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of elimination value, whether it would determine survival 

 or elimination, and make all the difference between passing 

 or being plucked in life's great competitive examination. 

 But if Mr. Ball likes to maintain that every advantage, no 

 matter how slight, is of elimination value, there, so far as he 

 is concerned, is an end of the matter. It is, of course, open 

 to any one to argue thus : Selection is all-pervading ; the 

 slightest advantage is selected ; therefore all advantageous 

 modifications have been effected through selection, and there 

 is no necessity to imagine the existence of any other factor. 

 Although logically correct, I regard such an attitude as 

 biologically and scientifically false. Even if selection be 

 rightly regarded as by far the most potent factor in evolu- 

 tion, this does not of itself justify " grave doubts of the 

 alleged inheritance of the effects of use and disuse," but 

 rather shows the difficulty of proving or disproving such 

 use-inheritance by special examples. In Science we must 

 not say : Here are the major factors ; these practically do 

 all the work. Never mind about minor factors, the major 

 factors are quite strong enough without them. We must 

 endeavour to study the minor factors, or test their existence 

 by the careful elimination of the major factors. 



It is, however, as a source of origin of variations that use- 

 inheritance is operative if operative at all. Granted that 

 the imbecile ducks have been steadily selected ; granted 

 that the thickened sole has been favoured by natural selec- 

 tion ; the true question is whether a tendency to variations 

 in the direction of thickened epidermis and in the direction 

 of diminished brains has been generated or fostered by use 

 and disuse. Or take the case of the shifted eyes of flat- 

 fishes. The question is not whether, given sufficient time, 

 natural selection could or could not reach these results through 

 the elimination of those fishes in which this particular varia- 



