374 



WILLIAM L. DOLLEY, JR. 



tional eye) and performed a circus movement. This was fol- 

 lowed by a fairly straight course for 7.5 cm. At this point the 

 organism turned again to the right as if to make a circus move- 

 ment but did not complete it, turning instead to the left toward 

 the source of light. In the third trial the insect made a circus 

 movement as soon as it was placed in the beam and then crossed 

 the beam at an angle of about 95 degrees with the rays of light, 

 and went 3 cm. into the shaded region where it turned toward 

 the blackened eye and moved in a course nearly parallel with 

 the edge of the beam. In the fourth the behavior was like that 

 in the preceding trial except that after the organism passed the 



Fig. 2 Reproduction of 20 successive trails made by butterfly 10/25-a (left 

 eye blackened) on the first day of the tests, a and b, limits of horizontal beam of 

 light; 1-20, trails made in successive trials; small arrows, direction of movement 

 of animal; large arrows, direction of rays of light; illumination at x, 624 mc.;' 

 at y, 250 mc. 



edge of the beam it did not turn toward the glower, but con- 

 tinued on in a fairly direct course until it reached the edge of the 

 table. In the fifth trial the butterfly continued across the beam 

 at about the same angle as in the previous trials until it had 

 gone 2.5 cm. beyond the edge. At this point it turned toward 

 the blackened eye and moved fairly directly toward the glower. 

 In the sixth the organism again made a circus movement imme- 

 diately upon being placed in the beam. It then crossed the 

 beam at right angles with the rays, and on reaching the right 



' Throughout this paper the abbreviation 'mc' will be used to indicate meter- 

 candles. 



