Marvels of the Microscope.

New Zealand Illustrated Magazine, Volume VII, Issue 5, 1 February 1903, Page 353

Marvels of the Microscope.

By HENRY ALLISON,

THE world is to each of us just what we have eyes to see in it, for what our senses do not reveal is, to a large extent, a terra incognita. Yet our senses are very imperfect, and very limited in their scope. We know that the ear, with all its marvellous range of sensitiveness, from the low chirping of insects at our feet to the crash of thunder overhead — from the low musical

note of perhaps sixteen vibrations per second to the very highest which either instrument or voice can produce, is after all very limited in range, and, indeed, stone deaf to sounds produced by more than thirty- eight thousand vibrations per second. And is there not room for whole worlds of sound beyond ? So is it| with the eye ; though here we have more successfully extended its range in one direction by means of the tele-

* See footnote, page 357,

Vol. VII.— No. 5.— 53.

scope and photographic plate, penetrating the depths of star- strewn space, in the other by means of the microscope, pushing our quest into the no less wonderful region of the minute. And if in the one direction we find our ideas of the universe enlarged and are staggered at its vastness, so in the other we shall see abundant evidence of the lavish beauty and perfection characteristic of many of the most minute ob-

jects which, more truly than alpine flowers, seem to waste their sweetness on the desert air.

There is, too, a peculiar pleasure in tracing things back from the complex to the simple, from the highly-organised animal to those small structureless beings, like the amoeba, without parts or passions, which, through tens, perhaps hundreds of thousands of years, while others have undergone remarkable modification and development, have

form and yet appeared to be animal, and in many of its early forms is a deceiver still ! Among such I may mention diatoms, which at one time were thought to be animals, owing to the fact that they appear to have the power of voluntary movement, and certainly while watching their gliding- motions under the microscope it is hard to think otherwise ; but on other and more conclusive grounds they are now generally considered to belong to the vegetable kingdom. However, apart fiom controversy, they have a special interest for the microseopist in tie facts of their minuteness, their general distribu-

remained as far as we can tell just what they are to-day. But it is just when we come to the simpler forms of life that we find, not only the' disappearance of organic distinctions, but the obscurity, if not obliteration, of those broader marks which generally serve to divide the animal from the vegetable kingdom, for the microscope reveals to us, not only animal-like plants, but plant-like animals. Life seems, indeed, to have begun its course in paradox, for it started in plant

tion, their singular beauty, and the fineness and delicacy of the tracery which mark them all. They are of almost all conceivable shapes, but considering their minuteness, it is a perfect marvel thai; they should be so: symmetriqal in form, aoid yet how common are they ! They are to be found in every part of the world wherever tliere is water, whether fresh or salt. In the sea they can alwrays be got from soundings, and on. the land from almost every pond and stream. Of course like other plants different species are found in different locali-

ties, and a knowledge of their distribution may sometimes have practical bearings beyond the power of the unsophisticated to appreciate, or even to conceive. Who would have thought that the discovery of

certain diatoms in the mud found on ice- floes on the east coast of Greenland could have been an important factor in the evidence whicjh led Nan sen to undertake his polar expedition ? Yet it was just because he was satisfied that those diatoms must have drifted from the shores of Siberia across the North Pole that he was led to think of the possibility of building a vessel that would drift in the same way if it could only be built strong enough to survive the deadly grip of the ice on the polar sea, which he concluded must exist, though as yet unexplored.

Owing to the indestructible silicious envelope which is the distinguishing feature of diatoms, they are largely found in a fossil state. There are enormous deposits of diatomacious earth in various parts <>f the world, as in the neighbourhood of the Mediterranean, where the diatomacious strata are found to alternate with chalk formation, consisting chiefly of minute shells.

