152 R. R. HUMPHREY. 



these germ cells do not interfere with the increase of sperma- 

 togonia at the central apex of the lobule. In early fall, con- 

 sequently, spermatogonia are more abundant and farther 

 advanced in development here than in the body of the testis. 

 \Yith the extrusion of the spermatozoa from the latter region, and 

 its consequent reduction in size, the distinction between body and 

 appendage is obliterated, as in Plethodon. 



The caudal part of the testis, in October and November, 

 always contains spermatocytes in the growth period. Just as 

 in Plethodon the germ cells of this region precede in development 

 those of more anterior lobules. In Gyrinophilus, however, the 

 spermatocytes do not begin their maturation divisions in the fall. 

 No spermatids appear in a specimen killed on November 19. In 

 Plethodon glutinosus the caudal fourth of the testis may contain 

 spermatids as early as November I . 



How, then, does the appendage of Gyrinophilus arise? No 

 spermatids are formed in autumn, to degenerate during the 

 winter as in Plethodon. Nevertheless the appendage is of almost 

 as constant occurrence in one species as in the other. A clue to 

 its origin in Gyrinophilus is furnished by specimens killed in late 

 March. In these the testis is already greatly reduced in diameter 

 at its posterior end. Here the lobules contain, in addition to 

 their apical spermatogonia, only a very few primary sperma- 

 tocytes. The majority of these latter cells have completely 

 disappeared ; the peripheral portions of the lobules they occupied 

 are now greatly reduced in size and contain only a syncytium of 

 Sertoli cells. Toward the body of the testis, however, the 

 diameter of the appendage increases. Lobules in this region 

 show within the syncytium of Sertoli cells, traces of cell debris and 

 cells far advanced in degeneration. Still farther forward, in 

 lobules of approximately the normal size, the earlier stages of this 

 cell degeneration are to be encountered. Here one finds all 

 intermediate conditions between the small, densely-staining 

 masses characteristic of karyolytic cells in advanced stages, and 

 primary spermatocytes in which the first indication of degenera- 

 tion is to be seen in a slight contraction of the nucleus and a 

 massing of its chromosomes. Degeneration seems to begin when 

 the spermatocytes are in the midst of their growth period, with 

 the chromosomes already well-defined and definitely oriented 



