Abstract
Two problems are fundamental in biocoenology: (1) the regulation of a stable combination of spp., and (2) the separation of the biocoenoses into individualized natural constructive unities or types in spite of an uninterrupted change in the external conditions. Field observations on plant and animal material elucidating these relations are summarized, and a description is given of some original experimental data on the effect of a gradual change in pH on the formation of an artificial biocoenosis of Protozoa under laboratory conditions. It is concluded that in young immature biocoenoses there is no sharp separation into individualized types at different pH levels, and the differences between the types are continuous. At the same time, mature biocoenoses are separated into individualized types, and are also characterized by a specific way in which the whole biomass is distributed between separate spp.