C. L. Walton 
265 
On one occasion, in November, 1914, a sample of ten L. truncatula 
was obtained near Aberystwyth, and from two of these, in addition to 
the cercariae of Distomum, five of another species were noted, two from 
one snail, and three from another. 
It was difficult to isolate these from among the others and an 
attempted sketch was not sufficiently good for publication. The chief 
points of difference were: 
(a) The “tail” was much longer than in the cercaria of Distomum 
hepaticum (and the margin showed a crenate appearance), white in hue, 
and vigorously lashed. 
(b) The body distinctly cordate when swimming and noticeably 
darker than the tail. 
In April, 1914, cercariae indistinguishable from those of D. hepaticum 
were obtained from a sample of L. peregra : but although repeated 
attempts were made no further examples have been observed. These 
specimens were taken from a ditch containing numerous infected 
truncatula. 
Summary. 
1. Certain flocks in the Aberystwyth Area having suffered con¬ 
siderably from Liver Rot, a Survey of the Agricultural Zoology was 
carried out between October, 1913, and October, 1916, special attention 
being given to the above disease and the bionomics of the host snail 
L. truncatula. 
2. The Area comprised some 250 sq. miles of North Cardiganshire, 
etc., including Plynlymon, and falls into six natural divisions. 
3. The presence of the disease has caused a number of local modifi¬ 
cations in farm practice, designed to prevent, or mitigate losses. The 
disease was found to be on the wane within the Area, though endemic 
in certain places. 
4. L. truncatula and L. peregra are the only abundant local species 
of the Genus. Considerable differences occur in the distribution of 
these two species. L. peregra was only studied in order to better 
understand the habits of L. truncatula. This latter species occurs in 
shallow water floored with Diatomaceous clayey mud, and is absent 
from soft mud, and peat. There is a marked coincidence between the 
distribution of clay and L. truncatula, and L. truncatula and Liver Rot. 
5. The growth of the snails takes place throughout the year unless 
interrupted by drought or severe frost. Ova are deposited in March- 
April and hatch in May. The resulting snails, when they become 
