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MODERN SCIENCE

EDITED BY SIR JOHN LUBBOCK, BART., M.P.

THE

FAUKA OF THE DEEP SEA

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MODERN SCIENCE.

Edited by SIR JOHN LUBBOCK, Bart., M.P.
Price 2s. QcL each.

I.

THE CAUSE OF AN ICE AGE.

By SIR ROBERT BALL, LL.D., F.R.S.,

Lou-ndean Professor of Astronomy and Geometry in the

University of Cambridge.

II.

THE HOUSE:

A Study in Natural History.

By SIR WILLIAM HENRY FLOWER, K.C.B.,

Director of the British Natural History Museum,

III.

THE OAK :

A Popular Introduction to Forest-Botany.
By H. MARSHALL WARD, F.R.S., F.L.S.

IV.
ETHNOLOGY IN FOLKLORE.

By GEORGE LAURENCE GOMME, F.S.A.
President of the Folklore Society.

V.
LAWS AND PROPERTIES OF MATTER,

By R. T. GLAZEBROOK, F.R.S.
FrJlow of Trinity College, Cambridge.

VI.
THE FAUNA OF THE DEEP SEA.

By SYDNEY J. HICKSON, M.A.
Fellow of Downing College, Cambridge.

London : KEGAN PAUL, TRENCH, TRUBNER & CO. LTD.

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THE

FAUNA OF THE DEEP SEA

BY

SYDNEY J. HICKSON, M.A. (CANTAB. ET OXON.)

D.8C, (LOXD.), FELLOW OF DOWXIXG COLLEGE, CAMBRIDGE

WITH TWENTY-THREE ILLUSTRATIONS

LONDON
KEGAN PAUL, TRENCH, TRUBNER & CO. LTD.

PATERNOSTER HOUSE, CHARING CROSS ROAD

1898

(The rights of translation and of reproduction arc reserved.)

PEEEACE

THE time may come when there will be no portion of
the earth's surface that has not been surveyed and
explored by man.

The work of enterprising travellers has now been
carried on within a measurable distance of the North
Pole ; the highest mountain ranges are gradually
succumbing to the geological surveyor ; the heart of
Africa is giving up to us its secrets and its treasures,
and plans of all the desert places of the earth are
being made and tabulated.

The bottom of the deep sea was until quite
recently one of these terras incognitas. It was re-
garded by most persons, when it entered into their
minds to consider it at all, as one of those regions
about which we do not know anything, never shall
know anything, and do not want to know anything.

viil PREFACE

But the men of science fifty years ago were not
disposed to take this view of the matter. Pushing
their inquiries as to the character of the sea-fauna
into deeper and deeper water, they at length de-
manded information as to the existence of forms of
animal life in the greatest depths. Unable them-
selves to bear the heavy expenses involved in such
an investigation, they sought for and obtained the
assistance of the Government, in the form of national
ships, for the work, and then our knowledge of the
depths of the great ocean may be said to have com-
menced.

We know a good deal now, and in the course of
time we may know a great deal more, about this
interesting region ; but it is not one which, in our
generation at any rate, any human being will ever visit.

We may be able to plant the Union Jack on the
summit of Mount Everest, we may drag our sledges
to the South Pole, and we may, some day, be able to
travel with ease and safety in the Great Sahara ; but
we cannot conceive that it will ever be possible for
us to invent a diving-bell that will take a party of
explorers to a depth of three and a half miles of

PREFACE IX

water. We may complete our survey of the ocean
beds, we may analyse the bottom muds and name
and classify the animals that compose their fauna,
but there are many things that must remain merely
matters of conjecture. We shall never know, for
example, with any degree of certainty, how Bathy-
pterois uses its long feeler-like pectoral fins, nor
the meaning of the fierce armature of Lithodes ferox ;
why the deep-sea Crustacea are so uniformly coloured
red, or the intensity of the phosphorescent light
emitted by the Alcyonaria and Echinoderms. These
and many others are and must remain among the
mysteries of the abyss.

Our present-day knowledge of the physical con-
ditions of the bottom of the deep sea and the animals
that dwell there is by no means inconsiderable.

It may be found in the reports of the scientific
expeditions fitted out by the English, French, Ger-
man, Italian, Norwegian, and American Governments,
in numerous volumes devoted to this kind of work,
and in memoirs and notes scattered through the
English and foreign scientific journals.

It is the object of this little book to bring together

X PREFACE

in a small compass some of the more important facts
and considerations that may be found in this great
mass of literature, and to present them in such a
form that they may be of interest to those who do
not possess a specialist's knowledge of genera and
species.

When it was found that animals can and do live
even at the greatest depths of the ocean, the interest
of naturalists was concentrated on the solution of
the following problems. Firstly, do the animals con-
stituting the fauna of the abyss exhibit any striking
and constant modification in correlation with the
physical conditions of their strange habitat ? And,
secondly, from what source was the fauna of the
abyss derived? Was it derived from the shallow
shore waters, or from the surface of the sea ? Is it
of very ancient origin, or the result of, comparatively
speaking, recent immigrations ?

These questions cannot be answered in a few lines.
Any views that may be put forward regarding them
require the support oi% a vast array of facts and
figures ; but as the limits of this little book would
not permit of my giving these, I have endeavoured

PREFACE xi

to select a few only of those which bear most directly
upon the points at -issue.

To overburden my work with the names of genera
or the lists of species would not, it seemed to me,
either clear the issues or interest the general reader.
These may be found in the ' Challenger ' monographs,
and other books dealing with the subject.

Those who wish to pursue the subject further will
find in the ' Voyages of the " Blake," ' by Alexander
Agassiz, an excellent and elaborate discussion of
deep-sea problems, and numerous illustrations of some
of the most interesting forms of abysmal life.

In Volume XXIII. of the ( Bulletin of Compara-
tive Zoology ' the same author gives a most interest-
ing account of the deep-sea work that has recently
been done by the ' Albatross ' expedition.

Filhol's ' La Vie au Fond des Mers ' is also a book
that contains a great deal of new and interesting
matter, together with some excellent coloured plates
of deep-sea animals.

SYDNEY J. HICKSON.

DOWNING COLLEGE, CAMBRIDGE :
September, 1893.

CONTENTS

CHAPTER PAGE

I. A SHORT HISTORY OF THE INVESTIGATIONS . 1
II. THE PHYSICAL CONDITIONS OF THE ABYSS . .17

III. THE RELATIONS OF THE ABYSMAL ZONE AND THE

ORIGIN OF ITS FAUNA 45

IV. THE CHARACTERS OF THE DEEP-SEA FAUNA . 59

V. THE PROTOZOA, CCELENTERA, AND ECHINODERMA

OF THE DEEP SEA 86

VI. THE VERMES AND MOLLUSCA OF THE DEEP SEA 109
VII. THE ARTHROPODA OF THE DEEP SEA . . . 123

VIII. THE FISH OF THE DEEP SEA 148

INDEX 167

33567

LIST OF ILLUSTRATIONS

STOMIAS BOA. AFTER FILHOL, ' LA VIE AU FOND

DES MERS ' . . . Frontispiece

JIG. PAGE

1 DIAGRAM ILLUSTRATING THE PASSAGE OF AN

OCEAN CURRENT ACROSS A BARRIER . . 32

2 Sicycnis crassa. AFTER HERTWIG, '"CHALLENGER "

REPORTS ' ...... 36

3 GLOBIGERINA OOZE. AFTER AGASSIZ, ' VOYAGES OF

THE " BLAKE"' ....... 38

4 SECTION THROUGH THE EYE OF Serolix

AFTER BEDDARD, ' " CHALLENGER " REPORTS ' 74

5 SECTION THROUGH THE EYE OF Serolis bromleyana.

AFTER BEDDARD, '"CHALLENGER" REPORTS' 74

6 Opostomias Micripmis. AFTER GUNTHER, '"CHAL-

LENGER" REPORTS' ...... 78

7 HEAD OF Pachystomiax microdon. AFTER VON

LENDENFELD, ' " CHALLENGER " REPORTS ' . 79

8 SECTION THROUGH THE ANTERIOR SUB-ORBITAL

PHOSPHORESCENT ORGAN OF Pachystomias mi-
crodon. AFTER VON LENDENFELD, ' " CHAL-
LENGER" REPORTS' 80

XVI LIST OF ILLUSTRATIONS

'"'• PAGE

9 Challengeria Murrayi. AFTER HAECKEL, ' " CHAL-
LENGER" REPORTS' ... 90

10 Umbellula Guntlieri. AFTER AGASSIZ, ' VOYAGES OF

THE "BLAKE '" 97

11 Ithlzocruius lofotcnsis. AFTER CARPENTER, '" CHAL-

LENGER " REPORTS ' . . 100

12 Rluibdoplewa normani. AFTER LANKESTER, ' CON-

TRIBUTIONS TO OUR KNOWLEDGE OF RHABDO-
PLEURA AND AMPHIOXUS ' . 112

13 A SINGLE POLYPIDE OF RJiabdopleura normani.

AFTER LANKESTER, torn. cit. . . 114

14 Bathyteutliis abyssicola. AFTER HOYLE, ' " CHAL-

LENGER " REPORTS ' . .121

15 Batliynomus giganteus. AFTER FILHOL, torn. cit. . 131

1G Euphausia lat ifrons. AFTER SARS, ' " CHALLENGER"

REPORTS' 134

17 Bentheu/phau&ia aniblyops. AFTER SARS, " CHAL-

LENGER " REPORTS' ... 134

18 Polycheles laccata. AFTER SPENCE BATE, '"CHAL-

LENGER" REPORTS' .... . 133

19 Collosendeis arcuatus. AFTER FILHOL, torn. cit. 141

20 Hypolythius calycodes. AFTER MOSELEY, ' " CHAL-

LENGER " REPORTS ' . . 145

21 Melanocetus Murrayi. AFTER GUNTHER, ' " CHAL-

LENGER " REPORTS ' 156

22 Saccopliarynx ampullaceus. AFTER GUNTHER,

' " CHALLENGER " REPORTS ' 104

THE FAUNA OF THE DEEP SEA

CHAPTER I

A SHORT HISTORY OF THE INVESTIGATIONS

OUR knowledge of the natural history of the deep
seas may be said to have commenced not more than
fifty years ago. There are, it is true, a few frag-
ments of evidence of a fauna existing in depths of
more than a hundred fathoms to be found in the
writings of the earlier navigators, but the methods
of deep-sea investigation were so imperfect in those
days that naturalists were disposed to believe that in
the abysses of the great oceans life was practically
non-existent.

Even Edward Forbes just before his death wrote
of an abyss ' where life is either extinguished or
exhibits but a few sparks to mark its lingering
presence,' but in justice to the distinguished natu-

2 THE FAUNA OF THE DEEP SEA

ralist it should be remarked that he adds, ' Its
confines are yet undetermined, and it is in the
exploration of this vast deep-sea region that the
finest field for submarine discovery yet remains.'

Forbes was only expressing the general opinion
of naturalists of his time when he refers with evident
hesitation to the existence of an azoic region. His
own dredging excursions in depths of over one
hundred fathoms proved the existence of many
peculiar species that were previously unknown to
science. ' They were like,' he says, ' the few stray
bodies of strange red men, which tradition reports to
have been washed on the shores of the Old World
before the discovery of the New, and which served to
indicate the existence of unexplored realms inhabited
by unknown races, but not to supply information
about their character, habits, and extent.'

In the absence of any systematic investigation of
the bottom of the deep sea, previous to Forbes's time
the only information of deep-sea animals was due
to the accidental entanglement of certain forms in
sounding lines, or to the minute worms that were
found in the mud adhering to the lead.

As far back as 1 753, Ellis described an Alcyonarian
that was brought up by a sounding line from a depth

A SHORT HISTORY OF THE INVESTIGATIONS 3

of 236 fathoms within eleven degrees of the North
Pole by a certain Captain Adriaanz of the ; Britannia.'
The specimen was evidently an Umbellula, and it is
stated that the arms (i.e. Polyps) were of a bright
yellow colour and fully expanded when first brought
on deck.

In 1819 Sir John Ross published an account of
his soundings in Baffin's Bay, and mentions the ex-
istence of certain worms in the mud brought from a
depth of 1,000 fathoms, and a fine Caput Medusas
(Astrophyton) entangled on the sounding line at a
depth of 800 fathoms.

In the narrative of the voyage of the ' Erebus ' and
'Terror,' published in 1847, Sir James Ross calls
attention to the existence of a deep-sea fauna, and
makes some remarks 011 the subject that in the light
of modern knowledge are of extreme interest. { I
have no doubt,' he says, ' that from however great a
depth we may be enabled to bring up the mud and
stones of the ocean, we shall find them teeming with
animal life.' This firm belief in the existence of an
abysmal fauna was not, as it might appear from the
immediate context of the passage I have quoted, simply
an unfounded speculation on his part, but was evi-
dently the result of a careful and deliberate chain of

B 2

4 THE FAUNA OF THE DEEP SEA

reasoning, as may be seen from the following passage
that occurs in another part of the same book : — ' It is
well known that marine animals are more suscep-
tible of change of temperature than land animals ; in-
deed they may be isothermally arranged with great
accuracy. It will, however, be difficult to get
naturalists to believe that these fragile creatures could
possibly exist at the depth of nearly 2,000 fathoms
below the surface ; yet as we know they can bear the
pressure of 1,000 fathoms, why may they not of two ?
We also know that several of the same species of
creatures inhabit the Arctic that we have fished up
from great depths in the Antarctic seas. The only
way they could get from one pole to the other must
have been through the tropics ; but the temperature
of the sea in those regions is such that they could not
exist in it, unless at a depth of nearly 2,000 fathoms.
At that depth they might ^pass from the Arctic to the
Antarctic Ocean without a variation of five degrees
of temperature ; whilst any land animal, at the most
favourable season, must experience a difference of
fifty degrees, and, if in the winter, no less than 150
degrees of Fahrenheit's thermometer — a sufficient
reason why there are neither quadrupeds, nor birds,
nor land insects common to both regions.'

A SHORT HISTORY OF THE INVESTIGATIONS 5

In the year 1845, Goodsir succeeded in obtaining
a good haul in Davis Straits, at a depth of 300
fathoms. It included Mollusca, Crustacea, Asterids,
Spatangi, and Corallines.

In 1848, Lieutenant Spratt read a paper at the
meeting of the British Association at Swansea, on
the influence of temperature upon the distribution
of the fauna in the ^Egean seas, and at the close of
this paper we find the following passage, confirming
in a remarkable way the work of previous investiga-
tors in the same field. He says : c The greatest depth
at which I have procured animal life is 390 fathoms,
but I believe that it exists much lower, although the
general character of the ^Egean is to limit it to 300
fathoms ; but as in the deserts we have an oasis, so in
the great depths of 300, 400, and perhaps 500 fathoms
we may have an oasis of animal life amidst the barren
fields of yellow clay dependent upon favourable and
perhaps accidental conditions, such as the growth of
nullipores, thus producing spots favourable for the
existence and growth of animal life.'

The next important discovery was that of the
now famous Globigeriiia mud by Lieutenants Craven
and Maffit, of the American Coast survey, in 1853,
by the help of the sounding machine invented by

6 THE FAUNA OF THE DEEP SEA

Brooke. This was reported upon by Professor
Bailey.

Further light was thrown upon the deep-sea
fauna by Dr. Wallich in 1860, on board H.M.S.
' Bulldog,' by the collection of thirteen star-fish liv-
ing at a depth of 1,260 fathoms.

Previous to this Torell, during two excursions to
the Northern seas, had proved the existence of an
extensive marine fauna in 300 fathoms, and had
brought up with the ' Bulldog ' machine many forms
of marine invertebrates from depths of over 1,000
fathoms; but it was not until 1863, when Professor
Loven read a report upon Torell's collections, that
these interesting and valuable investigations became
known to naturalists.

Nor must mention be omitted of the remarkable
investigations of Sars and his son, the pioneers of
deep-sea zoology on the coasts of Norway, who, by
laborious work commenced in 1849. failed altogether
to find any region in the deep water where animal
life was non-existent, and indeed were the first to
predict an extensive abysmal fauna all over the floor
of the great oceans. One of the many remarkable
discoveries made by Sars was Rhizocvinus, a stalked
Crinoid.

A SHORT HISTOEY OF THE INVESTIGATIONS 7

Evrer since that time the Norwegians and the
Swedes have been most energetic in their investi-
gations, and the publications of the results of the
Norske Nord-havns expeditions are regarded by all
naturalists as among the most valuable contributions
to our knowledge of the deep-sea fauna.

Notwithstanding the previous discovery of many
animals that undoubtedly came from the abysmal
depths of the ocean, there were still some persons who
found a difficulty in believing that animal life could
possibly exist under the enormous pressure of these
great depths. It was considered to be more probable
that these animals were caught by the dredge or sound-
ing lines in their ascent or descent ; and that they
were merely the representatives of a floating fauna
living a few fathoms below the surface.

The first direct proof of the existence of an inverte-
brate fauna in deep seas was found by the expedition
that was sent to repair the submarine cable of the
Mediterranean Telegraph Company. The cable had
broken in deep water, and a ship was sent out to
examine and repair the damage. When the broken
cable was brought on deck, it bore several forms of
animal life that must have become attached to it and
lived at the bottom of the sea in water extending

8 THE FAUNA OF THE DEEP SEA

down to a depth of 1,200 fathoms. Among other
forms a Caryophyllia was found attached to the cable
at 1,100 fathoms, an oyster (Ostrea cochlear), two
species of Pecten, two gasteropods, and several worms.

The discoveries that had been made indicating
the existence of a deep-sea fauna led to the commis-
sion of H.M. ships c Lightning ' and ' Porcupine,' and
the systematic investigation that was made by the
naturalists on these vessels brought home to the
minds of naturalists the fact that there is not only an
abysmal fauna, but that in places this deep-sea fauna
is very rich and extensive. The ' Lightning ' was
despatched in the spring of 1868 and carried on its
investigations in the neighbourhood of the Faeroe
Islands, but the vessel was not suitable for the
purpose and met with bad weather. The results,
however, were of extreme importance ; for, besides
solving many important points concerning the
distribution of ocean temperature, ' it had been
shown beyond question that animal life is both
varied and abundant at depths in the ocean
down to 650 fathoms at least, notwithstanding the
extraordinary conditions to which animals are there
exposed.'

Among the remarkable animals dredged by the

A SHOKT HISTORY OF THE INVESTIGATIONS 9

'Lightning' were the curious Echinoderm, Brisinga
coronata, previously discovered by Sars, and the
Hexactinellid sponges, Holtenia and Hyalonema, the
Crinoids Rhizocrinus and Antedon celticus, and the
Pennatulid Baihyptilum Carpenteri, not to mention
numerous Foraminifera new to science.

In the spring of the following year, 1869, the
Lords Commissioners of the Admiralty despatched
the surveying vessel ' Porcupine ' to carry on the work
commenced by the ' Lightning.'

The first cruise was on the west coast of Ireland,
the second cruise to the Bay of Biscay, where dredg-
ing was satisfactorily carried on to a depth of 2,435
fathoms, and the third in the Channel between Faeroe
and Scotland.

The dredging in 2,435 fathoms was quite successful,
and the dredge contained several Mollusca, including
new species of Dentalium, Pecten, Dacrydium, &c.,
numerous Crustacea and a few Annelids and Gephyrea,
besides Echinoderma and Protozoa. A satisfactory
dredging was also made in 1,207 fathoms.

The third cruise was also successful and brought
many new species to light, including the Porocidaris
purpurata, and a remarkable heart urchin, Pourtalesia
Jeffrey si.

10 THE FAUNA OF THE DEEP SKA

Concerning Pourtalesia Sir Wyville Thomson
says :-

' The remarkable point is that, while we had so
far as we were aware no living representative of this

peculiar arrangement of what is called "disjunct'
ambulacra, we have long been acquainted with a fossil
family — the Dysasteridas — possessing this character.
Many species of the genera Dysaster, Collyrites, &c.,
are found from the lower oolite to the white chalk, but
there the family had previously been supposed to have
become extinct.'

The discovery of two new Crinoids led to the
anticipation that the Crinoidea, the remarkable group
of Echinoderma, supposed at the time to be on the
verge of extinction, probably form, rather an impor-
tant element in the abysmal fauna.

One of the most interesting results was the
discovery of three genera in deep water, Ccdveria,
Neolampas and Pourtalesia, almost immediately after
they were discovered by Pourtales in deep water
011 the coasts of Florida, showing thus a wide
lateral distribution and suggesting a vast abysmal
fauna.

A year before the ' Lightning ' was despatched,
Count Pourtales had commenced a series of investi-

A SHORT HISTORY OF THE INVESTIGATIONS 11

gations of the deep-sea fauna off the coast of Florida.
The first expedition started in 1867 from Key West
for the purpose of taking some dredgings between
that port and Havana. Unfortunately yellow fever
broke out on board soon after they started, and only
a few dredgings were taken. However, the results
obtained were of such importance that they encouraged
Pourtales to undertake another expedition and enabled
him to say very positively ' that animal life exists at
great depths, in as great a diversity and as great an
abundance as in shallow water.'

In the following years, 1868 and 1869, the expe-
ditions were more successful, and many important
new forms were found in water down to 500 fathoms.
Perhaps the most interesting result obtained was the
discovery of Boiirguetticrinus of D'Orbigny ; it may
even be the species named by him which occurs fossil
in a recent formation in Guadeloupe.

By this time the interest of scientific men was
thoroughly excited over the many problems connected
with this new field of work. The prospect of obtain-
ing a large number of new and extremely curious
animals, the faint hope that living Trilobites, Cystids,
and other extinct forms might be discovered, and
lastly the desire to handle and investigate great

12 THE FAUNA OF THE DEEP SEA

masses, of pure protoplasm in the form of the famous
but unfortunately non-existent Bathybius, induced
some men of wealth and leisure to spend their time
in deep-sea dredging, and stimulated the govern-
ments of some civilised countries to lend their aid
in the support of expeditions for the deep-sea
survey.

Mr. Marshall Hall's yacht, the ' Nornia,' was em-
ployed for some time in this work, and an extensive
collection of deep-sea animals was made. About the
same time Professor L. Agassiz was busy on board the
American ship, the ' Hassler,' in continuing the work
of Count Pourtales, and later on the Germans fitted
out the ' Gazelle,' and the French the still more famous
' Travailleur ' and ' Talisman ' expeditions. Nor must
we omit to mention in this connection the cruise of
the Italian vessel, the ' Vittor Pessani,' nor those of
the British surveying vessels, the ' Knight Errant '
and the ' Triton,' and the American vessels, ' The
Blake ' and the ' Fish Hawk.'

