or more intermediate species, which show
that the transition from the Eocene Eohippus to the modern Equus
has taken place in the order indicated"[187] (see Fig. 33).

[Illustration: FIG. 33.--Geological development of the horse tribe
(Eohippus since discovered).]

Well may Professor Huxley say that this is demonstrative evidence of
evolution; the doctrine resting upon exactly as secure a foundation as
did the Copernican theory of the motions of the heavenly bodies at the
time of its promulgation. Both have the same basis--the coincidence of
the observed facts with the theoretical requirements.

_Development of Deer's Horns._

Another clear and unmistakable proof of evolution is afforded by one of
the highest and latest developed tribes of mammals--the true deer. These
differ from all other ruminants in possessing solid deciduous horns
which are always more or less branched. They first appear in the Middle
Miocene formation, and continue down to our time; and their development
has been carefully traced by Professor Boyd Dawkins, who thus summarises
his results:--

"In the middle stage of the Miocene the cervine antler consists
merely of a simple forked crown (as in Cervus dicroceros), which
increases in size in the Upper Miocene, although it still
remains small and erect, like that of the roe. In Cervus
Matheroni it measures 11.4 inches, and throws off not more than
four tines, all small. The deer living in Auvergne in the
succeeding or Pliocene age, present us with another stage in the
history of antler development. There, for the first time, we see
antlers of the Axis and Rusa type, larger and longer, and more
branching than any antlers were before, and possessing three or
more well-developed tines. Deer of this type abounded in
Pliocene Europe. They belong to the Oriental division of the
Cervidae, and their presence in Europe confirms the evidence of
the flora, brought forward by the Comte de Saporta, that the
Pliocene climate was warm. They have probably disappeared from
Europe in consequence of the lowering of the temperature in the
Pleistocene age, while their descendants have found a congenial
home in the warmer regions of Eastern Asia.

"In the latest stage of the Pliocene--the Upper Pliocene of the
Val d'Arno--the Cervus dicranios of Nesti presents us with
antlers much smaller than those of the Irish elk, bu