SEA-WORMS AND SEA-ANEMONES
LET us now leave the beach-pebbles and go down on to the rocks at low
tide in order to see some of the living curiosities of the seashore.
There are some seaside resorts where, when the tide goes down, nothing
is exposed but a vast acreage of smooth sand, and here the naturalist
must content himself with such spoils as may be procured by the aid
of a shrimping-net and a spade. Wading in the shallow water and using
his net, he will catch, not only the true "brown shrimp," but other
shrimp-like creatures, known as "crustacea"--a group which includes
also the lobsters, hermit-crabs, true crabs, and sand-hoppers, as well
as an immense variety of almost microscopic water-fleas.
He will also probably catch some of the stiff, queer little
"pipe-fish," which are closely related to the little creatures known as
"sea-horses." Pipe-fish are very sluggish in movement, almost immobile,
whilst the "sea-horse" or hippocampus--only to be taken by the dredge
amongst corallines in deep water on rocky bottoms (as, for instance,
in the Channel Islands)--goes so far as to curl his tail, like a South
American monkey, round a stem of weed and sit thus upright amidst the
vegetation. Even when disturbed he merely swims very slowly and with
much dignity in the same upright position, gently propelled by the
undulating vibratory movement of his small dorsal fin. The male in both
pipe-fish and sea-horses is provided with a sac-like structure on the
ventral surface in which he carries the eggs laid by the female until
they are hatched.
[Illustration: FIG. 4.--British Marine Worms or Chætopods.
a, Arenicola piscatorum. Lug-worm largely used for bait by
sea-fishermen. It burrows in sea-sand and clay as the earth-worm does
in soil. Half the natural size, linear.
b, Nephthys margaritacea, actively swimming. It also burrows in the
sea-sand. Natural size.
c, Eunice sanguinea, a very handsome marine worm (often used for bait)
which lives in clefts in the submarine rocks and also swims actively.
The numerous filaments on the sides of the ringed body are the gills
of a rich blood-colour. The figure is one-third of the natural size,
linear.]
The shrimper will probably catch also some very young fish
fry--including young flat-fish about 2 inches long. If he explores the
exposed surface of sand near the low-tide limit, he will find a variety
of indications of burrowing animals hidden beneath. Little coiled
masses like the "castings" of earth-worms are very abundant in places,
and are produced by the fisherman's sand-worm, or "lug-worm" (Fig.
4, a). A vigorous digging to the depth of a foot or two will reveal
the worm itself, which is worth bringing home in a jar of sea-water
in order to see the beautiful tufts of branched gills on the sides of
the body, which expand and contract with the flow of bright red blood
showing through their delicate walls. Other sand-worms, from 2 to 6
inches long, will at the same time be turned up,--worms which have some
hundred or more pairs of vibrating legs, or paddles, arranged down the
sides of the body, and swim with a most graceful, serpentine curving of
the mobile body (Fig. 4, b). These sea-worms are but little known to
most people, although they are amongst the most beautifully coloured
and graceful of marine animals. Hundreds of different kinds have been
distinguished and described and pictured in their natural colours.
Each leg is provided with a bundle of bristles of remarkable shapes,
resembling, when seen under a microscope, the serrated spears of South
Sea Islanders and mediaeval warriors. These worms usually have (like
the common earth-worm) red blood and delicate networks of blood-vessels
and gills (Fig. 4, c), whilst the head is often provided with eyes and
feelers. They possess a brain and a nerve-cord like our spinal cord,
and from the mouth many of them can suddenly protrude an unexpected
muscular proboscis armed with sharp, horny jaws, the bite of which is
not to be despised. These "bristle-worms," or "chætopods," as they are
termed by zoologists, are well worth bringing home and observing in a
shallow basin holding some clean sea-water.
At many spots on our coast (_e.g._ Sandown, in the Isle of Wight, and
the Channel Islands) rapid digging in the sand at the lowest tides will
result in the capture of sand-eels, a bigger and a smaller kind, from
1 foot to 6 inches in length. These are eel-shaped, silvery fish,
which swim near the shore, but burrow into the soft sand as the tide
recedes. They are excellent eating. We used at Sandown to make up a
party of young people to dig the smaller "sand-eels," or "sand-launce."
The agility and rapid disappearance of the burrowing fish into the sand
when one thought one had safely dug them out, rendered the pursuit
difficult and exciting. Then a wood fire on the beach, a frying-pan,
fat, flour, and salt were brought into operation, and the sand-eels
were cooked to perfection and eaten.
[Illustration: FIG. 5.--The shell of the Heart-urchin (Spatangus
purpureus) with its spines rubbed off. One-fourth the actual diameter.]
Some of the marks or small heaps of sand on the flats exposed at low
tide are characteristic of certain shell-fish. The "razor-fish" (Fig.
