and
many even their genera and species companions, in the living world, but
also those genera whose nearer relations are now extinct--as, for instance,
the club-moss-trees, the trilobites, the ammonites, the belemnites, the
sauria, the nummulites,--show still a very perceptible relationship with
living genera, and can be quite accurately included in the botanical and
zooelogical systems; nay, they even fill up gaps in it. The anatomical,
morphological, and, so far as we can judge, the physiological and
biological relationship of the fossil with living organisms, is so great
and comprehensive that in the present state of science a systematic botany
or zooelogy, that should only treat of the fossils or of living organisms
alone, would be imperfect. But the relationship of the fossil organisms
with the natural systems of botany and zooelogy is apparent not only in this
respect, but also in the fact that the single species during the long
periods of time which are shown by geology to have elapsed, came into
existence in a series, which again pretty closely corresponds to the
natural system of the organic kingdoms; and that the fossil representatives
of all classes and families, the nearer they come to the present world,
appear the more nearly related to the living organisms, so that the fauna
and flora of the ante-human time are lost in those of the human period by
transitions gliding from the one to the other. For instance, in the Miocene
formation of the tertiary epoch {65} we find thirty per cent. of species
still living to-day; in the Pliocene, even sixty to eighty per cent., and
toward its end even about ninety-six per cent. of species which are
identical with those now living.

A brief glance may still more closely illustrate this analogy between the
geological series and the organic systems. Plants and animals seem to have
appeared nearly at the same time, and at first in the form of the very
lowest organisms. The earliest plants found by geology belong also to the
lowest stage of the vegetable kingdom; they are the algae. They are followed
again by higher cryptogamous plants, especially ferns and club-mosses. Only
at a later period flowering plants appear, among them being first the
plants with naked seeds standing lower in the systems, as the cycad-trees
and pine-forests; later, those with enclosed seeds, among them being again
first the monocotyledons, last the dicotyledons,--all of them precisely
corresponding to