50 4 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



to H. J. Carter, "confine itself to the water of the 

 watch-glass in which it may be placed, when away 

 from the sawdust and chips of wood among which it 

 has been living ; but if the watch-glass be placed upon 

 the sawdust it will very soon make its way over the 

 side of the watch-glass and get to it. " This act probably 

 depends on a sense-perception of the presence and posi- 

 tion of the tan-bark, and of a feeling of desire to reach 

 it. This may have been due to a sense of discomfort 

 due to the surrounding water, or to a recollection of 

 superior comfort associated with the tan-bark. 



Ordinary observation of most animals leads to the 

 belief that their movements are provoked by sensa- 

 tions, as of hunger, thirst, temperature, etc. ; also of 

 sight, hearing, smell, etc., when they possess those 

 senses. There are physiologists who deny that such 

 is the case, but I must insist on the importance of a 

 psychological rather than a physiological study of ani- 

 mals as a most important source of information in 

 this direction. The students of dead or mutilated 

 animals miss important evidence as to the phenomena 

 of consciousness. The attempt has been made to 

 identify hunger, for instance, with chemical energy, a 

 proposition which is simply irrational. It may be none 

 the less true, however, that hunger is a necessary con- 

 comitant of a molecular condition. Observation on 

 living animals shows in the most conclusive manner 

 that by far the greater number of species are capable 

 of the performance of acts in response to new situations 

 and circumstances for the performance of which no 

 automatic mechanism exists. Memory is clearly pres- 

 ent in them, and, as a consequence, judgments are 

 formed which determine the succeeding acts. The 

 process, be it ever so simple, is "representative, " and 



