162 LAWS OF VAKIATION. Chap. V. 



cases : if, for instance, we did not know that the rock- 

 pigeon was not feather-footed or turn-crowned, we could 

 not have told, whether these characters in our domestic 

 breeds were reversions or only analogous variations ; but 

 we might have inferred that the blueness was a case of 

 reversion, from the number of the markings, which are 

 correlated with the blue tint, and which it does not ap- 

 pear probable would all appear together from simple 

 variation. More especially we might have inferred this, 

 from the blue colour and marks so often appearing 

 when distinct breeds of diverse colours are crossed. 

 Hence, though under nature it must generally be left 

 doubtful, what cases are reversions to an anciently ex- 

 isting character, and what are new but analogous varia- 

 tions, yet we ought, on my theory, sometimes to find 

 the varying offspring of a species assuming characters 

 (either from reversion or from analogous variation) 

 which already occur in some other members of the 

 same group. And this undoubtedly is the case in 

 nature. 



A considerable part of the difficulty in recognising a 

 variable species in our systematic works, is due to its 

 varieties mocking, as it were, some of the other spe- 

 cies of the same genus. A considerable catalogue, also, 

 could be given of forms intermediate between two other 

 forms, which themselves must be doubtfully ranked as 

 either varieties or species ; and this shows, unless all 

 these forms be considered as independently created 

 species, that the one in varying has assumed some of 

 the characters of the other, so as to produce the inter- 

 mediate form. But the best evidence is afforded by 

 parts or organs of an important and uniform nature 

 occasionally varying so as to acquire, in some degree, 

 the character of the same part or organ in an allied 

 species. I have collected a long list of such cases ; but 



