URINOGEXITAL ORGANS. 165 



Ganoids ; one of these is Lepidosteus of which we have a 

 description from the pen of Balfour,* and the other Polypterus 

 in which their structure has been recently elucidated by 

 Budgett.f 



In Lepidosteus the kidneys extend forward from the anus 

 about three-fifths of the length of the body cavity (Fig. 93, Jc). 

 Anteriorly they are continuous with a band of lymphatic tissue 

 of a very similar appearance. The ureters (sg), which lie on 

 their ventral side and receive the openings of numerous collecting 

 tubes, enlarge posteriorly, and approaching each other coalesce 

 to form an unpaired vesicle (bl) which opens by a median pore 



FIG. 92. Diagrammatic view of the pronephros of Lepidosteus (from Balfour), 

 isolated and seen from the side, pr.n Coiled tube ; sd longitudinal duct of kidney ; 

 v malpighian body of pronephros ; / tube leading from v to the body cavity (peri- 

 toneal funnel) ; bv blood vessel of glomsrulus oi v. 



on a papilla (ug) behind the anus. The ovary is a hollow sac, 

 attached about its middle to the oviduct and continued back- 

 wards and forwards from this attachment into a blind process. 

 The oviduct is a thin- walled tube, continuous in front with the 

 ovarian sac and opening behind (od) into the dilated part of the 

 kidney duct of its side. In the male the testis is lobulated and 

 the vasa efferentia pass in the mesorchium to the kidney, where 

 they open into a longitudinal canal. From the longitudinal 

 canal pass off tubules which open into the kidney tubules them- 

 selves. Near the testis the vasa efferentia are united into an 



* Phil. Trans., 1882. 



f Trans. Zool. Soc., 15, 1901, p. 323. 



