Contents ; List of Contributors ; Introduction ; I. General Problems of Sponge Biology. S. M. Efremova: Once more on the position among Metazoa - Gastrulation and germinal layers of sponges ; N. N. Marfenin: Sponges viewed in the light of up-to-date conception on coloniality ; A. V. Ereskovsky & G. P. Korotkova: The reasons of sponge sexual morphogenesis peculiarities II. Developmental Biology of Sponges. O. M. Ivanova-Kazas: Analysis of the sponges ontogeny at sexual reproduction ; R. P. Anakina: The cleavage specifity in embryos of the Barents Sea sponge Leucosolenia complicata Montagu (Calcispongiae, Calcaronea) ; L. V. Ivanova: New data about morphology and metamorphosis of the spongillid larvae (Porifera, Spongillidae). 1. Morphology of the free-swimming larvae ; L. V. Ivanova: New data about morphology and metamorphosis of the spongillid larvae (Porifera, Spongillidae). 2. The metamorphosis of the spongillid larvae ; L. V. Ivanova & V. V. Semenov: Feeding habits of the larvae of sponges ; N. A. Sizova & A. V. Ereskovsky: Ultrastructural peculiarities of the early embryogenesis in a White Sea sponge Halisarca dujardini (Demospongiae, Dendroceratida) ; III. Ecology of Sponges. R. P. Anakina & E. I. Slepian: Spiculas' malformations of freshwater sponges as indicators of water environment in St. Petersburg City ; A. S. Plotkin & A. V. Ereskovsky: Ecological aspects of asexual reproduction of the White Sea sponge Polymastia mammillaris (Demospongiae, Tetractinomorpha) in Kandalaksha Bay ; I. S. Smirnov & V. M. Koltun: Symbiosis of the antarctic sponge genus lophon (Porifera) and ophiuroid genus Ophiurolepis (Ophiuroidea, Echinodermata) ; IV. Palaeontology and Systematics. L. V. Bolshakova: Stromatoporoids - the fossil sponges ; E. V. Veinberg, 0. M. Khlystov, S. S. Vorobyova, E. G. Kornakova, 0. V. Levina, S. M. Efremova, & M. A. Grachev: Distribution of sponge spicules in sediments of the underwater Akademichesky ridge of Lake Baikal ; K. R. Tabachnik & C. Levi: Amphidiscophoran Hexasterophora (Part I & II) ;