hell the outline of a
horn, as in the Toxoceras; or the coil is entirely lost, and the shell
reduced to its primitive straight form, as in the Baculites, which,
except for their undulating partitions, might be mistaken for the
Orthoceratites of the Silurian and Devonian epochs. I have presented
here but a few species of these extraordinary Cretaceous Ammonites, and,
strange to say, with this breaking-up of the type into a number of
fantastic and often contorted shapes, it disappears. It is singular that
forms so unusual and so contrary to the previous regularity of this
group should accompany its last stage of existence, and seem to shadow
forth by their strange contortions the final dissolution of their type.
When I look upon a collection of these old shells, I can never divest
myself of an impression that the contortions of a death-struggle have
been made the pattern of living types, and with that the whole group has
ended.

[Illustration: Crioceras.]

[Illustration: Turrilites.]

[Illustration: Ancyloceras.]

[Illustration: Scaphites.]

[Illustration: Toxoceras.]

[Illustration: Baculites.]

Now shall we infer that the compact, closely coiled Ammonites of the
Jurassic deposits, while continuing their own kind, brought forth a
variety of other kinds, and so distributed these new organic elements as
to produce a large number of distinct genera and species? I confess that
these ideas are so contrary to all I have learned from Nature in the
course of a long life that I should be forced to renounce completely the
results of my studies in Embryology and Palaeontology before I could
adopt these new views of the origin of species. And while the
distinguished originator of this theory is entitled to our highest
respect for his scientific researches, yet it should not be forgotten
that the most conclusive evidence brought forward by him and his
adherents is of a negative character, drawn from a science in which they
do not pretend to have made personal investigations, that of Geology,
while the proofs they offer us from their own departments of science,
those of Zooelogy and Botany, are derived from observations, still very
incomplete, upon domesticated animals and cultivated plants, which can
never be made a test of the origin of wild species.[11]

[Footnote 11: The advocates of the development-theory allude to the
metamorphosis of animals and plants as supporting their view of a change
of one species into another.