INTERSTITIAL CELLS OF URODELE TESTIS 243 



mediate sizes resemble the larger in their fuchsinophile nature. 

 I have not succeeded in staining them and the mitochondria 

 differentially, though the latter do, of course, retain their stain 

 less tenaciously. 



Several attempts to stain the mitochondria intra vitam with 

 janus green after the method of Cowdry ('16) proved unsuc- 

 cessful. Mitochondria were faintly stained, if at all, and other 

 structures, such as some of the larger granules or even lipoid 

 droplets, took the stain, appearing to have a film of stainable sub- 

 stance at their periphery. The specificity of janus green as a 

 mitochondrial stain would appear, from my results, somewhat 

 questionable; Bensley ('11) similarly describes it as staining 

 small granules in the islet cells of the pancreas as well as the mito- 

 chondria of those cells. 



Even as the origin of the larger fuchsinophile granules from 

 smaller mitochondrial ones is suggested by their sizes 'and order 

 of appearance, so, too, is there a suggestion that these granules 

 may in turn give rise to the droplets which blacken with osmic 

 acid. The smallest of these droplets in Bensley preparations are 

 often of the same size as the larger fuchsinophile granules (figures 

 29 and 30) ; frequently blackened droplets seem to stain with the 

 red as well ; the droplets usually appear first in that region around 

 the centrosphere in which the granules are most numerous; with 

 the increase in numbers of the droplets, fuchsinophile granules 

 may be much less numerous — in some cells, indeed, almost none 

 at all may remain. 



The lipoid droplets blackening with osmic acid appear early 

 in the transformation of the stromal into interstitial cells, some 

 often being seen before the nuclei have assumed the rounded form. 

 They increase in size, some attaining diameters of 6 to 8 m; 

 they increase in number as well, until the cell, except in the 

 region of the centrosphere, may be fairly packed with them, the 

 fuchsinophile granules then appearing much less numerous. 



The lipoid droplets of the interstitial cells, after osmic-acid 

 fixers, are much more difficult to retain than are those in the 

 degenerating lobules. The latter droplets are retained, as a rule, 

 in covered sections from which the interstitial cell lipoids are 



