minute studies of an American silk worm, the cecropia (common along
the Atlantic coast), which spins as strong and delicate threads as the
Japanese or Italian domesticated silk worms. The cocoon is a marvel of
apparent ingenuity, made of a single thread almost a mile long. It is
made in three layers, roughly after the design of a thermos bottle. The
outer layer is a tightly woven, waterproof silk bag. Inside this is a
layer of loosely spun material which serves as an insulating layer.
The third layer, woven around the body of the worm itself, is a bag
of exceedingly fine, soft silk. Through each layer a “hatchway” is
provided directly in front of the creature’s head. These must be placed
one in front of the other with mathematical exactitude. Through them
the self imprisoned animal must escape when the time comes, and the
slightest error probably would make it a prisoner forever in a coffin
of its own creation.
Inside the cocoon the worm remains, adequately protected from cold and
damp, for nine months. It emerges as a winged moth, whose sole function
in life apparently is to lay eggs to produce more silkworms.
Spinning such a cocoon with its three quite different layers requires
extreme precision of movement. Nature has not allowed for any possible
variations. Yet the masterpiece obviously is not the result of any
thinking, education or practice. The little worm’s life span, for
one thing, would not allow for any training. Every movement must be
instinctive and presumably unconscious, directed by the same part of
the nervous system into whose structure the pattern has been built by
nature.
The house building must start at precisely the right time. Until that
time, according to the Harvard physiologists, the responsible area
of the brain is held in restraint by a hormone secreted from two
tiny glands in the head. At the foreordained instant this inhibiting
secretion ceases and the mushroom body can go into action. The spinning
can be started at any time, however, by destroying the glands.
Williams and Van der Kloot tried effects of two gasses, carbon dioxide
and carbon monoxide. Both acted as potent brain depressants, but in
quite different ways. The first eliminated the spinning behavior
entirely and permanently. The worms wandered about aimlessly,
apparently trying in vain to remember what some overwhelming internal
drive was pushing them to do. The automobile exhaust gas, carbon
monoxide, fatal to humans but without any serious lasting effects on
invertebrates because of the lack of the red cells in the blood with
which it combines in higher animals, caused them to spin a worthless
and meaningless flat layer of silk as long as the effect continued.
When this ended the worm started to spin what remained of the mile-long
thread in the customary pattern, starting from the point it normally
would have reached had it not been gassed.
The biologists then resorted to their unbelievably delicate surgery.
They proceeded to destroy the silk worm brain a few score cells
at a time. The brain contains hundreds of thousands of cells. The
destruction had no effect on the spinning behavior until they reached
the mushroom body. When a few cells of this area were killed by
the electric current the worm no longer could spin a cocoon but
continued to wind and weave its silken thread into three flat sheets,
corresponding to the three normal capsules. The weaving continued with
the destruction of a few more cells, but only in a single sheet. When
a few more were destroyed the entire cocoon-making behavior came to an
end.
Thus, Doctors Williams and Van der Kloot concluded, they had located a
physical unit of behavior. Within it was capsuled the whole “memory” of
the silk worm race with respect to spinning. More than a century ago
this mushroom body was discovered by the French physiologist Dujardin,
who called it the “seat of instinct.” At that time this was only a wild
speculation on his part, without any supporting facts whatsoever.
The instinct center is found in the brains of all insects in whom
group instinctive behavior has manifestation. In the honeybee worker,
intellectual giant of the insect world, it reaches its greatest size.
In drones and queens, who do not display much behavior of any sort, the
area of the brain is quite small.
_The Strange World of the Sea_
Under the tossing surface of southern seas is an inferno-like realm of
everlasting darkness, inhabited by multitudes of strange animals which
exist almost altogether by the laws of beak and fang. Some of them are
grotesque beyond the reaches of a nightmare.
Countless generations ago their ancestors, driven by hunger and
competition, abandoned the familiar sun-lit world for the perpetual
night of the abysmal depths. Then with each family, it was a case of
survival of the fittest and variation of form and structure to fit the
environment.
Here is the stark struggle for survival with the mask of sunlight,
green fields and flowers discarded. It is not different in kind but in
degree from the struggle that goes on continually between living things
at the surface of the ocean and on the land. Down there all must eat
flesh. There is no plant life intermediary between beast and beast.
