THE CRAYFISH. 35 



the gullet trace nerves to the eyes, antennae, and 

 antennulae. 

 9. Cut open the stomach, wash it out with water, and 

 look on its inner walls for teeth. 



10. Study the joint in one of the big pinchers. Pick out 

 the muscle from the end of the segment, and find the 

 thin, tough, white tendons. Seize these with the 

 forceps and pull alternately, to see how the claw is 

 shut and opened. 



11. In what characters is the crayfish like the grass- 

 hopper ? In what do these animals differ ? 



12. Why should the name Crustacea be applied to such 

 animals as the crayfish? 



THE DEVELOPMENT OF THE CRAYFISH. 



The eggs are glued in masses to the swimmerets, under 

 the abdomen of the female, and thus carried till they are 

 hatched, and for some time afterward the young cling to the 

 swimmerets. In its growth the crayfish sheds its crust, or 

 moults, several times. In this process the carapace 

 separates from the abdomen above, and cracks along the 

 back. By a series of severe efforts the crayfish extricates 

 itself, at first soft, defenceless, and correspondingly 

 timid. Great difficulty is experienced in withdrawing the 

 legs ; often they are broken off in the effort to withdraw 

 them. The legs are frequently broken off at other times, 

 but grow out again. 



Read "The Crayfish," Huxley, the chapter on "The 

 Fresh-water Crayfish" in "Practical Biology," Huxley and 

 Martin. 



