Photographs of a front view of the two skulls shewn in profile in the frontispiece, taken so as to shew the breadth of the ‘forehead’ or prefrontal area, which is seen to be very much greater in the Greek skull (Fig. 2) than in the Javanese _Pithecanthropus_ (Fig. 1). The prefrontal area is marked out by a black dotted line, the outline of a plane (the prefrontal plane) which is at right angles to the sagittal plane and passes through the meeting point of the frontal with the two parietal bones above; whilst below it passes through the median point called ‘ophryon.’ The plane of the picture is parallel with this prefrontal plane. The white dotted line gives the breadth of the boss-like prefrontal area. It is identical in position with the line _d_ in the side view of the same skulls given in the frontispiece. The black dotted line is identical in position with the line A C in those figures. The two specimens are equally reduced in the photograph. (Original).] [Illustration: FIG. 3. Photographs of eight Eoliths of one and the same shape, namely, with a chipped or worked tooth-like prominence, rendering the flint fit for use as a ‘borer’--photographed of half the actual size (linear measurement) from specimens found near Ightham, Kent, in the high-level gravel--which form part of the Prestwich collection in the Natural History Museum, Cromwell Road, London. Many others of the same shape have been found in the same locality. These and the trinacrial implements photographed in Fig. 4 are far older than the oval and leaf-shaped ‘palæoliths’ of the low-lying gravels of the valleys of the Thames, Somme, and other rivers. (Original).] [Illustration: FIG. 4. Photographs of six Eoliths of the ‘shoulder-of-mutton’ or ‘trinacrial’ type--from the same locality and collection as those shewn in Fig. 3. The photographs are of half the length of the actual specimens. A considerable number of worked flints of this peculiar shape have been found in the same locality. Possibly their shape enabled the primitive men who ‘chipped’ and used them to attach them by thongs to a stick or club. The descriptive term ‘trinacrial’ is suggested by me for these flints in allusion to the form of the island of Sicily which they resemble. (Original).] 9. THE ENLARGED BRAIN.