t virulent and widespread opposition for a lengthy
period, but even thirty years later, when its principles were generally
recognised and adopted, the application of them to man was energetically
contested by many high scientific authorities. Even Alfred Russel
Wallace, who discovered the principle of natural selection independently
in 1858, did not concede that it was applicable to the higher mental
and moral qualities of man. Dr Wallace still holds a spiritualist and
dualist view of the nature of man, contending that he is composed of a
material frame (descended from the apes) and an immortal immaterial soul
(infused by a higher power). This dual conception, moreover, is still
predominant in the wide circles of modern theology and metaphysics,
and has the general and influential adherence of the more conservative
classes of society.

In strict contradiction to this mystical dualism, which is generally
connected with teleology and vitalism, Darwin always maintained the
complete unity of human nature, and showed convincingly that the
psychological side of man was developed, in the same way as the body,
from the less advanced soul of the anthropoid ape, and, at a still more
remote period, from the cerebral functions of the older vertebrates. The
eighth chapter of the "Origin of Species", which is devoted to instinct,
contains weighty evidence that the instincts of animals are subject,
like all other vital processes, to the general laws of historic
development. The special instincts of particular species were formed
by adaptation, and the modifications thus acquired were handed on to
posterity by heredity; in their formation and preservation natural
selection plays the same part as in the transformation of every other
physiological function. The higher moral qualities of civilised man
have been derived from the lower mental functions of the uncultivated
barbarians and savages, and these in turn from the social instincts
of the mammals. This natural and monistic psychology of Darwin's was
afterwards more fully developed by his friend George Romanes in his
excellent works "Mental Evolution in Animals" and "Mental Evolution in
Man". (London, 1885; 1888.)

Many valuable and most interesting contributions to this monistic
psychology of man were made by Darwin in his fine work on "The Descent
of Man and Selection in Relation to Sex", and again in his supplementary
work, "The Expression of the Emotions in Man and Animals". To u