534 



Willi mn Morton Barrows 



usually the case, a record of one circle was put down for the fly 

 when it had turned continuously through an arc of 360 degrees in 

 one direction. A circle was called positive if the fly moved with 

 its normal antenna on the side toward the center and negative if 

 it moved in the opposite direction; /. e., a fly having its left antenna 

 cut and moving always with its right side next the center would be 

 said to be describing a positive circle, etc. Table IX shows the 

 records of twelve flies tested in the manner described. 



TABLE IX 



The numbers of positive and negative circles made by twelve fies which had only one functional antenna. 

 Each fly was tested singly for a period of five minutes in a uniformly odorous atmosphere 



Numbers of the flies 



Normal antenna 



The number of circles made in a 



positive 

 direction 



negative 

 direction 



3-- 



4a. 

 6.. 



7a. 



right 



left 



right 



left 



left 



right 



right 



left 



left 



left 



left 



left 



Totals 



46 



From this set of experiments it will be seen that forty-six out of 

 fifty of the circles, or 92 per cent, were made in a positive direction, 

 i.e.y toward the normal antenna. As this antenna is obviously the 

 one stimulated, it is clear that the flies must orient to unequal, 

 unilateral stimulation.- 



2 Since this paper was written Kellogg ('07, p. 153) has recorded circus movements in the males of 

 the silkworm moth after the removal of one antenna and on exposure to odors. 



