E. C. Faust 
213 
of which three are specific. Planorbis pfefferi from Durban has a high infection 
which continues into the summer. 
In all, 15 valid species may be recognised from the data in the writer’s 
hand. Three of these have been recorded from the Transvaal alone, nine 
have been found solely in Natal, while three species are common to both 
regions. The larva of Schistosoma haematobium is apparently ubiquitous, 
having been recorded from Rustenburg, Pietermaritzburg, Magaliesburg, 
Mulder’s Drift, Nijlstroom, Durban, and along the coast north of Durban. 
Of these species the largest group is that of the furcocercous cercariae, 
containing the two human parasites, cercariae of Schistosoma haematobium 
and of S. mansoni. The second largest group, that of echinostome larvae, 
has no species that is now known to infect man in that region of the world. 
Either of the remaining species or others yet undescribed may be correlated 
with the adult liver flukes of sheep, and with monostome and amphistome 
infection in cattle in South Africa. 
The life history of the schistosome is comparatively simple, as Leiper 
(1915), Manson-Bahr and Fairley (1920) and others have conclusively shown. 
The larva passes directly from the mollusk to the definitive host. Gilchrist 
(1918) has likewise shown that Cercaria comma is genetically related to 
Distoma luteum Gilchrist which is found in the frog. But analogy from life 
histories of some of the other groups leads one to believe that the solution 
of the problem in every case is not so simple, and that a second intermediate 
host may be expected. 
A synoptic table of the valid species collected by Dr Cawston in the course 
of his examinations, together with the record of Gilchrist (1918), is included 
in this paper. 
Material which the writer has recently had an opportunity to examine 
permits a description of Cercaria pigmentosa Cawston, previously inadequately 
described, and a new species of echinostome larva, Cercaria 30 -acanthostoma, 
previously confused, perhaps,-with Cercaria catenata Cawston, 1917. 
Cercaria pigmentosa Cawston 1919. 
Host: Lymnaea natalensis. 
Habitat: Natal. 
This species of cercaria is the first larva of its kind to be described from 
Cawston’s material (Fig. 1). The body is distinctly cordate with the apex 
directed forward. The head region is slightly protruded from the rest of the 
body. The body measures 333 g x 281/x. The tail is about two and one-half 
times the length of the body when fully extended and has a proximal diameter 
under these conditions of 56/x. Both body and tail are entirely covered with 
minute spines. The mouth is ventral in position. It has a diameter of 50/z. 
It leads almost directly into a small oesophagus surrounded by a small but 
powerful sphincter. Behind this organ the digestive tract forks to form two 