But of all these expeditions, by far the most com-
plete in all the details of equipment, and the arrange-
ments made for the publication of the results, was
the expedition fitted out in 1873 by the British
Government. The voyage of H.M.S. ' Challenger '

A SHORT HISTORY OF THE INVESTIGATIONS 13

is so familiar to all who take an interest in the
progress of scientific discovery, that it is not necessary
to do more than make a passing mention of it in this
place. The excellent books that were written by
Wyville Thomson, by Moseley, and by other members
of the staff, have made the general reader familiar with
the narrative of that remarkable cruise and the most
striking of the many scientific discoveries that were
made ; while the numerous large monographs that
have been published daring the past fourteen years
give opportunities to the naturalist of obtaining all
the requisite information concerning the detailed
results of the expedition.

The expenditure of the large sum of money upon
this expedition and the publication of its reports has
been abundantly justified. The information obtained
by the ' Challenger ' will be for many years to come
the nucleus of our knowledge of the deep-sea fauna,
the centre around which all new facts will cluster,
and the guide for further investigations.

To say that the ' Challenger ' accomplished all that
was expected or required would be to over-estimate
the value of this great expedition, but nevertheless it
is difficult for us, even now, thoroughly to grasp the
importance of the results obtained or to analyse and

14 THE FAUNA OF THE DEEP SEA

classify the numerous and very remarkable facts that
were gained during her four years' cruise.

It is, of course, impossible, in a few lines, to give
a summary of the more important of the Natural
History results of the ' Challenger ' expedition. Be-
sides proving the existence of a fauna in the sea at
all depths and in all regions, the expedition further
proved that the abysmal fauna, taken as a whole,
does not possess characters similar to those of the
fauna of any of the secondary or even tertiary rocks.
A few forms, it is true, known to us up to that time
only as fossils, were found to be still living in the
great depths, but a large majority of the animals
of these regions were found to be new and specially
modified forms of the families and genera inhabiting
shallow waters of modern times. No Trilobites, no
Blastoids, no Cystoids, no new Ganoids, and scarcely
any deep-sea Elasmobranchs were brought to light,
but the fauna was found to consist mainly of
Teleosteans, Crustacea, Coelentera, and other creatures
unlike anything known to have existed in Palasozoic
times, specially modified in structure for their life in
the great depths of the ocean.

In 1876 the s.s. 'Voringin' was chartered by
the Norwegian Government and was dispatched to

A SHORT HISTORY OF THE INVESTIGATIONS 15

investigate the tract of ocean lying between Norway,
the Faeroe islands, Jan Mayen, and Spitzbergen. The
investigations extended over three years, the vessel
returning to Bergen in the winter months.

The civilian staff of the ' Voringin ' included
Professors H. Mohn, Danielssen, and G . 0. Sars, and
the expedition was successful in obtaining a large
number of animals from deep water by means of the
dredge and tangles and by the trawl.

The results of this expedition have been published
in a series of large quarto volumes under the general
title of the Norske Nord-havns Expedition.

The most interesting forms brought to light by
the Norwegians are the two genera Fenja arid Aec/ir,
animals possessing the general form of sea anemones
but distinguished from all Coelenterates by the
presence of a continuous and straight gut reaching
from the mouth to the aboral pores which completely
shuts off the coelenteron or general body cavity from
the stomoda3um.

In more recent times the work has been by no
means neglected. With the advantage of employing
many modern improvements in the dredges and
trawls in use, the American steamer, the ' Albatross,'
has been engaged in a careful investigation of the

16 THE FAUNA OF THE DEEP SEA

deep-sea fauna of the eastern slopes of the Pacific
Ocean, while at the same time Her Majesty's survey-
ing vessel, the ' Investigator,' has been obtaining some
interesting and valuable results from a survey of the
deep waters of the Indian Ocean. But our knowledge
of this vast and wonderful region is still in its infancy.
We have gathered, as it were, only a few grains from
a great unknown desert. It is true that we may not
for many years, if ever, obtain any results that will
cause the same deep interest and excitement to the
scientific public as those obtained by the first great
national expeditions, but there are still many im-
portant scientific problems that may be and will be
solved by steady perseverance in this field of work,
and if we can only obtain the same generous support
from public institutions and from those in charge
of national funds that we have received in the past
two decades, many more important facts will doubt-
less be brought to light.

17

CHAPTER II

THE PHYSICAL CONDITIONS OF THE ABYSS

IT is not surprising that the naturalists of the early
part of the present century could not believe in the
existence of a fauna at the bottom of the deep seas.

The extraordinary conditions of such a region-
the enormous pressure, the absolute darkness, the
probable absence of any vegetable life from want of
direct sunlight- -might very well have been con-
sidered sufficient to form an impassable barrier to the
animals migrating from the shallow waters and to
prevent the development of a fauna peculiarly its
own.

The fragmentary accounts of animals brought up
by sounding lines from great depths might, it is true,
have thrown doubts on the current views ; but they
were not of sufficient importance in themselves,
nor were the observations made with such regard to
the possibility of error, as to withstand the critical
remarks that were made to explain them away.

c

18 THE FAUNA OF THE DEEP SEA

The absence of any evidence obtained by accurate
systematic research, together with the consideration
of the physical character of the ocean bed, were quite
sufficient to lead scientific men of that period to
doubt the existence of any animal life in water deeper
than a few hundred fathoms.

We now know, however, that there is a very
considerable fauna at enormous depths in all the
great oceans, and we have acquired, moreover, con-
siderable information concerning some of those
peculiar physical conditions of the abyss that fifty
years ago were merely matters of speculation among
scientific men.

The relation between animals and their environ-
ment is now a question of such great interest and
importance that it is necessary in any description of
the fauna of a particular region to consider its
physical conditions and the influence that it may be
supposed to have had in producing the characteristics
of the fauna.

The peculiar physical conditions of the deep seas
may be briefly stated to be these : It is absolutely
dark so far as actual sunlight is concerned, the
temperature is only a few degrees above freezing
point, the pressure is enormous, there is little or no

THE PHYSICAL CONDITIONS OF THE ABYSS 19

movement of the water, the bottom is composed of a
uniform fine soft mud, and there is no plant life.

All of these physical conditions we can appreciate
except the enormous pressure. Absolute darkness
we know, the temperature of the deep seas is not an.
extraordinary one, the absence of movement in the
water and the fine soft mud are conditions that we
can readily appreciate ; but the pressure is far greater
than anything we can realise.

At a depth of 2,500 fathoms the pressure is,
roughly speaking, two and a half tons per square
inch — that is to say, several times greater than the
pressure exerted by the steam upon the piston of
our most powerful engines. Or, to put the matter in
other words, the pressure per square inch upon the
body of every animal that lives at the bottom of the
Atlantic Ocean is about twenty-five times greater
than the pressure that will drive a railway train.

A most beautiful experiment to illustrate the
enormous force of this pressure was made during the
voyage of H.M.S. ' Challenger.' I give the description
of it in the words of the late Professor Moseley.

' Mr. Buchanan hermetically sealed up at both
ends a thick glass tube full of air, several inches in
length. He wrapped this sealed tube in flannel, and

c 2

20 THE FAUNA OF THE DEEP SEA

placed it, so wrapped up, in a wide copper tube,
which was one of those used to protect the deep-sea
thermometers when sent down with the sounding
apparatus.

' This copper tube was closed by a lid fitting
loosely, and with holes in it, and the copper bottom
of the tube similarly had holes bored through it.
The water thus had free access to the interior of the
tube when it was lowered into the sea, and the tube
was necessarily constructed with that object in view,
in order that in its ordinary use the water should
freely reach the contained thermometer.

' The copper case containing the sealed glass tube
was sent down to a depth of 2,000 fathoms and
drawn up again. It was then found that the copper
wall of the case was bulged and bent inwards
opposite the place where the glass tube lay, just as if
it had been crumpled inward by being violently
squeezed.

' The glass tube itself, within its flannel wrapper,
was found when withdrawn, reduced to a fine powder,
like snow almost. What had happened was that the
sealed glass tube, when sinking to gradually increas-
ing depths, had held out long against the pressure,
but this at last had become too great for the glass

THE PHYSICAL CONDITIONS OF THE ABYSS 21

to sustain, and the tube had suddenly given way and
been crushed by the violence of the action to a fine
powder. So violent and rapid had been the collapse
that the water had not had time to rush in by
means of the holes at both ends of the copper cylinder
and thus fill the empty space left behind by the
collapse of the glass tube, but had instead crushed
in the copper wall and brought equilibrium in that
manner. The process is exactly the reverse of an
explosion, and is termed by Sir Wyville Thomson an
" implosion."

It is but reasonable to suppose that the ability
to sustain this enormous pressure can only be acquired
by animals after generations of gradual migrations
from shallow waters. Those forms that are brought
up by the dredge from the depths of the ocean
are usually killed and distorted by the enormous
and rapid diminution of pressure in their journey
to the surface, and it is extremely probable that
shallow-water forms would be similarly killed and
crushed out of shape were they suddenly plunged
into very deep water. The fish that live at these
enormous depths are in consequence of the enormous
pressure liable to a curious form of accident. If, in
chasing their prey or for any other reason, they rise

22 THE FAUNA OF THE DEEP SEA

to a considerable distance above the floor of the
ocean, the gases of their swimming bladder become
considerably expanded and their specific gravity
very greatly reduced. . Up to a certain limit the
muscles of their bodies can counteract the tendency
to float upwards and enable the fish to regain its
proper sphere of life at the bottom ; but beyond that
limit the muscles are not strong enough to drive
the body downwards, and the fish, becoming more
and more distended as it goes, is gradually killed
on its long and involuntary journey to the surface
of the sea. The deep-sea fish, then, are exposed to
a danger that no other animals in this world are
subject to, namely that of tumbling upwards.

That such accidents do occasionally occur is
evidenced by the fact that some fish, which are now
known to be true deep-sea forms, were discovered
dead and floating on the surface of the ocean long
before our modern investigations were commenced.

Until quite recently, every one agreed that no
rays of sunlight could possibly penetrate the sea
to a greater depth than a few hundred fathoms.

Moseley says that ' probably all is dark below
200 fathoms excepting in so far as light is given out
by phosphorescent animals,' and Wyville Thomson

THE PHYSICAL CONDITIONS OF THE ABYSS 23

speaks of the 'utter darkness of the deep-sea
bottom.'

Within the last few years a few authors have
maintained that it is quite possible that a few rays
of sunlight do penetrate even to the greatest depths
of the ocean — a view mainly based on the fact that so
many deep-sea animals possess extremely perfect and
complicated eyes and very brilliant colours. Verrill
says : ' It seems to me probable that more or less
sunlight does actually penetrate to the greatest depths
of the ocean, in the form of a soft sea-green light,
perhaps at 2,000 or 3,000 fathoms equal in intensity
to our partially moonlight nights and possibly at the
greatest depths equal only to starlight. It must be
remembered that in the deep sea far away from land
the water is far more transparent than near the coast.'
Packard is of a similar opinion.

There seem to me to be very slight grounds for
this view. The fact that, comparatively speaking,
shallow-water fish avoid nets that are rendered
phosphorescent by entangled jelly-fish does not
justify us in assuming that deep-sea fish avoid
regions where there are phosphorescent Gorgonians
or Pennatulids. It is not by any means certain
that fish avoid sunken nets on account of their

24 THE FAUNA OF THE DEEP SEA

phosphorescence. Most fish possess, as is well
known, a very acute sense of smell, and it is very
probable that they avoid such nets on account of
the putrid odours of the dead animals that remain
attached to them.

Nor is there much strength in the further
argument that it can hardly be possible that there
can be an amount of phosphorescent light regularly
evolved by the few deep-sea animals, having this
power, sufficient to cause any general illumination, or
powerful enough to have influenced, over the whole
ocean, the evolution of complex eyes, brilliant and
complex protective colours, and complex commensal
adaptations.

We have no sound information to go upon to be
able to judge of the amount of light given off by
phosphorescent animals at the bottom of the deep sea.
The faint light they show on deck after their long
journey from the depths in which they live to the
surface may be extremely small compared with the
light they give in their natural home under a pressure
of 2J tons to the square inch. The complex eyes
that many deep-sea animals exhibit were almost
certainly not evolved as such, but are simple modifi-
cations of eyes possessed by a shallow-water ancestry.

THE PHYSICAL CONDITIONS OF THE ABYSS 25

The more recent experiments that have been
made, tend to show that no sunlight whatever pene-
trates to a greater depth, to take an extreme limit,
than 500 fathoms.

Fol and Sarasin, experimenting with very sensitive
bromo-gelatine plates, found that there was no reac-
tion after ten minutes' exposure at a depth of 400
metres on a sunny day in March.

But although it is highly probable that not a
glimmer of sunlight ever penetrates to the depths
of the ocean, there is in some places, undoubtedly, a
very considerable illumination due to the phosphor-
escence of the inhabitants of the deep waters.

All the Alcyonarians are, according to Moseley,
brilliantly phosphorescent when brought to the sur-
face. Many deep-sea fish possess phosphorescent
organs, and it is quite possible that many of the deep-
sea Protozoa, Tunicates, Jelly-fish, and Crustacea are
in their native haunts capable of giving out a very
considerable amount of phosphorescent light.

If we may be allowed to compare the light of
abysmal animals with that of surface forms, we can
readily imagine that some regions of the sea may
be as brightly illuminated as a European street is
at night — an illumination with many very bright

26 THE FAUNA OF THE DEEP SEA

centres and many dark shadows, but quite sufficient
for a vertebrate eye to distinguish readily and at a
considerable distance both form and colour.

To give an example of the extent to which the
illumination due to phosphorescent organisms may
reach, I may quote a passage from the writings of
the late Sir Wyville Thomson.

' After leaving the Cape Verde Islands the sea
was a perfect blaze of phosphorescence. There was
no moon, and although the night was perfectly clear
and the stars shone brightly, the lustre of the heavens
was fairly eclipsed by that of the sea. It was easy
to read the smallest print, sitting at the after-port in
my cabin, and the bows shed on either side rapidly
widening wedges of radiance so vivid as to throw the
sails and rigging into distinct lights and shadows.'

A very similar sight may frequently be seen in
the Banda seas, where on calm nights the whole
surface of the ocean seems to be a sheet of milky fire.
The light is not only to be seen where the crests of
waves are breaking, or the surface disturbed by the
bows of the boat, but the phosphorescence extends
as far as the eye can reach in all directions. It is
impossible, of course, to say with any degree of cer-
tainty whether phosphorescence such as this exists at

THE PHYSICAL CONDITIONS OF THE ABYSS 27

the bottom of the deep sea, but it is quite probable
that it does in some places, and hence the well-
developed eyes and brilliant colours of some of the
deep-sea animals.

On the other hand the entire absence or rudimen-
tary condition of the eyes of a very considerable pro-
portion of deep-sea animals seems to prove that the
phosphorescent illumination is not universally dis-
tributed, and that there must be some regions in
which the darkness is so absolute that it can only be
compared with the darkness of the great caves.

It is difficult to believe that the eves of such

i/

animals as crabs and prawns for example would
undergo degeneration if there were a glimmer of light
in their habitat, a light even so faint as that of a star-
light night in shallow water. With the faintest light
the eyes would be of use to them in seeking their
prey, avoiding their enemies, and finding their mates,
and any diminution in the keenness of this sense
would probably be of considerable disadvantage to
them and tend to their ultimate extinction.

It might be argued that the animals of the abysses
of the ocean probably feed chiefly upon the carcases
of pelagic animals that have fallen from the upper
regions of the sea, and that the sense of smell is

28 THE FAUNA OF THE DEEP SEA

probably the most important for them in searching for
their food. That is quite probable ; but many shallow-
water animals invariably seek their food by their
sense of smell without showing any traces of a weak-
ness in their sense of sight. It may be taken as an
axiom of biology that unless a particular sense is
absolutely useless to an animal or a positive disad-
vantage to it, that sense will be retained.

It may be stated then with some confidence that
in the abysmal depths of the ocean there is no trace
of sunlight. It is highly improbable, on the face of
it, that any ray of light could penetrate through a
stratum of water four miles in thickness, even if the
water were perfectly pure and clear, but when we
remember that the upper regions, at least, are crowded
with pelagic organisms provided with skeletons of
lime and silica, we may justly consider that it is im-
possible.

The temperature of the water in the abyss is by
no means constant for a constant depth nor does it
vary with the latitude. It is true that, as a rule, the
water is colder at greater depths than in shallower ones,
and that the deeper the thermometer is lowered into
the sea, the lower the mercury sinks. This is consist-
ent with physical laws. If there is any difference at

THE PHYSICAL CONDITIONS OF THE ABYSS 29

all in the temperature of a column of water that has
had time to settle, the thermometer will always reach
its highest point at the top of the column and its
lowest at the bottom, for the colder particles being
of greater specific gravity than the warmer ones will
sink, and the warmer ones will rise.

The truth of this will be clear if we imagine a
locality at the bottom of a deep ocean with a source
of great heat such as an active volcano.

Such a source of heat would, it is true, raise the
temperature of the water in its immediate vicinity,
but the particles of water thus heated would im-
mediately commence to rise through the superjacent
layers of colder water, and colder particles would fall
to take their places. Thus the effect of an active
volcano at the bottom of the deep sea would not
be apparent at any very great distance in the same
plane. In fact, unless the bottom of the ocean was
closely studded with volcanoes we should expect to
find, as indeed we do find, that the temperature of
the sea rises as the water shallows.

If then we were to consider a great ocean as
simply a huge basin of water, we should expect to
find the water at the surface warmer than the water
at the bottom. The temperature of the surface

30 THE FAUNA OF THE DEEP SEA

would vary constantly with the temperature of the
air above it. That is to say, it would be warmer at
the equator than in the temperate regions. The
temperature at the bottom would be the same as the
lowest temperature of the basin, that is, of the earth
that supports it.

The great oceans however cannot be regarded as
simple basins of water such as this. The tempera-
ture of the surface water varies only approximately
with the latitude. It is generally speaking hottest
at the equator and coldest at the poles, but surface
currents in the intermediate regions produce many
irregularities in the surface temperature.

Again, although we have no means of knowing
what the temperature of the earth is at 1,000 fathoms
below the surface of the ocean, it is very probable
that in the great oceans the temperature of the
deepest stratum of water is considerably lower than
the true earth temperature. This is due to currents of
cold water constantly flowing from the poles towards
the equator. If these polar currents were at any time
to cease, the temperature of the lowest strata of water
would rise.

Although the polar currents cannot be actually
demonstrated nor their exact rapidity be accurately

THE PHYSICAL CONDITIONS OF THE ABYSS 31

determined, the deduction from the known facts of
physical geography that they do actually exist is
perfectly sound and beyond dispute. A few con-
siderations will, I think, make this clear.

If the ocean were a simple basin somewhat deeper
at the equator than at the poles, the cold water at
the poles would gradually sink down the slopes of
the basin towards the latitude of the equator, and
the bottom temperature of the water would be
constant all the world over.

A few hills here and there would not affect the
general statement that for a constant depth the tem-
perature of the lowest stratum of water would be
constant.

But in some places ridges occur stretching across
the oceans from continent to continent, and these
ridges shut off the cold water at the bottom of the
sea 011 the polar side from reaching the bottom of
the sea on the equator side.

If A (fig. 1) represents a ridge stretching from
continent to continent across an ocean, and the arrow
represents the direction of the current, then the water
that flows across the ridge from the polar side to the
equator side will be drawn from the layers of water
lying above the level of the ridge, and consequently

32 THE FAUNA OF THE DEEP SEA

none of the coldest water will ever get across it,
and from the level of the ridge to the bottom of the
sea on the equatorial side the water will have the
same temperature as the water at the level of the
ridge on the polar side.

It follows from this that in places where there are
deep holes in the bed of the ocean surrounded on all
sides by considerable elevations, the temperature of

I^O/O

•30 I Superficial

on°t w3c.ers

^u

\ 1 -1 i

1 /ncermeoiBce

.V..~"~— "_- V— --VI 4

; waters

50

50

co / A \

5 / A \

5o / \

* Bottom

. / \

i° wster';

ro

j *

2°

^ "~

~~-

. 1. — Diagram illustrating the passage of an
ocean current across a barrier (A).

the water at the bottom will be the same as the
temperature of the water on the summit of the
lowest ridges that surrounds them.

This explains why it is that we find that the bottom
temperature for a given depth is frequently less in
one place than it is in another, even in places of the
same parallel of latitude. One or two examples may
be taken to illustrate these points. The temperature
off Rio Janeiro in lat. 20° S. was found by the

THE PHYSICAL CONDITIONS OF THE ABYSS 33

' Challenger ' to be 0'6° C. at a depth of 2,150 fathoms.
In a similar latitude north of the equator at a depth of
2,900 fathoms the temperature was found to be 2-2° C.,
and at a point near Porto Rico there is a deep hole of
4,561 fathoms with a bottom temperature of 2-2° C.

Again it has been shown by the American ex-
pedition that the temperature of the water at the
deepest point in the Gulf of Mexico, 2,119 fathoms,
is the same as that of the bottom of the Straits of
Yucatan, 1,127 fathoms, namely 4- 1° C . And, passing
to another part of the world altogether, we find in the
small but deep sea that lies between the Philippines
and Borneo that, at a depth of 2,550 fathoms, the
temperature is 10'2°C.

These facts then show that, although at the
bottom of the deep seas the water is always very
cold, the degree of coldness is by no means constant
in the same latitude for the same depth.

We must now return to the polar currents. We
have assumed above that these currents do exist, and
it is probable that by this time the reader must have
seen why they are assumed to exist.

The water at the bottom of the ocean is exceed-
ingly cold. Where does this coldness come from ?
It is obvious that in temperate and tropical climes

D

34 THE FAUNA OF THE DEEP SEA

it does not come from the surface. Nor is it at all
probable that it comes from the earth upon which
the water rests ; for, if it were so, the temperature for
water of a given depth would always be the same.
We should not find the bottom temperature of 0-4° C.
at 2,900 fathoms off Rio de la Plata and a tempera-
ture of 2-2° F. in 4,561 fathoms off Porto Rico.

In fact the only hypothesis that can with any
show of reason be put forward to account for the
temperature of the bottom of the ocean is that which
derives its coldness from the Polar ice.

We have at present very little evidence to enable
us to judge of the force and direction of the polar
currents in the two hemispheres, but the researches of
the ' Challenger ' prove almost conclusively that in the
Atlantic Ocean there is a very strong predominance
of the Antarctic polar current. In fact it seems very
probable that the Arctic polar current, if it exist at
all, is very small and confined to the eastern and
western shores of the North Atlantic.

