proceeded to the east, and personally engaged in picking the
mulberry-leaves. On this occasion the married and single ladies were
forbidden to wear their ornaments, and the usual employments of females
were lessened, in order to encourage attention to the silkworms. When the
rearing of the silkworms was completed, the cocoons were divided (for
reeling) and the silk weighed (for weaving), each person being rewarded
according to her labour, in order to provide dresses for the celestial and
ancestorial sacrifices. In all this none dared indulge in indolence.
[Illustration: _Photo by J. Peat Millar_] [_Beith._
CONVOLVULUS HAWK-MOTH.
A grey moth, with pink bands on the body.]
[Illustration: _Photo by C. N. Mavroyeni_] [_Smyrna._
GREAT PEACOCK-MOTH.
Brown with pale borders. The largest moth found in Europe.]
[Illustration: _Photo by Dr. R. W. Shufeldt_] [_Washington._
POLYPHEMUS MOTH.
On leaves of linden-tree, just out of cocoon. A native of North America.]
"In the last month of summer the order was given to the female officers to
dye the silk of various colours, in order to weave chequered sarcenets,
comprising black and white, black and green, green and red, with
red-and-white checks--all of which was to be done according to the ancient
rule, without the least variation; the black, yellow, azure, and red tints
were all to be correct and good, without the least fault, in order to
provide dresses for the celestial and ancestorial sacrifices, and standards
for distinguishing the high and low degrees.
[Illustration: Photo by W. Saville-Kent, F.Z.S.] [_Milford-on-Sea._
WHITE PLUME-MOTH.
A very delicate insect. The wings are cleft almost to the base into
separate feathers, two on the fore wings and three on the hind wings.]
"In ancient times the emperor and his princes had a public mulberry garden
and a silkworm establishment erected near some river. On the morning of the
first day of the third month of spring, the sovereign, wearing a leather
cap and a plain garment, ascertained by lot the chief of his three queens,
with the most honourable amongst his concubines, and caused them to attend
to the rearing of the silkworms in the above-named establishment. They then
brought the eggs of the worms, and washed them in the river above alluded
to, after which they picked the mulberry-leaves in the public garden, and
aired and dried them, in order to feed the worms.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
INDIAN SWALLOW-TAILED MOTH.
Resembles the American Luna Moth figured on page 718, and of an equally
delicate green.]
"When the season was over, the royal concubines, having completed the
business of rearing the silkworms, brought the cocoons to show them to the
prince, when he presented the cocoons again to his consort, whereupon his
consort said, 'This is the material of which your highness's robes are to
be formed.' Having said which, she covered herself with her robe, and
received the cocoons. On this occasion the ladies of the court were
honoured with the present of a sheep. This was the mode in which the
presentation of the cocoons was anciently conducted."
In the reign of Justinian eggs of the Chinese mulberry-silkworm were
smuggled into Europe by two monks, and the culture of silk rapidly spread
through Southern Europe, where it has continued to form a staple industry
ever since. In the Peloponnesus especially such large plantations of
mulberry-trees were grown for the purpose of rearing silkworms as to give
the peninsula its modern name of Morea. Silk is obtained in different parts
of the world from the cocoons of various other moths, chiefly belonging to
the group of Emperor-moths; but these products are only of local
importance, and are not likely to compete with the mulberry-silkworm.
HALF-WINGED INSECTS, OR BUGS AND FROG-HOPPERS.
BY W. F. KIRBY, F.L.S.
[Illustration: _Photos by W. P. Dando, F.Z.S._]
SHIELD-BUG.
In tropical countries these bugs are often as large as cockchafers.]
[Illustration: JUNIPER-BUG.
Some species of this family are carnivorous as well as herbivorous.]
The order including the Bugs and Frog-hoppers is divided into two
sub-orders. There are also one or two small groups, sometimes treated as
separate orders, and sometimes regarded as aberrant sections of the order,
to which we shall allude later.
The TRUE BUGS have their fore wings of a horny texture, but generally
overlapping, and the extremities form a transparent membrane, resembling
that of the hind wings. They have a long sucking-proboscis curved down
beneath their bodies, and their antennæ usually consist of only four or
five long joints. Most are vegetable-feeders, but some species feed on the
juices of other insects, while a few attack warm-blooded animals, either
casually or habitually.
The first family includes the SHIELD-BUGS. These derive their name from the
unusual development of a part of the thorax called the "scutellum." In most
insects it is only a small plate of no great importance, attached to the
end of the thorax; but in the Shield-bugs it forms a great solid arch,
covering the whole of the wings, and protecting them as the wing-cases
protect the wings of beetles. There are only a few small species in
England, but a great number of beautiful species inhabit warm countries,
some of a brilliant blue or green or yellow, or spotted. Many of them are
comparatively large insects, nearly an inch long, and resemble brilliantly
coloured beetles, from which, however, they can easily be distinguished by
the antennæ, the proboscis, and the shield, the latter of which is not
divided down the middle like the wing-cases of beetles.
[Illustration: _Photo by J. Edwards_] [_Colesborne._
LACE-WING BUG.
An elegant little insect, injurious to pear-trees.]
Next to the Shield-bugs, and considered by many entomologists as belonging
to the same group, are the PENTAGONAL SHIELD-BUGS, so called because the
scutellum, though much smaller than in the Shield-bugs, is often half as
long as the abdomen, and forms a broad triangle, sometimes broken at the
sides, so as to make a five-sided plate, lying above the bases of the
wings. Several green or brown species of this family, about half an inch
long, are common in England among bushes. Many have a very disagreeable
smell, and hence they are called STINK-BUGS in America. They feed on
vegetable juices, and also frequently on soft-bodied insects. Several
species (chiefly foreign) among the Shield-bugs and the present group have
a strong spine, or else a blunt protuberance, projecting from each
shoulder.
The remaining plant-bugs are much more numerous--at least in England--than
those already mentioned, and form several families, which cannot be noticed
in detail. Many species are rather small and delicate creatures, narrower
and softer than the Shield-bugs and Pentagonal Shield-bugs, and are adorned
with various colours, black and red predominating. Some have more
transparent wings than the others, such as the beautiful little LACE-WINGED
BUGS, one species of which is often very destructive to pear-trees.
The BED-BUG is a reddish-brown, somewhat oval insect, common in many old
houses, hiding in cracks and crevices in walls and woodwork, and coming out
at night to suck the blood of sleepers with its sharp proboscis. There are
allied species, sometimes found in hen-houses, pigeon-houses, and places
where bats congregate. The bed-bug has only been known in England for a few
centuries, and though now a great pest in all parts of the world, was
probably a native of Africa originally.
The bed-bug, notwithstanding its offensive odour, is preyed upon by several
other insects, among which are the common cockroach and the MASKED BUG. The
latter is a black-winged bug about three-quarters of an inch long, and
remarkable for the habits of its larva, which conceals itself with dust or
fluff, so that it may steal upon its prey unobserved. The masked bug and
its larva feed on soft-bodied insects of various kinds, and are more
frequently found in outhouses than in dwelling-rooms. This bug occasionally
attacks warm-blooded animals; and a short time ago a great deal of nonsense
was published in the newspapers about a mysterious insect-pest in North
America, called the KISSING-BUG, which seems to have been nothing more
unusual than this insect. There are, however, some much larger species
belonging to the same family, which are formidable pests in the Southern
States of North America, Chili, and various other countries.
[Illustration: _Photo by P. Danado, F.Z.S., Regent's Park._
MASKED BUG.
The larvæ of these insects cover themselves with dust, in order to creep
upon their prey unnoticed.]
After these insects come the WATER-BUGS, of which there are several
families, though the number of species is comparatively small. Some are
very slender insects, with long, slender legs, and may be seen running on
the surface of ponds in England; while others, which are tropical species,
are marine, and are met with running on the surface of the water in the
open sea.
The largest members of the group are some of the great water-bugs found in
Africa, India, and America. Their fore wings are of a light brown, and
measure from 3 to 5 inches in expanse. Their legs are short and strong, and
the front legs are adapted for grasping their prey, which consists of
insects and small fishes. There are some smaller species in which the
female lays her eggs in a cluster on the back of the male, which carries
them about till they are hatched. These bugs fly about in the evening, and
are frequently attracted by electric light.
In England there are two allied species called WATER-SCORPIONS, from their
long front legs, which somewhat resemble the nippers of a scorpion. The
commonest is a brown insect, with the abdomen red beneath. It is about an
inch long, including the breathing-tube, which sticks out behind the body
like a tail, and is formed of two separable parts. It is an oval insect,
half as broad as long, and is common in stagnant water. The other species
is twice as long, and is much more slender, with longer and more slender
legs. It is yellowish brown, like most of the other water-bugs, and is a
sluggish and rather scarce insect, creeping about in the mud at the bottom
of deeper water than that preferred by the commoner species.
The WATER-BOATMEN are yellowish-brown insects, measuring half an inch in
length, with smooth bodies, and long, hairy hind legs, with which they row
themselves about on the water, as if with oars, while floating on their
backs. All the larger water-bugs are capable of inflicting a severe
puncture with their sharp proboscis, if handled incautiously.
[Illustration: _Photo by W. P. Dando, F.Z.S._] [_Regent's Park._
GREAT WATER-BUG.
Very similar species are found in Africa, Asia, and America.]
[Illustration: _Photo by W. P. Dando, F.Z.S._] [_Regent's Park._
GREAT WATER-BUG.
These insects live in water during the day, and fly about in the evening.]
The FROG-HOPPERS and their allies differ from the Bugs in the fore wings
being uniform in texture throughout, and not membranous, with the tips
transparent. Sometimes the fore wings are of a more or less horny texture,
but they are frequently as transparent as the hind wings. All the species
are plant-feeding insects.
[Illustration: _Photo by J. Edwards_] [_Colesborne._
INDIAN CANDLE-FLY.
Erroneously stated to be luminous.]
The first family, the CICADAS, includes a number of large or moderate-sized
species, in which the males are provided with a large, drum-like apparatus
on the abdomen, and some of which make the loud noise for which they have
long been celebrated. There is only one comparatively small species in
England, which is rare, and almost confined to the New Forest. It is black,
with transparent wings, about 1½ inch in expanse, and has red transverse
lines on the abdomen. The largest Indian species, however, sometimes
expands 8 inches. Cicadas have broad heads, broad short bodies, ending
rather abruptly in a point, and their larvæ live in the ground, where they
are sometimes injurious to the roots of trees. The wings are usually, but
not always, transparent--a very common Indian and Chinese species, about 3
inches in expanse, being black, with large yellow spots on the fore wings.
In North America and Australia cicadas are often miscalled Locusts.
The LANTERN-FLIES, or CANDLE-FLIES, which form the next family, derive
their name from having been stated to be luminous, a statement which is now
considered very doubtful. They are insects of considerable size and bright
colours, occasionally resembling butterflies and moths; the largest
species, the LANTERN-FLY of South America, sometimes measures as much as 5
inches across the wings, which are of a pale yellowish or greenish tint,
with a large round spot on the hind wings, formed of black rings or
crescents, and enclosing one or two large white spots. On the head is an
immense hollow, blunt protuberance, marked with one or two longitudinal red
lines. In some species there is a curved horn in front of the head; in some
the horn forms a short cross; in others it ends in a red knob; while others
are destitute of such an appendage. The hind wings are often brightly
coloured, red or yellow usually predominating.
The TRUE FROG-HOPPERS are small insects about a quarter of an inch long,
found among grass and bushes. The fore wings are of rather a stout
consistency and uniform in colour (often yellowish), and the hind wings
transparent. The larvæ are soft grubs, and live in the masses of froth so
common in grass and bushes, which are vulgarly known as "cuckoo-spit."
Passing over several families of small species, we arrive at two which
contain many very destructive insects. The APHIDES, PLANT-LICE, or
SMOTHER-FLIES are the small green or brown winged or wingless insects which
frequently cover the shoots of roses and other trees and plants, and exude
a sweet sticky substance, called "honey-dew," very attractive to ants. One
species, known as the AMERICAN BLIGHT, is extremely destructive to
apple-trees, patches of a substance resembling white cotton appearing on
the bark. Under these patches the bark rots from the attacks of the
insects, the pest being very difficult to eradicate.
[Illustration: _Photo by W. P. Dando, F.Z.S., Regent's Park._
APHIS.
A sexual wingless form.]
[Illustration: _Photo by W. P. Dando, F.Z.S., Regent's Park._
SCALE-INSECT.
The females die, covering their eggs with their own bodies.]
[Illustration: _Photo by W. P. Dando, F.Z.S., Regent's Park._
SCALE-INSECTS.
Showing their appearance when crowded together on a branch.]
Many of the Aphides exhibit the curious phenomenon known as "alternation of
generations." The first brood consists of winged males and females; but the
eggs which the latter lay produce exclusively wingless females, or rather
sexless creatures capable of laying eggs, and these multiply indefinitely
for a time, till perfect males and females are again reproduced. In some
cases the winged forms live on the leaves of trees, and the wingless forms
at the roots of grass, etc. One of the most destructive of all these
insects is the VINE-APHIS, which was probably introduced into Europe from
America, and which threatened at one time almost to destroy the vine
industry in France. Wingless sexless forms live and multiply at the roots
of vines; and in summer winged males and females are produced, which fly
up, and lay eggs on the leaves; while some of the wingless insects also
quit the ground, and form small galls on the vine-leaves. Although very
abundant in America, the insect is not nearly so destructive to the plants
which it attacks as in Europe.
