SPERMATOGENESIS OF CANCER MAGISTER. 289 



wanders from its position within the cytoplasm to the periphery 

 of the cell and is soon expelled to the outside (Figs. 40-42), thus 

 playing no further role in the transformations. From now on all 

 the spermatids are exactly alike and they undergo the same 

 modifications. 



At about this time a densely staining mass makes its appear- 

 ance in the cytoplasm (Figs. 46 and 47, m). This mass has been 

 called a mitochondrial mass by Koltzoff ('06) and Binford ('13). 

 It stains like the chromatin of the nucleus, and first makes its 

 appearance at about the stage in the spermatid transformations 

 where the chromatin of the nucleus becomes reduced to two 

 clumps (Fig. 46). As to whether this mass consists of mitochon- 

 dria or not is a debated question. The fact of the matter is that 

 cytologists themselves are not clear as to which bodies within 

 the cell are mitochondria and which are not (see Cowdry, '16). 

 In the cells under consideration, no traces of mitochondria have 

 been observed in the earlier stages of the maturation. This 

 darkly-staining mass makes its appearance only after most of the 

 chromatin within the spermatid nucleus has been much reduced. 

 This would lead one to suspect that the mass might consist of 

 chromatin which has diffused out of the nucleus and has accumu- 

 lated within the cytoplasm (see Figs. 43-47). At any rate, this 

 seems a likely probability. 



The spermatids now reveal the following distinct structures, 

 (i) a rather homogeneous nucleus (Fig. 47, n), with a karyosome- 

 like body in the center, (2) a cytoplasm in which are found (3) 

 a centrosome (Fig. 47, c), and (4) a mitochondria-like mass 

 (Fig. 47, m), which stains like chromatin. These elements must 

 be clearly kept in mind in order to follow up the later changes of 

 the spermatids. In linking up these changes it is also necessary 

 to exercise great care. Sectioned material, while helpful, is by 

 itself wholly inadequate for this purpose. Smear preparations 

 of the entire cells, on the other hand, give a true picture of what 

 happens, and these were used almost entirely in the study of 

 transformations. 



The nucleus wanders to one pole of the spermatid (Figs. 

 48-50, n), while at the opposite pole a clear vacuole (Fig. 50, v), 



