232 R. R. HUMPHREY 



later stages do not appear. The granules present are presuma- 

 bly mitochondria, and will be referred to as such. 



It was, doubtless, from a study of the testes of Triton cristatus 

 and axolotl at periods such as this that Friedmann ('98) came to 

 the conclusion that no interstitial cells were formed in these two 

 urodeles, he stating that only ordinary connective tissue could 

 be found between the lobules. That a study of these species 

 in a different season of the year might have caused him to modify 

 these conclusions would appear from the work of Champy ('13) 

 and Ganfini ('02). The latter described and figured 'granular 

 cells' in the testis of Triton cristatus, but his work is somewhat in- 

 conclusive, as he does not state when and in what part of the testis 

 these cells appear. Champy undoubtedly observed the interstitial 

 cells in both triton and axolotl, and recognized the fact that they do 

 not appear between lobules during the progressive phases of 

 spermatogenesis. One would certainly seem justified in conclud- 

 ing that no interstitial cells existed in Necturus if he limited his 

 observations to the period during which the maturation divisions 

 and the transformations of the spermatid are taking place; 

 neither would he be able to detect them in the testes of Crypto- 

 branchus, Plethodon, Diemyctylus, Spelerpes, and Gyrinophilus, 

 nor in Desmognathus except in the caudal shrunken portion of 

 the testis in which spermatozoa had matured in the preceding 

 summer. To the fact that interest in the urodele testis has 

 centered chiefly about this maturation period and its all-absorb- 

 ing problems may be ascribed the failure of the majority of 

 investigators to note that in a later season interstitial cells 

 become extremely numerous and prominent. Their presence 

 in the urodele testis, however, is rarely mentioned by workers 

 on the problems of spermatogenesis. 



b. Differentiation of interstitial cells ; their mitoses. In Septem- 

 ber and October spermatozoa are maturing and leaving the 

 lobules. During the period when the lobules are still distended 

 with transforming spermatids, the interlobular tissue remains 

 in the condition characteristic of the preceding months. With 

 the formation of the spermatozoa, however, the balance of 

 metabolic conditions within the testis is disturbed; physical condi- 



