for which the various created organisms exist and have their being. This I should call the philosophical mode of study.

Of the many curious fields of thought which this latter mode opens out to the inquirer, not the least remarkable is that connected with form.

Resemblances or analogies of form in nature are sometimes very interesting, and not a little startling. Many instances of this analogy will doubtless at once occur to my readers. For example, the remarkable resemblance various genera of the Mantide and Phasmide (Orthopterous insects) bear to portions of plants, which has procured for them the

Fig. 243. Sponge spicule.

popular names of "walking-sticks," "walkingstraws," leaf-insects," &c., &c. These, and other cases of analogy of form which might be cited, are no doubt designed by a beneficent Providence with

Fig. 244. Astromma Aristotelis.

the view of preserving the insects from certain of their enemies.

Other cases, however, occur of no less perfect

Fig. 246. Triceratium castellatum.

Ascending higher in the scale of creation, it will be found that similar instances of analogy occur. Many species of Orchids, for example, so much resemble animal forms that the names Bee Orchis, Fly Orchis, Butterfly Orchis, &c., have been given to them. The most remarkable of these, perhaps, is the Butterfly Orchis (Oncidium Papilio). The likeness is in this case very complete. Another instance is that of the resemblance of the shell of the Chitons, a family of gasteropod Mollusca, to the carapace of the Isopoda or Wood-lice, and even, in fact, to the carapace of the Tortoises.

The subject is a wide one, and more examples of analogy of form might have been adduced; but I preferred giving these few only in order that my readers might perhaps be induced, by what has been said, to enter on this field of inquiry, and to see, correlate, and think for themselves. It has long been one of great interest to me, and I doubt not if they will pursue it that it will prove no less so to them.

G.

Fig. 247 is a representation of a female Torpedo, the skin B having been flayed from the under-surface of the fish to show the electric organs A. The mouth, having the form of a crescent, is shown at d; the branchial apertures, five in number, at E; ggg the place of the anterior transverse cartilages; hh the exterior margin of the great lateral fin; i its inner margin on the confines of the electrical organ; 7 the abdomen; m m the place of the posterior transverse cartilage, which is single, united with the spine, and sustains the smaller lateral fins nn on each side; o is the anus, and p the fin of the tail. Each electrical organ is about 5 inches long and about 3 inches broad at the anterior end, and an inch at the posterior extremity. Each organ consists wholly of perpendicular columns reaching from the upper to the under surface of the body, and varying in their lengths according to the thickness of the parts of the body where they are placed. The longest column is about 14 inch, the shortest about of an inch, and their diameter about of an inch. The figures of the columns are irregular hexagons or pentagons, and sometimes have the appearance of being quadrangular or cylindrical. The number of columns in the fish examined by John Hunter was 470 in each organ; but in a very large fish, 44 feet long and weighing 73 pounds, the

number was 1,182 in each organ. The number of partitions in a column 1 inch long was 150.

The Torpedo must be irritated to cause it to give a shock, in the delivery of which it moves its pectoral fins convulsively; the shock is felt on touching the fish with a single finger, and it can give a long series of shocks with great rapidity. When the Torpedo is placed on a metallic plate, so that the plate touches the inferior surface of the organs, the hand that supports the plate never feels any shock; though another insulated person may excite the animal, and the convulsive movement of the pectoral fins may denote the strongest and most reiterated discharges. Direct contact with the electrical organs of the fish is indispensably necessary for the reception of the shock, but the Torpedo has not the power of directing its electrical discharge through any particular object.

By passing the discharge from a Torpedo through a spiral of copper wire enclosing a steel needle, the needle becomes magnetized in such a manner as to show the direction of the current to be from the back to the under part of the belly. Heating and chemical effects have likewise been obtained. According to the experiments of Matteucci:-1. All the dorsal parts of the electrical organ are positive to all the ventral parts. 2. Those points of the organ on the dorsal face which are above the nerves which penetrate this organ are positive relatively to other points of the same dorsal face. 3. Those points of the organ on the ventral face are negative relatively to other points of the same ventral face.

The Gymnotus.

This electrical fish is a native of the warmer regions of America and Africa. There are several species of the Gymnotus, but only one is electrical. In general aspect it very much resembles an eelthe body is smooth, and without scales (a peculiarity of all electrical fishes). The electric organs consist of alternations of different substances, and are most abundantly supplied by nerves; their too frequent use is succeeded by debility and death. The electric organs may be removed without injury to the fish.

