uninitiated, is thought to be a creature incapable of movement of
any kind. But this is far from being the case, for in its native
element it moves along the bottom of the sea with the greatest ease,
being provided with an apparatus specially adapted for the purpose.
Ordinarily its arms are kept upon the same level, but in passing over
obstacles that lay in its path, the animal has the power of raising
any one of its several arms. Elevations are ascended with the same
ease and facility as progression on plane surfaces is effected.
Perforating the arms, or rays, and issuing from apertures, will be
found large numbers of membranous tubes, which prove to be the feet
of the animal. Upon careful examination the latter will be found to
consist of two parts, a bladder-like portion, resident within the body,
and a tubular outlying projection, ending in a disk-shaped sucker, thus
showing the feet to be muscular cylinders, hollow in the centre, and
very extensible. In progression the animal extends a few of its feet,
attaches its suckers to the rocks or stones and then, by retracting its
feet, draws the body forward. Like that of the tortoise, its pace is
slow and sure. But the most singular thing about this singular animal
is its manner of overcoming obstructions, which it must certainly
perceive, judging from the preparations to surmount them which it makes
at the opportune moment.
In addition to organs of locomotion Star-fishes possess blood-vessels,
digestive and respiratory apparatus, and a nervous system of a very
low order, an inference to which its seeming capacity of enduring
vivisection without pain unmistakably leads.
Interesting as its manner of progression, even under the most trying
circumstances, must be, yet there is nothing in the life of this
lowly-organized animal that has half the charm to the true lover and
student of nature than the mother Star’s devotion to her young. Her
eggs she carries in little pouches placed at the base of the rays. When
emitted through an opening, which occasionally and unintentionally
occurs, the mother does not abandon them to the cruel charities of the
ocean world, but gathers them together, forming a kind of protecting
cover of them, very much like a hen brooding over her chickens. Her
actions bespeak an anxiety which could only be born of an affection, as
real and sympathetic as that which a human mother feels for the loss of
any of her offspring. No matter how often the eggs become accidentally
scattered, the mother does not grow weary of her charges and leave
them to themselves, but gathers them to the maternal fold with the same
tender, patient solicitude as characterized her first efforts. Confined
to a tank, when with ova, the mother Star has been known to traverse
the entire length of the vessel until she has found and recovered her
scattered treasures.
Reproduction by eggs is not the only means of generation in vogue. In
common with other sea animals the Star-fish has the strange capacity
of detaching one or more of its arms, each of the cast-off members
becoming in time a perfect creature of its own kind, while a new arm,
fully equipped to perform all necessary functions, will grow out in
place of the lost member. From twelve to fifteen weeks are required
to reproduce a lost ray, the animal meanwhile seeming not the least
discontented, but acting as utterly unconscious of any changes in its
anatomy.
As found upon the shore, Star-fishes appear dead when really they are
alive. Put one of these perfectly still creatures into fresh sea-water,
and in a short time it will probably be disporting itself as freely as
ever it did. But as the dead and the living, when stranded by the tide,
present nearly the same appearance, some certain test seems necessary
to distinguish them apart. If a Star-fish hangs loose and limp, it
is dead; but, however dead it may look, if on touching it there are
manifest a firmness and consistency in its substance, one may feel
reasonably sure that it is playing the ’possum and will revive when
placed in the water. Quite as certain a mode of ascertaining whether
your starry friend is living or dead, is to lay it upon its back, when,
if alive, a number of semi-transparent globular objects will be seen
to move, reaching this way and that, as though feeling for something
to lay hold of wherewith to restore it to its normal position. These
globular appendages are the _ambulacra_, or locomotory organs, seeking
to acquire this end. If, however, no movement is manifested, you can
wisely conclude that your animal is dead.
