Now, however, we must turn aside to look at other objects. Attached to the base of the Lobster-horn, we find several examples of an interesting Cirripede.[135] It is of a dirty buff, or drab hue, semi-transparent, in outline something like a butcher’s cleaver, handle and blade, or still more like a silver butter-knife, but much thicker in proportion; the handle represented by the cartilaginous and flexible stalk, the blade by the compressed valves. These vary much in regularity of form, some being nearly oval, little wider than the stalk, others angular and much wider. The body throws itself vigorously about on the stalk, when disturbed. The valves open, and out comes a widely radiating hand, of brilliantly glassy fingers, the joints and comb-like bristles of which glitter and sparkle as I hold it up in a tumbler of sea-water, examining it with a lens, with a lamp behind. It remains some seconds expanded, as if enjoying contact with the water; or perhaps, if I may draw inferences from some slight twitchings, feeling and testing for the accidental presence of invisible atoms that might serve it for food; then suddenly the fingers close together, and the hand is drawn in with a snap, as if it had taken some prize, though the lens had revealed nothing there. Soon it opens again, and exhibits the same manœuvres. A front view of the hand, the bristle-like fingers radiating in all directions, is a very attractive object for a low magnifying power. There are several tiny ones in another group, the bodies of which are not bigger than hempseed; these make their grasps apparently at random, with regular alternation, much as the commoner Barnacles do.

Of these latter we have no lack, many of the rough shells and small pebbles being incrusted with crowded colonies of the commonest Acorn Barnacle.[136] We see the same species, by tens of thousands, covering roods and roods of the seaward surfaces of our rough rocks between tide-marks. They rarely exceed one-third of an inch in diameter at base; but there is a much more massive kind, rough with ridges and furrows, and hence called porcate, occasionally found adhering to the jutting angles of rocks hereabout, and much more commonly on the coast of South Wales, around Tenby.

These Acorn Barnacles have no foot-stalk, but adhere by the whole broad base to the rock or shell, on which a floor either of strong stone, or of thin membrane is formed, and from whose margin the stony plates arise, enclosing a more or less conical chamber, with an orifice at the summit. If we look in at this during the life of the animal, we discern, a little below the rim, some angular valves, which meet with a straight suture, and close the interior. These are moveable, however; and under water they open like folding-doors, and a hand of many fingers, each composed of many joints, modelled on the same plan as that of the Scalpellum, but less delicate, protrudes, which makes its cast for prey, and is withdrawn beneath the again-closed valves.

The winds and waves not unfrequently bear into our harbours fragments of spars, old water-casks, or planks, from the hull of some ill-fated ship foundered in the inhospitable ocean, which are teeming with life. Conspicuous on such “flotsam and jetsam,” as our ancient maritime law-codes term these relics, we mark the Necked Barnacles,[137] so long believed by our ancestors, with a most implicit credence, to be legitimately descended from, and to be in turn the regular and normal parents of, a certain species of goose, common enough on our northern shores. That myth may, however, be dismissed with a mere recollection.

In this form the neck or stalk is greatly developed, frequently reaching to eight inches and upwards in length, with a thickness of half an inch. Externally it is very tough and leathery, yet it is sufficiently flexible to be jerked vigorously in various directions, and thrown into contorted curves, by means of muscles that run through it. The lower part adheres firmly to the support, which is generally wood, and I believe only in a floating condition. The bottoms of ships in warm climates are generally much infested with these parasites, which acquire a great size in the course of a voyage of only a few months.

The valves resemble delicate shells, and are elegantly painted with various tints of light blue varied with white, the edges of the valves being often rich scarlet or orange. The hand is deep purplish black, the fingers stout and massive; but not differing in their structure or in their mode of use, from those of their sessile fellows.

