BLASTOGENIC VARIATIONS. 



149 



are strongly prepotent, probably because they are purer 

 bred than other races. 



A numerical estimate of the frequency with which 

 different grades of prepotency are distributed appears 

 to have been attempted for the first time quite recently 

 by Mr. Galton.* From data given in Wallace's Year 

 Book of American Trotting Horses, he has determined 

 the numbers of offspring of a certain standard, pro- 

 duced by various sires and dams. A standard per- 

 former is a horse which has succeeded in trotting a mile 

 in 2 min. 30 seconds or less, or in pacing (ambling) a 

 mile in 2 min. 25 seconds or less. Data concerning the 

 offspring of 716 sires and 494 dams were available, and 

 the following were the percentage proportions of 

 " standard performers ' ' produced by them. 



This table would seem to show that the prepotency of 

 certain sires is enormous, even allowing for the tend- 

 encv of breeders to send the best mares to the best 



ts 



horses. Thus the horse Happy Medium had 92 dis- 

 tinguished offspring, and Electioneer no less than 154. 

 The same results are indicated by the produce of the 

 dams, though the figures are less striking owing to the 

 relative fewness of their offspring. A sire produces 

 * Nature, vol. Iviii. p. 246, 1898. 



