Transcriber’s Notes
Obvious typographical errors have been silently corrected. Variations
in hyphenation and accents have been standardised but all other spelling and
punctuation remains unchanged.
Italics are represented thus _italic_.
THE STRANGEST THINGS IN THE WORLD
THE STRANGEST THINGS
IN THE WORLD
_A Book About Extraordinary
Manifestations of Nature_
THOMAS R. HENRY
Public Affairs Press, Washington, D. C.
Copyright, 1958, by Public Affairs Press
419 New Jersey Avenue, S. E., Washington 3, D. C.
Printed in the United States of America
Library of Congress Catalog Card No. 58-10881
INTRODUCTION
The challenges of Nature’s paradoxes have been sharp spurs to man’s
search for knowledge since the start of science.
Fortunately the number of these paradoxes is infinite, and so the
quests are endless. Man never will know a wonderless world. In the
phenomena of life especially we have come only to the zone of morning
twilight. The bright day of understanding is ahead. As its hours pass
we can expect a constant succession of new paradoxes, new spurs to
further advances.
Man would be in a sad situation were it otherwise. For the bright light
of noon and afternoon inevitably precedes sunset and darkness and sleep.
This book is a compendium of some of Nature’s curiosities and
contradictions in the field of life and as such it well may awaken that
wonder which, as somebody has said, is the beginning of knowledge.
The author is one of the world’s best-known and most respected science
writers. This book is a personal and unique distillation of the wisdom
he has developed in a lifetime of dealing with man’s effort to resolve
the paradoxes of nature.
LEONARD CARMICHAEL
_Secretary of the
Smithsonian Institution_
PREFACE
Life has invaded nearly every crack and crevasse of the world during
the billion years since it left its first traces on this planet. It
has adjusted itself to all extremes of living, from nearly airless
mountaintops five miles high to lightless floors of oceans five miles
deep. It has found abodes in boiling hot springs and in the everlasting
ice of Antarctic peaks. It very likely has invaded the cold, red
deserts of Mars. Everywhere it has succeeded in altering the garments
it wears to meet the stresses it has experienced.
It has achieved semi-infinite variety. There are approximately a
quarter million species of plants now known in the world. Most abundant
and varied life is that of the insects who may be on their way to
displace man and his fellow mammals as lords of the earth. A rough
estimate of the number of species identified up to now is 800,000.
Several thousand hitherto unknown are described each year. Of mammals,
including man, there may be as many as 14,000 distinct species and
geographic races extant. About 8,500 species of birds are catalogued.
Sub-species and geographic races increase this number to about 30,000.
Known fishes number 40,000 species and sub-species.
Still, naturalists say, there are great mansions of life almost unknown
to man. The collections of the Smithsonian Institution in Washington
grow at the rate of about a million specimens a year, always including
forms hitherto uncatalogued. Much of the material in the following
pages is based on Smithsonian information, although other sources and
personal observations have been liberally drawn upon.
The Smithsonian specimens, as well as those in other museums and
collections throughout the world, are types. Once they were individuals
with passions, fears, hungers, perhaps some dim wonderings and
questionings. The type is the eternal reality. The individual is the
brief-lived example of this reality, the flame of a candle fluttering
in a windy moment.
I have brought together in these pages notes about the most
extraordinary manifestations of nature that have come to my attention
in the course of thirty years as a science reporter. Each example is,
of course, based upon a distinctly individual expression of nature, but
all are very much interrelated in this truly amazing world of ours.
THOMAS R. HENRY
_Washington, D. C._
_The Invisible Underground Jungle_
There may be as many as twenty-five million invisible plants and
animals in a gram of soil about the size of a grain of sand. It would
take a thousand such grains to make a marble.
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.
Standing from three to four feet high and looking and acting
deceptively like a human being, the emperor penguin undoubtedly is one
of the most remarkable birds in existence. It presumably is confined to
the Ross Sea side of the Antarctic continent. The bird—actually it is
about two-thirds feathers—remains an evolutionary enigma. Theories have
been advanced that it is the last surviving member of the fauna of the
Antarctic continent about fifty million years ago when the shorelines
were free of ice. It certainly is off any known road of evolution.
