On physical nature of radiation regulating quantity of cells in population

It is shown, that spontaneous ultraviolet radiation of cells (infusoria) plays the role of agent, restricting the upper limit of the quantity of cells in quasi-stationary phase of cultire's development. The spectral region of this radiation defined experimentally occurred to be in the range of 200-290 nm. As the filter cutting off the short wave length part of the spectrum (below 290nm) 1 mm thick plexiglas has been used, while as the filters transmitting short wave part of the spectrum - 5 mkm thick fluorostatic film or 1 mm thick optical quartz has been selected. It has been shown, that dynamics of development of the cells in the culture depends on transparency of nutrient medium to spontaneous ultraviolet radiation of the cells. Conclusion has been made, that superweak chemiluminescence of the cells is not a worthless metabolism product, but plays significant biological role.