812 



COMPARATIVE ANATOMY 



as well as the young in viviparous animals may be carried to the outside 

 of the body. The sperm-ducts of the mammal are known as vasa defer- 

 entia. (Fig. 457.) The egg ducts of the female are called oviducts 

 (Fallopian tubes). The vasa deferentia are usually the Wolffian ducts, 

 but in the female the oviducts may be either the Mullerian ducts, or 

 specially developed tubes or even merely abdominal pores. In prac- 

 tically all the forms we are studying the Wolffian ducts serve as the out- 

 let for the sperm. 



At the same time that the tubules, which are to carry the sperm, 

 are developing, there is an outgrowth of cells from the Bowman's cap- 

 sules at the cephalic end of the mesonephros, forming what are called 

 medullary cords. These latter continue their growth into the genital 

 ridge until they connect with the seminiferous tubules. All of these 

 acquire a lumen and both together form a continuous transverse 

 tubule, known as the vas efferens. (Fig. 458.) This continuous 

 tube leads from the genital cells to the Malpighian corpuscles and thence 

 by the mesonephric tubules to the Wolffian duct. The vasa efferentia 

 become connected by a longitudinal canal before actually entering the 

 Wolffian body ; and there is also usually a second longitudinal canal 

 which connects them in the body of the testes. The connection of testis 



Fig. 457. 



I, Diagrams of urogenital systems of female fishes. A, Afri- 

 can lungfish Protopterus; B, African ganoid Polypterus; Ameri- 

 can ganoid Amia; D, the garpike Lepidosteus ; E, most teleosts ; 

 F, trout and salmon, ap, abdominal pore ; cb, cloacal bladder ; 

 cl, cloaca ; /, funnel of oviduct ; gp, genital pore or papilla ; m, 

 mesonephros ; o, ovary ; od, oviduct ; r, rectum ; s, urogenital 

 sinus; up, urinary pore (papilla) ; ugp, urogential pore (papil- 

 la) ; w, Wolffian ducts. (From Kingsley after Goodrich.) 



