When excited, they do not themselves move or change form, but transmit
a motor impulse to the bending part of their own and adjoining
tentacles, and are thus carried towards the centre of the leaf.
Stimulants applied to the glands of the short tentacles on the disc
indirectly excite movement of the exterior tentacles, for the stimulus
of the glands of the disc acts on the bending part of the latter
tentacles, near their bases, and does not first travel up the pedicels
to the glands, to be then reflected back to the bending place. Some
influence, however, does travel up to the glands, causing them to
secrete most copiously, and the secretion to become acid, just such
an influence as that which in animals is transmitted along the nerves
to glands, modifying their power of secretion, independently of the
condition of the blood-vessels. Over organic substances that yield
soluble matter the tentacles remain clasped for a much longer time
than over those not acted upon by the secretion, or over inorganic
objects. That they have the power of rendering organic substances
soluble, that is, that they have the power of digestion, is no longer
a question of dispute. They certainly have this power, acting on
albuminous compounds in exactly the same manner as does the gastric
juice of mammals, the digested matter being afterwards absorbed. In
animals the digestion of albuminous compounds is effected by means of
a ferment, pepsin, together with weak hydrochloric acid, though almost
any acid will serve, yet neither pepsin nor an acid by itself has any
such power. It has been observed that when the glands of the disc are
excited by the contact of any object, especially of one containing
nitrogeneous matter, the outer tentacles and often the blade become
inflected, the leaf thereby becoming converted into a temporary cup or
stomach. The discal glands then secrete more copiously, the secretion
becoming acid, and, moreover, some influence being transmitted by them
to the glands of the exterior tentacles, causing them to emit a more
abundant secretion, which also becomes acid. This secretion is to a
certain extent antiseptic, as it checks the appearance of mould and
infusoria, and in this particular acts like the gastric juice of the
higher animals, which is known to arrest putrefaction by destroying the
microzymes.
With animals, according to Schiff, mechanical irritation excites
the glands of the stomach to secrete an acid, but not pepsin. There
is strong reason to believe, too, that the glands of Drosera, which
are continually secreting viscid fluid to replace the losses by
evaporation, do not secrete the ferment proper for digestion when
mechanically irritated, but only after absorbing certain matters of
a nitrogeneous nature. The glands of the stomachs of animals secrete
pepsin only after they have absorbed certain soluble substances
designated peptogenes, showing a remarkable parallelism between the
glands of Drosera and those of the stomach in the secretion of their
appropriate acid and ferment.
Not only animal matter, but also the albumen of living seeds, which
are injured or killed by the secretion, are acted upon by the glands
of Drosera. Matter is likewise absorbed from pollen, and from fresh
leaves. The stomachs of vegetable-feeding animals, as is only too well
known, possess a similar power of extracting nourishment from such
articles. Though properly an insectivorous plant, but as pollen, as
well as the seeds and leaves of surrounding plants, cannot fail to be
often or occasionally blown upon the glands of Drosera, yet it must be
credited with being to a certain extent a vegetable feeder.
That a plant and an animal should secrete the same, or nearly the same,
complex digestive fluid, adapted for a similar purpose, is a wonderful
fact in physiology, but not more remarkable than the movements of a
tentacle consequent upon an impulse received from its own gland, the
movement at the bending place of the tentacle being always towards
the centre of the leaf, and so it is with all the tentacles when
their glands are excited by immersion in a suitable fluid. The short
tentacles in the middle part of the disc, however, must be excepted,
as these do not bend at all when thus excited. But when the motor
impulse comes from one side of the disc, the surrounding tentacles,
and even the short ones in the middle of the disc, all bend with
precision towards the point of excitement, no matter where it may be
located. This is in every way a remarkable phenomenon, for the leaf
appears as if endowed with animal sense and intelligence. It is all the
more remarkable when the motor impulse strikes the base of a tentacle
obliquely to its flattened surface, for then the contraction of the
cells must be restricted to one, two or a very few rows at one end, and
different sides of the surrounding tentacles must be acted on that all
may bend with precision to the point of excitement. The motor impulse,
as it spreads from one or more glands across the disc, enters the bases
of the surrounding tentacles, and instantly acts on the bending place,
but does not first proceed up the tentacles to the glands, causing them
to reflect back an impulse to their bases, although some influence
is sent up to the glands, whereby their secretion is soon increased
and rendered acid. The glands, being thus excited, send back some
other influence, dependent neither on increased secretion nor on the
inflection of the tentacles, which causes the protoplasm to aggregate
in cell beneath cell. This maybe called a reflex action. How it differs
from that which proceeds from the nerve-ganglion of an animal, if it
differ at all, no one can say. It is probably the only known case of
reflex action in the vegetable kingdom.
