PREFACE TO THE SECOND EDITION. 



THE interest with which this essay was received, 

 has made a second edition necessary. In order 

 to do justice to recent objections of our scientific op- 

 ponents, we had to enlarge it in various places. Still 

 we confine ourselves to real and positive objections. 

 Moreover, we have inserted a chapter on the different 

 Forms of Learning. 



The present work is closely connected with our 

 Comparative Studies on the Mental Faculties of Ants 

 and Higher Animals (German, second, enlarged edi- 

 tion, Freiburg i. Br., 1900). Besides, we desire to 

 call attention to an essay written for Zoologists, and 

 entitled "The Mental Faculties of Ants" (German). 

 Zoologica, Heft 26, Stuttgart, 1899. It may well serve 

 as a supplement to the views we advanced in the above 

 mentioned writings, as it supplies new material for 

 argument, 



