28 THE THEORIES OF EVOLUTION 



metaphysical idea (for it is not sure that, by the 

 primordial type to which he traced back the modified 

 forms, Goethe meant a tangible ancestral form and 

 not an entity existing only in his imagination) became 

 with Lamarck a generalisation based on concrete 

 facts. 



Born in 1744, Lamarck wrote at first several 

 books on various questions of zoology and botany. 

 He originated the division of animals into vertebrate 

 and invertebrate; Cuvier's division into four funda- 

 mental types, vertebrate, molluscs, articulate and 

 radiate is a more recent conception. He gave specisl 

 attention to the lower animals in his course of lectures 

 at the Paris Museum of Natural History and in his 

 great work on "Animals without Vertebrae," but his 

 capital work, which is also the first transmutationist 

 manifesto, was his "Philosophic Zoologique" pub- 

 lished in 1809. 



In this book, Lamarck showed how relative and 

 superficial the idea of an absolute species is, and how 

 little it agrees with what we observe in nature. "If 

 the various species appear invariable," he wrote, "it 

 is because we observe them for a very short period of 

 time, that is the span of our own life. In reality they 

 are changing continuously under the influence of their 

 environment and habits, of the climate, of the tem- 

 perature and of the living environment constituted by 

 other closely allied species." , . . "It is not the 



