BASIS OF INVESTIGATION. 6l 



capacity. Organs of a given size and shape are transmitted from 

 generation to generation with great persistency and with very little 

 variation, but the functional capacity of these organs varies greatly 

 and often varies rapidly. We know that use will cause an organ to 

 vary in power much more rapidly than it varies in size or shape, 

 and when we observe that an organ is transmitted in its normal 

 size and shape, but with tremendously increased power, it is hard 

 to conceive how such a variation could occur except through an 

 ancestor having acquired such power in the same organ and having 

 transmitted that power to the offspring. We have justification for 

 this view from the fact that we see structure arising without having 

 any assignable cause, but we never find functional capacity arising 

 during the life of an individual except through use. From this we 

 see that the inheritance of acquired characters means use-inherit- 

 ance, and use-inheritance means the inheritance of acquired func- 

 tional capacity. 



It is from this standpoint of the inheritance of acquired func- 

 tional capacity that we will investigate the subject of the transmis- 

 sion of acquired characters, and the organ selected will be the brain, 

 because the brain varies more widely in power than any other organ. 

 It is only necessary to compare the brain of a Humboldt with the 

 brain of an ordinary mental incompetent to see how great may be 

 the difference in functional capacity when the difference in size is 

 slight. 



THE LAW OF PROBABILITIES. 



If the Weismannian theory be true in that part which says that 

 ancestral use is absolutely without effect upon descendants, and that 

 variations arise fortuitously within the germ plasm, then advan- 

 tageous and disadvantageous variations will occur according to the 

 law of probabilities. Thus, if we take one thousand births as they 



