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Frontispiece.
THE DEPTHS OF THE OCEAN
MACMILLAN AND CO., Limited
LONDON . BOMBAY • CALCUTTA
MELBOURNE
THE MACMILLAN COMPANY
NEW YORK • BOSTON • CHICAGO
DALLAS . SAN FRANCISCO
THE MACMILLAxN CO. OF CANADA,
TORONTO
THE "^'"'
DEPTHS OF THE OCEAN
A GENERAL ACCOUNT
OF THE MODERN SCIENCE OF OCEANOGRAPHY
BASED LARGELY ON THE SCIENTIFIC RESEARCHES
OF THE NORWEGIAN STEAMER
MICHAEL SARS
IN THE NORTH ATLANTIC
BY
Sir JOHN MURRAY, K.C.B., F.R.S., etc.
OF THE 'challenger' EXPEDITION
AND
Dr. JOHAN HJORT
DIRECTOR OF NORWEGIAN FISHERIES
WITH CONTRIBUTIONS FROM
Professor A. APPELLOF, Professor H. H. GRAN
AND Dr. B. HELLAND-HANSEN
MACMILLAN AND CO., LIMITED
ST. MARTIN'S STREET, LONDON
1912
COPYRIGHT
PREFACE
At the International Congress for the Exploration of the Sea
held on the invitation of the Swedish Government in Stockholm
in 1899, Sir John Murray was the chief British delegate, and
acted as president of the physical and chemical section, which
drew up a programme of work for the proposed investigations
in the North Sea and in the Norwegian Sea. Although his
official connection with these marine researches came to an end
with the close of the first Congress, it is well known that he
has followed with great interest all the proceedings of the
International Council during the past ten or twelve years.
In the year 1909 he chanced to visit Copenhagen at a time
when one of the annual meetings of the Council was going on,
and was invited by the members to take part in some of their
deliberations. In the course of the conversations which
followed he expressed the opinion that systematic observations
in the Atlantic might throw much light on some of the problems
then being studied in our more northern seas.
Subsequently Sir John Murray wrote to me that if the
Norwegian Government would lend the "Michael Sars " and
her scientific staff for a four months' summer cruise in the
North Atlantic, he would pay all the other expenses.
When this proposal was laid before the Norwegian Govern-
ment it was favourably received, and within a few weeks a
satisfactory financial agreement was drawn up and adopted.
My scientific colleagues. Professor Gran, Dr. Helland- Hansen,
Mr. E. Koefoed, and Captain Thor Iversen, who had long been
vi DEPTHS OF THE OCEAN
associated with me in oceanographical investigations in the
Norwegian Sea, likewise received the proposal with enthusiasm.
A large part of the winter of 1909-10 was spent in making the
necessary rearrangements on board the ship, in the selection
and installation of new apparatus and instruments, and in
choosing the routes where we might expect to get the most
interesting results.
By the ist of April 19 10 the ship was fully equipped and
ready for sea. The first port of call was Plymouth, where
Sir John Murray embarked, and the last piece of apparatus —
a large centrifuge — was installed on board. After being
hospitably entertained by scientific men in London and
Plymouth, we sailed on the 7th of April for the south-west of
Ireland, where it was arranged that we should occupy our first
observing station. The ship worked down the western coasts
of Europe as far as the Canaries, then proceeded across the
Atlantic, by way of the Azores, to Newfoundland, afterwards
re-crossing from Newfoundland to the coast of Ireland, and
returned to Bergen by way of the Faroe Channel. About
1 20 observing stations were established, and the expedition was
in all respects successful.
It was agreed that the zoological and all other collections
and observations made during the cruise should be sent to
Bergen, Sir John Murray generously agreeing to provide ^500
to enable the collections to be sorted out and arranged for
study by specialists.
