SENSORY ADAPTATIONS OF BATS. 177 



perception of objects are in the internal ear. The hairs of the 

 body and membranes also have a sensory function. The exter- 

 nal ears, the tragi and the eyes are not necessary for the guid- 

 ance of the animals, although there is reason to believe that 

 when they are flying in the light they depend, to some extent, 

 upon the sense of sight to perceive objects. 



Additional Observations. 



A large brown bat, Eptesicus fuscus, brought into the experi- 

 ment room May 2 seemed wholly unable to avoid the wires. It 

 flew rapidly, was not seen to dodge any obstacle, and struck the 

 wires 67 times out of 100 chances when uninjured. It appeared 

 to be frightened by its unusual surroundings. 



A long eared bat, Corynorliimis niacrotis, captured May i, 

 struck 52 times out of 102 chances. After it had been flying in 

 the room for ten or fifteen minutes it began flying against the 

 windows. It returned to the same point time and again, strik- 

 ing the pane when the window was closed or the wire screen, if 

 the window was open. Usually it struck with considerable force 

 and fell to the sill, but immediately got up and repeated the per- 

 formance. An adult Myotis hicifugus liberated in the house on 

 April 30 acted in the same way and other individuals of both 

 the common species of Myotis flew against the glass and window 

 screen. 



There were great and unaccountable individual differences in 

 this regard. A male M. siibulatus on September 3 struck the 

 screen repeatedly, both when the eyes were normal and when 

 they were blindfolded. Another male of the same species used 

 on the following day flew directly toward the screen a number 

 of times but always turned in time to avoid it. Apparently in 

 these instances the animals were depending upon the sense of 

 sight in guiding their movements. The window glass would 

 be invisible to an animal that had never had experience with trans- 

 parent objects and the wire screen was not very apparent against 

 the background of trees among which the house is situated. 

 The actions of the bats in flying about the room at certain times 

 seemed to indicate that they were depending on sight for guid- 

 ance in avoiding the wires. The flight when the eyes were cov- 



