What is the X in X-mas?
Any of various, mostly small marine invertebrates of the phylum Ctenophora, having transparent, gelatinous bodies bearing eight rows of comblike cilia. Ctenophores have a branched digestive tract that also has circulatory function. Most ctenophores feed on plankton and are bioluminescent, producing brilliant displays of blue or green light at night. Ctenophores are related to cnidarians but are more highly evolved because their bodies have a true mesoderm. Also called comb jelly.