Page:Popular Science Monthly Volume 30.djvu/708

686 branches of the coral, we behold animated life; a world in itself is spread before us; here dwell most of the various inhabitants of the sea—snails, shells, and sea-urchins, fishes and crabs of the queerest shapes. Here in the domain of color, where everything seems brilliantly attired, they are less easily discovered by their enemies than in the ocean. In fact, one can often observe that the exterior of animals is in accordance with their surroundings. The inhabitants of the desert have a sand-like color; those of the polar regions are of light shade; some caterpillars resemble the twig of a tree; some butterflies look like dried leaves; and a grasshopper has, on account of the shape of its body, received the name of "wandering leaf."

But the beautiful aspect presented by a branch of coral, when under water, immediately vanishes when it is removed from its native element, as the many little arms are then contracted. The skeletons of various species are, however, much sought for as ornaments, above all the black coral of India, which is considered a talisman. Next in value ranks the red coral, found near Algiers, and third in rank comes the white.

Another kind of plant-animals, which build structures like those of the coral, only not so large, not so hard, nor so lasting, are the sponges, sea-animals in the strictest sense of the term. The eastern part of the Mediterranean, and the Red Sea particularly, abound in valuable sponge-beds, on rocky soil. Numerous vessels arrive there every summer to collect the crop. Recently the cultivation of artificial sponge-plantations has been tried by taking a piece of fresh sponge, which still contained the slimy bodies of the sponge-animals, and planting the same in a favorable spot. The experiment succeeded admirably.

It seems easy and natural enough to turn our attention from the sponges to chalk. This very important writing-material is, as is well known, an accumulation of minute animal remains, or, more correctly speaking, of their calcareous shells. What large deposits they are capable of forming is shown by the chalk-cliffs of Rügen, by those of Great Britain, to which the island owes the name of "Albion" (white), and by those of Crete, from which the German word "Kreide" (chalk) is derived.

The chalk-cliffs arose from the ocean, but their later upheaval is due to volcanic eruption. The minute animals, which form the masses of chalk, are of various shapes; some resemble the houses of snails, some the cone of a pine, others again are staff-like.

The largest of the existing three hundred kinds have been known since the oldest of times, for they were found in the stones used by the builders of the Pyramids. Their incasement is greatly perforated, and from their pores they send forth numerous fine, slimy feet, which constantly fluctuate to and fro. By adhering closely to one another they cover their food-supply, and then gradually assimilate the same.

As the aurora borealis flashes through the darkness of the polar