INTERSTITIAL CELLS OF URODELE TESTIS 257 



persists even after the interstitial cells have largely degenerated 

 or undergone reversion. That scattered interstitial cells and 

 such traces of degenerated lobules appear in the testis in Novem- 

 ber and December is indicative of the short time required for 

 the completion of lobule degeneration and the disappearance 

 of the interstitial cells. Two animals killed in January and 

 February show comparatively few interstitial cells present, 

 though in all probability they had been numerous earlier in the 

 winter. There is never a definite, elongated, shrunken, caudal 

 region occupied by interstitial cells and degenerating lobules as 

 in Desmognathnis. 



The emptying of the remaining lobules of spermatozoa during 

 the spring mating period is followed by lobule degeneration 

 and interstitial cell development as in the autumn. Usually 

 the larger number of lobules empty and degenerate in the spring, 

 making the picture a trifle more striking. As in the autumn, 

 the disappearance of lobule and interstitial cells is rapid. An 

 animal killed June 30th had traces of but one or two degenerated 

 lobules still distinguishable and a few scattered interstitial cells; 

 this perhaps represents the extreme of early disappearance. In 

 an animal killed in early August no interstitial cells or degen- 

 erating lobules could be found. 



My study on this form has not included cytological detail of 

 the cells; they resemble those of Desmognathus, though tending, 

 perhaps to possess a greater number of lipoid droplets. The cell 

 form is irregularly polyhedral; the eccentric nucleus is usually 

 somewhat oval; centrospheres have been seen, but not in the 

 enlarged condition noted in Necturus. Mitoses were not ob- 

 served, though an increase in the number of the cells is apparent 

 and suggests their multiplication as observed in Desmognathus, 

 Necturus, Salamandra atra, and Cryptobranchus. 



It is apparent, I believe, without further description, that in 

 Diemyctylus the interstitial cells as in other urodeles are closely 

 related to lobule degeneration. Their early disappearance is of 

 course in decided contrast with their longer cycle in Desmogna- 

 thus. Such a difference, however, only shows more clearly that 

 they have no functional relation to the progressive phases of 



