, Hetcerius brunneipennis, Randall (Hister) is found in ants’ nests. The paper of Major John Le Conte on this family may be consulted in the Boston Jour. Nat. Hist.

The stirps Lamellicornia is extensive and contains numerous distinct forms. The distinctive character is in the antennæ, which are short, of nine or ten articulations, the last (generally three) forming a club composed of flat plates closing upon each other like the leaves of a book. The anterior tibiae are generally dentate. The males often differ from the females in having large mandibles and horn-like projections. This stirps contains the largest and some of the handsomest and most splendid among known insects. Some feed upon pollen and honey, some upon leaves, and many frequent excrementitious and decaying vegetable substances. The larva is a long fleshy grub, generally white, curved in a semicircle, having six feet, little capable of locomotion, and generally living in the ground. The families are: 1, Lucanidæ (pl. 81, fig. 124); 2, Geotrupidæ (fig. 143); 3, Scarabæidæ (figs. 132, 136–142); 4, Aphodiidæ (figs. 133–35); 5, Trogidæ; 6, Dynastidæ (figs. 145–8); 7, Rutilidæ; 8, Anaplognathidæ; 9, Melolonthidæ (figs. 129–131); 10, Glaphyridæ; 11, Cetoniadæ (figs. 125–127).

The Lucanidæ (Lucanus, pl. 81, fig. 124) are considered by Westwood and others to form a group equal in value to the remaining families united, named respectively Priocera and Petalooera by Duméril. The American Passalus cornutus belongs to this family. Its larva is white, and presents the remarkable peculiarity of having but four feet, the posterior pair being represented by a small scale upon each side, which can be moved rapidly, as if it were a real foot. It is found beneath the bark of rotten logs, and is not bent in a semicircle, but walks freely upon its inferior surface. The adult burrows in rotten wood, and may be recognised by its shining black color, large size, flattened parallel form, and quadrate prothorax separated from the striate elytra. The strongly elbowed antennæ in this family indicate an affinity with the Histeridæ.

The Scarabæidæ (pl. 81, figs. 132, 136, 140–144) have the front of the head extended into a flat clypeus used in working in the ground, and in the dung upon which they feed. Many of them form a ball of dung (said to contain the eggs) which one or two of them roll along until they have found a suitable place, when they commence working the earth from beneath it, and gradually burying it. The American Canthon læve (or C. volvens) generally works in pairs, one pushing the ball backwards with its hind feet, its posterior extremity raised up, the other walking up the ball on the opposite side, thus causing it to roll. The ball is about three fourths of an inch in diameter, and quite globular. Copris carolina makes a small ball, which it buries at once. Deltochilum gibbosum of the southern states makes a small ball, in the exterior of which there is a great deal of cow’s hair. The genus Ateuchus (pl. 81, fig. 132) entered largely into the mythology of the ancient Egyptians, and models and figures of it are common among Egyptian antiquities. In Lethrus cephalotes (fig. 144), a European insect, the pronotum and elytra nearly correspond in size and convexity, the feet are long, and inserted near each other, and the antennæ terminate in a reversed cone.

The Aphodiidæ (figs. 133–5) are small oblong insects found in dung, some of which are black, and some of brighter colors. They may be seen flying slowly along the roads in the warm days of autumn. The elytra cover the entire abdomen.

The Dynastidæ include some of the largest Coleoptera, as Dynastes hercules (fig. 148), D. acteon (fig. 147), D. alsoëus (fig. 146), Oryctes nasicornis (fig. 145). During the day they live in the earth, or in the decomposed matter of old trees, and fly about at night. Scarabæus tityus, of the United States, is found in old apple trees. In general, the male alone has the horn-like projections.

Melolonthidæ. Melolontha vulgaris (pl. 81, fig. 131), M. fullo (fig. 130), Rhizotrogus (fig. 129), Serica (fig. 126), are examples of this family, which is important in its relations with agriculture.

The Cetoniidæ, of which Cetonia (pl. 81, fig. 125) and Trichius (fig. 127) are examples, contain some of the handsomest of known insects. They feed upon the fluids of plants, as honey and sap, and also upon parts of the blossoms.

The Serricornia constitute the fourth sub-tribe of the Pentamera, and include many handsome forms of vegetable feeders, in which the antennæ are generally short, and serrate, pectinate, or filiform, the apex rarely thickened. The form is lengthened, and the elytra generally cover the abdomen. They include the two stirpes, Macrosternia and Aprosternia.

The Macrosternia (Sternoxi of Latreille, pl. 81, figs. 22, 23) contain the genera Buprestis, and many more having the same general characters. They are included in the three families, Buprestidæ, Eucnemidæ, and Elateridæ.

The Buprestidæ include a great number of brilliant, large, and medium species resembling gold or precious stones. The body is hard, cylindrical, flattened, elliptic or oval, the feet short and weak, the elytra narrowed towards the end, the wings adapted for a rapid flight, the head vertical and deeply inserted in the prothorax, which is attached by a wide surface to the mesothorax, so that there is but little motion between these parts. They are chiefly inhabitants of warm climates, and the size of the species varies from a line to two and a half inches. Buprestis mariana (fig. 22), to which this generic name properly belongs, is much like the North American M. virginiana. Fig. 23 represents Euchroma gigas, which inhabits Cayenne. The larvae in this family bore in wood, and may be frequently discovered mider the bark of pine logs.

The Elateridæ (pl. 81, figs. 30–33) are closely allied to the Buprestidæ, but the colors are not so brilliant, and the body is less hard. The chief difference is in the structure of the prothorax, which moves so freely in a vertical direction that the insect can employ this power to throw the body about, either to regain its position upon its feet or to escape. The prosternum has a projecting spine, which fits into a corresponding impression in the mesosternum. They are generally found among living vegetables. We have found the larva of the large North American Alaus oculatus in the wood of ash trees. This species extends from the northern part of the United States to the latitude (19°) of Yera Cruz in Mexico.

The Aprosternia (or Malacodermia) have the antennæ generally long and serrated, sometimes clavate, and not lodged in a groove of the prosternum, the head deflexed and deeply seated, the body elongate and generally soft, and the feet rather long and slender. The greater part of them are winged. The larvæ feed either upon wood or insects, and the adults are found upon flowers or plants, in dead wood, or upon the earth. Some are predaceous. The Malacodermes of Latreille include the families Cebrionides, Lampyrides, Melyrides, Clairones, and Ptiniores; but Stephens and Westwood extend the group considerably further, and the latter adds the family Scydmænidæ, which Stephens places with the Heteromera. With this exception, the families of these two authors agree, and are as follows: 1, Cebrionidæ; 2, Cyphonidæ; 3 Lampyridæ; 4, Telephoridæ; 5 Melyridæ; 6, Cleridæ; 7, Ptinidæ; 8, Lymexylonidæ; 9, Bostrichidæ; 10, Scydmænidæ.

The Lampyridæ are well known as the family containing the fireflies and glow-worms. The body is lengthened and depressed, and with the elytra of a soft consistence, and the head is more or less hidden by the prothorax. Most of the species seem to be carnivorous. When disturbed they draw in their members and simulate death. The common glow-worm of the middle United States is the female of Photuris versicolor.

In the Melyridæ, some of the species of Malachius are remarkable for having red lateral organs which they can swell or relax at pleasure, the use of which is not known. The species of this genus feed upon insects.

In the Cleridæ, the larva of the genus Clerus is remarkable for destroying the larvæ of bees. Necrobia and Corynetes are found about old animal carcases, particularly upon the bones.

The family Ptinidæ contains various small oval insects with the head placed deep in the prothorax, the antennæ eleven-articulate, filiform, or sometimes pectinate. They are of obscure colors, and counterfeit death. They are very destructive to the woodwork of houses and furniture, and some destroy books and collections of dried plants and insects. The genus Anobium sometimes strikes its jaws upon the wood in which it has its station, in such a manner as to imitate the ticking of a watch.

Lymexylon, the type of the family Lymexylonidæ, is very destructive to ship timber in the dockyards of Europe.

The Bostrichidæ have a hard cylindrical body, a deeply seated globular head, clavate antennæ, strong mandibles, and the pronotum projecting over the head, and often scabrous. They live in timber, boring holes in the wood and bark.

With few exceptions, the section Heteromera have four articulations to the posterior tarsi, and five to the others. They are generally vegetable feeders, and differ much in their habits. Some live upon plants, and are variously colored; others live in dark places, and are of obscure colors; and some, which are allied to the latter, are found in desert plains. Latreille divides this section into four groups, named Melasoma, Taxicornia, Stenelytra, and Trachelides. Westwood divides them into three stirpes, Trachelia, Varicolores, and Melasomata. The Trachelia (Pyrochroa, pl. 81 fig. 40) are an extension of Latreille’s group Trachelides, and contain a number of active insects, with the body and elytra soft. They are found upon plants, and are generally of bright colors. The head is enlarged behind the eyes, and the antennæ are slender and branched.

Westwood indicates the following families in his tribe Trachelia: 1, Notoxidæ; 2, Pyrochroidæ; 3, Lagriidæ; 4, Horiidæ; 5, Mordellidæ; 6, Meloidæ; 7, Salpingidæ; 8, Oedemeridæ; 9 Melandryidæ.

There is a good deal of confusion in the names of several genera of Heteromera, on account of an endeavor to set aside names which should stand on the ground of priority. Linnæus, the inventor of the modern nomenclature, applied certain ancient names, as Cicindela, Buprestis, and Cantharis, to insects, without caring particularly to what insects they were applied by the ancients, and properly, because with the ancients these were worthless vernacular names; and as we do not go either to Pliny or to a modern retailer of drugs to learn entomology, we have no particular interest in knowing the names objects bear with them.

With Linnæus, the blistering flies formed a part of his genus Meloe, and he formed a genus, Cantharis, in 1735, for an insect to which Schæffer applied the useless synonym of Telepliorus, in 1766. In 1764, Geoffroy properly separated the blistering flies from Meloe, assigning to them the name Cantharis of the druggists, which he had no right to do, that name being already applied to a genus, so that it was virtually without a name until Fabricius, in 1775, rectified the blunder of Geoffroy, by naming the blister flies Lytta, a name adopted by Dejean, Say, Erichson, and others.

Many of the Meloidæ have the power of raising blisters when applied to the skin, and different species are used for this purpose in different countries. In Meloe (pl. 81, fig. 7), one of the elytra laps over the other at the base.

The tribe Atrachelia have the head enlarged and deeply set; they are in general dark-colored, living in dark places, and running slowly upon the ground. A few of the families are bright-colored, and are found upon flowers. The families are: 1, Cistelidæ; 2, Helopidæ; 3, Diaperidæ; 4, Tenebrionidæ; 5, Blapsidæ; 6, Pimeliidæ. Of these, the three first are variously colored, and constitute Westwood’s sub-tribe Varicolores. The remaining three are black or obscure, and constitute the Melasomata of Latreille.

The Tenebrionidæ are well known from the meal bug (Tenebrio molitor), the round hard larvæ of which, as well as the perfect insect, are found in flour, sea-biscuits, &c., upon which they feed.

The Blapsidæ of the United States occur in the region of the Rocky Mountains, whence they extend to Texas.

The insects of the section Tetramera include those Coleoptera which have four movable articulations to all the tarsi. They are very numerous, and all of them are vegetable feeders, both in the larva and perfect state. They are divided into three stirpes, of which the Rhincophora have the head produced into a rostrum, and the antennæ generally short and elbowed. The Longicornia have long antennas and an oblong body; and the Phytophaga have a short round body and short antennæ. There are many beautiful insects among the Tetramera, but except among the Longicornia, they are generally less than an inch long.

The Rhincophora (pl. 81, figs. 65–76) are numerous in species, of which about 8000 have been described in the great work of Schœnherr. The mouth is situated at the end of the rostrum, which is sometimes very slender, and as long as the rest of the body. The insects known as weevils, which are destructive to various kinds of seeds, belong here, and the seeds of a great many vegetables are attacked by peculiar species. The elytra are often connate, or united in a single piece, and with the exterior parts, they are often so hard that it is difficult to stick a pin through them. Some are beautifully marked with brilliant minute scales, which are favorite objects for viewing with the microscope. The English have named several of these diamond beetles, on account of the appearance of these scales. The divisions of Rhincophora by Schœnherr are here given, from the fifth volume of his Genera et Species Curculionidum, 1839. It will be observed that his use of the words order, family, &c., is peculiar to himself.

• Sub-fam. 1. Genuini.
  • Ordo I. Gonatoceri. Antennæ geniculate, basal articulation received into a groove in the side of the rostrum.
    • Legio 1. Brachyrhynchi. Rostrum short and robust. Divisions (Phalanx 1): Brachycerides, Entimides, Pachyrhynchides, Brachyderides, Cleonides, Molytides, Byrsopsides; (Phalanx 2) Phyllobides, Cyclormides, Otiorhynchides.
    • Legio 2. Mecorhynchi. Rostrum cylindric, lengthened, with the antennæ between its base and middle. Divisions: Erirhinides, Apostasimerides (sub-divisions: Cholides, Baridides, Cryptorhyncides), Conophorides, Cionides, Rhyncophorides, Cossonides.
  • Ordo II. Orthoceri. Antennæ not geniculate, basal articulation not very long, and not received into a groove in the rostrum. Divisions: Tanaonides, Ithycerides, Carnerotides, Antliarhinides, Attelabides, Belides, Apiouides, Ramphides, Cylades, Ulocerides, Oxyrliynchides.
• Sub-fam. 2. Spurii.
  • Legio 1. Palpi hidden, very short, antennæ geniculate and clavate, tarsi pentamerous. Division: Dryoplithorides.
  • Legio 2. Palpi hidden, antennæ straight, not properly clavate, tarsi indistinctly pentamerous. Divisions: Oxycorynides, Brenthides.
  • Legio 3. Palpi exserted and filiform, tarsi distinctly tetramerous. Divisions: Rhinomacerides, Anthrihides, Bruchides.

Schœnherr excludes the Scolytidæ from the Rhynchophora, and Westwood places them at the end of them. They include various genera destructive to forest trees.

The Longicornia (pl. 81, figs. 44–60) have the antennæ long and tapering, generally as long as the body, and not clavate; the eyes generally reniform, and the body elongated. The head is sometimes horizontal and sometimes vertical, the front generally impressed, the prothorax varying, being convex or flattened, transverse, globular, cylindrical; spinose, nodulous, or smooth; presenting in Acrocinus a movable spine (umbo) on each side. The feet are generally slender, the tarsi clothed with short hair beneath, and the third articulation cordate. Some of the females have an ovipositor to insert the eggs in the bark of trees. They are graceful in form, and many of them are brilliantly colored. Some run and fly with, great facility, whilst others are tardy in their movements. Some are deprived of wings and confined to the ground and low shrubs. Some frequent flowers and other forest trees, and the larvae of the latter are often destructive to useful trees. The beautiful American Clytus pictus, a species marked with yellow lines like fig. 51, is very destructive to locust trees, in the branches of which the larva bores. It also destroys young hickory saplings which have been cut for hooping casks.

The larva of Oncideres cingulatus lives within the dead branches of hickory, eating the dead wood; and to supply it with this food, the female deposits the eggs in little perforations which she makes in the bark towards the end of the branches, which she kills, by gnawing a groove entirely round, through the bark and into the wood, which efiectually accomplishes the object. The dead branch retains its position long after the dead insect has left it. The upright stem is often thus attacked, when a lateral branch shoots forth to supply its place, which may be similarly attacked the next year, and this sometimes happens for four or five years in succession, so that the top of a young hickory tree sometimes presents a curious and mutilated appearance.

There are three families of Longicornia: Prionidæ, Ceramhycidæ, and Lepturidæ. Among the genera figured in plate 81, are Prionus (fig. 61), Clytus (figs. 51, 52), Astynomus (fig. 54), Saperda (fig. 56), Leptura (fig. 46), Molorchus (fig. 45). In the last the elytra are very short, and the wings are not folded under them. Serville is the chief authority in the arrangement of the Longicornia. For the species inhabiting the United States, the papers of Say, Haldeman, and Le Conte, may be consulted.

The Phytophaga is an extensive group of short and often polished and bright colored insects which inhabit and feed upon plants, and many of the species are destructive to garden vegetables. Latreille divided them into Eupoda (from the size of the posterior feet) and Cyclica (from their circular form). The families are: 1. Sagridæ; 2, Crioceridæ; 3, Cassididæ; 4, Galerucidæ; 5, Chrysomelidæ. The first and second of these belong to the Eupoda.

In the Chrysomelidæ the antennæ are eleven-articulate, and are inserted in front of the eyes; the head is small, and inserted in the prothorax, which is narrower than the elytra. The colors are generally bright, and resemble polished copper, gold, or steel. There are between six and seven hundred species known. They abound in tropical climates, and are common in temperate regions.

In the last section, Trimera (pl. 81, figs. 83–101), of the Coleoptera, the tarsi have three movable and distinct articulations, with the addition of a minute and immovable one. The species are of a small size, the body is short and often hemispherical, and the antennæ are short, with a tri-articulate club. Some feed upon plants, some upon fungi, and others upon the genus Aphis. The families are: Erotylidæ (Clampalpi, Latr.);  2, Endomichidæ (Fungicola, Latr.); 3, Coccinellidæ (Aphidiphagi, Latr.). To these some add the Pselaphidæ, the characters of which assimilate them to the Brachelytra.

Fam. 1. Erotylidæ. These insects are sometimes placed at the end of the preceding section, on account of their tetramerous tarsi. The antennæ have eleven articulations, they end in a compressed club, and are usually inserted in front of the eyes. The edges of the elytra are turned in upon the venter laterally, and they are often marked with impressed points. They live upon plants, and the great majority of the species belong to the American continent. The genera Triplax, Languria, Erotylus, and Dacne, have representatives in the United States.

Fam. 2. Endomychidæ. These are found in fungi, both in the larva and imago state. Their size is small, the antennæ are eleven-articulate, placed near the eyes, and they are larger than the head and prothorax together. Mulsant terms them Sulcicolles, from the longitudinal grooves of the pronotum.

Fam. 3. Coccinellidæ (pl. 81, figs. 93–100). This family includes the little hemispherical insects known as lady bugs. They are of bright colors, and are often marked with spots. When disturbed they emit a yellow fluid from the joints of the feet, which was formerly supposed to be a specific for the toothache. They feed upon Aphides, but the common large yellow American species with the black spots (Coccinella borealis), eats cucurbitaceous plants both in its larva and perfect state. These insects pass the winter in crevices, or under bark, in little colonies. Mulsant has added a considerable number of genera to the family.

Order 5. Orthoptera. In this order (pl. 80, figs. 78–93) the anterior wings (or teginina) are somewhat coriaceous and veined, with the inner margins overlapping and not meeting in a straight line as in the Coleoptera. The mouth is mandibulate, and much like that of the Coleoptera; the mandibles and maxillæ are well developed, each of the latter being protected by an external jointed galea. The labrum is transverse, the labium four-parted, and with the tongue, labial palpi, and maxillary palpi, well developed. The body is generally long, the head vertical, the antennæ slender, and the thorax much as in the Coleoptera. In some cases the wings are wanting, and sometimes they are so small as to be useless. Some have the anterior wings only, and in one genus the posterior ones are alone present. The feet are well developed, but whilst some forms are very active, the movements of others are remarkably slow. The grasshoppers are perhaps more destructive to growing vegetation than any other family. The Mantidæ eat other insects, and the Blattidæ or cockroaches destroy both animal and vegetable substances. The Orthoptera are generally of a large size, and although in bulk they probably do not surpass the gigantic beetles, in the length of the body and the expanse of their feet and wings the Phasmidæ much exceed them, some of them being eight or ten inches long.

