Mayr has stated:
"Mendelian genetics did not seem to support the possibility of gradual adaptive changes, which Darwinism required. Geneticists favored the idea that species evolved suddenly through massive mutations. 'But we naturalists realized that species develop gradually. The only evolutionary theory that was gradual was Lamarckism, and so to oppose the mutationists, we all became Lamarckians."
John Rennie, "Profile: Ernst Mayr - Darwin's Current Bulldog," Scientific American, Aug. 1994, pp. 24-25
A who's who of evolutionists
Darwin and the search for an evolutionary mechanism