URINARY ORGANS. 



303 



division of the mesonephros into an anterior and a posterior section 

 may be observed (comp. Figs. 237, pd, and 238, m.d, w.d, s.t). In 



FlG. 237. DlAGKAM OF THE PRIMITIVE CONDITION OF THE KlDNEY IN AN 



ELASMOBRANCH EMBRYO. (After Balfour.) 



pd, segmental duct : it opens at o into the body-cavity, and its other extremity com- 

 municates with the cloaca ; x, line along which the division appears which 

 separates the segmental duct into Leydig's (Wolffian) duct above, and the 

 Mullerian duct below ; s,t, segmental tubes : they open at one end in the body- 

 cavity, and at the other into the segmental duct. 



FIG. 238A. DIAGRAM OF THE ARRANGEMENT OF THE URINOGENITAL ORGANS IN 

 AN ADULT FEMALE ELASMOBRANCH. (After Balfour.) 



m.d, Mullerian duct; w.d, Leydig's (Wolffian) duct; d, ureter; s.t, segmental 

 tubes : five of them are represented with openings into the body-cavity : the 

 posterior segmental tubes form the mesonephros ; ov, ovary. 



FIG. 238B. DIAGRAM OF THE ARRANGEMENT OF THE URINOGENITAL ORGANS IN 

 AN ADULT MALE ELASMOBRANCH. (After Balfour.) 



m.d, rudiments of Miiilerian duct ; w.d, Leydig's (Wolffian) duct, marked vd in 

 front, and serving as vas deferens ; s. t, segmental tubes : two of them are 

 represented with openings into the body-cavity ; d, ureter ; t, testis ; nt, canal 

 at the base of the testis ; VE, vasa efferentia ; Ic, longitudinal canal of the 

 Wolffian body. 



the male, the former comes into connection with the genital gland 

 (Fig. 238B, VE, nt, ), and its tubules open directly into the 