_The Strategy of Warrior Ants_
Total war is the way of life for army ants. The picturesque,
devastating drives of their vast hordes have nothing whatever to do
with exhaustion of food or anything of the sort. The wars come in fixed
cycles, regardless of supplies.
There are two species of these ants on Barro Colorado Island in the
Panama Canal Zone. Each species has approximately 50 colonies and each
colony consists of from a few hundred thousands to more than a million
individuals. At the head of each colony is a single queen who lays all
the eggs.
There is a new lot of larvae every 33 days—all workers or incompletely
developed females. Development is restricted by the amount of food
available. Since each brood consists of about 60,000 individuals, a
colony theoretically might reach titanic proportions. However, it does
little more than maintain its population. The death rate of soldier
ants, in constant combat, is very heavy.
Once each year, at the start of the dry season in the tropics, a colony
queen produces a sexual brood of about 3,000 males and six queens. The
rest of the 60,000 eggs laid at this time are incapable of hatching and
are fed to the new-born sexed individuals. They apparently have some of
the nutritious properties of the royal jelly fed to queen bees.
This sexual brood is produced in what has been called a statory period
in which the army maintains a fixed bivouac for about three weeks.
During this time the new queens develop and around at least one of them
a new group of workers, about half the whole, tends to congregate. A
strange antagonism seems to develop between the old and new groups.
Eventually the colony divides in two and each half starts moving in
opposite directions. The other new queens are lost in the shuffle.
Most of the newly developed males are ‘excess baggage.’ During the
winged, or mating, stage they fly into the forest where the great
majority of them are eaten by birds. When the surviving ants light on a
tree, on the ground or on some other object, the wings drop off. Then
they apparently wander about aimlessly until they come to an army ant
trail which they recognize by the odor and follow it until they come to
the colony which has made it. If this happens to be a colony of their
own relatives, they probably are killed by the workers. If it happens
to be an entirely foreign colony, they may be accepted. This apparently
is one of nature’s mechanisms for intruding new genes into a strain.
The raiding activities of a colony are carried out during the day from
a central headquarters. During the daytime raiding individuals return
to the colony from their forays and by dusk all have returned. At
night the bivouac is changed, the whole colony moving forward along
one of the trails blazed by the raiders. A new headquarters is thus
established. A colony moves from six to seven hours before striking a
new bivouac. Not infrequently, if no promising site is found, it moves
from dusk to dawn.
This would seem like constant activity, too strenuous even for the
constitution of an army ant. Actually the individual workers probably
get plenty of rest. Each colony is divided into two units—the raiders
and those that constitute the structural unit. The walls of the
“headquarters” are made up of the bodies of the latter. These “living
brick” do nothing throughout the day. They may be asleep. When the
raiders return at dusk the structural unit breaks up and the members
lead the migration to a new bivouac. The erstwhile raiders follow
leisurely in the rear and in turn become the structural unit when a
stopping place is selected.
When to rest? When to raid? There apparently is an irresistible war
rhythm, like the rhythm of the tides, in the basic constitution of
these ants. Some have postulated the same sort of thing, on a lesser
scale, in man who goes to war every so often but camouflages the war
tide with economic or political explanations.
These ants are remarkable not only as warriors but as architects.
They build complex, air-conditioned, hanging houses out of thousands
of their own suspended bodies. Within these structures the queen is
sheltered, eggs laid, young hatched and reared. Much of the time the
“houses” are constructed anew each night.
This home-building behavior is unique in nature, as Dr. T. C. Schneirla
of the American Museum of Natural History has pointed out:
“Without any active excavating and without any manipulating of fallen
materials, colonies of these species form a domicile with their own
bodies. A typical bivouac is a cylindrical mass hanging from the
underside of some projecting surface to the ground. In addition to the
sides or under-surface of logs, other typical places are the spaces
between gut tressed tree roots, masses of brush, undercut banks of
stream beds, or the overhanging edge of a rock.