It is very probable, however, that these cur-
rents at the bottom of the ocean are extremely slow,
and, as the water is never affected by tides or storms,
the general character of the deep sea is probably
one of calm repose. This is a matter of no little

THE PHYSICAL CONDITIONS OP THE ABYSS 35

importance ; for, in the consideration of the characters
presented by the fauna of any particular region, it is
always necessary to take into account the physical
difficulties the animals have to contend against and
the modifications of structure they present to combat
these difficulties.

Thus in a region such as that presented by the
deep sea, where there are no rapid tides, we should
not expect to find such a powerful set of body
muscles in the free-swimming forms nor such a firm
vertebral column as in the animals that live in

more livelv water.

«/

Perhaps it is of the nature of an assumption to
say that there are no rapid currents and tides in the
abysmal depths of the ocean, for we have no means of
demonstrating or even of calculating the rate of flow of
these waters. But it is a reasonable hypothesis and
one that we may well use until the contrary is proved.

A fact of some importance that supports this
hypothesis, as regards some parts of the ocean at
least, is presented by the sea-anemones.

Many of the shallow-water Actimaiis are known
to possess minute slits in the tentacles and disc,
affording a free communication between the general
body cavity or ccelenteron and the exterior.

D 2

36

THE FAUNA OF THE DEEP SEA

In many deep-sea forms the tentacles are consid-
erably shorter and the apertures larger than they are
in shallow- water forms. It is difficult to believe that
such forms, perforated by, comparatively speaking,
large holes, could manage to live in rapidly flowing
water, for if they did so they would soon be smothered

- • M

---T

FIG. 2. — Sicyonis crassa. M, mouth ; s, ciliated groove ; T, ten-
tacles. Each tentacle is perforated by a single large aperture.
(After Hertwig.)

by the fine mud that composes the floor of all the deep
seas. In fact anemones of the type presented by such
forms as Sicyonis crassa are only fitted for existence
in sluggish or still water.

Another character that must be taken into con-

THE PHYSICAL CONDITIONS OF THE ABYSS 37

sideration is that presented by the floor of the great
oceans. The floor of the ocean, if it were laid bare,
would probably present a vast undulating plain of
fine mud. Not a rock, not even a stone would be
visible for miles.

The mud varies in different parts of the globe
according to the depth, the proximity to land, the
presence of neighbouring volcanoes or the mouths of
great rivers.

The Globigerina ooze is perhaps the best known '
of all the different deep-sea deposits. It was dis-
covered and first described by the officers of the Ameri-
can Coast Survey in 1853. It is found in great
abundance in the Atlantic Ocean in regions shallower
than 2,200 fathoms. Deeper than this, it gradually
merges into the c Red mud.' It is mainly composed of
the shells of Foraminifera, and of these the different
species of Globigerina are the most abundant. It is
probably formed partly by the shells of the dead
Foramimfera that actually live on the bottom of the
ocean and partly by the shells of those that live near
the surface or in intermediate depths and fall to the
bottom when their lives are done.

So abundant are the shells of these Protozoa that
nearly 95 per cent, of the Globigerina ooze is com-

38

THE FAUNA OF THE DEEP SEA

posed of carbonate of lime. The remaining five per
cent, is composed of sulphate and phosphate of lime,
carbonate of ammonia, the oxides of iron and
manganese, and argillaceous matters. The oxides of
iron and manganese are probably of meteoric origin ;
the argillaceous matter may be due to the trituration

FIG. 3. — Globigerina ooze. (After Agassiz.)

of lumps of pumice stone and to the deposits caused
by dust storms.

Globigerina ooze may be found on the floor of
the ocean at depths ranging from 500 to 2,800
fathoms of water in equatorial and temperate lati-
tudes. The reason that it is not found in Arctic
seas may be that the cold surface waters of these
regions do not bear such an abundant fauna of Fora-

THE PHYSICAL CONDITIONS OF THE ABYSS 39

minifera. This is supported by the fact that it
extends ten degrees further north than south in the
Atlantic, the warm water of the Gulf Stream bear-
ing a richer fauna than the waters of a corresponding
degree of latitude in the Southern Sea.

The Pteropod ooze has only twenty-five per cent,
of carbonate of lime. It contains numerous shells
of various Pteropods, Heteropods, and Foramini-
fera, but nearly fifty per cent, of its substance is com-
posed of the siliceous skeletons of Radiolaria and the
frustules of diatoms.

According to Murray it is found in tropical
and subtropical seas at depths of less than 1,500
fathoms.

The Radiolariau ooze is found only in the deepest
waters of the Central and Western Pacific Ocean. In
some of the typical examples, not a trace of carbonate
of lime was to be found, but in somewhat shallower
waters a few small fragments occurred.

A Diatom ooze, mainly composed of the skeletons
of diatoms, has also been found in deep water near the
Antarctic Circle, but it has not apparently a very wide
range.

Of all the deep-sea deposits, however, the so-
called * Red mud ' has by far the widest distribution.

40 THE FAUNA OF THE DEEP SEA

It is supposed to extend over one- third of the earth's
surface. It is essentially a deep-sea deposit, and one
that is found in its typical condition at some con-
siderable distance from continental land. Like the
Globigerina ooze it is never found in enclosed seas,
To the touch it is plastic and greasy when fresh, but
it soon hardens into solid masses. When examined
with the microscope it is seen to be composed of ex-
tremely minute fragments rarely exceeding 0*05 mm.
in diameter. It contains a large amount of free silica
that is probably formed by the destruction of numer-
ous siliceous skeletons, and a small proportion of sili-
cate of alumina. It usually contains the remains of
diatoms, radiolaria, and sponge spicules, and occasion-
ally lumps of pumice stone, meteoric nodules, and, in
colder regions, stones and other materials dropped
by passing icebergs.

In the great oceans, then, we find in the deepest

•
places red mud, or, where there is an abundant radio-

larian surface fauna, Radiolarian ooze ; in water that
is not deeper than about 2,000 fathoms, we find the
Globigerina ooze ; in shallower waters and in some
localities only Pteropod ooze.

It must not be supposed that sharp limits can
anywhere be drawn between these different kinds of

THE PHYSICAL CONDITIONS OF THE ABYSS 41

deposits, for they pass gradually into one another and
present many intermediate forms.

It is probable that the sea-water by virtue of the
free carbonic acid it contains in solution is able to
exert a solvent action upon the calcium carbonate
shells of animals as they sink to the bottom, and
during the long and very slow journey from the sur-
face to the bottom of the deepest seas these shells are
completely dissolved.

The first to be dissolved would be the thin
delicate shells of the Pteropods and Heteropods, for
besides the fact that they present a wider surface to
the solvent action of the water they are probably in-
fluenced more by tide and currents, sink more slowly
and erratically, and thus have a longer journey to
perform.

Then the smaller but more solid and compact
shells of the Forarninifera are dissolved, and lastly, in
the deepest water only the siliceous skeletons of the
radiolaria and diatoms are able to reach their last
resting place at the bottom of the ocean.

These four oozes then are characteristic of the
floor of the deep oceans. In the proximity of land
and in inland seas where deep water occurs, other
muds are found differing from one another in accord-

42 THE FAUNA OF THE DEEP SEA

ance with the character of the coasts in their vicinity.
It is not necessary to give a detailed account of them,
but a few remarks on some of the more pronounced
forms may not be without interest.

The blue mud contains eighty per cent, of a mix-
ture of quartz, mica, felspar, hornblende, and other
minerals, mixed with a considerable quantity of de-
composing animal and vegetable substance, the cal-
careous remains of foraminifera, mollusca, worms,
echinoderms, alcyonaria and corals, and the siliceous
skeletons of radiolaria and diatoms.

The green mud is characterised by a large per-
centage of glauconite.

The red muds characteristic of the Brazilian
coast contain a large amount of ochreous matter
brought into the sea by the great rivers.

In the neighbourhood of active volcanoes there is
a characteristic volcanic mud, and in the coral seas
the deep-sea deposits contain a large percentage of
the calcareous remains of dead corals.

One more character of the deep-sea region must
be referred to before we pass on, and that is the
absence of vegetable life. It has not been determined
yet with any degree of accuracy where we are to
place the limit of vegetable life, but it seems probable

THE PHYSICAL CONDITIONS OF THE ABYSS 43

that below a hundred fathoms no organisms, except-
ing a few parasitic fungi, are to be found that can be
included in the vegetable kingdom. While then the
researches of recent times have proved beyond a doubt
that there is no depth of the ocean that can be called
azoic, they have but confirmed the perfectly just
beliefs of the older naturalists that there is a limit
where vegetable life becomes extinct. It is not diffi-
cult to see the reason for this. All plants, except a
few parasites and saprophytes, are dependent upon
the influence of direct sunlight, and as it has been
shown above that the sunlight cannot penetrate
more than a few hundred fathoms of sea- water,
it is impossible for plants to live below that
depth.

The absence of vegetable life is an important
point in the consideration of the abysmal fauna, for
it is in consequence necessary to bear in mind that
the food of deep-sea animals must be derived from
the surface. It is possible that deep-sea fish, in
soTue cases, feed upon one another and upon deep-sea
Crustacea, that deep-sea Crustacea feed upon deep-sea
worms, that deep-sea echinoderms feed upon deep-
sea foraminifera, and so on through all the different
combinations ; but the fauna would soon become

44 THE FAUNA OF THE DEEP SEA

exhausted if it had no other source of food supply.
This other source of food supply is derived from the
bodies of pelagic organisms that fall from the upper
waters of the ocean, and is composed of protozoa,
floating tunicates, Crustacea, fish, and other animals,
together with diatoms and fragments of sea-weed.

45

CHAPTER III

THE RELATIONS OF THE ABYSMAL ZONE AND THE
ORIGIN OF ITS FAUNA

IN the study of the geographical distribution of
terrestrial animals one of the great difficulties met
with is the impossibility of denning exactly the
limits of the regions into which we divide the surface
of the earth. In a general way we recognise that
there is an Australian region, an Ethiopian region,
&c. ; but, when we come to discuss the exact posi-
tion of the frontier lines that separate these regions
from their neighbours, we find all kinds of difficulties
to overcome and inconsistencies to meet.

For the sake of convenience it is useful to adopt
certain arbitrary limits for these regions, notwith-
standing these difficulties and inconsistencies, but we
must recognise the fact that nature recognises no
such limits, that every region overlaps its neighbours
to a greater or less extent, and that there are many

46 THE FAUNA OF THE DEEP SEA

debateable grounds in the world where the fauna
characteristic of one region is mixed with that
characteristic of another.

But this difficulty in defining the exact limits
of the terrestrial faunistic regions is even more pro-
nounced in the case of the regions and zones of the
marine fauna.

On the dry land we find mountain ranges, forests,
deserts, and other barriers, that to a very considerable
extent prevent the mixing of one fauna with another,
but in the sea there are no barriers of anything like
the same importance, but one fauna gradually merges
into the neighbouring fauna according to the temper-
ature, the pressure, the amount of light, the salinity
of the water or the food supply. This then is one of
the difficulties met with in the study of the geo-
graphical distribution of the marine fauna.

But there is another that leads to almost greater
complications. In considering terrestrial life it is
customary to refer only to regions of geographical,
or perhaps it would be more correct to call it-
superficial distribution. It would be quite possible,
however, to subdivide the geographical areas into
zones of elevation above the sea-level, not very
clearly marked off from one another, it is true, but

THE RELATIONS OF THE ABYSMAL ZONE 47

nevertheless each showing a number of characteristic
features. This idea is expressed, for example, when
we speak of the Alpine fauna, the Himalayan fauna,
or the fauna of the great Andes.

In the study of the marine fauna and flora we
must notice, it is the depth of the water, or in other
words the depression of the habitats below the sea-
level, that forms the most important consideration.
Geographical sub-regions may be recognised and
defined with a certain amount of accuracy, especially
in the case of the fauna of the shallow waters, but by far
the most important changes in the general characters
of the fauna are found when we pass from one ' zone '
of depression to another. Thus in describing any
particular marine fauna we should mention first of
all its zone or sub-zone of depression and then its
geographical region and sub-region. For example,
we may speak of the fauna of the pelagic zone of
the British sub-region of the European region, or the
fauna of the abysmal zone of the Northern sub-region
of the Atlantic region.

We can recognise three primary zones of the
marine fauna which we may call the ' Pelagic,' the
4 Neritic,' and the ' Abysmal ' zones.

The Pelagic zone includes the superficial waters

48 THE FAUNA OF THE DEEP SEA

of all seas extending from the surface to a depth
which cannot at present be very accurately determined,
but is probably the same as the limit of the influence
of direct sunlight.

The animals of this zone are frequently charac-
terised by a general transparency of their tissues,
a white or sea-water (i.e. blue or green) colour,
an organisation capable of prolonged swimming or
floating movement, and by giving birth to floating
eggs which hatch out transparent larvae or embryos.

The pelagic zone may be divided into several
geographical regions and sub-regions, which it would
be beyond the scope of this book to enumerate here,
but there is one that calls for a few brief remarks. In
many parts of the ocean there may be found vast
areas of floating sea- weed, which carry with them a
population of Crustacea and other animals peculiarly
their own. This ' sargasso ' fauna presents so many
characteristics and so many features different from
that of the ordinary pelagic fauna, that the tracts of
sea bearing this weed must be considered to rank as
a special region of the pelagic zone, which may be
called the Sargasso region.

The zone of shallow water for which we shall adopt
Professor Haeckel's term — theNeritic zone— embraces

THE EELATIONS OF THE ABYSMAL ZONE 49

all parts of the seas of less depth than 500 fathoms,
including the inland seas, the shores of great con-
tinents and islands, and the shallow banks in the
great oceans. It does not include the superficial
waters — which belong to the pelagic zone — but ex-
tends only from the actual bottom to a distance of
a few fathoms above it. The fauna of this zone is
extremely varied, consisting of animals that swim,
crawl, or are permanently fixed to the bottom,
animals of almost every variety of colour and mark-
ing, and of every size and shape.

The exact limits of the Neritic sub-zones are not
easy to define. The distinguished naturalist Forbes,
to whom the abysmal zone was unknown, divided
the seas from 0-50 fathoms in depth into three zones
-the littoral zone lying between tide marks, the
laminarian zone extending from 0-15 fathoms, and
the coralline zone from 15-50 fathoms.

The first of these will stand as a sub-zone, the
animals that are able to withstand exposure to the
sun and air either in pools or upon the rocks and
sand even for a few minutes frequently possessing
features that distinguish them from those dwelling
beyond low-water mark, just as those more active
creatures that migrate backwards and forwards with

E

50 THE FAUNA OF THE DEEP SEA

the ebb and flow of every tide differ from the
dwellers in the open sea. There is, it is true, at
every low tide, a migration of part of the fauna
of this sub-zone into the next, but still it is suffi-
ciently well defined to be allowed to remain in
our category.

The second sub-zone is not so easy to define.
The terms ' lamiiiarian ' and 'coralline' used by
Forbes are only applicable to certain geographical
regions and must be abandoned for general use.

We can only recognise one sub-zone between the
littoral sub-zone and the abysmal zone, for notwith-
standing the important varieties it exhibits in the
nature of the bottom, whether it be rocky, sandy, or
weedy, the amount of light, the temperature of the
water, and the rapidity of the currents, it is not
possible at present to point to any general characters
of the fauna of its different parts to justify us in
subdividing it.

The name that may be given to this second sub-
zone of the neritic zone is the Katantic — the sub-zone
of the slopes.

The last well-marked zone is the abysmal, ex-
tending from the 500-fathom line to the greatest
depths of the ocean, one of enormous superficial area,

THE KELATIONS OF THE ABYSMAL ZONE 51

one that it is most difficult to investigate, and one
about which we know but little.

In the present state of our knowledge we cannot
divide it into any well-marked sub-zones nor even into
geographical regions or sub-regions. It is not divided
into sections by any important geographical barriers,
and the general characters presented by its fauna are
practically the same all the world over.

Professor A. Agassiz has pointed out in his
' Challenger ' monograph that the deep-sea echinoids
of the Atlantic Ocean differ from those living in
corresponding depths in the Pacific Ocean, but it is
doubtful whether any such well-marked differences
can be observed in other groups of animals. If, in
the course of time, increased knowledge of deep-sea
animals emphasises the difference between the
abysmal fauna of the Pacific and that of the Atlantic,
then we can divide this zone into two geographical
regions ; but at present it seems more correct to
consider the abysmal zone as one that is indivisible
either bathymetrically or geographically.

Before passing on to the consideration of the
general characters of the abysmal fauna, there are
still one or two points that must be just briefly
referred to.

K -2

52 THE FAUNA OF THE DEEP SEA

It is the function of every true naturalist to con-
sider animals from every possible point of view. Not
only must he regard them as members of a certain
species belonging to a genus, a family, an order, and
so on, presenting certain peculiarities of structure
and development ; not only must he regard them as
inhabitants of a certain locality or zone of depth, but
he must also pay attention to their habits and mode
of life.

Now amongst marine animals we can recognise
three principal modes of life. Some animals simply
float or drift about with the currents of the sea and
are unable to determine for themselves, excepting,
perhaps, within very small limits, the direction in
which they travel. Such are the countless forms of
protozoa, the jelly-fishes and medusse, numerous
pelagic worms and Crustacea, the pyrosomas and
salps, and many other forms well known to those
who are in the habit of using the tow-net. This
portion of the fauna has recently been called the
Plankton.

Then there are the animals that are capable of
very considerable swimming movements, animals
that are able to stem the tide and migrate at will
from one part of the sea to another, such as the

THE RELATIONS OF THE ABYSMAL ZONE 53

cetacea, most fishes, and perhaps also many cephalo-
pods. This portion of the fauna has been called the
Nekton.

And lastly we have those animals that remain
perfectly fixed to the bottom or are capable only
of creeping or crawling over the rocks and sand,
such as the sponges, hydroids, sedentary tunicates,
gasteropods, most larnellibranchs, and many crus-
tacea. This portion of the fauna has been called the
Benthos.

Although it will not be necessary to use these
terms very frequently in this little book, it may be
advisable for the reader to bear in mind that in any
exhaustive treatise on the marine fauna such terms
would be employed, and that in the chapters dealing
with the fauna of the abysmal zone we should find
accounts of the ' bathybial plankton,' the ' bathybial
nekton,' and the ' bathybial benthos.'

Lastly we must consider quite briefly the views
that have been held concerning the origin of the
abysmal fauna.

As soon as it became clear to naturalists that
there is no part of the ocean, however deep it may
be, that deserves the name ' azoic,' but that almost
every part has a fauna of greater or less density,

54 THE FAUNA OF THE DEEP SEA

the problem of the origin of this fauna presented
itself.

Whence came the curious creatures that live
mostly in total darkness and can sustain without
injury to their delicate and complicated organisation
the enormous pressure of the great depths ? Are
they the remnants of the fauna of shallow prehistoric
seas that have reached their present position by the
gradual sinking of the ocean basins ? Or, are we to
look upon the abysmal region as the nursery of
the marine fauna, the place whence the population
of the shallow waters was derived ? Neither of these
answers is supported by the facts with which we
are now well acquainted. The fauna of the abysmal
region does not show a close resemblance to that of
any of the past epochs as revealed to us by geology,
nor are we justified in assuming without much
stronger evidence than we now possess, that the
oceans have undergone any such great depression as
this first theory presupposes.

Nor can we consider for a moment that the abyss
was the original source of the shallow-water fauna ;
for not only do we find but few types that can be
considered to be, in any sense of the word, ancestral
in character ; but on the contrary most of the animals

THE RELATIONS OF THE ABYSMAL ZONE 55

of the deep sea seem to be specially modified types of
shallow-water forms. The most probable explanation
of the origin of the deep-sea fauna is the one that was
put forward by Moseley and has been since supported
by almost every authority on the subject, namely, that
the fauna of the deep sea has been derived from suc-
cessive immigrations of the animals from the shallow
water.

This view is supported by the fact that the deep-
sea fauna is much richer in the neighbourhood of land
than it is in regions more remote from it. Many
examples could be given to illustrate this point.
The extraordinary richness of the deep-sea fauna on
the western slopes of the floor of the Atlantic has
been frequently commented on by the naturalists con-
nected with the expeditions of the American vessels,
the ' Blake/ the ' Fish Hawk,' and the ' Albatross.'
Moseley called attention several years ago to a few
localities in the neighbourhood of the land especially
rich in deep-sea forms in comparatively shallow
waters, such as one near the island of Sombrero in
the Danish West Indies, where within sight of the
lighthouse a haul of the dredge in 450 fathoms brought
up a rich fauna of blind Crustacea, corals, echino-
derms, sponges, &c. Another off Kerrnadec in 630

56 THE FAUNA OF THE DEEP SEA

fathoms brought up numerous curious blind fishes,
ascidians, cuttlefishes, Crustacea, Pentacrinus, and
large vitreous sponges, and there are similar locali-
ties lying between Aru and Ke and between the
Nanusa archipelago and the Talaut islands. The
deep water off the Norwegian, Scotch, Irish, and
Portuguese coasts also seems to be particularly rich
in various forms of animal life. The same is pro-
bably true of the deep sea of many other regions
in the neighbourhood of land, and, although it
cannot be taken to be a rule without exceptions —
the abysmal fauna off the western coasts of the
Panama region being, according to the recent
researches of Alexander Agassiz in the ' Albatross,'
particularly poor — yet we can assert as a statement
of very general application that the further removed
from continental land, the poorer is the abysmal
fauna.

Another argument that has been brought forward
by Moseley in support of his view is that there is a
certain relationship between the deep-sea fauna of
any particular region and the shallow-water fauna of
the nearest coasts. This is a point that is not easy
to illustrate by examples, but as Moseley's argument
has not, so far as I am aware, been disputed by any

THE RELATIONS OF THE ABYSMAL ZONE 57

of the naturalists who have followed him in this line
of work, and the recent results of the ' Albatross ' in
comparing the deep-sea fauna of the eastern and
western sides of the isthmus of Panama seem if any-
thing to support it, we can take it as a point in
favour of his view of the origin of the abysmal fauna.

It is impossible to say at present at what time in
the world's history these migrations commenced, but,
as Agassiz points out, none of the palaeozoic forms
are found in the deep sea, and this seems to indicate
that the fauna did not commence its existence earlier
than the cretaceous period.

It is quite possible, however, that part of the fauna
of the deep sea has been derived directly from the
pelagic zone. The occurrence of bathybial Radiolaria,
Foraminifera and Siphonophora, and among fishes
genera and species of the pelagic families Sternopty-
chidas and Scopelidas, suggest that this zone may have
contributed very largely to the fauna of the abyss.

