Wilson — Polygamous MeudeUun Factors. 303 



1887 and 1888. Unfortunately this was before the discovery of Mendel's 

 work, and it is not unlikely that Dr. Crampe, had he known of Meudelism, 

 would have formulated a complete scheme to explain the inheritance of horse 

 colours : for he made two observations which would not only have given him 

 a start but carried him some part of the way. 



The first to deal with the question since the Mendelian discovery and to 

 make an important advance was Mr. C. C. Hurst^ who, from data collected 

 in Weatherby's " General Stud Book," came to the conclusion that chestnut 

 breeds true and is recessive to bay and brown : these two colours being taken 

 together as one. Mr. Hurst dealt of course with Thoroughbreds only, among 

 which tliere are now only five colours. Chestnuts, bays, and browns are by 

 far tbe most numerous, but there are also some greys and perhaps a few 

 true blacks ; but most of the animals entered as blacks are browns of so dark 

 a shade that they are mistaken for blacks. Mr. Hurst dealt with the first 

 three colours. The figures on which his conclusions were based are these : — 



(1) 101 chestnut sires with chestnut mares get . 



(2) 12 bay and brown sires with chestnut mares get . 

 (y) 6 bay and brown sires with chestnut mares get . 



The point to be noted at present is that the twelve impure bay and 

 brown sires get 347 chestnut and 355 bay and brown foals, from which 

 it can be inferred that chestnut differs from bay and brown in one pair of 

 characters. 



In the present writer's two papers bay and brown were assumed to be 

 separate colours, and, although it was clear that neither was an intermediate, 

 it could not be determined which was the dominant of the other. It is now 

 quite apparent that the assumption was a mistake and that the two colours 

 are really different varieties or shades of a single colour. For, if either were 

 the dominant, one of the two would not produce the other when mated with 

 chestnut. Yet both colours produce both colours by tliis mating, and they do 

 so in numbers which indicate that the factor or factors wliich make bay and 

 brown bay are dominant to those which make it brown : an inference confirmed 

 by the fact that a chestnut sire, Cyllene, gets bays and chestnuts only when 

 mated witii browns and that an impure bay sire, Avington, breeds in a similar 

 manner. This point was missed when the 1910 and 1912 papers were 

 written. 



1 Proc. Roy. Soc, B, vol. Ixxvii, 1906, p. 388. 



8 B 2 



