116 ON THE ORIGIN OF SPECIES 



judged of by the general tenor and balance of evidence 

 given in the following chapters. But we already see 

 how it entails extinction ; and how largely extinction 

 has acted in the world's history, geology plainly de- 

 clares. Natural selection, also, leads to divergence of 

 character ; for more living beings can be supported on 

 the same area the more they diverge in structure, 

 habits, and constitution, of which we see proof by 

 looking to the inhabitants of any small spot or to 

 naturalised productions. Therefore during the modifica- 

 tion of the descendants of any one species, and during 

 the incessant struggle of all species to increase in 

 numbers, the more diversified these descendants 

 become, the better will be their chance of succeeding 

 in the battle for life. Thus the small differences 

 distinguishing varieties of the same species, steadily 

 tend to increase till they come to equal the greater 

 differences between species of the same genus, or even 

 of distinct genera. 



We have seen that it is the common, the widely- 

 diffused, and widely-ranging species, belonging to the 

 larger genera, which vary most ; and these tend to 

 transmit to their modified offspring that superiority 

 which now makes them dominant in their own coun- 

 tries. Natural selection, as has just been remarked, 

 leads to divergence of character and to much extinction 

 of the less improved and intermediate forms of life. 

 On these principles, I believe, the nature of the 

 affinities of all organic beings may be explained. It is 

 a truly wonderful fact — the wonder of which we are 

 apt to overlook from familiarity — that all animals and 

 all plants throughout all time and space should be 

 related to each other in group subordinate to group, in 

 the manner which we everywhere behold — namely, 

 varieties of the same species most closely related 

 together, species of the same genus less closely and 

 unequally related together, forming sections and sub- 

 genera, species of distinct genera much less closely 

 related, and genera related in different degrees, 

 forming sub-families, families, orders, sub-classes, and 



