204 



A HISTORY OF EECENT CRUSTACEA 



Smitli has studied its development, and carefully described 

 the embryo as it appears some time before hatching, also 

 the first, second, and third larval stages, and the first post- 

 larval stage. In this genus it appears that the Zoea stage 



Fjg.18. — AstacusAmericanus (Milne-Edwards), 

 early larral form, lateral view [S. 1. Smith], 



Fig. 17. — Astacus Amerlcanus (Milne- 

 Edwards), early laival form, dorsal 

 view [S. I. Smith]. 



is omitted, as far as the free existence of the animal is con- 

 cerned, and that the young one is hatched in the Mysis 



Vm.lQ.—Aslacus .4mmca?i«s (Milne-Edwards), third stage [S. I. Smith]. 



form. Professor Smith did not accurately ascertain the 

 age of the youngest larvae he described, but supposed them 

 to be at most a few days old and not to have moulted more 



