LIFE AND WORKS OF COPE. XXIX 



Marsupialia and Toxodontia, but he especially broke down 

 Cuvier's classification of the Ungulates by distinguishing 

 the Perissodadyla from the Artiodactyla upon the basis of 

 foot structure, the importance of which Cuvier himself had 

 only dimly perceived. 



In this country the earlier contributions of Jefferson, 

 Harlan, and Gibbes were overshadowed in the mid-century 

 by the numerous valuable works of Leidy, who became at 

 once the founder of American Vertebrate Palaeontology, 

 although he entirely lacked the philosophical spirit either 

 in anatomy or in evolution. Thus, from all this long post- 

 Cuvierian period an immense number of facts issued, but 

 only two generalizations, the first of what may be regarded 

 as the great laws or principles in the evolution and classifi- 

 cation of the Mammalia. These laws are as follows : 



I. — The Law of Brain- Growth. — This principle, that the 

 older Mammalia had smaller brains, and that in order of 

 succession there was a steady increase in brain size, was 

 enunciated bj^ Lartet, and has been subsequently elaborated 

 and demonstrated by Marsh. 



II. — The Classification of the Hoofed Animals by Foot 

 Structure. — This was discovered by Owen in his division 

 above alluded to, which first directed attention to the im- 

 portance of differences in the feet. 



The three vertebrate paleontologists of the new period 

 who responded most fully to the Darwinian movement 

 were Huxley, who unwillingly entered the field, but soon 

 found an opportunity of overthrowing Cuvier's Law of Cor- 

 relation. Huxley's greatest generalization was the central 

 position of the order Insectivora. He had few opportunities 

 of working upon fossil mammals. He erroneously placed 

 Faloplotherium instead of Hyracotherium in the horse line, 

 and erroneously supported Reichert's theory of the homol- 

 ogy of the quadrate. Cope and Marsh alike responded to 



