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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 the 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

REVIVALS.

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

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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

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time, however, in the latter part of March 1850, it was observed that on the mouth of one specimen a fresh, thin, glassy covering (called by conchologists the epiphragm) had very recently been formed. The specimen was immediately detached, and immersed in tepid water. After the lapse of a period not exceeding ten minutes, the animal began to move, put forth its horns, and cautiously emerged from its shell. In a few minutes more it was walking along the surface of the basin in which it was placed. The last time it had exercised its locomotive faculty was in the sandy plains of Egypt, not far from the banks of the Nile. Now it awoke to find itself crawling on the surface of a delf basin in the heart of London! Great care was taken of this "helix rediviva." It was placed in a tall glass-jar, eighteen inches high, with considerable space to move about in, and supplied with food, which it ate readily, though in small quantities. Cabbage-leaves formed its favourite repast, and were preferred to lettuce or any other vegetable. In this tranquil state of existence it remained till March 1851, when it resumed its torpid condition, shut itself up in its shell, and took an eight months' nap, awaking once more on the 9th of November to eat cabbage-leaf and perambulate the circumference of its glassy prison. Though quite lively, it again became torpid on the 15th, as if conscious the season of the year was not propitious, and never afterwards emerged from its shell. It was found dead, and perfectly dried up, in March 1852. Such was the end of the Egyptian snail, and it was with some feeling of regret that its death was recorded. The accompanying figure of this interesting animal-the picture of it as it looked in life-is from the first volume of an excellent little work by Mr. Woodward, of the British Museum, "A Manual of Mollusca, or Treatise on Recent and Fossil Shells," a work which we may recommend to our readers as containing a brief but

most comprehensive analysis of the numerous genera of which the mollusca are composed. The second volume is now in the press.

A short history of the patriarch belonging to Mr. Gaskoin, mentioned at the commencement of this notice, has been given by that gentleman in the "Proceedings of the Zoological Society." In this case the most extraordinary part of its history is, that after it was resuscitated and had lived, isolated and alone, for a period of six months, a family of about thirty little ones made their appearance, creeping about the large glass-bell in which the mother had been confined. Many of these little ones lived; and some of them at the end of twelve months after they had first made their appearance, had acquired nearly the size of their parent. During the time in which these snails remained torpid, no accurate information as to the condition of the animals themselves was ascertained. Did the circulation continue to go on, or was it stopped? Was respiration completely suspended, or was the contact of air essential to vitality? These questions we cannot answer in the present state of our information, but must conclude, with Dr. Johnston, that though it is difficult to believe, that all the functions as well as the signs of life ceased entirely, "it is yet scarcely less so to suppose that, for the space of four or five years or more, these functions could exist without some supply of food to keep up the waste and secretions, however trivial, which necessarily flow from a circulation, or without some air to purify the circulating fluid."

The fact, however, that snails can remain in this state of torpidity, or apparent complete suspension of life, for a number of years without losing their vitality, is now beyond a doubt.

W. B.

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