Such is the accumulation of facts, already very considerable, which M. Hamy and I have consulted in arranging the first part of our _Crania-Ethnica_. The importance of the skull in anthropology is well known. It is of itself sufficient to furnish the principal elements of the distinction of human races. The study and comparison of quaternary skulls enables us, therefore, to form a tolerably definite conception of these ancient populations, of the principal relations and most striking differences which, from this period, have distinguished human groups. The examination of the bones of the trunk and limbs tends, moreover, to confirm the results furnished by that of the skull. Thus we feel ourselves justified in expressing the hope that the future, by completing our work in many respects, by modifying it perhaps in others, and by filling up gaps in it, will at least confirm the essential conclusions. It is evident that I here speak in M. Hamy’s name as well as my own. The truth is, that what I am about to say on the subject of fossil man is almost the summary, not only of our book, but of many other general studies and of many discussions. It belongs, in fact, as much to my coadjutor as to myself. II. Let us, in the first place, briefly describe the climate in which the fossil human races lived. The quaternary or glacial period imposed severe conditions of existence on man. What then existed of Europe was surrounded on all sides by the sea, and was subject to all the consequences of an insular climate, that is to say; it was very damp, and moderately uniform in temperature, but chilled, to a great extent at least, by the Polar ice which extended even into France. The heavy rains, frequent in all seasons, took the form of falls of snow upon the high lands, and supported vast glaciers, the traces of which may still be seen in all our mountain chains. Immense water-courses hollowed out valleys in some parts, and deposited thick beds of alluvium in others. This vexed and watery land supported a fauna comprising, besides existing species, others which have partly disappeared, partly emigrated to distant countries. Thus, on the one hand, there were the mammoth (_elephas primigenius_), the woolly rhinoceros (_rhinoceros tichorhinus_), the gigantic Irish elk (_megaceros hibernicus_), the cave bear (_ursus spelæus_), the cave hyæna (_hyæna spelæa_), the cave tiger (_felis spelæa_), the horse (_equus caballus_); on the other hand, the reindeer (_cervus tarandus_), the elk (_cervus alces_), the musk-ox (_ovibos moschatus_), the aurochs (_bison europæus_), the hippopotamus (_hippopotamus amphibius_), and the lion (_felis leo spelæa_).