56 



THE PHYSIOLOGY OF THE COMMON CRAYFISH. 



a broad plate, hairy on its inner surface, which enters 

 into the lateral wall of the cardiac chamber. There are 

 various other smaller skeletal parts, but the most im- 



P:P 



Fig. 10. — Astacns fluviatiris. — Long-itudinal section of the stomach ( x 4), 

 c, cardiac ossicle; ccp, cajciim ; c.p.v, cardio-pyloric valve; cs, cushion- 

 shaped surface ; //(/, hind-gut ; Jqy, aperture of rig-ht bile duct ; Ijy, 

 lateral pouch ; It, lateral teeth ; mg, mid-gut ; mt, median tooth ; ces, 

 oesophagus ; p, pyloric ossicle ; jjc. pterocardiac ossicles ; p}^^ prepy- 

 loric ossicle ; ?/c, urocardiac process ; v^, median pyloric valve; v^, 

 lateral pyloric valve; a?, position of gastrolith; zc, zygocardiac ossicle. 



j)ortant are those which have been described ; and these, 

 from what has been said, will be seen to form a sort of 

 hexagonal frame, with more or less flexible joints at the 

 angles, and having the anterior and the posterior sides 



