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WILLIAM L. DOLLEY, JR. 



between the beams, it was marked "plus" or " minus" 10 degrees, 

 depending upon whether the butterfly deflected toward the right 

 or the left. The intermittent light was always to the right. 

 Deflection toward it was consequently always " plus" (see figure 1). 

 The methods used in the experiments described in section V 

 of this paper were similar to those described above except that 

 the light conditions were slightly different and other means of 

 recording the movements of the animals were used. As light 

 sources two small 36 candle power automobile lamps run on 

 storage batteries were used. The motor, sectored disk, and 

 lamps were all in the same room as that in which the experiments 



t T I T'T I I 



FIG. 1. Diagram to show methods used in recording the reactions of Vanessa ID 

 a field of light composed of two horizontal beams crossing at right angles. (Re- 

 duced by three-fourths). Arrows, direction of rays of light; A, intermittent 

 light; B, continuous light; C, line bisecting the angle made by the two beams; D, 

 path of butterfly making an angle of +10 degrees; E, path of butterfly making 

 an angle of 10 degrees. 



were performed. The vibration caused by the motor was very 

 slight and did not affect the results, as was shown by tests. 

 Instead of using sheets of paper covered with soot to record the 

 movements of the animals, very fine charcoal dust was sprinkled 

 on the sheets mentioned above with a pepper shaker. After an 

 insect had moved across a sheet so prepared a pencil was drawn 

 along the trail left by the organism. After removal of the char- 

 coal the sheet with no further treatment bore a permanent record 

 of the reactions of the animal. 



