444 journal of Comparative Neurology and Psychology. 



unlike mechanisms are required for the two processes that this 

 distinction seems well justified. 



Since it is certain that the palaeencephalon persists quite unchanged 

 even after a well developed neencephalon has been added to it, there 

 is no ground for regarding those activities which we recognize as 

 palaeencephalic in one class of animals as anythingelse or as other- 

 wise localized in higher animals. Furthermore, we may regard an 

 entire series of acitvities as common to all vertebrates, and we inay 

 then seek to ascertain how other activities are added to these when 

 a new structure is added to the palcBencephalon. All sense impres- 

 sions and movement combinations belong to the palceencephalon. 

 It IS able to establish simple neiu relations betiueen the tiuo, but it 

 IS not able to form associations, to construct memory images out of 

 several components. It is the bearer of all reflexes and instincts. 



Through the separation of palaeencephalic and neencephalic 

 activities we gain an entirely new point of view and statement of the 

 problem for sense physiology. If the palaeencephalon can not form 

 associations, then those animals which depend upon it entirely, or 

 almost entirely, must remain unaffected by many sense impressions 

 to which, according to our own experiences or according to our 

 knowledge of the sense organs of these animals, we should expect 

 them to give some response by movement. A lizard which listens 

 to the slight rustling of an insect in the grass remains quite at 

 rest, as my own investigations have shown, when one pounds upon 

 a stone just over its head, or when one calls loudly, sings, or makes 

 an uproar. The animal, otherwise so shy that an unexpected 

 shadow or a slight shaking of the ground caused by my step makes 

 it disappear, does not flee. With these new sounds, which bio- 

 logically it never encounters, it associates nothing, just as a warn- 

 ing placard written in Chinese could never save me from an abyss. 

 The mechanism for conveying new stimulations to the old inherited 

 movement complexes is entirely lacking to it. The reptiles must 

 all appear to us practically deaf, although they do hear. It is 

 said that turtles react to music, but that is yet to be proved. 

 Yerkes has demonstrated to us that amphibians do not flee from 

 noises and the sound of a bell. Yet his talented researches have 

 shown us that the acoustic nerve is in some way stimulated by 

 these sounds. It is well known, however, that frogs call loudly 

 at mating time in order to attract the female, and Professor 

 BoTTCHER has informed me that he was able to attract a tree-frog 



