Footnote 49. Hippocampus.

to be often carried by floating weed even into the open ocean, and make up for his feeble powers. In one thing he surpasses most other fishes, for he is a most careful father, carrying the mother’s eggs in a little pouch under his body till the young ones escape. There is one form of these sea-horses in tropical seas which has long red fringes floating from its body, so that it cannot be distinguished from the seaweed in which it hides.

So we see that the deep sea, the open sea, and the shore, are filled so full of different forms that there are enough not only to make use of every part, but also to provide food for each other, and we also see that by far the larger number even of widely-spread fish come near to the shore to leave their spawn, while the young ones often make their way into the brackish water at the mouths of rivers, and spend their youth in the shelter of the still fresh water.

Now it is very natural that many such fish should learn to remain in this quiet refuge, and in time to live there altogether. And because fish-life in the rivers is comparatively uneventful and little varied, we find much fewer peculiarities in river-fish. Many of them are very near relations of sea forms. There is the salmon, a true sea-fish, which wanders up the river to spawn in the pebbly shallows; and there are the trout, his near relations, which have learned to live entirely in the rivers. There are the sea-perches, large strong fish, and the smaller river perch, which have made their homes very successfully in the rivers, for their spines are so sharp that even the greedy pike hesitates to swallow them. There are Fig. 14. STICKLEBACKS AND THEIR NEST. Gasterosteus aculeatus.) Toface p. 6j.

the sea-sticklebacks, and the little river-stickleback.[50] This last is a very clever little fish, which hollows out the foundation of his nest very carefully in the bed of the river, and then builds it up for several inches with blades of grass and weeds (Fig. 14), gumming them together with the slime of his body. Then, when all is ready, he swims about to drive and coax the mother to the nest, sending her in to lay her eggs, and then driving her right through and out at the other side, so that a stream of water flows constantly over the eggs till they are hatched. Nay, his care does not end here, for when the young fish come out of the egg with a bag of yelk hanging under the body, as all young fish have at first, and so cannot swim easily and escape their enemies, the courageous little father will defend them and fight fiercely with any fish which thinks to make a meal upon them, not leaving them till all the yelk is absorbed, and they are able to swim and feed themselves.

Fig. 14.

STICKLEBACKS AND THEIR NEST. (Gasterosteus aculeatus.)

Besides these active river-fish there are the little stupid Miller’s Thumbs,[51] hiding under the stones to feed on tiny animals; they are feeble relations of the gurnards which we saw walking on the bottom of the sea. Then there are the purely freshwater fish, the Pike and the large Carp family, with its many branches, the Roach, and Dace, and Gudgeon, and Minnow; and the enormous family of Cat-fish and Sheat-fish,[52] of which we have none in England, but plenty in America and other parts of the world, a family in which the fathers sometimes carry the eggs in their mouths till hatched. And last but not least among the freshwater forms is that irrepressible

Footnote 50. Gasterosteus.

Footnote 51. Cottus.

Footnote 52. Siluridæ.

family of the Eels which we saw wandering in the deep sea, and which are also to be found near the shores all over the world. These fish will even travel through pipes and into cisterns; and will climb up trees so as to drop into neighbouring streams and continue their wanderings; they sleep in the mud in winter; and even after being frozen come to life again; and in the spring they go to the sea to spawn, giving rise to those shoals of young ones from three to five inches long which come in incredible numbers up the rivers in summer, making the eel-fairs,[53]—

“The silver eel, in shining volumes rolled,”

so much spoken of in old books, when the eels will often climb high banks, nay, even pass over miles of dry land, closing down their narrow gill-openings, and so shutting in water to serve them as they go.

All these, and many other freshwater families, show us how the fish have wandered into every possible nook of the waters, so that even in those inland salt lakes of North America and Asia into which no rivers flow fish-life is abundant; and we can only suppose that the eggs must have been carried by water-birds in their flight, or by gusts of wind, or have arrived there in ages long ago, before these lakes were cut off from the rest of the watery world.

Yet some few fish besides the eels have been known to travel over land to find watery “pastures new;” the Climbing Perch[54] of India and the Doras

Footnote 53. More properly eel-fares (fare, Saxon, to travel; ex., way-faring man).

