BRILLIANT ANIMALCULES.

111

scarcely form an idea of the beauty of these little animals. Engravings of many of them, and technical descriptions, are, indeed, to be found in published works; but of their brilliant transparency, their high refractive power, resembling that of flint-glass, their sudden and sprightly motions, their general elegance and delicacy, and the appearance of intelligence which they display, neither books nor engravings will give any adequate conception.

On the surface of stagnant ponds may often be seen, especially in spring, a stratum of what looks like a bright green powder. If a small quantity of this be taken up and examined, many curious and beautiful forms will be discovered. A large portion of the substance will probably consist of different species of the genus Euglena, little active creatures, somewhat resembling fishes in shape, of a rich green hue, with a large red eye. Among them we may find what is sometimes called the High-priest's Breastplate (Gonium pectorale), consisting of sixteen oval green masses, disposed regularly in a transparent shell of square form, like emeralds set in a plate of the purest glass. Another brilliant casket of gems is the Pandorina morum (see Fig. 2, in last No.), a species which we have taken in the neighbourhood of London. It is a crystal globe enclosing about thirty globose animals of a rich green hue, from each of which proceeds a long, whip-like proboscis, about as long as the radius of the globe. By means of these filaments it proceeds rather quickly, rolling over in an irregular manner as it goes. Its appearance is very rich and beautiful, particularly when the light is transmitted, as it sometimes is, through the interstices of the animalcules, and gleams through their dark-green bodies. The newly-invented paper-weights, consisting of balls of solid glass, in which are imbedded some beautiful coloured objects, will give an idea of this creature.

Many kinds are interesting from the close resemblance

in form which they display to other well-known objects, animate or inanimate. The Volvox (Fig. 3) rolls majestically through the water, revolving regularly on its axis like an artificial globe; and as it is of greatly superior dimensions to most others of the class, we may compare it to the planet Jupiter surrounded by a host of moons. The Stentors, also, are of comparatively large size, being distinctly visible to the naked eye; these resemble trumpets in form. One beautiful species, hence named Trachelocerca olor, charms the eye by its close resemblance to a swan. It has a plump, rounded body, a slender-pointed tail, and a very long and graceful neck, the motions of which, thrown into arching curves, and protruded in every direction, give the most lively representation of the elegant water-fowl after which it is named. Indeed, in one species of this genus, T. biceps, we may see the living representative of the celebrated bird usually considered to be as scarce as the lost Dodo itself— the swan with two necks.

The genus Amaba has long been celebrated among microscopists, from its power of constantly changing its form, whence it is sometimes called the "Proteus." It consists of a mass of clear, jelly-like matter, with a few granules, two or three of the supposed stomachs, and a contractile bladder. But its peculiarity is, that which we have just mentioned. It is ever altering its outline; and to so great a degree, that not only are no two ever found alike, but the same specimen does not retain the same shape for two successive minutes. Here a point projects and gradually pushes out more and more, while a sinuosity is forming in some other part; one portion is contracting, another enlarging; so that the only idea that can be given of its shape, is by comparing it to the figure of a country upon a map, which is perpetually transformed into that of some other country.

DIRECTIONS FOR STUDY.

113

These are but a few examples of the variety of form which this curious class of animals presents to us: it remains now only to give to those who may be desirous of examining them for themselves a few instructions to aid their researches. A good microscope is, of course, indispensable; if the study is intended to be pursued scientifically, a compound achromatic, with magnifying powers ranging from fifty to five hundred diameters, must be employed; but very much entertainment, and a good idea of many of the forms, may be obtained with an ordinary simple microscope of three powers. The penetrating and defining properties of a microscope are of more importance than mere enlarge

ment.

If we were asked where specimens are to be obtained, we might reply, Almost everywhere, provided water be present: but even in the air they have been lately detected by the eminent Prussian Professor. In ditches and ponds, in the trenches of meadows, in the ruts of highroads, in marshes, in lakes and rivers, in estuaries, and even in the sea, various species may at almost all times be found. Stagnant waters, especially such as are covered with a thick scum, contain some species in immense abundance, but these are generally of the simplest structure: little hollows in boggy ground, especially where a red sediment betokens the presence of oxide of iron, frequently contain species of great rarity and beauty ; but clear standing water, in which the more delicate aquatic plants grow, and particularly when covered with duck-weed, will be found the most productive resource both for number and variety.

The mode of collecting them is very simple. The water must be dipped up in a phial, which may be tied to the end of a walking-stick; a moment's examination of its contents with a pocket lens will determine whether the water is worth carrying home. If no moving particles are seen,

another dip may be taken elsewhere; should this likewise prove valueless, another locality should be sought.

When brought home, a small drop may be taken at random, and placed in what microscopical observers call an aquatic box or live-box; a small fragment of duckweedroot, or the stem of some slender water-plant, put in also, I will aid the search: this should then be examined with a low power at first, the observer proceeding to the use of higher powers for the closer examination of particular specimens.

Should any of our readers who may possess a microscope, or access to one, be disposed to investigate these minims of existence, we shall be disappointed if they do not find objects which will not only please their fancy and inform their understanding, but also give them fresh and unexpected ideas of the ways of Him whose glory is no less displayed in the construction of an animalcule than in the creation of a solar system.

P. H. G.

PAPERS ON THE AIR AND SKY.

OUR ATMOSPHERIC FOOD.

We have now to explain the beautiful arrangement by which the due proportion of oxygen and carbonic acid in the atmosphere is maintained. As has already been stated, animals in breathing diminish the amount of oxygen. This is true in respect to insects, fishes, and the boneless denizens of the earth or sea, as well as in regard to man, birds, and quadrupeds. All these in respiration absorb the vital oxygen into their lungs or gills, and there, uniting with the carbon of which their bodies so largely consist, it forms carbonic acid; and in this close and wonderful alliance, wrought by the power of chemical affinity, it is breathed forth again, and thus returned to the atmosphere. As this process has been going on continuously, and as, during the long ages with which geology makes us acquainted, myriads and myriads of mouths have incessantly been breathing the vital air, we should naturally expect that the oxygen would by this time have been wholly converted into carbonic acid, and in that case man and every other living creature must have perished. But it has been so ordered that the animal kingdom, which owes its own sustenance to the vegetable, should restore to the air what the vegetable itself requires.

At this season many of us have in our houses hyacinths, each of which, a short time ago, was placed a dry bulbous root at the top of a glass filled with water. Since then it has put forth long rootlets, and shot upwards leaves green and large and graceful, and a stalk which we hope soon to see covered with a thick cluster of richly-tinted and fra