n
finished, he invites his chosen mate to lay her eggs. As soon as these
precious treasures have been entrusted to his care, he makes himself
their sole guardian, forcing currents of fresh water through the nest by
the violent fanning motion of his breast-fins, and driving away all that
come near. Strangely enough, he has to exercise the greatest care to
keep out his mate, who would eat every single egg if she could but get
the chance! Every now and then he holds an inspection, shakes up the
material of the nest, drags out the eggs, and pushes them back into
their places again just to make sure that they are safe, and to keep
them bathed in clear water. But soon the little fish appear, and then
his labours are increased a hundredfold. If they rise more than a
certain height above the bottom of the stream, or stray beyond what he
regards as a safe limit from the nest, they are immediately seized in
his mouth, brought back, and gently puffed or jetted into the nest
again. Day and night his watch is kept, till at last they grow too big
to be controlled, and are allowed to stray whither they will.

[Illustration: FIG. 1 THREE SPINED STICKLEBACK]

Another of our native fishes, found in the Thames among other places,
builds a nest for its young. This is the 'spotted goby' or 'pole-wing.'
Here an old shell is made to do duty for a nursery. The shell is turned
over so that its hollowed portion forms a roof; the mud from below is
scooped away and a tunnel is then made leading away from the chamber so
formed. When all is complete, the mother enters and deposits her eggs,
and leaves her mate to mount guard over the nest till the young are
hatched and make their way out.

In the 'butter-fishes' or 'gunnels' which are found round our coasts,
the eggs are rolled into a ball, and jealously nursed by the parents,
each in turn coiling its body round the mass, and so protecting it from
injury (see fig. 2).

[Illustration: FIG 2 BUTTER FISH]

Many of those crafty 'hooligans' of the sea, the skates, are most
affectionate as parents. One of the giants of the tribe, the great
'devil-fish,' will defend its young with great ferocity. Its capture is
at all times attended with danger, but is especially perilous when it is
accompanying its offspring; at such times it has been known to attack
and upset a boat!

In one of the 'cat-fishes'--the Aspredo (fig. 3)--the mother carries the
eggs about with her, and this is managed in a very remarka