178 
ANIMAL CURIOSITIES 
in colour. Their incubation period varies from 
twenty to forty days, according to the degree 
of temperature they are subjected to; the 
young eventually eating their way through 
the enveloping skin and commencing a free 
existence. 
Beyond forming an item of diet for human 
beings, snails are also appreciated by various 
kinds of birds. Sheep, moreover, are said to 
fatten on a small species of Helix which inhabits 
sandy districts in this country. 
On the other hand, a small water snail 
(Limncea truncatula) is responsible for spreading 
the dangerous disease known as “ liver-fluke ” 
among sheep, the liver-fluke itself being a flat¬ 
tened and leaf-like worm, about an inch in 
length, that passes the early state of its existence 
within the snail. 
As the metamorphosis of the fluke proceeds, 
it eventually takes leave of its host, making its 
way out of the water and fixing itself upon a 
blade of grass. Should this grass be eaten 
by a sheep, the fluke continues to make a 
further transformation within the animal’s 
stomach, finally finding its way to the liver 
of its new host and setting up the dreaded 
malady. 
A well-known snail found inhabiting ponds 
and slow-running streams in this country is 
