This book was first published in 1983.

The authors offer a detailed and systematic critique of Piaget's theory of cognitive development, examining it in relation to other theories of development.

In the dozen years since the first edition appeared, there has been a great advance in understanding of the Earth's deep interior. This is not because there have been breakthroughs in understanding, or even many changes of ideas, but largely because of many small advances, often the result of improved tech niques. This has led to a complete revision of the book. For instance, we have a much better idea of how the cloud of gas that formed the Solar Nebula evolved into the Sun and the planets, and of the chemical processes that accompanied its evolution and determined the mix of elements in the Earth. We have a better understanding of convection and how plates are an essential part of it, and how it is accompanied by chemical processes that have extracted the materials to build continents. Although the major variation within the Earth is radial, improved geophysical and geochemical techniques have made progress in investigating and under standing the lateral heterogeneities, and it is encouraging that when geochemists and geophysicists talk about lateral heterogeneities they can sometimes be referring to the same thing. Plumes have become very fashionable as the cause of hot-spot magmatism and associated geochemical anomalies, probably origi nating at the base of the mantle (though clear evidence for their existence is lacking)."

Current research into formal methods for hardware design is presented in the papers in this volume. Because of the complexity of VLSI circuits, assuring design validity before circuits are manufactured is imperative. The goal of research in this area is to develop methods of improving the design process and the quality of the resulting designs. The major trend apparent at the workshop is that researchers are rapidly moving away from post hoc proof techniques with their great expense. A number of papers were presented that dealt with problems of synthesizing correct circuits and of designing with the goal of verification. Researchers are also beginning to deal with the theoretical issues of reasoning about concurrent systems and asynchronous systems, and to introduce new logical tools such as constructive type theory and category theory. Most of the research reported was performed in the United States.

The blood cell system has provided a model system that has been used by many researchers to investigate how a stem cell can give rise to a wide variety of mature cell types. The principles that emerged in developmental biology have been applied to the structure of tissues throughout the body. However, many of the principles have been challenged by recent findings, changing the way we view blood cell development. In turn, this has impacted our understanding of the origin and nature of leukaemia, as well as cancer in general. Like the development of any body tissue, cancer is an organised and hierarchical tissue with its own identity. A new viewpoint is that the mutations that give rise to cancer re-programme cancer cells to their own abnormal pattern of tissue development. Understanding how the hierarchy of tumour identity differs from that of normal tissue provides important new avenues to the development of new treatments for cancer. No doubt further refinement to our understanding of normal and cancer cells will continue for many years to come. Even so, we appear to be moving towards an exciting prospect of providing the key to unlocking the long standing mystery of primary cellular events that undermine and distort our normal cells and give rise to the disease of cancer. The importance of this is the prospect of developing new treatments for cancer. In particular, the distorted behaviour of cancer cells might be reversible so that they can be restored to their normal state. Diversity, Versatility and Leukaemia examines how normal and cancer cells are inextricably linked, and focuses on the changes to how we view the development of normal cells and the subversion of this process in cancer.

For many years the mammalian blood cell system has provided cell biologists and haematologists with one of the best experimental models in which to unravel how one stem cell -- the hematopoietic stem cell -- gives rise to many different types of progeny. Numerous models of lineage relationships have emerged, but the most influential of these, in which differentiating cells undergo a series of binary choices, has been increasingly challenged in recent years -- to the extent that the accumulation of new findings recently culminated in a Nature commentary suggesting that "the latest research will necessitate revision of textbook accounts". This book brings together contributions from many leading experts in the field of blood cell development who each discuss both the overall process of hematopoiesis and the origins and development of each of the cells of the blood and immune systems. It describes how new molecular, cellular and -- particularly -- transgenic tools are helping us understand the processes that control the lineage fates of hematopoietic stem and progenitor cells and how lineage-committed progeny develop along particular maturation pathways.