Fig. 6. Neural crest cells impart morphological features to skeletal and ectodermal structures. Sagittal sections of the beaks of control duck (A) and quail (B) embryos. (C,D) Beak sections of duck-quail chimeras after orthotopic replacement of quail neural crest (NC) into duck host (`Quck' chimera) (C), and reciprocal graft of duck NC into quail embryo (`Duail') (D), showing that the host upper bill morphology is modified according to the species origin of the NC [reproduced, with permission, from Schneider and Helms (Schneider and Helms, 2003)]. (E) Chimeric hyoid skeletal structures of a quail at embryonic day (E) 9, after unilateral replacement by duck NC (Alcian Blue staining). (F) Higher magnification of the entoglossum: on grafted side, the ipsilateral half has acquired a duck-shaped morphology [reproduced, with permission, from Tucker and Lumsden (Tucker and Lumsden, 2004)]. Arrows indicate the proximal limit of the cartilages on both sides. d, dentary; et, egg tooth; ey, eye; Mk, Meckel's cartilage; nc, nasal capsule; np, nasal passage; pm, premaxilla; pp, prenasal process; V, trigeminal sensory neurons.