422 HAYATO ARAI 
ovigerus is well developed. These follicles contain ripe ova, 
whose diameter is usually 60 to 66 wu. Sometimes we observe a 
very large ovum with a diameter of 76 u or more, but such an 
ovum may be in an early stage of degeneration, because both the 
nucleus and cell body are not well stained, as in the case in the 
normally ripened ovum. 
The numbers of the mature follicles and of largest ova in both 
ovaries are given in table 5. 
As is shown in table 5, the number of the mature follicles is 
not strictly proportional to the number of the largest ova with 
TABLE 5 
The numbers of maton follicles and of largest ova in both ovaries 
ee  Mideoms ) | (Seamen on |S dee 0 wanes | | eee 
days daus 
46 15 60 140! 22 62 
64 34 66 150! 26 42 
641 39 47 198! 16 18 
80? 38 145 206? 12 32 
80 23 42 262? 15 15 
100 2A 39 318? 18 29 
100 16 24 385? 9 18 
110 23 41 559? 13 20 
110! 25 46 947} 19 21 
1 Shows presence of corpora lutea. 
2 Stands for pregnancy. 
a diameter of 60 u and more. Nevertheless, if we consider the 
data from forty-six to one hundred days the number of largest 
ova are a little more than twice as numerous as the mature fol- 
licles, while in the remainder of the table they are a little less 
than twice. Thus there is a tendency for the proportion of 
largest ova to slightly diminish with age. 
We notice also that in the rat from sixty-four to eighty days the 
number of mature follicles ranges from thirty-one to thirty-nine, 
and this large number of follicles may be related to the attain- 
ment of sexual maturity, since after eighty days the number of 
follicles tends to decrease. ‘The mean number of these mature 
follicles in all eighteen cases is twenty-one. 
