Chap, iv.] GASTRIC MILL OF CRAYFISH. 125 



separated from the intestine, which lies behind it, by a 

 filtering apparatus of valves and bristles. "Within 



Fig. 59. The Parts of the " Gastric Mill " of the Crayfish in situ (A), 



and disarticulated (B). 



this stomach there is developed a hexagonal frame- 

 work of calcareous and chitinous pieces, some of which 

 are provided with powerful grinding teeth. The fore 

 (Fig. 59 ; c) and hind (p) sides of the hexagon give 

 off, the one forwards and the other backwards, an 

 elongated ossicle (uc, pp) t each so placed in relation to 