Much of course still remains to be done before
we can consider any of these interesting problems
connected with the deep-sea fauna to be definitely
solved. All we can do at present is to speculate
upon the direction in which the facts at our disposal
seem to point, and by following up one clue after

58 THE FAUNA OF THE DEEP SEA

another hope that we may eventually arrive at the
truth. The task may be a difficult one, but it will
reward our efforts. If truth is hard to find when
it lies at the bottom of a well, how much more
inaccessible must it be when it lies hidden in the
darkness of the sea's abyss !

59

CHAPTER IV

THE CHARACTERS OF THE DEEP-SEA FAUNA

THE general characters presented by animals living
in deep water may be considered under several
headings. The most important are those that are
directly or indirectly related to the fact that the
animals live either in total darkness or in the faint
and probably intermittent light emitted by phos-
phorescent animals ; namely, the colour of the skin
and the peculiarities of the eyes.

The colours of the skin of the deep-sea animals
vary to a very remarkable extent in the different
groups. It cannot be said that there is any one
colour at all predominant, and it is only in certain
classes that black, white, or dull-coloured animals are
more numerous than others. The colours are how-
ever usually very evenly distributed, and we find but
few examples of animals with spots, stripes, or other
pronounced markings.

The majority of the fish are dark brown or black,
but many other colours are represented. Thus

60 THE FAUNA OF THE DEEP SEA

Ipnops Murrayi, a typical deep-sea fish, is yellowish
brown with colourless fins, and it exhibits a further
character not uncommon in these abysmal forms,
namely black buccal and branchial cavities. Typh-
lonus nasuSj again, is said to be of a light brownish
colour, with black fins. Many other examples
could be given to show the prevalence in these
regions of these black, dull, and pale uniform colours.
But there are many exceptional cases. Neoscopelus
macrolepidotuSj for example — a form that according to
Gunther undoubtedly belongs to the bathybial region-
is distinguished by its brilliant colours. It is bright
red mixed with azure blue, the whole relieved by
silver spots with circles of black on the abdomen.

Prorogadus nudus is of a pale rose colour, with the
under and lateral sides of the head bluish black.

Rhodichthys regina, found in 1,280 fathoms of
water, is uniformly bright red in colour.

A. Agassiz says in his reports on the dredging
operations on the west coast of America : ' The
coloration of the deep-sea fishes is comparatively
monotonous. The tints are all a light violet base,
tending more or less to brownish or brownish yellow,
or even to a greenish tint, especially among the
Macruridae. Some of the Liparidae were of a dark

THE CHARACTERS OF THE DEEP-SEA FAUNA 61

violet, and one species was characterised by a brilliant
blue band. The Ophidiidge, Nemichthys, and the like,
are usually of an ashy violet tint, while in Ipnops
and Batlujpterois the tints were of a decidedly
yellowish brown.'

That the deep-sea fish are usually devoid of any
pronounced spots, stripes, and other markings, is now
well recognised. It may not be altogether out of place,
however, to refer briefly to a few exceptions.

The black circles on the abdomen of Neoscopelus
macrolepidotus have already been referred to.

Halosaurti.s johnsonianus has a black spot on the
tail.

Aulostoma longipes has three pairs of large black
spots on the ventral side, but the specimen taken
in 1,163 metres of water by the 'Talisman' was
probably a young one.

It is very probable that in all the exceptional
cases, when fish taken in deep-sea water have exhibited
such spots and markings, they are examples either
of fish that have quite recently adopted an abysmal
habitat or of young specimens exhibiting ancestral
inherited characters.

In referring to a specimen of Raja drcularis, taken
by the ' Triton ' in 516 fathoms, Giinther says : ' It is

62 THE FAUNA OF THE DEEP SEA

notable that the spot on each side of the back which
in littoral specimens is variegated with yellow is
much smaller in the deep-sea specimen and uniformly
black without yellow.'

It seems to be then a very general rule among
fishes that as they migrate into deeper water the
spots and stripes, so conspicuous among many forms
living on the surface and in shallow water, disappear,
and the coloration of the body becomes more evenly
distributed and uniform.

Among the Mollusca, the deep-sea Cephalopods
seem to be usually violet, but an Opisthoteuthis Agas-
sizii caught by the ' Blake ' is stated to be of a dark
chocolate colour, a Nectoteuthis Pourtcdesii reddish-
brown, and a Mastigoteuthis orange brown, while of
the specimens brought home by the ' Challenger,'
Cirroteuthis mayna was said to be ' rose ' when cap-
tured, and the spirit specimens of Cirroteuthis pacifica
and Bathyteuthis abyssicola wrere purplish madder
and purplish brown respectively.

The shells of the Gasteropods and Lamellibranchs
living in the abyss are frequently so thin as to be
almost transparent, and are, with very few excep-
tions, white or pale straw coloured. The colour of the
only specimen of nudibranchiate Mollusca that has

THE CHAEACTEES OF THE DEEP-SEA FAUNA 63

been found in the abysmal zone, namely, Bathydoris
abyssorum, is described by Mr. Murray as follows :
; The body of the living animal was gelatinous and
transparent, the tentacles brown, the gills and pro-
truding external generative organ orange, the foot
dark purple.'

Among the Crustacea various shades of red are
the prevailing colours. c The deep-sea types, like
Gnathophausia, Notostomus, and Glyphocrangon,' says

• *

Agassiz, ' are of a brilliant scarlet ; in some types, as
in the Municlae and Willemoesise, the coloration tends
to pinkish or yellowish pink, while in Nephrops and
Heterocarpus the scarlet passes more into greenish
tints and patches.' l But perhaps the most remark-
able point in the colour of the Crustacea is that wrhich
immediately follows the paragraph I have just quoted.
' The large eggs of some of the deep-sea genera are
of a brilliant light blue, and in one genus of Macrura
we found a dark metallic blue patch on the dorsal
part of the carapace in marked contrast to the bril-
liant crimson of the rest of the body.'

1 In the recent researches of the ' Investigator ' a few Crustacea
of rather exceptional colour were found. Whilst the great
majority of them are described to be pink or red in colour when
alive, Gnatliopliansia bengalensis is deep purple lake, Haliporus
neptunus lurid orange, and Aristaeus corusoans bright orange.

64 THE FAUNA OF THE DEEP SEA

The occurrence of this blue colour in Crustaceans
of the deep sea is very remarkable, for blue is a colour,
as Moseley pointed out many years ago, that is rarely
met with in the fauna of the abyss, and it is certainly
very exceptional in the Crustacea of that zone.

Among the deep-sea Echinoderma we find a
wonderful variety of coloration. Moseley says that
many deep-sea Holothurians, for example, are deep
purple, and Agassiz reports that in one species the
colour was of a delicate green tinge. ' We obtained,'
he adds, ' a white Cucumaria and some species of
Bentliodytes of the same colour,' while others vary
from transparent milky white to yellow and light
yellowish brown and even pinkish colours. The
Crinoids are described by the authorities to be white,
purple, yellow and brownish-chestnut, and of the
other groups of the echinoderms we read that the
star-fishes are, as a rule, of duller colours than the
Crustacea, but all more or less pink or red. < The
Hymenasteridae, on the contrary, vary from light
bluish violet to deep reddish chestnut colours.' The
brittle stars are red and orange or dullish grey,
while the urchins may be deep violet, claret coloured,
brownish, or of a delicate pink.

It is impossible to account for this extraordinary

THE CHARACTEES OF THE DEEP-SEA FAUNA 65

variety of colour in the deep-sea echinoderms. It is
hardly probable that it can be protective or warning in
function, and it is difficult to suppose that it is due
to any peculiar excretory process. Whether it is due
in any way to the influence of the environment, or,
like the colour of autumn leaves, to the chemical
degeneration of colours that in the shallow-water
ancestry were functional, are problems that must be
left for the future to decide.

The colour of the deep-sea Coelenterates has un-
fortunately not been recorded in all cases, but still
the few observations that we have, show that in this
group, as in the last, almost every tint and shade
are represented.

The colouring of the deep-sea jelly-fishes is said
to be usually deep violet or yellowish red. However
' a species of Stomobrachium,' says Agassiz, ' is re-
markable for its light carmine colour, a tint hitherto
not observed among Acalephs.'

Moseley records most minutely the colour of some
of the deep-sea anemones and corals, and calls atten-
tion to the very general presence of madder brown
in the soft parts. Agassiz says : ' Among deep-sea
Actinias, a species of a new Cereanthus was of
a dark brick-red, while other actinians allied to

F

66 THE FAUNA OF THE DEEP SEA

Bunodes were of a deep violet. Actinauge-like forms
with tentacles of a pinkish- violet tinge frequently
have the column of a yellow shade. The Zoanthidae
were greyish-green.' And again, in his narrative of
the voyage of the ' Blake,' he records that ' some of
the deep-sea corals are scarlet, deep flesh-coloured,
pinkish orange, and of other colours,' and in referring
to the Gorgonian Iridogoryia he says : ' The species
are remarkable for their elegance of form and for the
brilliant lustre and iridescent colours of the axis, in
some of a bright emerald green, in others like bur-
nished gold or mother-of-pearl.'

The fauna of the deep sea then, taken as a whole,
is not characterised by the predominance of any one
colour. The shades of red occur rather more fre-
quently than they do in the fauna of any other zone
or region, but whether this is in any way connected
with the fact that red is the complementary colour to
that of the phosphorescent light, in which many of
these animals live, it is at present difficult to say ;
it is possible that, when we have further information
concerning the colours of the animals living in the
deeper parts of the Neritic zone, another explana-
tion may be forthcoming.

Moseley points out that there are no blue animals

THE CHARACTERS OF THE DEEP-SEA FAUNA 67

known to live in deep water, and it might be added
that green is extremely rare as a colouring matter in
abysmal animals, although the phosphorescent light
given out by some of the echinoderms is green.

Blue, as a colouring matter of marine animals,
living on the surface or in shallow water, is not un-
commonly met with, distributed in the form of bands
or stripes, but green is extremely common in fishes,
Crustacea and coelenterates, and it is a point of very
considerable importance that in this respect there
is a very great difference between the deep-sea and
the shallow-sea faunas.

If a considerable collection of living abysmal forms
could be placed upon one table and a similar collec-
tion of shallow-water forms upon another, I believe
that the first general impression upon the mind of
one who saw them both for the first time would
be the presence of green colours in the last-named
collection, and the absence of it in the other.

The eyes of the animals that live in deep-sea
water undergo curious modifications. If the fauna
of the abysmal region were confined to conditions of
absolute darkness, we should expect to find either a
total absence of eyes or mere rudiments of them only
in those forms that have recently migrated from

F 2

68 THE FAUNA OF THE DEEP SEA

the shallow water. This is the case with the fauna
of the great caves. There is probably total darkness
in these underground lakes and streams, and there
is only the remotest possibility of the animals living
in them ever seeing, even temporarily, a ray of
sunlight or even a glimmer of phosphorescence
during the whole of their life-time. We find then
that the cave fauna is totally blind.

The conditions in the deep sea are not quite the
same. In some regions there is probably a very con-
siderable illumination by phosphorescent light, and it
is quite possible that many of the characteristic deep-
sea forms may occasionally wander into shallower
regions where faint rays of sunlight penetrate, or even
that the young stages of some species may be passed
at or near the surface of the sea. Taking these points
into consideration, then, it is not surprising to find
that, in the deep seas, there are very few animals,
belonging to families usually provided with eyes, that
are quite blind.

In the majority of cases we find that the eyes are
either very large or very small. Only in a small
minority of cases do we find that the eyes are recorded
to be moderate in size. The relation between the
large-eyed forms and the small-eyed forms is not the

THE CHARACTERS OF THE DEEP-SEA FAUNA 69

same in all the regions of deep seas. In depths of
300 to 600 fathoms the majority are large-eyed forms.
This is as we should expect, for it is more than
probable that many of these forms occasionally wander
into shallower waters where there is a certain amount
of sunlight.

In depths of over 1,000 fathoms, the small-eyed
and blind forms are in a majority, although many
large-eyed forms are to be found.

Among fishes, for example, we find the species of
Haloporphyrus found in depths of 300-600 fathoms
with large eyes ; and so with Dicrolene, Ci/ttus

<il,l>reci<itus, and many other forms that are known

t/

to live in water of less depth than 700 fathoms ;
while on the other hand in Melanocetus Miirr/n/i, Ipnops
Murrwyij many deep-sea eels and other fish that are
truly abysmal and live chiefly in depths of over 1,000
fathoms, the eyes are either very small or absent.

Some interesting examples may be found in the
species of widely distributed genera to illustrate
these points. Thus in Neobythites grandis, from
1,875 fathoms, the eye is small, only one-eleventh
the length of the head, but in Neobythites macrops,
N. oeellatus. and iV. qillii from shallower water it is

* t/

much larger.

70 THE FAUNA OF THE DEEP SEA

N. grandis . 1,785 fms. Eye ^th length of the head

2
» 9 » »»

„ macrops . . 375 ,,

„ ocellatus . 350 „
„ gillii . Ill „

1
3§

Similarly in the species of the widely distributed
deep-sea genus Maorurus : the species M. parallelus,
ja/ponicuSj M. fasciatus, &c., usually living in water
less than 1,000 fathoms deep, have large and in some
cases very large (M. fasciatus) eyes, but Macrurus
filica/uda, M. fernandezianus, M. lioceplialus, M.
Mwrayij M. armatus have small eyes.

Some deep-sea fish have their eyes reduced to
a mere rudiment ; such as Ceratias uranoscopus, C.
carunculatus, Melanocetus Murrayi, Typhlonus nasus,
and Apliyonus gelatinosus, but not even a rudiment
of an eye is to be found in Ipnops Murray i.

But the fish of the greatest depths are by no means
always characterised by small eyes. Malacosteus, a
typical deep-sea form, has very large eyes, and so
have Bathylayus, living in the enormous depth of
3,000 fathoms, and Bathytroctes, in 1,090 and 2,150
fathoms.

The result of recent deep-sea work, then, has been
to show that as we proceed from shallow shore water
to depths of 500 to 900 fathoms the eyes of the
fish become larger, but in greater depths than 1,000

THE CHARACTERS OF THE DEEP-SEA FAUNA 71

fathoms the eyes of some fish become considerably
reduced, but those of others become still more en-
larged. In the greatest depths of the ocean in fact
it seems very probable that nearly all the fish are
characterised by either very large eyes or very small
ones.

We cannot expect to learn very much at present
from the study of the eyes of deep-sea mollusca.
The Cephalopoda form the only class of this Phylum
whose genera invariably possess large and well-
developed eyes, and there does not seem to be any
very marked increase or decrease in the size of the
eyes of the few deep-sea cuttlefish that are known
to us.

The eye of Xtutti'lnx is certainly remarkably
interesting, but as this genus is the only represen-
tative of its order, and is known at times to float
upon the surface of the ocean, it would certainly be
erroneous to attribute the peculiarity of the structure
of its eye to its 'temporary' deep-sea habits. We are
still ignorant of the usual habitat of the remarkable
genus Spirula, notwithstanding the fact that many
of the tropical beaches are very largely composed of
its empty shells. Whether it is a deep-sea dweller or
not, we know nothing at present of the character of

72 THE FAUNA OF THE DEEP SEA

its eye, so that it can throw no light upon the pro-
blems we are now discussing.

Among the deep-sea gasteropods we find the
same irregularity in the possession of eyes that we
have just described among fishes. Thus a species of
Pleurotoma, dredged by the ' Porcupine,' in 2,090
fathoms, has a pair of well-developed eyes on short
footstalks, but Pleurotoma nivalis, obtained by the
'Talisman/ is blind. Again a species of Fusus, ob-
tained by the ' Porcupine,' in 1,207 fathoms, is pro-
vided with well-developed eyes, but Fusus abyssorum,
obtained by the ' Talisman,' is blind. Among the
Lamellibranchs there are very few genera that possess
well-marked eyes. The genus Pecten is one of those
that in shallow waters possess numerous highly com-
plicated visual organs situated on the edge of the
mantle. In the deep-sea species, Pecten fragilis, these
eyes are wanting, but we have not sufficient evidence
at present to enable us to assert that all the deep-
sea species of this genus are blind.

Among the Crustacea there is a very general
tendency to lose the eyes at a depth of a few hundred
fathoms of water.

In Ethusa granulata, for example, the eyes dis-
appear at 500 fathoms and the eye-stalks become

THE CHAEACTEES OF THE DEEP-SEA FAUNA 73

firmly fixed, greater in length, and take the place
of the rostrum which disappears. In some forms
-such as Thaumasioclieles zaleuca and Willemoesia
— the eye-stalks themselves have completely dis-
appeared.

In the deep-sea Isopoda some forms lose their eyes
entirely, but Bathynomus giganteus possesses a pair
of enormous eyes, each provided with 4,000 facets.

To illustrate the distribution of eyes in this group,
we may take as an example the genus Serolis. All
the species of this genus are provided with eyes
except Serolis anlnrrtica — a species that extends from
600 to 1,600 fathoms.

The eyes of all the deep-sea species are relatively
larger than those of the shallow- water ones, except
Serolis gracilis, whose eyes seem to be disappearing.

But these large eyes of the deep-sea species of
Serolis are not capable of any greater perceptive
power. In fact, the evidence of degeneration they
show, both in minute structure and in the diminution
of pigment, proves that they can be of very little use
to these animals for perception (see Figs. 4 and 5).

This increase in size, accompanied by degeneration
of structure, is just what we should expect to find in
the eyes of deep-sea animals, and it is difficult to

74

THE FAUNA OP THE DEEP SEA

explain why it is that we do not find more examples
of it.

If the animals that now live in the depths of the
sea are descended from the shallow-water forms of
bygone epochs, they must have passed through many

FIG. 4. — Semi-diagrammatic sec-
tion through the eye of Sero-
lis schythei, a shallow-water
species (4-70 fat horns), c, lens;
v, crystalline cone; E, rhabdom;
N, nerve. (After Beddard.)

FIG. 5. — Diagrammatic sec-
tion of the eye of Serolis
bromleyana, a deep-sea
species (400-1,975 fa-
thoms), showing the de-
generate character of the
eye. The corneal facets
c, and the crystalline
cones v, are the only
structures that can be re-
cognised. (After Beddard.)

different habitats with diminished light until they
reached their present dark abode in the abyss.

In every new region they came to, the forms with
larger and better eyes would be at an advantage in
the fainter light, and would be more likely to survive

THE CHARACTERS OF THE DEEP-SEA FAUNA 75

and transmit their favourable variation in this respect
to their offspring, than their less fortunate neighbours.
Thus down to the depth of the limit of sunlight we
should expect to find, as we do find in fishes, large-
eyed species.

Beyond the limit of direct sunlight the eyes would
be of very little use to them, the pigment would dis-
appear and the tissues become degenerate. This is
precisely what has occurred in the genus Serolis.

The disappearance of the sense of sight in the
animals of the deep sea is sometimes accompanied by
an enormous development of tactile organs.

Thus, among fishes we find Bathypt&rois, a form
that possesses extremely small eyes, provided with
enormously long pectoral fin rays that most probably
possess the functions of organs of touch.

Among the Crustacea we find the blind form,
Galathodes Antonii, with an extraordinary development
in length of the antennas, and Nematocarcinus} with
enormously long antenna3 and legs.

The subject of the power of emitting phosphores-
, cent light possessed by some deep-sea animals is much
more difficult to deal with.

The presence of distinct organs in many of the
deep-sea fish that can only be reasonably interpreted

76 THE FAUNA OF THE DEEP SEA

as phosphorescent organs, the presence of well-
developed and evidently functional eyes in many deep-
sea animals, and many other considerations render it
very highly probable that some, if not many, forms
emit a phosphorescent light.

The power and constancy of the light emitted,
however, must for the present remain a matter of
conjecture. We cannot judge at all of the amount
of light given out by an animal in deep water by its
appearance when thrown out of a dredge upon the
deck. Whether the phosphorescent light given out
by an Alcyonarian or a Crustacean is more or less at
a temperature of 40° Fahr, and a pressure of one ton
per square inch than it is at 60° Fahr. and the ordi-
nary barometric pressure of the sea-level, is a question
that has not yet been brought to an experimental test.

Whatever the answer to this question may be,
the fact remains that a greater percentage of animals
from the deep sea exhibit some sort of phosphorescent
light when brought on deck than animals that live
in shallow water.

The curious organs possessed by some fishes that
are supposed to be organs for the emission of phos-
phorescent light have recently been subjected to a
minute examination by von Leiidenfeld.

THE CHARACTERS OF THE DEEP-SEA FAUNA 77

It has been known for some years now, that the
slime secreted by the skin glands of certain sharks
is highly phosphorescent. It is not difficult, then,
to understand how it came about that certain fish
developed complicated phosphorescent organs.

From the phosphorescent slime secreted by a simple
skin gland to the most complicated eye-like phos-
phorescent organ, we have a series of intermediate
forms that are quite sufficient, even in the imperfect
state of our knowledge at the present day, to enable
us to understand the outlines of the evolution of these
peculiar and interesting organs.

We can distinguish two kinds of phosphorescent
organs in the deep-sea fish. There are the curious
eye-like or ocellar organs situated usually in one or
more rows down the sides of the fish's body, forming
as it were a series of miniature bull's-eye lanterns to

•/

illuminate the surrounding sea (fig. 6) ; and various
glandular organs that may be situated at the extremity
of the barbels or in broad patches behind the eyes or
in other prominent places on the head and shoulders.
Ocellar organs have been known for many years
to occur on the sides of the interesting pelagic fish,
Scopelus. Most of the species of this genus live in
the open sea at moderate depths, coming to the sur-

78

<D

^

-i—

S3
:3
O

f-i
o>

4--

q-i

a

c

THE FAUNA OF THE DEEP SEA

face only at night, but other
species are found in almost
every depth down to 2,000
fathoms of water.

In Opostomias micripnus, a
dark black fish living at a
depth of over 2,000 fathoms,
there are two rows of ocellar
organs running down the sides
of the body from the head to
the tail. In the living animal
they are said to shine with a
reddish lustre. In addition,
to these, the conspicuous or-
gans, there are groups of fifty,
a hundred, or even more very
much smaller organs situated
on the sides and back of the
fish, each of which is lenticular
in shape and consists of a
number of short polygonal
tubes containing a granular
substance with rounded bases
resting on the subjacent tissue.
The whole organ is covered

§

THE CHARACTERS OF THE DEEP-SEA FAUNA 79

by a simple continuation of the cuticle of the body
wall. The granular substance contained in the tubes
is most probably the seat of luminosity.

