Part 11

These details convey but a feeble and imperfect notion of the numerous and elaborate contrivances which are so profusely bestowed upon these mean and grovelling worms; but they show how careful is the Creator of their well-being; how lavish of His mercies towards His meanest creatures. How unreasonable, then, is it for those to doubt His ever-watchful and unerring tenderness towards themselves, who have been made the objects of His _redeeming_ love, and who, on the ground of redemption, “are of more value” in His sight, than all these His lower creatures put together!

FOOTNOTES:

[66] _Aplysia punctata_, of which two specimens, one viewed sidewise, and the other mounting an angle of rock, showing the front of its head, are depicted in Plate XVI. Sowerby applied the name of “_hybrida_” to the species, and Forbes and Hanley have adopted it; but even the inflexible law of priority does not warrant the perpetuation of a name which is glaringly absurd, and expresses a manifest contradiction; for if the creature were a hybrid, it would not be a species, and not be entitled to a specific name.

[67] _Outlines of Comp. Anatomy_, p. 371.

[68] _De Anim. Marin._, quoted in Johnston’s _Introd. to Conchology_, p. 18.

[69] This animal will be described in a subsequent chapter.

[70] _Journal of Researches_, chap. i.

[71] Johnston.

[72] _Dentalium entalis_, represented at the right-hand corner of the foreground in Plate XVII.

[73] _Pileopsis Hungaricus_, of which a specimen is represented in the attitude of life, adhering to the dark rock, in Plate XVII.

[74] _Litt. de la France_, i. 133.

[75] _Gammarus locusta._

[76] Bate and Westwood’s _Crustacea_, p. 382.

[77] Bate and Westwood, p. 380.

[78] Bate and Westwood, p. 391.

[79] It is named _Ligia oceanica_, and is represented in Plate XVII., in the centre of the picture.

[80] _Phyllodoce viridis_.

[81] _P. laminosa_, represented in the middle and right of Plate XVIII.

[82] _Litt. de la France_, ii. 223.

[83] _Nereis margaritacea_, of which the head and fore parts of the body crawling over a stone are depicted at the left-hand corner of Plate XVIII.

[84] _Polynoe cirrata._

[85] Dr. Williams, _On the British Annelida_, p. 219.

VII.

JULY.

TWO-SPOTTED SUCKER.

A mile or two eastward of Babbicombe and Petit Tor, in from ten to fifteen fathoms water, there lies a stretch of flat stony bottom, reaching away from the island known as the Ore Stone, towards the mouth of the river Exe. This is a bit of ground to which a boatman whom I occasionally employ often resorts with the dredge, and rarely or never without a fair harvest of curious and interesting creatures. Among other things he brings me from time to time numerous specimens of what Yarrell calls the Bimaculated Sucker;[86] the propriety of which name will be evident the moment you examine one of these little fishes alive. Cuvier named the group in which they are found (a group comprising very few species) _Discoboles_, because the ventral pair of fins are united so as to form a circular disk or saucer, by means of which the fishes have the power of adhering firmly to any solid object larger than the circumference of the disk. Yarrell substitutes the term _Cyclopteridæ_ for the family group; the name _Cyclopterus_, used for the principal genus, expressing the same thing, that the fins are united in a circular fashion. The word _bimaculatus_, signifying two-spotted, alludes to two remarkable and conspicuous oval spots of dark purplish brown or red, situated one on each side of the body, just behind the pectoral fin. These spots, being comparatively large, and separated from the general colour of the body by a well-defined white ring, constitute a very striking and beautiful feature in these little fishes.

Their form is flattened; they have a broad shovel-shaped muzzle, prominent eyes, looking rather upwards, and the head much widened behind; the head, indeed, constitutes more than one-fourth of the entire length; and at its hinder part, or where the gills open, is far wider than any other part of the fish. They rarely exceed an inch and a half in length. The general hue above is pale red; but in some specimens they become a nearly uniform lake-purple, in others the hue is a clear orange; while yet in others it is almost white. A band of white, bounded by darker lines, almost invariably connects the two eyes. Frequently the hue of the body is varied by clouds and patches of dark reddish brown, which patches have a tendency to assume a constant pattern, quite recognisable when you look at a good many specimens together. In the hinder half and on the sides the ground colour is apt to be minutely divided or mottled, the interspaces being of a delicate azure or lilac; and when examined with a lens, the whole surface seems sown with gold dust. The dorsal fin is set very far back, and, as well as the caudal, is prettily pencilled with dark brown: the under parts are pearly white.

The eyes are exquisitely beautiful, and as they are prominent, very movable, and especially as they are moved quite independently of each other, they at once attract and fix the admiration of the beholder. The large pupil is of a deep lustrous green, the iris of the most brilliant orange gold, and the whole set as it were in the midst of a globe of the purest glass. On the whole I scarcely know of a more attractive little fish than this.

