FIXED LUMINARIES OF THE SEA.
We have examined and admired the movable and the moving luminaries of
the ocean world, in the firmament of the deep, we may call it,--slowly
moving stars of extreme minuteness, but great brilliancy, in one group,
and the large orbs, more or less moving in erratic spheres, trailing in
long lines of coruscating light, representing the lowest grand branches
of the animal kingdom, the protozoans, and the vast colony of the
sea-jellies, or _medusæ_.
We now come to the third chapter, which embraces those animals forming
the grand branch of the animal kingdom which included in Cuvier’s time
the radiated animals.
All who have visited the New-England shores, or those beyond, farther
north, or the warmer waters of our semi-tropical regions, have probably
become acquainted with the soft and leathery forms, which, when seen
undisturbed in the water, appear like flowers. For example, should
we visit the delightful beaches and coves of Lynn, or Nahant, or
Swampscott, the loved hunting-grounds of Agassiz and his disciples, we
would see, on well-advised instruction from some one informed, what
at first would suggest a moss pink in full bloom, nestled perhaps in
groups, in crevice or open pool, among the crags or broken boulders.
These are the common, and well nigh the only, representative of its
family on our coast, within reach. Others there are, living in deeper
water, within reach of a hand dredge, as work with such, in former
years, well informed us. These are beautiful and very showy, like large
asters and zinnias. But we dwell upon the in-shore one because it is
always at hand and easily obtained, if you know where to look; and it
well represents the characters of the group. Time was, when, forty
years since, if some medical doctor of the town, or some of that ilk,
did not have a sort of half knowledge of the creature, no one about
did. But a few years before that, scientists in Europe were quarrelling
over the question, Is it a vegetable, or an animal? Dr. Marsigli, a
nobleman, asserted that such were vegetable, with further seeming good
argument that the creatures looked like flowers and nothing else,
therefore they must be flowers of the sea, notwithstanding that a poor,
but educated Londoner, by the name of Ellis, demonstrated in good round
science that they were animals. The striking case of mistaken identity,
with the force of nobility, carried it. But Ellis lived to see his
theory prevail.
Scarcely any in the whole range of Nature’s objects are more surprising
and more beautiful. The _Urticena nodosa_ is a form found off our
shores, which is luminous; the light being confined to its tentacles,
and to the soft portion near the summit.
One of the most brilliant of this group of animals is the _Ilyanthus
scoticus_, a kind usually found in ooze, the tentacles appearing at
the surface, and gleaming brightly, like the rays of some fixed star.
Even when brought up on the dredge, these animals emit a brilliant
light.
Some of these sea-anemones are said to attach themselves to the shells
of hermit crabs; and, if luminous, we may imagine the spectacle of the
gleaming, living light-house, moving about at the will of the little
crustacean, possibly attracting prey to it instead of being the warning
beacon that we might suppose. The anemones being, as a rule, fixed, one
naturally likens this one to a light-ship which is drifting about away
from its moorings.
The sea-anemones well repay examination and study, and thrive well in
the aquarium, where their habits and development may be watched. As a
rule, they are fastened to the rocks by a sucking disk. Some live in
the mud; others float upon the surface, or are parasitic upon the great
jelly-fishes. Some, as we have seen, ride about upon hermit crabs, or
fasten themselves upon the claws of others; thus showing the greatest
diversity in their life habits. The corals may be termed anemones
which have the faculty of secreting or depositing lime, and among them
are several which at times appear phosphorescent. The little cup-like
_Caryophyllia_ has been seen to emit a gleam of light, an idea of
which is given in Plate III., Fig. 2.
The phosphorescence of reef-building corals has rarely been observed.
Col. Nicolas Pike, our late consul to Mauritius, and an enthusiastic
naturalist, informs me that he has witnessed the luminosity of their
young. The account is so interesting an addition to the literature of
the subject in general, that I give the colonel’s letter entire:--
BROOKLYN, N.Y., December, 1886.
