Extrusomes are membrane-bound structures in some eukaryotes which, under certain conditions, discharge their contents outside the cell. There are a variety of different types, probably not homologous, and serving various functions. Notable extrusomes include mucocysts, which discharge a mucous mass sometimes used in cyst formation, and trichocysts, which discharge a fibrous rod. The stinging nematocysts found in Cnidarian animals may be regarded as extrusomes as well. Extrusomes are found in pyrrophyta organisms, such as dinoflagellate, and are important in the formation of red and black tides. Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Cnidocytes are prey-capture and defensive cells found on animals of the phylum Cnidaria. ... Classes Anthozoa - Corals and sea anemones Cubozoa - Sea wasps or box jellyfish Hydrozoa - Hydroids, hydra-like animals Scyphozoa - Jellyfish Cnidaria (from New Latin cnida nematocyst, fr. ...