Perhaps the most interesting of all our native forms of these Cirripedes—for true parasitism is always a subject of peculiar interest—is that little species[138] which invariably selects as its support the stony walls of a coral. Our beautiful Cup-coral, so common at extreme low-water level on both the north and south coasts of Devon and Cornwall, is the favourite species of the Pyrgoma. So far as my experience goes, extending over a very extensive series of specimens, I think about one in six of these corals carries the parasite, generally situated either on, or just without, the margin of the cup. I say, “generally,” because Mr. Guyon has lately recorded what he thinks an exception to the rule, in two Pyrgomata situated on the rock close to the base of the coral. But Mr. Holdsworth, an excellent authority, considers that the exception is more apparent than real. The number of these little intruders varies from one upwards. I possess specimens, one of which carries nine, the other eleven; the appearance of the ovate barnacles, each with its conspicuous orifice, crowded all round the edge of the coral, is exceedingly curious and novel. Mr. Holdsworth mentions, however, that he has seen fourteen Pyrgomata attached to a single Caryophyllia, which was dredged in Plymouth Sound.[139]

The transformations of these animals, as investigated by Mr. Darwin, are of great interest. The Cirripede, whatever its genus, and whatever its peculiarities of adult existence, begins its life in a form exactly like that of a young Entomostracous Crustacean, with a broad carapace, a single eye, two pairs of antennæ, three pairs of jointed, branched, and well-bristled legs, and a forked tail. It casts off its skin twice, undergoing, especially at the second moult, a considerable change of figure. At the third moult it has assumed almost the form of a Cypris, or Cythere, being enclosed in a bivalve shell, in which the front of the head with the antennæ is greatly developed, equalling in bulk all the rest of the body. The single eye has become two, which are very large, and attached to the outer arms of two bent processes like the letters U U, which are seen within the thorax.

In this stage the little animal searches about for some spot suitable for permanent residence; a ship’s bottom, a piece of floating timber, the back of a whale or turtle, or the solid rock. When its selection is made, the two antennæ, which project from the shell, pour out a glutinous gum or cement, which hardens in water, and firmly attaches them. Henceforth the animal is a fixture, glued by the front of its head to its support. Another moult now takes place; the bivalve shell is thrown off, with the great eyes, and their U-like processes, and the little Cirripede is seen in its true form. It is now in effect a Stomapod Crustacean, attached by its antennæ, the head greatly lengthened (in Lepas, etc.), the carapace composed of several pieces (valves), the legs modified into cirri, and made to execute their grasping movements backwards instead of forwards, and the whole abdomen obliterated, or reduced to an inconspicuous rudiment.

Let us resume our grubbing in the heterogeneous heap of matters with which the dredge has enriched us. The tube-dwelling Annelida are generally prominent in such collections, and accordingly we see conspicuous here great and small heaps of contorted tubes, that look as if a batch of tobacco-pipe stems had become agglutinated together, and strangely twisted in the baking. These are the shelly tubes of the beautiful scarlet Serpula,[140] a general favourite in our aquaria, easily and abundantly procured, and readily maintained in health and beauty for a considerable period. I need scarcely describe the general appearance of an object so commonly kept, and so frequently gazed upon. Many tubes are usually found growing together, adhering to the same shell, bit of broken pottery, or small stone; all much intertwined, and mutually adherent, so that it is practically hopeless to attempt to isolate one. Yet by studying many specimens we are able to ascertain that each individual is at first a very slender tube of white calcareous shell, not thicker than sewing-cotton;[141] this rapidly increases both in thickness and in length, soon rising from its support, to which it at first adhered by the lime deposited in a soft state, and continuing the rest of its growth free, in a direction forming various angles with the ground line, and most irregularly twined and contorted. For the final half of its length, or thereabout, the tube attains a diameter of one-fourth of an inch, the walls being sufficiently thick to be solid, yet leaving an ample cavity for the residence of the industrious mechanic, who thus skilfully builds up his own house.

