XVIIl. — ^The Nephrostomes of Rana. By Oliver C. Far- 



RINGTOK. 



In the Urodela, as is well known, nephrostomes are always present, 

 serving as a means of free communication between the body cavity 

 and uriniferous tubules. According- to Hoffman,* both Spengel and 

 Meyer, whose elaborate investigations independently made, first gave 

 us accurate knowledge of the structure and office of the nephrostomes 

 of Urodela, state that these organs exist also in the Anura, but they 

 were unable to determine with certainty the point of connection 

 between them and the tubules. The nephrostomes appear, according 

 to these authors, on the ventral surface of the kidney, where this is 

 covered by the peritoneum. Their number varies in different genera, 

 but in Rana there are from 200 to 250. In most genera they open 

 directly inward, but in some they take a short horizontal course on 

 the surface before entering the kidney. As before stated, their point 

 of junction with the tubule is difficult to establish with certainty, but 

 according to the view of Sjjengel they unite with the fourth, section 

 of the tubule rather than with the first section or neck as in Urodela. 

 Nussbaum also investigated this question and his first resultsf con- 

 firmed Spengel's views. Later investigations,! however, led him to 

 the belief that although during the tadpole stage the nephrostomes 

 connect with the neck of the tubule, as development proceeds they 

 are forced away from it and open, in the adult frog, into the branches 

 of the renal-portal vein. Haslam,§ the most recent writer on the 

 subject, controverts all the previous views, stating that neither in 

 microscopic sections or teased preparations has he been able to find 

 any trace of such organs. The conclusions which he draws from 

 various experiments on the frog are as follows : " If the peritoneal 

 funnels exist in the adult frog, (1) they are very difficult to find ; 

 (2) they do not form a free communicating path between any part 

 of the uriniferous tubules and the abdominal cavity ; (3) their super- 

 ficial terminations have no free cilia." Heidenhain, according to 

 this author, was also unable to find these organs. 



* Bronn's Klassen und Ordnungen des Thier-reichs, vol. vi, p. 461. 



f Sitzungsb. d. Niederrheinischen Gesell. in Bonn, 1877, p. 122. 



t Zool. Anzeiger, 1880, No. 67, p. 514. 



§ Ecker's Anatomy of the Frog. Translated by Geo. Haslam, 1889, p. 336. 



