Fig. 4. Sections at anus level of wild-type larvae aged (A) 48 hpf, (B) 72 hpf and (C) 96 hpf, and nic^b107 larvae aged (D) 48 hpf, (E) 72 hpf and (F) 96 hpf stained for propidium iodide with muscle fibre trajectories superimposed. Trajectories are visualised by a white circle for the anterior starting position and a line segment that represents the direction and projected distance travelled over the next 5 µm. Azimuth and elevation can be inferred from the components in the X and Y direction of the line segment (see main text). All sections are viewed from the anterior side, and the projections are of fibres running from anterior to posterior (below the surface of the figure) over a distance of 5 µm. This implies that the left side of the embryos is to the right and vice versa in this view. Neural tube (nt) and notochord (nc) are indicated. Scale bars, 20 µm.