What is Intelligence, and What is Instinct? 29 



certain likeness to man and made it fully competent to 

 direct its own activity in a suitable manner. 



Consequently instinct signifies both from an etymo- 

 logical and historical point of view, a sensitive impulse 

 which induces a being to perform certain actions the 

 suitableness of which is beyond the perception of the 

 agent that performs them. 1 



It is instinct that induces the male larva of the stag- 

 beetle (Lucanus cervus), before its transformation into 

 a pupa, to produce a cocoon, the size of which is far 

 greater than that of the pupa, and thus to provide in 

 advance for the length of the future antlers of the imago 

 which is to come forth from that larva. It has never 

 even seen a developed stag-beetle, and no amount of 

 "reflection" on its part could hit upon the clever idea of 

 its eventual destiny to become a male stag-beetle with 

 mighty antlers on its head. It is instinct that impels the 

 female of the leaf-roller (Rhynchites betulse) to make 

 an incision into a birch-leaf after an extremely ingenious 

 mathematico-technical problem, that was by the way 

 not introduced into human science before 1673, and then 

 to roll up that leaf in the shape of a funnel as a depos- 

 itory for its eggs. 2 Neither by experience nor by reflec- 

 tion could the little weevil gain an idea of that problem, 

 nor could it even know that it would lay "eggs" at all, 

 from which young leaf-rollers would eventually develop. 

 It is instinct that makes the young bird which is unac- 



*) We say expressly: "the suitableness of which is beyond its per- 

 ception," for the immediate object to which any instinctive activity is 

 directed and this activity itself are the subject matter of sensitive cog- 

 nition. 



2 ) See Debey, "Beitraege zur Lebens und Entwicklungsgeschichte 

 der Ruesselkaefer aus der Familie der Attelabiden," Bonn, 1846. Was- 

 mann, "Der Trichterwickler," Muenster, 1884. 



