68 SUMMARY. Chap. II. 



forming little clusters round certain other species. Species 

 very closoly allied to other species apparently have restricted 

 rang'cs. In all these several respects the species 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 in- 

 explicable if species are independent creations. 



We have, also, seen that it is the most nourishing or dom- 

 inant species of the larger genera within each class which on 

 an average 3'ield 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 be- 

 come larger ; and throughout Nature the forms of life which 

 are now dominant tend to become still more dominant by leav- 

 ing 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 through- 

 out the universe become divided into groups subordhiate to 

 groups. 