The Star-fish, not unlike all other animals of the sea, has an appetite
that is never satisfied. Dinner is always welcome. The procurement of
food seems its chief concern in life. It is a scavenger of no mean
importance, keeping up an incessant chase after all kinds of dead
animal matter, and thus largely contributing, it is probable, towards
the maintaining of the waters of the ocean in a state of purity. But
its feeding is not exclusively restricted to decaying matters. Any
species of mollusk, from the humble whelk, not more than five-eighths
of an inch in length, to the lordly oyster, so esteemed by epicures,
constitutes a dainty tidbit. No more inveterate ravager and brigand,
not even excepting man himself, have the oyster-beds to disturb
the equanimity and serenity of their existence than the audacious,
insinuating Star-fish.
With its five arms, and apparently without any other organ, this
comparatively insignificant little being accomplishes a work which man,
without the aid of extraneous appliances, is quite unable to execute.
It opens an oyster as deftly and effectually as an expert oysterman
would do, and that, too, without the habitual oyster-knife, and
swallows the slimy bivalve in the same manner as the lords of creation
do. Man, with all his genius and skill, were he deprived of all other
means of subsistence than the oyster, and having no implement with
which to open it, would be severely puzzled to get at the savory morsel
shut up in its obstinate valves, yet the Star-fish performs the task
seemingly without the least difficulty.
How the Star-fish manages the problem was at first a matter of
guess-work. For a long time it was confidently believed that the animal
waited for the moment when the oyster opened its shell to introduce one
of its arms into the opening. This much gained, the other four arms
were got in without much trouble, and the whole business ended with
the devouring of the inmate. This belief is no longer tenable. Careful
observation has revealed to us the true inwardness of the proceeding.
The oyster is seized between the arms of the Star-fish and held under
its mouth by the aid of its suckers. Thus secured, the Asterias, or
Star-fish, everts its stomach, and envelops the whole oyster in its
interior recesses, distilling a poisonous fluid, a secretion from its
mouth, which causes the oyster to open its shell, when the robber, as
it were, crawls in and takes its dessert. Incredible numbers of oysters
are destroyed by Star-fishes, but the oystermen fail to see that their
own barbaric ignorance is largely to blame. Star-fishes drawn up in
nets, rakes and dredges in immense quantities are tied into bundles,
but the cords are made so tight that the pile is cut in twain, the
result being that all the pieces, when afterwards thrown overboard,
become new and perfect Star-fishes.
[Illustration: STAR-FISH OPENING AN OYSTER.]
Not often has one the pleasure of meeting with these animals on the
New Jersey coast, but yet they are occasionally seen, more frequently,
perhaps, in the North. _Asterias berylinus_, the commoner form, is
a fairly large species, of a more or less greenish color, sometimes
waning to brown, and roughly covered with tubercles. Its five arms, at
the extremity of each of which is situated a single red-eye speck, are
somewhat irregularly arranged, and not rarely one is stumpy through
breakage or unequal development.
When a Star-fish is alarmed, or finds itself in strange quarters,
it will be seen to curl up the tips of its rays, and there under
the point of each ray will be found a thick red spot seated on the
extremity of a nerve, and having in it as many as from one hundred
to two hundred crystal lenses surrounded by red cells. With such a
highly-developed eye, which is far better than the jelly-fish enjoys,
it is no wonder that the Star-fish is so quick in discerning food,
or enrages the fisherman by the discovery of the bait which he had
intended for other animals, for it turns out that this stupid-looking
animal is more wide-awake than it is given credit for. Sometimes, as
in the beautifully delicate Star-fish, called the “Lingthorn,” a soft
lid, or feeler, hangs over the eye-spot, which gives to the creature a
curiously intelligent look, but in the case of our common form this lid
is notably absent.
From all that has been written it must be evident that our first
walking animal is by no means a poor or feeble creature. He has a chain
armor woven into his leathery skin, with sharp, pointed spines, and
snapping, beak-like claws to protect him; an excellent digestion and a
capacious mouth to feed his greedy stomach, and a fine array of nerves,
quick feeling and eyesight, and a wonderful apparatus for moving over
the ground. When it is added to all these possessions the ability to
close over the wound in the case of a lost ray and the growing of a new
one, we see that his powers of living satisfactorily are by no means
insignificant. But this curious walking apparatus of the Star-fish
is far from being perfect in all his relations. They do not all walk
by means of suckers any more than all sponge-animals build toilet
sponge, or all slime-animals make chambered shells. Sure, the Rosy
Feather-stars, for example, have no use for feet-tubes, as their lives
are generally spent upon the rocks or nestled in bunches of sea-weed.
