50 Darwin, and after Darwin. 



less assistance must be lent to natural selection in 

 its work of evolving adaptive modifications '. And 

 inasmuch as we know to what a wonderful extent 

 adaptive modifications are secured during individual 

 life-times — by the direct action of the environment on 

 the one hand, and by increased or diminished use of 

 special organs and mental faculties on the other — it 

 becomes obvious of what importance even a small 

 measure of transmissibility on their part would be 

 in furnishing to natural selection ready-made varia- 

 tions in required directions, as distinguished from 

 promiscuous variations in all directions. Contrari- 

 wise, if functionally-produced adaptations and adapta- 

 tions produced by the direct action of the environ- 

 ment ai'e never transmitted in any degree, not only 



' Mr. Piatt Ball has, indeed, argiied that "use-inheritance would often 

 be an evil," since, for example, "the condyle of the human jaw would 

 become larger than the body of the jaw, because as the fulcrum of the 

 lever it receives more pressure " ; and similarly as regards many other 

 hypothetical cases which he mentions. ( The Effects of Use and Disuse, 

 pp. 1 28-9 et seq^ But it is evident that this argument proves too much. 

 For if the effects of nse and disuse as transmitted to progeny would be 

 an evil, it could only be because these effects as they occur in the parents 

 are an evil — and this they most certainly are not, being, on the contrary 

 and as a general rule, of a high order of adaptive value. Moreover, in the 

 race, there is a superadded agency always at work, which must effect- 

 ually prevent any undue accumulation of these effects — namely, natural 

 selection, which every Darwinist accepts as a controlling principle of all 

 or any other principles of change. Therefore, if, as first produced in 

 the life-time of individuals, the effects of use and disuse are not injurious, 

 much less can they become so if transmitted through the life-time of 

 species. Again, Mr. Wallace argues that, even supposing use-inheritance 

 to occur, its adapting work in the individual can never extend to the 

 race, seeing that the natural selection of fortuitous variations in the 

 directions required must always produce the adaptations more quickly 

 than would be possible by use-inheritance. This argument, being one 

 of more weight, will be dealt with in a future chaptei. 



