SEASONAL CHANGES IN INTERSTITIAL CELLS 489 



normal scrotal testis in this particular case, the abdominal one 

 was fmictionless as far as internal secretion is concerned, and 

 hence the interstitial cells of the cryptorchid testis had under- 

 gone a pigmentary degeneration. As will be disclosed later, 

 the origin of these cells in the woodchuck is undoubtedly of 

 this order, having resulted from the degeneration of some of 

 the ordinarj^ interstitial cells when they undergo retrogression 

 in mid-summer, at which time the very soluble fat of the periph- 

 eral cytoplasm undergoes a radical change such that from these 

 fatty globules there is evolved a pigmented substance much 

 less soluble. Sehrt ('04) considered the pigment usually found 

 in the interstitial cells as a lipochrome. These pigment cells as 

 well as the ordinary interstitial cells are distributed at all stages 

 about equally in all parts of the testis. 



At this stage there are also a number of ordinary adipose cells 

 scattered through the interstitial tissue. Small fatty granules 

 are also found in the tubules, in fact at no time are the tubules 

 free from demonstrable fat which blackens with osmic acid 

 (figs. 14, 22, and 26). 



Within the tubules early stages of spermatogenesis are in prog- 

 ress. The lumen is filling up with spermatocytes, which are 

 enlarging. No karyokinetic figures appear in them, however, 

 till about October. 



The interstitial cell picture undergoes but little change till 

 after hibernation, or until early in March in these particular 

 animals. There is a slight gradual decrease in pigmentation 

 due to a disappearance of some of the pigment granules in the 

 ordinary interstitial cells and probably a slight decrease in the 

 number of pigment cells, which usually become smaller and 

 somewhat more irregular. The weight of the testis by Novem- 

 ber or December has increased to about 0.034 per cent of the 

 reduced body weight. This increase is evidently due to a fill- 

 ing up of the tubules with spermatocytes, for as seen in figure 1, 

 which especially represents this stage, the tubules are gorged 

 with spermatocytes showing open karyokinetic figures. 



There is no sudden change in the testis with the onset of 

 hibernation as might be expected if the testis is an organ of 



