INTERSTITIAL CELLS OF URODELE TESTIS 259 



a centriole is seen; the peripheral cytoplasm appears less 

 dense and is occupied by lipoid droplets of larger size. Tn the 

 most caudal part of the ' testis' the rings of cells become reduced 

 in size and numerous degenerating nuclei appear; Indications 

 are that the degeneration and reversion of the interstitial cells 

 occupy a relatively short period, as in Diemyctylus. Champy 

 ('13) states that in the related form, Salamandra maculosa, the 

 interstitial cells are likewise temporary. The association of 

 interstitial cells with lobule degeneration and their absence from 

 other regions of the testis are as apparent in Salamandra as in 

 other urodeles. 



The testis of Cryptobranchus is essentially the same in struc- 

 ture as that of Necturus. The spermatogenetic wave, however, 

 passes over its entire extent miich more rapidly. In early 

 September, for example, the entire length of the testis is filled 

 with spermatozoa, though the caudal lobules may at that time 

 be beginning to emptj^ This condition is in decided contrast 

 with that in Desmognathus, Diemyctylus, and Salamandra, in 

 which the testis is markedly polar and the wave moves forward 

 over only a part of the organ during any one sexual cycle. 



During June, July, and early August the growth of the sperma- 

 tocytes, their maturation divisions, and the transformation of 

 the spermatids occur in rapid succession. During this period 

 the lobules are greatly distended, and, as in other urodeles, only 

 flattened nuclei appear between them. These are round or 

 broadly oval when seen in surface view, or of spindle form when 

 cut across, as they more frequently are seen. In late August 

 and early September, when the lobules are filled with sperma- 

 tozoa, occasional mitoses may be seen, even as at a similar period 

 or one slightly later they are common in Necturus. 



Developments after complete extrusion of the spermatozoa 

 have not been followed. Animals killed in early September 

 either showed no empty lobules or none sufficiently long emptied 

 for interstitial cells to have developed. These observations, 

 therefore, merely show that Cryptobranchus agrees with other 

 urodeles in lacking interstitial cells in association with the earlier 

 or progressive phases of its spermatogenetic cycle. 



