THE ORIGIN OF ANIMAL SPECIES 451 



support his theory, and it failed to meet with the ap- 

 proval of his contemporaries. Lamarck (1744-1829) 

 afterward adopted this view, collected many facts in its 

 favor, and also advanced the hypothesis, in 1801, that 

 the use and disuse of organs would cause structural 

 modifications in them, producing either increased devel- 

 opment or atrophy of parts. These modifications, being 

 inherited by successive generations, would eventually 

 become characteristic of new species thus evolved from 

 the older ones. Lamarck's theory was opposed by 

 Cuvier, the greatest comparative anatomist and paleon- 

 tologist of his time, who insisted that, if the theory were 

 true, there ought to be among fossils transition forms 

 connecting the extinct with the living species, but that 

 no such forms were known, nor could a process be sug- 

 gested by which transition could take place. Under 

 Cuvier's leadership the belief became current among 

 geologists that the earth has passed through a series of 

 catastrophes or cataclysms which destroyed all living 

 things, and that it has successively been repeopled with 

 new forms quite unlike those which had perished. The 

 Lamarckian theory passed into obscurity, and was not 

 seriously considered again until it was brought forth for 

 comparison with Darwin's theory of natural selection. 

 The opinions of geologists regarding cataclysms under- 

 went a change after Hutton (1726-1797) urged that in 

 order to understand how the present condition of the 

 earth came about, the changes now taking place must be 

 studied. This view was later vigorously upheld and ex- 

 tended by Lyell (1797-1875), who contended that cata- 

 clysms have never occurred, but that the earth has 

 gradually reached its present state through the action 

 of natural forces which are still in operation. Thus the 

 way was prepared for the appearance of the theory 

 which, elaborated and maintained by numerous observa- 