Fig. 248 is a copy of Hunter's engraving of the Gymnotus, and fig. 249 is a correct representation of a fine specimen which was for some time in the possession of the proprietors of the Royal Polytechnic Institution. In Hunter's engraving the skin is removed to show the structure of the fish; a is the lower surface of the head; e the cavity of the belly; b the anus; e the back where the skin remains; g g the fin along the lower edge of the fish; e e the lateral muscles of this fin removed and laid back with the skin to expose the small organs; 7 part of the muscle left in its place; ff the large electrical organ; hh the small electrical organs; m m'm the substance which separates the two

The electrical organs consist of two parts, viz., flat partitions or septa, and thin plates or membranes intersecting them transversely. The septa are thin parallel membranes stretching in the direction of the fish's length, and as broad as the semidiameter of the animal's body. They vary in length, some of them being as long as the whole body. The very thin plates which intersect the septa have their breadth equal to the distance between any two septa. There is a regular series of these plates, from one end of any two septa to the other end, 240 of them occupying a single inch.1

The electric organ of the Gymnotus depends entirely on its will. It does not keep its organs always charged, and it can direct its action towards the point where it feels itself most strongly irritated. When two persons hold hands, and one touches the fish with his free hand, the shock is commonly felt by both at once. Occasionally, however, in the most severe shocks, the person who

comes into immediate contact with the fish alone receives it.

A fine specimen of this remarkable fish was for some time in possession of the proprietors of the late Gallery of Practical Science in Adelaide Street, and was made the subject of some interesting experiments by Faraday (Ex. Researches, 15th series, 1838). This fish was 40 inches long. It remained in a healthy and vigorous condition till March, 1842, when it died from the effects of a rupture of a blood-vessel.

1. The Shock.-This was very powerful when one hand was placed on the body near the head, and the other near the tail. It was like that of a large Leyden battery charged to a low degree; and great as was the force of a single discharge, the fish was able to give a double and even a triple shock with scarcely a sensible interval of time. From some comparative experiments, Faraday thought it may be concluded that a single medium discharge of the fish was at least equal to that of a Leyden battery of fifteen jars, containing 3,500 square inches of glass coated on both sides, and charged to the highest degree.

2. The Spark.-Through the upper cap of a glass globe a copper wire was passed, a slip of gold leaf being attached to its extremity; a similar wire terminating in a brass ball within the globe was passed through the lower cap. The gold leaf and brass ball were brought into all but actual contact, the fish being provoked to discharge through the wires, the gold leaf was attracted to the ball, and a spark passed.

3. Chemical Decomposition.--Polar decomposition of iodine of potassium was obtained by moistening three or four folds of paper in the solution, and placing them between a platinum plate and the end of a platinum wire, connected respectively with two saddle conductors grasping the body of the fish. The middle of the fish was found to be negative to the anterior parts, and positive to parts towards the tail.

4. Magnetic Effects.-By causing the fish to send powerful discharges through an instrument of no great delicacy, a deflection of the needle amounting to 30° was produced; the deflection was constantly in a given direction, the electric current being always from the anterior parts of the animal, through the galvanometer wire to the posterior parts. When a little helix, containing 22 feet of silked wire wound on a quill, was put into the circuit, and an annealed steel needle placed in the helix, the needle became a magnet, and the direction of its polarity in every case indicated a current from the anterior to the posterior parts of the Gymnotus through the conductors used.

When a number of persons all dip their hands at the same time into the water in the vessel in which the Gymnotus is confined, they all receive a shock

of greater or less intensity when the fish discharges, proving that all the conducting matter round the fish is filled at the moment with circulating electric power, resembling generally in disposition the magnetic curves of a magnet. The Gymnotus feeds on other fish, which it kills by giving them a shock; this it does by forming a coil round the fish, so that it should represent a diameter across it. Living, as the Gymnotus does, in the midst of such a good conductor as water, it seems at first surprising that it can sensibly electrify anything; but, in fact, it is the very conducting power of the water which favours and increases the shock by moistening the skin of the animal through which the Gymnotus discharges its battery.

Fig. 250.

The Silurus electricus.-This fish is shown in fig. 250. It is found in the Senegal, the Niger, and the Nile. It is about 20 inches long. The shock is distinctly felt when it is laid on one hand, and touched by a metallic rod held in the other. Its electrical organs are much less complicated than those of other electrical fishes. Other known electrical fishes are the Tetraodon electricus, found in the Canary Islands, and the Trichiarus electricus, which inhabits the Indian seas; several others have been met with, but not hitherto accurately described.

[The above account has been taken from "The Student's Text Book of Electricity," by H. M. Noad. London Lockwood & Co.; and the woodcuts from the same work were kindly lent by the publisher.-Ed.]

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:

PUFF-BALLS.

