man takes a hand in it. Soon the trail is not enough: it must be
widened so that a wagon-load of boards for a new house can be carried
in (for the settler has found a wife). After the first cart-track is
made to carry the boards and shingles in, a better road will be needed
to haul firewood and grain out (for the wants of the new family have
increased, and things must be bought in the neighboring village with
money, and money can only be had by selling the products of the farm).
By and by the neighborhood is so well inhabited that it is to the
advantage of the villages all around it to have good and safe and easy
roads there; and the road is declared a public one, and it is
regularly kept in repair and improved at the public expense. Do not
forget the squirrels of long ago. They were the projectors of this
road. Their successors use it now,--men and squirrels alike,--and stop
at the spring to drink, and under the huge oaks to rest.
A few years more, and it becomes to the advantage of all to have a
railway through the valley and over the hillside. Then a young
surveyor, just graduated from college, comes with his chain-men and
flag-men, and finds that the squirrels, and bears, and hunters, and
all the rest have picked out the easiest way for him long centuries
ago. He makes his map, and soon the chief enigneer and the president
of the road drive along in a buggy with a pair of fast horses
(frightening the little squirrels off their road-way and into their
holes), and the route of the Bear Valley and Quercus Railway is
finally selected, and here it is. See! there comes a train along the
track. This is the way a railway route grew out of a squirrel path.
There are thousands of little steps, but you can trace them, or
imagine them, as well as I can tell you.
It is the same all over the world. Stanley cut a track through the
endless African forests. But it lay between the Pygmy villages, along
the paths they had made, and through the glades where they fought
their battles with the storks.
Sometimes the first road is a river--the track is already cut. Try to
find out where the settlements in America were in the very early
days--before 1800. You will find them along the Hudson, the Juanita,
the St. Lawrence, the James, the Mississippi Rivers. But when these
are left, men follow the squirrel-tracks and bear-tracks, or the
paths of hunters, or the roads of Roman soldiers. It is a standing
puzzle to little children why all the great rivers flow past the great
towns. (Why do they?) The answer to that question will tell you why
the great battles are fought in the same regions; why Egypt has been
the coveted prize of a dozen different conquerors (it is the gateway
of the East); why our Civil War turned on the possession of the
Mississippi River. It is the roadways we fight for, the ways in and
out, whether they be land or water. Of course, we really fought for
something better than the mere possession of a roadway, but to get
what we fought for we had to have the roadway first.
The great principle at the bottom of everything in Nature is that the
fittest survives: or, as I think it is better to say it, in any
particular conflict or struggle that thing survives which is the
fittest to survive _in this particular struggle_. This is Mr. Darwin's
discovery,--or one of them,--and the struggle for existence is a part
of the great struggle of the whole universe, and the laws of it make
up the methods of Evolution--of Development.
It is clear now, is it not, how the railway route is the direct
descendant of the tiny squirrel track between two oaks? The process of
development we call Evolution, and you can trace it all around you.
Why are your skates shaped in a certain way? Why is your gun rifled?
Why have soldiers two sets of (now) useless buttons on the skirts of
their coats? (I will give you three guesses for this, and the hint
that you must think of cavalry soldiers.) Why are eagles' wings of
just the size that they are? These and millions of like questions are
to be answered by referring to the principle of development.
Sometimes it is hard to find the clew. Sometimes the development has
gone so far, and the final product has become so complex and special,
that it takes a good deal of thinking to find out the real reasons.
But they _can_ be found, whether they relate to a fashion, to one of
the laws of our country, or to the colors on a butterfly's wing.
There is a little piece of verse intended to be comic, which, on the
contrary, is really serious and philosophical, if you understand it.
Learn it by heart, and apply it to all kinds and conditions of things,
and see if it does not help you to explain them to yourself....
"And Man grew a thumb for that he had need of it,
And developed capacities for prey.
For the fastest men caught the most animals,
And the fastest animals got away from the most men.
Whereby all the slow animals were eaten,
And all the slow men starved to death."
[Illustration]
HOW THE SOIL IS MADE
(FROM THE FORMATION OF VEGETABLE MOULD.)
