CYTOPLASMIC JNCLUSIONS OF THE GEKM-CELLS. 587 
The Manner of Metamorphosis of an Indifferent 
Germinal Epithelial Cell into an Oogonium. 
It has been agreed almost unanimously among workers on 
the ovotestis that the presence of a group of yolk cells is the 
determining factor in the appearance of the female cell. I 
consider this explanation inadequate, for it can be shown that 
spermatogonia appear in regions choked with yolk cells, and 
oogonia may appear in regions where little or no yolk is present. 
I feel that it would be quite a mistake to entertain the view 
that a yolk cell exclusively determines the awakening of an 
indifferent cell into the egg generation. But it might be 
true to say that the presence of abundant yolk was the sine 
qua non for the successful growth of an oocyte to maturity. 
It would also be quite true to say that in the majority of cases 
the transition from an indifferent cell to an egg took place 
behind or between some yolk cells. Despite careful observa- 
tion of a large number of cases I find it difficult to formulate 
a statement of any differences between male and female 
nuclei till after the growth stage begins. This is not the case 
with the cytoplasm. The drawing in PI. 30, fig. 6, was 
thought by me to be an oogonium in contraction stage, firstly 
because it was so closely embedded behind yolk cells that its 
exit into the lumen would have been difficult, and secondly 
because the epithelium in this region was seen to be producing 
many oocytes. 
What I take to be the Nebenkern (N.K.) is very like that 
in the male cell drawn at a little later stage in PL 33, fig. 31, 
while the mitochondria are not very characteristic. The 
nucleus is unlike the male generation nucleus drawn in PI. 32, 
fig. 21, but almost identical with that drawn in PI. 33, fig. 30. 
Apropos of the statement that the spermatogonia appear in 
yolk regions compare Text-fig. 1, x, and especially Text- 
fig. 3, ii, at S.P.P. On the other hand, in an epithelium like 
that in Text-fig. 2, ii, a solitary oocyte may grow. This all 
shows that the matter is somewhat more complicated than at 
first supposed. Having shown that to the end of the pro- 
