376 MONTGOMERY — MORPHOLOGICAL SUPERIORITY. [Oct. 7 



there is in the male a common urogenital duct, the segmental duct, 

 which is a duct persisting from a very early stage of the embryo. 



In the female of gnathostomatous Vertebrates but two kinds of 

 genital ducts are found, (i) The oviduct is a direct backward 

 growth of the ovary: Lepidosteus and most Teleostei, (2) The 

 oviduct is a Miillerian duct, separate from the ovary and from the 

 segmental duct. This may arise as an off-splitting from the ventral 

 side of the segmental duct (most Selachii)^ but it more usually 

 develops independently of the latter as a fold or ingrowth of the peri- 

 toneal epithelium {Batrachia, Amniota and possibly Dipnoi). In 

 the female there is accordingly never a urogenital duct, but the 

 oviducts are separate from the ureters. Further than this, while the 

 vas deferens of the male usually possesses dilations in the form of 

 seminal vesicles, also a prostrate gland, the oviducts are much more 

 specialized whenever there is intra-parental development of the 

 young. For the oviducts, besides the possession of special glands, 

 have very complicated dilations, the uteri, much more specialize! 

 than the seminal vesicles ; and in most of the Mammals the oviducts 

 are fused for a great portion of their extent, so that in the place of 

 paired uteri there is but a single one — a further advance beyond the 

 male condition. The uterus is not only a receptacle for the young, 

 but a complicated nourishing apparatus, with recurring profound 

 morphological changes. Even in some Teleostei {e.g., Zoarces) 

 uteri may be present, though most species of this group are ovipar- 

 ous. The complications of the female reproductive ducts are 

 induced by viviparity. 



From this comparison of the ducts of the reproductive organs, it 

 follows that in respect to these structures the female is morphologi- 

 cally the more advanced. The most important fact is the embryo- 

 logical one that in the male there is generally a persisting uro- 

 genital duct, in the female never a urogenital duct but oviducts 

 separate from the ureters. 



With regard to other differences in the sexual organs, the most 

 important is the relative position in the body of ovaries and testes. 

 Both arise in gnathostomatous Vertebrates as parallel longitudinal 

 ridges of the peritoneum, close to the dorsal mesentery. Of these 

 ridges only a portion fully develops, the remainder becomes 

 arrested. An ovary is a growth at about the middle of such a 

 ridge, a testis at a point of the ridge somewhat further back. Both 

 ovaries and testes retain their abdominal position in most Verte- 



