sea-bed. Divers go down and obtain them; or else they are dredged up,
cleaned, dried, and sorted, and then sent to the market. Some Sponges,
called Slime Sponges, have no skeleton, being merely a living mass of
slime.
Coral is also the hard skeleton of a little animal, known as the Coral
Polyp. The rest of the polyp's body is soft jelly, which many fish
regard as good food. The Sea Anemone--another jelly-animal--is first
cousin to the Coral Polyp. And we may call the Jellyfish second cousin
to these two, for it is in the same big division of the animal kingdom.
The pretty red Coral, then, is really the hard part of a little
jelly-animal. This animal is much like a Sea-anemone, with a hard
skeleton of lime. Coral, as you know, looks like a solid rock; it is
really made of needles of lime, fastened together into a solid mass by
the little Coral Polyp.
Now, many of the Coral animals have the strange habit of budding. The
buds become perfect polyps, and then they, too, begin to bud. In this
way, those marvellous _coral-reefs_ and _coral-islands_ have been made.
Branch by branch, layer by layer, the hard Coral is built up by myriads
of the small, soft-bodied creatures. This kind of polyp can live only in
warm, clear water. So it is not found in the cold depths of the sea, nor
in the seas near our islands, but in the warm shallow waters near
tropical lands it flourishes so well that it builds up most wonderful
Coral walls. So strong are they that they can defy the terrific force of
the waves.
[Illustration: THE PICTURE STORY OF A CORAL ISLAND.]
Some coral-reefs are of immense size and strength. One, near the coast
of Australia, is nearly a thousand miles in length. These marvellous
works of the polyp are of great use, for they break the force of the
waves, and so make a calm shelter for vessels.
The brilliant masses of Coral make a world of colour in the clear seas
of the tropics, a gay garden inhabited by fishes of gaudy hues. In dull
seas we have, as a rule, dull creatures to match. And in bright, warm,
sunny seas the fishes are also brightly coloured. A dull fish would show
up amid such rich colours, so it is easy to know why Coral fish wear
such fine clothes.
Many of them spend all their time among the Coral, their food being the
living tips of the Coral "branches," which they nip off with fine, sharp
teeth. Others have teeth like millstones, fit for crushing the hard
Coral, and eating the fleshy body of the polyp within.
Blue, red and yellow, striped and spotted, and of wonderful shapes, are
the fish which swim in these coloured gardens of the sea. Some of them
have golden bands round their bodies, and fine spines which wave in the
water like shreds of weed--all to help them hide in the bright, sunlit
groves of Coral.
Gorgeous Sea-anemones of all shapes and sizes add to the brightness; and
even the Shrimps, Prawns, and Crabs are coloured to fit their
background. Crabs are always surprising us with their queer ways and
quaint "dresses"; and here, among the Coral, it is the same story. For
there are Crabs whose shelly coats are covered with coloured knobs and
spikes, so that the sharpest eye cannot pick them out from the Corals on
which they rest.
EXERCISES
1. How does the Sponge obtain its food? 2. What is Coral? 3. How are
Coral-reefs formed? 4. Why are there no Coral-reefs in our seas?