It was further arranged that a general account of the cruise
and of the results of the observations should be published as
soon as possible after the return of the expedition, and this
volume has accordingly been prepared. Its main object is to
indicate the most important results of the voyage in so far as
these can be stated at the present time, although the biological
collections and the physical observations have as yet only been
examined in a preliminary way. In preparing the various
DEPTHS OF THE OCEAN vii
chapters the previous investigations of the " Michael Sars " in
the North Sea and in the Norwegian Sea generally have been
taken into consideration, in order to compare the physical and
biological conditions prevailing in northern waters with those in
the Atlantic. In this way it is hoped that the book as a whole
will present the student with a fairly complete epitome of recent
advances in the modern science of oceanography, even though
it has proved impossible to give a complete review of the
literature of the subject.
The historical chapter and the chapter on the Depths and
Deposits of the Ocean have been prepared by Sir John Murray ;
that on Physical Oceanography by Dr. Helland- Hansen ; that
on Phytoplankton by Professor Gran ; and that on the Bottom
Fauna by Professor Appellof, while the chapters dealing with
the equipment of the ship, the working of the gear, the narra-
tive of the cruise, the fishes from the sea-bottom, the pelagic
animals, and general biology have been written by myself
In the examination of the zoological collections I have
received most valuable assistance from Mr. James Grieg,
Mr. Einar Koefoed (who took part in the expedition and also
in the special examination of the fishes), Mr. Einar Lea,
and Mr. Oscar Sund. All the original drawings have been
made by Mr. Thorolv Rasmussen, who also took part in the
cruise, and was continually engaged in making drawings and
sketches on board ship. To all these gentlemen I acknowledge
my indebtedness.
The biological collections have been distributed to
specialists in different parts of the world, and the following
have sent me preliminary reports on their results, which I
have been able to use in this book : —
Mr. Paul Bjerkan, Bergen ;
Dr. Kristine Bonnevie, Christiania ;
Dr. August Brinkmann, Bergen ;
Dr. Hjalmar Broch, Trondhjem ;
viii DEPTHS OF THE OCEAN
Professor Carl Chun, Leipzig ;
Mr. C. Dons, Tromso ;
Dr. P. P. C. Hoek, Haarlem ;
Dr. O. Nordgaard, Trondhjem ;
Professor G. O. Sars, Christiania ;
Professor R. Woltereck, Leipzig.
Sir John Murray's secretary, Mr. James Chumley, has
given us most valuable assistance by correcting the English
manuscript and taking care of all printing arrangements. Sir
John Murray wishes also to acknowledge the co-operation of
Dr. Caspari and the other assistants in the " Challenger " office
in correcting proofs and preparing the indexes of this book.
The authorities of the Bergen Museum have undertaken to
publish a detailed account of the voyage and of the physical and
biological observations, in a series of quarto volumes which
will be issued from the press at intervals during the next few
years. These more detailed reports will undoubtedly form
valuable contributions to the science of oceanography. I
hope also that this general account will be of use to those
engaged in the study of oceanography, and that it may lead to
further investigations in the North Atlantic — that wonderful
ocean bordered by nearly all the seafaring countries. As will be
seen from several of the following chapters. Sir John Murray's
well-known scientific views and his original ideas have been of
great value to this expedition. I wish therefore to express my
indebtedness to Sir John Murray, not only for the opportunity
of engaging in this interesting Atlantic cruise, but also for
his kindness in giving the benefit of his great experience to
the advancement of the undertaking.
JOHAN HJORT.
Bergen, February 19 12.
^1HABDM.74-T0ill,
CONTENTS
Table I. for converting Metres into Fathoms . . . xiii
„ II. for converting Degrees Fahrenheit into Degrees
Centigrade ...... xiv
,, III. showing Mean Temperature at Various Depths for
THE Whole Ocean ..... xvi
„ IV. showing Positions of " Michael vSars " Stations , xvii
CHAPTER I
A Brief Historical Review of Oceanographical Investigations
CHAPTER II
The Ship and its Equipment
CHAPTER III
The Work and Cruises of the " Michael Sars
52
CHAPTER IV
The Depths and Deposits of the Ocean .
