RECAPITULATION AND CONCLUSION 519 



of embryological and homologous structures, but we are too 

 blind to understand her meaning. 



I have now recapitulated the facts and considerations 

 which have thoroughly convinced me that species have been 

 modified, during a long course of descent. This has been 

 effected chiefly through the natural selection of numerous 

 successive, slight, favourable variations ; aided in an im- 

 portant manner by the inherited effects of the use and dis- 

 use of parts; and in an unimportant manner, that is in rela- 

 tion to adaptive structures, whether past or present, by the 

 direct action of external conditions, and by variations which 

 seem to us in our ignorance to arise spontaneously. It ap- 

 pears that I formerly underrated the frequency and value of 

 these latter forms of variation, as leading to permanent modi- 

 fications of structure independently of natural selection. 

 But as my conclusions have lately been much misrepre- 

 sented, and it has been stated that I attribute the modifica- 

 tion of species exclusively to natural selection, I may be per- 

 mitted to remark that in the first edition of this work, and 

 subsequently, I placed in a most conspicuous position — 

 namely, at the close of the Introduction the following words : 

 "I am convinced that natural selection has been the main 

 but not the exclusive means of modification." This has been 

 of no avail. Great is the power of steady misrepresenta- 

 tion; but the history of science shows that fortunately this 

 power does not long endure. 



It can hardly be supposed that a false theory would ex- 

 plain, in so satisfactory a manner as does the theory of nat- 

 ural selection, the several large classes of facts above speci- 

 fied. It has recently been objected that this is an unsafe 

 method of arguing; but it is a method used in judging of 

 the common events of life, and has often been used by the 

 greatest natural philosophers. The undulatory theory of 

 light has thus been arrived at; and the belief in the revolu- 

 tion of the earth on its own axis was until lately supported 

 by hardly any direct evidence. It is no valid objection that 

 science as yet throws no light on the far higher problem of 

 the essence or origin of life. Who can explain what is the 

 essence of the attraction of gravity? No one now objects 

 to following out the results consequent on this unknown 



