448 HAYATO ARAI 
the ninth week, which probably corresponds to the age of puberty. 
Myers did not discuss the relation of this rapid growth to pu- 
berty. Thesuggestionisthat these various organs might be, some 
or all of them, related to the process of ovulation in the sense of 
forming stimulating substances causing ovulation, and it is my 
hope to make further studies along this line in the future. 
Corpora lutea 
I now wish to consider the relation between the first appear- 
ance of corpora lutea and puberty. 
For this purpose I have assembled the data from seventy-nine 
albino rats, ranging in age from thirty days up to about thirty- 
two months. For some of them the weights of the ovaries were 
not determined. 
As is shown in table 15, the corpora lutea first appear in a rat 
at sixty-one days, but after sixty-one days, though corpora lutea 
are present in most cases, they are not present in all. The ab- 
sence of the corpora lutea in the rats after sixty-one days is always 
associated with a body weight too small for the age, showing poor 
nutrition. The weights of the ovaries are also small. 
I have next rearranged some of the data, given in table 15, 
according to the body weights of rats, omitting those with body 
weights less than 75.5 grams and greater than 113.5 grams (table 
16). 
We notice the first appearance of the corpora lutea in the rats 
with a body weight of 78.5 grams, but they are not always present 
until the rats reach 100 grams in body weight. 
Beyond 100 grams we always find corpora lutea in ovaries. 
So far, then, as the body weight is concerned, the first appear- 
ance of the corpora lutea occurs at from 78.5 up to 100 grams. 
These body weights of 78.5 to 100 grams correspond to sixty-one 
and seventy-one days, respectively, as given in Donaldson’s table. 
Thus in my series the appearance of puberty approximately co- 
incides with the observation of Donaldson (715). From these 
data it appears that while puberty is attained as a rule between 
sixty-one to seventy-one days in rats that have grown approxi- 
