GENERATIVE ORGANS. 



313 



The test is of Elasmobranchs is always paired and sym- 

 metrical, and usually lies, supported by the mesorchium, towards 



a 



FIG. 245. FEMALE URINOGESITAL APPARATUS OF Protoptcrus annccLcns. (From 

 the ventral side, natural size.) (After H. Ayers.) 



a, vent ; h.d, rectum ; Hg, apertures of ureters into cloaca ; L, L, lymphoid tissue ; 

 Mg, Miillerian duct ; M.tr, abdominal aperture of latter ; N, kidney ; 0, ovary ; 

 p, lung ; V.c.a, postcaval vein ; V.u, urinary bladder. 



the anterior portion of the body-cavity. The relations of the 

 vasa efferentia to the mesonephros have been already mentioned 

 (comp. pp. 298 and 303, and Fig. 238B), and a somewhat similar 

 arrangement is seen in Lepidosteus. 



Amongst Ganoids, the female organs of Lepidosteus l are formed on the 

 same type as those of the Teleostei, while in cartilaginous Ganoids a more 

 or less incomplete splitting of the segmental duct into a Miillerian and a 



a superficial resemblance to the amnion and chorion of Mammals, but these are 

 both formed from the maternal tissues (T. J. Parker). 



1 The cavity within the ovary of Lepidosteus is formed by a fold of peritoneum 

 on either border of the gland growing towards its fellow, and meeting in the middle 

 line ; into this cavity the ova are shed, and are carried to the exterior by an oviduct 

 which is probably formed by continuations of these peritoneal folds behind the 

 ovary. A similar mode of development of the oviduct possibly also obtains in 

 Teleostei. 



