APPENDIX C. 



THE INHERITANCE OF FUNCTIONALLY-WROUGHT MODIFI- 

 CATIONS: A SUMMARY. 



The assertion that changes of structure caused by changes of 

 function are transmitted to descendants is continually met by the 

 question — Where is the evidence ? When some facts are assigned 

 in proof, they are pooh-poohed as insufficiento If after a time the 

 question is raised afresh and other facts are named, there is a like 

 supercilious treatment of them. Successively rejected in this way, 

 the evidences do not accumulate in the minds of opponents ; and 

 hence produce little or no effect. When they are brought together, 

 however, it turns out that they are numerous and weighty. We 

 will group them into negative and positive. 



Negative evidence is furnished by those cases in which traits 

 otherwise inexplicable are explained if the structural effects of 

 use and disuse are transmitted. In the foregoing chapters and 

 appendices three have been given. 



(1) Co-adaptation of co-operative parts comes first. This has 

 been exemplified by the case of enlarged horns in a stag, by the 

 case of an animal led into the habit of leaping, and in the case of 

 the giraffe (cited in " The Factors of Organic Evolution ") ; and 

 it has been shown that the implied co-adaptations of parts cannot 

 possibly have been effected by natural selection. 



(2) The possession of unlike powers of discrimination by dif- 

 ferent parts of the human skin, was named as a problem to be 

 solved on the hypothesis of natural selection or the hypothesis of 

 panmixia ; and it was shown that neither of these can by any 

 twisting yield a solution. But the facts harmonize with the 

 hypothesis that the effects of use are inherited. 



(3) Then come the cases of those rudimentary organs which, 

 like the hind limbs of the whale, have nearly disappeared. 

 Dwindling by natural selection is here out of the question ; and 

 dwindling by panmixia, even were its assumptions valid, would 

 be incredible. But as a sequence of disuse the change is clearly 

 explained. 



Failure to solve any one of these three problems would, I think, 



