Mechanisms of Morphogenesis: The Creation of Biological Form. Jamie A. Davies. Elsevier Academic Press, Burlington, MA, 2005. 374 pp., illus. $99.95 (ISBN 012204651X paper).

Jamie A. Davies is a reader in developmental cell biology at the University of Edinburgh and editor in chief of the journal Organogenesis. His research focuses on mammalian organs and integrates practical, theoretical, and bioinformatics approaches to the subject.

In Mechanisms of Morphogenesis, Davies presents a detailed analysis of up-to-date literature on the mechanisms of morphogenesis (the generation of shape). He describes experimental examples from animals, plants, and fungi. The book is organized by scale, beginning with the self-assembly of supramolecular complexes and the adaptive self-organization and morphogenesis of individual cells, moving upward in size toward tissues and organs, and briefly touching on embryos. Chapters 2 and 3 are dedicated to examples of cellular processes, including the formation of cell shape, the migration of cells using chemotaxis and galvanotaxis, cell-to-cell communication, and the condensation of cells to form new structures. Chapter 4 covers several well-understood examples of epithelial morphogenesis, including the closure of holes, the making of tubes and folds, fusion, and branching. Chapter 5 discusses morphogenesis by cell proliferation and death. There is a wealth of information packed between the book's covers. The chapters present a broad array of the better-understood processes, tied together under the themes of adaptive self-organization and emergence.

“Emergence” is a term used in physics, biology, economics, mathematics, philosophy, and robotics. Davies uses the term with respect to embryonic behavior to mean the way in which systems that involve only simple interactions can give rise to complex morphogenetic form. The introductory chapter illustrates this principle using “The Game of Life,” a cellular automaton devised by the British mathematician John Horton Conway and available on the Web as a computer simulation. “The Game of Life” demonstrates that the behavior of a few cells on a grid can vary tremendously and nonintuitively even though their movements are dictated by only four simple rules. The game illustrates the power of simple, local processes that result in highly complex behaviors, ultimately giving rise to a rich diversity of form. The simulation demonstrates that understanding the mechanism alone is insufficient for understanding biological form.

Davies hopes that the concept of emergence will unite the reductionist view of biochemistry and molecular biology with the holistic view of systems biology. Mechanics of Morphogenesis aims to explain the morphogenesis of macro-molecular and cellular processes, of epithelial tissue morphogenesis, and of the construction of the early embryo. Because biological form is ultimately based on interactions among molecules, Davies begins by discussing self-assembly: the coming together of subunits to make a structure because their association is energetically favored. An example of this is actin monomers assembling to form microfilaments.

Moving upward in biological complexity, he then introduces the term “adaptive self-organization,” the process by which structures are assembled under the guidance of feedback loops and thus modified and optimized for a specific function. For example, the orientation, quantity, and location of the animal cell cytoskeleton are constructed when information, in the form of mechanical tension, is applied to the cell. Examples of morphogenesis using feedback loops are provided at several “layers” of development (genes, proteins, cells, tissues, and so on). I was left with an appreciation of the morphogenesis of form not as a bottom-up, scalar process but as a process whereby any “layer” of development may dictate change either up or down the chain of complexity.

Davies considers the idea of hierarchy in biological systems as heresy because communication in development does not flow solely from one level (the gene level) up. The presence of many layers that communicate through feedback loops can make them amenable to modification by the environment and thus confer selective advantage on morphogenetic systems.

A unique contribution of this book is that it concentrates solely on mechanisms of morphogenesis; it takes for granted the processes of differentiation and of signaling and pattern formation covered in other works. So, if the reader is looking for an update on body plan development or the development of structures involving several cell types, such as a limb, this book may not be appropriate. Moreover, the book has little to offer the reader hoping to get a better feel for the evolution of form. It nicely covers many conserved cellular and tissue processes and almost completely omits the morphogenetic processes that result in divergent organisms. The great advantage of this narrow but detailed approach is that it immediately brings the reader up to date with recent reports and reviews that are central to the field.

In the closing chapter, Davies stresses the importance of the multilayered organization of morphogenetic processes, sends up warning flares on the metaphor of modularity, and addresses the inappropriate use of the word “hierarchy” in development. This struck me as an odd or at least incomplete selection of topics. My feeling is that if Davies wants to explore developmental concepts then they should be discussed more completely. I would have liked to see a brief discussion of homology, homoplasy, phenotypic plasticity, canalization, co-option, and evolvability, because these topics are touched on, albeit implicitly, in the earlier text. They relate directly to work in the field today and would have made a natural extension to the book. The little that Davies does offer in the closing chapter is quality scholarship, but I wished I could have read more of his thoughts.

Mechanisms of Morphogenesis is written in accessible prose. Each chapter outlines experiments that explore a basic central concept. The book is richly illustrated with drawings and well supported by an impressive, up-to-date literature base. Young scientists could profit immensely from this book, as it points to potential avenues of further fruitful research. For the established researcher, the book will provide an excellent update on current advances, and several simple exercises provided in footnotes will be useful in the classroom. Davies wisely makes no attempt to provide comprehensive coverage, but uses persuasive logic to draw out the robust argument that although form is ultimately dependent on cells constructing tissues, complexity in biological systems can and does arise by simple mechanisms at the cellular level. The result is a unique perspective on a set of problems of fundamental importance to molecular, cell, and developmental biologists.