 The ZLI together with the prethalamus and thalamus make up the mid-diencephalic territory (MDT).Cell lineage restriction boundaries, across which replicating cells cannot migrate, were first discovered in invertebrates, where the expression of various Hox genes in each compartment confer the differentiation of observable segments in the adult body of Drosophila melanogaster.Analogous structures were discovered in the developing vertebrate brain.