If we carefully break, by a moderated blow with a hammer, the shelly tube, so as not to crush the tenant, we are able to expose the latter to view. We then see that its length is by no means commensurate with the length of its house, of which indeed it inhabits only the last-made portion, having behind a roomy space into which to retire in case of need. It is not more than an inch or an inch and a quarter long, rather wide in proportion, and flattened, with a well-marked distinction between the corslet and the abdomen. The former carries on each side prominent foot-warts, which are vigorously protrusile, and within which bundles of strong bristles are thrust to and fro. On the upper part of each foot, extending half across the back, is a row of microscopic hooks, wielded by long thread-like tendons, which are fixed, on mechanical principles, to the attached end of each hook. By the aid of these, the Serpula so cleverly withdraws with lightning-like rapidity on alarm. By the action of muscles of indescribable delicacy, the hooks are projected to some distance beyond the surface of the body. These organs are formed on the model of a hedger’s bill-hook, only that the edge is cut into long teeth. Carefully counting them I have found that each Serpula carries about 1900 such hooks on its corslet, and that each of these being cut into seven teeth, there are between 13,000 and 14,000 teeth employed in catching the lining membrane of the tube, and in drawing the animal back.

The protrusion of the fore parts, which takes place in a much more leisurely manner, is performed by quite another set of instruments, formed on a totally different principle. Their action is a pushing or shoving. The instruments for effecting this are the fine but strong bristles which run through the feet. Each bristle is composed of a strong rigid unyielding shaft, having an expanded shoulder drawn out into a point. On one side of this pointed shoulder may be remarked a double row of fine teeth, admirably calculated to catch against any roughnesses of the surface with which they come into contact, against which they then push with the force of the proper muscles. Acting diagonally backwards, from the two sides of the animal, the result of the combination of the forces is that the animal itself is pushed forwards, and so protruded from the mouth of the tube. The feet on the hinder portion of the body are, according to Dr. Williams,[142] modified in structure with express reference to the duties of mopping, sweeping, scraping, and wiping the inferior closed end of the habitation. I think, however, he has forgotten that this end, formed by the animal in its infant state, must now be very much too strait to be reached by any portion of the body, or by any of its organs.

Dwelling in a tubular house, the Serpula would find its breathing organs scarcely available, if these were placed, as in most Annelida, in pairs on the body-segments. They are therefore much modified, and that not only in position but in form. They consist of most elegant comb-like filaments, richly coloured, arranged in two rows around the front extremity, one row on each side of the mouth. They are graduated in length, and are so affixed, that, where the rows meet behind, they can be thrown-in, so that a vertical view of the circular coronet shows a great sinus in it. These brilliant gill-tufts form the most attractive feature in these elegant Worms, and are individually most exquisite examples of mechanical contrivance. Examined under a low microscopic power, they present a most charming spectacle. Each filament consists of a pellucid cartilaginous stem, from one side of which springs a double row of secondary filaments like the teeth of a comb. Within both stem and filaments the red blood may be seen, with beautiful distinctness, driven along the artery, and back by the vein (which are placed close side by side) in ceaseless course, constituting a very striking spectacle.

The exterior of these organs is set with strong cilia, so arranged that the water-current is vigorously driven upward along one side of the filament, and downward along the other. Yet the combined result of all the branchial currents is to bring a powerful vortex into the enclosed funnel, the bottom of which terminates in the mouth. The food which sustains nutrition is thus brought to be swallowed, a large quantity of water being at the same time constantly poured into the body; this is discharged (by the agency of a ciliated lining of the hinder parts) in the form of a strong current, which, impinging against the closed end of the tube, is turned upward, carrying with it all extraneous or fœcal matters, and is ever pouring out of the frontal extremity around the neck of the creature. What a beautiful and effective contrivance is this for constantly keeping in a state of the most unsullied cleanness the interior of the house! It reminds one of the fabled Hercules cleansing the Augean stable by driving the river Peneus through it.

On each side of the mouth there springs a lengthened horny thread, appearing to answer to the antennæ which in other Worms, as well as in Insects and Crustacea, project from the front of the head. Such seems their true relation considered structurally, but in function and office they are very remarkable and quite peculiar. To these organs is assigned the duty of closing up the tube when the animal has withdrawn its gaily-coloured plumes; and for this end, one of these antennæ is much lengthened, and at the end is expanded into a broad trumpet-shaped club, the extremity of which is somewhat concave, and is delicately marked with radiating grooves. This organ is usually painted with the same brilliant colours as the gill-tufts, and by its length, size, and form, makes a very conspicuous feature in the charming Serpula. Its length is such, that when the gill-filaments are rolled up and withdrawn, the conical club enters after all, and is found accurately to fit the trumpet-like orifice of the tube, just as a cork fits tightly into the mouth of a bottle.

