Jovan Hadži theories of animal evolution. He devised a system of classification in which he divided the animal kingdom into six phyla: Protozoa, Parazoa, "Ameria" (animals with no segments), "Oligomeria" (animals with few segments), "Polymeria" (animals with many segments) and Chordata. His choice of characters important for classification was generally discredited by his contemporaries, and the system was never accepted by zoologists. However, due to its simplicity, the system was widely used in science education in former Yugoslavia. His other major theory was that of the origin of metazoa - he developed an existing hypothesis stating that the first multicellular animals resembling
Lattice of subgroups finite lattice is isomorphic to a sublattice of the subgroup lattice of some finite group . Subgroups with certain properties form lattices, but other properties do not. However, neither finite subgroups nor torsion subgroups form a lattice: for instance, the free product formula_3 is generated by two torsion elements, but is infinite and contains elements of infinite order. The fact that normal subgroups form a modular lattice is a particular case of a more general result, namely that in any Maltsev variety (of which groups are an example), the lattice of congruences is modular . Lattice theoretic information about the