There hangs a mystery greatly more profound over the fact of the _degradation_ than over that of the _reduction_ and _diminution_ of classes. We can assign what at least _seems_ to be a sufficient _reason_ why, when reptiles formed as a class the highest representatives of the vertebrata, they should be of imposing bulk and strength, and altogether worthy of that post of precedence which they then occupied among the animals. We can also assign a _reason_ for the strange reduction which took place among them in strength and bulk immediately on their removal from the first to the second place. But why not only _reduction_, but also _degradation_? Why, as division started up in advance of division,—first the reptiles in front of the fishes, then the quadrupedal mammals in front of the reptiles, and, last of all, man in front of the quadrupedal mammals,—should the supplanted classes,—two of them at least,—fishes and reptiles,—for there seem to have been no additions made to the mammals since man entered upon the scene,—why should they have become the receptacles of orders and families of a degraded character, which had no place among them in their monarchical state? The fishes removed beyond all analogy with the higher vertebrata, by their homocercal tails,—the fishes (_Acanthopterygii_ and _Sub-brachiati_) with their four limbs slung in a belt round their necks,—the flat fishes, (_Pleuronectidæ_,) that, in addition to this deformity, are so twisted to a side, that while the one eye occupies a single orbit in the middle of the skull, the other is thrust out to its edge,—the irregular fishes generally (sun-fishes, frog-fishes, hippocampi, &c.) were not introduced into the ichthyic division until after the full development of the reptile dynasty; nor did the hand that makes no slips in its working “form the crooked serpent,” footless, grovelling, venom-bearing, the authorized type of a fallen and degraded creature, until after the introduction of the mammals. What can this fact of degradation mean? Species and genera seem to be greatly more numerous in the present age of the world than in any of the geologic ages. Is it not possible that the extension of the chain of being which has thus taken place—not only, as we find, through the addition of the higher divisions of animals to its upper end, but also through the interpolations of _lower links_ into the previously existing divisions—may have borne reference to some predetermined scheme of well-proportioned gradation, or, according to the poet, “Of general ORDER since the whole began?”