Ordinarily those organs which appear in pairs are formed so as to be the counterparts of each other. But here is an exception. One only, sometimes the right, sometimes the left, indifferently, takes the remarkable form that I have been describing, the other being much shorter, and terminating only in a small knob, like the head of a pin. Why should there be this difference? Why this exception to an all but universal rule? The reason is obvious. Yes, obvious enough when seen and noticed; but it tells an eloquent tale of the Divine forethought and care. If both of the antennæ were furnished with the terminal cone, one would interfere with the other in the performance of their closing, corking-up function; they would jam in the doorway, and the tube would be left open. Hence the one is left undeveloped, yet retaining, as I believe, the latent power of expanding into a cone, if it should ever be needed by the accidental loss of the fellow now so furnished. I thus judge, because experience shows me that the conical club is occasionally thrown off, and quickly renewed, in captivity.

My esteemed friend, the Rev. Sir Christopher Lighton, has indeed put on record an example of a Serpula of this species possessing two equal antennæ, that had replaced the single one accidentally lost. They were both perfectly developed, and joined together near the base. Each was decidedly smaller than the single one that had formerly occupied their place.[143] This exceedingly interesting case can, of course, only be regarded as a monstrosity of redundancy, as children are sometimes born with a superfluous finger. But it is valuable as showing that there is a power of development latent in the crownless antenna. I wish very much that the excellent observer had added a note, telling us to what extent the tube was closed, and how the work was performed without mutual interference.

It has been sometimes brought as an objection to our assigning a certain service to certain organs, that the necessity for such service is a gratuitous supposition, since other creatures similarly formed in most respects, and in which we might infer a like need, have no such supply. We may admit the facts, but refuse the reasoning. There can be no manner of doubt that the conical antenna does act as a stopper to the Serpula, as our eyes can see; and surely it would be most unphilosophical to suppose that the function so performed is not serviceable to the creature. Yet its near cousins, the Sabellæ, similarly constructed, and of similar habits of life, and as we should have à priori supposed, quite as liable to injury in the same direction, are entirely destitute of this contrivance for protection, and of anything compensating for it, so far as is known. Why the need of one should be met by such a beautiful contrivance, while the same need in the other is wholly unmet, though both are formed by the same Infinite God, is one of those unanswerable questions which, while they leave unimpeached His wisdom, make us deeply conscious of our own ignorance.

We find numerous examples of this genus Sabella in our confused heap of tangled life and death. By their vigour and their abundance we have proof enough that their wants are supplied, though they do not enjoy this special contrivance: they manage to live and thrive and enjoy themselves, with open doors, taking all risks of insidious robbers,—such, for instance, as that vile burglar, the Longworm,[144] that we found under a stone the other day; which is ever on the watch to insert its snaky head within the unprotected tube, and to tear away with merciless clutch the beauteous gill-tufts.

One species of this genus[145] can by the cursory observer be distinguished from the Serpulæ, only by this absence of the antennal stopper. For it dwells in a shelly tube, essentially resembling those which we have just been examining. It has peculiarities of detail, however. It is never found associated with numbers of its fellows in agglutinated groups, but always, so far as my experience goes, singly. It is more common on shells than on stones, generally attached to the old valve of some cockle or scallop. It is straight or nearly so, never at least contorted. Attached only for a very short portion of its smaller end, perhaps for an inch or so, for which it creeps along the surface, it then rises into a more or less erect position, extending sometimes to a height of seven or eight inches perfectly free. The tube is of about the same diameter as that of the Serpula, but is slighter in structure, or perhaps it appears so, because it is destitute of those expansions which here and there in that species indicate the trumpet-lips of successive stages of development. The extremity of the tube here is simple, not expanding. Slight annular rings, however, do here and there vary the shelly surface of the tube.

