Dr. Francis B. Sumner 



The photographs above show the results of experiments made by Dr. Francis 

 B. Sumner of the University of California. He first photographed flounders in 

 aquariums in which the flounders rested on different natural backgrounds of sand, 

 mud, and stones. The fish always changed their color markings to blend with 

 their background, as we see in figures 1 and 2. What advantage would this be 

 to the fish ? He then changed the fish into aquariums having artificial back- 

 grounds like figures 3 and 4. What happened ? Can you account for these 



changes ? 



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