_THE CŒLENTERATES--JELLY-FISHES, ANEMONES,
AND THEIR ALLIES_
One of the most interesting groups of marine life is that including
jelly-fishes and anemones. In it are the pretty little sea firs, so
often mistaken for sea-weeds by the youthful admirers of these plants,
who almost always include them in their collection of marine _algæ_; the
transparent, bell-shaped jelly-fishes, which may often be seen in
thousands during the summer, carried by the tides, and swimming gently
by graceful contractions of their bells; and, most beautiful of all, the
lovely anemones--the ‘sea flowers’ of the older naturalists, by whom
they were regarded as forms of vegetable life.
[Illustration: FIG. 77.--THREAD CELLS OF A CŒLENTERATE, MAGNIFIED
1. Thread retracted 2. Thread protruded]
The simplest animals of this group are minute jelly-like creatures, of a
more or less cylindrical form, usually fixed at one end, and having a
mouth at the other. The body is a simple hollow cylinder, the wall of
which is made up of two distinct layers, while the cavity within serves
the purpose of a stomach. The mouth is surrounded by a circle of arms or
tentacles by means of which the creature is enabled to capture its prey.
These arms are capable of free movement in every direction, and can be
readily retracted when the animal is disturbed. They are also armed with
minute oval, hollow cells, each of which has a slender filament coiled
up into a spiral within its cavity. Each filament is capable of being
suddenly protruded, thus becoming a free whip-like appendage, and these
are so numerous as to be very effectual in seizing and holding the
living beings on which the animal feeds. This would undoubtedly be the
case even if they were capable of mechanical action only, but, in many
instances at least, they seem to be aided by the presence of some
violent irritant, judging from the rapidity with which the struggling
prey is paralysed when seized, especially in the case of some of the
larger members of the group.
The simple forms referred to increase by a process of budding, the buds
appearing first as simple swellings on the side of the parent creature,
and afterwards developing a mouth and tentacles, thus becoming exactly
like the adult form. Clusters of eggs also are developed in the outer
layer of the body-wall, and these are set free at intervals, and
produce new individuals. These animals possess no blood system of any
kind, and have no special organs for respiration, but the nutrient
matter absorbed from the body-cavity permeates the soft structures of
the flower-like body, and the oxygen required for respiratory purposes
is readily absorbed from the surrounding water.
[Illustration: FIG. 78.--THE SQUIRREL’S-TAIL SEA FIR (_Sertularia
argentea_), WITH A PORTION ENLARGED]
The higher cœlenterates differ in certain particulars from the lower
forms just referred to. Thus, they frequently have a large number of
tentacles around the mouth, often arranged in several distinct whorls.
They have also a stomach separate from the general body-cavity, but
communicating with the latter below; and the body-cavity is divided into
compartments by a number of radiating partitions. Some, also, develop a
hard, stony skeleton by secreting carbonate of lime obtained from the
water in which they live.
[Illustration: FIG. 79.--_Sertularia filicula_]
We often see, when collecting on the beaches of rocky coasts, and
especially after storms, a number of vegetable-like growths, of a
greyish or brownish colour, each consisting of one or more main stalks
bearing a number of delicate branches. Some of them, by their peculiar
mode of growth, have suggested the name of sea firs, and a few of these,
together with other animals of the same group, may readily be recognised
by the accompanying illustrations. They are the objects already referred
to as being commonly included in collections of sea-weeds by young
naturalists, but they are in reality the horny skeletons of colonies of
cœlenterates of the simplest type, belonging to the division
_Hydrozoa_.
[Illustration: FIG. 80.--_Sertularia cupressina_]
If we examine them with a lens we find that there are little cup-like
bodies projecting from each portion or branch of the stem-like
structure, and that the stem itself is hollow, with a communicating pore
at the base of each cup. This constitutes the skeleton only of the
colony--the dead matter, so to speak, which persists after the living
creatures have perished; but if the specimens collected have been
obtained fresh from the sea, placed in a glass of sea water, and then
examined with the aid of a lens, little jelly-like _hydroids_ or
_polypites_ will be seen to protrude from the cups, and extend their
short arms in search of food.
[Illustration: FIG. 81.--THE HERRING-BONE POLYPE (_Halecium
halecinum_)]
Each of the little creatures has a tubular stalk which passes through
the hole at the base of the cup, and is continuous with a tube of
gelatinous material in the interior of the horny stem, and thus each
member of the colony is directly connected with all the others, so that
any nutrient matter collected and digested by one member may be absorbed
into the central tube for the nourishment of the entire company of
little socialists, the activity of the one being thus made to compensate
for the laziness or incompetency of others. And this provision seems to
be absolutely necessary for the well-being of the colony as a whole, for
a close examination will often show that a kind of division of labour
has been established, since it includes two or three distinct kinds of
polypites, each adapted for the performance of a certain function. Thus,
in addition to the feeding or nutritive members of the community, there
are some mouthless individuals whose sole function seems to be the
production of eggs for the propagation of the species, while others,
also mouthless, develop an enormous number of stinging cells, probably
for the protection of the whole community against its enemies, and these
must therefore be provided, as we have seen they are, with a means by
which they may derive nourishment through the agency of the feeding
polypites.
