Part 15

The little specimens before us appear to belong to _Ebalia Bryerii_. It is porcellaneous white, tinged with pale scarlet. The little feet are painted scarlet on a white ground, especially the swollen-jointed claws, which are very gay, and under a lens show a marbled pattern of rich scarlet. This little Crab has an unique appearance, very attractive. Its motions are quick and sudden, mostly lateral, when alarmed; but it is habitually sluggish. Sometimes it appears to sham death; for if pushed, it at first tries to escape by running; but if the annoyance continues, it stiffens its limbs, and allows itself to be pushed without resistance; and when laid on its back in the water, will lie motionless for a minute or more, then suddenly turn over and crawl away.

Hosts of other things we capture in this summary sweeping of the sea-bottom, and by the time we have drifted down towards the Orestone, till we are close enough to make out the noble leaves of the tree-mallows that grow out of its rocky heights, we have accumulated a marvellous store,--almost enough, indeed, to set up a little provincial museum. Brittle-stars and urchins; cucumbers great and small; bivalve and univalve mollusks; swollen ascidians, smooth and warty; active, shuffling, sucking fishes; heaps of mossy _Bryozoa_; long bristling tufts of Hydroid zoophytes; naked worms, twining and writhing amidst the mass, gleaming in purple and pearl; sea-mice “armed in gold,” like Virgil’s Orion; tangled masses of Serpula-pipes, every one with its scarlet-crowned tenant; these, and multitudes of creatures besides, come up from the teeming sea-floor, and all at once claim our bewildered attention. And there is not one of the host that is not worthy of it; not one that would not be an eloquent witness of its Creator’s glory; but we must for the present neglect them all (not without hope of another meeting with some of them at least), in order to devote a few moments to one group of remarkable interest.

It is that unaccountable association of diverse and unrelated creatures, which, if we had not repeatedly seen it, we should not believe; the companionship of the Hermit-crab with the beautiful Cloak-anemone.

HERMIT-CRAB AND CLOAKLET.

Every one is familiar with that impudent and intrusive species of Hermit-crab,[119] which, with its foxy-brown head and legs protruding, rolls over shells and pebbles with rattling patter, on almost every beach. The species I speak of is quite distinct from that homely and amusing subject. Though attaining a size fully equal, its proportions are much slenderer and more elegant; and the colours,--a light fawn, set off with soft tints of azure, lilac, and scarlet,--are far more beautiful than those of its fellow; not to speak of technical characters which abundantly distinguish the two.

The companion of the Cloaklet, which bears the name of Mr. Prideaux of Plymouth, who first made it known, is exclusively a deep-water species. Found on various parts of our coast, it invariably occurs in this association. I believe the Crab in no instance lives without the Anemone, the Anemone in no instance without the Crab. Examples, indeed, do now and then occur, as mentioned by Forbes, in which the one comes up in the dredge without the other; but I believe this is only when the rude action of the dredge has frightened the Crab, and induced it suddenly to vacate the shell and desert its friend. The Bernard is never attended by any such companion.[120]

The history of the tenancy of univalve shells by these curious Crabs is well known; and the comic scenes that take place in the process of flitting from one tenement to another, larger and more commodious, have been so fully narrated by myself and other observers, that I shall assume the reader to be conversant with them.[121] And the rather because the association of the Crab with the Zoophyte is a thing so much more singular, so much more unaccountable, and so much less generally known, that I shall seek to tell the story in some detail.

HERMIT AND CLOAKLET.

To premise:--the Cloaklet is an anemone of the _Sagartia_ family, beautiful in its colours and remarkable in its form. It is generally reddish-brown on the outer (lower) part of its body, which hue melts into snowy white on the upper parts; the whole studded with rosy-purple spots, and surmounted by a marginal line of pale scarlet. The tentacles and disk are pure white. It attains a rather large size, and has the peculiarity of being not round in its basal outline like other Anemones, but oblong, the base expanding in two lateral directions. It always selects the inner lip of an univalve shell for its place of adhesion, and the two lateral ends of its base gradually extend around the mouth of the shell till they meet on its outer edge, and unite with a suture: thus the outline of the animal forms a ring.

