to those of the human mind. With respect to the development of surplus energy, however, it matters little whether Jennings's affirmation or Loeb's denial of consciousness is right. It is perfectly clear that the structural change represented by the difference between Amœba and Paramecium permits greater adaptation of the individual to its environment and, other things equal, tends to permit a greater expenditure of energy in non-sustaining activity. Further improvements in structure encountered as we proceed higher in the scale of evolution likewise imply greater adaptation and still greater surplus.
Before leaving Paramecium to discuss behavior of a distinctly more advanced type one more point of special interest to the sociologist must be noted. This is the fact that Paramecia in their individual efforts to find the optimum environment are brought into physical proximity. Further, it has been demonstrated that for certain individual Paramecia the optimum seems to be created, other things being equal, by the presence of carbon dioxide. Inasmuch as carbon dioxide is produced by the Paramecia themselves, this means that such Paramecia not only tend to form groups, but indirectly to influence the behavior of each other. If subjective phenomena accompany response to stimulation by carbon dioxide we have here a state of consciousness modified by the presence of organisms of like kind, even if there is, strictly speaking, no consciousness of kind—that is, even if there is no recognition of the presence of another of its own kind by the animal. The formation of groups by Paramecia as a result of their own production of carbon dioxide, according to Jennings, explains many peculiar phenomena in their behavior. For example, Paramecia in a solution of carbon dioxide react to other agents in a manner entirely different from the action of individuals in water not containing carbon dioxide. Now membership in a group is often an important protection to the individual. It is, therefore, often a factor in survival and is of importance in the production of a surplus.
The important facts to be noted up to this point are, first that change in structure may mean more complex behavior and an increased surplus, and second, that congregation if not association modifies both behavior and safety and this also affects surplus.
In Stentor roeselii there enters a new factor affecting surplus. This is the modification of behavior because of past experience. Stentor roeselii is a colorless or whitish trumpet-shaped water-inhabiting animal consisting of a slender stalk-like body bearing at its end a broadly expanded disk. The surface of the body is covered with cilia. The smaller end of the body is known as the foot and at this end fine pseudopodia are sent out by which the animal attaches itself. The lower half of the body is surrounded by the so-called tube or sheath formed by a mucus-like secretion from the surface of the body. If, now, some such