Publications on the mechanisms of the cationoid polymerisations are collected together in this present volume. Each paper or group of papers is preceded by an introductory prologue in which the authors assesses the current relevance of his work and indicates why even the oldest findings are still worth keeping in mind when facing new work. Professor Plesch directs the ruthless critical scrutiny, for which he became well known, to his own work, pointing out errors revealed by hindsight.