458 GERTRUDE MAREAN WHITE 



mined that the fishes were not able to distinguish between the 

 imitation baits and the food when both were offered out of water 

 under the same conditions. The use of this method usually 

 caused some delay on account of the necessary training of a week 

 or two at the beginning of a set of experiments. The proportion 

 6f mudminnows successfully trained was only about two out of 

 every five, but nearly all the sticklebacks could be taught to 

 take food as desired. 



EXPERIMENTS WITH MUDMINNOWS 



Experiments with colored papers 



The first set of experiments with mudminnows was carried 

 on during the winter of 1914 to 1915. Five were placed in sep- 

 arate bowls to be trained, but only two of these could be induced 

 to eat with regularity. The experiments were performed by 

 day before a large window. Discs of colored' papers were cut 

 7.3 cm. in diameter and stiffened with cardboard. An aperture 

 was made in the center of each large enough to allow the discs 

 to be slipped down over the ends of the forceps from which the 

 fishes were fed. The fishes were at first somewhat disturbed by 

 the paper discs and required a little time to become accustomed 

 to them. In a week this timidity vanished; the appearance of 

 a colored disc became a signal for the fishes to dart to the surface 

 .and spring out of the water after food. When this association 

 with one color seemed to be thoroughly established, a disc of 

 another color was substituted with paper closely resembling the 

 food in color and appearance in the forceps. The same pair of 

 forceps was never used for both food and paper so that there 

 should be no possibility that the taste of food might be trans- 

 ferred to the paper. The colored discs slipped down over the 

 forceps were offered alternately. This furnished a severer test 

 of the power of association than did the experiments of Wash- 

 burn and Bently ('06) in which the forceps of two different 

 colors with only one holding food were thrust into the water 

 -simultaneously. 



-' 2 xhe colors correspond with the following numbers in Klingsiek and Valette's 

 Code de Coleur: red: rouge no. 2, blue: blue no. 431, violet: blue-violet, no. 481. 



