h will naturally be understood that the narrowing of the 

 subject to a relatively small field of Animal Psychology 

 compels the author to use only a very small number out of 

 the many hundreds of facts and observations on the intel- 

 lectual life of animals, which have been sent to him from 

 &11 parts of the world in answer to his public request, and for 

 which he here again returns his public acknowledgment ; 

 further, the greater number of these communications give the 

 result, as might be expected, of daily and private observa- 

 tions on the more accessible animals. The author therefore 

 ventures to refer his respected correspondents to a later work 

 from his own pen which, as compared with the present 

 book, undertakes a far wider task. He will therein endeavor, 

 by means of a psychological classification, to trace the dif- 

 ferent affections and manifestations of man's emotional and 

 intellectual life throughout the great circles of the animal 

 world. Here also most of the communications will be found 

 under the names of the several observers, and the author 

 trusts that this will be accepted as his personal acknowledg- 

 ment for individual help. 



Darmstadt, October, 1876. 



