turally excited the most widespread
attention. This book, which took the author three years to write, was
published in 1871, a second and carefully revised edition appearing
three years later. The data brought together occupy more than six
hundred pages. The conclusions reached may be summed up in a few
paragraphs. The principal induction from the evidence is that man is
descended from some less highly organized form. It was Darwin's
conviction that the grounds upon which this conclusion rests will never
be shaken, for the close similarity between man and the lower animals in
embryonic development, as well as in innumerable points of structure and
constitution, both of high and of the most trifling importance,--the
rudiments which he retains and the abnormal reversions to which he is
occasionally liable,--are facts which cannot be disputed. Viewed in the
light of our knowledge of the whole organic world, their meaning is
unmistakable. The great principle of evolution stands out clear and firm
when these groups of facts are considered in connection with others,
such as the mutual affinities of the members of the same group, their
geographical distribution in past and present times, and their
geological succession. It is pronounced incredible that all these facts
should speak falsely. He who is not content to look like a savage at the
phenomena of nature as disconnected cannot any longer believe that man
is the product of a separate act of creation. He will be forced to admit
that the close resemblance of the embryo of man to that, for instance,
of a dog,--the construction of his skull, limbs, and whole frame on the
same plan with that of other mammals, independently of the uses to which
the parts may be put; the occasional reappearance of various structures,
for instance, of several muscles which man does not normally possess,
but which are common to the Quadrumana, and a crowd of analogous
facts,--all point in the plainest manner to the conclusion that man is
the co-descendant with other mammals of a common progenitor.

Darwin recognized that the high standard of our intellectual powers and
moral disposition constitutes the greatest difficulty which presents
itself after we have been driven by the mass of biological evidence to
accept his conclusion as to the origin of man. Touching this point, he
observes: "Every one who admits the principle of evolution must see that
the mental powers of the higher animals, which are t