The sawfishes, of which several tropical species are known, besides one common in the Atlantic and Mediterranean, are among the most remarkable of oceanic fishes. The body is slender, sharklike, and of great power. The head is flattened, and the snout projects into a hard, flat, sword-shaped beak, the edges of which are thickly studded with sharp teeth; and this singular weapon places all the large inhabitants of the ocean at the mercy of this powerful marauder—it is the worst enemy of whales, even, in the warmer seas, as is the "killer" in the Arctic region. With it the sawfish cuts and slashes, tearing off pieces of flesh, or ripping open the abdomen of its opponent, then seizing the detached pieces. One can easily picture to himself the slaughter when a sawfish dashes into a school of fishes, squids, or porpoises, and slashes right and left with his ripsaw of a beak. Some of the Oriental species reach, and even exceed, twenty feet in length, and Dr. Day, the Indian ichthyologist, says that such monsters have been known to cut bathers completely in two. The saw of a twenty-foot fish would measure six feet in length and a foot across the base.
| Photo, Ewing Galloway |
| ABOVE, THE GILA MONSTER, FEARED THOUGH ITS BITE IS NOT ALWAYS DEADLY TO MAN BELOW, THE IGUANA, A REMARKABLE LIZARD OF THE NEW WORLD |
The most famous of the rays, probably, are the torpedos, a family with a rounded, instead of the customary triangular outline, and a rather short tail, species of which occur on all tropical and temperate coasts, and are noted for their power to give electric shocks to any living thing touching them.
The electric organs are a pair of large masses lying between the head and the pectoral fins. These are derived mainly from four nerves, which originate from an electric lobe of the medulla oblongata. By means of the electric shocks which they are able to administer at will, the torpedo rays are able to ward off the attacks of enemies, and to kill or paralyze their prey. The action is that of a galvanic battery. The dorsal surface is positive, the ventral negative, and the discharge of a large torpedo is sufficient to temporarily disable a man; yet it is not so powerful as that from a big electric eel.
The huge "sea devils" of which thrilling stories are related are the eagle rays of the family Myliobatidæ, some of which are fifteen or twenty feet across the "wings"; and they are among the most frightful of the dangers to which pearl divers are exposed in their perilous occupation. They are savage beasts, and will even attack a small boat with men in it. The worst of these belong to the vicinity of Panama.
CHAPTER XVI
BONY FISHES—TELEOSTOMI
We come now to the fishes proper—those with skeletons of bone, although in some of the lower forms the ossification is incomplete. The mouth contains supplementary tooth-bearing bones that form secondary jaws corresponding to the functional jaws of the higher craniates; hence the group name "Teleostomi," or perfect-mouthed fishes. The body, as a rule, is coated with scales, and a gill cover (operculum) is always present.
The Teleostomi include four orders, the Crossopterygii, the Chondrostei, the Holostei, and the Teleostei.
The crossopterygians are mostly strange extinct fishes found as fossils from the Devonian down; but some have survived, and live in the sluggish African rivers an eellike existence, of which the bichir of the Nile is a familiar example. The Chondrostei also are largely fishes of the Paleozoic time, but two families survive to the present—the spoonbills and the sturgeons. Of the former one species is Chinese, and the other is the shovel-nosed spoonbill or paddlefish of the lower Mississippi River. It is a big, sluggish creature, that stirs up the mud with its long flat beak, and consumes it, getting sustenance from the minute organisms it contains. They make caviar from its eggs. As for the sturgeons, we have five species in the United States, and one abounds in the Black Sea and the rivers that drain into it, from whose eggs the Russian caviar is made. One or two species are exclusively fresh-water, but most sturgeons are migratory fishes, living in the sea, but ascending rivers for spawning. Their food consists of worms, mollusks, the smaller fishes and aquatic plants; and in feeding the mouth is protruded downward in the form of a cylindrical, spout-like structure and thrust into the mud. Our common eastern-coast sturgeon is also a native of the Mediterranean and French coasts, and was formerly in England a "royal" fish, reserved to the king's use.
Of the third order, Holostei or "ganoids," whose history may be traced in fossils almost to the earliest of fossiliferous rocks, we possess in our rivers the only two survivors: one is the many-named bowfin of the Mississippi Valley, and the other the widely distributed billfish or gar pike. Both these relics of a very ancient order are of great interest to naturalists; and the names "mudfish," "John H. Grindle," and many others, show how well known the bowfin is to the farmer boys. The bowfin attains a length of about two feet and a weight of twelve pounds, and, unlike its cousins the garfishes, is covered with hard, rounded scales; the forepart of the body is cylindrical, the head stout and blunt, and the mouth filled with powerful teeth. It is exceedingly hardy, enduring absence from the water for a long time, as well as grievous injury; hence the young are the favorite bait of anglers in the Mississippi Valley, and make interesting captives in an aquarium, where, however, nothing else but snails can remain alive. These fish are strong, active, voracious and gamy. They feed on all sorts of small aquatic creatures.
