Page:The American Cyclopædia (1879) Volume V.djvu/453

 CRAB 449 from the egg, the common crab (cancer) of our Atlantic coast is a little free-swimming animal, having a somewhat globular body armed with a long spine projecting down between the enormous eyes, another spine upon the back longer than the whole animal, and another smaller one upon each side, and a slender tail without appendages, but with the last segment expanded into a broad, horizontal caudal fin. In this stage the claws and legs are wholly wanting, and there are no gills ; but some of the jaw-like appendages of the mouth are developed -into long, two-branched swimming appendages, by means of which the animal swims rapidly about in the water, where it lives most of the time at the surface. The young in this condition were long ago de- scribed under the name of zoea, and it is still called the zoea stage. After casting the skins several times and increasing much in size, swimming legs, like those of shrimps, are de- veloped on the under side of the tail, and soon the claws and legs appear, the mouth appen- dages become much like those of the adult, and the spines upon the body have either disap- peared or become much smaller. This is called the megalops stage, the name having been applied to them before it was known that they were the young of crabs. Finally, at one cast- ing of the skin, the swimming legs upon the abdomen and the spines upon the body disap- pear, and the little crab, now about an eighth of an inch long, comes forth in something like the adult form, gives up its free-swimming ex- istence, and afterward lives upon the shore or bottom. Most species pass through similar changes, but there are apparently exceptions in some of the .land and fresh- water crabs, which are said to be hatched in a form much like the adult. The subsequent increase in size takes place only at the times of casting the shell, which occurs frequently at first, but finally, in most species, only once a year, and in old individuals of some species still less fre- quently. At this period the animal seeks some sheltered situation, the whole integument be- comes detached from the new one forming beneath it, the carapace separates from the body just above the bases of the legs nearly all round, and the legs and other appendages are slowly drawn out of their old shells. The shells of the big claws and other appendages are not cracked or broken, but the new integument is so soft and yielding and the muscles in such a flaccid condition that the limbs are drawn through the small openings at the joints, much as a sack nearly tilled with some fluid may be drawn through an opening much smaller than the sack itself. For some time after leaving the old shell the crabs are in a very soft and defenceless condition, as the new shell hardens quite slowly. In this state the common edible or blue crabs (callinectes hastatus) of our At- lantic coast are sold in the markets as "soft- shelled crabs," and are much more highly es- teemed for food than when in the normal or hard-shelled condition. Many species are ex- tensively used for food in different countries, and nearly all of them would probably be found edible. They are eagerly devoured by fishes, American Edible Crab (Callinectes hastatus). and constitute a large part of the food of many valuable kinds. The one of most importance as an article of food on the Atlantic and gulf coast of the United States is the blue crab just referred to. 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 genus, found in the West Indies and on both coasts of Central and South America, are extensive- ly used for food. The common or rock crabs (cancer irroratus and borealis), large, mottled, reddish brown species, with nine small teeth on each side of the carapace, are also sometimes sold in the markets of New England ; and sim- ilar species of the same genus are common in San Francisco, while another species (cancer pagurus) is much used on the coast of Europe. The species most extensively used in many parts of Europe is, however, the green crab Common Crab of Europe (Cancer pagurus). (carcinus mamas), which is smaller and has only five teeth on each side of the carapace. This is common upon the southern coast of New England, but is here seldom if ever used for food. Upon the coast of the southern states