VII] Colours of Thorough-bred Horses 125 



The time has not arrived for any attempt to analyse 

 the relations of horse-colours in general. By microscopical 

 methods Miss Durham has found in horses the three pig- 

 ments, black, chocolate, and yellow seen in other types. 

 The term chestnut is used somewhat loosely in describing 

 colours, and though usually a chestnut is a horse possessing 

 yellow pigment only, there is a dark type of chestnut, 

 sometimes spoken of as liver-chestnut ^ which is actually 

 chocolate"^. Nothing is known of the genetic relation of 

 this to the yellow chestnut, or of the respective properties 

 of those various chestnuts distinguished by the colour of 

 their manes and other subordinate differences. 



Among thorough-bred or race horses, types intermediate 

 between chestnut and the dominant bays and browns must 

 be exceedingly rare, for though entries indicating doubt 

 between bay and brown are rather common in the Stud 

 Books, alternative designations are scarcely ever given in 

 regard to chestnuts. 



Among common horses and hackneys such animals 

 though exceptional can be found by looking out for them, 

 and one or two may usually be seen in a day's walk through 

 London streets. I have no information as to their genetic 

 capacities, but presumably they are due to dilution-stages 

 of the black pigment, corresponding to those which in the 

 mouse &c. constitute the blue varieties. They may also be 

 cases of imperfect dominance. 



not be taken into account together. The tables thus provide answers to 

 questions as to the probable colour of a foal by a chestnut sire, the dam's 

 colour being taken as unknown ; as to the probable colour of the brother 

 or half-brother of a chestnut foal, when the colours of both sire and dam 

 are taken as unknown ; with solutions of other problems of equal signifi- 

 cance. Since however the colours of both sire and dam are recorded, and 

 must indeed have been actually extracted from the Stud Book for the 

 purposes of the tabulations, the investigators, by refraining from an 

 inspection of these data till they had been separated, placed themselves at 

 a gratuitous disadvantage. The true nature of the inheritance was therefore 

 not discovered. 



The failure was due to want of analysis. The similar failure of bio- 

 metrical methods to find the plain rule of inheritance in the case of human 

 eye-colour was due to the same defect of method, though in that case 

 further obscurity arose from the use of faulty and uncritical observations. 



* When very dense this type of colour might carelessly be mistaken 

 for black. 



