250 
Liver Rot of Sheep 
In the case of L. peregra the ova masses may be either rounded, 
oval, or sausage shaped, and contain up to 40 ova arranged roughly in 
either two or four rows (in the latter case two above and two below::), 
a:id may measure 15 x 5 x 3 mm. 
Ova were collected and hatched in the Laboratory and ova deposited 
in the Laboratory were also hatched, the time taken varying from four 
to six weeks. Ova that had been completely dried for periods up to 
48 hours and then re-immersed hatched in the normal time; ova 
dried for longer periods were longer in hatching and the numbers 
surviving were greatly reduced, while in 1915 a few hatched from ova 
that had been dried for 100 hours. A number of Laboratory experi¬ 
ments failed owing to the ova being attacked by fungoid or bacterial 
parasites and careful and elaborate experiments begun under controlled 
conditions in ditches in the spring of 1916 with ova dried for 100 hours 
and over, failed, owing to unusual weather conditions which twice 
destroyed the apparatus. 
Drought, and its effects upon the Snail. 
Before discussing other points in the bionomics of L. truncatula, 
some statements of Prof. Thomas may be quoted, he says 1 “ Limnaeus 
truncatulus is a fresh water snail with a brown spiral shell...it never 
reaches more than half an inch in length, while it is usually much smaller, 
a common variety in England, scarcely ever measuring so much as a 
quarter of an inch. Owing to its small size it often escapes notice.... 
Two or three kinds of snails most closely allied to L. truncatula (for 
instance L. peregra) may occasionally crawl out of the water for short 
distances, but in L. truncatula itself, the habit is so much more strongly 
developed that the snail should be termed amphibious. Indeed it is 
oftener out of the water than in it. When kept in an aquarium it quits 
the water and as often as it is put back insists on crawling out again, 
so long as strength remains. It is said to breed upon the mud on the 
banks of ditches.” He then mentions that after eight days drought and 
then heavy rain, he found many dead snails, but others were capable 
of being revived; he continues “I collected a number of specimens 
and placed them in an open vessel on a shelf in a dry laboratory, 
in a position where the sun fell upon them for an hour or so daily. I 
found that rather more than half of them withstood 26 days of this 
treatment and some few recovered after more than six weeks. That 
1 Journ. Boy. Agric. Soc. 1883, pp. 292-3 et seq. 
