INTERSTITIAL CELLS OF URODELE TESTIS 251 



laden cells in the connective tissue about the primary spermato- 

 gonia, where interstitial cells in the adult are never developed. 

 Such cells, however, were not seen in the others. In none of 

 these immature animals were interstitial cells found comparable 

 in position, size, numbers, and contents with these cells in the 

 adult. That testicular degenerations in still younger males may 

 give rise to such cells is not impossible, such cells then disappear- 

 ing as do the interstitial cells of adults. Examination of numer- 

 ous younger stages, such as have not been available for this 

 study, would be required to settle this point. Extensive sperma- 

 togonial degenerations, in one immature animal, had apparently 

 not resulted in interstitial-cell development. 



The interstitial cells of other urodeles 



a. Desmognathiis fusca. The presence of interstitial cells in 

 the testis of this urodele was recognized by Kingsbury and Hirsh 

 ('12), who, in their paper on the degenerations in the secondary 

 spermatogonia of Desmognathus, suggest the growth of the in- 

 terstitial cells as a possible factor in determining the inception of 

 such degeneration. No further mention of these cells in Desmog- 

 nathus has been encountered, 



Kingsbury and Hirsh outline the spermatogenetic cycle in 

 this Urodele as follows: It ''may be said to begin in the fall or 

 late summer after the extrusion from the testis of the spermatozoa 

 formed during that season. During the fall and winter months 

 there is a multiplication of spermatogonia and a tardy growth of 

 the spermatocytes I, , . , In the spring the growth of the 

 spermatocytes begins actively, characterizing particularly the 

 months of March, April, and May, while divisions of the sperma- 

 tocytes occur in May, June, and July, The transformation of 

 the spermatids into spermatozoa preponderates in August and 

 September." 



During the occupation of the lobules by spermatogonia, 

 spermatocytes, and spermatids there are, as under like conditions 

 in Necturus, no interstitial cells present between them. Flat- 

 tened nuclei, which, however, seem to be of more nearly a true 



