408 



ESSENTIALS OF ZOOLOGY 



Pi. H. M 



Pi. 



B. 



D. 



Fig. 165. — Development of the crayfish. A, Young crayfish clinging to swini- 

 niereis of mother. B, Second larval stage {2) attached by its chelipeds to hairs 

 (PIH.) on swimmeret (PI.) of the parent. The molted shell of the first larval 

 stage (i) is clinging bv chelipeds. A portion of the egg-membrane (m) and shell 

 (Sh.) are still attached to the swimmeret by a stalk (St.). When the first larva 

 hatches it remains attached to the shell by a filament (Tf). The second larva is 

 similarly attached to the molted shell of the first by filament Af. By means of these 

 filaments the young remain fastened to the mother during development. C, first 

 larva hatching through shell. D, the second larva. (Reprinted by permission aftt-f 

 Andrews, 1916, Smithsonian Contributions, Vol. 35.) 



