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which position, it immediately turned sharply toward the 

 abocular side (fig. 5, c), remained here a few moments, vibrating 

 continuously, and then, turned toward the resting position, 

 sometimes reaching it, remained here a moment, after which it 

 again turned toward the abocular side. Thus it continued 

 to swing back and forth, but usually only a short time. 



Fig. 5 Outline of Amaroucium pellucidum tadpole representing reaction to 

 increase in illumination, a, resting position of tail; b, position assumed after 

 decrease in illumination; c, position assumed after increase in illumination; 

 arrows, extent of vibration. 



Neither the position assumed in the shadow nor that assumed 

 in the strong light was held for any considerable length of time 

 if the luminous intensity continued without change. No record 

 was made of the time it was held in this specimen, but in others 

 it was found to vary from 1 hm. to 10 hm. It could be fairly 

 clearly seen, however, that it was usually held considerably 

 longer after increase than it was after decrease in illumination. 

 Three series of ten readings each were made in reference to this 

 period, two after reduction and one after increase in illumina- 

 tion. The averges of the results obtained in these series are, 



