412 'Journal of Comparative Neurology and Psychology. 



experiments planned to solve a problem not discussed in this paper, 

 two stages were used, from each of which an incline of the same 

 kind led to the island. In one case the incline was attached to 

 the right side of the stage and in the other to the left. Incline num- 

 ber two was nearer the nest opening than was incline number one. 

 An ant that had thoroughly learned the way up and down incHne 

 number one, would occasionally start up incline number two. 

 Sometimes it would continue on to the stage, but more frequently, 

 when only part of the way up, it would turn about and return to 

 the island and continue on to incline number one; either directly, 

 or else after having first retreated to some point farther back on 

 the trail. The same thing sometimes happened where two inclines 

 were attached to opposite sides of the same stage. 



From a psychological point of view, there were only two differ- 

 ences between incline number one and incline number two; incline 

 number one was scented with the footprints of the ant, while 

 incline number two was not; and incline number one was farther 

 from the nest than incline number two. Since it has been shown 

 that the substitution of an unscented incline for one scented by the 

 tracks of ants is not a disturbing stimulus to ants that are moving 

 in a well known path, the difference in the distance traveled seems 

 the only thing that could have caused the inhibition. 



The grouping of all these data in one section does not imply 

 that they are of the same psychic order. Some may be simple and 

 others complex. Some may even be the derivatives of others 

 mentioned here. To discuss such issues is not the purpose of this 

 section. Its sole aim is to show that the psychic impression that 

 confronts the home-going ant is not a simple olfactory stimulus, 

 as most writers seem to suppose, but that it is a complex impres- 

 sion composed of contributions from the olfactory (topochemical), 

 visual, tactile and kinesthetic and auditory senses. 



v. HAVE ANTS ASSOCIATIVE MEMORY .? 



"By associative memory, I mean the two following peculiarities 

 of our central nervous system: First, that processes which occur 

 there leave an impression or trace by which they can be reproduced 

 even under different circumstances than those under which they 



originated The second peculiarity is, that two processes 



which occur simultaneously or in quick succession will leave 



