INTERSTITIAL CELLS OF URODELE TESTIS 263 



products of intralobular degeneration; their position around 

 the lobule, rather than around the blood vessels, suggests this. 

 There is no evidence that the products of degeneration find their 

 way out of the testis via the collecting duct and ductuli efferentes. 

 Their return to the circulatory system by way of the stromal 

 cells seems probable, with the consequent assumption by the 

 latter of the interstitial-cell character. The disappearance of 

 the interstitial cells shortly after the degeneration of the lobule 

 is completed is further indication of their dependence upon its 

 influence. On the other hand, the hypertrophy of stromal cells 

 around the lobule may be in part due to their accumulation of 

 substances normally passed on into the lobule, but now piled up 

 just short of their former destination through the inability of 

 the Sertoli cells to utilize the accustomed quantity. This, 

 presumably, is the explanation of the occasional presence of 

 lipoids in the stromal cells during the progressive phases of 

 spermatogenesis, when degeneration within the lobule is relatively 

 improbable. Supply and consumption are so balanced, as a 

 rule, during these phases that there is little or no lipoid demon- 

 strable in the stromal cells. Consumption being curtailed, 

 lipoids accumulate. 



It is suggested that the accumulation of lipoids within the 

 lobule is, similarly, an expression of the acquisition by the 

 Sertoli cells of materials which they can no longer utilize. 

 A comparatively enormous amount of lipoid is seen in the lobule, 

 in Necturus especially, before the interstitial cells reach their 

 maximum. That the diminished ability of the Sertoli cells to 

 receive materials, after the germ cells which utilize them have 

 left the lobule as spermatozoa, should result in a secondary 

 'backing up' of the incoming supply into the stromal or intersti- 

 tial cells, seems within the realm of possibility. There is the 

 further possibilitj^ that by their accommodating hypertrophy at 

 this time these cells may help preserve the nutritive balance for 

 the region in which they occur, and, by so doing, prevent dis- 

 turbance of the normal growth processes of the testis. 



The interstitial cells of urodeles may also serve to avert a too 

 sudden collapse of the greatly distended lobules, thus preventing 



