ECHINODERMATA. 



107 



or Antedon), species of which ai'e found in ahnost 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. — Crinoidci. Comatida rosaccn, a free Crinoid, viewed from ity dorsal 

 or aboral asx^ect. 



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 iu locomotion, and the reproductive 

 organs are lodged iu 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 Ophiuroidea. 



