state of things very similar to that which now
obtains; but that the likeness of the past to the present would
gradually become less and less, in proportion to the remoteness of his
period of observation from the present day: that the existing
distribution of mountains and plains, of rivers and seas, would show
itself to be the product of a slow process of natural change operating
upon more and more widely different antecedent conditions of the mineral
framework of the earth; until, at length, in place of that framework, he
would behold only a vast nebulous mass, representing the constituents of
the sun and of the planetary bodies. Preceding the forms of life which
now exist, our observer would see animals and plants not identical with
them, but like them: increasing their differences with their antiquity,
and at the same time becoming simpler and simpler; until, finally, the
world of life would present nothing but that undifferentiated
protoplasmic matter which, so far as our present knowledge goes, is the
common foundation of all vital activity.

The hypothesis of evolution supposes that in all this vast progression
there would be no breach of continuity, no point at which we could say
"This is a natural process," and "This is not a natural
process"; but
that the whole might be compared to that wonderful process of
development which may be seen going on every day under our eyes, in
virtue of which there arises, out of the semifluid, comparatively
homogeneous substance which we call an egg, the complicated organization
of one of the higher animals. That, in a few words, is what is meant by
the hypothesis of evolution.

* * * * *

I have already suggested that in dealing with these three hypotheses, in
endeavoring to form a judgment as to which of them is the more worthy of
belief, or whether none is worthy of belief--in which case our
condition of mind should be that suspension of judgment which is so
difficult to all but trained intellects,--we should be indifferent to
all _a priori_ considerations. The question is a question of historical
fact. The universe has come into existence somehow or other, and the
problem is, whether it came into existence in one fashion, or whether it
came into existence in another; and, as an essential preliminary to
further discussion, permit me to say two or three words as to the nature
and the kinds of historical evidence.

The evidence as to the occ