CORPUS STRIATUM OF MAMMALS 127 



1 91 7), both the subcortical strio-amygdaloid com- 

 plex and the cerebral cortex are more extensive than 

 in the turtles and the behavior shows corresponding 

 increase in complexity of both innate instinctive and 

 more plastic or modifiable types. In birds, as we 

 have seen, the subcortical structures are enormously 

 hypertrophied and the cortical sheets are actually 

 reduced; and the behavior again exhibits the cor- 

 related increment of complexity of instincts. In mam- 

 mals, on the other hand, the subcortical or basal 

 structures are relatively reduced and the cortex is 

 progressively elaborated parallel with the rise of in- 

 telligent types of adjustment. 



