478 GENETICS IN RELATION TO AGRICULTURE 
dicate that the character differences depend upon single factor differences. 
As a matter of fact most instances of imperfect dominance are probably 
due to complex factor interaction, and they, therefore, require further 
study. The list as it stands is more interesting than useful, but it gives 
a rather vivid idea of the variety of character contrasts which may be 
obtained in the barnyard fowl. Aside from a few additions and changes 
in wording, this list is essentially the same as that compiled by Hadley 
for the 1915 “American Poultry Yearbook.” 
Fic. 191.—Results of crossing White Plymouth Rock and White Leghorn. <A, Pic’, 
White Leghorn; C, Pi, White Plymouth Rock; B, Fic", showing a little flecking of black 
and a barred tail feather; D, P29, type of barred birds obtained in Fs. (After Hadley.) 
The most important kind of Mendelian work is that which leads to 
some definite analysis of the factor complex characteristic of a given 
breed. As an illustration of such investigations we have Hadley’s 
analysis of the genetic constitution of the White Leghorn breed. .White 
is often dominant in fowls, so that white breeds may carry latent color 
and pattern factors in their makeup. Hadley finds the White Leghorn 
to be of the genetic constitution CCII(BZ)(BZ), if a male, and CCII 
(BZ)W, if a female, the factors having the following effects: 
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