NATURAL SELECTION 187 



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 within each class, which vary most; and 

 these tend to transmit to their modified offspring that 

 superiority which now makes them dominant in their 

 own countries. Natural selection, as has just been re- 

 marked, leads to divergence of character and to much 

 extinction of the less improved and intermediate forms 

 of life. On these principles, the nature of the affinities, 

 and the generally well-defined distinctions between the 

 innumerable organic beings in each class throughout 

 the world, 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 groups, 

 subordinate to groups, in the manner which we every- 

 where behold; namely, varieties of the same species most 

 closely related, species of the same genus less closely and 

 unequally related, 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 classes. The several subordinate 

 groups in any class cannot be ranked in a single file, 

 but seem clustered round points, and these round other 

 points, and so on in almost endless cycles. If species 

 had been independently created, no explanation would 

 have been possible of this kind of classification; but it 

 is explained through inheritance and the complex action 

 of natural selection, entailing extinction and divergence of 

 character, as we have seen illustrated in the diagram. 



