When, first arrived, they feel the stronger blast, They lie supine and skim the liquid waste.

The natural barks out-do all human art When skilful floaters play the sailor's part.

Two feet they upward raise, and steady keep; These are the masts and rigging of the ship: A membrane stretch'd between supplies the sail, Bends from the masts, and swells before the gale.

Two other feet hang paddling on each side, And serve for oars to row and helm to guide.

'Tis thus they sail, pleased with the wanton game, The fish, the sailor, and the ship, the same.

But when the swimmers dread some dangers near The sportive pleasure yields to stronger fear.

No more they, wanton, drive before the blasts, But strike the sails, and bring down all the masts; The rolling waves their sinking sh.e.l.ls o'erflow, And dash them down again to sands below."

[75] The octopus.

Montgomery also thus exquisitely paraphrases the same idea in his 'Pelican Island':--

"Light as a flake of foam upon the wind, Keel upwards, from the deep emerged a sh.e.l.l, Shaped like the moon ere half her orb is filled.

Fraught with young life, it righted as it rose, And moved at will along the yielding water.

The native pilot of this little bark Put out a tier of oars on either side, Spread to the wafting breeze a twofold sail, And mounted up, and glided down, the billows In happy freedom, pleased to feel the air, And wander in the luxury of light."

Byron mentions the Nautilus in his 'Mutiny of the Bounty' as follows:--

"The tender Nautilus, who steers his prow, The sea-born sailor of his sh.e.l.l canoe, The ocean Mab--the fairy of the sea, Seems far less fragile, and alas! more free.

He, when the lightning-winged tornadoes sweep The surge, is safe: his port is in the deep; And triumphs o'er the armadas of mankind Which shake the world, yet crumble in the wind."

The very names by which this animal is known to the science which some persons erroneously think must be so hard and dry are poetic. In Aristotle's day it was called the _Nautilus_ or _Nauticus_, "the mariner," and though two thousand two hundred years have pa.s.sed since the great master wrote, the name still clings to it. As the Pearly Nautilus, a very different animal, also bears that name, Gualtieri perceived the necessity of distinguishing the Paper Nautilus from it, and was followed by Linnaeus, who therefore ent.i.tled the genus to which the latter belongs, _Argonauta_, after the ship _Argo_, in which Jason and his companions sailed to Colchis to carry off the "Golden Fleece"

suspended there in the temple of Mars, and guarded by brazen-hoofed bulls, whose nostrils breathed out fire and death, and by a watchful dragon that never slept. According to the Greek legend, the _Argo_ was named after its builder Argus, the son of Danaus, and was the first ship that ever was built. Oppian ('Halieutics,' book I.) expresses his opinion that the Nautilus served as a model for the man who first conceived the idea of constructing a ship, and embarking on the waters:--

"Ye Powers! when man first felled the stately trees, And pa.s.sed to distant sh.o.r.es on wafting seas, Whether some G.o.d inspired the wondrous thought, Or chance found out, or careful study sought; If humble guess may probably divine, And trace th' improvement to the first design, Some wight of prying search, who wond'ring stood When softer gales had smoothed the dimpled flood, Observed these careless swimmers floating move, And how each blast the easy sailor drove; Hence took the hint, hence formed th' imperfect draught, And ship-like fish the future seaman taught.

Then mortals tried the shelving hull to slope, To raise the mast, and twist the stronger rope, To fix the yards, let fly the crowded sails, Sweep through the curling waves, and court auspicious gales."

Pope, too, in his 'Essay on Man' (Ep. 3), adopted the idea in his exhortation--

"Learn of the little Nautilus to sail, Spread the thin oar, and catch the driving gale."

Poetry, like the wizard's spell, can make

"A nutsh.e.l.l seem a gilded barge, A sheeling seem a palace large,"

but the equally enchanting wand of science is able by a touch to dispel the illusion, and cause the object to appear in its true proportions. So with the fiction of the "Paper Sailor."

I have elsewhere described the affinities of the Nautili and their place in nature, therefore it will only be necessary for me here to allude to these very briefly, to explain the great and essential difference that exists between the two kinds of Nautilus which are popularly regarded as being one and the same animal.

