78 A MANUAL OF MENDELISM 



But this would mean that some bays differ from chestnut 

 in two pairs of characters : a result entirely opposed 

 to that brought out by Mr. Hurst's figures. Clearly, 

 therefore, there are not two pairs of characters, and, 

 since there are three colours, there must be three factors, 

 one for each colour, and each factor must mate with 

 the other two severally and indifferently. If this be 

 so, then, since no fourth colour, intermediate or other, 

 is produced, either black or bay must be dominant 

 the one to the other and the two must differ in one 

 pair of characters only. In the Shire Stud Book 14 

 sires were found which, by their progeny with bay 

 mares, were proved to be pure bays ; and these sires, 

 with black mares, got bay foals only. Dr. Walther 

 found also 11 German sires which, with black mares, 

 got bay foals only. Thus bay is dominant to black. 

 The actual figures, with erroneous entries enclosed within 

 brackets, are as follows : 



Bays Blacks Chestnuts 



With bay mares 14 bay Shires get 618 (2) (2) 



With black mares the same sires 



get 163 (6) — 



With black mares 11 German sires 



get 200 — (9) 



But in how many factors do bay and black differ ? 

 Sixteen bay Shires, which got both bays and blacks 

 when mated with bay mares and thus showed that 

 they carried the factor for black in addition to that for 

 bay, were mated with black mares, and got equal 

 numbers of bay and black foals. Dr. Walther also found 

 10 similar German sires. Thus bay differs from black 

 in one pair of characters. The figures, with the erro- 



