. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. CRUSTACEANS 223 toms; in such localities they are caught in great numbers in nets or traps baited with decaying meat. They are, indeed, among our most valuable sea scavengers, although they are car- nivorous hunters as well. The body of the crab is short and broad, being flattened dorso-ventrally. The abdomen is much reduced in size. Usually it is carried close to the under surface of the cephalothorax; in the female the eggs are carried under its ventral surface, fastened to the rudimentar
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. CRUSTACEANS 223 toms; in such localities they are caught in great numbers in nets or traps baited with decaying meat. They are, indeed, among our most valuable sea scavengers, although they are car- nivorous hunters as well. The body of the crab is short and broad, being flattened dorso-ventrally. The abdomen is much reduced in size. Usually it is carried close to the under surface of the cephalothorax; in the female the eggs are carried under its ventral surface, fastened to the rudimentary swimmerets. The young crabs differ considerably in form from the adult. They undergo a complete metamorphosis (change of form), and their method of life differs from the adult. Immediatelv after molting, crabs are greatly desired by man as an article of food. They are then known as ''shedders," or soft-shelled The fiddler crab. From photograph loaned by the American Museum of Natural History. Other Crabs. — Other crabs seen along the New York coast are the prettily colored lady crabs, often seen running along our sandy beaches at low tide; the fiddler crabs, interesting because of their burrows and gre- garious habits; and perhaps most interesting of all, the hermit crabs. The hermit crabs use the shells of snails as homes. The abdomen is soft, and unprotected by a limy exoskeleton, and has adapted itself to its conditions by curling around in the spiral snail shell, so that it has become asym- metrical. These tiny crabs are great fighters and wage frequent duels with each other for possession of the more desirable shells. They exchange their borrowed shells for larger ones as growth forces them from their first homes. The habits of these animals, and those of the fiddler crabs, might be studied with profit by some careful boy or girl who spends a summer at the seashore and has the time and inclination to devote to the work. Of especial interest would be a stud
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