ends during starts during marginal zone dorsal involuting marginal zone xenopus_anatomy DIMZ dorsal IMZ XAO:0005136 Tissue which during gastrulation involutes into the interior of the embryo, where its deep mesenchymal cells form the notochordal and somitic mesoderm and its superficial epithelial cells form the endodermal roof of the archenteron. 2016-09-03T19:21:41Z eriksegerdell NF stage 10 NF stage 12