ITS HABITS.

This little Sucker is easily reconciled to captivity. I have in my aquariums some individuals which were captured nearly a year and a half ago; and they are still in the full enjoyment of health and activity. They are pleasing little things: they scuttle from spot to spot with a spasmodic sort of bustle, wagging their tails much from time to time, so that in movement as well as in form they remind one of tadpoles. They are generally seen, however, anchored to the sides of the vessel, or to the prominent knobs of the stones by their sucker, and here they remain for an indefinite time, sometimes for hours, at others only a few seconds, throwing their beautiful eyes about in insatiable curiosity, fanning the water with their transparent pectorals, or whisking the painted tail about. Now and then they make a sudden snap, doubtless at some passing animalcule, with an audible sound, and the emergence of a bubble of air from the top of the water, whence the muzzle is frequently projected. They have an awkward habit of throwing themselves out of a shallow vessel; and if you are not on your guard you may find your little pets dead and dry on the carpet. They are inquisitive little things; if a new stone or shell or tuft of serpulæ is put into their vessel they soon discover it, and may be seen exploring it in every part; and it is amusing, when _you_ are examining _them_ with a lens, to note how thoroughly mutual is the investigation; for you can see by the direction and motion of the eyes that the little fish is watching you as interestedly as you are observing him.

I do not think that the adhesion of the ventral sucker is effected exactly as has been supposed, by a vacuum produced in the area of the united ventral fins; but by the combined action of some minute fleshy sucking disks, which are arranged in two groups, in front of and behind the united fins. The conjoined fins do not appear to me to make a vacuum. The fish has a curious habit of coming to the surface of the water, and there floating perfectly still, back downward, the entire belly-surface dry. The ventral disk is then seen as a shallow cup, quite dry and shining. If touched, the little fish hurries along the surface, with some splashing, till it acquires impetus enough to go under at an oblique angle, when it presently turns over, and adheres to the bottom, or side of some stone. I have seen this practice frequently, but only, I think, at night.[87]

* * * * *

This principle of a vacuum produced by the retraction of the centre of a fleshy disk, while the margins remain in close contact with a solid body, is of extensive application in the lower forms of animal life, and especially in the class ECHINODERMATA, comprising what are popularly known as Star-fishes, Sea-urchins, and Sea-cucumbers.

I have on other occasions noticed the elaborate and wonderful mechanism of the sucker-feet as they appear in the commoner species of the class. I need not therefore repeat those details, but look at a few other particulars in the economy of the animals whose locomotion is dependent on this curious contrivance.

There is a pretty little species abundant enough hereabout, chiefly affecting shores on which numerous angular masses of stone lie irregularly scattered and heaped one on another. Yet they seem to have a predilection, for they do not occur in all our localities even though these conditions be not lacking. Livermead Point, and the south side of Anstey’s Cove, beneath the cliffs, are favourite spots for them, the former especially, where we can find the little Gibbous Starlet,[88] for such is its name, at all times of the year, when the tide is sufficiently out. The retiring tide here leaves a shallow pool of considerable area, which then continues to run out by a narrow channel among the rock boulders, a winding rivulet of salt water; along whose borders, by turning over the loose blocks, scores of this pretty Star are exposed, clinging to the wet sides and roofs of the dark passages by means of their sucker-feet. Forbes has given two figures of the species, but manifestly taken from dead specimens, and from very small ones too. He says, “large specimens measure only an inch across;” from which I infer that on the shores of the Isle of Man, where he was familiar with it, the Starlet does not attain the dimensions it reaches on our mild southern coast. He indeed alludes to one in Mr. Ball’s collection, which measured one inch and five lines in diameter. Specimens, however, of this size are quite common with us, nor would one of an inch and a half be looked upon as at all exceeding the modest and proper range of the species.

ITS EYES.

It is of a pentagonal figure, with the margin a little receding between the angles, but not so as to cause the latter to form distinct arms. The body is flat below, and plump and cushion-like above, of a yellowish olive hue, with the very edge of a golden orange tint, while a spot of the latter colour, a little out of the centre, marks the situation of a remarkable organ called the madreporiform tubercle, the proper use of which has not as yet been satisfactorily determined. Just at the extremity of each angle, but a little below, is situated a wart of rich crimson hue, which is supposed to be an eye, being seated on a small ganglionic swelling of a nerve that passes along the ray. It is true no crystalline lens has as yet been detected on the pigment dot, either in this species or any other (for the specks are found in the same position in all the proper Star-fishes), but they are manifestly of the same character as similar specks in _Rotifera_, and other humble animal forms, which in some examples are connected with an indubitable lens. It might seem at first as if the situation of these eyes were not very favourable to vision; but, in truth, they command the ground just before and around the ray-tip, and also the water in a horizontal direction; and as there is one at each of the five angles, the entire circumferent space is viewed at each moment. Add to this, that the animal is in the habit of very frequently turning up the tip of one or other of its rays, when the range of vision would take in the zenith; and we shall perceive that no position in any other part of the body could be so suitable for the location of eyes as these selected. It is not to be supposed that distinct definition of objects is attained by these rudimentary organs; but the animal is probably conscious of the difference between light and darkness, and may also discern the sudden approach of any object, either by its interception of light, or by its colours, though its features and form may be indistinct. Such a degree of visual perception, though very imperfect in our esteem, may be of great use to this sluggish creature, and amply sufficient for its need.