Plants cannot grow below the light line of the sea depths.
Out of this fierce war for existence have come creatures mostly
conspicuous for their defensive and offensive equipment. Some of the
fish seem to have become little more than enormous mouths with rows
of long, razor-like teeth with which they seize and kill. The bodies
attached to these mouths are small and slender. Such a creature is
mostly head and the head is mostly mouth. Nearly all the fish carry
light organs of some kind near the mouth with which other animals are
probably attracted within grabbing distance.
One of the largest collections of deep sea animals was assembled a few
years ago near the Puerto Rico Deep, the deepest part of the Atlantic
Ocean, by a Smithsonian Institution expedition led by Dr. Paul Bartsch.
This collection constituted a fair representation of the sea life at
depths of about 3200 feet, nearly 2500 feet below the farthest reaches
of the sun’s rays. There were shrimps with long, sharp claws which fold
up after the fashion of an old-fashioned straight razor. Any small
creature which came within striking distance of such a razor probably
would be an immediate victim. There were strange mollusks with shells
like corkscrews and eels like darning needles with long, sharp beaks.
Among the most fantastic was the needle-fish. It jaws are prolonged
into extraordinarily slender points, like fine needles, so that the
head is nearly as long as the rest of the body—that is, about six
inches. This fish was lured to the net by an electric light.
A group of flat fish, or flounders, was obtained, all of which have two
eyes on one side of the head and none on the other. Instead of right
eye and left eye there is upper eye and lower eye.
Other strange forms in the collection:
The hunchback fish, a creature whose strangely shaped body suggests its
name.
The lance fish with long, backward-reaching spines suggestive of lances
just behind the eyes.
The forceps fish, one of the most aberrant of all with its greatly
extended, forceps-like jaws. There is apparently but a single genus and
species in existence.
The family of snout fish with snouts almost as long as the rest of the
body. At the end of the snout is a mouth.
Another strange creature taken out of the depths by this expedition was
Johnsonia eriomma—the “big eye fish.” Each of its two eyes is about a
fifth as long as the diameter of its body. A man’s eye, in the same
ratio, would be about a foot long and protrude about eight inches from
its socket. It also has two false eyes on its sides, near the tail.
They are of the same size and approximately the same pattern as the
true eyes. They probably are indistinguishable from them by other fish.
They are, however, only color spots and have no visual function. They
constitute a feature hitherto unknown in the fish world. The purpose
of the false eyes is unknown, unless they are intended to deceive
the creature’s enemies. Since it is a slow-moving fish, these color
spots probably create the illusion of fast movement which would fool a
predatory animal of the abysses.
This fish is the second of its family ever found in the western world.
The other was discovered a half century ago the genus have been found
in Asiatic waters.
This eye-fish was obtained from a depth of between 150 and 300
fathoms—just about on the borderline of eternal darkness where
eyes would be of no use. Fish of the depths have evolved in two
directions—toward enormous eyes and toward greatly diminished ones.
The first represents a struggle to see in the strange dusk. The second
trend denotes giving up of a futile struggle on the part of the race.
This trend is noteworthy among fish of the greater depths.
Another strange denizen of the depths is Peristedion bartschi, named in
honor of Dr. Bartsch. It is an armored gurnard, of the family sometimes
known as “sea robins.” The shell-growing tendency among fish is largely
confined to certain fresh-water catfish of South America. This creature
obviously is a bottom dweller. Its entire body is covered with spiny
plates which probably would make it safe from any enemy. Each plate
bears a very sharp spine, about a quarter inch long. There are nearly
a hundred of these on the body. This fish would probably be about the
most unappetizing morsel any predatory animal ever swallowed. It is
bright red.
Still another species obtained by the expedition was one of the
“lantern-fish” group. These are small, minnow-like creatures who live
only in the open ocean. While most fish either remain near shore or
have at least an association with the bottom these are found only
in deep water far from land, and never near the sea floor. Most of
the millions of them in the sea doubtless live and die without any
realization that there is either bottom or shore. All have rows of
luminous spots along their sides which probably serve as recognition
marks.
