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
Subgroups of cyclic groups by "e" if and only if "e" is a divisor of "d". Divisibility lattices are distributive lattices, and therefore so are the lattices of subgroups of cyclic groups. This provides another alternative characterization of the finite cyclic groups: they are exactly the finite groups whose lattices of subgroups are distributive. More generally, a finitely generated group is cyclic if and only if its lattice of subgroups is distributive and an arbitrary group is locally cyclic if and only its lattice of subgroups is distributive. The additive group of the rational numbers provides an example of a group that is locally