[Illustration: FIG. 82.--_Tubularia indivisa_]
[Illustration: FIG. 83.--THE BOTTLE BRUSH (_Thuiaria thuja_)]
When the eggs are liberated from what we may call the reproductive
members, they are carried away by the currents or tides, and soon
develop into little _larvæ_ which are very unlike the parent, since they
are covered with minute vibratile cilia by means of which they can swim
freely. This they do for a period, and then settle down, lose their
cilia, become stalked, and thus constitute the foundation of a new
colony. A tubular stalk grows upward from its root, new members are
added as outgrowths or buds from their progenitor, and so the growth
proceeds until an extensive colony of hundreds of individuals has been
formed.
We have spoken of the hydroid communities as being washed up on the
beaches of our rocky coasts, but the collector of these interesting
objects should not depend on such specimens for purposes of study. It is
undoubtedly true that splendid examples of the sea firs and their allies
are frequently washed up by the waves, including some species that
inhabit deep water, and which are, consequently, not to be found by the
ordinary collector in their proper habitat, and that these may often be
secured with the polypites still alive; but several species are to be
obtained between the tide-marks, especially at extreme low water,
growing on rocks, weeds, and shells; and we have often met with good
specimens, still alive, attached to the shells of whelks, scallops, &c.,
in fishmongers’ stores, even in inland towns.
[Illustration: FIG. 84.--_Antennularia antennia_]
Sometimes individual polypites become detached from a colony, and
develop into little umbrella-shaped jelly-fishes, about a fifth of an
inch in diameter; and these float about freely, keeping themselves near
the surface by rhythmic contractions of their ‘bells,’ the margins of
which are fringed by numerous fine tentacles. The mouth is situated
centrally on the under side, and is surrounded by a circular canal from
which proceed radiating tubes; and pigmented spots, supposed to be
rudimentary eyes, are formed round the edge. These little bodies are
called _Medusoids_, and may frequently be seen floating round our coasts
towards the end of the summer. In the water they are almost invisible on
account of the extreme transparency of their bodies; but if a muslin
net be drawn through the water from the stern of a boat, and the net
then gently turned inside out in a vessel of sea water, a number of
medusoids may be obtained for examination. These creatures produce eggs
which yield small ciliated larvæ that swim about freely for a time, and
then settle down and establish stalked colonies as previously described.
The larger jelly-fishes or _Medusæ_ so frequently seen floating in
enormous numbers near the surface of the sea during the summer months
are allied to the medusoids. Their bodies are so soft that it is a
difficult matter to remove them from the water without injury, and when
removed their graceful forms are completely destroyed by the pressure of
their own weight. When left stranded on the beach, as is often the case,
they seem to dissolve almost completely away, so readily does the soft
animal tissue disintegrate in the large proportion of water, which forms
about 95 per cent. of the weight of the whole body.
Those who desire to examine the nature and movements of the medusæ will
find it necessary to observe them in water. The creatures may be lifted
out of the sea in a vessel placed below them, and then transferred to a
glass tank or a still rock pool by submerging the vessel and allowing
them to float out. It will then be observed that the mouth is situated
at the summit of a tube that projects from the middle of the under side
of the ‘bell,’ and is surrounded by lobed or frilled lips. Marginal
tentacles also generally fringe the edge of the bell, projecting
downwards into the water. Round the circumference of the body may be
seen a circular canal, from which several tubes converge towards, and
communicate with, the cavity of the stomach.
When a medusa is inactive, its body gradually sinks to the bottom, being
usually slightly heavier than the water in which it lives; but it is
enabled to keep afloat by those rhythmic contractions of the bell with
which we are so familiar. It seems that the medusæ are very sensitive to
various external conditions, for they frequently disappear
simultaneously from the surface water, and as suddenly reappear in
shoals when the conditions are more favourable; but it is difficult to
understand the causes which give rise to these remarkable movements.
The medusæ are often termed the _Acalephæ_--a word which signifies
‘nettles,’ and they are popularly known as sea nettles. They all possess
stinging cells, which are distributed most thickly in the tentacles, and
some of the larger species are undoubtedly able to produce an
impression on the bodies of unwary bathers, while almost all have the
power of paralysing the living prey on which they feed.
By far the commonest of the jelly-fishes of our seas is the beautiful
blue medusa--_Aurelia aurita_. This species appears in enormous shoals
during the summer, and large numbers are washed upon flat, sandy
beaches. They vary in size from two or three inches to nearly a foot in
diameter, and may be recognised from our illustration. The ‘bell’ is
umbrella-shaped, and is so transparent that the stomach with its
radiating canals may be seen through its substance. Around the margin
there are little pigment spots which are supposed to be rudimentary
eyes, and little cavities, containing a clear fluid, that are thought to
serve the purpose of ears.
[Illustration: FIG. 85.--_Aurelia aurita_]
On the under surface may be seen the square mouth, furnished with four
long and graceful frilled lips, which are richly supplied with stinging
cells; also the four ovaries or egg-producing organs, rendered
conspicuous by their violet colouring.
The life history of _Aurelia_ is most interesting. The eggs are produced
in pouches that communicate directly with the stomach-cavity, and these
give rise to little ciliated larvæ that are ejected through the mouth,
and then swim about freely in the water for a time. After this they
settle at the bottom, lose their cilia, and become little cylindrical
jelly-fishes, fixed by a short stalk-like foot to rocks or weeds.