The Orthoptera are much less numerous in species than the Coleoptera, although in the number of individuals they are at times extremely abundant. There are six families: 1, Forficulidæ; 2, Blattidæ; 3, Mantidæ; 4, Phasmidæ; 5, Gryllidæ; 6, Locustidæ; 7, Acridiidæ.

Fam. 1. Forficulidæ. This family is considered an order by some authors, under the name of Dermaptera, &c. They resemble (Forficula, pl. 81, figs. 1, 2) the Brachehlytra, having a slender body, and the elytra short, but they differ in the organs of the mouth, which correspond to the type of the Orthoptera. From these they differ in the wings, which have a peculiar structure, and in the peculiar pincer-like organ at the extremity of the abdomen. The wings fold both longitudinally and transversely to bring them under the elytra. They are active, and feed during the pupa state, in which they resemble the typical Orthoptera. They run and fly well, live in damp places, and feed upon vegetable food. In Europe they feed upon flowers, and are considered a great pest by gardeners, but the American species seems not to destroy anything valuable, nor is it popularly known by any name. Forficula sits over her eggs and carefully watches the young when they appear. The larvæ resemble the adults, but they are without wings, whilst the pupæ slow indications of them in an undeveloped state. These insects are trimerous, and the antennæ are long, slender, and composed of many articulations. Some authors admit but one genus in the family.

Fam. 2. Blattidæ (Blatta, pl. 80, fig. 93). The family of the cockroaches has the body depressed, the head more or less hidden under the prothorax, the elytra horizontal, with the inner edges passing over each other; the antennæ are long and setaceous, the feet cursorial, the tarsi five-articulate, and the apex of the abdomen with two slender appendages. The wings of this family are generally better developed in the male than in the female, and the latter has a wider abdomen, with one or two segments less than in the male. The eggs are contained in a capsule resembling a small bean, with one edge serrulate, and this the female carries at her abdomen for some time.

These insects are nocturnal, hiding by day and roaming about in search of food at night. In houses they are most abundant about fireplaces. They infest ships, which have distributed several species over the world, so that it is difficult to tell the original country of some of them. In tropical regions they are extremely troublesome, from their variety and their numbers.

Fam. 3. Mantidæ (figs. 90, 91). Body lengthened, prothorax longer than in the remaining thoracic portion, anterior feet raptorial, tarsi five-articulate, antennæ sometimes pectinate, apex of the abdomen with two slender appendages. They are carnivorous, and seize their prey with the anterior feet. The wings are horizontal, and the elytra in the males are larger and narrower than in the females. They remain stationary, waiting for their prey, their prothorax and raptorial feet raised as if in the attitude of supplication, whence they have been called praying insects, and Mantis religiosa (pl. 80, fig. 90) has received its trivial name from this circumstance. They are pugnacious, and when confined together will eat each other. The Chinese make them fight for amusement, and it often happens that one will cut off the head of its antagonist by getting its neck within the grasp of one of its raptorial feet. The eggs are deposited in a single body, and covered with a gummy mass which hardens in the air. The egg mass of Mantis Carolina, of the Southern United States, will serve as an example. In Empusa (E. gongylodes, pl. 80, fig. 91), the antennæ are bipectinate in the male, and setaceous in the female. This genus is remarkable for the leaf-like expansions upon the feet.

Fam. 4. Phasmidæ (pl. 80, figs. 89, 92). Here the elytra are rudimentary, the prothorax shorter than the remaining thoracic portion, the antennæ setaceous, all the feet ambulatory, and the tarsi are usually pentamerous. These insects are phytophagous, and live upon trees; and they present some very curious forms. Some species have wrings, whilst others have not the least rudiment of them. In the species which have large wings their anterior margin is thickened, and covers the inner fan-like portion like the outer stiff edge of a fan. Some of these have been named walking-sticks from their resemblance to a stick. Cyphocrana gigas (fig. 92, from the Moluccas, is ten inches long. The foliaceous expansions upon the feet of the genus Phyllium (P. siccifolium, fig. 89), and the shape and color of the wings, give it the appearance of a leaf, whence its scientific name, that of walking leaf, sometimes given to it in English.

Bacteria femorata, figured in Say’s American Entomology, is found from Pennsylvania to Carolina, upon chestnut trees, the leaves of which it eats. The eggs resemble certain seeds; they are mature in autumn, and they are probably laid upon the ground. This is generally a rather rare insect, but Dr. Hiester has discovered that they occur in great numbers in the Monocasy hills in eastern Pennsylvania. He says: “In the latter part of September, 1846, I observed, at a great distance, the forest on the Monocasy hills to be stripped of its leaves, and to have a peculiar brown appearance. On inquiry, I was told that within a month or six weeks myriads of strange insects had suddenly made their appearance, and were voraciously devouring all the leaves of the forest trees. I had learned, a few days previously, that some insect was committing great ravages on the forest trees at the distance of twenty-four miles in the opposite direction. Individuals from both localities being procured, were found to be the same insect,”

Fam. 5. Gryllidæ (pl. 80, figs. 86–88). The family of the crickets were included by Linnæus in his great genus Gryllus, and on this account there is some confusion of names. This family was named Gryllides by Latreille, and Achetidæ by the English. The antennæ are long and filiform, the tarsi generally trimerons, and the abdomen terminating with two long setae. In the crickets the males produce a monotonous stridulating noise, by rubbing together a peculiar apparatus upon their elytra. Although they have a general resemblance to the grasshoppers, they differ in their habits, being altogether terrestrial, and having the power of burrowing to a greater or less extent. They run well, but do not leap as well as the grasshoppers.

The true crickets generally remain in their burrows during the day, and search for their food at night. In some countries they infest houses, particularly the kitchens, where they are attracted by the warmth. They seem to live both upon vegetable and animal food. The crickets are referred to the genus Gryllus, Linn. (pl. 80, figs. 86, 87), although the English entomologists use the Fabrician name Acheta.

Gryllotcalpa (fig. 88) is a genus in which the anterior feet are short and broad, and adapted for digging, like those of the mole, and like this animal, they burrow beneath the soil, forming a small bridge which marks their course. In Europe it is regarded as a noxious insect, but the American species seems not to be knothe to horticulturists.

Fam. 6. Loacstidæ. Variations of this family name are used by the French and Germans, but the English name them Gryllidæ and the Gryllidæ they name Locustidcæ apparently for the purpose of making a concession to the vulgar name locust, as used in England. In this family the antennæ are setaceous and very long, the wing-covers deflexed, the posterior feet very long and adapted for leaping, the tarsi tetramerous, the abdomen with a pair of small filiform appendages, that of the female having a sharp flattened ovipositor. The males make a loud stridulation by means of their upper wings, near the base of which is a plate of a peculiar construction for this purpose. Locusta viridissima (pl. 80, fig. 85), the cigale of the French, is a noisy European species, and the Platyphyllum concavum or Catydid, is a familiar American example. Decticus apterus (fig. 83). D. verrucivorus (fig. 84), are European species; Poccilocera morbillosa (fig. 82) is from the Cape of Good Hope. These insects are more arboreal in their habits than those of the next family, and from the fine green color of many of them, they are easily overlooked among foliage.

Fam. 7. Acridiidæ (pl. 80, figs. 78–81). This family is named Acridiens by the French, Locustidæ by the English, and by Burmeister Acridiodea. The body is flattened and robust. The antennæ are short, the posterior feet saltatorial, the tarsi trimerous, the abdomen has two very short appendages, and that of the female is without a prominent ovipositor. These insects produce a stridulation by rubbing their hinder thighs against the wing-covers, and the large common species of the United States (Œdipoda carolina), which is found in dry places, such as dusty roads, may be seen hovering a yard or two above the ground over a single spot, the wings then producing a fluttering sound which is not heard in its ordinary flight. This species is brown, with the wings black, margined with yellow,

Acridium cristtatum (fig. 81), Œdipoda stridula (fig. 78), O. cœrulescens (fig. 79), O. migratoria (fig. 80). The last is two inches long, and inhabits central, southern, and eastern Europe, where it occasionally commits great ravages upon the vegetation. Various species are abundantly distributed over various parts of the world.

Order 6. Neuroptera (pl. 79, figs. 51–76). This is a somewhat irregular mandibulate order, the characters presented by it being varied, and on this account various modifications have been proposed for it. In the Libellulidæ, the trophi make an approximation to those of the Orthoptera, to which the order has been united by Erichson, whilst Kirby separates the Trichoptera as a distinct order. The antennæ are generally setaceous and short. The four wings have usually reticulate nervures; they are generally of equal size; and consistence, and the posterior pair is not generally folded. The pupa is sometimes active and sometimes quiescent. The larvæ are hexapod, mostly predaceous, and they are either terrestrial or aquatic.

Blanchard divides the order into nine tribes, named after the genera Termes, Embia, Psocus, Perla, Ephemera, Libellula, Myrmeleon, Raphidia, and Phryganea, the last belonging to one section, and all the rest to another. Westwood (who considers the Trichoptera to be a distinct order) adopts the following arrangement: 1, Termitidæ; 2, Psocidæ; 3, Perlidæ; 1, Ephemeridæ; 5, Libellulidæ; 6, Myrmeleonidæ; 7, Hemerobiidæ; 8, Sialidæ; 9, Panorpidæ; 10, Raphidiidæ; 11, Mantispidæ.

The Thripsidæ (pl. 80, fig. 51) form a group of small extent, which Burmeister includes in his great order Gymnognatha. The species are minute and linear, with four narrow and equal wings, deprived of nervures, strongly fringed with long hairs, and not folded. The mouth is mandibulate the tarsi dimerous and ending in a vesicle, as in some of the lower Arachnida. They are considered hurtful to plants, and it is probable that an American species attacks the human skin, causing an itching like that of Simulium. The pupae are active, and their affinities are with the Neuroptera. There are various species in Europe and America. They form Haliday’s order Thysanoptera, and include a number of genera.

The Termitidæ include the genus Termes (pl. 79, fig. 56, a, b, c, d) or white ant, which presents many curious features in its economy. The body is white and oblong, the antennæ short and moniliform, the eyes lateral, the stemmata two in number, and the mouth mandibulate, resembling that of the Orthoptera in having a galea; and the tarsi are four-articulate. They live together in societies composed of various kinds of individuals. Besides the male and female, there are some with a large head and mandibles, which are the soldiers, named neuters by Latreille. Pupro with the wings folded under the integument, are sometimes seen, and the great mass is made up of apterous individuals, which, from occurring of all sizes (some of them being very small), must be larvæ. They are active in all their stages, and the larvæ present the curious fact of being the general workers of the colony. In the American Termes frontalis, Hald., the pupæ take their final form in the spring, when they take wing in the morning in great numbers. In a few days the wings drop off, and no winged individuals are seen. This species works galleries in logs and stumps of trees, and is equally abundant in localities suited for ants, or beneath stones, when it forms galleries in the ground, plastering them with a hard mixture of clay. They are never seen out of their burrows except in the winged state. A species in Western Africa, T. fatalis (pl. 79, fig. 56 c), builds conical nests ten or twelve feet high, with turrets rising from the surface, and having the entrances beneath the ground. When gravid, the female of this species (pl. 79, fig. 56 d) has the abdomen many thousand times its natural size, being nearly three inches long and three fourths of an inch in diameter, and containing about eighty thousand eggs, which are discharged in twenty four hours. The female, at the time of depositing her eggs, is walled within a hollow prison of clay shaped like a flat apple or turnip, the margin of which is perforated with a row of small holes through which the eggs are said to be ejected. A small species in France destroys furniture, woodwork, and records, its presence being seldom known until it is too late. T. frontalis has not been known to appear about houses. Dr. T. S. Savage made extensive observations upon T. fatalis, which are detailed in the fourth vol. of the Proceed. Acad. Nat. Sci.

The little apterous louse-like insect, Troctes pulsatorius, found among books, belongs to the family of Psocidæ. Perla bicaudata (pl. 79, fig. 67) is a representative of the Perlidæ.

The Ephemeridæ (pl. 79, figs. 70, 71, 72) are well known by the four wings with nervures in both directions, the anterior pair much the largest, the organs of the mouth but little developed, and the abdomen ending with long setæ. The larvæ live in the water, and the adults are fond of flying in the air, rising vertically above a certain spot, then falling slowly with their wings expanded. These insects were known to Aristotle and Ælian, who named them in allusion to their short life, which in general extends from three hours to a day, although by keeping the sexes apart they will live from one to three weeks. When they leave the pupa state they fly off apparently perfect insects, but the succeeding night they cast off another thin pellicle from all parts, including the wings, and this being found at a distance from the water, and bearing a considerable resemblance to the pupa case as it stands attached by the feet to various objects, conveys the false impression that the pupae are able to walk a great distance before they are transformed. Pictet of Geneva is the chief authority upon this family.

The Libellulidæ are composed of various genera, among which are Agrion (pl. 79, fig. 73), Calepteryx (fig. 74), Libellula (fig. 75), and Æschna (fig. 76). They have the body slender, the wings large and reticulated, the head, and particularly the eyes, large, the mouth well developed, and they are of predaceous habits in the larva and imago state. In the latter the feet are slender, adapted for standing rather than for locomotion, and they resemble the swallow in passing most of their time and taking their prey in the air. They are sometimes found in forests, but generally along water courses. The larvæ are aquatic, and the eggs are deposited upon the water by the female, who allows the tip of her abdomen to touch the surface at the time of exclusion.

Among the Mynneleonidæ, the genus Myrmeleon (M. libelluloides, pl. 79, fig. 60; M. formicarius, fig. 61 a) is remarkable for the habits of the larva (fig. 61 b), which forms a conical depression in the ground where the earth is dry and pulverulent (the dust of decayed wood being preferred in the United States). Beneath the bottom of this cavity the larva lies either entirely covered, or with the mandibles exposed. When an ant or other insect wanders across one of these pits, it slides down the sloping side, and the particles which roll to the bottom indicate the presence of an object, upon which the larva, by upward jerks of the head, tosses up a little shower of dust, which, falling on and around the intruder, carries it within reach of its wily enemy. In Virginia this insect is called a hoodlbug, and the repetition of this word over its opening in a half singing tone, is said to cause the bug to come from beneath its cover, although it is probable that the breath of the operator is the true cause. Ascalaphus (A. barbarus, pl. 79, fig. 59) is remarkable for having the antennæ knobbed, as in some of the butterflies.

In the family Hemerobiidæ, the larvæ of Chrysopa (pl. 79, figs. 63, 64) are found upon plants, where they feed upon Aphides. Drepanepteryx phalænoides is remarkable for its resemblance to some of the small butterflies.

The remarkable American genus, Corydalis belongs to the Sialidæ. The insects of this genus are of a large size, the mandibles of the male resembling the horns of an ox. The larva is aquatic and predaceous.

In the Panorpidæ (pl. 79, fig. 58), the head is produced into a rostrum. Panorpa (pl. 79, fig. 58), Bittacus (fig. 57).

In the Raphidiidæ (Raphidia, pl. 79, fig. 55), the prothorax is long and the head flattened, presenting a distant resemblance to a snake.

The Mantispidæ (Mantispa, pl. 79, fig. 51) have the body somewhat as in Panorpa, and the anterior feet are raptorial, resembling those of Mantis, with which they were classed by some of the earlier entomologists.

The Phryganeidæ (pl. 79, figs. 65–69) constitute Kirby’s order Trichoptera, which is adopted by a considerable number of entomologists. The body is soft, the wings are membranous, the posterior pair the larger, and generally folded longitudinally, the anterior generally pilose (whence the name of the order), and the antennæ setaceous. The mouth is mandibulate, but is unfitted for mastication, and the mandibles are obsolete. The pupa is inactive, and the larvæ are aquatic, and generally construct a case with bits of gravel, sticks, or grass, which the generally drag with them, but some of these cases are affixed permanently to stones. A few species form their cases in the shape of turbinated shells, and these have been described as Mollusca. In most cases their food is vegetable. The adults inhabit damp places near the water; they run with tolerable ease, but do not fly well. Hydropsyche (pl. 79, fig. 65), Limnophilus (fig. 68), Phryganea (figs. 66, 69).

Order 7. Hymenoptera (pl. 79, figs. 1–53). In this order the body is generally of a hard consistence, divided into three distinct portions. The wings are four in number (although sometimes absent) with few nervures; in repose the tips cross each other horizontally; and the posterior pair is the smallest, and attached to the anterior pair during flight by a row of minute hooks. They have a pair of biting mandibles, membranous maxillæ, with palpi, and a labium or tongue. The feet are well developed, and the tarsi are generally pentamerous. The female has an ovipositor or sting. The head and eyes are generally large, and the stemmata rarely absent. The antennas are variable, but generally slender, and with thirteen articulations in the male, and twelve in the female. The prothorax is much reduced, and the mesothorax well developed for the insertion of the anterior wings. The larvæ are with or without feet, and the pupa is incomplete and incapable of locomotion. The habits of this order excite more interest, and their instincts are more striking than those of any other. The nervures or veins of the wings (at least the anterior pair) are extensively used in classification, each longitudinal or transverse part, and each intermediate area or cell having its peculiar name.

The larvæ of the Tenthredinidæ (the only ones which have feet) bear a considerable resemblance to those of the Lepidoptera. These feed upon leaves, others feed upon the juices of living plants and animals in which the eggs have been inserted by the mother. Some larvae feed upon animal food placed near them by the adult, whilst others, like those of ants and bees, are regularly fed by the neuters. The limbs of the pupae are free, but inclosed in a filament. Adult Hymenoptera are mostly found upon flowers and fruits, the mouth being adapted for taking fluids. In general they do not feed much, and in a few cases they are without a mouth.

These insects fly and run well, and some leap with facility. A few simulate death when taken, bringing the abdomen in contact with the thorax at such times. Some defend themselves by biting, and others by a poisonous sting at the extremity of the abdomen, which can be extended or retracted at will. They are of medium size, the largest species (as Pompilus formusus, Say) being much smaller than the large Coleoptera, Lepidoptera, or Orthoptera, whilst the small species rival in minuteness those of other orders.

Blanchard divides the Hymenoptera into thirteen tribes, with French names, corresponding to the family names: 1, Apidæ; 2, Vespidæ; 3, Eumenidæ; 4, Crabronidæ; 5, Sphegidæ, 6, Formicidæ; 7, Chrysididæ; 8, Chalcididæ; 9, Proctotrupidæ; I0, Ichneumonidæ; 11, Cynipidæ; 12, Siriddæ; 13, Tenthredinidæ.

Westwood, who follows Latreille pretty closely, adopts the following arrangement:

• Sect. I. Terebrrantia, Latr. Abdomen with a saw or borer for depositing the eggs.
  • Sub-sect. 1. Securifera. Abdomen sessile, larvæ feeding upon vegetable matter, and having a well developed mouth. Fam. 1, Tenthredinidæ; 2, Uroceridæ.
  • Sub-sect. 2. Pupivora. Abdomen pedunculated, having a borer, larva without feet, having mandibulate trophi slightly developed, and generally parasitic in other living insects.
    • Division 1. Spiculifera. Abdomen with an elongate plurivalve oviduct; larvæ generally parasitic in other insects. Fam. 3, Cynipidæ; 4, Evaniidæ; 5, Ichneumonidæ; 6, Chalcididæ; 7, Proctotrupidæ.
    • Division 2. Tubulifera, Latreille. Extremity of the abdomen tubular, retractile, and furnished with a minute sting. Larvae feeding upon the larvæ of other Hymenoptera, or upon dead insects deposited by the parent of such larvæ for the support of the latter. Fam. 8, Chrysididæ.
• Sect. II. Aculeata. Abdomen of the females and neuters armed with a poison sting. Antennæ of the male with thirteen, and the female with twelve articulations.
  • Sub-sect. 1. Prædones, Latr. Basal articulation of the posterior tarsi cylindrical, not dilated, nor formed for collecting pollen. Larvæ feeding upon other insects stored up, or upon animal or vegetable fluids provided by the neuters. Fam. 9, Crabronidæ; 10, Larridæ; 11, Bembecidæ; 12, Sphecidæ; 13, Scoliidæ; 14, Mutillidæ; 15, Formicidæ; 16, Eumenidæ; 17, Vespidæ.
  • Sub-sect. 2. Mellifera, Latr. Basal articulation of the posterior tarsi dilated and pollinigerous. Larvæ feeding upon honey or pollen paste deposited by the parent or collected by the neuters. Fam. 18, Andrenidæ; 19, Apidæ.

