variability_, as it may be called, still present in a high degree. 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.
The principle included in these remarks may be extended. It is
notorious that specific characters are more variable than generic. To
explain by a simple example what is meant. If some species in a large
genus of plants 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 an explanation is not in this case applicable, which
most naturalists would advance, 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 subject in our chapter on Classification. It would be almost
superfluous to adduce evidence in support of the above statement, that
specific characters are more variable than generic; but I have
repeatedly noticed in works on natural history, that when an author has
remarked with surprise that some _important_ organ or part, which is
generally very constant throughout large groups of species, has
_differed_ considerably in closely-allied species, that it has, also,
been _variable_ in the individuals of some of the species. And this
fact shows that a character, which is generally of generic value, when
it sinks in value and becomes only of specific value, often becomes
variable, though its physiological importance may remain the same.
Something of the same kind applies to monstrosities: at least Is.
Geoffroy St. Hilaire seems to entertain no doubt, that the more an
organ normally differs in the different species of the same group, the
more subject it is to individual anomalies.
On the ordinary view of each species having been independently created,
why should that part of the structure, which differs from the same part
in other independently-created species of the same genus, be more
variable than those parts which are closely alike in the several
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