PHYSIOLOGY OF THE JNVERTEBRATA. 



6i 



previously described, it is important that a full detailed 

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

 stomach of Astacus is divided into cardiac and pyloric 



Fig. 15. — Longitudinal Section of Stomach of Astacls. 



= oesophagus. i = position of gastrolUh. c = lateral tooth. d = ptero- 

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

 cardiac process. A = zygocardiac ossicle, i = pre-pyloric ossicle. A = median 

 tooth. / = pyloric ossicle. m = posterior gastric muscle. n = CEecum. 

 = median pyloric valve. ^ = aperture of "bile" duct, q = lateral pouch. 

 r = cardio-pyloric valve, s = intestine, t = 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 

 Huxley* describes the' gastric mill of Astacus in the following 



Fig. 16. — Structure of so-called Liver) 

 OF Astacus. 



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

 c = ferment cells. 



* The Anatomy of Inverki.-ated Animals, p. 318. 