“The characteristic ability to cluster their bodies, as well as
the manner of clustering, depends first of all upon an anatomical
characteristic—the opposed, recurved hooks on the terminal tarsal
segments of the workers’ legs. The first ants to settle in a new place
catch into a rough or soft surface by means of the tarsal hooks, or
rather are pushed into this anchored position as newcomers run upon
them as they stand and stretch them out in a hanging position. In fact,
the hooks are really anchored by the added weight of others that have
crawled down over the body of the first ant, fixing it in place and
soon immobilizing it.
“In the nomadic phase a new bivouac is formed at the end of each day of
raiding. In the advanced and most complicated stages of raiding in the
afternoon, caches of booty tend to be formed at each busy junction of
raiding trails, increasing in size as more and more ants are knocked
around and forced out of traffic. As darkness comes and raiding ceases
such clusters grow. Several hanging clusters start from elevated
ceilings. As each new cluster begins, the initial slender hanging
threads may become ropes which extend to the ground. As the ropes
continue to grow they are joined together into a single columnar mass.
“At first this mass is small in diameter, but as more and more ants
pour into it the wall spreads outwards from the center and so a
symmetrical cylinder results.”
In the tropical environment of the army ants some sort of air
conditioning is necessary for comfortable living—perhaps, with this
particular species, for any living at all. It has been well developed
during the more than 50 million years the insects have been on earth.
Says Dr. Schneirla:
“The interior of the bivouac, where the brood is sheltered and the
single colony queen rests, offers an impressively stable environment to
these more susceptible members of the community as well as a central
resting place for the worker population. The hanging cluster traps
a cubic area for atmosphere which does not reach the extremes of
temperature and dryness attained by the general forest environment,
but in general is somewhat warmer and more humid at night and somewhat
cooler and dryer during the day.
“This result is achieved mainly as a result of worker behavior. Workers
cluster more closely together at night in reaction to the lower
temperature of the forest at the time. The bivouac walls become tighter
and thus better conserve heat produced internally by the brood.
“Conversely, after dawn, when increasing light excites growing numbers
of ants to leave the bivouac, as the raid grows, this wall thins out,
usually develops small apertures, and is undercut at the bottom. The
effect is to increase internal air circulation as well as to cool the
atmosphere of the interior through evaporation, so that the internal
temperature of the bivouac does not rise to the height reached at
midday in the environs.
“The incubation properties of the bivouac represent an important factor
in echelon life, for with less regular atmospheric conditions in the
nest the stages of brood development could not have their typical
regularity in timing.”
_Uganda’s Miniature Dinosaur_
A grotesque creature abundant in the Kishasha Valley of Uganda is
the three-horned chameleon. It grows to a length exceeding twelve
inches and the males look like miniature versions of the ancient
dinosaur monster, triceratops. Three curious horns, an inch to an
inch-and-a-half in length, protrude from the nose and between the eyes
of males.
These are extremely pugnacious animals; they use their horns in fights
to the finish. At times the contests develop into prolonged pushing
matches with the horns interlocked, but a really vigorous fighter can
dispose of an adversary in a few minutes. African natives are terrified
of these demoniacal-looking little animals.
_The Strange Ways of Spiders_
“With other classes of animals, and even with plants, man feels a
certain kinship—but spiders are not of his world. Their strange
habits, ethics and psychology seem to belong to some other planet
where conditions are more monstrous, more active, more insane,
more atrocious, more infernal than on our own. Frightfulness and
ruthlessness appear a part of their nature and we stand appalled when
it dawns upon us that they are far better armed and equipped for their
life work than we for ours.”
Thus writes Dr. W. E. Stafford, U. S. Department of Agriculture
naturalist. There probably is quite general agreement with his
sentiments. One chills at the picture of some other planet where
spiders and their kin who have evolved minds equal to that of humans
are the dominant animals.