It had often been an interesting speculation with me, in what manner the due relation of size is maintained between the _Adamsia_ and the shell, in the progressive growth of the former. There is a manifest proportion between the two, the young Cloaklet occupying a small shell, such as that of a _Littorina_ or _Trochus_; the full-grown individual a large one, such as that of a _Natica_ or _Buccinum_. The Crab is able to shift from a smaller to a larger shell when he needs enlarged accommodation; and since we know that his congener, _P. Bernhardus_, does this habitually, we naturally conclude that such is the habit of _P. Prideauxii_. Presuming then that this is the case, what becomes of the _Adamsia_? If the Crab shifts his quarters and leaves the _Adamsia_ behind, the association is broken, and we should constantly find _Paguri_ without _Adamsiæ_, and _Adamsiæ_ without _Paguri_. But we find neither the one nor the other.

On the other hand, if _Adamsia_ is able to shift its quarters also, how does it proceed in its search for a new shell? If it forsakes the old tenement at the same time as the Crab, and together with it takes possession of the new one, by what means is unity of will and action secured? What communication of thought takes place from the one to the other? As the _Adamsia_ does not adhere to the Crab, but to the shell, that is, as they are independent of each other’s movements, who takes the initiative? Who goes to seek the lodging? And at what point of the transaction does the other come in? All these questions I had mused upon with interest; and at length received some light towards their solution.

On the 10th of January, 1859, I obtained, by dredging, in Torbay, a specimen of _Adamsia palliata_, about half-grown, on a rather small shell of _Natica monilifera_, tenanted by a _Pagurus Prideauxii_, which seemed already too big for his habitation. Having put them into a well-established tank of large dimensions, the contents of which were in excellent condition, I succeeded in doing what I had never done before, domiciliating both Crab and _Adamsia_. Both continued in the highest health, and became quite at home.

After about three months, however, I noticed that the _Adamsia_ was not looking so well. One side or wing had gradually loosed its hold of the shell-lip, so that it hung loosely down beneath the breast of the Crab. Yet in other respects the zoophyte seemed healthy. Latterly, too, the Crab had manifested symptoms of uncomfortable straitness, in the great extrusion of his fore-parts; so great, indeed, as to expose even the front of the soft abdomen. Yet I felt reluctant to present to the Crab a larger shell, fearing that he would, in availing himself of it, desert his zoophyte friend, which would then die, and I should lose the specimen.

At length the desire to solve a problem in science prevailed over this feeling. A fact is better than a specimen. And so (on April 21st) I selected from my cabinet a full-grown _Natica_ shell, and placed it on the tank-floor, not far from the disconsolate trio.

The _Pagurus_ presently found the new shell, and immediately began to overhaul it. He did not do, however, as his brother Bernhard would have done, at once shift into the new house. Having turned it mouth upward, he took hold of the outer and inner lip, each with a claw, and began to drag it about the tank. Occasionally he relinquished the hold of one claw, and probed the interior in the usual manner, and then resumed his march. I watched the proceedings for an hour or more, when, having other work to do, I left him alone.

The thought did occur to me--Can this delay be intended to make the _Adamsia_ cognizant of what is in contemplation, and to prepare it for the change? But I dismissed it as unlikely.

After about an hour’s absence I returned to the examination. The _Pagurus_ was comfortably lodged in his new abode, and the old one, which now looked small indeed, lay deserted at some little distance. I eagerly turned the latter over, to see what was the condition of the _Adamsia_. Lo! no _Adamsia_ was there; and the _Pagurus_, presently approaching the front of the tank, I saw, to my great gratification, that the old association was unbroken. There was the _Adamsia_, with one wing adhering to the lip of the new shell, and apparently the opposite wing also; but, from the position of the group, this I could not be quite certain of. The situation of the zoophyte was quite normal,--the centre immediately below the breast of the Crab, and in contact with the inner lip of the shell, while that wing which I could clearly see was creeping round upon the outer lip.

Examining now more closely the condition of things, with a lens, I saw that the central part of the _Adamsia’s_ base was adherent by a small point of its surface to the under side of the thorax of the Crab, between the bases of the legs.

Now this adhesion to the Crab is a circumstance which, so far as I know, never takes place in the ordinary relations of the animals; and therefore I could not but think it an extraordinary and temporary provision for the removal of the _Adamsia_ from the old to the new shell, and for the correct adjustment of its position on the latter.

How then can we avoid the conclusion, that, as soon as the Crab had found the new shell to be suitable for exchange, the _Adamsia_ also was made cognizant of the same fact; and that, during the two hours which followed, the latter loosened its adhesion to the old shell, and, laying hold of the bosom of its protector, was by him carried to the new house, where immediately it began to secure the like hold to that which it had just relinquished?

