ORIGINS OF THE CEREBRAL CORTEX 8i 



No experiments on reptiles adequate to test these 

 suppositions have been published, though it probably 

 would not be a very difficult matter to devise them. 

 In the mammals we have an extensive series of such 

 experiments, and these will be examined critically in 

 due course. 



The Amphibia are only partially emancipated 

 from hfe in the water. Their tadpoles are practically 

 fishes, and the adults of most of the species are more 

 at home in the water than on land. In neither one 

 of these environments are they very competent. 

 Most of the fishes are better adapted for aquatic 

 life, and on land the Amphibia avoid their innumer- 

 able and more aggressive enemies only by leading a 

 retired life hidden away in sheltered nooks. This sort 

 of an evasive existence demands no highly compli- 

 cated cerebration, and indeed this is never exhibited 

 by any of these humble creatures. Most of the 

 reptiles, however, are fully adjusted to the more 

 diversified conditions of terrestrial life; they are 

 enterprising and aggressive in habit and far more 

 complex in bodily structure. 



The reptilian brain stem is fishlike in many re- 

 spects; but these animals can do more different kinds 

 of things with their bodies than fishes and according- 

 ly their apparatus of immediate motor control (that 

 is, the co-ordination centers of the brain stem) is 

 more elaborate. It is in the cerebral hemispheres, 

 however, that the departures from the patterns seen 



