Fig. 3

3D reconstructions (a, c and e) of the vomeronasal organ and associated structures and transverse sections (b, d and f) through the snout of the grass snake embryos at different developmental stages. a The medial aspect of the vomeronasal organ (blue) and its relation to the vestige of the choanal groove (green) and the lacrimal duct (orange) at the developmantal stage VI. b The posterior part of the vomeronasal organ at developmental stage VI. The section at the level of the vestige of the choanal groove (green dashed line) connected with the lacrimal duct (orange dashed line). c The ventral aspect of the vomeronasal organ at developmental stage VI. The colours of the structures are the same as in the a. d The lateral part of the ventral channel (indicated by black dashed line) at developmental stage VI. e The ventral aspect of the vomeronasal organ at developmental stage VIII. The colours of the structures are the same as previously. f The lacrimal duct and the vestige of the choanal groove at developmental stage VIII. The colours of the dashed line are the same as in 3b. Nine sections posterior to the level of the connection of the vestige of the choanal groove to the palate. Abbreviations: A anterior, CMB cartilage of the mushroom body, D dorsal, DV duct of the vomeronasal organ, L lateral, LDL lateral diverticulum of the lacrimal duct, LDV lateral eminence of the VNO duct, LV lumen of the vomeronasal organ, M medial, MB mushroom body, MDL medial diverticulum of the lacrimal duct, OC oral cavity, P posterior, SE sensory epithelium, V ventral, VCH ventral channel, VNO vomeronasal organ. Scale bars 50 μm (b and f); 20 μm (d). 3D reconstructions are not scaled