Pasturing at once, and in broad hoards upsprung.
The grassy clods now calved; now half appears
There is no doubt as to the meaning of this statement, or as to what a man of Milton's genius expected would have been actually visible to one who could witness the process of the origination of living things.
The third hypothesis, or the hypothesis of evolution, supposes that at any given period in the past we should meet with a state of things more or less similar to the present, but less similar in proportion as we go back in time; that the physical form of the earth could be traced back in this way to a condition in which its parts were separated, as little more than a nebulous cloud making part of a whole in which we should find the sun and the other planetary bodies also resolved; and that, if we traced back the animal world and the vegetable world, we should find preceding what now exist animals and plants not identical with them, but like them, only increasing their differences as we go back in time, and at the same time becoming simpler and simpler, until finally we should arrive at that gelatinous mass which, so far as our present knowledge goes, is the common foundation of all life.
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 series of changes which may be seen going on every day under our eyes, in virtue of which there arises, out of that semifluid, 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—and our condition of mind should be that suspension of judgment which is so difficult to all but trained minds—we should be indifferent to all a