part_of part of part of contained in develops_from develops from existence overlaps existence starts during or after existence ends during or before material entity anatomical entity anatomical entity Stage 1 Stage 2 Stage 3 Stage 4 Stage 5 aboral hemisphere ectolecithal embryo embryonic wall oral hemisphere zygote embryonic cell blastomere PMID:28072387 An undifferentiated, cycling embryonic cell in Stage 1-5 embryos that expresses piwi-1, numerous adult asexual neoblast enriched genes, and early embryo enriched genes. Blastomeres give rise to temporary embryonic tissues during Stage 2, continue dividing asynchronously in the embryonic wall, and ultimately give rise to neoblasts and adult lineage progenitors beginning in Stage 5. https://orcid.org/0000-0003-2569-1939 | https://orcid.org/0000-0002-7535-4451 Planarian_Anatomy