There were six subjects in experiments conducted during the winter of 1900-1901, and six (five being new ones) in experiments of the fall of 1901. They were all good visualizers, though they differed in the readiness with which they visualized respectively form or color. The experiments of the first few weeks were designed to establish the fact of control by the subjects over a single visual memory image as to its position, size, outline, color, movement and presence. In general it was established that a considerable degree of control in these particulars existed in these subjects. Later, two objects were presented at a time, and were such small articles as a glass ball, a book, a silk purse, an eye-glass case, an iron hook, and so forth. Still later, colored squares, triangles, or discs were used exclusively. The investigation followed these lines: I. Movements of a single image; II. Changes of color of a single image; III. Movements of two images in the same and in different directions; IV. Suppression of one of two images; V. Movements of a single image, the object having been moved during the exposure. I. MOVEMENTS OF A SINGLE IMAGE. The first table gives the time in seconds taken to move voluntarily a single image (of a colored square or disc) to the right, left, up or down, and in each case to restore it to its original position. There were thirty movements of each kind for each of the six subjects, making one hundred and eighty for each direction and also for each return, the total of all movements being fourteen hundred and forty. The distance to which the subjects moved the images was not fixed, but was in most cases about twelve inches. The time was taken with a stop-watch, and includes the time between the word of command, 'right,' etc., of the director and the verbal report 'now' of the subject. It includes, therefore, for each movement two reaction times. The subject reported 'now' the instant the color reached, or appeared at, the designated place, not waiting for the completion of the shape which usually followed. Two of the subjects (H. and K.) took much longer than the other four, their combined average time being almost exactly four times the combined average time of the other four. TABLE I. MOVEMENTS OF A SINGLE IMAGE. 30 Movements of Each Kind for Each Subject Average Time in Seconds. To To Subjects Right Return Left Return Up Return Down Return Averages B. 1.30 1.07 1.06 1.11 1.13 0.58 0.73 0.46 0.45 0.55 G. 1.44 1.15 0.99 0.82 1.10 0.92 0.89 0.76 0.57 0.78 H. 7.12 6.42 5.96 5.85 6.34 4.51 4.41 4.36 4.40 4.42