STUDIES ON GERM CELLS 455 



tion studied by Montgomery, twenty-five were found with a 

 rod and one hundred and seventeen without. That this ratio 

 is less than one to three (1:3) is explained by the fact that some 

 of the spermatogonia with rods may already have become Ser- 

 toli cells. The further history of the rod in the Sertoli cell is 

 as follows : A primary rodlet is produced by a splitting of the rod 

 (fig. 25, C) after which the rod either disappears at once or else 

 persists for a time, in which case it may split longitudinally as 

 shown in figure 25, D, R. However, in four-fifths of the cells 

 examined (one hundred in number) the large rod disappeared 

 before the growth of the SertoU cell had begun. Each primary 

 rodlet splits longitudinally into two approximately equal parts, 

 called secondary rodlets (fig. 25, D, r^), which persist until the 

 end of the cycle of the Sertoli cell. 



Neither Montgomery nor von Winiwarter was able to deter- 

 mine the origin of the rod. They do not consider it mitochondrial 

 in nature, although it may arise from granules lying in the cyto- 

 plasm. Montgomery found in one cell a mass of granules from 

 which the rod may have developed (fig. 25, A, X), and von 

 Winiwarter noted that the rod had a granular appearance in the 

 earliest stages he examined. It is also perfectly distinct from the 

 idiozome (see fig. 25, B, I) and is apparently not directly derived 

 from the nucleus. Von Winiwarter is not as certain as Mont- 

 gomery regarding the history of the spermatogonia, the 'cristal- 

 loide de Lubarsch,' and the 'gastonnets accessoires,' as he calls 

 the rodlets. He was unable to decide regarding the number of 

 spermatogonial divisions and believes it to be indeterminate. 

 He finds, contrary to Montgomery, the rod persisting in fully 

 developed Sertoli cells, and considers the fragmentation or fission 

 of the rod to form the primary rodlets as doubtful. Further 

 investigations with more favorable material are very desirable, 

 but notwithstanding certain differences of opinion between the 

 two writers whose results have been briefly stated above, it seems 

 certain that Sertoli cells and germ cells are both derived from 

 primordial germ cells, and that the Sertoli cells differ from the 

 ultimate spermatogonia in the possession of a peculiar rod prob- 

 ably of cytoplasmic origin. Montgomery considers this a sort 



JOURNAL OP MORPHOLOGY, VOL. 25, NO. 3 