Fam. 1. Tenthredinidæ. In this family the body is short and sub-cylindrical, the thorax robust, and bearing large wings with more numerous areas than in the other families. The antennæ are short, the mandibles strong, and the maxillary palpi are six-articulate. The abdomen of the female is provided with a pair of saws, which are regularly toothed, and present various modifications, probably adapted to the nature of the material to be sawed, as we know that the saws used in mechanical operations must be varied according as the wood is wet or dry, hard or soft. The two saws are applied together and worked with an alternate motion, one being drawn back when the other goes forward, sawing a groove in tender bark, or in leaves, in the latter case either beneath the ribs, or in the edge. In this groove the egg is inserted. The young live either in galls which are the result of the wounds, or, coming forth, they feed upon leaves. Some species do not saw grooves for the eggs, but affix them to leaves and branches. The larvæ in this family have a close resemblance to those of the Lepidoptera, having, like them, six thoracic feet; but they have generally from twelve to sixteen abdominal or false feet, whilst those of the former have not more than ten. They are destructive to various cultivated vegetables, and some feed upon the leaves of the pine.

Lophyrus (pl. 79, fig. 43) is remarkable for having the antennæ multi-articulate, those of the male being bi-pectinated, and those of the female serrate. The larva of L. pini is sometimes very destructive to the pines in Europe. Nematus (fig. 44) has the antennæ slender and nine-articulate in both sexes. The larvae have six true and fourteen false feet. They live upon leaves and change in the ground, where they form a cocoon. Cimbex (figs. 45, 47) has a heavy body, and the antennæ with five articulations, in addition to a terminal club. The species are of rather large size, and some of them are finely colored. C. americana is described by Dr. T. W. Harris in his report on injurious insects.

Fam. 2. Uroceridæ. The genus Urocerus, Geoff., 1764 (Sirex, Linn., 1767), of which the European U. gigas (pl. 79, fig. 42) is a good example, is the type of this family. The body is lengthened, cylindric, and the abdomen united by its entire base, and furnished in the female with a borer for inserting the egg in living trees, chiefly of the resinous kind, to which the larvæ are at times very destructive.

Fam. 3. Cynipidæ (figs. 48–53). This is a family of small insects, the larvas of which are generally parasitic in plants, where they cause the excrescences named galls. The antennæ are straight, and have from thirteen to sixteen slender articulations. The female has a slender ovipositor, which is internal and spiral in a state of repose. The irritation of depositing an egg in the plant causes an excrescence, and the continued feeding of the larva upon its internal part continues to keep up the abnormal action until a gall is formed, of large size, compared with that of the little insect which finally leaves it.

Fam. 4. Evaniidæ. In this family the posterior feet are the stoutest, and the abdomen is affixed to the metanotum. Evania has a very small abdomen, and is parasitic in the Blattæ. Dr. Reinhardt found a species upon the U. S. ship Constitution, in various parts of the world (including Cochin China and Rio), where it doubtless accompanied the Blattæ which infest shipping. In the American genus Pelecinus, the abdomen of the female is remarkably long and slender.

Fam. 5. Ichneumonidæ (pl. 79, figs. 32, 33, 37–39, 45). The body of these insects is narrow, the antennæ rather long, of numerous articulations, and vibratile. The feet are long, and adapted for running, and the ovipositor straight. These insects are abundant in species and individuals, the size varies considerably, but the greater part are small, and some are minute. The larvae are the chief enemies of the Lepidoptera, under the skin of the larvæ of which the eggs are deposited by means of the ovipositor of the female Ichneumon. The young feeds upon the internal parts of the caterpillar, avoiding the vital organs, and by the time the young Ichneumon has acquired its full growth, the caterpillar is ready to die. Sometimes the caterpillar changes into the pupa state, from which the parasite makes its appearance. A caterpillar may contain a single larva of an Ichneumon of a large size, or fifty or more small ones. They are not confined to Lepidoptera, but attack Coleoptera, Diptera, and probably members of all the orders. Among the Hemiptera, the Aphides are extensively destroyed by minute Ichneumons. In some cases a parasitic Hymenopter is itself attacked by a smaller member of the same order. The eggs of insects and spiders are similarly attacked, and spiders also. These insects are very active, flying and running about in a restless manner, and vibrating the antennæ as if excited. In their perfect state they are found upon flowers. They are generally black or red colored, varied with white or red, the middle of the antennæ being often white.

Fam. 6. Chalcididæ (pl. 79, figs. 34, 35). This is an extensive family mostly of minute parasitic insects, many of which have bright or metallic colors. In some forms the hinder femora are very thick, in some the antennæ of the male are branched, and in Leucospis (fig. 23), the ovipositor of the female, when unemployed, is turned up along the dorsum.

Fam. 7. Proctotrupidæ. This family contains minute species, with habits like the two preceding families. Some of them are so small, that a number of them may be parasitic in a single egg of a butterfly.

Fam. 8. Chrysididæ (Chrysis, pl. 79, figs. 24, 26). This is a family of small, oblong-bodied, brilliant, metallic-colored insects, which have the power of rolling themselves into a ball, or at least of applying the venter to the thorax beneath. The abdomen is attached by a short peduncle, its extremity has a tubular exsertile ovipositor, which is moved like the joints of a telescope, and the termination is a sharp point. They are very active, and may often be seen during hot weather upon fences or dry sand, vibrating their antennas and moving about. Westwood thinks the egg is deposited upon the food intended for the larvae of other species, and of which it deprives the proper owner.

Fam. 9. Crabronidæ (Crdbro, fig. 29). In this, the first family of the Aculeata, the head is large and quadrate, the antennæ short, the feet slender, the anterior tibia with a pectinated spur, and the abdomen of the female provided with a sting. The general color is some dark tint varied with yellow spots. The adults frequent flowers, but feed their young with insects. They gnaw holes in wood, in which they lay their eggs, and a stock of provisions consisting of other larvæ or adult insects; and we have on two occasions found dead branches of trees (bored probably by members of this family) filled with Diptera, a single species of the latter being taken in each case. The insects taken for the food of the young are not killed entirely, but rendered torpid, so that they may not decay before they are wanted. When the store is complete the aperture is closed.

Fam. 10. Larridæ. This is a small family allied to the preceding; the labrum is hidden, and the mandibles have a notch near the external base.

Fam. 11. Bembecidæ. This is the smallest family in the order. The mandibles are pointed, have an internal tooth, and the labrum is exserted. It contains the genera Bembex, Monedula, and Stizus. These insects lay up a store of insects in the ground for their young. Some of the species of Stizus are considerably larger than hornets; of black or dark colors, generally ornamented with yellow spots. The common species of the United States, S. speciosus, Drury, kills and carries off Cicada (pl. 80, fig. 75) pruinosa, a large locust much larger than itself, the locust, during the attack (if a male), making a great noise with its sounding organs.

Fam. 12. Sphegidæ (pl. 79, figs. 27, 28, 30, 31). Here the body is elongated, the abdomen is attached by a long slender peduncle, and is armed with a sting. The mandibles are slender and curved, and the feet long, and generally fossorial. These insects are very active and restless, running about dry places, or along water courses, keeping their wings in a state of vibration. They suck the fluids of flowers, but the larvae are provided with animal food by the adult. Ammopliila sabulosa (fig. 31), which seems to inhabit the United States as well as Europe, digs a hole in sandy places, and stores it with spiders for the young. Pelopæus (fig. 30). P. flavipes, the mud-wasp of the United States, may be seen forming small balls of mud along water courses, especially where cattle are watered, as there is no grass present, and the earth and water meet gradually and nearly on the same level, so that the ground is generally made wet a few inches from the margin by the capillary attraction and the small ripples. When the ball of mud (which is about an eighth of an inch in size) is ready, the wasp takes it to its nest, which may be in a garret, or under the eaves of a house. Here the nest is formed, a cell at a time, each after the first one being attached parallel with the preceding ones, and generally (perhaps always) in a horizontal direction, or nearly so. Sometimes a space of three inches in length will be covered by allowing successive cells to be attached side by side, but in other cases not more than three will be attached (perhaps to the lower side of a rafter), and the succeeding ones will be attached or suspended to these until the mass assumes the form of an elongated sub-quadrate prism attached by one end. In rare cases the nest is built upon the upper surface of a rafter. The cells are filled with spiders for the larvae, and then closed with mud. The pupa is inclosed in a translucent yellow cocoon resembling very thin oiled paper. Westwood (Introduction, ii. 207), judging from observations made by W. W. Saunders, thinks that these constructions are made by Eumenes, but if the latter is concerned, it is probably the parasite, or the Pelopæus may take a cell already formed in preference to building one. The United States species of Eiunenes are not known to enter houses, where Pelopceus is constantly seen, although they may both be found in the same vicinity out of doors.

Some authors separate Pompilus (figs. 27, 28), and some allied genera, to form a separate family.

Fam. 13. Scoliidæ. Some authors divide this family into two portions (considered sub-families by Westwood) of which Scolia and Sapyga are the types. In the former the antennæ are short and curled, and the feet thick and spinose; whilst in the latter the antenna3 are straight and long, and the feet thin. The first contains some large species. The European S. flavifrons deposits its eggs in cavities in the earth occupied by the larva of the large Coleopter, Oryctes nasicornis (pl. 81, fig. 115), upon which it lives.

Fam. 14. Mutillidæ. This family approaches the Formicidæ (ants) in general appearance, but the species are solitary, and provided with a long curved sting which can be used very effectually, on account of the flexibility of the abdomen. There are but two kinds of individuals, male and female, the latter being apterous. The species inhabit hot and sandy localities, and they are often covered with short hair, sometimes vividly colored with red, yellow, and black. Mutilla (pl. 79, fig. 1), Apterogyna (fig. 2).

Fam. 15. Formicidæ (pl. 79, figs. 3–9). This is the family of the ants, in which the head is triangular, the antennæ filiform, and elbowed at the end of the basal articulation, the mandibles robust, the abdomen oval and attached by a narrow pedicle, and the feet slender and cursorial. These insects live in society in burrows of their own construction, which are found in the earth, or in dead trunks of trees. Some form a rough hill out of clay mixed with bits of vegetable material. Formica merdicola, of Brazil, builds a nest of dry horse excrement, upon the stems of reeds and trunks of trees. A somewhat similar nest (figured in Kirby’s Bridgewater Treatise) is constructed upon the branches of trees by Myrmica kirbii.

The Brazilian Formica elata of Dr. Lund makes a nest upon the trunks of trees out of clay and leaves. A minute species of the United States, which seems to be Myrmica domestica, is found in small colonies under stones, but it occasionally takes up its residence in old galls upon oak shrubs, entering by the aperture made by the retiring Cynips, and adapting the interior to its purpose. The same species swarms in some houses, both in America and England.

A few individuals like workers, but with a very large head, are sometimes found. Among the driver ants of Western Africa, according to the observation of Dr. T. S. Savage, there are three or four kinds: neuters, soldiers, workers, and carriers.

Besides the ordinary males and females, which are not numerous, the societies of ants are made up chiefly of workers, sometimes named neuters, which are abortive females without wings, of a smaller size and more industrious habits than the others. These have all the work of the establishment to perform, whether in building, collecting food, or taking care of the eggs and young. The difference between a worker and a female is probably due to a peculiar mode of feeding, as with the bees, where the larva, if a worker, is transformed into a queen when accident deprives the hive of the latter. The male and female are winged, but the wings are dropped after a certain time, and the latter is larger than the former.

In cold climates the male and female ants die in winter, and the neuters remain torpid, so that they do not require a stock of food. But under other circumstances a store of food is collected. Thus an East Indian species collects a great quantity of grass-seed, which is brought to the surface to dry after the heavy rains of that country. Ants are fond of the liquid matter exuded by the Aphides, and they frequent the trees where they are found, for the purpose of getting it; and by annoying the Aphis they can cause it to furnish a globule. Certain species of Membracis are treated similarly before they have attained their perfect state. Sometimes Aphides are kept prisoners by the ants; and we have observed a number of one of the species which infests the roots of grass, in their natural position upon the roots beneath a stone occupied as an ants’ nest.

In the genus Polyergus the mouth is not adapted for building; and as the economy of the nest must be carried on, they make predatory excursions to the nests of two other species of ant, and take their young workers in the pupa state. These assume their perfect state in the domicile of their captors, and become the slaves of their community, all the labor of building, collecting food, and taking care of the young, falling to them.

St. Fargeau thinks that Polyergus exhibits the “perfection of instinct,” being capable of laboring, but preferring idleness; but Huber asserts that they have no talent except that of war, and on placing some of them in a glass with their pupæ, they began to die from want, until an individual of Formica fusca was introduced, which preserved the remainder. In Europe, a true working Formica makes slaves of two other species, although it assists in the work; and in the United States the large yellow ant makes slaves of the black ones, both being true Formicæ and both working. (See Westwood’s Introduction, ii. 232.)

The habits of the driver ants of West Africa (which are the neuters of the genus Dorylus) are carefully detailed in the Proceed. Acad. Nat. Sci., iv. 196. They are very fierce, have no permanent abode, and live temporarily in crevices. They travel at night or in cloudy weather, and if overtaken by the sun they protect themselves by an arch of earth made adhesive by a fluid from the mouth. Without this they would die, the direct rays of the sun killing them in two minutes. It being necessary to protect the young in migrating, an arch is made of the bodies of the soldiers, which interlock their jaws and feet for the purpose of forming it. They move in great armies, and when they enter a house, rats, lizards, &c., and even man, take their departure. They destroy large serpents, and domestic animals confined in stables. Dogs and asses are afraid to leap over their line when on a march.

Fam. 16. Eumenidæ. In this family the sexes appear in their ordinary condition, and the species do not live in society. They resemble wasps, and construct mud cells in which the egg is placed with insects, larvæ, or spiders, the aperture being then closed.

Fam. 17. Vespidæ (pl. 79, figs. 20–22). This includes the wasps, which in some points of their economy approach the bees, and like these, there are males, females, and workers. Many of the species are black or dark colored, varied with white and yellow. They are widely distributed, especially in warm regions, and they live in societies during the summer, building nests of hexagonal cells, made of a paper-like material, and often inclosed in a globular covering of the same material, as in the case of the hornets. They feed upon insects, fruit, honey, and other materials; and the large American hornet, Vespa maculata, often comes about houses to catch flies. The larvæ are fed by the adults, and when they are ready to assume the pupa state they inclose themselves by spinning a convex cap over the mouth of their cell. The fecundated females survive the winter, and each commences a new colony, building cells, depositing eggs, and feeding the young, until these are old enough to take part in the labors of the establishment, which is about a month from the time the eggs are laid. Two or three broods are raised successively from the same set of cells during a season. The nests of Vespa may be seen upon trees (where they are sometimes from twelve to eighteen inches in diameter), or under the projecting parts of houses. The small American species known as “yellow jackets,” build under ground; and the “paper-wasp,” Polistes fuscata, attaches its comb (with the mouth of the cells downwards) to the branch of a tree, to the shelving parts of houses, or beneath a stone which has a cavity under it. Polistes (fig. 20), Vespa vulgaris (fig. 21), Vespa crabro (fig. 22). A few species of Polistes collect stores of honey.

Fam. 18. Andrenidæ. In this family, which is allied to the bees in form, there are only males and females. They are solitary; the female digs a hole in the ground where she deposits her eggs and a stock of paste made of pollen and honey, the hole being afterwards closed.

Fam. 19. Apidæ (pl. 79, figs. 10–18). The family of the bees contains various groups differing in their character and habits, Xylocopa (X. violacea, fig. 11) bores passages in wood in which the young are placed with a quantity of pollen paste. In the United States, X. victima bores in the lower surface or edge of white pine structures, particularly about houses. The species of Bombus (figs. 10, 13) known as bumble bees, make their nests under ground, in fields and pastures. The females (which are not restricted in number) assist the neuters in working. The colony does not remain together in the winter. Megachile (fig. 12 a, male; b, female). Nomada (fig. 15) is distinguished by its bright colors, and Eucera (fig. 16) by its long antennæ.

Apis mellifica (fig. 18 a, female; b, male; c, worker) is the common hive bee. The male (or drone) is somewhat larger than the workers, it is without a sting, the eyes meet upon the top of the head, the posterior tarsi have the basal articulation lengthened, and not square, as in the neuters, the thorax and abdomen are less distinctly separated, and the wings are longer than in the female and neuter. There may be from six or seven hundred to two thousand males in a hive, but this number is not in proportion to the other inmates. The females have the wings abbreviated, and the abdomen lengthened and provided with a curved sting, that of the workers being straight. The antennæ and feet are paler than in the workers.

Bees collect honey, pollen, and propolis, the young being fed with a mixture of the two former, whilst the latter (which is a mixture of one part wax to four of resin) is used to stop crevices and make repairs. The wax is a secretion between the segments of the lower side of the abdomen of the workers, where it appears in the form of small scales.

When accident or death deprives a hive of its queen, great confusion follows, but in a few hours several cells containing worker larvæ two or three days old are enlarged, and these young are supplied with the peculiar food given to queen larvæ. Several new queens finally appear, and a conflict ensues, till one only survives. If a strange queen is introduced soon after the original one has been removed, it is surrounded and starved, but never stung; though if the interval of eighteen hours has elapsed, the stranger will be at first surrounded, but afterwards allowed to go. If, however, the hive has been twenty-four hours without a queen, the new comer takes her place as queen. When two queens come together they fight until one of them is killed.

Most of the eggs laid by the female bee are those of workers, until she is about eleven months old, when two or three thousand male eggs are laid at the rate of forty or fifty a day, and this generally happens in March and April, a smaller amount of male eggs being laid in autumn. Whilst laying the male eggs, the queen also lays the few which are to produce females, and these are deposited in “royal cells” constructed for the purpose, of a large size, and not placed in regular series like the others. These eggs are not laid faster than one a day, and seldom to the number of twenty; and they are placed at once in the royal cells by the queen, who inserts her abdomen for the purpose.

When the young females approach their adult state, the queen becomes uneasy, she communicates her uneasiness to the workers, and in their confusion they all go forth with the old queen, thus forming a new swarm; but as this occurs in fine weather when many of the bees are abroad, these, upon their return, take care of the hive, and others soon leave the pupa state.

The female eggs (not being laid simultaneously) come to maturity at different times; and when the young female leaves its pupa state, it begins to gnaw an aperture for its egress, but the workers prevent this for two days by stopping the place with wax. When she finally emerges, she endeavors to go to the other royal cells to destroy them and their inmates, but she is prevented by the workers, and another scene of confusion ensues which, in a full hive, ends in a second swarming. This reduces the workers so much, that when another female emerges she cannot be prevented from destroying the royal cells and their contents, so that she becomes queen of the hive, although she may have to fight with others which emerge about the same time. Small hives do not send off swarms, and in this case royal cells are not made nor female eggs laid. After swarming the males are killed, and being without a sting, they readily succumb under the stings of the workers.

Various species of the bee are kept for the honey. That of Italy is different from the Apis mellifica of Northern Europe and the United States.

