and kangaroos, but you find rhinoceroses, elephants, lions, tigers,
etc.,--of different species to those now living,--but still their close
allies. If you turn to South America, where, at the present day, we
have great sloths and armadilloes and creatures of that kind, what do
you find in the newest tertiaries? You find the great sloth-like
creature, the 'Megatherium', and the great armadillo, the 'Glyptodon',
and so on. And if you go to Australia you find the same law holds
good, namely, that that condition of organic nature which has preceded
the one which now exists, presents differences perhaps of species, and
of genera, but that the great types of organic structure are the same
as those which now flourish.

What meaning has this fact upon any other hypothesis or supposition than
one of successive modification? But if the population of the world, in
any age, is the result of the gradual modification of the forms which
peopled it in the preceding age,--if that has been the case, it is
intelligible enough; because we may expect that the creature that
results from the modification of an elephantine mammal shall be
something like an elephant, and the creature which is produced by the
modification of an armadillo-like mammal shall be like an armadillo.
Upon that supposition, I say, the facts are intelligible; upon any
other, that I am aware of, they are not.

So far, the facts of palaeontology are consistent with almost any form
of the doctrine of progressive modification; they would not be
absolutely inconsistent with the wild speculations of De Maillet, or
with the less objectionable hypothesis of Lamarck. But Mr. Darwin's
views have one peculiar merit; and that is, that they are perfectly
consistent with an array of facts which are utterly inconsistent with
and fatal to, any other hypothesis of progressive modification which