MENDELISM IN DOMESTIC ANIMALS 473 
is merely a heterozygous condition of red and white, or in terms of the 
above factors, the expression of the He genotype, would be satisfactory. 
The black color of Aberdeen-Angus and Galloway cattle is definitely 
dominant to red. This is shown by the fact that such cattle occasionally 
produce red calves. Since red was a common color in the early founda- 
tion stocks of the two breeds, it follows that the production of occasional 
red calves is merely a consequence of the handing down of the factor b in 
a heterozygous condition, and of the rare matings of animals both of which 
are heterozygous for it. In the black-and-white Dutch cattle of various 
types it is also not uncommon to have red-and-white offspring produced 
from black-and-white matings, but red-and-white matings never produce 
black-and-white calves. The factor B, as well as b, is affected by the 
extension factor H. Lloyd-Jones and Evvard have demonstrated this 
fact in the F. of Galloway white Shorthorn matings, the white animals 
of which had black ears and muzzle like the Chillingham Park cattle. 
An excellent representation of such an animal is given in Fig. 188. Black 
is, also, affected by the roan factor in the same way as red, giving a 
blue-roan or blue-gray. The famous blue-gray cattle produced by 
mating Galloway, or less frequently Aberdeen-Angus, cows to white 
Shorthorn bulls are evidence of this fact; but the critical test necessary 
to decide between the two rival hypotheses of blue-gray as a simple 
heterozygote between black and white or as a consequence of the action 
of a separate roan factor has not yet been carried out. 
Of the relations of other colors to each other, we know very little. 
J. Wilson states that there are five colors in cattle which breed true, 
namely black, red, light dun, brown, and white, and that aside from 
matings of black and red which give blacks, matings of different colors give 
what may be called, for convenience, intermediates. The exact colors 
which represent the heterozygotes are given in Fig.189. But there is no 
satisfactory way of determining the relations of the factors to each other 
save by the experimental test. Wilson presents some data gleaned from 
the Highland Cattle Herdbook on the relation between black, red, brindle, 
yellow, dun and light dun; but they are not of such a nature as to be capa- 
ble of accurate Mendelian interpretation. The data do, however, indicate 
that black is the highest member of the series, and that red comes next to 
it. As to the relation between black and yellow, dun, light dun, and 
brown, we are still in some doubt in spite of positive statements by Wilson. 
On the one hand we have evidence that the foundation stock of Aberdeen- 
Angus cattle contained animals black, red, yellow, dun, light dun, 
brown-backed and other mixtures of these, only one of which, red, has 
survived as a simple recessive. This would lend support to Wilson’s idea 
that the relation of blacks to the colors other than red is not that of 
simple dominance. Black, however, appears to be dominant to the fawn 
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