378 K. MASUI: 
with sublimate) were chiefly used, but only the former two gave satisfactory 
results. 
The sections were cut 5—10 in thickness. For the staining HEIDEN- 
HAIN’S iron-haematoxylin and FLEMMING’s triple stain were used, and for the 
staining of the nucleolus ZIMMERMANN’S method (iodine green, fuchsin). 
Smeared preparations were also used which were stained with the same 
stains as those for the sections. 
Tn the testes of adult animals various stages of germ cells could be seen 
in a single section, but mitotic figures were rarely found. Therefore for the 
studies of the reduction division and the mitosis of the spermatogonia, testes 
of young individuals were chiefly used. In quite young animals amitotic 
divisions of the spermatogonia frequently occur while the mitotic divisions are 
rare. 
The author wishes to express his hearty thanks to Prof. IsHIkAwA to 
whom he is greatly indebted for much valuable advice given him during 
the study. Thanks are also due to Prof. Yarsu of the Science College who 
kindly lent the necessary literature on the subject. 
I. The Amitotic Division of the Spermatogonia. 
The amitotic division of the spermatogonia in the earliest generation is 
very frequently found in the testes of embryos and of quite young animals (Fig. 
2). In the testes of such animals, some of the cells of the wall of the tubule 
are seen to grow rapidly in size, becoming about two or three times as large 
as they were at the beginning of this stage (Figs. 1, 3). Subsequently they 
fall into the lumen of the tubule (Fig. 1). Their nuclear organization and 
their cytoplasmic structure are quite similar to those of the spermatogonia 
found in the testes of adult animals (Figs. 1, 2, 31, 32). The nucleus is 
relatively large compared with the amount of cytoplasm, and the chromatin 
granules are scattered throughout the nucleus (Figs. 2, 4). The nucleoli 
usually appear round in shape, in most cases they number only one but 
sometimes two or three (Figs. 4 to 6). These cells are the spermatogonia in 
the earliest generation. 
The cell increases steadily in size and the shape of the nucleus becomes 
