By some naturalists a separate class is made out of the Amphibia, including the Frog kind, Toads, and Newts (fig. 47), which they call "Batrachia," and which takes a place between Reptiles and Fishes, as the young of this class have a totally different form from the adult animal, and much resemble a fish, breathing by gills and having no legs, but as they become mature the gills are replaced by lungs, and the legs make their appearance.
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 they swallow whole. The Frogs are furnished with webbed feet and swim well; they progress on land by leaps, their powerful hind legs carrying them to a great distance. The young of the Amphibia are brought forth as eggs, which float on the water, and when they first come to life form the curious little creatures called Tadpoles, having long tails and no feet, and, as before stated, more resembling Fish than Reptiles. The Toads are for the most part nocturnal in their habits, living in the daytime in gardens and holes; they feed upon insects, as do Frogs, and lay their eggs in the water. The stories of Toads being found alive in rock and the heart of trees, arise from the following circumstances: Toads when small will often creep into holes in rocks and hollows in trees, and in these situations they find abundance of food; being slothful in their habits, and capable of existing upon but little food, and abstaining from it a long time, they are apt to remain in their snug quarters and content themselves with what insects may come to them. In this way they grow too large to get out of the hole, and live for a great time in it; when chance discovers them, by the rock being broken open or the wood of the tree cleft, the opening into which they had crept is overlooked. The Water Newt (Triton cristatus) inhabits pools and ditches, and (like the others of this order) is first formed as a Tadpole; it is of a brown and bright yellow colour, with a crest down its back and tail, and has the most extraordinary powers of reproducing any part cut off or removed, such as a leg or the tail.
2. Ophidia (Snake-like order).
FIG. 48.—1, ROCK SNAKE (Python molurus); 2, SPECTACLED SNAKE (Cobra de Capello); 3, BOA CONSTRICTOR.
This includes the Serpents, Boas, and Pythons. These creatures are peculiar from their long and flexible form, and the absence of legs. They move by a sinuous winding action, and when about to seize their prey, make a sudden dart with great rapidity. They are covered with regular scales, and mottled with different colours; some, as the Adder and Rattle-snake, are very venomous, the poison is contained in small glands connected with the poison-fangs, which are two long pointed teeth, having a groove or small canal leading from the side of the tooth to the poison-bag, upon which, when they bite, they press, and inject the poison into the wound while the tooth is in the flesh. These poison-fangs lie flat down when the creature is not excited, but are drawn up by muscles, when they are about to spring on anything. It is a common mistake to think that Serpents have a "sting," arising from their having a thin, long forked tongue, which they protrude and retract with great rapidity, and which has been mistaken for a sting; the greater number of Snakes are not at all venomous. Serpents have no teeth fit for eating with, but they are used to hold their prey, while they swallow it, and they serve admirably for this purpose, as each tooth turns backwards. These creatures have mouths and throats capable of enormous distension (the lower jaw not being fixed to the upper one), so that they can swallow their food whole, which they always do; a Frog or Toad is often swallowed by the common Snake, which is quite disfigured by it when in its stomach. The Pythons and Boas (fig. 48) are the largest of this class, they kill their prey by coiling round it, and gradually tightening their folds till it is suffocated and almost crushed, when it is swallowed; these great creatures will grow to the length of 30 or 40 feet, and are capable of swallowing considerable quadrupeds, as Hares, Goats, Deer, &c.; after having their food, they lie torpid for several days. All Serpents lay eggs, and the Pythons coil themselves round upon their eggs to protect them; the Boa-constrictors are inhabitants of America, the Pythons of the Old World.
3. Sauria (Lizards).
The Sauria include the Crocodiles, Alligators, Skinks, Geckos, Iguanas, and Lizards; they are carnivorous, the smaller ones feeding on insects, and the larger members on whatever they can catch. They have four legs, and are covered with hard rough scales running in ridges on their backs, they have large strong tails, and their jaws are furnished with sharp teeth. The Alligator is found in great numbers in the Mississippi, and is a most formidable creature, attacking any who may venture into the water. In winter they bury themselves in the mud and remain there in a torpid state, they are from 15 to 20 feet long. The Crocodile is a native of Africa and the West Indies, there are many found in the Nile, it is larger than the Alligator, reaching often to 30 feet. Dr. Baird gives the following account of the Alligators and Crocodiles:—
