For in this case the variability will seldom as
yet have been fixed by the continued selection of the individuals varying
in the required manner and degree, and by the continued rejection of those
tending to revert to a former and less modified condition.
SPECIFIC CHARACTERS MORE VARIABLE THAN GENERIC CHARACTERS.
The principle discussed under the last heading may be applied to our
present subject. It is notorious that specific characters are more
variable than generic. To explain by a simple example what is meant: if
in a large genus of plants some species had blue flowers and some had red,
the colour would be only a specific character, and no one would be
surprised at one of the blue species varying into red, or conversely; but
if all the species had blue flowers, the colour would become a generic
character, and its variation would be a more unusual circumstance. I have
chosen this example because the explanation which most naturalists would
advance is not here applicable, namely, that specific characters are more
variable than generic, because they are taken from parts of less
physiological importance than those commonly used for classing genera. I
believe this explanation is partly, yet only indirectly, true; I shall,
however, have to return to this point in the chapter on Classification. It
would be almost superfluous to adduce evidence in support of the statement,
that ordinary specific characters are more variable than generic; but with
respect to important characters, I have repeatedly noticed in works on
natural history, that when an author remarks with surprise that some
important organ or part, which is generally very constant throughout a
large group of species, DIFFERS considerably in closely-allied species, it
is often VARIABLE in the individuals of the same species.
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