[Mechanisms of growth and morphogenesis of hydroid polyps as revealed by time lapse microcinematography]

By means of time lapse microcinematography, parameters of growth fluctuations in hydroid polyps Obelia and Dynamena were improved, the pulse pattern of morphogenetic processes was shown, the "antiphase" phenomenon was established in the growth fluctuations of adjacent rudiments of Dynamena. In the phase of rudiment stretching, the length of ectodermal epithelial-muscular cells reduces and their orientation changes, thus leading to the displacement of the whole cellular "column" in the distal direction. In the phase of rudiment partial shortening, endodermal cells loose and lengthen, their internal ends displace in the proximal direction and their external ends slide rapidly in the distal direction with respect to hydrotheca. Changes in the form of rudments arise as a direct mechanical result of periodical contractions of cells densely packed in the epithelial layer. On the basis of these data, morphogenetic processes in hydroid polyps related to the appearance and development of folds and to the rudiment flexures are analyzed.