ARION ATER. 173 
is believed to be impregnated with its matter, the slug is then securely 
impaled upon a thorn, where it dies, and gradually withers up, by which 
time the wart will also have disappeared. In Northamptonshire it is con- 
sidered necessary to repeat the operation on nine successive nights, by 
which time the wart will have gone. 
In 1890 Mr. Kew observed an old man in a garden at Highgate, in the 
suburbs of London, engaged in gathering A. ater for the purpose of making 
ointment; while in Lincolnshire the appearance of “black snails” is regarded, 
especially at harvest time, as a most reliable sign of impending rain. 
In former times, the ancients in their ignorance of mollusca, believed 
that slugs in general, and this one in particular, as being the most obvious 
and conspicuous of them, to be the same animals as those possessed of 
shells, and Albertus Magnus and Gesner, influenced in part by a passage 
in Allian, believed that snails had the power of quitting and returning to 
their shells at pleasure, while Kramer in 1736 attempted to prove that 
this was actually the fact. 
Fossil.—The chalky granules, believed to be the internal shells of 
A. ater, are recorded by Sandberger from the gravels and brick-earths of 
the Upper Pleistocene beds of this country. 
PLeIsTocENE.—Messrs. Kennard and Woodward report it as found in the 
beds at Swalecliffe, a mile west of Herne Bay, in East Kent; and in the 
same deposits at Ilford and Uphall, in South Essex. 
In France it is known from beds of similar age in the Somme Valley. 
Ho tocent.—In West Kent, the same authors chronicle its occurrence at 
Maidstone, in a disused chalk-pit, near Otford railway station, and in a 
deposit on face of chalk escarpment, at Exedown, near Wrotham. In 
Surrey, at the Horse-shoe deposit, Colley pit, Reigate, the internal granules 
were very abundant between the 2-feet and 3-feet levels. In Essex, they 
have been found in the alluvium at Walthamstow. In Berkshire, in the 
Kennet Valley deposits at Newbury; and in Oxfordshire at Westbury and 
Clifton-Hampden, near Oxford. 
Parasites and Enemies.—In addition to the numerons enemies of 
the mollusca generally, Avion ater is internally infested by three different 
species of Leptodera, a genus of Nematoid worms. Leptodera appendicu- 
lata, a species remarkable for the possession of a pair of caudal fringes, 
inhabits the foot of this species while in the larval state, becoming sexual 
in the decomposing body of the snail at its death. Another species is 
found in the intestinal canal, and the third species in the salivary glands. 
Fic. 203.—An Entozoic Parasite from Avion ater var. rufa X 50 (after Van den Broeck). 
Professor Owen records that the larva of a Tania is found encysted in 
the pulmonary sac, which is believed to attain its full sexual maturity only 
when occupying the intestinal canal of some warm-blooded animal. 
M. Van den Broeck records the abundance of a species of Entozoon 
in the intestinal canal of the var. rufa, but which was first detected within 
the egg of Limar arborum. 
