Advances in Cell Biology has been initiated as a continuing, multi-volume series to report on the progress of a wide spectrum of problems of cell structure and cell func­ tion. In arranging these volumes individual contributors are asked not only to review the major new information, but especially to present the state of a given problem or area by discussing the current central issues, speculations, concepts, hypotheses, and technical problems. We intend, in addition, that these volumes will not be concerned with comprehensive reviews of the recent literature but will consist rather of presenta­ tions of an interpretative and integrative nature, based on selection of major research advances. It is our aim that these volumes should provide the means whereby cell biologists may keep themselves reasonably well informed about the current progress in research areas in cell biology in which they are not immediately or directly involved themselves. The articles, nevertheless, are expected to bring into focus the experimental objectives of the specialists in a given research area. D.M.P. L. G. E. M. vii Contents v Contributors Preface vii Bacterial Chromosome Replication 3 I. Peter L. Kuempel 57 2. Structure and Replication of Eukaryotic Chromosomes David M. Prescott Ultrastructure and Interaction of the Kinetochore and Centriole 3.