BlastodermBlastulaEmbryo, NonmammalianGastrulaSea UrchinsGene Expression Regulation, DevelopmentalBody PatterningBlastocystNodal Signaling LigandsDrosophilaOrganizers, EmbryonicZebrafishBlastodiscMesodermEmbryonic InductionEctodermMorphogenesisDrosophila ProteinsChick EmbryoDrosophila melanogasterZebrafish ProteinsXenopus ProteinsTriboliumGenes, InsectOvumEndodermNodal ProteinIn Situ HybridizationGerm LayersZygoteXenopusCleavage Stage, OvumHomeodomain ProteinsCoturnixBlastomeresXenopus laevisInsect ProteinsHeteropteraEmbryonic DevelopmentQuailMolecular Sequence DataTranscription FactorsFushi Tarazu Transcription FactorsNervous SystemGoosecoid ProteinStrongylocentrotus purpuratusNotochordBase SequenceGerm CellsVitelline MembraneHemicentrotusAmino Acid SequenceInsect HormonesEchinodermataRNA, MessengerTranscription Factor 3Genes, HomeoboxActivinsAminopterinLarvaPleurodelesAnimals, Genetically ModifiedCloning, Molecular