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THE AMERICAN NATURALIST [Vol. LV 



If, however, after a long-continued search, it becomes 

 increasingly evident that R and E are indeed allelo- 

 morphs, as originally suggested by Bateson and Punneit 

 (1905), it was suggested (p. 113) that hope might be seen 

 in the progressive selection of the darker, that is, more 

 fully pigmented, blue-splashed individuals, there being 

 considerable variation among the latter in this regard. 



There is a further possibility which should not be over- 

 looked, namely, that other factors might be found, per- 

 haps in other breeds, which would act on black pigment 

 to give the blue appearance on the one hand, or extend it 

 to 'give self-colored individuals on the other. If dupli- 

 cate factors for E or R should be found, a means of 

 producing the long sought true-breeding blue would seem 

 to be at hand. The fact that three factors are known 

 which produce white in fowls lends emphasis to the possi- 

 bility. It would seemingly make little difference in the 

 ultimate outcome whether the new factor was linked to 

 R and E, or was located on a different chromosome pair. 

 In either case it would be possible to get a "self -coloring" 

 and a "bluing" factor in the same gamete which, it ap- 

 pears, has so far not been done. 



XIV. Summary 



1. It has been showm that the development of black 

 pigment in the blue-splashed, blue and black races of the 

 Andalusian and Orpington breeds, and of black Lang- 

 shans, depends upon the action of a dominant hereditary 

 factor P, for which they are normally homozygous. 



2. The allelomorph of P is p. Individuals homo- 

 zygous for p arc white. ;is in Ihc white AVyandotte and 

 white Plymouth Rock hiceds. 



3. The extension of M;iek pi-iiieiit In \\ atluTs of the 

 body, resulting if no patlei-n fm-tors .•iiv pivseiit, in self- 

 coloi'ed in.li\i.lu;iK. .lep.n.U up..,, dnminniit f.-ictor h\ 