The garfish (or more properly gar pike, Lepidosteus, because certain sea fishes of another sort are also called gars) is an elongated active fish of our rivers, covered with hard, flat, ivorylike scales set in oblique rows, and its snout is prolonged into a bill filled with sharp teeth. They have many peculiarities of structure indicating their ancient ganoid lineage; and besides our common species two others are known, one of which, the alligator gar, belongs to the Gulf Coast and Central American rivers. These gars are nocturnal and predatory in their habits, and in early summer resort in large numbers to shallows to lay their eggs, which are covered with a sticky envelope that adheres to any object on which they fall. The long bill develops after infancy.
CHAPTER XVII
MODERN FISHES—TELEOSTEI
The lower orders of teleosts retain many characteristics of the Holostei, and several of their families are known only as fossils in the Cretaceous and Tertiary rocks. The most primitive survivor of these ancient forms is the great tarpon of Florida and southward, another species of which occurs in India—such wide differences in habitats being an evidence of antiquity in nearly all cases among animals. The extraordinary mormoids of northern Africa, and the eellike gymnarchus of Gambia, are other relics of the past, as also are several other queer African families, the barramundi of Australia, and the arapaima of the Amazon region. The one last named is the largest fresh-water fish known, specimens exceeding fifteen feet in length, and weighing 400 pounds, all of which is excellent food. The mother protects her offspring which, when young, swim in front of her. Several of these old-fashioned teleosts, like our bowfin and the primitive Dipneusti, make elaborate nests in which their eggs are deposited, and they and the fry are carefully guarded by the parent. In this same suborder come the most familiar and useful game and food fishes—the shad, herring, trout, salmon, whitefish, smelt, etc.
The shad family is a very large one, numbering about 200 species, most of which are marine, but a few are "anadromous," that is, they ascend rivers of fresh water to spawn in the shallows near their sources. This is the habit of American shad, of which there is only one species in spite of the many local names in use; and it is regarded by the fisheries authorities as the most valuable river fish in the country except the Chinook salmon; but the supply of it would have been exhausted long ago had it not been for the incessant and energetic methods of replanting of fry, artificially bred, in all the eastern rivers, and the transplanting of them to rivers on the Pacific Coast, the credit for which valuable public service belongs to the United States Bureau of Fisheries.
The shad is to be found from Florida to Newfoundland. Little is known of its life in the ocean, but in spring it approaches the coast in great numbers, and may be had in the St. John's River in Florida in winter, but it is not numerous until March. It next appears in the Savannah and Edisto Rivers, and so successively northward, the height of the run in the Potomac being in April, in the Delaware early in May, and in the Miramichi River in New Brunswick late in May. The main body ascends when the water temperature is 56 degrees to 66 degrees. They come in successive schools, the males preceding the females. They ascend the rivers, often nearly to their heads, and deposit their eggs on suitable spawning grounds, pouring out about 30,000 in most cases. The eggs are very small, semibuoyant, and usually require six to ten days for hatching, depending, as does the whole operation, on favoring temperature. After the spawning the shad show hunger, and will often bite at an angler's fly.
"The herring is beyond question the most important of food fishes in the Atlantic, if not in the world," declared the late G. Brown Goode, formerly Assistant U. S. Fish Commissioner. It affords occupation for immense fleets of boats, and thousands of men, nowhere more numerously than in the North Sea and along the Norwegian coasts. Professor Huxley once gave 3,000,000,000 as the number of herring taken annually from the North Atlantic; but Dr. Goode showed that this was far too low an estimate, and added that it probably was "no greater than the number contained in a single shoal if it covers half a dozen square miles, and shoals of much greater size are on record. And ... at one and the same time scores of shoals must be scattered through the North Sea and the North Atlantic, any one of which would go a long way toward supplying the whole of man's consumption of herring." Herrings are surface swimmers, and their food consists of the small organisms, chiefly crustaceous, which have been described as "plankton" in the early pages of this book. They themselves afford food to every predatory fish, squid, whale, and bird that frequents their region (mainly north of the fortieth parallel of latitude), and which has the wit and ability to seize them. They move here and there in shoals for food, and in spring migrate to the shallows and rivers of the northern coasts to spawn. Besides the Atlantic herring, a very similar species throngs in the North Pacific, and several others live in the Great Lakes and other waters of this country.
No fishes are better known in America than the salmon, trout, and whitefish, which are near relatives. Of the salmon there are many kinds in all the northern parts of the world and in the open ocean. Some ascend rivers to spawn, and some do not. Our Atlantic salmon, once so abundant in every river from Connecticut northward, is the same as the salmon of Europe, and the king of game fish. Now it is at all numerous only in the Maritime Provinces of Canada, climbing the waterfalls of those mountain streams to their very springs to deposit its eggs, whence few individuals survive to return to the ocean. The heaviest salmon on record is one of eighty-three pounds captured in England in 1821; an American example of forty pounds is considered very large.
