THE EYEBALL //;y J 

 REMOVED ''''/* 



PLATE 36. Eyes of various vertebrates, showing the nictitating membrane, indicated by the 

 letter A 7 . In some reptiles and birds the nictitating membrane can be drawn over the whole front 

 of the eyeball. From Romanes' Darwin and After Darwin, by the courtesy of The Open Court 

 Publishing Company. 