Order 8. Lepidoptera. In this order the metamorphosis is complete, the antennæ multi-articulate, the labrum and mandibles rudimentary, the maxillæ forming a spiral sucker, the labial palpi are large, the wings broad with branching nervures, and having both surfaces covered with minute scales.

These insects are known under the general name of butterflies; some small species which destroy cloth in their larva state (or the larvæ themselves) are called moths, and the species of Sphinx are named hummingbirds. The body is generally clothed with a hairy covering, the eyes are usually large, and the steinmata, when present, are usually hidden by the hair. The antennæ present several types of form, but in their details they offer some important variations from the simple types. The scales of the wings contribute much to the variety and splendor of the tints observable in these insects, which probably surpass all the other orders in their coloring. In a few the disks of the wings are without scales, leaving them transparent. The distribution of the nervures in the wings varies, and is now employed in classification. The wings are reduced in size, or wanting, in some females. In some genera they are carried vertically over the back, in some they are horizontal, and in others deflexed. The feet are pentamerous, generally hairy, and in most cases of equal length; but in some the anterior pair are so much reduced in size as to be of no use in walking.

The liquids of flowers furnish the Lepidoptera with food, but in some cases they require none in. the adult state.

In the larva state they are known as voracious eaters, under the name of caterpillars. These have a mandibulate mouth, composed of a pair of corneous mandibles, a pair of maxillæ each with a small palpus, and a labium with two palpi. They have six thoracic feet corresponding to those of the imago, and a number of abdominal or false feet, varying from four to ten. These are used chiefly for holding, and the former for walking. They generally move forwards, but those of the Tortricidæ can move rapidly backwards, and some, by bending and straightening the body suddenly, can leap. Some caterpillars are smooth, some covered with hair, which may be harmless, or with the quality of nettles, and it may be long or short, dense or sparse, bristly or woolly; and some of them have horn-like projections. Some are ornamented with various bright colors; some which feed upon leaves are green, some found among lichens have their color, and others which feed upon branches resemble a projecting stick, as if to prevent their numerous enemies from readily recognising them. In a few cases the caterpillar forms a case for itself, with which it moves about, and into which it withdraws when danger threatens. In growing, caterpillars moult frequently, and undergo various changes in color. They usually rest by day and feed by night. Some are solitary and wandering, and some live in society, either in large webs, or congregated upon a single spot. A few live upon skins, hair, and wool, but the great majority of caterpillars feed upon vegetables, including leaves, roots, seeds, and grain. The most acrid and acid leaves are eaten by some species; some devour almost every kind of plant, and some plants feed various species. The pupa has the feet, &c., hidden, and is motionless, except that the articulations of the abdomen are capable of moving. Some of these are inclosed in a silken cocoon, some in a cocoon formed chiefly of the hair of the caterpillar, whilst others suspend themselves without any exterior covering.

These insects are divided according to their habits into three sections by Latreille: The first (Diurna) include those which fly by day, and with very few exceptions they have the antennæ knobbed; the second (Crepuscularia), those which fly by twillght, and have the antennæ gradually thickened; and the third (Nocturna), the night-fliers, in which the antennæ are usually filiform. These sections correspond respectively to the extensive Linnæan genera, Papilio, Sphinx, and Phalæna. But the terms of these sections are not exact, because some of the Crepuscularia and Noctnrna are day-fliers, and on this account Boisduval applied the name Rhopalocera (meaning club-horned) to the Diurna, and Heterocera to the others, on account of their antennæ being variously formed. Blanchard names the latter Chalinoptera, because they (generally) have a kind of bridle to unite the posterior to the anterior wings, and the former (the Diurna), Achalinoptera, because they want this contrivance. The Achalinoptera (or Diurna) he separates into five tribes: Papilioniens, Nymphaliens, Eryciniens, Hesperiens, and Cydimoniens.

The Chalinoptera he divides into nine tribes; Castniens, Sesiens, Zygæniens, Sphingiens, Bombyciens, Noctueliens, Uraniens, Phaleniens, and Pyraliens.

Westwood divides the Rhopalocera into the families: 1, Papilionidæ; 2, Heliconiidæ; 3, Nymphalidæ; 4, Erycinidæ; 5, Lycænidæ; 6, Hesperiidæ; and the Heterocera into: 1, Sphingidæ; 2, Uraniidæ; 3, Anthroceridæ (or Zygænidæ); 4, Trachiliidæ (or Sesiades, Latr.); 5, Hepialidæ; 6, Bombycidæ; 7,Arctiidæ; 8, Lithosidæ; 9, Noctuidæ; 10, Geometridæ; 11, Pyralidæ; 12, Tortricidæ; 13, Yponomeutidæ; 14, Tineidæ; 15, Alucitidæ.

In the Nomenclator Zoologicus of Agassiz the following families are admitted, but a uniform termination is not given: Papilionides, Nyctalideæ, Sphingides, Sesiæ, Zygænides, Chelonarii, Bombyces, Noctuæ, Geometræ, Pyralides, Tortrices, Tineæ, Pterophorii.

Fam. 1. Pterophoridæ. This family includes several genera of small insects remarkable for having all the wings deeply split into narrow pieces which are fringed and resemble feathers, whence one of the genera has been named Pterophorus (P. pentadactylus, pl. 79, fig. 77). The rays of the wings can be folded over each other.

Fam. 2. Tineidæ (pl. 79, figs. 81–87). This is an extensive family of small narrow-winged butterflies, with the rostrum generally rudimentary, and the antennæ ordinarily raised over the head. These insects are among the smallest of the Lepidoptera, and although their colors are generally sombre, many of them are beautiful objects. In their larva state various species, as Tinea pellionella (fig. 84), are destructive to clothing, feathers, hair, and similar materials, which are used as food, and to construct a kind of cocoon which the larva carries with it. The larvæ of other species (as Tinea granella, fig. 81) feed upon stored grain.

Gallerea cereana (fig. 83) lives in beehives, where it destroys the honey and causes the death of the bees. The larva seems to feed upon the wax. Some authors separate Hyponomeuta and a few other genera in which the wings inclose the sides, and the posterior ones are the largest, and folded. Hyponomeuta (figs. 86, 87), Plutella (fig. 82), Lemmatophila (fig. 85).

Fam. 3. Tortoricidæ (pl. 79, figs. 78, 79, 90, 91, 92). In this family the wings are enlarged near the shoulder, a little deflexed, and when closed, forming a triangle. The larvæ are naked, and have sixteen feet. They feed chiefly upon leaves, the edges of which they roll up into a tube and fasten with silk. In this they readily move backwards and forwards.

The larva of Carpocapsa pomonella (fig. 79), known as the apple worm, lives in apples, causing them to fall prematurely. Tortrix viridana (fig. 91) is very destructive to the foliage of oak forests. The larvæ of Coccyx resinosa (fig. 78), and two other species, eat the buds and leaves of pine trees in Germany; and being very abundant, they cause great damage. Sciaphila literata (fig. 90), Halias prasinana (fig. 92).

Fam. 4. Pyralidæ (pl. 79, figs. 80, 88, 89). These insects are of a small size; in repose the wings generally form a triangle, and the feet are long, particularly the anterior ones, which are often fasciculate. Hypena (H. rostralis, fig. 88) is found in grass; and the larva, which has fourteen feet, rolls the edges of a leaf in which it undergoes its transformations. Hercyna (H. palliotalis, fig. 80) has a stout body, the wings short and dark satin colored, and the species inhabit mountainous regions in Europe. The larva of Botys (B. verticalis, fig. 89) has sixteen feet, and has the habits of that of Hypena. The adult inhabits moist and shady places, and is generally found upon the lower side of leaves.

Fam. 5. Geometridæ (pl. 79, figs. 93–101). The name of this family is derived from the locomotion of the larvæ, which, having often but four false feet, and these placed at the posterior extremity, move by stretching the body, holding by their thoracic feet, and then bringing up the posterior portion, forming a loop with the central part; and when the posterior false feet have taken a new hold, the anterior part is again stretched forward. Some of the larvae have twelve or fourteen feet; they feed upon the leaves of various plants; and like the caterpillars of some other families, they can suspend themselves by a thread. The body of the imago is slender, and the wings are sometimes irregularly shaped, and somewhat varied in their coloring. They are nocturnal, and common in forests. When disturbed during the day, they fly a short distance, and hide in the herbage.

The species figured in pl. 79, are Abraxis grossulariata (fig. 94), Acidalia brumata (fig. 93), A. viridata (fig. 97), Boarmia hortaria (fig. 95), Geometra papilionaria (fig. 96), Crocallis elinguaria (fig. 98), Fidonia wavaria (fig. 99), Ennomos syringaria (fig. 100), E. alniaria (fig. 101), Ourapteryx sambucaria (fig. 102).

Fam. 6. Noctuidæ (pl. 79, figs. 103–123, 129, 136). In this family the body is robust, the tergum often with a bunch of hair, the antennæ simple, but sometimes pectinate or crenulate in the males, wings often declivent in repose, and marked in many species with undulating lines. The larvæ are generally sixteen-footed, and live upon trees between leaves which they join with silk. The pupa occupies the same places, or a cocoon upon or beneath the earth. The distinctions between many of the genera are slight and difficult to identify. The mouth is well developed, and the maxillae long. The species figured are Heliothis delphinii (fig. 103), Mamestra pisi (fig. 104), M. oleracea (fig. 105), M. brassicæ (fig. 107), Trachea atriplicis (fig. 108), Tr. præcox (fig. 111), Polia chi (fig. 112), Acronycta rumicis (fig. 106), A. psi (fig. 113), Miselia oxycanthæ (fig. 109), Plusia triplasia (fig. 110), P. gamma (fig. 118), Xilina exoleta (fig. 114), Cucullia umbratica (fig. 115), C. verbasci (fig. 116), Phlogophora meticulosa (fig. 117), Triphæna pronuba (fig. 119), Catocala fraxini (fig. 120), C. pacta (fig. 121), C. sponsa (fig. 122), C.paranympha (fig. 123), Scoliopteryx libatrix (fig. 129), one of the few species found in America as well as in Europe; Episema cæruleocephala (fig. 136).

Fam. 7. Bombycidæ (pl. 79, figs. 130–135, 137–151; pl. 80, figs. 4–7). This is the family of the silkworms, which contains some of the largest and handsomest species of nocturnal butterflies. The mouth is in most cases rudimentary, the wings in repose are either horizontal or deflexed, and the antennæ bi-pectinate in the males. The larvæ have sixteen feet; they feed upon leaves, and spin a silken cocoon out of a single thread, with the aid of a gummy matter, which soon hardens. Several species are reared for the silk, and this valuable material might be furnished in greater quantity, were it not that in some cases warm water will not dissolve the gum of the cocoon as it does in Bombyx mori (pl. 79, fig. 149), and in others the silk is so intermixed with leaves, and wrapped about branches, that there is a difficulty in unwinding it. Some of the larvæ are gregarious, living together in large numbers, spinning webs upon trees, and often destroying vegetation. Some of the large members of this family, as the Chinese Hyalophora atlas, have a bare space in the wings which is as transparent as mica. In others this is replaced by colored spots.

Cossus ligniperda (pl. 79, fig. 135), is three inches or more the expanse of the wings; its color is whitish varied with brown, and streaked with black. The larva burrows in the living wood of willows, poplars, and ash, feeding upon the chips which it separates with its powerful jaws. It grows three years in the larva state, when it becomes a pupa in one of its galleries, in a cocoon made of silk mixed with fragments of wood.

Clisiocampa castrensis (pl. 79, fig. 146), C. neustria (fig. 147), Eriogaster lanestris (fig. 150), Pæcilocampa populi (fig. 140), Lasiocampa rubi (fig. 151), Notodonta camelina (fig. 130), N. ziczac (fig. 134), Cerura vinula (fig. 148), Orgya antiqua (fig. 133), O. fascilena (fig. 137), Liparis chrysorhæa (fig. 141), L. dispar (fig. 142), Pygæra bucephala (fig. 128), Clostera curtula (fig. 138), Demas coryli (fig. 139).

Lasiocampa quercus (pl. 80, fig. 1), Dendrolimus pini (fig. 2), Odonestis potatoria (fig. 3), Gastropacha quercifolia (fig. 5), Aglia tau (fig. 6), Nagelflecknusstrauchrothbuchenspinner.

Fam. 8. Arctiidæ. This family is named Chelonides by Boisduval, and is recognised by the spotted abdomen, and the bright colors of the wings, particularly the inferior ones. Westwood places Notodonta and its allies in this family, whilst Boisduval and Stephens place them in a distinct one. The genus Arctia, as given here, admits of a division into various sub-genera.

Callimorpha jacobææ (pl. 79, fig. 124), Arctia fuliginosa (fig. 125), A. matronula (fig. 126), A. dominula (fig. 127), A. purpurea (fig. 131), A. lubricipeda (fig. 132), A. hera (fig. 143), A. caja (fig. 144).

Fam. 9. Zygcenidæ. This family is sometimes namea Anthroceridæ, but as the genus Zygæna, Fabr., 1775, has priority of Anthrocera, Scopoli, 1777, it must be preferred. The generic name Zygoena, applied to a fish by Cuvier, in 1817, can have no influence against the former name. The members of this family resemble Sesia and Ægeria in being diurnal fliers, and in some the antennæ are terminated in a club. The wings are narrow, and have numerous nervures, and the feet and maxillae are long. They are of small size and bright colors, and their movements are sluggish.

Zygæna filipendulæ (pl. 80, fig. 8) has the upper wings black, spotted with crimson, and the lower ones of the latter color margined with blue. Its expanse is an inch or more. Europe.

Fam. 10. Trochiliidæ. The insects of this family are day-fliers, and bear some resemblance to Sesia (pl. 80, fig. 9), but the body is more slender, and the movements are more sluggish. Some of them are gaudily colored, and have naked wings, which, with their form, give them a general resemblance to Hymenoptera and Diptera, whence have been derived the trivial names of Sphecia apiformis, Trochilium vespiforme, sphegiforme, culiciforme, and many similar ones. The larvae bore under the bark and in the wood of trees, which they sometimes damage, as in the case of the American Egeria exetiosa, which destroys peach trees by attacking them below the surface of the ground. In this species the wings are transparent in the male alone. A closely allied, but smaller species (Trochilium cerasi), causes rough excrescences upon the branches of cherry trees in the United States.

Fam. 11. Sphingidæ, (pl. 80, figs. 10–21). These have a robust hairy body, the abdomen conical, the antennæ thickened towards the end, and prismatic; the rostrum is in some cases longer than the body, and the wings are narrow and strong, with the posterior pair small. Their flight is rapid and well sustained, resembling that of birds; and as the common words bird and fish are applied in a general and not in a technical sense, the common name of these nocturnal butterflies is humming-birds. The species fly from flower to flower, in the dusk of evening, balancing themselves on the wing in front of a flower, and without alighting, inserting their rostrum and sucking the honey. A similar mode of taking food, and an equally rapid flight, being subsequently observed in the class more generally known as birds or fowls, the term humming-bird was extended to the genus Trochilus among feathered vertebrate animals. The larvæ have sixteen feet, and often a curved horn near the posterior extremity. They often raise up the anterior part of the body, giving somewhat the appearance of the Egyptian sphinx, which has become the name of one of the genera. The larvæ known as the tobacco-worm, which eat the leaves of growing tobacco, are those of Sphinx. The imago is often found about the flowers of Datura stramonium (or jimson weed). The posterior wings have a projection which passes through a ring upon the anterior ones, tending to keep the two together.

Chærocampa (Ch. nerii, fig. 21) is remarkable for the structure of the larva, the head and anterior part of the body being retractile. As in Macroglossa, the cocoon is placed upon the ground. Deilephila (D. euphorbiæ, fig. 12; D. elpenor, fig. 13; D. celerio, fig. 14). The maxillæ are not very long in this genus. Sphinx (S. pinastri, fig. 11; S. ligustri, fig. 16; S. canvolvuli, fig. 17). In this genus the spiral maxillæ are very long, and the antennæ somewhat lengthened, and hooked at the apex. Most of the caterpillars have oblique pale stripes upon the sides, and a horn near the posterior extremity. The pupæ have the rostrum case detached, and forming a hook. They change in the earth. Sphinx Carolina and S. quinquemaculata are common in the United States. Aclterontia atropos (fig. 15) is the largest member of this family in Europe. It is known by a mark upon the thorax in the shape of a human skull. Smerinthus (S. tiliæ, fig. 18; S.populi, fig. 19; S. ocellata, fig. 20) has the maxillæ very short, and the outer margin of the anterior wings irregular. The species are of sluggish habits, and do not feed upon the wing. The larva enters the ground to change, and the pupa is without the hooked rostrum case. Dr. T. W. Harris has published a valuable paper upon this family in the 36th vol. of the Am. Jour, of Science.

Macroglossa (M. stellatarum, pl. 80, fig. 10) is a day-flying genus having a tuft at the end of the abdomen. Its habits on the wing are those of Trochilus, with which it may be readily confounded.

Sesia fuciformis (pl. 80, fig. 9). This small group has no characters sufficient to separate it from the Sphingidæ, with which Westwood unites it. Sesia has the wings transparent, and the body robust and hairy. The species fly about flowers in the bright sunshine. This genus differs but little from Macroglossa, and both are called humming-birds.

Fam. 12. Uraniidæ (or Nyctaloideæ). These splendid insects have the general appearance of the diurnal Lepidoptera, except that instead of having the antennæ knobbed, the basal half is filiform, and the remainder gradually thickened, and then tapering to the point. The discoidal cell of all the wings is open. The chief color is a bright golden green, mixed with black and sometimes red. They fly during the day; and their flight is high and rapid, so that they cannot readily be taken except by rearing them from the larvæ.

Fam. 13. Papilionidæ, Diurna, or Rhopalocera. This family contains a great many large and beautiful insects which fly about in the brightest sunshine, but become dull in damp and cloudy days. They are sometimes of a large size, the expanse of the tropical genus Ornithopterus reaching ten inches. The colors are at times very gorgeous, reflecting like polished metal. The patterns are very various, composed of stripes, spots, or rings. Sometimes the lower surface of the wings differs but little from the upper one, but in other cases the pattern is very distinct. In most cases, the upper surface presents the most variety, and the brightest tints. The coloring is sometimes uniform through certain genera and groups: Colias being yellow and white, with the margins of the wings black; Polyommatus, blue; and Argynnis fulvous, with black spots above and silvery ones below. Butterflies seldom live over one season, but a few survive the winter and appear early in spring. Some are solitary, and others gregarious. The genus Papilio is very extensive, containing about three hundred species. It is well represented in the United States, where it includes the large diurnal species. One of the most common is Papilio turnus, which is yellow, ornamented with black stripes, like pl. 80, fig. 48. The posterior edge of each posterior wing has a spatulate projection.

The group to which Hesperia (H. malvarum, pl. 80, fig. 22) belongs, sometimes have a small hook at the end of the knob of the antennæ, and the discoidal cell of the inferior wing is open. They fly about with a succession of jerks, and when they sit, the lower wings are held in a horizontal position. The larvæ are smooth, with a large head. That of Eudamus tityrus is green with the head rufous. It feeds upon the leaves of Robinia.

Lycæna hippothoë (pl. 80, fig. 23), Polyommatus argiolus (fig. 24), P. argus (fig. 25), Thecla quercus (fig. 27), T. pruni (fig. 28), T. betulæ (fig. 29). These insects (the Lycænidæ of Leach) are small and slightly made, with delicate marks and spots, the colors pale beneath and dark above, as brown in Thecla, coppery in Lycaena, and blue in Polyommatus.

