b-fins are
useful chiefly as balancers, while the tail-fin is what sends the fish
darting through the water, or turns it to right or left, with incredible
swiftness.

If we were able to examine some inhabitant of the planet Mars our first
interest would be to know with what senses they were endowed, and these
finny creatures living in their denser medium, which after a few seconds
would mean death to us, excite the same interest. They see, of course,
having eyes, but do they feel, hear, and smell!

Probably the sense of taste is least developed. When a trout leaps at and
catches a fly he does not stop to taste, otherwise the pheasant feather
concealing the cruel hook would be of little use. When an animal catches
its food in the water and swallows it whole, taste plays but a small part.
Thus the tongue of a pelican is a tiny flap all but lost to view in its
great bill.

Water is an excellent medium for carrying minute particles of matter and
so the sense of smell is well developed. A bit of meat dropped into the
sea will draw the fish from far and wide, and a slice of liver will
sometimes bring a score of sharks and throw them into the greatest
excitement.

Fishes are probably very near-sighted, but that they can distinguish
details is apparent in the choice which a trout exhibits in taking certain
coloured artificial flies. We may suppose from what we know of physics
that when we lean over and look down into a pool, the fishy eyes which
peer up at us discern only a dark, irregular mass. I have seen a pickerel
dodge as quickly at a sudden cloud-shadow as at the motion of a man
wielding a fish pole.

We can be less certain about the hearing of fishes. They have, however,
very respectable inner ears, built on much the same plan as in higher
animals. Indeed many fish, such as the grunts, make various sounds which
are plainly audible even to our ears high above the water, and we cannot
suppose that this is a useless accomplishment. But the ears of fishes and
the line of tiny tubes which extends along the side may be more effective
in recording the tremors of the water transmitted by moving objects than
actual sound.

Watch a lazy catfish winding its way along near the bottom, with its
barbels extended, and you will at once realise that fishes can feel, this
function being very useful to those kinds which search for their food in
the mud at the bottom.

* * * * *

Not a b