366 STUDIES IN GENERAL PHYSIOLOGY 



which has been cultivated in the North it is to be attributed 

 to a difference in the constitution of the tissues of the 

 two plants, possibly to a difference in the amount of water 

 contained in the two tissues. The periodic depth migra- 

 tion of the Medusa are, as I believe, brought about through 

 a periodic change resulting from internal causes in the 

 amount of water contained in the animal, which, in the 

 temperate zones, corresponds in its period with the change 

 of day and night. (I suspect that the light brings about 

 a change in the amount of water contained in the animal 

 in one sense, while darkness brings it about in the oppo- 

 site sense.) When the Medusa is then transferred to the 

 North there is no occasion for a change in the period. In 

 associative memory, on the other hand, we have to deal, it 

 seems to me, with a definite mechanical arrangement which, 

 from experiment and pathological experience, has to be 

 sought in the brain and which is ^JYWHtf only in cerfain 

 animals, while it is missing in others. Correspondingly 

 consciousness is present also only in certain animals, and in 

 these only after a certain stage in embryonal development 

 has been reached. To claim, as does one English author, 

 that a "subconsciousness" exists in the egg, I consider just 

 as wrong as though one would say that a subphonograph 

 exists in a drop of water. The Darwinian habit of seeing 

 transitions everywhere becomes erroneous when it attempts 

 to take into consideration machines which yield qualijicd 

 energy. And we have to do with such machines in the case 

 of associative memory, as well as in many other physiological 

 apparatus. 1 



4. If, therefore, a decided difference exists between 

 many vertebrates and the worms (and other lower animals) 

 so far as associated memory and consciousness are concerned, 



1 In many respects my views coincide with those expressed by DKIESCH in his 

 excellent booklet Die Biologic als selbststandige Wissenscliaft. 



