LIGHT OF DIFFERENT WAVE-LENGTHS BY FISH 99 



crimination. Instead of the usual 

 direct approach there was a weaving 

 back and forth in front of the door or 

 circHng around the end of the discrim- 

 ination compartment or remaining still 

 in a corner. 



F. Experiments with equated energies. 



32. When in the blue-red discrimination 

 experiments the energies reaching the 

 two stimulus plates were equated by 

 the use of a silver-bismuth thermopile 

 the percentage of correct choices con- 

 tinued to be significantly high. (p. 53 

 and postscript.) 



G. Tests of apparatus and manipulations 



33. Check tests to determine whether shift- 

 ing of slits and filters, changes in the 

 position of the experimenter, or dif- 

 ference in appearance of any part of 

 the apparatus on the positive and 

 negative sides might afford the fish a 

 clue gave negative results. 



VI. CONCLUSIONS 



Sunfish (Eupomotis gibbosus L.), horned-dace (Semo- 

 tilus atromaculatus, Mitchill) discriminate light of longer 

 wave-length from light of shorter wave-length and from 

 white light. This is shown not only by innate differential 

 reaction but by the results of experiments in which a feed- 

 ing response was associated with a stimulus of restricted 

 wavelength. 



Acknowledgments 



I am obligated to Professor Jacob Reighard, under whose 

 direction the work has been carried on, for unstinted aid 

 in planning the work and for careful oversight of the details 

 of the problem. To Professor John F. Shepard I am much 

 indebted for constant suggestions and stimulating criti- 

 cism. For the use of physical apparatus and for advice 

 thanks are due to Professor H. M. Randall. 



