Organization of the hood elevators and the esophageal musculature in Phoronopsis harmeri larvae. A. Fine morphology of hood elevators (arrows) (SEM). B. Cross section of hood elevator; muscle cells contact basal lamina via hemidesmosomes (open arrowheads). C. Semi-thin sagittal section of the esophagus (eso) with complete muscular lining (mc). D, E. Longitudinal fine section of muscular lining of the esophagus. D. Muscule cells contact basal lamina via hemidesmosomes (open arrowheads). E. Thick collagenous fibers between membranes of muscle cells are indicated by arrowheads (closed arrowheads). Abbreviations: bc – blastocoel; bl – basal lamina; ep – epidermis; mf – myofilaments; nf – nerve fibers.