58 THE HORSE AND ITS RELATIVES 



impure, when they may give rise to chestnuts. It 

 thus follows that bays, as being capable of produc- 

 ing offspring of a colour different to their own, are 

 a dominant type (D), while chestnuts, which lack 

 this capacity, are recessive (R). Chestnut horses, 

 as having but one kind of sexual cells, may accord- 

 ingly all be symbolised as RR, whereas bays may 

 be classed either as DD or DR, according as to 

 whether they are pure or whether they contain an 

 admixture of chestnut cells. Now if a DD stallion 

 be mated with an RR mare, all the foals will be 

 DR bays. On the other hand, the foals of an RR 

 mare by a DR stallion will, in the long run, consist 

 of bays and chestnuts in nearly equal numbers. 

 When chestnuts are bred together, their offspring 

 should be all chestnuts (RR), but if chestnuts be 

 crossed with bays, the foals may be either all bays 

 or half chestnuts (RR) and half bays (DR), the 

 former case, as mentioned above, being due to the 

 fact that the parent bays were DD, and the latter 

 to their being DR. Certain apparent exceptions 

 to these conditions occurring in the Stud-book are 

 shown to be due to incorrect registration of colour, 

 and it is probable that the same is the case with all 

 the rest. As regards greys, it is stated that in all 

 cases one of the parents must be of this colour. 



At the meeting of the British Association held 

 at Portsmouth in 191 1 Mr. C. C. Hurst discussed 

 the question whether there is any connection 