Some species of SCALE-INSECTS are almost equally destructive, especially to
greenhouse plants. The male is slender and two-winged, but the female is
wingless and often legless, and after depositing her eggs usually dies
above them, thus forming a covering to protect them from injury. Cochineal
consists of the bodies of a species of scale-insect which infests the
leaves of a cactus in Mexico.
The TRUE LICE are found on various species of mammals, and imbibe their
food through a proboscis. The BIRD-LICE, or BITING-LICE, form a
well-defined group by themselves. They are sometimes regarded as forming
distinct orders of insects; but some authors treat the first group as a
degraded family of insects allied to the Frog-hoppers, and the second group
as an equally degraded and aberrant family allied to the Lace-winged
Insects.
TWO-WINGED INSECTS, OR FLIES.
BY W. F. KIRBY, F.L.S.
This order of insects is probably one of the most numerous in individuals,
though it may be that, when we know more of the insect population of the
world, we shall find that it is outnumbered in species by the Beetles or
the order to which the Bees and Ants belong. It differs from all other
orders in possessing only two wings instead of four, which is the usual
number in insects. The metamorphoses are complete, and the mouth is
furnished with a proboscis for imbibing liquid food. Hind wings are
represented in many species by a pair of organs called "poisers,"
resembling a knob at the end of a stick, and other species have two small
additional lobes attached to the wing, called "winglets "; but there is no
such thing as a really developed hind wing in any insect belonging to the
group. They are always two-winged flies, except in the case of a few
aberrant species, such as the Fleas, in which no wings, or only mere
rudiments of wings, are to be met with. The Gnats, Daddy-long-legs, and
House-flies are among the commonest representatives of this order.
[Illustration: _Photo by C. N. Mavroyeni_] [_Smyrna._
CICADA AND PUPÆ.
Noted for the loud drumming sound produced by the males.]
The first section of the group includes the GNATS and the DADDY-LONG-LEGS,
or CRANE-FLIES, the members of which may be distinguished by having
moderately long antennæ, composed of more than six joints, and never
terminating in a bristle. They are all vegetable-feeders, with the
exception of the females of gnats and sand-flies, which are furnished with
a lancet-like arrangement for sucking the blood of warm-blooded animals.
The GALL-FLIES, WHEAT-MIDGES, etc., have rather long, jointed antennæ,
which are not feathered, though sometimes tufted on the sides, and their
maggots produce small galls on various trees and plants, or distort and
otherwise injure them. They resemble small gnats, and there are two
particularly destructive species which attack corn in England and
elsewhere,--the WHEAT-MIDGE, an orange-yellow fly with black eyes, which
produces little yellowish or reddish maggots which injure the growing grain
in the ear; and the HESSIAN FLY, which is brown, and produces
semi-transparent maggots, which afterwards grow darker, and when full grown
become pupæ resembling flax-seeds. The maggots attack the stalk, feeding on
the sap till the stalk cracks and bends over. This is an infallible sign of
their presence, and of the mischief they are doing.
Among the best-known insects of this group are the GNATS, or MOSQUITOES, of
which there are many genera and species. There is no difference, however,
to permit of their being classified in two separate popular categories. In
England any of these troublesome insects are called Gnats; out of England
they are termed Mosquitoes, if we are tormented by them, even though they
may belong to the same species as the English ones--for "mosquito" is
merely the Spanish word for "gnat" Anglicised.
[Illustration: BROWN MOSQUITO.
Observe the proboscis in front of the head.]
Gnats breed in standing water, fresh or otherwise, but seem to prefer
rain-water, for they are very numerous about small pools and water-butts.
Consequently they were formerly far more abundant in England than at
present, when the fens were still undrained, and when every house had its
rain-water butt. The females of some species construct small rafts of eggs,
which float about on the surface of the water till hatched, and then
produce small maggots with a breathing-apparatus at the end of the tail. In
this condition they swim head-downwards, while the more compact pupa floats
head-upwards. They may be destroyed by pouring a little kerosene into their
breeding-places; and as this floats on the surface of the water, it does
not interfere with the use of the water in water-butts, which is usually
drawn off by a tap below. The males of gnats often have feathered antennæ
and long, slender legs. The females, however, are more nocturnal in their
habits, and come into houses in the evening, and keep people awake by their
humming and painful "bites," or rather punctures, which frequently cause a
distressing irritation for a day or two afterwards. What is worse is that
they are now known to disseminate various diseases, such as elephantiasis
and also malarial fever of every kind, in this manner--from the
comparatively mild ague of the English fens (now nearly extinct) to the
terrible malaria of Southern Europe, India, and Africa, formerly attributed
to the unhealthy atmosphere of marshy countries, or to exposure to the
night air in warm countries, but now known to be caused by the bites of the
gnats, or mosquitoes, which breed in swampy places, and fly about in the
evening. It is believed that only certain species of gnats convey the germs
of these diseases; and it has been stated that, though ague-bearing species
of gnats are still found in England, those which have been examined for the
purpose have been free from these germs, and are therefore incapable of
propagating the disease.
[Illustration: _Photo by W. P. Dando, F.Z.S., Regent's Park._
HORNET ROBBER-FLY.
Common in the south of England.]
[Illustration: _Photo by W. P. Dando, F Z.S._] [_Regent's Park._
DADDY-LONG-LEGS.
Large species, with variegated wings.]
In many parts of the world gnats are excessively numerous and troublesome
at certain seasons of the year, filling the air like clouds of dust, so
that it is difficult to sleep or eat from the annoyance and irritation
caused by their attacks. This will be readily credible to those who have
experienced the pain which they cause even when not very numerous, and have
been kept awake at night by their shrill piping as they approach. They
appear to be equally numerous in cold and warm countries--Lapland, France,
South Russia, Italy, various parts of America, and in fact most parts of
the world being liable to the inordinate multiplication of different
species.
In England they were formerly so abundant in the fenlands that
mosquito-curtains were in use less than a century ago, and may be so still.
But their numbers have so diminished of late years that, whenever gnats are
a little more troublesome than usual, it is reported that there has been an
invasion of mosquitoes. A year or two ago there was a report that
"mosquitoes" had been brought to Cromer in some fishing-vessel, and the
newspapers contained paragraphs about "mosquitoes" having caused much
annoyance in different parts of London. But many of the specimens submitted
to the inspection of entomologists proved to be nothing more than the
commonest of all the blood-sucking gnats, called the PIPING-GNAT by
Linnæus, on account of its shrill note. The note is produced by the rapid
vibration of the wings, which has been estimated at the rate of 3,000 per
minute. Gnats do not always fly near the ground. Sometimes they have been
seen ascending from cathedrals and other high buildings in such vast swarms
that they resembled clouds of smoke, and gave rise to the idea that the
building was actually on fire.
Equally troublesome and annoying are the SAND-FLIES, as they are called in
England, or the BLACK-FLIES, as they are called in America. They are very
small flies, short and broad, and with broader wings than gnats; and one of
them, which actually destroys many mules and other domestic animals in the
Mississippi Valley, as we learn from Professor Comstock, is called the
BUFFALO-GNAT, from a fancied resemblance of the side-view of the insect to
a buffalo. Other species are equally destructive to the cattle in the Banat
of Hungary. It is a curious circumstance that, in the case of nearly all
two-winged flies which attack men and animals, it is usually only the
females which suck blood, the males frequenting flowers and being perfectly
harmless.
[Illustration: _Photos by W. P. Dando, F.Z.S._
HOVER-FLY.
This fly has a superficial resemblance to a bee. (See page 734.)]
[Illustration: RAT-TAILED LARVA.
Common in filthy water.]
Respecting mosquitoes in South America, Mr. H. W. Bates writes, in his work
"The Naturalist on the Amazons," when passing a night in a boat about
twenty-five miles from the town of Villa Nova: "At night it was quite
impossible to sleep for mosquitoes; they fell upon us by myriads, and
without much piping came straight at our faces as thick as rain-drops in a
shower. The men crowded into the cabins, and then tried to expel the pests
by the smoke from burnt rags; but it was of little avail, although we were
half suffocated during the operation." But the sand-flies, encountered a
little higher up the river, were much worse: "We made acquaintance on this
coast with a new insect-pest, the Piúm, a minute fly, two-thirds of a line
in length, which here commences its reign, and continues henceforward as a
terrible scourge along the upper river, or Solimoens, to the end of the
navigation on the Amazons. It comes forth only by day, relieving the
mosquito at sunrise with the greatest punctuality, and occurs only near the
muddy shores of the stream, not one ever being found in the shade of the
forest. In places where it is abundant, it accompanies canoes in such dense
swarms as to resemble thin clouds of smoke. It made its appearance in this
way the first day after we crossed the river. Before I was aware of the
presence of flies, I felt a slight itching on my neck, wrist, and ankles,
and, on looking for the cause, saw a number of tiny objects, having a
disgusting resemblance to lice, adhering to the skin. This was my first
introduction to the much-talked-of Piúm. On close examination, they are
seen to be small two-winged insects, with dark-coloured body and pale legs
and wings, the latter closed lengthwise over the back. They alight
imperceptibly, and, squatting close, fall at once to work, stretching
forward their tiny front legs, which are in constant motion, and seem to
act as feelers, and then applying their short, broad snouts to the skin.
Their abdomens soon become distended and red with blood, and then, their
thirst satisfied, they soon move off, sometimes so stupefied with their
potations that they can scarcely fly. No pain is felt whilst they are at
work, but they each leave a small circular raised spot on the skin, and a
disagreeable irritation. The latter may be avoided in great measure by
pressing out the blood which remains in the spot; but this is a troublesome
task when one has several hundred punctures in the course of a day [like
Prince Siror, in one of Bulwer Lytton's stories, who fell "pierced by five
hundred spears"]. I took the trouble to dissect specimens, to ascertain the
way in which the little pests operate. The mouth consists of a pair of
thick fleshy lips, and two triangular horny lancets, answering to the upper
lip and tongue of other insects. This is applied closely to the skin, a
puncture is made with the lancets, and the blood then sucked through
between these into the oesophagus, the circular spot which results
coinciding with the shape of the lips. In the course of a few days the red
spots dry up, and the skin in time becomes blackened with the endless
number of discoloured punctures that are crowded together. The irritation
they produce is more acutely felt by some persons than others. I once
travelled with a middle-aged Portuguese who was laid up for three weeks
from the attacks of Piúm, his legs being swelled to an enormous size, and
the punctures aggravated into spreading sores."
[Illustration: _Photo by by W. P. Dando, F.Z.S., Regent's Park._
HOUSE-FLY (MALE AND FEMALE).
The larvæ of the house-fly live in refuse, so do not thrive where
cleanliness abounds.]
However, the traveller in Amazonia has one consolation: the great rivers
which traverse the forests are of three different colours; and the
black-water rivers--so called from the dark colour of the water, owing
apparently to the amount of vegetable matter which they hold in
solution--are never infested with mosquitoes. Probably the character of the
water renders it unsuitable to them for breeding purposes.
The CRANE-FLIES, or DADDY-LONG-LEGS, are also very injurious insects, but
in a different manner, for their subterranean maggots feed on and destroy
the roots of grass in the same way as the grubs of the Cockchafers. They
are insects of considerable size, with slender bodies, terminating in a
short, horny point (the ovipositor) in the female, and with long, slender
legs, which are liable to break off at the least touch. The commonest
species has a grey body and transparent wings; but there is a larger one
with the wings prettily variegated with brown, and a smaller one in which
there are yellow markings towards the end of the body.
The more typical FLIES have usually shorter and broader wings, and thicker,
shorter, and more hairy legs, than those just mentioned; and the antennæ
have usually only three or four joints, and are often furnished with a
long, slender bristle at or before the end of the last joint.
As in the case of the Gnats and Crane-Flies, so as regards the more typical
Flies, we have only space to notice a few of the more important families.
Some of the GAD-FLIES are no larger than house-flies, but others are as
large as wasps or larger, with broader wings, and of a black, grey, or
yellowish colour; they frequent fields, and settle on cattle, or on our
clothes or hands. Some have transparent and others dark-coloured wings, but
they are all capable of inflicting a severe puncture, often sufficient to
draw blood, even in the case of the smaller species.
[Illustration: _Photo by W. P. Dando, F.Z.S., Regent's Park._
BLUE-BOTTLE FLY, OR BLOW-FLY.
These flies deposit their eggs on meat, when it becomes "fly-blown."]
The prettiest of the gad-flies are the GOLDEN-EYED FLIES. They are black,
with the abdomen more or less marked with yellow; and black, or black and
transparent, wings. The eyes are of a beautiful golden green, dotted and
lined with purple. They are moderately stout insects, about the third of an
inch long, and are not uncommon. Another insect, known as the BLOOD-SUCKING
RAIN-FLY, has a rather long and slender body for a gad-fly, and is nearly
half an inch long. It is of a lighter or darker grey, with reddish markings
on the sides of the abdomen in the male. The wings are greyish brown with
whitish dots, and a white mark towards the tip. Both these flies are very
troublesome, the latter chiefly on the edges of woods or near water,
especially in rainy weather.
