494 ANDREW T. RASMUSSBN 



these changes described in the hypophysis during hibernation 

 are simply the effects of the chronic inanition involved since 

 he finds similar changes in the hypophysis of the albino rat 

 subjected to inanition and ref ceding. 



The interstitial cells do not reach their maximum develop- 

 ment until the last of April when spermatogenesis is at its lowest. 

 Although many free spermatozoa may remain in the tubules 

 as late as this, the epithelium has been reduced to a single layer 

 of cells and thus a wide empty lumen results. The new sper- 

 matogenic cycle may be considered to date from the last of April 

 or early May, since spermatogonia begin to increase from this 

 time on. 



The interstitial cells remain at their height of development 

 until as late as July, or for at least two months after the end 

 of the corresponding spermatogenic cycle. These dates will, 

 of course, vary somewhat from year to year. 



During this time when the interstitial cells are enormously 

 enlarged, from about April to June — a period during which 

 the testes usually are scrotal — the testis represents from 0.078 

 per cent to 0.132 per cent of the reduced body weight. The 

 tubules are forced far apart as will be seen in figure 15, or still 

 better in figure 19, which is at a lower magnification and is 

 intended to show an especially large compact node of highly 

 vacuolated interstitial cells at the point marked with a +. In 

 the center of this mass the boundaries of the individual cells 

 are not evident and so gives the appearance of numerous nuclei 

 entangled in an open network. Such nodules were found in two 

 of the eight cases representing this stage. Several smaller 

 areas of this sort may be encountered in a single cross section. 

 The vacuoles are filled in life with fatty globules. 



As mentioned above, half of the woodchucks killed during 

 this stage showed the 'nest' arrangement of many and in one 

 Case practically all of the interstitial cells as seen in figure 

 10. This grouping was first described by Nussbaum ('80) as 

 the typical arrangement. Each group of cells seems to be sur- 

 rounded by an epithehal sheath of flat cells and the individual 

 cell boundaries are very indistinct. Ganfini ('03) states that 



