from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Alternative form of blastodisk.
from the GNU version of the Collaborative International Dictionary of English
- n. a disc-shaped layer of cells on the surface of the yolk mass of an egg (such as that of a bird) which develops to form the embryo.
from The Century Dictionary and Cyclopedia
- n. An aggregation of formative protoplasm at one pole of the fertilized ovum.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a layer of cells on the inside of the blastula
Sorry, no etymologies found.
If the egg is not fertile the white mark will not be perfectly round and may be smaller (called a blastodisc).