Fig. 3. Whole mount RNA in situ localization of Evi-1 transcripts during Xenopus development. Anterior is to the right in all panels. Representative cleared embryos of increasing age are shown (A) stage 22, (B) stage 25, (C) stage 28, (D) stage 37. Transverse section planes, Fig. 4(B)E), are indicated by the vertical labeled lines (C). Note in panel (D) the avoidance of the otic vesicle by Evi-l expressing neural crest cells. Faint Evi-l signal is visible over a localized region of the developing foregut in later tadpoles, tentatively identified as the stomach (D). Comparison of Pax8 and Evi-1 expression patterns at stage 23 indicates staining in the pronephric duct anlage (E). Scale bar: 100 mm. Abbreviations: a, archenteron (developing gut cavity); cg, cement gland; cnh, chordoneural hinge; dfb, dorsal forebrain; e, eye, hb, hindbrain; hm, head mesenchyme; mb, midbrain; op, olfactory placode; ov, otic vesicle; pn, pronephric duct; st, developing stomach; vfb, ventral forebrain.