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 determination 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: 811-819, 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 



