ECTOMERE

Noun

ectomere (plural ectomeres)

Any of the blastomeres from which the ectoderm forms

Source: Wiktionary

Ec"to*mere, n. Etym: [Ecto- + -mere.] (Biol.)

Definition: The more transparent cells, which finally become external, in many segmenting ova, as those of mammals.

Source: Webster’s Unabridged Dictionary 1913 Edition