the less civilized countries where there has been but little artificial
selection. Careful observers are convinced that a damp climate affects
the growth of the hair, and that with the hair the horns are
correlated. Mountain breeds always differ from lowland breeds; and a
mountainous country would probably affect the hind limbs from
exercising them more, and possibly even the form of the pelvis; and
then by the law of homologous variation, the front limbs and even the
head would probably be affected. The shape, also, of the pelvis might
affect by pressure the shape of the head of the young in the womb. The
laborious breathing necessary in high regions would, we have some
reason to believe, increase the size of the chest; and again
correlation would come into play. Animals kept by savages in different
countries often have to struggle for their own subsistence, and would
be exposed to a certain extent to natural selection, and individuals
with slightly different constitutions would succeed best under
different climates; and there is reason to believe that constitution
and colour are correlated. A good observer, also, states that in cattle
susceptibility to the attacks of flies is correlated with colour, as is
the liability to be poisoned by certain plants; so that colour would be
thus subjected to the action of natural selection. But we are far too
ignorant to speculate on the relative importance of the several known
and unknown laws of variation; and I have here alluded to them only to
show that, if we are unable to account for the characteristic
differences of our domestic breeds, which nevertheless we generally
admit to have arisen through ordinary generation, we ought not to lay
too much stress on our
ignorance of the precise cause of the slight analogous differences
between species. I might have adduced for this same purpose the
differences between the races of man, which are so strongly marked; I
may add that some little light can apparently be thrown on the origin
of these differences, chiefly through sexual selection of a particular
kind, but without here entering on copious details my reasoning would
appear frivolous.
The foregoing remarks lead me to say a few words on the protest lately
made by some naturalists, against the utilitarian doctrine that every
detail of structure has been produced for the good of its possessor.
They believe that very many structures have been created for beauty in
the eyes of man, or for mere variety. This doctrine, if true, would be
absolutely fatal to my theory. Yet I fully admit that many structures
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