The _Pearly_ Nautilus (_Nautilus pompilius_) and the Argonaut, which from having a fragile sh.e.l.l of somewhat similar external form is called the _Paper_ Nautilus, both belong to that great primary group of animals known as the _Mollusca_, and to the cla.s.s of it called the _Cephalopoda_, from their having their head in the middle of that which is the foot in other mollusks. In the Cephalopoda the foot is split or divided into eight segments in some families, and in others into ten segments, which radiate from the central head, like so many rays. These rays are not only used as feet, but, being highly flexible, are adapted for employment also as prehensile arms, with which their owner captures its prey, and they are rendered more perfect for this purpose by being furnished with suckers which hold firmly to any surface to which they are applied. The Cephalopods which have the foot divided into ten of these segments or arms are called the _Decapoda_, those which have only eight of them are called the _Octopoda_. All of these have _two_ plume-like gills--one on each side--and so are called _Dibranchiata_; and in the eight-armed section of these is the argonaut or Paper Nautilus. Of the Pearly Nautilus and the four-gilled order I shall have more to say by-and-by: at present we will follow the history of the argonaut.

[Ill.u.s.tration: FIG. 28--THE PAPER NAUTILUS (_Argonauta argo_) RETRACTED WITHIN ITS Sh.e.l.l.]

Notwithstanding all that has been written of it, it is only within the last fifty years that this has been correctly understood. An eight-armed cuttle was recognised and named _Ocythoe_, which, instead of having, like the common octopus, all of its eight arms thong-like and tapering to a point, had the two dorsal limbs flattened into a broad thin membrane. Although this animal was sometimes seen dead without any covering, it was generally found contained in a thin and slightly elastic univalve sh.e.l.l of graceful form, and bearing some resemblance to an elegantly shaped boat. It did not penetrate to the bottom of this sh.e.l.l; it was not attached to it by any muscular ligament, nor was the sh.e.l.l moulded on its body, nor apparently made to fit it. Hence it was long regarded as doubtful, and even by naturalists so recent and eminent as Dumeril and De Blainville, whether the octopod really secreted the sh.e.l.l, or whether, like the hermit-crab, it borrowed for its protection the sh.e.l.l of some other mollusk. Aristotle left the subject with the faithful acknowledgment: "As to the origin and growth of this sh.e.l.l nothing is yet exactly determined. It appears to be produced like other sh.e.l.ls; but even this is not evident, any more than it is whether the animal can live without it." Pliny, as usual, instead of throwing light on the matter, obscured it. He regarded the sh.e.l.l as the property of a gasteropod like the snail, and the octopod as an amateur yachtsman who occasionally went on board and took a trip in the frail craft, and a.s.sisted its owner to navigate it for the fun of the thing. This is what he says about it[76]: "Mutia.n.u.s reports that he saw in the Propontis a sh.e.l.l formed like a little ship, having the p.o.o.p turned up and the prow pointed. An animal called the _Nauplius_, resembling an octopus, was enclosed in the sh.e.l.l with its owner, for its amus.e.m.e.nt in the following manner. When the sea is calm the guest lowers his arms, and uses them as oars and a helm, whilst the owner of the sh.e.l.l expands himself to catch the wind; so that one has the pleasure of carrying and sailing, and the other of steering. Thus, these two otherwise senseless animals take their pleasure together; but the meeting them sailing in their sh.e.l.l is a bad omen for mariners, and foretells some great calamity."

[76] Naturalis Historia, lib. ix. cap. 30.

Although the animal was never found in any other sh.e.l.l, and the sh.e.l.l was never known to contain any other animal, and though, when the sh.e.l.l and the animal were found together they were always of proportionate size, this octopod, as I have said, was looked upon by some conchologists as a pirate who had taken possession of a ship which did not belong to him, until Madame Jeannette Power, a French lady then residing in Messina, having succeeded in keeping alive for a time an argonaut the sh.e.l.l of which had been broken in its capture, discovered that the animal quickly repaired the fracture, and reproduced the portions that had been broken off. Induced by this to make further experiments, she kept a number of living argonauts in cages sunk in the sea near the citadel of Messina, and in 1836 laid before the "Academy"

at Catania the following results of her observations of them:--

1st. That the argonaut constructs the sh.e.l.l which it inhabits.

2nd. That it quits the egg entirely naked, and forms the sh.e.l.l after its birth.

3rd. That it can repair its sh.e.l.l, if necessary, by a fresh deposit of material having the same chemical composition as its original sh.e.l.l.

4th. That this material is secreted by the palmate, or sail, arms, and is laid on the outside of the sh.e.l.l, to the exterior of which these membranous arms are closely applied.

