 There is a discontinuity between the appearance of the offspring; de Vries coined the term allele for a variant form of an inherited characteristic.This reinforced a major division of thought, already present in the 1890s, between gradualists who followed Darwin, and saltationists such as Bateson.The two schools were the Mendelians, such as Bateson and de Vries, who favoured mutationism, evolution driven by mutation, based on genes whose alleles segregated discretely like Mendel's peas; and the biometric school, led by Karl Pearson and Walter Weldon.