482 ANDREW T. RASMUSSEN 



in the epididymis and other genitals. The increase in the 

 size of the testis is due to development of the generative part 

 of the organ. Interstitial cells are present only as small islands. 

 The cytoplasm of the individual cell is homogeneous. At the 

 end of March when most of the sperms are gone, the interstitial 

 cells are still only minimal in quantity. As summer approaches 

 the whole testis and the tubules decrease, reaching their lowest 

 in July. The interstitial cells, however, increase till their indi- 

 vidual boundaries are nearly obliterated. The cytoplasm stains 

 more brilliantly with eosin. The nucleus, on the other hand, re- 

 mains about the same size; but the chromatin is less evident. By 

 July the tubules are separated from each other by masses of in- 

 terstitial cells whose cytoplasm is greatly vacuolated and whos^ 

 nuclei have lost their definite nuclear structure. From the end 

 of September and on, spermatogenesis advances again and the 

 interstitial cells slowly decrease so that by February, when 

 spermatozoa are nearly free, they are limited to a few scattered 

 individual cells. Thus when spermatogenesis is at its highest, 

 the interstitial cells are at their lowest, and vice versa. This 

 latter condition the authors compare to the foetal type as did 

 Regaud. They think that the increased interstitial cell growth 

 which occurs at the low ebb of spermatogenesis, has something 

 to do with the coming spermatogenic cycle. 



A few incidental statements made by Gushing and Goetsch 

 ('15) may be referred to here, since the observations concern 

 the woodchuck. The authors examined the testis of a woodchuck 

 killed March 22, having been captured a few days previously 

 (March 17, 1913). Judging from the weight of the animal 

 (2360 grams), the testis (1 cm. by 1.75 cm.) was enlarged as 

 compared with the testis during the autumn and winter. His- 

 tologically they found no spermatozoa but a few spermatids 

 and an abundance of interstitial cells. In another animal 

 killed January 12, 1914 — an animal which they were not positive 

 had hibernated — the testis showed active stages of spermato- 

 genesis but no spermatozoa. The interstitial cells were abun- 

 dant, but no statement is made as to how the interstitial cells 

 compared with those of the first animal examined. 