Numerous tentacles develop as the creatures increase in size, and a
number of transverse furrows appear at the surface. The furrows
gradually increase in depth until, at last, the body is broken up into
several star-like discs, each of which floats away and develops into a
new medusa.
[Illustration: FIG. 86.--THE EARLY STAGES OF _Aurelia_]
Other jelly-fishes, some of which are considerably larger than
_Aurelia_, frequent our seas, and are often to be seen stranded on the
beach. Two of these--_Rhizostoma_ and _Chrysaora_--are figured. Although
they differ considerably in form from the blue aurelia, they closely
resemble it in general structure and habits.
[Illustration: FIG. 87.--_Rhizostoma_]
[Illustration: FIG. 88.--_Chrysaora_]
When strolling on flat, sandy beaches, especially in the spring and
early summer, we commonly see what appear to be little balls of
exceedingly transparent and glassy jelly, no larger than an ordinary
marble. If picked up and examined, we observe that they are not quite
spherical, but oval in form, with a little tubercle at one end, and
eight equidistant bands running from this to the opposite end, like the
meridians on a globe.
This extremely beautiful little creature is one of the cœlenterates,
belonging to the division _Ctenophora_, or comb-bearing jelly-fishes, so
called because they possess comb-like ciliated plates, and is called the
Globular Beroe (_Cydippe pileus_).
The ctenophores are very active creatures, swimming freely in the open
seas by means of their numerous cilia; and, although of such delicate
structure, are very predaceous, devouring small crustaceans and other
marine animals. They are usually globular in form, but some are like
long ribbons, and almost all are remarkable for their wonderful
transparency, which renders them nearly invisible when floating in
water. They have not the power of stinging or paralysing their prey, as
the medusæ have, but their fringed arms are provided with adhesive cells
by which they hold their prey tenaciously.
[Illustration: FIG. 89.--_Cydippe pileus_]
In order to observe the form and habits of the Beroe we transfer it to a
vessel of sea water, when it immediately displays its regular spheroid
form, and its eight rows of comb-like plates which form the meridians
before alluded to. Its mouth is situated on the little tubercle at what
we may call the lower pole, for it is the habit of the Beroe to swim in
an inverted position, and the digestive cavity may be seen through its
glassy body.
At first no appendages of any kind are visible, but soon the animal
protrudes two long and exceedingly slender arms, fringed with slender
gelatinous threads, from two cavities, at opposite sides of the body,
into which they can be withdrawn. A close examination will also reveal
the rapid movements of the cilia of its combs, and it is remarkable that
these do not always work together, the animal being able to move any of
its plates independently, and to reverse their motion when occasion
requires. It has no tentacles corresponding with those of jelly-fishes
and anemones, but is assisted in the capture of its prey by its two long
arms, the chief use of which, however, seems to be that of a rudder for
steering.
If the Beroe is left out of water for some time, the water which forms
such a large proportion of its body evaporates, leaving an almost
imperceptible residue of solid matter; and if left in water after it is
dead, its substance rapidly dissolves away, leaving not the slightest
trace of its presence. There seems to be no satisfactory way of
preserving this beautiful form of animal life. If placed in strong
spirit the water is rapidly extracted from its body, and its animal
substance shrivelled to a minute, shapeless mass; while in weak spirit
and in other fluid preservatives it becomes more or less distorted, and
deprived of its beautiful transparency, or else it disappears
altogether.
We now come to the great favourites among the cœlenterates--the
beautiful anemones-the animated flowers of the ocean, remarkable not
only for their lovely flower-like forms, but also for the great variety
of colour and of habits which they display. These, together with the
corals, form the division of the cœlenterates known as the
_Zoantharia_, characterised by the possession of simple tentacles, the
number of which is a multiple of either five or six. The latter differ
from the former mainly in the power of secreting a calcareous skeleton
which remains attached by its base after the animal substance has
decayed.
The expanded anemone exhibits a more or less cylindrical body, attached
by a suctorial base to a rock or some other object, and a broad circular
disc above. In the centre of this disc is the mouth, surrounded by the
tentacles, often very numerous, and arranged in one or more whorls. When
the animal is inactive the tentacles are usually completely withdrawn,
and the body contracted into a semiglobular or pear-shaped mass which is
very firm to the touch.
The general internal structure of an anemone may be made out by simple
dissections, and the examination conducted with the specimen submerged
in water. A longitudinal section will show that the body is a double
tube, the outer being formed by the body-wall, and the inner by the
wall of the stomach. Thus there is a body-cavity distinct from that of
the stomach, but the two will be seen to communicate below, since the
stomach-wall does not extend as far down as the base. It will be seen,
too, that the body-wall is made up of two distinct layers--an outer
one, that is continued inward at the mouth to form the inner wall of the
stomach, and an inner one that lines the whole of the body-cavity. The
latter contains the muscular elements that enable the anemone to
contract its body.
When the animal is expanded, the whole interior is filled with sea
water, as are also the tentacles, which are hollow tubes, really
extensions of the body-cavity, and formed by prolongations of the same
two layers that constitute the body-wall. As it contracts this water is
expelled, partly through the mouth, and partly through small openings
that exist at the tips of the tentacles.
