Fig. 3.

DiI/DiO labelling of the occipital lateral mesoderm and ectoderm reveals extensive cell movements. Dorsal (A, B) or lateral (C–E) views of the chicken head–neck interface at the stages indicated on top of the panel, rostral to the top. In each, the lateral mesoderm and overlying ectoderm next to somites 1, 3, 5, 7, and 9/10 (lm+ect 1, 3, 5, 7, and 9/10) had been labelled at stages HH8+ to HH10− with DiI (red) and DiO (green) as shown in (A). As development proceeded, the labelled cell groups became compressed rostrocaudally and stretched mediolaterally. Cell groups next to somite 1 (arrowhead) took the circumpharyngeal route, eventually extending rostrally along the floor of the arches and towards the mandibular arch; cells groups labelled next to somites 3–10 spread laterally–caudally. The cell movements matched the extension of Alx4 and Wnt6 expression shown in Fig. 1. Abbreviations: ma, mandibular arch and ov, otic vesicle.