LAMARCK'S THEORY OF DESCENT 



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all the inhabitable regions of the globe, each species 

 has received, through the influence of circumstances to 

 which it has been exposed, the habits which we have 

 observed, and the modifications in its organs which 

 observation has shown us it possesses. 



" The first of these two conclusions is that believed 

 up to the present day — namely, that held by nearly 

 every one ; it implies, in each animal, an unchanging 

 organization and parts which have never varied, and 

 which will never vary ; it implies also that the circum- 

 stances of the places which each species of animal 

 inhabits will never vary in these localities ; for should 

 they vary, the same animals could not live there, and 

 the possibility of discovering similar forms elsewhere, 

 and of transporting them there, would be forbidden. 



" The second conclusion is my own : it implies that, 

 owing to the influence of circumstances on habits, 

 and as the result of that of habits on the condition 

 of the parts and even on that of the organization, 

 each animal may receive in its parts and its organiza- 

 tion, modifications susceptible of becoming very con- 

 siderable, and of giving rise to the condition in which 

 we find all animals. 



" To maintain that this second conclusion is un- 

 founded, it is necessary at first to prove that each 

 point of the surface of the globe never varies in its 

 nature, its aspect, its situation whether elevated or 

 depressed, its climate, etc., etc. ; and likewise to 

 prove that any part of animals does not undergo, even 

 at the end of a long period, any modification by 

 changes of circumstances, and by the necessity which 

 directs them to another kind of life and action than 

 that which is habitual to them. 



" Moreover, if a single fact shows that an animal 

 for a long time under domestication differs from the 

 wild form from which it has descended, and if in such 

 a species in domesticity we find a great difference in 

 conformation between the individuals submitted to 



