34 THE ORIGIN OF SPECIES 



it seems as improbable that any part should have been suddenly 

 produced perfect, as that a complex machine should have been 

 invented by man in a perfect state. Under domestication mon- 

 strosities sometimes occur which resemble normal structures in 

 widely different animals. Thus pigs have occasionally been born 

 with a sort of proboscis, and if any wild species of the same genus 

 had naturally possessed a proboscis, it might have been argued 

 that this had appeared as a monstrosity; but I have as yet failed 

 to find, after diligent search, cases of monstrosities resembling 

 normal structures in nearly allied forms, and these alone bear on 

 the question. If monstrous forms of this kind ever do appear in a 

 state of nature and are capable of reproduction (which is not al- 

 ways the case), as they occur rarely and singly, their preservation 

 would depend on unusually favorable circumstances. They would, 

 also, during the first and succeeding generations, cross with the 

 ordinary form, and thus their abnormal character would almost 

 inevitably be lost. But I shall have to return in a future chapter 

 to the preservation and perpetuation of single or occasional varia- 

 tions. 



INDIVIDUAL DIFFERENCES 



The many slight differences which appear in the offspring from 

 the same parents, or which it may be presumed have thus arisen, 

 from being observed in the individuals of the same species inhabit- 

 ing the same confined locality, may be called individual differ- 

 ences. No one supposes that all the individuals of the same species 

 arc cast in the same actual mould. These individual differences 

 are of the highest importance for uc, for they are often inherited, 

 as must be familiar to every one; and they thus afford materials 

 for natural selection to act on and accumulate, in the same manner 

 as man accumulates in any given direction individual differences 

 in his domesticated productions. These individual differences gen- 

 erally affect what naturalists consider unimportant parts; but I 

 could show, by a long catalogue of facts, that parts which must be 

 called important, whether viewed under a physiological or clas- 

 sificatory point of view, sometimes vary in the individuals of the 

 same species. I am convinced that the most experienced naturalist 

 would be surprised at the number of the cases he could collect on 

 good authority, as I have collected, during a course of years. It 

 should be remembered that systematists are far from being pleased 

 at finding variability in important characters, and that there are 

 not many men who will laboriously examine internal and important 

 organs, and compare them in many specimens of the same species. 



