Development of P. lamarckii. Light microscopical images. Scale bars: A-C = 50 μm; D = 1 mm. Apical is towards the top of the figure in all panels unless indicated. A. Complete trochophore, right lateral view. a, anus, ao. apical organ. at, apical tuft. in, intestine. m, mouth. mt, metatroch. pt, prototroch. st, stomach. B. Metatrochophore, dorsal view. ey, eyespot. Segments indicated by arrows. C. Early juvenile, dorsal view. bc, branchial crown. co, collar. op, operculum. t, tube. tm, thoracic membrane. D. Adult worm removed from tube, the anterior end possesses the branchial crown. ab, abdomen.