Networklike structures are observed in various materials and nature. The networklike structures in viscoelastic phase separation of polymer mixtures have been explained by a model with a couple of hydrodynamic equations. On the other hand, the large-scale structure of the universe has been explained by a multi-dimensional extension of the Burgers equation. The networklike structures of the two very different systems have some morphological similarities. To see origins of the similarities and differences the Burgers equation is derived from the model of the polymer mixtures using several approximations. The meaning of the approximations is discussed in connection with the morphology. (c) 2012 Elsevier B.V. All rights reserved.