xxxviii Trans. Acad. Sci. of St. Louis. 



The fourth school, which includes L. Buchner, Huber, MacCook, 

 Romanes and others, insists that the difference between human con- 

 sciousness and that of ants is one of degree and not of kind. 



About ten years ago Dr. Turner began a series of experiments on 

 the behavior of ants, the aim of which was to see which of these 

 sets of men was right. Some of the results of these studies were pub- 

 lished in 1907. The purpose of this evening's paper was to discuss the 

 bearing of those experiments on the homing of ants and compare with 

 them the published results of experiments on the same subject con- 

 ducted by two independent workers, Cornetz of Algeria and Santsci 

 of Tunis. The experiments of these two men were performed during 

 the years 1909-1911. 



From a series of experiments Dr. Turner came to the following con- 

 clusions: 



1. The movements of ants are not tropisms and ants are not 

 guided by a homing instinct. 



2. In their wanderings, ants are influenced by olfactory, topochem- 

 ical, optic, auditory, kinesthetic and tactile stimuli. 



3. Ants have fairly definite impressions of direction in both hori- 

 zontal and vertical planes, and also impressions of distance. 



4. Ants have associative memory and in their home-goings they 

 display marked individual variations. 



Cornetz's experiments made in the field on ants in Algeria lead him 

 to the following conclusions: 



1. There is no homing instinct, for ants that are carried away 

 from home cannot find the way back. 



2. Ants are not lead home by the odor trail, because an ant never 

 returns to the nest along the path by which it left it. 



3. Ants have memory of location and persistent sensory ideas of 

 direction and these have been acquired independently of vision, touch 

 or smell. 



From field observations and field experiments on ants of Tunis Dr. 

 Santschi arrived at the following conclusions: 



1. Among ants we find two kinds of trails; in one kind the ants 

 are guided largely by odors and topochemical sensations, in the other 

 they are guided by perceptions that are based largely upon visual 

 sensations. 



2. Among the Tapinomas and, perhaps, other harvesting ants, the 

 trails are started by odors secreted intentionally by a single worker. 



3. Such an intentionally scented trail is utilized by workers that 

 do not slavishly follow it, to teach other workers the way to the food. 



4. This trace of odor is not sufficient to fully explain the behavior 

 of the ants guided by it. 



5. As a rule orientation among ants is a complex phenomenon 

 based upon a variety of sense stimuli; the predominant stimulus de- 

 pending upon the species and the condition under which it is operat- 

 ing. 



