LOCOMOTION IN GASTROPODS
159 «
fully than the foot alone canadhere to the glass. ‘
-
That this
attachment is due chiey to the adhesive properties of the mucus
jÏ
and not to the sucking action of the foot, is seen from the fact that
:
…
the attachment can be completely accomplished
minute
hole in a plate of glass. When a snail in such a position is seized
,
and drawn off, ’air is sucked in through the hole in the glass as the
'
middle of the foot rises, showing that under these extreme cir—
cumstances, the foot does act as a,sucker,_ butin the
'
resting state of the snail no such suction is exerted. All snails
with which I am acquainted deposit more or less mucus and
,
‘
though this is sometimes so small in amount that it can be demon—
.
strated only by means of powdered
i believe,
in so far as it is present, as a means of attachment.
Tbis.produc—
tion of mucus is highly developed in the pulmonates. Its rela—
tion to creeping on the surface—lm of water, as exhibited by many
_
fresh—water snails,_has long been recognized.
_
_
_
,
In some snails the f00t serves as an organ of attachment chiey
through its power of
The general surface of the foot is
_
applied closely to the substrate latter which the Central portion
is lifted thus converting the foot into a such—en This‘kind. of
-
_
attachment is well exemplied in Patella, Grepidula,_
Crep-*
idula fornicata can be made to créeporer
a Surface of glass and
can move with case and
hole in the glass.
'
If, however, the snail is diSturbed
times
when its foot is over
itself by
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endeavoring to
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llto. repletion thef01mmg COHC&V1ËYOÏIÈhSHÜÔGÏSIdGOf
f00t
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By suckingwater7throu‘g‘htheundeymgh16 Wen‘°ne1“în‘
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trasts the dîîcultyf,
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m…mi surface—hf attachmentpa1tlcularlyaellthas bce1i”in—
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