The common theme in the essays of this book is the emergence and sur­ vival of spatial structures. How are economic structures created in an otherwise homogeneous environment? The answer must be sought through an analysis of economic forces that operate in the two dimensional contin­ uum of space. Ultimately these forces emanate from the fundamental fact that spatial concentration is needed to reap increasing returns to scale. i. e. to gather the fruits of the division of labour. Adam Smith's dictum: "The division of labour is limited by the size of the market" poses a fundamental question to spatial economic analysis: just how do markets operate when extended over distances? Although these essays were written at different times they all relate to the problem of economic structures generated in spatial markets. They approach the phenomena of spatial order from different angles, but it is hoped in a connected and logically consistent way. We thank the editors and publishers of the Annals of Regional Science for permission to reprint parts of the articles "On the Shape and Size of Market Areas" and "Population Growth and Dispersal" to be published this year. It is our pleasure to thank Mrs. I. Strohlein for drawing several figures and Dr. H. Mittermeier for compiling the index. Last not least we are grateful to Mrs. B. Schwarzwalder for her patient job of typing and retyping this manuscript.