XIII 
THE GEOLOGICAL EVIDENCES OF EVOLUTION 
389 
reason for the extinction has yet been given. Besides the 
characters I have mentioned, there are many others in the 
skeleton, skull, teeth, and brain of the forty or more inter¬ 
mediate species, which show that the transition from the 
Eocene Eohippus to the modern Equus has taken place in the 
order indicated” 1 (see Fig. 33). 
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 promulga¬ 
tion. 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 develop¬ 
ment 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 dicro- 
ceros), 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 11A 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 Kusa 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 
1 Lecture on the Introduction and Succession of Vertebrate Life in America, 
Nature, vol. xvi. p. 471. 
