Chap. U.] INDIVIDUAL DIFFEEENCES. 53 



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 

 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 

 confined locality, may be called individual differences. 

 No one supposes that all the individuals of the same 

 species are cast in the same actual mould. These 

 individual differences 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 accumulates in any given direction individual 

 differences in his domesticated productions. These 

 individual differences generally 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 classificatory 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 of variability, even in im- 

 portant parts of structure, which he could collect on 

 good authority, as I have collected, during a course of 

 years. It should be remembered that system atists 

 are far from being pleased at finding variability in 

 important characters, and that there are not many 



