172 



A HISTOKY OF EECENT CRUSTACEA 



the Porcellana and so institute a comparison. The zoea of 

 Porcellana longicornis (see Plate VII.) has not unfrequently 

 been studied, and the reality of its connection with the adult 



Fig. 15. — Porcellana longicornis (Linn.), an early post-larval form [Stebbiug]. 



form need not be doubted, but the extraordinary difference 

 between the one and the other can scarcely fail to surprise 

 any one who for the first time compares them. It is 

 strange that the smooth circular carapace of the grown-up 

 Porcellana should result from a larval form in which the 



