Amphibia

“ The Amphibia are bound absolutely to the land and to fresh water; transportation across salt water is not excluded, but must be accidental, and is not a case of regular "spreading." Speaking generally, the older a group, the more likely is it to be widely distributed. ”

“ AMPHIBIA, a zoological term originally employed by Linnaeus to denote a class of the Animal Kingdom comprising crocodiles, lizards and salamanders, snakes and Caeciliae, tortoises and turtles and frogs ”

“ We know now that all the blood and passion of our life were represented in the Carboniferous time by something—something, perhaps, cold-blooded and with a clammy skin, that lurked between air and water, and fled before the giant amphibia of those days. ”

“ If we glance back to the far-off time when the ancient fishes were wandering round the shores and in the streams of the coal-forests, we find that the amphibia were not then the small, scattered groups they are now, but huge and powerful creatures, which sported in the water or wandered over the land with sprawling limbs, long tails, and bones on which gills grew, while their heads were covered with hard, bony plates, and their teeth were large, with folds of hard enamel on the surface. ”

“ During the dry season, that is in summer, these strange animals bury themselves in a nest of leaves in the dry mud, and then breathe air through lungs like the Amphibia. But during the wet season, in winter, they live in rivers and bogs, and breathe water through gills like fish. Externally, they resemble fish of the eel kind, and are like them covered with scales; in many other characteristics also—in their internal structure, their skeleton, extremities, etc.—they resemble Fish more than Amphibia. ”

“ The Amphibia are the oldest and the lowest group of vertebrates that are able to lead an active existence on land, and the characters which distinguish them most definitely from the fishes are all to be interpreted as adaptions to the new mode of life. One of the most obvious external differences between the two groups is in the structure of the extremities, the fish having fins, while the amphibian has limbs constructed on the same general lines as our own arms and legs. ”

“ This Carboniferous age, this age of the amphibia, was an age of life in the swamps and lagoons and on the low banks among these waters. Thus far life had now extended. The hills and high lands were still quite barren and lifeless. Life had learnt to breathe air indeed, but it still had its roots in its native water ”

“ Examples of their peculiar distribution will be given when we treat of the fauna of some islands in which they abound.
The Dispersal of Amphibia and Fresh-water Fishes.—The two lower groups of vertebrates, Amphibia and fresh-water fishes, possess special facilities for dispersal, in the fact of their eggs being deposited in water, and in their aquatic or semi-aquatic habits. They have another advantage over reptiles in being capable of flourishing in arctic regions, and in the power possessed by their eggs of being frozen without injury. ”

“ The Amphibia differ widely from Reptiles in their power of enduring cold; one of their chief divisions, the Urodela or Tailed-Batrachia, being confined to the temperate parts of the Northern Hemisphere. To this class of animals the northern and southern routes of migration were open; and we accordingly find a considerable amount of resemblance between South America and Australia, and a still stronger affinity between North America and the Palæarctic continent. ”

“ The Amphibia, as here enumerated, consist of 22 families, 152 genera, and nearly 700 species. Many of the families have a very limited range, only two (Ranidæ and Polypedatidæ) being nearly universal; five more extend each into five regions, while no less than thirteen of the families are confined to one, two, or three regions each. ”

“ The Amphibia have soft skins, which appear to serve as lungs or gills when they are under the water, extracting the air from it, and enabling them to remain a long time there without coming up to breathe; they are partly aquatic, and feed upon insects and other small creatures, which they capture by darting out the tongue, which is covered with a glutinous secretion, and drawing it in again instantly with the insect adhering to it, which [Pg 272] they swallow whole. ”

“ The canals have been described in all known orders of fossil Amphibia and the system is found likewise in all the living orders, including the Gymnophiona, which have "a strong line of lateral sense-organs" (Gadow) . In the Branchiosauria, the earliest of the true Amphibia (Euamphibia) and ancestral to the modern Caudata, the lateral-line system is known on the tails of two genera (462, 478) from the Mazon Creek, Illinois, shales—Micrerpeton and Eumicrerpeton. ”

