THE URIXOGENITAL SYSTEM 



191 



FIG. 103. A SERIES OF WHOLLY DIAGRAMMATIC FIGURES TO ILLUSTRATE THE 

 COMPARATIVE MORPHOLOGY OP THE URINOGENITAL ORGANS OF THK VERTEBRATA. 

 A, The pronephros stage of the Auamnia ; B, a later stage of the same ; C, the urinogenital 

 apparatus of the male Amphibian ; D, the same of the female ; E, pronephros 

 stage of the Amniota, the mesonephros as yet rudimentary ; F, urinogenital apparatus 

 of the Amniota, at a stage at which the sexes are not differentiated ; G, urinogenital 

 apparatus of the male Amniota; H, the same of the female; p.n., pronephros; 

 d.pn., duct of the pronephros ; ms., the developing mesonephros ; ms.s., part of 

 the mesonephros, becoming converted into the epididymis and parovarium ; ms.v., 

 vestiges of the mesonephros, the paradidymis and the paroophorou ; t, rete and 

 vasa efferentia testis ; t"t", a network homologous with these structures at the hilus 

 ovarii ; hy.s., stalked hydatid ; nis.r., portion of the mesonephros which in Amphi- 

 bians and Selachians becomes the so-called pelvic kidney; d.ms., duct of the 

 mesonephros, which in male Amphibians and Selachians becomes (Fig. C) the urino- 

 genital, and in females (Fig. D) the urinary duct. In the male Amniota it gives 

 rise to the seminal duct (Fig. G), and in the female to the Gartner's duct (Fig. H). 

 v.a., the seminal vesicle, an outgrowth of the duct of the mesonephros ; d.-m., 

 Mullerian duct, which in Mammals becomes differentiated (Fig. H) into the Fallopian 

 tube (/.), the uterus (ut.\ and the vagina (vg.) ; os., its ostium abdominale tubae ; 

 hy. and u.m. (Fig. G), unstalked hydatids and uterus masculinus (vestiges, in the 

 male, of the Mullerian duct, d.m.) ; mt., the definitive kidney or metanephros of the 

 Amniota, asserted to arise from the ureter (itr.), itself an outgrowth of the mesonephric 

 duct ; of'., allantois (urinary bladder) ; sn. t sinus urogenitalis ; p.g., genital pro- 

 minence ; g.g., genital glands, undifferentiated stage; en:, ovary; ts., testis; cl. t 

 cloaca ; al., hind-gut ; p.a., porus abdominalis ; g.c., Cowper's glands. 



Tabulated Resume of the Facts pictorially illustrated on the 

 opposite Page. 



