268 THE WEALTH OF THE SEA 



lost legs and claws. If a crab is caught and held by a 

 leg or claw, it throws off the appendage and thus 

 escapes with its life. The loss is not a serious matter, 

 for a protuberance forms in the end of the old stump, 

 which enlarges and becomes a thin-walled sac. At 

 molting-time the sac is discarded with the old shell, 

 and the new limb, which was folded up in it, appears 

 in its normal shape. The new limb is somewhat smaller 

 than the corresponding member of its pair, but at 

 subsequent molting it gradually increases in size 

 until it eventually attains full growth. Adult males 

 which have molted for the last time do not possess 

 the power of regeneration, or at least grow append- 

 ages very slowly. 



Curiously a crab can walk forward, backward, and 

 sidewise; the usual direction is sidewise. The crab 

 swims either backward or sidewise. 



In winter, crabs retire to deeper water, where they 

 lie on the bottom in a dormant condition. In summer 

 they migrate to shallow water, where they mate or 

 spawn. Sponge-crabs (female crabs with eggs 

 attached) are found chiefly in the southern part of 

 the Chesapeake Bay. The young crabs slowly migrate 

 to the northern part of the bay, where they are 

 found in great abundance during the latter part of 

 the summer. At first the young crabs molt every ten 

 days or two weeks, but as they near maturity the 

 period gradually lengthens until it reaches a month. 

 The shell of a soft crab hardens in two or three days 

 after molting. 



In this, the most important crab fishery, crabs 

 are taken by means of scrapes, dredges, dip-nets, and 



