There is geologic evidence, as has been shown, that in the course of creation the higher orders succeeded the lower. We have no good reason to believe that the mollusc and crustacean preceded the fish, seeing that discovery, in its slow course, has already traced the vertebrata in the ichthyic form, down to deposits which only a few years ago were regarded as representatives of the first beginnings of organized existence on our planet, and that it has at the same time failed to add a lower system to that in which their remains occur. But the fish seems most certainly to have preceded the reptile and the bird; the reptile and the bird to have preceded the mammiferous quadruped; and the mammiferous quadruped to have preceded man,—rational, accountable man, whom God created in his own image,—the much-loved Benjamin of the family,—last-born of all creatures. It is of itself an extraordinary fact, without reference to other considerations, that the order adopted by Cuvier, in his animal kingdom, as that in which the four great classes of vertebrate animals, when marshalled according to their rank and standing, naturally range should be also that in which they occur in order of time. The brain which bears an average proportion to the spinal cord of not more than two to one, came first,—it is the brain of the fish; that which bears to the spinal cord an average proportion of two and a half to one succeeded it,—it is the brain of the reptile; then came the brain averaging as three to one,—it is that of the bird; next in succession came the brain that averages as four to one,—it is that of the mammal; and last of all there appeared a brain that averages as _twenty-three_ to one,—reasoning, calculating man had come upon the scene. All the facts of geological science are hostile to the Lamarckian conclusion, that the lower brains were developed into the higher. As if with the express intention of preventing so gross a mis-reading of the record, we find, in at least two classes of animals,—fishes and reptiles,—the higher races placed at the beginning: the slope of the inclined plane is laid, if one may so speak, in the reverse way, and, instead of rising towards the level of the succeeding class, inclines downwards, with at least the effect, if not the design, of making the break where they meet exceedingly well marked and conspicuous. And yet the record does seem to speak of _development and progression_;—not, however, in the province of organized existence, but in that of insensate matter, subject to the purely chemical laws. It is in the style and character of _the dwelling-place_ that gradual improvement seems to have taken place;—not in the functions or the rank of any class of its inhabitants; and it is with special reference to this gradual improvement in our common mansion-house the earth, in its bearing on the “conditions of existence,” that not a few of our reasonings regarding the introduction and extinction of species and genera must proceed.