220 



RAYMOND PEARL 



TABLE 26 



Showing the results in respect to fecundity of daughtefs from pure Barred Rock rnat- 

 ings in which the families were too small in size or number to permit classifica- 

 tion as to gametic constitution 



It will be seen from this table that these families had on the 

 average fewer than two adult daughters each, too small a number 

 with which to work. This makes clear again the difficulty with 

 which one has always to contend in practice in work with fecun- 

 dity, namely that of getting even reasonably large families of 

 normal adult daughters. One hatches a large number of chicks 

 in order to supply thieves, crows, rats, hawks, etc., and finally 

 get a small number of adult females available for the study of 

 fecundity. Fecundity in fowls is not, as has been pointed out 

 before, in all respects an ideal character for the investigation of the 

 laws of inheritance. 



Summary of results of all pure Barred Rock matings 



The data presented in detail in this section of the paper, which 

 deals with the matings of Barred Plymouth Rock males and 

 females inter se, wquld appear to demonstrate the following 

 points. 



1. That there is a definite and clean-cut segregation (in the 

 Mendelian sense) of high fecundity and low fecundity, the char- 

 acter 'fecundity' being here measured by winter egg production. 

 The mode of inheritance is such as to indicate that winter egg 



