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THE AMERICAN NATURALIST [Vol. XLV 



effect in inheritance without a specific chemical unit 

 determiner for such effect, and the spotted and roan 

 Shorthorns are not blends in the old sense of the term. 



Angus cattle which are black sometimes throw dark red 

 colors, exemplifying the fact that in cattle, as with 

 animal pigments generally, the darker pigments are 

 epistatically dominant over the lighter, hence the cattle 

 colors— black, red, yellow with its variations— are domi- 

 nant over "albinic" white (w), like the white of the Silkie 

 Fowl, but " positive" white (W), like the white of the 

 Leghorn Fowl and such as that of the British Park 

 cattle, is dominant over any and all pigments. Corrob- 

 orative of this, recall the instance reported by Prof. 

 Wentworth, wherein pure-bred Holstein cows were bred 

 to a deep red Shorthorn bull, and in the offspring "the 

 color pattern showed no trace whatever of the Shorthorn 

 parentage." Now conceive the white Shorthorn coat to 

 be made up of an admixture of "albinic" and "positive" 

 whites, and let the duplex red be mated with the white of 

 this nature— the offspring are the familiar roans, for the 

 "positive" white persists and the "albinic" white is 

 covered by the red pigment. In explanation of the black 

 cattle crosses : Mate a white Shorthorn of type No. 9, or 

 a roan of type 7 or 8, with a black Angus or Galloway ; the 

 dominant white persists, the black covers the red (as in 

 human hair) and the familiar blue-roan hybrid results in 

 exact accordance with the theory of gametic purity. Con- 

 ceive of the white-faced Hereford mated with the black 

 Angus— the "positive" white persists, the black pigment 

 covers the red and the familiar white-faced, black-bodied 

 hybrid results. Thus it is determined that the white of 

 the areas of the face, the two flank belts and the underline 

 are largely "dominant white," while those of the neck, 

 barrel and quarters are mostly "albinic white." 



The old single-unit coat hypothesis, even when amended 

 to permit the simplex condition in some reds and in some 

 whites, does not explain hoiv the simplex condition could 

 run the entire color gamut ; neither has the "first genera- 

 tion blend, later generation segregation" theory yet been 



