Fig. 2

SEM images of Schizocardium karankawa. A Ventral view of a 1ate stage tornaria equivalent to Fig. 1K. B Dorsal view of a two gill pore stage juvenile worm. C Apical organ of the juvenile worm develops from that of the larva. In life, the organ is outward projecting and exploratory, but under SEM it is a concave fixation artifact. D Dorsal view of a late stage tornaria with ciliated anus. E Lateral view of a juvenile worm at the seven-gill pore stage. Elongation occurs primarily at the posterior trunk. F Details of the gills at the three-pore stage. The gill bars with lateral bar cilia can be seen through the gill pores. af anal field, an anus, ao apical organ, c collar, gb gill bars, gp gill pores, lbc lateral bar cilia, pdl primary dorsal lobe, pds primary dorsal saddle, pof postoral field, pr proboscis, pt protuberances, t trunk, tt telotroch. Scale bars: A, D and E = 500 \(\mathrm{\mu m}\); C, B = 30 \(\mathrm{\mu m}\), F = 50 \(\mathrm{\mu m}\)