282 



ECHIXODEHMATA. 



The Pluteus larvse of the Ophiurids possess long lateral arms on 



the anterior dorso- 

 ventral arch of the 

 band, on the dorso- 

 lateral edge, and on 

 the edge of the pos- 

 terior ventral hood. 

 The Pluteus larva of 

 the Sea-urchin has no 

 Literal arms, but pro- 

 cesses are developed 

 en the edge of the 

 anterior ventral hood 

 (fig. 226). The larvae 

 of the Spatangidce are 

 characterised by an 

 unpaired apical rod, 

 and those of Echinus 

 and Echinocidaris by 

 the presence of ciliated 

 epaulettes (fig. 227). 

 The transformation of the laterally symmetrical larva with its 



bilateral processes and com- 

 plicated organization into the 



body of the adult Echino- 



darm is not in all cases 



ejected in the same manner. 



In the Sea-urchins and Star- 

 fishes the young animal is 



developed by a process of 



now formation within the 



body of the larva, the 



stomach, intestine, and dorsal 



sac alone persisting; while 



the transformation of the 



Auricularia into Synapta 



takes place without the loss 



of so many parts of the larva, 



the young passing through a 



vo lita infprmPfliitp staffe FlG 227. PJirf larva of Echinus liridui with four 



pupa-like mtermed ciUated epaulettes (We) (after K Metachnikoff) 



In the first Case a maSS of from the ventral side. O, Mouth ; A, anus. 



FJCJ. 223. Pluteus of a Spatungut with so- Called apical rod 

 (StJ (after J. Miiller). 



