1.Light plays an important role in the emergence of Schistosoma japonicum cercariae from their Chinese snail host, Oncomelania Hupensis.
2.Temperature plays a less important role since in our experience no quantitative difference was observed between 15° and 35°C. Shedding from some snails occurred at 5°C. but the number of cercariae shed was small.
3.Water with pH values ranging from 6.6 to 7.8 seemed equally suitable for the shedding of S. japonicum cercariae.
4.Tap water and filtered river water were both suitable for shedding of the cercariae but distilled water was unfavorable.
5.Infected snails kept moist showed a greater readiness to shed cercariae than those kept dry.