PHYSIOLOGY OF THE INVERTEBRATA. 



83 



species of the Adinice, only the digestive ferment secreted by 

 the cells of these animals does not appear to have the same 

 degree of activity as that extracted from the Porifera. Its 

 action is much slower. 



The digestive apparatus of Urastcr ruhcns (one of the 

 Asterideci) has been examined by the author. The walls and 

 contents of the wide sacculated stomach, and its five sacs do 

 not contain digestive ferments ; for the digestive fluid is 





>^" 



f^ 



>^^ 



r^ 



• 





f^'^ * TP^'^^^'^ ^'"^ 



Fig. 23.— Stomach anu Pyloric C.eca of Ur aster. 



derived from the pyloric casca situated in each ray. The 

 pyloric sac, or stomach, gives off five radial ducts, each of 

 which divides into two tubules (Fig. 23) bearing a number of 

 lateral follicles, whose secretions are poured into pyloric sac 

 and intestine.* 



The secretion (of the casca) was obtained from a large 

 number of star-fishes, and gave the following reactions : — 



* Proceedings of Poi/al Society of Eduihiir<jh, vol. 15, p. in ; and Pro- 

 ceeditifjs of lioyal /Society of London, vol. 44, p. 325. 



