If we could dive under the water and watch the fishes at home we should see at once how much more agile and easy the bony fish are in their movements than their gristly companions. Look at a shoal of silvery herrings as they swim and leap and gambol, or a fine salmon sailing up the river or springing over a waterfall, or a tiny stickleback darting across the stream, and compare their graceful motion with the ponderous though powerful movements of an unwieldy shark. Any one who has done this will feel at once that though the sharks have still kept their power as tyrants of the sea, because they are so strong and big, yet these light skirmishers are much more at their ease, and move with much less effort in the water, so that it is natural they should have made their way into all parts of the rivers and seas. But where have they come from? We know very little of their early history, but what little we do know leads us to think that long ago they branched off from the enamel-scaled fish, and struck out a path of their own to make the most of the watery world.

Turn back for a moment to our little minnow, and recall his tender backbone made of joints hollowed out before and behind, with cushions of gristle between; those cushions, when the minnow was growing out of the minnow egg, were one long gristly cord, like the cord of the sturgeon, and it was only as the minnow grew that the bony joints hardened round it and separated it. Moreover, that huge bony pike which we find now wandering in the American lakes has bony joints hollowed out like the minnow's, although by his enamel-scales and uneven tail we know him to be one of the ancient fishes. Some time or other, then, the sturgeon, the bony pike, and the modern minnow, must have had a common ancestor, though we should have to reach him through millions of generations. In the same way, too, we find the red-folded gills covered by a scaly lid, both in the sturgeon and the minnow, though in other ways they are not exactly alike; while even the V-shaped tail of the modern fish is not so different from the ancient shape as it seems, for the end of the backbone runs up into the top branch of the fork as it does in the uneven tails of the olden fish. Lastly, the delicate rounded scales on our minnow's body are not entirely the property of bony fishes, for we find such scales on the mud-fishes, the Amia  and Ceratodus  (see p. 33); while the little modern stickleback, on the other hand, has bony plates, reminding us of those of olden times. We see, then, that the bony fish still carry upon them many signs of their origin from the older fish, and when once the coast was left clear, and they got a fair start, we can easily imagine that the fish of this younger race which was still in its childhood, and easily moulded to suit different kinds of life, would press forward in every direction and make the most of every chance.

And so we find that little by little, from the time of those chalk seas till now, the remains of enamel-scaled fish grow rarer and rarer in the hardened mud, and the bones and scales of modern fish take their place, till this bony race has spread so far and wide that in our own day, if we were to start from the head of a rive and swim down into the open sea of the Atlantic or Pacific, we should meet on our way bony fish of all shapes and sizes and habits of life. River-fish and lake-fish and sea-fish; shore-fish, surface-swimming fish, and fish of the deep sea; flat-fish like the sole, half hidden in the sand, and long rounded fish like the eel, threading their way through holes and passages all over the world; flying fish with long arm-fins, and clinging fish whose fins form a sucking disk; nay, even so strange a thing as an angling-fish, whose back fin is turned into a fishing-rod to attract his prey.

All these, during the long ages since they first started in life, have been learning to make use of some area in the wide expanse of water spread over our globe, and it remains for us now to see how they have succeeded. Where shall we make our start? If we begin at home in the rivers we should have to work, as it were, backwards, for the sea is the chief home of fishes, and the rivers only the refuge of a few stray kinds. The sea-shore would be, perhaps, our truest starting-point, but then we should have to travel two different ways. Will it not be best to dive down first into the silent depths of the ocean, and learn what little is known of those which have taken refuge there? Thence we can rise up to the open sea, from there swim in to the shore, and then up the rivers and back to our own land-home.

It makes but little difference where we take our plunge into the deep sea, for changes of climate are scarcely or not at all known there, and the fish seem to wander over every part. Wherever it may be, us say in the seas of the Tropics, which have given us most of our specimens—let us dive down, down, till we reach about 1800 feet (300 fathoms).

We shall be groping more and more in darkness as we go, for the sunlight scarcely reaches beyond i000 feet, and we have left its last rays behind us, and the water is growing icy cold. How strange, then, that the first fish we meet should have large wide-open eyes! This is the Beryx, shaped something like a perch, but about a foot and a half long, and genealogists ought to look at him with respect, for his ancestors (see heading of Chapter) are almost the oldest known bony fish, and lived in the chalk seas.

