The _chef-d'œuvre_ of the late Acheulean industry is the Levallois flake, first found at Levallois-Perret, near Paris, which de Mortillet believed to be fashioned out of a divided coup de poing with a flat under-side, but which may have been evolved from the very large primitive flakes of Pre-Chellean date. These flakes date back earlier than the Chellean coup de poing but continued in use after its invention and may have been greatly perfected into the Levallois type. This type of 'couteau' is a large, wide, thin flake of fairly symmetrical shape, with a flat back formed by the original smooth surface of the flake. These implements are pointed, oval, or sharply rectangular in form and present the most characteristic tool of the closing stage of the Acheulean industry. It is most interesting at this point to observe the two modes of evolution which seem to pervade all nature: first, the gradual perfection and modification in size and proportion of a certain older form; second, the sudden change or mutation into a new form, which in turn enters the stage of gradual improvement. The late Acheulean is seen to present the climax of a gradual and unbroken development from the early Chellean industries and ideas; and to our mind this is strongly suggestive of a corresponding evolution of manual skill and mental development in the workmen themselves, who may have been partly of Pre-Neanderthaloid race. The next industrial stage, namely, the Mousterian, which certainly presents the closing workmanship of the Neanderthal race, shows a marked retrogression of technique in contrast to the steady progression which we have observed up to this time. We have, in fact, witnessed a number of successive stages of progression, which are to be followed in the Mousterian by a stage of retrogression. Such a retrogression in industrial development may for certain known or unknown reasons occur in the same race. It is a noteworthy parallel that in the Upper Palæolithic, where the Solutrean culture represents the climax and perfection of flint working, the succeeding Magdalenian shows marked retrogression in the technique of flint retouch. THE KRAPINA NEANDERTHALOIDS