THE MODERN STUDY OF ZOOLOGY 17 



evidence on the point tends to prove that such 

 periods never have occurred. 



Though catastrophism thus received its death- 

 blow so far as the crust of the earth was concerned, 

 men still hesitated to apply the same reasoning to 

 the fossil remains of animals, and in spite of the 

 geological evidence the doctrine of catastrophism, 

 i.e., of periodical annihilations and re-creations, 

 continued to meet with acceptance so far as these 

 fossil remains were concerned. 



All this time there was steadily developing and 

 gradually acquiring definite shape a doctrine des- 

 tined ultimately to overthrow Cuvier's theories 

 concerning fossils as completely as the geologists 

 had done those dealing with the earth's crust. 

 This was the doctrine of the Mutability of Species. 



Cuvier, as we have seen, maintained that species 

 were all due to separate acts of creation ; the new 

 doctrine maintained that species were not immutable, 

 but that one species might give rise to two or more 

 new ones. The actual birth of this doctrine is 

 involved in some obscurity ; it is not quite clear 

 when it first arose, or to whom the credit of its 

 origination is due. It was clearly recognised and 

 advocated by the illustrious Goethe in 1796, but 

 whether this is the date of its birth is not clear. 



Its greatest advocates were Lamarck and St. 

 Hilaire, its greatest opponent Cuvier, and long and 

 bitter was the struggle. Though the two former, 

 and more especially Lamarck, worked out the 

 doctrine in the most elaborate manner, yet they 

 were unable to point out the causes at work in the 



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