INTRODUCTION. 



Fis. 1. 



carapace, the rostrum is produced, the important change 



Yxcr.m. ^^ ^^^^ eye^ from the 



sessile to the pedun- 

 culate form has now- 

 taken place, the true 

 feet have become 

 evolved, developed, 

 and rudimentary ab- 

 dominal members are 

 perceived, and in fig. 

 m, all these develop- 

 ments are far more ad- 

 vanced, and the animal 

 has nearly approached 

 its final state. 



Such is, as far as it 

 appeared to me neces- 

 sary to detail it, the 

 state of our present 

 knowledge of this very 

 interesting phase in the 

 economy of this class 

 of animals, I have 

 entered more into de- 



I 



i 



