A series of electron diffraction patterns displaying continuous transformation of the octagonal quasicrystal into the β-Mn type structure were obtained in a rapidly quenched Cr-Ni-Si alloy. This transformation is interpreted in terms of a gradual introduction of short-range periodical translational order to the octagonal quasicrystal. The presence of nuclei of the β-Mn type structure in the octagonal quasicrystal and the short-range periodical translational order in it have been observed by means of high-resolution electron microscopy.