GastrulaGastrulationNotochordEmbryo, NonmammalianFetal ProteinsMesodermXenopus ProteinsXenopus laevisEmbryonic InductionOrganizers, EmbryonicBody PatterningEctodermMorphogenesisT-Box Domain ProteinsXenopusEndodermGene Expression Regulation, DevelopmentalNervous SystemIn Situ HybridizationMicroscopy, Electron, ScanningMolecular Sequence DataAmino Acid SequenceCell MovementSignal TransductionBase Sequence