Full text: papers communicated to the first International Eugenics Congress held at the University of London, July 24th to 30th, 1912

56Section I.R. Pearl. 
From the data set forth in the above table there can be no doubt as to the 
fact of the Mendelian segregation of fecundity, nor as to the entire 
distinctness of the things segregated. 
In order to give a general survey of the results, and to demonstrate 
the reality of segregation over the wide range of material included in the 
experiments, the summary Table III. is presented. 
Table III. 
Showing the Observed and Expected Distributions in Res feet of Fecundity 
of the Adult Female Offspring from all Matings in each of the Classes 
Tested in the experiments. 
Winter Production of Daughters. 
Class.Over 30.Under 30.Zero. 
All Barred Plymouth Rock xObserved3654259431 
Barred Ply. RockExpected38*'45257'2517-30 
All Cornish Ind. Game x CornishObserved22315 
Ind. GameExpected025*5 
All F1 (B. P. R. x C. I. G. andObserved36798 
reciprocal cross)Expected26586-759-75 
All F2 (Fx x F15 and Fj x parentObserved57498423 
forms in all possible com­ 
binations)Expected68 6095'0015 '40 
Considering the nature of the material and the character dealt with the 
agreement shown between observation and hypothesis is certainly as close 
as could reasonably be expected. Such discrepancies as are shown in the 
above table are fully discussed and their probable physiological explanations 
set forth in detail in the complete account of these experiments. 
The detailed data given in the complete paper, of which the above 
discussion and tables give merely a very incomplete abstract, appear 
definitely to establish the following points:— 
1. That fecundity, in the domestic fowl, is inherited strictly in 
accordance with Mendelian principles. 
2. That observed individual variations in fecundity here depend upon 
two separately inherited physiological factors, Lx and L2. 
3. That high fecundity is manifested only when both of these factors 
are present together in the same individual.
        

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