152 BLASTOGENIC VARIATIONS. 



proportion of 6 to 5. "Whatever the degree of pre- 

 potency of one parent over another and with similarly 

 bred stocks it is probably never very great we must 

 conclude that the average contribution of both parents 

 together still remains at a half, that of grandparents at 

 a quarter, and so on. It is only the relative propor- 

 tions contributed by the two sexes which differ. Thus 

 it will be remembered that it was the Basset hound 

 data which afforded Galton such valuable evidence in 

 support of his law. 



But what view are we to take of the more striking 

 instances of prepotency mentioned above? Are they 

 also conformable to the law of heredity, or are they ab- 

 normal and exceptional? Galton himself has come to 

 the conclusion that high prepotency does not arise 

 through normal variation, but must rank as a highly 

 heritable sport. As has been mentioned in a previous 

 chapter, there is no adequate proof that sports transmit 

 their characters more persistently than other varia- 

 tions, and in any case it is probably unnecessary to as- 

 sume that prepotency is other than a special case of the 

 law of heredity. Thus we saw in the above-mentioned 

 case of the black grajrhound, that the dog had a prepon- 

 derance of black in his blood, both on the sire and dam 

 side, whilst both the instances of prepotency mentioned 

 by Professor Ewart seem largely attributable to in- 

 breeding. This inbreeding, according to Professor 

 Ewart, induces prepotency by fixing the characters of 

 the particular variety selected. But what is really 

 meant by fixing a character? To adequately com- 

 prehend the meaning of the term it is only neces- 

 sary to examine Galton's law of ancestral heredity a 



