first, Nature exhibits, in the power of sensibility, the consummation of those vital forms (the _nisus formativi_) the adequate and the sole measure of which is to be sought for in their several organic products. But as if a weakness of exhaustion had attended this advance in the same moment it was made, Nature seems necessitated to fall back, and re-exert herself on the lower ground which she had before occupied, that of the vital magnetism, or the power of reproduction. The intensity of this latter power in the fishes, is shown both in their voracity and in the number of their eggs, which we are obliged to calculate by _weight_, not by _tale_. There is an equal intensity both of the _immanent_ and the _projective_ reproduction, in which, if we take in the comparative number of individuals in each species, and likewise the different intervals between the acts, the fish (it is probable) would be found to stand in a similar relation to the insect, as the insect, in the latter point, stands to the system of vegetation. Meantime, the fish sinks a step below the insect, in the mode and circumstances of impregnation. To this we will venture to add, the predominance of _length_, as the _form_ of growth in so large a proportion of the known orders of fishes, and not less of their rectilineal path of motion. In all other respects, the correspondence combined with the progress in individuation, is striking in the whole detail. Thus the eye, in addition to its moveability, has besides acquired a saline moisture in its higher development, as accordant with the life of its element. Add to these the glittering covering in both, the splendour of the scales in the one answering to the brilliant plates in the other,—the luminous reservoirs of the fire-flies,—the phosphorescence and electricity of many fishes,—the same analogs of moral qualities, in their rapacity, boldness, modes of seizing their prey by surprise,—their gills, as presenting the intermediate state between the spiracula of the grade next below, and the lungs of the step next above, both extremes of which seem combined in the structure of birds and of their quill-feathers; but above all, the convexity of the crystalline lens, so much greater than in birds, quadrupeds, and man, and seeming to collect, in one powerful organ, the hundred-fold microscopic facettes of the insect’s _light_ organs; and it will not be easy to resist the conviction, that the same power is at work in both, and reappears under higher auspices. The intention of Nature is repeated; but, as was to have been expected, with two main differences.