472 THE POPULAR SCIENCE MONTHLY 



abandoned, and to which he never returned. 10 Its most characteristic 

 point was the contention that nature knows only individuals and that 

 species are entia rationis merely. The most characteristic point of 

 nearly all his subsequent references to the subject is the contention that 

 species are real entities, definable in exact and strictly objective terms, 

 and necessary to take account of in any study of natural history. 



This change already was manifest in the second volume, published 

 in the same year as the preliminary discourse (1749). In this volume 

 Buffon propounded his celebrated definition of species, which was des- 

 tined to have so great an influence upon the biological ideas of the 

 later eighteenth century. 



We should regard two animals as belongng to the same species if, by 

 means of copulation, they can perpetuate themselves and preserve the likeness 

 of the species; and we should regard them as belonging to different species if 

 they are incapable of producing progeny by the same means. Thus the fox will 

 be known to be a different species from the dog, if it proves to be the fact that 

 from the mating of a male and a female of these two kinds of animals no off- 

 spring is born; and even if there should result a hybrid offspring, a sort of 

 mule, this would suffice to prove that fox and dog are not of the same species — 

 inasmuch as this mule would be sterile (ne produirait rien). For we have 

 assumed that, in order that a species might be constituted, there was necessary 

 a continuous perpetual and unvarying reproduction (une production continue, 

 perpetuelle, invariable) — similar, in a word, to that of the other animals. 17 



This language, it will be observed, implies not only that species are 

 real entities, but also that they are constant and invariable entities. 

 The same implication may be found again later in the volume ; Buffon 

 thus concludes the exposition of his embryological hypotheses — which 

 embraced a theory of pangenesis: 



There exists, therefore, a living matter, universally distributed through all 

 animal and vegetal substances, which serves alike for their nutrition, their 

 growth and their reproduction. . . . Eeproduetion takes place only through the 

 same matter's becoming superabundant in the body of the animal or plant. 

 Each part of the body then sends off (renvoie) the organic molecules which it 

 can not admit. Each of these particles is absolutely analogous to the part by 

 which it is thrown off, since it was destined for the nourishment of that part. 

 Then, when all the molecules sent off by all the parts of the body unite, they 

 necessarily form a small body similar to the first, since each molecule is similar 

 to the part from which it comes. It is in this way that reproduction takes place 

 in all species. . . . There are, therefore, no preexisting germs, no germs con- 

 tained within one another ad infinitum; but there is an organic matter, always 

 active, always ready to be shaped and assimilated and to produce beings similar 

 to those which receive it. Animal or vegetable species, therefore, can never, of 

 themselves, disappear (s'epuiser). So long as any individuals belonging to it 



16 Kadi 's account, already quoted, of Buffon 's attitude towards transf ormism 

 and towards the conception of species, is apparently based chiefly upon the first 

 volume. For virtually all of Buffon 's views, except his early and quickly repudi- 

 ated one, Badl's statement is almost the exact reverse of the truth. 



17 "Hist. Nat.," Vol. II., 1749, p. 10. 



