ECHINODERMATA. 107 



or Antedon\ species of which are found in almost all seas. In this 

 group the organism consists of a central body or disc, from which 

 proceed five radiating arms, which divide almost directly after their 

 origin into two secondary branches, so that ultimately there are 

 produced ten long and slender rays. Each arm is furnished on 

 both sides with a number of little jointed lateral processes or 

 " pinnae," so as to assume a feather-like appearance, from which its 



Fig. 66.— Crinoidea, Comatula rosacm, a free Crinoid, viewed itoiii its dorsal 

 or abordl aspect. 



popular name is derived (fig. 66). The digestive system is furnished 

 with both a mouth and a vent ; the water- vascular or ambulacral 

 system appears to take no part in locomotion, and the reproductive 

 organs are lodged in the lateral processes of the arms. The most 

 remarkable point, however, about a Feather-star, is the manner in 

 which development takes place. When fully grown (fig. 66) it pre- 

 sents no small superficial resemblance to some of the Ophhiroidea. 



