987.080 Vertexial Spheres Form Rigids

987.081 In addition to the four vertexial spheres of the precleavage primitive tetrahedron, we find after the cleavage all six vertexial unit-radius-vertex spheres of the octahedron also occurring in the outermost structure of the nonnucleated system. Neither the primitive tetrahedron nor the primitive octahedron have internal or nuclear unit-radi us-vertex spheres. For an illustration of these structural “rigids” see Fig. 987.081.