# Page:Popular Science Monthly Volume 81.djvu/377

371
THE INHERITANCE OF FECUNDITY

which carry the excess production factor ${\displaystyle L_{2}}$ are heterozygous in respect to it.

We have fecundity practically determined, then, by two physiological factors, one of which is sex-correlated in its inheritance and the ether not.

Table II

Showing Some Results of Mating Together Barred Plymouth Bock Males and Barred Plymouth Rock Females of Different Fecundity Genotypes.
Summarized Data
[1]

The accordance between observed fact and theoretical expectation on this interpretation of the results is shown in the following tables

1. The records of 12 refer to birds whose winter production record was exactly 30 eggs. Each one of the few birds of this sort is divided between the "Over 30" and the "Under 30" classes.