the eye was a test case for natural selection; and for Helmholtz, it was a brilliant compromise — a flawed device to a brass and glass instrument-maker, but a structure nonetheless capable of ...

If evolution occurs through gradations, the critics say, how could it have created the separate parts of the eye -- the lens, the retina, the pupil, and so forth -- since none of these structures ...

Light passes through the eyeball to the retina. There are two main types of light receptors called rods and cones. Rods are more sensitive to light than cones so they are useful for seeing in dim ...