Organization of the uninjured RNC. (A – D) Microscopic anatomy of the RNC shown on transverse (A, B) and longitudinal (C, D) paraffin sections, Giemsa staining. (B) and (D) show higher magnification views of the RNC in (A) and (C), respectively. (E – I) Representative micrographs showing double immunolabeling of the RNC with the echinoderm radial glia-specific antibody ERG1  and other glial and neuronal markers; cryosections. (E) ERG1 and AFRU (a rabbit polyclonal antiserum recognizing Reissner’s substance ), transverse section. (F) ERG1 and anti-GABA antibodies, longitudinal section. (G) ERG1 and anti-GFSKLYFamide  antibodies, longitudinal section. (I, H) ERG1 and anti-Nurr1 antibodies in the hyponeural (H) and ectoneural (I) neuroepithelia, longitudinal sections. Note a short bridge connecting the ectoneural and hyponeural neuroepithelia marked by an arrowhead in (H). bw, body wall connective tissue; c, coelom; ec, epineural canal; en, ectoneural neuroepithelium; h, hemal lacuna; hc, hyponeural canal; hn, hyponeural neuroepithelium; lmb, longitudinal muscle band; p, thin connective tissue partition separating the ectoneural and hyponeural neuroepithelia; re, roof epithelium; rnc, radial nerve cord; wvc, water-vascular canal.