250 



MANUAL OF ELEMENTARY ZOOLOGY 



a smaller hind part or filter-chamber ', often known as the 

 "pyloric division of the stomach," separated from the 



,z.car. !P- C ar. 

 ' ,u,cdr. ,car. 



^y. 



Fig. 159. — The proventriculus of the crayfish. 



A , The whole organ from above ; B, the same from the right side ; C, the left half from 

 within, the muscles being relaxed ; D, the ossicles of the mill in median section, 

 the anterior and posterior gastric muscles being contracted ; E, the- mill in plan. 

 All the figures are semi-diagrammatic, much detail being omitted. 



car., Cardiac ossicle ; cm,, caecum \/.c, pyloric or filter-chamber ; glth. y position of 

 gastrolith ; Lfi., lateral pouch; l.t., lateral tooth; /.u., lateral valves guarding 

 opening into mesenteron ; m.c, mill-chamber ; m.t., median tooth ; m.v., median 

 valve ; o.b., opening-of bile duct ; <zs., oesophagus ; p.car. t pterocardiac ossicle ; 

 p.py., prepyloric ossicle ; Py., pyloric ossicle ; u.car., urocardiac ossicle ; z.car., 

 zygocardiac ossicle. 



mill-chamber by a pit in the roof. From the filter-chamber 

 the short mid-gut or mesenteron leads backwards to the long 

 hind-gut^ sometimes called the " intestine." The epidermis 



