RESEMBLE VARIETIES. 58 



species. Species very closely allied to other species appar* 

 ently have restricted ranges. In all these respects the spe- 

 cies of large genera present a strong analogy with varieties. 

 And we can clearly understand these analogies, if species 

 once existed as varieties, and thus originated ; whereas, these 

 analogies are utterly inexplicable if species are independent 

 creations. 



We have also seen that it is the most flourishing or domi- 

 nant species of the larger genera within each class which on 

 an average yield the greatest number of varieties ; and varie- 

 ties, as we shall hereafter see, tend to become converted into 

 new and distinct species. Thus the larger genera tend to 

 become larger ; and throughout nature the forms of life which 

 are now dominant tend ' to become still more dominant by 

 leaving many modified and dominant descendants. But, by 

 steps hereafter to be explained, the larger genera also tend 

 to break up into smaller genera. And thus the forms of life 

 throughout the universe become divided into groups subordi- 

 nate to groups 



