124 Colours of Thorough-bred Horses [ch. 



the complicated phenomena elsewhere observed in regard 

 to pigments ostensibly the same. The colours of race 

 horses are recorded with great accuracy in Weatherby's 

 General Stud Book, By a careful analysis of these returns 

 Hurst was able to show that chestnut on the one hand is 

 recessive to bays and browns, which are dominant. Chest- 

 nuts are distinguished from bays and browns by the fact 

 that in their hair no black pigment is developed. Bays 

 always have black in the mane, tail and fetlocks. Browns 

 have more or less black in the same parts, and generally 

 black pigment is distributed to some extent over the whole 

 coat. 



As the records show, there are only about i per cent. 

 of alleged exceptions to the rule that chestnut x chestnut 

 produces chestnut exclusively. Of the dominants some 

 are pure dominants and give — again with about i per cent, 

 of exceptions — bays and browns only, whether the other 

 parent is chestnut, or bay or brown. Other dominants are 

 shown also to be DR in constitution, giving, when bred 

 with chestnuts, equal numbers of dominants and recessives. 



With regard to the few exceptions of both kinds ap- 

 pearing in the Stud Book records some are demonstrably 

 mistakes, and the actual frequency of exceptions must be 

 considerably less than i per cent., if indeed there are any 

 genuine exceptions at all. The relation of bays to browns 

 has not yet been made out, and as the two classes grade 

 into each other somewhat, the detection of their relation- 

 ship would demand observations of a sort somewhat more 

 critical than those which the Stud Book provides. So far 

 however as the segregation of black from the absence of 

 black is concerned, the case is simple and regular*. 



* The inheritance of coat-colour in horses was the subject of an extensive 

 investigation by Professor K. Pearson and his assistants (219). The records 

 of the Stud Books were tabulated and investigated by the application of bio- 

 metrical methods. Various propositions have been enunciated as the result 

 of this inquiry, amongst others the statement that nothing corresponding to 

 Mendel's principles appears in the case of horse-colours. The key to the 

 phenomena was of course the fact that chestnuts mated with chestnuts 

 breed true — with rare and dubious exceptions. It would seem at first 

 sight impossible to devise a system of tabulation which could fail to 

 disclose so prominent a feature. Nevertheless Professor Pearson's correla- 

 tion-tables, which were compiled from the records of more than 6000 

 horses, were made in such a way that the colours of sire and dam could 



