The Hexacorallia are distinguished from the other subclass of Anthozoa, the Octocorallia, because they have six or less axes of symmetry in their body structure and only single rows of tentacles. They are formed of individual soft polyps which in some species live in colonies and secrete a calcite skeleton. As with all Cnidarians, these organisms have a complex life cycle including a mobile planktonic phase and a later sessile phase. 