Concerning the mechanism of the movements and the character of the
motor impulse little is known. During the act of inflection fluid
surely passes from one part to another of the tentacles. In explanation
of the fact it is claimed that the motor impulse is allied in nature
to the aggregating process, and that this causes the molecules of
the cell-walls to approach each other, as do the molecules of the
protoplasm within the cells, thereby causing the cells in all to
contract. This is probably the hypothesis that best accords with the
observed facts, although some strong objections may be urged against
this view. The elasticity of their outer cells, which comes into
activity as soon as those on the inner side cease contracting with
prepotent force, leads largely to the re-expansion of the tentacles,
but there is reason to suspect that fluid is continually and slowly
attracted into the outer cells during the act of re-expansion, thus
augmenting their tension.
With respect to the structure, movements, constitution and habits of
_Dionæa muscipula_ and _Drosera rotundifolia_, as well as kindred
species, little has been made out by patient study and investigation
in comparison with what remains unexplained and unknown. Many of
their movements, especially of Dionæa and Drosera, seem so sensible
and intelligent that the reflecting mind of man can hardly hesitate
to assign them high positions in organic nature and the possession,
even though in a very small degree, of that consciousness with which
animal life is endowed. That man is psychically related to all life
is the belief of millions in the old world, and the hope of millions
in the new. In this thought is the escape from materialism, that
threat of the ignorant and unbelieving. Higher conceptions of beauty
and greatness are now being entertained by the multitudes, and we
begin to feel that the next great step is being taken when we shall
become, instead of poor trembling denizens of a perishable world, proud
and conscious citizens of an imperishable universe. That we of the
upper ranks of God’s creation alone possess an inner life which shall
transcend all change is no longer a general belief, but there is a
growing hope that all nature shares it, and that love is its expression
and its method. All existence is a unit. Life, law and love are divine.
Man, looking calmly about him, cannot set himself apart as something
essentially different from nature, but must recognize himself as a
part, and include love in the universal scheme of development. All
other expressions of life must share with him in the divine love and
progress. His dogmas, founded on mistaken traditions, have given way to
science, and he cannot but believe that love is in and of the soul, and
that all life has some sort of development of soul. Because plant-life
has no brain, and therefore has no intelligence, no mind, no soul, is
preposterous to contemplate. Who can positively affirm that brain alone
is the seat of conscious intelligence? None but He alone, the Giver of
all life, who sits enthroned and exalted in the everlasting heavens.
SLIME-ANIMALS.
Possibly the simplest of life’s children are the singularly unique and
structureless little Finger Slimes, which live not only in the sea but
also in puddles and pools, and in the gutters of our streets and of
our house-tops. Anywhere that stagnant water abounds these tiny drops
of slime will grow up and make it their home. Sometimes few and far
between, and sometimes in such immense crowds that the entire pond
would seem, if they could be seen with the unaided vision, literally
alive with them, they live, and multiply and die under our very feet.
Nothing can be less animal-like than one of these shapeless masses
of pure protoplasm, yet under a microscope of strong power it may be
seen moving lazily along by pulling out a thick finger of slime and
then letting all the rest of its body flow after it. When coming into
contact with food it may be said to flow over it, dissolving the soft
parts and sending out the hard, indigestible refuse anywhere, no matter
where, for its body is devoid of skin, being merely one general mass of
homogeneous slime.
