134 



ARTHROPODA 



FIG. 155. Crayfish or crawfish (Cambarus bartoni). Photograph natural size. The 

 antennae are the two long backward projections from the head and the auten- 

 nules the short forward projections. 



FIG. 156. Crayfish with the left half of the body structures removed ; a, intestine ; 

 6, ventral artery ; c, brain ; e, heart ; et, gastric teeth ; i, oviduct ; /, liver ; m, 

 muscles ; n, green gland (kidney) ; o, ovary ; p, pyloric stomach; r, nerve cords ; 

 s, cardiac stomach ; st, mouth ; u, telson ; w t openings of veins into the pericar- 

 dial sinus. Twice natural size. 



the bases of the main stems attached below. A median 

 spine, the rostrum, projects between the eyestalks support- 

 ing the compound eyes on movable stalks, beneath which 



