THE SELECTION PROBLEM IN ANIMAL BREEDING 507 



egg production in the domestic fowl by Harris, Blakeslee and Warner. 

 This study dealt with the relationship between the concentration of 

 yellow pigment in the ear lobe of White Leghorn hens and their egg re- 

 cords of the preceding months. It was found that there is a very close 

 interdependence between October ear-lobe color and the egg production 

 of the pullet year. 



"Expressed in absolute instead of relative terms, the correlations 

 determined indicate that on an average birds differing by 5 per cent, in 

 the amount of yellow in the ear lobe will differ by about 7 eggs in their 

 annual production. Thus the difference is one of real practical signific- 

 ance. For example, birds showing only 10-20 per cent, of yellow in their 

 ear lobes in October will have laid on an average about 185 eggs each, 

 whereas birds exhibiting 55-65 per cent, of yellow will have an average 

 annual production of only about 130 eggs." 



These results prove that in the fowls used in this investigation color 

 of the ear lobe (and presumably, of the leg, beak and vent) would have 

 served as a practical index for selection of high layers. The authors 

 point out, however, that the flocks from which their data were obtained 

 represent a selected class of birds (in certain egg laying contests). "Such 

 birds show, because of better breeding, better feeding and care, or both, 

 a far higher annual egg production than the average flock. Unfortun- 

 ately data of the kind presented here are not as yet available for the 

 unselected class of layers." This correlation has long been known and 

 utilized by poultry breeders (according to Kent it was noted in published 

 form in 1879) and Blakeslee and Warner made earlier statistical studies 

 than the one we have considered. Both Kent and Warner point out that 

 degree of pigmentation is only one of several characters that may be 

 utilized in selecting high laying hens, the other more important ones being 

 time and duration of molting and size of abdomen. 



