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 
Fra. 31.—Astacus fluviatilis.—The male reproductive organs (x 2) ; 
t, 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 they 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 ovary and the testis are very much larger 
