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 hematoxylin. 
As stated above, the cytoplasm 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 primary 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 Versen’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 cytoplasm contains a large 
quantity of a more or less distinctly granular material staining with the 
plasma stain. ‘lhis 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. 
