he best;_ and, moreover, it serves for the correlation
of rocks all over the world." Now observe how, in the following, the
geologist leans upon the evolutionist: _"The life of the globe has
changed with the progress of time. Each epoch has had its peculiar
species, or peculiar groups of species._ Moreover, the succession of
life has followed a grand law of progress, involving under a single
system a closer and closer approximation in the species, as time moved
on, to those which now exist. It follows, therefore, that _identity of
species of fossils proves approximate identity of age."_ Let us bear
this in mind. Dana _takes for granted_ the evolutionary process. The
simpler forms of animal life indicate the older strata, the complex
forms, the more recent. We do not misunderstand Mr. Dana. Such
expressions as the following abound: "Where direct paleontological
observation has ascertained in particular cases the steps of progress in
the development of organs, as, for example, those of the teeth in
Mammals, the facts become a basis for further use in the same
direction." (p. 402.) "The grander divisions of geological time should
be based, in a comprehensive way, on organic progress" (from simple to
more complex structures) (p. 404.) "When the relations of the beds to
those recognized in other regions have been ascertained through
fossils..." (p. 405.)

The principle announced by Dana is accepted by geologists generally.
Angelo Heilprin in _"The Earth and its Story,"_ p. 153 ff. has the
following: "There has been a steady and progressive advance in the
general type of organization from the oldest to the newest periods; more
highly developed or more complicated forms have successively replaced
forms of simpler construction; and this advance is still continuing
to-day. Once more, the correctness of the evolutionary hypothesis is
taken for granted. In the oldest rocks, for example, no trace of
backboned animals has yet been detected; when such do appear for the
first time, they show themselves in their lowest types, the fishes;
these are succeeded later by the amphibians (frogs, newts, salamanders),
and these again by reptiles. And if we take the fishes by themselves, we
find that they, too, begin with their lower, if not absolutely the
lowest types, and progressively develop their higher ones. This history
is repeated in the cases of the reptiles and quadrupeds--in fact, with
every class of animals that is known to us. _Natu