390 WILLIAM L. DOLLEY, JR. 



such that the rays of light were now at right angles to their 

 former direction. When this was done, it was found that the 

 butterflies usilally reoriented. That is, they usually turned until 

 they again assumed the same axial position with reference to the 

 direction of the rays of light that they had taken before the glower 

 was moved. This occurred no matter if the glower was moved 

 to the right or to the left. Thus, it is evident that in the process 

 of reorientation the animals may turn either toward the blinded 

 or the functional eye (figs. 11 and 12). 



Thirty-one butterflies were used in this experiment, and it 

 was found that, of these, twenty-two reoriented both to the right 

 and to the left. Nine, however, although they reoriented toward 

 the functional eye, did not turn toward the blackened eye. 

 Three of these were kept and tested for several successive days. 

 The behavior shown in these tests is recorded in table 5. 



These results show clearly that Vanessa with only one eye 

 functional can reorient, and in this process can turn either toward 

 the blinded eye or toward the functional eye. They also show 

 that the behavior may become modified since those insects that 

 do not reorient by turning toward the blinded eye when first 

 tested are able to do so after a certain amount of experience 

 (fig. .12, 1-3). Moreover they seem to support the conclusion 

 derived from results described previously that the performance 

 of circus movements seems to be favored by a sudden change in 

 light conditions, since in four of the trials described in table 6 

 the butterflies either performed circus movements, or apparently 

 began to perform them, when the position of the glower was 

 suddenly changed. 



The ability of the butterflies with only one eye functioning to 

 reorient, and so follow the source of light as its position is changed 

 is important in a consideration of the factors in the process of 

 orientation. It has a direct bearing on whether or not orienta- 

 tion in light is dependent upon stimulation of symmetrically 

 located photosensitive areas, as demanded by Loeb's theory of 

 orientation. In reorientation, such as has been described, only 

 one retina is affected by light. The chemical changes taking 

 place in the two photosensitive areas are not at all identical. 



