Fig. 6

Transverse sections (a, b, d and f) and 3D reconstructions (c and d) of the lacrimal duct in the grass snake embryos at the different developmental stages. a The bud of the lacrimal duct (indicated by orange dashed line) at the beginning of developmental stage II. b The lacrimal duct (orange dashed line) in apposition to the Choanengang at the end of developmental stage II. c The lacrimal duct (orange) in relation to the vomeronasal organ (blue), nasal cavity and choanal groove (green) at developmental stage V. d The lacrimal duct (orange dashed line) in relation to the choanal groove (green dashed line) at developmental stage V. The section at the level of area indicated by the dashed line on c. e The ventral aspect of the lacrimal duct (orange) in relation to the vomeronasal organ (blue), the vestige of the choanal groove (green), associated cartilages (transparent purple; short arrows indicated the cylindrical part of the lamina transversalis anterior) the vomer (bright red) and the septomaxilla (dark red) at developmental stage VI. f The restricted areas of patency (short black arrows) of the lacrimal duct (orange dashed lines) at developmental stage VIII. The section at the level of the posterior part of the vomeronasal organ. Abbreviations: A anterior, C concha of the nasal cavity, CHG choanal groove, CHNG Choanengang, D dorsal, DNP nasopharyngeal duct, DPS dorsal process of the septomaxilla, DV duct of the vomeronasal organ, EN external naris, L lateral, M medial, MNC main nasal cavity, NC nasal cavity, OC oral cavity, P posterior, V ventral, VCH ventral channel, VNO vomeronasal organ. Scale bars 100 μm (f); 50 μm (a, b, d). 3D reconstructions are not scaled