26 THE THEORIES OF EVOLUTION 



dawn of ages, mankind, impressed undoubtedly by 

 floods or earthquakes, has believed in world-wide cata- 

 clysms. Those "revolutions of the earth's crust" as 

 Cuvier called them, geological upheavals of the most 

 violent character extending over considerable areas, 

 were responsible for the annihilation of one fauna 

 after another, each fauna being replaced by another 

 fauna introduced by migration, he thought, or, as 

 some of his disciples suggested, created especially in 

 the same locality. 



The great services rendered by Cuvier to science 

 caused Ms views to prevail for many years, and the 

 weight of his opinions delayed for many years the 

 advent of the transmutation idea. 



We find this idea expressed for the first time at the 

 close of the eighteenth century. In his essay on the 

 "Metamorphosis of Plants," published in 1790, Goethe 

 advanced the contention that whenever we study 

 organs, we must compare them with one another, de- 

 termine the points they have in common, find out their 

 original shape, and then consider the various forms ob- 

 served as the result of modifications, of some "meta- 

 morphosis." 



He held, for instance, that all the organs of a plant 

 are produced by the metamorphosis of one single 

 organ, the leaf. Applying this method to zoology, 

 he originated simultaneously with Oken, though in- 

 dependently of him, the vertebral theory of the skull : 



