ECHINODERMATA. 569 



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. 267. FULL-GROWN LARVA OF STRONUYLOCENTRUS. (From Agassiz.) 

 The figure shews the largely-developed abactinal disc of the young Echinus 

 enclosing the larval stomach. Reference letters as in previous figs. 



(fig. 268 A), and becomes bilateral, owing to a flattening of the 

 ventral surface. On the flattened surface appears a ciliated 



