In the tank, it is not particularly interesting; it grovels on the
bottom among the pebbles, and will cover its body with the sediment so
far as it is able; where it lies for hours, watching upward. Doubtless
this is its habitual mode of obtaining its food; lying motionless in
wait, nearly concealed, the eyes and the mouth both opening upwards,
so that the former can observe, and the latter seize, any vagrant
crustacean, or annelid, or young fish-fry that unsuspectingly swims
within reach. Its motions when its energies are aroused are rapid,
sudden, and forcible; and it probably rarely misses its victim when
it makes its snap; while the multitude of minute creatures that
roam continually over every part of the sea-bottom give no lack of
opportunities for the exercise of its instincts. He fares sumptuously,
no doubt.
Here is in the drag a specimen of an interesting tribe of fishes. It is
the young of the common Thornback, a little thing about five inches in
width, and in its infantile grace and beauty much more attractive than
the older ones we are accustomed to see on the fishmonger’s table. It
flaps and flutters in impatience at being dragged out of its element,
and exposed to ungenial air: we will quiet its anxiety by lifting it
into yonder shallow rock-pool. Now watch it. How easily and gracefully
it glides around its new abode, moving along by an undulation of the
edges of the broad pectoral fins, a movement which Yarrell describes
as something between flying and swimming. Now it lies still on the
sand-floor of the pool, motionless, save that the two oval orifices
just behind the eyes are constantly opening and closing, by the drawing
across each or back, of a film which exactly resembles an eyelid, and
which on examination with a lens we see to be edged with a delicate
fringe. The action is so closely like the winking of an eye, that an
observer seeing the fish for the first time might readily suppose
the orifices to be the organs of vision. They are, however, outlets
of the gills, called spiracles; the ordinary gill-apertures are five
on each side, placed semi-circularly on the inferior surface of the
body, as you see when I turn the fish on its back, a demonstration
which it resents and resists with all its might: these upper orifices
communicate with the gill-chambers by canals, and you may see the water
now and then strongly driven out of them.