Fig. 132.—Paddles of lobster.
Fig. 133.—Fresh-water crayfish.
The crustaceans deposit eggs which they carry about with them attached to the swimmerets, and resembling minute bunches of grapes. When first hatched (Fig. 134) the young crustaceans are totally unlike the parent in appearance, passing through several stages before they reach the adult form. When the crustacean grows too large for its shell, what are known as casting hairs appear on the inner side, which push the shell upward.
Fig. 134.—Stages of development in a crab.
I have watched this process in the California sea crayfish, and it is generally accomplished at night. The flesh of the animal appears to become very watery and soft at this time. Finally the animal bursts the shell and by a slow and convulsive effort drags the flesh from claws, eyes, swimmerets, and antennæ, and escapes through the upper portion of the division between the head and tail, and presto! we have two animals; one flabby and very nervous, the other the deserted shell, yet seemingly alive. The crayfish is very helpless now, and secretes itself for several days until the new skin hardens, when it appears in a freshly colored coat of yellow and black.