Volume X 
APRIL, 1918 
No. 3 
Iz^Soi' 
THE LIFE HISTORY OF DISTOMA LUTEUM n. sp. 
WITH NOTES ON SOME CERCARIAE AND REDIAE 
FOUND IN S. AFRICA. 
By J. D. F. .GILCHRIST, M.A., D.Sc., Ph.D. 
Some years ago, in endeavouring to obtain various stages in the life 
history of the liver-fluke in' South Africa for teaching purposes, I found 
that, although the parasite is fairly common on some farms in this 
country, the intermediate host had not yet been definitely ascertained. 
In Europe, as is well known, the intermediate host is the fresh-water 
snail Limnaea truncaiula, but this species has not been recorded with 
certainty from South Africa. The commonest fresh-water snail here is 
Physa {Isidora) tropica and a preliminary examination of a few specimens 
of this mollusc from Muizenberg Lake revealed abundant stages of fluke 
very closely resembling those of the liver-fluke. Additional specimens 
procured from the neighbourhood also afforded abundant material of 
the same stages. The only difficulty in accepting this as a solution of 
the problem was that, though placed in the most favourable conditions, 
the free swimming form (cercaria) was never observed to encyst. 
I called attention in the Agricultural Journal of the Cape of Good Hope, 
Dec. 1910, to the occurrence of this fluke-like stage and requested the 
assistance of South African farmers in following up the investigation. 
Some replies were received describing the serious damage done to sheep 
by the liver-fluke, but no further light was thrown on the subject. One 
correspondent forwarded a specimen of Achatina zebra as the possible 
host, but as this is not a water snail, it is very improbable that it har¬ 
bours the intermediate stage of the fluke; another stated that he had 
found the intermediate stage in a worm in which he had actually seen 
the free swimming form developing and escaping into the water. This 
most interesting observation however again proved a false trail for the 
“ worms ” proved to be the worm-like strings of frogs’ eggs in which the 
tadpole, developing and escaping into the water, had been observed! 
In addition to the Cercaria found in Physa, I noted also in the 
Agricultural Journal the occurrence of three other kinds, found in the 
Parasitology x 21 