Argynnis paphia (pl. 80, fig. 30), A. aglaia (fig. 31), Vanessa c-album (fig. 32), V. atalanta (fig. 33), V. urticæ (fig. 34), V. antiopa (fig. 35), V. cardui (fig. 38), V. orithia (fig. 41), V. io (fig. 42), Apatura iris (fig. 37), Hipparchia semele (fig. 39), H. galathea (fig. 40), H. pamphilus (fig. 43). These constitute a group, considered a family (Nymphalidæ) by some. They are finely ornamented, and the inferior surface is often marked with eye-like circles and silvery spots. The anterior feet are rudimentary.

Gonepteryx rhamni (pl. 80, fig. 44), Colias hyale (fig. 45), Pontia cardamines (fig. 46), belong to Westwood’s sub-family Pierides.

Dorites apollo (pl. 80, fig. 47), Papilio podalirius (fig. 48), P. machaon (fig. 49), P. æneus (fig. 50), are typical members of the family.

Order 9. Hemiptera (pl. 80, figs. 52–77). This order is distinguished by the compound rostrum formed for piercing and sucking, and of which the lower lip incloses the mandibles and maxillæ, which are in the form of bristles. These insects live upon vegetable and animal juices, those which feed upon the former being the most numerous. The Linnæan name Hemiptera indicates a character which some members of the order possess, namely, a thickening of the basal portion of the anterior wings, whilst the remaining part is thin and transparent. Fabricius and Burmeister reject this name as inapplicable, and apply one (Rhynchota) founded upon the character of the mouth. The larva and pupa are active and take food at all times, so that the metamorphosis is not complete.

This order is divisible into two sections, according as the wings are of a uniform or varied texture; and this slight distinction has been taken as a sufficient basis to form these sections into orders named Homoptera and Heteroptera.

Blanchard divides the order into eight “tribes,” of which the four first are homopterous and the four last are heteropterous, as follows: Cocciniens, Aphidiens, Fulgoriens, Cicadiens, Nepiens, Reduviens, Lygéens, Scutelleriens.

Burmeister divides the Rhynchota into tribes and families, as follows:

1. Tribe (1). Fam. 1, Pediculina.
2. Tribe (2). Fam. 2, Coccina.
3. Tribe (3) Phytophthires. Fam. 3, Aphidina; 4, Psyllodes.
4. Tribe (4) Cicadina. Fam. 5, Cicadellina; 6, Membracina; 7, Fulgorina; 8, Strididantia.
5. Tribe (5) Hydrocores. Fam. 9, Notonectici; 10, Nepini; 11, Galgulini.
6. Tribe (6) Geocores. Fam. 12, Hydrodromici; 13, Riparii; 14, Reduvini; 15, Memhranacei; 16, Caspini; 17, Lygæodes; 18, Coreodes; 19, Scutati.

Westwood, who admits the Homoptera as a distinct order, divides them as follows:

1. Section 1. Trimera. Fam. 1, Cicadidæ; 2, Fulgoridæ; 3, Cercopidæ.
2. Section 2. Dimera. Fam. 4, Psyllidæ; 5, Aphides; 6, Aleurodidæ.
3. Section 3. Monomera. Fam. 7, Coccidæ.

The Heteroptera he distributes as follows:

1. Section 1. Hydrocorisa. Fam. 1, Notonectidæ; 2, Nepidæ.
2. Section 2. Aurocorisa. Fam. 3, Galgulidæ; 4, Acanthiidæ; 5, Hydrometridæ; 6, Reduviidæ; 7, Cimicidæ; 8, Tingidæ; 9, Capsidæ; 10, Lygæidæ; 11, Coreidæ; 12, Scutelleridæ.

Fam. 1. Coccidæ. The principal genus of this family is Coccus, one of which (Coccus cacti, pl. 80, fig. 54 a b) has been named cochineal in commerce. This family was named Gallinsectes by Latreille, on account of the resemblance which the female bears to galls, neither wings nor articulate structure being present, the inert oval or hemispherical body being attached during life to the branch of a tree. They affix themselves by means of their rostrum, which is inserted so as to reach the sap, and their rudimentary feet when these are present. They resemble the lower Crustacea in having a retrograde metamorphosis, the larvae being active and capable of moving about to select a place upon which to affix themselves. The young remain for some time beneath the dead body of the female, which is well adapted for their protection. The males are active and winged, and their antennæ are longer than in the females. Some genera secrete from the skin a waxen or cottony substance which covers the body, and is often blown off by the wind in little flakes. In some genera the females are active.

Some of these insects increase rapidly, and are very hurtful to vegetation. Coccus cacti, on account of its beautiful crimson color, is used as a coloring material, and is extensively cultivated for this purpose, particularly in Mexico, its native country. It has been introduced into the Canary islands, Spain, Algeria, and St. Domingo, and it is cultivated in Guatemala and Honduras. It is probable that it would flourish in the southern United States wherever the species of cactus suitable for its food are found. Humboldt calculated the annual amount of cochineal imported into Europe to be 800,000 pounds, and it requires about 70,000 insects to make a pound. Lac (or shell lac), which is used in making sealing-wax, varnishes, &c., is the product of a coccus. Manna has a similar origin; and a white wax is collected from another species. Lecanium (figs. 52, 53), Dorthesia (fig. 56), and Chermes (fig. 58), belong to this family.

Fam. 2. Aphidæ (figs. 57, 59). The plant lice, like the preceding family, are small insects which infest the tender shoots of vegetables, and by their numbers sometimes cause great damage. The body is robust, the head small, the antennæ seven articulate, the feet slender, the wings transparent, with few nervures, and the abdomen is sometimes provided with two tubular stylets connected with glands bearing a saccharine liquid, upon which the newly excluded young are said to feed, and which is eagerly sought by ants. The Aphides are generally without wings, although they are anomalous in sometimes having and sometimes being without them in the same species. The apterous individuals are generally females. The pupae are active, and can be distinguished by their incipient wings, unless they are to produce wingless individuals. A single impregnation will fecundate several generations, the offspring being females which are capable of continuing the race. Kyber thus continued a species for four years, and Bonnet raised nine generations in three months. In some cases eggs are produced, and in others living young, and of these about ninety are produced at a time.

Fam. 3. Psyllidæ (fig. 55). A small family allied to the Aphides, but they are more active. They have ten articulate antennæ, the females have an ovipositor, and the male several abdominal appendages.

Fam. 4. Cercopidæ. This is an extensive and widely spread family of small and handsome insects, which suck the juices of plants, and are found abundantly in grass and low vegetation. The antennæ are tri-articulate, the stemmata two, the feet slender and adapted for leaping. The larva of Aphrophora (fig. 74) pierces small branches, and causes the sap to exude, which forms a mass of bubbles like spittle, under which the larva is hidden.

Fam. 5. Membracidæ. This family is closely allied to the preceding one in natural characters and habits, and is united with it by some authors. The pronotum is dilated so as to cover the posterior part of the body entirely or in part, forming a conspicuous object, and giving to some of these insects a very strange appearance.

Fam. 6. Fulgoridæ. This family is remarkable for the large projecting head, bright colors, and large size of some species. The Chinese Fulgora candelaria (fig. 76) is yellow, and the elytra black, marked with flavous spots. F. laternaria (fig. 77) inhabits South America.

Fam. 7. Cicadidæ. This family, is named from the genus Cicada (C. fraxini, pl. 80, fig. 75), which has attracted attention from a remote period on account of the noise of the male. This sound differs considerably in the different species, that of C. pruinosa, Say, for example, being very different from that of C. septendecim. The body is robust, the head large and triangular, with three stemmata, the eyes prominent, the antennæ short and thin, with six articulations, and the wings are large, and generally transparent.

The history of Cicada septendecim, known in the United States as the seventeen year locust, has been given in a valuable pamphlet by Dr. Potter, of Baltimore, who, deceived by the popular name, fancied that anything called locust must belong to the genus Locusta, and he accordingly names the insect Locusta Septentrionalis Americanæ decern septima, confounding these hemiptera with the grasshoppers, and naming the latter Cicada. Vernacular names being entirely independent of the scientific ones, attempts to make them correspond generally result in confusion. Dr. Harris gives some useful details in his Injurious Insects of Massachusetts, and Dr. S. P. Hildreth has written upon it in Silliman’s Journal, vol. xviii. p. 47, and 2d Series, vol. iii. p. 216. See also vol. xiii. p. 224. The pupa of this insect leaves the ground in the Southern States in February and March, in Pennsylvania in May, and in Massachusetts in June. The female cuts openings with her ovipositor in the tender branches of trees, where her eggs are inserted; this causes the branches to die, and one observer relates an instance in which “the tops of the forests for upwards of a hundred miles appeared as if scorched by fire.” It requires fifty-two days for the young to hatch, when they immediately precipitate themselves to the ground, which they enter and attack the roots, the juices of which they suck. Miss M. A. Morris (Proceed. Acad. Nat. Sci., vol. iv. pp. 132 and 190) has ascertained that these larvæ do much damage to fruit trees by their attacks upon the roots. She found them in great numbers upon all the roots which were more than six inches beneath the surface, and the trees were evidently suffering under their attacks. The larvæ were firmly attached to the roots by the insertion of their rostrum, and inclosed in a compact cell of clay without outlet, rendering it probable that they are sedentary where they first attach themselves. According to Miss Morris, they are destroyed by moles. The anterior feet of the larva and pupa are robust and adapted for digging, but those of the imago do not exhibit this character.

Fam. 8. Notonectidæ (pl. 80, figs. 72, 73). This family of small predaceous insects is named from the habit which the species have of swimming with the back below. They are aquatic, the head and eyes are large, the antennæ small, with four articulations, and the posterior feet are long and fringed, held out in repose like a pair of oars, and used like them in swimming. They are able to fly from one piece of water to another. Corixa striata (pl. 80, fig. 72 a b); Notonecta glauca (fig. 73).

Fam. 9. Nepidæ, (pl. 80, figs. 68-71). This family is predaceous and aquatic, the species living at the bottom of quiet waters. The body is generally depressed, the antennæ about as long as the head, and inserted below the eyes so as to be hidden. The tarsi are dimerous, and the anterior feet raptorial. Ranatra linearis (fig. 68); Nepa cinerea (fig. 69); Naucoris cimicoides (fig. 70); Belostoma (fig. 71). The last genus attains a length of three inches, and is sufficiently strong to kill small fish and frogs. Dr. Joseph Leidy has given the anatomy and characters of several North American species in the Journal Acad. Nat. Sci.

Fam. 10. Galgulidæ. Galgulus oculatus is a small North American insect, with an oval, depressed form, a broad head, and pedunculated lateral eyes. It may be seen during the day running along the grassy and sandy shores of rivers, but it is not aquatic, although it can swim to the shore if thrown into the water. It has the power of leaping a few inches, although the feet do not present saltatorial characters. When pursued they do not endeavor to escape by flight.

Fam. 11. Hydrometridæ. The members of this family live upon the surface of the water, over which some of them move with great rapidity. Hydrometra moves rather slowly over the surface, with the body elevated above it. The ordinary boat-shaped species, with four of the feet adapted to locomotion, belong to the genus Hydrometra. The larva of this genus has the abdomen very small, and as this is a characteristic of the corresponding oceanic genus Halobates, it sustains Professor Agassiz’s view that freshwater forms are higher than marine ones. Halobates being rarely found with the wings developed, Westwood thinks they are not to be considered as imagos, especially as the abdomen is small; but an extension of the views of Agassiz affords a more satisfactory explanation. Many individuals of Gerris, which seem to be perfect, are without wings, and seem never to acquire any.

Fam. 12. Leptopidæ. This is a small family with the body oval and depressed, the eyes large, the feet slender, and the rostrum long. These insects are small and active, running and flying along the margins of water. The principal genus is Salda, improperly named Acanthia by Latreille, a name used previously by Fabricius for the Cimex lectularius. This family is named Riparii by Burmeister.

Fam. 13. Reduviidæ. This family includes active predaceous species with a short, stout rostrum, sufficiently strong to pierce insects with a tolerably hard integument. The head is narrow behind, forming a kind of neck, the eyes are prominent, and there are two stemmata. The North American Arilus novenarius, Say, Am. Ent., has the pronotum arched above, and notched like the cogs of a small wheel. The puncture of these insects is-somewhat poisonous.

Fam. 14. Tingidæ. The species of Tingis have a small body with the wings strongly reticulated, and a membranous expansion upon each side of the prothorax. They move very slowly, and are found upon leaves, the juices of which they suck in all their stages. It is probable that the larvæ do not move from their first station. Syrtis is also very torpid in its movements; it lives upon trees, and probably feeds upon insects, as the anterior feet are very stout, and apparently raptorial. The genus Acanthia, first separated from the Linnæan genus Cimex by Fabricius, includes the bedbug, Acanthia lectidaria (pl. 80, fig. 67). Amyot and Serville state that the name Acanthia, Fabr., 1776, must stand, being the first given after the dismemberment of the old genus Cimex, and on this account they reject the name Cimex, which Olivier proposed for the bedbug (or chinch) in 1789. They also reject Pentatoma of this author, using Cimex instead. Hist. Nat. des Ins. Hemipt., pp. 149, 311.

Fam. 15. Capsidæ. This family contains Capsus, Phytocoris, and other genera of small and ornamental insects found upon plants, upon the juices of which they seem to feed. They run and fly well; they have no stemmata, the ovipositor is contained in a groove of the abdomen, and the rostrum is four-articulate.

Fam. 16. Lygæidæ. This family is allied to the preceding, the species are small or of medium size, and the colors varied. They inhabit plants. Pyrrhocoris apterus (pl. 80. fig. 60).

Fam. 17. Coreidæ. The first articulation of the antennæ is as long as the head or longer, and the last one thickened or lengthened in this family. These insects are large, of varied colors and active habits, and they frequent plants. In some species the hind feet have various forms and foliaceous expansions. Coryzus hyoscyami (pl. 80, fig. 61).

Fam. 18. Scutelleridæ. Some of the members of this family have the scutellum so large as to cover the abdomen and wings. The body is robust, sometimes subglobular, the antennæ long, and the feet slender. Some of the species are above the medium size, and many of them are ornamented with brilliant colors. They are vegetable feeders, sucking the juices of leaves, and some of them have glands which secrete a fluid with a very disagreeable scent. There are three sub-families corresponding to the genera Scutellera, Cimex, and Cydnus (fig. 62). The first have a very large scutellum; the second and third a smaller one; and the third is distinguished from the second by having spinose feet. Fabricius left the name Cimex for insects subsequently named Pentatoma, with which Amyot and Serville agree, although they admit a genus Pentatoma. Other authors improperly reject the name Cimex entirely. Cimex rufipes (pl. 80, fig. 66). This species is also referred to the genus Tropicoris of Hahn, and to Pentatoma. Pentatoma juniperinus (fig. 63); P. baccarum (fig. 64); Acanthosoma (fig. 65).

Order 10. Strepsiptera. This order of Kirby was subsequently named Rhipiptera by Latreille. It includes a limited number of insects of small size, which are parasitic in the bodies of Hymenoptera. The anterior wings are replaced by a kind of twisted halteres, and the posterior ones are large and folded like a fan. The mouth has two small awl-shaped jaws, and two bi-articulate antennæ; the eyes are large, prominent, and lateral, with a few large facets, and these separated by partitions raised above their surface. The antennæ are simple or furcate, with few articulations; the thorax very robust, the metathorax very long, removing the posterior feet far back. The tarsi have from two to four articulations. Specimens of certain wasps and bees may be sometimes seen with the abdomen distorted, and an examination discloses one or more heads of a minute insect sticking from between the segments, which belong to these parasites when near the time of their appearance. Siebold has discovered the winged individuals to be males, and the females to be without wings, and never leaving the wasp. The larvæ resemble minute parasites; they have six feet, and are active, running about to find an insect upon which they may become parasitic. When they have penetrated to a proper place they lose their feet and become larvæ of a different form, presenting an example of a retrograde metamorphosis.

Order 11. Diptera (pl. 77, figs. 87–129). In this order the body and integument are rather soft, the head generally free, and attached by a very short thin neck. The labium forms a kind of soft extensile rostrum adapted for suction; its sides are turned up to form a canal, and it incloses a varying number of sharp slender organs, sometimes adapted for piercing. These are well developed in the bloodsucking genera, in which the mandibles, maxillæ, labrum, and tongue are present. The two palpi of the Diptera are supposed to correspond to those of the maxillae of the other orders, although the question is not settled. In some cases the mouth is obsolete. There are two or three stemmata; the eyes are large, being in some males larger than in the females, and in some cases they occupy nearly the entire head. The antennæ are sometimes composed of a succession of simple articulations, as in other orders; but in general they are short, composed of few articulations, the last of which bears a bristle (arista) on its upper surface. The prothorax is reduced to a narrow collar, the metathorax is also much reduced, having no wings, and bearing their representatives, the small knobbed organs named halteres, so that the thorax is made up chiefly of the mesothorax, which bears the single pair of wings, constituting the distinguishing character of the Diptera. The wings are absent in some cases, but the halteres are nearly always present. The precise use of the halteres is not known. They are vibrated in flight, and if they are removed an insect is prevented from flying. Many Diptera have a pair of single or double membranes (calypta) in connexion with the halteres, and varying in size in inverse proportion with them. The tarsi are pentamerous, and the abdomen has from four to seven segments apparent.

The pupæ of the Diptera are of two kinds: in one the integument of the larva is not cast, but contracts into the form of a cocoon, from the inside of which the pupa becomes disengaged; in the other the larva skin is cast, and the pupa takes the incomplete form (in which the limbs are visible) without a cocoon. In the Culicidæ the pupæ are active.

The larvæ are cylindric and without feet, the head corneous or fleshy, and the mouth is generally provided with a pair of hooks. The aquatic larvæ have jaws and palpi, and respiration is sometimes effected by means of tubes which are held at the surface of the water, and they swim with the aid of appendages at the posterior extremity.

The larvæ occur under various circumstances, as in carrion, fungi, in galls, like those of Cynips; or in living caterpillars, like Ichneumon. Some are to be found in vessels of vegetables pickled with vinegar, and others in the acrid brine of salted fish, or in the brine vats of salt works. The greater part are produced from eggs laid by the female; some are excluded alive; and in the Pupipara the young are not excluded until they have reached the pupa state. In their perfect state the Diptera are found upon flowers or plants, feeding upon vegetable juices, or upon various decaying animal and vegetable products. Some suck the blood of vertebrate animals, or kill insects to suck their juices. They are very abundant, and are found in all climates, including the polar regions.

Although the Diptera are generally of a small size, they are so abundant in individuals that they occupy a prominent place in the economy of the animal creation. They fill the air in clouds, and afford food to various birds, whilst they are always ready to remove liquid decaying matter. The rapidity with which certain carrion flies increase under favorable circumstances, caused Linnæus to assert that three of them with their progeny can consume the carcase of a horse in as short a time as a lion would.

The Diptera contain a considerable number of noxious species, among which may be mentioned mosquitoes, the flies which torment cattle, botflies, and the grain flies which destroy wheat and other cereals.

Macquart divides the Diptera as follows, most of the names being latinized. The names between parentheses are called families, and the numbered names are given as tribes.