The whole upper surface of this Starlet is covered with six-sided convex plates, each of which is crowned by a group of short blunt spines; the number in each group varying from one to nine; four to six, however, most commonly; arranged in a diverging tuft. Over the madreporiform tubercle, the tufts are stouter, and bend towards each other, as if to protect this delicate organ, which, whatever its function, is grooved with sinuous furrows, visible only with a considerable magnifying power, like the rounded masses of coral from the tropical seas, called brain-stones.

On the under surface similar stout short spines are arranged in transverse bands across each ray, interrupted, however, by the central furrow, which is perforated with two ranges of orifices to give issue to the sucker-feet, which thus form a double row. These organs do not differ importantly either in structure, function, or appearance, from those in the Cross-fishes, in the Sea-cucumbers, or in the Urchins.

In health and activity the whole upper surface is covered with a forest of short pellucid tubes, closed at the tips, which protrude from pores in the plates, and stand erect, moving, however, to and fro at the will of the animal; they are evidently filled with fluid. I cannot find any notice of these organs: they are probably connected with respiration.

SEA-URCHIN.

What a wonderful piece of mechanism is a Sea-Urchin! Accustomed as I am to the multitudinous contrivances and compensations that present themselves at every turn to the philosophic naturalist, often as surprising and unexpected as they are beautifully effective, I am yet struck with admiration at the structure of an _Echinus_ whenever I examine it anew. A globular hollow box has to be made, of some three inches in diameter, the walls of which shall be scarcely thicker than a wafer, formed of unyielding limestone, yet fitted to hold the soft tender parts of an animal, which quite fill the concavity at all ages. But in infancy the animal (and, of course, its box, as this must be full) is not so big as a pea; and it has to grow till it attain its adult dimensions. The box is never to be cast off, and replaced by a new one; the same box must hold the infant and the veteran Urchin. The limestone, not being a living tissue, but an inert earth, can grow only by being deposited. Now the vascular tissues are within, and the particles they deposit must be on the interior walls. This would indeed augment the amount of limestone in the box, but it would be at the expense of the contained space. The thicker the walls, if thickened from within, the less room in the cavity; but what is wanted is _more_ room, ever more, and more. The growing animal feels its tissues swelling day by day, by the assimilation of food, and its cry is, “Give me space! a larger house, or else I die.”

How is this problem solved? Ah! there is no difficulty. The inexhaustible wisdom of Jehovah the Creator has invented a beautiful contrivance for the emergency. The box is not made in one piece, nor in ten, nor in a hundred; six hundred distinct pieces go to make up the hollow case; all so accurately fitted together, that the perfect symmetry of the outline is not broken; and yet, thin as their substance is, they retain their relative position with unchanging exactness, and the slight brittle box possesses all requisite strength and firmness.

Each of these symmetrical pieces of shell is enveloped by a layer of living flesh, a vascular tissue of exceeding thinness, which passes up between the joints where one meets another, on every side, and not only so, but actually spreads itself over the whole exterior surface. So that when you take up an Urchin into your hand, and having rubbed a small space clear of spines, look on it; you have not, as you may suppose you have, exposed the surface of the shelly box, but only the flesh that covers it; yet this is so transparent and colourless, so inconceivably thin, so absolutely adherent at every point, that its presence will not be discernible to feeling or sight, without the aid of high microscopic powers.

This being so, the glands of the investing fleshy tissue secrete lime from the sea-water, which holds it in solution, and constantly deposits it, after a determinate and orderly pattern, on every part of the surface of each shelly piece; the inner face, the outer face, and each of the sides and angles of the polyhedron grow together, and all so evenly, that while the dimensions increase, both of thickness and superficies, the form characteristic of that individual piece is maintained with immutable mathematical precision. Thus the volume and capacity of the box grow with the growth of the individual segments, and it ever keeps the globose shape at first imposed upon it.

ITS MECHANISM.