The ROBBER-FLIES are large flies, with long, tapering bodies, of a black or
partly yellow colour, and feed on smaller flies and other insects of
different kinds. They have very thick, hairy and a strong proboscis. A
handsome Australian species, allied to these, but with a broader body, is
represented in the Coloured Plate.
The HORNET ROBBER-FLY, represented on page 731, is one of the most
conspicuous of the British species. Among other places, it may be seen
flying over the short grass at the top of the cliffs between Brighton and
Rottingdean. They are very predaceous, and are probably rather beneficial
than otherwise, by contributing to keep down injurious insects. But in
North America there is a species called the BEE-KILLER, which is an
extremely destructive insect, taking up its station in front of a hive, and
killing large numbers of bees as they fly backwards and forwards from the
hive.
The HOVER-FLIES are brightly coloured, rather smooth flies, and are
familiar objects in gardens, and in open places in woods. They have the
habit of hovering motionless in the air, and then darting off suddenly.
Some of the larger species proceed from curious maggots, with long tails,
which have been compared to the tail of a rat. These live in putrid water;
and as the flies have a slight resemblance to bees, the fact is believed to
have given rise to the old fable that bees are generated from the rotting
carcases of oxen or other large animals.
The BOT-FLIES are remarkable for being parasitic on warm-blooded animals,
their maggots living in tumours on the skin of oxen, known as "warbles," or
in the stomach and intestines of horses, or in the nostrils and other
cavities in the heads of sheep or deer.
[Illustration: _Photo by W. P, Dando, F.Z.S., Regent's Park._
BLUE-BOTTLE FLY, OR BLOW-FLY.
This photograph shows the wings expanded.]
The HOUSE-FLIES and their allies form a very large group, divided into many
families. The true house-fly is an autumn insect; but there are other flies
which resemble it which live in houses at different times of the year. Most
of them are harmless, although there is one species, very like a house-fly,
which comes into houses in rainy weather, and inflicts a puncture like a
gad-fly. This is the meaning of the popular saying that "the flies bite in
rainy weather."
Although house-flies do not bite, yet they are sometimes exceedingly
troublesome when they are in unusual numbers; and as they settle
everywhere, they may convey infection mechanically, though not as the
principal agents in the dissemination of definite diseases, like the
mosquitoes. Thus, in Egypt, they are said frequently to convey ophthalmia,
a very prevalent disease in that country.
The very first paper published in the "Transactions of the present
Entomological Society of London" (for the existing Society had several
short-lived predecessors) was a paper read by William Spence at the meeting
on April 7, 1834, about a year after the Society had been definitely
founded, entitled "Observations on a Mode practised in Italy of excluding
the Common House-fly from Apartments." This desirable result is attained
simply by stretching a net of white or coloured thread, with meshes of an
inch or more in diameter, across an open window, which the flies will not
venture to pass, if the room is lighted from one side only--"for if there
be a _thorough_ light either from an opposite or side window, the flies
pass through the net without scruple." Mr. Spence's son also referred to a
passage in Herodotus where he says that Egyptian fishermen in his time
defended themselves from the gnats by covering their beds with the nets
which they had used in the day for fishing, and through which these
insects, though they bit through linen or woollen, did not even attempt to
bite. The matter seems to have been overlooked in recent years, though it
is evidently well worthy of consideration when flies or gnats are
troublesome.
There is a conspicuous insect allied to the house-flies, but a little
larger, measuring about half an inch in length. It is called the NOON-DAY
FLY, and is often seen in considerable numbers, in the hottest part of the
day, flying round and settling on the trunks and leaves of trees; it also
settles on cow-dung. It is a shining black fly, with the sides and under
surface of the head golden yellow in the male; the wings are transparent,
slightly tinged with pale brown, and bright rusty yellow towards the base.
The African TSETSE-FLY is not very unlike a house-fly, and is one of the
worst pests to cattle in those parts of Africa which it infests; for any
horse, ox, or dog attacked by it will infallibly die after a longer or
shorter period of suffering, though wild animals and sucking calves are not
affected by it. It used to be supposed that the fly itself infused some
deadly venom with its puncture; but later experiments have led naturalists
to the conclusion that the fly is not itself poisonous, but that it forms
the channel of communication of some fatal disease, just as some species of
mosquitoes convey the infection of malaria.
[Illustration: _Photo by W. P. Dando, F.Z.S., Regent's Park._
TSETSE-FLY.
Destructive to horses and cattle in Africa.]
The BLOW-FLIES, or BLUE-BOTTLES, of which there are several species closely
allied to each other, are common in houses; and a smaller brilliant green
fly, called the GREEN-BOTTLE FLY, is common on hedges. These are all flies
which lay their eggs on fresh or putrid meat, when it is said to be
"fly-blown." They will also lay their eggs in open sores; and in former
days the sufferings of the wounded after a battle were often frightfully
aggravated by this cause; and at the present day farmers would frequently
lose sheep through their attacks, if they were not carefully tended in hot
weather.
Various species of flies in Eastern Europe, the Southern States of America,
Jamaica, etc., habitually lay their eggs in the mouths or nostrils of men
and animals, and the resulting maggots cause dreadful suffering and often
death. In India, and especially in the Eastern Archipelago, there are some
brilliantly coloured, smooth, metallic blue and green flies as big as
bumble-bees. There is also a family of flies allied to the house-fly, which
have very bristly bodies, and are parasitic on caterpillars, like
ichneumon-flies.
[Illustration: _Photo by W. P. Dando F.Z.S._] [_Regent's Park._
TSETSE-FLY (ENLARGED).
Showing the proboscis and veining of the wings more distinctly.]
There are other flies which easily attract attention, such as the yellow
hairy fly found about cow-dung, and some rather small species with prettily
variegated wings, which feed on flowers or fruit. The cheese-hoppers are
also the maggots of a small black fly.
Besides these, there are some aberrant parasitic families of flies with
long, hairy legs, and only one or two joints to the antennæ. These are the
FOREST-FLIES and BIRD-FLIES, which attack horses and birds; and also some
wingless insects, such as the so-called SHEEP-TICK (easily distinguished
from a true tick by possessing only six legs), the BEE-PARASITES, and the
spider-like BAT-PARASITES. This parasitic group is also remarkable for
depositing full-grown larvæ or pupæ instead of eggs.
The FLEAS are a small group of small wingless insects, with such powers of
leaping that it has been said that if a man was as agile as a flea he could
jump over the dome of St. Paul's. The larvæ of fleas are small, worm-like
creatures, with bristles, but without legs; they probably live on any sort
of animal or vegetable refuse. They subsequently change to pupæ in small
cocoons, and emerge as perfect fleas, which live by sucking the blood of
warm-blooded animals; or, when that fails them, they may attack
caterpillars, or other small soft-bodied creatures. Though not very
particular about their food, different species are more or less attached to
different animals; and while in Europe the most troublesome species is the
one considered to be most particularly attached to man, the species most
troublesome in North America is known in Europe as the DOG-FLEA. They are
all very similar in habits and appearance. Fleas are not only annoying,
but, in conjunction with rats, are believed to be among the principal
agents in the spread of the plague. There is another insect called the
JIGGER, or SAND-FLEA, common in most of the warmer parts of America, and
which has more recently been introduced into Africa. The female burrows
into the feet of men or animals, where her body swells up with eggs to the
size of a pea; and serious and sometimes fatal ulcers are the ordinary
result, unless the insect is carefully extracted at an early stage of the
attack.
[Illustration: _Photo by W. P. Dando, F.Z.S._] [_Regent's Park._
BEE-FLY.
Similar to the fly which destroys the locust eggs in Cyprus.]
USES OF FLIES.
It must not be supposed from the foregoing observations that flies are
simply and solely pests to man and beast, without any redeeming qualities.
Their services are less required in cold and settled countries, but in warm
climates their value as scavengers can hardly be over-estimated. As regards
the removal of carrion alone, Linnæus declared that the progeny of only
three blow-flies would devour the carcase of a dead horse as quickly as a
lion--a statement which, even if slightly exaggerated, conveys a vivid idea
of their voracity and the rate at which they increase.
Flies are also useful in keeping down the multitudes of destructive
insects. Numbers of caterpillars fall victims to the bristly flies alluded
to on the last page; and the Bee-flies, which form a family placed next to
the Gad-flies, render far greater service in destroying locusts. They much
resemble small bumble-bees, being very much the same shape, and they are
clothed with yellow down in the British species, and the transparent wings
are conspicuously marked with black bands (as in the photograph above), or
with brown shading and spots. The insects have a very rapid flight, and use
their long proboscis to suck the honey of flowers; but their grubs are
parasitic--at least in some instances--on wild bees; and it is probable
that their resemblance to bees has some reference to this mode of life. But
in Cyprus, Algeria, North America, etc., the larvæ of allied species feed
inside the egg-cases of locusts, sometimes destroying as large a proportion
as four-fifths of the whole brood. Locusts have many enemies, but it will
easily be seen that the attacks of foes like these must reduce their
numbers considerably, notwithstanding the swarms which frequently survive,
and which are liable to the attacks of other enemies, such as robber-flies,
locust-birds, etc., after they have actually arrived at maturity.
Nor must we omit to notice the use of flies as articles of food for man or
useful animals. Many persons are very fond of cheese-hoppers, which are
really the maggots of a small fly; and we read in Kirby's "Textbook of
Entomology," page 92: "The Rev. A. E. Eaton informs me that he believes
that two species of _Ephemeridæ_ (May-flies) form a portion of the
so-called 'Kungu Cake,' manufactured by the natives of South Africa of
gnats, and probably any other insects which can be obtained in sufficient
abundance." "Gentles," which are the maggots of flies, are used by anglers
for ground-bait.
[Illustration: _Photo by W. Saville Kent, F.Z.S. Milford-on-Sea._
PORTION OF INSHORE CORAL REEF AT THURSDAY ISLAND, TORRES STRAITS.
In the foreground are hemispherical masses of the so-called Brain-Stone and
Star-Corals. In the background the rocks are encrusted with various species
of soft-fleshed corals allied to the similar "Dead Men's Fingers" of the
British Seas.]
----
_BOOK VI. SHELL-FISH, LAMP-SHELLS, SEA-URCHINS, STAR-FISHES, MOSS-ANIMALS,
WORMS, CORALS, JELLY-FISHES, AND SPONGES._
BY W. SAVILLE-KENT, F.L.S., F.Z.S.
----
CHAPTER I.
_SHELL-FISH, OR MOLLUSCS._
The Molluscan Group or Sub-kingdom represents one, if not the most
important, of the invertebrate sections of living animals with relation
both to its numbers and variety and in its commercial and economic utility
to mankind. In its ranks are included all those animals generally known as
Shell-fish, and familiar to the non-scientific in the shape of Oysters,
Mussels, Whelks, Periwinkles, and the innumerable varieties of gorgeous or
delicately tinted shells of tropical seas.
[Illustration: _Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea._
AN OCTOPUS CROUCHING IN A ROCK-POOL.
Green shore-crabs constitute the chief food of the octopus.]
Collectively, Molluscs differ from all such invertebrate groups as Insects,
Crustaceans, and Worms in that they possess neither jointed limbs nor
jointed bodies, their body-substance being enclosed by a more or less
distinct muscular sac, or integument, technically known as the "mantle."
Molluscs possess no internal skeleton; but for the protection of their soft
and otherwise defenceless bodies the mantle is among the great majority of
species endowed with the property of secreting a more or less indurated
calcareous shell, within which, when danger threatens, the creature can
entirely withdraw. In some species the shell secreted is relatively small,
and serves only as a protective shield to especially vital areas; while in
a third very considerable assemblage a shell is altogether absent. The
minute yet technically recognisable structural differences between the
shells of even the most closely allied specific forms, and the wider and
distinctly evident divergences that separate the more remotely connected
varieties, furnish the basis for their classification and nomenclature by
the systematic conchologist. Molluscan shells, being so extensively
preserved in the fossil state, furnish the geologist with invaluable data
for his determination of the age and respective relationship of the
fossil-bearing strata of the earth's crust.
[Illustration: _Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea._
AN OCTOPUS ON ITS BACK AT BAY, LEFT HIGH AND DRY BY THE RETREATING TIDE.
In this attitude the octopus can use its many-suckered tentacles and its
formidable parrot-like beak as defensive weapons.]
Having no jointed limbs, molluscs are dependent upon some other mechanical
adaptation for their powers of locomotion. This, in the majority of
species, is represented by a modification of the lower surface of the
animal's body, which is so richly supplied with muscular tissues as to
constitute an effective creeping-base. As a locomotive organ this muscular
area is usually known as the "foot."
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
OCTOPODS.
A blue-spotted West Australian species.]
