pineal eye

views updated May 29 2018

pineal eye (epiphysial eye, median eye) In Sphenodontidae (tuatara), some lizards, Petromyzonidae (lamprey), and many fossil vertebrates, a structure on the top of the head that resembles an eye, with a lens and a retina, linked to the brain by a nerve. It is the larger and more developed of a pair of sacs that form by evagination of part of the brain. Above it there is a gap in the skull covered by almost transparent skin. The function of the eye is uncertain but probably it is involved in regulating diurnal rhythms.

pineal eye

views updated May 18 2018

pineal eye See median eye.