establishment of the complete life cycle of the parasite under laboratory conditions. An active breeding colony of the suitable snail host must be established to provide a reliable source of snails for exposure to miracidia at regular intervals so as to insure a steady supply of cercariae for animal infections. The study of Schistosoma haematobium infections under laboratory conditions has been seriously hampered by the inability to infect, routinely, Bulinus truncatus or other suitable molluscan hosts with this parasite. REVIEW OF LITERATURE Cawston (1922 a and b), working in South Africa, was the first to successfully infect laboratory reared snails (Physopsis africana) with S. haematobium. He observed the discharge of cercariae from the snails 35 days after exposure. Brumpt (1928) exposed Bulinus contortus to miracidia obtained from the crushed liver of an infected mouse. After 9 weeks he found 7 snails shedding cercariae out of 35 snails surviving. In another study, Brumpt and Werblunsky (1928), working in Corsica, exposed 35 snails; 28 of these shed cercariae. In this study, Brumpt and Werblunsky emphasized the importance of temperature and recommended 2425? C. as the optimum temperature for snails exposed to infection. Archibald (1933) studying schistosomiasis in the Sudan reported that young Bulinus snails, 3-4 weeks old, were more susceptible to infection than adult snails. He reported that the interval between exposure of the snails and shedding of cercariae was 6-8 weeks. He observed a maximum shedding period of 75 days. Gordon et al (1934), working in Sierra Leone, exposed a total of 262 laboratory reared Physopsis globosa to varying numbers of S. haemtatobium miracidia. Seventy-five snails died during the course of the experiment. They examined 48 snails by dissection and found 23 (47.9%) harboring sporocysts. They allowed 114 snails to show evidence of infection by discharging cercariae and found 95 (83.3%) infected snails. They also performed several experiments to determine the effect of temperature on the development of the infection in the snails. They found that at 26-28? C., which was considered normal, the snails shed cercariae from the 36th day on. When the temperature was raised (27-32? C.), the incubation period was shortened to 23 days but fewer snails survived the incubation period. Lower temperatures retarded the development of the infection, and at 14? C. little or no development occurred. Stunkard (1946) reported the successful laboratory infection of Bulinus truncatus