Sponges are the oldest living Metazoans and they exhibit many original features not found in any other group of organisms. Knowledge of sponge features contributes probably more to our understanding of life on earth - or rather to that of marine and freshwater habitats - than that of any other animal group. This book contains a state-of-the-art overview of current research issues in this intriguing group, based on the results of the 1993 conference.