The salmon of the North Pacific are of a different genus (Onchorhynchus) and consist of several species, some Asiatic. On the American side we have five species, and most of them have been seen in all the rivers from central California to Alaska, Siberia and Japan; but the blueback predominates in Fraser River and in the Yukon; the silver salmon in Puget Sound; the quinnat or Chinook salmon in the Columbia and Sacramento; while the comparatively worthless dog salmon is seen everywhere. The quinnat and blueback enter and "run" the rivers in the spring, and are caught when in prime condition, whereas the other three run in the fall, and are more usually caught after deterioration; hence "spring" salmon are best in fact and in trade.
The habits of the salmon in the ocean are not easily studied, but Jordan, Evermann, and other diligent students have come to certain conclusions from a great number of facts. They believe that the king and the silver salmon probably remain not far from the rivers where they were born. The blueback and dog salmon probably seek deeper water. It is the prevailing impression that the salmons have some special instinct which leads them to return to spawn on the same grounds where they were hatched, but Dr. Jordan says:
"We fail to find any evidence of this. It seems more probable that the young salmon hatched in any river mostly remain in the ocean within a radius of twenty, thirty or forty miles of its mouth. These, in their movements about in the ocean, may come into contact with the cold waters of their parent river, or perhaps of any other river, at a considerable distance from shore. In the case of the quinnat and the blueback, their 'instinct' seems to lead them to ascend these fresh waters, and in a majority of cases these waters will be those in which the fishes in question were originally spawned."
As to the fate of the spawning fish, after the eggs and milt have been voided, and their duty is done, the salmon begin to float downstream tail foremost. The great majority of them die—certainly all at the headwaters of the big streams; and it is the opinion of the best judges that none ever get back from anywhere alive into the ocean after spawning, but that the race is sustained wholly by the escape of the young each year. It is supposed that non return from the sea, or attempt to ascend the rivers until at least three years old.
Trout are in most cases simply small species of salmon, and a great number of kinds inhabit the ocean, lakes, and rivers of all northern countries, for none of this great family occur in the tropics or in the southern hemisphere. Our western trout—the widely distributed and variable cutthroat, the steel-head of the northwestern coast, the beautiful rainbow trout of the Coast Ranges, and others are examples. The common brown "brook" trout of Great Britain belongs here; but our brook trout, the "speckled beauty" of anglers and poets, is of a slightly different kind (genus Salvelinus), for it is classed with the European charrs. The Dolly Varden trout of the Rocky Mountains and the Sunapee trout are also charrs. The graylings, namaycushes, and smelts are members of this family, whose final representative among us is the numerous and very valuable section of whitefish and lake herrings of the Great Lakes and Canada generally.
No family of fish is of more importance as food for man, not to speak of the sport many of its members afford, than this; yet, doubtless, it would have been nearly destroyed by this time had it not been for the intelligent and patient work of fish culturists and the farsightedness of governments, both Federal and State, and Canadian, in supporting and extending economic replenishing of depleted waters. The organization and breeding habits of the salmon tribe lend themselves to this work.
Passing by some families of deep-sea fishes, of small size and most bizarre outlines, we come to the suborder that contains the carps, catfishes and "minnows" of our lakes and streams. Here, the first to present itself, in the large family Characinidæ, is that fierce little brute of South American rivers, the "piranha" or "caribe," of which Col. Theodore Roosevelt had so much to say in describing his explorations in Brazil in 1913 and 1914. One of his companions was Leo E. Miller, who has since published another account and increases the bad reputation of the caribe by what he has to tell of its ferocity:
"In the Orinoco they attain a weight exceeding three pounds, and are formidable indeed. The natives will not go in bathing except in very shallow water, and I know of two instances where men were attacked and severely bitten before they could escape. The fish somewhat resembles a bass in shape, although the mouth is smaller; the jaws are armed with triangular, razor-edged teeth; and as they travel in immense shoals they are capable of easily devouring a man or large animal if caught in deep water.... Usually they are slow to attack unless their appetite has been whetted by a taste of blood from a wound; then, however, their work is done with lightninglike quickness.... To catch them we used a large hook secured to a long wire leader and baited with any kind of raw meat, and they always put up a good fight."
A related fish in the Rio La Plata is almost equally dreaded because of its much greater size and formidable teeth, but it works singly; and Africa has many similar characinids, whose flesh is good food, though full of bones. In this order, too, is now classified the family of the "electric eels" (Gymnotidæ) which are not, however, eels, but merely long, cylindrical fishes, naked and almost finless. The well-known one of the Amazon region grows to a length of eight feet and the thickness of a man's thigh, and is justly feared. It is found only in marshes and in comparatively shallow parts of rivers, to the annoyance of travelers who have to ford at such points, beasts of burden being frequently knocked down by the electric shocks. About four-fifths of the length of the fish is occupied by the tail, which contains the electric organ. This consists of two huge masses filled with a jellylike substance, below the spine, and separated by a narrow median septum. This apparatus is under the control of the fish, which by it may stun or kill an enemy or an intended prey, even at a considerable distance.
The family of the cyprinids—the carp, goldfish, chubs, shiners, loaches, and other "minnows" of this and other countries—contains about 1,300 species, scattered over the whole world except South America, Madagascar, and Australasia. All are fresh-water fishes, feeding on vegetation and small animals; and they vary in size from two or three inches to a six-foot carp—the original home of which, now the cosmopolitan giant of the family, was Asia.