1. Divis. I. Nematocera. Antennæ with at least six articulations, palpi with four or five.
   1. Subdivis. 1. Rectipalpi. 1, Culicidæ.
   2. Subdivis. 2. Curvipalpi. 2, Chironomidæ; 3, Tipulidæ; 4, Mycetophilidæ; 5, Cecidomyiidæ; 6, Ryphides; 7, Phalænoides; 8, Bibionidæ.
2. Divis. II. Brachocera. Antennæ with three, and palpi with one or two articulations.
   1. Subdivis. 1. Entomocera; last articulation of the antennæ divided into segments. (Tabaniens.) 9, Tabanidæ. (Notacantha.) 10, Acanthomeridæ; 11, Sicarii; 12, Xylophagidæ; 13, Stratiomydæ.
   2. Subdivis. 2. Aplocera; last articulation of the antennæ not annulate.
      1. § Tetrachætes, mouth with four lancets. 14, Midasidæ; 15, Asilidæ; 16, Hybotidæ; 17, Empidæ; 18, Vesiculosa; 19, Nemestrinidæ; 20, Xylostomes; 21, Leptides; 22, Bombylidæ; 23, Syrphidæ; 24, Dolichopidæ.
      2. §§ Dichætes, mouth with two lancets. (Athericera.) 25, Scenopinidæ; 26, Cephalopsidæ; 27, Lonchopteridæ; 28, Platypezidæ; 29, Conopsidæ; 30, Myodariæ; 31, Œstridæ; 32, Muscidæ. (Pupipara.) 33, Coriacea; 34, Phthiromyiæ.

The following is Westwood’s classification as given in his Introduction.

1. Section 1. Cephalota, Westwood. Head distinct from the thorax; claws not dentated; larva annulose, not undergoing its transformations to the pupa state within the body of the parent; oviparous (or larvaparous in some Muscidæ).
   1. Divis. 1. (Stirps 1.) Nemocera, Latr. Antennæ of more than six joints; palpi four- or five-jointed; pupa incomplete. Fam. 1, Culicidæ; 2, Tipulidæ.
   2. Divis. 2. Brachocera, Macq. antennæ short, not having apparently more than three distinct joints; palpi one- or two-jointed.
      1. (Stirps 2.) Notacantha, Latr. Antennæ apparently composed of only three joints, the last, however, being articulated; proboscis exserted, seldom inclosing more than two lancets. The structure of the mouth is very incomplete, and the number of setee variable. Pupa coarctate, the skin of the larva, however, nearly retaining its previous form. Fam. 3, Stratiomydæ; 4, Beridæ; 5, Cœnomyidæ.
      2. (Stirps 3.) Tanystoma, Latr. Antennæ with only three joints, ordinarily terminated by a seta (Tabanus and Midas excepted); proboscis exserted, generally with four setæ (six in female Tahanidæ; mouth obsolete in Acroceridæ); larva with a scaly head; pupa incomplete. Fam. 6, Tabanidæ; 7, Bombyliidæ; 8, Anthracidæ; 9, Acroceridæ: 10, Empidæ; 11, Tachydromiidæ; 12, Hyhotidæ; 13, Asilidæ; 14, Mydasidæ; 15, Therevidæ; 16, Leptidæ; 17, Dolichopidæ; 18, Scenopinidæ.
      3. (Stirps 4.) Athericera, Latr. Antennæ with only two or three joints, terminated by a seta; proboscis generally withdrawn into the oral cavity, with two setæ (four in the Syrphidæ; mouth obsolete in the Œstridæ); pupa coarctate, the skin of the larva forming an oval case. Fam. 19, Syrphidæ; 20, Conopidæ; 21, Muscidæ; 22, Œstridæ.
2. Section 2. Thoracocephala. (Stirps 5.) Pupipara, Latr. (Order Homaloptera, Leach). Head immersed in the thorax; claws denticulated; larva nourished in the abdomen of the mother, and not deposited until after it has passed to the pupa state. Fam. 23, Hippoboscidæ; 24, Nycteribiidæ.

The first section includes a great majority of the Diptera (including those to which the term fly is popularly assigned), in which the head and antennæ are free. The mouth is a soft rostrum, containing several bristle-shaped organs in a groove along its upper surface, which also forms a channel for the liquid food.

The Culicidæ is a family of which Culex (including the mosquitoes) is the best known genus, and notwithstanding their small size, their organization is very perfect. The rostrum is very long and slender, apparently simple, but composed of seven organs. The male, which does not sting, can be readily distinguished by the feathery antennæ. These tormenting insects do not move about much during the day; but where they abound, as soon as the sun sets, they fill the air in myriads, and become a serious evil. They abound in warm climates; and in the low regions of the lower Mississippi, they fill the houses and the cabins of the steamboats as evening advances. In many parts of the United States it is necessary to exclude them from beds by a netting of gauze called a mosquito bar. In districts where they are rare, a house may be infected with them from a vessel used to catch rain water, and in which a passing female may deposit her eggs. These are laid upon the surface of stagnant water one at a time, but in contact with each other, and to the number of two or three hundred. In two days the larva make their appearance, in fifteen days they become pupæ, and instead of respiring through the posterior extremity, they have two horn-like tubes on the thorax for this purpose. The pupæ are active, but do not take food. The entire period required for the transformations is about three weeks. Culex (pl. 77, figs. 95, 96), Anopheles (fig. 94).

The Tipulidæ are an extensive family, which bear a considerable resemblance to the Culicidæ, on account of their slender body and feet. The rostrum is short, robust, and ending in a pair of fleshy lips; the palpi are generally four-articulate, and turned back. The abdomen of the male is often thickened at the tip, the antennæ have in general from fourteen to sixteen articulations, those of the male being often verticillate or pectinate. The larvae of some are aquatic; some live in the ground, where they destroy the roots of grass; some in fungi or decaying matter, and some in galls. The minute but destructive insects of the genus Cecidomyia (Hessian fly) belong to this family. There are several sub-families which Westwood names Chironomides, Cecidomyides, Mycetophilides, Tipulides, and Bibionides. The genera figured are, Chironomus (pl. 77, fig. 118), Anisomera (fig. 119), Ctenophora (fig. 120), Psychoda (fig. 121), Mycetophila (figs. 122, 124), Bibio (fig. 123).

The Stratiomydæ are generally gaudily colored; they are found upon flowers, and have the body usually depressed, and the scutellum often spinose. The larvae are aquatic or terrestrial, and the pupa is formed within the skin of the larva. Stratiomys (pl. 77, fig. 117), Clitellaria (fig. 110).

The Tabanidæ have the eyes large, the mouth well developed, that of the female having six and that of the male four piercers. The labium is fleshy, with the end lobed; and the palpi have two articulations, of which the second is long. Tabanus (T. tropicus, fig. 97, T. bovinus, fig. 98) has the third articulation of the antennæ excised upon one side. The genus contains some of the largest of the Diptera, and from their size, number, and the perfection of their oral organs, they are a great pest to cattle when numerous. The males frequent flowers the females alone sucking blood.

The Bombyliidæ (Bombylius, pl. 77, fig. 87) resemble certain bees, and the analogy is preserved by the buzzing sound they make in flying. The rostrum is very long, and projecting in front, and with this they suck flowers without alighting. Their wings stand horizontally, and their flight is very rapid.

In the Empidæ (figs. 92, 93) the body is narrow, the head small and round, with a distinct neck, the wings are large, and the feet generally long. The males generally live upon honey, and the females upon the juices of insects which they take on the wing with the aid of their feet.

The Asilidæ include several large predaceous Diptera, with a slender bristly body, a depressed head, bearded below, and a robust thorax. They fly with a buzzing noise, and take other insects upon the wing. The larvæ feed upon roots. Dioctria (fig. 88), Asilus (fig. 89).

The Midasidæ contain a number of very large Diptera with clubbed antennæ. Midas filatus (black, with a transverse orange band near the base of the abdomen) inhabits the United States.

Leptis (fig. 116) is the representative of a family (Leptidæ) of small flies of varied colors. In this genus the head is depressed, the antennæ end in a bristle, and the thorax is tuberculate.

The Athericera contain the four families Syrphidæ, in which the labium incloses four setæ; Conopsidæ, Muscidæ, having two setæ; and Œstridæ, with the mouth obsolete.

The Syrphidæ are tolerably large variously colored flies, which move swiftly through the air, and often hover over a spot for some time without changing their position. They have a hemispherical head, a great part of which is taken up by the eyes, a soft rostrum elbowed towards the base, with a pair of lip-like expansions at the tip, and the palpi small and inarticulate.

The genus Volucella (V. pellucens, pl. 77, fig. 111) is remarkable for its resemblance to the genus Bombus (bumble bee), which was designed to enable it to reach without suspicion the nests of the latter, in which the larvæ are parasitic, feeding upon the larvæ of the bees.

The eggs of Syrphus are deposited among the Aphides, upon which the larvæ feed. Other larvæ are vegetable feeders, and those of Eristalis (E. tenax, fig. 114) and Helophilus (fig. 115) are aquatic, and have the posterior part of the body attenuated into a breathing tube. These leave the water to transform in the ground. Scæva pyrastri (fig. 112), Chrysotoxum (fig. 113).

The family Conopsidæ (Conops macrocephala, fig. 90) are parasitic in the nests of bees in the larva state, and the images frequent flowers. Latreille reared a species which was parasitic in bees, and we have met with a living grasshopper in Pennsylvania, with the abdomen filled with several dipterous larvae which we did not succeed in rearing. They may have belonged to this genus, or to Tachinus. Latreille placed the genus Stomoxys (S. calcitrans, fig. 91) in this family.

The family Muscidæ (figs. 101, 103, 106, 108) is very extensive, and contains many minor groups. The habits of the species are very various. Sarcophaga carnaria (fig. 109) deposits its larvæ upon rotten vegetables, caterpillars, and even on earthworms, which they penetrate, leaving their posterior extremity at the surface. Several genera deposit their eggs upon flesh the moment it has become tainted; and Tachina and allied genera resemble the Ichneumonidæ in being parasitic in other living insects. Musca domestica, the house fly, accompanies civilized man in his migrations. The transformations of this species are said to take place in dung. Various larvæ attack different kinds of fruits, roots, and branches, causing galls, and decaying vegetable matter of different kinds. The larva of Piophila casei (fig. 103) infests cheese, and that of P. petasionis is found in preserved hams. Both are known as skippers. The larvæ of Oscanis and Chlorops are destructive to growing grain.

The Œstridæ (figs. 125–129) are a singular family of flies which live at the expense of different Mammalia, each species being generally confined to a single species of the latter. Among the animals subject to their attacks are the horse, ass, ox, various species of deer and antelope, camel, hare, and in Peru there is a species which attacks man under the skin. Animals which do not fear ordinary biting flies, often exhibit great uneasiness and terror at the presence of these insects. The larvæ occur in three different modes, some in subcutaneous tumors, as in oxen; some in the head, as that of the sheep; and some in the stomach, as in the horse. The eggs of the first kind (as Œstrus bovis, fig. 129) are deposited on the skin; those of the second (as Cephalemyia ovis, fig. 125) within the nostrils; and those of the third (as Gasterophilus equi, fig. 127) upon the hairs of those parts which can be reached by the tongue of the animal, or about the nostril, as in the case of Gasterophilus nasalis.

The moisture and warmth of the mouth of the horse hatch the eggs of Gasterophilus equi, when the larva passes to the stomach with the food. Here it affixes itself to the inner surface by means of a pair of oral hooks, forming a little cavity for its head. The eggs are mostly laid in August, and the larva remains upon the stomach until the next summer, when it is an inch long. It now detaches itself and is passed through the intestines, when it becomes a pupa in the ground, and in the course of a few weeks it emerges as a fly. The male dies after fecundation, and the female after depositing her fifty or a hundred eggs. The larvas sometimes affix themselves to the windpipe, or pass on to the small intestines, when a horse is apt to die from the irritation, and in a few cases they perforate the stomach. In most cases the presence of bots (as these larvæ are named) causes no injury to a horse, and their head is so deeply imbedded that no medicine sufficiently active for their expulsion can be administered with safety.

The presence of Cephalemyia ovis, or the fly of the sheep, puts the animals to flight and causes them to huddle together upon some sandy or bare spot (as if to prevent the fly from having a resting place), with their heads down and turned together, and their feet in continual motion to keep it from effecting its object. The fly, however, by a rapid dart, reaches the nostril, where it deposits an egg, the larva of which ascends the nostril, causing great uneasiness to the sheep, which runs around with every mark of distress. The larva makes its way to the frontal sinus, the antrum, or the nasal bones, where it affixes itself with its oral hooks, and remains until the next spring, when it crawls out and enters the ground to change. It remains in the earth six or eight weeks in the pupa state, and when it becomes an imago it is as short-lived as the horse bot-fly.

The Œstrus bovis, the larva of which lives beneath the skin of the back in oxen, causes great terror among these animals, which run for protection to bodies of water. The larvæ of Œstrus taraudi (fig. 128) are found under the skin of the reindeer. Another member of the family infests the frontal sinus, throat, and mouth (under the tongue) of the same animal.

The Pupipara are a singular group of insects, having the antennæ (which are of one or two short articulations) deeply set in the head. The mouth is without a fleshy exsertile labium, but it is provided with a sharp spicula and several bristles. They are separated into two families, Hippoboscidæ and Nycteribiidæ.

The Hippoboscidæ have a depressed, tough, and hairy body, and they live upon beasts and birds, moving quickly (and sometimes sideways) among the hair and feathers. The wings, and even the halteres, are sometimes absent, as in Melophagus ovis (pl. 77, fig. 85), known as the sheep tick. The feet are short, and the claws denticulated. The larva remains unexcluded until it becomes a pupa, and as but one is developed at a time, it is, when excluded, nearly as large as the abdomen of the female.

The Nycteribiidæ are without wings and halteres, the feet are very long, and so is the basal articulation of the tarsi, which present an analogy with the feet of some of the Arachnida in being annulated, presenting the appearance of being divided into numerous minor parts. These insects infest bats; and from the position of the head, which is small and turned up on the thorax so as to be dorsal, it is necessary for them to turn over and stand with the back downwards when they suck. This is readily effected, the feet being so constructed as to allow them to stand erect or inverted. They move rapidly through the hair, but cannot walk upon a smooth surface. Some authors have classed these insects with the Arachnida.

Vertebrata

Class I. Pisces. Fishes

The animals of this class are distinguished from those already examined, by their countless numbers, their varied shapes, their brilliant colors, and especially by their economical value. Destined by nature to inhabit and people the water, ail their structures and functions tend to this end. Their most general characteristics lie in the possession of cold red blood, breathing by gills instead of lungs, a bicamerated or two-chambered heart, fins as organs of progression, and a skin either naked or covered with scales of varied structure.

To consider these characteristics more closely, the fins consist of a delicate membrane investing a series of bony or cartilaginous rays, projecting from the body along the median line, and from the four homologues of the extremities of the terrestrial vertebrata. They have received names derived from their situation upon the body. The dorsal fin is on the median line of the back, usually single, sometimes sub-divided into two or three fins, of various degrees of contiguity. The caudal fin terminates the vertebral column in the median line, and is situated in a vertical plane; the true fishes differing in this respect from the fish-like mammalia, the caudal fin in the latter being placed horizontally. The third median single fin is the anal, situated anteriorly to the caudal, on the anterior median line. This also is sometimes divided into two or more portions. The remaining four fins, two pectoral and two ventral, situated in pairs, are the homologues of the anterior and posterior extremities of the other vertebrata. Their relative positions may vary, but they are always found rather on the inferior surface, between the anal fin and the head. The pectoral fins are always situated just behind the head, and are articulated directly to the skull. The ventrals may be entirely posterior to the pectorals, exactly inferior to them, or entirely anterior and under the throat. The fins serve as organs of motion, and to sustain the fish in an upright position. The principal instrument of motion is the caudal fin, which, by its rapid and vigorous strokes from one side to the other, causes the animal to move forwards in a straight line, the resultant of this lateral flexion. The median fins serve to balance the fish; the pectorals and ventrals, although to a certain extent instruments of motion, yet act almost entirely in balancing the fish, and diverting its course to the right or left, as also to regulate the rising and sinking in the water. Sometimes the rays of several of the fins are thickened into regular spines, retaining, to a greater or less extent, the proper integument. Fins without distinguishable rays, or where the rays are enveloped in a mass of fatty matter, or else entirely wanting, are called adipose. A fin of this character is found on the back of the trout (Salmo fontinalis) posterior to the main dorsal.

The gills consist of bony or cartilaginous spines, arranged parallel to each other, like the teeth of a comb; over which run blood-vessels from the heart, for the sake of the purification to be experienced by contact with the oxygen dissolved in the water. Sometimes the gills, instead of being pectinate, are arranged in bunches. The gill-cover consists of four bones, of which the one immediately behind the orbit is called the pre-operculum. Posterior to this are the operculum and inter-operculum, the former above the latter. Inferior to these, or slightly posterior, is the sub-operculum. Anterior to the lower part of the opercular bones is the branchial membrane, supported by the branchiostegous rays. In cases where the gill-covers are wanting or concealed, there are generally five to seven apertures in each side. Respiration in the fish is performed by taking in water through the mouth, and forcing it through the gill-openings by muscular contraction. By the contact of water with the venous blood in the gills, oxygen is imparted, and the requisite decarbonization effected. The entire circulation of the blood is as follows: Venous blood collected from the venous system, is accumulated in the single auricle. Thence it is forced into the ventricle, and this drives it into the gills. Here the blood is changed from venous to arterial, and is distributed to the different parts of the body. The heart thus never contains any but venous blood, the arterial first proceeding from the gills.

The swimming bladder of the fish is the true homologue of the lungs in the higher vertebrata; a fact well shown by its intermediate character in Amia and other fishes. Whenever present, it appears to contribute, to a greater or less extent, to the function of respiration. It exhibits various forms, bi-lobed, bi-partite, &c., and in the young fish, or even in some adults, there is a distinct communication by a tube with the œsophagus, answering to the trachea. It usually contains a gas, with oxygen in greater proportion than in atmospheric air. Some species are destitute, either entirely, of an air-bladder, or possess it in a very rudimentary state, as in Cobitis. Those without it are generally ground fish, which keep close to the bottom. Besides the use of the air-bladder in respiration, it serves an important purpose in enabling the fish to vary its specific gravity, and thus float at any desired elevation in the water.

The body of the fish, with a few exceptions, is longer than broad, and compressed. There is little expression in the face, the features being on the same level, and the nose not projecting. The line of distinction between the head and body is difficult to draw, owing to the entire absence of neck. The heart is situated far forward, between the branchial apparatus. The simple brain does not fill the cavity of the cranium. The tongue is mostly cartilaginous, sometimes covered with teeth. The salivary glands are inconspicuous, and it is not probable that the fish possesses much sense of taste. There is no external ear, and the entire auditory apparatus is here at its minimum of vertebrate development; although not so simple as in the Cephalopoda. The eyes are characterized by their immovable position, flattened cornea, spherical crystalline lens, and brilliant color, as well as by certain internal anatomical peculiarities. The organs of touch lie either in the lips, or in the apparently sensitive barbels or cirri so conspicuous in some species.

The teeth are rarely entirely wanting, although sometimes absent from the mouth. In this case they are generally to be found in the posterior arch of the gills, when they are called pharyngeal teeth. Such is the case in most of the Cyprinidæ. Some fish have teeth in nearly every bone in the mouth; on the maxillary, intermaxillary, palatine, vomerine, spheroidal, as well as on the tongue and gill arches. The shape of the teeth, as also their disposition, varies greatly.

As already remarked, the skin is either naked, or covered with scales; these occurring in various conditions of development, as true imbricated scales, as isolated scales, as spiny prickles, bristles, hard bony enamelled plates, &c. The side of the fish generally exhibits a longitudinal row of scales, in each of which is a perforation. These holes, constituting by their linear arrangement, the lateral line of the fish, were formerly supposed to secrete mucus. The recent researches of Professor Agassiz have, however, shown that these are the openings of tubes, which, together with similar tubes opening on the skull, penetrate all parts of the body, brain, muscles, bones, and viscera; freely admitting water, whose hydrostatic action thus equalizes the pressure of the incumbent water, both on the outside and within.

The colors of fishes are among the most beautiful in nature, being only assimilated, and that in an inferior degree, by those of birds. All shades are represented, as well as all lustres. These hues, however, are very evanescent, sometimes departing immediately after death.

