PHYSIOLOGY OF THE INVERTEBRATA. 



6i 



previously described, it is important that a full detailed 

 description of it should be given. As already stated, the 

 stomach of Astttcnn is divided into cardiac and pyloric 



Fig. 15. — LoNGiTLDiNAL Skction of Stomach oi' Astacls. 



tt = cEsophagus. /' = position of gastrolith. c = lateral tooth. d = ptero- 

 cardiac ossicle. e = anterior gastric muscle. / = cardiac ossicle. g = uro- 

 cardiac process. // = zygocardiac ossicle. / = pre-pyloric ossicle, k = median 

 tooth. / = pyloric ossicle. m = posterior gastric muscle. » = ctecum. 

 o ■-- median pyloric valve. / = aperture of "bile" duct. 1/ = lateral pouch. 

 r = cardio-pyloric valve. s = intestine. / = lateral pyloric valve v — small 

 inferior tooth. 



portions. The internal 

 walls of the anterior 

 half of the cardiac por- 

 tion are membranous 

 and are invested with 

 numberless minute 

 hairs ; but in the pos- 

 terior half the walls 

 are strengthened by 

 calcified and chitinous 

 ossicles which are so 

 arranged as to form a gastric mill or gizzard. Professor 

 Huxlev* describes the gastric mill of Astucus in the following 



XJ- 



Fig. 16.- 



-STKL'CTfKK Ol'- SO-CALLED LlVERi 

 OF AST.\CU.S. 



a = epithelium cells, b = so-called hepatic cells. 

 c = ferment cells. 



* Tl,e Anatomy of Invertibrated Animals, p. 31S. 



