vol. iv, page 468) has ably given the arguments for and against the
hypothesis of the development and modification of species: he seems to
lean toward the side of change.

The "Vestiges of Creation" appeared in 1844. In the tenth and much
improved edition (1853) the anonymous author says (page 155): "The
proposition determined on after much consideration is, that the several
series of animated beings, from the simplest and oldest up to the
highest and most recent, are, under the providence of God, the results,
FIRST, of an impulse which has been imparted to the forms of life,
advancing them, in definite times, by generation, through grades of
organisation terminating in the highest dicotyledons and vertebrata,
these grades being few in number, and generally marked by intervals
of organic character, which we find to be a practical difficulty in
ascertaining affinities; SECOND, of another impulse connected with the
vital forces, tending, in the course of generations, to modify organic
structures in accordance with external circumstances, as food, the
nature of the habitat, and the meteoric agencies, these being the
'adaptations' of the natural theologian." The author apparently believes
that organisation progresses by sudden leaps, but that the effects
produced by the conditions of life are gradual. He argues with much
force on general grounds that species are not immutable productions.
But I cannot see how the two supposed "impulses" account in a scientific
sense for the numerous and beautiful coadaptations which we see
throughout nature; I cannot see that we thus gain any insight how, for
instance, a woodpecker has become adapted to its peculiar habits of
life. The work, from its powerful and brilliant style, though displaying
in the early editions little accurate knowledge and a great want of
scientific caution, immediately had a very wide circulation. In my
opinion it has done excellent service in this country in calling
attention to the subject, in removing prejudice, and in thus preparing
the ground for the reception of analogous views.

In 1846 the veteran geologist M.J. d'Omalius d'Halloy published in an
excellent though short paper ("Bulletins de l'Acad. Roy. Bruxelles",
tom. xiii, page 581) his opinion that it is more probable that new
species have been produced by descent with modification than that they
have been separately created: the author first promulgated this opinion
in 1831.

Professor Owen, in 184