Biofilm Guide 2 Kingdom Animalia Phylum Cnidaria -­‐ meaning "stinging nettle" (cnidos, greek). There are four classes, Anthozoa, Hydrozoa, Cubozoa and Scyphozoa. Multicellular organisms known for their "hollow cavity" and “stinging cells” (Shown here are the following hydrozoan organisms: Hydra, Colonial Hydroid, White Anemone). Hydra: this hydra is much smaller than the anemone but still has the ability to sting small prey. Colonial Hydroid: relative of the hydra but grows in a colony form with many branches and feeding structures. Biofilm Guide 2 White Anemone: anemones are well known for their flower-­‐
like appearance and have many tentacles. Anemones have the ability to completely withdraw their tentacles inside their body. Photo credit: J. Adam Frederick