A straightforward explanation, well laid out though somewhat ponderous in style, describing parts of the eye--chiefly the lens, the retina and its different cells, and the pupil--in terms of their functions. There's a little comparative anatomy woven into these discussions of the human eye and its workings, plus other sections on insect eyes, the simple and compound ""mirror"" eyes of shellfish, and the different eye features found among nocturnal and diurnal animals, predator and prey animals, and others. Simple experiments to demonstrate some of the concepts and phenomena are part of the text. With functional drawings and a generally older look and style than existing books by Elgin and others.