Il6 'Journal of Comparative Neurology and Psychology. 



The total times for the first ten tests were red, fourteen seconds, 

 green, thirteen seconds; and for the last ten, red, ten seconds, 

 green, eleven seconds. 



Neither the times nor the observed behavior of the fish indicated 

 any constant difference in the response to the two colors used. 

 The results do not, however, prove a lack of color-discrimination. 

 They are inconclusive. They simply show that even if color- 

 vision existed and if colors were "associated" with success or 

 failure in procurmg food, the discrimination and the "association" 

 were insufiicient to cause an inhibition of the "green reaction." 

 The outcome is not unaccountable, since brook fish have, at least 

 during a part of the year, a varied diet, and they may therefore be 

 expected to react positively and persistently to a wide range of 

 objects that offer the possibility of food. 



Although the result of the inhibition experiments was, for our 

 purposes, largely negative, the method was valuable both because 

 it made us acquainted at first hand with the behavior of our sub- 

 ject and because it suggested a second method which offered a 

 choice of stimuli without, at the same time, demanding the actual 

 inhibition of an old and firmly-rooted mode of response to stimu- 

 lation. 



//. The Method of Choice. — In the second set of experiments, 

 both pairs of forceps were presented at the same time, the red baited 

 and the green empty. In order still further to eliminate movement 

 of the stimulus the tank was divided by a thin wooden partition 

 into two like compartments. An opening about three inches 

 wide was left at either side of the partition, allowing the fish to 

 swim freely around the tank. These openings could be closed by 

 wooden gates, thus making it possible to confine the fish in either 

 half of the tank. With the subject in compartment A, the for- 

 ceps were suspended side by side in the middle of compartment B 

 and about two inches from the partition. They were held in place 

 by being slipped vertically into narrow grooves saw^ed in a horizon- 

 tal strip which ran across the tank just above the surface of the 

 water, parallel with, and attached to, the upper edge of the par- 

 tition. After the forceps had been set into position, one of the 

 gates, right or left, was opened and the fish allowed to swim to 

 compartment B and to secure the food from the forceps. 



The procedure involves two constant errors of space, one of 

 position of stimulus and one of direction of movement. The first 



