Fig. 1.

Distribution of LPM in stage 23/24 lamprey embryos. (A and B) Plastic sections through the midyolk ball of (A) Petromyzon and (B) Lethenteron embryos stained with toluidine blue. In both A and B, PLPM (plpm) extends laterally from the somites (som) along the dorsum of the yolk ball (yb). (C) Cryosection of whole mount in situ of Lethenteron embryo. Expression of LjHandA (blue) supports lateral plate identity of PLPM. Fig. S3 shows additional stages. ect, ectoderm; nc, notochord; nt, neural tube. (Scale bar: 50 µm.)