Several observations concerning cercarial sheddings of Fasciola gigantica from Lymnaea natalensis.

The shedding of cercariae from Lymnaea natalensis and their transformation into metacercariae occurred mainly at night, and 70.7% of the cysts were counted between 7 p.m. and 1 a.m. There is no infradian rhythm in the numerical distribution of the daily mean values as related to experiment duration or patent period duration. One quarter of the snails shed their cercariae in a single wave and the others in 2 to 13 waves. Floating cysts represent 35% of the total number of metacercariae and their number decreased during the two first waves of shedding. Aberrant metacercarial localizations were noted on the inner surface of the shell when the snail died.