Part 2

The population of this microscopic jungle is composed chiefly of single-celled organisms—bacteria, molds, yeasts and protozoa. Total numbers vary enormously—from time to time and place to place—chiefly because of variations in the food supply. Although thousands of species have been identified, the greater part of soil life still remains unknown.

This jungle is a place of the hunter and the hunted—of an incessant and merciless struggle for survival. Invisible plants eat invisible animals and invisible animals eat invisible plants. Plants devour other plants and animals devour other animals.

Giants of this nether world—largely invisible, although the average size is more than a thousand times that of the bacteria—are thread-like white worms from a hundredth to a fifth of an inch long. Relatively they are not very plentiful—less than six million to a cubic foot of soil in most places. In both size and numbers in the earth population, they are like elephants compared to mice. Still they probably are numerically the most abundant of all animals which consist of more than a single cell. In the entire animal kingdom only the protozoa outnumber them.

These creatures are the nematodes, or eel worms. About ten thousand kinds have been described; there are probably as many more unknown to zoologists. Less than a hundred of these varieties cost American farmers and gardeners more than half a billion dollars a year. The rest of those species living in the soil are, so far as known, harmless or even slightly beneficial. Seas and fresh waters are full of other kinds. Still others, some very much larger than the soil organisms, are among the most dangerous parasites of animals and men. The little soil worms, in the opinion of Dr. Geoffrey LaPage of Cambridge University, “must be considered one of the major menaces of our civilization.”

Although always invisible, the activities of these countless billions of organisms underfoot can be measured in various ways. For example, carbon dioxide is constantly escaping from the surface of the ground. This comes from the breathing of the unseen animals and plants. Measurement of the gas outflow gives a rough estimate of how many are present. It shows that the numbers vary greatly from hour to hour.

The soil organisms are relatively immune to heat and cold, flood and drought. Even when a grain of soil has been made absolutely dry in the laboratory and then crushed to a very fine powder, they still remain. If it is placed in a sterile container filled with some fermentable material, a seething mass of microörganisms will appear in a few hours.

Some day this vast, unseen mass of life may be harnessed to the service of man. Only beginnings have been made to achieve this end. Some of the microscopic life forms are definitely helpful to plant life, while others undoubtedly are destructive. One service, without which plant life would be unable to continue very long, is the fixation in the soil of nitrogen from the air. One group of bacteria, the azotobacteria, do this in the laboratory and long have been supposed to be the effective agents in nature. But actual examination of soil samples, say Department of Agriculture specialists, fail to show more than a few thousands of these organisms per gram of soil anywhere, and sometimes none at all can be found in places where it is known that nitrogen fixation is in progress. Some still unknown form of microscopic life must be doing part of the work.

Another unknown organism is an agent partly responsible for breaking down the cellulose of dead plants in the soil. The mold, Aspergillus fumigatus, world-wide in its distribution, does this in the laboratory. Nowhere, however, is it found in nature in sufficient numbers to accomplish the titanic job attributed to it.

The great, invisible jungle, of course, must eat to live. Some organisms demand fresh food and are responsible for root rot in plants. The majority, however, find their sustenance in the enormous mass of dead and dying roots of annual vegetation. Decomposition of annuals is an explosive process involving the development of countless billions of bacteria.

The Self-Perpetuating Sponge

Close to primaeval chaos is the sponge—lowliest of animals. It is an animal without a brain, nervous system, heart, lungs, stomach, muscles or blood. But it has an I Am.

The sponge is in essence an anarchical horde of numberless cells. When the conglomeration is split up as can be done by a technique of squeezing through fine-meshed silk gauze, the cells continue to live as individuals. They crawl about. They take nourishment. But when a few thousands of them are thrown together into a tank of sea water they will conglomerate again, apparently into the same sponge that existed before the disintegration. If sponge animals of two different species are mixed in the tank they will combine into two sponges, duplications of the conglomerations from which they came. If cells of two sponges of the same species are mixed it may be that they will recombine into the two original individuals—but this experiment never has been tried and would be quite difficult to interpret.

The sponge is the simplest, most primitive of metazoa, or many-celled animals. It acts as an individual, although there is apparently no central government, like a brain, controlling the behavior of the millions of individuals constituting the conglomeration. It ranges in size from organisms a fraction of an inch long, by far the most numerous, to masses several feet in diameter. Various species present about all the colors of the rainbow. There are red, scarlet, green, yellow, blue and violet sponges, especially in shallow, tropical waters. Abysmal species tend to be a drab brown.

The living sponge when taken from the water is a slimy, rather repulsive mass which has the general appearance of a piece of raw beef liver perforated with holes and canals. The commercial sponge is merely the skeleton, the supporting framework of the gelatin-like tissues, which is composed of a substance similar in chemical and physical properties to silk, horn and the chitin which forms the shells of insects and crabs. This material is distributed in a fibrous network the pattern of which varies for each species.

The sponge has the most remarkable powers of regeneration of lost parts known in nature. It can regrow its entire body from a small fragment of itself. Thus if a sponge were cut into fine parts and each fragment cemented to a bit of rock each would grow into a complete, normal animal. Also if a sponge is cut or torn away from the sea bottom in such a way that some fragment remains attached this fragment will continue growing.

