26]

"Not perceiving that species will not vary as long as the conditions in
which they are placed remain essentially unchanged, naturalists have
supposed that each species was due to a special act of creation on the
part of the Supreme Author of all things. Assuredly, nothing can exist
but by the will of this Supreme Author, but can we venture to assign
rules to him in the execution of his will? May not his infinite power
have chosen to create an order of things which should evolve in
succession all that we know as well as all that we do not know? Whether
we regard species as created or evolved, the boundlessness of his power
remains unchanged, and incapable of any diminution whatsoever. Let us
then confine ourselves simply to observing the facts around us, and if
we find any clue to the path taken by Nature, let us say fearlessly that
it has pleased her Almighty Author that she should take this path.[227]

"What applies to species applies also to genera; the further our
knowledge extends, the more difficult do we find it to assign its exact
limits to any genus. Gaps in our collections are being continually
filled up, to the effacement of our dividing lines of demarcation. We
are thus compelled to settle the limits of species and variety
arbitrarily, and in a manner about which there will be constant
disagreement. Naturalists are daily classifying new species which blend
into one another so insensibly that there can hardly be found words to
express the minute differences between them. The gaps that exist are
simply due to our not having yet found the connecting species.

"I do not, however, mean to say that animal life forms a simple and
continuously blended series. Life is rather comparable to a
ramification. In life we should see, as it were, a ramified continuity,
if certain species had not been lost. The species which, according to
this illustration, stands at the extremity of each bough, should bear a
resemblance, at least upon one side, to the other neighbouring species;
and this certainly is what we observe in nature.

"Having arranged living forms in such an order as this, let us take one,
and then, passing over several boughs, let us take another at some
distance from it; a wide difference will now be seen between the species
which the forms selected represent. Our earliest collections supplied us
with such distantly allied forms only; now, however, that we have such
an infinitely greater number of specimen