ECHINODERMA TA. 



475 



epidermis of the amnion, which is ruptured in the process and eventually 

 thrown off. 



Crinoidea. The larva of Antedon, while still within the egg-shell, 

 assumes an oval form and uniform ciliation. Before it becomes 

 hatched the uniform layer of cilia is replaced by four transverse 

 bands of cilia, and a tuft of cilia at the posterior extremity. In this 

 condition it escapes from the egg-shell (fig. 208 A), and becomes 



FIG. 268. THREE STAGES IN THE DEVELOPMENT OF ANTEDON (COMATULA). 



(From Lubbock ; after Thomson.) 



A. larva just hatched ; B. larva with rudiment of the calcareous plates; C. Penta- 

 crinoid larva. 