[Illustration: FIG. 90.--SECTION OF AN ANEMONE
_t_, tentacles; _m_, mouth; _s_, stomach; _b c_, body-cavity
_p_, mesentery; _o_, egg-producing organ]
The outer layer of the body-wall is provided with stinging cells which
serve not only to protect the anemone from its enemies, but also to aid
it in the capture of its prey, for which latter purpose they are
distributed in much greater abundance in the tentacles.
The body-cavity is divided into a number of communicating compartments
by means of vertical partitions running from the body-wall and
converging towards the centre of the cavity. These are called
mesenteries, and are extensions of the inner layer of the body-wall.
Five or six of these are larger than the others, extending from disc to
base, and are called _primary mesenteries_. Between these are an equal
number of smaller _secondary mesenteries_; and, sometimes, a third set
of still smaller _tertiary mesenteries_.
These internal partitions are best displayed in a transverse section of
the body, which shows the double tube formed by the walls of the body
and the stomach, together with the wheel-like arrangement of the
mesenteries. At one time all animals that had a radial symmetry--the
regular arrangement of parts round a common centre--were grouped
together under the title of _Radiata_; but it has since been recognised
that the creatures of this group exhibited such a great diversity of
structure that they have been re-classified into two main divisions, one
of which constitutes the cœlenterates which we are at present
considering, and the other containing such creatures as star fishes and
sea urchins.
[Illustration: FIG. 91.--STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED
_a_ and _c_, with thread protruded; _b_, with cell retracted]
[Illustration: FIG. 92.--DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE
_S_, stomach; _bc_, body-cavity; _m′_, _m″_, _m‴_, primary,
secondary, and tertiary mesenteries]
[Illustration: FIG. 93.--LARVA OF ANEMONE]
On the surface of the mesenteries of the anemone may be seen the ovaries
or egg-producing organs. These discharge the ova into the general
body-cavity, after which they are ejected through the mouth. The embryos
are minute jelly-like creatures that have an active existence, swimming
about freely in the ocean by means of vibrating cilia, but after this
period of activity they settle down and fix themselves, gradually
assuming the adult form common to the species.
The habits of sea anemones are particularly interesting, and it will
well repay anyone to make a study of these animals in their natural
haunts as well as in the aquarium. The gentle swinging of the tentacles
when searching for food, the capture and disposal of the prey, the
peculiar modes of locomotion, and the development of the young, are
among the chief points of interest. As regards locomotion, the usual
method of moving from place to place is by an exceedingly slow gliding
of the base or ‘foot’; and while some anemones are almost constantly on
the move, others hardly ever stir from the secluded niche in which they
have taken up their abode.
Sometimes an anemone will detach itself from the rock, and drag itself
along, but very slowly, by means of its tentacles, sometimes inverting
its body and walking on its head, as it were, and though one may never
have the opportunity of witnessing this manœuvre on the shore, we have
found it far from an uncommon occurrence in the aquarium.
The natural food of anemones consists of small crustaceans, such as
shrimps, and crabs, molluscs, small fishes, and in fact almost every
kind of animal diet, and there need never be any difficulty in finding
suitable viands for species kept in captivity. It is really astonishing
to see what large morsels they can dispose of with the assistance of
their extensile mouths and stomachs. It is not even necessary, indeed,
that the morsel be so small as to be entirely enclosed by the walls of
its digestive cavity, for the anemone will digest one portion while the
other remains projecting beyond its mouth. Further, it will even attack
bodies which it cannot swallow at all, by protruding its stomach so as
to partially envelope them, and then digesting the portion enclosed.
Indigestible portions of its food, such as the shells of small molluscs,
are ejected through the mouth after the process of digestion has been
completed.
We have already referred to the reproduction of sea anemones by means of
eggs, but it is interesting to note that they may also increase by a
division of the body into two or more parts, and that this division may
be either natural or artificial.
If an anemone be cut into halves longitudinally, each half will develop
into a complete animal. If cut transversely, the upper portion will
almost always develop a new suctorial disc, and produce a new individual
complete in every respect; and it has been stated that the basal portion
of the divided animal will also, occasionally, produce a new disc and
tentacles.
The natural division of the anemone has frequently been spoken of as by
no means an uncommon occurrence, but, as far as our experience of
captive anemones go, this mode of multiplication does not seem to take
place except as the result of some mechanical force applied, or as a
means by which the animal may relieve itself of a solid body that it is
unable to eject. Thus, on one occasion, when a stone had slipped so that
its narrow edge rested across the middle of the disc of a large
_Mesembryanthemum_, the animal, apparently unable to free itself from
the burden, simply withdrew its tentacles and awaited results. In a few
days two individuals were to be seen, one on either side of the stone,
both undoubtedly produced as the result of the pressure applied. This
instance seems to be exactly akin to artificial division, for it is far
more likely that the animal was severed by the simple pressure of the
stone than that it divided itself to be relieved of its burden.
On another occasion an anemone that had almost entirely surrounded a
mussel on which it had been feeding, gradually released itself of the
shell by a longitudinal division of its body; but here, again, it is
probable that the fission was the result of pressure applied rather than
of any power on the part of the animal.