Madame Power was mistaken on two points. Firstly, the construction of the sh.e.l.l does not commence after the birth of the animal, but, as has been shown by M. Duvernoy, its rudimentary form is distinctly visible by the aid of the microscope in the embryo, whilst still in the egg; and secondly, she continued to believe in the use of the membranous arms as sails, and of the others as oars. This fallacy was exploded by Captain Sander Rang, an officer of the French navy, and "port-captain" at Algiers, who carefully followed up Madame Power's experiments, and confirmed the more important of them. Thus were set at rest questions which for centuries had divided the opinions of zoologists.

The "Paper Nautilus" is, in fact, a female octopod provided with a portable nest, in which to carry about and protect her eggs, instead of brooding over them in some cranny of a rock, or within the recesses of a pile of sh.e.l.ls, as does her cousin the octopus. From the membranes of the two flattened and expanded arms she secretes and, if necessary, repairs her sh.e.l.l, and by applying them closely to its outer surface on each side, holds herself within it, for it is not fastened to her body by any attaching muscles. When disturbed or in danger she can loosen her hold, and, leaving her cradle, swim away independently of it. It has been said that, having once left it, she has not the ability nor perhaps the sagacity to re-enter her nest, and resume the guardianship of her eggs.[77] From my own observations of the breeding habits of other octopods I think this most improbable. The use and purpose of the sh.e.l.l of the argonaut will be better understood if I briefly describe what I have witnessed of the treatment of its eggs by its near relative, the octopus.

[77] Appendix to Sir Edward Belcher's 'Voyage of the "Samarang,"'

by Mr. Arthur Adams, a.s.sistant surgeon to the expedition.

"The eggs of the octopus," as I have elsewhere said, "when first laid, are small, oval, translucent granules, resembling little grains of rice, not quite an eighth of an inch long. They grow along and around a common stalk, to which every egg is separately attached, as grapes form part of a bunch. Each of the elongated bunches is affixed by a glutinous secretion to the surface of a rock or stone (never to seaweed, as has been erroneously stated), and hangs pendent by its stalk in a long white cl.u.s.ter, like a magnified catkin of the filbert, or, to use Aristotle's simile, like the fruit of the white alder. The length and number of these bunches varies according to the size and condition of the parent.

Those produced by a small octopus are seldom more than about three inches long, and from twelve to twenty in number; but a full-grown female will deposit from forty to fifty of such cl.u.s.ters, each about five inches in length. I have counted the eggs of which these cl.u.s.ters are composed, and find that there are about a thousand in each: so that a large octopus produces in one laying, usually extended over three days, a progeny of from 40,000 to 50,000. I have seen an octopus, when undisturbed, pa.s.s one of her arms beneath the hanging bunches of her eggs, and, dilating the membrane on each side of it into a boat-shaped hollow, gather and receive them in it as in a trough or cradle which exhibited in its general shape and outline a remarkable similarity to the sh.e.l.l of the argonaut, with the eggs of which octopod its own are almost identical in form and appearance. Then she would caress and gently rub them, occasionally turning towards them the mouth of her flexible exhalent and locomotor tube, like the nozzle of a fireman's hose-pipe, so as to direct upon them a jet of the excurrent water. I believe that the object of this syringing process is to free the eggs from parasitic animalcules, and possibly to prevent the growth of conferva, which, I have found, rapidly overspreads those removed from her attention."[78]

[78] 'The Octopus,' 1873, p. 57.

It has been suggested that the syringing may be for the purpose of keeping the water surrounding the eggs well aerated; but this is evidently erroneous, for the water ejected from the tube has been previously deprived of its oxygen, and consequently of its health-giving properties, whilst pa.s.sing over the gills of the parent. Week after week, for fifty days, a brooding octopus will continue to attend to her eggs with the most watchful and a.s.siduous care, seldom leaving them for an instant except to take food, which, without a brief abandonment of her position, would be beyond her reach. Aristotle a.s.serted that while the female is incubating she takes no food. This is incorrect; but in every case of the kind that has come under my observation the mother octopod, whenever she has been obliged to leave her nest, has returned to it as quickly as possible; and so I believe can, and does, the female argonaut to her sh.e.l.l, and that, too, without any difficulty. In her case the numerous cl.u.s.ters of eggs are all united at their origin to one slender and tapering stalk which is fixed by a spot of glutinous matter to the body-whorl of the spiral sh.e.l.l.