The gill-tufts are ample; they are two, considerably infolded, consisting of about forty-five filaments each, which are much longer and slenderer than those of the Serpula, the last filaments of the volutions diminishing rapidly. The secondary filaments, or pinnæ, are very fine and very numerous, so set on the main stem that the two rows form the sides of a narrow groove, facing inwards. The whole is yellowish-white with eight or ten bright scarlet dots set with intervals all along the back or outer side of the stem. When fully protruded, the base of the gills, and even a good deal of the neck, lolls out of the tube. If the animal be removed, the body is seen to be white, elegantly banded with scarlet, and furnished with a broad translucent collar, edged with scarlet: this collar ordinarily lines the mouth of the tube.

From the length and isolation of its shelly tube this is a remarkable species: the great tenuity of its filaments, however, requires a lens to bring out their beauties; but with this aid, the arrangement of the rich scarlet bands and spots on the pale yellow ground cannot fail to evoke admiration.

In general, the Sabellæ inhabit tubes which are not calcareous or shelly; they are composed of a soft flexible substance somewhat resembling wet parchment, made of a secretion from the animal’s body, in which the impalpable muddy sediment which the waves agitate, consisting of decomposed organic matter for the most part, is interwoven. The tissue so made is sufficiently tough and enduring, retaining its form long after the animal has died out of it.

In our dredge-hauls we find a pretty little kind[146] common enough, which lives in association, the tubes apparently from half-an-inch to an inch in length, forming dense masses on stones and shells, and projecting in every direction. A dozen or more may be in one group, and when all are alive, one or another protruding or retiring every moment, it makes a pretty object.

The gill-filaments are nine to eleven in each row, of a yellowish white, occasionally patched with dead-white, or red-brown: delicately and densely pinnate. The filaments, in the act of protruding, are closed together like a straight bundle of rods which suddenly fall open at the ends. In this moment of unfolding, their tips are seen to be a little hooked inwards. The tube is about as large as a crow-quill; under a lens it appears speckled, as if the inorganic matter imbedded in it were grains of the finest sand. On carefully removing all the surrounding tubes and other objects so as to isolate one, we see that it is truly about three inches in length, but that two-thirds of the whole are prostrate and adherent; this basal portion is horny and pellucid, no mud entering into its texture. The animal when extracted is an inch in length, of which the gill-tufts form one-third.

Mingled with these there are one or two specimens of a much more imposing species, the Hook-plumed Sabella.[147] It grows to a large size, the crown of gill-filaments sometimes attaining a height of an inch, and the same diameter. The two rows are incurved in regular spirals of half a turn, each consisting of about eighteen filaments, which are rather stout, the whole crown sometimes taking the form of a funnel, sometimes that of a cup, often arching inward at the tip. Their pinnæ are long and close, the two rows forming a groove, but nearly parallel. Each primary stem is set along the back with twelve pairs of feather-like processes, hooked downwards;—a very remarkable character, and one by which this species may be in a moment distinguished. Their colour is pale red-brown, mottled irregularly with deep brownish purple and with white; there is a pair of brown specks at the origin of each pair of hooks. The base of the crown is always concealed in the mouth of the tube, but it springs from a narrow frilled membrane of pure white. The body is destitute of a thoracic shield, or conspicuous collar. The tube is largely composed of soft homogeneous mud, usually of a pale purplish hue, of about the thickness of the shelly tube of S. tubularia.

The process of building the mud tubes of the Sabellæ is a very interesting one. It is performed, according to my own observations,[148] mainly by means of the gill-filaments and their pinnal grooves. The filaments are bent-over, till the inner or grooved face comes in contact with the soft mud on which the animal is lying, when the sensitive pinnæ close on a minute portion of the mud, taking it up in a pellet, which is then fashioned by the form of the groove; the filament is now erected, and the pellet, passing down the groove to the bottom by means of the cilia, is delivered to the care of two delicate moveable organs, like leaves or flaps, which place it on the edge of the tube, and then shape and mould it, smoothing both surfaces. Doubtless, either from these organs, or from some other part of the circumjacent region, the glutinous secretion is at the same time poured out, which consolidates the mud, and forms the true basis of the tube.

