The Common Frog. The Common Frog (Rana Temporaria) is now found all over the British Isles. Formerly unknown in Ireland it was introduced there about the year 1700 and has since spread all over the country. The frog is more sociable than the toad, and is often seen, and heard in large numbers; his habits, however, are very similar, and his mode of seizing his prey the same. The Edible Frog belongs to Europe, where it is used as an article of food, and is not found in England. The Bull Frog is an Indian Variety and attains to a great size. The American Bull Frog is also an interesting species.
The Ingenuity of the Frog. Mr. Jesse gives the following illustration of the ingenuity of the Frog: "I may mention a curious observation made in regard to some frogs that had fallen down a small area, which gave light to one of the windows of my house. The top of the area being on a level with the ground, was covered with some iron bars, through which the frogs fell. During dry and warm weather, when they could not absorb much moisture, I observed them to appear almost torpid; but when it rained they became impatient of their confinement, and endeavoured to make their escape, which they did in the following manner. The wall of the area was about five feet in height, and plastered and whitewashed, as smooth as the ceiling of a room. Upon this surface the frogs soon found that their claws would render them little or no assistance; they therefore contracted their large feet, so as to make a hollow in the centre, and by means of the moisture which they had imbibed in consequence of the rain, they contrived to produce a vacuum, so that by the pressure of the air on the extended feet (in the same way that we see boys take up a stone by means of a piece of wet leather fastened to a string), they ascended the wall and made their escape. This happened constantly in the course of three years."
The Tree Frog. The Tree Frog, of which there are numerous varieties, belongs to both East and West occurring in China and Japan or well as in North and South America. It is not found in England. Mr. Gosse says: "They are very numerous in the damp woods of tropical America, and reside by day in the tufts of those parasitical plants, which form reservoirs for rain-water. The under-surface of their bodies is very different to that of the terrestrial species; for the skin, instead of being smooth, is covered with granular glands, pierced by numerous pores, through which the dew or rain, spread on the surface of the leaves, is rapidly absorbed into the system, and reserved to supply the moisture needful for cutaneous respiration. The males make the woods resound throughout the night with their various cries, and, mingled with the shrill chirping of insects, quite banish sleep from the stranger's eyes."
CLASS V—PISCES.
Fishes. We come now to the fifth and last class of the Vertebrata, a class so large that it is impossible to deal adequately with it in a single volume of ordinary size, much less in a single section of one treating of the whole of the vertebrates. There are said to be 10,000 species, so that a book which devoted one page to each would make an enormous volume. All that can be done here is to deal with a few of the better known species, as far as possible selecting types of orders-without attempting to follow closely any classification. Günther divides the Fishes into six sub-classes, which are further arranged in thirteen orders. The first of these orders includes the Sticklebacks, the Perches, the Mullets, the Gurnards, the Mackerel and the Sword-fish besides others. Of these we can deal with but two or three.
The Stickleback. The Stickleback associated with the earliest efforts of the youthful angler, and most of us can remember capturing specimens of some fresh water variety, in the days of childhood, and carrying them home in triumph, in a bottle. There are a number of species of the stickleback, some living in fresh water and some being marine. They are extremely voracious and it is a good job for a large number of other living things that they are no bigger than they are. They are also very pugnacious, and fight among themselves with great determination. The Stickleback is about an inch and a half in length and is furnished with spines, which it uses with great effect when fighting with its enemies.
The Stickleback and the Leech. Mr. John Stark who experimented with some sticklebacks and leeches some years ago, gives the following description of his experiences.
"On putting the leeches into the water, the stickleback darted round the tumbler with lively motions till it found a leech detached, and in a proper situation for being seized. When the leech was very small, say about half an inch in length, it was often swallowed at once before it reached the bottom of the vessel, but when a larger one, about an inch, or an inch and a half in length in its expanded state, was put in, and had fastened itself by its mouth to the glass, the efforts of the stickleback to seize and tear it from its hold, were incessant, and never failed to succeed. It darted at the loose extremity, or, when both ends were fastened, at the curve in its middle, seized it in its mouth, rose to near the surface, and after a hearty shake (such as a dog would give a rat) let it drop. The leech, who evidently wished to avoid its enemy upon its release, again attached itself by its mouth to the glass; but again and again the attack was repeated, till the poor leech became exhausted, and ceased to attempt holding itself by its disc. The stickleback then seized it by the head in a proper position for swallowing, and after a few gulps the leech disappeared. The flattened leech being of an oval form, and having a hard skin, was not attacked, unless when very young, and small; and leeches of the other species when pretty well grown, or larger than himself when expanded, were killed in the manner above mentioned, but not swallowed. In one of his attempts to seize a leech, the stickleback having got it by the tail, the animal curled back and fixed its disc upon his snout. The efforts of the stickleback to rid himself of this encumbrance were amusing. He let go his hold of the leech, which then hung over his mouth, and darting at the bottom and sides of the glass with all his strength, endeavoured to rub off this tantalizing morsel. This lasted for nearly a minute, when at last he got rid of the leech by rubbing his back upon the bottom of the vessel. The leech, perfectly aware of the company he was in, no sooner loosed his hold, than he attempted to wriggle away from his devourer; but before he had reached mid-way up the tumbler, the stickleback had turned and finished the contest by swallowing him up."