[Ill.u.s.tration: FIG. 29.--THE PAPER NAUTILUS (_Argonauta argo_) CRAWLING.]

This "paper-sailor," then, whom the poets have regarded as endowed with so much grace and beauty, and living in luxurious ease, is but a fine lady octopus after all. Turn her out of her handsome residence, and, instead of the fairy skimmer of the seas, you have before you an object apparently as free from loveliness and romance as her sprawling, uncanny-looking, relative. Instead of floating in her pleasure boat over the surface of the sea, the argonaut ordinarily crawls along the bottom, carrying her sh.e.l.l above her, keel uppermost; and the broad extremities of the two arms are not hoisted as sails, nor allowed when at rest to dangle over the side of the "boat;" but are used as a kind of hood by which the animal retains the sh.e.l.l in its proper position, as a man bearing a load on his shoulders holds it with his hands. When she comes to the surface, or progresses by swimming instead of walking, she does so in the same manner as the octopus: namely, by the forcible expulsion of water from her funnel-like tube.

But if truth compels us to deprive her of the counterfeit halo conferred on her by poets, we can award her, on behalf of science, a far n.o.bler crown; namely, that of the Queen of the whole great Invertebrate Animal Kingdom. For, the _Cephalopoda_, of which the argonaut is a highly organised member, are not only the highest in their own division, the _Mollusca_, but they are as far superior to all other animals which have no backbones, as man stands lord and king over all created beings that possess them.

[Ill.u.s.tration: FIG. 30.--THE PAPER NAUTILUS (_Argonauta argo_) SWIMMING.]

[Ill.u.s.tration: FIG. 31.--Sh.e.l.l OF THE PAPER NAUTILUS (_Argonauta argo_).]

Although in outward shape the spiral sh.e.l.l of the Pearly Nautilus (_Nautilus pompilius_) somewhat resembles that of the argonaut, its internal structure is very different. A section of it shows that it is divided into several chambers, each of which is part.i.tioned off from the adjoining ones, the last formed or external one, in which the animal lives, being much larger than the rest. The object and mode of construction of these chambers is as follows. As the animal grows, a constant secretion of new material takes place on the edge of the sh.e.l.l.

By this unceasing process of the addition of new sh.e.l.l in the form of a circular curve or coil around the older portion, the whole rapidly increases in size, both in diameter, and in the length of the chamber.

The Nautilus, requiring to keep the secreting portion of its mantle applied to the lip of the sh.e.l.l, finds the chamber in which it dwells gradually becoming inconveniently long for it, and therefore builds up a wall behind itself, and continues its work of enlarging its premises in front. Each of these walls, concave in front, towards the mouth of the sh.e.l.l, and concave behind, acts as a strong girder and support of the arch of the sh.e.l.l against the inward pressure of deep water: and it was formerly supposed that each successive chamber so constructed and vacated remained filled with air, and _thus_ became an additional float by which the constantly increasing weight of the growing sh.e.l.l was counter-balanced. By this beautiful adjustment of augmented floating power to increased weight, the buoyancy of the sh.e.l.l would be secured and its specific gravity maintained as nearly as possible equal to that of the surrounding water. This adjustment does probably take place, but in a somewhat different manner. As the Nautilus inhabits a depth of from twenty to forty fathoms, it is evident that the air within its sh.e.l.l would be displaced by the pressure of such a column of water.[79]

Accordingly, in every instance of the capture of a Nautilus the chambers of its sh.e.l.l have been found filled with water. It is not improbable that the fluid they contain may be less compressed, and exert less pressure from within outwards than that of the external superinc.u.mbent column of water, and that by this unbalanced pressure--under the same hydro-dynamic law which governs its mode of self-propulsion when swimming, and possibly in some degree within the control of the animal--the latter is relieved of much of the weight of its sh.e.l.l. When the Nautilus is at the bottom of the sea its movement is like that of a snail crawling along upon the ground with its sh.e.l.l above it. The sh.e.l.l, in proportion to the size of the animal that inhabits it, is a heavy one, and unless it were rendered semi-buoyant, its owner's strength would be severely taxed by the effort to drag it along. By the means indicated this portable domicile is borne lightly above the body of the Nautilus, without in any way impeding its progress.