BY CHARLES DARWIN.
[Illustration: W]
Worms have played a more important part in the history of the world
than most persons would at first suppose. In almost all humid
countries they are extraordinarily numerous, and for their size
possess great muscular power. In many parts of England a weight of
more than ten tons (10,516 kilogrammes) of dry earth annually passes
through their bodies and is brought to the surface on each acre of
land; so that the whole superficial bed of vegetable mould passes
through their bodies in the course of every few years. From the
collapsing of the old burrows the mould is in constant though slow
movement, and the particles composing it are thus rubbed together. By
these means fresh surfaces are continually exposed to the action of
the carbonic acid in the soil, and of the humus-acids which appear to
be still more efficient in the decomposition of rocks. The generation
of the humus-acids is probably hastened during the digestion of the
many half-decayed leaves which worms consume. Thus the particles of
earth, forming the superficial mould, are subjected to conditions
eminently favorable for their decomposition and disintegration.
Moreover, the particles of the softer rocks suffer some amount of
mechanical trituration in the muscular gizzards of worms, in which
small stones serve as mill-stones.
[Illustration: DIAGRAM OF THE ALIMENTARY CANAL OF AN EARTH-WORM.]
The finely levigated castings, when brought to the surface in a moist
condition, flow during rainy weather down any moderate slope; and the
smaller particles are washed far down even a gently inclined surface.
Castings when dry often crumble into small pellets and these are apt
to roll down any sloping surface. Where the land is quite level and is
covered with herbage, and where the climate is humid so that much dust
cannot be blown away, it appears at first sight impossible that there
should be any appreciable amount of sub-aerial denudation; but worm
castings are blown, especially while moist and viscid, in one uniform
direction by the prevalent winds which are accompanied by rain. By
these several means the superficial mould is prevented from
accumulating to a great thickness; and a thick bed of mould checks in
many ways the disintegration of the underlying rocks and fragments of
rock.
[Illustration: A WORM CASTING, FROM NICE. (Natural Size.)]
The removal of worm-castings by the above means leads to results which
are far from insignificant. It has been shown that a layer of earth,.2
of an inch in thickness, is in many places annually brought to the
surface per acre; and if a small part of this amount flows, or rolls,
or is washed, even for a short distance, down every inclined surface,
or is repeatedly blown in one direction, a great effect will be
produced in the course of ages. It was found by measurements and
calculations that on a surface with a mean inclination of 9° 26', 2.4
cubic inches of earth which had been ejected by worms crossed, in the
course of a year, a horizontal line one yard in length; so that two
hundred and forty cubic inches would cross a line one hundred yards in
length. This latter amount in a damp state would weigh eleven and
one-half pounds. Thus, a considerable weight of earth is continually
moving down each side of every valley, and will in time reach its bed.
Finally, this earth will be transported by the streams flowing in the
valleys into the ocean, the great receptacle for all matter denuded
from the land. It is known from the amount of sediment annually
delivered into the sea by the Mississippi, that its enormous
drainage-area must on an average be lowered.00263 of an inch each
year; and this would suffice in four and a half million years to lower
the whole drainage-area to the level of the seashore. So that if a
small fraction of the layer of fine earth,.2 of an inch in thickness,
which is annually brought to the surface by worms, is carried away, a
great result cannot fail to be produced within a period which no
geologist considers extremely long.
[Illustration: SECTION THROUGH ONE OF THE DRUIDICAL STONES AT
STONEHENGE, SHOWING HOW MUCH IT HAD SUNK INTO THE GROUND.
(Scale, 1/2 inch to 1 foot.)]
Archaeologists ought to be grateful to worms, as they protect and
preserve for an indefinitely long period every object, not liable to
decay, which is dropped on the surface of the land, by burying it
beneath their castings. Thus, also, many elegant and curious
tesselated pavements and other ancient remains have been preserved;
though no doubt the worms have in these cases been largely aided by
earth washed and blown from the adjoining land, especially when
cultivated. The old tesselated pavements have, however, often suffered
by having subsided unequally from being unequally undermined by the
worms. Even old massive walls may be undermined and subside; and no
building is in this respect safe, unless the foundations lie six or
seven feet beneath the surface, at a depth at which worms cannot work.
