162 
LAWS OF VAEIATION. 
Chap. V. 
cases: 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 difSculty 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 
