252 R. R. HUMPHREY 



spindle shape, may be seen as in Necturus; little or no lipoid 

 appears between lobules even at times when there is much of it 

 within them. Pigment commonly occurs, but apparently in 

 extensions of the branched chromatophores rather than in relation 

 to the interlobular nuclei of ordinary flattened or spindle type. 



In August or September the spermatozoa of the most caudal 

 lobules become mature and begin to leave the testis. The lobules 

 become reduced in size; the cells surrounding them now appear 

 larger, less flattened, and more numerous (fig. 21). Though 

 shrinkage of the lobule brings nuclei closer together and thus 

 causes an apparent increase in their numbers, an actual increase 

 takes place as well, for mitotic figures may frequently be seen 

 at this time. 



As described by Kingsbury and Hirsh, a number of lobules in 

 the cephalic end of the testis degenerate during the summer; 

 this region marks the 'boundary plane' up to which the lobules 

 mature and discharge their spermatozoa during the current 

 season. Figures 6 and 21 indicate the location of this 'boundary 

 plane.' Cephalad of this the germ cells are held over for develop- 

 ment in the succeeding season. The lobules caudad of the 

 'boundary plane' usually are all free from spermatozoa by 

 February or March, as indicated by figure 6 D, only a very few 

 of the most cephalic, indeed, not being emptied by December 

 (fig. 6 C). The enlarged region filled with spermatozoa which 

 is seen posterior to the 'boundary plane' in September (fig. 

 6 B) appears in the following winter and spring as a greatly 

 shrunken region now only a third to a half the diameter of that 

 part of the testis anterior to it. This shrunken region is filled 

 with degenerating lobules, each of which is surrounded by its 

 greatly thickened sheath of enlarged stromal cells, now with the 

 usual characteristics of interstitial cells. Lipoid droplets are 

 numerous in their cytoplasm, the eccentric nuclei are oval or 

 rounded, and the cells are of an irregular polyhedral type, tending, 

 however, to remain somewhat elongated. At one side of the 

 nucleus is a more or less rounded mass of cytoplasm surrounded 

 by small granules; this contains the centrioles and appears quite 

 similar to the enlarged centrospheres seen in the interstitial cells 



