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
Libbie Hyman masterly integration of information." Declining health did not allow her to finish the entire subject. In it she developed her scientific theory that the Phylum Chordata, including all vertebrates, was evolutionarily related to the apparently very different and very much more primitive Echinodermata, such as starfish. This group is now known as the deuterostomes. Her theory was based upon the morphological data of classical embryology, and has since been confirmed by molecular sequence analysis. In addition to her major project, Hyman extensively revised "A Laboratory Manual for Comparative Vertebrate Anatomy" in 1942 into a textbook as well as laboratory manual;