There are also large deposits of diatomacious earth at Oran, in Algeria ; at Richmond, in Virginia, where the stratum is eighteen feet in thickness, underlying the whole city, and extending beyond to unknown limits ; and also in Norway and Sweden, where in times of scarcity the material has been used to mix with floiur in making bread, and where it is known as mountain flour ! Whether this is owing to any actual nutritive value due to the presence of any organic matter in the deposit, or whether it simply adds to the nutritive value of the flour by causing it to be more completely digested, in much the same way as pebbles and hits of glass, which diatoms really are, in the gizzards of our feathered friends, we do not know, though we can quite understand it may be filling ! However this may be it has other and less doubtful uses, being on account of its absorbent property specially valuable in the manufacture! of dynamite, and on account of the exceedingly fine scratches it can make it makes an excellent polishing powder.

The minuteness of diatoms is such that few comparatively can have any idea. It is said that in the deposit known as Billin slate one

It is by no means easy to photograph diatoms as they appear under the microscope, especially with high powers, and it requires these to reveal their beauty, and the marvellous minuteness of their markings. How fine is the tracery, how close are the lines or striae, as they are called, may be realized in some degree when we remember that they vary according to different observers from about twenty in one species to about 130 in another, in each one-thousandth of an inch of space !

And though we may examine with minuteness and care, it is hard to say when we have, with the best microscope, fully revealed the tracery. With one power we may

cubic inch contains about forty thousand millions of these wonderful forms.

There is a mud. bank four hundred miles long amd one hundred and twenty miles broad on the coast of Victoria Land wholly composed of diatoms. And there is in our own land a deposit of considerable extent in the neighbourhood of Oamaru, which Dr. C. J. de Latour, of that town, has done much to make known, and describes in a paper which may be found in volume 21, of the Transactions of the New Zealand Institute.

notice that the surface is covered with fine dots like the milling on a watch-case ; with another these dots will be resolved into hexagonal apertures honeycombing the whole surface ; then what at first appeared to be the several boundary lines of each hexagon are seen to be broken up into round dots ; and finally in some cases, while we are admiring the beautiful radiations and more minute markings of a disc, we become aware, by the careful use of the fine adjustment, that what we have observed has only

been the deeper and coarser markings, and that over all is spread a net of the finest gossamer, yet so beautifully clear that we see every mesh and every thread ! It is difficult to shew all this in book illustrations, but I have taken a number of photographs which I hope will give some idea of the variety and beauty of these objects. Let me say a few words in explanation so that the reader, unaccustomed to such objects, may know what he is looking at. Fig. 1* is a strewn slide of diatoms. They are magnified sixty

Fig*. 2 is not a strewn, but a selected slide of diatoms obtained from infusorial earth similar to that obtained at Oamaru, and is magnified to tjie same extent — say, a man to a Cathedral spire and a-hall They are shown on a dark ground, and the light is thrown across their surface. It will be noticed that they are very uneven, and that owing to some of them, chiefly the triangular sort, having been turned over with their hollow sides uppermost, the light has only

diameters, or about wliat a small man would be if lie were magnified to more than three hundred feet high, or half as higli again as the Christchurch Cathedral spire, and, of course, stout in proportion ! This is quite a low degree of magnification, but it means a good deal.

*In reproducing the author's photos it was necessary to reduce them by one fourth. This the reader must tear in mind and allow for, as the statements of the number of diameters they are magnified refer to the original photographs. It was judged best not to alter the author's figures to suit the reduction.

caught their edges, and shown them in outline. There is considerable variety of form, though for the most part they are circular or discoid, and though very regular they are too small in this photo to shew

much of the detail of their structure.

Fig. 3 shows a few diatoms on a similar slide more highly magnified — about 120 diameters, or three Cathedral spires, and it will be noticed that the detail is more apparent.

Fig. 4 shows a few diatoms still more highly magnified, and the detail still more apparent, but the triangular valve, or frustule, is only seen in outline. Let us now take another part of the same slide, and look at it with a higher power and a different arrangement of the light by which it will pass through the object, and what do we see ? More detail, and especially that the triangular form, which before was all but invisible, is now seen to be made up of hexagonal markings, as in Fig. 5, and if we employ a still stronger power, as in Fig. 6 we see those hexagons more distinctly still. And here I may remark (though it is not apparent in the

illustration) that a further degree of magnification t*hows that the sides of the hexagons are not lines, but dots.