Of living molluscs some 50,000 distinct species have been recorded. The
great majority of these organisms are, as is well known, marine. A very
considerable number, however, are inhabitants of fresh-water; while a yet
smaller proportion, like the Slugs and Snails and their allies, are
especially adapted for a terrestrial existence. Excepting two relatively
small and inconspicuous groups, the great natural division or sub-kingdom
of Molluscs is separated by systematic zoologists into three main sections
or classes. The particular modification of the locomotive organ, or foot,
serves, on the one hand, to readily distinguish the first or most highly
organised group from the second or central class; while the third or lowest
one is as clearly separated from the second and first by the character of
the shell. The first and most highly developed section includes such
species as the Octopus, the Cuttle-fish, the Squid, and the several
varieties of Nautiluses; to the second or central group are referred all
the marine and terrestrial Slugs and Snails with their innumerable
modifications; while the third and lowest group comprises all the
double-shelled or bivalve forms, such as Oysters and Mussels.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A TASMANIAN SQUID, OR CUTTLE-FISH.
Giant species of squids have been recorded in which the shorter tentacles
measured 12 feet, and the two longer ones as much as 30 or 40 feet in
length.]
In the OCTOPUS and its allies the creeping-base, or foot, is prolonged
round its margin into eight or more arm-like extensions. The anterior of
these in the earlier phases of their development grow round and enclose the
mouth, which consequently opens upon the centre of the locomotive surface.
The arms of the octopus and other forms are in most instances provided
throughout their length with complex sucking-disks, wherewith their owners
can seize and retain their prey or walk with ease and celerity over the
smoothest perpendicular or overhanging rock-surfaces. The octopus, as the
type of its class, possesses yet another most effective locomotive organ.
This is the so-called funnel, or siphuncle, a membranous tube connected
with the capacious gill-cavity which is formed by a folding of the mantle
on the under-surface. When at rest or moving leisurely, the water taken in
through the pocket-like entrance to this cavity is discharged through the
funnel without any particular effort. The animal can, however, at will
leave go its attachment to the rocks, and propel itself swiftly through
water by successive forcible expulsions of the water through the funnel. By
directing the aperture of the funnel to the right or left, the creature can
also direct its course in whatever direction it desires. When thus
swimming, its translation is necessarily backwards. Another notable feature
of the octopus is the "ink-bag," a huge gland secreting an inky-black
fluid, which, as produced by the common cuttle-fish, constitutes the sepia
of commerce. The contents of the ink-bag are discharged through the funnel
at the will of the animal; as soon as the ink is brought into contact with
the water, it becomes distributed through it in the form of a thick cloud,
under cover of which the mollusc makes good its escape from any attacking
enemy.
The octopus in British seas by no means attains to its maximum growth.
Examples with arms from 2 to 2½ feet in length are accounted large
specimens. In Mediterranean waters, however, these dimensions are much
exceeded, individuals with arms 5 feet long, which are capable of covering
a circular area no less than 10 feet in diameter with their fully extended
appendages, being frequently recorded. In the West Indies, on the
North-west American coast, and also in Chinese seas, similar, if not larger
dimensions are attained by these creatures. That these monster octopods, or
"devil-fish," as they are sometimes designated, prove a source of danger to
human life has been abundantly demonstrated. Lurking, as is their custom,
among rock-crevices, they seize hold of any moving object which approaches
within reach of their extended arms. Bathers in this manner have been
seized and drowned, it being impossible for even the strongest swimmer to
free himself from the clutches of one of these animals, which, while
retaining a firm hold on the rocks with a portion of its hundred-suckered
arms, has entwined the others around its victim.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SHELL OF THE PEARLY NAUTILUS.
The inner lining of this shell is brilliantly iridescent.]
The natural food of the octopus are crabs, lobsters, and their like; and in
places like the Channel Islands, where the tide retires very low, leaving
the rock-fissures inhabited by the molluscs more or less exposed, their
presence may be often foretold by the accumulation of empty, broken-up
crab-shells around the entrances to their retreats. In common with other
members of its tribe, the octopus is furnished with a strong, horny,
parrot-like beak, wherewith it can with ease break through the shells of
its accustomed food. The year 1900 was remarkable for the extraordinary
abundance of the octopus on the English south coast, the result of their
collective depredations very seriously affecting the local crab and lobster
fisheries. The pots laid down over-night, in place of yielding the
following morning their customary quota of marketable crustaceans, were
more often than otherwise found to contain nothing but broken-up shells and
a loathsome "devil-fish."
The SQUIDS and CUTTLE-FISHES, with their large lustrous eyes, are
especially adapted for an open sea life, and for this purpose are furnished
with lateral fin-like membranous expansions. A more important structural
distinction is their possession of two supplementary appendages, which,
usually retracted within special pouches when not in use, can be shot out
to a length at least twice that of the eight ordinary arms. Both the
cuttle-fish and the squid, or calamary, are also the possessors of an
internal calcareous or horny shell which underlies and strengthens the
upper-surface. The cuttle-bone used as a dentifrice and ink-eraser is the
product of the first-named mollusc. The Ten-armed group, as it is named,
with reference to the two supplementary arms, ten in all, possessed by its
members, is notable for including species whose dimensions not only exceed
those of any other invertebrate type, but whose fully extended length
rivals that of the largest vertebrates. Giant squids, or calamaries, have
been taken off the coast of Newfoundland, yielding, with their tentacular
arms extended, a linear measurement of over 50 feet, associated with an
estimated weight of as much as 1,000 lbs. There can be no doubt that these
giant squids have in many instances furnished the basis of the
oft-recurrent sea-serpent stories, more especially on those occasions where
the supposed marine reptile and a whale have been reported as seen engaged
in combat. As a matter of fact the sperm-whales habitually feed on deep-sea
squids, and have been known, when mortally wounded, to vomit forth detached
portions of these gigantic molluscs. The long tentacular arms of one of
these monsters, thrown around the whale with which it had entered upon a
death-struggle, might at a little distance be easily mistaken for some huge
snake-like organism.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SHELL OF THE ARGONAUT, OR PAPER-NAUTILUS.
The female animal only possesses a shell, and uses it as a cradle for her
eggs and young.]
The various species of NAUTILUS, including the so-called "Paper" and
"Pearly" species, belong likewise to this group of Molluscs. In the former
case, however, it is only the female animal which secretes a shell, and
this is used as a cradle wherein she deposits her eggs and rears her young.
The pretty romance of the PAPER-NAUTILUS, or ARGONAUT, as it is technically
termed, floating on the sun-lit waves with spreading sails and an even
keel, has unfortunately been entirely dissipated by the penetrating
search-light of modern science. The animal only floats on the surface when
ill, or when torn from its customary pasture-fields by abnormal storms,
otherwise it creeps about the sea-bottom, or disports itself in the
sub-marine grottoes like an ordinary octopus, with which, in point of fact,
the shell-less male agrees in all essential details. The shell-cradle of
the paper-nautilus is not vitally connected with the body of the animal, as
is that of the pearly species and all ordinary shell-fish. It is freely
detachable from the body, and during life is grasped and held closely to it
by the expanded extremities of the two lateral tentacles by which the
delicate shell is mainly secreted.
The next group comprises the great bulk of Simple-shelled Molluscs, of
which it is impossible in these pages to give more than a brief enumeration
of some of the most prominent. The Lung-breathing section, which is usually
awarded the first place on the list, includes the familiar GARDEN-SNAILS,
the SHELL-LESS SLUGS, the FRESH-WATER SNAILS which come to the surface to
breathe, and many distinct terrestrial species. The largest living
representative of this group is the huge Land-snail of tropical West
Africa, sometimes known as the AGATE-SNAIL, the shell of which is not
infrequently as much as 7½ inches long.
[Illustration: _Photos by W. Saville-Kent, F.Z.S._]
LIMPETS, WHELKS, AND BARNACLES.
On the rocks at Ilfracombe when the tide was low.]
[Illustration: SHELL BEACH, ABROLHOS ISLANDS.
Composed of iridescent top-shells.]
[Illustration: _Photos by W. Saville-Kent, F.Z.S._]
GREAT CLAM-SHELL ON CORAL-REEF.
The soft parts have been removed to show the size of the shell and the pure
whiteness of the interior.]
[Illustration: GIANT CLAM-SHELLS ON THE GREAT BARRIER REEF, AS EXPOSED AT
EXTREME LOW TIDE.
The shell in the foreground is 4 feet in diameter.]
The NAKED-GILLED SEA-SLUGS constitute a second clearly defined group. All
the species are essentially marine, and most abundant among seaweeds and
coral-growths, over twenty species occurring in British seas. They are
notable for the slug-like form of their body, which is usually supplemented
by the outgrowth from it of complex, variously modified gill-filaments. In
some species these external gills take the form of symmetrical flower-like
tufts at the posterior end of the back, while in others simple or variously
branched gills may be developed on the upper-surface. The colours of many
of these sea-slugs are more brilliant than those of any other molluscs,
this being especially the case with the tropical coral-reef-frequenting
species. Bright scarlet, yellows, and blues, separately or variously
combined, are among the dominant tints. Many of these tropical species are
also of considerable size. One particular kind, having a flower-like dorsal
gill-tuft, observed by the writer on the West Australian reefs, was over 10
inches long and 8 inches broad. Its general ground-colour was intense
vermilion, relieved, however, by a frilled border nearly an inch in width
of the purest white, with radiating streaks of scarlet. It is an
interesting circumstance that these naked-gilled molluscs, shell-less so
far as their adult phases are concerned, emerge from the egg with a
perfectly formed, but necessarily very minute, transparent shell,
resembling that of a garden-snail. It is consequently inferred that the
group has been derived from some permanently shell-bearing form.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
HIGHLY MAGNIFIED TONGUE OF A SEA-SNAIL.
With this structure its owner bores or files a hole through the shells of
other molluscs upon which it preys.]
The Comb-gilled section embraces the great majority of the marine molluscs
having a single more or less convoluted or spirally twisted shell. They
take their name from the circumstance that the gills have a compactly
disposed comb-like contour. This gill-tuft is situated in an excavated
chamber inside the shell, immediately over the neck. The COMMON WHELK, the
PELICAN'S-FOOT SHELL, and the WINKLE are a few typical British marine
representatives of this group, which, however, attains to the zenith of its
development in the size, variety of form, and ornate coloration of its
shells in tropical seas. The inter-tropical coral-reefs in particular yield
a most abundant harvest in this direction. The shells in common use
obtained from such a source include the ponderous HELMET-SHELLS, or CONCHS,
employed for the manufacture of cameos; the GIANT WHELKS and
TRUMPET-SHELLS, often over 18 inches long, used as signal-horns throughout
Polynesia and on the tropical Australian coast; and the capacious
MELON-SHELLS, made to do duty for boat-baling and as water-vessels and
general domestic receptacles throughout the same tropical area. To this
list may be added the HARP-SHELLS, VOLUTES, CONES, MITRES, OLIVES, THORNY
WOODCOCKS, and a host of others prized by the conchologist. To this section
must also be referred the innumerable species of COWRIES, of which the
large, boldly mottled "TIGER" and "PANTHER" species are well known. The
comparatively small, yellowish, thickly built, porcelain-like shell of the
"MONEY-COWRIE" constitutes, as is well known, the current coin throughout
extensive areas of Africa and India. It is recorded that as large a
quantity as sixty tons of these small shells, originally collected from
tropical seas, have been shipped from one British port alone to the African
coast for commercial use within a single year. One very diminutive cowrie,
pale pink in colour, with a delicately streaked surface, is indigenous to
British waters.
The third large group of Molluscs which demands attention is that of the
Bivalves, or Leaf-gilled group. Though not so numerous in species as the
last, it outrivals it in the enormous abundance in which the individuals of
many varieties are produced. OYSTERS, MUSSELS, COCKLES, SCALLOPS, and other
allied forms occur in closely associated colonies, constituting natural
"beds" or "banks," which may be of vast extent and, in at any rate the case
of oysters, several feet in thickness. From a commercial and economic
standpoint this group is undoubtedly of the highest importance to the human
race. Not only do its members, as instanced by the foregoing forms,
contribute largely to the world's commissariat, they also yield the
much-prized material known as "mother-of-pearl" and the purest and most
æsthetically beautiful gems--orient pearls. Pearls and mother-of-pearl are
the products of two groups of shell-fish, respectively known as
PEARL-OYSTERS and PEARL-MUSSELS. There are a considerable number of
species, mainly denizens of tropical seas, which, like ordinary oysters and
mussels, occur naturally in banks and beds of vast extent. In some species,
such as the CEYLON PEARL-OYSTER, the shell is small, and the
mother-of-pearl substance, or "nacre," as it is technically termed, so thin
as to be of relatively little value. Hence the fishery for this species is
conducted almost exclusively for the sake of the pearls, which are fairly
numerous and frequently of the finest quality. From the tropical Australian
seas pearl-shells of the largest size, which produce the thickest and most
valuable mother-of-pearl, are obtained. Pearls of the best quality are more
rarely found in this description of shell, and its fishery is prosecuted
primarily on account of the substantial substance and magnificent quality
of its nacre. A single pair of shells of this species will attain in its
adult state to a weight of from 12 to 18 lbs. The fishery for this
pearl-shell has, however, been prosecuted so relentlessly that bivalves of
such matured age and weight are now of rare occurrence, and obtained only
from almost inaccessibly deep waters. Unless, in point of fact, systematic
methods of conservation and cultivation are resorted to on an extensive
scale and on lines corresponding fundamentally with those successfully
followed in the culture of ordinary commercial oysters, there would seem to
be an imminent risk of the valuable Australian pearl-shell fisheries
becoming depleted to more or less complete exhaustion.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A SCORPION-SHELL.
