Abstract
As to the shedding of cercariae of Schistosoma japonicum from its snail host relatively few reports are available; Isobe (1923), Osaka (1938), Tominaga et al. (1950) in Japan and Baumann (1948), Mao et al. (1950) in other countries. They observed chiefly the effect of water temperature, light, character of water etc. on the shedding of cercariae and consequently the time of observation was limited.
Oncomelania nosophora, the snail host of S. japonicum in Japan, has an amphibious habit and is found chiefly on moist soils and moist vegetables above the level of water. When experimentally submerged into water in a depth of 20 to 30 cm. about 70% of snails were found to move out of the water within 24 hours (Komiya and Yasuraoka, 1953) . The majority of these snails would have a chance being submerged into water by occasional rainfalls, irrigations of rice fields etc., and such would be a good chance for schistosome cercariae to be liberated into water. The chief objective of this work is to know the general aspect of the shedding of schistosome cercariae when their snail host is submerged in water for a relatively long time.