XII.
DECEMBER.

December is here, with its short days, its feeble watery sunshine, its frequent gloom and mist, its hanging leaden skies; in short, as the poet describes it,—

It requires some zeal in the pursuit of scientific lore to leave the glowing fire and the pleasant book, the luxurious arm-chair and the elastic carpet, and to venture down to the wild sea-beach, to poke and peer among the desolate rocks. Yet even now we may find a few bright days, when Nature abroad looks inviting, and when an hour’s marine research will prove neither unpleasant nor unsuccessful.

On such a noon, then, calm and quiet, the sun bright and cheerful, if low and feeble, the tide tolerably low and the rocks accessible, we hie down to some one or other of those ledges which have so often already yielded their treasures to our search, and begin our wonted labours at turning over the heavy angular masses. We soon find, attached to the under surfaces of these, what seem to be irregular blobs of coloured jelly of somewhat firm consistence, as if an invalid had been here eating his calves’-foot jelly, whose trembling hand had dropped sundry spoonfuls on the stones. Some appear as flattish shapeless drops, but others take more elevated forms, like sacks set on end, and usually displaying two mouths. One of these is of a pellucid yellowish green, or olive hue, with a cloudy spot of rich orange in the interior. A slight shrinking from the touch, a yet closer contraction of the projecting points, is the only token of life that we can discern in it now; but if we place it in an aquarium,—not forcibly removing it from its attachment, but lifting the shell or stone on which it rests; or, if this be too large, detaching the fragment with a chisel,—and allow it to remain a few hours undisturbed, we shall see evidences of a vitality, indubitable if not very active.

The whole creature is now much plumper and more pellucid; it stands up boldly from its base on the stone; its upper portion is much lengthened, and the two wart-like eminences have become two short tubes with gaping extremities, appearing as if they had been soldered together side by side, of which the one is considerably higher than the other.[149]

We have before us one of the Tunicata, an order of molluscous animals which are closely allied to the Conchifera or bivalves, but somewhat lower in the scale than they. It has no shell; that is to say, lime is not deposited in the outer investment, so as to give it the hard, rigid, solid texture of shell; but the internal organs, which are essentially similar to those of an Oyster or a Sand-gaper, are enclosed in a tough leathery coat, known as the test, which is in fact a closed shell destitute of lime. The eminent physiologist, John Hunter, who had dissected some of these homely Squirters, as they are familiarly called, recognised, with his wonted acumen, the structural similarity of their leathery envelopes to the stony shells of the lower bivalves; and, associating them in a group, called them “soft-shells.” The naturalness of this group, since called Tunicata by Lamarck, has been recognised by modern zoologists.

If we watch our Ascidia for a few minutes, we perceive that at irregular intervals one or both of the gaping orifices are suddenly closed and contracted, commonly both at the same instant. They are, however, soon opened again; and we may discern, especially if the specimen is in a glass vessel, and we watch it by the aid of a lens, with the light of a window at its back, that a current of the surrounding water flows from all sides to the taller orifice, and pours down its tube; while occasionally we see the ejection of a stream from the orifice of the shorter tube. Thus we have here a receiving and a discharging tube, the exact representatives of the two siphons in such bivalves as Pholas, Venus, etc. The former leads down into a capacious sac in the interior, the walls of which constitute the breathing apparatus. The inner surface is marked by regular parallel ridges which run in a horizontal direction; and these are again connected by vertical ridges at right angles, very numerous, enclosing a vast number of oval compartments. The sides of these are richly ciliated; and if the whole apparatus be carefully dissected out, and laid upon the stage of the microscope, the course of the ciliary currents may be distinctly seen, continuing with unabated vigour and with unfaltering precision for a long time after the severance of the organ from the body of the animal. But all this is seen to most advantage, if we select one of the smaller species, which are brilliantly transparent, such as one which grows in groups of elegant tall vases, about an inch in height, around the edges of our rocky pools,[150] or a tiny thing which forms a little heap of transparent globules, like pins’ heads, attached to sea-weeds.[151] In either of these, placed in a stage-trough of sea-water, we can watch at leisure the performance of the various vital functions in healthy action, with the knowledge that the little subject has not been martyred to science, but is all the while enjoying its humble life with perhaps as much zest as if it were still environed by the rough walls of its little native basin of rock.

