Lhx9 expression in limbs and urogenital ridge. A, Coronal section through the caelomic cavity and the spinal cord (double arrow) at E11.5. Arrowheads point to the developing gonads (g), pancreas (p), and liver (l). Because sex discrimination is not easy at this stage, it should be noted that the same expression pattern was found in all embryos examined. B, Expression in E10 forelimb after in toto in situ hybridization.p, Proximal; d, distal.C–E, Transverse sections through developing hindlimbs and forelimbs at indicated stages. Arrowheads inC indicate absence of expression in the apical ectodermal ridge. See Results for details. Scale bars: A, C–E, 50 μm; B, 200 μm.