are digested and assimilated. The radiolaria generally reproduce by the formation of spores. The nucleus within the protoplasmic globule divides into two small nuclei, each of which surrounds itself with a quantity of plasm, and forms a new cell. What is this plasm? What is this mysterious "living substance" that we find everywhere as the material foundation of the "wonders of life"? Plasm, or protoplasm, is, as Huxley rightly said thirty years ago, "the physical basis of organic life"; to speak more precisely, it is a chemical compound of carbon that alone accomplishes the various processes of life. In its simplest form the living cell is merely a soft globule of plasm, containing a firmer nucleus. The inner nuclear matter (called caryoplasm) differs somewhat in chemical composition from the outer cellular matter (or cytoplasm); but both substances are composed of carbon, oxygen, hydrogen, nitrogen, and sulphur; both belong to the remarkable group of the albuminates, the nitrogenous carbonates that are distinguished for the extraordinary size of their molecules and the unstable arrangement of the numerous atoms (more than a thousand) that compose them. There are, however, still simpler organisms in which the nucleus and the body of the cell have not yet been differentiated. These are the _monera_, the whole living body of which is merely a homogeneous particle of plasm (the chromacea and bacteria). The well-known bacteria which now play so important a part as the causes of most dangerous infectious diseases, and the agents of putrefaction, fermentation, etc., show very clearly that organic life is only a chemical and physical process, and not the outcome of a mysterious "vital force." We see this still more clearly in our radiolaria, and at the same time they show us unmistakably that even the psychic activity is such a physico-chemical process. All the different functions of their cell-soul, the sense-perception of stimuli, the movement of their plasm, their nutrition, growth, and reproduction, are determined by the particular chemical composition of each of the 4,000 species; and they have all descended, in virtue of adaptation and heredity, from the common stem-form of the naked, round parent-radiolarian (_Actissa_).