Nictitating Membrane

Here is an interesting pic of Steppe Eagle, where you can see a translucent layer in its eye.



I got to know that its called membrane, present in birds, reptiles, amiphibians and fish. Here is the definition from wikipedia:

"The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten the eye while also keeping visibility"

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