436 HAYATO ARAI 
to discuss Kingery’s statement concerning the proliferation of the 
germ cells from the germinal epithelium in foetal life. However, 
in the ovaries of albino rats after birth the manner of the prolifer- 
ation of germ cells appears to be similar to that described by 
Kingery. In my case the oocytes from the germinal epithelium 
begin to form at about ten to fifteen days after birth. The nu- 
clei are large relatively to the cell body, nearly filling the cell, 
which begins to grow and enlarge in situ in the germinal epi- 
thelium. The shape of these cells is at first more or less spherical, 
and they are larger than the other epithelial cells. As they en- 
large, the adjacent epithelial cells are crowded to either side, and 
when the development of the egg cells proceeds further, they are 
enclosed by the flattened epithelial cells, thus forming the pri- 
mary follicle. 
At this time the layer of tunica albuginea appears to be single 
or double, but as the development proceeds the follicles pass 
through the tunica albuginea into the stroma. This new forma- 
tion continues with the growth of the ovaries, and the number of 
the follicles thus formed may reach its maximum at the period 
of puberty. | 
After puberty this process of new formation may yet con- 
tinue, but is not as active as before puberty. Within the first ten 
days after birth this proliferation of new egg cells eannot usually 
be seen. 
According to Kingery, in the mouse the cavity in the larger 
follicles begins to appear between fifteen and eighteen days after 
birth and a degeneration of the egg cells sets in at about the 
same time. In the albino rat the cavity in the large-sized fol- 
licles begins to appear at about twenty-days after birth, and at 
about twenty-six days the middle-sized degenerating follicles, 
according to my classification, are to be seen. 
Kingery stated that the formation of egg cells from epithelium 
is most rapid from three to twenty-five days after birth and that 
it goes on practically up to sexual maturity, although more slowly 
in the later part of this period. It is completed at forty or forty- 
five days after birth, at which age, as a rule, female mice are 
sexually mature. 
