eneralisations than with
details. It is my object to mark the epochs of palaeontology, not to
recount all the events of its history.

That which I just now called the fundamental problem of palaeontology,
the question which has to be settled before any other can be profitably
discussed, is this, What is the nature of fossils? Are they, as the
healthy common sense of the ancient Greeks appears to have led them to
assume without hesitation, the remains of animals and plants? Or are
they, as was so generally maintained in the fifteenth, sixteenth, and
seventeenth centuries, mere figured stones, portions of mineral matter
which have assumed the forms of leaves and shells and bones, just as
those portions of mineral matter which we call crystals take on the form
of regular geometrical solids? Or, again, are they, as others thought,
the products of the germs of animals and of the seeds of plants which
have lost their way, as it were, in the bowels of the earth, and have
achieved only an imperfect and abortive development? It is easy to sneer
at our ancestors for being disposed to reject the first in favour of one
or other of the last two hypotheses; but it is much more profitable to
try to discover why they, who were really not one whit less sensible
persons than our excellent selves, should have been led to entertain
views which strike us as absurd, The belief in what is erroneously
called spontaneous generation, that is to say, in the development
of living matter out of mineral matter, apart from the agency of
pre-existing living matter, as an ordinary occurrence at the present
day--which is still held by some of us, was universally accepted as an
obvious truth by them. They could point to the arborescent forms
assumed by hoar-frost and by sundry metallic minerals as evidence of the
existence in nature of a "plastic force" competent to enable inorganic
matter to assume the form of organised bodies. Then, as every one who is
familiar with fossils knows, they present innumerable gradations, from
shells and bones which exactly resemble the recent objects, to masses of
mere stone which, however accurately they repeat the outward form of the
organic body, have nothing else in common with it; and, thence, to mere
traces and faint impressions in the continuous substance of the rock.
What we now know to be the results of the chemical changes which take
place in the course of fossilisation, by which mineral is substituted
for organi