the marks of his finger and thumb.

Another is the Pilot-fish

(Fig. 152), celebrated for its attendance on the large Sharks,

and supposed by the ancients to have pointed out to navigators their desired course, and borne them company during their voyage. A third is the Tunny (Fig. 153), a fish of large size, though here represented by a very diminutive figure. One killed at Inverary

weighed 460lbs. and measured seven feet ten inches in length. The Tunny visits the shores of the Mediterranean in great shoals,

Fig. 153.-TUNNY.

and gives origin to an extensive and valuable branch of commerce. It is spoken of by the fishermen there as warmblooded, and observations show that in this they are quite correct. It swims near the surface of the water, in this respect resembling the Bonito, a fish with blood as warm as that of a man! The Bonito is frequently mentioned by navigators as one of the most ruthless pursuers of the Flying-fish.

In our progress through the different grades of animals, we occasionally meet with individuals which seem to combine the characteristics of two distinct groups, and render it

an interesting problem to determine, in which they should be placed. Such is the Lepidosiren (Fig. 154), an animal which inhabits a part of the river Gambia, which overflows extensive tracts. Such individuals as do not follow the retreating waters, escape from the scorching rays of the African sun by burrowing in the mud, which is soon baked hard above them. There they remain, in a torpid state, until the return of the rainy season again awakes them to activity.

Fig. 154.-LEPIDOSIREN.

This singular creature combines, to such an extent, the characters of a fish and of a reptile, that naturalists are not yet agreed as to which class it should belong. Professor Owen is of opinion it should rank among fishes. To us, in our onward course through the various groups of the animal kingdom, it presents itself as a connecting link between the two classes, and serves naturally to lead us from the Fishes to the Reptiles.

CLASS II.-REPTILES.

REPTILIA.

REPTILES Constitute another of the great divisions of vertebrated animals. Some of them breathe by lungs only; others by gills and lungs. The blood is cold. The young are produced from eggs. They are arranged in four orders -Frogs, Serpents, Lizards, and Tortoises.

ORDER I. TOADS, FROGS, &c.

AMPHIBIA.

THESE Reptiles may be separated into two divisions-those which possess both lungs and gills throughout the entire period of life, and those which have gills in their young state, and acquire lungs as they approach maturity. The former group contains some animals of very singular structure and habits; as the Axolotl (Fig. 155), the flesh of which is regarded

as an article of luxury by the inhabitants of the city of Mexico, near to which it is taken.

The latter group has, however, especial claims on our attention; for in the Frogs, Toads, and Newts of these countries, we have the opportunity of watching the successive steps by which they become fitted for breathing air, instead of continuing to use an apparatus adapted, like that of fishes, for respiration in water only.

The eggs of the common Frog are deposited at the bottom of a pool of water, each egg consisting of a black centre, surrounded by a covering of glutinous matter.

When the little Tadpole has burst from its prison, the leaf-shaped gills begin to appear, and increase rapidly in size until they attain their greatest development. They are now objects of singular beauty under the microscope; for such is their transparency that the course of every globule of blood, as it passes up or down the main stem, or enters the inlets presented by each leaf, is distinctly visible. This period of expansion is, however, more temporary than that of many of our cherished garden flowers. The tufted gills shrink in size until they are concealed, like the gills of fishes. The little Tadpole (Fig. 156), begins to feed on

decaying vegetable matter; the tail becomes a large and powerful organ for locomotion, and a rapid increase in the size of the body is perceptible. After a time the hinder-feet

become developed (Fig. 157); then the fore-feet (Fig. 159); the tail shrinks; the form of the perfect animal is assumed (Fig. 158); the remaining vestige of the tail disappears (Fig. 160); and instead of an aquatic animal, breathing by

Fig. 158.

Fig. 159.

Fig. 160.

gills, and subsisting on vegetables, we have one fitted for dwelling upon land, breathing by lungs, and feeding upon smaller animals, such as slugs and insects.

4

In some of the countries of both temperate and tropical regions there are Frogs which from their habitation are called Tree-frogs (Fig. 161). They are described as beautiful and active little animals, not unlike in their colours to those of the trunks and foliage, and furnished at the end of their toes with small cushions or pads, by means

of which they can adhere to smooth surfaces.

The Frog is believed to have been introduced into Ireland in the early part of the last century. The common Toad is there unknown, its absence, according to popular tradition and song, being attributed to Saint Patrick.