SPONGES: are popularly regarded as a kind of sea-plant, but in reality they are the skeletons of a low-type animal. They are reproduced by means of eggs, and the developed larvm are partly clothed with small hairs which enable them to swim or drift around until they find suitable places for adhesion. When, however, they have once fastened themselves to rocks or other submerged objects, they must, with few exceptions, remain there during their entire existence, the pressure of the water being the chief factor in holding them in place.
The living commercial sponge is a solid looking mass, rather slimy in appear ance, its exterior varying in color from light grey to nearly black, generally shading to lighter in the cavities. For sustenance, it sucks in the water through many small perforations, which pass it into a system of internal tubes, these distributing it into thousands of minute cells, which digest its microscopic animal or vegetable contents. The superfluous water is passed into drainage tubes and thence out of the large open ings, the "eyes" or "craters," in the surface of the sponge.
The Flesh of the sponge is the soft jelly-like tissue of the tubes and cells, varying from transparent to deep-colored. The Skeleton, of the commercial varieties, is the interwoven mass of elastic, horny threads which constitutes the sponge of commerce. When: cut, the interior flesh of a living Sheepswool Sponge resembles a much per forated piece of beef liver.
The large openings of the "skeleton" sponge familiar to the consumer, are pres ent in the living sponge, but the "tufts" and the depressions between them, and the smaller holes, are modified in appearance by the delicate membrane covering the exte rior and permitting entrance to the tubes by small perforations only. The variance in shape is the result of differences in the surrounding conditions, the direction of the water currents, etc.
Fine sponges are gathered by hand by divers, or by hooks on the ends of long poles. Coarser grades are dragged up by dredges. All types are exposed to the air for a short time after gathering and then thrown into pens or tanks of water to decay. When fully decomposed, they are squeezed or washed out to remove the mem brane, skin and internal tissues and then set to dry. Next come sorting, trimming, resorting, etc. The details of the processes vary in different localities.
The market value is determined by the comparative fineness, closeness and elas ticity. The most expensive are those known as the Turkey Cup and Mediterranean, or Turkey, Toilet—the best grades being obtained along the eastern shores of the Medi terranean, especially off the Syrian Coast. They are small in size but very fine, silky
and resilient. Another well-known type is the "Elephant's Ear," so-called because of its peculiar flat shape, which fits into the hand almost like a face-rag.
Cheaper Toilet Sponges are generally bleached West Indian Toilet Sponges or small sizes of regular Bath Sponges.
The Turkey, or Mediterranean, Bath Sponge and the American Sheepswool, or Wool, are the most widely used of good Bath Sponges. The best qualities of the Sheepswool come from the West Florida shore of the Gulf of Mexico.
Because of their darker color, the Sheepswool are generally bleached. The pro cess frequently shortens their life, but it has become popular, as it softens them and gives them a clean, bright appearance.
The next in grade of the American product for bath purposes is the Yellow Sponge, which is very cheap in comparison with the imported variety, yet is fairly satisfactory in quality.
Being a natural product, sponges vary greatly in appearance. Those of especi ally good shape and style bring much higher prices than others of the same quality but of less choice appearance. For ordinary family purposes, an "off shape" sponge is just as good as an expensive selected one of the same variety.
The Turkey Cup, Mediterranean Toilet and American Sheepswool and Yellow are shown in the page illustration opposite.
Sponges that have deteriorated in storage can be restored by immersing in a mix ture of one part glycerine to eight parts of water, then squeezing out and drying. Where this process is not required, they can be improved by similar immersion in salt and water, or a weak 'solution of soda.
In popular opinion, the chief use of the sponge is for toilet and bath purposes. These, however, account for only a small part of the crop, the bulk being employed in the arts and industries. There is a steadily increasing exportation of the American product to Europe for commercial purposes.
In common with other civilized governments, the United States is devoting a share of its attention to artificial propagation, as the increasing demand has for some years been confronted with a diminishing supply. After many experiments it has been found that the best results are attained by "planting" small pieces of cut sponges attached to cement disks. The illustrations on page 583 show experimental plants from cuttings, growing on cement triangles, at Anclote Key, Fla.