328 



COMPARATIVE MORPHOLOGY OF VERTEBRATES. 



tional to the total body length. The anterior end of each loses its excretory char- 

 acter and in the male becomes accessory to reproduction, as described above (p. 

 522). In the anura the organs are more compact and the differentiated anterior 

 end is lacking, though the efferent ductules of the testes pass through the organ. 

 The caecilians (fig. 334) resemble the urodeles, except in having the mesonephroi 

 more lobulated, the result of aggregates of tubules around the collecting tubules. 



pcs 



A 



FIG. 327 .Urinary organs of teleosts, after Haller. A , pronephros and ducts of young 

 Salmofario; B, excretory organs of adult perch, Percafluviatilis; C, of carp, Cyprinus carpio; 

 a, aorta; cv, caudal vein; d, urinary duct; m, mn, mesonephros; pcd, pcs, right and left 

 postcardinal veins; p, pn, pronephros; r, rectum; u, urinary bladder; w, wd, Wolffian duct. 



The Wolffian ducts are excretory in both sexes and are also reproductive in the 

 male. The ducts of the two sides open separately into the cloaca, with, usually in 

 the male, an enlargement, the seminal vesicle, which in the breeding season serves 

 as a reservoir for the sperm. The urinary bladder differs from that of the ichthy- 

 opsida in being ventral to the cloaca; it is of the allantoic type (p. 318). It is very 



