6 INTRODUCTION. 



organic beings throughout time ; in the twelfth and 

 thirteenth, their geographical distribution throughout 

 space ; in the fourteenth, their classification or mutual 

 affinities, both when mature and in an embryonic con- 

 dition. In the last chapter I shall give a brief recapitu- 

 lation of the whole work, and a few concluding remarks. 

 No one ought to feel surprise at much remaining as 

 yet unexplained in regard to the origin of species and 

 varieties, if he make clue allowance for our profound 

 ignorance in regard to the mutual relations of the many 

 beings which live around us. "Who can explain why one 

 species ranges widely and is very numerous, and why an- 

 other allied species has a narrow range and is rare ? Yet 

 these relations are of the highest importance, for they 

 determine the present welfare and, as I believe, the future 

 success and modification of every inhabitant of this 

 world. Still less do we know of the mutual relations of 

 the innumerable inhabitants of the world during the 

 many past geological epochs in its history. Although 

 much remains obscure, and will long remain obscure, I 

 can entertain no doubt, after the most deliberate study 

 and dispassionate judgment of which I am capable, that 

 the view which most naturalists until recently enter- 

 tained, and which I formerly entertained — namely, that 

 each species has been independently created — is erro- 

 neous. I am fully convinced that species are not 

 immutable ; but that those belonging to what are called 

 the same genera are lineal descendants of some other and 

 generally extinct species, in the same manner as the 

 acknowledged varieties of any one species are the de- 

 scendants of that species. Furthermore, I am convinced 

 that Natural Selection has been the most important, 

 but not the exclusive, means of modification. 