Once gigantic spider-like creatures ruled this world. They were as
big as lions or gorillas. Their realm was the earth of the Silurian
geological era of 350,000,000 years ago—a time of warm, quiet seas
which, especially in the northern hemisphere, covered large areas
that now are dry land. These creatures were the euripterids, or sea
scorpions, whose nearest extant relatives are the horseshoe crabs with
sky-blue blood that are common along the Atlantic coast of the United
States, and the venom-fanged land scorpions. They exceeded in size all
living invertebrate animals.
Many were five to six feet long; one was nine feet long. Presumably
they were free-swimming, predacious creatures with massive, crushing
jaws. Their chief prey, it is believed, were the much smaller,
crab-like trilobites with whom they shared a common ancestry. These
were shelled animals the imprints of whose hard shells in mud (which
later became rock) are among the most ancient records of animal life on
this planet. The trilobites were creatures who crawled on shallow sea
bottom. Their only defense was to roll themselves in balls. They appear
to have been the dominant form of life for at least 100,000,000 years.
They continued a precarious existence after the evolution of the great
pseudo-spiders, but were well on their way to extinction. The massive
jaws of the euripterids could crush their thin shells with ease. The
dominance of these new masters of the sea would be challenged only by
the gigantic mollusks, but for many millenia they appear to have held
their own against these frightful monsters.
Their decline had started by the end of the Silurian period and
they were extinct in another hundred million years. The reason for
their decline is unknown, but perhaps it was related to some decided
change in temperature and distribution of the waters. Remarkably
well preserved remains of the monsters have been found imbedded in
limestone on Oesel Island, in the Baltic. During the Silurian era
life was just starting to emigrate from the oceans and establish a
precarious foothold on land. Among the earliest land fossils are those
of small scorpions, distantly related to the erstwhile master race. The
euripterids themselves, however, never tried to leave the sea.
_Worms With a Thousand Eyes_
There are worms with a thousand eyes. They are, for the most part,
animals of the dank, dark floors of tropical rain forests.
They are narrow, brilliantly colored ribbons of slimy skin which glide
at a speed of about six feet an hour over damp moss and leaves in the
everlasting twilight. When alarmed they can break up instantly into
scores of “blobs of slime” and in a few hours each piece will become a
complete new worm. One of them can eat five-sixths of its own body and
entirely recover.
These fantastic creatures are the terricola or land planarians—lowliest
of worms and one of the lowliest forms of animal life. Only the
microscopic protozoa, the slime moulds, the sponges, jellyfish, and
corals are more primitive.
They range from fractions of an inch to nearly a foot in length. They
are hunters and scavengers. Nearly all are creatures of darkness
and dim light—survivors of the haunted dawn of life on earth. They
probably are quite close to the ancestral form of all worms. All are
free-living animals, although related closely to the degenerate flukes
and cestodes, which are internal parasites of man and other animals.
They belong to an enormous clan. There are several hundred known
species and perhaps as many more still unknown. These worms are found
over most of the world but most abundantly in the damp tropical and
sub-tropical rain forests. They are seldom seen in nature although they
are fairly well-known in experimental biology classes, for which they
are purchased from dealers. Australia has about sixty species. America
may have many more, most of which remain undescribed. One would be
likely to come upon them only by accident.
Among these land planarians are some of the most fantastic creatures
of the animal kingdom. They have been described as “gliding strips of
skin.” The family includes some of the most brilliantly colored of all
living things. They probably represent the earliest traces of eyes and
brains in the world.
The “eyes” of the terricola are black dots arranged in two parallel
rows along both sides of the back. Some species are two-eyed. Many
varieties are eyeless. Hundred-eyed worms are quite common. The black
dots are light-sensitive. Presumably they represent the beginning
of vision. By means of them the worms can distinguish between light
and darkness. They also tell the direction from which light comes.
Actually, however, planarians without eyes have the same ability, but
they are slower to react. This is demonstrably true for fresh-water
forms. For most of the land forms at least exposure to strong sunlight
would be fatal.
Each of the eye dots has a nerve connection with the brain. It is quite
unlikely, however, that the animals actually see anything, in the sense
of discriminating specific objects in their surroundings. In a few
species, however, from two to four of these black dots nearest to the
brain seem somewhat more complicated than the others. As the faculty
of vision evolves among animals these will become actual eyes and all
the other light-sensitive spots will be discarded. In most planarians,
however, the number of eyes increases with the age of the animal.
