 In particular, according to Wilkins, Waddington felt that the Neo-Darwinians badly neglected the phenomenon of extensive gene interactions and that the 'randomness' of mutational effects, posited in the theory, was false.Even though Waddington became critical of the neo-Darwinian synthetic theory of evolution, he still described himself as a Darwinian, and called for an extended evolutionary synthesis based on his research.Waddington did not deny the threshold-based conventional genetic interpretation of his experiments, but regarded it "as a told to the children version of what I wished to say" and considered the debate to be about "mode of expression, rather than of substance".