Marginal Sphincter Muscle: The circular muscles of the column may be accumulated at or near the margin and form a sphincter which either is endodermal or mesogloeal . In certain anemones, there is a transition between them, an endo-mesodermal or meso-endodermal sphincter. The primary function of this muscle is to draw the margin inwards over the tentacles during retraction (Stephenson 1928)

Sphincter Muscle Formation: Mesogleal or Endodermal

Images of Various Sphincters: (species names are linked to the Hexacorallian database)

Species: Aulactinia incubans

Caption: Cross sections of circumscribed, endodermal sphincter muscles of Aulactinia incubans. (a) Palmate form; (b) pinnate form.

Species: Sagartia nutrix

Caption. Cross-section of sphincter.

Species: Glyphoperidium bursa

Caption: Portion d'une coupe longitudinale du sommet de la colonne, destinée à montrer le sphincter endodermique sectionné en travers.

Species: Actinioides ambonensis

Caption: Sphincter.

Species: Epiactis adeliana

Caption: Cross section through the sphincter of Epiactis adeliana.

Species: Carcinactis ichikawai

Caption: Cross section of mesogloeal sphincter of Carcinactis ichikawai.

Species: Cribrina altifossa

Caption: Sphincter of Cribrina altifossa.

Species: Amphianthus armatus

Caption: Cross section through the sphincter.

Species: Calliactis algoaënsis

Caption: Sphincter.

Species: Stephanauge annularis

Caption: Sphincter.