VARIATION UNDER NATURE 55 



or dominant species of the larger genera which on an 

 average vary most ; and varieties, as we shall hereafter 

 see, tend to become converted into new and distinct 

 ■pedes. The larger genera thus 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 subordinate to groups. 



