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 function. Jn 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...

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...