Has he come down here because the upper world was too rough for him? If so, he has found comparative stillness, for he is far beneath the turmoil of the waves, and only the slowly creeping currents make any movement around him. But he has not escaped from the struggle for life, for not only is a good-sized shark coming his way, but a huge monster of the bony race, six feet long, with wide-opened jaw, sharp pointed teeth, and large keen eyes, is wandering near in search of prey, devouring large and small fish with great impartiality.

Still in the dense darkness the Beryx must surely escape? No! for, strangely enough, lights are travelling about in this midnight region. The monster himself carries lamps upon his body, and a shoal of small oblong fish, something of the size and shape of a gudgeon, come swimming by, carrying on their sides whole rows of shining spots giving out phosphorescent light; while not far off another fish, called in India the Bombay duck, glows all over, as if his whole body had been rubbed in phosphorus. Nay! so far as we know the Beryx himself is probably gleaming with light, for his body is covered with a large quantity of the same slimy fluid which makes the "Bombay duck" phosphorescent when he is freshly drawn out of the sea.

So these curious fish, living in eternal darkness except when they make an expedition to the surface, carry many of them their own lights; and as we go deeper still more and more of them are found with shining mother-of-pearl-like spots on their head, or sides, or tail, so that the very darkness is alive with light. What slaughter and hunting there is among them! for they all eat each other, and even their own young, there being no plants for any of them to feed on. There are the deep-sea cod-fish; strange forms with large heads, long tapering tails, and thread-like fins, chasing the smaller fish, and falling victims themselves to the fierce Stomias  which comes sailing along with its row of glowing lights, and its huge sharp teeth, ready to seize its prey. Both these fish go down as deep as ten thousand feet and more, accompanied by another fish quite as ferocious, though only a foot long, with large teeth sticking out of its mouth like the tusks of a boar, and curious round spots, with lenses in them, on its side, which may be eyes, or may be lanterns to light it on its road; and among these luminous fishes are wriggling along the deep-sea Conger eels, with toothless mouths and elastic stomachs, swallowing large fish whole; while another curious cod-like fish, whose stomach can stretch to more than four times its natural size, draws itself over its prey just as a snake does, and carries it in the hanging bag till it is digested. And deeper yet in the dead calm water roam many fishes with delicate feelers hanging from their mouths, while their fins are slender and tapering, so that they feel their way along the still depths. Among these are the Ribbon-fish, twenty feet long but only a foot deep, and never more than two inches thick in any part, with their long rosy fins floating like ribbons back from their heads and from under the body.

Strange monsters are all these deep-sea fish, some of them living as much as 16,000 feet under the surface of the sea, so that if Switzerland were turned upside down in mid-ocean, the peak of Mont Blanc would not reach down to where they swim. Yet they are only modified forms of ordinary fish from the world above, which have become fitted to live under that vast pressure of water. Their skeletons, though bony and well-knit together at that depth, are fibrous and slight compared to those of their surface relations, for although they have to resist a weight of from two to sixteen tons pressing all round them, a ton weight being added for every thousand feet, no special strength is required, because the dense water permeates their whole structure, and the pressures are everywhere equal. It is the same with them as with the most delicate and fragile insects living in our atmosphere, the pressure of which would tear them to pieces if unbalanced by equal pressures within and without.

But when these deep-sea fishes are brought up quickly to the surface, the outside pressure no longer balances that inside, and so their tissues loosen and their whole framework starts apart, so that they almost fall to pieces at a touch; and their air-bladder, if they have one, expands so much as to force the stomach out of the mouth, turning them almost inside out. Neither are their lanterns a special creation for their use, but merely adaptations of that slimy fluid which we saw oozing from the scales of the minnow. In some of the deep-sea fish even the outer bones are filled with this fluid, and the line of scales along the side has large openings, so that the body is bathed in glowing slime. In others it collects in glands on the sides, making the phosphorescent spots.

In this way the deep-sea fish have become fitted to make a home in the very heart of the ocean. Some with large eyes, seeing by means of their own and their neighbours' light, others with small eyes and delicate feelers, testing each step as they go, and feeding, probably, on the shower of minute sea-animals that falls continually from above; while some, like the Beryx, the Bombay Duck, and the light-carrying Scopelus, which live nearer the top, come up on still nights to feed at the surface of the sea.

