Leaving thine outgrown shell by life’s unresting sea!
—Oliver Wendell Holmes.
THE NAUTILUS AND OTHER CEPHALOPODS.
The highest group of mollusks belongs to the class Cephalopoda, which signifies head-footed, the name being given to them because the head is surrounded by a circle of eight or ten arms, which act both as arms and feet. Let us take as an example of this class the common squid of the Atlantic coast (Ommastrephes illecebrosa), and see how it is formed. The body is long and cylindrical and ends at the tail in a point; the dorsal side of the tail end has a pair of triangular fins. The body is practically a hollow cylinder or sac which contains the vital organs of the animal. The neck is in many genera fastened to this cylinder or mantle by an apparatus which may be likened to a button and button-hole. The head is rounded, has on either side the large, round eyes, and at the end it is split up into ten arms, two of which are longer than the others and are called the tentacular arms. On the inner side, the arms are provided with two rows of suckers, which are little, rounded cups placed on pedicels or stems and which form a vacuum when they touch an object and so cling to it. The two long arms are expanded and club-shaped at the end, each club being armed with four rows of suckers. Directly in the center of the circle of arms the mouth is placed and is provided with two sharp beaks like those of a parrot, only inverted. In addition to these organs there is a large siphon or tube on the ventral side, which is really an organ of locomotion, for it expels water from the mantle cavity with great force, thus rapidly sending the animal backward, its usual direction of propulsion. The body has no shell for protection, but in its place there is a long rod called a pen, which acts as a backbone to support the body of the animal, although of course not in the same sense as the backbone of vertebrated animals. In some cephalopods this pen is hard and stiff but in Ommastrephes it is thin and soft. Such is the general form of a cephalopod, familiar names of which are the Octopus, Squid, Nautilus, Paper-nautilus and Devil-fish. In this class, also, the majority of the shelled species are extinct, only a few living at the present time. The Ammonite is an example of the extinct cephalopods.
The most familiar member of this class to the layman is the Pearly Nautilus, the shell of which may be found on the mantel shelf or what-not of very many dwellings. The shell of the Nautilus is formed in a spiral and is made up of many chambers, all connected by a tube called a siphuncle, the outer chamber containing the animal and hence called the living chamber. The shell is called the “Pearly Nautilus,” but the pearly tints cannot be seen until the outer layer—which is yellowish-white with brown markings—is taken off, when the exquisite, rainbow-like colors may be observed.
While the shell of Nautilus is well known the animal is very rare in our museums, although the natives of the Fiji Islands, New Hebrides and New Caledonia are able to obtain it in large quantities for food and it is highly esteemed by them. During the voyage of H. M. S. Challenger around the world, a living Nautilus was captured by dredging in some three hundred and twenty fathoms near Mateeka Island, one of the Fiji group. This was placed in a tub and it swam about in a lively manner by ejecting water from its funnel. The tentacles, of which there are a larger number than in the other cephalopods, were spread out radially, like those of the sea anemone. The Nautilus lives among the coral reefs, at depths varying from three to three hundred fathoms or more.
BEAK OF OCTOPUS.
PAPER NAUTILUS.
(Argonauta tuberculata).
PEARLY NAUTILUS.
(Nautilus umbilicatus).
FROM COL. CHI. ACAD. SCIENCES.
The Fijian’s method of capturing the Nautilus for food is thus described (Tryon,—Structural and Systematic Conchology): “When the water is smooth so that the bottom, at several fathoms’ depth, near the border of the reef, may be distinctly seen, the fisherman in his little, frail canoe scrutinizes the sands and the coral masses below, to discover the animal in its favorite haunts. The experienced eye of the native may probably encounter it in its usual position, clinging to some prominent ledge, with the shell turned downwards. The tackle consists first, of a large, round, wicker-work basket, shaped very much like a cage rat-trap, having an opening above, with a circlet of points directed inward, so as to permit of entry but to preclude escape; secondly, a rough piece of rope of sufficient length to reach the bottom; and lastly, a small piece of branched wood, with the branches sharpened to form a sort of grapnel, to which a perforated stone is attached, answering the purpose of a sinker. The basket is now weighted with stones, well baited with boiled cray-fish (the principal food of the Nautilus is crabs of different species), and then dropped gently down near the victim. The trap is now either closely watched or a mark is placed upon the spot, and the fisherman pursues his avocation upon other parts of the reef until a certain period has elapsed, when he returns and in all probability finds the Nautilus in his cage, feeding upon the bait. The grapnel is now carefully let down, and having entered the basket through the opening on top, a dextrous movement of the hand fixes one or more of the points or hooks and the prize is safely hoisted into the canoe.”
The animal is made into soup by some of the natives while others boil it in a pot. The shells are used by the natives to make beautifully carved figures, the contrast of the dark outer coating against the light, pearly, inner coating producing a striking effect. The shell is also used in England and on the Continent to produce elegant cameos.