Editors of compilations such as this tend to stress in their prefaces that significant conceptual advances have been made recently, that novel technical developments have opened extraordinary opportunities for unprecedented discoveries and that the time seemed ripe to take stock and to point out developments which will advance the field in the near future. Well, all of this is true for this book too. It is also true that on such occasions we realize how much we have learned and yet how little we know. Since the publication nearly 40 years ago, of the landmark treatise on cell movement edited by Robert D. Allen and Noburô Kamiya.