DEAR MR. HOLDER,--I remember on one occasion, when
sailing on the Indian Ocean, the night was dark, but the crest
of every wave glowed with light. As our vessel moved swiftly
through the water, dashing the foamy waves on each side of her
bows, she left bright streaks of light that reached far behind
us. Every undulation of the water was lit up with scintillating
points of light; and the ocean round us was so luminous, it
would for splendor vie with the finest pyrotechnic display. So
intense was the glow, the hull and sails of the vessel were
illuminated by it; and, as I gazed at the glorious spectacle,
I was filled with wonder and delight. The scene changed
constantly, sometimes less brilliant than others, then again
every rope in the ship was lit up; this, I presume, from the
animals being more or less numerous. At the same time, darting
in every direction, could be seen numerous fishes, making
distinct streaks of light. Luminous spots from one to two inches
in diameter were observed some distance under the water. These
were _medusæ_. We captured many in our nets, and placed
them in buckets of water on the deck, where they still continued
to emit phosphorescent light. The grand scene lasted most of the
night, and was faintly visible till dawn of day.
In the year 1868 or 1869, as I was dredging and collecting on
the reefs near Port Louis, Mauritius, I met with one of the
most singular sights it is possible to conceive. My Lascar crew
gently moved my boat over the reefs, so that I could see any
object in the water. The day was beautiful, not a cloud in the
sky; but the bright sun shone down into the clear waters of the
Indian Ocean, scarcely marked by a ripple on the surface. As the
boat crossed over the shelving reef into deep water, what was my
astonishment to find the depths alive with hundreds of millions
of little creatures (which I supposed to be jelly-fish),
actively moving about in the water, as far as the eye could
penetrate. The little creatures, as they flitted about, emitted
all the colors of the spectrum; the most brilliant diamond could
not vie with the coruscations of light sent out by them. Such a
scene must be witnessed to form any idea of its magnificence:
the whole ocean was aglow with colored lights. I threw over
my hand-net, and drew many thousands into the boat, which I
placed in a large glass jar filled with sea-water, where I could
examine them. They proved to be _young polyps of different
species of the reef-building corals_. Those that I carried
home were still luminous in the evening, and I thought I would
pay a visit later, to see the effect at night; and it was truly
great. The sea was one vast area of luminosity. The illumination
extended for miles. Fishing-boats making for Port Louis harbor
could be plainly seen a long way off by the phosphorescent
light caused by the disturbance they made in passing through
the immense shoal of coral polyps. The sight was curious
and interesting; it had the appearance of an immense meteor
coming directly down on our boat, as they were all heading
for the entrance of the harbor where we lay. The bows of the
fishing-boats made a great disturbance as they struck them, and
the luminosity was most intense; but, as the waves were thrown
off from the bows at a wide angle, the disturbance continued,
and the colored light from the little creatures formed a long
streak from behind the boat, representing the head of a comet
with a long tail. Imagine twenty or thirty of these boats all
heading in one direction, and you may form a faint idea of
the scene. The polyps were not alone, but larger animals were
darting and gyrating about, sending out vivid streaks of light.
The phosphorescent light of these polyps is probably the effect
of a vital action; it appears as a single spark, like that of
various insects, and is repeated at short intervals.
In 1867 I passed through a belt of dark-colored water in a
large stream. It had been observed from the masthead for some
time before we reached it: it proved to be a belt, of miles in
extent, composed of animalcules. When taken up in a bucket,
they gave out the strongest phosphorescent light I have ever
witnessed. It required the highest power of my microscope to
define them, and they were of many species new to me. Our
steamer, a side-wheel vessel, made a great commotion as we
passed for hours through this belt of living matter. These belts
or patches, covering vast tracts of the ocean, are not uncommon.
They are often seen in the Indian Ocean after severe storms and
hurricanes. They vary in color. I have seen them of olive green,
of a yellowish tint, and often a dark blue. Once, after a spent
hurricane at Mauritius, I passed through a belt three miles
wide, of a deep purple, so much so it could be seen a long way
from shore.
