IAU Symposium 103 was held at University College London, August 9-13 1982. This volume contains the proceedings of the meetin- invited papers, abstracts of contributed papers, and discussion. As is nON custanary with the proceedings of IAU Symposia, the manuscript was canpiled fran camera-ready copy. The Editor was responsible for the preparation of the abstracts of the contributed papers and the discussion, the authors of the invited papers for the preparation of their 0Nn reviews. The discussion at the meeting was lively and infonnative, and the Editor hopes that a reasonably faithful and...