248 R. R. HUMPHREY 



lobules of the posterior part of the testis by this time are 

 very much reduced in diameter; they stand out in osmic- 

 acid preparations, however, because of the large droplets of 

 fat they contain. Though the Sertoli cells within these lobules 

 have largely degenerated, some few of them are found in appar- 

 ently normal condition late in the spring. The connective- 

 tissue membrane which surrounds the emptied lobules does not 

 degenerate in Necturus, but persists, and within this the cysts or 

 groups of spermatogonia push toward the periphery. 



During the course of the growth changes, the interstitial cells 

 become closely compressed between lobules which contain rapidly 

 growing spermatogonia (figs. 15 and 16). They earher become so 

 numerous in the more caudal parts of the testis as to crowd closely 

 together, rendering less apparent their original epithelioid ring 

 arrangement around the lobules. Now, as illustrated by figure 15, 

 they become closely packed between lobules, fihing all those 

 spaces which were earlier occupied by the loose connective tissue. 

 The changes that follow are the reverse of those by which they 

 originated. Their cytoplasm decreases in quantity and its 

 fuchsinophile granules and lipoids gradually disappear, while the 

 nucleus changes from a spherical to a flattened form. The cells 

 thus, after a time, are no longer recognizable as interstitial cells; 

 but such a series of stages is present, often around a single lobule, 

 as to enable one readily to follow the transformation. The typi- 

 cal interstitial cells are of course at the periphery, while inter- 

 mediate types appear in regions which were but a short time 

 previously subjected to the pressure of the growing spermato- 

 gonia. 



Since an increase in the number of these cells by mitoses, as I 

 have already described, occurs preceding and during their modi- 

 fication, a compensating reduction of their numbers through cell 

 degenerations is to be expected. Degeneration figures,, in fact, 

 appear early in the fall in the caudal region among cells which 

 have attained their maximal enlargement. Degenerations may 

 be frequently observed during the winter months as well. In 

 the spring months, however, they become especially prominent. 

 The earlier degenerations were noticeable chiefly through the 



