122 



Aquatic JLitt 



continued to take food under the colored 

 disc beneath which it had first been fed. 

 In this way red and blue, and red and 

 violet papers were distinguished. 



Since colored papers are never spec- 

 trally pure, monochromatic lights were 

 used in order to make more accurate tests. 

 The following lights were discriminated 

 by mudminnows, as was shown by asso- 

 ciations formed with them: Red and 

 green, red and blue, yellow and green. 

 Varying the intensity of the red and 

 green lights did not affect such discrimi- 

 nation, indicating that the reactions of the 

 fishes were to color rather than to inten- 

 sity. Sticklebacks also disinguished be- 

 tween red and green lights forming asso- 

 ciations of food and paper with them. 



An interesting piece of evidence was 

 obtained from an aquarium containing 

 fourteen Sticklebacks. These fishes were 

 kept under observation for several 

 months, during which they were regu- 

 larly fed, and became very tame. Calves' 

 liver was given to them nearly every day 

 from forceps. It was very amusing to 

 see all fourteen of them dart to the top 

 at a slight movement of any one near 

 them and begin sticking their noses out 

 of the water in anticipation of food. 

 When food was held a slight distance 

 out of the water, they would with one 

 accord leap out after it, and at times hang 

 on so tightly that they could be lifted sev- 

 eral inches out of water before letting go 

 their hold. On one occasion, after the 

 Sticklebacks had been given a small piece 

 of calves' liver, the forceps were held out 

 to them empty. None of the fishes ap- 

 proached the forceps, but the merest bit 

 of dark red liver was sufficient to attract 

 them. Small pieces of bright red and 

 dark red paper rolled into balls and sub- 

 stituted for the food were at once at- 

 tacked ; lavender which had a pinkish 

 tinge was snapped at twice, while tan yel- 

 low, yellow, dark blue, gray and green 



elicited no positive response. This ex- 

 periment indicates that the color of the 

 food which Sticklebacks take habitually 

 makes an impression difficult to eradicate. 



Since the theory has been proposed that 

 fishes see colors as shades of gray, as a 

 totally color-blind human being perceives 

 them, further experiments were per- 

 formed. If the fishes were reacting to in- 

 tensity rather than to color in the experi- 

 ments described above, they ought to be 

 able to form associations of food and un- 

 palatable substances with gray lights as 

 they had done with the colored lights. 

 Accordingly photographic plates were 

 "fogged" to different shades of gray and 

 food offered on the appearance of one 

 shade and paper on another. No asso- 

 ciations were formed by the fishes, since 

 they attempted in the same manner to 

 take whatever was offered with both 

 plates, which supports the conclusion that 

 the discriminations in the experiments 

 cited were due to the wave length of the 

 light. 



Only negative results were obtained in 

 experiments to test the perception of dif- 

 ferences in background by mudminnows 

 and sticklebacks, suggesting that such 

 discrimination does not have a very im- 

 portant function in their search for food. 

 The perception of color and movement 

 seems to be of the most importance. — 

 Author's abstract of paper in the Febru- 

 ary, 1919, number of The Journal of Ex- 

 perimental Zoology. 



The "one-time" advertiser abandons 

 the field right after sowing, and the weeds 

 of public forgetfulness grow over his 

 immature plant. To be sure, there are 

 exceptions to this rule. Some "one-time" 

 advertisements are highly productive, just 

 as some seeds grow into fine plants with 

 practically no care or attention after the 

 planting. However, these only prove the 

 rule. 



