PHYLUM ARTHROPODA — CLASS CRUSTACEA 



279 



Pi. 



D. 



Fig. 158. — Development of the crayfish. A, Toun^ crayfish clinging to swim- 

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

 (Pl.H.) on a swimmeret (PI.) of the parent. The molted shell of the first larval 

 stage {l) is clinging by chelipeds. A portion of the egg-membrane (wi) 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 (A/.). By means of these 

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

 larva hatcliing through shell. D, Tlie second larva. (Reprinted by permission 

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



