The much-debated life question has lately found an interesting exponent in Professor Benjamin Moore, of the University of Liverpool. His volume on the subject in the "Home University Library" is very readable, and, in many respects, convincing. At least, so far as it is the word of exact science on the subject it is convincing; so far as it is speculative, or philosophical, it is or is not convincing, according to the type of mind of the reader. Professor Moore is not a bald mechanist or materialist like Professor Loeb, or Ernst Haeckel, nor is he an idealist or spiritualist, like Henri Bergson or Sir Oliver Lodge. He may be called a scientific vitalist. He keeps close to lines of scientific research as these lines lead him through the maze of the primordial elements of matter, from electron to atom, from atom to molecule, from molecule to colloid, and so up to the border of the living world. His analysis of the processes of molecular physics as they appear in the organism leads him to recognize and to name a new force, or a new manifestation of force, which he hesitates to call vital, because of the associations of this term with a prescientific age, but which he calls "biotic energy." Biotic energy is peculiar to living bodies, and "there are precisely the same criteria for its existence," says Professor Moore, "as for the existence of any one of the inorganic energy types, viz., a set of discrete phenomena; and its nature is as mysterious to us as the cause of any one of these inorganic forms about which also we know so little. It is biotic energy which guides the development of the ovum, which regulates the exchanges of the cell, and causes such phenomena as nerve impulse, muscular contraction, and gland secretion, and it is a form of energy which arises in colloidal structures, just as magnetism appears in iron, or radio-activity in uranium or radium, and in its manifestations it undergoes exchanges with other forms of energy, in the same manner as these do among one another." Like Professor Henderson, Professor Moore concedes to the vitalists about all they claim--namely, that there is some form of force or manifestation of energy peculiar to living bodies, and one that cannot be adequately described in terms of physics and chemistry. Professor Moore says this biotic energy "arises in colloidal structures," and so far as biochemistry can make out, arises _spontaneously_ and gives rise to that marvelous bit of mechanism, the cell. In the cell appears "a form of energy unknown outside life processes which leads the mazy dance of life from point to point, each new development furnishing a starting point for the next one." It not only leads the dance along our own line of descent from our remote ancestors--it leads the dance along the long road of evolution from the first unicellular form in the dim palaeozoic seas to the complex and highly specialized forms of our own day.