The isotropy problem. If the plane is built up from square hodons, as in the paragraph above, then the hodons are arranged in such a way that every hodon touches four other hodons, i.e., the plane can be modeled as a square grid, then it is obvious that there are preferred directions, in this case, there will be two preferred directions. However if instead of squares, hexagons are taken as hodons, then there are three preferred directions. Thus no matter what the shape is of the hodon, there will be preferred directions and this implies that the space is anisotropic. Note that these cases are nothing but special instances of the general approach of Tobias Fritz, discussed above. However, for physical applications one would like to have isotropy (or at least as close as possible).