All sponges, however, have not a horny framework, but some, which are thereby rendered useless in a commercial point of view, are supported by a skeleton composed of siliceous particles imbedded in a tough, fibrous material. These particles, or spicula, as they are termed, are so uniform in the species to which they severally belong, that, in the words of Professor Grant, if the soft portion be destroyed, and a "few of them brought from any pan of the world on the point of a needle, they would enable the zoologist to identify the species to which they originally belonged." Professor R. Jones, however, considers that this opinion should be received with considerable limitations.
The last fact, trivial as it appears, assumes immense importance when we learn that to these spicula we must turn for an explanation of the isolated masses of flint which abound in various chalk formations. "The mere assertion," says Rhymer Jones, "that flints were sponges, would no doubt startle the reader who was unacquainted with the history of these fossil relics of a former ocean;" and yet a little reflection "will satisfy the most skeptical." For long ages the sponge is imbedded in the chalk, through which water is continually percolating. A well-known law of chemistry explains why similar matter should become aggregated; and thus the siliceous matter of the sponge forms a nucleus for the siliceous matter contained in the water, until at length the entire mass is converted into a solid flint. But we are not left, he adds, to mere conjecture or hypothesis on this point, "for nothing is more common in chalky districts than to find flints, which, on being broken, still contain portions of the original sponge in an almost unaltered state."
There is every reason to believe that the sponge-fisheries of the Ægean are at present conducted precisely in the same manner as they were in the time of Aristotle. The sponge-divers are mostly inhabitants of the islands which lie off the Carian coast, and of those situated between Rhodes and Calymnos. These men—who form a distinct society, and are governed by peculiar laws, which prohibit their marriage until they shall have attained a prescribed proficiency in their art—go out in little fleets, composed of caiques, each of six or seven tons' burden, and manned by six or eight divers: each man is simply equipped with a netted bag in which to place the sponges, and a hoop by which to suspend it round his neck; and thus furnished, he descends to a depth of from five to twenty, or even occasionally thirty fathoms. The sponges which he collects are first saturated with fresh water, which destroys the vitality, and decomposing the gelatinous matter, turns it black; this matter is stamped out by the feet of the divers, and the sponges are then dried in the sun, and strung in circles, after which they are ready for sale and exportation.
In a good locality an expert diver may bring up fifty okes in a day, and for each oke he obtains about twenty-five drachmas. The weight is calculated, says Forbes, when the sponges are dry, and a very large sponge may weigh two okes. The chief sponge-markets are Smyrna. Rhodes, and Napoli.
Blount, who wrote in 1634, affirms that these sponge-divers "are from infancy bred up on dry biscuites and other extenuatinge dyet, to make them extreme lean; then takinge a spunge wet in oyle, they hold it, part in their mouths, and part without, soe they go under water, where at first they can not stay long, but after practice, the leanest stay an hour and a halfe, even till the oyle of the spunge be corrupted.... Thus they gather spunges from more than an hundred fathom deep," &c. All this is very wonderful, but the narrator stamps the value of his tale by telling us immediately afterward that "Samos is the only place in the world on whose rocks the spunges grow." So that, in the words which he elsewhere makes use of, "we applaude hys belief, but keep our owne." We do not, however, mean to assert that there are not sponges of some species (though not the sponge of commerce) which exist at a depth as great as that which he mentions, for Forbes dredged a living specimen of one small kind from 185 fathoms in the Gulf of Macri.
The sponge of commerce (Spongia officinalis) was divided by Aristotle into three kinds—namely, the loose and porous, the thick and close, and the fine and compact. These last, which are rare, were called the sponges of Achilles, and were placed by the ancients in the interior of their helmets and boots, as protections from pressure and abrasion.
The same naturalist states that those sponges are best which are found on coasts where the water becomes suddenly deep, and attributes this superiority to the greater equality of temperature obtained in such waters—observations which have been corroborated by Professor E. Forbes.
Fifty-six species of sponges have been enumerated, ten or eleven of which are found in the British isles. A portion of these inhabit fresh water, among which we may mention the river sponge (S. fluviatilis), which abounds in the Thames. Among the British sponges, too, is the stinging or crumb-of-bread sponge (S. urens), a widely-diffused species, which, when taken out of the sea is of a bright orange color, and which will, if rubbed on the hand raise blisters. This stinging quality is highly increased by drying the sponge; a process which also gives it the color and appearance of crumbs of bread, whence its popular name.
Sponges, as may be imagined from the mode of their growth, are most sportive in their forms: some a tubular, others mushroom-like, a few almost globular, and still others branched or hand-shaped; in the warmer seas they hang in fantastic and gorgeous fans from the roofs of submarine caverns, or decorate the sides with vases of classic elegance, though of nature's handiwork. Nor are their colors less various: some are of the most brilliant scarlet or the brightest yellow, others green, brown, blackish, or shining white; while Peron mentions one procured by him in the South Sea which was of a beautiful purple, and from which a liquor of the same color was extracted by the slightest pressure; with this liquor he stained several different substances, and found that the color was not affected by the action of the air, and that it would bear several washings.
The value of the sponge in surgery is well known; and it is also used, medicinally, being for this purpose lightly burned to powder, and given in small doses in scrofulous complaints. It has also been regarded as a specific in leprosy and hydrophobia. It is, however, needless to say that in these last it can have no influence whatever.