370 



COMPARATIVE ANATOMY 



The testes of Sauropsida correspond in position with the ovaries, 

 and, like them, increase in size in the breeding-season, ihey have 

 an oval, round, or pyriform shape (Figs. 283 and 29o) and are made 



up of greatly convoluted seminal 

 tubules, held together by fibrous 

 tissue. In Reptiles (e.g. Lacerta, 

 Anguis), " yellow bodies," which cor- 

 respond to suprarenals (p. 385), lie 

 along the outer border of the testis, 

 and°at this point transverse canals 

 pass out from the testis to the par- 

 orchis. 



The latter consists of greatly con- 

 voluted canals, and from it arises 

 the vas deferens (Wolffian duct), 

 which either takes a straight course, 

 or is more or less coiled. In Birds 

 it opens by an independent aperture 

 into the cloaca, while in Lizards it 

 fuses with the ureter shortly before 

 entering the latter. 



Remains of the Miillerian ducts are 

 present in the male, corresponding in 

 position with those of the female. Their 

 lumen is not continuous througliout, but 

 the abdominal aperture may remain open 

 (Emys europtea), and exceptionally (e.r/. 

 Lacerta viridis) they may be as -well de- 

 veloped as in the female. 



Lymphoid organs are present in many 

 Reptiles, and probably have a physiological 

 relation to the generative organs (compare 

 p. 368). In many Lizards they are large 

 and variously coloured, and lie within the 

 pelvic region ; in Snakes they extend 

 along almost the entire body-cavity. 



Hermaphroditism has been observed 

 very exceptionally in the Chaffinch. Occa- 

 sionally the ovary of some Birds undergoes 

 structural changes, and no longer produces 

 ova, the female then taking on certain 

 secondary sexual characters of the male. 



Tig. 295.— Male Urinogenital 

 Organs of Anguis fragUis. 

 (After F. Leydig'.) 



Ho, testis ; t, theso-called "yellow 

 body " (suprarenal) ; Ep, paror- 

 chis ; Vd, vas deferens ; p, p, 

 common aperture of the ureter 

 {Vr, Ur^) and vas deferens on a 

 papilla on the dorsal wall of the 

 cloaca (C/) ; B, urinary bladder ; 

 7', rectum ; J\', kidney ; mg, rudi- 

 ment of the MuUerian duct. 



Mammals. — In Mammals the generative apparatus no longer 

 extends along the entire body-cavity, as in the lower Vertebrates, 

 but is confined to the lumbar and pelvic regions. Moreover, 

 in correspondence with the close relations which usually take 

 place between mother and embryo (p. 338), there is a much greater 

 differentiation of the generative organs than occurs in lower types. 

 The transition is not, however, a sudden one, for ia the lowest 

 Mammals, viz., the Montremes and Marsupials (Figs. 296 and 297), 