129
CHAPTER V
Physical Oceanography
39637
X DEPTHS OF THE OCEAN
CHAPTER \T
I'AGE
Pelagic Plant Life ....... 307
CHAPTER Vn
Fishes from the Sea-Bottom . . . . -387
CHAPTER Vni
Invertebrate Bottom Fauna of the Norwegian Sea and North
Atlantic . . . . . . .457
CHAPTER IX
Pelagic Animal Life ....... 561
CHAPTER X
General Biology ....... 660
INDEXES
Index of Proper Names ...... 787
Index of Genera and Species . . . . .791
General Index ....... S09
MAPS AND PLATES
Map I. Reproduction of Lieut. Maury's Map of the North Atlantic,
1854
„ II. Bathymetrical Chart of the Oceans showing the " Deeps,'
according to Sir John Murray
,, III. Depths of the North Atlantic compiled from the latest
sources, 191 1 .
,, IV. Deposits of the North Atlantic, after Sir John Murray
Plate I. Cyclothone .
,, II. Argyropelecus and Gonostoma
,, III. Red-coloured Shrimps
„ IV. Flying-Fish and Pilot-Fish .
„ V. Sargasso Fish
„ VI. Sargasso Crabs
„ VII. Coast Fishes from the bottom
,, VIII. Deep-Sea Fishes from the bottom
,, IX. Bathytroctes
DEPTHS OF THE OCEAN
I. Table for Converting Metres into Fathoms
Metres.
Fathoms.
Metres.
Fathoms.
I
0-55
200
109.36
~
1.09
300
164.04
3
1.64
400
218.73
4
2.19
SCO
273-41
5
2-73
600
328.09
'
3-28
700
382.77
7
3.83
800
437-45
8
4-37
900
492.13
9
4.92
1,000
546.82
lO
5-47
2,000
1,093.63
20
10.94
3,000
1,640.45
3°
16.40
4,000
2,187.27
40
21.87
5,000
2,734.08
50
27-34
6,000
3,280.90
60
32.S1
7,000
3,827.72
70
3S.2S
8,000
4>374-53
So
43-75
9,000
4,921.35
•90
49-21
10,000
5,468.16
100
54.68
DEPTHS OF THE OCEAN
II. Table for Converting Degrees of Fahrenheit into
Degrees of Centigrade
°F.
°c.
°F.
°c.
"¥.
°C.
°F.
"C.
°F.
°C.
1
80.0
26.67
75-5
24.17
71.0
21.67
66.5
19.17
62.0 \
16.67
79-9
26.61
75-4
24.'! r
70.9
21.61
66.4
19. II
61.9
16.61
79.8
26.56
75-3
24.05
70.8
21.56
66.3
19.05
61.8
16.56
79-7
26.50
75-2 :
24.00
70.7 !
21.50
66.2
19.00
61.7
16.50
79.6
26.44
■ 75-1
23-95
70.6 1
21.44
66.1
18.95
61.6
16.44
79-5 i
26.39
75-0 i
23-S9
70.5 1
21.39
66.0 1
18.89
61.5
16.39
79-4
26.33
74-9
23-83
70.4
21.33
65-9
18.83
61.4
16.33
79-3
26.28
74-8
23.78
70.3
21.28
65.8
18.78
61.3
16.28
79.2 j
26.22
74-7
23.72
70.2
21.22
65-7
18.72
61.2
16.22
79-1
26.17
74-6
23.67
70.1
21.17
65.6
18.67
61. 1
16.17
79-0
26.11
74.5
23.61
70.0
21. II
65.5
18.61
61.0
16. II
78.9
26.05
74-4
23-56
69.9
21.05
65-4
18.56
60.9
16.05
