200 P' G. Cawslon 



in the Umhlangana ; hidora tropica ( 1 ) at Prospect Hall ; Isidora 

 naialensis'> at Merebank, and Tiara iuherculata at Prospect Hall. 

 Tiara iuherculata has been suspected of being the intermediate 

 host for Bilharziella polonica in Egypt. See R. T. Leiper on 

 ** Bilharziosis in Egypt *' prcc. of Royal Society of Medicine, 

 1916, Vol. ix. By means of its stout operculum even infested 

 specimens can resist drying for several weeks. 



Cercariae resembling C. frondosa have been found in Isidora 

 tropica, Isidora forskali and Tiara tuberculata. This encysting 

 amphistome was very common in Isidora schackoi at the Potchef- 

 stroom golf links in 1917-1918. 



Eye-spotted schistosomes, C. oculata, have been found only in 

 two Ph})sopsis ajricana in the Durban suburbs. They are pro- 

 duced in bottle-shaped rediae and their eye-spots are readily visible 

 through the walls of the rediae. Some that I measured were 7.7 

 m.ms in total length. 



Chained cercariae were present in hidora tropica^ Planorbis 

 pfeifferi and Isidora natalensis from Umgeni, Mayville, Mere- 

 bank and Limnaea natalensis from Klerksdorp. 



Cystophorous cercariae were obtained from 1 8 out of llPlan- 

 orbis pfeifferi at Merebank. 



A large number of snails were examined microscopically and 

 found to be free from cercariae; but in every instance those were 

 set aside for microscopic examination which were considered most 

 likely to be infested. 



iNo cercariae were observed in Anc^lus or in brackish water 



inhabitants. 



An eye-spotted monostome was found in Tiara tuberculata 

 from Prospect Hall and another, C. fulvoculata in one Limnaea 

 natalensis in the Durban suburbs. 



In some instances those specimens which were suspected of har- 

 bouring cercariae were set aside in a test-tube for a few hours, 

 and occasionally infestation was determined by the presence of 

 free-swdmming cercariae in the water surrounding them. These 

 cercariae did not live as free-swimming organisms for more than 

 24 hours after their escape from the snail that produced them. 



