294 



PHYLUM ECHINODERMA 



by sensitive and pigmented cells, containing clear fluid, and 

 covered by cuticle. The skin is diflFusely sensitive. The 

 terminal tube-foot of each ray seems to be olfactory. 



Fig. 159. — Dissection of Asteyias rubens. — From a specimen. 



ST., Roof of central stomach ; A.G., two anal glands ; P.C, pyloric caeca, five pairs ; 

 A.O., ainbulacral ossicles, meeting like rafters ; A., ampullae ; S.C., stone canal 

 from the madreporic plate to the circumoral water-vessel ; S.St., saccular 

 dilatations of the stomach ; G., gonads, a pair in each arm. 



The starfish may be found with part of its stomach 

 extruded over young oysters and other bivalves. This 

 protrusible portion of the stomach is glandular and saccu- 



