localities gave frequency distributions closely following the normal or Gaussian curve. In a second paper, ‘On Certain Correlated Variations in Crangon vulgaris,’ published two years later, he calculated the numerical measures of the degree of inter-relation between two organs or characters in the same individual and tabled them for four local races of shrimps. These two papers were the foundation of that branch of zoological study afterwards known by the name of ‘biometrics.’
Meanwhile Weldon had been elected a fellow of the Royal Society in May 1890, and at the end of the year succeeded Prof. (Sir) E. Ray Lankester as Jodrell professor of zoology at University College, London. The tenure of the Jodrell chair (1891–9) was a period of intense activity. A brilliant lecturer and endowed with the power of exciting enthusiasm, Weldon soon attracted a large class, and his association with Professor Karl Pearson, who had been independently drawn towards biometrical studies by Galton's work, led to increased energy in the special line of research which he had initiated. In 1894 Weldon became the secretary of a committee of the Royal Society ‘for conducting statistical inquiries into the measurable characteristics of plants and animals,’ the other members of the committee being F. Galton (chairman), F. Darwin, A. Macalister, R. Meldola, and E. B. Poulton. The committee undertook an ambitious programme which was not fully realised; its most important result was the investigation, undertaken by Weldon and presented to the Royal Society in Nov. 1894 under the title ‘An Attempt to measure the Death Rate due to the Selective Destruction of Carcinus mœnas.’ To this were appended ‘Some Remarks on Variation in Animals and Plants,’ in which Weldon stated that ‘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.’ The report showed that an apparently purposeless character in the shore-crabs of Plymouth Sound is correlated with a selective death rate, and it evoked a storm of criticism, which led Weldon to continue his experiments, with the result that he demonstrated that the character in question was connected with the efficient filtration of the water entering the gill-chamber, a matter of great importance in Plymouth Sound, whose waters are rendered turbid by china clay and the sewage discharged into the harbour. These experiments, which were conducted on a large scale and were extremely laborious, formed the subject of Weldon's presidential address to the zoological section of the British Association in 1898.
In addition to these and other exacting lines of research and the ordinary duties of his chair, Weldon took a leading part in the work of the association for promoting a professorial university for London, and his friends, fearing that he was over-straining his energies, hailed with relief his election to the Linacre professorship of comparative anatomy at Oxford in February 1899. But though Oxford afforded opportunities for greater intellectual leisure, Weldon disdained to make use of them. He had on hand numerous exacting projects, and he tried to deal with them all at once. His leisure hours at Oxford were spent in long bicycle rides, during which he studied the fauna of the neighbourhood; his vacations were spent in journeys to various parts of the continent, where he worked at his statistical calculations and collected material for fresh lines of research. He added to his labours by undertaking the co-editorship of ‘Biometrika,’ a new scientific journal devoted to his special branch of study, and contributed to it twelve separate original and critical papers between 1901 and 1906.
The rediscovery of Mendel's memoirs on plant hybridisation in 1900 drew Weldon into an active controversy which culminated at the meeting of the British Association at Cambridge in 1904. Though Weldon was always critical of what appeared to him to be loose or insufficiently grounded inferences on the part of the Mendelian school, he was by no means unappreciative of the significance of Mendel's work. He would not admit its universal applicability, and even before the meeting at Cambridge he had planned and was engaged on a book (never finished) which was to set forth a determinal theory of inheritance, with a simple Mendelism at one end of the range and blended inheritance at the other. At the close of 1905 his attention was diverted by a paper presented to the Royal Society by Captain C. C. Hurst, on the inheritance of coat colour in horses. Disagreeing with the author's conclusions, Weldon made a minute study of the ‘General Studbook’ in the autumn of 1905, and in Jan. 1906 he published ‘A Note on the Offspring of Thoroughbred Chestnut Mares.’ This was his last scientific publication. In the Lent term he was still engaged on the ‘Studbook,’ and had collected material for a much more copious memoir on inheritance in horses. In the Easter vacation, while he was staying