Closely allied to the "Pelican's Foot," found on the British coast.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
ROCK-OYSTERS.
This is the ordinary commercial oyster of the Australian shores.]
The tropical Australian seas, and notably those which wash the Great
Barrier Reef, are famous for the production of the largest of living
bivalve molluscs. These are represented by the GIANT CLAMS, which, dwelling
among the coral-growths, are left exposed to view for brief periods during
abnormally low spring tides. A photograph of a colony of these monster
bivalves, taken by the writer amidst this mollusc's characteristic
surroundings, is reproduced on page 741. The example in the foreground
measured no less than 4 feet in diameter and weighed several
hundred-weights. In many clams the living tissues, or mantle-borders, that
are exposed to view when the shell-valves are partly open, are brilliantly
tinted.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A QUEENSLAND OYSTER-BANK.
Illustrating another characteristic growth-phase of the Australian
rock-oyster.]
Of the SCALLOPS many of the larger species are highly esteemed for the
table. It is notable of them that they can progress through the water in a
jerky, flight-like manner by the repeated flapping of their opposing
shells. In many scallops the jewel-like eyes are developed in a row round
the margin of the mantle.
The Bivalve Class includes certain representatives which are held in evil
repute, on account of their destructive habits. PHOLAS and its allies bore
their way into solid rock, bringing about its complete disintegration. From
the dreaded SHIP-WORM, or TEREDO, on the other hand, there would appear to
be no description of wood that can withstand its ravages.
The Bivalve Molluscs are not without fresh-water representatives. The
well-known POND- and RIVER-MUSSELS, which form the most conspicuous
examples of this group, number several hundred species. While insipid and
of no account for the human commissariat, many of its members produce
pearls of value. One such, obtained from the river Conway, in North Wales,
is said to occupy a place in the crown of England.
The CHITONS, or MULTIVALVE MOLLUSCS, invite brief notice. As the last-named
title implies, the shell-elements in this group are relatively numerous,
consisting of eight pieces, or plates, which may form contiguous transverse
shelly shields that entirely cover in and protect the dorsal surface of the
elongate, boat-shaped body, or may be more or less isolated from one
another. In the former instance the animal bears some considerable
resemblance to a gigantic limbless wood-louse, and, like that familiar
terrestrial crustacean, it is capable of rolling itself into a spheroidal
shape as a means of protection. None of the chitons are provided with eyes
in the adult state in that region of their body--namely, the head--where
they might be most naturally expected to exist. Recent scientific
investigation has, however, elicited the fact that in various species the
respective shell-plates are studded with minute eye-specks, the aggregate
number of visual organs thus possessed by certain forms reaching to the
astonishing figures of 11,000 or 12,000. The majority of the chitons are
shallow-water, rock-frequenting molluscs, which may be successfully sought
by turning over stones at low water. Several species are inhabitants of
British seas.
----
CHAPTER II.
_LAMP-SHELLS._
A little group of double-shelled creatures, formerly regarded as near
allies of the Oysters and Mussels, are the LAMP-SHELLS. Their scientific
appellation, signifying "arm footed," relates to the two spirally
convoluted arm-like structures which constitute the salient features in
these animals. That of lamp-shells bears reference to the small circular
perforation near the extremity, or "beak," of the united shells, which
imparts to the entire structure a not altogether remote resemblance to an
ancient Greek or Roman lamp with its sub-terminal wick-hole. In all
essential points of their organisation the lamp-shells differ so
essentially from ordinary bivalves that they are now generally recognised
as representing an independent animal class, having, as a matter of fact, a
closer relationship with Worms than with Molluscs. In their earlier
condition certain lamp-shells are indistinguishable from larval worms;
while the convoluted arms of the adult animals, thickly beset with bristles
and hairs, closely resemble the arms, or "cirrhi," of many sea-worms. The
superadded valves of the lamp-shells differ fundamentally from those of the
bivalve molluscs in the circumstance that they are developed upon the upper
and lower surfaces respectively of the enclosed animal, and not on the
sides. The union between the two valves is also accomplished through the
medium of interlocking calcareous teeth, in place of a horny or ligamentous
hinge-joint, as obtains in an oyster or a mussel. A supplementary
calcareous support, having a corresponding spiral shape, is also developed
in connection with the convoluted arms. This structure varies in the
contour of its minuter details in every specific form, which thus furnishes
zoologists with a basis for systematic classification. The lamp-shells
collectively form two natural groups or orders. In one of these the shells
are hinged together, and are of conspicuously unequal dimensions. The
larger shell of the two is more distinctly concave and produced into a
perforated beak. It is this structure that in some species resembles the
wick-hole of an antique lamp, and has given rise to the popular title by
which these shells are distinguished. The second or hingeless group is
further distinguished by the shells being of almost uniform shape and size.
In the most interesting example of this group, known as LINGULA, the two
shells are thin, horny, of a green tint, and mounted on a long, flexible,
worm-like stalk. Like a worm, this creature moves about in the mud, and
constructs a sand-lined dwelling-tube.
[Illustration: _Photos by W. Saville-Kent, F.Z.S._]
SOUTHERN CROSS PEARL, VALUED AT £10,000.
Consists of nine laterally united pearls corresponding in shape and size.]
[Illustration: PEARL-SHELL WITH GROUP OF GOLDEN PEARLS.
Many thousand shells may be opened without finding a single pearl.]
[Illustration: _Photos by W. Saville-Kent, F.Z.S._]
QUEENSLAND PEARLS ON BLACK-LIPPED PEARL-SHELL.
The black-lipped shell produces pearls of great value.]
[Illustration: PEARL PRODUCED BY OPERATION ON THE ANIMAL.
The pearl produced is a solid hemispherical or "button" pearl.]
Although lamp-shells are represented by comparatively few species at the
present day, in the older epochs they existed in enormous abundance. It is
further remarkable of this group that many species are scarcely
distinguishable from their fossil ancestors. Lingula, the type last
referred to, is especially notable in this respect.
----
CHAPTER III.
_STAR-FISHES, SEA-URCHINS, ETC._
The somewhat varied assemblage of marine animals familiarly known as
STAR-FISHES, FEATHER-STARS, BRITTLE-STARS, SEA-URCHINS, and SEA-CUCUMBERS
all agree structurally with one another and differ from all other living
organisms in several conspicuous features. Prominent among these is the
circumstance that their protecting skin is more or less extensively
impregnated externally and strengthened internally with calcareous elements
which take the form of plates and spines and spicules.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
COMMON OR SHORT-SPINED SEA-URCHIN.
This species is used for food in Italy and other Continental countries.]
The COMMON SEA-URCHIN may be cited as an example in which these calcareous
elements attain their maximum development. The subspherical box-like case
or shell, wherein all the vital organs are enclosed and safely protected,
is a common object of the seashore, and, empty and denuded of its external
coating of prickly spines, familiarly known as a "sea-egg." Examined
closely, this shell is found to consist of a series of calcareous plates,
which dovetail or fit together in juxtaposition with the utmost nicety. The
surface of the shell is studded throughout with rounded hemispherical
knobs, those of a larger size having a very distinctly symmetrical plan of
distribution. These rounded knobs are the bases of attachment of the
spines, which radiate at all points from the surface of the shell when the
animal is alive. It will be further recognised on a nearer examination that
the walls of the shell are pierced on a definitely symmetrical pattern with
minute perforations, such perforations being most distinctly visible on the
inner surface of the shell. These minute punctures are the apertures
through which in life the delicate tubular locomotive organs, or so-called
"feet," are thrust out and retracted. The majority of these tubular organs
terminate in a circular sucking-disk, wherewith, collectively, the urchin
is able to adhere to and travel over the surface of the smoothest rock, or
even up the glass walls of an aquarium. In the empty beach-gathered
urchin-shell a circular hole may be observed at the two opposite poles, the
one in the centre of the lower and flatter surface being the larger of the
two. It is within this lower and larger one that the mouth, with its
complex apparatus of teeth, is suspended. The membranous disk which covers
the upper and smaller circular aperture in the living animal is perforated
centrally by the vent, and around it are grouped the eye-spots and sundry
excretory apertures.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
LONG-SPINED SEA-URCHINS.
The needle-like spines of these sea-urchins are over a foot in length.
Acres of these creatures may be sometimes seen on tidally exposed areas of
the Queensland Great Barrier Reef, where this photograph was taken.]
A noteworthy feature associated with the greater portion of the structural
details of the sea-urchin which have been enumerated is the dominance of
the number five in the constituent elements. It is found, for instance,
that the perforated areas through which the tube-feet are protruded form,
as with the petals and other elements of many flowers, five symmetrically
corresponding segments. The dental apparatus comprises five equivalent
tooth-like structures, and there are five eye-spots and five excretory
apertures at the upper pole. This particular number, with multiples of the
same, is furthermore characteristic of all the typical members of the
class. Thus, in the COMMON STAR-FISH, there are five so-called arms, five
eye-spots, one at the tip of each arm, and five equivalent elemental
components of all the more important viscera. In the SEA-CUCUMBERS, which
have elongate worm-like bodies, there is a similar apportionment of the
nerves and muscles of the body generally into fives, and also of the
branching tentacles which surround the mouth. Tubular locomotive organs,
the so-called "tube-feet," are common to all the three types enumerated.
The calcareous plates and spinules, while attaining to a maximum
development in the urchins, are also abundantly represented in the other
groups. In the common star-fish these calcareous elements form within the
skin an openly reticulated trellis-like framework, while in the ordinary
sea-cucumbers they more usually take the form of innumerable
microscopically minute spicules. The two less familiarly known groups of
the FEATHER-STARS and BRITTLE-STARS fully agree with the previously
enumerated types in their five-fold structural composition. The
brittle-stars have almost invariably five arms only, but they are
independent outgrowths from the body proper, instead of being prolongations
of it, as in the common star-fish.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
THICK-SPINED SEA-URCHIN.
In large specimens the spines are as thick as a slate-pencil, and may be
used for the same purpose.]
The FEATHER-STARS, which include some of the rarest and most beautiful
representatives of the group, are mostly inhabitants of deep water, and
remarkable for the circumstance that either throughout life or in their
early phases they are affixed to submarine objects by slender stalks. This
peculiarity imparts to the animals such a flower-like aspect that, in
conjunction with the indurated calcareous nature of their skeletons, they
have received the title of "Stone-lilies." This appellation, however, was
originally more particularly applied to their fossilised remains, which
occur in remarkable abundance in the older geological strata.
The most familiar British representative of the group is the ROSY
FEATHER-STAR, occasionally obtained among seaweed in rock-pools on the
southern coast, but more often brought up with the dredge from deeper
water. In this form the elongate feather-like arms radiate from the
central, relatively small, five-rayed body. There is no supporting
foot-stalk in this adult stage, the animal being freely movable, and
clinging to seaweeds and other objects by means of a cluster of claw-like
filaments developed upon its under-surface. Releasing its hold upon its
temporarily selected position, it can crawl about with the aid of the
hooked extremities of its arms and their radiating joints. It can also
propel itself through the water in a somewhat clumsy fashion by the
consecutive flexion and extension of these appendages. This freedom of
locomotion was not, however, always possessed by the feather-star. In its
early days, and when of very small size, it was affixed to a slender
foot-stalk, and dependent for its food on the animalcules and other minute
organisms which drifted or swam within reach of its extended arms. The rosy
feather-star takes its name from the bright rose-red tints by which it is
usually characterised. Individuals of the species are, however, subject to
considerable colour-variation. On the Australian coast, where many forms
are abundantly represented, examples tinted deep crimson, black, bright
golden yellow, or sundry admixtures of these several hues are not
uncommonly found associated among a dredge-haul of these elegant sea-stars.
The PERMANENTLY STALKED STONE-LILIES are at the present day of rare
occurrence. Up to within comparatively recent years the so-called
MEDUSA'S-HEAD LILY was, indeed, regarded as the only living representative
of the group. This species has a pentagonal jointed foot-stalk that may be
3 feet long, with five slender appendages developed in whorls at short
sub-equal distances throughout its length. From the shallow cup-shaped body
at the apex of the stalk a tassel-like bundle of arms is developed, all of
these being produced by repeated bifurcation from one of the five
equivalent basal stem-joints. Dredging expeditions have within the last
quarter of a century revealed the existence of a considerable number of
previously unknown species of stone-lilies in the abysses of the ocean, a
depth of no less than 3,200 fathoms representing the habitat of one such
type.
[Illustration: _Photo by N. Lazarnick_] [_New York._
STAR-FISH IN WATER.
If pulled to pieces, each of the five arms, or fingers, will grow into a
perfect star-fish.]
