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]