William David McElroy died on Feb. 17 at Scripps Memorial Hospital in La Jolla, Calif., of complications resulting from lung cancer. He was 82. Born in 1917 in Rogers, Texas, McElroy walked barefoot to school, went to Stanford University on a football scholarship and rose to become chairman of the Hopkins Biology Department, director of the National Science Foundation and chancellor of the University of California at San Diego.

He came to Hopkins in 1948, with a doctorate from Princeton, where he had been introduced to the fascination of bioluminescence by the late E. Newton Harvey, the father of American studies of this previously esoteric subject. McElroy began his own program on the biochemical basis of firefly bioluminescence, which was to occupy his entire research career. Foreseeing the major role that biochemistry and molecular biology would play in biology, he almost single-handedly changed the direction of the department from classical embryology to this new field. He was appointed chairman of the department in 1956, a position he held until 1969, and, with a major donation to the university from the Pratt Foundation, he established within the Biology Department the McCullom-Pratt Institute to concentrate efforts in this new field of biochemistry.

At a time when some still looked askance, he was one of the first chairmen at a major university to establish a single policy for hiring university professors: only the best, regardless of their ethnic origins. Under his leadership the Biology Department at Hopkins soon became one of the top-rated departments in the country, despite its relatively small faculty of slightly more than 20 members.

McElroy's own bioluminescence research blossomed as he gathered around him a small group of dedicated chemists, biochemists and physicists. The work eventually culminated in the discovery of the role of ATP in the firefly reaction; the elucidation of the biochemical mechanisms for control and emission of light emission by bioluminescent organisms; new instrumentation for the measurement of bioluminescence in the laboratory and in nature; the study of the ecology of bioluminescent bays in Jamaica and Puerto Rico; the isolation of the firefly luciferase enzyme and, in collaboration with his second wife, the late Marlene DeLuca, the isolation of its gene; and finally in the application of bioluminescence as a tool in analytical biochemistry and as a probe for the incorporation of genes into organisms.

His vigorous leadership was again evident during his three-year tenure as director of NSF and during eight years as chancellor of the University of California at San Diego, where under his guidance the research budget grew from $40 million to more than $120 million.

McElroy was a member of the National Academy of Sciences, served on a number of national scientific boards and received 12 honorary degrees from universities in the United States and abroad.