Masterpieces of Science 



cellently fitted through natural selection to 

 browse without their aid; whereas in the calf, the 

 teeth have been left unaffected, and on the prin- 

 ciple of inheritance at corresponding ages have 

 been inherited from a remote period to the present 

 day. On the view of each organism with all its 

 separate parts having been specially created, 

 how utterly inexplicable is it that organs bearing 

 the plain stamp of inutility, such as the teeth in 

 the embryonic calf or the shrivelled wings under 

 the soldered wing covers of many beetles, should 

 so frequently occur. Nature may be said to have 

 taken pains to reveal her scheme of modification, 

 by means of rudimentary organs, of embryo- 

 logical and homologous [corresponding] struc- 

 tures, but we are too blind to understand her 

 meaning. 



I have now recapitulated the facts and con- 

 siderations 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 suc- 

 cessive, slight, favourable variations; 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 fre- 

 quency and value of these latter forms of varia- 

 tion, as leading to permanent modifications of 

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