(Concluded from page 680) Bilharziasis is known to occur in varying degrees of severity in the Northern and Eastern Transvaal-an area of over 60,000 square miles. The reasons are discussed why molluscicidal work is the only possible practical method by which the disease can be controlled in this area. The distribution of the more important fresh-water snails is given for different parts of the Transvaal for the four quarters of 1950, and the distribution in various habitats is given for the known vectors Physopsis Africana and Planorbis pfeifferi as they occurred during these four quarters. The close relationship between the occurrence of Physopsis africana and the incidence of B. Haematobium is demonstrated and discussed. Various molluscicides are discussed, and the opinion is given that copper sulphate is at present the molluscicide of choice (within economic limits). The instability of copper sulphate is demonstrated, and it is suggested how this chemical may best be used under our conditions. Urine examinations done during the years 1937-1938 and 1948-1950 give percentage incidences of bilharziasis among Native school-children which vary from 88% to 4 %, with the highest incidence in the low-lying country to the east of the Drakensberg mountains. The corresponding figures for European schoolchildren vary from 17% to 3%. The patchy distribution is emphasized. Problems created by the farming communityï¿½s fear that copper sulphate may injure their stock or their crops are discussed. The aestivation habits of certain snails are descriptionbed, and a mention is made of the difficulty of identifying cercariae obtained from snails collected in their natural habitat. It is indicated that this work has been of a preliminary and largely voluntary nature.