316 DARWINISM STATED BY DARWIN HIMSELF. 



p As we hare no facts to guide ns, specula- 



tion on the subject is almost useless. It is, 

 howcTer, an error to suppose that there would be no 

 struggle for existence, and, consequently, no natural se- 

 lection, until many forms had been produced : Tariations 

 in a single species inhabiting an isolated station might be 

 beneficial, and thus the whole mass of indiyiduals might 

 be modified, or two distinct forms might arise. But, as I 

 remarked toward the close of the Introduction, no one 

 ought to feel surprised at much remaining as yet unex- 

 plained on the origin of species, if we make due allowance 

 for our profound ignorance on the mutual relations of 

 the inhabitants of the world at the present time, and 

 still more so during past ages. 



THE AMOUNT OF LIFE MUST HAVE A LIMIT. 



Origin of "What, then, checks an indefinite increase 



Species, in the number of species ? The amount of life 

 (I do not mean the number of specific forms) 

 supported on an area must have a limit, depending so 

 largely as it does on physical conditions ; therefore, if an 

 area be inhabited by very many species, each or nearly 

 each species wiU be represented by few indiyiduals ; and 

 such species will be liable to extermination from acci- 

 dental fluctuations in the nature of the seasons or in the 

 number of their enemies. The process of extermination 

 in such cases would be rapid, whereas the production of 

 new species must always be slow. Imagine the extreme 

 case of as many species as indiTiduals in England, and 

 the first severe winter or very dry summer would extermi- 

 nate thousands on thousands of species. Rare species, and 

 each species will become rare if the number of species in 

 any country becomes indefinitely increased, will, on the 