And now, as we rise again from the dark still depths up to warm layers of the tropical seas into which the sun is pouring his penetrating rays, it may happen that a large dark body moves between us and the surface, as the Great Blue Shark, or one of his smaller relations, ploughs his way through the water. But what are these little dark brown fish, with round gaping mouths, which arc hanging by the top of their head and back from under the shark's belly? (see Fig. 9). Where he goes they go with him, and, as they are borne along, they feed upon the tiny sea-animals among which they are carried so easily. These cunning passengers, of whose very existence the shark seems unconscious, are the Remoras, or sucking-fish. You would scarcely think that they belong by descent to the mackerel tribe, a strong-swimming, active, and almost warm-blooded group of fish, with a large supply of nerves and blood-vessels to their muscles, so that they swim boldly out to sea, and make more use of the open ocean than almost any other group. But among all tribes there will be some weak members, and these must live by stratagem. The little remora is a feeble swimmer, and, having to live out at sea, has acquired a curious sucker by which he clings to sharks, and whales, and even ships, so that he is carried along without exertion. Yet this sucker, again, is only a special adaptation of the back-fin, which, instead of being single, as in other mackerel, has its spines divided and bent, one set to the left, the other to the right, and joined by a double set of plates, surrounded by a fringe of skin. This forms an oval disk, and, as the remora glides along under the shark's belly, he presses the damp membrane against the fish, and, drawing together the muscles of the plates, clings as firmly as a limpet to a rock.

Nor is the remora the only companion of the shark—

for the little steel-blue striped Pilot-fish, another distant connection of the mackerel tribe, Cotto-Scombriformes,  to which so many ocean fish belong, and even the sword-fish is allied.") ?> is hovering around, feeding upon the scraps of the shark's food, and finding protection in his neighbourhood, though in olden times he was supposed to protect the shark. A brave little fish this, which has succeeded in making the shark his friend: while near him he is safe from other fishes.

And now, as we continue our way in the open sea, it is nearly always forms more or less related to the mackerel tribe which cross our path. The slender Bonito and the heavier Tunny sometimes ten feet long, are hunting below or on the surface, and the beautiful Dorados, or gold-mackerel, as the Germans call them, with their silvery blue backs tinged with a sheen of gold, their dull-coloured fins, and their golden eyes, are driving by in large shoals in pursuit of the flying-fish. All these are powerful swimmers, and they have no air-bladder, which is an advantage to such active hunters which wish to turn rapidly, to go down deep or rise to the top, and change their position at every moment; for in all these movements a natural float inside is a hindrance to be overcome. And so we find that in fish, even of the same family, some have lost the air-bladder, while others have it enlarged to meet their wants, as in the case of the lovely blue and silver sun-fish for example, which, though quite near relations of the dorado, have very large air-bladders, enabling them to float quietly on the top of the water, waving their deep scarlet fins.

But while we are watching all these large and strong swimmers an active and bloodthirsty struggle is going on, for the bonitos and the dorados are looking to make their meal upon the little Flying-fish, which are straining every nerve to escape them, while here and there one drops down into their very mouths. Lovely little creatures these are, of the Pike family, which have taken to the open sea, where they rise with a stroke of the tail many feet out of the water, their bright purple backs and silvery sides gleaming in the sun, as, with their long transparent arm-fins outspread, they float for as much as two hundred yards before they fall back, to spring up again with another stroke. Their air-bladder, which is half as long as their body, and contains in a six-inch fish as much as three and ", "
", "center", "70", "5", "5", "[Illustration]", "Fig. 10.
Flying-Fish (Exocœtus) pursued by the Dorado (Coryphæna).") ?> a half cubic inches of gas, stands them in good stead, and they rise and fall with quick rapid flights out of the reach of their foe, so that in the open sea they do fairly well on the whole, though, if they venture near land, the sea-birds persecute them in the air. Nor do they stand alone in this curious habit of flying, or rather floating, in the air, for a larger fish of quite another family, the "Flying Gurnards," with a smaller but still ample air-bladder, and long arm-fins, may also be seen rising in the Mediterranean and tropical seas, out of reach of the fish-hunters of the water.

And now we must leave the open sea and steer for the shore. It is true that many other fish are wandering in the broad watery main, but many of them, such as the globe-fish, feeding on the small crustaceans and the sea-horses, whom we shall meet nearer shore, are feeble forms carried hither and thither by currents or on floating banks of seaweed, while others have no special interest. The sharks, the mackerel, and the flying-fish, are the most remarkable colonisers of the ocean-surface, for even the enormous Sword-fish, which attacks the bonitos and whales with its long wedge-shaped bony jaw, and is said to sail by raising his back-fin, is a distant off-shoot of the mackerel tribe.