But what can these little slime specks tell us about the wonderful
powers of life? Nothing at all, it would seem, for in these tiny
creatures life has nothing better to work with than a mere drop of
living matter, which is all alike throughout, so that if broken into
a hundred pieces every piece would be as much a living being as the
whole. And yet by means of the wonderful gift of life, with which
the all-wise Omnipotence has endowed it, this slime-drop lives, and
breathes, and eats, and increases, shrinks away when you touch it,
feels for its food, and moves from place to place, changing its shape
to form limbs and feeling-threads, which are let into the general
organism when they have served the purpose of their existing, only to
be succeeded by others as short-lived as themselves when necessity
requires their development.
So small are these creatures that the largest specimen will be found
to be smaller than the smallest pin’s head. Examine how we will, there
will be found no mouth, no stomach, no muscles, no nerves, no parts of
any kind. The animal looks merely like a minute drop of gum with fine
grains diffused throughout, floating in the water, some times with
outstretched arms, and at other times as a simple drop. An analysis
of the matter of which it is composed shows it to be much the same as
a speck of white-of-egg. Yet it is alive, for it breathes. Kept in a
drop of water, it uses up the oxygen it contains, and renders the water
foul by the carbonic acid it breathes out. The arms, so necessary in
the procurement of food, can be drawn in and thrown out when and where
the animal chooses, showing that some option is undoubtedly exercised
in the matter. Minute jelly-plants, that live in the water, and even
higher animals than itself, constitute its food. The presence of an
animal with a shell does not deter it from attack, for it is just as
able to deal with it as with the softer, shell-less kinds, sucking
their jelly-like contents, and discarding the empty, innutritious
shells.
Quite as interesting among the Moners, to which the Finger Slime
belongs, is the _Protomyxa aurantiaca_, a shapeless bit of transparent
matter, containing merely circulating granules. Locomotion is effected
by extending the body into pseudopodia, or false feet, and contracting
them. Its movement is slow and gliding. When at rest it appears as a
mere lump of jelly, but its whole demeanor changes when in the presence
of a living animal suited for food. Fine threads immediately begin to
shoot out from all sides, which fuse about the unsuspecting prey, while
all the little grains in the slime course to and fro. For five or six
hours the little fellow hugs closely round the prey until it has become
thoroughly absorbed, at least the nutritious parts, into its body-mass,
when it draws itself away, or back into its original place, leaving by
its side the skeleton of its late victim. Without eyes or ears or parts
of any kind it knows how to find its food; without muscles or limbs it
is able to seize it; without a mouth it can suck out its living body,
and without a stomach it can digest the food in the midst of its own
slime, and cast out the parts for which it has no use.
[Illustration: PROTOMYXA FEEDING.]
When Protomyxa has become a burden to itself it divides itself by a
simple process of fission, each part being complete in itself, or it
assumes a thick covering, becoming encysted, as it is termed. In a
little while the enclosed mass divides into spheres, the cell-wall
bursts, and the little spheres, which have now taken on a sort of
tadpole shape, float out upon the water, where they soon assume the
parent-form.
Like all living things, these Moners have a desire for food, which
their protoplasm first appropriates, then converts into available
material. They thus grow and increase in size, but when they become
too large to be comfortable they usually split into two, in obedience
to the law of their being, and each half goes its own way as a living
animal. This is the earliest form of parentage, the simplest form
of reproduction. Thus yielding to this necessity of a separation of
one into more than one, these Moners live on forever, or as long as
the earth continues to support life, thus becoming immortal in the
scientific sense in which the term is used to devote a continuance of
the physical life on earth. They only and their nearest relatives, as
simple in structure as themselves, achieve this stupendous result, for
in such a division of their entire substance they know no loss, no
death of any part, violence only being able to sunder them from life.
