This last term is used in both ways; sometimes the whole kind is
vari-coloured, as leopards and peacocks, and some fish, e.g. the
so-called 'thrattai'; sometimes the kind as a whole is not so, but
such individuals are found in it, as with cattle and goats and,
among birds, pigeons; the same applies also to other kinds of birds.
The whole-coloured change much more than the uniformly coloured,
both into the simple colour of another individual of the same kind
(as dark changing into white and vice versa) and into both colours
mingled. This is because it is a natural characteristic of the kind as
a whole not to have one colour only, the kind being easily moved in
both directions so that the colours both change more into one
another and are more varied. The opposite holds with the uniformly
coloured; they do not change except by an affection of the colour, and
that rarely; but still they do so change, for before now white
individuals have been observed among partridges, ravens, sparrows, and
bears. This happens when the course of development is perverted, for
what is small is easily spoilt and easily moved, and what is
developing is small, the beginning of all such things being on a small
scale.
Change is especially found in those animals of which by nature the
individual is whole-coloured but the kind many-coloured. This is owing
to the water which they drink, for hot waters make the hair white,
cold makes it dark, an effect found also in plants.
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