Some South African Cercariae 199 



SOME SOUTH AFRICAN CERCARIAE.* 

 By F. G. Cawston, M.D., Cantab. 



An examination of over 5,000 fresh-water snails which I have 

 collected during the last two years from rivers along the East 

 Coast reveals the presence of some twenty distinct species. 



Most of the specimens have been obtained from the rivers and 

 pools of water around Durban; others have been collected at 

 Grahamstown and Port Elizabeth in the Cape Province. 



Six different species were infested v^th various cercariae. 

 C.pigmentosa has been isolated only from Limnaea natalensis. 

 Specimens infested wdth this encysting cercaria which develops in 

 very large rediae have been obtained from Sydenham in the Dur- 

 ban suburbs and from a fluke-infested farm at Lake Chrissie in 

 the Transvaal. In guinea-pigs these cercariae have developed 

 into Fasciola gigantica. 



Cercariae closely resembhng the Bilharzia have been obtained 

 from Ph})sopsis africana (nearly 30 per cent, of the mature speci- 

 mens examined) : Isidora tropica (1 specimen) ; Planorbis pfeifferi 

 (I specimen) — Durban; Limnaea natalensis (5 specimens from 

 the Umgeni river harboured rediae containing cercariae closely 

 resembling the Bilharzia). 



C. gladii from Isidora schackoi Jickeli at Potchefstroom some- 

 what resembles the Bilharzia, but is also redia-produced. 



These cercariae from Phyjsvpsis africana have been given to 

 guinea-pigs and numerous Schistosoma haematobium and Schis- 

 tosoma hovis obtained from them post-mortem. 



Styletted cercariae resembling C. cawstoni have been obtained 

 from Limnaea natalensis (13) at Port Elizabeth, Umgeni, Umh- 

 langana, Umbilo and Prospect Hall. Ph^sopsis africana (2) 



* These researches have recently been assisted by a small grant 

 from the Royal Society. 



