NUMBER OF OVA: ALBINO RAT 427 
If we compare the body lengths of the rats here employed 
with those for the standard values given by Donaldson (06), 
we obtain the following relations (table 9). 
This shows the larger rats to be short for their age—a relation 
which would naturally follow from those found in table 7 for the 
body weights. 
5. On the number of ova and the weight of the ovaries 
The numbers of ova have been arranged according to the ob- 
served weight of both ovaries, in order to examine the relation- 
ship between these two characters (table 10). For convenience 
the data on the weights of the ovaries were divided into two 
TABLE 9 
Relations of body length on age 
STANDARD AGE CORRESPONDING 
BODY LENGTH AVERAGED AVERAGE AGE a ici Se RO 
mm. days days 
47 1 0 
100 31 29 
147 85 61 
groups: @) the ovaries without corpora lutea and, b) the ovaries 
with corpora lutea. 
We find rather high individual variations in this relation, as 
indicated in table 2. However, table 10 shows that when the 
weight of the ovaries reaches from 1.8 to 2.2 mgm., the ova 40 
to 60 u in diameter are present, and in the ovaries of 2.4 to 5.6 
mgm. the ova with aid ameter of more than 60 w are found. It is 
again to be noted that the first corpora lutea are seen in ovaries 
which weigh 20 mgm., and therefore in the ovaries which weigh 
more than 20 mgm., the relation between the number of ova and 
the weight of ovaries becomes highly complex, owing to the ap- 
pearance of corpora lutea, the number and size of which are the 
most important factors in modifying the weight of the ovaries. 
We notice from chart 4—based on table 10—that the number 
of ova falls steadily up to an ovary weight of 6.5 mgm. ‘This is 
