[Morphogenetic cellular interactions]

Morphogenetic cell interactions are considered during different periods of embryogenesis. The evidence is given which established that the determination of cells of the early mammalian embryos appeared to be due to their position and relations with the other cells. Morphogenetic cell interactions are heterogenous by their biological importance: there are both directive and permissive interactions. The cells might be multipotent and choose one of many paths of development what requires directive interactions, or they might be already "canalized" in a certain type of differentiation and their development requires, mainly, permissive interactions. Possible mechanisms of transmission of the morphogenetic stimuli to the reacting cells are analyzed.