480 ANDREW T. RASMUSSEN 



of those reported by Hansemann. Although the seasonal changes 

 were not followed out any farther, he concluded that the inter- 

 stitial cells do not degenerate parallel with the germinal epithe- 

 lium during the retrogressive changes in the spermatogenic cycle. 



It is to be noted that in the mole the testes are abdominal 

 and situated beside the bladder in December; but with the in- 

 crease in size which occurs from January on and culminates in 

 March, the testes come to occupy two pouches beside the root of 

 the tail. Periodic changes in the size of testis are well known 

 in many species, having been observed as far back as the days 

 of Aristotle (Marshall, '11). The tendency for the testes to 

 enlarge and also to descend into a sessile scrotum during rut 

 in most rodents was mentioned by Owen ('68) fifty years ago. 

 The general subject of the descent of the testis cannot be dis- 

 cussed here. The excellent papers by Hart ('09) and Frankl 

 ('00) present this subject most admirably. 



Champy ('08) reported that in Rana esculenta spermato- 

 genesis is at its highest in July and at this time the intersti- 

 tial cells are at a minimum. In the autumn there is a great 

 increase in the interstitial cells and spermatogenesis is at its 

 lowest. This observation seems to be rather an exception to 

 what Friedmann and later Mazzetti report in other species of 

 frogs. However, in view of a lack of details, there may not be 

 as much disagreement as the bare statement above would indicate 

 at first sight, the breeding season being about two months later. 



Lecaillon ('09) in general confirms the observations of Regaud 

 on the mole both in regard to the change in size of the testis 

 and the relation of interstitial cell development to spermato- 

 genesis. He claims, however, that in July there is much degen- 

 eration in the interstitial cells and that this is responsible for a 

 large part of the decrease in the size of the testis at this time ; but 

 some of the interstitial cells persist throughout the entire year. 



Mazzetti ('11) in working with frogs (Rana fusca and Rana 

 viridis) found the seasonal changes in the interstitial cells to 

 be essentially as had already been described by Friedmann. 

 He Incideiitally states that interstitial cells are extraordinarily 

 abundant in hibernating snakjes but not in the 'ghiro.' 



