The essential feature of the operational viewpoint is that an object 

 or phenomenon under experimental investigation cannot usefully be 

 defined in terms of assumed properties beyond experimental determi- 

 nation but rather must be defined in terms of the actual operations that 

 may be applied in dealing with it. . . . 



What is a gene in operational terms? 



L. J. Stadler, "The Gene," 

 Science, 120:81 1-819, 1954 



Must we geneticists become bacteriologists, physiological chemists 

 and physicists, simultaneously with being zoologists and botanists? 

 Let us hope so. 



H. J. Muller, "Variation Due to Change in the Individual Gene," 



American Naturalist, 56:32-50, 1922 



