THE AMERICAN NATURALIST [Vol. LII 



rately. It resembles the black phenotype in being self- 

 colored and the blue-splashed phenotype in having the 

 pigment restriction within the barbules, which gives the 

 blue-gray effect. 



The 1:2:1 ratio may therefore be analyzed as follows : 



nt re- Pigment re- 

 in bar- stricted in bar- 

 lis; ex- bule cells; not ex- 

 tended through tended through tended through 

 plumage ("self" plumage (self); plumage; pheno- 



notype°blacky h< 



Eatio of pheno- 1 



types | 



Eatio foyestric- j 



In reality, then, the 1 : 2 : 1 ratio is the result of the com- 

 bination of two 3:1 ratios. 



The foregoing facts appear to lend themselves equally 

 well to two interpretations. The first is that there are 

 two pairs of allelomorphic factors at work. The second, 

 that there is one pair of true allelomorphs (i. e., factors 

 having identical loci on homologous chromosomes), 

 neither of which is recessive to the other in its manifesta- 

 tion in the phenotype. 



The suggestion of two pairs of allelomorphic factors to 

 explain the case of the Andalusian is not a new one. 

 Goldschmidt (1913, p. 274) makes such a suggestion. 

 After pointing out that the offspring of a pair of blues 

 are black, blue, and " schmutzigweiss" in the ratio of 

 1:2:1, and that all three phenotypes carry pigment, he 

 proposed two factors to account for the condition. The 

 one is an " EntfaltungsfaMor," which brings about a full 

 development of the pigment. He represents this factor 

 by "Q" (Quantitat) which is possessed by the black race. 

 The other factor, which is possessed by the "Weisse" 

 race, he calls a " Mosaikfaktor," which finely divides the 

 pigment. This factor he designates M (Mosaik). He 