NE of the many amusements of country schoolboys, of which boys in town are innocent, is, or used to be, "when we were boys together," to puff in each other's faces the fine, brown, snuffy dust which fills the interior of ripe "puff-balls," or as they are called by some, with more of terseness than elegance, "devil's snuff-boxes." During the past autumn we took a stroll for a few miles into the country with a friend, when all of a sudden he stopped, and looking intently at some object at his feet shouted, in apparent delight, "Why here's a bulfer!" Here we must pause also, to inform our readers that in Norfolk these " puff-balls" are invariably called "bulfers." It was evident that our friend, doomed to a city life, had not seen a puff-ball for many years. Perhaps he had scarcely recognized one since his boyhood, and, as he afterwards confessed,

the thing and its provincial name were so associated together that he pronounced the latter at once as though it were classic, and immediately afterwards came the reflection that it was only a provincialism, which he had scarce heard since he went to school. Never had we suspected that our city friend was an East Anglian, until this one word told the tale, and henceforth a closer bond was knit between us by the confession, "and I'm Norfolk too."

The true "puff-balls" are a genus of fungi which bear the scientific name of Lycoperdon. They belong to a family in which an outer covering or peridium encloses a mass of dusty spores more or less mixed with delicate threads. In their early stage they are pulpy or gelatinous, and when ripe not unlike snuff. Of this genus the following seven species are found in our islands.

First of all there is the "smooth giant puff-ball," Lycoperdon giganteum, sometimes as large as one's head, and at first whitish

or of a parchment colour, and with an outer covering as soft to the touch as a kid-glove. Internally the substance is firm and of a creamy whiteness, but not hard like some others in an allied genus. The end of the finger makes, and leaves its impression, almost as readily as on a lump of fresh "putty." With the progress of growth the interior gets discoloured, assumes a greenish tint, which darkens into olive, and finally, when mature, the whole internal substance, except the spongy base, resolves into a greenish dust. In its young and fleshy state, whilst still of a creamy whiteness, it furnishes a dish which an epicure might envy. Many a time and oft, has our latter end been prophesied by astonished and alarmed villagers in rural districts, when we have informed them that we intended to eat the great white puff-ball, as big as a loaf, which we carried under our arm. Many a time have we made a similar meal, and the prophecy is not yet fulfilled. By dint, in some instances, of a little deception at the first, and in others by commencing the gastronomic attack, and protesting in favour of its harmlessness, we have introduced "fried puffball" to the breakfast-tables of many personal friends, but in no single instance was deception or protestation needed after the first experiment, for they have all become even more enthusiastic in its favour than the introducer of the article.

There is also a "rough giant puff-ball" (L. cælatum) which almost vies with the above in dimensions, but the surface is rough and the interior is filled when ripe with a mass of dingy yellow spores. This often forms large rings, or parts of rings in pastures, and, as far as we are aware, is in no phase of its existence edible, although we are informed by a gentleman to whom we introduced the smooth puff-ball as a breakfast relish, that he has also eaten this species, as well as Lycoperdon gemmatum, in its young and pulpy state.

It is not very common to find a puff-ball which attains six inches in height, of which the lower portion forms a stem, and the upper portion, when mature, contains the dust-like, dingy spores. In this species the stem occupies at least two-thirds of its height, and it should be called the "long stemmed puff-ball" (Lycoperdon saccatum). The receptacle or peridium is flattened, with regular depressions at the top of the stem, around the base of the peridium, so as to give a somewhat fluted appearance. The spores, moreover, when examined under the microscope, are rough or spiny; in which feature they

specimens. It occurs in pastures and has scarcely any stem, being nearly pear-shaped; this is named Lycoperdon atropurpureum. The mass of spores is of a dark, purple-brown colour, whereby it may be distinguished from all the others by the naked eye, and the spores are larger than in Lycoperdon saccatum, or indeed any other British species.

Fig. 251. Lycoperdon saccatum. a. Spore.

a

agree with only one other British species. At Albury in Surrey we met with hundreds of specimens in one wood during last October, but only an occasional solitary specimen elsewhere.

Fig. 253. Lycoperdon gemmatum.

The commonest puff-ball is the "mealy puff-ball," Lycoperdon gemmatum, which has its surface covered with mealy warts, and when these are rubbed off the scars are seen to be symmetrically arranged in hexagonal forms. This puff-ball is at times borne upon a long stem, but more commonly it is only narrowed downwards, and in size varies from one inch to three inches in diameter. If a section be cut through a specimen lengthwise before the spores are quite mature, a kind of column may be seen projected upwards in the centre, and which is not to be found in Lycoperdon saccatum. The spores, moreover, are yellowish, or almost of the colour of "Scotch snuff," small and smooth under the microscope.