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On the Origin of Species

Variation Under Nature
Variability -- Individual differences -- Doubtful species -- Wide ranging, much diffused,
and common species, vary most -- Species of the larger genera in each country vary more
frequently than the species of the smaller genera -- Many of the species of the larger
genera resemble varieties in being very closely, but unequally, related to each other, and
in having restricted ranges.
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 I 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 distinct 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 singly,
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.
INDIVIDUAL DIFFERENCES.
 
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