They resolve themselves into their own offspring, and nothing perishes.
PRIMITIVE LASSO-THROWERS.
Every one knows that the long cord or thong, called the lasso, is the
peculiar weapon of the South American hunter. Almost from his earliest
childhood the young Gaucho learns to amuse himself with it, and as soon
as he is able to walk takes great pleasure in catching young birds and
other animals around his father’s hut, hurling the long lash with such
dexterity that the noose drops over their bodies and brings them to his
feet. Did we wish to select from among all the denizens of life the
most brilliant, graceful, and sylph-like, whose very life-histories
read more like the romance of poetry than sober reality, we would
choose those which might be appropriately designated the lasso-throwers.
Now among animals, as is only too well known, any weapons which they
could be called upon to use must develop in their own bodies, and
therefore it could hardly be suspected that a simple jelly-animal could
be provided with a lasso ready grown in its own flesh. Yet it is so,
for in that class of animals, which ranks just above the sponges, we
discover a weapon of this kind as simple and as deadly, and far more
wonderful in its action than any used by man.
In fresh-water ponds, attached by its base to the under surfaces of
aquatic plants, may be found a very small animal, just large enough to
be seen without the aid of a lens, usually pale green, but sometimes
of a brown color. This is our common hydra, technically called _Hydra
fusca_. It is nothing more than a tube or sac, with a sucker at one end
to hold on with, and a mouth at the other, surrounded with from five
to eight hollow tentacles or feelers, which opens into a central cavity
or stomach. Firm and muscular are the walls of the sac, so that the
little creature, which is not fixed permanently to whatever it is found
clinging to, may stretch itself out or draw back as its own volition
dictates, or move slowly along by means of its sucker, or float easily
or contentedly upon the water. But the most remarkable, as well as the
most interesting thing about this odd creature is the power which it
possesses of overcoming animals more powerful and active than itself.
[Illustration: FRESH-WATER HYDRA MOORED AND SEARCHING FOR PREY.]
Groping about with its flexible arms, which are closely invested with
fine jelly-hairs, with which it seemingly feels, or attached to some
leaf or bit of floating stick, its tentacles reaching out in all
directions, the Hydra instantly paralyzes any minute insects, young
snail or infusorian that touches its feelers, and complacently closing
its arms over the helpless victim, carefully tucks it away, so to
speak, into its stomach, where it is speedily digested. This power of
paralyzing and thus readily capturing active living creatures is due to
the presence in the skin of the tentacles and body of what are called
lasso-cells, or nettling-organs, which are minute, transparent cells,
so small that two hundred of the largest would occupy but the distance
of an inch, each being armed with a long barbed thread coiled up within
its walls. This delicate thread, which is often from twenty to forty
times the length of the cell, lies bathed in a poisonous fluid, and
only waits for the cell-walls to burst, which they do when the Hydra
touches an animal swimming near it, when thousands of these little
barbed cords dart into the victim, quickly paralyzing it and rendering
it an easy prey to its captor. All Cœlenterates, such as jelly-fishes
and coral polyps, possess these nettling-organs.
Thus we see where the Hydra’s strength lies. He has no need to
struggle, for his victim, penetrated by a multitude of darts, and
made powerless by the poison instilled, becomes as manageable as an
equal bulk of inert matter. It behooves the little creature to take
things quietly, for a cell once burst cannot be used again, and he is
therefore compelled to wait until a new one is grown to take the place
of the one that has become exhausted. So he patiently bides his time
till his victim is half-conquered, when he draws him gently into his
body. He lives and catches his food, as must be apparent, without the
necessity of moving very far from the place where he had his birth.
