THE ULVA MARINA. 163 the rocks for miles round the west coast of Ireland. The average yield of British kelp is said to be ten thousand tons yearly, of the value of forty thousand pounds. In some of the countries bordering on the Baltic, sea-weeds are used for packing materials and for stuffing articles. The Ulva Marina is extensively employed in our own country for the latter purpose. Attempts have been made to manufacture paper from sea-weeds; marine sugar is obtained from several species. The Chinese derive from them a gum for making their lanterns and transparencies, also a varnish, and a size for the manufacture of silk and paper. You may see in the British Museum fishing-lines made of seaweed, and used on the north-west coast of America. HUS Homer describes Vulcan making a similar use of the that in which we now employ it, and showing through. how many ages of time that common but valuable material has been known and appreciated, for the great master of epic poetry is supposed to have lived eight hundred years before the birth of our Saviour. Among ancient nations the sponge was also used as a soft and elastic lining for the brazen helmets of their soldiers, and many other purposes. It is one of the many valuable spoils we take from the ocean, their birthplace and their nourishment; and this leads us to inquire into the nature of these singular productions. It has long been a matter of debate among naturalists whether sponges should be classed among the vegetable or animal kingdoms; they are now generally placed under the order Zoophyte, or plant-animals (from two Greek words signifying "animal" and "plant"). DR. GRANT'S EXPERIMENTS ON SPONGES. 165 Aristotle, the greatest of ancient philosophers, who was born three hundred and eighty-four years before Christ, described the sponge as a stationary or rooted animal; but from other statements he made it is certain that he considered its place as between the animal and vegetable. Some modern naturalists have placed sponges among marine vegetables, and their appearance, if you casually look at them, would seem to justify such an opinion; but the researches of Mr. Ellis, a merchant of London, who made similar branches of natural history a particular pursuit, gave additional interest to this case. In the course of his miscroscopic investigations, he was astonished at discovering that sponges possessed a system of pores (passages of perspiration) and vessels, in which sea-water passed with all the appearance of the regular circulation of fluids in animal bodies, and a seeming purpose of conveying animalculæ (small minute animals) to itself for food. More recently Dr. Grant gave the result of his experiments on the same subject. The account is so interesting that I will give it in the Professor's own words. "Having," he says, "placed a portion of sponge in a watch-glass with some sea-water, I beheld for the first time the splendid spectacle of this living fountain vomiting forth from a circular cavity an impetuous torrent of liquid matter, and hurling along in rapid succession opaque (cloudy) masses which it strewed everywhere around. The beauty and novelty of such a scene in the animal kingdom long arrested my attention, but after twenty-five minutes of constant observation I was obliged to withdraw my eye from fatigue, without having seen the torrent for an instant change its direction or diminish the rapidity of its course. In observing another species, I placed two entire portions of this together in a glass of sea-water, with their orifices opposite to each other at the distance of two inches. They appeared to the naked eye like two living batteries, and soon covered each other with the materials ejected. I placed one of them in a shallow vessel, and just covered its surface and highest orifice with water. On strewing some powdered chalk on the surface of the water, the currents were visible to a great distance, and on placing some pieces of cork or of dry paper over the 165 HOW SPONGES ARE OBTAINED. orifices, I could perceive them moving by the force of the currents at the distance of ten feet from the table on which the specimens rested." So interesting are the sponges, which, although ranked as creatures of very low intelligence, yet are by no means the least curious of those manifestations of the Divine Power "That built the palace of the sky, Formed the light wings that decorate the fly; Feeds the least gnat that gilds the evening air." Every one of my young readers must be conscious of the useful qualities of the sponge, but many are unacquainted with the manner in which and where they are obtained. The finest qualities of sponge come from the Ottoman Archipelago, and form one of the principal articles of commerce with Turkey. The island of Calymnos is the principal station for the sponge fishery, and more than three hundred boats are employed, averaging each about six tons, and carrying six to eight men, of whom two are rowers. The finest qualities are sent in large quantities to our own country, and the common and coarser kinds are forwarded to France, Austria, and Constantinople. The average depth at which the best sponges are found is about one hundred and eighty feet; those of an inferior quality are brought from a lesser depth. The method of diving is much the same as I have described in the coral-fishing. The diver, who goes head-foremost into the water, takes with him a triangularshaped stone, to which a strong line is attached to assist him in his descent, and direct him like a rudder to any particular spot. On reaching the bottom, the diver tears off a number of sponges, which adhere in masses to rocks and stones, sometimes to large shells, and are either round, flat, or hollow like a funnel; and then, pulling a line, he is drawn up, with the sponges in his arms, by the An experienced diver will make from eight to ten dives during the day. The proceeds of the fishery are divided into rowers. COMPOSITION OF THE SPONGE. 167 shares, the divers receiving a whole share, and the rowers twothirds of a share. Formerly the divers used to sell their sponges by weight, to increase which they put sand into them, a practice still continued, though now sold by quantity. The sponge in its natural state would not be recognized as that we are accustomed to use daily. In its primitive condition it is covered with a thin dark skin, inside of which there is a liquid like milk, and of the same consistency. If you examined a drop of this liquid by the microscope, it would appear entirely composed of very small transparent grains, nearly of the same size, with some moisture. This jelly matter connects the different parts of the framework of the sponge and lines the various canals or passages. The pores, or apertures for perspiration, are minute openings on the surface, protected by the framework, and into which the water enters in currents, and after traversing the interior passages, is ejected by means of openings which are larger than the pores, and in many species are elevated above the surface. To examine closely the framework or skeleton of the sponge, to which I have alluded, it is necessary to macerate it in hot water, which removes the gelatinous matter, and leaves it in a condition to be examined. by the microscope. This framework consists principally of two materials, one animal, the other mineral; the first of a thready, horny, elastic nature, the second (the species most commonly used for domestic purposes) of a flinty or chalk material. The thready portion consists of a light pale-coloured network, with some few exceptions always solid, and varying considerably in size. The mineral portion has little spines, which, if examined with the microscope, show traces of a central cavity or canal, the extremities of which are closed. How the growth and increase of the sponge is effected affords matter of the deepest interest, and this, like everything else in nature, shows the unerring wisdom of an all-sustaining Providence: "See through this air, this ocean, and this earth, |