THE CRAYFISH 



267 



power of casting off limbs is known as autotomy. It is 

 sometimes used as a means of escape from enemies which 

 have seized one of the limbs, but this is not so common 

 in the crayfish as in some animals that are related to it. 



Fig. 171.-^4, Two recently hatched crayfish holding on to one ot 

 the swimmerets of the mother ; B, pincers of such crayfish more 

 highly magnified. — From Huxley. 



e.c, Ruptured egg cases ; £«., endopodite ; ex., exopodite ; pr., protopodite. 



Segmented animals with jointed limbs, a thick cuticle, 



an open blood-vascular system, and a nervous 



ropo a. S y Stem jjkg tnat f t^g crayfish are known as 



Arthropoda. Crustaceans — waterfieas, Cyclops (Fig. 214), 

 crayfish, crabs, etc. — Insects, Arachnida (scorpions, spiders, 



