of the localities where the
broken edges of the strata expose the buried life within them, how
numerous this early population of the earth must have been. No one who
has held in his hand one of the crowded slabs of sand--or lime-stone,
full of Crustacea, Shells, and Corals, from any of the old Silurian or
Devonian beaches which follow each other from north to south across the
State of New York, can suppose that the manifestation of life was less
multitudinous then than now. Now, what does this fossil creation tell
us? It says this: that, in the Silurian period, the first in which
organic life is found at all, there were the three classes of Radiates,
the three classes of Mollusks, two of the classes of Articulates, and
one class of Vertebrates. In other words, at the dawn of life on earth,
the plan of the animal creation with its four fundamental ideas was laid
out,--Radiates, Mollusks, Articulates, and Vertebrates were present at
that first representation of life upon our globe. If, then, all the
primary types appeared simultaneously, one cannot have grown out of
another,--they could not be at once contemporaries and descendants of
each other.

The diagram on the opposite page represents the geological periods in
their regular succession, and the approximate time at which all the
types and all the classes of the Animal Kingdom were introduced; for
there is still some doubt as to the exact period of the introduction of
several of the classes, though all geologists are agreed respecting
them, within certain limits, not very remote from each other, according
to geological estimates of time.

RADIATES.
Polyps. Acalephs. Echinoderms.
T | Present,.........|.........|...........|......
E | | | |
R | Pliocene,........|.........|...........|......
T | | | |
I | Miocene,.........|.........|...........|......
A | | | |
R | Eocene,..........|.........|...........|......
Y | | | |
| | |
S | Cretaceous,......|.........|...........|......
E | | | |
C | Jurassic,........|.........|...........|......
O | | | |
N | Triassic,........|.........|...........|......
D |