Similarly, I placed the boxes for the ape on April 19, allowed him to get the banana and then gave him opportunity to try for himself after the boxes had been displaced.  This time he immediately reached for the smaller box and moved it about a little, thus indicating a new association.  He next turned to the larger box and worked with it persistently.  Later, he once more worked with the smaller box in an unusual manner.  He repeatedly stood on it, but made no attempt to lift it or to place it on the larger box.  Clearly the usually neglected smaller box had become associated with the satisfaction of obtaining the banana.  The same method was carried out on April 20.  As I placed the boxes in position beneath the banana, Julius watched with unusual intentness, and when it came his turn to try to obtain the food by the use of the boxes, he began at once to work with the smaller box, but as on April 19, he soon abandoned it and turned to the other.  While I was making note of this particular feature of his behavior, he suddenly seized the smaller box by two corners with his hands and by one edge with his teeth, and after a few attempts placed it on top of the larger box, climbed up, and obtained the banana.

Because of bad weather on April 21, the next test was made on April 22, with everything as usual.  Unaided, the ape was given an opportunity to obtain the coveted reward, while I stood ready to obtain records of his behavior with my camera.  He wasted no time, but piled the smaller box on top of the larger one immediately, and obtained his reward.  As soon as opportunity was offered, he repeated the performance.  The same thing happened on April 23 and several succeeding dates.

Julius had got the idea, and the only further improvement possible was in skill in manipulating the boxes.

One of the curious performances which appeared during the imitative period is pictured in figure 26, plate V, where the ape is seen lifting the smaller box into the air.  This he did three or four times one day, raising it toward the banana each time as though he expected thus to obtain the reward.  As he did not go up with the box (according to his expectation?), he abandoned this method, and looking about, discovered the larger box in a distant corner.  Thereupon, he promptly pulled the boxes to their proper position beneath the banana, stacked them, and obtained his food.

After considerable skill had been acquired in the placing of the boxes, the one upon the other, the height of the banana above the floor was increased so that three boxes were necessary.  Figure 25 of plate V shows him standing on three boxes and reaching upward, and figures 22, 27 and 28 show various modes of handling the boxes and of reaching from them.  He was not at all particular as to the stability of his perch, and often mounted the boxes when it seemed to the experimenter inevitable that they should topple over and precipitate him to the floor.  Only once, however, during the several days of experimentation did he thus fall.