Next to these are placed another extensive fresh-water family, that of the catfishes (Siluridæ). More than 1,000 species, mostly tropical, have been described; these are grouped in eight subfamilies, among which there is a wide diversity in shape and habits—in fact, few of those of foreign lands look at all like the catfishes with which we are familiar in America. Most of them are sluggish, but some actively inhabit swift streams. They can exist not only in foul water, but will live a long time out of this element, and some even make long migrations overland from river to river. One or more fin rays are sharp and poisonous in many species, as boys know who handle the little bullhead incautiously, and an African species is able to administer a strong electric shock. Its apparatus is not a battery of modified muscular tissue, as in other electric fishes, but consists of a thick coat of greasy material surrounding the whole body just beneath the skin. Another general characteristic is the protection and assiduous care given to their eggs and young, most species making some sort of a nest in which the eggs are deposited and the fry kept safe from attack.
The third suborder of teleosts contains eellike fishes of the tropics; and the fourth contains the true eels and their relatives. Our common eel is also "common" in most of the temperate countries of the world, but there are perhaps 150 other species of the family Anguillidæ, a large proportion of which live altogether in the sea, many of them at great depths, and showing strange shapes. The generation of the eel was, until recent years, one of the great mysteries of zoölogy, as no propagation, or any symptoms of it, ever appear in fresh water. Finally it was discovered that a queer, almost transparent, compressed creature, a fraction of an inch long that abounded in the surface waters of the ocean, and which had been a puzzle to naturalists, who called it Leptocephalus, was the larva of some sort of eel. This and other discoveries made it plain that when the eels (of the age of four or five years) leave the rivers and bays of all countries and coasts in the autumn, and go out to sea, they do so to spawn, leaving their eggs on the floor of the ocean, mostly south of Bermuda, according to J. Schmidt. From them hatch the minute larvæ that, as they grow, rise to the surface, and when about a year old appear as the silvery young, called "elvers," that drift on the northward-running currents to the coasts of Europe and North America, and ascend the streams by millions in spring. It is not probable that any of the adult eels that go down to the sea to spawn ever come back; and if any remain in landlocked waters whence they cannot migrate to the salt water, they do not breed; but it must be remembered that eels are able to travel a considerable distance overland, at night, from one piece of water to another, and so many may finally reach the sea.
The next suborder illustrates the remarkable difference in size and external appearance that often marks fishes grouped together by similarity of structure. It includes the muskellunge and all the other pikes and pickerels, and the tiny shiners and "bait minnows" of our rivers and brooks, and those of the Old World, one of which is the smallest fish known; it includes several families of deep-sea fishes, often of quaint form and with curious appendages; here, too, is the valuable blackfish of Alaska, the amphibious, phosphorescent little fish of Indian bays and estuaries which when salted and dried forms the Oriental delicacy called "Bombay duck"; and here are the blind fishes of the Mammoth and other American caves. The Heteromi and Cateosteomi are almost equally miscellaneous assemblages, the most notable members of the latter being the funny little pipefishes and sea horses that lurk in the eelgrass near shore, and the males of which carry the eggs and young about in a pouch on the belly. In the next suborder, Perceosces, we find more strange denizens of the mid-oceanic depths, especially the family Chiasmodontidæ, besides some surface ones of ancient lineage, such as the gar and snakeheads of tropical waters, the flying fish and the mullets. The Anacanthini is a small group containing the remarkable pelagic and abyssal macrurids, the fierce barracudas, and the most valuable single family of food fishes in the whole list—the cods.
The cod family (Gadidæ) has many species in northern seas and a few south of the equator. It includes, besides the cods, the haddock, hake, whiting, coalfish, capelin, ling, and several other market fish of importance. The cod is a deep-water fish which goes about in great schools whose movements are not well understood, but in winter they approach the northern shores of the continent, seeking shallows on which to spawn, and it is then on the "banks," off New England and Newfoundland, that the most profitable fisheries are followed. The cod is extraordinarily prolific, and in addition to this it is propagated artificially more extensively than any other fish.
Thus we come to the last suborder, Acanthopterygii, or "spiny-finned" fishes, in which are classified the greater number of really modern and more or less familiar swimmers in the "briny deep." Among American members are the sunfishes and black bass, the perches and darters; the great family (Serranidæ) of sea bass, snappers and West Indian groupers; the tilefish, which appears and disappears in a puzzling fashion; the grunting drums and their relatives of the Scienidæ; the porgies, sheepshead, and other Sparidæ; the brilliantly colored angel fish of the coral reefs of Bermuda and southward; the surf fishes, so important in California; the wrasses, parrot fish, and globefishes, or boxfishes, that inflate their horny hides when alarmed, until they bob about on the surface like corks.
