SEASONAL CHANGES IN INTERSTITIAL CELLS 479 



At the end of May the same condition prevails in the toad as 

 in the frog, there being only a few interstitial cells and mostly 

 spermatogonia in the tubules. As spermatogenesis advances, 

 there is a more or less parallel growth in the interstitial cells. 

 Active spermatogenesis continues on into the winter. Free sper- 

 matozoa are most numerous at the end of April at which time 

 the interstitial cells are maximal and loaded with fat, but con- 

 tain practicallj^ no pigment, as compared with the numerous 

 pigment granules present in the interstitial cells later in summer. 

 He also observed that the first fat .to appean was not interstitial 

 but intratubular. 



Ganfini ('03) found that in the hibernating marmot the inter- 

 stitial cells are not fewer in number than during the active 

 period, as was reported by Hansemann, but are only smaller in 

 size and different in structure. They stain less readily and 

 as a whole give the appearance of a structure which has ceased 

 secreting. During winter-sleep they also assume a rounder 

 form. He does not think these changes have anything to do 

 with spermatogenesis, but are due rather to the same causes 

 that arrest the processes going on in the other organs. In this 

 animal he describes the interstitial cells as being arranged in 

 lobes and cords bounded by endothelium, but some are also 

 found isolated. 



Regaud ('04) reported that spermatogenesis goes on in the 

 mole (Talpa europaea) during autumn and winter. In Decem- 

 ber the tubules occupy most of the testis. The tubules, although 

 latge, are separated from each other by wide spaces containing 

 only a few interstitial cells. By February the testis has become 

 more than 15 mm. in length. In June and July the interstitial 

 cells are voluminous, closely packed together and occupy more 

 space than the tubules. The cytoplasm of the interstitial cells 

 at this stage is greatly vacuolated. By July the testis has 

 decreased to only 3 or 4 mm. in length ; but the interstitial cells 

 still persist, giving the adult organ the appearance of a foetal 

 testis. Spermatogenesis has ceased and in the tubules there is 

 only a syncytium of Sertoli cells and a few spermatogonia. 

 Thus he considers these observations to be just the opposite 



