Primordia are populations of contiguous cells that are morphologically distinct and already correspond in extent to a later organ/tissue[FBbt, Hartenstein, V. (2004)]. [ http://flybase.org/reports/DJS.html http://flybase.org/reports/FBrf0178740.html http://flybase.org/reports/FBrf0089570.html http://purl.obolibrary.org/obo/BTO_0001886 ]