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The Tape-Worm

convey the aliment. Surrounding the opening of the mouth, are placed a number of projecting radii, which are of a fibrous texture, and whose direction is longitudinal. These radii appear to serve the purpose of tentacula, for fixing the orifice of the mouth, from their being inserted along the brim of that opening. After the rounded extremity or head has been narrowed nto the neck, the lower part becomes flatted, and has two mall tubercles placed on each flatted side; the tubercles are concave in the middle, and appear destined to serve the purpose of suckers, for attaching the head more effectually. The internal structure of the joints composing the body of this animal is partly vascular and partly cellular; the substance itself is white, and somewhat resembles in its texture the coagulated lymph of the human blood. The alimentary canal passes along each side of the animal, sending a cross canal over the bottom of each joint, which connects the two lateral canals together.

Mr. Carlisle injected, with a coloured size, at a single push with a small syringe, three feet in length of these canals, in the direction from the mouth downwards. He tried the injection the contrary way, but it seemed to be stopped with valves. The alimentary canal is impervious at the extreme joint, where it terminates without any opening analogous to an anus.

Each joint has a vascular joint occupying the middle part, which is composed of a longitudinal canal, from which a great number of lateral canals branch off at right angles. These canals contain a fluid like milk. great The tænia seems to be one of the simplest vascular animals in nature. The way in which it is nourished is singular; the food being taken in by the mouth, passes into the alimentary canal, and is thus made to visit in a general way the different parts of the animal. As it has no excretory ducts, it would appear that the whole of its alimentary fluid is fit for nourishment; the decayed parts probably dissolve into a fluid, which transudes through the skin, which is extremely porous. This animal has nothing resembling a brain or nerves, and seems to have no organs of sense, but those of touch. It is most probably propagated by ova, which may easily pass along the circulating vessels of other animals. We cannot otherwise explain the phenomena of worms being found in the eggs of fowls, and in the intestines of a fœtus before birth, except by supposing their ova to have passed through the circulating vessels of the mother, and by this means to have been conveyed to the fœtus.

The chance of an ovum being placed in a situation where it will be hatched, and the young find convenient subsistence, must be very small; hence the necessity for their being very prolific. If they had the same powers of fecundity which 1 they now possess, and their ova were afterwards very readily hatched, then the multiplication of these animals would be immense, and become a nuisance to the other parts of the creation.

Another mode of increase allowed to tænia, (if we may call it increase,) is by an addition to the number of their joints. If we consider the individual joints as distinct beings, it is so; and when we reflect upon the power of individuality given to each joint, it makes this conjecture the more probable. We can hardly suppose that an ovum of a tænia, which at its full growth is thirty feet long, and composed of four hundred joints, contained a young tænia composed of this number of pieces; but we have seen young tænia not half a foot long, and not possessed of fifty joints, which still were entire worms. We have also many reasons to believe, that when a part of this animal is broken off from the rest, it is capable of forming a head for itself, and of becoming an independent being. The simple construction of the head makes its regeneration a much more easy operation than that of the tails and feet of lizards, which are composed of bones and complicated vessels; but this last operation has been proved by the experiments of Spallanzani, and many other naturalists.

An article of great curiosity is, THE SHIP-WORM. This worm has a very slender, smooth, cylindrical shell; it inhabits the Indian seas, whence it was imported into Europe. It penetrates easily into the stoutest oak planks, and produces dreadful destruction to the ships, by the holes it makes in their sides: and it is to avoid the effects of this insect that vessels require sheathing.

The head of this creature is coated with a strong armour, and furnished with a mouth like that of the leech. A little above this it has two horns, which seem a kind of continuation of the shell; the neck is furnished with several strong muscles; the rest of the body is only covered by a very thin transparent skin, through which the motion of the intestines is plainly seen by the naked eye. This creature is wonderfully minute when newly excluded from the egg, but it grows to the length of four or six inches, and sometimes more. When the bottom of a vessel, or any piece of wood which is constantly under water, is inhabited by these worms, it is full of small holes; but no damage appears till the outer parts are cut away. Then their shelly habitations come into view, in which there is a large space for inclosing the animal, and surrounding it with water. There is an evident care in these creatures never to injure each other's habitations; by which means each case or shell is preserved entire. These worms will appear, on a very little consideration, to be most impor-