82 BASIS OF INVESTIGATION. 



RECAPITULATION. 



Use-inheritance means the inheritance of acquired functional 

 capacity. Before there can be such an inheritance a parent must 

 acquire a functional capacity above the average of the species to 

 which it belongs. The acquirement of such a functional capacity 

 demands a functional activity above the normal. To have the func- 

 tional capacity large the functional activity must have continued for 

 a considerable time, and it is largest when the activity is continued 

 as long as there is any increase in capacity. Applied to the brain 

 of man, the amount of acquired functional capacity would, within 

 limits, be proportional to the length of time devoted to its acquire- 

 ment, and would be greatest in comparatively old men. Hence, if 

 there be such a thing as the inheritance of acquired functional capac- 

 ity, it should be most marked in the descendants of old men, and 

 conversely, if it can be shown that the inherited functional capacity 

 of individuals is proportional to the age of their parents at the time 

 of reproduction, that fact would be evidence of the inheritance of 

 such acquirements. Furthermore, such evidence, if obtained, would 

 not be explainable on any other theory than use-inheritance, because 

 there is no other imaginable reason why great men should only be 

 produced by old fathers. 



