NUMBER OF OVA: ALBINO RAT 423 
3. On the number of ova in relation to body weight 
The data on the number of ova have been arranged according 
to the increasing body weight and the results are shown in table 6 
and chart 3. In order to eliminate the individual fluctuations as 
much as possible, I have averaged the data which belong to the 
rats whose body weights differ not more than 10 grams from one 
another. From this table the pregnant rats have been omitted, 
because the weight of the foetuses was not recorded and conse- 
quently the true body weight of these pregnant rats cannot be 
accurately estimated. When these average values are plotted, 
we obtain the graph shown in chart 3. 
It is evident from table 6 and chart 3 that the total number 
of ova decreases rapidly from 5.5 grams—one day after birth— 
until about 33 grams, and then after remaining at about the same 
value till 64 grams, decreases again gradually up to 238 grams. 
The corpora lutea appeared first in the ovary of a rat with a 
body weight of 102 grams, and all rats which ‘possessed a body 
weight heavier than 102 grams invariably showed corpora lutea. 
The general form of the graph shown in chart 2 is as a whole 
similar to that shown in chart 3. 
The graph showing the number of ova with diameters less than 
20 uw is approximately similar to the graph which shows the vari- 
~ ation of the total number, but the latter graph only has been 
drawn. The graph showing the number of ova in the three 
groups having diameters 20 to 40 yu, 40 to 60 uw, and over 60 py are 
quite similar to the corresponding graphs based on age (chart 2) 
and do not call for special comments. 
The number of the large corpora lutea is nearly the same 15 to 
14 at 102 to 122 grams, but increases to a maximum (29), and 
then after 142 grams falls off slightly. Similarly, the number of 
smaller corpora is at first nearly constant, but increases markedly 
toward the end of the series (chart 3). 
When we compare these graphs for the number of ova accord- 
ing to body weight (chart 3) with those according to age (chart 
2), we find a slight difference in their form. At twenty-three 
days we find in table 3 a body weight of 26.9 grams and at sixty- 
