II.] INCIPIENT STRUCTURES. 65 



cliances are against the preservation of any one 'sport' 

 (i.e. sudden, marked variation) in a numerous tribe. The 

 vague use of an imperfectly understood doctrine of chance 

 has led Darwinian supporters, first, to confuse the two 

 cases above distinguished ; and, secondly, to imagine that 

 a very slight balance in favour of some individual sport 

 must lead to its perpetuation. All that can be said is 

 that in the above example the favoured sport would be 

 preserved once in fifty times. Let us consider what will 

 be its influence on the main stock when preserved. It will 

 breed and have a progeny of say 100 ; now this progeny 

 will, on the whole, be intermediate between the average 

 individual and the sport. The odds in favour of one of 

 this generation of the new breed will be, say one and a 

 half to one, as compared witli the average individual ; the 

 odds in their favour will, therefore, be less than that of 

 their parents; but owing to their greater number, the 

 chances are that about one and a half of them \A'0idd 

 survive. Unless these breed together, a most improbable 

 event, their progeny would again approach the average in- 

 dividual ; there would be 150 of them, and their superiority 

 would be, say in the ratio of one and a quarter to one ; 

 the probability would now be that nearly two of them 

 would survive, and have 200 children, Avith an eightli 

 superiority. Eather more than t^A'o of ^:hese would survive: 

 l)ut the superiority would again dwindle, until after a few 

 generations it would no longer be observed, and would 

 count for no more in the struggle for life than any of the 

 hundred trifling advantages which occur in the ordinary 

 organs. An illustration will bring this conception home. 

 Suppose a white man to have been wrecked on an island 

 inhabited by negroes, and to have established himself in 



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