DEGENERATIONS, DESMOGNATHUS 233 



occupy ill this form a distinct place in the spermatogenetic cycle. 

 Their occurrence, in fact, is so closely associated with the annual 

 spermatogenetic cycle and with the 'polarity' of the testis in 

 Desmognathus that a brief description may be introduced, even 

 at the expense of essential repetition of descriptions which have 

 been previously published (Kingsbury, '02). 



The spermatogenetic cycle in Desmognathus 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 the sperma- 

 togonia and a tardy growth of the spermatocytes I, which in 

 midwinter seems practically suspended. Some spermatocytes 

 undergo division but the maturation divisions appear to be often 

 abnormal and the resulting cells to degenerate. In the spring 

 the multiplication of the spermatogonia and 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. 



In the late spring or early summer, transformation of the ' last 

 generation' of spermatogonia stops, no more spermatocytes 

 beginning their period of growth, until fall, and it is after this 

 time, when the growth of new spermatocytes has ceased, that the 

 degenerations in question occur. The cells undergoing degenera- 

 tion have been spoken of as secondary spermatogonia of the last 

 generation although, since they come intermediate between the 

 spermatocytes I and the secondary spermatogonia, they might, 

 perhaps, be equally as well designated as young spermatocytes I. 



The following out of the sequence of stages in the spermato- 

 genesis of Desmognathus is facilitated by the marked polarity 

 of the organ in this form. This polarity seems to be rather charac- 

 teristic of many at least of the tailed amphibia (Meves, McGregor, 

 Kingsbury, etc.) and particularly perhaps of the smaller or more 

 elongated ones. The changes of spermatogenesis proceed as a 

 ' wave' in a cephalo-caudal direction so that at the proper season 



JOURNAL OF MOnPHOLOGY, VOL. 23, NO. 2 



