thoroughly grind up the food passed between them, which then goes out at the orifice into the intestines.

These animals reside, for the most part, in the water. A few are found upon land. The former do not immediately die on being taken out of their natural element, but can live for some time in the air. They are generally carnivorous. Many of them furnish very delicious articles of food, although their flesh is sometimes heavy and difficult of digestion.

The term Vermes or Worms has been used with great vagueness in natural history, and employed to designate animals to which the name is not appropriate. It is now, however, more restricted in its application, and is made to include only a small class, which have some circumstances in common with each of the classes last described, but still not exactly resembling any. They are sometimes called, by way of distinction, Worms with red blood, as they are the only invertebral animals which have red blood; and sometimes Annelida, from the structure of their body, which is of a cylindrical, elongated shape, divided into a great number of rings.

Their nervous system resembles that of the Insects and Crustacea. Their organs of sense consist merely in some fleshy . tentacula, which surround the mouth, and answer the purpose of feeling and touching. In some species, certain black points appear around the head, which have been supposed to be eyes, but this is doubtful. Their blood is nearly of the color of that of the vertebral animals, but not of so bright a red. It circulates in a double system of vessels, but there is no distinct, fleshy heart to give it motion. They breathe by means of branchiæ, which are sometimes within and sometimes without their bodies. They have no limbs, but on each of the rings of which their bodies are composed, are little bristly projections, which answer in some sort the purpose of feet. Their mouths are sometimes armed with jaws, and sometimes consist in a mere tube or sucker.

Their bodies are soft and compressible. Nearly all inhabit the water. Many of them bury themselves in the sand; others form themselves a sort of tube or habitation of sand, bits of dirt, gravel, or other materials; and others exude from their

surfaces a calcareous matter, which produces a shell around

them.

Among the animals belonging to this class are the earth-worm, the leech, and the hair-worm.

The appearance of Earth-worms is familiar to all. They attain sometimes to the length of a foot, and have as many as a hundred and twenty rings, each of which is furnished with the little bristles or spines above mentioned. They emit through certain pores a slimy fluid, which lubricates their bodies, and thus gives them an easier passage through the earth, which they traverse in every direction. They feed upon roots, woody fibres, and the remains of animal and vegetable matter. They swallow earth also in considerable quantities, but this is probably on account of the animal or vegetable matter, in a state of decomposition, which it may contain. When cut through the middle, each portion becomes a distinct individual. And in some worms nearly resembling the earth-worm, but residing in the water, the power of reproduction is nearly equal to that of. the polypes.

The Leech has three jaws, or rather lancets, with which it pierces the skin of animals, in order to suck their blood. Its tail is furnished with a shallow cup or disk, by which it is able to fix itself firmly to different objects, while obtaining its nourishment in this manner; and by means of the same organ, it moves from place to place. There are several species of the leech, of which the medicinal is the most valuable, from the use made of it in local bloodletting. The horse-leech has the same power of drawing blood, but the wounds which it makes are sometimes followed by bad effects.

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The body of the Gordius, or Hair-worm, is long, shaped like a thread or hair, nearly smooth, and round. It is a vulgar notion that the hair of the human head, or of a horse's tail, if thrown into the water, acquires life, and is converted into a worm. species of the hair-worm, in Africa and the Indies, is extremely noxious. It is of a pale, yellowish color, and is frequently met with among the grass, especially when covered with dew. It often insinuates itself into the naked feet or limbs of children and unwary persons, where it produces an inflammation that is some

times fatal. Great care and attention are required in extracting it; for if it be broken during the operation, the part which remains in the flesh continues alive, and is quite as troublesome as the whole.

UNDER this division are included a great variety of animals, of most of which the structure, residence, and habits are less perfectly known than those of the preceding classes. In their internal structure and organization, they are, for the most part, superior to the members of the division of Articulata, but as to intelligence and instinct, they are upon the whole inferior. Among them are the cuttle-fish, squid, oyster, clam, snail, and nearly all those commonly known as the testacea or shell-fish.

