Well, one of the subjects in my insect-house would achieve a similar savage finery if he persisted in his attempts. I speak of the Cow Onthophagus (O. vacca). His nymph has on its forehead a big horn, one only, bent backward; on its corselet it possesses a similar horn, jutting forward. The two, approaching their tips, look like some kind of pincers. What does the insect lack in order to acquire, on a smaller scale, the eccentric ornament of the West-Indian Scarab? It lacks perseverance. It matures the appendage of the forehead and allows that of the corselet to perish atrophied. It succeeds no better than the Bull Onthophagus in its attempt to grow a pointed stake upon its back; it loses a glorious opportunity of making itself fine for the wedding and terrible in battle. The others are no more successful. I bring up six different species. All, in the nymphal state, possess the thoracic horn and the eight-pointed ventral coronet; not one benefits by these advantages, which disappear altogether when the adult bursts its wrapping. My near neighbourhood numbers a dozen species of Onthophagi; the world contains some hundreds. All, natives and foreigners, have the same general structure; all most probably possess the dorsal appendage at an early age; and none of them, in spite of the variety of climate, torrid in one place, temperate in another, has succeeded in hardening it into a permanent horn. Could not the future complete a work whose design is so very clearly traced? We are the more inclined to ask this, because appearances are all in favour of the question. Examine under the magnifying-glass the frontal horns of the Bull Onthophagus in the nymphal state; then with the same scrupulous care look at the spear upon the corselet. At first, there is no difference between them, except for the general configuration. In both cases we find the same glassy aspect, the same sheath swollen with colourless fluid, the same incipient organ plainly marked. A leg in process of formation is not more clearly announced than the horn on the corselet or those on the forehead. Can time be lacking for the thoracic growth to become organized into a stiff and permanent appendage? The evolution of the nymph is swift; the insect is perfect in a few weeks. Could it not be that, though this brief space suffices to promote the maturity of the horns on the forehead, the thoracic horn requires a longer time to ripen? Let us prolong the nymphal period artificially and give the germ time to develop. It seems to me that a decrease of temperature, moderated and maintained for some weeks, for months if necessary, should be capable of bringing about this result, by delaying the progress of the evolution. Then, with a gentle slowness, favourable to delicate formations, the promised organ will crystallize, so to speak, and become the spear promised by appearances.