420 'Journal of Comparative Neurology and Psychology. 



of happening to succeed after making many blunders. So far this 

 accords with the observations made by all students of vertebrate 

 animal behavior. During the first few trips, however, aided by 

 memory, certain associations of ideas are formed which persist 

 and enable the ant to orient itself. To men of Thorndike's con- 

 viction, this is a discordant note, but it accords perfectly with 

 Hobhouse's view concerning vertebrates. Although this does 

 not necessarily make the ant a self-conscious creature, it makes it 

 much more than a mere reflex machine. 



It is worth noting that in ascribing associative memory to ants, 

 I am in perfect accord, not only with Wasmann, but also with 

 such a stanch advocate of the tropisms as Loeb. In his chapter 

 on "The distribution of associative memory in the animal kingdom" 

 ('02, p. 224), Loeb says, "Although I heartily sympathize with 

 Bethe's reaction against the anthropomorphic conception of 

 animal instincts, I yet believe that he is mistaken in denying the 

 existence of associative memory in ants and bees." 



After the space occupied in attempting to show that the " assimi- 

 lation" and "determination of stimulus" hypotheses do not ade- 

 quately account for the conduct of home-going ants, I fear that by 

 "associative memory" I may be misunderstood to mean some high 

 type of rational life. Therefore, I wish to emphasize the fact that 

 I use the term as Loeb uses it in the quotation with which this 

 section opens. 



VI. DOES DIVISION OF LABOR AMONG ANTS SIGNIFY MUTUAL 

 COOPERATION ? 



In the course of my experiments many examples of division of 

 labor have been noticed. I have known one set of workers to 

 store the pupae under the incline, or in a dark chamber, or on the 

 stage in the open, while yet other workers conveyed them from 

 these places to the nest. I have seen one set of workers lay pupae 

 down on the island, while a difi^erent set carried them into the nest. 

 I have even seen cases where one set laid the pupae down in the 

 feed chamber, from which another set carried them into the nest 

 proper. I have noticed similar examples of division of labor in 

 most of the species experimented upon. It was with Prenolepis 

 imparis, however, that I took pains to investigate it carefully. 

 Here we have one set of workers bringing pupae to a certain spot 