A few of the British sea anemones are shown on Plates II. and III., and
although the coloured illustrations will probably suffice for purposes
of identification, yet a short description of each one represented may
be acceptable.
The most common and most widely distributed species is undoubtedly the
familiar Beadlet (_Actinia mesembryanthemum_--Plate II., figs. 1, 2, 3),
which is to be found on every bit of rocky coast around the British
Isles, and even on some stony beaches where there are no standing rocks
between the tide-marks.
The colour of this species is exceedingly variable, but the most
abundant variety is of a liver-brown colour, with crimson disc and
tentacles, brilliant blue spots round the margin of the disc, and a line
of bright blue around the base. In others the prevailing colour is deep
crimson, orange, yellowish brown, or green. Fig. 1 represents a variety
commonly known as the Strawberry Beadlet (_Fragacea_), which is
distinguished by its superior size, and in which the dark-red ground is
often conspicuously spotted with green.
Two members of the same genus are also shown on Plate III. One of
these--_A. glauca_ (fig. 3)--is of a bluish-green colour; while the
other--_A. chiococca_ (fig. 4)--is bright scarlet, with deep crimson
disc and white spots round the disc.
[Illustration: PLATE II.
SEA ANEMONES
1, 2, 3, Actinia mesembryanthemum.
4. Caryophyllia Smithii.
5. Tealia crassicornis.
6. Sagartia bellis.
7. Balanophyllia regia.
8. Actinoloba dianthus.]
The general form of this genus is that of an expanded flower on a
short column; the name Beadlet is applied on account of the little
bead-like projections on the margin of the disc. The tentacles number
nearly two hundred in a fully grown individual, and are arranged in
several rows; but when the animal is disturbed and the tentacles
retracted, its form is almost hemispherical.
It is interesting to note that _A. mesembryanthemum_ not only exists in
varieties distinguished by distinct colours, but that the same
individual will sometimes change its tint, as may be observed when it is
kept in the aquarium; and it may be mentioned, by the way, that it is
very easily reared in captivity, either in the natural or the artificial
salt water, for not only may the same individuals be kept alive for
years with only a moderate amount of attention, but their offspring may
be reared without difficulty.
On Plate II. (fig. 8) are two illustrations of the beautiful _Actinoloba
dianthus_, which grows to a length of five or six inches, and is easily
distinguished by its expanded and frilled disc, its very numerous short
and slender tentacles, and its tall, pillar-like body. Its colour is
somewhat variable, being either salmon, flesh-colour, cream, white, red,
orange, or brownish; but whatever be the tint of the body and tentacles,
the margin of the mouth is always red or orange. When young it may
easily be mistaken for another species, as its disc is not then frilled,
and the tentacles are much fewer in number.
This pretty anemone usually inhabits deep water, and is frequently
brought in, attached to shells and stones, by trawlers, but it may be
commonly observed in the dark crevices of rocks, a little above
low-water mark, where it is usually seen contracted into a ball, or even
so much flattened that it looks like a mere pulpy incrustation of the
rock. It is very common on the rocky coasts of Dorset, Devon, and
Cornwall, as well as in many parts of Scotland and Ireland.
Like the Beadlet, it is easily kept alive in the aquarium, where it
commonly multiplies by natural division; but as it does not generally
expand in full daylight, its beauty is often better observed at night by
artificial light.
On Plate II. (fig. 5) we have an illustration of the beautiful Dahlia
Wartlet (_Tealia crassicornis_), which may be readily recognised by its
thick, banded, horn-like tentacles, and the numerous little adhesive
warts that almost cover the surface of its body.
This species is as abundant as it is beautiful, for it is to be found in
plenty on almost every rocky coast, where it may be seen in the rock
pools and in the crevices of rocks near low-water mark. The diameter of
its cylindrical body often reaches two or three inches, while the
expanded tentacles embrace a circle of four or five inches. Specimens
even much larger than this are sometimes obtained by dredging in deep
water.
<div class="figcenter" style="width: 500px;">
<a name="fig94" id="fig94"></a>
<img src="images/i_167.jpg" width="500" height="567" alt="" />
FIG. 94.--THE TRUMPET ANEMONE (_Aiptasia Couchii_),
CORNWALL; DEEP WATER
</div>
The ‘Dahlia’ is not so frequently seen by sea-side collectors as its
abundance would lead one to expect, and this is principally due to the
fact that it not only conceals itself in narrow and out-of-the-way
crevices and angles of rocks, but also that, on the retreat of the tide,
it generally covers itself with small stones, fragments of shells, &c.,
held fast to its body by means of its numerous suckers. In this manner
it conceals its beauty so well that the sense of touch, as well as that
of sight, is necessary in determining its whereabouts. As a rule,
however, it does not resort to this method of concealment when it
inhabits deep water, or even a permanent rock pool between the
tide-marks, and thus it is in the latter home where one may expect to
see this sea flower in all its glory, for when permanently covered with
water it will seldom hide its crown, except when alarmed, or when in the
act of swallowing its food.
