8 CHARLES DARWIN 



another by slow modification of ancestral forms. Essen- 

 tially a popular essayist, writing in the volcanic priest- 

 suppressed France of the ancien regime, during the 

 inconsistent days of Louis XV. and Louis XVI., when 

 it was uncertain whether novel and heterodox opinions 

 would bring down upon their author fame and reputa- 

 tion or the Sorbonne and the Bastille, Buffon was 

 careful to put his conjectural conclusions in a studiously 

 guarded and often even ironical form. But time after 

 time, in his great discursive work, the ' Histoire Natu- 

 relle' (published in successive volumes between 1749 

 and 1788), he recurs anew to the pregnant suggestion 

 that plants and animals may not be bound by fixed and 

 immovable limits of species, but may freely vary in 

 every direction from a common centre, so that one kind 

 may gradually and slowly be evolved by natural causes 

 from the type of another. He points out that, under- 

 lying all external diversities of character and shape, 

 fundamental likenesses of type occur in many animals, 

 which irresistibly suggest the novel notion of common 

 descent from a single ancestor. Thus regarded, he 

 says, not only the ass and the horse (to take a parti- 

 cular passage) but even man himself, the monkeys, the 

 quadrupeds, and all vertebrate animals, might be viewed 

 as merely forming divergent branches of one and the 

 same great family tree. Every such family, he believed, 

 whether animal or vegetable, might have sprung ori 

 ginally from a single stock, which after many gener- 

 ations had here developed into a higher form, and 

 there degenerated into a lower and less perfect type 

 of organisation. Granting this -granting that nature 

 could by slow variation produce one species in the 



