8Section I.R. Pearl’
where the new being is organised. Now, this contest does not take
place en bloc, so to speak, as has been generally admitted. Each of
the characters of the two parents struggles on its own account against
the corresponding character (its antagonist, as has just been said).
When the hereditary energy is equal on both sides there necessarily
ensues a kind of process of which the consequence is the fusion of the
maternal and paternal characters in an intermediate character. If the
energies are very unequal the hybrid inherits a character borrowed
entirely from one of his parents; but this parent, conqueror on one
point, may be conquered upon another. Hence, there results with the
hybrid a juxtaposition of characters derived from each of the types of
which he is the child.”
Above all, I have wished to call attention to the so-called laws of domin
ance, because of their great importance. We may conclude that in the case
of man the dominant characters are also the original ones.
THE INHERITANCE OF FECUNDITY.
(Abstract.)
By Raymond Pearl,
Biologist, Maine Agricultural Experiment Station.
The purpose of this paper is to give an account (necessarily abbreviated,
and without presentation of complete evidence) of the results of an
investigation into the mode of inheritance of fecundity in the domestic fowl,
and to point out some of the possible eugenic bearings of these results.
It is shown that while the continued selection, over a period of years,
of highly fecund females failed to bring about any change in average
fecundity of the strain used, this character must nevertheless be inherited
since pedigree lines have been isolated which uniformly breed true to definite
degrees of fecundity.
It is further shown that observed variations in actually realized fecundity
(number of eggs laid) do not depend upon anatomical differences in respect
to the number of visible oocytes in the ovary. The differential factor on
which the variations in fecundity depend must be primarily physiological.
Fecundity in the fowl is shown to be inherited in strict accord with the
following Mendelian plan :—
1. Observed individual variations in fecundity depend essentially upon
two separately inherited physiological factors (designated Lx and L2).
2. High fecundity is manifested only when both of these factors are
present together in the same individual.
