parietal eye

"The pineal gland is present in most vertebrate, while the parietal eye is only present some lizards, the tuatara some frogs and salamander," Tosini explained to Salon.

Some fish, amphibians and reptiles have a third, so-called parietal, eye.

Then the researchers created caps with pieces of Ping-Pong ball, and attached them with surgical glue and cork as a cushion, to the heads of the anoles to interfere with polarized light that might reach an organ in the brain called the parietal eye.

The team didn’t just block all light to the parietal eye, because it controls the daily rhythms of the lizard.