Eleven days elapsed after the above observations were made, when I obtained another interesting fact bearing on this strange association. The _Adamsia_ had not looked well since the change of residence; its adhesion to the shell had been but partial at the best, some days more, some days less, extensive; but for the most part a considerable portion of the zoophyte was hanging down from the shell. The Crab, on the other hand, was evidently in clover, and showed no inclination to go back to his old lodging.

On the 2d of May I found the _Adamsia_ detached, and lying helpless on the bottom of the tank, beneath the Crab, who, when disturbed, walked off, leaving his companion behind. I thought now it was a gone case, and that it was all up with my elegant _protegée_.

An hour or two afterwards, however, how great was my surprise to see the _Adamsia_ fairly established again, adhering to the shell by a good broad base, and looking more healthy than I had seen her for many a day! Strangely enough, she was adhering in a false position, having taken hold on the outer lip of the shell, instead of the inner, as usual. Here was a fresh proof of intelligence somewhere; and I at once set myself to find where.

Carefully taking up the shell with the aquarium-tongs, and bringing it close to the surface, but not out of water, I gently dislodged the _Adamsia_ with my fingers, and allowed it to fall prone upon the bottom. I then released the shell with its tenant, and drove the latter towards the spot where the zoophyte lay.

No sooner did the Crab touch the _Adamsia_ than he took hold of it with his claws, first with one, then with both, and I saw in an instant what he was going to do. In the most orderly and expert manner he proceeded to apply the _Adamsia_ to the shell. He found it lying base upward, and therefore the first thing was to turn it quite round. With the alternate grasps of the two pincer-claws, nipping up the flesh of the _Adamsia_ rudely enough, as it seemed, he got hold of it so that he could press the base against the proper part of the shell, the inner lip. Then he remained quite still, holding it firmly pressed, for about ten minutes; at the end of which time he cautiously drew away first one claw, and then the other; and, beginning to walk away, I had the pleasure to see that the _Adamsia_ was once more fairly adhering, and now in the right place.

Two days after the _Adamsia_ was again lost. On searching I discovered it lying in a crevice, whence I plucked it, and laid it on the bottom. Here again the Crab found it, and immediately went through the same process as last described, and again made it adhere. But I saw that the _Adamsia_ was unhealthy, for it seemed to have but enfeebled power of retaining its hold. The manifestation of the mode in which the instinctive actings of the two creatures occur is, however, sufficiently clear. The Crab is certainly the more active promoter of the partnership; it is abundantly evident that he values the company of his elegant but very heterogeneous associate. These last observations compel the conclusion that the claws of the Crab are always employed in the transference of the Cloaklet from shell to shell.[122]

PROOFS OF INTELLIGENCE.

But what a series of instincts does this series of facts open to us! The knowledge by the Crab of the qualities of the new shell; the delay of his own satisfaction till his associate is ready; the power of communicating the fact to her; the power in her of apprehending the communication; her immediate obedience to the intimation; her relinquishment of her wonted hold, which for months at least had never been interrupted; her simultaneous taking of a new, unwonted hold, where alone it could have been of any use; the concerted action of both; the removal; her relinquishment of the transitory adhesion as soon as its purpose was accomplished; her simultaneous grasp of the new shell in the proper places; all these are wonderful to contemplate, wonderful considered singly, far more wonderful in their cumulation. Is there not here much more than what our modern physiologists are prone to call automatic movements, the results of reflex sensorial action? The more I study the lower animals, the more firmly am I persuaded of the existence in them of psychical faculties, such as consciousness, intelligence, will, and choice! and _that_, even in those forms in which as yet no nervous centres have been detected.

FOOTNOTES:

[113] _Solaster papposa_, represented, about one-third of the natural size, by the right-hand figure on Plate XXV.

[114] _Ophiocoma granulata_, seen in the upper left-hand corner of Plate XXV.

[115] _Gonoplax angulatus_, the principal figure in Plate XXVI., occupying the foreground.

[116] _Ebalia_; a male specimen of _E. Bryerii_ is represented in Plate XXVI., clinging to the stem of an aged tangle, in the upper left-hand corner.

[117] _E. Pennantii._

[118] _Aquarium_ (2d Ed.), p. 154.

[119] _Pagurus Bernhardus_; so called, I presume, from Bernard, the monk, in allusion to its passing its life in its cell: whence also “Hermit-crab.”

[120] In Plate XXVII. both species are represented. In the foreground is a full-grown _Pagurus Prideauxii_ tenanting a whelk-shell, which carries a fine specimen of the Cloak Anemone (_Adamsia palliata_). In the distance is seen _P. Bernhardus_, inhabiting a shell of _Natica_.

