XXX INTRODUCTION 



§ 4. Evolution. 



The most fundamental purpose of Lamarck's zoological 

 work was to controvert the belief in fixity of species. It 

 was at that time almost universally held that all species 

 had been created at the beginning of the universe by special 

 acts of creation. They were thus supposed to be all of 

 equal antiquity, and to be " as old as Nature." They were 

 supposed further to have subsisted without any sort of 

 structural change since the moment of their creation. 



These propositions Lamarck attacks. He holds that 

 species can only maintain their constancy of form so long 

 as their environment remains constant. Any change in the 

 environment necessitates a corresponding change in the 

 species. In support of this doctrine, he cites the case of 

 domesticated animals, and the altered shape which has in 

 their case followed upon an altered environment : the same 

 thing is found in cultivated plants. He draws attention 

 further to the linear series of animals arranged in order of 

 gradually-increasing complexity, so as to form a continuous 

 whole, strongly suggesting development. He is far from 

 wishing to attack the conceptions of theology. If " the 

 sublime author of the universe " can create all the different 

 species by separate acts of creation, so too, says Lamarck, 

 he can surely create one or two species to begin with, and 

 confer upon them the power of evolving into the rest. 



Lamarck held that as long as the environment remained 

 unaltered, the species living in it might also remain unaltered. 

 Geoffroy Saint-Hilaire had recently brought from Egypt an 

 extensive collection of mummified animals of great antiquity . 

 An examination of these animals revealed the fact that they 

 were in every respect identical with the existing fauna of 

 that country ; and this discovery was used as an argument 

 in favour of the permanent fixity of species. Lamarck's 

 position, however, was unaffected by it : for he pointed out 

 that there was every reason to believe that there had been 

 no change in the climate and conditions prevaihng in Egypt 



