The discussion of organogenesis in this edition has been expanded substantially. Among them, they provide a sampling of the complexities involved in coordinating the differentiation of multiple cell types to produce functional entities during development. Cell differentiation in differentiating organs and tissues is dependent upon the selective expression of cell-specific genes. Our understanding of the control over selective gene expression during cell differentiation has progressed rapidly in recent years with the application of the techniques of contemporary molecular biology. These topics are covered in Chapter 18.
Developmental biology is taught in a variety of formats.
We have attempted to write a versatile book that should be appropriate for courses that emphasize cellular and molecular aspects of development as well as those that focus on descriptive embryology and morphogenesis. However, the book will be particularly useful for those courses that cover both the molecular and descriptive aspects of development. The approach that we have taken should be compatible with courses at various levels of instruction, from undergraduate to graduate. Our objective while preparing this textbook has been to capture the spirit and flavor of this dynamic period in developmental biology while giving our readers an appreciation for the intellectual base embodied in the classical literature. We will have succeeded in this project if we have engendered in our readers a fascination and enthusiasm for studying the processes of change that typify development and have stimulated them to assist in unravelling the secrets of developmental biology.