This is the second volume of the late Dr. Larsell's comprehensive monograph on the cerebellum, the first volume of which is described below. A third volume, on the human cerebellum, will be published by the University of Minnesota Press next spring to complete the work. This second volume deals with the morphogenetic development and morphology of the cerebellum of all orders of mammals from monotremes through apes. The descriptions cover the cerebellum in about forty species with special emphasis on the cerebellum of the albino rate, rabbit, cat, and rhesus monkey. Dr. Larsell's comparative anatomical studies over a period of many years led to the conclusion that fundamentally the mammalian cerebellum is composed of ten subdivisions. With few exceptions (the smallest and most primitive cerebella) the subdivisions are identified in all mammals. The descriptions of the cerebella are based on the author's personal investigations but the relevant literature is thoroughly reviewed also.