ae 
246 HELIX ASPERSA. 
P robably these rock shelters origiflate in the shallow natural depressions 
so common in limestone, and these by being resorted to for untold centuries, 
bee ‘ome enlarged, deepened, and polished by the attrition of the foot; this 
is rendered the more likely as in certain cases the tracks leading to these 
Inbernacula have become channelled and worn by the repeated passage to 
and fro of countless generations of snails. 
These perforations were formerly assumed to be the work of the marine 
Pholauds, at a time when the rocks were immersed‘in the sea, and that 
ouly upon their upheaval were the perforations occupied by the snails; but 
that the snails themselves have formed these retreats is evidenced not only 
because //elices—and especially H. aspersa—are generally abundant im the 
vicinity and always occupying the freshest and least weathered holes, but 
also from the character of the perforations, which always have an ascending 
direction, with openings invariably below, features which clearly distinguish 
these Helicidian cavities from those of the marine boring bivalves, which 
always follow a descending direction with the opening above. 
These tunnels are usually about one inch in diameter, and three or more 
inches deep, smooth and regularly shaped inside, but may have subsidiary 
depressions in the walls, due to a persistent use of these places by many 
snails; these shelters must not, however, be confused with the oval or 
circular cavities due to weathering, nor with the bitterspar concavities so 
common in magnesian limestone, whose walls are often covered with 
crystals of lime, as such natural cavities frequently are. 
This habit of dinrnally or periodically resorting to permanent shelters 
unples the possession by these animals of a sense of direction or orientation 
and a power of memory. 
These perforated rock dwellings are found in many places i in Ireland, as at 
Nobber in Meath; Hillsport near the Gobbins Cliffs on Island Magee, 
Antrim; the neighbourhood of Lough Mask, and near Oughterard on the 
shores of Lough Gomi, West Galway. In Wales, at Great Orme’s Head, 
Llandudno, aa beneath the Castle Rock, Tenby. In England, they exist 
in Miller’s Dale, Derbyshire, at W helpington, Northumberland, and prob- 
ably at other places. 
Homine.— Helix aspersa is fond of home, and has frequently been 
observed to traverse with much labour, broad dusty roads, and climb 
rough walls to reach some favourite food, but instead of secreting itself 
at daybreak, near by, will retrace its toilsome journey morning after 
morning to 1ts retreat. 
Convincing evidence of the homing habit is furnished by an interesting 
experiment made by the late Mr. C. ‘Ashford in 1884. On April 19th he 
discovered in his garden at Christchurch behind the. innermost of three 
pieces of flagstone, leaning at an angle of about 75° against the green- 
house wall, a group of about a dozen individuals in siesta, all adhering 
to the stone about nine to twelve inches above the ground. He marked 
with white paint the shells of seven of the largest individuals, and at the 
saine time indicated the position of the group by scratching a line around 
them on the stone. 
On the 20th, at ten p.m., three of the marked shells were absent, having 
left for their feeding eround, and could not be traced, but on the following 
morning all the seven marked shells were again present, and resting within 
the circumscribed area. 
’ Ichi 
