Why have cuttle-fish small holes on their arms? Because, by means of them, they fix themselves in the manner of cupping-glasses. These holes increase with the age of the animal; and, in some species, amount to upwards of 1,000. They have the power of reproducing their arms, which are often torn or nipped off by shell and other fishes.

The suckers of the cuttle-fish, are irregularly scattered on the arms and feet. The back is strengthened by a complicated calcareous plate, lodged in a peculiar cavity. This plate has long been known in the shop of the apothecary, under the name Cuttle-fish bone, which was formerly prized as an absorbent, but is now chiefly sought after for the purpose of polishing the softer metals.-Fleming.

Why is it improper to call this plate "bone"?

Because, in composition, it is exactly similar to shell, and consists of various membranes hardened by carbonate of lime, without the smallest mixture of phosphate.-Hatchett, in Philos. Trans.

The most remarkable species of cuttle-fish inhabits the British seas; and, although seldom taken, its bone is cast ashore on different parts of the coasts, from the south of England, to the Zetland Isles. We have picked up scores of these bones, or shells, on the Sussex coast, but never found a single fish.

The cuttle-fish, it may be added, is the only animal of its class, in which any thing has hitherto been discovered, at all like an organ of hearing, or has been shown to possess true eyes.

Why are sea-grapes, as they are called, often picked up on the sea-shore?

Because many kinds are the ovaria, (or egg-bags) of cuttle-fish, and similar species.

Why are certain sea-worms called animal flowers? Because they display beautiful membraneous expansions, resembling the petals of flowers: these are, in

fact, the breathing organs, acting at the same time as tentacula.

Why does the stomach of some medusa resemble the roots of trees?

Because it has branching tentacula, on which canals commence by open orifices; these unite together to form large tubes; and the successive union of these vessels, forms at last four trunks, which open into the stomach, and convey the food into that cavity. Cuvier has formed a new genus, under an appellation derived from the above comparison-the rhizostoma; from the Greek words, a root and a mouth.

TESTACEA-SHELLS.

Why is the study of shells much more important than some would represent?

Because, being found in abundance, in a great variety of rocks and positions, they constitute the medals of the ancient world; and, from an accurate acquaintance with their different species, and with the nature of the animals that represented them, many curious and important deductions respecting the formation and changes of the crust of the earth may be drawn.-Thomson's Hist. Royal Soc.

Testacea, (or shell animals) are classed in families, according to the number and form of the shells. Thus multivalve, or with many valves; bivalve, muscles, &c.; univalve, with regular windings, snails; and univalves, without such windings.

Why have shells served many purposes more useful than that of ornament?

Because of their service in the domestic economy of various nations. Thus, in the south of China and in India, the thin layers of some large flat shells, when polished, are used instead of glass for windows. Many of the domestic utensils of savage people are shells; and it must have been observed, that we frequently

imitate these in our porcelain. In India, drinkingcups are formed of the nautilus; and in other less civilized nations, shells are converted into knives, spoons, fishing-hooks, razors, &c. In Zetland, a certain shell, suspended horizontally by a cord, is used as a lamp, the canal serving to hold the wick, and the cavity to contain the oil. Is it not probable that some of the most elegant patterns left us by the Greeks have been suggested by a similar primitive practice?

In mentioning the benefits of shells, we must not forget the celebrated Tyrian purple, which was procured from a univalve shell fish, and was contained in a transparent and branching vessel, placed behind the neck of the animal. A shell, called Purpura, of our own shores, furnishes a liquid of similar qualities, and is supposed to have been resorted to by the ancients. Why was the term "shell" formerly expressive of the greatest hospitality?

Because, in the days when Ossian sang, the hollow shells of the scallop were the drinking-cups of Fingal and his heroes, and the flat shells their plates. Thus, in Ossian: "Thou, too, hast often accompanied my voice in Branno's hall of shells." "The joy of the shell went round, and the aged hero gave the fair."

Why do shells increase in size?

Because they consist of layers of an earthy salt, with interposed membranes of animal matter, resembling coagulated albumen, and they grow, by the addition of layers of new matter, to the edges and internal surface. When broken, the animal can cement the edges, and fill up the crack, or supply the deficiency when a portion is abstracted.-Fleming.

As an instance of the great strength of such cement, it was, in 1829, stated in Brande's Journal, that the large snails which are found in gardens and woods, discharge a whitish substance, with a slimy and gelatinous appearance, which has been known to cement

two pieces of flint so strongly, as to bear dashing on a pavement without the junction being disturbed, although the flint broke into fragments by fresh fractures. Why are shells of different colours?

Because the colour is secreted by the animal, along with the matter of the shell.

Why is the inner surface of all shells very smooth, and apparently denser and harder than the outer?

Because the animals, to form this inner, layer, excrete the lime in nearly a pure state, that is to say, mixed with much less animal matter; so that, in concreting, the particles become very close and compact, and receive a polish from the repeated frictions of the soft parts.

Why does a dry thin skin cover the external surface of most shells?

Because, being a dried sheet of coagulated albumen effused at the same time, or, perhaps, even prior to the first layer, it may protect the subjacent or more chalky layers from the action of the air or water during their consolidation.—Mr. Gray, in the Zoological Journ. Blainville, and the French naturalists, generally, suppose that the above covering is the true epidermis, or scurf-skin, raised from its position by the deposition of the shell underneath it; but we think this is not tenable.

Why are old shells remarkably strong?

Because a shell having attained its full growth, the changes which the animal further effects are almost limited to some increase of its thickness; not, however, by the addition of any new layers, but by the effusion of vitreous matter. Hence, holes and canals, previously visible, are now filled up; the aperture contracted, and the margins strengthened and enlarged; the upper part of the spire, perhaps, filled and made more solid. The external layers now lose their epidermis; the colours become paler; parasites deform

and perforate the outer surface; death at length overtakes the architect, and the shell decays under the influences of the water and the air. What an epitome is this of the proudest life,-till death

Comes at the last, and with a little pin

Bores through his castle-wall, and-farewell king.

THE PIERCE-STONE.

Why is a certain worm called the pierce-stone? Because it bores passages in rocks, even in the hardest marble, in the stems of coral, oyster-shells, the bottoms of ships, &c. and excavates a habitation at the termination of the passage.-Blumenbach.

The Lithophagus is another of these stone-boring animals, and an instance of its depredations on the hardest marble is shown by the celebrated, but mysterious, phenomenon, of the three large columns of Cippolino antico, in the temple of Serapis, at Pozzuolo, which, though at an elevation of twenty-seven feet above the level of the Mediterranean near them, are perforated in a circular manner by these animals.

THE OYSTER.

Why is the shell of the oyster termed "fixed"? Because it has one valve cemented to the rock; and though the oyster itself has a heart, blood-vessels, brain, gills, and stomach, it depends on the bounty of the waves for all the objects of its sensation and nourishment. It is, however, an admirable provision of nature, that although the oyster and other natives of the water are thus stationary themselves, the fluctuations of the element in which they live, produce a variety in the scene, and daily bring new objects in contact with their organs of sensation.

Of oysters there are several species. Thus, in a little Manuel de l' Amateur d'Huitres, before us, we count upwards of forty-five different kinds which are known to naturalists.

Why does an oyster open its shell at the time of flood?