The Arabian fret differs in the use of the oblique line together with the right-angled key, obtaining a wonderful degree of complexity and richness. The Celtic fret is chiefly a diagonal one, but the recurrent angle is rounded to a curve. Chinese and Japanese frets are usually right-angled, and are used in great profusion, often in a secondary field or background. [Illustration: WALL MOSAIC OF COLOURED MARBLES] The Japanese key or “_Fret diaper_” is used in the greatest profusion; it is used alike on silks and brocades, damascened in metal, in cloisonné enamel and in lacquered work, and is frequently arranged in irregular shaped compartments or medallions. The Greek continuous fret border is rarely used by the Japanese, who generally use the disconnected or irregular fret. A similar irregular fret border was used by the Peruvians (plate 41), by the Mexicans, and by the natives of Polynesia. The Assyrian and Byzantine guilloche is but a curved fret, but additional interest is given by the introduction of radiating forms in the principal interstices of the fret (fig. 5, plate 11.) [Illustration: Plate 43. ] CONTINUITY OF STYLE in architecture and ornament has always been influenced by tradition, racial influence, and the myths and religious beliefs of the people, and it developed with the progress of the nation, often culminating in some great epoch. Frequently the continuity was carried on by some contemporary or succeeding race, modified by different conditions and environments, yet still retaining the style in its general characteristics, or, this thread of continuity was occasionally lost for a time, only to spring into new life, endowed with fresh vitality and beauty, culminating again in splendour. Then fresh religious ideas and conditions engrafted their symbolism and traditions upon the style, thus forming a new period in the history of art. Ornament is the expression of the people or of the priestcraft, and in its primitive state was used symbolically. The ornament of Polynesia and Melanesia probably shows this primitive state of ornamentation. Isolated as these islanders were from the influence of Eastern or Western art, and with but little communication among the various islands, the ornamental art of these people has its own traditions and characteristics, each province or group of islands showing different ideas and details in proportion to its culture or state of civilization, New Zealand showing the highest development and Australia the lowest, while with the Marquesans the ornament is almost pure picture writings. The illustration of the beautiful paddle in the Heape collection, with its geometric ornamentation, shows the continuity and ornamental development of the representation of the human figure, which was originally chosen by the priesthood for its significance or divinity.