DAVIS: SPERMATOGENESIS. 67 



or in some cases two, small, rounded plasmosomes, which are usually 

 stained with the Bordeaux red. However, if the preparations are not 

 strongly decolorized the plasmosomes may retain the iron hsematoxylin. 



As stated above, the cvtoplasm is especially abundant on one side of 

 the cell, and in this region there can be distinguished a rather diffuse 

 very finely granular material, staining more deeply with Bordeaux 

 than the surrounding cytoplasm. This apparently corresponds to 

 the mitochondrion of Benda. 



The jirimary spermatogonia divide exclusively by mitotic division, 

 the process being the same as in the secondary spermatogonia, where 

 it will be described in detail. 



The arrangement of the primary spermatogonia is characteristic. 

 They are always grouped in' a single layer about a peculiar cell 

 located at the distal end of the follicle. This cell appears to be 

 homologous with the apical, or Verson's cell described by a number of 

 investigators in the testes of various insects. There is always one of 

 these cells in each follicle, and it is surrounded on all sides by a layer 

 of primary spermatogonia so arranged that the sides containing the 

 most cytoplasm and the mitochondrion are in contact with it. The 

 apical cell (Fig. 1) is usually larger than the primary spermato- 

 gonia, irregularly polygonal and sometimes sends out short proc- 

 esses between the surrounding spermatogonia. Within the cell is 

 a large, eccentrically located nucleus, through which the chromatin 

 is distributed in flocculent masses. These masses are composed 

 largely of a chromatic material or linin in which fine chromatic gran- 

 ules are embedded. The linin also extends through the nucleus in 

 somewhat coarse strands connecting the chromatic masses with each 

 other and with the nuclear membrane. Suspended in the nuclear 

 network are several irregularly shaped plasmosomes, which appar- 

 ently are simply masses of linin. 



Directly surrounding the nucleus the c^ioplasm contains a large 

 cjuantity of a more or less distinctly granular material staining with the 

 plasma stain. This material is especially abundant on one side of 

 the nucleus, but extends as a thin layer almost entirely around it. 

 In this finely granular mass there are usually large numbers of larger, 

 rounded granules staining deeply with iron hematoxylin. In some 

 cases these granules are very abundant, while in others they may be 

 almost entirely absent. A careful study of a large number of these 

 cells has shown that there are all transitions between the two extremes, 

 and that the finely granular material is probably derived from larger 

 deeply staining granules, which gradually lose their affinity for hema- 

 toxylin and break down into very fine granules. 



