Shortly after this experiment I went to Chicago and made a record of a brown _Cebus_ monkey. This record was of a sound most commonly used by that species. I had no exact idea as to its meaning, but its frequent use caused me to select it as one of their most important words. Having secured this, I returned to New York. There I selected a monkey of the same species and to him reproduced the record. He instantly gave signs of understanding it and replied to it. Again and again this sound was reproduced and he repeatedly answered it. He looked at the horn from which it came, then at the moving instrument, and drew back from them. But as the sound continued to proceed from the horn his interest seemed to awaken. He approached the horn and cautiously peeped into it. The sound was repeated. He thrust his arm into the horn and peeped around the outside to see if he had scared the monkey out. Failing to find him, he again retired from the horn, but responded to the sounds. He appeared to regard the thing with a kind of superstition. He seemed conscious of the fact that there should be a monkey there, but failing to find it he evinced suspicion. I do not know to what extent he regarded this as a spook, but he evidently realized that it was some unusual thing. In this experiment certain facts may be observed. The record delivered to him nothing but the cold, mechanical sound. The elements of gesture, etc., were entirely eliminated as factors in the problem, so that the monkey had nothing to interpret except the sound. This would indicate that the speech sound of a monkey as well as that of man carried with it a fixed and constant meaning. This conclusion has since been confirmed by ample and varied experiments with mechanical devices of many kinds. Among the defects observed in this experiment was the fact that I had not provided a means of recording the sound made in reply to the record. Subsequently I secured another instrument to do this. In this manner I obtained a reply, and thus I had the two cylinders for comparison. In like manner I repeated the experiment of delivering the record with one machine and recording the reply with another, until I had secured records of the speech sounds of nearly all the monkeys in captivity in this country. Taking these records at my leisure, I carefully compared and studied them, until I was able to interpret nine sounds of the speech of the Capuchin monkeys, and, incidentally, a few sounds of a great number of other species.