Brittle-stars, as these are called, though closely related to the
Star-fishes, are not easily confounded with them, for their arms are
found to radiate from a clearly defined central disk, and there is no
prolongation of their stomachs and ovaries into their interiors. The
tube-feet pass out from the plates along the sides of the arms, instead
of from the under surface as in the Star-fishes proper, and probably
serve merely as a help for breathing, locomotion over the sands being
effected by their long flexible arms. Their home is chiefly among the
tangle and eel-grass, where their protecting covering affords them
security from their many enemies.
EARTH-WORMS IN HISTORY.
Earth-worms are found throughout the world. Though few in genera, and
not many in species, yet they make up in individual numbers, for it
has been estimated that they average about one hundred thousand to the
acre. Our American species have never been monographed, which renders
it impossible to judge of their probable number. Their castings may be
seen on commons, so as to cover almost entirely their surface, where
the soil is poor and the grass short and thin, and they are almost as
numerous in some of our parks where the grass grows well and the soil
appears rich. Even on the same piece of ground worms are much more
frequent in some places than in others, although no visible difference
in the nature of the soil is manifest. They abound in paved court-yards
contiguous to houses, and on the sidewalks in country towns, and
instances have been reported where they have burrowed through the
floors of very damp cellars.
Beneath large trees few castings can be found during certain parts
of the year, and this is apparently due to the moisture having been
sucked out of the ground by the innumerable roots of the trees, an
explanation which seems to be confirmed by the fact that such places
may be observed covered with castings after the heavy autumnal rains.
Although most coppices and woods support large numbers of worms, yet
in forests of certain kinds of tree-growths, where the ground beneath
is destitute of vegetation, not a casting is seen over wide reaches
of ground, even during the autumn. In mountainous districts worms are
mostly rare, it would seem, a circumstance which is perhaps owing to
the close proximity of the subjacent rocks, into which it is impossible
for them to burrow during the winter, so as to escape being frozen. But
there are some exceptions to this rule, for they have been found at
great altitudes in certain parts of the world, and especially is this
so in India, where they have been observed to be quite numerous upon
the mountains.
Though in one sense semi-aquatic animals, like the other members of the
great class of Annelids to which they belong, yet it cannot be denied
that earth-worms are terrestrial creatures. Their exposure to the dry
air of a room for a single night proves fatal to them, while on the
other hand they have been kept alive for nearly four months completely
submerged in water. During the summer, when the ground is dry, they
penetrate to a great depth and cease to work, just as they do in winter
when the ground is frozen. They are nocturnal in their habits, and
may be seen crawling about in large numbers at night, but generally
with their tails still inserted in their burrows. By the expansion of
this part of the body, and with the aid of the short reflexed bristles
with which they are armed inferiorly, they hold so securely that they
can seldom be withdrawn from the ground without being torn in pieces.
But during the day, except at the time of pairing, when those which
inhabit adjoining burrows expose the greater part of their bodies for
an hour or two in the early morning, they remain in their burrows.
Sick individuals, whose illness is caused by the parasitic larvæ of a
fly, must also be excepted, as they wander about during the day and
die on the surface. Astonishing numbers of dead worms may sometimes be
seen lying on the ground after a heavy rain succeeding dry weather, no
less than a half-hundred in a space of a few square yards, but these
are doubtless worms that were already sick, whose deaths were merely
hastened by the ground being flooded, for if they had been drowned
it is probable, from the facts already given, that they would have
perished in their burrows.
