parablast

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The nutritive yolk of a meroblastic egg.

from The Century Dictionary.

• noun The supplementary or nutritive yolk of a meroblastic egg or metovum, as distinguished from the archiblast,or formative yolk.
• noun Same as mesoblast.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Biol.) A portion of the mesoblast (of peripheral origin) of the developing embryo, the cells of which are especially concerned in forming the first blood and blood vessels.

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

• noun biology A portion of the mesoblast (of peripheral origin) of the developing embryo, whose cells are involved in the formation of the first blood and blood vessels.