specific_to existence overlaps existence starts during or after existence ends during or before independent continuant Stage 2 Stage 3 Stage 4 Stage 5 Stage 6 Stage 7 embryonic digestive system PMID:28072387 Planarian_Anatomy A cryptic digestive system in Stage 3-6 embryos comprised of temporary embryonic cell types and organs, including the embryonic pharynx and primitive gut cells. Embryonic gut cells, likely produced from blastomeres, form a phagocytic tissue layer surrounding the inner gut cavity during Stages 4-6. It is not known whether the embryonic gut is temporary embryonic tissue or a definitive tissue. For convenience, the embryonic gut is currently designated as an extraembryonic structure because cell type specific markers for the embryonic gut do not stain the definitive gut in hatchlings or adult animals. https://orcid.org/0000-0003-2569-1939 | https://orcid.org/0000-0002-7535-4547 extraembryonic structure embryo