UROGENITAL SYSTEM. 329 
4 
long in the cecilians (fig. 334) and Amphiuma, saccular in most urodeles, and bifid 
at the tip in most anura, being even divided into two sacs, connected only at the 
opening into the cloaca in some species. 
SAUROPSIDA.—In reptiles and birds, as in all amniotes, the pronephros is 
rudimentary at all stages and never functions as 
an excretory organ. The mesonephros takes its 
place in foetal life, and in some it continues to 
function for some time after hatching, but in all it 
is eventually replaced by the metanephros, though 
its degenerate remains persist in the reptiles (better 
preserved in the female) forming the so-called 
‘golden yellow body.’ Another part is retained 
in the male as a part of the efferent ductules of 
the testes, somewhat as in mammals. 
The metanephros (fig. 328) never has the ex- 
tent of the mesonephros of the ichthyopsida, but 
it is usually restricted to the posterior half of the 
body cavity, often to the pelvic region. It is usu- 
ally small and compact (snakes form an exception) 
or somewhat lobulated, in the snakes the lobulation 
sometimes being so extensive that the lobules’ are 
only connected by the ureter. In the lizards the 
Fic. 328. Fic. 329. 
Fic. 328.—Urogenital organs of Monitor, after Gegenbaur. d, opening of digestive 
tract into cloaca; e, epididymis; k, kidney; p, papille of urogenital system; 7, rectum; 
t, testes; u, ureter; od, vas deferens. 
Fic. 329.—Urogenital organs in pig embryo 67 mm. long, after Klaatsch. a, allantois; 
&, gonad; ms, mt, meso- and metanephroi; sv, adrenal. 
organs of the two sides may be connected behind. In the birds there are usually 
three lobes in each mesonephros, these lying in cavities in the pelvis between 
the sacral vertebra and the transverse processes. 
