" The notion that all the kinds of animals and plants may have 

 come into existence by the growth and modification of primordial 

 germs is as old as speculative thought ; but the modern scientific 

 form of the doctrine can be traced historically to the influence of 

 several converging lines of philosophical speculation and of physical 

 observation, none of which go farther back than the seventeenth 

 century. These are : 



"1. The enunciation by Descartes of the conception that the 

 physical universe, whether living or not living, is a mechanism, 

 and that, as such, it is explicable on physical principles. ..." 



HUXLEY, Science and Culture, p. 290 (" The 



Evolution of the Sum of Living Beings ") 



VI 



