THE URIXOGEXITAL SYSTEM 401 



condition is maintained permanently, as in some reptiles, or 

 not. 



The atrophy of the Wolffian body is much more complete in 

 the female than in the male; no part of it remains in a functional 

 condition, but the part corresponding to the epididymis of the 

 male remains as a rudiment, known as the epoophoron. It has 

 almost the same structure in young females as in young males, 

 but the sexual cords uniting it with the ovary do not become 

 tubular, nor does the rete ovarii. A rudiment of the non-sexual 

 part of the Wolffian body is also found in the hen between ovary 

 and kidney in the lateral part of the mesovarium; it has been 

 named the paroophoron. 



Development of the Genital Ducts. The Wolffian Duct. The 

 origin and connections of the Wolffian ducts have been already 

 sufficiently described. In the male they are connected with the 

 semeniferous tubules by way of the rete, vasa efferentia, and 

 epididymis, and function as vasa deferentia exclusively, after 

 degeneration of the mesonephros. Subsequently they become 

 somew^hat convoluted, acquire muscular walls and a slight ter- 

 minal dilatation. The details of these changes are not described in 

 the literature. In the female the Wolffian duct degenerates; at 

 what time is not stated in the literature, but presumably along 

 with the Wolffian body. 



The Milllerian Duct. The Miillerian duct, or oviduct, is laid 

 down symmetrically on both sides in both male and female em- 

 bryos; subsequently both right and left Miillerian ducts degen- 

 erate in the male; in the female the right duct degenerates, the 

 left only remaining as the functional oviduct. We have now to 

 consider, therefore, (1) the origin of the ducts during the in- 

 different stage, and (2) their subsequent history in the male 

 and in the female. 



The origin of the Miillerian duct is preceded by the formation 

 of a strip of thickened peritoneum on the lateral and superior 

 face of the W^olffian body extending all the way to the cloaca 

 (cf. Fig. 220). This strip, which may be called the tubal ridge, 

 appears first at the anterior end of the Wolffian body on the 

 fourth day, and rapidly differentiates backwards; it lies imme- 

 diately external to the Wolffian duct. The anterior part of the 

 Miillerian duct arises as a groove-like invagination of the tubal 

 ridge at the cephalic end of the Wolffian body immediately 



