born of partial isolation and a varied combination of environment.  The larger eastern half of the continent embraced in the plains of Poland and Russia shows monotony in every aspect of human life.  This comes out anthropologically in the striking similarity of head-form found everywhere north and east of the Carpathian Mountains, except in the secluded districts of Lithuania and Crimea, which shelter remnants of distinct races.  Over all this vast territory the range of cephalic variation is only five units or one-third that in the restricted but diversified territory of western Europe.  Italy, only one-eighteenth the size of European Russia, has a range of fifteen units, reflecting in the variety of its human types the diversity of its environment.[1035]

[Sidenote:  Conditions for fusion in plains.]

In the plains geography makes for fusion.  Russia shows this marked homogeneity, despite a motley collection of race ingredients which have entered into the make-up of the Russian people.  Without boundary or barrier, the country has stood wide open to invasion; but the intruders found no secluded corners where they could entrench themselves and preserve their national individuality.[1036] They dropped into a vast melting-pot, which has succeeded in amalgamating the most diverse elements.  The long-drawn Baltic-North Sea plain of Europe shows the same power to fuse.  Here is found a prevailing blond, long-headed stock from the Gulf of Finland to the Somme River in France.[1037] Yet this natural boulevard has been a passway for races.  Prehistoric evidences show that the dark, broad-headed Celtic folk once overspread this plain east to the Weser;[1038] it still tends to trickle down from the southern uplands into the Baltic lowland, and modify the Teutonic type along its southern margin throughout Germany.[1039] The Slavs in historic times reached as far west as the Weser, while the expansion of the Teutons has embraced the whole maritime plain from Brittany to the Finnish Gulf.  Here it is difficult to draw an ethnic boundary on the basis of physical differences.  The eastern Prussians are Slavonized Teutons, and the adjacent Poles seem to be Teutonized Slavs, while the purest type of Letto-Lithuanian at the eastern corner of the Baltic coast approximates closely to the Anglo-Saxon type which sprang from the western corner.[1040] A similar amalgamation of races and peoples has taken place in the lowlands of England and Scotland, while diversity still lingers in the highlands.  In the Lowlands of Scotland, Picts in small numbers, Britons, Scots from Ireland, Angles, Frisians, Northmen and Danes have all been blended and assimilated in habits, customs and speech.[1041]

[Sidenote:  Retardation due to monotonous environment.]