In the tiny pin-head of clear jelly, the microscope displays the branchial sac hanging free in the cavity, like a bag of clear muslin. The oval cavities divided-off by the rectangular ridges are about forty in number, around each of which the ciliary waves incessantly roll, as running spots of black. It is a very charming spectacle to see so many oblong figures set symmetrically, all furnished on their inner surface with what look like the cogs or teeth of a mill-wheel, dark and distinct, running round and round with an even, moderately rapid, ceaseless course. These black, well-defined, tooth-like specks are merely an optical effect; they do not represent any actual objects, but only the waves which the cilia make: the cilia themselves being hairs, so fine as to be defined only with high powers. Occasionally we see one or other of the ovals suddenly cease its movement, while the rest go on; and now and then the whole are arrested simultaneously, and presently all start off again together, with a very pleasing effect, as if we were looking at the wheels of a very perfect and complex piece of machinery. These phenomena appear to indicate that the movements are under the control of the animal’s will, capable of being suspended or continued, wholly, or in any degree, at pleasure; which is not the case in the higher animals; our own respiratory movement, for example, as well as the pulsations of the heart, going on without the concurrence of our will, and even without our consciousness.

The action of the heart in these transparent creatures is equally visible. Below the muslin curtain with its living chambers, down at the very bottom of the body-cavity, there is a transparent sac of membrane, which takes the appearance of a long bag, pointed at each end, but not closed, and strangely twisted on its long axis, so as to make three turns. This is the heart; and within it are seen many colourless globules, floating freely in a clear fluid, which answers to the blood. This circulates throughout the system in the following manner:—We see a spasmodic contraction at one end of the bag, which drives forward the globules contained there; the contraction in an instant passes onward along the three twists of the vessel, the part behind expanding immediately as the movement passes on, and the globules are forcibly expelled through the narrow but open extremity. Meanwhile the free globules surrounding the commencing end have rushed in as soon as that part resumed its usual width, and are in their turn driven forward by the periodic repetition of the pulsation. The fluid, with its globules thus put in motion, is then driven along through the interstices of the various organs of the body, not through a system of closed blood-vessels, some finding their way along the transverse lines that separate the rows of gill-ovals, until they sooner or later arrive at the point where they entered the heart, to take the same course over again.

As in the kindred forms of animal life, the same orifice, the same cilia, the same currents are subservient to breathing and to the reception of food; the stomach digesting the microscopic animalcules which are poured with the entering stream through the receiving siphon. At some distance within the interior of this orifice there are a series of thread-shaped tentacles, affixed in a ring, which we may suppose to exercise some kind of superintendence, by touch or other perception, over the atoms which indiscriminately enter upon the stream, accepting or rejecting. Probably it is in the exercise of the latter discretion that those irregular regurgitations of the current take place, accompanied by a momentary closing of the mouth, that we frequently notice.

Still further ancillary to the protection of the stomach from the intrusion of inimical matters, we may safely suppose certain eye-like specks which are placed at the very vestibule. In the larger species, as this red-clouded green Squirter, there are seated in special fissures at the very margin of the expanded siphon-orifices, red dots,—eight around the receiving, six around the ejecting, siphon. Each dot seems ascertained to be an eye of very rudimentary structure, seated on a mass of orange pigment. We should probably do wrong if we attributed any higher vision to these organs than a low degree of sensibility to the general stimulus of the light.

Some species have the orifices of the siphons four-cornered, whereas the sort I have been describing have them circular; there are differences also in the breathing sac, which in the square-mouthed species is folded lengthwise, while in the round-mouthed it is plain. Hence the former have been separated from the Ascidiæ, as a distinct genus, named Cynthia; both including a large number of species.

