86 THE ORIGIN OF SPECIES 



stated in the second chapter, showing that it is the common and 

 diffused or dominant species which offer the greatest number of 

 recorded varieties. 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 descend- 

 ants 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 natu- 

 ral selection, others will become rarer and rarer, and finally ex- 

 tinct. 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 Exist- 

 ence, 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; con- 

 sequently, each new variety 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 instances could be given 

 showing how quickly new breeds of cattle, sheep, and other ani- 

 mals, and varieties of flowers, take the place of older and inferior 

 kinds. In Yorkshire, it is historically known that the ancient black 

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

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

 writer) a as if by some murderous pestilence." 



DIVERGENCE OF CHARACTER 



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

 importance, and explains, as I believe, several important facts. In 

 the first place, varieties, even strongly marked ones, though hav- 

 ing somewhat of the character of species — as is shown by the hope- 

 less doubts in many cases how to rank them — yet certainly differ 

 far less from each other than do good and distinct species. Never- 

 theless, according to my view, varieties are species in the process 

 of formation, or are, as I have called them, incipient species. How, 

 then, does the lesser difference between varieties become aug- 

 mented into the greater difference between species? That this does 

 habitually happen, we must infer from most of the innumerable 

 species throughout nature presenting well-marked differences; 

 whereas varieties, the supposed prototypes and parents of future 

 well-marked species, present slight and ill-defined differences. Mere 



