NUMBER OF OVA: ALBINO RAT 441 
ripening may undergo degeneration and be resorbed. From 
thirty days on the proliferated definitive ova are added to the 
primitive germ cells which-are already present, and thus the 
definitive ova are very few at first, but increase rapidly concom- 
itantly with the degeneration of the primitive germ-cells. This 
process maintains an approximately constant number of the 
larger oocytes, and this continues with more or less fluctuation 
up to 947 days. 
The effect of pregnancy on the total number of ova is given in 
table 4, but the number of instances is too small to furnish a 
basis for any general statement. 
Stratz (98) considers that during pregnancy there are small 
follicles which become atretic before they can develop, and only 
toward the end of pregnancy the follicles begin to grow to a 
considerable size and come to maturity. On the other hand, 
Loeb (’11) maintains that while some of the large follicles degen- 
erate, the small, medium, and some of the large follicles also 
remain without degeneration in the last days of pregnancy. 
According to my own observations, the condition of the folli- 
cles as a whole agrees with part of the statements given by the 
two authors mentioned above, though differing in detail. Dur- 
ing pregnancy in young rats the small follicles are few compared 
with the medium and large follicles. In the later stages of preg- 
nancy in older rats the relative number of small follicles increases 
considerably (table 4), while the numbers of the medium and 
large-sized follicles are considerably reduced when compared 
with those found in non-pregnant rats of about the same age. 
We infer from these facts that in pregnancy in older rats the 
majority of the medium and large-sized follicles have degener- 
ated. However, this statement is based on a limited number of 
cases, and, in addition, cytological studies on the cells were not 
made, so that no great emphasis can be put on the conclusion. 
It is my hope to continue the study on these problems in the 
future. 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 27, NO 4 
