the outer layer of the blastoderm, also called epiblast; also, a term applied to the outer layer of the body of the Cœlenterata.
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1861 J. R. GreeneMan. Animal Kingdom II. 11 The ectoderm growing from within outwards.
1879 tr. E. Haeckel Evol. Man I. iii. 67 The upper germ-layer, from which the outer skin and the flesh proceed, Huxley named Ecto-derm, or Outer layer.