C06 TRANSACTIONS OF SUB-SECTION K. 



TUESDAY, SEPTEMBER 5. 



The following Papers were read : — 

 1. The Application of Genetics to Horse-breeding. By C. C. Hurst, F.L.S. 



Soon after the discovery of Mendel's work in 1900, my attention was directed 

 to the thoroughbred horse as a promising subject for investigation. The ques- 

 tion of coat-colour provided a useful beginning. A few years' investigation of 

 Wetherby's ' General Stud Book ' brought to light the fact that chestnut coat- 

 colour is recessive to bay and brown. Consequently chestnut horses always 

 breed true when mated together, notwithstanding their possible bay and brown 

 parents and ancestors. On the other hand, bay and brown horses are of two 

 kinds, either they throw chestnuts or they do not. 1 



Further investigation showed that grey coat-colour is dominant to bay, brown, 

 and chestnut. Consequently every grey horse must have a grey parent and a 

 grey ancestor in every generation in the direct line. In England grey thorough- 

 breds are few, and grey x grey matings are rare, consequently English grey 

 thoroughbreds are nearly all heterozygous, throwing bays, browns, or chest- 

 nuts. Mr. R. Bunsom has found a homozygous grey in Germany, the Arabian 

 stallion, Celle Amurath, which throws nothing but greys. - 



The genetic relationships between bay and brown, and between grey and roan, 

 are not yet known. 



With regard to black. Professor James Wilson has pointed out that in 

 thoroughbreds all the so-called ' blacks ' are really dark browns with tan muzzles. 



In the Shire and the Clydesdale, however, Professor Wilson finds true blacks, 

 which apparently behave as dominants to chestnuts, and probably as recessives 

 to bays, browns, and greys. 3 



With regard to chestnuts, it seems likely that several genetic types may exist. 

 Mr. J. B. Robertson has pointed out that the dark or liver chestnut behaves as 

 a dominant to the light or yellow chestnut. 



To the practical breeder the question of coat-colour is a minor consideration, 

 except, perhaps, in a few fancy breeds where certain colours are more popular 

 than others. In the thoroughbred, at all events, a good horse is of any colour. 

 A much more important question is : Can he win the Derby ? 



Coat-colour and Pacing-power. 



Generally speaking, coat-colour and racing-power do not seem to bear any 

 sort of relationship to each other, being apparently inherited quite indepen- 

 dently. On the other hand, evidence is gradually accumulating which suggests 

 that, in certain strains, there is. a partial coupling of coat-colour and racing- 

 power. 



For instance, the famous St. Simon was a homozygous bay that never threw 

 a chestnut. On the other hand, five of his most distinguished sons — Persimmon, 

 Diamond Jubilee, Florizel II., St. Frusquin, and William III. — were all 

 heterozygous bays and browns that threw chestnuts. These chestnut grand- 

 children of St. Simon have so far proved themselves to be much inferior in 

 racing-power to their bay and brown brothers and sisters. Thus, while these 

 chestnuts have between them only won two classic races, their bay and brown 

 brothers and sisters have between them won fifteen classic races, and are only 

 about twice as numerous. 



Another interesting point under investigation is the apparent partial trip- 

 ling of brown coat-colour, high racing-power, and female sex in St. Simon's 

 own offspring. St. Simon's brown fillies proved themselves to be strikingly 

 superior in racing-power to the bay fillies, the brown colts, and even to the 

 bay colts, a few individuals of which were extraordinarily good. This is the 

 more remarkable when we consider that in racing colts have many advantages 

 over fillies. 



It seems possible that the elucidation of such an apparently trivial thing as 



1 See Proc. Boy. Soc, 1906, B, vol. 77, p. 388. 



3 Mendel Journal, No. 2, 1911, p. 89. 



' Proc. Boy. Dull. Soc, xii. (N.S.), No. 28, 1910, p. 337. 



