acroblast

from The Century Dictionary.

• noun In embryology, that portion of the embryonic germ-layers in vertebrates which gives rise to the blood and connective tissue; the mesenchyme.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun medicine Material derived from the Golgi apparatus from which the acrosome develops during spermatogenesis.
• noun medicine (archaic) A type of embryonic cell forming a layer external to the mesoblast.