19, b)--a very much elongated clam, or mussel, with astonishing powers
of rapid burrowing--leaves a hole on the surface like a keyhole,
about an inch long. It can be dug up by an energetic spadesman, but
a spoonful of common salt poured over the opening of its burrow will
cause it to suddenly shoot out on to the surface, when it may be
picked up, and the hunter spared any violent exertion. The curious
heart-urchin (Fig. 5), as fragile as an egg-shell, and covered with
long, closely-set spines like a brush, is often to be found burrowing
in the sand, as well as the transparent, pink-coloured worm known as
Synapta, in the skin of which are set thousands of minute calcareous
anchors hinged to little sculptured plates. These burrowers swallow the
sand and extract nutriment from stray organic particles mixed in it.
The mere sand-flat of the low tide is not a bad hunting ground; but
the rock pools, often exposed when the tide is out, and the fissures
in the rocks and the under surfaces of slabs of rock revealed by
turning them over--are the greatest sources of varied delight to the
sea-shore naturalist. It is well to take a man with you on to these
rocks to carry your collecting bottles and cans, and to turn over for
you the larger slabs of loose stone, weighing as much as a couple of
hundredweight. The most striking and beautiful objects in these rock
pools are the sea-anemones (Fig. 6 and Frontispiece). They present
themselves as disk-like flowers from 1 to 5 inches in diameter, with
narrow-pointed petals of every variety of colour, set in a circle
around a coloured centre. The petals are really hollow tentacles
distended with sea-water, and when anything falls on to them or touches
them they contract and draw together towards the centre. The centre
has a transverse opening in it which is the mouth, and leads into a
large, soft-walled stomach, separated by its own wall from a second
spacious cavity lying between that wall and the body wall, and sending
a prolongation into each tentacle. The stomach opens freely at its
deep end into this second "surrounding" chamber, which is divided by
radiating cross walls into smaller partitions, one corresponding to
each tentacle. The nourishing results of digestion, and not the food
itself, pass from the stomach into the subdivided or "septate" second
chamber. There is thus only one cavity in the animal, separable into a
central and a surrounding portion.
In this respect--in having only one body cavity--sea-anemones and the
coral-polyps and the jelly-fishes and the tiny freshwater polyp or
hydra, and the marine compound branching polyps like it--agree with
one another and differ from the vast majority of animals, such as
worms, sea-urchins, star-fishes, whelks, mussels, crustaceans, insects,
spiders and vertebrates (which last include fish, reptiles, birds, and
mammals). These all have a second chamber, or body cavity, quite shut
off from the digestive cavity and from the direct access of water and
food particles. This second distinct chamber is filled with an animal
fluid, the lymph, and is called the "Cœlom" (a Greek word meaning a
cavity). These higher animals, which possess a cœlom as well as a
gut, or digestive cavity, are called "Cœlomata," or "Cœlomocœla,"
in consequence; whilst the sea-anemones, polyps, and jelly-fish form
a lower grade of animals devoid of cœlom, but having the one cavity,
or gut, continued into all parts of the body. Hence they are called
"Cœlentera," or "Enterocœla," words which mean that the cavity of
their bodies (Greek _cœl_) is made by an extension of the gut, or
digestive cavity (Greek _enteron_). The higher grade of animals--the
Cœlomocœla--very usually have a vascular system, or blood-vessels and
blood, as well as a cœlom and lymph, and quite independent of it; also
some kind of kidneys, or renal excretory tubes. Neither of these are
possessed by the sea-anemones and their allies--the Enterocœla--but
they have, like higher animals, a nervous system and also large ovaries
and spermaries on the walls of their single body cavity, which produce
their reproductive germs. These pass to the exterior, usually through
the mouth, but sometimes by rupture of the body wall.
All "one-cavity" animals, the Enterocœla or Cœlentera, produce
peculiar coiled-up threads in their skin in great quantity--many
thousands--often upon special warts or knobs. These coiled-up threads
lie each in a microscopic sac; they are very delicate and minute
and carry a virulent poison, so that they are "stinging" threads.
Excitement of the animal, or mere contact, causes the microscopic sac
to burst, and the thread to be violently ejected. The sea-anemones,
jelly-fish, and polyps feed on fresh living animals, small fish,
shrimps, etc., and catch their prey by the use of these poisonous
threads. Some jelly-fish have them big enough to act upon the human
skin, and bathers are often badly stung by them. The commonest
jelly-fish do not sting, but where they occur a few of the stinging
sort are likely to occur also. Even some sea-anemones can sting
one's hand with these stinging threads. One sea-anemone (known as
"Cerianthus"), occasionally taken in British waters, makes for itself
a leathery tube by the felting of its stinging threads, and lines its
long burrow in the sand below tidal exposure in this way.
