Isothermal crystallization of a low- molecular- weight polyethylene oxide) from both isotropic and structured melts at low undercoolings has been investigated via simultaneous measurements of small angle and wide angle X ray scatterings (SAXS and WAXS). An evolution of the SAXS pattern was observed prior to the appearance of crystallinity determined through WAXS. A possible interpretation of the experimental observation is provisted through the nucleation concept: primary nuclei exist in the melt due to localized large- amplitude density fluctuations in the isotropic medium.