We approached this subject by the study of a few art forms. We compared a number of art styles that make use of the spiral and found in each characteristic traits, as well regarding the form of the spiral as in the handling of the decorative field. In the same way we observed that in the art of the North American Indians the same kind of triangles and rectangles are used by all the tribes, but that there exist typical differences in the treatment of the decorative field. The problem was carried through in some detail by means of a study of the decorative art of the North Pacific coast which is highly symbolic in character. This example taught us an additional point, namely that in symbolic art the selection of symbols is of decisive importance in defining the style and that the arrangement of the symbols is subject to the same formal treatment of the decorative field which control the arrangement of geometrical motives. On the basis of this study we conclude that the particular types of geometrical motives that enter into the representative form, as well as the treatment of the decorative field determine the character of the design and that the degree of realism depends upon the relative importance of the geometric and representative elements. When the purely decorative tendency prevails we have essentially geometrical, highly conventionalized forms, when the idea of representation prevails, we have, on the contrary, more realistic forms. In every case, however, the formal element that characterizes the style, is older than the particular type of representation. This does not signify that early representations do not occur, it means that the method of representation was always controlled by formal elements of distinctive origin. The pattern of artistic expression that emerges from a long, cumulative process determined by a multiplicity of causes fashions the form of the art work. We recognize the permanence of pattern in those cases in which a useful form that has lost its function persists as a decorative element; in the imitation in new materials of natural forms used at one time as utensils, and in the transfer of forms from one technique to another. The fixity of the pattern does not permit the artist to apply natural forms unmodified to decorative purposes. His imagination is limited by the pattern. In cases of greater freedom the representative value may not be seriously encroached upon. Such is the case for instance, with the oriental palmetto and the ear ornaments of the Marquesas Islands, on which in olden times two deities were represented, back to back, while nowadays two girls in a swing are carved, in exactly the same spacial arrangement. When the pattern is highly formal and not adapted to representation, an apparent geometrization may be the result. The distinction between these two aspects appears clearly in those cases in which pictography and symbolic geometric art appear side by side.