[Illustration: FIG. 95.--_Peachia hastata_, S. DEVON]
It should be noted, too, that the rock pool is the right place in which
to study the habits of this anemone, for it is not nearly so easy to
rear in the artificial aquarium as the species previously described,
and, moreover, it requires a great deal of food. We have found it live
longest in running water, kept cool, and frequently renewed by supplies
fresh from the sea. It may be fed on almost any, if not every, form of
animal life inhabiting a rock pool. A small fish or a prawn is perfectly
helpless when once it is seized by the creature’s tentacles. Mussels,
winkles, limpets, &c., are eagerly swallowed, and the indigestible
shells disgorged after the animal substance has been dissolved by the
digestive fluid. Even the active shore crab, armed as it is with a coat
of mail and powerful pincers, is no match for its powerfully adhesive
tentacles; nor do the sharp spines of the prickly urchin preserve it
from so voracious a creature.
The rocky coasts of Devon and Cornwall are the chief haunts of the
pretty ‘Daisy Anemone’ (_Sagartia bellis_), and here it is very abundant
in places. This species lives in holes and crevices of the rocks, its
body usually entirely hidden from view, but its dark brown disc,
intersected by bright red radiating lines, and fringed with numerous
small tentacles, fully exposed to view as long as it is submerged. The
length of its body is always adapted to the depth of the hole or crevice
in which the animal lives, and may vary from half an inch to two or
three inches, the diameter of the columns being greatest where the
length is least.
[Illustration: FIG. 96.--_Sagartia pallida_, DEVON AND CORNWALL]
Sometimes the ‘Daisy’ may be seen living a solitary life, having settled
down in a hole just large enough to accommodate it, but more commonly it
is seen in company with several others of its species, occupying a
crevice in a rock pool, and often so closely packed together that the
tentacles of each individual are intermingled with those of its
neighbours, thus exhibiting a more or less continuous cluster or line of
‘flowers,’ each disc being from one to two or three inches in diameter
when fully expanded.
On account of the peculiar positions selected by this species, it is not
easily removed without injury, and hammer and chisel are almost always
necessary for its removal; but if it is obtained without injury, and
transferred to the indoor aquarium, but little difficulty will be found
in keeping it alive and in health. It is also very prolific, and a
single specimen placed in the indoor tank will frequently produce a
large number of young.
The colour of _S. bellis_, like that of many of our anemones, is very
variable, but the species may easily be recognised by the radiating
lines of the disc, and the numerous small tentacles. One variety,
however, deviates considerably in form, colour, and habit from the
normal. It (Plate II., fig. 6) is of a dull yellow colour, and has a
much less graceful form; and, instead of living in the holes and
crevices of rocky coasts, where it would be washed by fresh sea water at
every tide, it inhabits the muddy and fœtid waters of narrow inlets of
the sea in the neighbourhood of Weymouth.
[Illustration: FIG. 97.--_Sagartia nivea_, DEVON AND CORNWALL]
Three other species of the same genus are represented on Plate III. The
first of these--_Sagartia troglodytes_, sometimes called the
Cave-dweller (fig. 1)--though very variable in colour, may be known by
its barred tentacles, each with a black B-like mark near its base. It
lives in sheltered, sandy, or muddy hollows between the rocks on most
rugged coasts, often with its body entirely buried beneath the sediment;
or, if only partially buried, the projecting portion of the column
concealed by particles that adhere to its suckers.
The column is usually of an olive colour, striped longitudinally with a
paler tint, and sometimes reaches a length of two inches, while the
diameter of the expanded ‘flower’ may even exceed this length.
This anemone is not a very conspicuous object of the shore, since the
exposed portion of its column is usually more or less covered by
sedimentary matter, and the tentacles are generally of a tint closely
resembling that of the surrounding surface. Thus the anemone is
protected from its enemies by its peculiar habit and colouring, while at
the same time the spreading tentacles constitute an unseen but deadly
snare for the unwary victims that come within their range.
[Illustration: FIG. 98.--_Corynactus viridis_, DEVON AND CORNWALL]
This species is often difficult to secure without injury on account of
its preference for narrow chinks in awkward situations, but we have
found that it is sometimes easily removed by first clearing away the
surrounding débris, and then gently pushing it from its hold by means of
the finger-nail. It seems, in fact, that its base is occasionally quite
free from the underlying rock, being simply imbedded in sand or mud. In
other cases hammer and chisel are necessary to remove it from its snug
hole.
If placed in the aquarium it should be allowed to get a foot-hold in a
suitable hole or crevice, which should be afterwards partially filled
with sand. It is not difficult to keep, and although not a showy
species, and having a decided preference for shady places, yet its
habits will be found interesting.
The Orange-disked Anemone (_Sagartia venusta_) is represented in fig. 2
of the same plate. It may be easily distinguished by its brilliant
orange-coloured disc, surrounded by white tentacles, which, when fully
expanded, commands a circle of from one to one and a half inches.
South-west Wales is said to be the headquarters of this pretty sea
flower, but we have found it abundant on parts of the north Devon coast,
especially in places between Ilfracombe and Lynton. Like the last
species, it may be termed a cave-dweller, for it delights to hide in
corners and crevices that are so overhung with rocks and weeds that the
light is never strong.
