1 86 WALTER LOUIS HAHN, 



except myself in the room or adjoining halls, and outside noises 

 were not heard to a large extent. The only noises recurring 

 with any degree of regularity in the room were those made by 

 the steam in the heating pipes. These could have no direct as- 

 sociation with the giving of food while the movements of the 

 observer near at hand did have such an association and these 

 were perceived by several of the animals at times, as when they 

 left the cloth and started toward the sound of the opening door. 

 Therefore sound cannot be considered as a factor in guiding the 

 bats to the back or front of the cage. 



Taste and touch may also be counted out, because, if they 

 entered into the food associations at all, they would each tend to 

 guide the animal toward the cloth. 



It is not possible to say with so much assurance that sight is 

 not a factor. It was possible for the animals to look through the 

 sides of the cage, but there were no conspicuous objects near 

 and the door of the cage with its latch, and the white or red cloth, 

 were much more noticeable than anything else in sight. 



In describing the action of the bat in the cage I have said in a 

 number of places that it " looked around," but it is not certain that 

 this action was really for the purpose of seeing. In a number 

 of trials the animals were so placed that they faced the cloth and 

 if they had been looking for familiar objects as landmarks to 

 guide them to the food they would have noticed it first of all and 

 would have gone directly to it. 



The only way in which it seems possible that sight could have 

 aided in their orientation is through the direction of the rays of 

 light. This is not probable because the room was well lighted 

 by windows on two sides and the experimental cage always stood 

 back out of the direct sunlight and also out of the shadows. 

 Moreover, we should not expect to find that animals accustomed 

 to spending all their lives in total darkness or twilight, would de- 

 pend upon the visual sense for orientation. 



While it must be admitted that the experiments did not exclude 

 every possibility of some effective sensations being received 

 through the five senses we commonly know, yet it is not possible 

 to fully account for the behavior of the animals in the experi- 

 ments above described on the basis of these senses alone, unless 



