the animal lying on its back during the process. Prior to this in the crab, and probably in the lobster and others, the fleshy contents of the limbcases shrink very considerably; otherwise, the flesh could not be extricated, for it does not appear that their shells are fissured. The newly extricated crab-not unlike a lump of dough inclosed in membrane-has, at first, strength to crawl to some hole as a place of safety; there it absorbs as much fluid as will distend its organs and their common covering, now flexible as velvet, to the full extent of their capacity. Thus the deposition is made of the calcareous crust, according to the newly-acquired bulk of the animal, which is proportionately the most increased in the youngest individuals.

The Pea Crab.

The pea crab is another curious creature, very commonly found in the common mussel, and especially in those taken from rather deep water. "On one occasion," says Bell, “I dredged great numbers of these mollusca on the coast of Dorset, and found by far the greater number of them with one or two of these little soft-bodied crabs within their shells; for the females are much more common than the males. The latter sex I have occasionally taken apart from the mussel-shells; the former never. They also occasionally inhabit the common cockle, in which I have now and then found them, as well as very rarely in the oyster." The velvet crabs, so called from the velvety substance with which the shells are covered, and which extends even to the limbs of the animal, are among the most beautiful in appearance. They are of a reddish color, tinged with blue. One of them, very commonly found, has colors remarkably bright; it is about two inches and a-half long, and much esteemed for food.

The Hermit Crab.

The hermit crabs have the whole hinder part of the body covered with a coriaceous membrane, instead of a hard, calcareous armor. Apart, then, from special defence, how could they escape being bruised and broken among the rough stones of a rocky beach, when a rolling tide lashes the shore, or becoming an easy prey to their enemies? But instinct supplies all that is required. The hermit crab selects an empty turbinate shell fitted to its size, when, introducing its tail, it retreats backwards, and in the recesses of its appropriated dwelling finds security. It is only the right of one of its pincer claws that is largely developed, and with this it both shuts and guards the entrance to its home, the caudal paddle of other creatures being unnecessary in this instance. It is changed, in fact, into a sort of anchor, by which the hermit crab retains a firm attachment to the bottom of his dwelling. Here secure, he peers out in quest of prey;

and, carrying his castle with him, may be seen, often with others, enjoying

his repast.

Unlike the univalve or bivalve, which enlarges its dwelling on increasing its size, the hermit crab, when grown too large for its dwelling, seeks and finds a more spacious tenement. In no race of beings is such a practice known as this. Peculiar, however, as is their sagacity, one species is specially remarkable for forming so intimate an attachment to the cloak anemone, that the latter being fastened to the hermit crab's

shell,their mouths

are so combined that they always feed together, according most where many other creatures would least agree. On a change of dwelling, the hermit crab has been seen anxiously transferring his friend to his new abode, and even pressing him down with a claw to complete his adherence; and another has been beheld failing to do so, after many efforts, and sooner than give

up his friend, returning to endure the inconveniences of his old dwelling. Of the crustaceans, however, there is an endless variety; and we give an amusing instance of the green crab's fox-like craft, as related by Quatrefages: One day I threw a large arenicola (lug-worm) into a pool of water several feet in extent. A troop of little shrimps, which were sedately enjoying themselves in the clear element, dispersed in alarm, startled by the noise made by the fall of this strange body, but, recovering themselves in a moment, they rallied, and, while the annelid was endeavoring to bury itself in the sand, one of the youngest, and con

sequently the most venturesome of the party, seized the creature by the middle of its body.

