Walter Frank Raphael Weldon. 1860—1906. 
31 
dredge, or fish, or shoot something wonderful, and you describe it, and everyone sees that it is 
wonderful, and you all enjoy the wonder. And there is no solution, and if there were, it would 
not be worth the shadow of a shower flying across the country. 
And this is all wicked nonsense, and I am going to bed. Yours afl^'ectionately, 
W. F. R. Weldon." 
Weldon was a child of the open air and the breezes, and we hoped that he 
might have more of them, if not in lowland Oxford, at least on the hills around. 
There was space and air too for the experimental work that had been so cramped 
in Gower Street. The Daphnia studies, which had occupied so much energy 
under unfavourable conditions in London, were at once resumed on broader lines in 
the ponds and ditches round Oxford. Weldon, with a basket of bottles attached to 
his cycle handle, and a fishing creel, filled with more bottles, on his back, might be 
met even as far as the Chilterns, collecting not only Daphnia, but samples of the 
water in which they lived. His University College work had shown him how 
widely Daphnia are modified by their chemical and physical environment, and how 
this modification is largely due to selection. There exist elaborate drawings of the 
Daphnia from the Oxfordshire ponds, indicating their differentiation into local 
races, and notes on the peculiarity of their habitat and the chemical constitution of 
the water : 
"In the meantime I have been led into a non-statistical work for the moment. Get out of the 
library and read Klebs : Bedingungen der Fortpflanzung hei einigen Algen und Pilzen. 
By tricks of nutrition, light, etc., Klebs can make simple algae reproduce either a-sexually or 
sexually, or parthenogenetically, as he pleases. In cases where every textbook tells you that a 
regular alternation of sexual and a-sexual generation is the rule, he can make either form recur 
as often as he likes. 
If one can by similar tricks throw Daphnia into this condition, then the measuring machine 
can again come into play, and one can compare jiarthenogenetic inheritance with sexual 
inheritance as often as one pleases. 
That is a Nehensache. — The Hauptsache here is the great variation in the chemical com- 
position (pardon the phrase) of the water in the little rivers. Their percentage of dissolved salts 
varies enormously, and I hope to go about as I have begim, with a large fisherman's creel tied to 
the handle-bar of my bicycle, learning the correlation between the salts in the waters and the 
fauna. — Then again comes the measurement, and the attempt to derive one local form from the 
other under controlled conditions by direct selective destruction due to the conditions." 
This was precisely the same problem which a study of Kobelt's Stiidien zur 
Zoogeographie, 1897-9, led him later to take up with regard to land snails. What 
is the meaning of the slight but perfectly sensible differences in type to be found 
in shells from adjacent valleys, or even from different heights of the same 
mountain? Weldon attacked the problem in his usual manner; he spent two 
Christmas vacations collecting Sicilian snails of the same species from habitats 
extending over a wide area, the local environments were described, and the snails 
often photographed with their immediate surroundings. Innumerable shells were 
brought back to Oxford, and Weldon delighted to discourse on the significant 
differences in local type, and yet the gradual change of type to type from one spot 