FISHES WITH PRIMITIVE LUNGS
There remains the fourth subclass—Dipnoi or Dipneusti, the lungfishes. The reason why these creatures, whose organization is on an antique and lowly plane, judged by fish standards, have been elevated to subclass rank is that here the air bladder is modified into a single or double elongated sac with many cellular spaces, and is connected by a short tube with the mouth, and thus serves as a lung. The peculiar structure of the heart, narial openings, and the power of existing for a considerable period out of water, are extremely amphibianlike, and they have by various naturalists been regarded as scaly sirens—a sort of connecting link between the fishes and the amphibians. They are found fossil in Paleozoic rocks, especially in the Old Red Sandstone of Great Britain, and also in the Upper Jurassic strata in Colorado.
| AN AFRICAN LUNGFISH |
| (Protopterus annectens) |
The surviving species (family Lepidosirenidæ) are widely scattered, as is characteristic of all these very ancient families. A celebrated example is the barramundi of Queensland—an elongated, flat-sided fish, covered, except on the head, with large roundish scales, and having paired fins that look more like flippers than fins. It becomes four or five feet long. It lives in still pools in which the water in the dry season becomes extremely stagnant and overladen with decomposing vegetable matter; and it is only by rising to the surface occasionally, and taking air into its lung, that it is enabled to obtain sufficient oxygen for purposes of respiration. The barramundi does not leave the water, nor can it live long in the air. It is easily captured, and is eaten by the blackfellows.
Equatorial Africa possesses three species of the genus Protopterus, which dwell in marshes, and feed voraciously on young fishes, frogs, and small animals. The form is somewhat eellike, and the paired fins are soft, slender appendages of little use, locomotion being effected by the powerful tail. Like the barramundi this fish rises at intervals to take a breath of air; its "lungs" are double, while that of the barramundi is single. In the dry time of summer the protopterus burrows deeply into the mud of the dried-up marshes, where it curls up with its head highest and subsists wholly by breathing air until the autumnal rains bring water enough to enable it to wake up and resume its aquatic life. A similar eellike species abounds in the swamps, sluggish rivers and marshes of northern South America, named Lepidosiren, and all its habits closely resemble those of the African lungfishes.
CHAPTER XVIII
AMPHIBIANS—A CONNECTING LINK
We have now come to a class of vertebrates that in their manner of life, and presumably in their history, connect the dwellers in the waters with those on the lands of the globe. Dr. Gamble cites examples from various groups of animals to show that adaptation to a terrestrial existence is an advance on that requisite for aquatic life, and that the critical point in the evolution of the vertebrate phylum was passed when its members migrated from water to land. "When we come to land animals," he says, "the problem of weight has to be considered before that of locomotion. The lateral undulations of the body, even when aided by unjointed paddles, or fins, are not sufficient to insure rapid movement on land. Hence a system of levers has to be evolved, partly to support the body, and partly to propel it. The use of joints becomes a necessity, and we find that all active terrestrial animals, except snakes, have jointed limbs. The critical point in the history of this phylum is passed when its members migrated from water to the land. The step was taken by the ancestors of the Amphibia (that is, the frogs, toads, and salamanders). In them the breast fins of the fish have become the jointed forelegs, the pelvic fins have become the hind legs."
How this great change from the fish fin to the five-fingered hand occurred is, at present, just as obscure as the mode of conversion of the arms of reptiles into the wings of birds. The answer can only be supplied by further discoveries in the geological history of the order, and though this history can be traced back to the time of the Coal Measures, we find the earliest Amphibia as sharply marked off from the fishes by their feet as they are to-day. These forefathers (subclass Stegocephalia) are the earliest known four-footed animals, and their fossil skeletons are found from the Carboniferous up to the Trias, after which the race disappears. They had the general form of newts, and many were only a few inches in length. That some of these, at least, were terrestrial in habit is shown by the fact that they are often found in stumps and hollow logs of sigillarias and other fossil trees of the coal beds, especially in Nova Scotia. But there were also species several feet in length, with formidable teeth, which were no doubt carnivorous and predatory, so that it was well for the little ones to seek places of safety. These stegocephalians were unmistakably amphibians, with two condyles supporting the skull, but their skeleton contains many features that suggest reptilian anatomy, and it is agreed that the reptiles sprang from this stock. The peculiar feature of this group is that their flattish heads were covered by a broad shield of bony plates (ossified skin); and similar armor protected their bellies, and in a few cases the back also.
Geological formations furnish no ancestral connection between the Stegocephalia and modern salamanders; but the limbless, wormlike, burrowing and blind cæcilians of the tropics exhibit certain stegocephalian characteristics, especially a scaly skin, which put them into a division (Apoda) by themselves. The remainder of the class, that is, Amphibia (also called Batrachia) in general, have a soft, moist, naked skin, and are naturally divisible into two orders:
1. Urodela—Tailed amphibians: newts and salamanders.
2. Anura—Tailless amphibians: frogs and toads.
Modern amphibians in general are animals fitted for life both on land and in water. All are born from eggs hatched in water, and the young, at first in a larval form unlike the adult condition, have external gills adapted to breathing in that element; but in most cases they lose their gills, and as adults acquire lungs for breathing air. This metamorphosis of the young, comparable to that of the nymph-producing insects, is the especial characteristic of the class. The skeleton is of the vertebrate model, but in the Urodela is largely cartilaginous. The skin is smooth, soft, moist, and covered only with a filmy coat of horny texture that is molted from time to time as the animal needs room to grow. The skin abounds in sense organs about the head and along the sides of the body—an inheritance from the lateral line of fishes—which are most active in the larvæ, and disappear altogether with age in most frogs and toads, although they revive in salamanders in the breeding season.
