CHAPTER XXXVIII 

 GENEALOGY OF PRESENT-DAY SPECIES 



WE shall pay no more attention to the definition of species. 

 We ask one question only how beings of the present day 

 are derived from beings of other days. We know that the 

 differences are great between the starting-point and the 

 present ; but we do not seek to find just when the passing 

 of a step deserves to be called a change of species. 



Beings of the present day are extremely numerous and 

 most varied in form ; but there is nothing in their number or 

 their variation to surprise us. We observe that not-living 

 bodies are also very numerous and very varied. That 

 which strikes us most in living beings is their extremely 

 exact and co-ordinated mechanism, thanks to which each 

 animal at each instant does exactly what it ought to do in 

 order to continue living under the conditions in which it 

 exists. 1 In other words, an animal which has long lived 

 in a certain environment is adapted to the environment. 



Adaptation is that which the two great evolutionist schools 

 set out to explain both Lamarckian and Darwinian. 



Lamarck undertook to explain adaptation directly and 

 succeeded by means of the law of habit and the law of 

 heredity of acquired characters. A defect of Lamarck's 

 explanation was that, instead of considering en bloc the 



1 I take an animal rather than a plant, because we find in animals 

 the most wonderful co-ordinations. 



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