the economy of these animals, which appeared so anomalous, was the mode in which they were both naturally and artificially multiplied. They were manifestly animals, yet it was found that they could be propagated by slips or cuttings, like plants! In the warm weather of summer each polype is observed to shoot forth, from various parts of its body, little warts, or knobs, which increase rapidly, until in a few days they assume the form of the parent animal, each one being furnished with a circle of tentacles, though still attached at its lower end. The young one, which up to this period had received its nutriment from the parent's stomach, from which a channel had communicated with its own, now catches prey with its own tentacles, the duct closes, the connexion of the base with the mother becomes more slender, and at length the little animal falls off, and commences independent life. Such is the natural mode of increase-generation by gemmation. In autumn, the Hydra propagates by means of eggs, which are deposited around the parent; the basal portion of her body being spread over them, and becoming a horny protecting skin. She immediately dies, and the eggs are hatched in the ensuing spring.* But these strange animals may be artificially increased at pleasure, and that by means which, to higher animals, would inevitably destroy, instead of multiplying life. If the head of a polype, with all its tentacles, be cut off from the trunk with scissors, it will presently develope a new trunk and base, while the headless trunk begins to shoot out new tentacles; and thus, in a little time, two perfect animals are formed. If one of these be cut into three, four, or half-adozen pieces, each piece supplies the wanting parts, and so many animals are made, all as perfect and active, and endowed with the same functions, as the first. Nor does it *Laurent, L'Institut, No. 465. signify in what direction the mutilation is made; a longitudinal, a diagonal, or a transverse division, is equally successful; nay, even a small portion of the skin soon grows into a polype. It was from this power of perpetual reproduction, that this singular animal received the name of Hydra, by which it is known among naturalists; as if it realised the ancient monster of fabulous story, whose heads sprouted anew as fast as they were cut off by Hercules. Most curious monstrosities were produced by the experiments of philosophers on these animals, especially by partial separations. If a polype be slit from the summit to the middle, one will be formed having two heads, each of which will capture and swallow food. If these again be slit half-adozen times, as many heads will be formed surmounting the same body. If now all these be cut off, as many new ones will spring up in their place, while each of the severed heads becomes a new polype, capable of being, in its turn, varied and multiplied ad infinitum:-so that in every respect our little reality exceeds its fabulous namesake. The polypes may be grafted together. If cut-off pieces be placed in contact, and pushed together with a gentle force, they will unite and form a single one. The head of one may be thus planted on the trunk of another. Another method of uniting them, perhaps still more wonderful, is by introducing one within the other; the operator forced the body of one into the mouth of the other, pushing it down so that the heads were brought together. After forcibly keeping it for some time in this state, the two individuals at length united, and a polype was formed, distinguishable only by having twice the usual number of tentacles. There is one species which can actually be turned inside out like a glove, and yet perform all the functions of life a before, though that which was the coat of the stomach is now the skin of the body, and vice versâ. If it should chance that a polype so turned had young in the act of budding, these are, of course, now within the stomach. If they have arrived at a certain degree of maturity, they extend themselves towards the mouth of the parent, that they may thus escape when separated. But those which are less advanced turn themselves spontaneously inside out, and thus place themselves again on the exterior of the parent, A multitude of other variations, combinations, and monstrosities, have been, as it were, created by the ingenuity of philosophers; but these are sufficient to give a notion of he extraordinary nature of these animals, and to account for the wonder with which they were regarded. The Hydra was, until lately, considered as an animal of very simple structure, being composed of mere granules of jelly, set in a glairy, enveloping fluid. But the farther we push our researches, the more are we disposed to hesitate in pronouncing on the comparative simplicity or complexity of any organism. We have already seen the elaborate array of weapons in the tentacles. M. Gervais has shown that the component granules of the body are of diverse forms, and, in all probability, sustain different relations to the general economy. The whole body consists of a sac, with thin dilatable walls, enclosing a capacious cavity, which forms the stomach the granules which border this cavity are conical papillæ projecting into the stomach, and are supposed to have a digestive function; the exterior series are lengthened, and constitute an integument, while some of the intermediate ones are arranged in bands, which are, with little doubt, presumed to be muscular. The muscular bands in the tentacles are still more distinct, running in four series, which pass diagonally to and fro from side to side, forming lozenge-shaped spaces by mutual intersection. P. H. G. : SNAILS: THEIR LONG LIVES AND THEIR THERE are many facts connected with the physiology and habits of some of our most common animals that naturalists have not yet been able to account for- many queries they have not yet been able to answer, How long, for instance, does a snail live? Mr. Gaskoin informs us that about two months ago there died in his collection of live snails a patriarchal individual of "the milk-white Helix," the Helix lactea of authors, whose history in a state of captivity, to his knowledge, extended over a period of ten years. At the commencement of that time the snail was adult, but its exact age at the beginning of its captivity was unknown to him. Another question might be asked,- How long can a snail remain in a state of torpidity, and yet not lose its vitality? The animals belonging to the genus Helix - many species of which may be seen under our hedge-rows and on our way-sides-at the approach of winter retire into their shells, and go into a state of hybernation. When the temperature has become low, the animal takes up its position in a crevice of a rock, under the moss at the root of a tree, or under a stone, and begins to form a thin covering for its mouth, with which it attaches itself to the surface of the object nearest it. In this state it remains during the winter, without food and without showing any symptoms of life, and if removed into a dry place, and excluded from the external air, it may remain so for years. In hot climates a similar state of torpidity takes place during the continuance of the very dry season. Adanson, in his "Natural History of Senegal," mentions the fact of a large species of snail the Bulimus Kambeul of authors, and which is used by the natives of that country as an article of food - burying itself in moss at the foot of trees, or amongst grass in the brushwood at the commencement of the dry season, and remaining torpid for eight months together. Respiration in these animals is very slow-the act of inspiration and expiration being performed only about four times in a minute; and some very curious cases are on record where this action has been suspended far beyond any ordinary time of hybernation, "life, as it were, keeping watch and holding at bay every destructive agent, but without giving any outward sign of her presence and constant wakefulness." In the excellent "Introduction to Conchology," by Dr. Johnston of Berwick, several extraordinary instances of this tenacity of life in snails are detailed. For an account of these we must refer to this admirable work itself, and pass on to give the history of one of the most authentic instances of long-continued torpidity which have ever been recorded. It occurred in the British Museum a few years ago. In March 1846, a series of shells was presented to our national collection by Charles Lamb, Esq., from Egypt, Greece, &c. Amongst them were several specimens of an Egyptian species, the "Snail of the Desert," the Helix desertorum of authors, and which is found in great abundance living in the dry and arid deserts of Egypt and Syria. These shells had been packed up and carried through a considerable part of Europe before they found their way into the gallery of the Museum, where they were deposited and fixed with gum upon their tablets on the 25th of March. Immured in their prison they remained for four years, without giving any sign of vitality. At the end of that |