macromere

One of the large blastomeres found in a developing embryo.

In embryology, the larger one of two unequal masses into which the vitellus of a lamellibranch, as a fresh-water mussel, divides; the so-called vegetative cell of Rabl, which subdivides into blastomeres, partly by fission, partly by gemmation. See micromere.

In embryology:

One of the large yolk-laden cells, found about one pole of an egg in case of unequal segmentation, such as occurs in the hagfish, Myxine: contrasted with micromere.

A large blastomere.