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THE AMERICAN NATURALIST [Vol. XL VII 



White Plymouth Eocks, the chief difference in these two 

 races being that whereas the white of the White Eock is 

 a " recessive white," occasioned, in all probability, by 

 the dropping ont of a color factor, the White Leghorn is 

 a so-called "dominant white," determined by the pres- 

 ence of an inhibitor acting upon one or both of the color 

 factors, which also appear to be present in this breed. 



Conclusions 



These results serve to confirm suggestions made by 

 Davenport 3 regarding the presence of barring in some 

 of his White Leghorn stock, and also to explain some of 

 the results obtained by Hurst 4 in matings, which involved 

 the White Leghorn breed. They also help to explain 

 some of those cases known to many poultrymen 5 in 

 which barring (the "cuckoo marking") has resulted from 

 the crossing of black (or dark) with white breeds in 

 which the presence of the barred plumage pattern was 

 not suspected. 



Obviously this work has no bearing upon the origin 

 of the barred pattern. It merely indicates that the White 

 Leghorn breed of fowls, as studied, carries factors for 

 both black and barring. The failure of the black to show 

 depends upon the action of the inhibitor, I, while the 

 barred pattern can appear only in the presence of the 

 uninhabited N or C. 



March 4, 1913 



•Davenport, C. B., "Inheritance in Poultry," Publication No. 52 of the 

 Carnegie Institution of Washington; Papers of the Station for Experi- 

 mental Evolution, No. 7, 1906. 



of the Carnegie Institution of Washington; Papers of the Station for 

 Experimental Evolution, No. 14, 1909. 



• Hurst, C. C, Eeport II to the Evolution Committee of the Royal Society, 

 London, England, 1905. 



•Wright, L., "New Book of Poultry," London (Cassell), 1905. 



