314 
Distoma liiteum n. s]?. etc. 
1898. Linmaea truncatula, MiilL, M. and P. (Natal) Proc. Malac. Soc. 
vol. III. p. 184. Melvill and Ponsonby place it in a list of 
species introduced into Natal. 
1898. Lwmaeus umlaasianus, Kiist. = (fide Bourgt.) L. truncatula, 
Mllv. Sturany, Siidafr. Land mid Sussw. MollusJcen, p. 74 
(Natal). 
1874. Linmaea truncatula Mlill. ? (Tunis, Algiers, Abyssinia). C. F. 
Jickali, Fauna d. Land- und Siissw. Moll. N.O. Afr. p. 194. 
It may therefore be that L. truncatula does occur in South Africa, 
though not in great abundance, and if so, this would be a sufficient 
explanation of the presence of the disease here. It may be objected 
that it is very unlikely that a fresh-water snail could have been imported 
from Europe to South Africa, as the animal itself will not live long out 
of fresh water, and its eggs are readily dried up. A possible explanation 
may however be found in the fact that European carp were known to 
have been introduced into South Africa at an early time, and it is not 
improbable that fresh-water plants and snails were introduced with 
them, to keep the water fresh and to supply food. There is certainly 
no doubt that the snails could have been introduced at a later date, 
as even the South African Governments have introduced, not only 
fresh-water fish, but also plants and snails from Europe, and may thus 
be unwittingly keeping up a supply of the dreaded liver-fluke. The 
solution of the problem has therefore an important practical side. 
It not infrequently happens that, in the unsuccessful search for one 
thing, other new facts of equal interest are disclosed, and in this case 
though the liver-fluke question has not been cleared up, the occurrence 
of so many different cercariae is of itself of great interest and opens up 
a field for investigation of life histories for the student of Zoology in 
South Africa. 
Life History of Distoma luteum. 
About the beginning of the summer months (Oct. 1910) a number 
of Physa tropica from Muizenberg Lake were dissected, and about 
five per cent, were found to be infected with rediae and cercariae. At 
a later date additional specimens were procured, and from these there 
appeared in the collecting tubes a number of free smmming cercariae. 
When dissected a large proportion were found to be infected. Other 
lots were from time to time examined, and about the end of January 
all the specimens of the siiail procured were, with very few exceptions. 
