At another time I heard two making a noise among the plantains near me. I could only obtain a glimpse of them, but as well as I could see they were of good size, being almost grown. They were making a low sound from time to time, something like I have described, but I could not see them well enough to frame any opinion as to what it meant. They were certainly not quarrelling, and I am not sure that they were eating, for I afterwards went and looked to see if I could find where they had broken any of the stalks. Their trail was visible through the grass and weeds, but I could find no stalk broken. They were moving at a very leisurely gait, and must have been within hearing ten or twelve minutes. They were quite alike in colour, and appeared to be so in size, although it is well known that the adult male attains a much greater size than the female. On one occasion when I was standing outside of the cage some twenty yards away, Moses was sitting on a dead log near by. I turned to him, and was just in the act of sitting down by him when he gave an alarm. I looked around, and discovered a gorilla standing not more than twenty yards away. He had just that moment discovered us. He gazed for a few moments and started on, moving obliquely towards the cage. I turned to retreat. At this instant Moses gave one of his piercing screams, which frightened the gorilla and he fled. He changed his course almost at right angles. He was going at a good rate before Moses screamed, but he mended it at once. One day I heard three sounds which my boy assured me were gorillas; they were in different directions from the cage. It was not a scream nor a howl, but somewhat resembled the human voice calling out with a sound like "he-oo!" This sound was repeated at intervals, but did not appear to be in the relation of call and answer, and the animals making them did not approach each other while doing so. The sounds were the same except in volume, and one of them appeared to be made by a much larger animal than the other two. I must say that this sound rarely occurred within my hearing during all my stay in that part, and with the exception of this time I never heard them make any loud sound during the day.