SUPERFICIAL GEL LAYERS OF CELLS AND EGGS AND THEIR ROLE IN EARLY DEVELOPMENT

Resumen

Every cell and egg has a superficial gel layer and less viscous endoplasm. They are different states of the same cytoplasm. Gel layers always exert contractile tension. This is the motive force for ameboid locomotion, for blastodisk formation and gastrulation (epiboly) of fish eggs and for most movements of amphibian gastrulation. Movements occur when one part of the gel layer increases or decreases in viscosity (contractility).
Adhesion of cells to one another is essential for the active movements of locomotion and invagination of cells during gastrulation and for all passive movements due to pulls and pushes which result from the active movements.