Marine life appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton, and particularly phytoplankton, are key primary producers forming the general foundation of the ocean food chain. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters including breathing tubes (see
Malacological Society of London 1942. Molluscs range in size from cephalopods such as the octopus and giant squid to microscopic gastropod snails, and the Society is concerned with some 85,000 recognised extant species, which include 23 per cent of all named marine organisms as well as molluscs living in freshwater and terrestrial habitats. It is also interested in the species (including those of the two extinct classes of molluscs) preserved as fossils, which creates a relationship with the study of geology. In association with the Oxford University Press, the Society publishes the "Journal of Molluscan Studies", previously called "Proceedings of the Malacological Society", and