Emboldened by this example, the others lost no time in imitating it, and the poor arenicola was pulled about in all directions, until a fullgrown shrimp, darting from behind a tuft of corallines, dispersed his feebler comrades, and appropriated the booty to himself. I soon saw, however, that he would be compelled to divide the spoil, for at that very instant there poured forth from the moving sand some scores of small creatures, which, conscious that a victim was at hand, wished to participate in the feast. Without any sign of uncertainty or hesitation, they moved straight forward towards the arenicola, whose body was covered in the twinkling of an eye with those voracious mollusks. I thought his fate definitely settled, when a small shore-crab issued from beneath a stone, put to flight the shrimp, and, by dragging off the arenicola, very nearly upset all

the others, which forthwith hurried back to their sandy haunts. Then, however, a large edible crab appeared on the scene, and the poor little crab was obliged, in his turn, to beat a retreat, in order to escape out of reach of the formidable pincers of his stronger kinsman. But he still kept a watchful eye over the dainty morsel which he had tasted, and, taking advantage of a moment when the larger crab was withdrawing from the field, from some temporary emotion of alarm, he rapidly seized the long-disputed arenicola, and carried it for safety to some distance from the water's edge, where he might devour it at his ease on dry land.

The crab of most importance as an article of food on the Atlantic and Gulf Coast of the United States is the blue crab. This is one of the

swimming species, and is found especially in estuaries and brackish waters from Cape Cod to the Gulf of Mexico. Other species of the same class, found in the West Indies, and on both coasts of Central and South America, are extensively used for food. The rock-crabs are sometimes sold in New England, and similar species are common in California, while another species is much used on the coasts of Europe.

When the claw of a crab is bruised it bleeds, and the animal seems to suffer much pain. For a while it moves it from side to side, and then holding it steady in one direct position, the claw all of a sudden gives a sudden crack, and the wounded part drops off; not at the joint, but in the smoothest part of the limb. Crabs frequently have serious fights by means of their great claws, with which they break or cut off their adversary's legs. The American crab, with its enormous claws, is about a foot and a half in length. But its appearance is not so terrifying as that of the parthenope horrida; a crab frequently met with on the shores of the islands of Réunion, Madagascar, and the Mauritius. Its whole body, its claws and nippers, bristle with hard, long, sharp, and menacing joints. The figure given in our text is a reduced copy from an illustration in Milne-Edward's valuable monograph on the crustaceans of Réunion.

CHAPTER X.

MOLLUSKS WITH PECULIAR SHELLS.

A Choice Mineral Substance-Material for Ocean Builders-"See what a Lovely Shell"-Rare Mollusks-The Young Guarded-Repulsive Creatures in Beautiful Dwellings-The Sea-shore a Great School of Instruction-Curious Pearl Oyster-Helmet Shells-Cone Shells-Gorgeous Hues-Interesting Bivalves— Scallop Shell-Ornament of Pilgrims-Silken “Byssus”—Strange Material for Fabrics-Treasures of the Pearl Oyster-Fondness of the Ancients for a GemShakespeare on the Orient Pearl-Immense Wealth of Ceylon-Pearl Fishing by Cingalese-Picturesque Spectacle-Firing a Cannon at Day-break-Ropes, Knives, and Stones-Three Sieves-Form and Color-Pearls of Every HueAllusion of the Historian Tacitus-Origin of Pearls--Emerald Fringes-Marvels of Old Ocean's Bed.

HERE is a certain material spread throughout nature in prodigious abundance; the result of the combination of carbonic acid with lime, and which, according to the rules of chemical nomenclature, is scientifically known as carbonate of lime. This substance plays a most important part in the mineral kingdom, and under the different forms which it assumes constitutes for man one of those sources of wealth he appreciates so much the less because they are indispensable to him, and therefore bestowed by nature with a lavish hand. What is carbonate of lime? Why, it is marl-it is chalk-it is buildingstone-it is also alabaster and marble. It is that of which Tennyson sings in these lines :

See what a lovely shell,
Small and pure as pearl,

Lying close to my foot,

Frail, but a work divine,

Made so fairily well,

With delicate spire and whorl,

How exquisitely minute,

A miracle of design!

In the animal kingdom, the same substance absorbed, elaborated, and secreted by those myriads of seen and unseen workmen of which we have already spoken, becomes for them, too, as for us, the matter with which they build and fashion their asylum, their habitation. Carbonate of lime is the outer coat of those innumerable creatures which have aided in building up our capital cities; it is the polypid of the zoophyte, the armor of the crustacean, the house of the mollusk; it is those beautiful shells of all dimensions, of such varied forms, such vivid colors,