142 THE SURVIVAL OF THE UNLIKE. [v. 



gave up his pharmaceutical interests that he might de- 

 vote himself wholly to science. He received the degree 

 of Doctor of Medicine from the faculty of Paris in 1800, 

 and he was one of the savants of the Institute of France 

 from its formation. He came into correspondence with 

 Lavoisier, Berthollet, Chaptal, Fourcroy, Volta, and 

 other celebrities of the time. In 1817 Van Mons be- 

 came professor of physics and chemistry in tlie Univer- 

 sity of Louvain, where he remained until the last. He 

 was an expert linguist, a profuse correspondent and a 

 facile writer. He published important works upon 

 chemistry and electricity, many of which exerted wide 

 influence. 



This is the man who first propounded a complete 

 system or theory of the philosophy of the origina- 

 tion of varieties of cultivated plants. His system was 

 applied particularly to fruit trees, to which he devoted 

 most of his attention, but it was conceived tli.it tlie 

 principles which he enunciated are of general !ii>plie;i- 

 tion in the vegetable kingdom. This system wiis 

 expounded in various papers, chiefly in his admirable 

 "Arbres Fruitiers," which was published in 1885 and 

 1836, in two volumes, but he had conceived the funda- 

 mental idea of the propositions as early hs his twentieth 

 year, and the system had early become current amongst 

 naturalists. The various characteristic features of the 

 system were brought together and codified bj' the 

 illustrious Poiteau shortly following Van Mons' death. 

 They are as follows : 



1. A natural species of tree does not vary through 

 its seedlings, in the place in which it is born ; so long 

 as it remains in its natal place, it reproduces only plants 

 which resemble itself, or, at most, only sub -varieties. 