_The Cannibal Birds of the Pacific_
Hordes of big black birds, about the nearest creatures imaginable to
the harpies of Greek mythology, nest on desert-like South Pacific
Islands. These are the vulture-like frigate birds—the Polynesian “iwas”
or “thieves”—which are found by thousands in branches of the most
prominent shrubs, the eight-foot-high, white flowering scaevola bushes.
They are truly creatures of evil.
They carry in their feathers as parasites creatures nearly as
malevolent in appearance as themselves—louse flies which look like
giant, flattened black house flies. When these are shaken off they
sometimes fly to small black automobiles which they mistake for their
hosts.
The nests of the frigate birds are coarse, soil-cemented affairs
constructed haphazardly of twigs and driftwood. During showers, the
cement of this filthy building material dissolves away, allowing eggs
to fall to the ground. Nesting material evidently is rare and highly
prized, giving rise to theft. A bird in flight occasionally filches
a loose piece from a carelessly guarded nest. The iwa will stoop to
murder and cannibalism, flying off with an egg or newly hatched young
to eat on the wing. There usually is one egg to a nest, entirely white
and a little larger than a chicken egg.
Both sexes take turns sitting on the egg and later brooding the growing
chicks. This is necessary not only to incubate the egg and keep the
chick warm in cool weather, but also as protection against too intense
sunshine. At the incubation time the males are resplendent with blood
red, semi-transparent throat pouches blown out like balloons. These
extend forward to the beak and downward to hide the breast. The color
is due to innumerable blood-filled capillaries in the tissues of the
pouch.
Not far from the rookeries of the iwas are those of the stupid,
red-footed boobies, or gannets. The name booby is from the Spanish
word “bobo”, meaning “idiot”. At times the rookeries of the aggressive
marauders and the boob-victims overlap at the edges.
The frigate birds, according to a report of the Pacific Science Board,
“escort the stupid, spoon-billed gannets out to feed on schools of
squid and small fish. When the gannets get craws full and set sail for
home to feed their young, the cruel, curve-billed iwas dive screaming
after them, seize them by the tails, and sling the food out of the
mouths of the smaller birds. This the iwas scoop up on the wing. This
goes on from dawn to dusk. The war cries of the frigates and the
plaintive screams of the fleeing gannets quiver down the trade winds
like the wailings of lost souls.”
It is commonly reported that frigate birds, lacking webbed feet, never
land on the surface of the water because they cannot take off again.
This is not true; small flocks are frequently seen landing playfully on
the Canton island lagoon, floating, and rising again seemingly without
any effort whatsoever.
“The birds nesting in the scaevola,” says the report, “are tame or,
depending on the point of view, too innocent or stupid to fly from
their nests when approached. The explanation for this habit is their
nesting from time immemorial in areas where no predatory animals, two
or four legged, ever have existed. (This, by the way, is a notable
characteristic of bird life in the Antarctic. The notorious skuas, with
whom even the frigates could hardly compare for blood-thirstiness,
will not even bother to move when men pass through a flock of them on
the ice.) Tame birds were not killed off but lived to reproduce their
kind. Now, unfortunately, Pacific islanders employed as laborers,
occasionally club the nesting birds at night preparatory to a feast.
Such vandalism and resulting pandemonium in the rookeries should be
stopped by legislation.”
The ancestors of these and other kinds of sea birds have inhabited the
islands during the nesting seasons for milleniums, catching fish and
other sea life as food for themselves and their nestlings.
_Eagles as Indian Pets_
The proud eagle was once kept as a “domestic animal.” Memories of this
practice have been obtained from the Shoshoni Indians of the Nevada
desert. As recently as fifty years ago individual Indians owned eagle
aeries in the mountains. These constituted about the only private
property recognized by the tribe and rights were zealously maintained.
Expert climbers who scaled the cliffs took the young eagles from
their nests. They were subsequently reared in cages or tied to rocks.
The purpose was to harvest their feathers for arrows, decoration, or
magical rites. The birds were fed pocket gophers and young groundhogs.
When the birds were full grown the feathers were plucked. Then the
captives were taken to the top of a cliff and released.
