Upon returning to Cambridge in 1882, he was appointed university lecturer in
Invertebrate Morphology. Weldon's work was centred on the development of a fuller understanding of marine biological phenomena and selective death rates of these organisms. In 1889 Weldon succeeded Lankester in the Jodrell Chair of Zoology at
University College London, and as curator of what is now the
Grant Museum of Zoology, and was elected to the
Royal Society in 1890. Royal Society records show his election supporters included the great zoologists of the day:
Huxley, Lankester,
Poulton,
Newton,
Flower,
Romanes and others. His interests were changing from morphology to problems in variation and organic correlation. He began using the statistical techniques that
Francis Galton had developed for he had come to the view that "the problem of animal evolution is essentially a statistical problem." Weldon began working with his University College colleague, the mathematician
Karl Pearson. Their partnership was very important to both men and survived Weldon's move to the
Linacre Chair of Zoology at
Oxford University in 1899. In the years of their collaboration Pearson laid the foundations of modern statistics. Magnello emphasises this side of Weldon's career. In 1900 he took the DSc degree and as Linacre Professor he also held a Fellowship at
Merton College, Oxford. Weldon was one of the first scientists to provide evidence of stabilizing and directional
selection in natural populations. By 1893 a Royal Society Committee included Weldon,
Galton and
Karl Pearson 'For the Purpose of conducting Statistical Enquiry into the Variability of Organisms'. In an 1894 paper
Some remarks on variation in plants and animals arising from the work of the Royal Society Committee, Weldon wrote: :"... the questions raised by the Darwinian hypothesis are purely statistical, and the statistical method is the only one at present obvious by which that hypothesis can be experimentally checked." In 1900 the work of
Gregor Mendel was rediscovered and this precipitated a conflict between Weldon and Pearson on the one side and
William Bateson on the other. Bateson, who had been taught by Weldon, took a very strong line against the biometricians. This bitter dispute ranged across substantive issues of the nature of
evolution and methodological issues such as the value of the statistical method.
Will Provine and Gregory Radick give detailed accounts of the controversy. The debate lost much of its intensity with the death of Weldon in 1906, though the general debate between the biometricians and the Mendelians continued until the creation of the
modern evolutionary synthesis in the 1930s. After his death, the
Weldon Memorial Prize was established by the University of Oxford in his honour; it is awarded annually. ==Weldon's dice==