As the animal glides over the surface of the smooth weed, or over the
inequalities of the rough rock, we see that its thin papery margin is
frequently thrown up into waves, or folds, more or less distinctly
revealing the inferior surface. The movement is very even and uniform,
but the mode by which it is effected has not been satisfactorily
explained. It has been asserted that certain staff-like bristles which
project from the skin are used as oars, but this seems doubtful. It
is certain that the whole body of the animal, as of the entire class
to which it belongs, is densely clothed with minute vibratory cilia;
and these, while they probably serve as organs of locomotion in freely
swimming, do also without doubt make the whole skin a highly delicate
and sensitive organ of touch.
It is asserted of the near allies of this species, and probably is
equally true in this case, that if an individual be cut to pieces,
every portion continues to live and feel, from whatever part of the
body it may be taken; and what is not a little remarkable, each piece,
even if it be the end of the tail, as soon as the first moment of pain
and irritation has passed, begins to move in the same direction as that
in which the entire animal was advancing, as if the body were actuated
throughout by the same impulse; and, moreover, every division, even
if it is not more than the eighth or tenth part of the creature, will
become complete and perfect in all its organs.[63]
You would naturally expect to find the creature’s mouth at the front
end, where the two tentacles are placed, and the group of eyes, but
you would search for it there in vain. It is, in fact, situated most
strangely in the very midst of the belly; that is, at the very centre
of the inferior surface. And its structure is not less peculiar than
its locality. It consists of an orifice, in the midst of which lies a
sort of trumpet of enormous extent when opened, but when not in active
use thrown into many folds, which, when the animal wishes to seize
prey, are thrust forth, and being partly opened, take the appearance
of many irregular tentacles radiating in all directions, at the centre
of which is the œsophagus, leading immediately into a much ramified
intestine. The name which is given to this elegant and interesting
creature is _Eurylepta vittata_.[64]
[Illustration: