The four-eyed fish ( Anableps tetrophthalmus) swiminiiif; at the surface on the look-out for insects 

 and fishes. Connective tissue divides each eye into two parts, the upper part being adapted 

 for aerial vision and the lower for seeing under water. Photograph New York Zoological Society. 



South American cyprinodont fishes ( Mollienesia petenensis). Photograph New York Zoological 

 Society. 



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