Fig. 13 in The metatrochophore of a deep-sea hydrothermal vent vestimentiferan (Polychaeta: Siboglinidae)

Fig. 13 Mesoderm in specimen #308. a Mesoblastem (me) in anterior region of first segment with foregut (fg); b epitheliomuscle cells in visceral mesoderm (mu) adjacent to foregut (fg) in region of coelomic ducts in first segment, c peritoneal cells in visceral mesoderm (me), adjacent midgut (mg), and d hindgut (hg); e cross section through foregut area in middle region of first segment with epidermis (e), longitudinal muscles (mu), dorsal mesentery with dorsal blood vessel (dv), peritoneum (me) surrounding the foregut (fg); f detail of coelomic cavity of first (c1) and second segment (c2) with septum of two opposing layers of epithelio-muscle cells (mu); g coelomic cavity of second (c2) and third segment (c3) with septum of two layers of undifferentiated mesoblastem, arrow points to thin posterior part of mesoblastem surrounding coelomic cavity of segment 3