Thisvolume presents a broad panorama of the current status of research ofinvertebrate animals considered belonging to the phylum Cnidaria, such as hydra, jellyfish, sea anemone, and coral. In this book the Cnidarians aretraced from the Earth's primordial oceans, to their response to the warming andacidifying oceans. Due to the role of corals in the carbon and calcium cycles,various aspects of cnidarian calcification are discussed. The relation of theCnidaria with Mankind is approached, in accordance with the Editors' philosophyof bridging the artificial schism between science, arts and Humanities. Cnidarians' encounters with humans result ina broad spectrum of medical emergencies that are reviewed. The final section ofthe volume is devoted to the role of Hydra and Medusa in mythology and art.