"fly_anatomy.ontology"^^ . "Primordium that is a primary subdivision of the embryo into regions based on tissue and cell-type fate and specification. Germ layers first become morphologically distinct during gastrulation. As a result of gastrulation, the endoderm becomes the inner-most layer, the mesoderm becomes the middle layer and the ectoderm becomes the outer layer."^^ . . . . "FBbt:00000110"^^ .