ess embryonic, than _Belemnites_; or the modern
species of Lamellibranch and Gasteropod genera, than the Silurian species
of the same genera?

The ANNULOSA.--The Carboniferous Insecta and Arachnida are neither less
specialised, nor more embryonic, than these that now live, nor are the
Liassic Cirripedia and Macrura; while several of the Brachyura, which
appear in the Chalk, belong to existing genera; and none exhibit either
an intermediate, or an embryonic, character.

The VERTEBRATA.--Among fishes I have referred to the Coelacanthini
(comprising the genera _Coelacanthus, Holophagus, Undina_, and
_Macropoma_) as affording an example of a persistent type; and it is most
remarkable to note the smallness of the differences between any of these
fishes (affecting at most the proportions of the body and fins, and the
character and sculpture of the scales), notwithstanding their enormous
range in time. In all the essentials of its very peculiar structure, the
_Macropoma_ of the Chalk is identical with the _Coelacanthus_ of the
Coal. Look at the genus _Lepidotus_, again, persisting without a
modification of importance from the Liassic to the Eocene formations
inclusively.

Or among the Teleostei--in what respect is the _Beryx_ of the Chalk more
embryonic, or less differentiated, than _Beryx lineatus_ of King George's
Sound?

Or to turn to the higher Vertebrata--in what sense are the Liassic
Chelonia inferior to those which now exist? How are the Cretaceous
Ichthyosauria, Plesiosauria, or Pterosauria less embryonic, or more
differentiated, species than those of the Lias?

Or lastly, in what circumstance is the _Phascolotherium_ more embryonic,
or of a more generalised type, than the modern Opossum; or a _Lophiodon_,
or a _Paloeotherium_, than a modern _Tapirus_ or _Hyrax_?

These examples might be almost indefinitely multiplied, but surely they
are sufficient to prove that the only safe and unquestionable testimony
we can procure--positive evidence--fails to demonstrate any sort of
progressive modification towards a less embryonic, or less generalised,
type in a great many groups of animals of long-continued geological
existence. In these groups there is abundant evidence of variation--none
of what is ordinarily understood as progression; and, if the known
geological record is to be regarded as even any considerable fragment of
the whole, it is inconceivable that any theory of a necessarily
progressive development can sta