Giglioli, the Italian naturalist, refers to the phosphorescence of
madreporic polyps as being quite different from that of other forms.
He observed on the coast of Sumatra and Batavia, that, when the bottom
of his launch grounded upon the polyps, a brilliant display of
phosphorescence followed.
Doubtless nearly all the Alcyonarian[13] corals are light-givers, and
of great importance in the illuminating economy of the ocean.
The Alcyonarians include the sea-pens (_Pennatulidæ_), and the sea-fans
and the red coral of commerce (_Gorgonias_), and may be briefly
described as animals which, as a rule, secrete a horny or calcareous
stock, without the true dividing septa that we see in the corals proper.
The Alcyonarians dredged by the “Challenger” were almost invariably
brilliantly luminous, making the dredge appear as if red-hot coals were
being taken up. The light of the deep-sea forms was similar to that of
those dredged on shallow banks, where the phosphorescence is remarkably
brilliant; so that we can imagine the wondrous spectacle presented in
these little known regions.[14]
The sea-fans and plumes, known scientifically as Gorgonias, are
extremely common upon the outer Florida reef, and form the chief
ornaments of these wonderful gardens of the sea. We have drifted over
them by day and night, peering down into the depths, never wearying
of the display. There were two forms within diving distance on the
reef,--one, a rich yellow, reticulated fan; and the other, a vivid
lilac. On the yellow we often found a parasitic shell of almost the
exact hue of the Gorgonia; so like it, indeed, that it would not have
been noticed if the fan had not been closely examined,--an interesting
example of a protective resemblance.
At night these waters present a wondrous appearance, gleams of light
flashing from every direction. Even the sand at the bottom seemed to
give out fitful coruscations; while pale, dim lights told of rare
_medusæ_,--the phantoms of this world beneath the sea.
The gorgonias emit, as a rule, a light of a beautiful lilac hue; and in
some localities the bottom of the ocean is covered with similar forms,
all gleaming with this vivid phosphorescence. Imagine a cornfield
covering hundreds of acres, the ripe ears emitting a fitful, vivid
lilac light, through which dart various animals,--the birds of this
submarine region,--their passage creating a blaze of another hue; and
some idea can be formed of this scene that conjecture only can picture.
Sir Wyville Thompson states, that, when dredging in water nearly a mile
deep off St. Vincent, they must have passed over an immense field of
light-emitting gorgonias, as the trawls came up filled with a delicate
form, “with a thin wire-like axis slightly twisted spirally, a small
tuft of irregular rootlets at the base, and long exsert polyps. The
stems, which were from eighteen inches to two feet in length, were
coiled in great hanks round the trawl-beam, and entangled in masses in
the net; and, as they showed a most vivid phosphorescence of a pale
lilac color, their immense numbers suggested a wonderful state of
things beneath.”
Off our Eastern coast the little brush-like gorgonia, _Acanella_,[15]
has been observed by Professor Verrill to emit a pale light when
brought to the surface. The Gorgonias are all important light-givers.
_Primnoa_,[16] a brush coral, and _Paragorgia_[17] have become well
known in late years by specimens brought up by the Gloucester fishermen
on the Georges Banks. Even when dry and dead, they are extremely
attractive; the _Primnoa_ being richly tinted with pink, while the
latter has a reddish hue.
If we could descend into these depths, we would find a veritable
forest, with branches seeming on fire; many of the coral trees being
from ten to fifteen feet in height, and equally as wide, forming lanes
and open pathways through which the fishes pass, bathed in the wondrous
light. That this is not imagination is shown by the branches brought
up accidentally and by dredges; some limbs alone being four feet in
length, and stout in proportion. Specimens of these forms can be seen
in most of our museums of science; some sent by Dr. Holder from the
Florida reef to the Museum of Natural History, in Central Park, are
surprisingly beautiful.
