Glimpses of Ocean Life 21

Glimpses of Ocean Life 21

CHAPTER XII.

 

Terebella figulus.

 

(THE POTTER.)

 

 

'Whether progressing on the solid surface, or moving through the

water, or tunneling the sand, advancing or retreating in its tube,

the Annelid performs muscular feats distinguished at once for their

complexity and harmony. In grace of form the little worm excels the

serpent. In regularity of march, the thousand-footed Nereid outrivals

the Centipede. The leaf-armed Phyllodoce swims with greater beauty of

mechanism than the fish; and the vulgar earthworm shames the mole in

the exactitude and skill of its subterranean operations. Why, then,

should the "humble worm" have remained so long without a historian? Is

the care, the wisdom, the love, the paternal solicitude of the Almighty

not legible in the surpassing organism, the ingenious architectures,

the individual and social habits, the adaptation of structure to the

physical conditions of existence of these "degraded beings?" Do not

their habitations display His care, their instincts His wisdom, their

_merriment_ His love, their vast specific diversities His solicitous

and inscrutable Providence.'--DR. WILLIAMS.

 

 

 

 

[Illustration:

 

1 THE POTTER (_Terebella figulus_)

2 _Terebella littoralis_]

 

 

 

 

XII.

 

 

Having visited the sea-side a few weeks since, along with some

'aquarian naturalists,' among other objects we managed to capture

a very fine _Terebella Figulus_, commonly called the 'Potter.' The

specimen measured about five inches in length, and was nearly as

thick as a common drawing pencil. I could discover no signs whatever

of any tube in the rocky basin in which the Annelid was situated, a

circumstance that struck me as being rather curious.

 

On returning home, my much-valued prize was placed in a tumbler of

large dimensions, the base of which I strewed with newly-pounded shells

and gravel. By the following morning all the fine or powdered portion

of the 'Silver Willies' had been collected and used in the construction

of a tube, sufficient in length to cover half the contracted body of

the industrious little mason. After labouring for a fortnight, the tube

was gradually extended across the bottom of the vase in a cylindrical

form, but eventually it assumed a semi-circular shape, being built

upon the glass, and elevated by gentle stages up each side of the

vessel until the level of the water was reached, when all further

labours ceased for a time.

 

After the lapse of a few days the building operation was resumed,

and the tube carried fully an inch further, at right angles to its

former position. The opposite end of the structure was next extended

at an angle of 45° from the base of the vase, to a height of about two

inches. Then commenced a very curious phenomenon. Some of the tentacles

were incessantly elevated and extended across the vessel, until they

touched the opposite end of the tube, with what object I could not then

conceive. The design, however, was afterwards made evident: in less

than two days the animal succeeded _in making both ends of its tube

meet together, so as to form a continuous circle_. I happened to be

watching the mason, when the last stroke of his labial trowel was given

to the building, and shall never forget the cautious way in which the

animal crept for the first time over the newly-completed portion of the

work, and the seeming delight with which it continued to glide, hour

after hour, over the entire circuit of its dwelling-place.

 

Sometimes its body would be long drawn out, until the tips of the

tentacula would reach, and apparently tickle the extreme point of the

tail; then a race would commence, in character exactly resembling

that so often witnessed with the kitten, or the playful whelp, when

either of these animals foolishly imagine that the tip of their tail is

adorned with some coveted tit-bit.

 

The branchial organs of my specimen were very beautiful objects, being

formed of three blood-red spiral tufts, the effect of which were

heightened by their being placed in contact with the drab, coloured

cephalic[10] tentacles, which seemed to be almost innumerable. These

latter organs, although apparently so useless when seen closed, are in

reality of the greatest importance to the _Terebella_, for they not

only act as auxiliary organs of respiration, and aid most materially

in building its dwelling-place, but also constitute the real organs of

locomotion.

 

[10] Cephalic, belonging to the head.

 

'They consist,' says Dr. Williams, 'of hollow flattened, tubular

filaments furnished with strong muscular parietes. The band may be

rolled longitudinally into a cylindrical form, so as to enclose a

hollow cylindrical space, if the two edges of the band meet, or a

semi-cylindrical space if they only meet imperfectly. This inimitable

mechanism enables each filament to take up and firmly grasp _at any

point of its length_ a molecule of sand, or, if placed in a linear

series, a row of molecules. But so perfect is the disposition of the

muscular fibres at the extreme free end of each filament, that it is

gifted with the twofold power of acting on the sucking and muscular

principle.