We have a pretty attractive little Cynthia in our dredging,—the Currant Squirter.[152] It is not uncommon in deep water off this coast, and in Weymouth Bay; frequently occurring in family groups crowded together on old shells. Generally there is one of superior dimensions to the rest, the venerable parent of the colony; and, surrounding him, others of varying size, and (doubtless) age, down to very minute infants. The full size is about that of half a small cherry; but it is more usual to see them not exceeding that of half a red currant. These comparisons will also give a fair idea of their shape and colour, especially in a state of contraction, as when lifted from the water: for they are little hemispheres of a brilliant, scarcely pellucid, crimson hue, seated on the shell by the whole broad base. Under water, and at ease, the form becomes more conical, rising into a point; whence, in full expansion, the two siphons protrude, slightly divergent, and the one a little superior to the other, each opening by a distinctly quadrangular orifice.

Contrasting with this neat and pretty little family, we have here another species of the genus, the Four-angled Squirter.[153] You would hardly suppose this to be an animal at all, if uninitiated; but might readily pass it over as a rude stone, or a bit of wood roughly bruised and worn by the waves beating it among the rocks, so uncouth and coarse and shapeless it is. It forms a great mass, some two inches high, rudely four-sided, of a dull yellowish-olive hue, rising into two blunt eminences, which individually retain the quadrangular shape, and in activity open by symmetrically quadrangular orifices. It is a sluggish, unattractive lump of flesh, somewhat between leather and jelly in texture, coarsely pellucid, but not transparent, and its exterior is usually distinguished by various extraneous matters imbedded in the test, as well as by forests of tangled zoophytes which creep over it and root in it as on the rock. The surface itself, moreover, is much corrugated by an irregular network of depressions, marking off angular warty areas.

On the other hand, the little Currant is a pleasing inhabitant of the aquarium. Of manners, to be sure, it has not much, good or bad, but the form and colour are agreeable; as is also the effect produced by the grouping of the brilliant drops of jelly. Little of change takes place, beyond the occasional contraction and reprotrusion of the orifices; but sometimes you may see, as I have seen, at certain times, the laying of eggs by this species, which is an interesting phenomenon. These are perfectly globular, about the size of small shot or pins’ heads, of a rich scarlet-crimson hue: they are deposited in a singular manner. The oviduct does not extend to the exterior of the body, but discharges the eggs into a large cavity formed by the mouth, of which the discharging siphon is the outlet. From this orifice, then, they are expelled, shot out perpendicularly with considerable force, so that they describe arched courses through the water, like bombs shot from a mortar, rising to a height ten times that of the animal. I have observed a dozen or more eggs thus discharged in quick succession, which then fall to the bottom around the parent, destined to constitute one of those family groups in which we usually find the species.

I have not been successful in rearing these eggs to maturity. The development of the Tunicata has, however, been observed by various naturalists, and by none more thoroughly than by the late Sir John Dalyell, whose elaborate and costly works, profusely illustrated, are such a mine of information respecting the lower forms of marine life.

The young escapes from the egg in a form as unlike the parent as can be imagined. It is a flat ovate body with a long flat tail, altogether presenting a curious resemblance to the tadpole of a frog. In this condition I have found the larva of the Clavelina, and have followed it to the development of the Ascidia form. By means of the rapid vibrations of the powerful tail, the little tadpole swims for short distances through the water, with more effort than effect. After a while, it rests; swims again, and again rests; till at last it moves no more. A coloured eye-speck is visible on the surface, destined to be absorbed; the tail is beginning to disappear (in some cases it is separated by a spontaneous constriction at its junction with the body, in others it appears to be gradually absorbed); one or more warts are seen budding from the opposite extremity of the body. These last secrete a cement by which the animal is finally attached to its support, shell, stone, or sea-weed, either growing out into creeping and adherent root-threads, or enlarging into a broad base, from which the body begins to grow upward. After a while the two orifices are formed; first within, on the mantle, before the exterior test is pierced; then the internal organs, the gill-sac, and the pulsating heart, if it be one of the transparent species, become recognisable; the single eye-speck, a temporary organ, pales and disappears; and the permanent circles of visual organs are formed around the siphonal orifices. And thus the Ascidian is developed.