More remarkable than the Gorgonias are the strange animals belonging
to _Pennatulidæ_,[18] known popularly as the sea-pens (Plate VII.,
Fig. 2), from the resemblance of some to a quill pen,--an abnormally
large one, it must be confessed. One of the most familiar forms is
_Pennatula phosphorea_. When the animal is observed at night, and
disturbed, it emits quite a brilliant light. In specimens observed at
Oban by Professor Marchel, the more perfect females became vividly
phosphorescent when the leaves were gently irritated. When the polyps
were touched, they showed minute points of light, which appeared over
the whole surface, in rapid, irregular coruscations.
If one of these living pens can produce so interesting a display, what
must be the sight upon the bottom, where myriads of these curious forms
abound, either fixed or moving!
It is not impossible that the light-emitting faculty of sea-pens is
under control; at least, they have their periods of darkness and light.
If a specimen which is not luminous is disturbed, as we have seen, it
immediately becomes so. If the long axial stem is pinched, a seemingly
protesting light appears on the lowest branchlets nearest the stem,
quickly spreading, as if the polyps were igniting. When all those on a
branch have become luminous, the light begins to appear on the next,
and so on in succession until the whole glows brilliantly. Four-fifths
of a second occur between the stimulation and the appearance of the
light; so that in a sea-pen six and one-tenth inches in length, two
seconds and a fifth were required for its complete illumination. By
pinching the top or opposite end of the colony, the same phenomenon
resulted, but reversed. If a polyp at the end of a branchlet was
irritated, light immediately appeared, passed to its neighbor, and so
on; if a branch was touched at both ends, the light followed the act,
and met in the centre.
These interesting experiments, which were made by Panceri, can be
varied in many ways by those fortunate in securing a live sea-pen.[19]
The sea-pen _Pavonia_[20] is noted for its light-emitting properties;
and during the voyage of the English ship “Porcupine” the naturalists
on board had many opportunities for observing its display. Sir Wyville
Thompson, who was in charge, says, “Coming down the sound of Skye
from Loch Torridon on our return, we dredged in about one hundred
fathoms; and the dredge came up tangled with the long pink stems of
the singular sea-pen. Every one of these was embraced and strangled by
the twining arms of an _Asteronyx_,[21] and the round soft bodies of
the star-fishes hung from them like plump ripe fruit. The _Pavonariæ_
were resplendent with a pale lilac phosphorescence, like the flame
of Cyanogen gas; not scintillating like the green light of some
sea-stars,[22] but almost constant, sometimes flashing out at one point
more brightly, and then dying gradually into comparative dimness,
but always sufficiently bright to make every portion of a stem caught
in the tangles or sticking to the ropes distinctly visible. From
the number of specimens of sea-pens brought up at one haul, we had
evidently passed over a forest of them. The stems were a meter long
(over three feet) fringed with hundreds of polyps.”
When the ship “Venus” was lying off Simonstown, one of their boats
passed over a forest of sea-pens in shoal water, which gave out a
vivid light; while, where the ship lay at anchor, other forms of
phosphorescent animals illuminated the ports so that the men lay in
them and read by the wondrous light on the darkest night.
The _Renilla_[23] is a rich purple species common on our south-eastern
borders. Agassiz found it at Charleston, S.C., and says of its
phosphorescence, that “it emitted a golden-green light of wonderful
softness.”
_Virgularia_[24] is an attractive form; and in certain portions of the
Patagonian coast they have been seen, when left by the tide, emitting a
light of great brilliancy.
_Vertillum_ is an interesting genus, resembling a quill pen in which
the feathers have been curled or singed. Its color is a brilliant
orange; but in the darkness it develops a phosphorescence of great
beauty, and so penetrating that a glass containing numbers of them has
been used as a lamp to read by,--an interesting example of one of the
possible, though not remarkably practical, uses of living lights to
mankind.
[Illustration:
PLATE VIII.
LUMINOUS STAR FISHES.
(_Brisinga elegans._)
From 4,500 feet deep.]