  According to the universally accepted concept of the development of life on
the Earth, multicellular organisms initially emerged as a result of either the
union of identical unicellular organisms with the following functional
differentiation, or the union of symbionts, in which there already was a
certain simple functional separation. However, in either case the progenitors
of multicellular organisms were ensembles, communities of unicellular
organisms. For a certain number of unicellular organisms to be treated as an
ensemble, there must be some interconnection between its members. Colonies of
mechanically connected unicellular organisms were a later, more advanced stage;
here, unicellular organisms living separately are considered. Such
interconnection must, in particular, limit from above the total numbers of the
members of the ensemble, because an excessive increase in these numbers could
disturb the connections between members of the ensemble to the extent of its
destruction. In addition, too large numbers of members in the ensemble could
lead to nutrient depletion in its habitat. One can assume that such
interconnection between unicellular organisms was evolutionarily developed and
genetically fixed. I assumed that modern unicellular organisms retain such an
ability to regulate their total numbers. The validity of this assumption was
tested in experiments, whose results are presented in this paper.
