BREEDING POULTRY FOR EGG PRODUCTION. 1 55 



fecundity, but the only way to tell whether o.r 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 char- 

 acter. In the second place a very considerable practical diffi- 

 culty 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 necessary to 

 deal with relatively large numbers of birds. Some of the im- 

 portant conditions to be observed in work on fecundity have 

 been discussed elsewhere * and need not be repeated here. 

 Turning now to the results we may consider first 



THE EFFliCT OE SELECTION FOR FECUNDITY IN THE GENERAL 



POPULATION. 



On the "statistico-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 ex- 

 pected, if the highest layers only were bred from in each gen- 

 eration, that the general flock average would steadily, if per- 

 haps 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- 

 tion. In this experiment only such females were used as breed- 

 ers as had laid over 150 eggs in their pullet year (correspond- 

 ing roughly to an average winter production of 45 or more 

 eggs) and the only males used were such as were out of birds 

 laying 200 or more eggs in the year. This experiment was con- 

 tinued until the end of 1908. The selection, be it understood, 

 was based on the egg record alone, and no account was kept of 

 pedigrees or of genotypes. Every female with a record higher 

 than 150 eggs in the year was used as a breeder regardless of 

 whether her high fecundity was genotypic or phgenotypic. 



The results of this selection experiment covering a pe/iod of 

 nine years have been fully reported elsewhere.* Here it needs 



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



* U. S. Dept. Agr. Bur. Anim. Tnd., Bnl. iio, Parts I and IT, tqoq and 

 191 1. Zcifschr. f. indnkt. Ahst. a. Vererh.-Lehre, Bd. 2, 1909, pp. 257-275. 



