158 THE ORIGIN OF SPECIES 



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 of 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 exter- 

 mination among our domesticated productions, through 

 the selection of improved forms by man. Many curi- 

 ous instances 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 agricultural writer) "as if by some mur- 

 derous pestilence." 



Divergence of Character 



The principle which I have designated by this term 

 is of high importance, and explains, as I believe, sev- 

 eral important facts. In the first place, varieties, even 

 strongly-marked ones, though having somewhat of the 

 character 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 species. 

 Nevertheless, according to my view, varieties are species 



