Answer:
Pupil
Function: serves as site for entry of light into the eyeball.
Step-by-step explanation:
The hole in the center of the iris is called pupil. The light enters the eyeball through the pupil. The pupil is circular or oval in shape and appears mostly black in color. With the help of muscular iris, the size of the pupil changes according to the intensity of incoming light.
Hence, the pigmented portion of the eyes of vertebrates (the iris) has a hole in its center called pupil to allow the light to enter the eyeball.