The Making of Species 



sight of in the mental stagnation of the Middle 

 Ages. In that dark period zoological science 

 was completely submerged. It was not until 

 men shook off the mental lethargy that had 

 held them for many generations that serious 

 attention was paid to biology. From the 

 moment when men began to apply scientific 

 methods to that branch of knowledge the idea 

 of evolution found supporters. 



Buffon suggested that species are not fixed, 

 but may be gradually changed by natural causes 

 into different species. 



Goethe was a thorough-going evolutionist ; he 

 asserted that all animals were probably descended 

 from a common original type. 



Lamarck was the first evolutionist who sought 

 to show the means whereby evolution has been 

 effected. He tried to prove that the efforts of 

 animals are the causes of variation ; that these 

 efforts originate changes in form during the life 

 of the individual which are transmitted to its 

 offspring. 



St Hilaire was another evolutionist who en- 

 deavoured to explain how evolution had occurred. 

 He believed that the transformations of animals 

 are effected by changes in their environment. 

 These hypotheses were considered, and rightly 

 considered, insufficient to explain anything like 

 general evolution, so that the idea failed for a 

 time to make headway. 