The skin also contains many mucus glands and other larger glands, especially on the back. These emit under provocation a poisonous liquid that is fatal to small animals, and very irritating to the eyes, nose, and throat of larger ones. Most, if not all, Amphibia, says Dr. Gadow, are more or less poisonous, and it is significant that many of the most poisonous exhibit a very conspicuous yellow or orange upon a dark ground, which is so widespread a sign of poison. There is no venom in their bite—in fact, their teeth are too small, although numerous, to let anyone fear their biting. The skin is heavily laden with pigment, and this is displayed in many amphibians in striking patterns of bright coloring. Certain groups possess in a high degree the power of altering their colors to conform to their surroundings.
An interesting feature of the amphibians is that power of repairing mutilations of the body and replacing lost parts which is so well known in worms, hydroids, and other lowly creatures, and is termed "regeneration." This ability is most active in young specimens. Tadpoles frequently have their tails bitten off, whereupon new ones grow quickly. Salamanders fight bitterly, tearing off each other's gills and limbs, and turtles and fishes frequently bite off their tails. New tails are generated speedily, and usually in good and effective form, although they contain no regenerated caudal vertebræ, but only a rod of cartilage. The ability to rebuild lost parts is much less among the frogs.
Another notable fact is that here for the first time we meet with a voice organ, and a real voice expressing emotions, although in an extremely limited way. This is most noticeable in the tree frogs, which are the most advanced of the Amphibia in organization.
NEWTS AND SALAMANDERS
The Urodela are represented throughout the whole northern hemisphere except in desert regions, as far in North America as southern Canada, and also southward to Panama; and in the Old World, northward to the line of very cold winters and southward to the Mediterranean and Indo-China. In the main, however, our genera are different from those of Europe and Asia.
The largest and best known of American urodeles is a member of the family Proteidæ and genus Necturus, and is widely known as "water dog" or "mud puppy," because of the doglike shape of its head. It is a brown, robust creature, sometimes two feet long, with bushy gills, retained throughout its life, springing from open gill clefts in three bright red tufts on each side of the head. It inhabits cold, rapid streams, hiding under stones by day, and moving about at night in search of crawfish, worms, insect larvæ, frogs, etc., and dodging hungry snapping turtles. But little smaller, and even more ugly in appearance, is the "hellbender," representing the family Amphiumidæ. These blackish creatures are to be found in mountainous regions, and hide during the day under loose rocks. By the time they are about three years old their gills have been absorbed, and their lungs are in service, so that they are compelled to rise to the surface occasionally for drafts of air. They hunt at night for food, preferring crawfish and, fishermen say, fish eggs. The breeding habits of this animal have only lately become known, and Mr. B. G. Smith, who has made a special investigation of them, says that the breeding season begins (in Pennsylvania) in August, when hellbenders of both sexes come out more freely from their rock shelters and roam about, frequently in small companies. The small number of eggs produced are hidden in a pocket under a loose stone; and the young, which are more like tadpoles than the form of their parents, breathe by gills which do not completely disappear until the animals have reached nearly their maturity.
Otherwise our salamanders are small species found in brooks, ponds, and wet woods, and often getting into cellars and wells. Uninformed persons think them to be lizards, and foolishly fear them, but except for the irritation of the hands that may follow rough handling they are utterly harmless to man or his property, and serve him by devouring great quantities of insects and worms.
A common species in damp, neglected woodlands is the little red-backed fellow that is so light and leaping in its movements when disturbed, even throwing off its tail in its panic of fear. It is more terrestrial than most, laying its few eggs in rotting wood instead of going into the water for that purpose; and the young carry gills but a few days. This red-backed Plethodon must not be confused with the small newts, bright vermilion with a row of glowing spots along the sides, that are found in woods in summer. They are young specimens of Diemyctylus viridescens, which is common all over the eastern part of the United States and southern Ontario. The parents are green, and wholly aquatic in habits. The larvæ have gills and swim about until early autumn, by which time their gills have been gradually absorbed, and they go ashore, where their coats change in color from a mottled green to scarlet. This red condition and their residence on land continue until the autumn of the third, or the spring of the fourth year of their lives, when they become sexually mature, resume a greenish dress, go back to the water, and pass the rest of their lives there.
Mention can be made of only one more species—the black, yellow-spotted "tiger triton," which is the most widely spread and often seen of our terrestrial salamanders. It is especially noteworthy because of the extraordinary condition of suspended development exhibited by its larva, the famous edible axolotl of Mexican lakes, which, while still retaining larval gills and aquatic habits, grows nearly or quite to the size of its parents—three to four inches—and becomes capable of breeding. Similar cases are known in certain lakes in southern Europe; and it appears that this arrested development, together with natural growth of body, occurs occasionally in many other amphibians. The condition is termed "neotony," but the biological explanation of it is not clear.
