The knowledge work of higher education is carried out in every country in a differentiated structure that divides and allocates tasks within and among institutions; Certain features of differentiation are likely to be common among national systems: the basic sectioning of the natural sciences in such fields as physics, chemistry, and biology, and well-defined subfields thereof, has wide currency. But many features of differentiation, such as the division of labor among institutional types, vary widely among nations. Whatever the combination of sections and tiers within institutions, and sectors and hierarchies among them, the prevailing structure sets many of the problems of coordination and control and conditions nearly all important issues of continuity and reform. (Author/MSE)