358 K. MASUI: 
and ZENKER’s mixture. Of these, both FLEmMMING’s and Bovm’s fluid gave 
satisfactory results, while the mitochondria were beautifully brought out by 
Cuampy’s fluid. The sections were cut 5—10 x in thickness. For staining 
HEIDENHAIN’S iron-haematoxylin, DELAFIELD’s haematoxylin and FLEMMING’s 
triple stain (safranin, gentiana violet and orange G) were chiefly used. For 
the staining of the mitochondria a modification of Brnpa’s method was 
employed, but no precise differentiation was obtained, while HEIDENHAIN’S 
iron-haematoxylin stained them distinctly, when the preparations were previous- 
ly treated with Cxampy’s fluid. To differentiate the chromosome nucleolus 
Ogst’s method was employed, but did not give satisfactory results. 
The development of the tubules of the testis is quite different at different 
ages of the animals. In very young animals, spermatogonial cells in various 
stages and many Sertoli-cells are found along the wall of the tubule (Fig. 1). 
In animals a little older (Figs. 2, 3) the tubules usually contain spermato- 
gonia, young spermatocytes and Sertoli-cells. In mature animals, a few 
spermatogonia and Sertoli-cells are found along the wall of the tubules ; 
next to these the spermatocytes in various stages, the spermatids and the 
unripe spermatozoa appear (Figs. 5, 6). Toward the center of the tubule 
some ripe spermatozoa are found. 
II. The Spermatogonia. 
In the testes of adult individuals we can distinguish two generations of 
spermatogonia, a primary and a secondary (Figs..7, 8, 11, 12). The primary 
spermatogonia (penultimate spermatogonia) are more abundant in the im- 
mature testes of young individuals (Fig. 1). Their nuclear organization and 
their cytoplasmic structure are similar to those of the secondary spermatogonia 
(ultimate spermatogonia), but larger and less in number in comparison with 
the secondary spermatogonia (Figs. 7, 12). The resting nucleus of both 
spermatogonial generations usually contains one large nucleolus and several 
small chromatin masses (Karyosomes) (Figs. 7, 8). 
The earlier generation of the nutritive cells (Sertoli-cells), as shown in 
Fig. 1, is similar to the resting spermatogonia, but the latter contain many 
. chromatin granules. 
