346 SUPPLEMENT 
rottenness is produced. Many modes have therefore been 
thought of to destroy them as well as the slugs, or to hinder 
them from getting at the fruit. The best way of destroying 
them is, certainly, to hunt them morning and evening, or after 
a small rain, and crush them. But their propagation may 
also be hindered, by taking care always to avoid tufted borders, 
and especially those made with box, close hedges, and all 
those ancient ornaments of gardens, formed of yew and haw- 
thorn. In general every arrangement must be avoided which 
can present humidity and shelter to the snail, unless it be used 
as a sort of snare in which they may be found collected in 
greater or less numbers, and destroyed at once. Their hurt- 
ful effects upon the fruits of isolated trees may be prevented 
by investing a part of the trunk with any very viscous matter, 
and among others with a sort of pitch or tar, the residue of 
distillation from coal or charcoal. The same effect may be 
produced by ashes, or any pulverulent substance, strewed at 
the foot of the tree, but the pitch is better, because it stops 
the progress of many other pernicious animals. 
We now come to the aquatic pulmonaceous mollusca, 
which will not detain us long. The ONCHIDIA are without 
shells. The species called O. typhe, by Buchanan, has an 
oblong body, and is about an inch and three quarters long 
in a state of repose, but when it walks it becomes linear, 
obtuse at the two ends, and its length extends to two inches. 
The foot is formed by a great number of transverse wrinkles, 
by means of which the animal walks, and adheres pretty 
nearly after the manner of an earth-worm. The head changes 
form considerably when the animal walks, becoming extended, 
flat and oval. From the upper part of the head arise two 
tentacula entirely similar to those of the snails, and having 
the appearance of eyes at the extremity. 
This animal, says Buchanan, is not hermaphrodite, like 
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