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
Bacterial phyla prevents it to be validated, such as where the only evidence is DNA sequence data, even if the whole genome has been sequenced. When the species are members of a whole phylum it is called a candidate division (or candidate phylum) and in 2003 there were 26 candidate phyla out of 52. A candidate phylum was defined by Hugenholtz and Pace in 1998, as a set of 16S ribosomal RNA sequences with less than 85% similarity to already-described phyla. More recently an even lower threshold of 75% was proposed. Three candidate phyla were known before 1998, prior to the 85%