Artificial and Natural Selection 825 



cousins. In every group the best adapted in- 

 dividuals will survive, and soon the breeding- 

 differences between the parents must vanish 

 altogether. Manifestly they can, as a rule, 

 have no lasting result on the issue of the strug- 

 gle for existence. 



If now we remember that in Darwin's time 

 this principle, breeding-ability, enjoyed a far 

 more general appreciation than at present, 

 and that Darwin must have given it full consid- 

 eration, it becomes at once clear that this old, 

 but recently revived principle, is not adequate 

 to support the current comparison between ar- 

 tificial and natural selection. 



In conclusion, summing up all our arguments, 

 we may state that there is a broad analogy be- 

 tween breeding-selection in the widest sense of 

 the word, including variety-testing, race-im- 

 provement and the trial of the breeding-ability 

 on one side, and natural selection on the other. 

 This analogy however, points to the impor- 

 tance of the selection between elementary spe- 

 cies, and the very subordinate role of intra- 

 specific selection in nature. It strongly sup- 

 ports our view of the origin of species by 

 mutation instead of continuous selection. Or, 

 to put it in the terms chosen lately by Mr. 

 Arthur Harris in a friendly criticism of my 

 views : * ' Natural selection may explain the sur- 



