PHOTIC EEACTIONS OF HONEY-BEE 399 



ever, as well as the others, usually circled again toward the func- 

 tional eye upon reaching the non-directive region near and 

 directly beneath the lamp. The records shown in the figure do 

 not include this region. 



DoUey ('16, p. 402) states that he observed some modification 

 from day to day in the behavior of Vanessa in non-directive light. 

 The following evidence seems to indicate that the same is true, 

 to at least some extent, for the honey-bee also. In directive 

 light, individuals with one eye covered were sometimes observed . 

 to begin to swerve toward the functional eye, only to check them- 

 selves by a sharp turn in the opposite direction. Correcting 

 movements of this sort sometimes occurred repeatedly in a single 

 trial, with the result that the animal reached the source of light 

 by a much more direct course than it would have otherwise been 

 able to follow. Precisely the same sharp turns away from the 

 functional eye were occasionally seen in non-directive light also. 

 It seems probable, therefore, that modifiability through experi- 

 ence affects the behavior of bees in non-directive as well as in 

 directive light. 



B. Fluctuating factors 



The variables which have thus far been discussed are those 

 which continuously or progressively affect the behavior of bees 

 throughout an experiment. They probably account in a large 

 measure for such phenomena as the persistant turning toward 

 the covered eye in certain individuals or the apparent lack of any 

 tendency to turn at all in still others. They do not, however, 

 explain the many sudden changes of behavior which were ob- 

 served. Such variations are dependent upon factors of behavior 

 which fluctuate from time to time. A few of these factors result 

 from environmental changes. The majority, however, arise from 

 changes within the organism itself. 



a. External. In quantitative experiments every possible pre- 

 caution was exercised to keep all external factors uniform, except 

 the intensity of the light which was changed from trial to trial. 

 This, of course, was possible to a limited extent only. The 

 manipulation of the bees introduced varying mechanical stim- 



