The development theory is not more at fault in the rudimentary structure and primitive size of animals, as brought to light by the deepest researches of geology, than it is in the perfection and complication of the several organs with which they were endowed. These organs in the earlier types ought, upon the principles of this theory, to have all partaken of the simplicity and sameness of the germinal vesicles; varying, indeed, in their complexity, as in their completeness, in proportion as we ascend among the fossiliferous strata. But the facts are not so. Nay, so far otherwise, that in the very earliest specimens of Nature’s workmanship we find the mechanism of the parts as minute, varied, and multiplied, as in those of her most recent productions. Examine the eye of the Trilobite, the oldest of crustaceans, and the distinguishing type of the lowest of the fossiliferous rocks. These creatures swarmed in the Silurian seas. Their destiny was not fulfilled by the close of the tertiary periods, for they still exist. But in none of her subsequent creations has Nature displayed greater elaboration in the parts, or more skillful adaptive contrivance in their arrangement, than in the visual organ of this palæozoic family. The eye of the trilobite is formed of four hundred spherical lenses, arranged in distinct compartments on the surface of the cornea, which again projects conically upward, so as to enable the animal while resting, or seeking its food at the bottom of the waters, to take in the largest possible field of view—this, as it might require, either for the purpose of defense or attack. Fishes, birds, and mammals, have all, it is well known, an optical apparatus precisely adjusted to their respective habits and the element in which they live. Fishes and fowls have their eyes differently constructed.—The bat, which preys in the dark,—the eagle, which soars in the blaze of the sun,—and the mole, which burrows in the earth, have each peculiar and appropriate organisms. But in none is there greater complication or perfection, than what is manifested in the eye of these earliest and still living tribes of the waters.