CONTENTS 



PAGE 



I. STATEMENT OF THE PROBLEM 1 



II. EXPERIMENTAL WORK 1 



A. Introduction 1 



B. Apparatus and Methods 4 



1. General description of the apparatus 4 



2. General method of procedure 8 



3. Detailed description of the apparatus 9 



a. Experiment aquarium 9 



b. The lamphouse 10 



c. Food-bar 10 



d. Apparatus for the regulation of the intensity and of the 



distribution of light 12 



e. Color f-lters 13 



4. Detailed description of methods 14 



5. Determinations of the intensity and the distribution of light 



for stimulus patches 15 



C. Experiments to Test Discrimination by the Formation of a Food 



Association 20 



1. Intensity discrimination by dace 20 



2. Wave-length discrimination: White-red by dace 23 



3. Wave-length discnmination: Blue-red by dace 25 



a. Red chiefly at constant maximum intensity 25 



b. Tests for dace Md, Blue with Red decreasing in intensity 30 



c. Tests for dace H, Red decreasing in intensity 32 



d. Tests for Yl and YP, Red decreasing in intensity 32 



e. Discussions of Blue-red graphs of the dace M, Md, Yl, 



YP and conclusions 32 



4. Intensity discrimination by sunfish as indicated l^y response 37 



5. Wave-length discrimination: Blue-red by sunfish, with Red 



decreasing in intensity 38 



a. General account 38 



b. Large sunfish 41 



c. Small sunfish 42 



d. Sunfish 5S2 43 



D. Tests of the Apparatus and its Manipulation 44 



1. Check tests by changes in manipulation 45 



a. Shifts of si it and filters as a clue 45 



b. Position of the experimenter as a clue 45 



2. Check tests by changes in the apparatus 45 



a. Food-bar 45 



b. Lenses 46 



c. Filters 46 



d. Slits 46 



