278 Heredity. 



yariation, even when the variation is of the very great- 

 est advantage to its possessor; and tliat this difficulty is 

 very much greater when as must usually be the case, 

 the advantage gained is very slight. 



He says: " The advantage, whatever it may be, is ut- 

 terly out-balanced by numerical inferiority. A milhon 

 creatures are born; ten thousand survive to produce off- 

 spring. One of the million has twice as good a cliance 

 as any other of surviving; but the chances are fifty to 

 one against the gifted individual being one of the hun- 

 dred survivors. No doubt the chances are twice as great 

 against any one other individual, but tliis docs not pre- 

 vent their being enormously in favor of 8ome average in- 

 dividual. However slight the advantage ni'^y be, if it is 

 shared by half the individuals produced, it will probably 

 be present in at least fifty-one of the survivors, and in a 

 larger proportion of their offspring; bntihe chances are 

 against the preservation of any one ' sport ' {i^c, 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 favor of some individual sport 

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

 that in the above example the favored sport would be pre- 

 served 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 iirogeny 

 will, on the whole, be intermediate between the average 

 individual and the sport. The odds in favor of one of this 

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

 one as compared Avith the average individual; the odds in 

 their favor will, therefore, be less than that of their par- 

 ents; but, owing to their greater number, the chances 



