SPONGE, Spongida, a horny substance valued for its ready imbibition of water, and consisting of the keratode skeleton of certain Protozoa or lowest animals. A sponge is thus a colony of living ani mals. Such a colony communicates with the outer world by means of certain openings (capable of being closed at will), traceable in an ordinary sponge, and of which the larger are named oscula and the smaller pores. By the latter, currents of water are continually drawn into the sponge, while through the oscula currents are as continually discharged. These currents are kept up through the action of the minute vi bratile processes named cilia, which are limited usually to certain spaces of the canals named ciliated chambers. The main use of this circulation in the sponge is evidently nutritive. Particles of food are thereby swept into the organisms, while oxygen is also inhaled and effete matters exhaled.
Sponge reproduction is effected by means of specially developed masses of protoplasm named spores, which are formed in autumn, and which on libera tion in spring are found to contain small reproductive particles, which after a free existence develop into sponges. Sexual reproduction is represented by the union of certain cells representing ova or eggs, and other cells representing spermatozoa. After fecundation a sponge-egg undergoes the stages of seg mentation common to the developing eggs of all animals, till the morula or mulberry stage is reached. Thereafter the egg becomes elongated and swims freely about in the water. An internal cavity is next formed, this cavity com municating by a mouth externally, and being bounded by two layers (ectodern and endoderm). In this stage the young sponge is a gastrula. Latterly the outer cilia disappear, internal cilia are de veloped, and the sponge ultimately fixes itself, and circulation is established. Sponges are classified either as the kera tosa (horny), silicea (flinty, e. g., "Venus's flower basket," or euplectella), and calearea (e. y., sycon). A more philosophical arrangement divides the sponge class into families: (1) Fibre spongim (fibrous, including silicea) ; (2) Illyxospongix (Halisarea) ; Calci spongiw (e. g., sycon and calcareous generally). Fossil sponges are of fre quent occurrence.
The sponges of commerce come from the Eastern Mediterranean Sea, the West Indies, and the coasts of Florida. In the Archipelago, Crete, Cyprus, on the coasts of Asia Minor, Syria, Bar bary, and the Bahama Islands, sponge fisheries constitute a very important in dustry. The finest sponges are obtained
in Turkish waters.
Sponges of a coarse texture and large honey-combing are found all along the coast of Tripoli and Tunis. The West Indian trade is of importance. The Bahamas and the coast of Florida are the best fishing grounds. The qualities most in commercial demand are "wool," "reef," and "velvet"; the other kinds go by the names of "boat," "silk" or "glove," "grass," "hardhead," "mixed," "yellow," and "refuse." West Indian sponge is harsher, coarser, and less durable than its Mediterranean con gener.
About 2,250 men are engaged in Florida sponge fishery, and 156 vessels are employed. The fishing is generally confined to the S. W. part of the coast and reefs and shoals between St. Mark's and Anclote Keys.
The methods employed in the fishery differ greatly from those employed in the Mediterranean, where divers go down and bring up the sponges. Small vessels, carrying crews of from 5 to 15 men, are fitted out at Key West and Appalachicola for trips of from four to eight weeks on the sponge grounds. The crews are paired off into small row boats, or "dingies," to catch the sponges. One man stands in the stern, sculling the boat, while the other kneels in the bottom amidships, with the upper half of his body leaning over the side, and scans the bottom of the sea. To aid the eye an instrument called a "water glass," which is a common water bucket whose wooden bottom has been replaced by one of glass, is used by setting it in the water and thrusting the face as far into it as convenient. When a sponge is sighted the boat is stopped, and the kneeling man uses a two-pronged hook, attached to a slender pole 30 or 40 feet in length, to secure it. Considerable dexterity is required of both men. To cure the sponges they are first spread about the vessel's deck in their natural upright position, so that they will die, and while decomposing allow the gela tinous matter to run off freely. When they have been several days in this posi tion they are taken to the shore and thrown into the water in little pens, called "crawls," where the remaining substance is soaked and squeezed out.
There are several varieties of sponges caught in the Florida waters. There are first, sheep's wool; second, yellow sponges, and third, grass sponges, which are coarse in texture and not durable. In average years the yield is over 400, 000 lbs., valued at over $500,000.