5 2 ^ ANTS. 



" simple," meaning " light of different wave-lengths, or heat, or mois- 

 ture, or chemical o impounds, etc.," and "individualized" stimuli, by 

 which he understands specific typical bodies," or objects. That many 

 instinct actions are called into existence by simple stimuli admits of 

 no doubt, but it i.- an open question whether this may be accomplished 

 by individualized stimuli. In this connection Driesch (1908) says: 

 ' It is very important to notice that, // an actual case of a specific indi- 

 vidualized stimulus of an instinct should become known, the limits of 

 the possibility of a mechanical explanation would be exceeded. They 

 would be exceeded and an autonomic or vitalistic factor would be at 

 work, because we could by no means understand how the specifically 

 combined or ' individualized ' stimulus could be received by the organ- 

 ism in such a way as to become the cause of a specific and fixed series 

 of motions in the organism. Supposing that any organism were spe- 

 cifically affected in its instinctive movements by the mere sight of any 

 other typical organism, say of the same species, but of the other sex, 

 and that this affection were the same, whether the organism which 

 forms the stimulus were seen from before or from behind, or from 

 the side or at any angle whatsoever, what would follow from such a 

 fact ? A machine could only be fitted to receive the specific compli- 

 cated stimulus in a few typical positions, but how could a machine be 

 imaginable if an infinite variety of aspects had the same invariable 

 instinctive effect?' It seems probable, as Driesch suggests, that the 

 sexual instincts, at least in the higher animals, may be set going by 

 individualized stimuli He cites in support of this supposition the 

 observations of Mayer and Soule ( 1906) who found that female moths, 

 unless deprived of their sight, would not copulate with male moths 

 that had their wings removed. I am at a loss to see how the question 

 raised by Driesch can be answered satisfactorily through a study of 

 the ants. It is, of course, possible that many of their instincts are 

 initiated by individualized stimuli, such as perceptions of the young 

 in various stages and of the various castes as typical bodies, but as 

 the dominant senses of ants are mechanical and chemical, it is at least 

 equally probable that these objects may call forth appropriate instinctive 

 reactions merely as tactile and olfactory sensations, and hence as simple 

 stimuli. 2 



With a description of the instinct actions and their stimuli the 

 ethological and physiological consideration of instinct is exhausted. I 



2 Probably many authors would be inclined to doubt the dependence of in- 

 stincts on individualized stimuli on the ground that " purely inherited responses 

 can be adapted only to certain broad, roughly distinguished classes of stimuli, 

 for these are common to the experience of all members of the species" (Miss M. 

 F. Washburn, 1908). 



