two or three times; then he became wise. One day I worked a variation. Suddenly looking out the door, making believe that my eyes had been attracted by a moving form, I said coldly, as a child educated in turning away bill-collectors would say: "No, my father is not at home." Like a shot, Rollo was out the door. He even ran down the alley to the front of the house in a vain attempt to find the man I had addressed. He came back sheepishly to endure the laugh and resume the game.
And now we come to the test. I fooled Rollo, but how was the fooling made possible? What precisely went on in that brain of his? According to Mr. Burroughs, who denies even rudimentary reasoning to the lower animals, Rollo acted instinctively, mechanically responding to the external stimulus, furnished by me, which led him to believe that a man was outside the door. Since Rollo acted instinctively, and since all instincts are very ancient, tracing back to the predomestication period, we can conclude only that Rollo's wild ancestors, at the time this particular instinct was fixed into the heredity of the species, must have been in close, long- continued, and vital contact with man, the voice of man, and the expressions
