Five years ago, while on a visit to Glasgow, my attention was drawn by Mr. Peter Braid, M.R.C.V.S., to the occasional appearance of Dicroœlium dendriticum in the liver of sheep from the West of Scotland. Mr. Braid arranged to supply me with such livers as in future came to his notice and to ascertain, where possible, the place of origin of the sheep. In this way, I have received from him livers from sheep which came from Tiree, South Uist, Barra, Harris, Campbelltown, and from Berwickshire, Ayrshire and Lanarkshire. Enquiries locally at these places shewed that some at least were mere markets. In Berwick, for example, sheep were on sale which had come from the West; and in the West, sheep which had originated in the islands. In the case of the Hebrides, however, sheep are not habitually imported for subsequent re-sale and the great majority—certainly all the young animals—are bred locally. It seemed legitimate to conclude therefore, that in these cases, the disease also was acquired locally. The various islands were visited in autumn, 1929, and Tiree was selected as affording the best and most convenient situation for an investigation into the life-cycle of the parasite.