Nearly all are predatory meat eaters. They are both hunters and
scavengers. Some pursue, kill, and eat living animals, such as
earthworms and small mollusks, as big as themselves. They apparently
are able to locate their victims at some distances by an already
evolved sense of smell. One blind Brazilian species is said to pursue
earthworms into their burrows several feet underground.
When the victim is overtaken the planarian first enfolds it in its
sheetlike, slimy body. Then from its mouth, always on the underside
of the body near the middle instead of at the head end, it projects
its pharynx, a muscular tube which is part of the digestive system.
From this is exuded a substance of some sort which slowly liquifies
the flesh. Then the liquid is sucked into the body through the mouth.
Digestion then is completed within the digestive tract by special cells
which engulf minute particles in the same way as they are engulfed
and digested by one-celled animals, the amoeba. The nature of the
dissolving material exuded from the pharynx is unknown. It is believed,
however, to contain a mixture of enzymes such as those found in the
intestinal tracts of higher animals.
Planarians may attack healthy animals and overpower them in spite of
their violent struggles against being enfolded in the slimy skin. They
are, however, particularly attracted to the sick and injured which they
apparently locate by smell. Most of these worms are devourers of dead
flesh. A common method of capturing fresh-water forms is to leave a
bit of liver or other raw meat exposed in an area they are likely to
frequent. Both water and probably land forms will congregate around it.
Then the collector is likely to have a difficult job. As the naturalist
William Beebe says about one large Venezuelan rain forest species:
“To pry one loose and put it in a bottle is like pouring thick, cold
molasses mixed with thick glue.”
To their activities as scavengers of the forest floor these ancient
worms owe their place in the economy of nature. They normally feed
several times a week. When kept without food, however, they can
stay alive for months. They gradually shrink in size as they digest
themselves. The internal organs are reduced little by little as they
are absorbed for food. The first to disappear are the reproductive
organs. Most planarians have both male and female reproductive systems.
Then come the muscles of the body wall. Never however, do the worms
eat their own brains or nervous systems, although the brain may be
reduced greatly in size. The I Am of the worm can devour its vestments
of protoplasm; it cannot eat itself. When food is available again
the organs are regenerated and return to normal size. Instances are
recorded where planarians have reduced their length from slightly more
than an inch to less than a seventh of an inch in six months.
Closely related to this practice of “eating themselves” is the
remarkable ability of the terricolae to break themselves into small
fragments each of which will regenerate into a complete worm. This
capacity probably has been a major factor in their survival through the
aeons since multi-celled life began on earth. What might seem to be
their outstanding weakness in the constant struggle for survival—their
soft bodies and extremely loose organization—has become their major
strength. A planarian can lose at least nine-tenths of its body
and still preserve its individual existence. This self-shattering
phenomenon constitutes the worm’s chief defense in emergencies. It
comes into play when any danger threatens. The regenerating ability,
especially of fresh-water forms, differs considerably in degree from
species to species. Some are unable to regenerate a “brain” out of
fragments of the rear part of the body. Complete in every other
respect, the remade worms seem incapable of the typical gliding
movements of the race. They remain quiet most of the time but can
move forward slowly. A tendency to move in circles has been observed.
Fragments from the head section, however, quickly become complete
animals.
All planarians actually have heads and a “brain,” of sorts. The latter
consists of two minute bits of nerve tissue just behind the front of
the body, oval-shaped and enclosed in a tough capsule. It serves as
a center for nerve fibers extending throughout the animal. Here are
coordinated the stimuli received from light and heat, and possibly
those from odors and sound. When the worm goes forward, it moves its
head constantly from side to side. Presumably it is exploring the way
ahead for food and danger.