Yet another species of this genus (_S. rosea_) is depicted in Plate
III., fig. 8. It has been termed the Rosy Anemone, from the brilliant
rosy tint of its numerous tentacles. The column is generally of a dull
brown colour, with suckers scattered over the upper portion, and the
flower reaches a diameter of an inch or more. This anemone may be seen
at rest on overhanging rocks near low-water mark when the tide is out,
its disc only partially hidden, and the tips of its bright tentacles
just exposed. It may be seen on many parts of the Devon coast, and is,
or, at least, was, abundant in localities near Brixham and Shaldon.
On the same plate is an illustration (fig. 7) of one of the most
abundant and most interesting of our anemones. It is commonly known as
the Opelet, and its scientific name is _Anthea cereus_. Almost everyone
who has done a little collecting on the rocky shores of the south-west
of England, or on the shores of Scotland or Ireland, must have seen this
species, easily distinguished by its long, slender, smooth tentacles,
all of about equal length, and presenting a waxy appearance. These
appendages are usually green and tipped with pink, but sometimes pale
yellow or red, and are of such a length that they cover a circle of five
or six inches.
This species is decidedly of social disposition, for a number may
generally be seen in a cluster, crowded closely together; and when we
see them, as we often do, occupying a little tide pool that contains
scarcely sufficient water to enable them to give free play to their
tentacles, and exposed for hours to the full blaze of the summer sun, we
naturally form the opinion that they ought to require no special care in
the indoor aquarium. And this is actually the case, for they thrive well
with but little trouble.
Perhaps the chief interest attached to this anemone is the deadly nature
of its grip. The numerous long tentacles have considerable clinging
power throughout their length, and their paralysing power is very
considerable compared with that of many other species of the same size.
Even the human skin is more or less affected by the irritating influence
of this species, a sensation approaching to a sting being sometimes
produced, and the skin showing visible signs of the injury done. The
grip, too, is so tenacious that tentacles are sometimes torn off when
the hand is quickly withdrawn from their hold.
Our next example is the Red-specked Pimplet (_Bunodes Ballii_), shown in
fig. 5 of Plate III., which has received its popular name on account of
the numerous longitudinal rows of red-specked warts that run down its
short yellow column, and other red spots on the column itself, between
the rows. Its tentacles are usually pale yellow or white, but sometimes
grey or greenish, and often tinged with pink.
[Illustration: FIG. 99.--_Bunodes thallia_, WEST COAST]
This anemone is common on some parts of the coasts of Hampshire, Dorset,
Devon, and Cornwall, as well as on the south coast of the Isle of Wight,
and may be found in secluded crevices of the rocks, or under the large
stones that are scattered on the beach.
The Gem Pimplet (_Bunodes gemmacea_) is shown on the same plate (fig.
6). It is easily distinguished by the six conspicuous longitudinal rows
of large white warts, between which are several other rows of smaller
ones. The column is pink or brownish, and the thick tentacles are
conspicuously marked by light-coloured roundish spots. It is not
uncommon on the south-west coast of England, where it may be seen in the
rock pools and on the surfaces of rocks between the tide-marks. Both of
the species of _Bunodes_ above mentioned may be kept in the aquarium
without much trouble.
[Illustration: PLATE III.
SEA ANEMONES
1. Sagartia troglodytes
2. Sagartia venusta
3. Actinia glauca
4. Actinia chiococca
5. Bunodes Ballii
6. Bunodes gemmacea
7. Anthea cereus
8. Sagartia rosea]
All the anemones so far briefly described are quite devoid of any kind
of skeleton, the whole body being of a pulpy or leathery consistence,
but some of our British species develop an internal calcareous skeleton,
consisting of a hollow cylinder of carbonate of lime secreted by the
body-wall, and attached to the rock by means of a similar deposit formed
in the base, and also, within the cylinder, of a number of thin plates
attached to the skeleton of the body-wall and projecting inwards towards
the axis, thus resembling, in fact, the skeletons of a number of the
tropical corals with which we are familiar. The animals in question are
often collectively spoken of as British corals.
[Illustration: FIG. 100.--_Bunodes gemmacea_, WITH TENTACLES
RETRACTED]
One of the finest of these corals is the Devon Cup-Coral (_Caryophyllia
Smithii_), figured on Plate II. It may be found in many parts of Devon
and Cornwall, attached to the rocks between the tide-marks, often in
very exposed places, but is much more abundant in deep water.
Its skeleton is white or pale pink, and very hard, and is in itself a
beautiful object. The animal surrounding this stony structure is of a
pale fawn colour, with a white disc relieved by a deep brown circle
round the mouth. The tentacles are conical, almost colourless and
transparent, with the exception of the deep-brown warts scattered
irregularly over them, and are tipped by rounded white heads.
Of course a hammer and chisel are necessary for the removal of these
corals, but they are hardy creatures, and may be kept for a considerable
time in captivity. Their habits, too, are particularly interesting, and
two or more may sometimes be found with skeletons attached, suggesting
that branched arrangement so common in many of the corals from warmer
seas.
Another of these stony corals (_Balanophyllia regia_) is shown on the
same plate. It is much smaller than the last species, but exceedingly
pretty. It is also much less abundant, being confined almost exclusively
to the coast of North Devon, and is seldom seen far above the lowest ebb
of the tide.
