_Emotion_ is the stirring of the sensibilities by way of the intellect or the imagination. The following emotions are found in non-human beings: fear, surprise, affection, pugnacity, play, pride, anger, jealousy, curiosity, sympathy, emulation, resentment, appreciation of the beautiful, grief, hate, cruelty, joy, benevolence, revenge, shame, remorse, and appreciation of the ludicrous. Excepting the emotions of conscience and religion, which are really compounds, with fear as the main ingredient, this list of non-human emotions is coextensive with the list of human emotions. Many of these emotions germinate low down in the animal kingdom, fear, anger, sexuality, and jealousy all being found in fishes and in the higher invertebrates. In the higher vertebrates many of these emotions are almost as strong as they are in men. Does anyone who has felt the throbbing sides of a frightened puppy or hare have any doubt that these creatures suffer the keenest agony of fear? Apes have been known to fall down and faint when suddenly confronted by a snake, so great is their instinctive horror of serpents; and gray parrots, which are extremely nervous birds, have been known to drop from their perch unconscious under the influence of great fear.[2] The horse is, perhaps, of all animals, the one which occasionally gives itself over most completely to the emotion of fear, as everyone who has witnessed the terrible abandon of a runaway team can testify. Ants, fishes, birds, cats, dogs, horses, monkeys, porpoises, and many other animals play. Young kittens, colts, and puppies enjoy a scuffle about as well as boys do. Pugnacity originates among the spiders and insects, and is highly developed in the ant, cock, and bulldog. This emotion is strong in the males of nearly all vertebrates. Anyone who has observed the vigilance displayed by fishes in protecting their nests can have little doubt that these comparatively primitive beings possess pugnacity. I was one evening floating in a boat by the edge of a Long Island pond just over a village of perches. Each nest was guarded by an assiduous male, who hovered over it vigilantly, or darted this way and that to drive off the piscatorial _hoi polloi_ hanging about the neighbourhood, ready to slip in at the first opportunity and eat the eggs. Just to see what would happen, I put my hand down into the water and moved it slowly toward one of the nests. To my surprise, the guardian of the nest, instead of fleeing in alarm, proceeded to show fight. It chased my hand away time after time, and when the hand was not removed it would nip it vigorously, not once simply, but two or three times if necessary, and each time with increasing energy. It contended with the courage of a little hero. I pushed it and jostled it about, and even took it in my hand and lifted it clear out of the water. To my amazement, on getting back into the water, it returned promptly to the attack. It fought until it was