34 Chapter III. 



the end on the part of the agent, their positive essence 

 and their characteristic peculiarity consist, in contra- 

 distinction to reflex motions, in being due to impulse 

 and in being determined and directed by the sense 

 knowledge of the animal. Hence, they are caused by 

 the powers of sensitive perception and appetite, and the 

 hereditary disposition of this twofold power is their 

 source and principle. 



To the powers of sensitive cognition which guide 

 instinctive actions, evidently belong not only the ex- 

 terior senses (sensus externi) sight, hearing, taste, smell, 

 and touch, the last of which comprises all the sensations 

 of the skin, but also the interior sense (sensus internus), 

 which perceives the interior states of the agent and feels 

 the pleasant or disagreeable impression which the object 

 of the exterior sense perception makes upon it. Hereto 

 must be added the power of sensitive imagination (phan- 

 tasia) and a sensile memory (memoria), which repro- 

 duces exterior sense perceptions and interior sensile feel- 

 ings, and combines them one with the other and with 

 new sense perceptions according -to the nature and the 

 laws of sensitive imaginations. Because the interior 

 sense, the sensitive imagination and memory represent 

 as pleasant to the agent what is objectively useful for its 

 preservation and that of its kind, and thereby induce it 

 to perform instinctive actions which they guide and 

 regulate, they endow the animal moreover with a sensi- 

 tive power of appreciation (vis aestimativa.) 1 Yet, this 

 power of appreciation is not a new reality, it is only 



x ) We have developed our views on the power of appreciation in 

 animals more fully in the seventh chapter of our book "Der Trichter- 

 wickler" (Rhynchites betulae). 



