THE HISTORY OF MENTAL DEVELOPMENT 117 



very difficult to clearly imagine or at all express in 

 terms of our own mind. 



Some investigators have made the mistake of pro- 

 jecting into the animal mind all our emotions and com- 

 plicated trains of thought. Thus Schwammerdam 

 apparently credits the snail with remorse for the com- 

 mission of excesses. Others go to the other extreme 

 and make animals hardlv more than mindless auto- 



i/ 



mata. We are warned, therefore, by our very mode of 

 study, to be cautious, not too absolutely sure of our 

 results, nor indignant at others who may take a very 

 different view. And yet by moving cautiously and ac- 

 cepting only what seems fairly clear and evident we 

 may arrive at very valuable and tolerably sure results. 

 The human mind, and the animal mind apparently, 

 manifests itself in three states or functions. These 

 are intelligence, the realm of knowledge ; susceptibil- 

 ity, the realm or state of feelings or emotions ; will, 

 the power or state of choice. Let us trace first the de- 

 velopment of intelligence or the intellect in the ani- 

 mal. Let us try to discover what kinds of knowledge 

 are successively attained and the mode and sequence 

 of their attainment. Hydra appears to be conscious of 

 its food. It recognizes it partially by touch, perhaps 

 also by feeling the waves caused by its approach. It 

 seems also to recognize food at a little distance by a 

 power comparable to our sense of smell. Stronger im- 

 pacts cause it to contract. It neither sees nor hears ; it 

 probably does little or no thinking. Its knowledge is 

 therefore limited to the recognition of objects either in 

 contact with, or but slightly removed from, itself. And 

 its recognition of the objects is very dim and incom- 

 plete, obtained through the sense of touch and smell. 



