448 Animal Life and Intelligence. 



basis in intelligence ; many of them probably have not. 

 And though the great majority of individually acquired 

 modifications of habits have owed their origin to intelligent 

 direction, still it is conceivable that some of them have 

 not. An animal may have been forced by circumstances to 

 modify its habits, without any exercise of intelligence ; and 

 this modification, forced, through changed conditions, upon 

 all the members of a species, may, through inheritance, 

 have passed into the stereotyped condition of an instinct. 

 Under each factor, then, we have two several categories. 



1 Elimination . . \ ' of unintelli gent activities. 



I 6. of intelligent activities 

 9 e i t - ( a. of unintelligent activities. 



"I 6. of intelligent activities. 

 3. Inheritance . . / a ' of anintelli gent activities. 



\ b. of intelligent activities. 



In all cases, however, where intelligence has been a co- 

 operating factor, this intelligence has lapsed so soon as the 

 activity became truly instinctive. 



From the co-operation of the factors it is almost im- 

 possible to give examples which shall illustrate the exclu- 

 sive action of any one. The following table must therefore 

 be regarded as indicating the probable predominance of the 

 factor indicated : 



a. Caterpillars spinning cocoons. 



b. Instincts of social hymenoptera. 

 2 fa. Drumming of snipe. 



I 6. Procedure of Queensland bower-bird. 

 fa. Ants forming nests in trees in flooded parts of Siam. 

 \ b. Instinctive fear of man. 



In speaking of the instinct of caterpillars spinning 

 cocoons as unintelligent, I am regarding the final purpose 

 of the activity. Intelligence may very possibly have come 

 into play in modifying the details of procedure. In giving 

 the drumming of snipe as an example of unintelligent 

 activities furthered by selection, I am assuming that it has 

 a sexual import, and that the activity correlated with a 

 narrowing of the tail-feathers was not, in its inception, 

 intelligently performed with the object of exciting sexual 



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