Dictionary of Ichthyology  

bubble-eye goldfish = goldfish (Carassius auratus) having upward directed eyes accompanied by fluid-filled sacs. The fluid can be extracted for studies on its growth-promoting effects on fish cell cultures; the fluid regenerates and the fish need not be sacrificed.

Wikimedia Commons: http://commons.wikimedia.org/wiki/File:Goldfish_Bubble_Eye.jpg .

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