error to suppose that these organic remains were fragmentary relics. Our
museums exhibit fossil shells of immeasurable antiquity, as perfect as the
day they were formed; whole skeletons without a limb disturbed; nay, the
changed flesh, the developing embryos, and even the very footsteps of
primaeval organisms. Thus the naturalist finds in the bowels of the earth
species as well defined as, and in some groups of animals more numerous
than, those which breathe the upper air. But, singularly enough, the
majority of these entombed species are wholly distinct from those that now
live. Nor is this unlikeness without its rule and order. As a broad fact,
the further we go back in time the less the buried species are like
existing forms; and, the further apart the sets of extinct creatures are,
the less they are like one another. In other words, there has been a
regular succession of living beings, each younger set, being in a very
broad and general sense, somewhat more like those which now live.

It was once supposed that this succession had been the result of vast
successive catastrophes, destructions, and re-creations _en masse_;
but catastrophes are now almost eliminated from geological, or at least
palaeontological speculation; and it is admitted, on all hands, that the
seeming breaks in the chain of being are not absolute, but only relative to
our imperfect knowledge; that species have replaced species, not in
assemblages, but one by one; and that, if it were possible to have all the
phenomena of the past presented to us, the convenient epochs and formations
of the geologist, though having a certain distinctness, would fade into one
another with limits as undefinable as those of the distinct and yet
separable colours of the solar spectrum.

Such is a brief summary of the main truths which have been established
concerning species. Are these truths ultimate and irresolvable facts, or
are their complexities and perplexities the mere expressions of a higher