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 Ee 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 6 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 E. Lloyd-Jones and Evvard have demonstrated this 

 fact in the F z of Galloway X 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 & 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 



