The shape of this shell is pyramidal; it adheres to the rock with such strength, that it can only be removed by means of a knife or a strong blow. The apex of the shell is sometimes sharp, sometimes obtuse, and often surrounded with points and sharp prickles. When thoroughly cleansed the shell is generally of a beautiful purple tint of great brilliancy, though the animal that lives under this magnificent roof is a kind of snail, disagreeable to the eye and insipid to the palate. They are found on the rocks, which are incessantly beaten by the surges and breakers, on the sea-shores of almost every country in the world. It is not by any glutinous liquid, as it has been asserted, that this fish adheres so strongly to the rock; but by the simple process of producing a vacuum between its foot and the rock to which it affixes itself.
The variety which is thrown into the sum of animated beings is so wonderfully great, that naturalists have reckoned more than a hundred and twenty-nine species of Limpets, and nearly allied genera; the difference arising principally out of the diversity of the shells in form and colour.
THE GARDEN SNAIL, (Helix aspersa,)
Is furnished with four tentacula, two of which are smaller than the others; at the end of these tentacula, which the animal pushes out or draws back, like telescopes, are blackish knobs, which are the eyes. The snail lays eggs, which are about the size of small peas, semi-transparent, and of a soft substance. By closely examining with a magnifying lens the eggs which a Water Snail, kept in a bottle of water, had deposited against the glass, the young Snail was seen in the egg, with its embryo shell on its back; two have also been observed in one egg, each of them with the rudiments of the shell.
The Garden Snail is extremely tenacious of life, and remains in a state of torpor during the winter. It is said, indeed, that it can remain in this state for many years, and the following instance is probably without parallel in any other animal:—Mr. S. Simon, a merchant of Dublin, whose father, a Fellow of the Royal Society, and a lover of natural history, left him a small collection of fossils and other curiosities, had, among them, the shells of some Snails. About fifteen years after his father’s death, he gave to his son, a child of ten years old, some of these Snail-shells to play with. The boy placed them in a flower-pot, which he filled with water, and the next day put them into a basin. Having occasion to use this, Mr. Simon observed that the animals had come out of their shells. He examined the child respecting them, and was assured that they were the same which had been in the cabinet. The boy said he had a few more, and brought them. Mr. S. put one of these into water, and, in an hour and a half afterwards, observed that it had put out its horns and body, which it moved but slowly, probably from weakness. Major Vallancy, Dr. Span, and other gentlemen, were afterwards present, and saw one of these Snails crawl out; the rest being dead, probably from their remaining some days in the water. Similar observations have since been so frequently repeated, that there is now no doubt that Snails of various kinds may retain their vitality for years when preserved in a dry state.