pment, but is powerless against the doctrine of natural selection,
or the survival of the fittest, which implies only that variations or
individual differences of a favorable nature occasionally arise in a few
species and are then preserved." (p. 149)

This process of improvement under the law of natural selection includes
not only changes in the organic structure of animals, but also in their
instincts and intelligence. On entering on this part of his subject, Mr.
Darwin says, "I would premise that I have nothing to do with the origin
of the primary mental powers, any more than I have with that of life
itself. We are concerned only with the diversities of instinct and of
other mental qualities within the same class." (p. 255) He shows that
even in a state of nature the instincts of animals of the same species
do in some degree vary, and that they are transmitted by inheritance. A
mastiff has imparted courage to a greyhound, and a greyhound has
transmitted to a shepherd-dog a disposition to hunt hares. Among
sporting dogs, the young of the pointer or retriever have been known to
point or to retrieve without instruction. "If," he says, "it can be
shown that instincts do vary ever so little, then I can see no
difficulty in natural selection preserving and continually accumulating
variations of instinct to any extent that was profitable. It is thus, as
I believe, that all the most complex and wonderful instincts have
arisen." (p. 257) He was rather unguarded in saying that he saw no
difficulty in accounting for the most wonderful instincts of animals. He
admits that he has found very great difficulty. He selects three cases
which he found it specially hard to deal with: that of the cuckoo, that
of the cell-building bee, and of the slave-making ant. He devotes much
space and labor in endeavoring to show how the instinct of the bee, for
example, in the construction of its cell, _might_ have been gradually
acquired. It is clear, however, that he was not able fully to satisfy
even his own mind; for he admits that "it will be thought that I have an
over-weening confidence in the principle of natural selection, when I do
not admit that such wonderful and well established facts do not
annihilate the theory." (p. 290) This remark was made with special
reference to the instincts of the ant, which he finds very hard to
account for. He adds, "No doubt many instincts of very difficult
explanation could be opposed to the theory of natur