Footnote 54. Anabas.

of Tropical America will both travel many miles when their own ponds are dried, the perch breathing by the help of a special apparatus, and the doras probably shutting water into its gills; for necessity, even in fishes, proves the “mother of invention,” and in special works on fish you will find accounts of numberless strange devices and adaptations by which they manage to survive in the struggle for life.

And now, collecting together all we have learned, let us in conclusion form a rough picture of the history of the fish-world. All over our globe, from pole to pole, and from the Indian Ocean round to the east, back to the Indian Ocean again, is one vast world of waters, with inlets and land-locked seas bordering its margins, and rivers pouring into its depths. In the past ages of the world these rivers and coasts and inlets have varied innumerable times, but the great ocean-mother has always been there to bear the increasingly-varied forms in her bosom, and to enable them to wander where best they could preserve life.

And so from their beginning, when they were probably as feeble as the lancelet, these earliest and simplest backboned animals with their two pair of limbs as yet very variable both in their position and shape, have been spreading far and wide over the watery three-quarters of the globe. We have seen how the enamel-scaled fish had their time of glory, but were not able to hold their ground, because they were not agile and fish-like enough to escape their foes; and how the sharks by their strength and boldness remain monarchs of the sea to the present day. Then we have seen that in old chalk seas the new and active race of bony fish appear in force; some like the herring and the carp, with air-bladders, which had openings like the enamel-scaled fish, and these can dart from heights to depths; while others had closed air-bladders, and these remain with most ease at one level, and can sometimes, if necessary, use the gas in their bladder for breathing, if they are oppressed with muddy water; and lastly, some, such as the dorado, have lost their air-bladder altogether, and gain in freedom of action what they lose in lightness and buoyancy. And during the ages that have passed since this bony race began, different branches each in their own way have thrown out curious weapons and developed strange organs to help them in the battle of life, so that now we have deep-sea fish carrying their own light; fish with distensible stomachs swallowing prey larger than themselves; fish with large air-bladders and long arm-fins springing out of their own element and floating in air; angling-fish, walking-fish, clinging-fish, and hiding-fish; and even those whose shape is distorted, like the sole, to enable them to hide and hunt in safety; while, when the sea is full, we find new varieties pressing their way into every river and tiny stream, and even overland into enclosed waters. Nay! when we descend into the recesses of the earth and visit the underground pools of the dark caverns of Kentucky, there we come upon fish which have found a refuge in eternal darkness, and have lost not only the power of sight but actually the eyes themselves.

And here we must leave them to go to higher vertebrate animals. Although but little is known of fish-life, a very small part even of that little has been given here, and yet we take leave of it with the feeling that its changes and chances are greater than we can ever thoroughly learn. How much pleasure these creatures have in their water-world it would be difficult for us to say; but since we find them playing together, hunting together, sporting in the warm sunshine, and diving and gambolling in the open sea, and sometimes even calling to one another, we cannot but think that life has great charms for them in spite of the many dangers surrounding them. And when, low though they are in the scale of life, we find them (though curiously enough always the fathers) carrying the eggs, building nests for them, and defending the young, we see that even here, in the very beginning of backboned life, we touch the root of true sympathy, the love of parent for child.

--- THE HOME OF THE EARLY AIR BREATHERS

CHAPTER IV. HOW THE BACKBONED ANIMALS PASS FROM WATER-BREATHING TO AIR-BREATHING, AND FIND THEIR WAY OUT UPON THE LAND.

So the backboned animals, as fish, have peopled the seas and rivers, and, as the ages have past on, have become more and more fitted to their watery life, little dreaming of another and different life in the

world of air above them. And yet in the same pond with the little stickleback, so busy building his nest, there is a creature which could tell him that it is possible to live in both worlds, if only you have the proper machinery to do it with.

It is clear that if the backboned animals were ever to live upon land, after they had begun their career in the water, there must have been some among them which learned gradually to give up water-breathing, and to make use of free air; and we shall not have far to seek for creatures which will help us to guess how they managed it.

From almost every country pond, or ditch, or swamp, a chorus of voices rises up in the springtime of the year, calling to us to come and learn how Life has taught her children to pass from the water to the air; for it is then that the frogs lay their eggs, and every tadpole which grows up into a frog carries us through the wonderful history of an animal beginning life as a fish with water-breathing gills, and ending it as a four-legged animal with air-breathing lungs.

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