The Star-fish group is represented by the COMMON FIVE-FINGERS, or
CROSS-FISH, as it is sometimes called, and includes a very numerous
assemblage of species of varying size and shape and colour. The British
seas alone yield some twenty forms. Among the more notable of these is the
SUN STAR-FISH, which, departing from the rule of possessing five arms only,
has twelve or more, its contour, from which it derives its name, somewhat
resembling that of a symbolic sun. The colours of this species are
particularly brilliant, consisting usually of a variably patterned
admixture of crimson, pink, and white. An extreme contrast in contour to
the sun-star is presented by the so-called BIRD'S-FOOT species, in which
the body is pentagonal and so flattened out as to somewhat resemble the
foot of a duck. In the Cushion-stars the body, while pentagonal, is
comparatively thick.
[Illustration: _Photo by E. Connold._] [_St. Leonards._
STAR-FISH, OUT OF WATER, TURNING OVER.
The sucker-tipped tubes with which the star-fish effects locomotion are
well shown in this photograph.]
The so-called SNAKE-ARMED SAND-STARS and BRITTLE-STARS constitute a section
distinguished from the preceding by the character of the arms, which branch
separately from the central body, and are composed of an innumerable series
of calcareous joints, which snap asunder under the slightest provocation.
The great majority of the species are provided with five simple arms only.
In an exceptional form, however, known as the SHETLAND ARGUS, and its
allies, these five arms, while simple at their base, bifurcate repeatedly
and in geometrical progression to such an extent as to form in life a
complex network of writhing, snake-like tendrils, that has been
appropriately likened to a Medusa's head. It has been calculated that there
are no less than 80,000 terminal arm-subdivisions in adult examples of this
species.
Among the Sea-urchin Tribe there are many notable departures from the
typical form previously referred to. In some, while the sub-spheroidal form
of the case, or test, is still retained, the external spiny armature is
greatly varied. In one series these spines are exceedingly long, slender,
and of needle-like contour and sharpness. In others, while long, they are
abnormally thick and cylindrical, somewhat resembling slate-pencils, for
which they are sometimes used as a substitute; or they may be club-shaped,
branched, or reduced to flattened plates. In other forms the shell itself
is conspicuously modified. With some known as BISCUIT- or CAKE-URCHINS it
is flattened out to the resemblance of a cake or biscuit, the spines being
minute and inconspicuous. In another group, distinguished as HEART-URCHINS,
the shell is oval and bilaterally symmetrical, though the dominant number
of five still holds good with regard to the building up of its structural
details. One of the most interesting is the LEATHER-URCHIN, so called on
account of the flexible and loosely jointed character of its shell, the way
being paved by such a form to the normally soft- and flexible-skinned
sea-cucumbers. Sea-urchins are to a great extent vegetable-feeders, and the
larger species are appreciated as an article of food in many countries, the
ovaries, or roe, with which at certain periods the shell is mostly filled,
forming the edible portion.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A YOUNG BRITTLE STAR-FISH (MUCH MAGNIFIED).
The arms of the brittle-stars are composed of loosely fitting, readily
fractured joints.]
The SEA-CUCUMBERS--better known in the commercial world as Bêche-de-mer, or
Trepang--represent the only group which possesses a substantial
market-value. Its typical members present an elongate worm-like contour,
but progress by means of extensile tube-feet, after the manner of the
Urchins and Star-fishes, and have their dental, nervous, and muscular
systems fashioned on the same five-sectioned basis. The mouth, which is
situated at one extremity of the body, is surrounded by a series of ten or
twenty delicately branched or mop-like tentacles, which can be protruded or
retracted at the animal's will, and are used for seizing food. The skin of
the typical sea-cucumber is more or less soft and flexible, and has
embedded within its substance innumerable minute calcareous spinules.
The commercially valuable sea-cucumbers, or bêche-de-mer, are all
inhabitants of tropical waters, the North-eastern Australian coast and the
Malay seas yielding the most highly prized forms. The Queensland Great
Barrier Reef, consisting of a series of coral-reefs extending for upwards
of 1,000 miles at a little distance from the Australian mainland,
represents one of the most productive areas for this marine delicacy, the
bulk of which goes to the Chinese market. The fishery is prosecuted with
the assistance mainly of the Queensland natives, who, either by diving or
wading on the reefs at low tide, collect the creatures in vast quantities.
On being brought to the curing-stations, the animals are emptied from the
collecting-sacks into large caldrons, where they are allowed to stew in
their own juice for about twenty minutes. Taken out of the caldrons, they
are split open and eviscerated, dried for a short interval in the sun, and
then placed in tiers on wire gratings in a smoke-house, where they remain
for twenty-four hours. They should at this stage have shrunk up to about
one quarter of their normally extended size, much resemble charred sausages
in aspect, and should rattle like dry walnuts when bagged up for
exportation. From £50 to £150 per ton are the prices that the better
qualities of bêche-de-mer realise when well cured and delivered at Chinese
ports. The chief culinary use to which the cured sea-cucumbers are applied
is that of the concoction of soup, the best quality prepared taking rank
with that made from swallows' nests. At the hotels and clubs in the leading
Australian cities bêche-de-mer soup is held in high favour, and its more
extensive introduction on the menu-cards of Western civilisation may be
only a question of time.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A BRANCHING-ARMED BRITTLE-STAR.
The specimen is attached to a brilliant scarlet sponge.]
Many species of sea-cucumbers inhabit British seas, but none possess that
density of tissue which is essential for their economic conservation; the
majority, moreover, are of comparatively small size, some few inches long
only when fully extended, whereas the commercially valuable tropical ones
may measure as much as from 2 to 3 feet. The mode of feeding of
sea-cucumbers is somewhat interesting; the smaller species, with
much-branching tentacles, generally affix themselves by their tube-feet to
some object, and, extending their tentacles in all directions, utilise
them, like those of a sea-anemone, for seizing any minute and suitable prey
which may strike against them. The microscopic organisms on which they
chiefly feed abound in the waters they inhabit, and one after the other,
the branched tentacles having effected a capture, are gathered together and
tucked bodily into the creature's central mouth and apparently half-way
down its throat. The larger coral-frequenting species are provided mostly
with mop-shaped tentacles. They crawl about leisurely in search of their
food, mopping over the ground, and gathering up in their tentacles the
minute shells and other organisms on which they subsist, which are
collectively thrust with an indrawn tentacle into the throat. In some of
the lower forms the tube-feet have disappeared, the integument is thin and
semi-transparent, and the worm-like animal crawls about by means of its
skin-spinules, which take the form of anchors or grappling-hooks. In an
opposite direction they may develop a supplementary covering of dermal
plates and a more rigid integument, which indicate their nearer
relationship with sea-urchins.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SEA-CUCUMBERS, SOME WITH EXTENDED TENTACLES.
A West Australian species whose colours are bright pink and yellow.]
The majority of sea-urchins and star-fishes pass through a series of
interesting metamorphoses before arriving at the adult state. The larval
phases in these instances are free-swimming organisms, having arm-like
processes, strengthened by calcareous rods that have been likened in
contour to a clock-stand. A small spherical central area, like a clock in
its case, representing the stomach of the larva, develops spicules around
it, and becomes the body of the urchin, the other outlying portions
becoming gradually absorbed. Some of the brittle-stars and sea-cucumbers
bring forth their young in the adult form, nursing them from the egg in
special breeding-chambers.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SEA-CUCUMBER, OR BÊCHE-DE-MER.
These animals are collected in vast quantities on the Australian Great
Barrier Reef, smoked, and sent to the Chinese market.]
The capacity of a star-fish to renew its lost arms is commonly manifested.
A single detached arm, moreover, in such a type as the common five-fingered
species, can reproduce its body and the remaining four arms. Fishermen, who
are in the habit of tearing up star-fishes and throwing them back into the
water, under the impression that they are thus effectually incapacitating
them from further injury to their oyster-beds, commit an error, such
mutilation tending to the multiplication of their numbers.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
PRICKLY SEA-CUCUMBER.
This species of bêche-de-mer commands a high price in China, and makes
delicious soup.]
In the matter of colour-ornamentation the Star-fish group is richly
endowed. Allusion to the brilliant crimson and pink-and-white tints of the
British sun star-fish has been already made. As with most animal groups,
however, it is amid their tropical representatives that the most striking
colour-variations obtain. One form which is common among the coral-reefs on
the Queensland coast-line, and much resembles the common British
"five-fingers" in size and shape, is brilliant ultramarine-blue. Another
large pentagonal species, belonging to the group known as Cushion-stars,
has a golden-brown ground, upon which are thickly scattered small bead-like
tubercles of turquoise. A third form, not uncommon on the Tasmanian
coast-line, which is nearly related to the Bird's-foot species, previously
mentioned, is distinguished by tints which range through several shades of
crimson to brilliant violet.
Not a few of the star-fishes are notable for their eminent phosphorescent
properties. The group of the Snake-armed and Brittle-stars are more
especially distinguished in this respect. Many of these species occur in
such numbers in comparatively deep water that the dredge may be filled with
a tangled mass of their writhing snake-armed bodies. Should it be night
when the dredge is brought aboard, and its contents are emptied upon the
deck, the spectacle presented as the star-fishes scramble in all
directions, their bodies and arms aglow with pale green or blue phosphoric
coruscations, is highly remarkable.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
BLACK SEA-CUCUMBER.
This photograph was taken through the water in a coral-pool. A large
clam-shell, with its expanded fringe of tentacles, is close beside the
sea-cucumber.]
----
CHAPTER IV.
_MOSS-ANIMALS._
A little group of animals whose relationship with the sub-divisions
previously and hereafter described cannot be very definitely determined is
that of the MOSS-ANIMALS, sometimes designated CORALLINES, or LACE-CORALS.
All its members are of exceedingly minute size, and if living separately
would be scarcely discernible to the unaided vision. They are, however, in
the habit of forming stocks, or colonies, after the manner of corals, by a
process of continual budding, and in this way build up social aggregations
which may be of considerable dimensions. The majority are marine, and
largely in evidence on almost every seashore in the form of the so-called
SEA-MATS, consisting of masses of minute, light brown, horny cells, which
take the form of seaweeds, or are spread in thin, lace-like encrustations
upon the surfaces of shells, stones, and the larger seaweeds. The living
inhabitants of these cells are as transparent as glass, their most
characteristic feature being the elegant shuttle-cock-shaped crown of
tentacles which is thrust out or withdrawn at will from the aperture of
each tiny tenement. The assistance of the microscope is requisite for the
apprehension of these details, as also of the somewhat complex alimentary
and other organs enclosed within the component cells.
[Illustration: _Photo by W. Saville-Kent>, F.Z.S._] [_Milford-on-Sea._
MOSS-ANIMALS.
These coral-like masses are composed of many thousand closely united
dwelling-cells of microscopic dimensions.]
A comparatively small number of these moss-animals are inhabitants of
fresh-water, forming brown tubular aggregations on the under side of the
leaves of water-lilies or other submerged objects. It is interesting to
observe that the tentacular crown in almost all these fresh-water species
is horseshoe-shaped, instead of like a shuttle-cock, as in the marine
forms. One very notable fresh-water species is remarkable for the
circumstance that in place of horny tubes the component individuals secrete
a common transparent gelatinous matrix, which is provided with a
creeping-base, wherewith the colony-stock is enabled to travel over the
surfaces of the water-plants among which it lives, or up the glass sides of
an aquarium. In some respects, and more especially their earlier
developmental phases, the Moss-animals show affinities with the
Lamp-shells, while the tentacular crown of the adult individual is closely
imitated in certain worms.
----
CHAPTER V.
_WORMS._
The WORMS and their allies embrace a numerous assemblage of animals which
exhibit a remarkable amount of variation both in structure and habits. A
fundamental distinction which serves to separate readily even the most
highly organised members of the group from the other articulate or
jointed-bodied animals, such as Crabs, Insects, or Centipedes, is furnished
by the character of the locomotive appendages. These in the Worm Tribe
never assume a jointed character, but take the form of unjointed membranous
processes which may or may not be supplemented by bristles. Frequently
bristles alone constitute the essential locomotive organs. In certain
groups, such as the Leeches, Flat-worms, Thread-worms, and others, even
these are unrepresented.
The appropriate title of BRISTLE-WORMS has been conferred upon the section
in which the locomotive organs take the form of bristles. Among these the
COMMON EARTH-WORM is included. At first sight the worm's body appears to be
perfectly smooth and naked; it is found, however, on closer investigation
to be furnished, according to the species, with either two or four
longitudinal rows of fine, hook-like bristles. Although these bristles
project but slightly above the surface of the skin, they constitute very
effective aids to locomotion, enabling the animal to obtain a secure grip
upon the surface of the ground over which it may be travelling. Progression
under such conditions is effected, in fact, on the same principle as that
of the snake, the ends of the stiff bristles with which the segments are
armed fulfilling the same role as the projecting edges of the reptile's
scales. Earth-worms are chiefly vegetable-feeders, dragging into their
holes fallen leaves, straws, and every other description of vegetable
débris. They also swallow and pass through their systems large quantities
of earth, absorbing from it its organic constituents, and depositing the
indigestible residuum therefrom in the form of "earth-casts." The useful
function thus performed by worms in bringing up earth from considerable
depths and redepositing it upon the surface of the ground has been fully
demonstrated in one of Mr. Darwin's works. There are some twenty species of
British earth-worms, none of which, however, attain to the proportions of
certain kinds indigenous to Australia and South Africa. Some of these giant
species are as much as 3 or 4 feet long when unextended, and will on the
stretch measure twice such lengths. Their thickness, which is
proportionate, may vary from that of a man's finger to that of an ordinary
sausage.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
TUBE-WORMS.
