d falsely infer, because certain genera or families
have not been found beneath a certain stage, that they did not exist
before that stage. We continually forget how large the world is,
compared with the area over which our geological formations have been
carefully examined; we forget that groups of species may elsewhere have
long existed and have slowly multiplied before they invaded the ancient
archipelagoes of Europe and of the United States. We do not make due
allowance for the enormous intervals of time, which have probably
elapsed between our consecutive formations,--longer perhaps in some
cases than the time required for the accumulation of each formation.
These intervals will have given time for the multiplication of species
from some one or some few parent-forms; and in the succeeding formation
such species will appear as if suddenly created.

I may here recall a remark formerly made, namely that it might require
a long succession of ages to adapt an organism to some new and peculiar
line of life, for instance to fly through the air; but that when this
had been effected, and a few species had thus acquired a great advantage
over other organisms, a comparatively short time would be necessary to
produce many divergent forms, which would be able to spread rapidly and
widely throughout the world.

I will now give a few examples to illustrate these remarks; and to show
how liable we are to error in supposing that whole groups of species
have suddenly been produced. I may recall the well-known fact that in
geological treatises, published not many years ago, the great class
of mammals was always spoken of as having abruptly come in at the
commencement of the tertiary series. And now one of the richest known
accumulations of fossil mammals belongs to the middle of the secondary
series; and one true mammal has been discovered in the new red sandstone
at nearly the commencement of this great series. Cuvier used to urge
that no monkey occurred in any tertiary stratum; but now extinct species
have been discovered in India, South America, and in Europe even as far
back as the eocene stage. The most striking case, however, is that of
the Whale family; as these animals have huge bones, are marine, and
range over the world, the fact of not a single bone of a whale having
been discovered in any secondary formation, seemed fully to justify the
belief that this great and distinct order had been suddenly produced
in the interval