PHOTIC REACTIONS OF HONEY-BEE 405 



2. Orientation m the honey-bee 



As has been previously stated, the process involved in circus 

 movements must be regarded as identical in every respect with 

 that involved in normal orientation. The circus movement is 

 the orienting process. A normal creeping bee may be caused to 

 perform circus movements without having one eye blackened, 

 if the light is merely moved so as to keep it constantly to one side 

 of the animal. Whether the eye be blackened or the light be 

 moved, the case is the same. The orienting process is merely pro- 

 longed, and the final attainment of orientation prevented. 



The experimental data detailed in the present paper show con- 

 clusively that when one eye of a bee is blackened, the resulting 

 circus movements are produced by the continuous action of the 

 light upon the functional photoreceptor. In the experiments in 

 non-directive light, the only photic stimulation afforded was one 

 of constant, almost uniform intensity over the entire surface of 

 the eye. Under such conditions, the animals not only performed 

 circus movements toward the functional eye, but the amount of 

 turning increased with an increase in the stimulus. It is clear, 

 therefore, that the process of normal orientation, which is iden- 

 tical with that involved in the circus movement, must also be 

 dependent upon the continuous action of light. 



The impulses arising from this stimulation are, at least in part, 

 transmitted to the musculature of the opposite side of the body, 

 since upon hemisecting the brain, the bee suffers a complete loss 

 of phototropism (Holmes, '01, p. 227). Although his experi- 

 ments were not conclusive on the point, Holmes beHeved that 

 the result obtained was not entirely due to 'Hhe effect of the 

 shock of the operation, or of incidental injury to other paths of 

 photic impulses." It must, therefore, have been due to the sev- 

 erance of crossed tracts or commissures which served in the trans- 

 mission of such impulses. There are present in the dorsocerebron 

 of the bee at least three commissures in more or less intimate 

 connection with the optic tracts (Kenyon, '96), and it is possible 

 that these are the elements concerned. There is thus neurologi- 

 cal as well as physiological evidence for the crossed transmission 

 of photic impulses. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGT, VOL. 29, NO. 3 



