But the facts of geology, from its remotest periods, are in themselves no less strongly opposed to this extravagant, untenable hypothesis. This might be presumed from the distinct teachings of geology, as already stated, against the theory of a scale of beings becoming more perfect as we ascend from the faunas of the older to those of the newer formations. The families of the various formations are distinct, and consist of real non-interchanging forms of structure, whether they die out and disappear with a particular formation, or are carried forward and intermixed with the fossils of another. The fishes of the silurian rocks, are as perfect after their kind as those of the Devonian, Carboniferous, or Cretaceous deposits; and not less perfect than they are genuine types of all their successors. The _sauroids_ of the old red sandstone have reptilian resemblances, but yet the _saurians_ of the oolite age have no affinities of true kindred descent; while, again, of all the mammalia of the tertiary period, there is not one that boasts a likeness, in habit or organization, to a single creature of an antecedent or posterior epoch. “Thus between the _palæotherium_ and the species of our own days,” says Cuvier, “we should be able to discover some intermediate forms: and yet no such discovery has ever been made. Since the bowels of the earth have not preserved monuments of this strange genealogy, we have a right to conclude, that the ancient and now extinct species were as permanent in their forms and characters as those which exist at present: or at least, that the catastrophe which destroyed them did not leave sufficient time for the production of the changes that are alleged to have taken place.” Agassiz, in his own department of fishes, is equally opposed in all his deductions to the transformation of species from one formation to another, which he asserts, “the imagination invents with as much facility as the reason refutes.” Professor Owen, after minutely examining the organic structure of the nine orders of fossil reptiles, declares no less strongly against the theory, and adds—“The nearest approximation to the organization of fishes is made by the _Ichthyosaurus_, an extinct genus which appears to have been introduced into the ancient seas subsequent to the deposition of the strata inclosing the remains of the thecodont lizards. But by no known forms of the fossil animals can we diminish the wide interval which divides the most sauroid of fishes from an _Ichthyosaurus_.”[12]