58 EMBRYOLOGY OF THE STAEFISH. 



odd terminal tentacle has an eye at its base, and no disk is ever formed 

 at the extremity of this tentacle. The abactinal surface is very arched, 

 the spines are arranged in regular rows, and the arrangement of the plates 

 reminds us of the plates of Crinoids ; the plates first formed retaining 

 their embryonic or crinoidal character. The anus opens near the edge of 

 the disk, on the lower side ; the madreporic body is situated on the 

 edge, but moves to the abactinal area, in more advanced stages. About 

 a fortnight is required for the egg to pass through its different stages, 

 or the embryo to be hatched, and the larva to have reached the condi- 

 tion when the young Starfish is ready to resorb the Bracliiolaria ; and 

 another week must elapse before it reaches the stage represented in PI. 

 VI. Fig. 11. Those which I raised from eggs artificially fecundated re- 

 tained this shape four months. 



