the reproductive ducts 349 



The Reproductive Ducts 



The reproductive products formed in the gonads have to be 

 carried to the exterior, either as spermatozoa, or as eggs or young in 

 different stages of development, the ducts in the male being called 

 vasa def erentia, those of the female being oviducts. The former are 

 usually the WoMan ducts, the latter may be either the MuUerian 

 ducts or tubes developed for the special purpose, or lastly, the abdom- 

 inal pores. 



Male Ducts. — In the elasmobranchs, amphibia and amniotes the 

 Wolffian ducts (fig. 368) serve as the outlet for the sperm. While 

 the seminiferous tubules are developing, there occurs a proliferation 

 of cells from the wall of the Bowman's, capsules in the anterior end of 

 the mesonephros. These medullary cords extend through the adja- 

 cent connective tissue and into the genital ridge where they come into 

 close connexion with the developing seminiferous tubules (fig, 371). 

 When the latter acquire their lumen the medullary cords also become 

 canaUzed, so that both form a continuous transverse tubule (vas 

 efferens) leading from the genital cells to the Malpighian corpuscles, 

 and thence by the mesonephric tubules to the Wolffian duct (fig. 

 373, A). These vasa efferentia become connected by a longitudinal 

 canal before entering the Wolffian body, while usually there is 

 another longitudinal testicular canal connecting them in the body of 

 the testis (fig. 373, B). Usually this connexion of testis and Wolffian 

 body takes place at the anterior end of the mesonephros, but in some 

 dipnoi the posterior end of the mesonephros alone is involved. This 

 is frequently accompanied by a degeneration of the glomeruli of the 

 tubules concerned, so that this part of the mehsonephros loses its 

 excretory character and becomes subsidiary to reproduction (fig. 

 368, B, C). With this formation of vasa efferentia the sperm never 

 enters the ccelom except as this is represented in the cavities of the 

 mesonephric tubules. 



As a farther result the anterior end of the Wolffian duct becomes 

 purely reproductive in the male and is usually greatly coiled, this 

 portion being called the epidid3miis. In the amniotes, where the 

 hinder portion of the mesonephros is supplanted by the true kidney 

 (metanephros), the whole Wolffian duct is a sperm duct (vas deferens) 

 in the male, while in the female it largely or completely degenerates. 

 In the amphibia and elasmobranchs the hinder end of the duct is both 

 reproductive and excretory in the male; in the female it is purely 

 excretory. 



