[14] William Hamilton Gibson, _Sharp Eyes_, p. 307. [15] I have a distinct purpose in introducing these and other queer-eyed individuals while discussing the sense of sight. I wish to demonstrate through one or more of them the correlation of morphology, physiology, and psychology, as formulated in the first chapter of this work. This is one of the most important facts in the doctrine of evolution, and upon it is based the law of progressive psychical development from the simple manifestations of conscious determination in the lowest organisms to the most complex operations of the mind in man. The queerest of all queer-eyed animals is, probably, the Periophthalmus, a fish inhabiting the coasts of China, Japan, India, the Malayan Archipelago, and East Africa.[16] [16] Semper, _Animal Life_, p. 374 _et seq._ I use the word coasts advisedly, for this strange creature when in pursuit of its prey leaves the sea and comes out on the sands, thus existing, for the greater portion of its life, in an element which, according to the general nature of things, ought to be fatal to it. The laws of evolution have, however, eminently prepared it for its peculiar mode of life, for its gill-cavities have become so enlarged that when it abandons the sea it carries in them a great quantity of water which yields up the necessary supply of oxygen. Its locomotion has been provided for likewise, for continued use along certain lines has so developed its pectoral fins that the creature uses them as legs, and jumps along at a surprising rate of speed. Its eyes are very large and prominent, and possess, for a fish, the peculiar faculty of looking around on all sides, hence its name, "periophthalmus," which is derived from the Greek words, περί, around, and ὀφθαλμός, eye. These eyes are situated on top of the animal's head, and present a very grotesque appearance. The favorite food of this fish is Onchidium, a naked mollusk. And, in the matter of eyes, this last-mentioned creature is itself worthy of remark. Its cephalic, or head, eyes are like those of other mollusks of its genus, and are not worthy of special mention, but its dorsal eyes, sometimes several dozen in number, are truly remarkable. These eyes, although they are very simple in structure, in type are the same as those of vertebrates, having corneæ, lenses, retinæ, and "blind spots." (In the vertebrate eye, the spot where the optic nerve pierces the external layer of the retina is not sensitive to light impressions; hence, it is called the "blind spot.")