THE NEUTRAL AND THE FAVOURABLE
EVIDENCE.

In the preceding lecture I pointed out that there are three hypotheses
which may be entertained, and which have been entertained, respecting
the past history of life upon the globe. According to the first of these
hypotheses, living beings, such as now exist, have existed from
all eternity upon this earth. We tested that hypothesis by the
circumstantial evidence, as I called it, which is furnished by the
fossil remains contained in the earth's crust, and we found that it was
obviously untenable. I then proceeded to consider the second hypothesis,
which I termed the Miltonic hypothesis, not because it is of any
particular consequence whether John Milton seriously entertained it or
not, but because it is stated in a clear and unmistakable manner in his
great poem. I pointed out to you that the evidence at our command as
completely and fully negatives that hypothesis as it did the preceding
one. And I confess that I had too much respect for your intelligence
to think it necessary to add that the negation was equally clear and
equally valid, whatever the source from which that hypothesis might be
derived, or whatever the authority by which it might be supported.
I further stated that, according to the third hypothesis, or that of
evolution, the existing state of things is the last term of a long
series of states, which, when traced back, would be found to show no
interruption and no breach in the continuity of natural causation.
I propose, in the present and the following lecture, to test this
hypothesis rigorously by the evidence at command, and to inquire how
far that evidence can be said to be indifferent to it, how far it can be
said to be favourable to it, and, finally, how far it can be said to be
demonstrative.

From almost the origin of the discussions about the existing condition
of the animal and vegetable worlds and the causes which have determined
that condition, an argument has been put forward as an objection to
evolution, which we shall have to consider very seriously. It is an
argument which was first clearly stated by Cuvier in his criticism of
the doctrines propounded by his great contemporary, Lamarck. The French
expedition to Egypt had called the attention of learned men to the
wonderful store of antiquities in that country, and there had been
brought back to France numerous mummified corpses of the animals which
the ancient Egyptians revered and preserved, a