244 TRANSMISSION OF ACQUIRED CHARACTERS 



" Persistent modification through many generations, though not 

 transmitted to the germ, nevertheless affords the opportunity for 

 germinal variation of like nature. 



" Suppose that a group of plastic organisms is placed under new 

 conditions. Those whose innate plasticity is equal to the occasion 

 are modified and survive. Those whose plasticity is not equal to 

 the occasion are eliminated. . . . Such modification takes place 

 generation after generation, but, as such, is not inherited. . . . But 

 any congenital variations similar in direction to these modifications 

 will tend to support them and to favour the organism in which they 

 occur. Thus will arise a congenital predisposition to the modifica- 

 tions in question. 



" The plasticity still continuing, the modifications become yet 

 further adaptive. Thus plastic modification leads, and germinal 

 variation follows ; the one paves the way for the other. 



" The modification as such is not inherited, but is the condition 

 under which congenital variations are favoured and given time to 

 get a hold on the organism, and are thus enabled by degrees to reach 

 the fully adaptive level." 



15. Practical Considerations 



We have seen that the scientific position in regard to the 

 transmissibility of modifications should be one of active scep- 

 ticism, that there seems to be no convincing evidence in support 

 of the affirmative position, and that there is strong presumption 

 in favour of the negative. * 



A modification is a definite change in the individual body, 

 due to some change in " nurture." There is no secure evidence 

 that any such individual gain or loss can be transmitted as such, 

 or in any representative degree. How does this affect our esti- 

 mate of the value of "nurture " ? How should the sceptical or 

 negative answer, which we believe to be the scientific one, affect 

 our practice in regard to education, physical culture, ameliora- 

 tion of function, improvement of environment, and so on ? Let 

 us give a practical point to what we have already said. 



(a) Every inheritance requires an appropriate nurture if it is 



