Form and Function: A Contribution to the History of Animal Morphology

by E. S. Russell

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 Traité d'Insectologie (Œuvres, i., 1779) he gives a long table, headed "Idée d'une Échelle des êtres naturels," and rather resembling a ladder, on the rungs of which the following names appear:—

Man.	Shell Fish.	Stones.
Orang-utan.	Tube-worms.	Figured stones.
Ape.	Clothes-worms.	Crystals.
Quadrupeds.	Insectes.	Salts.
Flying squirrel.	Gall insectes.	Vitriols.
Bat.	Taenia.
Ostrich.	Polyps.	Metals.
	Sea Nettles.
Birds.	Sensitive plant.	Half-metals.
Aquatic birds.
Amphibious birds.	Plants.	Sulphurs.
Flying Fish.	Lichens.	Bitumens.
	Moulds.
Fish.	Fungi, Agarics.	Earths.
Creeping fish.	Truffles.	Pure earth.
Eels.	Corals, and Coralloids.
Water sepents.	Lithophytes.	Water.
	Asbestos.
Serpents.	Talc, Gypsums.	Air.
Slugs.	Selenites, Slates.
Snails.		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]

He limits himself to a consideration of the Vertebrates, deeming that the economy of an oyster ought not to form part of his subject matter! He has a clear perception of the unity of plan which reigns throughout the vertebrate series.[27] What is new in Buffon is his interpretation of the unity of plan. For the first time we find clearly expressed the thought that unity of plan is to be explained by community of origin.

Buffon's utterances on this point are, as is well known, somewhat vacillating. The famous passage, however, which occurs in his account of the Ass shows pretty clearly that Buffon saw no theoretical objection to the descent of all the varied species of animals from one single form. Once admit, he argues, that within the bounds of a single family one species may originate from the type species by "degeneration," then one might reasonably suppose that from a single being Nature could in time produce all the other organised beings.[28] Elsewhere, e.g., in the discourse De la Dégéneration des Animaux,[29] Buffon expresses himself with more caution. He finds that it is possible to reduce the two hundred species of quadrupeds which he has described to quite a small number of families "from which it is not impossible that all the rest are derived."[30] Within each of the families the species branch off from a parent or type species. This we may note is a great advance on the linear arrangement implied in the idea of an Échelle des êtres.[31]

It is a mistake to suppose that Buffon was par excellence a maker of hypotheses. On the contrary he saw things very sanely and with a very open mind. He expressly mentions the great difficulties which one encounters in supposing that one species may arise from another by "degeneration." How does it happen that two individuals "degenerate" just in the right direction and to the right stage so as to be capable of breeding together? How is it that one does not find intermediate links between species? One is reminded of the objections, not altogether without validity, which were made to the Darwinian theory in its early days. I cannot agree with those who think that Buffon was an out-and-out evolutionist, who concealed his opinions for fear of the Church. No doubt he did trim his sails—the palpably insincere "Mais non, il est certain, par la révélation, que tous les animaux ont également participé à la grace de la création,"[32] following hard upon the too bold hypothesis of the origin of all species from a single one, is proof of it. But he was too sane and matter-of-fact a thinker to go much beyond his facts, and his evolution doctrine remained always tentative. One thing, however, he was sure of, that evolution would give a rational foundation to the classification which, almost in spite of himself, he recognised in Nature. If, and only if, the species of one family originated from a single type species, could families, be founded rationally, avec raison.

Buffon was, curiously enough, rather unwilling to recognise any systematic unit higher than the species. Strictly speaking there are only individuals in Nature; but there are also groups of individuals which resemble one another from generation to generation and are able to breed together. These are species—Buffon adheres to the genetic definition of species—and the species is a much more definite unit than the genus, the order, the class, which are not divisions imposed by us upon Nature. Species are definitely discontinuous,[33] and this is the only discontinuity which Nature shows us. Buffon put his views into practice in his Histoire Naturelle, where he describes species after species, never uniting them into larger groups. We have seen, however, how the facts forced upon him the conception of the "family."