Further Observations on South African Larval Trematodes

Abstract

1. Fourteen species of larval trematodes are described from South African material, of which thirteen are new to science.2. These forms are described and their relationship to previously described cercariae and to adult flukes is discussed.3. The cercariae of the human blood flukes of South Africa are brought up for detailed consideration. A restudy of the material in the writer's possession, including the original experimental material ofSchistosoma mansonifrom Venezuela, is presented.4. The writer restates his original thesis:The essential differentiating features of the apharyngeal fork-tailed cercariae consist in the number and microchemical reactions of the secretory cells. These structures can be studied and differentiated from well-preserved material as well as from fresh material.5.Isidora (Physopsis) africanafrom Natal is known to harbour three species of mammalian schistosome larvae, of which (a) one, originally diagnosed by the writer as the “Cercaria ofSchistosoma haematobium,” is found on re-examination to correspond to the larva which Blacklock and Thompson have found experimentally to be this species; (b) a second species corresponds exactly with that known experimentally to be the cercaria ofSchistosoma mansoniin Venezuela; while (c) a third (C. octadena) is probably that ofSchistosoma bovis, which is known to be présent in Natal.6. A table is presented which embodies the important diagnostic features of the three human blood-fluke cercariae.7. The systematic position of the thirty-eight species of larval trematodes described from Cawston's collections and their host relationships are summarised.