rom much that occurs in domestication, we could
show, if our space permitted.

As to the sterility of hybrids, that can no longer be insisted upon as
absolutely true, nor be practically used as a test between species and
varieties, unless we allow that hares and rabbits are of one species.
That it subserves a purpose in keeping species apart, and was so
designed, we do not doubt. But the critics fail to perceive that this
sterility proves nothing against the derivative origin of the actual
species; for it may as well have been intended to keep separate those
forms which have reached a certain amount of divergence as those which
were always thus distinct.

The argument for the permanence of species, drawn from the identity
with those now living of cats, birds, and other animals, preserved in
Egyptian catacombs, was good enough as used by Cuvier against St.
Hilaire, that is, against the supposition that time brings about a
gradual alteration of whole species; but it goes for little against
Darwin, unless it be proved that species never vary, or that the
perpetuation of a variety necessitates the extinction of the parent
breed. For Darwin clearly maintains--what the facts warrant--that the
mass of a species remains fixed so long as it exists at all, though it
may set off a variety now and then. The variety may finally supersede
the parent form, but it may coexist with it; yet it does not in the
least hinder the unvaried stock from continuing true to the breed,
unless it crosses with it. The common law of inheritance may be
expected to keep both the original and the variety mainly true as long
as they last, and none the less so because they have given rise to
occasional varieties. The tailless Manx cats, like the fox in the
fable, have not induced the normal breeds to dispense with their
tails, nor have the Dorkings (apparently known to Pliny) affected the
permanence of the common sort of fowl.

As to the objection, that the lower forms of life ought, on Darwin's
theory, to have been long ago improved out of existence, replaced by
higher forms, the objectors forget what a vacuum that would leave
below, and what a vast field there is to which a simple organization
is best adapted, and where an advance would be no improvement, but the
contrary. To accumulate the greatest amount of being upon a given
space, and to provide as much enjoyment of life as can be under the
conditions, seems to be aimed at, and this is effected by