More essential than this seems to be the possession of a perfect technique, which involves great accuracy and steadiness of movement. These in themselves must lead necessarily to regular lines. When the uncertain wobbling of the cutting tool is eliminated, smooth curves will result. When the potter turns the pot he is making and his movements are quite regular the pot will be circular. Perfectly controlled coiling of basketry or of wire will lead to the formation of equidistant spirals. [Illustration: Fig. 21. Face painting, Tierra del Fuego.] A number of other characteristic features may be observed in the art of all times and all peoples. One of these is symmetry. Symmetrical forms are found even in the simplest forms of decorative art. The tribes of Tierra del Fuego[24] decorate their faces and bodies with designs, many of which are symmetrical. Vertical lines on both sides of the body or a series of symmetrically arranged dots running from ear to ear across the nose are of this kind (fig. 21). They also use symmetrically decorated boards with which they adorn their huts (see fig. 7, page 23). The Andaman Islanders like to decorate their bodies with symmetrical patterns (Plate II). Many of the designs of the Australians are symmetrical (fig. 22) and in paleolithic painting geometrical forms occur that exhibit bilateral symmetry (fig. 23). In a few cases the elements arranged symmetrically are so complex that the symmetry can have been attained only by careful planning. Examples of this kind are necklaces of Indians in British Columbia in which we find as many as eighteen beads of different colors irregularly arranged, but repeated in equal order right and left.[25] [24] W. Koppers, Unter Feuerland-Indianern, p. 48, Pl. 7. [25] See Gladys A. Reichard, American Anthropologist, N. S., Vol. 24 (1922) p. 191. [Illustration: PLATE II. Andaman Islander.] The causes that have led to the widespread use of symmetrical forms are difficult to understand. Symmetrical motions of the arms and hands are physiologically determined. The right and left are apt to move symmetrically and the motions of the same arm or of both arms are often performed rhythmically and symmetrically from right to left and from left to right. I am inclined to consider this condition as one of the fundamental determinants, in importance equal to the view of the symmetry of the human body and of that of animals; not that the designs are made by right and left hand, rather that the sensation of the motions of right and left lead to the feeling of symmetry. [Illustration: Fig. 22. Australian shields.] [Illustration: Fig. 23. Paleolithic paintings.] In by far the greatest number of cases symmetrical arrangements are to the right and left of a vertical axis, much more rarely above and below a horizontal one.