58 THE MENDEL JOURNAL 



mum winning distance of every horse and mare over 

 two years of age which has been successful under the 

 Eules of Flat Racing in the years 1906-1910 inclusive, 

 Irish races of less value than 90 sovs. being ignored. 



For one hundred and thirty-nine winners of the 

 most important and highest class long distance races 

 of fourteen furlongs or over, 1900-1911 inclusive, the 

 ratio of horses to mares is 112 : 27, that is 4 '15 : 1. 



It would appear that the inhibition of the staying 

 factor is due to the presence in certain mares of a unit 

 character. The exact nature of this character can 

 only be guessed at, but it is permissible to surmise that 

 it is an enzyme connected with an ovarian secretion. 

 Evidence goes to show that a mare possessing the 

 inhibiting character may transmit it to both her sons 

 and daughters, and that it is dominant in mares, and, 

 necessarily, recessive in horses. In the absence of 

 this character mares carrying one unit of R and one 

 unit of P will be intermediates, and those carrying 

 two units of R will be stayers. Conversely, the 

 presence of the inhibitory factor, I, would reduce an 

 intermediate mare carrying R and P to a sprinter, 

 the R factor being inhibited in her soma. But, never- 

 theless, a mare of this composition would give off 

 gametes containing R and P alternatively and approx- 

 imately in equal numbers. The effect of the presence 

 of inhibition and two units of R is not quite clear. 

 Theoretically the inhibitory factor should have the 

 same effect on the muscular tissues of mares of RR as 

 of PR gametic composition. But the facts do not 



