This motive power is caused by countless cilia, the rapid vibration of which creates constant currents. This action preserves the health of the poor mollusc by ærating the water which passes over his respiratory organs.
That some such wonderful contrivance is adopted, for conveying food within the valves, too, is evident, when we consider that the Mussel is always affixed to some foreign substance, that it cannot hunt after prey, and therefore can subsist only upon whatever nutritious particles may be contained in the element in which it lives. These consist of minute animalculæ, principally crustacea, which are drawn within the shell by powerful currents.
I have often watched this phenomenon through a hand lens, and have seen the young shrimps and skip-jacks, for instance, notwithstanding the nimbleness of their movements, irresistibly drawn into the gulf of destruction. Even tolerably sized specimens that were seated in fancied security upon a valve of the Mussel, have suddenly been drawn in, out of sight. As an instance of the power of these currents, I may state that the water in a small aquarium is often seen to be affected by the respiratory action of a single bivalve. The same thing has even been apparent to the writer, while watching the movements of a colony of Barnacles attached to a Limpet, the most distant part of the fluid being gradually drawn near, in obedience to the beck of these delicate and graceful little creatures.
[CHAPTER XII.]
Terebella figulus.
(THE POTTER.)
'Whether progressing on the solid surface, or moving through the water, or
tunneling the sand, advancing or retreating in its tube, the Annelid performs
muscular feats distinguished at once for their complexity and harmony. In
grace of form the little worm excels the serpent. In regularity of march, the
thousand-footed Nereid outrivals the Centipede. The leaf-armed Phyllodoce swims
with greater beauty of mechanism than the fish; and the vulgar earthworm shames
the mole in the exactitude and skill of its subterranean operations. Why, then,
should the "humble worm" have remained so long without a historian? Is the
care, the wisdom, the love, the paternal solicitude of the Almighty not legible
in the surpassing organism, the ingenious architectures, the individual and
social habits, the adaptation of structure to the physical conditions of
existence of these "degraded beings?" Do not their habitations display His
care, their instincts His wisdom, their merriment His love, their vast
specific diversities His solicitous and inscrutable Providence.'—Dr. Williams.