- a disklike spot in a fertilized ovum in which the first traces of the embryo are visible
- the disklike spot on the yolk of a heavily yolked egg where segmentation begins after fertilization
See germinal disk in American Heritage Dictionary 4
A flattened, disklike region of cells from which the embryo begins to develop in the fertilized ovum of many vertebrate species. Also called blastodisk, embryonic disk.
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