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
Rudolf Leuckart of Parasitology). Leuckart is credited with splitting George Cuvier's "Radiata" into two phyla: Coelenterata and Echinodermata. As a scientist, his provided excellent descriptions of morphologic details giving credence to the idea that zoological evolution can be learned through its anatomical changes. Between 1877 and 1892, he developed a series of zoological wall charts that have been used worldwide as teaching aids. In the field of entomology, he conducted investigations into the micropyle and fertilization of insect eggs, the reproduction and development involving members of Pupipara, parthenogenesis among insects, and studies on the anatomy and life history of the honeybee. A