N ORTH-EASTERN Asia has entered the field 1N as one of the competitors with southwestern Asia as the home of man. The discovery of some fossil vertebrates that are common to Europe and western America but are absent from eastern America led Prof. H. F. Osborn in 1900 to predict that these animals had developed in northern Asia and thence migrated eastward into Europe and westward into America. The ocean they crossed was therefore the Pacific and not the Atlantic. Faith in this theory led Dr. R. C. Andrews to organise an expedition to search for the remains of these animals in the steppes which they must have crossed during their migration from inner Asia to the Rocky Mountains. The generosity of American patrons of science provided £50,000 for the purpose, and Dr. Andrews led to Mongolia a series of well-equipped expeditions which there made several sensational discoveries. The most dramatic was the finding of the eggs of Cretaceous dinosaurs. They were found in such abundance in one locality that one Mongolian woman brought in fragments of egg-shells in tinfuls. The eggs belong to three genera, one of which, Protoceratops, is a primitive form of the Ceratopsidoe. Dr. Andrews describes this locality as a dinosaur incubator, and he attributes its selection as the breeding-ground to the nature of the sand, which would have formed comfortable nests. Of still greater importance was the discovery, also in the Middle Cretaceous beds, of some mammal skulls. The first found had been sent to New York as a reptile, and recognised by Dr. W. D. Matthew as a primitive mammal. Stimulated by his report of the importance of the discovery, the search was renewed and other specimens found-. A preliminary account of the skulls is given in the volume, but a more detailed account has been recently published elsewhere. The expedition also discovered a series of important Eocene mammals. The first of the vertebrate fossils found by the expedition were some bones of the Baluchitherium, an Oligocene mamma], which was discovered by Cooper in northern India. The expedition found later a skull and a skeleton of this mammal, and Dr. R. C. Andrews was led by the discovery to the expectation that, as the human family probably began to diverge from the ordinary primates in the Oligocene, the remains of some primitive ancestors of man should be found in Mongolia. Large numbers of stone implements were found; they represent two periods-Neolithic and Upper Pal.Tolithic. The age of the latter is suggested as Azilian. Some members of the expedition were at first under the impression that the rough stone cores represented a pre-Chellean culture; but ultimately they were convinced by the large series collected and arranged by the archeologist, Mr. Nelson, that the cores were the residue of Upper Palholithic flaking. Nothing human was obtained by the expedition earlier than the Mousterian, of which implements have already been found in China, in the valley of the Hoang-ho. While the paleontologists were excavating the fossils, the two geologists with the expedition-Prof. Berkey and Mr. F. K. Morris-surveyed the area, worked out its history, and thus made a valuable contribution to Asiatic geology. Amongst other points of interest they find that there is no evidence of glaciation in the district, except in some small corries on the highest hills.The volume tells the narrative of the expedition. It is graphically and racily written, and gives a delightful picture of a group of men in cordial co-operation and all enthusiastic in their work. Probably in the effort to be popular the author constantly states the age of the beds in years, reporting, for example, that the earlier implements date from 40 thousand, and the later from 15 thousand years ago; such estimates are about as useful as if a historian tried to date an Act of Parliament by reference to the birth of John Smith. The book is well illustrated by photographs showing the expedition at work and the nature of the country, and by ideal pictures of the fossils skipping about in their native haunts