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blastopore blas·to·pore (blās'tə-pôr')
The opening into the archenteron formed by the invagination of the blastula to form a gastrula.
the opening by which the cavity of the gastrula, an embryonic stage in animal development, communicates with the exterior. During maturation of some animals it evolves into the anus or the mouth; in others it is covered over and contributes to the canal joining the primitive gut with the cavity of the neural tube, the primitive nervous system.