Cells at the junction between the midbrain and hindbrain express all three engrailedgenes. Parasagittal sections through the heads of 12 h (A-C) and 32 h (E-G) embryos and 22 h (D) and 32 h (H) whole-mount embryos were hybridized with probes for the eng1 (A,E), eng2 (8,F) or eng3 (C,D,G,H) genes. A cartoon of the engrailed expression domains at the midbrain/hindbrain junction is shown in (I). The domain expressing only eng3 is shown in blue, the domain expressing both eng2 and eng3 is shown in red, and the domain expressing all three is shown in green. Anterior is oriented to the left and dorsal to the top in this and subsequent figures. AC and E-G are double exposures with bright field (blue) and clarkfield (red) illumination. The red signal in the lower part of I A is due to the yolk, rather than specific hybridization, as shown in control sections without hybridization. Arrows in H indicate hindbrain cells expressing eng3 (see Fig. 8). Scale bar, 80 μm in A-D, 50 μm in E-G and I, 100 μm in H.