LOCOMOTION IN GASTROPODS
169
waves, because in the gallop the body waves of this species, as
reported by Carlson, were retrogmde whereas the pedal waves in
all Helices thus far reported are direct.
SUMMARY
Ordinary gastropod locomotion is accomplished either without
pedal waves (arhythmic) or with pedal waves (rhythmic).
ln
rhythmic locomotion the waves may run from posterior to ante—
rior (direct) or the reverse (retrograde).
The foot may exhibit
one
(monotaxic), two (ditaxic), or four (tetrataXic) series, of
waves.
In the ditaxic foot the waves may be alternate or oppo—
site.
The gastropod foot is an organ of attachment through adhesion
(mucus) or suction, or both.
The pedal wave is an area of the foot that is lifted off the sub—
strate as compared with the rest of the foot and thereby freed
more or less from adhesion.
It is also the region of the foot that
moves forward, the rest of the foot remaining temporarily station—
ary.
Locomotion is the cumulative result of local forward motion
on the part of one section of the foot after another till the whole
foot has been moved.
The same type of muscular movement as
that seen in rhythmic locomotion can be present in a diffuse form
(not wave—like) in a gastropod foot and will result in locomotion.
169
waves, because in the gallop the body waves of this species, as
reported by Carlson, were retrogmde whereas the pedal waves in
all Helices thus far reported are direct.
SUMMARY
Ordinary gastropod locomotion is accomplished either without
pedal waves (arhythmic) or with pedal waves (rhythmic).
ln
rhythmic locomotion the waves may run from posterior to ante—
rior (direct) or the reverse (retrograde).
The foot may exhibit
one
(monotaxic), two (ditaxic), or four (tetrataXic) series, of
waves.
In the ditaxic foot the waves may be alternate or oppo—
site.
The gastropod foot is an organ of attachment through adhesion
(mucus) or suction, or both.
The pedal wave is an area of the foot that is lifted off the sub—
strate as compared with the rest of the foot and thereby freed
more or less from adhesion.
It is also the region of the foot that
moves forward, the rest of the foot remaining temporarily station—
ary.
Locomotion is the cumulative result of local forward motion
on the part of one section of the foot after another till the whole
foot has been moved.
The same type of muscular movement as
that seen in rhythmic locomotion can be present in a diffuse form
(not wave—like) in a gastropod foot and will result in locomotion.