ADAPTATION. 231 



that beyond a limit, usually soon reached, very little, if any, 

 further modification can be produced. The experiences which 

 we colligate into the one induction thrust the other upon us. 

 After a time no training makes the pugilist or the athlete 

 any stronger. The adult gymnast at last acquires the power 

 to perform certain difficult feats; but certain more difficult 

 feats no additional practice enables him to perform. Years of 

 discipline give the singer a particular loudness and range of 

 voice, beyond which further discipline does not give greater 

 loudness or wider range: on the contrary, increased vocal 

 exercise, causing a waste in excess of repair, is often followed 

 by decrease of power. In the exaltation of the per 



ceptions we see similar limits. The culture which raises 

 the susceptibility of the ear to the intervals and harmonies 

 of notes, will not turn a bad ear into a good one. Life 

 long effort fails to make this artist a correct draftsman or 

 that a fine colourist : each docs better than he did at first, 

 but each falls short of the power attained by some other 

 artists. Nor is this truth less clearly illustrated 



among the more complex mental powers. A man may have 

 a mathematical faculty, a poetical faculty, or an oratorical 

 faculty, which special education improves to a certain extent. 

 But unless he is unusually endowed in one of those directions, 

 no amount of education will make him a first-rate mathe 

 matician, a first-rate poet, or a first-rate orator. Thus 

 the general fact appears to be that while in each individual 

 certain changes in the proportions of parts may be caused 

 by variations of functions, the congenital structure of each 

 individual puts a limit to the modifiability of every 

 part. Nor is this true of individuals only: it holds, 

 in a sense, of species. Leaving, open the question whether, 

 in indefinite times, indefinite modifications may not be pro 

 duced by inheritance of functionally wrought adaptations; 

 experience proves that within assigned times, the changes 

 wrought in races of organisms by changes of conditions fall 

 within narrow limits. Though by discipline, aided by selec- 

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