Man must have experienced the following phases of development in the transition from the prehuman to the human stage: first, the utilization of chance stones and sticks; second, the casual adaptation of flints by a minimum amount of chipping; third, the deliberate manufacture of the simplest implements from flint nodules; and fourth, the invention of new forms of weapons and tools in ever increasing variety. Of the last two stages we have an extensive and clear record. Of the second stage we have in the eoliths intermediate forms ranging from flints that are evidently results of natural causes to flints that are clearly artifacts. The first and earliest stage, of course, could leave behind it no definite record and must in the present state of our knowledge rest on hypothesis. II PALEOLITHIC MAN With the deliberate manufacture of implements from flint nodules, we enter the beginning of Paleolithic time and from here on our way is relatively clear. The successive stages of the Paleolithic were of great length but are each characterized by some improvement in the manufacture of tools. During long ages man was merely a tool making and tool using animal and, after all is said, that is about as good a definition as we can find to-day for the primate we call human. The Paleolithic Period or Old Stone Age lasted from the somewhat indefinite termination of the Eolithic, some 150,000 years ago, to the Neolithic or New Stone Age, which began about 7000 B. C. The Paleolithic falls naturally into three great subdivisions. The Lower Paleolithic includes the whole of the last interglacial stage with the subdivisions of the Pre-Chellean, Chellean and Acheulean; the Middle Paleolithic covers the whole of the last glaciation and is co-extensive with the Mousterian Period and the dominance of the Neanderthal species of man.[1] The Upper Paleolithic embraces all the postglacial stages down to the Neolithic and includes the subdivisions of the Aurignacian, Solutrean, Magdalenian and Azilian. During the entire Upper Paleolithic, except the short closing phase, the Cro-Magnon race flourished. Footnote 1: The Middle Paleolithic Period is suggested here for the first time.—EDITOR’S NOTE. It is not until after the third severe period of great cold, known as the Riss glaciation, nor until we enter, some 150,000 years ago, the third and last interglacial stage of temperate climate, known as the Riss-Würm, that we find a definite and ascending series of culture. The Pre-Chellean, Chellean and Acheulean divisions of the Lower Paleolithic occupied the whole of this warm or rather temperate interglacial phase, which lasted nearly 100,000 years.