ABSTRACT
I. INTRODUCTION "Morphogenesis" literally means the creation of form. As it is applied to the development of multicellular animals, this term refers to those processes responsible for organizing embryonic cells into complex structures such as tissues and organs, thereby molding the physical shape of the embryo. Morphogenesis has been distinguished from another key developmental process, cell differentiation, in that although the latter can be studied largely at the subcellular level, the former requires a consideration of cellular and supracellular properties that regulate the collective behavior of cells in embryos (1). These processes are obviously interrelated, since it is partly through differentiation that cells show the specialized motile or adhesive properties that regulate morphogenesis. The distinction between the two terms is useful, however, because it draws attention to the special problems that must be considered in analyzing morphogenesis and prevents the use of the term simply as a synonym for development. The principal goal of modern research in this field is challenging: to provide an integrated explanation of morphogenetic processes that bridges molecular mechanisms with the behaviors of cells and tissues in embryos. It is an exciting prospect that is now being realized in several systems.
