IX URINOGENITAL ORGANS 451 



close relation with the generative organs, and gives rise to 

 a glandular body — the epididymis {A, ep) — with which the 

 long, convoluted Wolffian duct {spd), serving exclusively 

 as a spermiduct, is closely connected ventrally ; in the female, 

 this part of the kidney and its duct becomes vestigial {B,k'). 

 The hinder half of the embryonic kidney in each sex is 

 retained in the adult as the renal organ (k), which is some- 

 what swollen posteriorly. The ureters {ur) are independently 

 developed tubes, about five in number on each side. In 

 the female they open separately into the swollen persistent 

 posterior ends of the Wolffian ducts, which unite together to 

 form a median urinary sinus {B, u.s), opening by a single 

 aperture into the cloaca : while in the male [A, ur) most of 

 them unite to form a wide main ureter before communicat- 

 ing with a similar median sinus, which, as it receives the 

 products both of the spermaries and kidneys, is called the 

 urinogenital sinus {u.g.s). 



The spermaries are a pair of large, elongated, soft 

 organs united with one another posteriorly, and suspended 

 to the dorsal body-wall by a fold of peritoneum. From 

 the anterior end of each {A, is) arise delicate efferent ducts 

 (ef. d), which pass to the epididymis to become connected 

 with the convoluted spermiduct. The latter dilates pos- 

 teriorly, where it underlies the functional kidney, forming 

 an elongated, spindle-shaped seminal vesicle (s.v) which opens 

 (s.v') into the base of a thin-walled blind reservoir of about 

 the same length, the sperm-sac (sp. s) ; and just to the inner 

 side of its aperture are the openings of the ureters (ur). The 

 sperm-sac is continuous posteriorly with the urinogenital sinus, 

 the opening of which into the cloaca is situated on a papilla. 



The female Scyllium has a single ovary. {B,ov), suspended 

 by a fold of peritoneum. In the adult it is studded all 

 over with rounded ova in different stages of development, 



G G 3 



