76 THE ORIGIN OF SPECIES 



thus their abnormal character would almost inevitably 

 be lost. But I shall have to return in a future chap- 

 ter to the preservation and perpetuation of single or 

 occasional variations. 



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 inhabiting the same con- 

 fined locality, may be called individual differences. No 

 one supposes that all the individuals of the same species 

 are cast in the same actual mold. These individual dif- 

 ferences are of the highest importance for us, 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 accu- 

 mulates in any given direction individual differences in 

 his domesticated productions. These individual differ- 

 ences generally affect what naturalists consider unimpor- 

 tant parts; but I could show by a long catalogue of 

 facts, that parts which must be called important, whether 

 viewed under a physiological or classificatory point of 

 view, sometimes vary in the individuals of the same spe- 

 cies. I am convinced that the most experienced natural- 

 ist would be surprised at the number of the cases of 

 variability, even in important parts of structure, which 

 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 varia- 

 bility in important characters, and that there are not 

 many men who will laboriously examine internal and im- 



I 



