ogical 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 most 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 {304} 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, for its thickness, 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. Had it not been for the rare accident of the preservation of
footsteps in the new red sandstone of the United States, who would have
ventured to suppose that, besides reptiles, no less than at least thirty
kinds of birds, some of gigantic size, existed during that period? Not a
fragment of bone has been discovered in these beds. Notwithstanding that
the number of joints shown in the fossil impressions correspond with the
number in the several toes of living birds' feet, some authors doubt
whether the animals which left the impressions we