Metacoel lining and blood vessels in Phoronopsis harmeri larvae. A-B: Longitudinal fine sections (TEM); longitudinal myofilaments are indicated by concave arrowheads; circular myofilaments are marked by straight arrowheads. C-D: Semi thin cross sections. A. Lining of the body wall. B. Lining of the digestive tract. C. The dorsal blood vessel (dv). D. The lateral blood vessel (lv). Abbreviations: bc – blastocoel; bl – basal lamina; cds – cells of the digestive system; c3 – trunk coelom; cl – cells of coelomic lining; st – stomach; vm – ventral mesentery.