Bonnet (1720-1793) deserves special mention here, since in his _Traite d'Insectologie_ (1745), and more fully in his _Contemplation de la Nature_ (1764), he gives the most complete expression to the idea of the _Echelle des etres_. This idea seems to have taken complete possession of his imagination. He extends it to the universe. Every world has its own scale of beings, and all the scales when joined together form but one, which then contains all the possible orders of perfection. At the end of the Preface to his _Traite_ _d'Insectologie_ (OEuvres, i., 1779) he gives a long table, headed "Idee d'une Echelle des etres naturels," and rather resembling a ladder, on the rungs of which the following names appear:-- MAN. Orang-utan. Ape. QUADRUPEDS. Flying squirrel. Bat. Ostrich. BIRDS. Aquatic birds. Amphibious birds. Flying Fish. FISH. Creeping fish. Eels. Water serpents. SERPENTS. Slugs. Snails. SHELL FISH. Tube-worms. Clothes-moths. INSECTS. Gall insects. Taenia. Polyps. Sea Nettles. Sensitive plant. PLANTS. Lichens. Moulds. Fungi, Agarics. Truffles. Corals, and Coralloids. Lithophytes. Asbestos. Talcs, Gypsums. Selenites, Slates. STONES. Figured stones. Crystals. SALTS. Vitriols. METALS. HALF-METALS. SULPHURS. Bitumens. EARTHS. Pure earth. WATER. AIR. FIRE. More subtile matter. The nature of the transitional forms which he inserts between his principal classes show very clearly his entire lack of morphological insight--the transitions are functional. The positions assigned to clothes-moths and corals are very curious! The whole scheme, so fantastic in its details, was largely influenced by Leibniz's continuity philosophy, and is in no way an improvement on the older and saner Aristotelian scheme. Robinet, in the fifth volume of his book _De la nature_ (1761-6), foreshadows the somewhat similar views of the German transcendentalists. "All beings," he writes, "have been conceived and formed on one single plan, of which they are the endlessly graduated variations: this prototype is the human form, the metamorphoses of which are to be considered as so many steps towards the most excellent form of being."[23] The idea of a gradation of beings appears also in Buffon (1707-1788), but here it takes more definitely its true character as a functional gradation.[24] "Since everything in Nature shades into everything else," he says, "it is possible to establish a scale for judging of the degrees of the intrinsic qualities of every animal."[25] He is quite well aware that the groups of Invertebrates are different in structural plan from the Vertebrates--"The animal kingdom includes various animated beings, whose organisation is very different from our own and from that of the animals whose body is similarly constructed to ours."[26]