[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 oöcytes 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 L1, and L2).
2. High fecundity is manifested only when both of these factors are present together in the same individual.