Figs. 7 and 8 are not remarkable for beauty, but they give an idea of the way in which the microscope reveals unknown wonders, fot the former shows several diatoms which to the naked eye would be invisible except as iridescent dust in a strong light. Here they are magnified 60 diameters, or a Cathedral spire and a-half, and yet they shew nothing more than the general form — something like a double-pointed sword-blade.

Fig. 8 shows a part only of one of those sword-blades, near the point, magnified not sixty, but twelve hundred diameters, or what a man would be if -he were more than half as high as Mount Cook— the towering monarch of our Southern Alps.

Fig 1 . 9. — I close my illustrations of diatoms with a beautiful disc called heliopelta or sun-shield. Another class of beautiful objects are the polycystina, which, like dia-

Toms, are minute silicious shells of wonderful variety of form, but, unlike them, are representative, not of the vegetable, but of the animal kingdom, in which they are, notwithstanding the beauty of their

shells , allied to the lowest and simplest forms — those which consist of structureless protoplasm, the primary form of living matter which Professor Huxley called " the physical basis of life ; " a form which we ever find associated with life, and

Fig 12 is a set slide of polycystina and diatoms, which I found rather difficult to photograph in a satisfactory manner, but seen through the microscope it forms a very beautiful object. These forms appear to be very widely distributed, having been found in the North and in the Antarctic Seas, and there are extensive fossil deposits in Barbadoes and other places.

Like the polycystina, foraminifera, or very minute carbonaceous shells, are relics of am early and low type of animal, such as the amoeba — mere structureless protoplasm — but it is curious that both forms should be mainly, if not wholly, distinguishable by their shells, and ye^ that these shouM exist in ; such variety as to enable the naturalist to distinguish many separate species. The difference in the protecting shell surely indicates a difference in the animal, and it may be that the superficial distinctions by means of "which so many species have been determined really corres-

which some therefore prefer to call bioplasm. It is the same thing essentially, whether we find it in connection with the lowest weed, or the lordliest pine ; in the lowest fungus or the loveliest flower ; whether in plant or animal ; whether in such forms as bacteria and amoebae ; the worm beneath our feet, or the highest types of human beauty ! But, although consisting of mere structureless protoplasm, these animals have the faculty of extending fine threads of their substance through the tiny apertures in their shells, and thus securing the food which they are able to digest, although such a commonplace organ as a stomach has no part in their constitution.

Fig. 10 shows a strewn slide of these forms, of which there are some hundreds of varieties.

pond to deeper- seated differences which bave not. yet been discovered, and which may for ever evade our search. These shells may generally be obtained from soundings, or on sandy beaches where they exist in abundance in the white ridges left

Fig. 11 shows four forms more highly magnified, two of which represent the living animal with the fine threads of its substance radiating from the shell, the other two only showing the silicious shell.

by the receding waves. How many millions of these delicate shells are unwittingly trodden beneath our feet during a stroll by the sea, each one being to us no more than a " Speck of sand, Lost on the long beach where the tides flow free, And no one metes ifc in his hollow hand, Or cares to ponder it how small it be ! At ebb it lies forgotten on the land, And at full tide forgotten in the sea." Even less do we think of the liv-

ing creatures that occupied the shells, eacli now void of " the little living will " that made it stir on the shore ; and we are untouched by the poet's imagination which made him wonder whether in life the tinycreature " stood at the door of his house in a rainbow frill/ or pushed when he was uncurled a " golden foot or a fairy horn through his dim water world."

Fig, 13 will give some idea of the variety and beauty of forms to be found in these minute carbonaceous shells, while fig. 14 shows a number

that were picked out of the fine sand on the Forty-mile Beach, Pegasus Bay, Canterbury. Shells such as these are the chief constituents of chalk and limestone, and so we may understand how large a .part of the earth's crust is made up

of the remains of once living forms, much more ancient than man, and likely to last when he and all his works (as far as this life is concerned) have perished and left not a rack behind. Even in a living state it is curious to, think •' how capable they are, considering their delicate structure, to withstand the violent shocks of " cataract seas " that surge along the rockiest coast, when no vessel — not even the strongest ironclad — can escape destruction.