It is probable that many monoliths and some old walls have fallen
down from having been undermined by worms.
Worms prepare the ground in an excellent manner for the growth of
fibrous-rooted plants and for seedlings of all kinds. They
periodically expose the mould to the air, and sift it so that no
stones larger than the particles which they can swallow are left in
it. They mingle the whole intimately together, like a gardener who
prepares fine soil for his choicest plants. In this state it is well
fitted to retain moisture and to absorb all soluble substances, as
well as for the process of nitrification. The bones of dead animals,
the harder parts of insects, the shells of land mollusks, leaves,
twigs, etc., are before long all buried beneath the accumulated
castings of worms, and are thus brought in a more or less decayed
state within reach of the roots of plants. Worms likewise drag an
infinite number of dead leaves and other parts of plants into their
burrows, partly for the sake of plugging them up and partly as food.
The leaves which are dragged into the burrows as food, after being
torn into the finest shreds, partially digested and saturated with the
intestinal and urinary secretions, are commingled with much earth.
This earth forms the dark-colored, rich humus which almost everywhere
covers the surface of the land with a fairly well-defined layer or
mantle. Von Hensen placed two worms in a vessel eighteen inches in
diameter, which was filled with sand, on which fallen leaves were
strewed; and these were soon dragged into their burrows to a depth of
three inches. After about six weeks an almost uniform layer of sand, a
centimetre (.4 inch) in thickness, was converted into humus by having
passed through the alimentary canals of these two worms. It is
believed by some persons that worm-burrows, which often penetrate the
ground almost perpendicularly to a depth of five or six feet,
materially aid in its drainage; notwithstanding that the viscid
castings piled over the mouths of the burrows prevent or check the
rain-water directly entering them. They allow the air to penetrate
deeply into the ground. They also greatly facilitate the downward
passage of roots of moderate size; and these will be nourished by the
humus with which the burrows are lined. Many seeds owe their
germination to having been covered by castings; and others buried to a
considerable depth beneath accumulated castings lie dormant, until at
some future time they are accidentally uncovered and germinate.
[Illustration: A WORM CASTING FROM SOUTH INDIA. (Natural Size.)]
Worms are poorly provided with sense-organs, for they cannot be said
to see, although they can just distinguish between light and darkness;
they are completely deaf, and have only a feeble power of smell; the
sense of touch alone is well developed. They can, therefore, learn
little about the outside world, and it is surprising that they should
exhibit some skill in lining their burrows with their castings and
with leaves, and in the case of some species in piling up their
castings into tower-like constructions. But it is far more surprising
that they should apparently exhibit some degree of intelligence
instead of a mere blind, instinctive impulse, in their manner of
plugging up the mouths of their burrows. They act in nearly the same
manner as would a man, who had to close a cylindrical tube with
different kinds of leaves, petioles, triangles of paper, etc., for
they commonly seize such objects by their pointed ends. But with thin
objects a certain number are drawn in by their broader ends. They do
not act in the same unvarying manner in all cases, as do most of the
lower animals; for instance, they do not drag in leaves by their
foot-stalks, unless the basil part of the blade is as narrow as the
apex, or narrower than it.
* * * * *
When we behold a wide, turf-covered expanse, we should remember that
its smoothness, on which so much of its beauty depends, is mainly due
to all the inequalities having been slowly levelled by worms. It is a
marvellous reflection that the whole of the superficial mould over any
such expanse has passed, and will again pass, every few years through
the bodies of worms. The plough is one of the most ancient and most
valuable of man's inventions; but long before he existed the land was
in fact regularly ploughed, and, still continues to be thus ploughed
by earth-worms. It may be doubted whether there are many other animals
which have played so important a part in the history of the world, as
have these lowly organized creatures. Some other animals, however,
still more lowly organized, namely, corals, have done far more
conspicuous work in having constructed innumerable reefs and islands
in the great oceans; but these are almost confined to the tropical
zones.
