Plate XI.—Synapta Duvernæa. (Quatrefages.)
"It was nearly four o'clock when the Malays finished their operations. In less than half an hour they had embarked their cargo; the tents were struck, and, together with the boilers, carried back to the boats, which were already preparing to set sail. At eight o'clock in the evening they hoisted sail and left the bay."
Some idea may be formed of the extent and importance of the Holothuria fishing by the number of ships which it attracts in this part of the East. Captain King assures us that two hundred vessels annually leave Madagascar to fish for the sea slug, as it is sometimes called. Captain Flinders, being on the coast of Australia, learnt that a fleet of sixty vessels, having a hundred men on board, had left Madagascar two months previously in the same pursuit.
Among the Holothurias, one particular genus, the Synapta, is distinguished from others of the family by the absence of the ambulacral feet, and by the fact of its uniting both sexes in one individual. This remarkable Echinoderm, Synapta duvernæa, is represented in Pl. XI. M. Quatrefages, who discovered it in the Channel, gives the following description of it in his great work, "Le Souvenirs d'un Naturaliste." "Imagine," he says, "a cylinder of rose-coloured crystal, as much as eighteen inches long and more than an inch in diameter, traversed in all its length by five narrow ribbons of white silk, and its head surmounted by a living flower, whose twelve tentacles of purest white fall behind in a graceful curve. In the centre of these tissues, which rival in their delicacy the most refined products of the loom, imagine an intestine of the thinnest gauze gorged from one end to the other with coarse grains of granite, the rugged points and sharp edge of which are perfectly perceptible to the naked eye.
"But what most struck me at first in this animal was, that it seemed literally to have no other nourishment than the coarse sand by which it was surrounded. And then when, armed with scalpel and microscope, I ascertained something of its organisation, what unheard-of marvels were revealed! In this body, the walls of which scarcely reach the sixteenth part of an inch in thickness, I could distinguish seven distinct layers of tissue, with a skin, muscles, and membranes. Upon the petaloid tentacles I could trace terminal suckers, which enabled the Synapta to crawl up the side of a most highly polished vase. In short, this creature, denuded to all appearance of every means of attack or defence, showed itself to be protected by a species of mosaic, formed of small calcareous shield-like defences, bristling with double hooks, the points of which, dentated like the arrows of the Caribbeans, had taken hold of my hands."
If one of these Synapta is preserved alive in sea-water for a short time, and subjected to a forced fast, a very strange phenomenon will be observed. The animal, being unable to feed itself, successively detaches various parts of its own body, which it amputates spontaneously. A great compression or ring is first formed, and then the separation of the condemned part takes place quite suddenly. "It would appear," says M. Quatrefages, "that the animal, feeling that it had not sufficient food to support its whole body, was able successively to abridge its dimensions, by suppressing the parts which it would be most difficult to support, just as we should dismiss the most useless mouths from a besieged city."
This singular mode of meeting a famine is employed by the Synapta up to the last moment. After a few days, in fact, all that remains of the animal is a round ball, surmounted by its tentacles. In order to preserve life in the head, the animal has sacrificed all the other parts of its body.
In order to find natural novelties—to find unforeseen subjects of study and reflection, it is not necessary to run over the world or travel great distances. It is only necessary to visit the banks of the nearest river, or descend to the sea shore, and leave the sea to reveal a fragment of the marvels which it conceals in its bosom.