the light of the natural history survey of analogy, these phenomena appear in their true significance, testifying at once to the inherent progress, despite reversions, and to the underlying unity of constitution and purpose, through which these phenomena acquire their deeper and more human interest. THE MIND'S EYE _Hamlet._ My father,--methinks, I see my father. _Horatio._ O, where, my lord? _Hamlet._ In my mind's eye, Horatio. I It is a commonplace taught from nursery to university that we see with our eyes, hear with our ears, and feel with our fingers. This is the truth, but not the whole truth. Indispensable as are the sense organs in gaining an acquaintance with the world in which we live, yet they alone do not determine how extensive or how accurate that acquaintance shall be. There is a mind behind the eye and the ear and the finger-tips which guides them in gathering information, and gives value and order to the exercise of the senses. This is particularly true of vision,--the most intellectual of all the senses, the one in which mere acuteness of the sense organ counts least and the training in observation counts most. The eagle's eye sees farther, but our eyes tell us vastly more of what is seen. The eye may be compared to a photographic camera, with its eyelid cap, its iris shutter, its lens, and its sensitive plate,--the retina; when properly adjusted for distance and light, the image is formed on the retina as on the glass plate, and the picture is taken. So far the comparison is helpful; but while the camera takes a picture whenever and wherever the plate happens to be exposed, the complete act of seeing requires some coöperation on the part of the mind. The retina may be exposed a thousand times and take but few pictures; or perhaps it is better to say that the pictures may be taken, but remain undeveloped and evanescent. The pictures that are developed are stacked up, like the negatives in the photographer's shop, in the pigeon-holes of our mental storerooms,--some faded and blurred, some poorly arranged or mislaid, some often referred to and fresh prints made therefrom, and some quite neglected.