Ephyra muscle forms de novo in P. noctiluca and C. quinquecirrha, regardless of life cycle. (A, B) For both species, the first signs of ephyra muscle are actin-rich bundles (arb) found oral to the future rhopalia (fr) at the base of each future rhopalial lappet (frl). (C, D) Slightly later, actin-rich bundles are more numerous at the site of future radial and circular muscle. (E, F) As the ephyrae develop and rhopalial lappet curl orally (away from the viewer), actin-rich bundles appear elongate and striated. (G, H) At maturity, muscle extends around the ephyra as circular muscle (cm) and into the rhopalial lappets (rl) on either side of the rhopalia (r) as radial muscle (rm). Scale bar (A-F) 50 μm, (G-H) 100 μm.