metimes a
little more in one point, and sometimes in another, yet on the whole
gradually approaching in character to our present race or dray-horses,
which are so admirably fitted in the one case for fleetness and in the
other for draught.

Although natural selection would thus[836] tend to give to the {335} male
elk its present structure, yet it is probable that the inherited influence
of use has played an equal or more important part. As the horns gradually
increased in weight, the muscles of the neck, with the bones to which they
are attached, would increase in size and strength; and these parts would
react on the body and legs. Nor must we overlook the fact that certain
parts of the skull and the extremities would, judging by analogy, tend from
the first to vary in a correlated manner. The increased weight of the horns
would also act directly on the skull, in the same manner as, when one bone
is removed in the leg of a dog, the other bone, which has to carry the
whole weight of the body, increases in thickness. But from the facts given
with respect to horned and hornless cattle, it is probable that the horns
and skull would immediately act on each other through the principle of
correlation. Lastly, the growth and subsequent wear and tear of the
augmented muscles and bones would require an increased supply of blood, and
consequently an increased supply of food; and this again would require
increased powers of mastication, digestion, respiration, and excretion.

_Colour as Correlated with Constitutional Peculiarities._

It is an old belief that with man there is a connexion between complexion
and constitution; and I find that some of the best authorities believe in
this to the present day.[837] Thus Dr. Beddoe by his tables shows[838] that
a relation exists between liability to consumption and the colour of the
hair, eyes, and skin. It has been affirmed[839] that, in the French army
which invaded Russia, soldiers having a dark complexion, from the {336}
southern parts of Europe, withstood the intense cold better than those with
lighter complexions from the north; but no doubt such statements are liable
to error.

In the second chapter on Selection I have given several cases proving that
with animals and plants differences in colour are correlated with
constitutional differences, as shown by greater or less immunity from
certain diseases, from the attacks of parasitic plants and animals, from
burning by the sun, and