THE URINOGENITAL ORGANS OF VERTEBRATES. 141 



pass through a glandular portion of the kidneys before they 

 enter the Wolffian duct, by which they are finally carried away 

 to the exterior. 



In the adult female, then, there are the following parts of 

 the urinogenital system (fig. 4) : 



(i) The oviduct, or M tiller's duct (fig. 4, md.}, split off from 

 the segmental duct of the kidneys. Each oviduct opens at its 

 upper end into the body-cavity, and behind the two oviducts 

 have independent communications with the cloaca. The ovi- 

 ducts serve simply to carry to the exterior the ova, and have no 

 communication with the glandular portion of the kidneys. 



s.f 



FIG. 4. DIAGRAM OF THE ARRANGEMENT OF THE URINOGENITAL ORGANS IN 

 AN ADULT FEMALE SELACHIAN. 



Hid. Mullerian duct ; wd. Wolffian duct ; st. segmental tubes ; d. duct of the 

 posterior segmental tubes ; ov. ovary. 



(2) The Wolffian ducts (fig. 4, wd.} or the remainder of the 

 segmental ducts of the kidneys. Each Wolffian duct ends 

 blindly in- front, and the two unite behind to open by a common 

 papilla into the cloaca. 



This duct receives the secretion of the whole anterior end of 

 the kidneys 1 , that is to say, of all the anterior segmental tubes. 



(3) The secondary duct (fig. 4, d.} belonging to the lower 

 portion of the kidneys opening into the former duct near its 

 termination. 



(4) The segmental tubes (fig. 4. st) from whose convolutions 

 and outgrowths the kidney is formed. They may be divided 



1 This upper portion of the kidneys is called Leydig's gland by Semper. It would 

 be letter to call it the Wolftian body, for I shall attempt to shew that it is homologous 

 with the gland so named in Saumpsida and Mammalia. 



