Causality--i.e., the gift of tracing a recondite connection of cause and effect--is another faculty which many varieties of monkeys possess in a decidedly ultra-instinctive degree. I remember the surprise of a picnic-party who had borrowed my young Rhesus and on their return tied him up on the porch of a garden-house. During the trip the little scamp had behaved with the decorum of a well-bred youth, but, finding himself unobserved, he at once made a vicious attempt to tear his rope with his teeth. Whenever his boon companions approached the porch he would resume his attitude of innocence, but as soon as they turned away, which they often did on purpose to try him, he promptly recommenced his work of destruction. Their giggling, however, excited his suspicions, and, seeing them peep around the corner, he suddenly became a model of virtuous inactivity. One of the picnickers then entered the garden-house by a rear door, to watch the little hypocrite through a crack in the board wall, while his companions ostensibly walked away and out of sight. As soon as everything was quiet. Master Rhesus went to work again, but at the same time kept his eye on the corner till he was interrupted by a tap on the wall and a mysterious voice from within, "Stop that, Tommy!" Tommy started, peeped around the corner, and looked puzzled. He was sure there was nobody in sight. How could an invisible spy have witnessed his transgression? He then scrutinized the wall more closely, discovered the crack, and dropped the rope with a curious grin, as he squinted through the tell-tale aperture. He had traced the effect to its cause.