HEREDITY OF RACEHORSE STAMINA 67 



brood mares were really PR in gametic composition, 

 but carried a factor which inhibited R in their own 

 soma. For none of these mares could run more 

 than seven furlongs, yet they produced 156 stayers. 



The mating of the RR sires with the PR mares 

 comes close to expectation, that is PR (intermediates) 

 and RR (stayers) in equal numbers. The solitary 

 sprinter from this mating is the colt Leisure Hour, by 

 *S^. Simon out of Love in Idleness, a mare who with 

 difficulty could get a mile. 



In the group RR sires mated to RR mares, which 

 should give RR only, the intrusion of a sprinter 

 needs a little consideration. The colt in question is 

 Carburton, by Carbine out of Mrs. Butterwick. This 

 mare won the Oaks, but, like many other winners of 

 that race, was not really a stayer. Still she must 

 have carried one R factor, else she would not have 

 bred Phaleron to Gcdlimde and Wombwell to Isinglass, 

 both of which won races of twelve furlongs or over. 

 Why, then, did Carburton so belie his ancestry ? A 

 reference to Vol. XIX. of The General Stud Book gives 

 the answer. Carburton was Mrs. ButterwicFs first 

 living foal. She produced a dead filly to Morion in 

 1895, was barren in 1896, 1897, and 1898, and Car- 

 burton was foaled in 1899. Here, unmistakably, is 

 an instance of some defective quality in reproduction, 

 or some segregable factor in the germinal plasm 

 leading to weak viability in the offspring. Her next 

 foal, Greatorex (1900), also by Carbine, was a great 

 improvement on Carburton. As a two-year-old he 

 could stay seven furlongs in the best class, but, being 



