*238 
Liver Rot of Sheep 
to field work, in fact, so much time was taken up by visiting farms, etc., 
that little consecutive laboratory work was possible. The Area 
surveyed is a wide one and in parts rough and inaccessible. It was 
necessary to visit series of farms at different times of the year, and 
mountain farmers were often hard to find; this involved a return to 
many places. In addition spots inhabited by L. truncatula had to be 
visited regularly in all parts of the Area. The weather in the mountains 
was frequently very adverse and much arduous walking had to be 
undertaken, other methods of transport being negligible and train 
services by no means convenient during the winter. 
Many of the local agriculturists have been most helpful, and have 
given all the information and assistance in their power, only a small 
minority being either uninterested, or unwilling to give information or 
facilities for investigation. 
My sincere thanks are due to Prof. C. Bryner Jones, M.Sc., Prof. 
PI. J. Fleure, D.Sc., Prof. 0. T. Jones, D.Sc., Messrs W. E. Whitehouse, 
M.Sc., F. S. Wright, J. Pryse Howell, E. Morgan, M.R.C.V.S., D.V.H., 
J. J. Griffith, B.Sc., R. G. Stapledon, M.A., F. W. Flattely, T. A. Stephen¬ 
son, and many others for kind assistance and advice. I am greatly 
indebted to Miss Thomas of Aberystwyth for permission to use local 
Meteorological data collected by Dr A. Thomas; also to the British 
Rainfall Association and the Meteorological Observers at Machynlleth 
and Gogerddan. 
I also tender my thanks to numerous friends throughout the Area 
surveyed for much help and hospitality. 
II. Liver Rot. 
Distomum hepaticum in the Area. 
This Trematode flat worm is the cause of perpetual trouble to a 
number of sheep farmers within the Area and has in past years caused 
very severe losses among the flocks. The last outbreak was waning 
when the Agricultural Survey commenced in the autumn of 1913. 
The life history of this parasite is now so well known, and has been 
so often described that it is not necessary to recapitulate the details 
here. During the progress of my work particular attention was given 
to the life history and bionomics of the intermediate host, the mollusc 
Limnaea truncatula without which the worm cannot complete its life 
cycle. Consequently its distribution is entirely dependent upon the 
distribution of the snail, and the factors governing the latter have been 
