(i. L. biyoloji). Blastulanın bir noktasından çukurlaşarak iç içe hücre tabakası şekline girmiş hali. (bk.) Blastula.

An embryonic form having its origin in the invagination or pushing in of the wall of the planula or blastula on one side, thus giving rise to a double- walled sac, with one opening or mouth which leads into the cavity lined by the inner wall.

See Illust. under Invagination.

In a more general sense, an ideal stage in embryonic development.

Of or pertaining to a gastrula. double-walled stage of the embryo resulting from invagination of the blastula; the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm.