GERM CELLS IN THE ARTHROPODA 133 



Montgomery found in one cell a mass of granules 

 from which the rod may have developed (Fig. 41, A, 

 X), and von Winiwarter noted that the rod had a 

 granular appearance in the earliest stages he ex- 

 amined. It is also perfectly distinct from the io- 

 zome (see Fig. 41, B, I) and is apparently not 

 directly derived from the nucleus. Von Winiwarter 

 is not so certain as Montgomery regarding the history 

 of the spermatogonia, the " cristalloide de Lubarsche," 

 and the " batonnets 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 Mont- 

 gomery, 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 cer- 

 tain 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 probably of cytoplasmic 

 origin. Montgomery considers this a sort of secon- 

 dary somatic differentiation (the Sertoli cells repre- 

 senting the soma of the testis) ; the first somatic dif- 

 ferentiation occurring when the tissue cells become 

 differentiated from the germ cells in the embryo. 



AMITOSIS. Wilson (1900) defines amitosis as 

 " mass-division of the nuclear substance without 



