Reighard. — Senses and Learning in Fishes 163 



different way, and far less frequently than a blue or 

 white. This indicates that the plates differ for them in 

 color. Flounders when placed on back grounds of differ- 

 ent colors (Mast, 1916), become after a time of the same 

 color as the background. Blinded flounders do not un- 

 dergo this color change, and hence it is concluded that 

 color differences are appreciated through the eyes. Mast 

 has illustrated these color changes by some very striking 

 color-photographs. 



And so in spite of the strong scientific opinion to the 

 contrary, our age-long belief in the value of color in our 

 artificial flies is shown to be warranted. But the warrant 

 extends to blue and red only; we may say that we know 

 that fish discriminate these. It is probable that they dis- 

 criminate other colors as well. 



III. LEARNING. 



Some instances of learning by fish have been already 

 referred to. The catfish quickly learns to tell a bit of 

 cotton wool soaked in meat juice, from one not so soaked. 

 The sunfish and dace learn to come for food to a patch 

 of blue light. The trout learns to come toward the man 

 who feeds him. To cite in detail all other known in- 

 stances of learning would take too long. A few will 

 suffice. 



Some years ago I carried on experiments on the gray 

 snapper of the Gulf of Mexico (Reighard, 1908). There 

 was a school of about 75 of these fish under a dock at 

 the Dry Tortugas. For a time I fed them by throwing 

 to them small fish known as hard-heads. These were 

 greedily eaten. The little fish were eaten even when they 

 were stained bright blue or red. They were eaten when 

 soaked in various noxious chemicals. Finally I cut some 

 tentacles of jelly fish into small bits and placed these bits 

 in the mouths of the red stained hard-heads that were 

 being given to the grey-snappers. These tentacles, which 

 were so placed that they projected from the mouths of 

 the hard-heads, are covered with stinging nettle cells. 



