Round 7: The Darbishire Affair (1902–1905)

An important episode in the biometry-saltationismbiometry-saltationism debate debate occurred when, in 1901, WeldonWeldon, Walter Frank Raphael urged his student DarbishireDarbishire, Arthur D. to conduct crossing experiments with albino and Japanese waltzing mice. In his first report, DarbishireDarbishire, Arthur D. found variability in the coat color of F1 hybrids and interpreted these as evidence against MendelismMendelism. In his second report, DarbishireDarbishire, Arthur D. reported results on coat color that were compatible with the Mendelian hypothesis when F1 mice were intercrossed and backcrossed with parental albinos. However, he rejected a Mendelian explanation for eye color. In his fourth report, DarbishireDarbishire, Arthur D. performed a key experiment involving crosses between two heterozygotes (in F2) in three sets of experiments such that the parents (F1) in each set had a different number of recessive alleles. He reported that as the number of recessive alleles in F1 increased, the proportion of recessive trait (albinism) in F3 increased, as predicted by the ancestral lawancestral law. However, CastleCastle, William Ernest pointed out a serious error in Darbishire’sDarbishire, Arthur D. key experiment: the F2 crosses did not all involve a pair of heterozygotes, as DarbishireDarbishire, Arthur D. had thought. When Darbishire’sDarbishire, Arthur D. error is accounted for, his results are in accordance with Mendelian predictions. In his next paper, DarbishireDarbishire, Arthur D. acknowledged that his results did not contradict MendelismMendelism.