By the term "bulbous dome" we understand a pointed dome which swells, so as to overhand the drum below. Bulbous domes have appearedin various areas at different periods. Their' form cannot be explainedconvincingly by purely technical developments(l). Neither are hemis-pherical domes transformed into bulbous domes merely by the evolution of styles.

There are no remaining bulbous domes which clarify the problemof the origin of this form. Therefore, every attempt to trace this origin must resort to theories. In the following paper, an attempt will be made to fill the historical gaps through the examination of undercurrents and through conclusions drawn from extant monuments of later origin which have retained traits of earlier stages of the devel-opment. A history of art "in strata," rather than an evolutionist wayof thinking, holds out a fair chance of a satisfactory result, if theproblem in question involves several countries and periods. For alogical transformation of styles, like that of the.Renaissance into the Baroque, so keely analyzed by Wilfflin, presupposes an unbrokensuccession of forms. Such a succession, however, can take place onlyin a limited area and a limited time, for no culture circle remainsstable forever. Political and military events change boundaries; revolutions and economic developments change the social order; mass migrations and persecutions change the ethnical structure of the society; and personal or intellectual contacts introduce foreign influ-ences into an established- civilization. Not all strata of the art ofan area which is affected by one or by several of these changes aretransformed in the same degree. Folk art and other substrata have pre-served ancient forms over an almost unlimited period. Given favorablesocial or historic conditions, latent undercurrents in art can rise tothe surface and stimulate new developments. Sometimes such a development takes a circuitous path. The Renaissance and other revivals inart result from the rise of obscure undercurrents into the manifestlevel of an advanced art.