Chap. IV. 
DIVEEGENCE OF CHAEACTEE. 
119 
I am far from thinking that the most divergent varieties 
will invariably prevail and multiply: a medium form 
may often long endure, and may or may not produce 
more than one modified descendant; for natural selec¬ 
tion will always act according to the nature of the 
places which are either unoccupied or not perfectly 
occupied by other beings; and this will depend on in¬ 
finitely complex relations. But as a general rule, the 
more diversified in structure the descendants from any 
one species can be rendered, the more places they will 
be enabled to seize on, and the more their modified 
progeny will be increased. In our diagram the line of 
succession is broken at regular intervals by small num¬ 
bered letters marking the successive forms which have 
become sufficiently distinct to be recorded as varieties. 
But these breaks are imaginary, and might have been 
inserted anywhere, after intervals long enough to have 
allowed the accumulation of a considerable amount of 
divergent variation. 
As all the modified descendants from a common and 
widely-diffused species, belonging to a large genus, will 
tend to partake of the same advantages which made 
their parent successful in life, they will generally go 
on multiplying in number as well as diverging in 
character: this is represented in the diagram by the 
several divergent branches proceeding from (A). The 
modified offspring from the later and more highly im¬ 
proved branches in the lines of descent, will, it is pro¬ 
bable, often take the place of, and so destroy, the 
earlier and less improved branches: this is represented 
in the diagram by some of the lower branches not reach¬ 
ing to the upper horizontal lines. In some cases I do 
not doubt that the process of modification will be con¬ 
fined to a single line of descent, and the number of the 
descendants will not be increased; although the amount 
