LAWS OF VARIATION 223 



manner; so that the varieties of two or more species 

 would resemble each other, or that a variety of one spe- 

 cies would resemble in certain characters another and 

 distinct species — this otber species being, according to our 

 view, only a well-marked and permanent variety. But 

 characters exclusively due to analogous variation would 

 probably be of an unimportant nature, for the preserva- 

 tion of all functionally important characters will have 

 been determined through natural selection, in accordance 

 with the different habits of the species. It might further 

 be expected that the species of the same genus would 

 occasionally exhibit reversions to long-lost characters. As, 

 however, we do not know the common ancestor of any 

 natural group, we cannot distinguish between reversionary 

 and analogous characters. If, for instance, we did not 

 know that the parent rock-pigeon was not feather-footed 

 or turn-crowned, we could not have told whether such 

 characters in our domestic breeds were reversions or only 

 analogous variations; but we might have inferred that the 

 blue color was a case of reversion from the number of 

 the markings, which are correlated with this tint, and 

 which would not probably have all appeared together 

 from simple variation. More especially we might have 

 inferred this, from the blue color and the several marks 

 so often appearing when differently colored breeds are 

 crossed. Hence, although under nature it must generally 

 be left doubtful what cases are reversions to formerly 

 existing characters, and what are new but analogous vari- 

 ations, yet we ought, on our theory, sometimes to find 

 the varying offspring of a species assuming characters 

 which are already present in other members of the same 

 group. And this undoubtedly is the case. 



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