.1. D. F. Gilchrist 
:313 
afterwards several cercariae were found swimming about, obviously 
quite different from those previously procured from the same species 
of snail, as they were of a very dark, almost black colour. This was 
not the only difference, for by the time Cape Town was again reached, 
several had encysted on the sides of the glass tube, the cysts being 
of the same black colour. This was interesting, but obviously did not 
throw light on the liver-fluke, as its cercariae and cysts are not black. 
This cercaria had eyes, and is, without much doubt, the free swimming 
stage of the cercaria previously noted in the Agricultural Journal. 
The method of formation of the cyst is of interest in this form. 
The whole process could readily be observed. The animal settled 
down with violent wriggling of the tail, which ultimately became * 
detached. Meanwhile the body extruded a great number of short dark 
rhabdite-like bodies. These were applied, the one to the other, till a 
dome-like structure was formed over the body. At the periphery this 
extended over the substratum so that a very Arm attachment was secured. 
Some time later (1911) on a visit to Natal some fresh-water snails 
were procured with the assistance of Mr Burnup, a recognised authority 
on South African shells, and Dr Warren kindly placed his laboratory 
at my disposal for their examination. A large redia was found in 
Limnaea natalensis, but the corresponding cercaria was not found. 
The cercaria may be C. obscura of Sonsino who found it in Limnaea 
natalensis. C. obscura was about 1 mm. long and developed from 
rediae of 2 mm. 
Several specimens of Physojysis africana with characteristic cercaria 
of the bifurcated-tail type were also found, but no traces of stages any¬ 
thing like those of the liver-fluke. Another characteristic cercaria was 
found at the same time, it was oblong measured about 0-3 x 0-05 mm. and 
had a clear rod-like spine about 0-01 mm. long anteriorly. The tail was 
comparatively short. Their rediae were short, thick and colourless. 
In discussing the problem of the liver-fluke, Mr Burnup mentioned 
that some shells resembling L. truncatida had been collected by Mr J. 
McBean at Pretoria, and were now in the Burnup Collection in the 
Pietermaritzburg Museum. These were compared carefully with 
specimens of this shell from Madeira, in the same collection, and in 
Mr Burnup’s opinion, they seemed to be identical. For the following 
records of L. truncatida in South Africa I am indebted to Mr Burnup. 
1899. Limnaea umlaasiana Kiist. = (fide Bourgt.) L. truncatida Drap 
(sic) Ann. and Mag. Nat. Hist. ser. 7, vol. iv. p. 112 (Natal). 
21—2 
