Hence, though under nature it must
generally be left doubtful, what cases are reversions to an anciently
existing character, and what are new but analogous variations, 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 species 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
intermediate 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
here, as before, I lie under a great disadvantage in not being able to
give them. I can only repeat that such cases certainly do occur, and
seem to me very remarkable.
I will, however, give one curious and complex case, not indeed as
affecting any important character, but from occurring in several
species of the same genus, partly under domestication and partly under
nature.
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