But this is but a small part of the mechanism of this interesting tribe. If you put into a basin of sea-water one of the pretty kind[89] which we find so abundantly under stones at low water,--whose green spines are tipped with rosy purple, like the tentacles of an _Anthea_,--you will presently observe it marching majestically along by means of the hundreds of sucker-feet, which it possesses in common with the Star-fish. Now, if you have in your cabinet the empty box of an Urchin of this same kind, and taking it in your hand, hold it up to the light, and look into the cavity from the under or mouth side, you will have a very interesting spectacle. The light streams in through a multitude of minute holes, as smooth and regular as if drilled with a fairy’s wimble; and these holes are arranged in a pattern of elegant symmetry. They run in lines, like meridians, from pole to pole of the flattened globe; but instead of being set at uniform intervals, they constitute five principal sets or bands, with blank intervals between, about twice as wide as the drilled bands. Then each band comprises two series, each of which contains a double row of orifices. These last, again, do not constitute a single unbroken line, but an interrupted or zig-zag line, which is, in fact, made up of a number of short diagonal rows; three holes in each diagonal, set one after another.

Put the living and the dead together. These tiny orifices, as minute as the point of the finest cambric-needle could make in a bit of paper, afford exit to the suckers, which are, of course, equally numerous. Through these pass the slender pellucid tubes, filled with elastic fluid, which carry at their tips a flat ring of calcareous shell, affording to each the form and firmness to make each one an adhesive sucking disk, in the centre of which a tiny vacuum is created at will by muscular retraction.

ITS SPINES.

But this is not all. Again, look at the living Sea-Urchin. It bristles with the rosy-tipped spines, which have a satiny lustre, owing to the reflection of the light from the delicate ridges and furrows with which the whole is fluted, like an Ionic column in miniature. How they are all moving, and swaying to and fro on their bases, quite independently of each other, however, making circles and traverses in the water with their points, as the mast-heads of a ship do among the clouds in a gentle swell, when seen from the deck. Professor Agassiz fell into the egregious blunder of supposing that the spines were the organs of locomotion in the Urchins, denying, with much contempt, the theory which attributed this office to the suckers. One can only wonder whether he ever saw a living Urchin in motion, as one moment’s glance at the phenomenon is sufficient to prove how utterly his theory was false, as Forbes has well shown.

However, let us once more observe the empty denuded box from the cabinet; and now on the exterior. Between the principal bands of pores (called _ambulacra_, from their fancied resemblance to walks in a garden), as also between the two series which constitute each band, the space is studded with hemispherical warts, of very diverse size, which look as if turned in ivory, unpolished; and each wart is crowned with a smaller wart of like material, but bearing the most perfect polish.

At the bottom of each spine there is a cavity exactly fitting this second wart, and equally highly-polished in its interior. During life the spine was seated on the wart, not united to it, but moving upon it in all directions, with perfect smoothness and freedom; a ball and socket joint, in fact. It was held in its place by an investment of muscle, which completely enclosed both the wart and the base of the spine, having one insertion in the unpolished wart, and the other in a remarkable ring or shoulder of the spine, visible just above the socket.

These are but two or three salient points of interest in the structure of this little unvalued, disregarded creature. I could relate much more; indeed, I think it would not be difficult to write a bulky volume of the history and biography of a single Sea-Urchin, of which every page would display the glory of God. But I have not space for that here.

We sometimes, but very rarely, find on this coast a very lovely form of this class of animals, the Rosy Feather-star.[90] It consists of ten long attenuated arms, radiating from a common centre, composed each of about forty slender joints of stone, and each joint carrying a pair of diverging beards, also many-jointed, all of which together, by their number and arrangement, give to the arm the aspect of a beautiful feather. Around the central point of radiation, a small cup-like body gives origin to the arms, which are double, a pair springing from a single basal joint. Within the cup the soft parts of the animal are chiefly located, the organs of the vital functions; and from the convex surface spring a number of jointed stony threads, like necklaces, much shorter and slenderer than the arms, which serve as claspers, gripping and holding firmly the projections of the rock, by means of strong curved claws with which they are terminated, in shape like those of an eagle.

The whole elegant creature is of a lively rose tint, interrupted by patches of bright yellow, disposed with no regularity or apparent order; the whole, both the yellow and the rosy portions, studded with crimson dots. Edward Forbes, if I rightly understand him, considers these dots to be ovaries, which he estimates at upwards of 57,000 in number.

INFANT FEATHER-STAR.

In infancy the Feather-star is seated at the extremity of a long slender jointed stalk, attached at its lower end, whence it rises erect, like a plant. Indeed the whole animal, in this condition, with its cup-like base and elegantly incurving arms, seated on its tall stem, has so close a resemblance of outline to a flower, that the fossil specimens, which are very numerous, and of large size, are known as Lily-stones, and technically as _Encrinites_, which word has the same allusion. After a while, the radiating portion, or flower, separates from the stalk, and swims freely, contracting its arms to give the impulse, in the manner of a _Medusa_.