Recall from lecture that humans have a little fold of skin in the inside corner of each eye. this fold is called the 'plica semilunaris', and is a vestige of a 'third eyelid' (nictitating membrane). last quarter, a student wrote "the 'third eyelid' (or nictitating membrane) is still with humans to show the related common ancestry [with] other species." a. describe one error in this statement. explain why it is incorrect. b. how would you explain why humans still have parts of a 'third eyelid'.