Inordertorepeatapublishedexperiment,orhavesomeoneelserepeatyours,itisimportanttousethesamematerials.Fordevelopmentalstudies,thatmeansknowingtheprecisepointindevelopmentthattheembryoshavereached.Thetimeofincubationgivesonlyanapproximationofthedevelopmentalage.Forthisreason,stagingseriesbasedonmorphologiccriteriahavebeenprepared.Zebrafishembryosarelaidoverapproximatelyanhouranddevelopveryrapidly.Agivenbatchwillcontainembryosatarangeofdevelopmentalstages.ToobtainareproducIBLegroupofembryosforexperimentation,sortembryosaftercollectionandmaintainataconstanttemperature.ZebrafishembryosarestagedusingaseriespreparedbyM.Westerfield,TheZebrafishBook,orKimmeletal.,Develop.Dynam.203:253-310.