“ We are no longer content, however, with these approaches to actual contact and genetic kinship, we have toiled so long both by discovery and by the elimination of one error after another, and are so near the promised land, we can hardly restrain our impatience. I venture to predict that the contact of the Amphibia with the fishes will be found either in America or Europe. ”

“ Some years ago it was usual to class together as “four-legged creatures that lay eggs,” all turtles, tortoises, newts, salamanders, snakes, toads, frogs, lizards, and crocodiles. The great naturalist, Linnæus, named all these creatures amphibia, because they can live with equal ease in the water or on the land. After this some of the French naturalists concluded that the creeping method of locomotion of these animals was a more general characteristic than their amphibious habit, and called them reptiles, or crawling creatures. ”

“ An appeal made by Müller for observations on the development of the Caeciliae, and of those Amphibia which retain gills or gill-clefts throughout life, has unfortunately yielded no fruits.
In 1825 P. A. Latreille [6] published a new classification of the Vertebrata, which are primarily divided into Haematherma, containing the three classes of Mammifera, Monotremata and Aves; and Haemacryma, also containing three classes—Reptilia, Amphibia and Pisces. ”

“ Dr. Robert Brown and Professor D. M. S. Watson have given conclusive proofs of the origin of mammals and birds from primitive reptiles, and the latter zoologist has pushed back the ancestry of these higher vertebrates still further, and shown how the reptiles were derived from primitive Amphibia, and the changes that occurred in vertebrate anatomy when certain fishes crawled out of the water and developed into four-footed Amphibia. ”

“ Naked, tailless Amphibia of compact form, and with usually procœlous vertebræ. Caudal vertebræ coalesced into a slender elongate piece, the urostyle. Two elements of the tarsus ossified and greatly elongated. Development by metamorphosis; gills never present in adult. Ilium greatly elongated.
The order is suggested in the Coal Measures by a single species, known from a single poorly preserved specimen (plate 24, fig. 1) . The form Pelion lyelli Wyman was the first known of the Linton Amphibia, and its striking frog-like (123, 639) appearance was early noticed. ”

“ The amphibia have always a considerable dislike and some degree of contempt for all land-animals, and the five sailors, with their skipper, who formed all the crew so small a craft required, would probably have driven below the intruder upon their labors, had they had time, leisure, or light to notice him at all. ”

“ Aquatic or terrestrial Amphibia; development by metamorphosis; external branchiæ present in the young; bones almost entirely perichondral; carpus and tarsus never ossified; osseous pubis absent; vertebræ usually amphicœlous with persistent notochord; ribs short and straight or flat and slightly curved, or absent; digits 4 in the hand and 5 in the foot; skull never grooved or pitted, nor cut by the lateral-line canals; lateral-line organs present in the skin; sclerotic plates present or absent; tail long and flattened or absent. Ribs in Triton walthi are secondarily long and curved. ”

“ The naturalists' belief that these Amphibia are closely akin to fish in many ways is borne out in their breeding habits; for, like fish, they have more or less complex 'instincts' that lead the males and females together at the laying season, and then, like fish, they separate till the next period of egg-laying. ”

“ Thus, early in the geological history of the land vertebrates, we have, among the Coal Measures Amphibia, various forms which had specialized into strictly aquatic, terrestrial, subterrestrial, and arboreal, or at least partly arboreal. Specialization had extended to the loss of limbs, ribs, and ventral armature in a few species, and to the acquirement of claws, running legs, or a long propelling tail with expanded neural and hæmal arches in others. The forms range in size from small creatures less than an inch in length to large species which must have attained a length of several feet. ”

“ The question of the origin of land vertebrates, which has appealed so strongly to students of fossil Amphibia, is by no means solved from the material furnished by the Coal Measures of North America. The Amphibia are, however, well known from several localities in the Coal Measures of this continent, where skeletons have been recovered which are sufficiently well preserved to afford a fair knowledge of their anatomy. ”