CHAPTER XIX
AMPHIBIANS—Continued
FROGS, TOADS AND TADPOLES
The frogs and toads of the order Anura differ from the inferior batrachians principally in form. The tail is absent, and instead of long, slender bodies and small legs, or none, they have short, squat, triangular bodies and hind legs, at least, of relatively great size and strength, whereby they progress when on land by leaps instead of by running or creeping; some are almost wholly aquatic in habit, others almost wholly terrestrial or arboreal. The ossification of the bones is far more complete, the eyes and ears (represented by the large tightly drawn membrane, the "tympanum," on each side of the head, covering the internal ear) are well developed, and the voice is louder than in the urodeles, which can do little more than squeak. The mouth is usually large and cleft to beyond the eyes. The tongue, used to capture prey, is not thrust straight forward, but thrown "overhand," as it were, catching the insect aimed at in its curling and sticky tip.
All frogs and toads are flesh eaters, mainly of worms and insects and larval or small water animals; but the big species, such as the bullfrog, may seize prey of considerable size as it comes within reach, such as young ducklings. None hunt about for prey, but, aided by the concealing nature of their colors, wait quietly until a victim comes within reach of their quick and accurate tongues. All lay their eggs in still water, varying in number from a few score to several thousands, according to the species. In all cases the young are hatched in a larval form, called "tadpole," having a tail and gills, and this gradually changes into the adult, tailless form of the adult. On emerging from the egg the embryo has a very large head and body. In a frog the external gills and the long, compressed tail are only feebly developed when the tadpole is first hatched, while the mouth is provided with a much developed adhesive apparatus, by means of which the young attach themselves to plants or other objects. The tadpole changes by regular stages into the adult form, the tail being slowly absorbed into the body from which the legs grow out.
The Anura are separable into two suborders:
1. Aglossa—Having no tongue.
2. Phaneroglossa—Possessed of a tongue.
The Aglossa are few in number, and belong to southern Africa and tropical America, where the group is represented by the famous Surinam toad, whose eggs are fixed in separate pits or "pouches" in the spongy skin of the mother's back, where they are placed as fast as laid, by aid of the male.
The Phaneroglossa contains several families, the first of which, Discoglossidæ, is characterized by the round, nonprotrusible tongue, and includes species of toads belonging mainly to the Mediterranean region, two of which are familiar to most readers of natural histories.
It may be well to say at this point that the terms "toad" and "frog" do not express scientific distinctions, although generally applied by naturalists to the first three families of the list, and especially to the Bufonidæ; but mark the facts of popular observation that the members of these families are more terrestrial than the members of the families that follow them, and that they have rough warty skins in place of smooth and shiny ones; but many exceptions confuse both the classification and the use of the words—as, for example, in the case of the hylas, which you may call either "tree frogs" or "tree toads," according to your liking.
The two species mentioned above are the "unke," or firebellied toad of Germany, which when alarmed displays its scarlet underparts by a peculiar attitude calculated to surprise and frighten away an enemy. The other is the "midwife toad," most common in Spain and Portugal.
The spade-foot toads (Pelobatidæ) are a strangely distributed family inhabiting the western United States, Mexico, eastern Europe, and the Indo-Malayan region. Their special characteristic is the fact that the inner tarsal tubercle is large and is transformed into a shovel, which is covered with a hard, sharp-edged, horny sheath. Having this excellent tool these small and noisy toads rapidly excavate deep holes in the soil, preferring sand, and lie hidden during the day, but come forth at night to hunt. They resort to water only for a week or so of egg-laying in the spring, and remain unknown to most persons in whose neighborhood they are really numerous. Our common American one (Scaphiophus solitarius) is about two inches long, and brown above with darker patches.
This brings us to the typical toads, Bufonidæ, represented in all parts of the world except certain islands. A hundred pages might be filled with interesting accounts of the manners and customs of the hundred or so species, many very different from those familiar to us.
All breed in water, resorting to ponds and pools in the early spring. Where many broods have hatched the young can be met with in myriads, the ground literally swarming with them; and as they are naturally stirred up by a sudden warm rain, perhaps after a drought, people will occasionally affirm as an observed and well-ascertained fact that "it has rained toads"—something that never occurs except in the very rare cases when a cyclone has scooped the water and everything in it out of a pond and scattered it abroad.
Most of these young, migrating toads disappear as food for birds, snakes, etc., or die of disease. The food of young and old consists of insects, worms, snails, and the like; and it is an easy thing to tame toads and have much amusement in watching them at work in the early evening, for they are crepuscular in habits; and the wise gardener will see that they are not disturbed in their beneficial service of catching and devouring insect pests, unless they are so numerous as to be a nuisance.
The smallest North American toad is the oak toad of the Southern States, which is only an inch long. When, in the breeding season, these diminutive toads flock to the pools in great numbers, they keep up an ear-splitting chorus of shrill peeps, like so many young chickens.
