SEASONAL CHANGES IN INTERSTITIAL CELLS 481 



IMarshall ('11), from a study of fourteen hedgehogs, found no 

 spermatogenesis in this animal during winter, at which time the 

 sexual organs are small. Beginning about the end of March, 

 shorth^ after the close of the hibernating period and at the 

 approach of the rutting season, these organs enlarge, reaching 

 complete development in May. Spermatogenesis is going on 

 simultaneously and by the end of April free sperms are recog- 

 nizable. The testis does not, however, enlarge to the same 

 extent as in the mole. While the increase in the size of the 

 testis is due in part to an increase in the spermatogenic tissue, 

 a greater factor in the growth of this organ is the proliferation 

 of interstitial cells, which leaves the tubules widely separated 

 £rom each other, especially in the central part of the testis. 

 Large blood vessels apparetnly also develop in this interstitial 

 tissue. This condition persists till October, after which retro- 

 gression sets in, the interstitial cells largely disappear and with 

 them the blood vessels just mentioned. The tubules are thus 

 brought almost into contact and spermatogenesis is in abeyance. 

 There is little or no change till after hibernation when the 

 next rutting season begins. The female produces one litter in 

 May or June and another again in August or September. During 

 the period from about April till as late as October, the testes 

 are descended into sac-like continuations of the abdominal 

 cavity in the neighborhood of the perineum, where they may be 

 detected from the exterior. The author concludes that the simul- 

 taneous growth in the accessory generative organs, especially 

 noticeable in the case of the seminal vesicles, is probably due to 

 an internal secretion elaborated by the interstitial cells during 

 their period of increase. 



The most detailed description so far encountered in the lit- 

 erature on this subject is that given by Tandler and Grosz ('11) 

 who examined the testes of moles (Talpa europaea) sacrificed 

 at various times during more than two years so that every 

 month was represented in the series. They concluded that 

 rutting goes on during the month of March at which time the 

 testis has enlarged to about three times the usual diameter and 

 the tubules contain active spermatozoa. Similar changes occur 



