CHAPTER II
VARIATION UNDER NATURE
BEFORE applying the principles arrived at in the last chapter to
organic beings in a state of nature, we must briefly discuss whether
these latter are subject to any variation. To treat this subject
properly, a long catalogue of dry facts ought to be given; but these
shall reserve for a future work. Nor shall I here discuss the
various definitions which have been given of the term species. No
one definition has satisfied all naturalists; yet every naturalist
knows vaguely what he means when he speaks of a species. Generally the
term includes the unknown element of a distant act of creation. The
term "variety" is almost equally difficult to define; but here
community of descent is almost universally implied, though it can
rarely be proved. We have also what are called monstrosities; but they
graduate into varieties. By a monstrosity I presume is meant some
considerable deviation of structure, generally injurious, or not
useful to the species. Some authors use the term "variation" in a
technical sense, as implying a modification directly due to the
physical conditions of life; and "variations" in this sense are
supposed not to be inherited; but who can say that the dwarfed
condition of shells in the brackish waters of the Baltic, or dwarfed
plants on Alpine summits, or the thicker fur of an animal from far
northwards, would not in some cases be inherited for at least a few
generations? And in this case I presume that the form would be
called a variety.
It may be doubted whether sudden and considerable deviations of
structure such as we occasionally see in our domestic productions,
more especially with plants, are ever permanently propagated in a
state of nature. Almost every part of every organic being is so
beautifully related to its complex conditions of life that it seems as
improbable that any part should have been suddenly produced perfect,
as that a complex machine should have been invented by man in a
perfect state. Under domestication monstrosities sometimes occur which
resemble normal structures in widely different animals. Thus pigs have
occasionally been born with a sort of proboscis, and if any wild
species of the same genus had naturally possessed a proboscis, it
might have been argued that this had appeared as a monstrosity; but
I have as yet failed to find, after diligent search, cases of
monstrosities resembling normal structures in nearly allied forms, and
these alone bear on the question. If monstrous forms of this kind ever
do appear in a state of nature and are capable of reproduction
(which is not always the case), as they occur rarely and singularly,
their preservation would depend on unusually favourable circumstances.
They would, also, during the first and succeeding generations cross
with the ordinary form, and thus their abnormal character would almost
inevitably be lost. But I shall have to return in a future chapter
to the preservation and perpetuation of single or occasional
variations.
Previous section | Next section
