And the higher power of association and inference which we call understanding, aided by memory, results in the power of learning by experience, so characteristic of higher vertebrates. The hunted bird or mammal very quickly becomes wary. A new trap catches more than a better old one until the animals have learned to understand it, and young animals are trapped more easily than old. Cases showing the limitations of mammalian intelligence are interesting in this connection. A cat which wished to look out and find the cause of a noise outside, when all the windows were closed by wooden blinds, jumped upon a stand and looked into a mirror. Her inference as to the general use of glass was correct; all its uses had not yet come within the range of her experience. A monkey used to stop a hole in the side of a cage with straw. The keeper, to tease him, used to pull this out. But one day the monkey tugged at a nail in the side of his cage until he had pulled it out, and thrust it into the hole. But when it was pushed back he fell into a rage. His inference that the nail-head could not be pulled through was entirely correct; he had failed to foresee that it could be pushed back. Many such instances have probably come within the range of your observation, if you have noticed them. But many of the facts which Mr. Romanes gives us concerning the intelligence of monkeys, apes, and baboons would not disgrace the intelligence of children or men. Mr. Romanes relates the following account of a little capuchin monkey from Brazil: