[213] E.F. im Thurn, Among the Indians of Guiana, pp. 167-171, 202-207.
London, 1883.

[214] W.Z. Ripley, Races of Europe, p. 237. New York, 1899.

[215] _Ibid._, p. 469.

[216] H. Barth, Human Society in Northern Central Africa, _Journal of
the Royal Geog. Society_, Vol. XXX, p. 116. London, 1860.

[217] Moritz Wagner, _Die Entstehung der Arten durch räumliche
Sonderung_. Basel, 1889.

[218] H.W. Conn, The Method of Evolution, pp. 282-295. New York, 1900.

[219] McGee and Thomas, Prehistoric North America, pp. 418, 424, Vol.
XIX of _History of North America_. Philadelphia, 1905.

[220] Ratzel, History of Mankind, Vol. II, pp. 280-283. London,
1896-1898.

[221] Cæsar, _Bella Gallico_, Book II, chap. IV.

[222] H. Helmolt, History of the World, Vol. VI, pp. 32-33. New York,
1902-1906.

[223] Hodgkin, Italy and Her Invaders, Vol. I, Part I, pp. 75, 81, 82.
Oxford, 1895.