Dr Sera supports his argument by an appeal to existing conditions: he claims demonstration of the association (regarded by him as one of cause and effect) between arctic latitudes or climate on the one hand, and the flattening of the cranial vault on the other. Passing lightly over the Eskimo, although they stand in glaring contradiction to his view, he instances above all the Ostiak tribe of hyperborean Asia. The platycephalic character has a geographical distribution. Thus the skull is well arched in Northern Australia, but towards the south, in South Australia and Tasmania, the aboriginal skull is much less arched. It is thus shewn to become more distinctly platycephalic towards the antarctic regions, or at least in the regions of the Australian Continent considered by Professor Penck to have been glaciated. So too among the Bush natives of South Africa as contrasted with less southern types. The demonstration of a latitudinal distribution in the New World is complicated by the presence of the great Cordillera of the Rocky Mountains and Andes. Great altitudes are held by Dr Sera to possess close analogy with arctic or antarctic latitudes. Therefore the presence of flat heads (artificial deformation being excluded) in equatorial Venezuela is not surprising. It is felt that the foregoing statement, though made with every endeavour to secure accuracy, gives but an imperfect idea of the extent of Dr Sera's work. Yet in this place, nothing beyond the briefest summary is permissible. By way of criticism, it cannot be too strongly urged that the Eskimo provide a head-form exactly the converse of that postulated by Dr Sera as the outcome of 'glacial conditions.' Not that Dr Sera ignores this difficulty, but he brushes it aside with treatment which is inadequate. Moreover, the presence of the Aurignac man with a comparatively well-arched skull, following him of the Mousterian period, is also a difficulty. For the climate did not become suddenly cold at the end of the Mousterian period, and so far as evidence of arctic human surroundings goes, the fauna did not become less arctic in the Aurignac phase. _Conclusion._ In section A of this chapter, an outline was given of the mode in which the evolution of the human form appears to be traceable backwards through the Neanderthal type to still earlier stages in which the human characters are so elementary as to be recognisable only with difficulty.