Double-wavelength cytophotometry of the Feulgen-stained nuclei was used to detect the different ratio of condensed and non-condensed chromatin in the anther tissues in the course of their differentiation on the basis of hydrolysis curves in IN HCl at 60 degrees C. Formaline added to the fixating mixture diminishes the DNA losses during hydrolysis in all types of cells under study. Meanwhile, its effect is manifested depending on physiocochemical state of chromatin.