314 0. G. Farrington — The JSTephrostomes of Rnna. 



A few points may be mentioned regarding the macroscopic appear- 

 ance of the nephrostomes. The writer found they could be seen 

 plainly from the surface by staining the kidney in 0*5 per cent, silver 

 nitrate solution from 3 to 5 minutes. By this treatment the nephro- 

 stomes are made to appear like minute craters scattered over the sur- 

 face. As noted by Hoffman, they are most abundant in the region 

 medianward from the adrenal gland and are especially numerous near 

 the large branches of the vena cava. Fig. 5 is an attempt to repre- 

 sent their distribxxtion and appearance, though it is difficult to do this 

 by a drawing. The nephrostomes are represented by dots and the 

 little circles indicate lighter spots on the surface Avhich are often 

 mistaken for their openings but are in reality produced by the 

 Malpighian capsules showing through. The largest number of 

 nephrostome openings counted on any one kidney was 150. 



In conclusion the writer wishes to acknowledge his indebtedness 

 to Prof. S. I. Smith, at whose suggestion the investigation was under- 

 taken and whose valuable advice and assistance have been freely 

 rendered during the work. 



Sheffield Biological Laboratory, June, 1891. 



EXPLANATION OF PLATE XXIV. 



Pig. 1. Dorso-ventral section of kidney of Diemyctylus virescens. 9fj, in thickness. 



Fig. 2. Ventral portion of dorso-ventral section of kidney of Bana Cateshiana. 9// 

 in thickness. 



Fig. 3. Similar section showing single nephrostome. 6// in thickness. 



Fig. 4. Similar section entire, showing the distribution of the carmine in the blood 

 vessels. 



Fig. 5. Right kidney of Eana Cateshiana, female. Ventral view. 



a. artery; h. v. blood vessel; c. carmine; M. Malpighian capsule; n. nephrostome; 

 n. t. nephrostome tube ; u. t. uriniferous tubule ; v. i. large vein leading 

 to vena cava. The ventral surface in the figures is to the left, dorsal to 

 the right. The carmine where not lettered is represented by black dots. 



