Figure 11

Schematic representation of sections through the axial complex of Sphaerechinus granularis (Echinoida). A Horizontal section through the echinoid axial complex at the level of head process and dorsal sac. B Horizontal section through the echinoid axial complex at the level of the axial organ. The insert between A and B (compare Fig. 1) roughly outlines where the virtual sections were made. C Schematic representation of the columnar epithelium of the stone canal. D Schematic representation of the flat epithelium of the somatocoel. E Schematic representation of the myoepithelium that lines head process and pulsating vessel. F Schematic representation of the specialized epithelium with podocytes found in the axial coelom. ac = axial coelom, ao = axial organ, bl = basal lamina, ca = canaliculus, ci = cilium, ct = connective tissue, dm = dorso-ventral mesentery, ds = dorsal sac, ec = epithelial cell, fm = free mesentery, hl = haemal lacuna, hp = head process, pv = pulsating vessel, sc = stone canal, so = somatocoel.