NUMBER OF OVA: ALBINO RAT 453 
On the other hand, Sobotta (’06), from his study on the mouse, 
expressed the view that the persistence of the corpora lutea and 
their ultimate size are not altered by conception. 
In the present study we have examined four pregnant rats, 
and found that, as Loeb described, the corpora lutea in the preg- 
nant rats were larger than those in rats not pregnant. How- 
ever, the difference is slight. The completely formed corpora 
lutea at about ten days after conception, judging from the size of 
the fetus, are about 2.7 mm. in diameter. This size has dimin- 
ished to about 2.4 mm. in diameter about seventeen days after 
pregnancy, that is, in the later phase. 
So long as I did not collect the material with a view to studying 
the fate of corpora lutea, I am unable to discuss their age. If, 
however, we divide the entire population of corpora lutea into 
two groups, the larger and the smaller ones, it is possible to 
study the influence of these on the weight of ovaries. 
As is shown in tables 3, 6, 8, and 10, both the total number of 
the corpora lutea, as well as the number of small ones, show an 
unmistakable tendency to increase, despite great individual vari- 
ation, according to the age or other measurements of the rats. 
On the other hand, the number of corpora lutea of large size 
remains approximately constant. 
From these results we conclude that after puberty the accumu- 
lation of the smaller corpora lutea is mainly responsible for the 
increase in the weight of the ovaries with increasing age. 
The degeneration of the follicles 
So far I have simply stated the relation which exists between 
the total number of ova and of the degenerated follicles; but I 
now wish to consider these degenerated follicles in their relation 
to the corpora lutea. As has been mentioned already (table 13), 
the degenerated follicles are not found in the rat until about 
twenty-six days. The failure to find any degenerated follicles 
up to this time may be due partly to the extreme difficulty in 
recognizing them and partly to a possible resorption immediately 
after they are formed. However this may be, after twenty-six 