FIG. 7. — Head of Pachystomias microdon (after Von
Lendenfeld). A, anterior sub-orbital phosphor-
escent organ ; B, posterior sub-orbital phosphor-
escent organ.

As a type of the glandular organs we may take
one of the sub-orbital organs found on the head of
Pachystomias microdon.

In this fish there are two very conspicuous white
organs immediately below the eye. The anterior
one, which lies below and in front of the eye, is oval,
with its upper margin slightly concave. In section
it is seen to be surrounded by a thin layer of black
pigment, and to consist of a reticular glandular
substance in which is embedded a hammer-shaped
lens-like body. Between these two structures there

80 THE FAUNA OF THE DEEP SEA

is interposed a thick layer of light reflecting
spicules.

The exact part that is played by the different
components of these curious phosphorescent organs is
not yet known, but sufficient has been said to indicate
to the reader the degree of complexity that these

FIG. 8. — Section of the anterior sub-orbital phosphor-
escent organ of Pachystomias microdon (after
Von Lendenfeld). L, lens ; o, phosphorescent
gland ; P, pigment sheath.

organs may reach in the fish of the great depths of
the ocean.

But the power of emitting phosphorescent light
is by no means confined to the group of fishes. Some
of the Macrurous Decapoda among the Crustacea
are known to be phosphorescent. In the case of
Heterocarpus Alphonsi, for example, the naturalists
of the ' Investigator ' found that ' clouds of a pale

THE CHARACTERS OF THE DEEP-SEA FAUNA 81

blue highly luminous substance, which not only
illuminated the observers' hands and surrounding
objects in the vessel in which the creature was con-
fined, but also finally communicated a luminosity to
the water itself, were poured out apparently from
the bases of the antennae.'

1 The Willemoesictj too, was luminous at two cir-
cumscribed points somewhere near the orifices of
the genital glands.'

Again, all the Alcyonarians dredged by the * Chal-
lenger ' in deep water were found to be brilliantly
phosphorescent when brought to the surface, the
light consisting, according to Moseley, of red,
yellow, and green rays only.

Among the Echinoderms we have not many
recorded instances of a phosphorescent light being
emitted, but it is quite possible that many, if not all
of them, may possess this power. The curious deep-
sea form Brisinga, that was first discovered by Ch.
Asbjornsen, is known to be so brilliantly phosphorescent
that it has been called a veritable gloria marls, and
writing of the curion s brittle-star Ophiacantha spimdosa
(dredged by the 'Porcupine' in 584 fathoms of water),
Professor Wyville Thomson remarks that the light
was of a ' brilliant green, coruscating from the centre

G

82 THE FAUNA OF THE DEEP SEA

of the disc, now along one arm, now along another,
and sometimes vividly illuminating the whole out-
line of the star-fish.'

According to Filhol many of the abysmal Annelid
worms are in the habit of emitting a vivid phosphor-
escent light, and capable thereby of illuminating the
medium in which they live.

We have now considered all those characters ex-
hibited by deep-sea animals that may be associated
with the absence of direct sunlight. To run through
them again briefly we may say : that the deep-sea
species, belonging to classes of animals that usually
possess eyes, show some modification in the size of their
eyes, in that they are either very large, very small,
or altogether wanting. That deep-sea animals are
nearly always uniformly coloured. Very frequently
they are black or grey or white, less frequently
bright red, purple, or blue. But whatever the
colour may be, spots, stripes, bands, and other
markings of the body are very rarely seen. That
deep-sea animals are brilliantly phosphorescent, the
light being emitted either by special organs locally
situated on the head, body, or appendages, or by the
general surface of the body.

But there are some other characters that cannot
be thus associated with the absence of sunlight.

THE CHARACTERS OF THE DEEP-SEA FAUNA 83

In the first place bathybial fish, mollusca, crnsta-
cea, and other animals usually possess a remarkably
small amount of lime in their bones and shells.

In fishes we are told that the bones have a fibrous,
fissured, and cavernous texture, are light, with
scarcely any calcareous matter, so that the point of
a fine needle will readily penetrate them without
breaking. In some the primordial cartilage is
persistent in a degree rarely met with in surface
fishes, and the membrane bones remain more or
less membranous or are reduced in extent, like the
operculuni, which is frequently too small to cover
the gills.

This cannot be due in all cases to a deficiency of
carbonate of lime in the sea water, for we find these
characters well marked in some of the fish, such as
Melanocetus Murrayi, Chiasmodus rtiger, and Osmodus
Lowii, that are found on the Globigerina mud.

Then again, the shells of the deep-sea Lamelli-
branchs, Gasteropods, Brachiopods, and Crustacea
are very frequently remarkably thin and transparent,
a character that is probably more generally due to
a weakness in absorptive or secretive activity than
to a deficiency in the supply of lime.

There are one or two characters of the deep-sea

G 2

84 THE FAUNA OF THE DEEP SEA

fish that it is not easy to account for, and it is
necessary only to mention their occurrence without
attempting to offer any explanation of them.

One of the most common of these is the very
dark pigment occurring in certain parts of the
epithelium of the mouth and respiratory passages
and the endothelium of the peritoneum. For ex-
ample, in Bathysaurus mollis, living at a depth of
2,000 fathoms, the mouth and buccal cavities are black.
The same thing occurs in Ipnops Murray i, and indeed
in all the strictly deep-sea forms.

Another important character of very frequent
occurrence is the reduction in size, length, and number
of the gill laminae.

Among invertebrates we may mention as a fact
of some interest, dependent perhaps on the soft
character of the bofctoni, the preponderance of stalked
forms over those of more sessile habits.

Thus among the Alcyonaria the characteristic
forms of the deep water are the Pennatulids, and
more particularly the genus Umbellula with its long
graceful stem and terminal tuft of polyps. Among
the Echinoderma we find many forms of stalked

«/

Crinoids. Among the Tunicates several curious
genera characterised by their long peduncles.

THE CHARACTERS OF THE DEEP-SEA FAUNA 85

Taking the fauna as a whole, Moseley regarded it
as similar in some respects to the flora of the high
mountains. Some forms are dwarfed in size, such as
the species of Radiolaria, Cerianthus, some of the
Cephalopoda, &c., while others are very much larger
than their shallow-water allies, such as the Pycno-
gonids, nearly all the Crustacea, Alcyouarians (as
regards the size of the polypes). Siphonophora, and
many others.

86 THE FAUNA OF THE DEEP SEA

CHAPTER V

THE PROTOZOA, CCELENTERA, AND ECHINODERMA
OF THE DEEP SEA

•

THE most important, but perhaps somewhat dis-
appointing, result of the deep-sea researches of recent
years has been to prove that the abysmal fauna does
not possess many very extraordinary forms.

It seemed probable, before the dispatch of the
'Challenger' expedition, that when the dredge and
the trawl should be successfully employed in depths
of over 2,000 fathoms, a new and remarkable fauna
would be brought to light. Some naturalists thought
it even possible that, not only would many genera
be found alive that are known to us only by their
fossilised skeletons in the secondary and tertiary rocks,
but that there might be many other new creatures
whose anatomy would throw much light on the
theories of the evolution of the animal series.

But none of the great expeditions that have sailed
since the year 1874 have yet succeeded in showing

PKOTOZOA, CCELENTERA, AND ECHINODEEMA 87

that the hopes and wishes of these naturalists were
really justified. Although thousands of species of
animals have been described in the volumes that
have been devoted to deep-sea work, the number of
the sub-kingdoms and classes remains the same,
and indeed the number of new families and genera
has not been increased in any very unprecedented
manner.

We have found no animals in the depths of the
sea of such interest and importance as Ornitho-
rhynchus, Amphioxus, Balanoglossus, Peripatus,
Millepora, or Yolvox among the living, or Hipparion,
Archseopteryx, Ammonites, Slimonia, and the Trilo-
bites among extinct animals.

The abysmal fauna is not in fact remarkable for
possessing a large number of primitive or archaic
forms. It is mainly composed of a number of species
belonging to the families and genera of our shallow-
water fauna that have, from time to time, migrated
into greater depths and become modified in their
structure in accordance with the extraordinary con-
ditions of their new habitat.

There is very good reason to believe that this
migration has been going on from time immemorial,
and consequently we find a few forms typical of the

88 THE FAUNA OF THE DEEP SEA

bygone times, left to struggle for existence with
the more recent immigrants from shallow waters.
But after all the proportion of ancient forms to
modern ones in the fauna of the abyss is not larger
than it is in the fauna of fresh-water lakes and
streams or even of the dry land. Nor is there any
reason why it should be. The land and the fresh
water have been peopled by migrations from the
shallow water of the sea from generation to gener-
ation in precisely the same way, and they each can
show a certain number of archaic forms.

We must now consider briefly some of the most
interesting deep-sea representatives of the various
classes of the animal kingdom, referring as we pass
on to the extent to which these classes contribute
to the fauna of the abyss.

We find a great difficulty in determining with
any degree of certainty the actual depths at which
the supposed abysmal forms of Protozoa actually
live. All the Radiolaria and Foramiiiifera — the only
Protozoa that are largely represented in the fauna of
the open seas — are planktoiiic in habit; that is to say,
they float or drift about in the water without ever
becoming attached to the sea bottom ; and when the
contents of a dredge, that has been hauled up from a

PKOTOZOA, CCELENTERA, AND ECHINODEEMA 89

great depth, are examined, it is impossible to say at
what points in its long journey from the bottom the
Protozoa it contains were caught. Even if dredges
and nets are used which can be closed by a messenger
at any particular depth, the problem cannot be very
easily settled ; for even if the protozoa shells that are
captured are found to contain a certain amount of
protoplasm, it must be proved that that protoplasm
is actually alive when brought on deck before we
know for certain that the species actually live on the
bottom, When the pelagic Foraminifera and Radio-
laria die and sink to the bottom, their protoplasm
probably disintegrates very slowly, and it is quite
probable that the floor of the ocean is littered with
the shells of truly pelagic protozoa, each containing a
greater or smaller amount of andecomposed proto-
plasm.

However, there is little doubt that there are
some truly abysmal Protozoa. Among the Radio-
laria, for example, it seems extremely probable
that the majority of the Phasodaria and many Spu-
mellaria live only in veiy deep water. ' A character
common to these abyssal forms,' says Haeckel, ' and
not found in those from the surface or slight depths, is
found in their small size and massive heavy skeletons,

90 THE FAUNA OF THE DEEP SEA

in which respects they strikingly resemble the fossil
Radiolaria of Barbadoes and Nicobar islands/ The
Pheeodaria are very widely distributed over the floor
of the ocean, and occur in some districts in such
numbers that the ' Challenger ' was able to bring home
some hundreds of thousands of specimens. They are
distinguished from other Radiolaria by the thick outer
and thin inner capsule, by the typical main opening
or atropyle placed on the oral pole of the main axis
with a radiate operculum provided with a tubular

proboscis, and lastly by the presence
of the phgeodium, a voluminous pig-
ment body which lies invariably on
the oral half of the calymma and
is composed of numerous singular
pigment granules of green, olive,

IG. 9. fallen- brown> °r black Col°Ur-
f/evia luiiTV(iyi, mi. a v<a o rA -ill o -pi \r Q<p-n AVH

n j T T-»l U.O1C5 <M\-\J -LLldl-L V ci V^-LJ.V>1 C\J

one of f"° ^n^^- •>

3—-

daria (2,250 fa- - t th Foraminifera that are

thorns). A, phseo-

dium; B, central yer prokably inhabitants of abys-
capsule; c, strands *

of protoplasm in mal depths, but they do not seem

the calymma.

After Haeckel. ^ pOSSess any special characters,

unless it be a greater thickness and density of
their shells, to distinguish them from their shallow-
water allies.

PROTOZOA, CCELENTERA, AND ECHINODERMA 91

Passing now to the group of the sponges or
Porifera, we find that the calcareous sponges are not
represented at all in the abysmal zone. Two species
are found at a depth of 450 fathoms, but none are
truly bathybial in habit. The same remark applies
to the horny sponges. These forms chiefly belong
to the littoral or very shallow-water fauna, and never
descend to greater depths than 400 fathoms. Of the
other groups of Porifera — the Monaxonia, the Tetrac-
tinellidse, and the Hexactinellida? — several genera are
known to extend down to some of the greatest depths
at which trawling operations have been successfully
carried on. It is difficult to point to any characters in
these sponges that can be attributed in any way to the
conditions of deep-sea life, but nevertheless we do find
in deep water some of the most remarkable and beautiful
forms of sponge skeleton that can be found anywhere.

Amongst the Ccelentera we find in the deep water
a remarkable sub-family of Medusa?, which has been
named by Haeckel the Pectyllidee. It is distinguished
from the other jelly-fish by the curious sucking cups
situated at the ends of the tentacles. It seems probable
that they are used for purposes of locomotion, the
animal walking over the muddy bottom as on a
series of stilts.

92 THE FAUNA OF THE DEEP SEA

Like most of the deep-sea Hydroids, the Pectyl-
lidas are usually devoid of sense organs, but a single
specimen of Periphylla mirabilis, captured by the
naturalists of the ' Challenger,' possessed well-marked
eyes.

There is also a peculiar family of the Siphonophora,
called the Auronectas, consisting of a few specimens
that have been hitherto found only in very deep
water. Like the well-known Portuguese man-of-
war Physalia of the surface waters, the Auronectae
possess a large swimming bladder or pneumatophore,
but they have in -addition another peculiar bladder-like
cavity, called the aurophore, communicating with it,
which may be an organ for secreting gas.

A very interesting genus allied to Velella was also
found in depths of over 2,000 fathoms by the ' Chal-
lenger ' expedition. It is supposed to be a survival
of the ancestral form of the Disconectas, or, at any
rate, to be a link connecting the Siphonophora with
the Medusas. The very well marked octoradial
arrangement of the parts of Discalia, as this genus
has been termed, is certainly a point of great interest
and importance.

There is no large family of the sea anemones that
is peculiar to deep water, but several genera that

PEOTOZOA, CCELENTERA, AND ECHINODERMA 93

occur only in the abyss exhibit some curious modifi-
cations. The manner in which the tentacular pores
have become enlarged, and the tentacles themselves
diminished in size and flexibility, has already been
referred to in a previous chapter (p. 36).

The family of sea anemones that has been named
the Corallirnorphidas, characterised by the stiffness
and slight contractility of the body, the knobbed
nature of the tentacles, and their distribution in
several series, was, until quite recently, considered to
be a true abysmal family. The two species, Coralli-
morphus rigidus and C. profundus, are known to occur
only in very deep waters, and present some curious
modifications of structure in relation to their habit ;
but it seems probable that to this family should
be added the remarkable littoral form TJiehf '•?,•!,*
rhizvphorce found on the coast of Celebes attached
to the roots of the mangrove trees in the swamps.

The fact that all the principal groups of the
Actiniaria, except, perhaps, the group that includes
those forms with only eight mesenteries, the Edwardsiae,
have representative genera or species in the great
depths of the ocean, points to the conclusion that the
sea anemones have migrated from the shallow waters
in comparatively recent times, and that the migra-

94 THE FAUNA OF THE DEEP SEA

tions have been successive, each period of their history
sending some specimens to survive or to become
extinct in the struggle for life in the deep sea.

Of the Madreporarian corals, several genera are
now known to inhabit very deep water, but they do
not present many very remarkable points of diver-
gence from the shallow-water forms.

It is true that as we pass from the shallow waters,
of those parts of the world where the great colonial
madrepores build up the greater part of the vast coral
reefs, into the deeper water beyond them, the solitary
forms become relatively more abundant, but no new
groups characterised by any special deep-sea attributes
make their appearance. We must remember, not only
that a great many solitary corals occur in shallow
water in different parts of the world, but that some
colonial forms, such as Loplwlielia prolifera for ex-
ample, are found only in very deep water.

Until quite recently it was usually stated in works
dealing with the structures of coral reefs that the
so-called reef-building corals, that is to say the large
madrepores, astraeids, and others, are confined to water
not deeper than thirty fathoms. This limit must
now be somewhat extended, in consequence of the
discovery by Captain Moore of an abundance of

PEOTOZOA, CCELENTERA, AND ECHINODEEMA 95

growing coral at a depth of forty-four fathoms in the
China seas ; but, nevertheless, it is perfectly true that
the corals do not grow in such profusion in very deep
water as to form anything that can be compared with
the reefs of the shores. It is quite possible that the
advantages afforded by the light, warmth, and abun-
dance of food of the shallow water may account for
the luxuriance and vigour of the reef corals, and that
where the food is scarce, and the water cold and dark
as it is below fifty fathoms, the power of continuous
gemmation is lost, and the rapidity of the growth and
reproduction of the individual polyps is considerably
diminished.

The fact remains, however, that, as with the sea
anemones, so with the madrepores, nearly all the
great divisions have a few isolated representatives in
the abyss, and that no great family occurring in large
numbers has yet been discovered peculiar to this zone.

The Alcyonaria, on the other hand, do present us
with at least one example of a true deep-sea family.
This great class of Anthozoa, distinguished from the
Zoantharia by the presence of not more than eight
tentacles and mesenteries and by the pinnate character
of the former, falls into four principal divisions. The
Stolonifera, the Alcyonidas, the Gorgonidas, and the

96 THE FAUNA OF THE DEEP SEA

Pennatulida3. The first three of these divisions
principally inhabit the shallow water. Each of them
sends a few representatives into the great depths, but
by far the greater number of the genera and species
are to be found between tide-marks or in depths of
less than fifty fathoms.

The Pennatulids, on the other hand, are rarely
found in very shallow water, and nearly half the
known genera live in deep water. At least two
families may be said to be characteristically abysmal.
These are the Umbellulida3 and the Protoptilidae.

The Pennatulidse are regarded by naturalists as
the most complicated or highly organised group of
the Alcyonaria. Three different forms of polype build
up the colony or sea-pen as it is called. There is
a single very much modified and enormously large
polype, without tentacles, forming the axis, a large
number of ordinary Alcyonarian polypes (antozooids)
arranged in the form of leaves, or simply scattered
irregularly on the surface of the central polype, and
a number of very small undeveloped polypes
(Siphonozoids) without tentacles, whose function
seems to be to pump water into the canals of the
colony, and thus to keep up the circulation of water.

The deep-sea genus Umbellula possesses a very

FIG. 10.— Uinbellula Gimtheri. Nat. size. After Aga-siz.

H

98 THE FAUNA OF THE DEEP SEA

long and delicate axial polype, and the Autozooids and
Siphonozooids form a little cluster only at its extreme
summit. The small number of these polypes and
the very limited area over which they extend are the
two most characteristic features of the genus. It
would take me too far into the anatomy of the group
if I were to add any further details ; but I cannot pass
on without noting that the whole structure of
Umbellula shows that it is far more primitive and
simple than the shallow-water genera. And, generally
speaking, this holds good for all the deep-sea Pen-
natulids. In fact, we have here one of the rare ex-
amples of a series of genera, that can be regarded as
a slightly modified ancestry of the shallow-water
genera, that has been brought to light by the explora-
tion of the abysmal depths of the ocean.

We have seen, then, that of the Ccelentera, the
only order that has a large proportion of its genera
living in deep water, is the only one whose members
all possess a stalk by which they fix themselves into
the mud or sand at the bottom of the sea.

It is not uninteresting to note, then, in passing
on to the Echinoderma, that the stalked Crinoids, the
only Echinoderms that can permanently fix themselves
to the bottom, are nearly all found in deep water.

PROTOZOA, CCELEXTEEA, AND ECHINODEEMA 99

Several years before the ' Lightning ' was
despatched on her memorable pioneering voyage,
Vaughan Thomson had proved that the common
feather star of the shallow waters of the British
coasts passes through a stage in its development which
resembles the fossil genera of the order in being
provided with a stalk for attachment.

But it was left for the naturalists of the
c Porcupine,' the ' Challenger,' the Talisman,' and
other vessels employed in deep-sea researches to prove
that adult stalked Crinoids are still living in nearly
all parts of the world at the great depths of the sea.

The genera of stalked Crinoids now living
are the remains of a family that at one time had
many representatives in all parts of the world.
Nearly all the marine deposits of bygone epochs,
including even those of such remote periods as the
Cambrian and Sub-Silurian, contain the fossilised
skeletons of these Crinoids. In some strata they are
represented by only a few genera, but in others they
are found in such enormous numbers that the sea-
beds of those early times must have been literally
carpeted with them,

At the present day the few genera that survive
have been driven from the shore waters, and are

H 2

100

THE FAUNA OF THE DEEP SEA

FIG. \l.—Rhizo-
crinus lofotensis,
one of the deep-
sea stalked Cri-
noids. (After
Carpenter.)

chiefly found at depths of more
than 200 fathoms, a few only
extending into 140 and even
70 fathoms.

There are six genera known,
and of these, two, Hyocrinus
and Bathycrinus, are not found
in less than 1,000 fathoms of
water.

There can be no doubt that
these modern stalked Crinoids
are closely related to many of
those that flourished in bygone
periods of the history of the
earth. As Carpenter has
pointed out, the family Pen-
tacrinidas are remarkable for
their long geological history.
The genus Pentacrinus itself
first appeared in the Trias and
persisted through the Secondary
and Tertiary times to the pre-
sent day.

The general character of
the fossil Pentacrinidas is es-

PROTOZOA, COELEXTERA, AND ECHIXODEEMA 101

sentially the same as that of their recent repre-
sentatives, except that they often had much longer
stems which reached to a length of as much as 50 or
even 70 feet ; while the number of arms was frequently
limited to ten, which is not the case in any recent
species but Pentacrinus naresianus.

But the deep-sea Echinoids, or sea-urchins,
also present some features of particular interest.
Professor Agassiz in his report says, ' One of the
very first results clearly indicated by the deep-sea
dredgings of Count Pourtales and the subsequent
investigations of the " Porcupine " expedition was the
antique character of the new genera discovered in
deep water, and especially their resemblance to
the cretaceous genera ; and the study of the " Chal-
lenger ' Echinoids has brought this out still more
clearly.'

No fewer than twenty-four genera extend into the

*

abysmal regions ; of these no less than sixteen, nearly
all belonging to a new group of Spatangoids, do not
live at all in shallow water.

The most interesting forms among these are the
Pourtalesise, a group that has existed since the Chalk.
These are heart-shaped urchins with a very peculiar
test. c They all have large coronal plates, recalling

102 THE FAUNA OF THE DEEP SEA

the Echini, with a disconnected apical system
characteristic of many caiiiozoic spatangoids ; they
have a sunken anal system, some of them a most
remarkable anal beak and a very striking pouch in
which the mouth is placed.' They are found only in
very deep water, and have no allies among the modern
littoral fauna.

