[Electron microscopic study of rapid morphogenetic processes in embryonic tissue explants of amphibia].

Submicroscopic rearrangements are described. They serve as the bases of rapid (up to 20 min) changes in the form of the common frog neurula explants: formation of filamentous layer under "naked" surface, appearance of lobopodia on "naked" surface, their "flow", cell polarization and submersion. In all these processes an active part appears to be played by microtubules and microfilaments the bundles of which are always oriented along the long axes of active cells or the directions of passive mechanical tensions. In the cells which are not yet polarized the microtubules form under the surface adjacent to the already polarized cell. This may be considered as one of the chains of cooperative cell polarization.