Distribution of the intermediate hosts of bilharziasis in relation to hydrography; with special reference to the Nile Basin and the Sudan.

The author has made a collection from certain parts of the Sudan of snails of the genera Bulinus and Biomphalaria that are actual or potential vectors of bilharziasis. The snails were identified by anatomical examination and a preliminary interpretation of the findings is given. The results are related to information already available, not only from the Sudan, but also from adjacent areas, especially from the Nile basin in general. The distribution of the snails is shown both in tabular and in map form. With a view to providing a basis for a better understanding of the true relationships among this group of African planorbids, special consideration has been given to the hydrographic and hydrogeological factors which have brought about the present distribution.