All the summer through the Hydra puts out buds from its side, which,
when their tentacles have grown, drop from the parent-body, and settle
down in life for themselves. But when winter comes, and before all life
has become extinct, an egg appears near the base of the tubes of those
that are living, and these eggs lie dormant till the next spring, when
they are hatched, and a new generation of Hydras is produced. Budding,
which is but a process of natural self-division, is carried on to a
large extent, more individuals being produced in this way than from
eggs. These buds are at first a simple bulging out of the body-walls,
the bud enveloping a portion of the stomach, until it becomes
constricted and drops off, the tentacles meanwhile budding out from the
distal end, and a mouth-opening arising between them. In the Hydra,
the Actinia, and other polyps, and in truth in all the lower animals,
budding is simply due to an increase in the growth and multiplication
of cells at a special place on the outside of the body. As in the
vertebrates, man included, the Hydra arises from an egg which, after
fertilization, passes through two stages, the germ consisting at first
of two cell-layers, but the sexes are not separate as in the marine
Hydroids, which grow in colonies that may be either male or female.
Like some other animals of simple structure, the Hydra is capable of
reproducing to a most wonderful degree when cut into pieces. Divided
in two, each becomes a perfect Hydra, and even when sliced into any
number of thin rings each ring will grow out a crown of tentacles. You
may split them into longitudinal strips and each strip will eventually
become a well-shaped Hydra. Two individuals may be fastened together
by a horse-hair and in a short time they will have become like Siamese
twins, but there will never arise the slightest disagreement between
them. A Hydra turned inside out will readily adapt itself to the
change, and in a few days will be able to swallow and digest bits
of meat, its former stomach-lining having now taken upon itself the
condition of skin.
_Hydra fusca_ is our simplest lasso-thrower, and the only one to be
found in fresh waters in this country. Such a wonderful and deadly
weapon is his, that it is easy to understand how his numerous relatives
in the wide ocean have made good use of the weapon with which nature
has provided them, and secured, under all kinds of shapes and forms,
homes and resting-places throughout the vast waste of waters. From the
Arctic to the Tropics, and from the shallow seaside pools at low tide
to the fathomless abysses of the ocean, we meet the lasso-throwers.
Now in the form of huge jelly-fishes, covering the sea for miles and
miles, transparent domes by day and phosphorescing lights by night, and
now as tiny balls of jelly, glistening by millions in some quiet bay
and splintering into light upon the beach; or in the form of living
animal-trees waving their graceful arms over rocks in waters deep, or
creeping like delicate threads over shells and stones and seaweed on
the shore, where they often lose their identity and are mistaken for
plants. There is scarcely a nook or cranny in the bed of ocean where
these tree-like forms, associated with the beautiful sea-anemone, whose
brilliant crimson, green and purple are unmatched in color by gem and
flower, are not to be found.
All these beautiful creatures, as well as the living coral that nestles
in the bosom of the warm Mediterranean or the sea that lashes our
Southern shores, or that struggles boldly against Pacific’s waves,
are lasso-throwers. _Cœlenterata_, the “hollow-bodied animals,”
because of the large cavity within their bodies, is the name by which
they are known to science. They naturally fall into two families,
the _Hydrozoa_, or Water Animals, and the _Actinizoa_, or Ray-like
Animals, our little Hydra, about which so much has been written, being
representative of the former and the Anemones of the latter division.
FIVE-FINGERED JACK ON THE OYSTER.
Quite as infinite in number, variety and form is the life of the
sea as that of the land. But of all marine animals, however, there
is none more curious than the echinoderm, a name derived by science
from two Greek words, indicating an animal bristling with spines like
the hedgehog. These creatures are sometimes free, but quite as often
attached by a stem, flexible or otherwise, and radiate after the
fashion of a circle or star, or are of the form of a star, with more
or less elongated arms. They are covered with shell-like plates, which
they secrete for themselves, and are still further protected by spines
or scales.
Perhaps the most common of the echinoderms is the Star-fish, or
Five-fingered Jack, as it is called by sailors. Whoever has spent
any time on the seashore has doubtless made the acquaintance of
this animal, for it is readily distinguishable by its shape, its
upper surface being rough and tuberculous, and armed with spine-like
projections, while the under portion is soft, containing the essential
organs of life and locomotion.