There is no doubt as to the meaning of this statement, nor as to what a
man of Milton's genius expected would have been actually visible to an
eye-witness of this mode of origination of living things.

The third hypothesis, or the hypothesis of evolution, supposes that, at
any comparatively late period of past time, our imaginary spectator
would meet with a 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 operation of
development which may be seen going on every day under our eyes, in
virtue of which there arises, out of the semi-fluid comparatively