“ The Amphibia, Fishes, Animalcules, etc., must conclude our sketch of the zoology of the Arctic regions.
In the class Amphibia, the most notable personage is the Greenland shark, Squalus borealis. It has not, I believe, been described. The ventral fins are separate. It is without anal fin, but has the temporal opening, and it belongs, therefore, to the third division of the genus. The spiracles on the neck are five in number on each side. The colour is cinereous grey. The eyes are the most extraordinary part of the animal. The pupil is emerald green, the rest of the eye blue. ”

“ The term Amphibia, having reference to the two-fold medium and manner in which is carried on the most important function of life, the renewing of the vitality of the blood, is with literal strictness applicable to these singular forms: for it is descriptive, not of a preparatory and rudimentary condition of existence, but of that which, subsisting through life, is truly proper to the animal. “The simultaneous existence and action of branchial tufts and lungs in these animals,” observes Cuvier, “can no more be contested than the most certain facts of natural history ”

“ In the adult or perfect condition, the form of these animals differs much from that common to the Amphibia, the body being short, broad, and flattened horizontally, and destitute of every vestige of a tail. ”

“ The embryonic development of most of the higher Amphibia still faithfully reproduces the stem-history of the whole class, and the various stages of the advance that was made by the lower Vertebrates in passing from aquatic to terrestrial life during the Devonian or the Carboniferous period are repeated in the spring by every frog that develops from an egg in our ponds. ”

“ Such sudden and violent transitions from utter idleness to the most tremendous exertion as they continually experience do not seem to harm these toughened amphibia. Plenty of them do of course “go under,” in more or less distressing circumstances, but though their own tiny circle laments their loss, their tragic fate makes no more disturbance than the drop of a pebble outside of it. There are plenty to take their place. For even in so precarious a calling as hovelling there are grades. ”

“ The Amphibia, then, have all, at some stage of their existence, both gills and lungs co-existent: respiring by means of branchiæ or gills while in the water, and by lungs on emerging into the open air. 10
All these creatures seem to have been well known to the ancients. The monuments of the Egyptians abound in representations of Frogs, Toads, Tortoises, and Serpents. Aristotle was well acquainted with their form, structure, and habits, even to their reproduction. Pliny's description presents his usual amount of error and exaggeration. ”

“ Considering the postembryonic developmental stages of modern Amphibia, there can be no doubt that a gill-bearing, four-legged larva of a salamander, in which lateral line pores and a gular fold are present, represents much more closely the type of larva found in labyrinthodonts than does the limbless, plant-nibbling tadpole of the Anura. ”

“ The Reptiles, of which the majority possess the faculty of living upon land and in water,—whence their name of Amphibia,—never pass beyond the limits of warm and temperate climates: their blood, which has the same temperature as the medium wherein they live—whence their name of "cold-blooded animals"—does not circulate where the mean annual temperature descends below freezing-point. ”

“ A rather interesting parallel, though of no phylogenetic significance, can be drawn between the Amphibia of the North American Coal Measures and the reptiles of to-day. The snakes are represented by the limbless, snake-like forms, such as Ptyonius and Phlegethontia. The lizards find their counterpart in the Hylonomidæ and the Tuditanidæ. No known characters of these animals tend to ally them directly with any known group of fishes, except in the most general way. ”

“ They were formed in the warm waters of the primary ages. While there were yet no continents nor islands emerging from the universal ocean, there were no air-breathing organisms. The first aquatic beings were succeeded by amphibia and reptiles. ”

“ Our modern tailless Amphibia, frogs and toads, appear much later in the story of the earth, but they are not without interest here on account of the remarkable capacity which they show to adapt themselves to different surroundings. ”

“ How difficult a matter it is to decide whether the lung-fish of Brazil and Senegambia belong to the amphibia or to the fishes, which in other instances are known to always breathe by their gills! In the rainless season of the year the swamps, the homes of these animals, dry out; they then coat themselves with a crust of earth, and are dependent on their lungs for every breath they draw. ”