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 some few generations? and in this case I
presume that the form would be called a variety.

Again, we have many slight differences which may be called individual
differences, such as are known frequently to appear in the offspring
from the same parents, or which may be presumed to have thus arisen,
from being frequently observed in the individuals of the same species
inhabiting the same confined locality. No one supposes that all the
individuals of the same species are cast in the very same mould. These
individual differences are highly important for us, as they afford
materials for natural selection to accumulate, in the same manner as
man can accumulate in any given direction individual differences in his
domesticated productions. These individual differences generally affect
what naturalists consider unimportant parts; but I could show by a long
catalogue of facts, that parts which must be called important, whether
viewed under a physiological or classificatory point of view, sometimes
vary in the individuals of the same species. I am convinced that the
most experienced naturalist would be surprised at the number of the
cases of variability, even in important parts of structure, which he
could collect on good authority, as I have collected, during a course of
years. It should be remembered that systematists are far from pleased at
finding variability in important characters, and that there are not
many men who will laboriously examine internal and important organs, and
compare them in many specimens of the same species. I should never
have expected that the branching of the main nerves close to the great
central ganglion of an insect would have been variable in the same
species; I should have expected that changes of this nature could have
been effected only by slow degrees: yet quite recently Mr. Lubbock has
shown a degree of variability in these main nerves in Coccus, which may
almost be compared to the irregular branching of the stem of a tree.
This philosophical naturalist, I may add, has also quite recently shown
that the muscles in the larvae of certain insects are very far from
uniform. Authors sometimes argue in a circle when they state that
important organs never vary; for these same authors practically rank
that character as important (as some few naturalists have