F. G. Cawston 95 
this place I found a pool heavily infested with Physopsis and a few small 
specimens of Planorbis and Ancylus. 
On December 8th, I visited the Schoonspruit at Klerksdorp, to investigate 
a recent outbreak of Bilharziasis amongst the lads who swim in this river, 
and brought back with me 95 specimens of fresh-water snails from the 
stagnant water. This river flows into the Vaal. A number of these were 
Planorbis gibsoni Nelson, others were Limnaea natalensis. This establishes a 
new locality for Planorbis gibsoni. They also included an interesting variety 
of Isidora which does not agree with any of the other forms I have collected 
elsewhere— Isidora tropica from Durban, Isidora forskali and Isidora compla 
M. & P. from Maritzburg or the Isidora I have collected at Potchefstroom. 
There were probably four distinct species of trematode worm represented 
among the cercariae with which these Isidora from the stagnant pools at 
Klerksdorp were infested. Each of these cercariae was about 0-6 mm. in 
length; the elliptiform body being about 0*2 mm. by 0-2 mm.; but varying 
considerably in shape, as the cercaria by means of its two suckers moved 
along the surface of the glass slide. In each case the long slender tail was 
very motile, even after becoming detached from the body. Three of the 
snails contained motile rediae, producing leptocercous cercariae, which were 
found to be escaping from the liver-substance of the snail. The liver-substance 
of one of these snails was orange in colour, from the presence of numerous 
golden granules in the rediae it contained. These granules would appear to 
exist outside the gut and outside the cercariae produced in the rediae. In 
each case the redia was provided with an oral sucker, an alimentary canal 
and two pairs of locomotor appendages. In two of the specimens, the lepto¬ 
cercous cercariae were seen to possess small pharynxes at the commencement 
of the oesophagus. Another specimen was seen to possess sporocysts producing 
daughter-sporocysts without the formation of rediae. 
CERCARIA ARCUATA. 
One of these Isidora from the Schoonpoort at Klerksdorp contained rediae 
with terminal oral sucker and two small lateral locomotor appendages. 
These contained leptocercous cercariae without pharynx which possessed a 
chain of cystogenous vesicles on either side of their divided gut. In most of 
these cercariae, the chains had the appearance of being joined, posterior to 
the ventral sucker, so that the pair of chains presented the appearance of an 
inverted horse-shoe. I have suggested the name Cercaria arcuata for this 
varietv. 
V 
CERCARIA F RON DOS A. 
I have collected over 400 specimens of Isidora from a stagnant pool at 
the Golf Course at Potchefstroom. On reference to Jickeli’s Fauna N.-O.- 
Afr., Mr Henry C. Burnup of Maritzburg has no hesitation in identifying 
these Isidora as Isidora schakoi Jickeli. This he does in full knowledge that 
