process, but we may suspect that the causes underlying gradation lie outside of consciously directed activities.
1. Teit, 1900. I; 1909. I; 1906. I.
2. Spinden, 1908. I.
3. Lowie, 1909. I.
4. Lewis, 1906. I.
5. Kroeber, 1904. I.
6. Boas, 1906. I; Krause, 1885. I.
7. Boas, 1907. I.
8. Dall, 1877, I.
9. Solberg, 1907. I.
10. Boas, 1907. I.
11. Stefánsson, 1914. I.
12. Pike, 1892. I, chapter 4; Grant, 1902. I.
13. Morice, 1890. I; 1895. I; 1906. I.
14. Hearne, 1795. I.
15. Mackenzie, A., 1902. I.
16. Hearne, 1795. I.
17. Jones, W., 1906. I; Skinner, 1913. I; 1915. I; Hoffman, 1897. I.
18. Morgan, 1904. I.
19. MacCauley, 1887. I.
20. Swanton, 1911. I; Speck, 1909. I; Mooney, 1900. I.
21. Holmes, 1886. I.
22. Goddard, 1913. I; Hough, 1915. I.
23. Kroeber, 1917. I.
24. Hough, 1915. I.
25. Russell, 1908. I.
26. Tozzer, 1907. I.
27. Joyce, 1914. I; Spinden, 1917. I.
28. Bandelier, 1878. I; 1879. I.
29. Joyce, 1912. I.
30. Markham, 1910. I.
31. Dobrizhoffer, 1822. I.
32. Church, 1912. I, p. 300.
33. Whiffen, 1915. I.
34. Im Thurn, 1883. I.
35. Maximilian, 1820. I; Von den Steinen, 1897. I.
36. Church, 1912. I.
37. Bowman, 1916. I.
38. Fewkes, 1902. I.