_The Giant Insects of the Carolines_
Giant walking sticks seven to nine inches long, titan spiders that walk
on water, little black crickets that dive and swim long distances under
water are some of nature’s curiosities on mountainous, jungle-covered
Kusaie, easternmost of the Caroline Islands.
Especially unusual are the winged-blue-and-green walking sticks with
their fantastic hand-over-hand way of walking. Among the largest of
all insects is a walking stick found on the nearby island of Truk. It
is reddish-brown and wingless with a body nine inches long. The huge
spider’s usual abode is the foliage of long grasses overhanging jungle
streams. There it lies in wait for the insects which are its usual
prey. When alarmed the big spider drops off the grass into the water
and starts running swiftly over the surface. It is provided with “water
shoes,” bristle arrangements on its feet. Probably it does not even get
its feet wet.
The submarine crickets are little black insects about an inch long
which live on damp basalt rocks along the sides of, and in, the
streams. They are almost invisible in the dim jungle light but make
themselves known by their continuous chirping. When frightened they
make long, high dives from the rocks and swim for undetermined
distances a few inches under water, where they are invisible.
By far the most fantastic spectacle found on Kusaie is that of the
ghostly light which marks the banks of rivers. It is due to some
species of ground-growing fungus. A Smithsonian party once was
overtaken by darkness high in the mountains where no trails could be
followed through the dank jungle. They started wading down a stream
which, they knew, eventually must lead to the lowlands and the coast.
They waded, sometimes neck deep, in a tunnel of overhanging branches
through whose thick foliage no light could penetrate. But always,
glowing on both sides of them, were the lines of luminous fungi.
_The Valley Where Dusk is Death_
A belt of poison night where death strikes with the dusk extends
down the western slope of the Peruvian Andes. This death belt, first
reported by a Spanish physician in 1630, consists of a few narrow
valleys at an elevation of from 3,000 to 8,000 feet in an arid, very
desolate and sparsely inhabited country. Nearly everyone who spends
a night there is afflicted a few days later by a severe anemia which
often proves fatal. This is the “verruga” disease. The red blood cell
count drops very rapidly. It is not known whether the cells actually
are destroyed by the disease, or whether it inhibits the forming of new
ones from the bone marrow. The effect in either case is the same. The
blood loses its capacity to carry oxygen and the victim slowly smothers.
The malady is known as Carrión’s disease. In 1885 a Peruvian medical
student named Carrión inoculated himself with it to prove its identity.
He succeeded in showing the cause, at the cost of his own life. He
had been inspired to the foolhardy act by extreme patriotism. The
Chile-Peru war was just over. Most work on the disease had been done
by Chileans. Carión desired that the credit for medical research should
come back to Peru.
If one recovers from the anemia a second stage of the malady sets in.
The body is covered with wart-like growths, presumably due to some
alteration in the blood supply to the skin. One attack gives immunity
for life, but the death rate during the first stage is very high.
During daylight the death belt is perfectly safe. This has long been
recognized by natives who travel through it freely between sunrise and
sunset. The only permanent inhabitants of the region are persons who
have recovered from the disease. The borders are sharply defined within
a few yards of altitude.
For some years it has been recognized that the infection comes from
the bite of a single species of sand fly—a vicious pest smaller than
a mosquito. Protection is afforded only by special screens. Ordinary
mosquito netting is worthless. The death belt is a place of bright
sunshine nearly every day. The insects cannot endure light. They remain
secluded and it is difficult to secure specimens, even when the hiding
places are known. As soon as darkness comes they emerge in enormous
numbers.
Harvard entomologists who investigated the death belt a few years ago
spent the hours between sunset and sunrise in a specially screened
railroad car. A few moments outside might have proved fatal.
Due to some delicate balance of nature this sand fly seems to be
confined almost exclusively to this locality. It is credited with
causing about 7,000 deaths in the decade before the last war.
_Enigma of Evolution: the Snake_
Snakes once had legs. There is evidence in their anatomy that they
are descended from four-legged land animals. This evidence is found
especially in certain bones near the base of the tail of one of the
largest of living snakes, the python, which is the most primitive of
the order and presumably nearest to the hypothetical ancestor.
