This is a very odd-looking fish indeed—quite the most curious of all the fishes which live in the rock-pools. And as it is very common, you ought to be able to find it without any difficulty.
In the first place, although it grows to a length of eighteen or nineteen inches, its body, even in the largest part, is no bigger round than a slate-pencil. For this reason it is often known as the Needle Fish.
Besides this, its jaws are drawn out to a most wonderful length, and are fastened together all the way along, so that they really form a kind of tube. So, you see, a pipe-fish can never open or shut its mouth, but has to suck in its food through the tiny hole at the tip of the jaws.
Sometimes, as you look down into a rock-pool, you may see one of these fishes feeding; and the way in which it does so is very curious indeed. It suspends itself almost upright in the water, with its tail upwards and its head downwards. It then fills its tube-like mouth with water, which it squirts out again as hard as it possibly can. The result is, of course, that the sand at the bottom of the pool is blown away, and the various tiny creatures which were lying hidden underneath it are uncovered. Then the fish sucks them up into its mouth, and swallows them.
Another curious fact about the pipe-fish is that instead of being clothed with scales, as most fishes are, it is covered all over with hard bony plates, just like a suit of armour. But the strangest thing of all about it is that underneath the body of the male fish is a kind of pouch, into which the female puts her eggs, so that he can carry them about in safety until they hatch! Isn’t that odd? And it is even said that after the little fishes are hatched they will go back into their father’s pouch if they are frightened, just as baby kangaroos do into that of their mother, and remain there until the danger has passed away!
PLATE IV
THE FLOUNDER
This is one of the “flat fishes,” as everybody calls them, like the turbot and the sole. Yet, really and truly, these creatures are not flat at all. They are thin. For what we always call the back of a sole is not really its back. It is one of its sides. And what we always call its lower surface is not its lower surface, but its other side!
This sounds very strange, doesn’t it? But the fact is that when these so-called “flat” fishes are first hatched they swim upright, just as all other fishes do. Then their backs are upwards, of course, and their lower surfaces are downwards, and one of their sides is on either side. For about a month they swim about in this way. At the end of that time a strong desire comes over them to go and lie down on the sand or mud at the bottom of the sea. Now, in order to do this, of course, they have to lie upon their sides. Then three very strange things happen.
In the first place, their colour changes. Until now, both sides of the body have been pearly or silvery white. A white fish, however, lying on yellow sand or brown mud, would be very easily seen, and some hungry creature would be sure to catch sight of it and devour it. So as soon as the little fish lies down the upper side begins to get darker, and in a very short time it is of just the same colour as the sand or mud all round it. If you look into a shallow pool in which some of these fishes are lying you will find it very difficult indeed to see them, for they look exactly like the surface on which they rest.
In the second place, their way of swimming changes. When they first hatch out from the egg these little fishes swim just as other fishes do—upright, by means of their tails. For of course you know that fishes do not swim with their fins, which merely help them to keep their balance in the water. But when they lie down at the bottom of the sea they give up this way of swimming, and wriggle their way, as it were, through the water, still lying upon one side.