WATER SNAILS. 
91 
Sowed a considerable quantity of salt and then applied farmyard 
manure to a piece of land, and, after ploughing in, sowed White 
Turnips : this was on light land. Besult, a first-rate crop. General 
opinion that salt consolidates too much to answer on heavy land.” 
With regard to prevention of spring attack from caterpillars which 
have hybernated, or have in some way or other lived through the 
winter where the crop has been on the ground continuously, 
probably as yet the only method of checking attack is the well-known 
one of turning the grubs out of the ground by a body of workers sent 
with strong-pointed sticks, or any other implement, and collecting 
these and destroying them. But where ground is known to have 
been infested in autumn, and it can be worked, it is best treatment to 
stir the surface well. The caterpillars which are within reach of 
operations will then be exposed to weather influence, which will act 
strongly on them, although it would not in ordinary amount of cold 
have done them any harm in their own naturally-formed or chosen 
shelters. In the course of the past winter I turned some Surface- 
caterpillars out from the ground in which they had been buried for 
experiment, or had buried themselves last autumn, and found them in 
a condition in which they would certainly have soon died if left on the 
surface. 
From state of weather or other circumstances there may be 
exceptions here and there, but as a rule the plan of a thorough stir¬ 
ring will act well. Thorough cultivation of the surface also destroys 
the weeds which feed or shelter the grubs, and therefore is a good 
measure in summer on a field where the crop has been destroyed; 
and chemical dressings which will annoy the grub are of use. The 
two treatments joined greatly help to clear infested land by starving 
and poisoning the pest. 
MARSH SNAILS. 
Wandering Marsh Snail, Limnwus pereger, F. & H.; Truncate 
Marsh Snail, L. truncatula, F. & H.; Pond Marsh Snail, 
L. stagnalis , F. & H. 
The amount of the presence of Marsh or Water Snails is a subject 
which might most usefully be inquired into relatively to one or more 
kinds of Water Snails 1(or Limnceus) being the “ host ” of the liver- 
fluke of the sheep in its early stage. 
The life-history of the Fluke and its connection with the Limnceus 
are given in minute detail by the long and profound research of Prof. 
A. P. Thomas, F.L.S., in the 17th and 18th vols. of the Journals of 