[79] "At 100 fathoms the pressure exceeds 265 lbs. to the square inch. Empty bottles, securely corked, and sunk with weights beyond 100 fathoms, are always crushed. If filled with liquid the cork is driven in, and the liquid replaced by salt water; and in drawing the bottle up again the cork is returned to the neck of the bottle, generally in a reversed position."--Sir F. Beaufort, quoted by Dr.

S. P. Woodward in his 'Manual of the Mollusca.'

[Ill.u.s.tration: FIG. 32.--Sh.e.l.l OF THE PEARLY NAUTILUS (_Nautilus pompilius_).]

[Ill.u.s.tration: FIG. 33.--THE PEARLY NAUTILUS (_Nautilus pompilius_), AND SECTION OF ITS Sh.e.l.l. _After Professor Owen._

_a a_, Part.i.tions; _b b_, chambers; _b'_, the last-formed chamber, in which the animal lives; _c c_, the siphuncle; _d_, attaching muscle; _e e_, the hollow arms; _f f_, retractile tentacles; _g_, muscular disk, or foot; _h_, the eye; _i_, position of funnel.]

The chambers are all connected by a membranous tube slightly coated with nacre, which is connected with a large sac in the body of the animal, near the heart, and pa.s.ses through a circular orifice and a short projecting tube in the centre of each part.i.tion wall, till it ends in the smallest chamber at the inner extremity of the sh.e.l.l. Dean Buckland believed this "syphon" to be an hydraulic apparatus acting as a "fine adjustment" of the specific gravity of the sh.e.l.l, by admitting water within it when expanded, and excluding it when contracted. As it contains an artery and vein near its origin at the mantle, Professor Owen has regarded it as subservient to the maintenance of a low vitality in the vacated portion of the sh.e.l.l. Dr. Henry Woodward is of the opinion that, whilst in the early life of the Nautilus this siphuncle forms the main point of attachment between the animal and its sh.e.l.l, it is in the adult "simply an aborted embryonal organ whose function is now filled by the sh.e.l.l-muscles, but which in the more ancient and straight-sh.e.l.led representatives of the group (the Orthocerat.i.tes) was not merely an embryonal but an important organ in the adult."

Every one knows the sh.e.l.l of the Pearly Nautilus. It may be purchased at any sh.e.l.l-shop in a seaside watering-place, and is imported by hundreds every year from Singapore.[80] It is abundant in the waters of the Indian Archipelago, especially about the Molucca and Philippine Islands, and on the sh.o.r.es of New Caledonia and the Fiji and Solomon Islands. It has also been found alive on Pemba Island, near Zanzibar. It seems strange, therefore, that until about half a century ago hardly anything was known of the animal that secretes and inhabits it.

Rumphius, a Dutch naturalist, in his 'Rarities of Amboyna,' published, in 1705, a description of one with an engraving, incorrect in drawing, and deficient in detail; and until 1832 this was the only information which existed concerning it. The great Cuvier never saw one, and being acquainted only with the two-gilled cephalopods, he regarded the head-footed mollusks as absolutely isolated from all other animals in the kingdom of nature, even from the other cla.s.ses of the mollusca. It seemed, however, to Professor Owen, then only nineteen years of age, that in the only living representative of the four-gilled order, _Nautilus pompilius_, might be found the "missing link." When, therefore, in the year 1824, his fellow-student, Mr. George Bennett, was about to sail from England to the Polynesian Islands, young Richard Owen earnestly charged his friend to do his utmost to obtain, and bring home in alcohol, a specimen of the much-coveted Pearly Nautilus. The opportunity did not occur till one warm and calm Monday evening, the 24th of August, 1829, when a living Nautilus was seen at the surface of the water not far distant from the ship, in Marekini Bay, on the south-west coast of the Island of Erromango, New Hebrides, in the South Pacific Ocean. It looked like a dead tortoise-sh.e.l.l cat, as the sailors said. As it began to sink as soon as it was observed, it was struck at with a boat-hook, and was thus so much injured that it died shortly after being taken on board the ship. The sh.e.l.l was destroyed, but the soft body of the animal was preserved in spirits, and great was the joy of Mr. Owen when, in July, 1831, Mr. Bennett arrived with it in England, and presented it to the Royal College of Surgeons. Mr. Owen was then a.s.sistant-Conservator of the Museum of the College under Mr. Clift, who was afterwards his father-in-law. He immediately commenced to anatomise, describe, and figure his rare acquisition, and in the early part of 1832 published the result of his work in the form of a masterly treatise, which proved to be the foundation of his future fame.[81]