tures of
which no monuments happen to remain. Professor Forbes has remarked, that
few geologists are aware how large a proportion of all known species of
fossils are founded on single specimens, while a still greater number
are founded on a few individuals discovered in one spot. This holds true
not only in regard to animals and plants inhabiting the land, the lake,
and the river, but even to a surprising number of the marine mollusca,
articulata, and radiata. Our knowledge, therefore, of the living
creation of any given period of the past may be said to depend in a
great degree on what we commonly call chance, and the casual discovery
of some new localities rich in peculiar fossils may modify or entirely
overthrow all our previous generalizations.

Upon the whole then we derive this result from a general review of the
fossils of the successive tertiary strata, namely, that since the Eocene
period, there have been several great changes in the land quadrupeds
inhabiting Europe, probably not less than five complete revolutions,
during which there has been no step whatever made in advance, no
elevation in the scale of being; so that had man been created at the
commencement of the Eocene era, he would not have constituted a greater
innovation on the state of the animal creation previously established
than now, when we believe him to have begun to exist at the close of the
Pleiocene. The views, therefore, which I proposed in the first edition
of this work, January, 1830, in opposition to the theory of progressive
development, do not seem to me to require material modification,
notwithstanding the large additions since made to our knowledge of
fossil remains.

These views may be thus briefly stated. From the earliest period at
which plants and animals can be proved to have existed, there has been a
continual change going on in the position of land and sea, accompanied
by great fluctuations of climate. To these ever-varying geographical and
climatal conditions the state of the animate world has been unceasingly
adapted. No satisfactory proof has yet been discovered of the gradual
passage of the earth from a chaotic to a more habitable state, nor of
any law of progressive development governing the extinction and
renovation of species, and causing the fauna and flora to pass from an
embryonic to a more perfect condition, from a simple to a more complex
organization.

The principle of adaptation to which I have alluded, appear