 

'When the tentacle is about to seize an object, the extremity is

drawn in, in consequence of the sudden reflux of fluid in the hollow

interior. By this movement a cup-shaped cavity is formed, in which

the object is securely held by atmospheric pressure. This power is,

however, immediately aided by the contraction of the circular muscular

fibres. Such, then, are the marvellous instruments by which these

peaceful worms construct their habitation, and probably sweep their

vicinity for food.'

 

The foregoing beautifully and accurately describes the tentacular

cirri. The use of these organs in the formation of the tube in which

the Annelid dwells, I will now endeavour to make clear, from close

personal observation.

 

It is an extremely interesting sight to watch a Terebella extend its

tentacles in all directions in search of building materials, catching

up the surrounding molecules (sometimes visible along the whole length

of each filament), and then, by a strong muscular contraction, bringing

the collected atoms to the opening of the tube, around which, as is

generally supposed, they are then immediately attached by a secretion

which is exuded from the body of the animal. Such, however, is not the

case.

 

When the filaments bring their 'subscriptions,' the material thus

gathered, instead of being used at once for building purposes, _is,

in reality, first eaten by the animal, and, after undergoing a kind

of mastication, becomes coated with a salivary secretion, and is then

ejected in mouthfuls at the extremity of the tube_, which, by such

means, becomes gradually elongated. The shell work, when deposited as

above mentioned, is held in position, and prevented from falling over

the outside of the cavity, by the filaments which are made to hang

down in a most ingenious manner; the animal, at the same time, putting

itself in motion, allows the slimy surface of its body to press and

rub against the new addition to the tube, which is thus effectually

strengthened and soldered together.

 

The animal does not always wait until the opening of the tube is

reached, but gently disgorging while lying at its ease, it then pushes

forward by aid of its head and tentacles the mass of building material,

which soon becomes distributed and moulded to its proper shape.

 

If your specimen should happen to build a complete tube, its mode of

working cannot be well seen; but should it economize its labours, and

run its house up in a semi-circular form against the transparent side

of the vessel, as the animal I write of did, you will be enabled to see

distinctly every movement that goes on in the interior.

 

It seems somewhat singular that the Terebella should possess the power

of turning itself within its tube, so as to be able to extend its

habitation from either end at will. I have very often watched the

operation with emotions of pleasure, not unmixed with wonder.

 

Wishing to test the powers and intelligence of my specimen, I

dropped within its tube, which was curved in shape lengthways, some

particles of sand, and a pebble which nearly filled up the 'bore' of

the cylinder. The great annoyance occasioned by this intrusion to

the master of the house was painfully evident. For a whole day the

Terebella endeavoured to push out the objectionable matter by means of

its head and cephalic tentacula, but without success; for although the

mass frequently neared, it never touched or toppled over the mouth of

the aperture, and consequently fell to its original position at the

bottom of the tube as soon as the animal removed the pressure.

 

Apparently despairing of its efforts, though still oftener repeated,

being eventually prosperous, the poor Annelid literally 'turned tail,'

and very coolly proceeded to elongate the opposite end of its dwelling.

This operation did not last long; for in the course of a few hours, on

peering again into the vessel, I saw that the humble and insignificant

worm had mustered up courage to 'face the enemy' once more, and had,

in fact, apparently conceived a new idea, the wisdom of which was

soon made palpable; for slowly, but surely, most of the arenaceous

particles were eaten, and nothing being left but the pebble, it was

speedily and triumphantly ejected from the tube, and the sand soon

after employed for building purposes. The Terebella having completed

its laborious and well-executed task, seemed to be quite exhausted, and

lay to all appearance lifeless for the succeeding four and twenty hours.

 

When walking along the sandy beach, myriads of peculiar objects may be

seen swayed to and fro by the roll of the waves. Frequently, when the

tide has receded, these tubes remain sticking out of the sand to the

height of two or three inches, each terminating in a tuft, like the end

of a piece of cord that had been teazed out.

 

Within such a fragile habitation dwells the _Terebella littoralis_,

the most common species of the marine tubiculous Annelids. I have very

often tried, by aid of my fingers only, or a strong spade, to capture

one of these creatures, but have never been successful, even in a

solitary instance. Yet several authors tell their readers the task is

perfectly easy. Mr. Lewes, for instance, made me feel ashamed of my

previous manipulative efforts when I read his vivid description of a

Terebella hunt, and caused me lately to journey a distance of six miles

to try my hand again, with no better result than hitherto.