Eutectic Al-5.6 wt% Ni was directionally solidified with and without magnetic stirring, and the eutectic rod-like microstructures were characterized. Rod-like eutectics are generally described by rod distance and number of the nearest neighbors. During the examinations, a previously unknown phenomenon was found. In case of intensive melt flow, the spacings between rods show a significant periodic inhomogeneity. This inhomogeneity can be explained by the formation of vortices in the melt at the solidification front.