This slide shows a cross section through the pharyngeal region of the sea anemone Metridium, an anthozoan cnidarian.  Although the life cycles of anthozoans only include the polyp body form, these polyps differ in several respects from those of hydrozoans. For example, in anthozoans the mouth opens into a tubular pharynx rather than directly into the gastrovascular cavity, which unlike that of hydrozoans, is divided by many sheets of tissues called septa, or mesenteries.  Some of these mesenteries (called primary septa) extend from the body wall all the way to the pharynx while others (secondary and tertiary septa) extend only part way into the gastrovascular cavity.  Bundles of retractor muscles are found within the primary septa.  When contracted, these muscles shorten the sea anemone.   In Metridium a ciliated groove called the siphonoglyph extends down once side of the pharynx from the mouth.  The cilia in this groove conduct water currents into the sea anemone.