158
_
G. H. PARKER
,
of ”Ilyanassa with carmine suspended in seawater, not the least evi4
'
dence of cilia could be discovered.
I therefore believe that Ily—
;
anassa moves by a form of muscular activity that does not appear
as pedal waves and it is not improbable that other gastropods
‘
will be found that have the same peculiarity.
That Vlès recognized something of this kind may be inferred from his statement
that no changes in color can be seen in the creeping foot of Nassa,
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.
Buccinum, Aeolis, etc., and that the direction of the waves in
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_
these instances can be judged only by the deformations produced
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*
at the edge of the foot. As Vlès makes no further mention of
,
:NaSsain his subsequent account, I suspect that it is more or less
,
\
like Ilyanassa and is capable of little or no pedal—wave movement.
“
Thelocoinotion ofsuch gastropods I should designate as due to
=
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,
arhythzic pedal movements as contrasted with rhythmic pedal
_
such as have been fully classied by Vlès.
It is asignicant fact that all gastropods, irrespective of their
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_
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typeof mOvement (direct or retrograde), are restricted to
_
forward…locpmotion. None, so far as I am aware, can reverse
and move backWard as,
for instance, an earthw0rm can.
What—
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ever differences these various types of pedal movements possess,
_
they still lead to but one result, the forward locomotion of the
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_
_
THE
FOOT
AS
A HOLDFAST
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,
snail’s foot subser‘Ves‘ the
attachment
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and locomotion; As means of attachmentsnas Secrets abed
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_
and
the foot as a sucker; Both methods are com—
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meth@dÿ î$
în ÇXÎC‘>ÇSS of. the
FOI“
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Instance mHth P0maüaL1maxmæmsandotheraled
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Speœesthe m01stsuaceoftheeXpandedf@otwlsückmth
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