[Illustration]
ZOÖLOGICAL MYTHS
(FROM FACTS AND FICTIONS OF ZOÖLOGY.)
BY ANDREW WILSON.
[Illustration]
When the country swain, loitering along some lane, comes to a
standstill to contemplate, with awe and wonder, the spectacle of a
mass of the familiar "hair-eels" or "hair-worms" wriggling about in a
pool, he plods on his way firmly convinced that, as he has been taught
to believe, he has just witnessed the results of the transformation of
some horse's hairs into living creatures. So familiar is this belief
to people of professedly higher culture than the countryman, that the
transformation just alluded to has to all, save a few thinking persons
and zoölogists, become a matter of the most commonplace kind. When
some quarrymen, engaged in splitting up the rocks, have succeeded in
dislodging some huge mass of stone, there may sometimes be seen to hop
from among the débris a lively toad or frog, which comes to be
regarded by the excavators with feelings akin to those of
superstitious wonder and amazement. The animal may or may not be
captured; but the fact is duly chronicled in the local newspapers, and
people wonder for a season over the phenomenon of a veritable Rip Van
Winkle of a frog, which to all appearance, has lived for "thousands of
years in the solid rock." Nor do the hair-worm and the frog stand
alone in respect of their marvellous origin. Popular zoölogy is full
of such marvels. We find unicorns, mermaids, and mermen; geese
developed from the shell-fish known as "barnacles"; we are told that
crocodiles may weep, and that sirens can sing--in short, there is
nothing so wonderful to be told of animals that people will not
believe the tale. Whilst, curiously enough, when they are told of
veritable facts of animal life, heads begin to shake and doubts to be
expressed, until the zoölogist despairs of educating people into
distinguishing fact from fiction, and truth from theories and
unsupported beliefs. The story told of the old lady, whose youthful
acquaintance of seafaring habits entertained her with tales of the
wonders he had seen, finds, after all, a close application in the
world at large. The dame listened with delight, appreciation, and
belief, to accounts of mountains of sugar and rivers of rum, and to
tales of lands where gold and silver and precious stones were more
than plentiful. But when the narrator descended to tell of fishes that
were able to raise themselves out of the water in flight, the old
lady's credulity began to fancy itself imposed upon; for she
indignantly repressed what she considered the lad's tendency to
exaggeration, saying, "Sugar mountains may be, and rivers of rum may
be, but fish that flee ne'er can be!" Many popular beliefs concerning
animals partake of the character of the old lady's opinions regarding
the real and fabulous; and the circumstance tells powerfully in favor
of the opinion that a knowledge of our surroundings in the world, and
an intelligent conception of animal and plant life, should form part
of the school-training of every boy and girl, as the most effective
antidote to superstitions and myths of every kind.
[Illustration: FLYING FISH.]
The tracing of myths and fables is a very interesting task, and it
may, therefore, form a curious study, if we endeavor to investigate
very briefly a few of the popular and erroneous beliefs regarding
lower animals. The belief regarding the origin of the hair-worms is
both widely spread and ancient. Shakespeare tells us that
"Much, is breeding
Which, like the courser's hair, hath, yet but life,
And not a serpent's poison."
The hair-worms certainly present the appearance of long, delicate
black hairs, which move about with great activity amidst the mud of
pools and ditches. These worms, in the early stages of their
existence, inhabit the bodies of insects, and may be found coiled up
within the grasshopper, which thus gives shelter to a guest exceeding
many times the length of the body of its host. Sooner or later the
hair-worm, or _Gordius aquaticus_ as the naturalist terms it, leaves
the body of the insect, and lays its eggs, fastened together in long
strings, in water. From each egg a little creature armed with minute
hooks is produced, and this young hair-worm burrows its way into the
body of some insect, there to repeat the history of its parent. Such
is the well-ascertained history of the hair-worm, excluding entirely
the popular belief in its origin. There certainly does exist in
science a theory known as that of "spontaneous generation," which, in
ancient times, accounted for the production of insects and other
animals by assuming that they were produced in some mysterious fashion
out of lifeless matter. But not even the most ardent believer in the
extreme modification of this theory which holds a place in modern
scientific belief, would venture to maintain the production of a
hair-worm by the mysterious vivification of an inert substance such as
a horse's hair.
