URINOGENITAL ORGANS 



343 



FIG. 273. A SERIES OF DIAGRAMMATIC FIGURES ILLUSTRATING THE ACCOUNT OF 

 THE COMPARATIVE MORPHOLOGY OF THE URINOGENITAL ORGANS OF THE 

 YERTEBRATA GIVEN IN THE FOLLOWING PAGES. 



A, the pronephros stage of the Anamnia ; 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 Anmiota, 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 male Amniota ; H, the same 

 of female Amniota. 



p.n., pronephros; d.pn., duct of the pronephros; ms., the developing me- 

 sonephros ; ms.s, part of the mesonephros, becoming converted into the 

 epididymis and parovarium ; ms.r, vestiges of the mesonephros, the para- 

 didymis and the paroophoron ; f, rete and vasa efferentia testis ; ft, a 

 network homologous with these structures at the hilum of the ovary ; hy.s, 

 stalked hydatid ; ms.z, portion of the mesonephros which in Amphibians and 

 Elasmobranchs becomes the so-called pelvic kidney ; d.ms, duct of the 

 mesonephros, which in male Amphibians and Elasmobranchs becomes 

 (Fig. C) the urinogenital, 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 

 Gartner's duct (Fig. H) ; r.s, the seminal vesicle, an outgrowth of the duct 

 of the mesonephros ; d.m., Miillerian duct, which in Mammals becomes 

 differentiated (Fig. H) into the Fallopian tube (fl ), the uterus (ut), and the 

 vagina (vg) vs, its abdominal aperture; hy, and u.m (Fig. G), unstalked 

 hydatids and uterus masculinus (vestiges, in the male, of the Miillerian duct, 

 d.m.) ; m.t., the definitive kidney or metanephros of the Amniota, said to 

 arise from the ureter (nr), itself an outgrowth of the mesonephric duct ; al, 

 allantois or urinary bladder ; su, urinogenital sinus ; p.g, genital prominence, 

 y.g, gonads, undifferentiated stage; ov, ovary; ts., testis; d, cloaca; al, 

 rectum ; p. a, abdominal pore ; g.c, Cowper's glands. 



TABULATED RESUME OF THE FACTS PICTORIALLY ILLUSTRATED ON THE OPPOSITE 



PAGE. 



Anamnia. 



Amniota. 



s-l.ll 

 3* 



Develops in all Anamnia, but 

 rarely persists as a permanent 

 excretory organ. 



Still develops in the Amniota, 

 but as an excretory organ under- 

 goes entire degeneration in the 

 embryo : it may take part in the 

 formation of the suprarenal 

 body (?) 



In Elasmobranchii, appears to Probably persists as the meso- 

 give origin by subdivision to nephric (Wolffian) duct, and con- 

 both mesonephric (Wolffian) ; tributes in some to the forma- 

 and Miillerian ducts. In Am- i tion of the Miillerian duct, 

 phibia, becomes converted into 

 the mesonephric duct. Its fate in 

 other Anamnia is not yet fully 

 investigated. 



Functions in all Anamnia as a 

 urinary gland. In Elasmo- 

 branchs, Amphibians, and one 

 or two higher Fishes, its anterior 

 portion becomes related to the 

 male genital apparatus, the 

 posterior portion persisting as a 

 permanent kidney. 



Loses its renal function in all 

 Amniota (as a rule in the em- 

 bryo), and becomes vestigial, 

 except so far as it becomes an 

 accessory portion of the repro- 

 ductive apparatus in the male 

 and enters into the formation of 

 the suprarenal body (?) 



