Wright: Color Inheritance in Mammals 



525 



type of pattern can be produced by 

 selection. The conditions strongly sug- 

 gest that the pattern is the resuHant of 

 two very different kinds of factors, 

 factors which determine a certain gen- 

 eral level of some essential for pigment 

 production and factors which affect the 

 course of development so as to bring out 

 particular lines of weakness in which the 

 pattern of white shall appear if the 

 general level is low enough. On this 

 view a Hereford, a Dutch-belted cow 

 and a Holstein might possess the iden- 



BB black 

 BR black 

 BL dun 

 RBr dark brindle 

 BW blue roan 



RR red 

 RL 3^ellow 

 BBr red brindle 

 RW red roan 



brindle and dun has been made by Wil- 

 soni2 in a study of Highland herd books. 

 Black, dun, brown, red, yellow, light 

 dun and brindles are recorded. Occa- 

 sionally whites appear as has been 

 discussed. The palest yellows appear 

 to be registered as light duns although 

 free from the black of the true duns. As 

 has been noted, Wilson explained the 

 results by a system of multiple allelo- 

 morphs. He considers each of factors 

 B, R, L. Br and W to be a Mendelian 

 alternative of any other : 



LL light dun 

 LBr dun brindle 

 LW 



BrBr brown 



BrW WW white 



tical piebald factor as regards quantity 

 but differ in hereditary factors which 

 determine the type of regional differ- 

 entiation. As far as the writer knows 

 no Mendelian differences of this second 

 kind yet have been demonstrated in any 

 mammal. 



Spillman^^ early showed that red is a 

 simple recessive to black. Red calves 

 appear from time to time in purebred 

 Angus and Galloway cattle which are 

 nearly fixed for black. In crosses dis- 

 cussed by Jones and Ev^^ard, red vShort- 

 horn by black Galloway produced black 

 in Fi with a few exceptions, while red 

 segregated out in the expected ratio in 

 F,. 



INTERGRADES BETWEEN BLACK AND RED 



Several types of apparent intergrades 

 between red or yellow and black are 

 known. These are the brindles, duns 

 and dark mahogany browns. In the 

 brindles, however, there may be any 

 ground color according to Wilson, red, 

 yellow, dun or even black. The brind- 

 ling consists in irregular streaks of black 

 (or especially dense black if the ground 

 color is black). In duns the coat is 

 largely of a dull brownish black, the 

 hairs showing a yellowish tip and the 

 yellow color tending to predominate 

 especially along the mid-dorsal line. 

 The mahogany brown as in some 

 Ayrshires may look almost black but 

 appears to be simply a very intense red. 



The most extensive investigation of 



Reasons have already been given for 

 separating the factor for white from this 

 series, as far as black and red are con- 

 cerned. As regards brindle, the very 

 fact that it can be visibly combined with 

 any color suggests that it is as independ- 

 ent in inheritance as piebald. Brindle 

 evidently means so many different 

 things in Highland cattle that little can 

 be learned from the data. In Wilson's 

 tables brindle by brindle produces only 

 about 50% brindles which may per- 

 haps be taken as indicating its usual 

 heterozygous nature. Brindle by red 

 gives only about 23% brindles, 67% reds 

 and a few others which shows that it 

 cannot be due to a simple dominant if 

 it is recorded at all accurately. The 

 larger part of the brindles have at least 

 one brindle parent but this is far from 

 invariable. On the whole brindle can 

 better be fitted as dominant than reces- 

 sive but further study is necessary before 

 any form of Mendelian inheritance can 

 be considered established. For the 

 present it seems safest to separate 

 brindle from the other factors, as due to 

 unanalyzed factors of class las which 

 determine an increase in the density of 

 black in irregular streaks on any ground. 

 The fact that brindle by red gives only 

 4% black shows that brindle in the 

 records generally means red brindle as 

 might be expected and that factor e, not 

 E, is present. Probably black brindles 

 are usually simply called black. 



1' S^niiman, W. J. 1907. Set. N. S., 23:545. 

 "Wilson, J. 1909. Set. Proc. Roy. Dub. Soc, 12-66. 



