Time and Life | Page 5

the general condition of the earth
through geologic time, may feel compelled by what he knows of
causation, and by the general analogy of nature, to suppose that our
solar system was once a nebulous mass; that it gradually condensed,
that it broke up into that wonderful group of harmoniously rolling balls
we call planets and satellites, and that then each of these underwent its
appointed metamorphosis, until at last our own share of the cosmic
vapour passed into that condition in which we first meet with definite
records of its state, and in which it has since, with comparatively little
change, remained.
The doctrine of uniformity and the doctrine of progression are,

therefore, perfectly consistent; perhaps, indeed, they might be shown to
be necessarily connected with one another.
If, however, the condition of the world, which has obtained throughout
geologic time, is but the sequel to a vast series of changes which took
place in pre-geologic time, then it seems not unlikely that the duration
of this latter is to that of the former as the vast extent of geologic time
is to the length of the brief epoch we call the historical period; and that
even the oldest rocks are records of an epoch almost infinitely remote
from that which could have witnessed the first shaping of our globe.
It is probable that no modern geologist would hesitate to admit the
general validity of these reasonings when applied to the physics of his
subject, whence it is the more remarkable that the moment the question
changes from one of physics and chemistry to one of natural history,
scientific opinions and the popular prejudices, which reflect them in a
distorted form, undergo a sudden metamorphosis. Geologists and
palaeontologists write about the "beginning of life" and the
"first-created forms of living beings," as if they were the most familiar
things in the world; and even cautious writers seem to be on quite
friendly terms with the "archetype" whereby the Creator was guided
"amidst the crash of falling worlds." Just as it used to be imagined that
the ancient world was physically opposed to the present, so it is still
widely assumed that the living population of our globe, whether animal
or vegetable, in the older epochs, exhibited forms so strikingly
contrasted with those which we see around us, that there is hardly
anything in common between the two. It is constantly tacitly assumed
that we have before us all the forms of life which have ever existed;
and though the progress of knowledge, yearly and almost monthly,
drives the defenders of that position from their ground, they entrench
themselves in the new line of defences as if nothing had happened, and
proclaim that the 'new' beginning is the 'real' beginning.
Without for an instant denying or endeavouring to soften down the
considerable positive differences (the negative ones are met by another
line of argument) which undoubtedly obtain between the ancient and
the modern worlds of life, we believe they have been vastly overstated
and exaggerated, and this belief is based upon certain facts whose value
does not seem to have been fully appreciated, though they have long
been more or less completely known.

The multitudinous kinds of animals and plants, both recent and fossil,
are, as is well known, arranged by zoologists and botanists, in
accordance with their natural relations, into groups which receive the
names of sub-kingdoms, classes, orders, families, genera and species.
Now it is a most remarkable circumstance that, viewed on the great
scale, living beings have differed so little throughout all geologic time
that there is no sub-kingdom and no class wholly extinct or without
living representatives.
If we descend to the smaller groups, we find that the number of orders
of plants is about two hundred; and I have it on the best authority that
not one of these is exclusively fossil; so that there is absolutely not a
single extinct ordinal type of vegetable life; and it is not until we
descend to the next group, or the families, that we find types which are
wholly extinct. The number of orders of animals, on the other hand,
may be reckoned at a hundred and twenty, or thereabouts, and of these,
eight or nine have no living representatives. The proportion of extinct
ordinal types of animals to the existing types, therefore, does not
exceed seven per cent.--a marvellously small proportion when we
consider the vastness of geologic time.
Another class of considerations--of a different kind, it is true, but
tending in the same direction--seems to have been overlooked. Not
only is it true that the general plan of construction of animals and plants
has been the same in all recorded time as at present, but there are
particular kinds of animals and plants which have existed throughout