SEVERAL OBSERVATIONS CONCERNING CERCARIAL SHEDDINGS OF FASCIOLA-GIGANTICA FROM LYMNAEA-NATALENSIS

The shedding of cercariae from Lymnaea natalensis and their transforma tion into metacarcariae occurred mainly at night, and 70.7 % of the cy sts were counted between 7 p.m. and 1 a.m. There is no infradian rhyth m in the numerical distribution of the daily mean values as related to experiment duration or patent period duration. One quarter of the sna ils shed their cercariae in a single wave and the others in 2 to 13 wa ves. Floating cysts represent 35 % of the total number of metacercaria e and their number decreased during the two first waves of shedding. A berrant metacercarial localizations were noted on the inner surface of the shell when the snail died.