[121] See my _Aquarium_, p. 156, _et seq._

[122] These facts were originally published in the _Zoologist_ for 1859 (p. 6580). In the _Quarterly Journal of Science_ for January 1864, some observations of Colonel Stuart Wortley are cited, confirmatory of mine, which, however, are wholly ignored by the Editors.

X.

OCTOBER

PORTUGUESE MAN-OF-WAR.

The naturalist who has occasion to make a voyage over the warmer regions of the ocean, is continually delighted by the sight of numberless forms of animals, principally of the lower invertebrate classes, which either habitually swim at the surface of the sea, or come thither at intervals to enjoy the stimulus of the atmospheric air. Many of these are exceedingly curious and interesting; many totally unlike any forms that occur on the shores of temperate countries; many elegant in contour, and adorned with brilliant colours. Perhaps there is scarcely any that takes a stronger hold on the fancy, certainly none is more familiar, than a little thing that he daily marks floating in the sunlit waves, as the ship glides swiftly by, which the sailors tell him is the Portuguese man-of-war.[123] Perhaps a dead calm has settled over the sea; and the observer, as he leans over the bulwarks of the ship, has opportunities of scrutinizing the ocean-rover at leisure, as it lazily rises and falls on the long sluggish heavings of the glassy surface. Then he sees that the comparison of the stranger to a ship is a felicitous one; for, at a little distance it might well be mistaken for a child’s mimic ship, shining in all the gaudy painting in which it came out of the toy-shop; and he is ready to pity the forlorn urchin in tunic and knickerbockers, whose cherished boat has broken her moorings of thread, and drifted with winds and tides far, far out of reach of land.

Not unfrequently does one of the tiny vessels come so close alongside that, by means of the ship’s bucket, with a little assistance from a smart fellow, who has jumped into the “chains” with a boat-hook, it is captured, and brought on deck to be subjected to scientific examination. A dozen voices are however lifted, warning you by no means to touch it, for well the experienced seaman knows its terrific powers of defence. It does not now appear so like a ship as when it was at a distance. It is an oblong bladder of tough membrane, varying considerably in shape (and hence no two original figures agree in this respect), and also in size, from less than an inch in length to the size of a man’s hat. Once in a voyage to Mobile, when rounding the Florida Reef, I was nearly a whole day passing through a fleet of these little Portuguese men-of-war, which studded the smooth sea as far as the eye could reach, and must have extended for many miles. These were of all sizes within the limits I have mentioned. Generally, there is a conspicuous difference between the two extremities of the bladder, one end being rounded, while the other is more pointed, or is terminated by a small knob-like swelling, or beak-shaped excrescence, where there is a minute orifice. Sometimes, however, no such excrescence is visible, and the orifice cannot be detected.

The bladder is filled with air, and therefore floats almost wholly on the surface. Along the upper side, nearly from end to end, runs a thin ridge of membrane, which is capable of being erected at the will of the animal to a considerable height, fully equal at times to the entire width of the bladder, when it represents an arched fore-and-aft sail, the bladder being the hull. From the bottom of the bladder, near the thickest extremity, where there is a denser portion of the membrane, depends a crowded mass of organs, most of which take the form of very slender, highly contractile, and moveable threads, which hang down into the deep to a depth of many feet, or even occasionally, of several yards.

THE BLADDER.

The colours of this curious creature are very vivid: the bladder, though in some parts transparent and colourless, and in some specimens almost entirely so, is in general painted with the richest blues and purples, mingled with green and crimson to some less extent; these all being, not as sometimes described, iridescent or changeable reflections, but positive colours, independent of the incidence of light, and, for the most part possessing great depth and fulness. The sail-like erectile membrane is transparent, tinted towards the edge with a lovely rose-pink hue, the colours arranged in a peculiar fringe-like manner.

When examined anatomically, the bladder is found to be composed of two walls of membrane, which are lined with cilia, and have between them the nutritive fluid which supplies the place of blood. Besides this, the double membrane is turned in, somewhat as the foot of a stocking is inverted, when ready for putting on; and thus there is a bladder within a bladder, both having double walls. The inner (_pneumatocyst_) is much smaller than the outer (_pneumatophore_); and the point where it is turned in is contracted to the almost imperceptible orifice that has been mentioned. The inner bladder sends up closed tubular folds into the crest, which, being invested by the membranous walls of the outer sac, give to the sail that appearance of vertical wrinkles which is conspicuous.

EFFECTS OF POISON.