322 



THE AMERICAN NATURALIST 



[Vol. LV 



lusian males, though no attempt was made to isolate and 

 identify them. 



Since these blue Leghorns arose in an unpedigreed 

 flock, their origin is conjectural. A plausible explana- 

 tion seems to be that two individuals heterozygous for /, 

 the dominant Leghorn factor described by Hadley (1913), 

 which inhibits the production of pigment shown (also by 

 Hadley, 1914) to be normally present in the white Leg- 

 horn, happened to mate and that at least one of them 

 carried the factor .R as a cryptomere. That white Leg- 

 horns may sometimes carry the factor seems to be shown 

 by the fact that Dryden (1916, p. 67) secured blue chicks 

 in an generation from a barred Plymouth Rock X white 

 Leghorn cross. And further, in the course of the breeding 

 operations reported in this paper, blues appeared in the 

 progeny of a black Andalusian and a white crossbred, the 

 latter being the product of a black Andalusian X white 

 Leghorn cross. In both cases it appears that the factor 

 R must have been brought in by the white Leghorn. This 

 suggestion also involves the assumption that the white 

 Leghorn carries the factor E. That this is the case is 

 shown by the fact that in the from a blue-splashed 

 Andalusian X white Leghorn cross, the details of which 

 are reserved for later publication, both blacks and blues 

 appeared. 



XIII. The Problem op True-breeding Blues 

 The fact that the blue varieties of both Andalusians 

 and Orpingtons as now constituted do not breed true is a 

 matter of considerable importance to their breeders. It 

 is a heavy handicap to both varieties. While one hun- 

 dred per cent, of blues may in each case be secured by 

 mating blue-splashed individuals with black, as a matter 

 of practical breeding this mating is seldom made. This 

 is owing to the fact that there are several more or less 

 variable qualities of color for which rigid selection is 

 practised which are not apparent in either the blue- 