So we cannot do better than follow our own common Mackerel, as they migrate in shoals out of the deep sea to feed on the fry of the herring or the pilchard in shallower water, or to leave their eggs floating not many miles from land, so that the tiny mackerel, when hatched, may live in the quiet bays till their strength comes.

But stop! Long before we have come so far as this, and while we are still a hundred miles or more from the shore, let us peep down into the sea-valleys, where forests of seaweed and marine plants are growing, and myriads of tiny sea-lice and crustaceans throng the water. What is that army of thin spindle-shaped forms rising and falling in such numbers? It is a shoal of herring, which have come there to feed upon the sea-animals, keeping out of sight of the sea-birds above, and the cod and sharks and ravenous fish which hunt them without mercy, so that they only venture to come to the surface on calm dark nights. It was in valleys such as these that the herrings were living when the older naturalists thought they were gone away to the Polar Seas, because they only saw them in spring and autumn, when they come into shallower water to drop their myriads of eggs, which sink down, and stick to the seaweed and stones below.

But now they are revelling in the deep ocean, rising and falling with ease, for their air-bladder has two openings, one to the stomach and one to the outside of the body, so that the gas can adjust itself to their movements; and surely if the shark is the type of the old, lumbering, powerful, slow-breeding fish, the herring, with its narrow lissome body, light playful movements, and myriads of young, is the type of the new and active race. They are as truly social animals as any herds on land, for they travel in shoals of many hundreds of millions; and as they can squeak, and have a very good apparatus for hearing, it is more than likely that they call to each other. They make both the salt and fresh water their own; for when the eggs are hatched at the mouths of rivers the tiny fish take refuge there from the violent persecutions of the cod and mullet and haddock, flat-fish and whiting, and, together with the small fry of other fish, stroll up the rivers, where we call them "white-bait."

And now, as we come nearer to the shore, where countless numbers of small fry are filling the water, and all creatures are struggling together to accomplish three objects, namely, to get food, to avoid being turned into food, and to lay their eggs, we find many strange weapons and devices adopted by the different fish for protection and attack.

There are the Mullets, with tender feelers under their chin, with which they brush the ground lightly as they swim, feeding on the tiny creatures. There are the walking fish, the Gurnards, which have three of the spines of their arm-fins separate, and moved by strong muscles and nerves, so that they can walk on the sea-bottom, feeling their way, while the stiff, spiny rays of their back-fin stand up to wound any enemy attacking them from above. There are the tiny Blennies which walk too, but by means of the few rays which alone remain of their leg-fins growing close under the head. Then there are the clinging-fish, the Gobies, living on the rocky shores, where the waves beat and roar, and they have their leg-fins joined together, so as to form a kind of funnel under their throat, with which they cling to the rocks and then dart across the waves to feed, coming to anchor again out of the dash of the water; some of these little fellows make nests and guard their eggs after the mother has left them, till the young can shift for themselves. More curious still, the Lumpsucker has its arm-fins and leg-fins all joined together into a round disk under the throat, and so holds on bravely against the dashing tide, defending the eggs which have been laid in the seaweed near the shore, and even remaining to take up the young ones when hatched, and carry them safely back into deep water as they cling to his sides.

Meanwhile, close down upon the sand are the hiding-fish, the Weevers, the Anglers, and the Flat-fish.

The weevers are the most dangerous. Their shaded yellow colour hides them from view, while the sharp spines of their back-fins, which they keep raised, will inflict very severe, if not poisonous, wounds on any creature striking against them. Nor is this all, for behind the checks, fastened on to the horny gill cover, are daggers with which they can strike, deliberately jerking them back so as to give a sharp blow. These are fighting aggressive fish, waging the war that goes on so sharply all round our coasts.

