ABSTRACT

This chapter describes how cell behavior can determine body shape—a process called morphogenesis. One factor that can contribute to the shape of an animal is the position of the cleavage furrow at cell division; this determines the relative size and the positions of the daughter cells. Toward the front of the embryo, the depression is wider, and so the hollow tube has there a keyhole shape. These changes in cell shape appear to originate from within the cell rather than from outside pressure, because if the cell layer is dissected out and incubated in a culture medium, the cells elongate normally and finally fold into a tube. Early in the 20th century it was believed that cell division localized to a small group of cells is widespread in determining the shape of an embryo, and it was wrongly believed to cause the buckling of epithelial cells to form the neural tube.