8 



AMPHINEURA. 



the chief material for the formation of various organs (circulatory, 

 excretory and genital organs). 



— hi-. 



au* 



FlG. &.—A — V, transverse sections through embryos or larvae (O) of Chiton Polii 

 (after Kowalevskt) ; A, through the posterior part of the body of a young embryo, 

 B and O, through the anterior part of the body of more advanced embryos ; au, eye ; 

 c, shell; coe, coelom ; f, foot; fd, pedal gland; hi, lateral nerve-cord; md, 

 enteron ; mes, mesoderm ; pn, pedal commissures; r, radular sac; st, spines; vd, 

 stomodaeum. 



