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WILLIAM L. DOLLEY, JR. 



a moderately straight course until it fell off the table. The 

 behavior in the next three trials was very much alike, the organ- 

 ism performing a circus movement upon first being placed in the 

 beam, and then, after having gone a few centimeters beyond the 

 edge, it turned and went toward the glower. The eleventh trial 

 is interesting in that, although the organism was started very 

 much nearer to the glower, and consequently in much stronger 



Fig. 3 Reproduction of 34 successive trails made by butterfly 10/25-a (left 

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

 light; 1-34, 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. 



light, it, after having performed a circus movement, deflected 

 at an angle of only 40 degrees with the rays of light, while in 

 several of the previous trials in which it had started further 

 away from the source of light it deflected at a much greater 

 angle. In the twelfth trial the butterfly made a circus move- 

 ment when first started and then after having gone 1.5 cm. 

 beyond the edge of the beam it again performed a circus move- 



