R. Pearl.Biology and Eugenics.5i
We may next consider in greater detail these factors influencing fecundity,
taking firstThe Anatomical Basis of Fecundity.
Since, as already pointed out, egg production obviously depends in part
upon the presence of ova in a normal ovary, a question which demands
consideration is the following:—
To what extent are observed variations in fecundity (i.e., in the number
of eggs laid) to be referred to anatomical differences. In other words does
the ovary of a high producing hen with, for example, a winter record of
from 75 to 115 eggs, contain a larger number of oocytes than does the
ovary of a hen which is a poor producer, laying no eggs in the winter
period and perhaps but 10 or 15 eggs in the year?
To get light upon this question the observations to be described have
been made. The object was to arrive at as accurate a relative judgment
as possible regarding the number of oocytes in the ovaries of different
individual birds. It is, of course, impossible practically to determine
accurately the total absolute number of oocytes in the ovary. What can be
done, however, is to count the number of oocytes which are visible to the
unaided eye. While such results do not tell us, nor enable us to estimate
with great accuracy, the total number of oocytes in the ovary, they do
nevertheless throw interesting and useful light on the questions raised above.
Some counts of this kind are shown in Table I.
Table I.
Showing the Number of Visible Oocytes in the Ovary of Certain Fowls.
Case No.Bird No.Breed.Winter Production.Total Visible
Oocytes.
I8021Barred Plymouth Rock31228
2801799 99 9901666
3803099 99 990914
4800599 99 9951174
5136799 99 9932306
6801899 99 9901194
7800999 99 9902101
8801099 99 9951576
942599 99 99 •••01521
103546White Leghorn542452
11206799 99323605
12345399 9901701
13383399 9902145
1452Cornish Indian Game131550
IS7iFi Cross ...........................1062000 E 2
