From Wikipedia, History of Evolutionary thought.
Expanding Darwin's theory: the Mendelian-biometrician debates
While the scientific community generally accepted that evolution had occurred, many disagreed that it had happened under the conditions or mechanisms provided by Darwin. In the years immediately following Darwin's death, evolutionary thought fractured into a number of interpretations, neo-Darwinism, neo-Larmarckism, orthogenesis, Mendelism, the biometric approach, and mutation theory. Eventually this boiled down to a debate between two camps. The Mendelians, advocating discrete variation, were led by William Bateson (who coined the word genetics) and Hugo de Vries (who coined the word mutation). Their opponents were the biometricians, advocating continuous variation; their leaders Karl Pearson and Walter Frank Raphael Weldon, following in the tradition of Francis Galton.
An important issue in the debate between the Mendelians and the biometricians was the nature of variation in species. Darwin and Wallace believed that small variations were more important than large ones, since small variations hewed closely to an already-proven model. The biometricians agreed with this position, while the Mendelians insisted that discontinuous species were unlikely to arise from a continuous process of change. While the immediate issue of speciation was resolved in large part by the clear definition of a species as a reproductively isolated population, the rate of evolution would arise again as a point of contention in the late 20th century with the proposal of punctuated equilibrium. Most other questions resolving variation were resolved with the recognition that the size of a genotypic change did not always correspond with the size of the resulting phenotypic change.
