In 1953–1954, he was a research assistant at Princeton University; 1954–1956, research associate at Princeton (while being employed by RCA); 1956–1960, Assistant Professor of Zoology at Harvard University; 1960–1963, Associate Professor of Anatomy at Cornell University Medical College; 1963–2011, Professor of Biology at Georgetown University; and 2011–2016, Professor Emeritus at Georgetown.