original and direct created adaptation of species to climate and other
conditions, why were these types not reproduced, when, after the colder
intervening era, those regions became again eminently adapted to such
animals? Why, but because, by their complete extinction in South
America, the line of descent was here utterly broken? Upon the ordinary
hypothesis, there is no scientific explanation possible of this series
of facts, and of many others like them. Upon the new hypothesis, "the
succession of the same types of structure within the same areas during
the later geological periods ceases to be mysterious, and is simply
explained by inheritance." Their cessation is failure of issue.

Along with these considerations the fact (alluded to on p. 114) should
be remembered, that, as a general thing, related species of the present
age are geographically associated. The larger part of the plants, and
still more of the animals, of each separate country are peculiar to
it; and, as most species now flourish over the graves of their by-gone
relatives of former ages, so they now dwell among or accessibly near
their kindred species.

Here also comes in that general "parallelism between the order of
succession of animals and plants in geological times, and the gradation
among their living representatives" from low to highly organized,
from simple and general to complex and specialized forms; also "the
parallelism between the order of succession of animals in geological
times--and the changes their living representatives undergo during their
embryological growth,"--as if the world were one prolonged gestation.
Modern science has much insisted on this parallelism, and to a certain
extent is allowed to have made it out. All these things, which conspire
to prove that the ancient and the recent forms of life "are somehow
intimately connected together in one grand system," equally conspire to
suggest that the connection is one similar or analogous to generation.
Surely no naturalist can be blamed for entering somewhat confidently
upon a field of speculative inquiry which here opens so invitingly; nor
need former premature endeavors and failures utterly dishearten him.

All these things, it may naturally be said, go to explain the order, not
the mode, of the incoming of species. But they all do tend to bring out
the generalization expressed by Mr. Wallace in the formula, that "every
species has come into existence coincident both in time