the flowing of cells and cell layers in the developing embryo of an animal, which results in the formation of germ layers and organ primordia.
The most intensive morphogenetic movements occur during gastrulation, when part of the cellular material is shifted to the interior of the embryo (invagination), while the remaining cells form its surface (epiboly). As a result, the material of the primordia of axial organs occupies a terminal position. Morphogenetic movement in almost all chordates has been studied by marking certain areas of the egg or blastula and tracing the subsequent fate of the marked areas.
Morphogenetic movements may involve the flow of cells and their layers over relatively long distances (for example, during invagination of the chordamesoderm in amphibians); they may also involve changes in the shape of primordia remaining at the same site by the formation of folds and bends in the cell layer (for example, invagination of the wall of the optic vesicle and the division of the brain rudiment into the cerebral vesicles). The basis for morphogenetic movement lies in the capacity of cells to move and to form contacts with one another and with a substrate (adhesiveness). Cells of different types differ in their degrees of mobility and adhesiveness; contacts between homogeneous cells are formed more readily than between cells of different types (elective affinity).
G. M. IGNAT’EVA