12 THE DARWINIAN THEORY 



impressed by the difficulty of settling which were 

 distinct species and which might have come from 

 the same parents. On this point he observes : " The 

 more we know of animals and plants, the more 

 difficult we find it to settle which are related to 

 each other and which are not." 



Lamarck was also impressed by the variability of 

 animals and plants, according to their surroundings, 

 and by the influence of drier soil or mountain 

 habitat in causing stunting of growth and other 

 alterations. In his " Philosophic Zoologique," pub- 

 lished in- 1809, ar >d in the " Histoire Naturelle des 

 Animaux sans Vertebres," published in 1815, he 

 upholds the doctrine that all species of animals, in- 

 cluding man, are descended from other species. 

 With respect to the manner of modification, he attri- 

 butes something to the direct action of environment, 

 and much to use and disuse — i.e., to the effects of 

 habit ; for example, the use of the long neck of the 

 giraffe for browsing on trees. He writes: "The 

 systematic divisions of classes, orders, families, 

 genera, and species are the arbitrary and artificial 

 productions of man. Species arise out of varieties. 

 In the first beginning only the very simplest and 

 lowest animals and plants came into existence ; those 

 of a more complex organisation only at a later 

 period. The course of the earth's development and 

 that of its organic inhabitants was continuous, and 

 not interrupted by violent revolutions. Life is 

 purely a physical phenomenon." If man can make 

 such changes in a few hundred years, as for example, 

 to produce the various domestic races of pigeons or 