But besides these microscopic shells there are many other interesting objects to be collected at the seaside, among which may be mentioned those plant-like animals which the common observer mistakes for seaweed ; and very interesting it is to get these in a living 1 state and watch their movements under the microscope. Fig. 15 shows an object of this class which all will agree looks more like a plant than, an animal, and yet every apparent bud or floret is a tiny mouth with ten-

tacles to seize its food, and when actively engaged in -this way they look like living plants instead of the zo ophites they really are. These zoophites vary in size from the microscopic form here shown to the huge tree-like Gorgonias and the large Madrepores and corals of the tropical seas. Very interesting objects also are the tongues or palates of many shell fish, such as the periwinkle, the limpet and the whelk. The latter, I understand, is largely consumed in London, and seems to have long been a prominent article of fish diet, for Dr. Johnson tells us that no less than 8,000 whelks were dressed as side dishes for some feast in r connection with the enthronization of William Warrham as Archbishop of Canterbury in 1504 — a fact which is hardly suggestive of asceticism in the clergy of those days !

Fig. 16 shows part of a limpet's tongue, which is many times the length of its body, and very formidable, with its double row of claw-

like teeth ; surely exceeding in both respects all that one has ever heard of those of the most lingual of our kind !

Fig. 17 shows part of a totally different tongue belonging to another gasteropod with a horny slate-coloured back which may often be found sticking to its native rock side by side with the limpet.

Similar objects may be found nearer home in the palates of slugs and garden snails, whose destructiveness is sufficiently accounted for by the twenty-six thousand teeth with which the palate of a single specimen of the latter is provided ! JSTor need one go far from home to find much to interest in the insect life about him which will bear, and will reward the minutest examination.

For instance, the tongue of a bee shown in fig. 18 gives us some idea of the means by which that useful insect extracts the honey from the flower ; while fig. 19, "showing the interior of the gizzard of a grasshopper, brings home to us the fact that the smallest insects, no less than the larger animals, have an organic structure perfectly adapted to their needs.

Look also at the powerful mandibles with which insects are unabled to seize their prey, as exemplified in Fig. 20, which shows part of the head of a female saw-fly.

This insect has- also fine cutting instruments at the other extremity of its body in the shape of a pair of sharp-pointed lancets, and a pair of saws which, are reially half saws and half blades, the peculiar construction of which, one would think, must have suggested the American bread-knife.

These are clearly seen in Fig. 21, where also will be noticed the feelers which so much resemble a pair of ass's ears ! The knives and saws are used to cut into the bad?: of a tree, which often results in the formation of warty excrescences that in the case of the oak are known as oak apples, from which tannin is made.

I close these few specimens of insect parts with an object — Fig. '22, which at first sight seems to belongspecially to this country in that it resembles part of a Maori lady's dress made of flax, but which is really only a portion of a moth's wing, closely covered with scales,. which are better seen when detached from the wing.

I now pass on to one or two vegetable specimens.

Fig, 23 is part of a slide of potato starch, as seen with polarized light, which, it will be noticed, has the effect of marking each grain

with dark cross lines. Without the use of the polariscope the grains are too pale to be clearly discernible. The starch grains of other plants are of quite different form ; and thus we find that plants differ in the minutest details of their structure, a fact which is also well illustrated in the variety and character of the pollen grains of different plants as shown in Figs. 24 and 25, the former being from a lily bloom, and the latter from the geranium. This striking difference in the minutiae of plants finds a parallel in. the animal kingdom in the distinctive character, for instance, of the blood corpuscles of

different animals, from the small round human corpuscle to the large oval corpuscle of the frog.

I hope I have said enough to show that while the microscope is a valuable aid to scientific study, it may also be made a means of much innocent recreation. It affords, too, a means of closer contact with Nature, and a more accurate knowledge, not only of the physical constitution of things, but of the living world in which we have so conspicuous a place. And while providing a refuge from the sordid and mean in human life it, can hardly fail to elevate and enlarge our ideas of the universe.