xlii GENERAL INTRODUCTION. 



tency only declares itself when intermarriages take place. 

 On the other hand, any given member of a non-prepotent 

 race may, through inbreeding (sib-breeding), be more 

 prepotent than any given member of a decidedly prepo- 

 tent race. Hitherto prepotency has almost invariably 

 been associated v>rith inbreeding, and many believe not 

 only that it can be induced by inbreeding, but that apart 

 from inbreeding it is impossible. On the other hand, 

 sports * and certain marked variations are often prepo- 

 tent, i. e. they resist the swamping influence of inter- 

 crossing, and hence it would be difficult to prove in many 

 cases that prepotency has not originated with, or is an 

 attribute of, sports. Mr. Galton has recently gone 

 further than this, and given it as his opinion that prepo- 

 tency is, in itself, a sport ; to use his own words, " high 

 prepotency does not arise through normal variation, but 

 must rank as a heritable sport or aberrant variation. "t 

 That sports are frequently prepotent has been placed 

 beyond doubt, but that prepotency is in itself a sport 

 has not yet been px'oved. When we are able to account 

 for prepotency, why any given variety is able to with- 

 stand the swamping influence of intercrossing, we shall, 

 I think, be nearer an explanation of the origin of 

 species. 



Mr. Galton, in his suggestive paper on prepotency, says 

 nothing about interbreeding. Perhaps, while believing 

 *^ high prepotency " rapidly acquired is due to an aber- 

 rant variation, he will be prepared to admit that a lower 

 grade of prepotency may be induced by inbreeding. I 

 believe inbreeding is common amongst wild animals, and 

 that by inducing prepotency it plays an important part 

 in the origin of species. Variation is of fundamental 



* A sport is an abnormal or aberrant variety tlie result of sudden and 

 pronounced variation in one or more directions. The horse compared witli 

 a dog, or its old enemy the woll', is a poor jumper. If a liorse were 

 suddenly to appear that could leap nearly twice its own height it would be 

 a sport, as would be a horse with extremely sliort legs or without a tail. 

 An upright mane might either be a sport or the result of reversion, while 

 a hairless horse would be considered a sport. 



t Nalure, July 14th, 1898. 



