PALAEONTOLOGY AND GEOLOGY 



between animals and vegetables, but that nature 

 descends by subtle gradations from what we deem 

 the most perfect animal to one which is less so, and 

 again from this to the vegetable. The fresh-water 

 polypus may perhaps be considered as the lowest ani- 

 mal, and as at the same time the highest plant."" 



Variation within a species is caused, in Buffon's 

 opinion, by the direct effect on the organism of changes 

 in food and climate. Such variations are slower and 

 less pronounced upon animals in the wild state than 

 they are upon domesticated animals, which are forced 

 by man to follow him into different climates and to 

 consume the food he imposes on them. But he becomes 

 doubtful when one tries to extend this principle of 

 variation to the extent of changing a species into a 

 different one, because then it must be assumed that 

 the effect of food and climate is sufficient, "to change 

 radically the nature of beings which have had their 

 impress stamped upon them in that surest of moulds 

 — heredity." Probably his most mature belief is ex- 

 pressed by the moderate opinion that: "The type of 

 each species is founded in a mould of which the prin- 

 cipal features have been cut in characters that are 

 ineffaceable and eternally permanent^ but all the ac- 

 cessory traits vary; no one individual is the exact 

 facsimile of any other, and no species exists without 

 a large number of variations." But, here, too, the 

 problem is complicated by the fact that he practically 



^^ Histoire naturelle, Furne et Cie., 1842, tome III, p. 3. 



C 143 3 



