Fig. 4 Epidermis and trochi, all #308 except c, f, g #675. a Epidermis containing nucleus (n) and mitochondria (mi), with thin cuticle (cu) and microvilli (arrow) above which bacteria (ba) are located; ECM of epidermis adjacent to longitudinal muscles (mu); b detail of cuticle with epicuticle (ec) and microvilli and basal cuticle (bc); c bacteria (ba) on and in tube; d prototroch (pr) with trochoblast and nuclei (n), mitochondria (mi), and tonofilaments (tf), adjacent mesoderm with nuclei (nm) with ECM (arrows); e cilia of prototroch with basal bodies (bb) and rootlet (ro), in between microvilli (mv) and thin cuticle; f neurotroch (nr); g cilia of neutroch with basal bodies (bb) and rootlets (ro), in between microvilli (mv) and thin cuticle