Ctenophora, also known as comb jellies, are a phylum of marine animals characterized by the presence of cilia or combs that they use for locomotion. These creatures are typically transparent and have a gelatinous body. They are found in various sizes and shapes, ranging from a few millimeters to over a meter in length. Ctenophores do not have a true digestive system or an anus; instead, they consume their food through their mouth and excrete waste through the same opening. They primarily feed on small organisms such as plankton and other ctenophores. Some species of ctenophores are bioluminescent and produce light through a chemical reaction in their bodies.