LAMARCK'S THEORY OF EVOLUTION 249 



Appendix (p. 141). 

 On Species in Living Bodies. 



" I have for a long time thought that species were 

 constant in nature, and that they were constituted 

 by the individuals which belong to each of them. 



" I am now convinced that I was in error in this 

 respect, and that in reality only individuals exist in 

 nature. 



" The origin of this error, which I have shared with 

 many naturalists who still hold it, arises from the long 

 duration, in relation to us, of the satne state of things 

 in each place which each organism inhabits ; but this 

 duration of the same state of things for each place 

 has its limits, and with much time it makes changes 

 in each point of the surface of the globe, which pro- 

 duces changes in every kind of circumstances for the 

 organisms which inhabit it. 



" Indeed, we may now be assured that nothing on 

 the surface of the terrestrial globe remains in the 

 same state. Everything, after a while, undergoes 

 different changes, more or less prompt, according to 

 the nature oi the objects and of circumstances. Ele- 

 vated areas are constantly being lowered, and the 

 loose material carried down to the lowlands. The 

 beds of rivers, of streams, of even the sea, are gradu- 

 ally removed and changed, as also the climate ; * in a 

 word, the whole surface of the earth gradually under- 

 goes a change in situation, form, nature, and aspect. 

 We see on every hand what ascertained facts prove ; 

 it is only necessary to observe and to give one's at- 

 tention to be convinced of it. 



" However, if, relatively to living beings, the diver- 



* I have cited the incontestable proofs in ray HydrogSologie, and I 

 have the conviction that one day all will be compelled to accept these 

 great truths. 