Although the snake remains an enigma of evolution, there is no doubt
that it got rid of its legs because they were a distinct hindrance to
its peculiar ways of life.
The serpent is not very ancient, as animal types go. Evidently it first
appeared in the Cretaceous geological period, about 100,000,000 years
ago, when the great dinosaurs were the earth’s dominant animals. There
are, however, no unquestioned fossils of snakes from the dinosaur days.
The first snake-like creature known is represented by fossils from the
Eocene, or “dawn”, age in North America. This was quite lizard-like in
bone structure. It lived about sixty million years ago, when mammals
were developing on earth. Rocks in Germany, laid down about twenty
million years later, yield fossils of true snakes of the generalized
viper type. Sometime later come fossils of snake giants from Egypt.
Some of these probably were sixty feet long. But all these were real
snakes, with no traces of external limbs. The ancestor seems lost
forever because snake skeletons are brittle and delicate and do not
easily fossilize.
Having discarded legs, serpents evolved means of locomotion suitable
to their ways of life. This has sometimes been described as “walking
on the ribs.” It requires a highly intricate coordination of ribs and
muscles and can be compared best to rowing a boat.
“The life of a serpent,” according to Dr. Alfred Leutscher of the
British Museum of Natural History, “is a matter of adjustments for
what it has lost. It cannot masticate its food so it swallows it
whole. It can put a healthy human appetite to shame yet it can, if
forced to do so, starve for more than a year. Limbs are missing, so
it walks on its ribs, swims and grips with its tail, and climbs with
its scales. The outer skin does not grow, so from time to time it is
peeled off neatly, even to the scales over the eyes. Taste is poor,
but this is compensated for by a strong sense of smell, in which the
harmless tongue assists by catching the smell particles from the air.
It is proverbially deaf, but may receive ample warning of danger from
vibrations through solid objects, which reach its sensitive skin more
swiftly than sound can travel through air.”
_The Fastest Growth on Earth_
In the beginning was vestureless life. It was the capacity for self
perpetuation and growth in nature, the property of a single complex
chemical mixture—protoplasm.
This protoplasm may have come here from another star, a single grain of
cosmic dust blown out of the infinite. It may have been mixed by chance
in the warm seas of the earth at the beginning of time. It may have
been put together according to the design of some cosmic intelligence.
It tended to segregate into billions of trillions of infinitesimally
minute particles, each sufficient unto itself. The particles were
purposeless, voracious, irresistible and immortal. They threatened to
devour space and time and all that was in them.
A cell culture of elemental, inchoate life stuff whose original
substance increased theoretically 10,000,000,000,000,000,000-fold
in forty weeks has been described by Dr. Phillip R. White of the
Rockefeller Institute. In his experiments he started with a pellet
about the size of a grain of mustard seed cut from a wart-like
excrescence on a tobacco plant. He watched it multiply until,
arithmetically speaking, if no part had been discarded it would have
been an unorganized, purposeless monster spheroid of life 600,000,000
miles in diameter, comparable in size to the whole solar system inside
the orbit of Pluto.
It had twelve weeks to complete its first year. At the same rate of
growth it then would have been a lusty infant the size of 400,000 solar
systems. In a few more weeks it could have swallowed the whole Milky
Way galaxy. By the end of its second year it would have filled all the
space in known creation, consumed the substance of all the galaxies,
and perished of starvation as it bulged outward into the emptiness of
infinity.
Such a nightmare actually happened, in reverse. Dr. White had to do
everything in a few test tubes, but he was able to witness such a
phenomenon of growth as man had not hitherto imagined. First he placed
his pellet in a special nutrient solution. It began to expand by the
continuous process of splitting in two. Two cells become four, four
eight, and so on infinitely. After about two weeks Dr. White cut away a
few pellets from the original mass and discarded the rest. These were
placed in new nutrient solutions. Every two weeks the experimenter
would discard the bulk of each mass which had accumulated and start new
cultures with the few pellets which he saved. Each culture increased in
size about fifty percent a day. At the end of forty weeks he was left
with something not much bigger than he had at the start, but the actual
original pellet constituted only about a ten-quintillionth of the final
mass.