Figure 1. (a) One-day-old zebrafish embryo, lateral view. (b) Dorsal view of the neurons of the pineal gland. (c) Expression pattern of an early neurogenic marker in the neural plate at the end of gastrulation (dorsal view). (d) Primary axonal tracts in a 2-day-old brain. (e) Lateral view of the zebrafish brain showing telencephalic emx-1 gene expression (blue) and transplanted cells in the eye (brown). (f) Rescue of a telencephalon (expressing emx-1 in blue) in a brain mutant after transplant of wild-type anterior neural plate cells (brown). (g) Transplanted kriesler mutant cells cannot contribute to rhombomere 5 and 6 in a wild-type embryo. Brown cells (g) are kreisler cells. Blue cells are rhombomere 3 and 5 krox-20-expressing cells. (g) is adapted from Moens et al. (1998).

Figure 2. (a–d) Lateral views of mutants affected in notochord and tail formation (a is wild-type). (e, f) Lateral view of the brain of the acerebellar mutation (f, arrow) compared to wild-type (e, arrow). Alcian blue staining of the jaw in wild-type (g) and a jaw mutant (h). Lateral view of a 5-day-old wild-type (i) and colourless pigment mutant (j) embryos. (k) Wild-type (top, arrow) and heart mutant (bottom, arrow) 5-day-old embryos. (l) Axonal staining (brown) of a forebrain mutant masterblind (left) and wild-type (right) 2-day-old embryos. All panels but (l) are adapted from the zebrafish issue, Development 123 (December 1996).