NUMBER OF OVA: ALBINO RAT 439 
From these references we see how diverse are the opinions re- 
garding the new formation of the oocytes; Van Beneden, Lane- 
Claypon, Winiwarter and Sainmont believing in a new formation 
of ova after birth in some mammals, and Van der Stricht con- 
sidering the definitive ova to be developed from the second pro- 
liferation of the germinal epithelium, meaning probably a new 
formation of ova after birth. On the other hand, Kingsbury 
and Felix find no evidence of the new formation after birth. 
Lastly, Kingery concludes after birth that a new formation of 
ova occurs from the germinal epithelium and these in turn form 
the definitive ova. 
As far as my observations go, the new formation of germ cells 
from the germinal epithelium occurs at ten to fifteen days 
after birth, and this new formation is much more active in the 
period from fifteen to sixty days—i.e., up to puberty—but after 
puberty the process becomes slow, differing from that found in 
the mouse. 
Thus my own observations on the rat agree with the observa- 
tion of Kingery that there is a new formation of the germ cells 
from which the definitive ova originate. 
In chart 2 the total number of ova, which include the soe 
germ cells, formed in embryonic life, and the definitive ova, so- 
called second postnatal proliferation of the germ cells from the 
germinal epithelium, are shown, but it would be impossible to de- 
termine the relative number of the primitive germ cells and the 
definitive ova, owing to the lack of structural characters differ- 
entiating these two kinds of ova, at a glance, while counting. 
In chart 2 also two characteristic features are shown between 
four and sixty-three days, and I have attempted to interpret 
these in the following way: 
From four days after birth the total number of ova decreases 
very rapidly up to twenty-three days. This rapid decrease is 
probably due to the degeneration and resorption of the primi- 
tive germ cells. But even during this period of rapid fall the 
formation of the new germ cells is going on since these are found 
from ten days of age. However, on account of the much greater 
number of the degenerating cells, the graph inevitably shows arapid 
