urus' had the same parts completely ossified. [7]

The regularity and evenness of the dentition of the 'Anoplotherium', as
contrasted with that of existing Artiodactyles, and the assumed nearer
approach of the dentition of certain ancient Carnivores to the typical
arrangement, have also been cited as exemplifications of a law of
progressive development, but I know of no other cases based on positive
evidence which are worthy of particular notice.

What, then, does an impartial survey of the positively ascertained
truths of paleontology testify in relation to the common doctrines of
progressive modification, which suppose that modification to have taken
place by a necessary progress from more to less embryonic forms, or
from more to less generalized types, within the limits of the period
represented by the fossiliferous rocks?

It negatives those doctrines; for it either shows us no evidence of any
such modification, or demonstrates it to have been very slight; and as
to the nature of that modification, it yields no evidence whatsoever
that the earlier members of any long-continued group were more
generalized in structure than the later ones. To a certain extent,
indeed, it may be said that imperfect ossification of the vertebral
column is an embryonic character; but, on the other hand, it would be
extremely incorrect to suppose that the vertebral columns of the older
Vertebrata are in any sense embryonic in their whole structure.

Obviously, if the earliest fossiliferous rocks now known are coeval
with the commencement of life, and if their contents give us any just
conception of the nature and the extent of the earliest fauna and flora,
the insignificant amount of modification which can be demonstrated
to have taken place in any one group of animals, or plants, is quite
incompatible with the hypothesis that all living forms are the results
of a necessary process of progressive development, entirely comprised
within the time represented by the fossiliferous rocks.

Contrariwise, any admissible hypothesis of progressive modification must
be compatible with persistence without progression, through indefinite
periods. And should such an hypothesis eventually be proved to be true,
in the only way in which it can be demonstrated, viz. by observation
and experiment upon the existing forms of life, the conclusion will
inevitably present itself, that the Paleozoic, Mesozoic, and Cainozoic
faunae and florae, taken together,