at care for their young have small families, but
the babies have a much better chance of living than the baby Cod. It is
one of Nature's wise laws.

Our common Stickleback--"Tiddler," or "Red-throat," as boys call
him--builds a nest in ponds. He has a seaside cousin, the fifteen-spined
Stickleback, who is also a nest-builder. This little fish is fairly
common round our coasts, living in weedy pools by the shore, where it
devours any small creature unlucky enough to come near. It is about six
inches long, this sea Stickleback, with a long snout, and its body is
very thin near the tail.

To build his nest, this little fish chooses a quiet corner, then gathers
pieces of green and purple seaweed. He takes the pieces in his mouth,
pushing them about until the shape is to his liking. Having got his
nursery to the right size and shape, the little builder next fastens it
together. How can he do this? What mortar can he find in the sea? It is
quite simple. He uses threads, which come from his own body. He swims
round the nest, again and again; and, each time, a thread is spun,
binding the clump of weed into a safe, tight nest for the eggs. When the
task is done there is a weed-nursery about the size of your fist. Now
all is ready for the eggs to be laid by the female Stickleback. You
would expect them to be kept in a hole amid the nest, would you not?
Instead of that, they are tucked a few here, a few there, in the weed.

Then the father Stickleback mounts guard. Woe betide any small fish
looking for a dinner of Stickleback eggs! The gallant little sentry will
rush at him, with spines as stiff as fixed bayonets, ready to do battle
to the death. When the young are hatched out he still keeps guard. They
are not allowed out of the nursery for some time. The watchful parent
forces them back if they try to wander out into the perils of the
shore-pool.

[Illustration: _Photo: A.F. Dauncey_. SKATE'S EGG CASE]

Let us look at another nest-builder--the Sand Goby, or Spotted Goby, He
is common enough in the pools at low tide, but not easy to find. You can
look at him, yet not see him! For he takes the same colour as the rocks
and sands of his home. Amid the glinting lights and shadows of his
rock-pool, with a background of sand, rock, and weed, this little fish
is nearly invisible. Of course it is a dodge, and a useful one, to
escape the eye of the enemy!

Perhaps you will not think the Spotted Goby so clever at nest-building
as