Species with three eyes. On Earth third eyes are found on amphibians, arthropods, crustaceans, and reptiles. In species that retain a third eye into adult hood one finds the eye connected to the Pineal gland which regulates metabolism and hormone production. The eye also effects an individual's biological clock via photo-receptors in the eye which give the brain information regarding day and night cycles. For some sight is so poor in the third eye that it's only practical use is the detection of UV light. Reptiles and Amphibians are frequent examples of this.

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