[Primary excitatory rhythms in locomotor activity of scyphomedusae].

Periodic organization of autorhythmic motor activity which is typical of ontogenetically earlier stages of development of the nervous functions in vertebrates has been found in larval scyphomedusae. In hydromedusae which exhibit less complex nervous system, periodic organization of excitation persists also in adult individuals. It is suggested that already at the level of scyphomedusae, periodic form of organization of autorhythmic excitation in the nervous system was transformed in a category of recapitulating characters and in this quality passed along all phylogenetic pathways.