FROM LAIVIARCK TO ST. HILAIRE 231 



upon the causes of its development, and upon its 

 progressive composition. It is important to note 

 that in this work he projects a scale of life some- 

 what similar to that of Bonnet and of Aristotle. 

 This shows that at that time the history of life 

 presented itself to his mind as a vertical chain of 

 masses of organisms, not of species ; so far as ap- 

 pears, he had not then developed the branching 

 idea which he expressed in the word embranchC' 

 meiit. This chain he puts forth to show the 

 ^de gradation^ or downward stages or gradations 

 from the highest to the lowest forms, indicating 

 the march of Nature in its progressive develop- 

 ments. Here and elsewhere Lamarck acknowl- 

 edges his indebtedness to the Greeks, especially 

 to Aristotle. Two main principles are brought out 

 in this work anticipating his later theory of the 

 causes of Evolution: first, it is not organs which 

 have given rise to habits, but habits, modes of 

 life, and environment which have given rise to 

 organs ; this is illustrated by the blindness of the 

 mole, by the presence of teeth in mammals, and 

 the absence of teeth in birds. His second principle 

 is, that life is an order and condition of things in 

 the parts of all bodies which possess it, which ren- 

 ders possible all the organic movements within. 



1 We do not find the word 'evolution' in Lamarck ; he used the 

 word degradation in the sense of steps or stages {changement in- 

 sensible et confinu) and the word 'gradation' (Lat. gradus) in the 

 sense of evolution. See pp. 19, 20. 



