generation. Organs have been
gradually developed in these low forms, and these organs have in the
course of time increased in diversity and complexity. The power of
growth in each living body has given rise to various modes of
reproduction, and thus progress, already acquired, has been preserved
and handed down to offspring.[237] With sufficient time, favourable
conditions of life [_circonstances_], successive changes in the surface
of the globe, and the power of new surroundings and habits to modify the
organs of living bodies, all animal and vegetable forms have been
imperceptibly rendered such as we now see them. It follows that species
will be constant only in relation to their environments, and cannot be
as old as Nature herself.

"But what are we to say of instinct? Can we suppose that all the tricks,
cunning, artifices, precautions, patience, and skill of animals are due
to evolution only? Must we not see here the design of an all-powerful
Creator? No one certainly will assign limits to the Creator's power, but
it is a bold thing to say that he did not choose to work in this way or
that way, when his own handiwork declares to us that this is the way he
chose. I find proof in Nature--meaning by nature the _ensemble_ of all
that is,[238] but regarding her as herself the effect of an unknown
first cause[239]--that she is the author of organization, life, and even
sensation; that she has multiplied and diversified the organs and mental
powers of the creatures which she sustains and reproduces; that she has
developed in animals, through the sole instrumentality of sense of need
as establishing and directing their habits, all actions and all habits,
from the simplest up to those which constitute instinct, industry, and
finally reason.[240]

"Against this it is alleged that we have no reason to believe species to
have changed within any known era. The skeletons of some Egyptian birds,
preserved two or three thousand years ago, differ in no particular from
the same kind of creatures at the present day. But this is what we
should expect, inasmuch as the position and climate of Egypt itself do
not appear to have changed. If the conditions of life have not varied,
why should the species subjected to those conditions have done so?
Moreover, birds can move about freely, and if one place does not suit
them they can find another that does. All that these Egyptian mummies
really prove is, that there were animals in Egypt two o