FIG. 3. Internal anatomy of Actinostella bradleyi (Verrill, 1869). A, longitudinal section of the distal column showing distal verrucae (v), vesicles (ve) in the marginal ruff, marginal sphincter muscle (s), and the fosse; B, cross section at the actinopharynx level showing four cycles of mesenteries; numbers between pairs of mesenteries indicate the corresponding cycle; C, detail of the endodermal marginal sphincter muscle; D, cross section of a tentacle showing the ectodermal longitudinal muscles; E, detail of developing spermatic cysts (sc); F, detail of developing oocytes (o); G, detail of a cross section showing the retractor (r) and parietobasilar (p) muscles; H, cross section of proximal end showing the basilar muscles (b). Abbreviations: b, basilar muscles; ep, epidermis; ga, gastrodermis; me, mesoglea; o, oocytes; p, parietobasilar muscle; r, retractor muscle; s, sphincter; sc, spermatic cysts; t, tentacle; v, verrucae; ve, vesicles. Scale bars: A, B, G, H, 0.5 mm; C–F, 0.1 mm.