HELIX ASPERSA. DAS 
In addition to the weight of its shell, it can also without perceptible 
effort draw or bear on level ground a weight tifty times its own, or can 
ascend vertically carrying a burthen nine times the weight of the animal 
and shell combined, a feat equivalent to that of an ordinary man carrying 
a weight of about a ton. 
The locomotory waves! or muscular contractions as seen on the foot-sole 
during progression are very noticeable, and [ have invariably counted seven 
of these as being visible at one time, while the mucus-track left by its 
progress is, according to the observations of Mr. Lionel EH. Adams, peculiar 
and strikingly characteristic, not constituted as might be supposed by a 
more or less continuous trail of slime, but by a series of mucus-patches at 
practically regular intervals. 
—>w_ a8 VY EDP A HD 
a Fa e%awvnp BS 
Fic. 318.—Facsimile of a line of slime-tracks of a Helix asfersa upon th outer wall of Oalchill 
House, Reigate, reduced to half natural size (after a nature sketch by lL. E. Adams) 
H. aspersa at ordin: ary times respires about four times per minute, and, 
according to Mr. C. Ashford’s observations, with a pulse or heart-beat 
during siesta of about sixty-one times per minute, quicke wing to elghty- 
three contractions per minute when emerging from its shell, but the activity 
of these processes 18 very susceptible to modifications by heat or cold. 
‘his species from its size and habit of living in close association with 
human habitations has shown that under certain circumstances, as when 
crawling over a thin sheet of glass or other suitable vibratory substance, 
it can produce audible musical sounds, resembling those of the Alolian 
harp and analogous to those resulting from drawing «a moist finger over 
the edge of a wine glass. 
Though the shell is a great protection against enemies and vicissitudes 
of climate, yet its vital connection with the animal inhabitant 1s not 
essential to the continuance of the life and vigour of the suail, as specunens 
have been known which have continued active and well although the 
organic connection with the shell has been completely severed. 
It is rapidly disappearing from the “Black Country” of the midland 
counties, and is rare around the smoky manufacturing towns of the north 
of England: but whether this scarcity is due to the baleful influence of 
the smoky atmosphere and the consequent poisoning of the vegetation, or 
to the greater prevalence of thrushes and other birds preying upon them, 
has not been determined, 
In the Pyrenees it ascends to a considerable height, and was regarded 
y Dr. Fischer as the characteristic species of the region between 3,000 
and 4,000 feet above the sea: while Nevill records it as reachine 4,000 
feet in the Alps of Menton. 
1 Monog. 1., p. 192, f. 376 
