BUFFON AND THE PROBLEM OF SPECIES 567 



eyes of many learned men of his own and later generations, perhaps his 

 chief single contribution to science was his definition of species. This, 

 as I have recently pointed out, 30 was regarded as of immense importance 

 by Kant, and was, indeed, the starting point and the controlling prin- 

 ciple of that philosopher's biological speculations. " It is Buffon," 

 wrote Flourens as late as 1844, " who has given us the positive char- 

 acter of a species." Now before the Buffonian criterion of species was 

 propounded, there already existed a tendency towards evolutionism, 

 fostered by the principle of continuity and by such embryological con- 

 ceptions as those of Maupertuis — a tendency to disregard species alto- 

 gether and to infer from the variability of individuals to an unlimited 

 and rather promiscuous mutability of the successive generations of liv- 

 ing things. If it had not been for Buffon, transformism would prob- 

 ably have developed at first 40 through the increase and diffusion of this 

 tendency ; and its development might well, in that case, have been more 

 rapid. But when species came to be regarded as real " entities of na- 

 ture," determined by the objective criterion of the sterility of hybrids, 

 this somewhat too facile evolutionism received a check, and a certain 

 presumption of the constancy of true species seemed to be created. 

 This presumption had all the more force because it left room for a 

 large measure of mutability in the case of varieties, and thus gave a 

 sort of appeasement to the strong impulse towards genetic modes of 

 thought which was already active in the mid-eighteenth century. But 

 more than all this, Buffon, as we have seen, from the first managed to 

 associate with his definition of species the assumption that the sterility 

 of one kind of animal when crossed with another was a character that 

 (unlike almost all others) could not have been produced in the course 

 of descent with modification. And this supposition that the sterility 

 of hybrids was incapable of an evolutionary explanation long remained 

 a serious obstacle to the acceptance of the theory of descent, even with 

 those little influenced by theological prejudices against the theory. We 

 find even Huxley in 1862 troubled over the difficulty. In his Edin- 

 burgh lectures of that year " he warned his hearers of the one missing 

 link in the chain of evidence — the fact that selective breeding has not 

 yet produced species sterile to one another." The doctrine of descent 

 was merely to be " adopted as a working hypothesis, . . . subject to the 

 production of proof that physiological species may be produced by se- 

 lective breeding." 41 Since Buffon appears to have been the first to 

 emphasize the notion of physiological species, and to give currency to 

 the supposition that the sterility of hybrids affords a presumption 

 against any thorough-going transformism, he must be regarded as hav- 

 ing done more than almost any man of his time to counteract the tend- 

 ency which he also, perhaps, did more than any other to promote. 



39 Popular Science Monthly, January, 1911, pp. 37-38. 



40 Cf . Lovejoy, Popular Science Monthly, July, 1904, p. 248. 

 "Huxley's "Life and Letters," I., 193. 



