ECHINODERMS. 



283 



the mouth is a circle of tentacles (in reality enormously 

 developed ambulacra), and with these the animals obtain 

 their food, which consists of small organisms living in the 

 sand and in some instances of decaying animal matter. 



FIG. 97. Sea-cucumber (Cucumaria frondosa). From Emerton. 



Inside, the pharynx is surrounded by calcareous plates, the 

 whole resembling slightly the lantern of the sea-urchin, 

 but no teeth are ever developed. In most species the 

 madreporite is inside the body, and in many the branchial 

 trees (p. 277) become developed into large tree-like strnc- 



