CRABS AND SHRIMPS. 187 



Thus, under Mr. Couch's eye, the Zoea had changed to 

 a Megalopa ; and this latter became after a short time a 

 Crab, in which were all the characters that belong to the 

 order to which the parent belongs ; but not those of the 

 genus nor even of the family. Its form bore a close 

 resemblance to that of the Sargasso Crabs (Grapsidce) ; 

 for the shield, instead of being large and arched in front, 

 and narrowed behind, was nearly square, while the front 

 was (taking in the eyes) almost straight, the lateral angles 

 much advanced. 



THIRD STAGE OF SHORE-CI1AB. 



(Grapsoid.) 



This Crab, however, was still very minute ; and many 

 sloughings were before it. In the course of these it was 

 destined gradually to attain not only the dimensions of its 

 parents, but also their form. This, however, would be 

 matter of development rather than metamorphosis : the 

 lateral outlines of the shield would more and more ap- 

 proach each other behind, while the series of points that 

 now belonged to these lateral outlines would become thrown 

 into the front margin, which would by degrees assume an 

 arched form, as you may see in the figure of the adult Crab. 



Though I cannot at this moment show you specimens of 

 the Carcinus in its earlier stages, yet I have here a good 

 number of the Zoeas of one of those intermediate forms 

 which are the connecting links between the Crabs and 