But there is one even more cunning than they, lying hidden in the seaweed or the sand—a large, flat, soft fish, about three feet in length, and quite half as broad as he is long, with a soft stumpy tail, stretching out behind, and a kind of wrist-joint to arm and leg fins, by which he can creep noiselessly along. His wide mouth is gaping open, so that a two-foot rule could be passed crossways into it, and his pointed teeth arc bent back to allow his prey to enter. But how is this prey to be caught, for he is not going to move to fetch it? Notice all round his head and his body, the skin is fringed like blades of seaweed and plays about in the water; while above his head and back the spines of his fin stand up quite separate, and the front one is tapering and long like a fishing-rod, with a lappet at the end like a bait. And now, as the shallow water ripples over his head, the lappet plays to and fro, and the unwary fish come up to nibble at it, lower and lower he waves it, and the nibblers follow, till, opening his wide gape, he gulps them down, even if they are as large as himself, and lies passive with his swollen stomach till they are digested. This is our own Fishing-frog, of which one was once found with seventy herrings in his stomach. He has relations all over the world—in the open sea and down in its depths, and all of them more or less follow his fishing habits. Yet there is no creation of special parts for these strange weapons; the altered back-fin and the jagged skin do all the work, just as in some curious fish of the weever family in the tropics, called the Stargazers, the feelers on their lips, longer than those of other fishes, and a lengthened thread from below the tongue, play in the watery currents and attract the small animals, while the fish with upturned eyes watches them as they are lured to destruction.

Lastly, among all these curious forms upon our shores there is an abundance of flat-fish—soles and turbot, brill and plaice—flapping along at the bottom, covering themselves with sand, or rising up with that strange wavy movement of the whole body in which they use what look like long side-fins, but which are really the back-fin and the belly-fin.

If we wanted to pick out the strangest and strongest proof of how the shape of fish is altered to suit their wants, we need seek no further than the flat-fish When we were speaking of the shark order we saw that the rays and skates are flattened forms suited to hide in the sand, and these fish are truly spread out as if they had been squeezed under a heavy-weight, their broad arm-fins edging the sides of their body. But the bony flat-fish, the Soles and Turbot, have a far stranger history. The young sole, when it comes out of the egg, is not flat like the young skate, but a very thin spindle-shaped fish, something like a minnow. He is then about the size of a grain of rice, very transparent, and lives at the top of the sea. He has one eye on each side, like other fish, only one eye is higher up than the other, and the single fin on its back and the one under its body reach almost from head to tail. In this way he swims for about a week, but he is so thin and deep, and his fins are so small, that swimming edgeways is an effort, and soon he falls down on one side, generally the left, to the bottom of the sea. Many times he rises up again, especially at first, till he has got used to breathing at the muddy bottom, and meanwhile the eye that lies underneath is gradually working its way round to the upper side, his forehead wrinkles so as to draw the under eye up, while his whole head and mouth receive a twist which he never afterwards loses. His skeleton, it must be remembered, is still very soft, and the bones of his face are easily bent; and at last this eye is screwed round, and as he lies at the bottom he can look upwards with both eyes and save the under one from getting scratched by the sand, as it must have done if it had remained below.

Nor is this all, for while his under side, shaded from the sunlight, remains white and colourless, his upper side gradually becomes coloured like the sand in which he lies, and he is safely hidden from attack as he flaps along, feeding on worms and other animals. And now when he swims he no longer uses his arm and leg fins, which are quite small and insignificant, but bends his whole body, using the back and belly fins to help him. What we then call the top of the sole is really his side, where you may see the dark line of scales running along the middle, and one arm-fin lying close to his head. Yet he can swim strongly and to far distances, for in the winter the soles, too, migrate into the open sea, where they may be found in the deep water of the Silver Pit, between the Dogger Bank and the Well Bank.

And now, before we leave the shore, we must glance at a curious weakly little fellow clinging by his curly tail to the seaweed, whom you will certainly not take for a fish, even if you can find him out, so entangled is he generally in weeds of the same colour as himself. Yet the Sea-horse is a true fish, covered not with scales but with plates, with which he makes a clicking noise by scraping them together. What look like large ears are really his arm-fins, while at the end of his long snout is a mouth shaped like an ordinary fish's mouth, but toothless, and he breathes with fish's gills arranged in round tufts instead of folds. What the use of his strange shape is to him we cannot tell, but at any rate his fleshless bony body must protect him from other fish, while his power of clinging causes him 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 cf 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 the sea-sticklebacks, and the little river-stickleback. 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.

Besides these active river-fish there are the little stupid Miller's Thumbs, 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, 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 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,%— fare,  Saxon, to travel; ex., way-faring  man).") ?>

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 of India and the Doras 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 arc 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 backhoned life, we touch the root of true sympathy, the love of parent for child.