dachshund are both expressed in the compound eye but not the simple eye, no reported 'developmental' genes are uniquely expressed in the simple eye. Epidermal growth factor receptor (Egfr) promotes the expression of orthodenticle [and possibly eyes absent (Eya) and as such is essential for simple eye formation. See also Arthropod eye Evolution of the eye Eyespot apparatus Mollusc eye Parietal eye Ocelloid References Further reading External links Eye Invertebrates