science is chiefly interested in inquiries into the state of the
animate creation as it now exists, with a view of pointing out its
relations to antecedent periods when its condition was different.

Before offering any hypothesis towards the solution of so difficult a
problem, let us consider what kind of evidence we ought to expect, in
the present state of science, of the first appearance of new animals or
plants, if we could imagine the successive creation of species to
constitute, like their gradual extinction, a regular part of the economy
of nature.

In the first place it is obviously more easy to prove that a species,
once numerously represented in a given district, has ceased to be, than
that some other which did not pre-exist has made its
appearance--assuming always, for reasons before stated, that single
stocks only of each animal and plant are originally created, and that
individuals of new species do not suddenly start up in many different
places at once.

So imperfect has the science of natural history remained down to our own
times, that, within the memory of persons now living, the numbers of
known animals and plants have been doubled, or even quadrupled, in many
classes. New and often conspicuous species are annually discovered in
parts of the old continent, long inhabited by the most civilized
nations. Conscious, therefore, of the limited extent of our information,
we always infer, when such discoveries are made, that the beings in
question had previously eluded our research; or had at least existed
elsewhere, and only migrated at a recent period into the territories
where we now find them. It is difficult, even in contemplation, to
anticipate the time when we shall be entitled to make any other
hypothesis in regard to all the marine tribes, and to by far the greater
number of the terrestrial;--such as birds, which possess such unlimited
powers of migration; insects, which, besides the variability of each
species in number, are also so capable of being diffused to vast
distances; and cryptogamous plants, to which, as to many other classes,
both of the animal and vegetable kingdom, similar observations are
applicable.

_What kind of evidence of new creations could be expected?_--What kind
of proofs, therefore, could we reasonably expect to find of the origin
at a particular period of a new species?

Perhaps it may be said in reply that, within the last two or three
centuries, some forest tree or ne