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- 



FIG. 10. Astacusfluviatilis. Longitudinal section of the stomach ( x 4), 

 c, cardiac ossicle; C(P, caecum ; c.p.v, cardio-pyloric valve ; cs. cushion- 

 shaped surface ; //</, hind-gut ; lip, aperture of right bile duct ; lp, 

 lateral pouch ; It, lateral teeth ; nig, mid-gut ; mt, median tooth ; -*, 

 oesophagus ; p, pyloric ossicle ; pc. pterocardiac ossicles ; pp, prepy- 

 loric ossicle ; iic, urocardiac process ; r l , median pyloric valve; r-, 

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



portant 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 



