Fig. 5. Transverse sections of ICR embryos through mid-prorhombomere c (ProRhC) (A,C) or somite 2 (B,D-I). Embryos were fixed at different time points after labelling at the 5-6 somite stage by WGA-Au injection (A-G,I) or grafting of a WGA-Au-labelled neural crest fragment (H). At the 7-somite stage, WGA-Au-labelled cells, which carry dark silver granules (arrowheads in A,B), are seen leaving the dorsal part of the neural tube and some labelled cells are found in the mesenchyme beneath the surface epithelium (arrows in A) or at the dorsal tip of the somite (arrows in B; so, somite). At 11 somites after labelling at ProRhC (C), labelled cells (arrows in C) are located in the dorsolateral pathway beneath the surface epithelium and lateral to the anterior cardinal vein (acv in C). At the same stage after labelling at the somite-2 level (D,E), labelled cells (arrows in D) are observed in the dorsolateral pathway, between somite and surface epithelium, and also in the medial pathway (arrowheads in D) between neural tube (nt) and the somite (so). Another embryo shows WGA-Au-labelled neural crest cells in the intersomitic pathway (arrows in E). By the 13-somite stage, labelled cells (arrows in F) are more ventrally located, in the region adjacent to the dorsal aorta (da). At 17 somites (G), some labelled cells (arrows in G) have migrated beyond the somite to the region lateral to the developing pharynx (ph). By 21 somites, labelled cells (arrows in H) have reached the ventral side of the pharynx. Note that the spatio-temporal distribution of the labelled cells following grafting of a piece of neural crest tissue (H) is very similar to that observed after WGA-Au injection (G), although the number of labelled cells is smaller after grafting than labelling. At 23 somites (I), no more labelled cells are seen emigrating from the dorsal part of the nt, which exhibits a smooth contour on its basal surface. Scale bars: 50 µm in A-H; 20 µm in I.