ory of the earth's evolution have had to meet numerous and
exasperating difficulties which do not confront the embryologist and
anatomist who study living materials. Nevertheless the library of
palaeontological documents is one which has been founded for over a
century, and it has grown fast during recent decades, so that consistent
accounts may now be read of the great changes in organic life as the earth
has altered and grown older. And in all this record, there is not a single
line or word of fact that contradicts evolution. What definite evidence
there is tells uniformly in favor of the doctrine, for it is possible, in
the first place, to work out the order of succession of many of the great
groups of animals, and this order is found to be the same as that
established by the other bodies of evidence. Secondly, some fossil groups
are astonishingly complete, so that the ancient history of a form like the
horse can be written with something approaching fullness. Finally, the
remains of certain animals have been found so situated in geological ways,
and so constructed anatomically, that the zooelogist is justified in
denoting them "missing links," because they seem to have been intermediate
between groups that have diverged so widely during recent epochs as to
render their common ancestry scarcely credible.

With these general results in mind, we must now become acquainted with
such subjects as the interpretation of fossils, the causes for the
incompleteness of the series, the conditions for fossilization, the forces
of geological nature, and other matters that make the fossils themselves
intelligible as scientific evidence.

* * * * *

Many views have been entertained regarding the actual nature of the relics
of antiquity exhumed from the rocks or exposed upon the surface by the
wear and tear of natural agencies. In earliest times such things were
variously considered as curious freaks of geological formation, as sports
of nature, or as the remains of the slain left upon the battle-ground of
mythical Titans. Some of the Greeks supposed that fossils were parts of
animals formed in the bowels of the earth by a process of spontaneous
generation, which had died before they could make their way to the
surface. They were sometimes described as the bones of creatures stranded
upon the dry land by tidal waves, or by some such catastrophe as the
traditional flood of the scriptures. In medieval ti