Dep. Embryology, Biology and Soil Faculty, St.-Petersburg State University, Universitetskaya nab. 7/9, St.-Petersburg 199034, Russia.

Abstract

The analysis of peculiarities of individual development in Porifera based on the idea of phase evolution of onthogenesis as multilevel and non-linear process was done (Korotkova, 1979, 1987). Correlative variability of different types of morphogenesis in sponges (gametogenesis, embryogenesis, growth processes, blastogenesis, reconstructive morphogenesis, etc.) is conditioned by different reactions of different stages of the same morphogenesis to the same stimuli as well as by different morphogenesises. To understand the reasons of changes of gametogenesis and relations between gametocyte and somatic cells the complete life cycle and peculiarities of morphogenetic processes in postgenerative period were analysed. The main attention was given to the participation of somatic cells with some polypotentic features and to the ability of some somatic cells to direct transformation to different cell types. Criteria of morphogenesis primitiveness and progress, taking place in sponges during life cycle were evaluated. It was shown that the more anatomical, tissue and cell systems formed in sponge body with high level of differentiation, the more probable is the existence of stable reproduction forms and the development of specific forms of blastogenesis and embryogenesis. Peculiarities of sponge onthogenesis are explained not only by their specific place in evolution system, but also by the low specialization of cells, tissues and anatomical systems, as well as by low level of individuality and specialization of morphogenetic processes.