DIVERGENCE OF CHARACTER. 101 



able variations within any given period. "We have evi- 

 dence of this, in the facts stated in the second chapter, 

 showing that it is the common and dififnsed or dominant 

 species which offer the greatest number of recorded vari- 

 eties. Hence, rare species will be less quickly modified or 

 improved within any given period; they will consequently 

 be beaten in the race for life by the modified and improved 

 descendants of the commoner species. 



From these several considerations I think it inevitably 

 follows, that as new species in the course of time are 

 formed through natural selection, others will become rarer 

 and rarer, and finally extinct. The forms which stand in 

 closest competition with those undergoing modification 

 and improvement, will naturally suffer most. And we 

 have seen in the chapter on the Struggle for Existence 

 that it is the most closely-allied forms, — varieties of the 

 same species, and species of the same genus or related 

 genera — which, from having nearly the same structure, 

 constitution and habits, generally come into the severest 

 competition with each other consequently, each new vari- 

 ety or species, during the progress of its formation, will 

 generally press hardest on its nearest kindred, and tend to 

 exterminate them. We see the same process of extermina- 

 tion among our domesticated productions, through the 

 selection of improved forms by man. Many curious in- 

 stances could be given showing how quickly new breeds of 

 cattle, sheep and other animals, and varieties of flowers, 

 take the place of older and inferior kinds. In Yorkshire, 

 it is historically known that the ancient black cattle were 

 displaced by the long-horns, and that these " were swept 

 away by the short-horns" (I quote the words of an agricul- 

 tural writer) "as if by some murderous pestilence." 



DIVERGESrCB OF CHARACTER. 



The principle, which I have designated by this term, is 

 of high importance, and explains, as I believe, several im- 

 portant facts. In the first place, varieties, even strongly 

 marked ones, though having somewhat of the charac- 

 ter of species — as is shown by the hopeless doubts 

 in many cases how to rank them — yet certainly differ 

 far less from each other than do good and distinct 