The Mollusca are destitute of bones and of articulated limbs. Their bodies are generally of a soft texture, and in many, at first sight, appear to be little else than a simple mucous mass, without parts, and almost without organization. Their muscles are fixed into the skin, which is naked, very sensible, and constantly moistened by a fluid furnished by its pores. The contractions of these muscles produce various motions of their whole bodies, often obscure and indistinct, by means of which, nevertheless, they are enabled to swim and crawl, or even seize those objects which are adapted to their nourishment. But as no part is supported by any solid foundation, like the bones of vertebral animals, their motions are for the most part slow, awkward, and limited.

Their bodies are generally covered by a fold or reflection of the skin, which envelops them completely, and is called their mantle. (Fig. 8, Oyster.) In some species, the two folds of the mantle are united at their edges, so as to form a complete bag,

in which the body of the animal is contained, opening only at one end by a sort of canal or snout: in some, it extends in two opposite directions, so as to answer the purpose of fins or oars. Sometimes there is only this simple membranous covering; but more frequently there is a hard external shell, which serves as a retreat into which the animal may withdraw itself, and which it can carry about upon its back in all its changes of place. These shells differ a good deal in shape, color, and texture, in different species; and among them are found some, whose form, polish, and splendid tints place them among the most beautiful objects in nature.

The Mollusca have no brain nor spinal nerve. Their nervous system consists merely of a number of masses, distributed in different parts of their bodies, from which are sent out a great many small branches, that mutually unite with each other. The principal of these, which is sometimes called the brain, is situated around the œsophagus, and envelops it like a collar. In a few species it is contained in a cartilaginous case. Their respiration is not uniform. It is generally carried on by organs resembling the gills of fishes, which are acted upon either by fresh or salt water; but, in some cases, air is respired directly from the atmosphere. The circulation is double; that is to say, there is a passage of the blood through the respiratory organs, distinct from that through the rest of the body. This circulation is carried on by either one or more hearts. When there is only one, it is situated so as to receive the blood from the gills, and circulate it through the body. When there are two, the second is situated so as to circulate through the gills the blood coming from the body. In some species, there are three hearts; and in this case, as there are two sets of gills, a distinct heart is devoted to each. The blood in the Mollusca is thin, of a bluish white, and of the temperature of the medium in which they live.

The organs of digestion vary very much. Sometimes there are organs for mastication, and sometimes not. Some species have only a single stomach, and others have several; the structure of this organ, in some species, very much resembling that of the gizzard of birds. In some species there are four stomachs, which bear a great analogy to those of the ruminating animals,

and have been supposed to answer a similar purpose. In the intestines there is as great a variety.

This branch is divided into several classes, according to the general form and structure of the species composing it. A few of the most important particulars that distinguish some of them will be pointed out.

In the first class, containing the cuttle-fish, squid, and nautilus, the body consists of a sack formed by the mantle, enveloping all the parts except the head, which projects from it, and is provided with a number of fleshy arms or feet, tapering towards their end, frequently of great length and of great power. These arms

are capable of being moved in every direction, and are furnished with a large number of suckers in the form of cups, by which the animal can attach itself very closely to whatever object it embraces. They serve for swimming, for creeping, and for seizing prey. In all its motions, the head goes last, so that the animal in a manner pushes itself backward in whatever direction it wishes to move. Between the arms is placed the mouth, which is furnished with two strong jaws of a horny texture, and in shape resembling the beak of a parrot.

Some of these animals have the power of ejecting a peculiar liquid of a black color, when in any danger, for the purpose of discoloring the water of the sea around them, and thus concealing themselves from their enemies. The cavity containing this liquid is situated in the abdomen, and is sometimes found in the very substance of the liver. It has been supposed, that the celebrated paint called Indian ink, is made by the Chinese from the inky fluid of some animal of this kind.

Their eyes are large and perfect. They have an ear; but no organ for smelling has been discovered, although they probably possess that sense. Their nature is fierce and cruel. They are very voracious, and devour great numbers of fishes and other aquatic animals.

Some of these animals grow occasionally to a great size. This is more particularly the case with the eight-armed cuttlefish. In the Indian seas, it is popularly supposed to attain to such a magnitude, that its arms are nine fathoms in length, and the other parts of its body large in proportion. The natives hold