Multiple micromeres contribute to the region surrounding the presumptive anus. (A-L) Z-stacks of merged, confocal images of late stage 6 larvae 5 days after labeling micromeres 2d (column 1), 3c (column 2), 3d (column 3) or 4d (column 4) with DiI. The channels are DiI (red), phalloidin (green) and TO-PRO-3 (blue). Panels labeled with an apostrophe (for example, A', B') are single-channel images of DiI that correspond to panels with the same letter (for example, A, B). The depths of the confocal z-stacks, starting at the surface (A-D) and progressing into the larva, are indicated to the left of each row. The diagrams at the top of each column are of the posterior rosette cells and are drawn from the images immediately below them (that is, surface z-stacks). In (L) an arrow points to the forming gut lumen (gl). All images are from a posterior view with ventral down.