PHOTIC REACTIONS OP HONEY-BEE 411 



9. The variability of response displayed by bees with one eye 

 blackened, when creeping in non-directiVe Ught, is never due to 

 a loss of phototropism or to after-effects of one intensity upon 

 trials in a second intensity. It is attributable to the following 

 causes : 



a. Conditions of temperature and humidity. 

 h. Failure to eliminate completely the photoreceptors on one 

 side of the body. 



c. Effect of contact stimulus afforded by the covering of eye. 



d. Natural asymmetry of individuals. 



e. Modifiability through experience. 



/. Mechanical stimuli attendant upon manipulation. 

 g. Internal factors which may affect behavior from time to 

 time, but not necessarily continuously. 



10. Photic orientation in the normal honey-bee is effected 

 through the continuous action of light on both photoreceptors. 



11. The following considerations afford strong evidence that 

 among arthropods generally, orientation to light is effected 

 through the continuous action of the stimulus rather than inter- 

 mittent changes of its intensity. 



a. Circus movements are of general occurrence among photo- 

 tropic arthropods. 



h. The process involved in circus movements is identical with 

 that involved in normal orientation. 



c. Circus movements in directive Ught are explainable only on 

 the assumption of continuous photic stimulation. 



d. Circus movements are performed under conditions of non- 

 directive illumination where the only stimulus afforded is on& 

 of approximately constant intensity. 



12. Circus movements, as Bohn has suggested, furnish a cri- 

 terion for testing the 'continuous action theory' of orientation.. 

 The failure of the test, however, does not necessarily invalidate' 

 the theory. 



Postscript. The preparation of this paper has been much 

 retarded by the absence of the author, who is still in government 

 service in France. Hence it has not been possible to include im 

 the discussion Carrey's recent paper (Jour. Gen. Physiol., vol. 1„ 



