AbstractThe formation of positional information in cells involves the determination of a geometrical point pattern in a developing system. The translation of genetic information into a spatial pattern is achieved in the unicellular ciliateChilodonella cucullulusby the two‐dimensional cortical surface which specifies a non‐random distribution of continuously dispersed organelles during the early stage of divisional morphogenesis.The supposed mechanism of positioning operates in a system of spatial coordinates and the system possesses definite reference points and boundaries. One reference point is the site of the oral apparatus. This site, at the stage of early divisional morphogenesis ofChilodonella, acts as a source of positional information specifying the sites of the daughter reference points (centers). These centers specify the sites of differentiation of primordia of the contractile vacuole pores (CVPs). This positional information is regulated by the boundaries of the ventral surface and the topography of the postoral sector. Specified sites of differentiation may be shifted somewhat eventually by structural guidance factors.Inter‐ and intraclonal polymorphism of C.cucullulussuggests that a genie basis for parameters of positioning also exists.The congruence between the model of positional information in multicellular systems (Wolpert, '69, '71) and the analysis of morphogenetic pattern in C.cucullulusis discussed. The cell surface membrane is envisaged as the possible structural site of the mechanism of positi