332 



COMPARATIVE MORPHOLOGY OF VERTEBRATES. 



The testes, supported by mesorchia, lie at various levels in the coelom. The 

 relations of their ducts to the mesonephros are typical (p. 521) . The vasa deferentia 

 of the two side unite just before entrance into the cloaca to form a urogenital sinus, 

 with which an oval sperm sac is connected on either side. In Chimaera the genital 

 portion of the mesonephros (fig. 331) is 

 widely separated from the functional por- 

 tion, the two being connected by the 

 Wolffian duct. In the male the Miillerian 

 duct is rudimentary and frequently is with- 

 out a lumen. 



GANOIDS. Nothing is known of the 

 development of the sexual organs of the 

 ganoids, except as to the origin of the germ 

 cells in two species. In most species the 

 ovary is band-like and the oviducts open by 

 broad funnels into the ccelom, but in Lepi- 

 dosteus the ovary is saccular, the eggs pass- 

 ing into the central cavity, the duct being 

 apparently a sterile, backward prolongation 

 of the ovary. In the male the testes are 

 frequently lobulated and a system of effer- 

 ent ductules, connected by a longitudinal 

 canal, pass from the testes into the meso- 

 nephros (fig. 325) and thence separately 

 or by a single tubule into the Wolffian 

 duct. In the males of all but Lepidosteus 

 there are short tubes with funnels, appar- 

 ently the homologues of the oviducts of the 

 females. 



TELEOSTS. In some of the lower 

 teleosts (salmonids, etc.) the elongate ovary 

 is solid and the eggs pass from it into the 

 coelom and are carried thence to the exterior 

 by short peritoneal funnels (fig. 332), or the 

 tubes and funnels may be absent and 



the eggs then pass out by abdominal pores. In most teleosts, however, each ovary 

 is a closed sac (like that of Lepidosteus, fig. 326) continued behind by a slender 

 oviduct. The ducts of the two sides may open separately, but usually their hinder 

 ends are united and open by a single genital pore between the anus and the rectum 

 In some instances (fig. 325, E), the urinary and genital pores are on a urogenital 

 papilla. In the male the elongate testes are either simple or lobulated. Internally 

 each consists of radial chambers of varying shape which are connected with a 

 complicated system of tubules which lead to a vas deferens running back to open 

 into the hinder end of the Wolffian duct, or separately to the exterior (fig. 333, go). 



In most teleosts the number of eggs produced in a season is very large, sometimes 

 numbering millions. Usually, after passing from the oviducts, they are left to the 



FIG. 331. Testis and anterior end 

 of mesonephros of Chimcera, after Par- 

 ker and Burland. bv, blood-vessel; 

 cvl, longitudinal tubule; m, Miillerian 

 duct; ms, anterior end of mesonephros 

 (Leydig's gland); spd, sperm duct; ve, 

 vet, vasa efferentia; vs, seminal vesicle. 



