132 GENETICS AND EUGENICS 



Red cattle have an intensified yellow pigmentation. They 

 probably represent derivatives of an original all-yellow sport, 

 comparable with the yellow sports of rodents, which originate 

 through restriction of black pigment to the eye. Among 

 cattle yellows vary in shade from a very deep red (Devons 

 and short-horns) to a light cream color (some South German 

 and Swiss breeds). The extremes in both directions were 

 doubtless secured through repeated selection. Whether the 

 different shades or intensities of yellow are alternative is un- 

 known, but it seems probable that in cattle as in rodents 

 intensity of pigmentation is independent of its specific char- 

 acter as black or yellow. 



Black breeds of cattle are represented by the Galloway and 

 Aberdeen Angus of Scotland. In them we have either deriva- 

 tives of an all black sport, or the end result of a gradual in- 

 crease of black in the coat through selection. Pure-bred 

 Aberdeen Angus cattle sometimes produce red calves, red 

 being obviously a Mendelian allelomorph recessive to black 

 in cattle as it is in rodents. As red is not favored in the 

 standard of the breed, it will doubtless be entirely eliminated 

 in time, as seems already to be the case in the best families 

 of the Galloway breed. (See Fig. 73.) 



In most breeds of cattle white spotting occurs and this is 

 a Mendelian alternative to unifonii coloration, though nei- 

 ther condition is entirely dominant over the other. The 

 self-coloration of breeds which are all black or all white has 

 a strong tendency to prevail in the offspring. Black breeds 

 in wliich white spotting occurs are represented by the Hol- 

 stein-Friesian cattle originally bred in Holland and Denmark, 

 but now extensively kept in this country, also by the belted 

 cattle of Holland. (See Figs. 66 and 69.) Red-and-white 

 and yellow-and-white cattle are represented by Hereford and 

 Guernsey cattle respectively. (Figs. 68 and 67.) Black- 

 and-white breeds may produce red-and-white offspring as 

 recessives, but red-and-white breeds never produce black- 

 and-white calves, which shows clearly that black is dominant 

 over red. In the Hereford breed a definite pattern of white 



