118 



ZOOLOGY 



is almost, but not exactly, like an adult crayfish except 

 in size. The telson of the just-hatched crayfish has, to be 

 precise, a somewhat more oval form, and the first pair of 

 swimmerets are undeveloped; but these differences soon 

 disappear. 



FiG.lloa. Third larval stage, 

 lateral view. Note the dif- 

 ference between this and 

 the adult. X 11. From 

 Herrick. 



Regeneration of Lost Parts. - -If you attempt to pick up 

 a crab 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 ; namel} r , be- 

 tween the second and third segments. This is the place 

 where a fusion occurs between two segments which are free 



