een our consecutive formations, longer perhaps in many 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 parent-form: and in the succeeding formation, such groups or
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; and consequently
that the transitional forms would often long remain confined to some one
region; but that, when this adaptation had once 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 spread rapidly and widely throughout the world.
Professor Pictet, in his excellent Review of this work, in commenting
on early transitional forms, and taking birds as an illustration, cannot
see how the successive modifications of the anterior limbs of a supposed
prototype could possibly have been of any advantage. But look at the
penguins of the Southern Ocean; have not these birds their front limbs
in this precise intermediate state of "neither true arms nor true
wings?" Yet these birds hold their place victoriously in the battle for
life; for they exist in infinite numbers and of many kinds. I do not
suppose that we here see the real transitional grades through which
the wings of birds have passed; but what special difficulty is there in
believing that it might profit the modified descendants of the penguin,
first to become enabled to flap along the surface of the sea like the
logger-headed duck, and ultimately to rise from its surface and glide
through the air?

I will now give a few examples to illustrate the foregoing remarks, and
to show how liable we are to error in supposing that whole groups of
species have suddenly been produced. Even in so short an interval as
that between the first and second editions of Pictet's great work on
Palaeontology, published in 1844-46 and in 1853-57, the conclusions on
the first appearance and disappearance of several groups of animals
have been considerably modified; and a third edition would require still
further changes. I may recall the well-known fact that in geological
treatises, published not many years ago, mammals were always spoken of
as having abruptly