The [peppered-moth] experiments show the effects of predation on the survival of the dark and of the normal forms of the Peppered Moth in a clean environment and in one polluted by smoke. The experiments beautifully demonstrate natural selection--or survival of the fittest--in action, but they do not show evolution in progress, for however the population may alter in their content of light, intermediate or dark forms, all the moths remain from beginning to end Biston Betularia.