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 Despite these lineages not being officially recognised (due to the ever-increasing number of sequences belonging to undescribed phyla) the ARB-Silva database lists 67 phyla, including 37 candidate phyla (Acetothermia, Aerophobetes, Aminicenantes, aquifer1, aquifer2, Atribacteria, Calescamantes, CKC4, Cloacimonetes, GAL08, GOUTA4, Gracilibacteria, Fermentibacteria (Hyd24-12), Hydrogenedentes, JL-ETNP-Z39, Kazan-3B-09, Latescibacteria, LCP-89, LD1-PA38, Marinimicrobia, Microgenomates, OC31, Omnitrophica, Parcubacteria, PAUC34f, RsaHF231, S2R-29, Saccharibacteria, SBYG-2791, SHA-109, SM2F11, SR1, TA06, TM6, WCHB1-60, WD272, and WS6), the Ribosomal Database Project 10, lists 49 phyla, including 20 candidate phyla (Acetothermia, Aminicenantes, Atribacteria, BRC1, Calescamantes, Cloacimonetes, Hydrogenedentes, Ignavibacteriae, Latescibacteria, Marinimicrobia, Microgenomates, Nitrospinae, Omnitrophica, Parcubacteria, Poribacteria, SR1, Saccharibacteria, WPS-1, WPS-2, and ZB3),