130 



THE PHYSIOLOGY OF THE COMMON CRAYFISH. 



and more elongated : the hinder median division lies 

 under the heart ; the anterior divisions are situated 

 between the heart behind, and the stomach and the liver 

 in front (figs. 5 and 12, t). From the point at which the 



Fig. 31. — Astacus fluviatiUfi. — The male reproductive organs ( x 2) ; 

 f , testis ; vd, vas deferens ; vd', aperture of vas deferens. 



three divisions join, proceed two ducts, which are termed 

 the vasa deferentia (fig. 31, vd). These are very narrow, 

 long, and make many coils before the}^ reach the apertures 

 upon the bases of the hindermost pair of walking limbs, by 

 which they open externally (fig. 31, vd\ and fig. 35, vd). 

 Both the ovar}" and the testis are very much larger 



