We have also seen that it is the most flourishing or dominant species of the larger genera within each class which on an average yield the greatest number of varieties, and varieties, 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 subordinate to groups.