THE URINOGENITAL SYSTEM. 95 
presence of this kidney in embryo mammals, together with its duct, 
determines the form and connections of the ductus deferens with 
the terminal portions of the urinary system. The pronephros, on 
the other hand, is a vestigial kidney in all vertebrates, but its duct 

Fic. 52. The male urinogenital ducts and related 
structures, viewed from the lateral surface. After Rau- 
ther: a., anal aperture; bu., bulbourethral gland; ci.c., 
corpus cavernosum; d.d., ductus deferens; g.a., anal 
(rectal) gland; g.i., inguinal gland; g.p., glans penis; par., 
paraprostatic glands; pr., prostate; r.,rectum; ur., ureter; 
u.v., urethra (membranous portion); v.s., seminal vesicle; 
v.u., urinary bladder. 
system, open proximally to the body cavity plays an important 
part in the formation of the oviduct in the female of all classes of 
vertebrates. The development of the kidney reveals a condition, 
also suggested in a less perfect way by the mesonephros, in which 
it is shown that the primary connections of the kidney tubules are 
