Darwin recorded of one of his sons, that in the fifth month he repeatedly smiled at his father's image and his own in a mirror and took them for real objects; but he was surprised that his father's voice sounded from behind him (the child). "Like all infants, he much enjoyed thus looking at himself, and in less than two months perfectly understood that it was an image, for if I made quite silently any odd grimace, he would suddenly turn round to look at me. He was, however, puzzled at the age of seven months, when, being out of doors, he saw me on the inside of a large plate-glass window, and seemed in doubt whether or not it was an image. Another of my infants, a little girl, was not nearly so acute, and seemed quite perplexed at the image of a person in a mirror approaching her from behind. The higher apes which I tried with a small looking-glass behaved differently. They placed their hands behind the glass, and in doing so showed their sense; but, far from taking pleasure in looking at themselves, they got angry and would look no more." The first-mentioned child, at the age of not quite nine months, associated his own name with his image in the looking-glass, and when called by name would turn toward the glass even when at some distance from it. He gave to "Ah!" which he used at first when recognizing any person or his own image in a mirror, an exclamatory sound such as adults employ when surprised. Thus Darwin reports. My boy gave me occasion for the following observations: In the eleventh week he does not see himself in the glass. If I knock on the glass, he turns his head in the direction of the sound. His image does not, however, make the slightest impression upon him. In the fourteenth and fifteenth weeks he looks at his image with utter indifference. His gaze is directed to the eyes in the image without any expression of pleasure or displeasure. In the sixteenth week the reflected image is still either ignored or looked at without interest. Near the beginning of the seventeenth week (on the one hundred and thirteenth day) the child for the first time regards his image in the glass with unmistakable attention, and indeed with the same expression with which he is accustomed to fix his gaze on a strange face seen for the first time. The impression appears to awaken neither displeasure nor pleasure; the perception seems now for the first time to be distinct. Three days later the child for the first time undoubtedly laughed at his image. When, in the twenty-fourth week, I held the child again before the glass, he saw my image, became very attentive, and suddenly turned round toward me, manifestly convincing himself that I stood near him. In the twenty-fifth week he for the first time stretched out his hand toward his own image. He therefore regarded it as capable of being seized.