pineal eye

noun

1. an eyelike structure that develops from the pineal apparatus in certain cold-blooded vertebrates.

noun

1. an outgrowth of the pineal gland that forms an eyelike structure on the top of the head in certain cold-blooded vertebrates

1. A sensory structure capable of light reception, appearing as a spot on the top of the head in lampreys, hagfish, amphibians, and some reptiles, especially the tuatara. Pineal eyes can contain a rudimentary cornea, lens, cone cells, and retina, and are thought to be sensitive to light and dark but not to be able to form images.