facts of more importance than biological in their interpretations of society; and why it is reasonable, for the present at least, to hold the eugenist's fear of decadence a trifle overdrawn.
Surplus energy, as used in this paper, means the amount of energy available for life-processes which is possessed or obtainable, by any organism, over and above the amount which is necessary for survival at any given time.
Surplus energy, in this sense, assumes many forms. Bodily vigor and long life are not the only manifestations of it. Such material goods, also, as are immediately available for restoration of depleted bodily vigor come under the general heading. Moreover, any structural or other changes in an organism which improve its chances of survival, increase the surplus. The development of useful instincts and the discovery of useful methods of controlling nature and producing wealth—these, too, increase the surplus. Bettered social organization plays its part as well. In fact, in close analysis, every trait and every act of any unit of a group in some way affects the surplus. It is evident, therefore, that only the more important phases of the subject can be considered here. The term social surplus follows directly from the meaning of surplus energy. The social surplus is merely the sum total of surplus energy existing in the individuals composing a social group or immediately available to such individuals.
What were the first-steps in the development of surplus energy in the long series of organic changes that led to the evolution of the higher animals and man, none can say. If it is permissible to hold, however, that the earliest ancestors of man were similar in character to the lowest forms of animal life now existing on this planet, we may at least surmise the general character of those early advances.
Consider, for a moment, the great advantage over the lowest protozoa, certain structural differences give that large group of single-celled animals called Ciliata. The microscopic Amœba proteus, which may be taken as representative of the very lowest animals, is structurally most simple. Its form is irregular and is continually changing in response to stimulation. Although the internal substance of its body shows some differentiation, there is nothing remotely resembling specialized sense organs. According to Jennings, one of the foremost authorities on the behavior of the lower organisms, the amœba has three characteristic reactions to stimulation. These are, the negative, the positive and the food-taking reactions. The first is a contraction of the part of the animal stimulated when, for example, it comes into strong contact with a solid obstacle. The negative reaction may cause movement in a direction opposite to the point of stimulation. A positive reaction to solid bodies occurs when a pseudopodium is pushed forward in the direction of the stimulus and the animal moves toward the solid. The