152 THE DESCENT OF MAN. Part I. 



through the increased or decreased use of other parts, 

 to other changes of a quite unexpected nature. It is 

 also well to reflect on such facts, as the wonderful 

 growth of galls on plants caused by the poison of an 

 insect, and on the remarkable changes of colour in the 

 plumage of parrots when fed on certain fishes, or in- 

 oculated with the poison of toads ; 80 for we can thus 

 see that the fluids of the system, if altered for some 

 special purpose, might induce other strange changes. 

 We should especially bear in mind that modifications 

 acquired and continually used during past ages for 

 some useful purpose would probably become firmly 

 fixed and might be long inherited. 



Thus a very large yet undefined extension may safely 

 be given to the direct and indirect results of natural 

 selection ; but I now admit, after reading the essay by 

 JSTageli on plants, and the remarks by various authors 

 with respect to animals, more especially those recently 

 made by Professor Broca, that in the earlier editions of 

 my * Origin of Species ' I probably attributed too much 

 to the action of natural selection or the survival of the 

 fittest. I have altered the fifth edition of the Origin 

 so as to confine my remarks to adaptive changes of 

 structure. I had not formerly sufficiently considered 

 the existence of many structures which appear to be, 

 as far as we can judge, neither beneficial nor injurious ; 

 and this I believe to be one of the greatest oversights as 

 yet detected in my work. I may be permitted to say 

 as some excuse, that I had two distinct objects in view, 

 firstly, to shew that species had not been separately 

 created, and secondly, that natural selection had been 

 the chief agent of change, though largely aided by the 



80 ' The Variation of Animals and Plants under Domestication.' vol. 

 ii. p. 280, 282. 



