SO THE NATUKAL HISTORY OF THE COMMON CRAYFISH. 



the cavity of the stomach ; while the opposite side, being 

 convex and rough with irregular prominences, is some- 

 thing like a " brain-stone " coral. 



Moreover, when the stomach is laid open, three large 



B 



FIG. l.Astacvs fiumatilis. A gastrolith ; A, from above ; B, from 

 below ; C, from one side (all x 5) ; D, in vertical section ( x 20). 



reddish teeth are seen to project conspicuously into its 

 interior (fig. 6, It, mt) ; so that, in addition to its six 

 pairs of jaws, the crayfish has a supplementary crushing 

 mill in its stomach. On each side of the stomach, there 

 is a soft yellow or brown mass, commonly known as the 



