Chap. XV. Conclusion. 42 1 



bryological 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 varia- 

 tions ; aided in an important manner by the inherited effects of the 

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

 in relation 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 appears that 

 I formerly underrated the frequency and value of these latter 

 forms of variation, as leading to permanent modifications of struc- 

 ture independently of natural selection. But as my conclusions 

 have lately been much misrepresented, and it has been stated 

 that I attribute the modification of species exclusively to natural 

 selection, I may be permitted to remark that in the first edition of 

 this work, and subsequently, I placed in a most conspicuous posi- 

 tion — 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 misrepresentation; but the history 

 of science shows that fortunately this power does not long endure. 



It can hardly be supposed that a false theory would explain, in 

 so satisfactory a manner as does the theory of natural selection, the 

 several large classes of facts above specified. 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 revolution 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 element of attraction ; not- 

 withstanding that Leibnitz formerly accused Newton of introducing 



occult qualities and miracles into philosophy." 



I see no good reason why the views given in this volume should 

 shock the religious feelings of any one. It is satisfactory, as 

 showing how transient such impressions are, to remember that the 

 greatest discovery ever made by man, namely, the law of the 



