Fear of the dark, and especially of _being alone_ in the dark, which includes not only the nocturnal dread of the dark bedroom, but that of closets, caves, woods, and other gloomy places, is no doubt very common among children. It does not show itself in the early months. A baby of three or four months if accustomed to a light may no doubt be upset at being deprived of it; but this is some way from a dread of the dark. This presupposes a certain development of the mind, and more particularly what we call imagination. It is said by Dr. Stanley Hall to attain its greatest strength about the age of five to seven, when images of things are known to be vivid. So far as we can understand it the fear of the dark is rarely of the darkness as such. The blackness present to the eye in a dark room does no doubt encompass us and seem to close in upon and threaten to stifle us. We know, too, that children sometimes show fear of mists, and that many are haunted by the idea of the stifling grave. Hence, it is not improbable that children seized by the common terror and dizziness on suddenly waking may feel the darkness as something oppressive. This is borne out by the fact that a little boy on surmounting his dread told his father that he used to think the dark "a great large live thing the colour of black". A child can easily make a substantial thing out of the dark, as he can out of a shadow. Yet in most, if not all, cases imagination is active here. The darkness itself offers points for the play of imagination. Owing to the activity of the retina, which goes on even when no light excites it, brighter spots are apt to stand out from the black background, to take form and to move; and all this supplies food to a child's fancy. I suspect that the alarming eyes of people and animals which children are apt to see in the dark receive their explanation in this way. Of course these sources of uneasiness grow more pronounced when a child is out of health and his nervous tone falls low. Even older people who have this fear describe the experience as seeing shadowy flitting forms, and this suggests that the activity of that wonderful little structure the retina is at the bottom of it. The same thing seems to be borne out by the common dread in the dark of _black_ forms, _e.g._, a black coach with headless coachman dressed in black. A girl of nineteen remembers that when a child she seemed on going to bed to see little black figures jumping about between the ceiling and the bed.