[Role of provisionality principle in realization of phylembryogeneses].

The analysis of histogenesis of skeletogenic tissues and of organogenesis of the mesonephros and metanephros in higher mammalian animals and man, is presented. The new conception of provisionality is formulated, according to which embryonic primordium and/or its derivatives possess a determined capacity to form, on its course to definitive state, temporary structures (tissues or organs), which fulfil the vital functions in the developing organism and modeling the mechanisms of development and formation of structural and functional units or the whole organ at the level of definitive morphological substrate. Provisionality is regarded as the universal principle in realization of of phylembryogeneses.