 Waddington carried out a similar experiment in 1953, this time inducing the "cross-veinless" phenocopy in "Drosophila" with a heat shock, with 40% of the flies showing the phenotype prior to selection.Again he selected for the phenotype over several generations, applying heat shock each time, and eventually the phenotype appeared even without heat shock.Waddington called the effect he had seen "genetic assimilation".