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The growing or extending of one part, such as the upper hemisphere of a blastula, over and around another part, such as the lower hemisphere, in embryogenesis.



a method of gastrulation by which cells of the embryo’s animal hemisphere spread through its vegetal hemisphere, the future entoderm (in animals with meroblastic ova, the yolk).

References in periodicals archive ?
At approximately 13 hours postfertilization, epiboly began, and involution marked the start of gastrulation.
Important developmental processes observed included cleavage, formation of a blastula, epiboly, gastrulation, neurulation, organogenesis, and hatching.
Several mutations even disrupted epiboly, the very first cellular move- ments of the embryo.