THE CllAYFISn 



149 



larly to the lobster, — from a large egg filled with yolk. The 

 early stages are much like those of the lobster; but those 

 changes which in the loljster take place during the first three 

 stages of free life are in the crayfish passed in the egg. Con- 

 sequently at the time the crayfish hatches it is almost, but 

 not exactly, like an adult crayfish except in size. The tail- 



FiG. 149. — Surface ^w of embryo Fig. 150. — Lobster embryo. 61 days 

 with all of thoracic appendages old; eyes have developed pigment, 



formed. The forked telson partly x IS. From Herrick. 



overlies the brain. Note the large 

 eyes, which are yet without pig- 

 ment. Embryo about 21 day.^ old. 

 X 25. From Herrick. 



fin of the just-hatched crayfish has, to be precise, a somewhat 

 more oval form, and the first pair of swimmerets are undevel- 

 oped ; but these differences soon disappear. 



Regeneration of Lost Pa.rts. — If you attempt to pick up 

 a era)) by one of its claws, you frequently find yourself in 

 possession of a portion of the leg only, while the crustacean 

 has made good its escape. Moreover, it will be seen that the 

 leg always separates at a certain place ; namely, Jjetween the 

 second and third segments. This is the place where a fusion 