The organs of voice are entirely wanting, and there are but few that are capable of making any sound whatever. The North American cat-fish (Pimelodus) is said to make a peculiar sound by a vibration of its cirri. The weak fish (Otolithus regalis) makes a peculiar grunting when caught, apparently abdominal in its character. The same applies to the black drum (Pogonias chromis).

While some fish are confined to salt water, and others to fresh, certain species live habitually in a mixture of the two. Others again, at different seasons of the year, occupy both salt and fresh, as the salmon. The distribution of species is much affected by the temperature of the water, and the character of the bottom. But few fishes can live out of water for any length of time, owing to the rapid desiccation of the gills, and the consequent asphyxia. The eel and the cat-fish (Pimelodus) can exist for some days in a simply moist or damp situation, as wet grass. Certain species, as the Anabas, habitually leave the water in search of food.

Fishes are almost incredibly prolific. It has been calculated that the progeny of a single herring, allowed to reproduce and multiply undisturbed for twenty years, would not only supply the whole earth with an abundance of these fish, but would become inconveniently numerous. Yet among millions of young herrings, hardly one comes to maturity, owing to the ravages made among their number by the rapacious fish and other animals, man not excepted. Yet although they form the food of myriads of fishes, of hundreds and thousands of men, the supply is always equal to the demand, and no perceptible decrease in number can be observed. Similar instances might be furnished by the cod, the shad, the mackerel, &c.

Of all oviparous animals, fish are perhaps the most prolific. Among these the cod-fish (Morrhua) is pre-eminently conspicuous. A single female has been calculated to produce as many as 9,000,000 eggs in a single season. There is no intercourse of sexes, excepting among a few of the Plagiostomes, the eggs being fertilized by the male after their evacuation by the female. Some species are ovo-viviparous, the eggs being hatched in the abdomen, or else in especially contrived pouches, as in Syngnathus. A slight approach to a placental connexion of mother and embryo, is made in some of the sharks. The eggs are deposited in various places, on sticks, stones, grass, in furrows of the sand, &c.; in rare cases a nest is built, consisting either of a single pile of stones, as in some of the North American Cyprinidæ, or else a more complicated structure of grass and sticks is built, as in the Callichthys of Demerara, and in various species of Gasterosteus. It is a little singular, that it is generally the male who takes upon himself the care of the eggs and the construction of the nest.

It is difficult to speak with any certainty as to the longevity of fishes, as few are permitted to reach their natural term of years. Some species, as Pike and Carp, kept in fish ponds, have, however, been known to live to a great age. Thus Buffon speaks of carp, in the moat of the Comte de Maurepas, 150 years old. Gesner refers to a pike having been caught in Suabia, in 1497, bearing an inscription purporting to have been appended in 1230, the age thus being (at least) 267 years. The animal was said to weigh 350lbs., and to have a length of nineteen feet.

The flesh of most fishes is edible, although that of some is difficult of digestion. They are rarely, or never, poisonous in themselves; a property only acquired by consuming poisonous plants or animals. Fresh-water fishes are more generally edible than marine, although, as a class, not so savory. Other parts of the fish are of economical value besides the flesh. The oil of some is very valuable; the air-bladder of the sturgeon furnishes the isinglass of commerce; the roes of the sturgeon, pike, carp, &c., furnish caviar. The shagreen skin of some Placoids is used for polishing, and for making ornamental coverings. The bones are used for fish-hooks, and other purposes. The Gymnotus or electric eel, the Torpedo, and the Silurus electricus, are capable of giving powerful electric shocks.

Classification of Fishes

The first scientific classification of fishes is that of Artedi (1738), who distinguishes them into cartilaginous (Chondropterygii) and bony; these being subdivided into fishes with bony branchiæ and soft fin rays (Malacopterygii), or with spinous rays (Acanthopterygii), and fishes with boneless branchiæ (Branchiostegi). Fifty-eight genera were distributed under these four heads, corresponding for the most part with those of Linnæus, whose arrangement comes next in order. This is based upon the position of the vertical fins, or the structure of the gills. The following tabular view exhibits the orders of Linnæus, with the genera of each order, taken from the thirteenth edition of 1767.

1. Apodes. Ventral fins none.
   1. Muræna.
   2. Gynmotus.
   3. Trichiurus.
   4. Anarchichas.
   5. Ammodytes.
   6. Ophidium.
   7. Stromateus.
   8. Xiphias.
2. Jugulares. Ventral fins before the pectoral.
   9. Callionymus.
   10. Uranoscopus.
   11. Trachinus.
   12. Gadus.
   13. Belnnius.
3. Thoracici. Ventral fins under the pectoral.
   14. Cepola.
   15. Echineis.
   16. Corphæna.
   17. Gobius.
   18. Cottus.
   19. Scorpæna.
   20. Zeus.
   21. Pleuronects.
   22. Chætodon.
   23. Sparus.
   24. Labrus.
   25. Sciæna.
   26. Perca.
   27. Gasterosteus.
   28. Scomber.
   29. Mullus.
   30. Trigla.
4. Abdominales. Ventral fins behind the pectoral.
   31. Cobitis.
   32. Amia.
   33. Silurus.
   34. Teuthis.
   35. Loricaria
   36. Salmo.
   37. Fistularia.
   38. Esox.
   39. Elops.
   40. Argentina.
   41. Atherina.
   42. Mugil.
   43. Mormyrus.
   44. Exocætus.
   45. Polynemus.
   46. Clupea.
   47. Cyprinus.

The remaining genera were arranged under the head of Amphibia, as Amphibia nantes, and characterized by having fixed gills without a bony structure.

5. Spiracula Composita.
   48. Petromyzon.
   49. Raja.
   50. Squalus.
   51. Chimæra.
6. Spiracula Soltaria.
   52. Lophius.
   53. Acipenser.
   54. Cyclopterus.
   55. Balistes.
   56. Ostracion.
   57. Tetraodon.
   58. Diodon.
   59. Centriscus.
   60. Sygnathus.
   61. Pegasus.

The classification of Cuvier is the one more generally adopted. He divides the entire class into bony and cartilaginous; the former again into spinous rayed and soft rayed; the latter into those with free gills, and such as have them fixed. We have here room only for the Orders and Families.

1. Acanthopterygia. Fin rays spinous.
   • Percidæ.
   • Triglidæ.
   • Sciænidæ.
   • Sparidæ.
   • Mænidæ.
   • Chætodontidæ.
   • Scombridæ.
   • Teuthidæ.
   • Tænidæ.
   • Atherinidæ.
   • Mugilidæ.
   • Gobidæ.
   • Lophidæ.
   • Labridæ.
   • Siluridæ.
2. Malacopterygii Abdominales. Fin rays soft. Ventrals behind the pectoral.
   • Cyprinidæ.
   • Esocidæ.
   • Fistularidæ.
   • Salmonidæ.
   • Clupeidæ.
3. Malacopterygii Subbrachiati. Fin rays soft. Ventrals beneath the pectoral.
   • Gadidæ.
   • Planidæ.
   • Cyclopteridæ.
   • Echineidæ.
4. Malacopterygii Apoda. Fin rays soft. Ventrals wanting.
   • Anguillidæ.
5. Lophobranchii. Gills in tufts; not pectinate.
   • Syngnathidæ.
6. Plectognathi. Bones of the head closely combined.
   • Gymnodontidæ.
   • Balistidæ.
   • Ostracionidæ.
7. Chondropterygii Branchiis Liberis. Gills pectinate, free. A single gill opening.
   • Sturionidæ.
8. Chondropterygii Branchiis Fixis. Gill apertures more than one on each side. Gills not free.
   • Squalidæ.
   • Raiadæ.
   • Petromyzonidæ.

A highly philosophical classification is that of Prof. Agassiz, which is especially applicable to the arrangement of fossil forms. This eminent naturalist divides fishes into four Orders from characters derived from the scales. They are as follows:

1. Placoids. Characterized by having the skin provided with osseous plates of various sizes and numbers, as in the sharks, rays, &c. The Plagiostomes of authors fall under this order. The families are: Rajacei, Cestracines, Hybodontes, Squalini, Chimæræ, Ichthyodorulithes.
2. Ganoids. Here the scales are bony and covered externally with enamel, generally angular and continuous. Most Ganoids are extinct; the most striking and typical recent representation is the Lepidosteus or gar-fish. Families: Sturionini, Lophobranchii, Gymnodontes, Schrodermi, Cephalaspides, Pycnodontes, Cœlacanthi, Sauroidei, Lepidosteini.
3. Ctenoids. This order corresponds nearly to the Acanthopterygii of Cuvier. It is characterized by the roughness of the scales, the border of which is generally dentated, and by the usual presence of spinous rays in the dorsal and anal fins. Families: Mugiloidei, Aulostomi, Pleuronectidei, Squamipennes, Theutyes, Gobioidei, Sciænoidei, Sparoidei, Percoidei.
4. Cycloids. These are represented by the greater number of the Malacopterygii of Cuvier. The scales are generally smooth, and not dentated. The dorsal and anal fins have generally soft rays. Families: Anguilliformes, Halecoidei, Esocini, Cyprinodontes, Cyprini, Labroidei, Lophioidei, Blennioidei, Sphyrænoidei, Xiphioidei, Scomberoldei.

The most recent classification of fishes is that of Prof. J. Müller (Ueber den Bau und die Grenzen der Ganoiden u. über das natiirliche System der Fische. 1846). We append a brief summary of this system as modified by several authors.

1. Order I. Dermopteri.

   Internal skeleton unossified: external skeleton and vertical fins mucous, naked. Shape vermiform, or without any lateral fins. No pancreas nor air-bladder.

   1. Sub-order 1. Pharyngobranchii.
      • Amphioxidæ.
   2. Sub-order 2. Marsipobranchii.
      • Myxinoidei.
      • Petromyzontidæ.
2. Order II. Malacopteri.

   Internal skeleton ossified. Scales of the external skeleton mostly cycloid, in some ganoid. Fins all supported by rays, all of these jointed excepting sometimes the first in the dorsal and pectoral; abdominal or apodal. Gills free, operculate. A swimming bladder and air duct.

   1. Sub-order 1. Apodes
      • Symbranchidæ.
      • Murænidæ.
      • Gymnotidæ.
   2. Sub-order 2. Abdominales.
      • Clupeidæ.
      • Salmonidæ.
      • Scopelidæ.
      • Characini.
      • Galaxidæ.
      • Esocidæ.
      • Mormyridæ.
      • Hypsocidæ.
      • Cyprinodontidæ.
      • Cyprinidæ.
      • Siluridæ.
3. Order III. Pharyngognathi.

   Internal skeleton ossified. Scales sometimes cycloid, sometimes ctenoid. Inferior pharyngeal bones coalesced. Air-bladder without a duct in the adult.

   1. Sub-order 1. Malacopterygii.
      • Scomberesocidæ.
   2. Sub-order 2. Acanthopterygii.
      • Chromidæ.
      • Cyclo-Labridæ.
      • Cteno-Labridæ.
4. Order IV. Anacanthini.

   Internal skeleton ossified. Scales sometimes cycloid, sometimes ctenoid. Fins sustained by flexible or jointed rays. Ventrals beneath the pectorals or entirely absent. Swimming bladder without air-duct.

   1. Sub-order 1. Apodes.
      • Ophididæ.
   2. Sub-order 2. Thoracici.
      • Gadidæ.
      • Pleuronectidæ.
      • Echineidæ.
5. Order V. Acanthopteri.

   Internal skeleton ossified. Scales ctenoid. Fins with one or more of the anterior rays unjointed or inflexible. Ventrals generally beneath or anterior to the pectorals. Swimming bladder without duct.

   • Percidæ.
   • Sclerogenidæ.
   • Sciænidæ.
   • Labyrinthi-branchii.
   • Sparidæ.
   • Mænidæ.
   • Atherinidæ.
   • Mugilidæ.
   • Notacanthidæ.
   • Scomberidæ.
   • Squamipennes.
   • Tænioidei.
   • Theutyidæ.
   • Fistularidæ.
   • Gobiidæ.
   • Blenniidæ.
   • Lophiidæ.
6. Order VI. Acanthopteri.

   Internal skeleton only partly ossified. Scales ganoid or spinous. Maxillaries and intermaxillaries firmly united. Swimming bladder without air-duct.

   • Balistidæ.
   • Ostracionidæ.
   • Gymnodontidæ.
7. Order VII. Lophobranchii.

   Internal skeleton only partly ossified. Scales ganoid or spinous. Gills tufted, gill-opening small. Swimming bladder without air-duct.

   • Hippocampidæ.
   • Syngnathidæ.
8. Order VIII. Ganoidei.

   Internal skeleton bony or cartilaginous. Scales ganoid. First fin-ray usually a spine. Swimming bladder with an air-duct.

   • Sauridæ.
   • Pycnodontidæ.
   • Lepidoidei.
   • Sturionidæ.
   • Acanthodei.
   • Dipteridæ.
   • Cephalaspidæ.
9. Order IX. Protopteri.

   Internal skeleton partly bony, partly cartilaginous. Scales cycloid. Pectorals and ventrals as flexible filaments. gills filamentary, free. No pancreas. Swimming bladder as double lung, with an air-duct. Intestine with a spinal valve.

   • Sirenoidei.
10. Order X. Holocephali.

    Internal skeleton cartilaginous. External skeleton as placoid grains. Most of the fins with a spinous first ray; ventrals behind the pectorals. Gills laminated, attached by their margins; a single external aperture. No swimming bladder. Intestine with a spiral valve. Copulation between the sexes.

    • Chimæroidei.
    • Edaphontidæ.
11. Order XI. Plagiostomi.

    Internal skeleton cartilaginous, or partly ossified. External skeleton placoid. Gills fixed; with five or more gill-openings. Swimming bladder none. Scapular arch not attached to head. Ventrals behind the pectorals. Intestine with spiral valve.

    • Hybodontidæ.
    • Cestraciontidæ.
    • Notodanidæ.
    • Spinacidæ.
    • Scylliidæ.
    • Nictitantes.
    • Lamnidæ.
    • Alopeciidæ.
    • Scymniidæ.
    • Squatinæ.
    • Zygænidæ.
    • Pristidæ.
    • Rhinobatidæ.
    • Torpedinidæ.
    • Raiidæ.
    • Trygonidæ.
    • Myliobatidæ.
    • Cephalopteridæ.

Descriptive Enumeration of Fishes

We come in the next place to the consideration of the more prominent of the families above mentioned; taking them up in the order in which they occur in the system of Müller, as modified above, and which we shall for the most part adopt. The subject of Ichthyology is of such vast extent, that our limits would be transgressed even by mentioning the names alone of all the species. We can only refer particularly to the species distinguished by their economical value or physiological interest.

Amphioxidæ. This family, at present represented by the single genus Branchiostoma, occupies the lowest position in the scale of fishes. It is characterized by the naked skin, the single dorsal extending over the entire length of the back, the absence of pectorals and ventrals. Mouth entirely inferior, elongated, or circular, the margins provided with a row of free filaments. Anterior to the anus is a median fin representing the transition embryonic fin of higher fishes. The brain, as an expansion of the nervous centres, is entirely absent; being represented by a simple extension of the spinal cord, which runs out to a blunt point. The absence of brain and of heart sufficiently distinguishes Branchiostoma from all other fishes. Its aspect, in fact, is hardly that of a fish at all, being highly vermiform in appearance. The species hitherto described are all from European or North African waters.

Myxinoidei. The Myzinoids are hardly more fish-like in their appearance than the Branchiostoma, having been classed, by Linnæus and other writers, among the worms. The vertebral column, as in Branchiostoma, exhibits the persistence of the usually temporary chorda-dorsalis. The mouth is terminal, nearly circular, and provided with a powerful hooked tooth on the palate, with others in the tentaculated mouth. The lateral fins are entirely absent, as in the other Dermopteri. The species of this family, though small in size, are formidable from the manner in which they attack their prey, which consists of larger fish. Myxine glutinosa, a European form, is most generally found embedded in the bodies of other fish, as the cod, haddock, and others. The manner of its entrance is not exactly known; probably, however, by a perforation made by the mouth, assisted by the powerful hook. No species of this family are found in North America.

Petromyzontidæ. This family, the last of the Dermopteri, is also without lateral fins: a continuous median fin is formed by the coalescence of the dorsal, caudal, and anal. Respiration is generally performed by means of fixed gills, the lateral openings to which are seven in number on each side. A single nostril is placed on the top of the head. The principal forms belong to the genera Petromyzon or true lamprey eel, and Ammocætes, or sand lamprey. The former have a circular mouth provided with numerous teeth, and fringed with ciliæ to assist the animal in attaching itself to the bodies of its prey. The mouth is a true sucker, adhesion being effected by atmospheric pressure. Fishes of various kinds are not unfrequently caught bearing the bloody circular scar produced by the bite of the lamprey, and quite often the lamprey itself. The catfish, or Pimelodus, appears to be especially liable to such attacks. The lampreys attain to great size, and are highly prized by some nations. The love borne them by the ancient Romans is a matter of classical history, and at the present day they are favorite food of epicures. A prominent European species is the Petroinyzon fluviatilis, shown m pl. 81, fig. 28. The Petromyzon americanus is the largest and best known American species. The genus Ammocætes, with the general characters of the lampreys, differs mainly in the form of the mouth. This, instead of being continuous and suctorial, is composed of a circular projecting upper lip, the lower being transverse. The opening of the throat is guarded by a fringe of ciliæ. This genus is extensively distributed over North America, where several species are known. They accumulate in vast numbers in certain sand or mud flats, as those of the Susquehanna river, whence they are dug from a depth of four or five inches below the level of the water, to serve as bait for other fishes.

The Symbranchidæ are anguilliform fishes, distinguished from their allies by the greater or less union of both branchial apertures into one. The fins also are variously suppressed, some being without pectorals, and others without either these or vertical fins. The next family.

The Murænidæ or eels, with the normal structure of the gill apertures, yet have them very small and capable of being completely closed. The body is serpentiform, and although provided with scales, these are scarcely apparent, being embedded in a thick mucous skin. The air-bladder is polymorphous, and the intestines without cœca. The eels, in their different species, are inhabitants of both fresh and salt waters; those living in the former belonging generally to the restricted genus Anguilla. Species of Anguilla occur in greater or less number throughout the United States, being, however, very rare in many if not most of the waters of the Mississippi basin. Popular opinion assigns to these species a viviparous reproduction, owing to the apparent absence of individuals containing eggs. The ova are yet, probably, present in a due proportion of the supposed males, escaping observation by their diminutive size. The eel hardly yields to any other fish in the power of sustaining a deprivation of its proper element for a considerable length of time. To transport these animals over a considerable space, all that is necessary is to pack them in damp grass or some similar substance. They even leave the water spontaneously at night in search of food, or of a body of water better suited to their convenience than the one in which they may happen to be placed. Eels are said to be very susceptible to magnetic or galvanic influence: the simple contact of a knife being sufl[icient to paralyse them. When a magnet is presented to the dish in which the living animal may happen to be, violent contortions, a painful gasping after breath, and other signs of inconvenience, are reported to be exhibited. Pl. 82, fig. 5, is a figure of Anguilla vulgaris.

The Gymnotidæ, highly interesting on account of their electrical properties, are characterized by the anterior position of the anus, the entire absence of dorsal fin, the extent of the anal, and the position of the gill-opening. The best known species, Gymnotus electricus or electric eel, is a native of the tropical portions of South America. It attains to a great size, being sometimes over six feet in length, and almost a full load for a strong man to carry. The electric or galvanic apparatus consists of four longitudinal bundles, disposed in two pairs, one larger above, and a smaller below, against the base of the anal fin. The fasciculi are divided by longitudinal partitions into hexagonal prisms, and transverse divisions separate these into small cells. The cells are filled with a gelatinous matter, and the whole apparatus is abundantly supplied with nerves from the spinal marrow. In the Torpedo, these nerves come directly from the brain.

