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1. A platelike mass of cells in the blastocyst from which a mammalian embryo develops. Also called embryonic shield.
2. See germinal disk.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
1. in the early embryo of mammals, the flattened inner cell mass that arises at the end of the blastocyst stage and from which the embryo begins to differentiate.
2. the blastodisk of yolky eggs.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.