[en] The paper shows that the problem of discriminating collective dynamic variables used in the nuclear statistical model is reduced to the solution of a similar variational problem within the framework of the hydrodynamic model. The derivation is based on the direct transformation of the functional of the nuclear statistical energy into a form similar to that determining the quasi-static drop nuclear model. The derivation is restricted to those deformations of the nuclear surface under which the size of the nucleus and the main curvature radii of its surface exceed several times in absolute value, the width of the diffuseness region of nucleon distribution