The amount of electricity furnished by the Gymnotus is enormous. Faraday made a calculation in regard to a specimen of ordinary size examined by him, that a single medium discharge was equal to that from a battery of 3500 square inches charged to its maximum. It need not then be a matter of surprise that the Gymnotus is capable of killing a horse by repeated discharges; which it does by applying its whole length along the belly of the animal when in the water. The method of capturing the Gymnotus made use of by the South American Indians, consists in driving a number of horses and other cattle into the muddy pools in which the electric eels abound. Roused from their retreats in the mud, the Gymnoti emerge into the water, and gliding in among the animals, give to them violent shocks. A succession of discharges results in weakening the eels to such a degree, as to make it a matter of little danger or difficulty to capture them. The Voltaic pile, formed by the electric apparatus of the Gymnotus, is much like that of the Torpedo; the column being longitudinal, however, in the natural position of the animal, instead of vertical. The anterior or cephalic extremity is positive; the caudal negative; and the animal is capable of discharging any portion of its column. The substance occupying the cells is a dense albuminous liquid, with a small amount of common salt. Each cell is separate and independent, answering to the cell of the galvanic battery. This electrical power is not confined to the Gymnotus. Various species of Torpedo, one of which is found on the coast of Massachusetts, exhibit the same property in a high degree. Other electrical fishes are Malapterurus electricus, Trichiurus electricus, and Tetraodon electricus. Some insects, too, as Redivivus serratus and Mantis electricus, are reported to give electric shocks. It may be proper to mention, in conclusion, that the electricity of the Torpedo and Gymnotus is capable of exhibiting all the effects of ordinary electricity, and is in most cases entirely at the command of the animal, whether to emit or withhold it.

Clupeidæ. The fishes of this family exhibit considerable analogies to the Salmonoids, differing, however, in the absence of an adipose dorsal. Both maxillaries and intermaxillaries are employed in forming the margin of the upper jaw, instead of the usual introduction of the latter alone. The body is well scaled, the scales sometimes very large. Bones of the mouth variously provided with teeth, these occurring sometimes on the pectinated tongue.

The fishes of this family are among the most useful and indispensable to man. It includes the anchovy, the sardine, the sprat, the various herrings, and the shad. The Anchovy, Engraulis encrasicholus (pl. 81, fig. 3), is a small fish, a few inches in length, distributed throughout Europe, and especially abundant in various parts of the Mediterranean. It is distinguished, as a genus, by the projecting and pointed upper jaw, and the long anal. The top of the head and back is blue; irids, sides, and belly, silvery white. This fish was well known to the ancient Greeks and Romans, who prepared from it a sauce called garum, held in great favor. They are taken in countless numbers on the coast of Sardinia, 400,000 having been caught at a single haul. The fishing is highly successful by night, when the anchovies are readily attracted by the glare of fire-pans. In preparing them for purposes of commerce the head and viscera must be removed; the former being bitter, and for this reason called Encrassicliolus by Aristotle. The anchovies, after being washed clean, are placed with the belly upwards in vessels, a layer of fish alternating with one of salt, until the whole is full. Pressure must be exerted to drive out the oil as much as possible. A hole is left in the top of the vessel, which is then exposed to the sun. After fermentation has commenced, the hole is stopped up, and the vessel removed to a store-house. The operation is not completed until the following year. The anchovy is taken from December to May.

The Clupeidæ, with non-projecting upper jaws, are divided into various genera, as Clupea, Sardinella, Harengula, Pellona, Meletta, Alosa, and others. A distinction was formerly made between a genus Alosa, characterized by an emargination of the upper jaw, and Clupea, with the border of the jaw continuous or entire. This division, however, has been found to be inadequate to the wants of the present system.

Alosa vulgaris, a European species, figured in pl. 81, fig. 1, is represented in America by one of much finer flavor, the A. sapidissima, or common American shad. This well known species commences its entrance into our rivers, at periods varying from January to May, according to the latitude. It penetrates all the Atlantic streams, and when unobstructed by dams or other impediments, travels to a considerable distance from the mouth for the purpose of depositing its spawn. They are taken in great numbers, especially in Chesapeake and Delaware bays, by various means, the most conspicuous of which are large seines and gill nets. The price varies from five to fifty dollars per hundred, according to the abundance or size. As already remarked, various herrings occur in immense numbers. Conspicuous among European species, in this respect, is the sprat, Harengula sprattus (pl. 81, fig. 4); but vastly more so the common herring, Clupea harengus (pl. 81, fig. 2). The true abode of the immense hordes of herring is not, even at this day, definitely ascertained, the fish being scarcely known, except in its wanderings. Some naturalists suppose it to come from the high north to deposit its spawn upon the shores of the North Sea; others, again, consider the bottom of the North Sea to be its home, since it is first visible at the Shetland Islands in April. Here myriads of herrings combine into armies many miles in length, and then pass on to the coasts of Norway, England, Germany, and the Netherlands. From the main army, branches go off in various directions, supplying almost the whole coast of Europe, and possibly extend their migrations even to the northern coast of North America. They have never been seen to return to the north, and their migrations themselves come neither at perfectly regular intervals nor in the same direction. The density of the columns also varies much in different parts of the army. In some seasons the numbers are countless, in others very limited; at one time the individuals will be fat and large, at another very lean. By the end of August they are no longer seen. The Dutch, who, since 1164, have prosecuted the herring fishery with the greatest success, sometimes employ whole fleets of boats in the pursuit. At no very remote period, the number of boats annually leaving the Texel, under the protection of vessels of war, amounted to not less than eleven or twelve hundred. This trade was at its highest state of prosperity in the year 1618, at which time the number of boats employed was 3000, manned by fifty to sixty thousand men. Since that time the trade has passed out of the hands of the Dutch, to a certain extent, and is carried on by many nations of northern Europe. According to Black, the fishermen of Gothenburg alone, in his time, took upwards of 700,000,000 herrings. More than 130,000 barrels have been exported from Bergen in Norway; the amount consumed in the entire land exceeding double this number. At the present day, the largest quantities are taken on the shores of England. Recent investigations have rendered it probable that the herring actually does live within a moderate distance of the localities where it is caught, coming in from the deep water for the sake of depositing its spawn.

A beautiful spectacle is exhibited when the herring approach the shores; the rays of the sun are reflected from myriads of silver scales, and above the army may be seen hovering hosts of gulls, terns, and other sea birds. Behind and alongside are numerous rapacious fish, which, with seals, porpoises, and other marine animals, devour immense numbers. The water is filled with loose scales, rubbed off by their close proximity. On account of their vast numbers, these fish are very easily captured. This is done by means of nets, either on shore or at sea. Every Dutch smack has four smaller boats along with it, to carry fresh fish to the sea ports, and for other purposes. They use nets of 500 or 600 fathoms in length, made of coarse Persian silk, as being stronger than hemp. These are blackened by smoke, in order that the fish may not be frightened by the white thread. The nets are set in the evening, buoyed by empty barrels, and stretched by weights; they thus rest at the surface of the sea. In the morning they are drawn in by means of a windlass. The herrings are sometimes attracted within reach of the nets by lanterns suspended at various intervals. But a faint idea can be formed of the actual number of these prolific fishes, which exists at one time in the ocean. When we remember, however, that an annual consumption of over two thousand millions in Europe, not to mention the myriads devoured by fishes, birds, and various marine vertebrata, scarcely appears to affect their number, we may obtain an approximate conception of what that number must be to which the sum of those annually destroyed is in such small proportion.

As the herrings are so abundant, and the flesh at the same time so excellent, various modes have been adopted to preserve them for a certain length of time. Even at sea many are salted down, and sold in this state. This is called by the French saler en vrac. To keep them longer than is permitted by this method, two other ways are made use of: they are called white-salting and red-salting (saler en blanc and saurer). To white-salt herring, they are gutted on being caught, and packed in barrels, with a thick brine poured over them. They are there retained, until it is convenient to give them a final packing. After the bustle of the fishing is over, the smacks or busses run in and discharge their cargoes, when the barrels are inspected, and the fish sorted under the inspection of official authorities. They are then repacked with fresh lime and salt, and the particular quality marked on the barrel by the brand of an inspector. The red-salting is efTected by allowing fat herrings to lie for a considerable time in the brine, then arranging them on hurdles, and placing them in ovens holding from ten to twelve thousand, for the purpose of being dried and smoked. The invention of pickling, as applied to herring, has been ascribed to Wilhelm Böekelson, or Beukelson, a fisherman of Viervliet in the province of Zealand (about 1440): he, however, only improved an art known before his time. The Emperor Charles V. eat a herring over his grave, in thankful acknowledgment of his worth, and erected a monument to his honor in 1556.

Several species of herring are caught in vast numbers on the coast and in the Atlantic rivers of the United States. The principal of these is the Clupea elongata, the representative of C. harengus. Besides Alosa sapidissima, or shad, already mentioned, Alosa tyrannus and A. menhaden are of economical value, the former as an article of food, the latter for manure. Immense numbers are taken and spread on poor lands, to which they impart a fertility not inferior to that produced by guano.

Salmonidæ. The Salmonidce, or trout family, agree with the Clupeidæ in the structure of the upper jaw, and are most prominently distinguished by the presence of an adipose dorsal, a small fatty fin behind the true dorsal, near the tail. The intestinal canal is provided with numerous cœca. The scales are more or less conspicuous. All the bones of the mouth are furnished with teeth, as is also the tongue. The branchiostegal rays are about ten in number.

The entire family is eminent for delicacy of flesh, and for the possession of those game qualities so dear to the angler. Species are spread over the more northern regions of America, Europe, and Asia; although the number of such is greater in North America than anywhere else. The principal genera are: Salmo, Thymallus, Osmerus, Mallotus, and Coregonus. Conspicuous among the species of Salmo, is S. salar, or the true salmon, found on the northern shores of both Europe and America. It attains to a great size, an individual of 8 libs, having been taken in England. The largest American specimens do not exceed 50lbs., the usual weight being considerably less. Salmon were formerly caught in large numbers in the Connecticut river, but at the present day few are taken south of the Kennebec river in Maine. Pl. 82, fig. 7, represents Salmo fario, a species very abundant in Europe, especially in England. Its maximum size is about 25lbs., although a weight of a few pounds is nearer the average standard. Its nearest representative in the United States is the Salmo fontinalis or common brook trout, occurring from Maine to the southern parts of Virginia, and perhaps below this in the mountainous regions. It does not attain a great size in running streams, a weight of four pounds being considered enormous. In small lakes, however, it is found much larger than this, being sometimes mistaken for the Mackinaw or great lake trout, Salmo amethystus of Mitchell. This most gigantic of all Salmonidæ inhabits the great lakes of North America, and is especially abundant about Lake Huron. Individuals of 35lbs. weight are of no great rarity, although 15 is perhaps the average. Dr. Mitchell records one weighing 120lbs., but at the present day they seldom exceed 80. Salmo confinis, a less gigantic species, inhabits the smaller lakes of the northern United States: S. siskewit is a native of Lake Superior, and numerous species are found represented in the waters of Arctic America. The genus Thymallus or greyling, represented in Arctic America by T. vexillifer, is distinguished from the true Salmo by the larger scales and the elongated dorsal. The European greyling is T. vulgaris. Mallotus villosus, or the capelin, is found on the coast of Labrador and Newfoundland, where it is used as a bait for the cod. It is sometimes found in a fossil state, in diluvial formations, on the eastern coast of the United States, as in New Hampshire. The genus Osmerus, or smelt, is represented by O. viridescens. It is known in some portions of the country as the frost fish, and is exceedingly abundant in the northern United States. In the winter season it congregates in large numbers in Lake Champlain, and may be taken with great ease through holes cut in the ice. Coregonus is another genus of the Salmonidæ, famed for the excellence of its flesh. The celebrated “white fish” of the lakes is included under several species of Coregonus. A species, C. otsego, from the small lakes of New York, is known as the Otsego bass. Additional species occur in the regions north of the United States. Species of this same genus are abundantly distributed over northern Europe.

Scopelidæ. Fishes of this family have the upper jaw formed entirely by the intermaxillaries. The branchiostegous rays are ten to fifteen in number. Mouth deeply cleft. A second adipose dorsal. The species are mostly marine, one occurring, however, in the Lake of Mexico, Saurus mexicanus. Another genus remarkable for its extreme beauty and diminutive size is Scopelus.

The Characini are salmonoid fish with a posterior adipose dorsal, and only six or seven branchiostegal rays. The divided air-bladder and tympanic ossicles ally them to the Cyprinidæ. The intestine has numerous cceca, and the superior maxillary enters considerably into the composition of the mouth. Many of them are highly ferocious, and characterize the rivers of South America, where they are sometimes dangerous even to man. The only exceptions to this distribution are to be found in the genus Percopsis of North America, one species of which is found in Lake Superior, another in Lake Champlain, and a third in the Alleghany river. They are highly interesting on account of their palæontological relations as well as their structure, which combines a ctenoid scale, with a general cycloid structure. These have recently been placed by Prof. Agassiz in a new family, Percopsidæ.¹¹

Galaxidæ, This family, containing but few forms, exhibits characters intermediate between the Salmonoids and the Esocidæ. With a structure somewhat similar to some of the former, it has the dorsal far back, and the intestinal character of the latter. The upper jaw is formed partly by a short intermaxillary, partly by the maxillary. The mouth presents much of the cyprinoid structure. The species are mostly oriental.

Esocidæ. In the Esocidæ the body is elongated, the single dorsal placed far back, and opposite the anal. The upper jaw is constituted by the inter-maxillaries, almost entirely; the maxillaries when they enter as an element are destitute of teeth. Intestines without cœca. Teeth generally well developed in various parts of the large mouth. Branchiostegous rays from three to eighteen.

The genus Esox is characterized by the broad depressed head and mouth; the latter with teeth on the tongue, vomer, palatines, and branchial arches. The jaws have long, sharp, compressed teeth. The Esoces, or pikes, are among the most formidable of all fresh-water fish. By reason of their slender elongated form, they are able to live in shallow waters; penetrating, even when of considerable size, into very small brooks. Tyrants of the fresh water, no fish can compete with them except the trout; and it is very seldom that both forms are found in the same waters. Of two branches of the same stream, one may be peopled by the former, and the other by the latter. The only species of pike found in Europe is the Esox lucius, shown in pl. 82, fig. 3. It is found in all the principal fresh waters of Europe; where, there is reason to suppose, they are much more abundant at the present time than formerly. This species attains to a weight of 70lbs., although individuals of this size are of rare occurrence. North America is especially rich in species of pike: those inhabiting the northern lakes, as the Maskalonge, Esox nobilior, Esox estor, and others, attain a great size. Specimens of the former have been known of over 70lbs. The more southern species, as Esox clathratus, and others, are of more moderate dimensions. The American species may all be referred to two types, one with the opercula entirely scaled, and with fasciated or reticulated darker markings, with a vertical bar under the eye; the other with the lower half of the operculum free from scales, and the marks in the form of light spots on a dark ground.

Mormyridæ. This family contains fish characterized by an elongated body provided with oblong scales. The entire head, not excepting the cheeks and operculum, covered by a thick skin completely concealing the bones of the head. This is drawn over the operculum, in such a manner as only to leave a vertical narrow slit in each side: this skin is perforated by a number of pores. Mouth, with the tongue, well armed with teeth. Two cœcal appendages. The fishesof this family are almost all inhabitants of Africa.

Hypsæidæ. This highly remarkable family is established on a single species, the Amblyopsis spelaens, or blind fish of the Mammoth Cave of Kentucky. It is characterized by a form much like that of a Hydrargira, to which it would at first be referred. The head, however, is much depressed, and the eyes are entirely wanting, none being evident even on dissection. The body is covered with scales, and the jaws provided with fine teeth. The intestinal canal is shorter than the body. Cœcal appendages two, pyriform, and opening by distinct orifices in each side of the intestine. Air-bladder heart-shaped, deeply cleft anteriorly. The anus is situated anterior to the base of the pectorals. The fins are provided with filamentous tips.

This very curious fish combines the characters of the Esocidæ, Salmonidæ, and Cyprinodontidæ, although its affinities are most with the latter. Like these, too, it is ovo-viviparous, the young being from ten to twenty in number. The color is a dull white. The animal is caught in a stream of water flowing across the Mammoth Cave, in which it is readily seen by the contrast of its white sides with the darker body of the water. A species of Astacus, A. pellucidus, likewise white and destitute of eyes, inhabits the same water in great quantity.

Cyprinodontidæ. The species of this family, which experiences its greatest development in America, are generally of small size. In fact a certain species found in South Carolina is not much over half an inch in length, even when comparatively large, and the others are not of much greater magnitude. Most are inhabitants of brackish water, although all the fresh waters of North America have their representatives. Body variously shaped, generally elongated and sub-depressed, especially anteriorly. The fins are all rounded, and the dorsal is situated far back, above the anal. The jaws are provided with small teeth which are sometimes denticulated. Hooked teeth on the pharyngeals. Air-bladder single. The principal genera are: Fundulus, Lebias, Mollinesia, Hydrargira, and Cyprinodon, Some of these are remarkably tenacious of life. Species of Hydrargira have resisted the influence of the air-pump vacuum, under circumstances where the same deprivation of air would have killed almost anv other fish. This genus can live for months buried in soft mud, after their native pond dries up, coming out again on the accession of fresh water

Cyprinidæ. We come now to the consideration of the family of the Cyprinidæ, which embraces by far the greater number of the exclusive residents of fresh waters. Every variety of size and shape occurs; the flesh, however, of but few, is worth much as an article of food. They are distributed over all the temperate and cooler waters of the globe, their occurrence in tropical waters being very limited. The family is characterized by the absence of teeth in the mouth, and the development of teeth of various kinds and shapes upon the posterior branchial arch, or pharyngeal bone. The shape and number of these teeth furnish excellent generic characters. The former are exceedingly varied, each region having some peculiar to it: as Schizothorax for Syria, Catastomus and Exoglossum for North America, &c. A prominent European form is Chondrostoma nasus (pl. 84, fig. 4). Alburnus lucidus, or the bleak, represented in pl. 84, fig. 7, is another; the silvery pigment lining whose scales is used in the manufacture of artificial pearls. Tinca vulgaris (pl. 84, fig. 12) sometimes attains a considerable size. Gobio fluviatilis (fig. 6) is likewise extensively distributed. Barbus vulgaris (pl. 84, fig. 10), or the barbel, a fish of some reputation among anglers, has been known to attain a weight of 15Mbs. Cyprinus auratus, or the common gold fish (pl. 85, fig. 12), is pre-eminently conspicuous among fresh-water fish for the beauty of the colors. The young fish is of a brown color, in which, after a time, there appear silver specks, which increase until the entire fish becomes silvery white. In this state it is known as the silver fish. Subsequently it gradually assumes a golden red color. The true home of this fish, called kin-yu in China, appears to be a lake near Tschang-Hon in the province of The-Kiang, whence it was carried to the different waters of China and Japan, and subsequently to Europe. It is generally kept in glass globes, or small vessels, in the house, care being taken to provide an abundance of fresh water every day. The gold fish are easily kept in fish ponds, where they multiply rapidly. In the cisterns or tanks used to contain the water for condensing the steam of steam-engines, they thrive remarkably well, owing to the amount of greasy matter floating on the surface; even though the temperature of the water reaches 100° F. and upwards. The river Schuylkill, near Philadelphia, is well stocked with gold fish, from individuals which escaped from certain fish ponds near that city. They also occur in the Hudson River.