248 THE NATURE-STUDY REVIEW [i, 6, nov. 1905 



psychologist. After several years study of the habits and activi- 

 ties of ants, I undertook, in 1904, to induce the ants to tell me 

 through actions, which always speak more loudly than do words, 

 whether they remembered past experiences. When such an in- 

 quiry is to be addressed to an animal, it is but fair that the ap- 

 peal should be made through the leading sense of that animal. 

 If it be to the eagle it should be through the sense of sight ; if to 

 the mole it should be through the sense of hearing; if to the 

 caterpillar it should be through the sense of touch ; if to the sea- 

 anemone it should be through the sense of taste. The leading 

 sense in the ant is olfactory, and through this sense I naturally 

 put my question to the ants. 



Among the ants, the workers have been shown by dissection 

 to have the largest brain, and I therefore chose the workers for 

 my tests of power of memory. That I might know whether the 

 action of an ant was influenced by memory, it was necessary for 

 me to know not only the customary behavior of the ant but to 

 know its individual experiences during its whole lifetime. I 

 therefore took from among the many nests in my formicary such 

 ant-workers as hatched in segregation at the same time, and 

 sequestered two or more species together in a very small nest 

 where their natural activities would cause them to touch each 

 other with the antennae during the first hours of life. Ants of 

 species ordinarily inimical were thus made friendly, forming a 

 mixed family whose congeniality was manifested by all sorts of 

 serviceable offices customary among ants of the same community. 

 After these ants had lived happily together for periods ranging 

 from twenty to forty days, I sequestered each species represented 

 in the mixed nest, putting each group into a new nest. I then 

 kept each group in strict segregation up to the time when the 

 odor of the other species, encountered only in their earliest days, 

 should again be presented to them for recognition. 



One mixed family consisted of large black ants and small 

 brown ants, and these were separated for seven months. In 

 bringing them together an extraordinary factor had to be 

 reckoned with, the afore-mentioned fact that worker ants change 

 their odor with advancing age, and that neither the black ants 

 nor the brown ants would bear the same progressive odor that had 

 characterized them when associated with the other species seven 

 months earlier. So great in fact had been the change of odor 



