ce; for
Professor Huxley, speaking in 1870, said, "If the expectation raised by
the splints of the horses that, in some ancestor of the horses, these
splints would be found to be complete digits, has been verified, we are
furnished with very strong reasons for looking for a no less complete
verification that the three-toed _plagiolophus_-like 'avus' of the horse
must have had a five-toed 'atavus' at some earlier period. No such
five-toed 'atavus,' however, has yet made its appearance." But since
then the "atavus" has made its appearance, if not with five complete
toes, at least with four complete and one rudimentary; and any day we
may hear that Professor Marsh has found in still earlier strata a more
primitive form with all five toes complete.

I have no space to go into the evidence of similar "missing links" which
have been recently supplied by palaeontological researches in the case of
several other groups of animals; but their consideration seems to me
quite to justify a more recent utterance of Professor Huxley, who, in
1878, wrote in the _Encyclopaedia Britannica:_ "On the evidence of
palaeontology, the evolution of many existing forms of animal life from
their predecessors is no longer an hypothesis, but an historical fact;
it is only the nature of the physiological factors to which that
evolution is due which is still open to discussion."

III.

THE ARGUMENT FROM GEOLOGY.

But this allusion to fossils leads me to the next division of my
subject--the argument from geology. It is not, however, necessary to say
much on this head, for the simple reason that the whole body of
geological evidence is for the most part of one kind, which although of
a very massive, is of a very simple character. That is to say, apart
from the increasingly numerous cases, such as the one just mentioned,
which geology supplies of extinct "intermediate links" between
_particular_ species now living, the great weight of the geological
evidence consists in the _general_ fact, that of all the thousands of
specific forms of life which palaeontology reveals to us as having lived
on this planet in times past, there is no instance of a highly organised
form occurring low down in the geological series.[1] On the contrary,
there is the best evidence to show that since the first dawn of life in
the occurrence of the simplest organisms, until the meridian splendour
of life as now we see it, gradual advance from the general to the
specia