[Illustration: FIG. 101.--_Caryophyllia cyathus_]
Our few brief descriptions of British anemones and corals have been
confined to those species which appear in our coloured plates, but we
have interspersed here and there between the text a few illustrations
which will assist in the identification of other species and also help
to show what a rich variety of form is exhibited by these beautiful
creatures. Some of these inhabit deep water only and are consequently
beyond the reach of most sea-side observers during the ordinary course
of their work; yet they may often be seen in fishing villages,
especially in the south-west, where they are frequently brought in among
the haul of the trawlers, attached either to shells or stones; and live
specimens of these deep-sea anemones may even be seen on the shells of
whelks and bivalve molluscs in the fishdealers' shops of London and
other large towns.
[Illustration: FIG. 102.--_Sagartia parasitica_]
One of the species in question--the Parasitic Anemone (_Sagartia
parasitica_) is generally found on the shell of the whelk or some other
univalve; and, if removed from its chosen spot, it will again transfer
itself to a similar shell when an opportunity occurs. This interesting
anemone is usually seen among the dredgings of the trawler, but may be
occasionally met with on the rocky coasts of the south-west, at extreme
low-water mark. Though sometimes seen attached to stones, shells may
undoubtedly be regarded as constituting the natural home of the species,
and many regard the former position as accidental or merely temporary,
and denoting that the animal had been disturbed and removed from its
favourite spot, or that circumstances had recently rendered a change of
lodgings necessary or desirable. Further, the shell selected by this
anemone is almost always one that is inhabited by a hermit crab; and
this is so generally the case that the occasional exceptions to the rule
probably point to instances in which the occupant of the shell had been
roughly ejected during the dredging operations.
[Illustration: FIG. 103.--THE CLOAK ANEMONE (_Adamsia palliata_) ON A
WHELK SHELL, WITH HERMIT CRAB]
The peculiar habit of the anemone just referred to makes it an
interesting pet for the aquarium, for if removed from its natural home,
and placed in the aquarium with a hermit crab, it will, sooner or later,
as the opportunity occurs, glide from its hole on the stone or rock, and
transfer itself to its favourite moving home.
It may be difficult at first to see what advantage can accrue to the
anemone by the selection of such a situation; and, moreover, it becomes
an interesting question as to whether the advantage is a mutual one.
Close observations may, and already have, thrown some light on this
matter, though it is probable that there still remains something to be
learnt concerning the relations which exist between the inside and
outside occupants of the portable house.
It may be noticed that the anemone almost invariably takes up a position
on the same portion of the shell, and that, when fully expanded, its
mouth is usually turned towards that of the crab. This seems to be a
very favourable position for the anemone, since it is one that will
enable it to catch the waste morsels from the crab’s jaws by its
expanded tentacles. But it is, perhaps, not so easy to suggest a means
by which the anemone can make an adequate return for free board thus
obtained. It is well to remember, however, that crabs are regarded as
such delicate morsels by fishes that we have already spoken of the value
of these crustaceans as bait; while the fact that sea anemones remain
perfectly unmolested in rock pools inhabited by most voracious fishes,
coupled with the fisherman’s experience as to the absolute worthlessness
of anemones as bait, is sufficient in itself to justify the conclusion
that these creatures are very distasteful to fishes. This being the
case, it is possible that the hermit crab is amply repaid by the anemone
for its liberal board not only by partially hiding the crab from the
view of its enemies, and thereby rendering it less conspicuous, but also
by associating its own distasteful substance with that which would
otherwise be eagerly devoured.
When the hermit grows too large to live comfortably in its shell, a
change of home becomes necessary, and it is interesting to observe that
the anemone living on the outside of the shell transfers itself at the
same time; and this is a matter of vital importance to the crab, since
it usually changes its lodging at the moulting period, at which time its
body is covered by a soft skin, and is then even more acceptable as prey
to the fishes. Thus the anemone accompanies its host, affording it
continued protection during the period of its greatest danger.
Before leaving the cœlenterates we must refer to one other form which,
though not often having its habitat between the tide-marks, is
nevertheless a very common object in the neighbourhood of fishing
villages, where the refuse from the nets used in deep water has been
thrown on the beach. We refer to the peculiar animal known to fishermen
as ‘Dead Men’s Fingers,’ and to the naturalist as the _Alcyonium_.
When seen out of water it is not by any means an inviting object, but is
apparently a mass of gristly matter, of a dirty yellowish or brownish
colour, sometimes flattened and shapeless, and sometimes lobed in such a
manner as to suggest the popular name so commonly applied. It is always
attached to some hard object, such as a stone or a shell, and is so
frequently associated with oyster shells that it is by no means an
uncommon object in the fishmonger’s shop, from which we have often
obtained live specimens for the aquarium.
When placed in sea water it gradually imbibes the fluid surrounding it,
becoming much swollen. Then little star-like openings appear, the
circumference of each of which protrudes so as to form a little
projecting tube. Finally, a crown of eight little tentacles is
protruded, and the mass, so uninteresting at first sight, reveals itself
as a colony of pretty polyps.
In general structure the Alcyonium resembles the sea anemone, but the
firm body-wall of the colony is supported and protected to some extent
by the presence of minute spicules of carbonate of lime; and it is
interesting to note that while the tentacles of anemones and corals make
up a number that is a multiple of either five or six, those of the
Alcyonaria and the allied ‘Sea pens’ are always in multiples of four.