SOUTir AFRICAN Cl^iC Ak I .!■:. 



377 



The molluscs most heavily infested with cercarije are Plaii- 

 orbis pfcifferi, Liniiuca natalriisis. f'/iysopsis afncaiia, and Isidora 

 Si'hakoi. The heavy infection of 



Plaiiorbis and Limiuca is caused l)v Distomes. 

 Isidora is caused hy AmpJTistomes. 

 Physof'sis is caused l\v Schistosomes. 



Eve-spots. 



There are several eye-spctted ccrcari.-e found in South Africa, 

 and it is of interest tliat an eye-S])otted form found in Eo-yi)t 

 was considered to be an avian parasite. In the Durban brick- 

 fields I have encountered three distinct species of eye-spotted 

 cercarire ; two of these were furcocercarise. At Potchefstroom 

 T found Isidora schakoi heavily infested with amphistomes. 

 possessino- a pair of leaf-like eye-spots surrounded with branching;- 

 pig-ment, C. jrondosa. AFr. Grobbelaar has sent me specimens 

 of the same cercaria from Stellenbosch. These also were found 

 to encyst, and it is probable that it is the same eye-spotted 

 cercaria that Dr. J. D. F. Gilchrist described as encysting in large 

 numbers in the course of an article entitled " The Life History 

 of Distoiiia hitcum n.sp., with Notes on Some Cercari?e and 

 Rediffi found in South Africa," " l^arasitology," Vol. X, No. 3, 

 April 29. 191 8. 



In South Africa h\e members of the binoculate group of 

 species are recorded. Two ( f them are Schistosomes, two are 

 leptocercous distomes, and one is an amphistome. 



Redia-Formation. 



The redia stage is not uncommon among our leptocercous 

 cercarise, though sporocysts without the formation of redi?e occur 

 in several species. A redia is an adult organism which i:)ossesses 

 a gut and pharvnx. A sporocyst is an adult which lias lost 

 its digestive tube. E. C. Faust has pointed out that some 

 s])orocysts are not easily differentiated from redi?c, and may have 

 been described as such, fie says, in the " Journal of Parasitology," 

 Vol. IV, March, 1918, " C". cciunocauda is described as the 

 offspring of a redia, whereas the evidence of studies on other 

 cercari?e of the furcocercous group pre])onderates in fa\our of 

 the development of these cercari?e within sporocysts." 



Recently I have observed undoubted redia- formation in 

 Physopsis africana. These redi?e were freely moving, and 

 possessed a distinct gut distended with jjarticles. Inside these 

 redi?e were furcocercous cercaria* with small eye-spots, C. 

 ocitlafa. 



At Potchefstroom I have isolated another species of furco- 

 cercous cercaria. C. gladii, without eye-spots. This cercaria also 

 develops in freely movable organisms having tlie appearance of 

 redi.-e. 



