ave no reason to suppose that links ever
existed directly intermediate between them, but between each and an
unknown common parent. The common parent will have had in its whole
organisation much general resemblance to the tapir and to the horse; but
in some points of structure may have differed considerably from both,
even perhaps more than they differ from each other. Hence in all such
cases, we should be unable to recognise the parent-form of any two or
more species, even if we closely compared the structure of the parent
with that of its modified descendants, unless at the same time we had a
nearly perfect chain of the intermediate links.

It is just possible by my theory, that one of two living forms might
have descended from the other; for instance, a horse from a tapir; and
in this case DIRECT intermediate links will have existed between them.
But such a case would imply that one form had remained for a very long
period unaltered, whilst its descendants had undergone a vast amount of
change; and the principle of competition between organism and organism,
between child and parent, will render this a very rare event; for in all
cases the new and improved forms of life will tend to supplant the old
and unimproved forms.

By the theory of natural selection all living species have been
connected with the parent-species of each genus, by differences not
greater than we see between the varieties of the same species at the
present day; and these parent-species, now generally extinct, have in
their turn been similarly connected with more ancient species; and so on
backwards, always converging to the common ancestor of each great class.
So that the number of intermediate and transitional links, between all
living and extinct species, must have been inconceivably great. But
assuredly, if this theory be true, such have lived upon this earth.

ON THE LAPSE OF TIME.

Independently of our not finding fossil remains of such infinitely
numerous connecting links, it may be objected, that time will not have
sufficed for so great an amount of organic change, all changes having
been effected very slowly through natural selection. It is hardly
possible for me even to recall to the reader, who may not be a practical
geologist, the facts leading the mind feebly to comprehend the lapse of
time. He who can read Sir Charles Lyell's grand work on the Principles
of Geology, which the future historian will recognise as having produced
a re