A terrestrial flat worm’s progress is described as “gliding,” rather
than creeping or crawling. The outer surface of the body has many
glands from which is exuded a mucus over which it slides. This mucus
quickly hardens. From it can be made slender threads by which the worm,
like a spider, can lower itself safely from projections. Because of the
glue-like quality of the secretion it is able to climb perpendicular
surfaces. From the hardened mucous, sometimes mixed with sand, it can
make for itself a shell into which it can retire for months at a time.
_Queer Fish, But Definitely_
There are more than 40,000 kinds of fish in the world. Their habitats
range from the profoundest depths of the seas to cold lakes and brooks
on mountain timberlines. They show a bewildering diversity in their
ways of life.
The smallest of fish is a Philippine goby, less than a third of an inch
long and weighing a fraction of an ounce. The largest is the whale
shark, found in all warm seas. Some individuals exceed twenty tons.
Some fish burrow in the mud, some swim, some walk, some fly, some
breathe air. Some are timid, some bold and bloodthirsty. Some are
placid, some easily irritated.
Some are highly venomous. One, found in Australian waters, weighs
nearly half a ton and has poison barbs a foot long. Some of the
deadliest are among the most beautifully colored.
Freshwater fish can sometimes be cut out of cakes of ice in which they
have been frozen for months at a time, and completely revive. Actually
the fish themselves are not frozen. The freezing point of their blood
is slightly lower than that of water. They were merely “hibernating”.
This may happen frequently in nature.
Some fish seem well on their way to becoming land animals. They can
breathe in air better than in water.
Surgeon fish are so-called because of a sharp spine on the tail which
can produce a cut like that made by a surgeon’s scalpel.
Parrot fish have beaks like parrots with which they scour algae from
the coral reefs for food.
Goat fish have two growths under the mouth which look like the chin
whiskers of goats.
Porcupine fish, whose skins are covered with sharp spines and which can
fill their sac-like bodies with water or inflate them with air until
they form a ball about twice their normal size. When the bodies are
puffed up the sharp spines are erected to protect the creatures against
their enemies. The inflation is a defense measure which takes place
almost automatically when the fish is alarmed.
Trigger fish are creatures with rigid spines which “lock” automatically
when the animals are in danger so that they cannot be bent. They can be
unlocked, presumably by a nerve reflex, only by the fish themselves or
by some scientist who knows the precise spinal process to touch.
Squirrel fish are brilliantly colored little creatures with large
deep-brown eyes which look like the eyes of a squirrel.
Scorpion fish have bodies covered with venomous spines whose poison is
reputed to be sometimes fatal even to man.
Flying half-beaks are fish with long, slender upper jaws and
practically no lower jaws. They make long glides over the water and may
represent an ancestral form of flying fish.
The elephant fish is so-called because of its very rough thick skin
and apparent extreme clumsiness of its body, both characteristics of
the elephant. Elephantichthys might be likened to a thick leather bag
about eight inches long stuffed loosely with vital organs. It has a
cartilaginous rather than a bony skeleton. It flattens out when laid on
a flat surface out of water. It is almost mollusk likee in the softness
of its body. Its skin is approximately a quarter of an inch long.
The aptocyclus, or “rattling fish”, is a close relative of
Elephantichthys in Arctic waters. It also seems to be a haphazard
conglomeration of vital organs stuffed in a bag. The fish actually
rattle inside when the skin is not filled with water. All fish of this
family live at the bottom of fairly shallow water, firmly attached
to flat stones by disk-like suckers. Although they have the power of
locomotion they seldom use it, remaining stationary on the bottom and
waiting for their food to come to them.
Most fish have a tail fin, usually forked, with which they propel
themselves, but the rat fish has a body tapering down to a long,
pointed extension that looks like a rodent’s tail. They are dwellers
in deep waters all over the world. Some are quite fantastic. One,
Macruroides inflaticeps, consists essentially of a head and a tail
without any apparent intermediate body; it looks like an enormous
tadpole.
Pearl fish are minute animals that are sometimes found inside oysters
and clams entirely encrusted with mother-of-pearl. They actually
become large pearls shaped like fish. These small, nearly transparent
creatures sometimes back into the open shell of an oyster or clam that
snaps once the fish are inside. When this happens the creature perishes
but sets up an irritation that leads to the pearl secretion over it.
