214 ARION HORTENSIS. 
Parasites and Enemies.—Probably almost equally lable with other 
species to destruction and annoyance by the ordinary enemies and para- 
sites of slug-life ; there is, however, little published evidence on the subject, 
although it has been observed that the Blindworm (Angus fragilis) which 
ereedily devours Agriolimax agrestis, would not eat the present species, 
possibly on account of its very leathery skin and sticky mucus. A further 
protective feature was suggested by the late Mr. Sherriff T'ye, who remarked 
upon the very remarkable likeness existing between this species and 
portions of the bloom-sheaths of the Black Poplar (Populus nigra), a pro- 
tective resemblance which is operative at a period of the slug’s greatest 
activity, and when its natural enemies, the thrushes, having young to 
provide for, are more industrious than usual in searching them out. 
Fossil.—Keunard and Woodward record calcareous particles, believed 
to be the vestigial shells of this species, from a holocene deposit on the 
face of a chalk escarpment at Exedown, near Wrotham, in West Kent. 
Variation.—he variation in this species runs in two chief lines, 
exemplified by the typical form and the large variety subfuscus. 
Férussae has remarked on the circumstance that succeeding generations 
do not invariably reproduce the variation prevalent during the preceding 
year, and Dr. Scharff has observed the same peculiarity in the locality at 
Killakee in the Dublin Mountains, the large brown variety swhfusca beimg 
exclusively found there in February, 1891, while in May of the previous 
year, in precisely the same spot all the specimens found were of the grey or 
typical form. In connection with this pomt, it may be remarked that 
Mr. Gain during his feeding experiments found a constant and marked 
difference as regards food in the likes and dislikes of the ordinary form 
and the var. subfusca. 
Dr. Simroth is of opinion that the light-coloured variations are the effect 
of warmth, while the darker-hued individuals owe their shade of colouring 
to cold ; but this alone does not universally apply. 
The grey variety is, however, found most prevalent in the open country, 
while the brown or yellowish variety are more numerous in other localities, 
though in gardens they may frequently be found in the closest association. 
The Arion cottianus Poll. from 
Piedmont, and Avion elongatus 
% 2 Collinge from Somerset, do not 
B seem to differ materially from 
» the typical form of the present 
JN species. 
yg) Prof. Cockerell, in The Concho- 
i OTA logist, 1891, p. 34, described an 
f Y} 7 immature Avion, found at Acton, 
a / \ Middlesex, which he named var. 
ah \ albipes. It was described as a 
form of Arion hortensis with 
ae] white foot and colourless slime. 
Mr. B. 'l'omlin, in The Journal 
re. _ Fic. 229. of Conchology, April 1887, re- 
BiG, 8 Proximal end of the Sexual ystemof cords two albine specimens found 
Fic. 229.—Proximal end of the Sexual system of at Hele, hear Ilfracombe, auaT 
Arion cottianus, enlarged (after Pollonera). 
, 
company with albine forms of 
other species, but he does not further allude to or describe them. 
