COLOR AND STRUCTURE OF PLUMAGE 87 



not dominate, but has color imposed on it. There is another kind 

 of white in chickens, the white of the White Leghorn. It is a domi- 

 nant wliite, and when this variety is crossed with colored chickens 

 the progeny are white, or nearly so. 



There is some factor in the White Leghorn which prevents the 

 formation of color. There is good evidence to show that there is a 

 tendency to black in the White Leghorn, but some factor in the 

 inheritance of this variety holds the color in check or in some manner 

 neutralizes it. This is called a restraining or prohibiting factor. The 

 result is that when the White Leghorn, carrying this pigment inhib- 

 itor, is crossed on colored fowls, the color is held in check and the 

 chicks produced from the cross are practically white. 



The white of the White Rock and White Wyandotte, however, is 

 due to the dropping out of that hereditary factor which is necessary 

 for the development of color. In these two varieties there is an 

 absence of color, not only in the plumage, but in the germ cells. 

 These varieties are not useful for crossing, because their white will 

 not predominate in the otifspring. "In my own breeding work," writes 

 Professor Lippincott, "I have found that all White Plymouth Rocks 

 carry a pattern for barring. In crossing them with a pigmented bird, 

 such as the Black Langshan or the Black Andalusian, one gets only 

 barred offspring if the sire is a White Plymouth Rock, while all the 

 males are barred and the female non-barred if the mother is the 

 White Plymouth Rock and the sire is the pigmented bird." The 

 first White Rocks appeared as sports of the original Barred Rock, and 

 White Wyandottes first came as sports of Silver Wyandottes. While 

 these early sports may be assumed to have carried the pattern for 

 barring and lacing, the factor for the development of color was 

 missing and therefore they were white. These two varieties, White 

 Rocks and White Wyandottes, are not useful for crossbreeding because 

 their white will not predominate in the offspring as will the white of 

 the Leghorn, the barring of the Barred Plymouth Rock, or the red 

 of the Rhode Island Red. How the inhibiting factor for color arose 

 in the White Leghorn, no one knows. We do not know how new 

 factors get into the germ cells. 



Inheritance of white color. It is much easier to grade up the 

 color of a mongrel flock by the use of Barred Rock males than by 

 the use of White Rock males. When you look at page 88 you see 

 at the top a mongrel hen. When she was mated to a White Rock 

 male she produced a barred daughter, and it took another dose of 

 pure White Rock blood to produce the white pullet shown in the 

 third illustration. At the top in this illustration is shown the orig- 

 inal dam, and below are successive generations which were the result 

 of grading up with purebred White Plymouth Rock males. 



In mating a pure Barred Rock male on a mongrel hen. the spe- 

 cialists on the L'nited States Government poultry farm observed that 

 out of 56 chicks, 52 carried dominicjue or barred markings, and 



