Fig. 2. Cell dynamics establishing the primary vascular plexus. Time points 1-11 show the cell configurations, at hour intervals, within the area delineated by the cyan colored box in Fig. 1. Each panel represents a 400x400 µm area enlarged from individual frames in Movie 1, and are shown in Movie 2 (see http://dev.biologists.org/supplemental). As a reference, the upper right-hand corner is centered on the lateral edge of the third somite pair 160 µm from the midline. The final panel is a merged image composed of the Cy3-QH1, experimental PEC label (red) and the post-experimental labeling of the vasculature using Cy2-QH1 (green). The open circles enclose the same endothelial structures on each panel to ease following movements. Note the lateral-to-medial movement of all denoted PECs. Green circles represent new features entering the field of view from a lateral position. Blue arrowheads indicate new cellular extensions and connections with existing polygonal structures. The red arrowheads represent retractions of vascular cords. In the last panel, a red arrowhead indicates where one connection once existed between two of the circled areas. In addition, some vasculature is formed (green) that is not recorded (red/yellow).