the skeleton of the Sea-urchin.
Sometimes you find this strange shell on the seashore, rather dirty, and
not always sweet-smelling. You might also find Sea-urchins half-dead,
washed into the rock-pools. The shells are wonderful objects, so you
should clean them in fresh water; they are well worth the trouble of
taking home.
All over the shell you will see little rounded knobs. These show where
the spines were fixed on; each spine fits into a hole in the shell, but so
loosely that it is able to move about. The Sea-urchin can walk by
moving its spines, tilting its body along from one place to another on
the bed of the sea. It can do much more than that. Like its cousin the
Starfish, it has numerous tube-feet, so you would not be surprised to
see this prickly ball walk up the face of a rock.
The tube-feet, or sucker-feet, are fixed to the shell in much the same
way as the spines. They can be bent this way or that. If the Urchin is on
a rock he clings tightly with these sucker-feet; then, if he wishes to
move away, you will see the long thin tubes stretch out and bend about.
They fix themselves to the rock, and the animal is drawn along.
[Illustration: TEST OR SHELL OF A SEA-URCHIN.]
Besides these spines and suckers, the Sea-urchin owns another set of
tools. Scattered over it, among the spines, are many tiny rods tipped
with little teeth or pincers. You will not be able to see them, except
under a magnifying glass. Of what use are these strange little pincers or
rods? It is thought that the Urchin uses them in several ways. They may
help in capturing small prey, or they may be used when the creature has
to fight a larger enemy. They are also certainly of use as cleansing tools.
That is to say, they can pick off tiny scraps of weed or dirt which settle
on the animal's body. Some Starfishes also own pincers of this sort, but
they are not so perfect as those of the funny little Urchin. We must not
forget that all these spines, tube-feet, and pincers are worked by a set of
muscles.
In the centre of the Urchin's shell is its mouth. The Starfish, we found,
had a terrible mouth, but that of the Urchin is worse still. Not only is it
of great size, but it is fitted with strong jaws and five long, sharp teeth,
You may see them poking out from the mouth of the animal, and feel
for yourself how hard they are.
There is a great deal more to know about Five-fingers; and the
Sea-urchin still has his secrets which no one can explain. We have but
glanced at their story in this lesson; but you can see that the Starfish,
lying limp on the sands, is not so dull as it looks.
EXERCISES
1. Where is the mouth of the Starfish placed?
2. Describe how the Starfish moves.
3. How does the Starfish feed on the oyster?
4. Why is the Brittle Star given that name?
5. How do the Starfish and Sea-urchin keep themselves clean?
LESSON II.
A STROLL BY THE SEA.
The sea and the land are always at war. When you are at the seaside,
with spade and bucket to make "castles" and "pies" of the sand, you can
see and hear the battle.
A wave comes rolling smoothly on towards the shore. It reaches the
land and can go no further, and then, with a roar and a crash and splash
of sparkling foam, it breaks. It spreads into a sheet of foaming water,
and, after rushing as far as it can up the beach, it seethes back as the
next wave takes up the battle.
What a grinding and tearing, as wave after wave is hurled at the land!
That is the battle-cry of the land and sea! Most of the pebbles and the
sand on the beach have been won from the land in the great fight. We
might call them the spoils of war. Once they formed part of the solid
land, the rock or cliff. Now they are loose fragments spread for mile
after mile round our coast.
Every wave takes them up and has fine fun with them. Pebbles and
sand are picked up, swirled along, and thrown at the shore. They are
sucked back as the wave is broken by the land. And then the following
wave takes them, grinds them and scrubs them together. Thus they are
jostled hither and thither, up and down the coast; and, as a result of the
long, long fight, rocks and cliffs become pebbles, sand, or mud.
Now if you look at the pebbles on the shore
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