No. 534] FECUNDITY IN THE DOMESTIC FOWL 325 



work was done, carried out before these investigations 

 were begun. 



In the second place it is desirable to call attention to 

 some of the difficulties which attend an attempt to analyze 

 the inheritance of the character egg production. The 

 most important of these is the fact that this char- 

 acter is not visibly or somatically expressed in the male. 

 A male bird may carry the genes of high fecundity, but 

 the only way to tell whether or not this is so is to breed 

 and rear daughters from him. All Mendelian workers 

 will agree that it is sometimes difficult enough to unravel 

 gametic complexities in the case of characters expressed 

 somatically. It is vastly more difficult when only one sex 

 visibly bears the character. In the second place a very 

 considerable practical difficulty arises from the fact that 

 egg production is influenced markedly by a whole series 

 of environmental circumstances. The greatest of care 

 is always necessary, if one is to get reliable results, to 

 insure that all birds shall be kept under uniform and 

 good conditions. Further, on this account, it is neces- 

 sary to deal with relatively large numbers of birds. 

 Some of the important conditions to be observed in work 

 on fecundity have been discussed elsewhere 6 and need 

 not be repeated here. 



Turning now to the results we may consider first 



The Effect of Selection for Fecundity in the 



General Population 

 On the "statistieo-ancestral" view of inheritance it 

 would be expected that if fecundity were inherited at all 

 this character would respond to continued selection. 

 That is, it would be expected, if the highest layers only 

 were bred from in each generation, that the general flock 

 average would steadily, if perhaps slowly, increase and 

 that any level reached would be at least maintained by 

 continued selection. In 1898 an experiment in selecting 

 for high egg production was begun at the Maine sta- 



' Me. Agr. Exp. Sta. Ann. Rept. for 1910, p. 100. 