The genera Calveria and Pkormosoma are two of
the most abundant Echinoids found in deep water, and
they are both representatives of forms that were very
abundant in cretaceous times. They are remarkable
for the extreme flexibility of their shells. In shallow -
water sea-urchins the shells are composed of a great
number of little plates that fit so closely to one
another that no movement is possible between them.
When the animal dies all the soft tissues decay
and the shell remains, to be tossed about by the
waves until crunched or dashed to pieces. In
Phormosoma, however, the tiny plates of which the
shell is composed are freely movable on one another,
and when the animal is alive very considerable con-
tractions and expansions can take place.

None of the modern shallow-water Echinoids
present this peculiarity, and it is a very interesting
and surprising fact that in this respect the fossils

PROTOZOA, CGELENTEEA, AND ECHINODERMA 103

of the chalk should resemble so closely the living
urchins of the abyss.

But before leaving the Echinoicls reference must
be made to two more points that have been made by
the illustrious American naturalist. Agassiz points
out that all those genera that have the greatest
bathymetrical range, extending from the littoral to
the abysmal region, are at the same time genera which
date back to the Cretaceous period, while those
having a somewhat more limited range go back to the
tertiaries, and those that extend only slightly beyond
the littoral area go back only to the later tertiaries.

This interesting generalisation brings home to
our minds the enormous length of time that it must
have taken these animals to migrate from the shallow
to the deep sea. In the struggles for existence
between marine animals it must always have been
the last resort of those unable to compete with the
younger generations in shallow water to migrate
into the deeps,

The scarcity of food, the darkness, and the pressure
of these regions can never be so favourable for the
support of animals as the conditions of the shores.
We can well imagine that a species would take every
opportunity that is afforded to return from such

104 THE FAUNA OF THE DEEP SEA

inhospitable habitats, and that only when, as it were,
every door is closed, when no island, continent, or
cape can afford it a free scope for life in shallow
water, does it become a true deep-sea species.

Steps taken towards the darkness in one period
may be retrieved in the next. The competing species
may itself have become extinct or have moved to
another locality. Organs may have become modified
or a new source of food supply tapped which enable
them to return ouce more to shallower waters. No
wonder that the steps in the progress, or rather retreat,
to the abyss have been the work of a time that can be
counted only by geological periods ; and no wonder
then at the remark made by many deep-sea natu-
ralists that the abysmal fauna becomes poorer the
farther it is from shallow water.

The group of the Asteroidea, or star-fishes, con-
tributes largely to the fauna of the abyss.

During the voyage of the ' Challenger ' no fewer
than 109 different species were found in depths of
over 500 fathoms, and in some localities a very large
number of star-fish were taken in one haul of the
dredge.

Nevertheless, there are not many abysmal genera
that differ to any remarkable degree from the littoral

PROTOZOA, CCELENTEEA, AXD ECHINODEBMA 105

ones ; and indeed it may be said that the recent work
on deep-sea Asteroids does not throw much new light
either 011 the phylogeny of the group or on their
palaeontological history.

The genus Brisinga,, at one time supposed to be
a connecting link between the star-fishes and the
brittle stars (Ophiurids), has recently been shown to
be closely related to the families Heliasteridea, Ech-
inasteridea, and others typical of the class Asteroidea ;
and, as Sladen has pointed out, the peculiarities of
structure that it exhibits are probably due to its ex-
treme isolation and the influence of its abysmal habitats.

But no work on the deep-sea fauna would be
complete without some reference to Brisinga. Dis-
covered by Asbjornsen in 1853, in 200 fathoms of
water in the Hardanger fjord, and described in a
splendid memoir by the elder Sars, it excited great
interest among naturalists. The great brilliancy of
the phosphorescent light that it gave out on being
brought on deck, the remarkable tendency that it had
to cast off some of its numerous long, thin, ophiurid-
like arms, and some of the general features of its
internal anatomy were points that were considered at
the time to be sufficient to justify the establishment
of a separate sub-order for the family Brisingidse.

106 THE FAUNA OF THE DEEP SEA

The more recent discovery, however, of genera
allied to Brisinga has bridged over the gap
separating it from other star-fish, and it is now
considered simply as the type of a family of the
order.

The numerous species of the genus that have been
found since Asbjornsen's original discovery are all
inhabitants of deep water, some of them going down
to the enormous depth of 2,000 fathoms ; indeed there
are very few genera in the animal kingdom, containing
so many species as the genus Brisinga, that have such
a uniform deep-sea habitat.

The last group of Echinoderms that we have to
consider is the Holothurians. It contains one order—
the Elasipoda — that may be considered to be truly
bathybial, as there is only one species belonging to
it, Elpidia glacialis, that extends into water as shallow
as fifty fathoms.

The Elasipoda are remarkable for their strongly-
developed bilateral symmetry. Adult Echinoderms
as a rule possess a well-marked radial symmetry, as
we see exemplified in the feather-star, star-fish, and
sea-urchin, but this radial symmetry is only adopted
when they undergo their metamorphosis from the free
swimming and bilaterally symmetrical larval stage

PROTOZOA, CCELEXTEKA, AND ECHINODERMA 107

They are not born radially symmetrical, but become
so as they grow up. Moreover, we must bear in
mind that the radial symmetry of the adult only
obscures, it does not obliterate, the bilateral symmetry
of the larva.

In the Holothurian, however, we can always dis-
cover a clear bilateral symmetry even in the adult.
That is to say, we can recognise an anterior and a
posterior end, a right and a left side of the body. It
is an organisation which emphasises, as it were, the
anterior and posterior ends, the right and left sides
and the dorsal and ventral surfaces that characterise
this interesting deep-sea order, the Elasipoda.

Here, then, we have an example of a character
common to all the larvae of the sub-kingdom and ex-
ceptionally well marked in the adults of a family
confined to deep-sea habitats.

Now we know that there is a tendency for some
of the peculiar characters of the ancestors of animals
to be recapitulated in the course of their develop-
ment from the egg, and accordingly most naturalists
are agreed that all the Echinoderms have descended
from some form, of bilaterally symmetrical ancestor.
Are we, then, to believe that the Elasipoda brought
from the depths of the sea are more closely related

108 THE FAUNA OF THE DEEP SEA

to these ancestral forms than the shallow-water
families ?

The state of our knowledge at the present day
hardly allows us to answer this question very defi-
nitely. However nearly they are related to such
ancestral Echinoderms in general form, they are
probably profoundly modified by a deep-sea life.
Nevertheless, in the simple shape of the calcareous
corpuscles of the skin, the simple form of the cal-
careous ring, the communication of the water-vascular
system with the exterior by one or several pores, and
in some other anatomical characters, they give evi-
dence of their primitive characters.

109

CHAPTER VI

THE VERMES AND MOLLUSCA OF THE DEEP SEA

IT has not been my intention in tins volume to con-
fine my attention to the truly abysmal forms, but
rather to consider all those animals living in deep
water that show any characters strikingly different
from their relatives living in shallow water.

The term deep water is, after all, only a relative

one.

To one accustomed only to shore collecting, ten
fathoms is deep water, while on the other hand, to
such naturalists as those on board the ' Challenger,'
who are accustomed to dredge in all seas, nothing
under 1,000 fathoms is considered deep water.

We must bear in mind, however, that at a depth
of only 200 fathoms, the conditions of life are very
different to those of the shore waters. A Ye find a
very great diminution in the amount of light, for in-
stance, that can penetrate through sea water teeming

110 THE FAUNA OF THE DEEP SEA

with floating organisms of all kinds to reach the fauna
attached to the bottom at such a depth. The diminu-
tion in the amount of light must mean a diminution
in the rapidity of growth of chlorophyll-bearing plants,
and consequently a diminution in the food supplies of
animals drawn from that source.

We might expect then to find, even in such shal-
low water as this, some forms of particular interest.
It is true that the greater part of the fauna is made
up of ordinary shallow-water forms that have migrated
quite recently, and perhaps only temporarily, into the
depths, but we expect to find, and actually do find, the
outposts of a new fauna.

These remarks lead me to the consideration of
one or two very remarkable animals that have recently
been brought to light.

In that strange assembly of animals which, for
want of a better word, the authorities call the Vermes,
there are three groups whose relations to one another
and to the other groups of Vermes have been and still
remain a puzzle to naturalists.

These three groups are the Gephyrea, the Polyzoa,
and the Brachiopoda. In external form they are as
different from one another as possible.

-The Gephyrea are solitary worm-like forms bur-

VEEMES AND MOLLUSCA OF THE DEEP SEA 111

rowing in the sand or perforating rocks ; the Polyzoa
are minute creatures that frequently build up by bud-
ding large colonies which assume in some cases den-
dritic forms like corals, and the Brachiopoda are pro-
tected by thick bivalve shells simulating in a striking
manner the shells of the Lamellibranchiate mollusca.

But external form is not the only character that
can be relied upon for purposes of classification. The
general and minute anatomy, together with the story
of the development of these animals, teach us that
they are in some way closely related.

It is not within the scope of this book to enter
into the discussion of what these relations are ; suffice
it to say that the controversy has within recent years
to a great extent turned upon the position in our
classification of three interesting genera. These are
Phoronis, Rhabdopleura and Cephalodiscus.

Phoronis occurs only in shallow water, Rhabdo-
pleura has been found in water from 40 to 200
fathoms deep off the Shetlands and on the Norwegian
coasts, while Cephalodiscus was discovered by the
1 Challenger ' at a depth of 245 fathoms off Magellan
Straits.

Rhabdopleura forms colonies consisting of
branched tubes growing upon the tests of Ascidians,

112

THE FAUNA OF THE DEEP SEA

on sea-weeds, corals, or other objects fixed to the sea-
bottom. In the open, free extremity of each of the

FIG. 12.— A portion of a colony of RhaMoplcura normam.

(After Lankester.)

branches may be found the polypide attached to a
filament or stalk which connects it with the other
polypides of the colony (fig. 12).

VEEMES AND MOLLUSCA OF THE DEEP SEA 113

Each polypide is provided with a single pair of
large pinnate arms, resembling the arms of a
Brachiopod, and a broad muscular epistome by means
of which it is able to creep up or down the tube.

The affinities of this interesting creature are by
no means sufficiently well understood. It is one of
those forms that, without being, strictly speaking,
a connectino; link between large and well-known

o o

groups of animals, indicates to us some of the lines
of evolution that these groups may have passed
through ; and, in so far as it does this, it has its
value and importance.

Cephalodiscus, though related to Rhabdopleura in
the presence of a structure corresponding to the
arms, and a broad epistome, seems to be more closely
connected with such a form as Balanoglossus in the
presence of a single pair of gill-slits, a small
rudimentary notochord and the position of the central
nervous system.1

t/

Whatever position these genera may ultimately
occupy in our systems of classification, there can be
little doubt that much valuable information will be
obtained by a farther study of their structure and

1 A rudimentary notochord projecting- forward from the buccal
cavity into the epistome has quite recently been discovered in
Khabdopleura.

114

THE FAUNA OF THE DEEP SEA

— y- s

FIG. 13. — A single polypide of Rhaldopleura normani. M,
mouth ; B, epistome ; s, polypide stalk. (After Lankester.)

YEKMES AND MOLLUSCA OF THE DEEP SEA 115

development — information that will probably shed
much light on the relationships to one another of the
many groups of Vermes. Their occurrence in water
of moderate depths only indicates perhaps that they
are gradually being crowded out from the more
favourable localities of shallow water, and are tending
towards extinction on the one hand, or a deep-sea
habitat on the other.

The Brachiopoda need not detain us long. Some
species are capable of existing at a great variety of
depths without any observable modification of shape
or characters. Thus Terebratulina caput serpent'^
has the extraordinary bathymetrical distribution of
0-1,180 fathoms, and Terebratula vitrea 5-1,456
fathoms. Atretia is the only genus peculiar to deep
water. It is a noteworthy fact in connection with
this order that the two genera, Lingula and Glottidia,
which compose the sub-order Ecardines, are both
confined to shallow water. Now the Ecardines are
anatomically, at any rate, the most primitive of the
Brachiopoda, and Lingula has the most ancient
geological history of any living genus of the animal
kingdom, shells almost, identical with those of the
living species being found abundantly in the Cambrian
strata. Why it is that Lingula has been able to

i 2

11G THE FAUNA OF THE DEEP SEA

maintain itself almost unchanged through all the
countless generations that have elapsed since
Cambrian times, and can now flourish amid the
desperate struggle for existence in the shallow waters
of the tropics, while its companions, the corals,
mollusks, arthropods, &c., have changed or passed
away, is one of those problems in natural history
that seems to us impossible of solution. The time
may come when we shall be able to appreciate better
than we do now the complicated relations between
animals and their environment, and then perhaps the
peculiar fitness of Lingula will be made manifest ;
but at present we can but mention the fact as a fact,
and leave the solution of the problem to the future.

The order Gephyrea is probably another very
ancient group of animals, although in the absence
of any hard calcareous, siliceous, or horny skeleton
the geological record can give us no confirmation of
their antiquity. As with the Brachiopods so with
the Gephyrea, some of the species have a very wide
bathymetrical distribution. Slpunculus midus, for
example, the commonest and best known of all the
Gephyrea, extends from quite shallow water to a depth
of over 1,500 fathoms. As Selenka has pointed out,
it is those Gephyreans that live in holes in stones, or

VERGES AND MOLLUSCA OF THE DEEP SEA 117

in shells such as Phascolion and Phascolosoma, that
are more frequently found at the greater depths ; but,
apart from this, there are no characters that exclu-
sively belong to the abysmal Gephyrea or are more
frequently found in them than in the shallow-water
forms. Nor are there any genera, at present brought
to light, that are confined to those regions of the sea.

The group of the Annelida is not very well
represented in the deep-sea fauna. The genera
Serpula and Terebella have been found very widely
distributed over the earth, at all depths from the shore
to the abyss, but there do not seem to be many genera
that are confined to deep water. In some cases, where
there is a scarcity of lime in the water, the thin pro-
tecting tubes of the sedentary forms are strengthened
by the adhesion of foreign particles, such as sponge
spicules and arenaceous foraminifera, but in others,
the tubes are formed of successive layers of a trans-
parent quill-like substance (NotJtria Willemoesii)
which is frequently armed with spiny projections.

Most of the errant Polychastes found at great
depths are said to be most brilliantly coloured, and
some of these, such as Eunice amphihelice, have the
power of emitting a bright phosphorescent light ; but
there seem to be no very definite and constant

118 THE FAUNA OF THE DEEP SEA

characters separating these forms from the Polychastes
of shallow waters.

As is the case with many other orders of animals,
the species of Annelida living in deep water are
either blind or possess eyes of a remarkably large
size. Genityllis oculata may be taken as an example
of a deep-sea annelid with large eyes. This annelid,
belonging to the family Phyllodocidse, was found at
a depth of 500 fathoms in the Celebes sea. It
possesses two enormous eyes which cover almost the
whole of the head, and there can be no doubt, from
the investigations of Dr. Gunn on their minute
anatomy, that they are perfectly functional.

Before leaving the Annelida a brief notice must
be made of the very extraordinary form Syllis ramosa,
found parasitic on a hexactinellid sponge at depths of
about 100 fathoms. It is chiefly remarkable for the
very complicated manner it has of producing bads
which do not immediately become detached from the
parent, but form a compound network which ramifies
through the interstices of the sponge like the colony
of a Hydromedusan.

Passing now to the sub-kingdom Mollusca, we
shall find that all the classes are represented in the
abysmal fauna.

VERMES AND MOLLUSC A OF THE DEEP SEA 119

The Lamellibranchiata, or bivalves, occur in al-
most all depths of the ocean, Callocardia pacifica and
Ccdlocardia atlantica having been found at the enor-
mous depth of 2,900 fathoms. Some species, such as
Venus mesodesma, have a very wide bathymetrical
distribution, but others are only known to occur in
deep water.

Concerning the characters of the deep-sea
Larnellibranchiates, Mr. Smith, in his report on the
Lamellibrancnia of the 'Challenger' expedition, says
' very deep-water benthal species certainly have
a tendency to be without colour, and of thin struc-
ture, no doubt resulting from the absence of light,
the difficulty of secreting lime, the scarcity of food
and other unfavourable conditions of existence.' But
notwithstanding this, the same author continues : ' The
species are apparently few in number in comparison
with those of shallow water ; and new and peculiar
generic forms which we naturally expected would
have been discovered are of even still rarer occur-
rence.'

As in the group of the Lamellibranchia, so in
the Gasteropoda, no very remarkable new genera or
species have been found in deep sea. Some shallow-
water genera, such as Fasus for example, have repre-

120 THE FAUNA OF THE DEEP SEA

sentative species in the abyss ; but, with the exception
of a want of brilliant coloration and marking and a
thinness of the shell, the deep-sea forms do not exhibit
any characteristic features. One of the most brightly
coloured shells found at great depths is that of Scalaria
mirifica, which is tinted rose and white, but this
seems to be quite an exceptional character among
the deep-sea Gasteropods. Several new genera were
found in the deep water, but their general characters
do not call for any special remark.

Among the Cephalopoda there seems to be little
doubt that the genera Cirroteuthis, Bathyteuthis,
and Mastigoteuthis are entirely abysmal, and the same
applies probably to one or two species of octopus ; but
as Hoyle remarks, * apart from the single fact that
Bathyteuthis and Mastigoteuthis both have slender
filiform tentacles with minute suckers, no structural
features have been discovered which will serve to
diagnose a deep-sea form from a shallow-water one.'

The exact habitat of the interesting genus Spirula
is unfortunately still unknown. In some parts of
the tropics the shores are covered with spirula shells,
and yet the animals that secrete them are still to
be reckoned amongst the greatest rarities of our
museums. The numerous dredgings of the ' Chal-

VERMES AND MOLLUSC A OF THE DEEP SEA 121

lenger ' only brought to light one specimen of this
animal, and that from a depth of 360 fathoms, and the

FIG. 14. — Batlnjteuthis abyssicola. (After Hoyle.)

Blake ' caught one at a depth of 950 fathoms, so that
there can be little doubt that Spirula lives in deep
water.

122 THE FAUNA OF THE DEEP SEA

It seems to be very probable that some day, when
the right place and depth are discovered, Spirilla
may be discovered in great abundance, but we have
at present no means of judging whether this will be
in very deep water or not.

Almost precisely similar remarks apply to the
distribution of the pearly Nautilus. The shells of
this Cephalopod are sometimes found in great number
on the shores of some of the islands of the Southern
Pacific Ocean and the Malay Archipelago, but the
living animal is but rarely captured. It has been
asserted by some travellers that the pearly Nautilus
floats on the surface of the ocean and possesses the
power of suddenly diving to great depths on being
disturbed ; but it must be remembered that Kuniphius
originally caught his Amboyna specimens of Nautilus
in traps set at a depth of 200 fathoms baited with
sea-urchins, and that the ' Challenger ' captured a
single living specimen off Maluku island in 300
fathoms.

The probability, then, is that both Nautilus and
Spirilla should be included in the deep-sea fauna, but
we are still in want of a srreat deal more information

o

concerning their life and habits before this point can
be definitely determined.

123

CHAPTER VII

THE ARTHROPODA OF THE DEEP SEA

THE deep-sea fauna seems to be particularly rich
in marine Arthropoda, many curious and interesting
forms being brought up with almost every haul of
the dredge. The Arthropoda, too, being very highly
organised animals, afford interesting and instruc-
tive examples of the effect of abysmal life in the
modification of the sense organs and the production
of varieties specially modified for the conditions of
the struggle for existence in their strange habitat.

Concerning the groups of Ostracoda and Copepoda
it may be said that the evidence is not yet conclusive
that they include any truly deep-sea species. The
largest known Ostracod, measuring somewhat more
than an inch in length and probably allied to the
genus Crossophorus, has quite recently been captured
by Professor Agassiz at depths of less than 200
fathoms, but he could obtain no evidence that it
descended into much deeper water than this.

124 THE FAUNA OF THE DEEP SEA

Mr. Brady, in writing the report of the ' Challenger '
Ostracocla, came to the conclusion that they do exist
in very limited numbers in the*most profound depths
of the sea ; but it is nevertheless quite possible that
all the Ostracods brought on deck by the trawl or
dredge were really captured either on the way down
or on the way up, and are, strictly speaking, pelagic
in habit.

Similar caution must be taken in dealing with the
Copepoda, an order of Crustacea that is essentially
pelagic in habit. The only species that has been
regarded as undoubtedly abysmal is Pontostratiotes
cibyssicola, a form whose carapace and antennas are
armed with exceedingly long and strongly toothed
spines, and was found in the mud brought up by the
trawl from a depth of 2,200 fathoms.

Calamus princeps, the largest species of its genus
of a deep reddish brown colour, may also belong to
the fauna of the deep sea, but we have less evidence

*

concerning the habitat of Hemicalamw acideatus,
Phyllopus bidentatus, and some of the Euchgetas.

The Amphipoda seem to be but poorly re-
presented in the fauna of the abyss ; in fact it may be
considered to be still an open question whether any
Amphipods habitually live in very deep water.

THE AKTHKOPODA OF THE DEEP SEA 125

In the reports on the 'Challenger' Amphipoda, the
Eev. T. R. Stebbing states that thirty-one specimens
are known to come from great depths, but it would be
more correct to say that these specimens were found
in the dredges and trawls that had been lowered into
the great depths. It should be noticed, however,
that some of these specimens do show characters
that suggest, at any rate, that they come from deep
water. Thus the genus Lanceola, for example, is
characterised by the sniallness of the eyes and a soft
membranous integument, while Cystisoma *j>/itu*um,
found in a dredge that had been at work at a depth
of over a thousand fathoms, has very large eyes.

In his report on the Crustacea of the i Norske
Nordhavns ' expedition, Professor Sars gives a full
description of many species of Amphipoda brought
by the dredge from depths of over 1,000 fathoms,
and nearly all of these were found to be quite
blind.

The form that seems to be most peculiar to the
great depths of the Northern Ocean is Harpima
abyssi. It was found at no less than fifteen different
stations at depths ranging from 350 to 2,215 fathoms,
and is characterised by its large size and the total
absence of eyes.

126 THE FAUNA OF THE DEEP SEA

Another point that should be considered in
coming to any conclusion on the supposed habitat of
such forms, is the similarity or dissimilarity of widely
distributed species.

I have had occasion to point out in a previous
chapter the general similarity of the abysmal fauna
all over the world, a very striking phenomenon, com-
mented on by almost every naturalist who has had
a wide experience of this kind of investigation.

