9th Stage: SENSATION OF THE HIGHER METAZOA, with differentiated nerves and sense-organs, but still without consciousness(?). The higher cœlenteria and most of the cœlomaria. 10th Stage: SENSATION WITH DAWNING CONSCIOUSNESS, with independent formation of the phronema. The higher articulata (spiders and insects) and vertebrates (amphibia, lower reptiles, lower mammals). 11th Stage: SENSATION WITH CONSCIOUSNESS AND THOUGHT: amniotes: higher reptiles, birds, and mammals: savages. 12th Stage: SENSATION WITH PRODUCTIVE MENTAL ACTION IN ART AND SCIENCE: civilized men. XIV MENTAL LIFE Mind and soul--Intelligence and reason--Pure reason--Kant's dualism--Anthropology--Anthropogeny--Embryology of the mind--Mind of the embryo--The canonical mind--Legal rights of the embryo--Phylogeny of the mind--Paleontology of the mind--Psyche and phronema--Mental energy--Diseases of the mind--Mental powers--Conscious and unconscious mental life--Monistic and dualistic theory--Mental life of the mammals, of savages, and of civilized and educated people. The greatest and most commanding of all the wonders of life is unquestionably the mind of man. That function of the human organism, to which we give the name of "mind," is not only the chief source of all the higher enjoyment of life for ourselves, but it is also the power that most effectually separates man from the brute according to conventional beliefs. Hence it is supremely important for our biological philosophy to devote a few careful pages to the study of its nature, its origin and development, and its relation to the body. At the very outset of our psychological inquiry we are met by the difficulty of giving a clear definition of "mind," and distinguishing it from "soul." Both ideas are extremely ambiguous: their content and connotation are described in the most various ways by the representatives of science. Generally speaking, we mean by mind that part of the life of the soul which is connected with consciousness and thought, and is, therefore, only found in the higher animals which have intelligence and reason. In a narrower sense reason is regarded as the proper function of mind, and as the essential prerogative of man in the animal world. In this sense Kant especially has done much to strengthen the prevailing conception of mental action, and has, by his _Critique of Pure Reason_, converted philosophy into a mere "science of reason." In consequence of this conception, which still prevails widely in scientific circles, we will first study the mental life in the action of reason, and try to form a clear idea of this great wonder of life.