That is what I mean by demonstrative evidence of evolution.  An inductive hypothesis is said to be demonstrated when the facts are shown to be in entire accordance with it.  If that is not scientific proof, there are no merely inductive conclusions which can be said to be proved.  And the doctrine of evolution, at the present time, rests upon exactly as secure a foundation as the Copernican theory of the motions of the heavenly bodies did at the time of its promulgation.  Its logical basis is precisely of the same character—­the coincidence of the observed facts with theoretical requirements.

The only way of escape, if it be a way of escape, from the conclusions which I have just indicated, is the supposition that all these different equine forms have been created separately at separate epochs of time; and, I repeat, that of such an hypothesis as this there neither is, nor can be, any scientific evidence; and, assuredly, so far as I know, there is none which is supported, or pretends to be supported, by evidence or authority of any other kind.  I can but think that the time will come when such suggestions as these, such obvious attempts to escape the force of demonstration, will be put upon the same footing as the supposition made by some writers, who are, I believe, not completely extinct at present, that fossils are mere simulacra, are no indications of the former existence of the animals to which they seem to belong; but that they are either sports of Nature, or special creations, intended—­as I heard suggested the other day—­to test our faith.

In fact, the whole evidence is in favour of evolution, and there is none against it.  And I say this, although perfectly well aware of the seeming difficulties which have been built up upon what appears to the uninformed to be a solid foundation.  I meet constantly with the argument that the doctrine of evolution cannot be well founded, because it requires the lapse of a very vast period of time; the duration of life upon the earth, thus implied, is inconsistent with the conclusions arrived at by the astronomer and the physicist.  I may venture to say that I am familiar with those conclusions, inasmuch as some years ago, when President of the Geological Society of London, I took the liberty of criticising them, and of showing in what respects, as it appeared to me, they lacked complete and thorough demonstration.  But, putting that point aside, suppose that, as the astronomers, or some of them, and some physical philosophers, tell us, it is impossible that life could have endured upon the earth for as long a period as is required by the doctrine of evolution—­supposing that to be proved—­I desire to be informed, what is the foundation for the statement that evolution does require so great a time?  The biologist knows nothing whatever of the amount of time which may be required for the process of evolution.  It is a matter of fact that the equine forms which I have described to you occur, in the order stated, in the