Some with their flower-like gill-tufts expanded.]
The most numerically abundant and structurally varied representatives of
the bristle-bearing worms are inhabitants of the sea, and are divisible
into two easily recognised natural groups. In one of these the animals
resemble earth-worms in their ability to move about freely from place to
place. In the other group they secrete and permanently reside within a
tubular edifice, which may be calcareous and of shell-like hardness, or
composed of particles of sand, mud, or other substances. The free-roving
group, which embraces by far the larger number, includes such forms as the
LUG-WORM, or LOB-WORM (held in high repute for fishing-baits), and a host
of other allied species. In all of these the development of bristles and
other appendages is more pronounced than in the Earth-worms. In another
group, known as the NEREIDS, the elongate worm-like body is more or less
flattened in shape; unjointed leg-like appendages, supplemented by
bristles, are developed from the majority of the segments, and the animal
presents a somewhat centipede-like aspect. This likeness is further
enhanced by the presence of antennæ-like organs at the anterior extremity,
while the mouth is armed internally with a pair of sharp-pointed, horny
jaws. In many of the nereids the lateral organs are flattened out and
paddle-like, constituting effective swimming-structures. Some of the larger
species attain a length of several feet, and are especially noteworthy for
the brilliantly iridescent tinting of their skins. The palm of beauty with
respect to its brilliant colouring must undoubtedly, however, be awarded to
the so-called SEA-MOUSE, frequently cast up by storms on the British coast.
In this creature the body is comparatively short and thick, 3 or 4 inches
long by 1½ to 2 inches wide. The centre of the back is covered in by a
felt-like mass of fine interlacing hairs of a brownish hue, underneath
which are broad, flat scales which protect the breathing-apparatus. The
sides are, however, thickly clothed with long, slender hairs and bristles,
each of which reflects the most brilliant prismatic tints.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SEA-WORMS, OR NEREIDS.
Their innumerable "false feet" impart to them a centipede-like aspect.]
The TUBE-DWELLING WORMS are noteworthy for the elegant and often
beautifully coloured flower-like gill-tuft with which the head is crowned.
Its separate filaments are clothed with vibrating hairs, which create
currents bringing food-particles to the mouth. In those forms which build
up a hard calcareous dwelling-tube, one of the gill-filaments is usually so
modified as to constitute a stopper-like organ, wherewith the animal, on
retreating into its domicile, can effectually bar out the ingress of
intruders. In some members of the group the gill-tufts are elegantly
branched and supplemented by long, simple, thread-like filaments, that are
thrust out to long distances in every direction both for food and the
materials required for the further lengthening and enlargement of the tube.
The LEECHES differ essentially from the Bristle-worms in the absence of
bristles or supplementary appendages, in the presence of an adhesive
sucking-disk at the posterior and sometimes also the anterior extremity,
and on their well-known blood-sucking propensities. While the MEDICINAL and
so-called HORSE-LEECHES inhabit fresh-water, some, more especially in
tropical countries, infest the moist jungles and scrubs in vast numbers,
and are among the most actively aggressive pests with which the traveller
has to contend. A few leeches also inhabit the sea, preying upon the skate
and other fishes. The bodies of these marine species are cylindrical, with
a sucker at each extremity, and roughly corrugated or warted.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SEA-MICE.
Worms, with remarkably iridescent hairs, which burrow in the sand.]
The FLAT-WORMS embrace a large number of intestinal and other parasitic
species, including TAPE-WORMS, THREAD-WORMS, LIVER-FLUKES, and others.
Among the free-living non-parasitic members of this group, the so-called
INDIA-RUBBER-WORM is remarkable for the extraordinary elasticity of its
tissues. Black in hue, it lives among rocks and seaweeds, and preys upon
small fishes and other organisms. These, being seized by the suctorial
mouth, are unable to effect their escape, the worm's body being capable of
stretching out to a length of 20 feet or more, and "playing" the captured
victim like a living elastic fishing-line until its struggles are
exhausted.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
PORTION OF THE GREAT BARRIER REEF OF AUSTRALIA.
Showing soft or leathery and other corals.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
ANOTHER PORTION OF THE GREAT BARRIER REEF.
Composed chiefly of stag's-horn corals. This coral varies in colour, being
sometimes brown with white tips, in other instances grass-green or even
brilliant violet.]
----
CHAPTER VI.
_CORALS, SEA-ANEMONES, AND JELLY-FISHES._
With the Sea-anemones and Jelly-fishes almost the lowest organised group of
living animals is reached. As typified by an ordinary sea-anemone, the body
may be described as a simple sac, the orifice of which is inverted for some
little distance, and held in position with relation to the outer wall by a
series of radiating partitions. One or more rows of tentacles, varying in
number and character according to the species, surround the mouth of this
partially inverted sac. There is no distinct intestinal track, the whole
space enclosed within the outer wall and ramifying among the radiating
partitions containing the digestive juices. The radiating membranous
partitions develop upon their surfaces the reproductive elements, and in
the case of Corals, which are merely skeleton-producing sea-anemones,
partly secrete within them the symmetrical radiating calcareous plates so
characteristic of the group.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A MUSHROOM-CORAL FULLY EXPANDED.
In this condition the coral, or skeleton of the animal, is entirely
concealed.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
|MUSHROOM-CORALS, WITH THE ANEMONE-LIKE POLYP EXPANDED.
Taken through the water on a coral-reef.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
PART OF THE GREAT BARRIER REEF OF AUSTRALIA.
Chiefly composed of star-corals, many of them resembling human skulls. The
Great Barrier Reef of Australia, consisting of innumerable detached reefs
and coral-islets, is over 1,500 miles in length.]
Some thirty odd species of sea-anemones are indigenous to British waters,
and one or more of these will be familiar to most readers. The
STRAWBERRY-ANEMONE, clinging to the rocks as a hemispherical lump of
crimson, green, brown, or red and yellow speckled jelly when the tide is
down, and expanding like a beautiful flower when the waters flow back upon
it, is the commonest and in many respects the most beautiful of all, the
circlet of turquoise beads, regarded as rudimentary eyes, developed around
the outer margin of the tentacles, adding a charm possessed by few other
species. The DAHLIA-ANEMONE, whose expanded disk and innumerable petal-like
tentacles may measure as much as 6 or 8 inches in diameter, is the largest
British species. These dimensions are, however, vastly exceeded by its
tropical allies. The Australian coast produces giant species which may
measure no less than from 18 inches to 2 feet across their expanded disks.
These giant anemones are further interesting on account of the circumstance
that they are self-constituted "harbours of refuge" to sundry species of
fishes and crabs, which nestle among their tentacles like birds in a leafy
bower. The anemones are themselves bright in colour, but the associated
fishes are even more so. In an example which was photographed by the writer
on the Western Australian coast, the anemone was olive-green, with the tips
of the tentacles bright mauve. The fishes, of which three examples were
present, were brilliant orange-scarlet with white bands. In addition to the
fishes a small flat-clawed crab shared the sheltering hospitality of the
anemone. Some of the tropical coral-reef-frequenting anemones, which have
their tentacles beautifully branched, must be cautiously handled, in
consequence of their notable stinging properties. All sea-anemones and
corals are, in fact, provided with peculiar stinging-cells, with which they
benumb and thus make an easy capture of the living organisms on which they
prey. While the majority of the sea-anemones live single or individually
separate lives, there are some which form aggregations or colony-stocks of
numerous units. These compound growths are brought about by repeated
budding, or the sub-division or fission, without complete separation, of an
originally single individual. It is by a similar process of recurrent
sub-division that the wonderful fabrications of the coral-polyps are built
up.
[Illustration: PORTION OF A STAG'S-HORN CORAL.
Each minute circular cell represents the situation in life of a small
sea-anemone-like animal, or coral-polyp.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A CLUMP OF STAG'S-HORN CORAL.
The life-colours of this coral are a delicate cream with brilliant magenta
tips.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
BLEACHED CORALS FROM THE GREAT BARRIER REEF.
Branching stag's horn corals are chiefly represented in this group. Several
of the large solitary mushroom-corals may, however, be observed in the
foreground.]
An ordinary coral-animal or polyp, as previously stated, differs in no
respect from a sea-anemone, excepting for the possession of a calcareous
skeleton secreted within its basal tissues, including portions of the
membranous radiating partitions. Some coral-animals, like the majority of
the Anemones, are solitary, and form single attached or loosely lying
corals. The well-known MUSHROOM-CORAL is one of the latter. One species
observed, which was photographed through the water by the writer as it lay
expanded in a tide-pool on the Australian Great Barrier Reef, might easily
be mistaken for a big sea-anemone allied to the dahlia-anemone. On being
disturbed, however, it immediately shrinks back upon its base, ejecting all
the water with which its expanded tissues were filled, and revealing the
presence of the hard radiating coral beneath. Each of the calcareous radii,
which are now clearly defined through the thin semi-transparent skin,
corresponds in position with one of the internal membranous partitions, and
also with the origin of one of the tentacles. New mushroom-corals are
produced as buds thrown off from the parent, which attach themselves and
secrete a foot-stalk, to which they remain affixed, like the young of the
feather star-fish, for the earlier epoch of their existence. Ultimately,
however, they become detached, and, falling from their stalks, lie loosely
on the sea-bottom, after the manner of their parents. The huge coral-masses
commonly known as MADREPORES, out of which coral-islands and reefs are
constructed, all commence as a single coral-animal, with its contained
skeleton analogous to the mushroom-coral, though in all instances much
smaller. The buds developed by the coral-polyp in these instances remain
attached to the parent. If they spread out laterally, they build up by
accumulation the large flattened or sub-spherical masses known as
BRAIN-CORALS and STAR-CORALS, which are most abundant on coast-line reefs,
or form the bases of the outer barrier-reefs. Where, on the other hand, the
budding is terminal or oblique, branching tree-like growths such as the
STAG'S-HORN CORALS, with their innumerable allies and variations, are
produced. The colours of the coral-polyps are as brilliant and diverse as
those of ordinary sea-anemones, living reefs, whereon a number of different
species are in a condition of healthy growth, yielding a spectacular effect
that vies with that of any floral parterre. Sometimes large areas, acres
upon acres in extent, may be covered with one almost uniform purple, green,
brown, or other coloured growth of the branching stag's-horn species. The
aspect presented is not unlike that of a heath-covered common.
In addition to the solid, calcareous-skeletoned Madrepores, or "Stony
Corals," as they are often termed, there are a number of species in which a
skeleton composed only of loosely aggregated calcareous spicules is
produced. The so-called FLEXIBLE CORALS, or SEA-FANS, belong to this
category, as also the precious CORAL OF COMMERCE. In the last-named species
the solid, brilliantly coloured skeleton so much prized as an article of
jewellery is deposited as a supplementary basis outside the tissues by
which the star-patterned skeletons of the stony corals are secreted.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A QUEENSLAND STAR-CORAL.
This species in life is of a pale lemon-yellow tint.]
A group which demands brief notice is that of the HYDROID POLYPS. These
include the majority of the JELLY-FISHES, a few coral-secreting species,
and the organisms whose seaweed-like horny skeletons, known as SEA-FIRS,
are, in common with those of Sea-mats, included among the flotsam and
jetsam on every sea-beach. In the COMMON HYDRA, or FRESHWATER POLYP, an
exceptional fresh-water representative of this group is presented. It may
be likened to a tiny sea-anemone, having, when extended, a slender
foot-stalk and long thread-like tentacles. Like a sea-anemone, it will
shrink up when disturbed into a mere button of jelly. Its organisation is
more simple than that of the anemone, its body-cavity being a simple sac,
without any intucking of the orifice, or strengthening by supplementary
membranous partitions. A similar simple structural plan is characteristic
of all the organisms belonging to the series. An interesting phenomenon
connected with the fresh-water hydra is the circumstance, demonstrated now
over a century ago, that, if one of these animals be cut up into little
pieces, each separate fragment is capable of repairing itself and growing
into a new polyp.
The JELLY-FISHES, or MEDUSAS, and their allies would appear at first sight
to possess but little structurally in common with the Coral-polyps and
Sea-anemones. In their most familiar form they are represented by a more or
less translucent bell-shaped body, which drifts with the current or propels
itself through the water by its alternate expansions and contractions. In
the centre of the lower surface, occupying the position of the bell's
clapper, a polyp-like, tubular mouth is usually discernible, and this is
frequently surrounded by a circle of tentacles, sometimes simple and
sometimes elaborately ramified. Long, thread-like tentacles are also
commonly developed around the margin of the swimming-bell.
[Illustration: _Photo by W. Saville-Kent. F.Z.S._] [_Milford-on-Sea._
A GIANT ANEMONE FROM THE GREAT BARRIER REEF.
From 18 inches to 2 feet in diameter when expanded. Bright apple-green in
colour, and with almost spherical bead-like tentacles.]
