It has ten legs; and, under each of the horny rings of its
body, you can see a pair of little paddles. They are fringed with hairs.
When the Prawn or Shrimp is not in a hurry, he swims slowly but surely
with the little paddles, or "swimmerets." If any danger threatens, he
uses his tail, in this way:--It is made of five fringed plates, which,
as you can see, spread out or close up, like a fan. As he doubles up his
body, the plates spread themselves out. They strike the water with great
force, and so send the Prawn or Shrimp quickly _backwards_. As the body
becomes straight again, the fan closes, ready for another stroke. To
move quickly, the Shrimp or Prawn merely bends his body, then
straightens it. The tail thus becomes a strong oar, driving him
backwards with rapid jerks.
Look now at the Prawn's long, hair-like feelers. There are two pairs. On
one pair are the ears, a special kind of ear for hearing in water.
You will notice that the Shrimp's eyes are on the end of short stalks.
Each big eye is really a cluster of little eyes, rather like the
"compound eyes" of insects. If you lift up the horny shield behind the
head, you see a row of what look like curly feathers.
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