276 FROGS, TOADS, AND NEWTS [CH. VIII 



beginning anteriorly on the dorsal surface, passes to the 

 outer edge of the kidney and runs backward close to its 

 fellow into the dorsal wall of the cloaca. 



The epithelium of the capsule removes water from the 

 blood ; nitrogenous compounds are eliminated by the 

 glandular portions of the tubes, and become dissolved in 

 the water which is swept along the tube by the action of 

 the cilia. 



Some authorities have described peritoneal funnels 

 (nephrostomes) to the number of about 300 upon the 

 ventral surface of the kidneys. According to Spengel 1 

 and Meyer 2 these open upon the ventral surface and are 

 connected with the last portions of the uriniferous tubes : 

 Nussbaum 3 however states that they open into the first 

 ciliated part in the young larvae. On the other hand, 

 Wiedersheim maintains that the funnels, though present, 

 do not open at the surface into the abdominal cavity, while 

 Heidenhain 4 and Ecker 3 were entirely unable to find any 

 such structures. There is no doubt that nephrostomes 

 exist in the tadpole and that they lead into the urini- 

 ferous tubes. In the adult, according to Nussbaum, Milnes 

 Marshall 6 , and others, whose experiments appear to be 

 conclusive, they establish connexion with the intra-renal 

 blood vessels. It is clear that the condition of these 

 funnels varies with the age of the individual. 



1 Centralbl. f. d. med. Wiss. 1875, and Arbeit, a. d. Zool. Zoot., Instil. 

 der Univ. Wiirzburg, Bd. in. 1876. 



2 Sitz. d. nat. Gesell., Leipzig, 1874. 



3 Sitz. d. Niederrhein. Gesell. in Bonn, 1877, xxxiv. 



4 Arch. f. mikrosk. Anat. 1874, x. 5 The Anatomy of the Frog. 

 6 Stud. Biol. : Lab. Owens Coll. 11. 