FROGS AS NURSERY MAIDS AND WEATHER PROPHETS
The tree frogs are a very large family (Hylidæ) distributed all over the world, except Africa, but most of the species belong to the steamy forests of tropical America. All are of small size, have smooth skins, normally greenish, but very changeable in color to adapt the creatures to the hue of their surroundings, as a protective device; and most of them inhabit trees. To enable them to do this the toes end in expanded, padlike disks, the contraction of which, when the foot is pressed against a surface, produces one or more furrows and, in addition, causes the exudation of a little mucilaginous liquid. The foot pressed against the surface expels the air, and this fact, aided by the stickiness of the pad, enables the frog to hold on to even a vertical plane of glass. All Hylidæ have a voice, often very loud, and enhanced by membranous sacs under or on each side of the throat, or in some cases internal; this sac, when blown out may be almost as large as the creature's body, as may be seen in our common gray tree frog when "singing." This species, like most others, becomes very noisy in the evening, in cloudy weather and before rain, with its not unmusical croaking; and a similar European species is kept in confinement by some people as an interesting pet and weather prophet.
The most interesting thing about the Hylidæ is their various methods of breeding, for while most of them lay their eggs, up to a thousand in number, in the water, many produce but a few, and attach them to the body.
A large tree frog called in Brazil "ferreiro" (smith), makes a sound like a mallet slowly and regularly struck on a metal plate. This frog actually builds a nursery in the shallow edge of a pond, where a basin-shaped hollow, with a rim, is formed by the broad-handed female. Here she leaves her eggs, safe from egg-eating fishes or insects, as the rim forms a wall higher than the surface of the water. A Japanese frog makes a similar basin, then produces a liquid which she kicks into a froth, and into the midst of this the eggs are dropped, and there the hatched larvæ develop, and remain until the gradual collapse of the mud rim sets them free.
In these and similar cases the eggs and tadpoles are abandoned by the parents; but many frogs watch over and care for their young. Some carry the young in a pouch on the back, but how it is accomplished is not known. A West African species carries its eggs in its mouth; and the male of Darwin's frog, of Chile, carries the eggs in a great vocal pouch beneath its throat, which subsequently forms a nursery for the tadpoles until they emerge as young frogs.
It must be noted, however, that some of these examples belong to the related family Cystignathidæ—a very extensive family largely represented in Central and South America.
The remainder of the tailless amphibians are assembled in the numerous and widely distributed family Ranidæ, which is that of the "true" frogs. The typical subfamily, Raninæ, is cosmopolitan, except as to Australia and South America south of the Amazon basin; but some less typical forms are confined to the tropics, and include several strange species, such as the little arboreal Dendrobates frogs of Brazil, one of which is famous for furnishing in the secretion of its skin a dye that when properly applied turns the green plumage of tame parrots into yellow—a fashionable tint. These small and pretty frogs are noted for their solicitude for their young, carrying baby tadpoles on their backs—where the infants creep and become attached—from place to place, as safety or better water conditions suggest.
The North American frogs are good examples of the ranine race, and those more commonly seen are the following:
Leopard frog (Rana pipiens), green with irregular black blotches, mostly in two rows on the back; legs barred above; belly pale. Eastern specimens are more olive than bright green.
Pickerel frog (R. palustris), light brown with two rows of large, oblong, square blotches of dark brown on the back, a brown spot above each eye, and a dark line from the nostril to the eye; upper jaw white and black. Habitat, eastern United States among mountains.
Wood frog (R. sylvatica), pale reddish brown; a black band across the pointed face. This smallest of our species is to be found only in damp woods, resorting to water only in early spring to deposit its eggs; and it is almost silent.
Green, or spring frog (R. clamatans), green or bronze-brown, brighter in front, with more or less small black spots; yellowish white below. This is a rather solitary frog, living in springs and small ponds, where it utters the familiar "chung" at frequent intervals. It is distinguished by the enormous size of its eardrum.
Bullfrog (R. catesbiana), greenish, brightest on the head, and with small dark spots on its back; legs blotched; eardrum large; toes broadly webbed. Length five to eight inches, breadth four to five inches. It utters a roar not unlike that of a distant bull, and a company of them on a still summer evening will awaken the neighborhood. Bullfrogs are present throughout the eastern United States and Canada, west to the dry plains; and furnish the market with "saddles" (their hind legs) as a table delicacy when fried. These frogs may lay 12,000 eggs apiece.
All our frogs lay their eggs in water in rounded masses, not in strings, as do the toads, usually attached to some submerged stick or plant stem. The tadpoles, light in color, are very voracious, and feed on every sort of flesh that they can bite off and chew with their horny jaws. On the approach of winter the frogs—except the wood frog, which hibernates in the loam of the forest, or in some rotten stump—sink into the mud of the pond or marsh where they live, and pass the cold months in torpidity. Their food is almost exclusively insects, caught by the tongue, but the big bullfrogs seize with their mouths any small creature that comes their way.
CHAPTER XX
REPTILES—MONARCHS OF THE
MESOZOIC WORLD
What is a reptile? It is a cold-blooded, air-breathing vertebrate, with one occipital condyle, complete right and left aortic arches, red blood and a covering of scales. The classification of the class (Reptilia) recognizes the existence of many distinct subdivisions, as follows: