-L^G THE HISTORY OF BIOLOGY 



it, which are in part valid at the present day — an instance among many 

 of how the scientist's personal conceptions influence his purely scientific 

 theories. 



His descent theory 

 The preformation theory, however, represents only one side of Bonnet's 

 curious speculative investigations. One idea that occupies his mind quite 

 as much is the thought of the progressive development going on in nature. 

 His firm conviction as to the wisdom of the Creator has made of him an 

 incorrigible optimist; he is absolutely convinced that nature is advancing 

 towards a high goal; he believes that there are heavenly bodies in which 

 this development, which he expects that the earth will eventually experience, 

 has already been attained — in which the stones possess organic structure, 

 the plants are sensible, the animals talk, and men are angels. And just as 

 he expects an advance beyond the present stage, so he believes that this is 

 the result of a process of evolution; the "germs" that are incapsulated 

 within one another in an individual are not alike and never have been; on 

 the contrary, he expressly maintains that if one were to see a horse, a hen, 

 a snake, under the form they had when they first came into existence, they 

 would be unrecognizable. These changes he accounts for by a series of stages 

 of development which the earth has undergone and each of which has been 

 cut short by some vast natural catastrophe, which destroyed all living things, 

 but always spared the germs out of which fresh life -forms arose. The last 

 of these catastrophes was the one that destroyed the earth before the six 

 days of the Creation referred to in the Books of Moses, the historical authen- 

 ticity of which Bonnet was naturally careful to maintain, but which he 

 interprets somewhat freely, according to the orthodox view. As the result 

 of a coming catastrophe he expects the perfecting of the world's existence, 

 as indicated above, while he assumes from the presence of fossils in the moun- 

 tains a series of previous epochs of existence with living creatures that did 

 not resemble those now existing and from which these latter have originated. 

 Just as Bonnet manifestly bases this geological theory on Buffon, so he 

 is the precursor of both Cuvier and Lamarck in the same way; Cuvier's 

 famous catastrophe-theory corresponds too closely with Bonnet's to justify 

 the assertion that the similarity was accidental, while, on the other hand, 

 Bonnet in his express statements regarding the change that takes place in 

 species has forestalled Lamarck's descent speculations, though, it is true, 

 both the biologists mentioned succeeded in elaborating their ideas into a 

 far more perfect whole. But in still another respect Bonnet foreshadows these 

 two great pioneers of biological science: he maintains — again an obvious 

 connexion with Buffon — that nature draws no sharply defined lines between 

 the species, but that all life-forms on the earth pass into one another. He 

 draws up what he calls ' ' une khelle des etres naturels " — a series proceeding 



