His work with sea urchins showed that it was necessary to have all chromosomes present in order for proper development of the embryo to take place. This discovery was an important part of the Boveri-Sutton chromosome theory. His other significant discovery was the centrosome (1888), which he described as the "especial organ of cell division". Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode "Parascaris".