Crustacea. 75 



injured, but his claws, being soft, are. useless as weapons of 

 defense. In molting, the hard lining of the stomach, with 

 the stomach teeth, is also shed. Crayfishes molt several 

 times the first year, the number of molts gradually decreas- 

 ing till in adult life the molt probably takes place but 

 once a year. 



"Crab's Eyes." Previous to the time of molting there 

 appear on the sides of the stomach two button-shaped 

 bodies of limy material. In molting they are shed into 

 the cavity of the stomach, together with the lining of the 

 stomach. It is believed that they break up, become dis- 

 solved, and are absorbed and then deposited as stiffening 

 matter in the chitin, which makes the basis of the envelop- 

 ing crust. 



Restoration of Lost Limbs. Crayfishes often lose their 

 legs while fighting. Sometimes also they seem to drop 

 them or throw them off when badly frightened, but 

 perhaps they are merely snapped off in the violent effort 

 to escape. The legs seem to break off always at the same 

 place, where the leg is most narrow, and this is the easiest 

 place to heal. The blood quickly coagulates, and such 

 loss seems not to be dangerous or even serious. The 

 mutilated stump at once begins to grow a new leg, but 

 for a long time it is smaller than its mate. If one looks 

 over a number of crayfishes, he is pretty sure to find some 

 in this condition. The big fighting limbs are ordinarily 

 the ones that have been lost. 



Are Crayfishes Beneficial or Injurious to Man ? Crayfishes are good 

 to eat, the only part, of course, being the muscle, most of which is in 

 the abdomen. They are used as food to a considerable extent in 

 Europe, but they are little used in this country. Crayfishes are very 

 useful as scavengers, eating dead fish, etc. Crayfishes are said to 

 benefit some heavy, clayey land by the holes they dig, perhaps by mak- 

 ing the soil more porous and helping to drain it. 



