The Book of the Aquarium/Part 3/Chapter 7

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The Frog.—The Ranidæ or true frogs, and the Bufoidæ or toad tribe, contribute, whether in the larva or perfect form, some very lively, entertaining, and instructive specimens. I am sorry that my space is so limited as to prevent the insertion here of such full notices as this subject deserves, and must content myself by assuring the reader that but little progress can be made in the study of Zoology without a patient study of the history of the frog.

During the spring and summer the brooks abound with what boys call “ loggerheads,” or tadpoles; these are the larva of the frog. They may be caught easily, and preserved in jars of growing weed, for observation of their development. I have now (August 18th,) several specimens of Bufoidæ, in which even the first stage of metamorphosis has not commenced, though, since June, some hundreds of toads and frogs have attained completeness in my vessels, many of which are now inmates of the garden, some of them exceedingly tame.

In the egg state we find abundance, during April, in every pond and brook, adhering in gelatinous masses to the under leaves of aquatic plants. The eggs gradually acquire a dark tint, and at last the young “ tads ” emerge, and begin their quiet existence in this first rudimental form. In this state they are very lively in their motions, the eyes are very distinctly visible, and the mouth is placed, as it were, on the breast. They are not wholly herbivorous; for though they nibble the fronds of Riccia and threads of Conferva, they do not scruple to eat their dead kindred, and half a dozen may be seen engaged upon the carcase of a defunct brother. In this stage the gills form a fine microscopic object. As the “ tad ” increases in bulk, the hinder part of the body swells, and at last the budding of the hind legs may be distinctly seen. These at last acquire some degree of completeness, and then the other

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pair of legs sprout in a similar manner, and the tail begins to shrink rapidly as the general bulk of the reptile increases. The gills now rapidly disappear and the body grows at the expense of the tail, and before the latter appendage is completely extinguished, the juvenile Ranus takes his first dose of atmospheric air, by mounting a leaf of frog-bit or a slice of cork. He now leads an amphibious life, and at last quits the water altogether, climbs up the glass side of the tank or jar, and escapes, unless confined by a glass lid or gauze. But he is now a true frog, delicately mottled, agile in his movements, very clever in jumping and swimming—his tadpole tail entirely absorbed, and his whole system metamorphosed. If he interested us before, he is still more interesting now, for in the structure and economy of his frame Nature reveals phenomena typical of animal life in all its orders and gradations. Hence the frog is the victim of the philosopher; he suffers spasm under the galvanic wire, blindness under the glare of the microscope lamp, tetanus through being dosed with strychnine, and innumerable other agonies in which operators detect analogies that throw a light on the fundamentals of animal life, and that even aid in the explanation of the subtle organism of man himself.

Management of the Cabinet.—The instructions already given for the management of Aquaria will be found to embrace most of the points involved in the management of beetle and larva jars, for these are but Aquaria on a smaller scale. The chief matter is to separate the species as much as possible, so that the carnivorous kinds shall not destroy the harmless ones; and on this plan the study of each kind is greatly facilitated. Since the jars afford the best means for the culture of choice aquatic specimens of the various kinds of Riccia, Conferva, Nitella, Lemna, and other minute water-weeds may be used for maintaining the necessary balance in each, and if some of the vessels are filled with brook-water only, the student will come into possession of many beautiful specimens of both animal and vegetable life, the search for the names and histories of which will be even more profitable than the contemplation of their beauty. The first specimen I ever possessed of the beautiful confervoid Hydrodictyon utriculatum was obtained in this way—the water, after depositing a green sediment, gave birth to a rich net-work of vegetation, in which this conferva was conspicuous. Several of the jars which I prize the most are those which have been simply filled at the brook side, and left for the minute germs of animal and vegetable life to develope in their own way, and it is not long before a rich growth takes place, that affords abundant material for observation with the microscope. Feeding is necessary only in the case of carnivorous larva and beetles, and for these small fish is undoubtedly the best; the herbivorous creatures supply themselves. As a general rule the water in the jars should never be changed; it is by leaving things to themselves that the best display is to be obtained, especially if chara and other low forms of vegetation are preserved.

Nitella is almost too delicate for the tank, but an admirable plant for growth in jars in which cabinet specimens of larvæ are kept. I rarely place it in the aquarium, considering it too choice a thing, its delicate structure rendering it barely perceptible amidst the more luxuriant growths with which it gets entwined. Still, it does well there, but cannot be studied unless a bunch is placed in a glass jar for separate culture. It consists only of joints and threads of a pale, but pleasing, green, grows rapidly, and gives out abundance of the vital phlogiston, about which aquarians are compelled to say so much.

The microscope at once increases a hundred fold the pleasure of instruction which the cabinet is capable of affording us. For the minuter forms of animal life, and for observing the circulation in the frog, or in vallisneria, &c., a good compound microscope is necessary. But for ordinary purposes, I should recommend a Coddington lens, or the pocket Aquarian lenses, sold by

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Mr. Cox, of 100, Newgate Street. They are made of three powers, fitting into a case, and may be used separately, or combined according to circumstances. The one here figured costs 7s. 6d., but a cheap common lens, fitted with frame and handle, may be had of Mr. Cox for from half-a-crown to five shillings.

The present work does not afford me space to discuss the educational and ornamental uses of the aquarium, and I have confined myself to its mere elements, dealing with those in a way that I think will be most useful to beginners. The aquarium has uses of a higher character than such as may suggest themselves by the perusal of these few pages, and is capable of extension so as to combine with it the most attractive features of the wardian case, and, to some extent, a vivarium for a selection of amphibious and true land animals. These matters are pretty fully discussed in my work on Rustic Adornments, to which I have already called the reader’s attention, and to its pages I once more refer for more extended information on this and other subjects of a kindred nature.

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