Walter Frank Raphael Weldon. XXXVII 
evolution has not taken place by leaps, but by continuous selection of the 
favourable variation from the distribution of the offspring round the 
ancestrally fixed type, each selection modifying pro rata that type, there 
must be a manifest want in Mendelian theories of inheritance. Reproduc- 
tion from this standpoint can only shake the kaleidoscope of existing 
alternatives; it can bring nothing new into the field) To complete 
a Mendelian theory we must apparently associate it for the purposes of 
evolution with some hypothesis of “mutations.” The chief upholder of such 
an hypothesis has been de Vries, and Weldon’s article on “ Professor de Vries 
on the Origin of Species” was the outcome of his consideration of this 
matter. During the years 1902 and 1903 an elaborate attempt was made to 
grow the numerous sub-races of Draba verna, with the idea that they might 
throw light on mutations. .The project failed, largely owing to difficulties in 
the artificial cultivation of some of the species. But for a time all other 
interests paled before Draba verna. 
A study of the work of von Guaita had convinced Weldon, early in 1901, 
that the cross between the European albino mouse and the Japanese waltzing 
mouse was not one which admitted of simple Mendelian description. In 
May, 1901, his letters contain inquiries as to Japanese mice dealers. During 
the summer and autumn the collection of Japanese mice was in progress. 
These mice were to be bred to test the purity of the stock ; during December 
about forty does had litters, and pure breeding went on until the autumn of 
1902, when hybridization commenced. The work on these mice was for two 
years entrusted to Mr. A. D. Darbishire, but the whole plan of the experi- 
ments, the preparation of the correlation tables, and the elaborate calcula- 
_ tions were in the main due to Weldon. On Mr. Darbishire’s leaving Oxford, 
Weldon again resumed personal control of the actual breeding arrangements, 
and from some second hybrid matings carried on the work to the sixth 
hybrids’ offspring. The work was nearing completion at his death, and 
through the energy of Mr. Frank Sherlock, the skins of the 600 pedigree 
mice forming the stud at that time have been dressed and added to those of 
the earlier generations. Weldon had this work much at heart, and his 
letters during 1904 and 1905 give many indications of the points he 
considered demonstrated. The experimental part of the work would have 
been nearly coinpleted had not his whole thought and energy been directed 
from November, 1905, into another channel. 
In the summer ‘ Biometrika’ was edited from Bainbridge in Wensleydale, 
and the co-editors cycled to the churchyards of the Yorkshire daies, 
collecting material for their joimt paper “On Assoriative Mating in 
Man” (34). From Bainbridge, the Weldons went to the British Association 
meeting at Belfast, where an evening lecture on Inheritance was given. At 
Christmas came one of the above-mentioned visits to Palermo to collect 
Sicilian snails. : 
In the spring of 1903, Weldon was busy, as were the whole available 
members of the biometric school, in studying the influence of environment 
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