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.

The many slight differences which appear in the offspring from the
same parents, or which it may be presumed have thus arisen, from being
observed in the individuals of the same species inhabiting the same
confined locality, may be called individual differences. No one supposes
that all the individuals of the same species are cast in the same actual
mould. These individual differences are of the highest importance for
us, for they are often inherited, as must be familiar to every one;
and they thus afford materials for natural selection to act on and
accumulate, in the same manner as man accumulates i