The larger number of the jellyfishes are, as a matter of fact, transitional
phases only of the fixed hydroid polyps previously referred to. In certain
instances the body of the fixed polyp becomes elongated, and splits up
horizontally into a series of jelly-fishes, or medusas, resembling a pile
of saucers, which consecutively break away and lead a free-roving
existence. In other forms a compound tree-like growth gives birth to
medusa-like buds, like the flowers on a plant, which ultimately become
detached and swim away. What are known as the COMB-BEARING
JELLY-FISHES--their locomotive organs consisting of comb-like bands of
vibratile hairs--are especially noteworthy. In some of these the body is
nearly spherical or ovate, one of the species, in reference to its shape,
being popularly known as the SEA-LEMON. A notable feature of these medusas
is their remarkable glass-like transparency, their presence in the water in
many instances being recognisable only by the prismatic glimmerings of
their rows of vibratile hairs when the light falls upon them at a
favourable angle. The most remarkable member of this particular group is
undoubtedly the form known as VENUS'S GIRDLE. This species takes the form
of a long, ribbon-like band of transparent jelly. The edges of the ribbon
are clothed with vibratile hairs, and the mouth is situated in the centre
of one of the edges. The animal progresses by the action of its hairs
alone, or may be assisted by the twistings and undulations of its
ribbon-like body.
[Illustration: _Photo by Saville-Kent, F.Z.S._] [_Milford-on-Sea._
A GIANT SEA-ANEMONE.
Measures, when opened, 18 inches in diameter. Is almost always associated
with companion or "commensal" fish and crabs of brilliant colour. The fish
cruise round in search of food, but always return to shelter among the
anemone's tentacles. Photograph taken through the water.]
Many jelly-fishes possess an unenviable reputation with reference to their
stinging properties. The so-called PORTUGUESE MAN-OF-WAR is one of the more
noteworthy of these. The organism consists of an ovately pointed
air-bladder, which floats on the water, and from which depend numerous
nutritive polyps and a mass of capturing-filaments, or tentacles.
----
CHAPTER VII.
_SPONGES AND ANIMALCULES._
The Sponges are regarded as a group standing on the borderland between the
Polyps and the lowly organisms which follow. The familiar BATH- and
TOILET-SPONGES of commerce represent but an insignificant fraction in
comparison with the many hundred species which find no place in the world's
market. Toilet-sponges owe their intrinsic value to the relative fineness
and elasticity of their component fibrous skeletons. In these particular
species the skeleton is composed of a substance akin to horn. In other
sponges the skeleton may consist of horny fibres mixed with flinty
spicules, or it may be of flint only, or of spicules of carbonate of lime.
Finally, there are sponges which possess no internally supporting skeleton,
fibrous or spicular, and whose substance is consequently little more than
gelatinous. All these numerous forms, however, agree with one another in
the identity of their most essential vital elements. In the living sponge
the skeleton, fibrous or otherwise, is embedded within a gelatinous matrix
by whose component cells it is excreted. Externally the sponge-body is
perforated over the greater portion of its extent by minute holes or pores,
while one or more holes of relatively large size occupy the summit of the
sponge, or are scattered here and there among the numerous smaller pores.
The smaller pores represent incurrent apertures, and lead to chambers
within the sponge's substance lined by cells. Each of these is provided
with a long whip-like appendage, with a transparent wineglass-shaped cup or
collar, which is a beautifully constructed food-trap. The lashings of the
whips of the collar-cells cause currents of water bearing nutrient
particles to flow in at all the smaller pores. Arriving at the chambers,
these particles are caught by the outstretched collar-traps and absorbed
into the cell's substance. The water, together with rejected and waste
materials given off by the sponge-body, is carried forward, and passes out
at the larger orifices or vents.
[Illustration: _Photo by W Saville-Kent, F.Z.S., Milford-on-Sea._
FRILLED SPONGE.
A species not infrequently dredged up by the pearl-shell fishers in Sharks
Bay, Western Australia.]
[Illustration: _Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea._
RETICULATED SPONGE.
The skeleton of this sponge is composed of fine horny fibres resembling
those of ordinary commercial sponges.]
Among the more remarkable sponges may be mentioned the NEPTUNE'S-CUP
SPONGE, like a huge chalice 3 or 4 feet high, indigenous to the South Seas;
the wonderful cornucopia-shaped LACE-SPONGE, consisting of a lace-like
reticulation of flinty fibres; and its near ally the GLASS-ROPE SPONGE,
forming a cup- or bird's-nest-shaped body, supported on a long cylindrical
stalk of flinty fibres that may be over a foot in height. One of the
compound or social sea-anemones is in the habit of forming bark-like
encrustations on this glassy stem, and it was for a long time doubtful
whether the sea-anemone or the sponge produced the supporting-stalk.
[Illustration: _Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea._
PORTUGUESE BIRD'S-NEST SPONGE.
Dredged from a depth of 600 fathoms off the coast of Portugal. In life the
body, or "cup," of this sponge was deep orange colour, from which the grey
beard-like mass of anchoring fibres depended.]
[Illustration: _Photo by E. Connold_] [_St. Leonards._
CHALINA SPONGE.
A British species, composed partly of horny and partly of flinty elements.]
The ANIMALCULES, which represent the simplest and lowest forms of living
animals, consist chiefly of organisms which are the equivalents of one of
the single cells, or, as they might be termed, the "life-bricks," out of
which all the higher animals, and also plants, are built up. They are of
minute dimensions, and require the aid of the microscope for their proper
investigation. Among the most highly organised members of this sub-kingdom
mention must be made of the CILIATED ANIMALCULES, or INFUSORIA, so called
because they were first discovered inhabiting decaying vegetable and animal
infusions. The so-called SLIPPER-ANIMALCULE is one of the commonest forms
which makes its appearance amidst such environments. The length of this
single-celled animal scarcely averages the one-hundredth part of an inch,
but within this restricted space an amazing degree of structural and
functional differentiation is included. Its outer surface is, in the first
place, densely clothed with hairs, which represent its organs of
locomotion. This outer cell-wall has a subjacent somewhat softer layer, in
which are developed as crowded a series (as compared with the hairs) of
minute rod-like bodies, which, under various stimuli, can be shot out like
darts through the skin, and are adjudged to be offensive and defensive
weapons, partaking much of the same nature as the thread- or stinging-cells
of sea-anemones. Among other noteworthy structures, the slipper-animalcule
has a distinct throat-opening, two rhythmically contracting cavities
fulfilling a respiratory function and a complex reproductive nodule, or
nucleus. Compared with a host of its kindred, this animalcule is a giant,
the longest diameter of many of the smaller varieties measuring no more
than the 1/5000th part of inch, or even less.
The elegant little BELL-ANIMALCULE, with its crystal wineglass-shaped body,
crown of vibrating hairs, and long spirally contractile foot-stalk, is a
familiar object to the possessor of a microscope. Most commonly these
single-celled organisms, like the single-celled elements of organic
tissues, multiply by repeated sub-division, the number that can be
reproduced in a short space of time by this simple process being almost
incredible. As many as a million, it has been calculated, of some species
may be thus derived from an original single individual within twenty hours.
In this connection these lowly organisms can among living animals most
logically lay claim to immortality. The individual, in point of fact, never
dies. Finding itself growing old and obese at the ripe age of, say, sixty
minutes, it has simply to split itself up into two offsets, which swim away
and repeat the process. Occasionally, for the rejuvenescence of the race,
two individuals coalesce completely with one another, and multiplication by
splitting takes place.
Some near relations of the little bell-animalcule, while sub-dividing so
far as their bodies are concerned, remain united by their foot-stalks, and
thus in time build up beautiful tree-like structures, laden as it were with
crystal bells or fruit. In some of these the common branching foot-stalk is
erect and rigid, while in others it is flexible, and contains, as in the
ordinary species, a central elastic ligament. Under these circumstances the
whole tree-like structure, with its crystal bells, collapses and expands
again under the slightest stimulus, and constitutes one of the most
beautiful objects that can be viewed through the microscope.
[Illustration: Photo by W. Saville-Kent, F.Z.S.] [_Milford-on-Sea._
CUP-SPONGES, PHOTOGRAPHED AS GROWING IN A CORAL-POOL.
The Neptune's cup Sponge, allied to this species, is sometimes 2 or 3 feet
in height and diameter.]
In lower forms of the infusorial animalcules one or more long, lash-like
organs take the place of locomotive hairs. In this category are included
the COLLAR-BEARING ANIMALCULES. Some of these build up tree-like growths by
repeated sub-divisions and imperfect separation, after the manner of the
bell-animalcules, while others excrete tubular dwelling-cases, inhabited by
the resultants of the splitting process. Such forms can with difficulty be
distinguished from skeletonless sponges.
The animalcule NOCTILUCA, which by its countless myriads is the chief
constituent of ocean phosphorescence, is a member of the Lash-bearing
group. This noteworthy form invites a somewhat more extended notice. It is
to the presence of the Noctiluca in countless myriads upon the upper
stratum of the water on calm summer nights that is especially due the
diffused form of phosphorescence which is more essentially characteristic
of temperate latitudes. Under the most favourable of these conditions, the
waves falling upon the strand leave as they retreat a glittering carpet of
scintillating points; the oars of the passing boat seem as it were to dip
into molten silver; while on the high seas the revolving screw or paddle of
the steam-vessel leaves in its wake a broad, luminous track as far as the
eye can reach. A glassful of water taken from the sea at such times
immediately reveals the origin of these wonderful phenomena. Here and there
will be seen floating minute bladder-like transparent spheres, resembling
as nearly as possible small granules of boiled sago. Investigated more
closely with the microscope, each individual speck will be found to exhibit
a pouch-like contour, having a central furrow, from which the lash
projects, and upon which the minute mouth-aperture opens. Irritated by
agitation in any shape or form, the Noctilucas at once respond by, as it
were, angry flashes of silvery-greenish light, and it is to the
coruscations in their aggregate condition of many millions of these minute
organisms that the several phenomena above recounted are produced.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
SHELLS OF FORAMS HIGHLY MAGNIFIED.
The chalk cliffs of Dover and many other strata are mainly composed of
similar microscopically minute shells.]
One other characteristic manifestation of ocean phosphorescence dependent
upon the presence in countless numbers of these minute animalcules may be
recorded. To those accustomed to a seafaring life the spectacle is a common
one, on nights when the luminosity is most in evidence, of fishes following
or darting away from the sides of the vessel apparently aglow themselves
with phosphoric light, and leaving behind them, in accordance with their
size, a more or less conspicuous luminous path in the murky waters. It is
commonly supposed that such form of luminosity is emitted by the fishes
themselves; but on closer investigation it will be found that this also is
due to the presence of the animalcules under notice in countless numbers,
which are disturbed into a sudden display of their phosphoric properties by
the passage of the fishes through their midst. This light is reflected, as
from a mirror, by the fishes' glittering scales, while the Noctilucas
continue scintillating for several seconds in the path or wake through
which the fishes have passed.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
NOCTILUCAS.
These are the animalcules which chiefly produce marine phosphorescence.]
There are other animalcules nearly allied to Noctilucas which sometimes
occur in such vast abundance in both salt and fresh water as to visibly
affect its character. In addition to a very long lash they have a girdle of
vibratile hairs. The fresh-water representatives of this group are
sometimes brilliant green, at others bright scarlet. That instance among
the Biblical Egyptian plagues in which the water of the Nile was as it were
"turned to blood, and all the fish died," has been attributed to a
phenomenal development of these animalcules, which, on dying, polluted and
putrefied the water. Instances of fishes being destroyed in vast quantities
through a like agency throughout even extensive sea-areas have been
occasionally recorded. While these pages are going to press an account has
appeared in an American journal of red water caused by these flagellate
animalcules, which occurred last July for an extent of at least 200 miles
along the coast of California, producing with their decomposition a most
sickening odour, and the death of shoals of fishes, octopods,
sea-cucumbers, and other organisms.
[Illustration: _Photo by W. Saville-Kent, F.Z.S._] [_Milford-on-Sea._
POLYCYSTS.
Flinty-shelled organisms of microscopic dimensions. The living animals
consist of tiny specks of transparent jelly, from which radiate innumerable
false feet of hair-like fineness.]
Next to the Flagellates come the ROOT-FOOTED ANIMALCULES, which possess no
mouth and no hairs or lashes, but progress by pushing out lobes of their
jelly-like substance in any desired direction, into which the rest of the
body flows. Food is picked up at any point with which an acceptable morsel
may be brought in contact. The little gelatinous animal known as an AMOEBA
is one of these. Related forms of this jelly animalcule secrete shells of
varying form and structure. Some of these, known as FORAMS, are of
carbonate of lime, and wonderfully like nautiluses and other of the higher
molluscan shells in aspect. Though so minute, scarcely visible to the
unassisted eye, they occur in the sea in such numbers as to form by their
aggregations the more considerable ingredients of vast areas of the earth's
strata, both past and present. The chalk cliffs of Albion and the white
tenacious ooze of the broad Atlantic are thus to a large extent composed of
the shells of minute organisms, which formerly flourished near the surface
of the ocean, but sank on their death to its abysmal depths.