The sea-anemones are very hardy, and they are wonderfully varied and
abundant on our coasts. Some sixty years ago a great naturalist, who
loved the seashore and its rock-pools enthusiastically, Mr. Philip
Henry Gosse, father of Mr. Edmund Gosse, the distinguished man of
letters, described our British sea-anemones, and gave beautiful
coloured pictures of them. One of these I have taken for the
frontispiece of this volume, and some of the outline figures of marine
animals in these chapters are borrowed from a marvelously complete and
valuable little book by him--now long out of print--entitled "Marine
Zoology." His books--of high scientific value--and his example, made
sea-anemones "fashionable." London ladies kept marine aquariums in
their drawing-rooms stocked with these beautiful flowers of the
sea. They were exhibited in quantity at the Zoological Gardens in
Regent's Park, and it is by no means a creditable thing to our London
zoologists that neither these nor other marine creatures are now to be
seen there. At a later date public marine aquaria were started with
success in many seaside towns,--Brighton, Scarborough, Southport,
etc.--and a very fine one was organized in Westminster and another at
the Crystal Palace. It is an interesting and important fact, bearing
on the psychology of the British people, that most of these charming
exhibitions of strange and beautiful creatures from the depths of the
sea were very soon neglected and mismanaged by their proprietors; the
tanks were emptied or filled with river water, and the halls in which
they were placed were re-arranged for the exhibitions of athletes,
acrobats, comic singers, and pretty dancers. These exhibitions are
often full of human interest and beauty--but I regret the complete
disappearance of the fishes and strange submarine animals. I have
some hope that before long we may, at any rate in the gardens in
the Regent's Park, see really fine marine and fresh-water aquaria
established, more beautiful and varied in their contents than those of
earlier days.
[Illustration: FIG. 6.--British Sea-Anemones.
a, Sagartia bellis, the daisy anemone, viewed from above when fully
expanded.
b, Bunodes crassicornis, half expanded; side view.
c, Anthea cereus. The tentacles are pale apple-green in colour, tipped
with mauve, and cannot be completely retracted.
d, Actinia mesembryanthemum. The disk of tentacles is completely
retracted. This is the commonest sea-anemone on our South Coast, and is
usually maroon colour, but often is spotted like a strawberry.]
There are four kinds of sea-anemones which are abundant on our coast.
They adhere by a disk-like base to the rocks and large stones, and
have the power of swelling themselves out with sea-water (as have many
soft-bodied creatures of this kind), with all their tentacles expanded.
They have, in that condition, the shape of small "Martello" towers,
with their adhesive disk below and the mouth-bearing platform above,
fringed by tapering fingers; and they can, on the other hand, shrink to
a fifth part of their expanded volume, drawing in and concealing their
tentacles, which are in some kinds perforated at the tip. One common on
the rocks at Shanklin and other parts of our South Coast, but not on
the East Coast, has very abundant, long, pale green tentacles, which
are tipped with a brilliant peach colour, and it is peculiar in not
being able to retract or conceal this beautiful crown of snake-like
locks, reminding one of the Gorgon Medusa. It is known as Anthea cereus
(Fig. 6, c). Many of them are known by the name "Actinia," and the
commonest of all (Fig. 6, d) is called "Actinia mesembryanthemum,"
because of its resemblance to a fleshy-leaved flower of that name
which grows on garden rockeries--sometimes called the "ice-plant."
This one is of a deep maroon colour, rarely more than an inch and a
half across the disk. The adhesive disk is often edged with bright
blue, and small spherical tentacles, of a bright blue colour, are set
at intervals outside the fringe of longer red ones. This anemone lives
wonderfully well in a small glass basin or in an aquarium holding a
gallon of sea-water, which is kept duly aerated by squirting it daily.
One lived in Edinburgh for more than fifty years, in the possession
first of Sir John Dalyell, and then of Mr. Peach. She was known as
"Granny," and produced many hundreds of young in the course of years.
This species is viviparous, the young issuing from the parent's mouth
as tiny fully-formed sea-anemones, which immediately fix themselves
by their disks to the glass wall of their habitation. Anemones kept
thus in small aquaria have to be carefully fed; bits of the sea mussel
(of course, uncooked) are the best food for them. This and many other
kinds are not absolutely stationary, but can very slowly crawl by
means of muscular movements of the adhesive disk. There are kinds of
sea-anemones known which spend their lives floating in the ocean; they
are thin and flat. Others adhere to the shells of hermit crabs and
even to the big claws of some crabs, and profit by the "crumbs" of
food let fall by the nippers of their host. A very handsome and large
sea-anemone is common on the East Coast, and is known as "crassicornis"
(its generic name is Bunodes). When distended it measures as much as
4 inches across (Fig. 6, b). I have one at this moment before me,
expanded in a bowl of sea-water. The tentacles are pale green or grey,
banded with deep red, and the body is blotched with irregular patches
of red, green, and orange. It attaches fine pebbles and bits of shell
to the surface of the body.