_Love Life Among the Spiders_
There is love and courtship among spiders, as among birds and mammals,
but with a unique—and fatal—difference. An observer thus describes a
courtship scene in the _Cambridge Natural History_:
“When some inches from her he stood still. She eyed him eagerly,
changing her position from time to time. He, raising his whole body
on the other side, leaned so far over he was in danger of losing his
balance which he only maintained by sidling rapidly toward the lower
side. Again and again he circled from side to side, she gazing toward
him in a softer mode and evidently admiring the grace of his antics.
This was repeated until we had counted 107 circles made by the ardent
little male. He approached nearer and nearer and when almost within
reach whirled madly around and around her. She joined him in the giddy
dance. Again he fell back and resumed his semi-circular motion. She,
all excitement, lowered her head and raised her body so that it was
almost vertical. Both drew nearer. She moved slowly under him, he
crawling over her head. Thus the mating was accomplished.
“A few minutes later, however, the female had eaten her ardent lover.”
_The Lace Weavers_
For 300,000,000 years tiny animals have been weaving delicate lace.
They weave constantly, rapidly and in lovely, open mesh patterns. They
make a stiff stable lace. Their own limestone entombed bodies are the
threads. Night and day, millenium after millenium, they weave and
weave, for the curse of weaving is forever upon them. Through time
they have covered hundreds of square miles with white and green veils.
For the most part these are fragile and short-lived, but in a few cases
they have been preserved untorn through the ages.
These lace weavers are the bryozoa, or moss animalcules—one of the
oldest, most abundant and least known forms of animal life. They have
much the same habits as the corals, but the two limestone secreting
creatures are not even remotely related. The weavers are far higher
in the scale of evolution than the island builders. Their family
associations long have been in dispute. They have been associated with
the rotifers and mollusks and even with some unknown ancestral form
leading to the vertebrates. Now, however, it is believed that their
nearest relatives are the nearly extinct brachiopods, or lampshells.
The two groups started at about the same time in the Cambrian
geological period of half a billion years ago, but they followed
different paths of development. Both might be considered
proto-mollusks—very remotely kin to clams and oysters. For milleniums
the brachiopods flourished in the primaeval seas. During the Permean
period, about 300,000,000 years ago, they constituted one of the most
abundant forms of animal life. Now they seem close to the end of the
road. The weavers are as flourishing, and busy, as ever.
Like a coral polyp or the larva of a clam, the bryozoan starts life
as an almost invisibly minute, free-swimming creature, usually less
than a thirtieth of an inch long. After a few weeks it settles on some
hard surface, usually a stone, and secretes its limestone shell. New
individuals rise from the body of the founder of the colony at various
angles, depending on the particular design of the tapestry being
produced. Each of the buds, after achieving its coat, sends out new
buds. This is the weaving process.
The outside of the stone coat often is marked with delicate and bizarre
designs discernable under a microscope. These designs always are the
same for members of a colony and quite similar for an entire species.
They make it possible to identify species in geological formations and
this eventually may be of considerable importance for oil geologists.
After death a colony usually is broken up quickly by wave action. Sea
bottom ooze often is filled with the remains. This ooze, over periods
of milleniums, becomes compacted into rock.
The weaving process may be very rapid. A colony, starting with a single
free-swimming larva, may cover as much as 100 sq. feet. Such colonies
have been found on a single stone. They often are found on mollusk
shells. At present the bryozoans are economically important chiefly as
a menace to the oyster industry. Once they have covered an abandoned
shell, oystermen believe, no other oyster will make use of it. About
their only other importance to man comes from the fact that some
fresh-water species may clog water pipes by their rapid growth.
Every bryozoan in a colony remains throughout its life a separate
animal, shut off from its fellows by a wall of limestone and leading an
independent existence. Nevertheless, in the species pattern it assumes,
each colony acts as if it were a single organism.
Moreover, a phenomenon unique in nature, every individual appears to
be two and in some species three animals in one. Each leads its own
life and dies its own death at its own time. But all make up a single
microscopic whole.