Among the Amphipoda we have a very striking
example of this. The species Orchomene musculosus
was taken by the ' Challenger ' off the southern part of
Japan at a depth of 2,425 fathoms, the bottom being
red clay and the temperature 35 • 5° Fahr. The
species Orchomene abyssorum was taken off the east
coast of Buenos Ayres at a depth of 1,900 fathoms,
the bottom being blue mud and the temperature
33' 1° Fahr. To the description of this last-named
species Mr. Stebbing adds, ' had this species been
taken within reesonable distance of 0. musculosus,
the resemblance is so great that one might have been
tempted to disregard the points of difference as due
to some other cause than difference of species.'

Such a striking similarity between two species
living so far apart from one another may, when we

THE ARTHKOPODA OF THE DEEP SEA 127

take into consideration the depth, the character of the
bottom, and the temperature from which they are
supposed to have been dredged, be taken to support
very strongly the view that these species are really
abysmal in habit.

Among the Isopoda we have several very charac-
teristic forms — no fewer than nine distinct genera
peculiar to the abysmal zone have been described by
Beddard — and of these two, Batliynomus and Anu-
ropus, are to be regarded as types of sub-families.
They seem to be very unevenly distributed over the
floor of the ocean, some regions, such as the whole
of the Central and Southern Atlantic and the Cen-
tral and Western Pacific, produce none ; whilst
the waters of the east coast of New Zealand, the
Crozets, and others, produce a great many varieties.
Many of the deep-sea Isopoda exhibit characters that
are usually associated with the bathybial life. Thus,
according to Beddard, thirty-four of the deep-sea
species are totally blind, and eighteen have well-
developed eyes. In four species there are eyes
which are evidently degenerating. If we compare,
for instance, the structure of the eye of Serolis schytliei,
a species found in shallow water ranging from 4 to
70 fathoms, with the eyes of Serolis bromleyena, a

128 THE FAUNA OF THE DEEP SEA

species living in deep water ranging from 400 to 1,975
fathoms, we cannot fail to see that the latter are
undergoing a process of degeneration ; the retinulas
and pigment being absent, and nothing left of the
complicated structure of the Isopod eye but the
remnants of the crystalline cones and corneal facets
(see figs. 4 and 5, p. 74).

Taking the genus Serolis alone, it has been
said ' that in all the shallow-water forms the eye
is relatively small but very conspicuous from the
abundant deposition of pigment ; in all the deep-sea
forms, with the exception of S. gracilis, where the eye
seems to be disappearing, it is relatively larger but
not so conspicuous, owing to the fact that little or no
pigment is present.'

In many groups of animals it has been shown
that some of the deep-sea species are relatively much
larger in size than the shallow-water species, and
that others, more rarely, are much smaller, the
abysmal fauna reminding us in this respect of the
characters of the alpine flora.

The Tsopoda show many examples of this large-
ness in size, thus Bathynomus c/iganteus, dredged by
Professor Agassiz off the Tortugas at a depth of over
900 fathoms, reaches the enormous size, for an Isopod,

THE ARTHROPOD A OF THE DEEP SEA 129

of 9 inches (fig. 15). Stenetrium haswelli, again, is
larger than any of the shallow-water species of the
genus, and the same remark applies to the deep-
sea species of the genus Ichnosoma, while lolanthe
acanthonotus, from a depth of nearly 2,000 fathoms,
is considerably larger than most of the shallow-water
Asellidas.

There is another very common character of deep-
sea Crustacea that is also well exemplified in the
group of the Isopods, and that is the extraordinary
length and number of the spines covering the body.

I have already referred to this character in the
supposed deep-sea Copepod Pontostratiotes abyssicola,
and I shall have again to refer to it in treating of the
Decapoda and other groups of the Crustacea.

Besides its enormous size Baihynomus possesses
some other characters that may be correlated with
its deep-sea environment. The respiratory organs are
quite different from those of other Tsopods ; instead
of being borne by the abdominal appendages, they
are in the form of branched outgrowths from the
body-wall containing numerous blood-lacunae, and
the appendages simply act as opercula to cover and
protect them. The eyes of the Bathy nonius too are
remarkably well developed, each one bearing 4,000

K

180 THE .FAUNA Ol< THE DEEP SEA

facets, and they are directed not dorsally as in the
Cymothoadre, but ventrally. The cause of these
curious modifications of structure in Bathynomus is
by no means clear, but it is quite probable that they
are connected with the conditions of pressure and light
in the deep sea. It is a remarkable fact that the other
deep-sea Isopods do not exhibit precisely these modi-
fications, and it might be supposed that the same
causes would produce the same or similar effects on
the structure of animals belonging to the same order.
That is perfectly true, but we cannot yet determine
how long ago any one species has taken to a deep-sea
life, or what length of time, in other words, these
conditions have been at work in modifying the
structure of the organism. A recent immigrant into
the abyss will naturally exhibit closer affinities with
its shallow-water allies than those that have dwelt in
the region since secondary or tertiary times. If we
take this into consideration we should expect to find
considerable differences occurring between deep-sea
species of the same order, which is precisely what we
do find.

Concerning the Cirripedia, that curious group
of profoundly modified Crustacea that includes the

FIG. 15. —Bathynomus giyanteus. From a depth of 1,740 metres

(From Filhol.)

K 2

132 THE FAUNA OF THE DEEP SEA

barnacles and acorn shells, Dr. Hoek writes in the
' Challenger ' monograph :-

' Though unquestionably by far the greater part
of the known Cirripedia are shallow-water species,
and though some of the species are capable of living
at a considerable variety of depths, as, for instance,
Scalpellum stroemii, yet it must be granted that the
number of true deep-sea species of Cirripedia is very
considerable.' Only two genera, however, occur in
depths of over 1,000 fathoms, and these — Scal/pellum
and Verruca — occur also as fossils in secondary and
tertiary deposits. The oldest of all fossil cirripedes,
however, namely, Pollicipes, never occurs, at the
present day, in deep water, but is purely littoral or
neritic in habit. But what is perhaps more interest-
ing still is the fact, that, when we come to compare
the living and the fossil species, we find that in the
one genus (Scalpellum) the deep-sea forms have pre-
served the more archaic characters, and in the other
(Pollicipes) the shallow-water forms.

Here then we are presented with a veritable
puzzle for which we can at present frame no manner
of answer. Pollicipes on the one hand — like Lingula
among the brachiopods — has been able to maintain
itself almost unchanged amid the tremendous struggle

THE ARTHROPOD A OF THE DEEP SEA 133

for life of the shallow water of the tropics ever since
the Lower Oolite epoch ; while Scalpelluni, on the
other hand, has either become profoundly modified,
or been driven into the abysmal depths of the ocean.
The group of the Thoracostraca, or stalk-eyed
Crustacea, including lobsters, crabs, hermit crabs,
prawns, and shrimps, is well represented in the deep
sea. Most of them are characterised by being quite
blind (in many cases even the eye-stalks are oblite-
rated), by being protected with a dense covering of
spines, by the thinness of their shells, and by their
brio-lit red or carmine colour.

D

The order Stomatopoda is almost entirely confined
to the shallow waters of the tropical or temperate
shores. Not a single species is known to inhabit the
deep sea, and only a very few specimens have been
captured in more than a few fathoms of water.

The Schizopoda, however, present us with many
curious abysmal forms. Most of the genera of this
order belong to the pelagic plankton, and many of
them are known to possess the power of emitting a
very strong phosphorescent light. Several genera,
however, such as Gnathopliausia, Chlaraspis, Eucopia,
Bentheuphau-sia, &c., never seem to leave the great
depths of the ocean, and nearly all of these genera

134

THE FAUNA OF THE DEEP SEA

are distinguished by being quite blind or possessing
very much reduced or rudimentary eyes.

If we compare, for example, the pelagic HJuphausia
latifrons (fig. 16) with the nearly allied but abysmal

FIG. 16. — Eujjhausia latifrons, from the surface of the sea,

(After Sars.)

FIG 17. — BenthewpTiausia amblyojjs, from 1,000 fathoms.

After Sars.

Bentheuphausia amblyops (fig. 17), the difference in
this respect between a Schizopod living in the sun-
light and one living in the darkness of the deep-sea
is very apparent.

THE AETHEOPODA OF THE DEEP SEA 135

The pelagic Schizopoda are usually quite pale and
transparent ; the deep-sea forms on the other hand
are frequently if not invariably of a bright red colour.
as is the case with many other deep-sea Cru&tacea to
which reference will be made later on.

Passing on to the group of the Decapoda, we find
that the most interesting of all the abysmal cray-
fish is the family of the Eryonidas ; indeed, in some
respects the discovery of these curious forms may be
reckoned among the most valuable results of the
1 Challenger ' Expedition. They are characterised by
the dorsal depression of the anterior part of the cepha-
lothorax, the absence of a rostrum, and the absence :
or very rudimentary condition of the eyes (fig. 18).

Their nearest relations seem to be certain genera
of Crustacea that are found in Jurassic strata, in the
lias, and more particularly in the lithographic slates
of Solenhofen.

They have a very wide bathymetrical range ex-
tending from a depth of 250 fathoms (Polycliele*
crucifera) to a depth of 2.000 fathoms (Wille-
moesia).

But there are many other curious forms of the
macrurous Crustacea that deserve a passing men-
tion. The graceful Nematocarciniis grac'tHpes, distin-

136 THE FAUNA OF THE DEEP SEA

guished by the extraordinary length of the aiitennaB
and last four pairs of legs, these appendages being

FIG. IS.—Polycheles baccata, one of the Eryonidas. The
eyes and eye-stalks are absent, and the margin and
sides of the carapace armed with spines. (After
Spence Bate.)

THE ARTHROPOD A OF THE DEEP SEA 137

three or four times the length of the body, is by
no means rarely met with in depths of over 400
fathoms.

The genus Glyplius captured by the ' Talisman J is
remarkable for the development of a peculiar pouch-
like arrangement on the abdomen for the protection of
the larvee during the younger stages of their existence.

The proof of the existence of a peculiar cray-fish,
Thaumastocheles zaleuca, at a depth of 450 fathoms,
was one of the most important contributions to
carcinology made by the ' Challenger ' Expedition.
The chelas of this remarkable form are of great but
unequal length and armed with long tooth-like spines
giving it an appearance not unlike that of the jaws
of some carnivorous fish. The shell is soft and the
abdomen broad and flattened. There are 110 eyes
nor even eye-stalks, but ' in front of the carapace/ as
Sir Wyville Thomson remarks, ' between the anterior
and upper edge and the insertions of the antennas,
in the position of the eyes in such forms as Astacus
fluviatilis, there are two round vacant spaces, which
look as if the eye-stalks and eyes had been carefully
extirpated and the space they occupied closed with
a chitinous membrane.' The deep-sea prawn, Psali-
dopus, recently taken in 500 fathoms of water by the

138 THE FAUNA OF THE DEEP SEA

< Investigator,' affords us an example of a common
bathybial character, the whole body being covered with
an extraordinary array of sharp needle-like spines.

Among the crabs many curious forms have been
found in deep water extending down to depths of
over 2,500 fathoms. They are nearly all characterised
by blindness and a remarkable development of tooth-
like spines covering the carapace and limbs.

The remarkable Lithodes ferox, from a depth of
from 450 to 800 fathoms, is perhaps the most perfectly
armed crab — in the way of spines — that exists.
Every part of the body and limbs is so covered with
spines that one has to be extremely careful in handling
even a dead specimen.

^

This is only one of the many examples that
might be given to illustrate this curious feature 01
the deep-sea Crustacea. Among the crabs alone we
have such forms as Galathodes Antonii, Pachygaster
formosus, Dicranodromia mahyeuxii covered with a
fierce armature of spines or bristles ; but there are
nevertheless some species in which this character is
not particularly noticeable, and in these we usually
find some other protection against their enemies.
An interesting example of this has been described
by A. Agassiz in a crab allied to the Maiadae,

THE ARTHROPOD A OF THE DEEP SEA 139

' in which the dorsal face appears like a bit of
muddy area covered by corals, with a huge white arm
resembling a fragment of an Isis-like gorgonian.'
It is evident that this is a case in which the animal
in protected by its resemblance to the surround-
ings.

The hermit crabs of the abyss, too, are not usually
characterised by any very great development of
spines. They find their protection in the shells they
inhabit. Some of the deep-sea hermit crabs carry
about with them on their shells a sea anemone, as we
find to be frequently the case among the shallow-water
species. Pagurus aby'ssorum, from a depth of 3,000
fathoms, is an example of this.

In cases where there is a scarcity of gasteropod
shells the hermit crabs are obliged to find some
other form of protection for their bodies. The ' Blake '
found in the West Indies a hermit crab that had
formed for itself a case of tightly compressed sand,
and another curious form, named Xylopagurus rectus,
makes its home in pieces of bamboo or in the holes
in lumps of water-logged wood.

The last group of the Arthropoda we need refer
to is that of the Pycnogonida, those curious creatures
seemingly made up entirely of legs, and by some

140 THE FAUNA OF THE DEEP SEA

naturalists considered to be related to the Crustacea
and by others to the scorpions and spiders.

Like the Brachiopoda the Pycnogonida are not
usually found in greater depths than 500 fathoms.
Out of the twenty- seven known genera, only five
extend into the abyss, and not one of these can be
called a true deep-sea genus.

There are three genera, Nynvphon, Collosendeis,
and Phoxichilidium, that show a very wide distribu-
tion over the floor of the ocean, and are capable of
existing at the greatest depths, and of these the
species of the genus Nymphon have a truly remark-
able range extending from the shore to a depth of
2,225 fathoms.

' As a rule,' says Hoek, * the deep-sea species are
slender, the legs very long and brittle, and the sur-
face of the body smooth.' They have further, either
no eyes at all or rudimentary eyes without pigment,
and in many cases — as, for example, Collosendeis —
they are distinguished for reaching to a gigantic size
compared with their shallow- water relatives.

The Tunicata is the group of animals that
includes all those curious vegetable-like organisms
found upon our coasts that are familiarly known as
sea-squirts, or Ascidians, besides the salps, pyrosomas,

OS

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o

s

o

O

A

-4J

a
2

142 THE FAUNA OF THE DEEP SEA

and the microscopic appendicularias of the pelagic
plankton.

Notwithstanding the apparent simplicity of their
adult structure, naturalists are now agreed that they
must be removed from the Mollusca, with which they
have hitherto been most frequently associated, and
placed in the group of the Vertebrata. It is the
study of embryology that has led to this unexpected
conclusion, for we find, when we study the larval forms,
that they possess both a notochord and gill-slits, two
features that are characteristic of the group of the
Vertebrata.

The species of the group Perennichordata, which
includes all those Tunicates that possess a noto-
chord persistent through life, are chiefly pelagic in
habit, the little creatures, rarely more than two or
three millimetres in length, swimming or drifting
about with the sagittas, copepods, ctenophores, and
medusae that compose the pelagic plankton. Fol has
recently described a gigantic form belonging to this
group, reaching a size of thirty millimetres in length,
called Megalocercus abyssorum, which he dredged
from a depth of 492 fathoms ; and other species have
been recorded down to a depth of 710 fathoms in the
Mediterranean Sea.

THE ARTHROPOD A OF THE DEEP SEA 143

Among the simple Ascidiaiis we find no family
that is peculiar to deep water ; but the Cynthiidae and
Ascidiidee both contain genera that are abysmal, and
the Molgulidae have one species, Mol<~fnl« pyriformis,
that extends into the abysmal zone to a depth of 600
fathoms.

In the genus Culeolus and in Fii/tyJiti* cinereus
and Bathi/oncii*, all deep-water Ascidians, there is a
very curious modification of the branchial sac, the
stigmata being apparently not formed, in consequence
of the suppression of the fine interstigmatic vessels.
This peculiar feature is only found in the deep-sea
simple Ascidians and, as we shall see presently, in one
species of the deep sea compound Ascidians, but it is
not apparently an essential character of those living
in the abysmal zone, notwithstanding the fact that
it is found in such widely separated genera ; for
Corynascidia, Abyssasc!<Hn. and Hypobythius, living in
depths lying between 2, 000 and 3,000 fathoms below
the surface, have branchial sacs of the ordinary type.
Professor Herdman is of opinion that this simple form
of branchial sac is not a primitive form, but most
probably a modification of a more complicated type.

In Culeolus Murrayi there is a remarkably abun-
dant supply of blood-vessels to the tunic, and these

144 THE FAUNA OF THE DEEP SEA

send special branches to a number of small papilli-
form processes on its outer surface. This system
of highly vascular processes probably constitutes, as
Professor Herdman suggests, an additional or com-
plementary respiratory apparatus. All these modifi-
cations of the branchial system are of particular
interest, for we find so many instances of a similar
kind among the inhabitants of very deep water.
I need only refer here to the modifications of this
system in the Isopod Bathynomus already referred
to (p. 129), and to the reduction in the number of
the gills of many of the deep-sea fishes. Why there
should be such modifications is a question upon which
the physical and natural history investigations of the
conditions of life in the great depths of the ocean at
present throw no light.

In a previous chapter 1 have referred to the fact
that many of the bathybial animals are character-
ised by being stalked. Among the simple Ascidia we
find many examples of stalked kinds living in deep
water, such as Culeolus and Fungulus, but also several
exceptions, such as Bathyoncus, Styela bytliii, and
Abyssascidia, that are sessile. It is a noteworthy fact,
however, that the genus that has the most deep-sea
species — namely, Culeolus — is a genus that is provided

FIG. 20. — HypolnjtltAus call/codes. G, nerve ganglion ; H,
heart ; JNI, the position of the atriopore. The large open-
ing on the upper side is the mouth. (From a drawing by
Professor Moseley in Herdman V Tunicata of the "CrmJ-
Expedition.')

L

lenger

146 THE FAUNA OF THE DEEP SEA

with a very long stalk. Furthermore, the only known
stalked forms of the very large family Ascidiidse are
the abysmal genera Corynascidia and Hypobyihius.

The most remarkable character of the genus
Hypobythius is the simple condition of its branchial
sac. reminding one of the structure of this organ in the
shallow- water genus Glavelina. 'There are no folds
and there are no internal bars,' to quote the descrip-
tion given by Professor Herdman ; ' only a single
system of vessels can be recognised, branching and
anastomosing so as to form a close net work, the small
rounded meshes of which are the stigmata. The
tentacles and dorsal lamina cannot be made out.'

Among the compound Ascidians only four families
extend into the abysmal zone, namely, the Botryllidae,
Polyclinidag, Didemnidae, and Ccelocormidse, and of
these only one species, Pharyngodictyon mirabile, of
the family Polyclinidas, extends into water of greater
depth than 1,000 fathoms. In Pharyngodictyon we
find the same curious simplification of the branchial
sac that we have just referred to in the genera of
simple Ascidians, Culeolus, Fungulus, and Bathyoncus.
Coelocormus Huxleyi from a depth of 600 fathoms is

•

a very peculiar form and the type of a separate family,
the CcelocormidaB.

THE ARTHROPODA OF THE DEEP SEA 147

The free-swimming Timicata included in the
group Ascidice salpiformes, which contains the genus
Pyrosoma, and the order Thaliacea containing the
salps, are in all probability mainly confined to the
surface waters. A few specimens of Pyrosoma were
captured by the ' Challenger ' dredges which came up
from very deep water, but it is doubtful at what point
in the journey to the surface the specimens entered
the net.

The most remarkable form of free-swimming
Tunicate that has come to light is Octacnemus bythius,
a form that is probably allied to Salpa. It was
found twice, once in the dredge that came from a
depth of 1,070 fathoms, and once from 2,160 fathoms.
The tunic of the animal is gelatinous and hyaline,
but the most important feature it possesses is an
imperforate membrane separating the branchial sac
from the peribranchial cavity. Octacnemus, in other
words, possesses no true stigmata, these structures
being represented only by little pits in the walls
of the branchial sac. This curious and extremely
interesting modification of the respiratory organs
points very strongly to the conclusion that Octacnemus
is truly a deep-sea animal.

i. 2

148 THE FAUNA OF THE DEEP SEA

CHAPTER VIII

THE FISH OF THE DEEP SEA

OF all the groups of animals that constitute the
deep-sea fauna, the fish show the greatest number
of peculiarly abysmal characters. Being much
more highly differentiated than the invertebrates,
they possess more organs liable to undergo modi-
fications of colour, size, and structure, and conse-
quently we are able to point to a great many more
features characteristic of deep-sea fish than we can
do in any other group of animals.

The first point that calls for remark in the con-
sideration of the fish fauna of the deep sea is the
almost entire absence of ancient and primitive types.
The Elasmobranchii, including the Sharks, Kays, and
Chiinsera, constituting the order that from anatomical
embryological grounds is always regarded by natura-
lists as the most primitive order of this class, is
represented in very deep water by only one species.

THE FISH OF THE DEEP SEA 149

Raia liyperborea and Chimcera monstrosa, it is true,
just enter into the abysmal zone, but Chimcera affi-ni$
is the only Elasmobranch that extends to depths of
over 1,000 fathoms.

The Ganoidei too, the order that in palaeozoic
and mesozoic times was so rich in genera and species,
is entirely absent from the abysmal zone, not a single
representative having been found at any time by any
of the deep-sea expeditions.

The Dipnoi, that remarkable order including the
three fresh-water genera, Geratodus from Australia,
Lepidosiren from Brazil, and Protopterus from West
Africa, has no representative and no ally m the deep
waters of the ocean.

The fishes of the deep sea, in fact, with only one
or two exceptions, all belong to the Order Teleostei,
the most modern and most highly differentiated order
of the class, the families that are most fully repre-
sented being the Macruridae and then the Ophidiidae

and Gadidae, and the Bervcidae.

i/

At the limits of the katantic and abysmal zones, a
large number of families of Teleosteans entirely dis-
appear, and as we approach the deepest parts of the
ocean, the number of fish that are found is consider-
ably reduced. As Dr. Giinther very wisely remarks.

150 THE FAUNA OF THE DEEP SEA

; this diminution in the number may be due to the
difficulty of capturing fishes at great depths, a diffi-
culty which increases in proportion to the depths at
which the dredge is worked. But it must also be
regarded as evidence of the actually diminished variety
of fishes.'

It may be interesting to the reader to give Dr.
Giinther's table of the number of species found at
different depths, as it shows, among other things, the
marked change that occurs in the character of the
fauna in passing from the katantic to the abysmal

zone.

Between 100-300 fathoms, 232 species

300-500 „ 142 „

500-700 „ 76

700-1,500 „ 56 „

„ 1,500-2,000 „ 21 „

„ 2,000-2,900 „ 23 „

As regards the general character presented by
the deep-sea fishes, I have already pointed out in the
chapter dealing with the general characters of the
deep-sea fauna, the peculiarities in the size of the eyes,
the colours and markings of the body, and the texture
of the bones and muscles. There are, however, a few
more characters of which mention must be made.

