1510 THE STORY OF THE UNIVERSE 



ganic beings diverge in structure, habits, and con- 

 stitution, by so much the more can a large number 

 be supported on the area of which we see proof 

 by looking to the inhabitants of any small spot, 

 and to the productions naturalized in foreign lands. 

 Therefore, during the modification of the descend- 

 ants of any one species, and during the incessant 

 struggle of all species to increase in numbers, the 

 more diversified the descendants become, the better 

 will be their chance of success in the battle for life. 

 Thus the small differences distinguishing varieties 

 of the same species steadily tend to increase, till they 

 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 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 everywhere behold ; 

 namely, varieties of the same species most closely 



