PREFACE TO THE FIRST EDITION. 



THE following essay is offered as a contribution to 

 comparative psychology. Its special purpose is 

 to submit the manner in which modern animal psychol- 

 ogy applies the notions of instinct and intelligence to 

 a careful examination. In a former publication we 

 endeavored to elucidate the doctrine of animal intelli- 

 gence according to St. Thomas Aquinas. For this 

 purpose we selected an example from insect life. 1 

 Besides numerous smaller essays on the life of ants and 

 their guests, which appeared mostly in German scien- 

 tific periodicals, we have published a biologic-psycho- 

 logical work on Mixed Ant-Societies. 2 It was prin- 

 cipally in discussing the latter publication that represent- 

 atives of modern animal psychology raised sundry 

 objections to our distinction between instinct and intel- 

 ligence. As, however, the exact meaning and use of 

 these terms is the essential point of difference between 

 the old and recent animal psychology, we deemed it 

 appropriate to treat this question in a special paper in 

 which the difficulties of our critics could be more closely 

 investigated. We shall try, as far as possible, to avoid 

 all abstract philosophical discussions; the more so, as 

 the present essay must be adapted to the views of mod- 

 ern naturalists. 



1 ) "The leaf-roller" (Rhynchites betulae). A scientific essay on 

 Animal Instinct. Muenster, 1884. 



2 ) "The Compound Nests and Mixed Colonies of Ants" (German). 

 Muenster, 1891. 



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