Notwithstanding the fact that all the abysmal
fibres are carnivorous and must consequently be

THE FISH OF THE DEEP SEA 151

capable — in the great number of cases — of rapid and
vigorous movement, the muscles of the trunk and
tail are usually thin, and the fascicles loosely connected
with one another.

Deep-sea fish are not characterised by an absence
of :he swimming bladder. This organ occurs just as
frequently and in the same families as in the shallow-
water fauna, but we do not know whether it possesses
any special peculiarities or not, as it is usually so
ruptured and destroyed by the change of pressure
it undergoes in being brought to the surface, that it
is impossible to make any thoroughly accurate in-
vestigation of its anatomy and relations.

The extraordinary development of glands in the
skin which secrete mucus, and the presence in many
forms of very highly specialised organs for emitting
phosphorescent light, are characters of the deep-sea fish
fauna, to which I have referred in a previous chapter.

As with the Tunicates, some of the Crustacea
and other groups, the fish of the abysmal zone show
curious modifications of the respiratory system. The
gill laminae of these animals are not only reduced
in number, but appear to be short and shrunken.
It is possible, of course, that during life they may
end in fine delicate points which are broken

152 THE FAUNA OF THE DEEP SEA

oft' or ruptured during their capture, but still the
horny rods that support them are shorter than they
are in shallow-water forms, and the general evidence
of their structure tends to show that they have
undergone profound modifications in the change to
the conditions of deep-sea life.

An extremely common and almost general
character of deep-sea fishes is the black coloration
of some of the body cavities ; this is limited to the
pharynx in many of the fishes that live about the
hundred fathoms limit, but the colour is more intense
and spread all over the oral, branchial, and peritoneal
cavities in typical deep-sea forms. It may seem very
difficult at first to account for this remarkable de-
velopment of black pigment in parts of the body that
are not usually, and, in some cases, cannot at any
time be exposed to view. It is obvious that it can-
not be functional as a hiding colour, either in offence
or defence. But it is quite possible that it is due to
some modification of the function of excretion. It is
well known that in many cases of disease or injury to
the kidneys in vertebrates, the colour of the skin is
affected, and every one recognises now the fact that in
many invertebrates the colour of the skin is greatly de-
pendent upon the function of the secretion of the urates.

THE FISH OF THE DEEP SEA 153

It would at least be interesting to know if this
dark coloration of the mucous membranes is in any
way correlated with any modification of the structure
or function of the kidneys. At present we have no
recorded observations on this point, but it is to be
hoped that, when we have a sufficient number of
specimens brought home from the deep water, a
systematic investigation of this subject will be made.

Lastly, it should be pointed out that our know-
ledge of the abysmal fauna has not. at present, brought
to light any evidence that the fish are of an extra-
ordinarily large size. In many groups of animals, as
I have frequently pointed out in the last few chapters,
the large and gigantic species or specimens are only
found in the abyss. This may also be the case with
fishes, but we have no evidence that it is so. The
only methods that have been used at present for the
investigation of the fauna living on or near the
floor of the deep oceans, are not of a kind to lead
to the capture of really large fish. That they may
exist is highly probable, but all that we know at
present is, that the fish with which we are acquainted
living at great depths are not in any way remarkable
for their great size.

Of the only two Elasmobranchs, one. namely -Ra

154 THE FAUNA OF THE DEEP SEA

hyperborea, has been found in water extending from
400 to 608 fathoms in depth. Only four specimens
have yet been taken, one by the Norwegian expedi-
tion off Spitzbergen and three by the ' Knight
Errant ' off the northern coasts of Scotland. It is
interesting to find that this, the only deep-sea species
of the Rays, shows some striking peculiarities. c The
teeth are remarkably slender,' says Gtinther, ' small,
irregularly and widely set, different from those of other
British Rays. In young specimens at any rate those
of the male do not differ from those of the female.
The mucous membrane behind the upper jaw forms
a pad with a lobulated surface. The mucous cavities
of the head are extremely wide, and finally the acces-
sory copulatory organs have a spongy appearance,
and are flexible, the cartilage by which they are sup-
ported being a simple slender rod.'

The other Elasmobranch, that extends into very
deep water, is Chimcera affinis, a species which can
hardly be distinguished from the better known
Chimcera monstrosa, a fish that itself very frequently
wanders within the limits of the abysmal zone.

Among the Teleostei, the family Berycidas has
several representatives in the deep water. They are
small fish rarely exceeding four inches in length, with

THE FISH OF THE DEEP SEA 155

large heavy heads, with functional but small eyes,
and an abundant supply of large mucous glands on
the skin.

Melam/jphaes beanii, belonging to this family,
has been captured at the enormous depth of 2,949
fathoms.

Bathy draco antarcticiis, belonging to the family
Trachinidae, from a depth of 1,260 fathoms, is an
example of a true abysmal fish possessing very large
eyes.

The Pediculati, the family of the anglers, is re-
presented at depths of over 2,000 fathoms by the
interesting form Melcmocetus Murrayi. The eyes are
very small indeed, the mouth huge and armed with
long uneven rasp-like teeth. At the end of the fish-
ing-rod tentacle hanging over the mouth, there is an
organ that has been supposed to be capable of emitting
a phosphorescent light. This curious modification of
the red worm-like bait of the common shallow-water
angler into a will-o-the-wisp lantern attracting little
fishes to their destruction in the deadly jaws of the
Melanocetus is one of the most interesting adaptations
that has been brought to light by our study of the
deep-sea fauna.

Several species of the family Lycodidpe occur in

156

THE FAUNA OF THE DEEP SEA

the abysmal zone, but they do not possess any
features that call for special mention in this place.

FiG.21.—MelanocetwMwrrayi, 1,850-2,450 fathoms. (After Giinther )

The family Ophidiidas contributes very largely to
the fish fauna of the abyss. Some of the deep-water
genera, such as Neobythites, have a wide bathy-
metrical distribution extending from 100 fathoms to
depths of over 2,000 fathoms, but others, such as
Bathyonus, Typhonus, and Aphyonus, only occur in
depths of over 1,000 fathoms.

The body is usually elongate and slender, ending
in a pointed tail, the head large and heavy, and the
eyes, in the genera confined to the abysmal zone,
usually so far degenerated that they are not visible at
all from the outside.

The Macruridse form a familv that contributes

THE FISH OF THE DEEP SEA 157

very largely to the deep-sea fauna ; uo fewer than
twenty-six different species are known to occur
within the limits of the abysmal zone. Not only
do the Macruridse contribute a large number of
different species, but they probably occur, in some
districts at any rate, in vast numbers.

During the voyage of the ' Talisman,' for example,
the French naturalists caught in one haul of the
dredge off the coast of Morocco in 500 fathoms of
water no fewer than 134 fish, of which number 95
belonged to the family Macruridae.

They are usually small fish, measuring from a few
inches to two feet in length, with a body terminating
in a long compressed tapering tail and covered
with spiny, keeled, or striated scales.

The Pleuronectidae or flat fish are not, as a rule,
found in the abysmal zone ; one species, however,
Pleuronectes cynocjlossu.*, was found by the American
ship ' Blake ' to extend into 732 fathoms of water.

The families Stemoptychidas and Scopelidee are
of particular interest to us, as almost all the genera
they contain belong either to the pelagic or abysmal
zones, and lend support to the view enunciated by
Moseley, that the deep-sea fauna has, partly at any
rate, been derived from the fauna of the pelagic zone.

158 THE FAUNA OF THE DEEP SEA

They are nearly all small slender fish with delicate
and frequently semi-transparent bodies, large gaping
mouths armed with numerous long irregular teeth,
and frequently provided upon the head and sides
of the trunk with rows of eye-like phosphorescent
organs.

These families, and others that have still to be
referred to, belong to the group of Teleostei that is
called Physostomi, the name referring to the open
communication that usually exists in all these families
between the swimming bladder and the alimentary
canal. It is a remarkable fact that in none of the
deep-sea representatives has this open communication
been discovered. It is true that many specimens are,
when examined, so lacerated by the diminution in
pressure as to render anatomical study a matter of
difficulty, but still a fair number of uninjured well-
preserved specimens have now been examined and
the duct has not been found.

Of the family Sternoptychidas, Gonostoma micro-
don has a most remarkable distribution. It has been
found at numerous stations in both the Pacific and
Atlantic Oceans at depths ranging from 500 to nearly
3,000 fathoms of water.

The Scopelidas are represented by some very

THE FISH OF THE DEEP SEA 159

extraordinary types. The genus Batliypterois, for
example, occurring in depths ranging from 500 to
2,500 fathoms, is characterised by the development of
enormously long pectoral fins to serve probably as
organs of touch. ' The rays of the pectoral fin,' says
Dr. Giinther, * are much elongated. The ventral fins
abdominal, with the outer rays prolonged, eight-
rayed. . . . Gill rakers long.' They are further
characterised by the absence of any true phosphor-
escent organs and the smallness of their eyes.

There can be little doubt, I think, that in these
fishes the sense of touch or taste to a great extent
takes the place of the sense of sight in other Sco-
pelids. Not being provided with well-developed eyes
or phosphorescent organs to attract their prey, the
pectoral fins and the outer rays of the pelvic fins
have become elongated and provided with special
sense organs for searching for their food in the fine
mud of the floor of the ocean.

These long pectoral rays must have a very curious
appearance in the living fish. Mr. Murray observes :
' When taken from the trawl they were always dead,
and the long pectoral rays were erected like an arch
over the head, requiring considerable pressure to
make them lie along the side of the body ; when

160 THE FAUNA OF THE DEEP SEA

erected they resembled the Pennatulids like
Umbellula.' Filhol considers that when the fish is
progressing through the obscurity of the abyss it
probably carries these organs directed forward, seek-
ing with them in the mud for any worms or otheiv
animals upon which it preys, or receiving through
them warning of the approach of an enemy from whom
it is necessary to make an immediate escape. One
of the most remarkable of the deep-sea fish is closely
related to Bathypterois, namely Ipnops Murrayi,
living in depths of over 1,000 fathoms. It is about
five inches long, of a yellowish brown colour, with an
elongated subcylindrical body covered with large thin
deciduous scales. There are no phosphorescent organs
of the ordinary type met with in the Scopelidge, but
upon the upper surface of the head there is found a
pair of organs somewhat resembling the ordinary
eyes of fishes but devoid of retina and optic nerve,
that, from the researches of Moseley, seem to be un-
doubtedly organs for emitting light. * The organs
are paired expanses, completely symmetrical in out-
line, placed on either side of the median line of the
upper flattened surface of the head of the fish, ex-
tending from a line a little posterior to the nasal
capsules nearly to a point above the posterior

THE FISH OF THE DEEP SEA 161

extremity of the cranial cavity.' They are covered
by the upper walls of the skull, which is extremely
thin and completely transparent in the region lying
over them. ' They are membranous structures
0*4 mm. in thickness marked by hexagonal areas
about 0*04 mm. in diameter. When their surface is
viewed by reflected light the appearance is that of a
number of glistening white isolated short columns
standing up in relief from its basal membrane.' Each
hexagonal column is composed of a number of trans-
parent rods disposed side by side at right angles to
the outer surface of the organ, with their bases applied
against the concave surface of a large hexagonal
pigment cell, one of which forms the basis of each
hexagonal column. It is still very doubtful what
are the true homologies of this extraordinary phos-
phorescent organ, but Moseley was of opinion that, ' 011
the whole, it seems not unlikely that the remarkable
head organs of Ipnops may be regarded as highly
specialised and enormously enlarged representatives
of the phosphorescent organs on the heads of such
allied Scopelidge as Scopelus rafinesquii and Scopelus
metopoclampus. It may be conceived that in Ipnops
the supra-nasal and sub-ocular phosphorescent organs
of these species on either side have united and

M

162 THE FAUNA OF THE DEEP SEA

become one with the result of the total obliteration
of the eye.'

Most of the species of the genus Scopelm are
undoubtedly pelagic in habit, descending during the
day to depths of semi-darkness but rising at night
to the surface waters. It is not certain how many
of the known species occasionally or habitually dwell
in very deep water, but there seems to be no doubt
that two species at least — S. macrolepidotus and
8. glacialis — belong to the abysmal zone. Both
of these species were found in dredges that had been
at work in depths of over 1,000 fathoms and showed
signs when examined of having been brought from
the abyss.

The Stomiatidge are almost entirely confined
to water from 450 to nearly 2,000 fathoms in
depth. They may be distinguished from the
Scopelidae by the long hyoid barbel close to the
symphysis of the lower jaw, but like many of the
genera of that family they have wide gaping mouths
armed with a profusion of vicious looking teeth and
a series of luminous spots on the sides of the head
and body. (See Frontispiece.)

In Eustomias obscurus, found in depths of over
1,000 fathoms in the Atlantic by the ' Talisman,' the

THE FISH OF THE DEEP SEA 163

barbel is provided with a terminal swelling, shaped
like a dumb-bell, which may be capable of emitting a
phosphorescent light and serve the animal as a lure
for the attraction of its prey. The genus Halacosteus,
too, presents us with some of the most remarkable
forms that are found in the abysmal zone. The
mouth is of enormous size and the integuments of
the abdomen present very definite longitudinal folds,
leaving no doubt that this fish is able, like several
others living in deep water, to swallow prey of an
enormous size.

But a perfectly unique structure in this fish l is
a thin cylindrical muscular band which connects
the back part of the mandibular symphysis with
the hyoid bone. It is probably the honiologue of a
muscular band which, in other Stomiatids, stretches
on each side from the mandible to the side of the
hyoid, the two bands coalescing into an unpaired one in
Malacosteits. It is, in the present state of preservation,
much elongated, like a barbel, but during life it is
notably contractile, and serves to give to the extremity
of the mandible the requisite power of resistance
when the fish has seized its prey, as without such a
contrivance so long and slender a bone would yield to
the force of its struggling victim.'

M 2

164

THE FAUNA OF THE DEEP SEA

Belonging to the family of the Salmons we find
one genus Bathylagus that is undoubtedly an abysmal
form. Although there may be some doubt as to the
exact depth at which the specimens were captured,
the thinness of the bones, the enormous size of the
eyes, and other bathybial characters prove that they
must live in very deep water. Closely allied to the
salmon and the herrings is the family of the Alepoce-

FIG. 22. — Saccopliarynx ampullaceus ; a deep-sea eel, with the head
of a large fish, which it has swallowed, showing through the
thin integuments of the body. (From Gunther.)

phalidae, a family that contributes several forms to
the fauna of the deep sea, but they do not possess
any characters that call for special comment. Their
vertical distribution varies between 345 and 2,150
fathoms.

The family Halosauridas contains five species all
confined to the abysmal zone. They have long bodies
tapering to a finely pointed tail, and the head is pro-

THE FISH OF THE DEEP SEA 165

vided with a snout that projects considerably in front
of the mouth.

Of the family of the Eels there are several re-
presentatives in the deep sea. They are character-
ised by a combination vof true eel characters with
special modifications due to a bathybial existence. ' To
enable them to seize upon prey more powerful than
themselves certain organs have undergone a degree
of specialisation, as is observed in bathybial members
of other families with a similar mode of life ; the
jaws are exceedingly elongate and the whole gape,
the pharynx and stomach capable of enormous dis-
tension.' The head is very large, the eye very small
and the tail long and tapering (fig. 22).

The lessons we learn from the study of the fishes
of the deep sea are particularly instructive. It would
take far more space than can be afforded here to
fully illustrate all of the points that seem clear to us,
but I hope I have said sufficient to show that the
fish fauna is made up of genera and species belong-
ing to several widely separate families of the Teleostei;
that some of them show, in a very marked way, what
may be looked upon as peculiarly bathybial characters,
whilst others are but slightly modified from their
shallow-water representatives. These facts by them-

166 THE FAUNA OF THE DEEP SEA

selves lend support to the view that the fauna of
the deep sea has been derived from the fauna of
shallower water by successive migrations at different
periods of the world's history. Those that exhibit in
a most marked degree the special bathybial characters
are probably those whose immigration took place
long ago, whilst those more closely related to shallow-
water forms are, comparatively speaking, recent
importations. The occurrence of Scopelidse and
Sternoptychidas in deep water suggests, as Moseley
pointed out many years ago, that the fauna is partly
derived from the pelagic plankton. But while these
points may seem clear to us, there are others that still
require much more investigation and consideration.
The whole question of the function and use of the
phosphorescent organs, the mucous glands, the
barbels and elongated fin rays, the mode of life,
the deposition of ova and their development, afford
problems which in the present state of our know-
ledge must remain unsolved. Let us hope that in
the future there may be a new stimulus given to
deep-sea research, and these problems may be again
seriously studied and eventually solved.

INDEX

ACTIXIAEIA, 36, 93
— two remarkable genera of, 15
Aegir, 15

Agassiz, A., on colour of Ccelen-
tera, 65

- on Echinoidea, 101, 103
Agassiz, L., on board the

' Hassler,' 12

'Albatross,' American vessel, 15
Alcyonaria, 95

- phosphorescence of, 81
Amphipoda, 124
Anemones of deep water, 36, 92

- two remarkable genera of,
15

Annelida, 117

Ascidia composite, 146

— salpiformes, 147

— simplices, 142
Asteroidea, 104

BAEBIERS of temperature, 32

Batkynomus, 129

Beddard, F. E., on Isopoda, 127

Benthos, 53

Berycidas, 154

'Blake,' American vessel, 12

Blue mud, 42

Brachiopoda, 115

Brachyura, 138

Brisinga, 9, 105

Buchanan's experiment, 19

CAEPENTER, P. H., on Cri-

noidea, 100
Ceplialodiscus, 113
Cephalopoda, 120
' Challenger,' H.M.S., voyage

of, 12

Cirripedia, 130
Coelentera, colour of, 65

— of deep sea, 91

Colour of the deep-sea fauna,
59, 66

- of the deep-sea fish, 60
Copepoda, 124
Corals, 94
Crinoidea, 99
Crustacea, 123

— colour of, 63

DARKNESS of the abyss, 22
Diatom ooze, 39
Dipnoi, 149

ECHINODEEMA, 99

- colour of, 64
Echinoidea, 101
Eels, 165
Elasipoda, 106
Elasmobranchii, 148, 153
Eryonidse, 135
Eyes of abysmal animals, 67
— of deep-sea Crustacea, 72

168

INDEX

Eyes of deep-sea fish, 69

- of deep-sea mollusca, 71

— of Genityllls, 118

- of Neobythites, 69

— of Serolis, 73

Fenja, 15

' Fish Hawk,' American vessel,
12

Fol and Sarasin's experiments,
25

Forarninifera, 90

Forbes, on the probable exist-
ence of a deep-sea fauna, 2

— on zones of distribution, 49

GANOIDEI, 149
Gasteropoda, 119
Gephyrea, 116
Gills of deep-sea fish, 151
Globerigina ooze, discovery
of, 5

- distribution and composi-
tion of, 37,

Green mud, 42

Gunn, Dr., on the eyes of

Grenityllis, 118
Gunther, Dr., on deep-sea fish,

150

HALL, Marshall, 12
Halosauridse, 164
' Hassler,' American ship, 12
Herdman, on Ascidians, 143,

146

Hermit crabs, 139
Hoek, Dr., on Cirripedia, 132

- on Pycnogonida, 140
Holothuridea, 106

Hoyle, on Cephalopoda, 120
Hydroids, 92

4 INVESTIGATOR,' H.M S., 16
Ipnops Murrayi, colour of, 60,
61

Ipnops Murrayi, phosphor-
escent organs of, 160
Isopoda, 127

KATANTIC sub-zone, 50

' Knight Errant,' H.M.S., 12

LAMELLIBRANCHIA, 119
' Lightning,' H.M.S., 8, 9
Lime, scarcity of, in bones of

bathybial fish, 83
— in shells of mollusca, 83
Littoral sub-zone, 49
Lycodidae, 155

MACRURA, 135
Macruridas, 156
Madreporaria, 94
Medusas, 91
Mollusca, 119

- colour of, 62
Moore, Capt., 94

Moseley, H. N., on colour of
Ccelentera, 65

- on phosphorescent organs of
Ipnops, 160

- on the darkness of the abyss,
22

- on the phosphorescence of
Alcyonarians, 25

Murray, on Bathypterois, 159

NEKTON, 53
Neritic zone, 48
' Norma,' Mr. Hall's yacht, 12
Norske Nord-havns expedition,
7, 15

OPHIDIID^E, 156
Ostracoda, 123

PACKARD, on the illumination
of the abyss, 23

INDEX

169

Pediculati, 155
Pelagic zone, 47
Pennatulidas, 96
Pkoronis, 111

Phosphorescence of Alcyo-
narians, 81

- of deep-sea Crustacea, 80

- of Echinoderma, 81
Phosphorescent light in the

abyss, 24

- organs of deep-sea fish, 77
Pigment in mucous membranes

of deep-sea fish. 84, 152
Plankton, 52
Pleuronectidae, 157
Polar currents, 30, 33
Polychaeta, 118
< Porcupine,' H.M.S., 8, 9
Porifera, 91
Pourtales, Count, 10
Pressure in the abyss, 19
Protozoa, 88
Pteropod ooze, 39
Pycnogonida, 139

RADIOLARIA, 89
Radiolarian ooze, 39
Red mud, 37

- off the Brazilian coasts,

42

Rhabdopleura, 111
Ross, Sir James, on the fauna

of the deep sea, 3

SALMONID^E, 163
Sargasso sub-zone, 48
Sars, 6, 9,
- on Amphipoda, 125

Sars, on Brisinya, 105

Schizopoda, 133

Scopelidas, 158

Serolis, 127

Siphonophora, 92

Size of deep-sea animals, 85

- of fish, 153
Smith, Mr., on Lamellibranchia,

119

Spatangoids, 101
Sponges, 91
Stebbing, Rev. T. R., on Amphi

poda, 125

Sternoptychidae, 158
Stomatopoda, 133
Stomiatidae, 162

« TALISMAN,' French vessel, 12
Teleostei, 149, 154
Temperature of the abyss, 28
Thomson, Sir Wyville, on
Pourtalesia, 10

- on Tha/umastocheles, 137

- on the darkness of the abyss,
22

— on the phosphorescence of

the sea, 26
Thoracostraca, 133
' Travailleur,' French vessel, 12
• Triton, ' H.M.S., 12
Tunicata, 140

VEGETABLE life, absence of, 42
Verrill, on the illumination of

the abyss, 23
' Vittor Pessani,' Italian vessel,

12
' Voring-in,' Norwegian vessel,

14

Spoltisu-oode A; Co. Printers, Neic-slreft Square,

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