After there has been a heavy rain the film of mud or of very fine sand
to be seen over gravel-walks in the morning is often distinctly marked
with the tracks of worms. From May to August, inclusive, this has been
noticed when the months have been wet. Very few dead worms are anywhere
to be seen on these occasions, although the walks are marked with
innumerable tracks, five tracks often being counted crossing a space
of only an inch square, which could be traced either to or from the
mouths of the burrows in the gravel-walks for distances varying from
three to fifteen yards, but no two tracks being seen to lead to the
same burrow. It is not likely, from what is known of the sense-organs
of these animals, that a worm could find its way back to its burrow
after having once left it. They leave their burrows, it would seem, on
a voyage of discovery, and thus they find new sites for the exercise of
their powers. For hours together they may often be seen lying almost
motionless beneath the mouths of their burrows. But let the ejected
earth or rubbish over their burrows be suddenly removed and the end of
the worm’s body may be seen rapidly retreating.
This habit of lying near the surface leads to their destruction to an
immense extent, for, at certain seasons of the year, the robins and
blackbirds that visit our lawns in the country may be observed drawing
out of their holes an astonishing number of worms, which could not be
done unless they lay close to the surface. But what brings the worms
to the surface? This is a question whose answer cannot be positively
asserted. It is not probable that they behave in this manner for the
purpose of breathing fresh air, for it has been seen that they can live
a long time under water. That they are there for the sake of warmth,
especially in the morning, is a more reasonable supposition, which
seems to be confirmed by the fact that they often coat the mouths of
their burrows with leaves, apparently to prevent their bodies from
coming into contact with the cold, damp earth, and by the still other
fact that they completely close their burrows during the winter.
Some remarks about the structure of the earth-worm now appear apropos.
Its body consists of from one hundred to two hundred almost cylindrical
rings, each provided with minute bristles. The muscular system is well
developed, thus enabling these animals to crawl backwards as well as
forwards, and to retreat by the help of their affixed tails into their
burrows with extraordinary rapidity. Situated at the anterior end
of the body is the mouth. It is furnished with a little projection,
variously called the lobe or lip, which is used for prehension. Behind
the mouth, internally located, is a strong pharynx, which is pushed
forwards when the animal eats, corresponding, it is said, with the
protrudable trunk of other Annelids. The pharynx conducts to the
œsophagus, on each side of the lower part of which are placed three
pairs of large glands, called calciferous glands, whose function is
the secretion of carbonate of lime. These glands are very remarkable
organs, and their like is not to be found in any other animal. Their
use is connected in some way with the process of digestion. The
œsophagus, in most of the species, is enlarged into a crop in front of
the gizzard. This latter organ is lined with a smooth, thick chitinous
membrane, and is surrounded by weak, longitudinal, but powerful
transverse muscles, whose energetic action is most effectual in the
trituration of the food, for these worms possess no jaws, or teeth
of any kind. Grains of sand and small stones, from the one-twentieth
to the one-tenth of an inch in size, are found in their gizzards and
intestines, and these little stones, independently of those swallowed
while excavating their burrows, most probably serve, like millstones,
to triturate their food. The gizzard opens into the intestine--a most
remarkable structure, an intestine within an intestine--which runs in a
straight line to the vent at the posterior end of the body. But this
curious structure, as shown by Claparède, merely consists of a deep
longitudinal involution of the walls of the intestine, by which means
an extensive absorbent surface is secured.
Worms have a well-developed circulating system. Their breathing
is effected by the skin, and so they do not possess any special
respiratory apparatus. Each individual unites the two sexes in its
own body, but two individuals pair together. The nervous system is
fairly well developed, the two nearly confluent cerebral ganglia being
situated very close to the anterior extremity of the body.
Being destitute of eyes, we would naturally conclude that worms were
quite insensible to light; but from many experiments that have been
made by Darwin, Hofmeister and others, it is evident that light
affects them, but only by its intensity and duration. It is the
anterior extremity of the body, where the cerebral ganglia lie, that is
affected, for if this part is shaded and other parts of the body are
illuminated no effect will be produced. As these animals have no eyes,
it is probable that the light passes through their skins and excites in
some manner their cerebral ganglia. When worms are employed in dragging
leaves into their burrows or in eating them, and even during the brief
intervals of rest from their labors, they either do not perceive the
light or are regardless of it, and this is even the case when the light
is concentrated upon them through a large lens. Paired individuals will
remain for an hour or two together out of their burrows, fully exposed
to the morning light, but it appears, from what some writers have said,
that a light will occasionally cause paired individuals to separate.
