For the ecologist systematic units are actors in a play. Whatever their christian- and family-names may be — it is their role, whether master or servant, whether villain or hero — which determines the character of the performance. This performance has, moreover, the property of being both continuous and simultaneous: all scenes are given at once. Such a continuous and simultaneous performance is called a biocoenosis. In a great many ways, a biocoenosis reminds us of an organism. For the coördination between organs or tissues, or even cells is also continuous and simultaneous. A biocoenosis is a higher vital unit, and may be approached by the same methods which we use for the study of organisms (V. D. KLAAUW (24)). In the systematic approach we establish the name, sex and age of the actors, in the anatomical approach the “pattern” of the constitutional units is established (“the dramatical situation”), while the physiological approach is concerned with the metabolism of the entity (“the plot”). As counterpart of these methods, however, we have to consider the study of the environment. The environment, which LOTKA has called “the stage of the life drama” (28).