INDIVIDUAL DIFFERENCES SB 



ations of structure such as we occasionally see in our domes- 

 tic productions, more especially with plants, are ever perma- 

 nently propagated in a state of nature. Almost every part 

 of every organic being is so beautifully related to its complex 

 conditions of life that it seems as improbable that any part 

 should have been suddenly produced perfect, as that a com- 

 plex machine should have been invented by man in a perfect 

 state. Under domestication monstrosities sometimes occur 

 which resemble normal structures in widely different animals. 

 Thus pigs have occasionally been born with a sort of pro- 

 boscis, and if any wild species of the same genus had nat- 

 urally 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 resem- 

 bling 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 reproduc- 

 tion (which is not always the case), as they occur rarely and 

 singly, their preservation would depend on unusually favour- 

 able 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 pres- 

 ervation and perpetuation of single or occasional variations. 



INDIVIDUAL DIFFERENCES 



The many slight differences which appear in the oft'spring 

 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 dift'erences. 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 im- 

 portance for us, for they are often inherited, as must be 

 familiar to every one ; and they thus aft'ord materials for 

 natural selection to act on and accumulate, in the same man- 

 ner as man accumulates in any given direction individual dif- 

 ferences in his domesticated productions. These individual 

 differences generally aft'ect what naturalists consider unim- 