The expression "crocodile's tears" has passed into common use, and it
therefore may be worth while noting the probable origin of this myth.
Shakespeare, with that wide extent of knowledge which enabled him to
draw similes from every department of human thought, says that
"Gloster's show
Beguiles him, as the mournful crocodile
With sorrow snares relenting passengers."
The poet thus indicates the belief that not only do crocodiles shed
tears, but that sympathizing passengers, turning to commiserate the
reptile's woes, are seized and destroyed by the treacherous creatures.
That quaint and credulous old author--the earliest writer of English
prose--Sir John Mandeville, in his "Voiage," or account of his
"Travile," published about 1356--in which, by the way, there are to be
found accounts of not a few wonderful things in the way of zoölogical
curiosities--tells us that in a certain "contre and be all yonde, ben
great plenty of Crokodilles, that is, a manner of a long Serpent as I
have seyed before." He further remarks that "these Serpents slew men,"
and devoured them, weeping; and he tells us, too, that "whan thei
eaten thei meven (move) the over jowe (upper jaw), and nought the
nether (lower) jowe: and thei have no tonge (tongue)." Sir John thus
states two popular beliefs of his time and of days prior to his age,
namely, that crocodiles move their upper jaws, and that a tongue was
absent in these animals.
[Illustration: CROCODILE.]
As regards the tears of the crocodile, no foundation of fact exists
for the belief in such sympathetic exhibitions. But a highly probable
explanation may be given of the manner in which such a belief
originated. These reptiles unquestionably emit very loud and
singularly plaintive cries, compared by some travellers to the
mournful howling of dogs. The earlier and credulous travellers would
very naturally associate tears with these cries, and, once begun, the
supposition would be readily propagated, for error and myth are ever
plants of quick growth. The belief in the movement of the upper jaw
rests on apparent basis of fact. The lower jaw is joined to the skull
very far back on the latter, and the mouth-opening thus comes to be
singularly wide; whilst, when the mouth opens, the skull and upper jaw
are apparently observed to move. This is not the case, however; the
apparent movement arising from the manner in which the lower jaw and
the skull are joined together. The belief in the absence of the tongue
is even more readily explained. When the mouth is widely opened, no
tongue is to be seen. This organ is not only present, but is,
moreover, of large size; it is, however, firmly attached to the floor
of the mouth, and is specially adapted, from its peculiar form and
structure, to assist these animals in the capture and swallowing of
their prey.
One of the most curious fables regarding animals which can well be
mentioned, is that respecting the so-called "Bernicle" or "Barnacle
Geese," which by the naturalists and educated persons of the Middle
Ages were believed to be produced by those little Crustaceans named
"Barnacles." With the "Barnacles" every one must be familiar who has
examined the floating driftwood of the sea-beach, or who has seen
ships docked in a seaport town. A barnacle is simply a kind of crab
enclosed in a triangular shell, and attached by a fleshy stalk to
fixed objects. If the barnacle is not familiar to readers, certain
near relations of these animals must be well known, by sight at least,
as amongst the most familiar denizens of our sea-coast. These latter
are the "Sea-Acorn," or Balani, whose little conical shells we crush
by hundreds as we walk over the rocks at low-water mark; whilst every
wooden pile immersed in the sea becomes coated in a short time with a
thick crust of the "Sea-Acorns." If we place one of these little
animals, barnacle, or sea-acorn--the latter wanting the stalk of the
former--in its native waters, we shall observe a beautiful little
series of feathery plumes to wave backward and forward, and ever and
anon to be quickly withdrawn into the secure recesses of the shell.
These organs are the modified feet of the animal, which not only serve
for sweeping food-particles into the mouth, but act also as
breathing-organs. We may, therefore, find it a curious study to
inquire through what extraordinary transformation and confusion of
ideas such an animal could be credited with giving origin to a
veritable goose; and the investigation of the subject will also afford
a singularly apt illustration of the ready manner in which the fable
of one year or period becomes transmitted and transformed into the
secure and firm belief of the next.