When a worm is suddenly illuminated and dashes into its burrow, one
is led to look at the action as a reflex one, the irritation of the
cerebral ganglia apparently causing certain muscles to contract in an
inevitable manner, without the exercise of the will or consciousness
of the animal, as though it was an automaton. But the different effect
which a light produces on different occasions, and especially the fact
that a worm when in any way occupied, no matter what set of muscles
and ganglia may be brought into play, is often regardless of light,
are antagonistic to the view of the sudden withdrawal being a simple
reflex action. With the higher animals, when close attention to some
object leads to the disregard of the impressions which other objects
must be producing upon them, we ascribe this to their attention being
then absorbed, and attention necessarily implies the presence of mind.
Although worms cannot be said to possess the power of vision, yet their
sensitiveness to light enables them to discriminate between day and
night, and thus they escape the attacks of the many diurnal animals
that would prey upon them. They are less sensitive to a moderate
radiant heat than to a bright light, as repeated experiments have
conclusively shown; and their disinclination to leave their burrows
during a frost proves that they are sensitive to a low temperature.
Investigation fails to locate in worms any organ of hearing, from
which must be concluded that they are insensible to sounds. The shrill
notes of a metallic whistle sounded near them, and the deepest and
loudest tones of a bassoon, failed to awaken the least notice. Although
indifferent to modulations in the air, audible to human ears, yet
they are extremely sensitive to vibrations in any solid object. Even
the light and delicate tread of a robin affrights and sends them deep
into their burrows. It has been said that if the ground is beaten,
or otherwise made to tremble, that worms believe they are pursued by
a mole and leave their burrows, but this does not stand the test of
experiment, for the writer has frequently beaten the ground in many
places where these creatures abounded, but not one emerged. A worm’s
entire body is sensitive to contact, the slightest puff of air from the
mouth causing an instant retreat. When a worm first comes out of its
burrow it generally moves the much-extended anterior extremity of its
body from side to side in all directions, apparently as an object of
touch, and there is good reason to believe that they are thus enabled
to gain a general knowledge of the form of an object. Touch, including
in this term the perception of a vibration, seems much the most highly
developed of all their senses. The sense of smell is quite feeble, and
is apparently confined to the perception of certain odors. They are
quite indifferent to the human breath, even when tainted by tobacco,
or to a pellet of cotton-wool with a few drops of Millefleur’s perfume
when held by pincers and moved about within a few inches of them. The
perception of such an unnatural odor would be of no service to them.
Now, as such timid creatures would almost certainly exhibit some signs
of any new impression, we may reasonably conclude that they did not
perceive these odors. But when cabbage leaves and pieces of onion were
employed, both of which are devoured with much relish by worms, the
result was different. These, with bits of fresh raw meat, have been
buried in pots beneath one-fourth of an inch of common garden soil, or
sometimes laid on pieces of tin foil in the earth, the ground being
pressed down slightly, so as not to prevent the emission of any odor,
and yet they were always discovered by the worms that were placed
in the pots, and removed after varying periods of time. These facts
indicate that worms possess some power of smell, and that they discover
by this means odoriferous and much-coveted kinds of food.
That all animals which feed on various substances possess the sense of
taste, is a wise presumption. This is certainly the case with worms.
Cabbage leaves are much liked by worms, and it would seem that they
are able to distinguish between the different varieties, but this may
perhaps be owing to differences in their texture. When leaves of the
cabbage, horse-radish and onion were given together, they manifestly
preferred the last to the others. Celery is preferred to the leaves of
the cabbage, lime-tree, ampelopsis and parsnip, and the leaves of the
wild cherry and carrots, especially the latter, to all the others.
That the worms have a preference for one taste over another, is still
further shown from what follows. Pieces of the leaves of cabbage,
turnip, horse-radish and onion have been fed to the worms, mingled with
the leaves of an Artemisia and of the culinary sage, thyme and mint,
differing in no material degree in texture from the foregoing four, yet
quite as strong in taste, but the latter were quite neglected excepting
those of the mint, which were slightly nibbled, but the others were all
attacked and had to be renewed.