Chap. IV. DIVERGENCE OF CHARACTER. 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 



