It so happens that according to special plans there is, at the University of Geneva, a large window opening upon an interior corridor, which is to the left as the students enter opposite the janitor's lodge. One day, M. Claparède questioned fifty-four students as to the existence of this window, which they passed by every day. Do you know how many asserted categorically that the window did not exist? Forty-four! Astounded, M. Claparède declares that such a collective testimony is disconcerting and discouraging. And who would not agree with him? Who does not think with horror, after this experiment, of all those criminal trials where a verdict is rendered on the strength of witnesses? testimony? M. Claparède comes to the conclusion that a single witness may be right despite many opposing witnesses whose stories agree. Unanimity itself should be severely controlled, and he adds, quite in accord with my own notions upon the matter: "One is led to ask whether it is not the rule to disregard those objects about us which are without interest to us, and if it is not only by accident, and exceptionally, that such objects leave an imprint upon the sensitive plate of our memory?" Accident, of a surety, or else a particularly sensitive plate. If indeed our eye functions mechanically somewhat in the manner of a photograph lens, we are compelled, in order not to clutter the storehouse of our memory, to make a choice of the images which we classify therein. In this an instinct guides us, though not always infallibly, and calls to our attention those images useful to the conservation or the defense of our life. Without education, without civilized habits, which constantly increase the number of our requirements of every kind, we should, like animals, have need to retain but a small number of images.