The volume is rather unique as it has neither preface nor introduction, but plunges at once into naming varieties of and discussing opinions concerning the nature of this most universally experienced and as little understood phenomenon. After considering the theories of Coleridge, Max Eastman, McDougall, etc., the subject of laughter in general is presented in terms of a hypothesis that there are many varieties, for example, laughters of triumph, of scorn and contempt, of self—congratulation, of superiority, of greeting, of play and of amusement.