Living “Stars” in Caves

There is a cathedral-like grotto under the earth whose roof is lit eternally by living stars. It is an enormous labyrinthine chamber cut by a slow-flowing river in the base of a limestone mountain.

Its dome is like the dome of the heavens on a frosty October night. There shine the Big Dipper, the Southern Cross and the Belt of Orion. The Clouds of Magellan are on the southern horizon. There are millions of pale stars grouped in all sorts of astrological configurations. Some are isolated in space. Some are packed in dense galaxies. There are black voids between them, like the curtain of star dust that hides the center of the universe. They are only a few feet overhead. One can reach up and pluck these stars, one by one, out of the sky. Unlike the heavenly bodies, they do not twinkle. They shine steadily in complete motionlessness. Pale and weird, they illumine a realm of eternal night. It is a domain of absolute silence. Around the walls the strange starlight falls on carved figures of winged angels, of human faces laughing and human faces contorted in agony. Each star is a predacious living animal, a flesh-hungry hunter and killer. From it is suspended four or five foot-long strings of shining pearls, so delicate that they shimmer at a human breath.

This star-lit cave near the little city of Te Awaamutu is New Zealand’s greatest curiosity and certainly one of the weirdest and most intriguing spots on earth. The grotto constitutes about a third of the Waitome caverns in the center of Maoriland in the North Island, otherwise rather featureless, water-chiseled rooms in the depths of a mountain with the customary stalagmite and stalactite formations.

The stars are luminous, slimy, dirty-grey worms. They are rarely found anywhere else, and never in very great numbers. This is the one spot on earth ideally adapted to their unbelievably queer life cycle. The worm is the larva of a dainty, dark-winged fly about twice as large as a mosquito, which looks like a miniature daddy longlegs. It has no common name. Scientifically it is classified as Boletophela luminosa, a member of the sub-order of arachenocampa. It falls somewhere between true insects and spiders. There is no relationship between it and any other luminous insect—glow-worm or firefly—anywhere.

The light is a lure for prey to satisfy a voracious appetite. The lovely strings of pearls are modifications of the spider’s web. Nature has provided few other creatures with so intricate and ingenious a food-gathering mechanism as that which enables this *none* to survive in its strange environment Here evolution has schemed in an unique way to ensure the preservation of a species which apparently serves no purpose in the economy of nature except to procreate a beauty spot

The floor of the glow worm grotto is a subterranean branch of a river. The water is warm and almost absolutely motionless, for no breezes penetrate that far under the mountain. Thus it is an almost ideal spot for all sorts of insects to lay their eggs. There is a high probability that the great majority of them will hatch. As the young rise from the water they are attracted by the star-filled heavens overhead. They fly toward them as moths to a lamp. The same is true of many of the small adult insects, some of which are essentially microscopic. Once such an insect is caught on one of the threads it is lost beyond all hope. There it sticks, struggle as it may. The vibrations caused by its struggles attract the attention of the glow worm which quickly winds up the hanging thread. If it is not hungry at the moment it has been observed to play with its victim, drawing in and then letting out the line after the manner of a fisherman. Finally the prey is drawn into the silken sheath and entirely devoured, chitinous shell and all. It is not merely sucked, as is the fashion of the spider or the fly.

The “lamps” apparently are under an extremely delicate nervous control. The strings of pearls suspended loosely in the air must be extraordinarily sensitive to sound waves. The instant they pick up any sound unusual for the cavern the lights automatically go out. Stranger still is the fact that the darkening of all the stars is nearly simultaneous. This, of course, is a safety measure. Any disturbance of the cave routine means danger for the transparent caterpillars. In order to see the star-lit heavens effect the row boat in which one enters the glow worm grotto must be handled by skilled oarsmen so that there is no sound of splashing water. Visitors are warned not even to whisper, lest some string be disturbed and instantaneously transmit the warning to all the others.

Parenthood Among Penguins

One of nature’s miracles is the egg-laying and incubating of the emperor penguin in the darkness of the Antarctic night at temperatures of from 50 to 80 degrees below zero.

Dr. Edward Wilson, surgeon of Sir Robert Falcon Scott’s 1901 south polar expedition, found the first emperor rookery and was able to observe it for several days. His account became one of the classics of science. The big birds hatched their eggs, he found, standing on one foot on the ice and holding them against the breast feathers with the other foot. The task evidently was shared by both males and females. The male would take the egg from the female while she trekked to open water to feed on fish. After a few days, Wilson supposed, she would return while the male went after fish.

In 1956 Dr. Bernard Stonehouse of the Falkland Island Dependencies Administration found another emperor rookery and maintained observations for about ten weeks. The behavior observed was even more of a miracle than Dr. Wilson supposed.

After laying their eggs on the ice, Stonehouse noticed, the females leave immediately for open water and remain there for sixty days, the full period of incubation. Presumably they feed constantly during this period. The males take over entirely at the rookery. For two months the husband remains standing on one foot and holding an egg against his breast with the other—presumably shifting his feet now and then. Through the entire hatching period he eats nothing. When the eggs are about to hatch the mothers return from the sea, tidy up the nursery, and get ready to take over rearing the chicks. Then the males, who have exhausted their reserve of fat, stagger feebly in their own mass migration to open water to rebuild their reserves on fish. By the time of the Antarctic sunrise in October the chicks are about ready to fend for themselves.