Bogart in chemistry; T. H. Morgan, E. B. Wilson, and Calkins in zoology; and Carlton Curtiss in botany. Student associates were Michael Heidelberger, George Scatchard, Herman Muller, A. H. Sturtevant, and Calvin Bridges—quite a galaxy of future scientists.

John's doctoral studies were supervised by Professor John M. Nelson, a man of broad interests. The subject of John's thesis was "The Essentiality of Phosphorus in Starch." In 1915 the award of his Ph.D. was accompanied by the W. Bayard Cutting Travelling Fellowship, but the turmoil in Europe and Jacques Loeb's acceptance of John to work at the Rockefeller Institute for Medical Research led him to forego the fellowship. This was an important decision because John retained an association with the Rockefeller Institute (later University) for 70 years.

On June 26, 1917, John Northrop and Louise Walker were married. Louise was a graduate of Barnard College, where she was elected president of her freshman class. She earned a master's degree in zoology at Columbia University and was working on her doctorate. This work took her to Woods Hole in the summer for studies at the Marine Biological Laboratory. It was there she met John. They lived in Mt. Vernon, New York until about 1925, when John, who strongly disliked commuting into New York City, became interested in offers from other institutions. He was persuaded by W. J. V. Osterhout to try working at the Rockefeller Institute's Animal Pathology Laboratory outside of Princeton, New Jersey, where he could walk to the laboratories. John's Princeton house looked out on Lake Carnegie, a great improvement over conditions in New York. He also became a member of several sporting clubs in New Jersey.

Mrs. Northrop gave up her professional studies and de-