- ectomesoderm
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n. [Gr. ektos, outside; mesos, middle; derma, skin]Mesoderm derived chiefly from the ectoderm during early embryology of animals; forming mesenchyme predominently in Porifera, Ctenophora and in certain mollusks and annelids.
Online Dictionary of Invertebrate Zoology. A.R. Maggenti and S.L. Gardne. 2005.