78.8
26.00
74-3
23-50
69.8
21.00
65-3
18.50
60.8
16.00
78.7
25-95
74.2
23-44
69-7
20.95
65.2
18.44
60.7
15-95
78.6
25.89
74-1
23-39
69.6
20.89
65.1
18.39
60.6
15.89
.78.5
25-83
74.0
23-33
69-5
20.83
65.0
18.33
60.5
15-83
78.4
25.78
73-9
23.28
69.4
20.78
64.9
18.28
60.4
15-78
78.3
25-72
73-8
23.22
69-3
20.72
64.8
18.22
60.3
15-72
78.2
25.67
73-7
23-17
69.2
20.67
64.7
18.17
60.2
15-67
78.1
25.61
73-6
23.11
69.1
20.61
64.6
18.11
60.1
15.61
78.0
25-56
73-5
23-05
69.0
20.56
64.5
18.05
60.0
15-56
77-9
25-50
73-4
23.00
68.9
20.50
64.4
18.00
59-9
15-50
77.8
25-44
73-3
22.95
68.8
20.44
64.3
17-95
59-8
15-44
77-7
25-39
73-2
22.89
68.7
20.39
64.2
17.89
59-7
15-39
77.6
25-33
73-1
22.83
68.6
20.33
64.1
17-83
59-6
15-33
77-5
25.28
73-0
22.78
68.5
20.28
64.0
17.78
59-5
15.28
77-4
25.22
72.9
22.72
68.4
20.22
63-9
17.72
59-4
15.22
77-3
25-17
72.8
22.67
68.3
20.17
63.8
17.67
59-3
15-17
77.2
25.11
72.7
22.61
68.2
20.11
63-7
17.61
59-2
15.11
77.1
25-05
72.6
22.56
68.1
20.05
63.6
17-56
59-1
15-05
77.0
25.00
72.5
22.50
68.0
20.00
63-5
17-50
59-0
15.00
76.9
24-95
72.4
22.44
67.9
19.95
63.4
17.44
58.9
14-95
76.8
24.89
72.3
22.39
67.8
19.89
63-3
17-39
58.8
14.89
76.7
24.83
72.2
22.33
67.7
19.83
63.2
17-33
58.7
14.83
76.6
24.78
72.1
22.28
67.6
19.78
63.1
17.28
58.6
14.78
76.5
24.72
72.0
22.22
67.5
19.72
63.0
17.22
58.5
14.72
76.4
24.67
71.9
22.17
67.4
19.67
62.9
17.17
58.4
14.67
76.3
24.61
71.8
22.1 1
67-3
19.61
62.8
17.11
58.3
14.61
76.2
24.56
71.7
22.05
67.2
19.56
62.7
17.05
58.2
14.56
76.1
24.50
71.6
22.00
67.1
19.50
62.6
17.00
58.1
14.50
76.0
24.44
71-5
21.95
67.0
19.44
62.5
16.95
58.0
14.44
75-9
24-39
71.4
21.89
66.9
19-39
62.4
16.89
57.9
14.39
75.8
24-33
71-3
21.83
66.8
19-33
62.3
16.83
57-8
14.33
75-7
24.28
71.2
21.78
66.7
19.28
62.2
16.78
57.7
14.28
75-6
24.22
71. 1
''■''
66.6
19.22
62.1
16.72
57.6
14.22
DEPTHS OF THE OCEAN ^
II. Table for Converting Degrees of Fahrenheit into Degrees of
C^^TlG^Mi-E— Continued
°F.
°C.
"F.
°C.
°F.
°C.
°F.
°C.
°F.
°C.
57-5
14.17
52-9
II. 61
48.3
9-05
43-7
6.50
39-1
3-95
57-4
14.11
52.8
11.56
48.2
9.00
43-6
6.44
39-0
3-89
57-3
14.05
52-7
11.50
48.1
8-95
43-5
6-39
38-9
3-83
57-2
14.00
52.6
11.44
48.0
8.89
43-4
6.33
38.8
3-78
57-1
13-95
52-5 i
11-39
47-9
8.83
43-3
6.28
38.7
3-72
57-0
13.89
52.4
11-33
47-8
8.78
43-2
6.22
38.6
3-67
56.9
13-83
52-3
11.28
47-7
8.72
43-1
6.17
38.5
3.61
56.8
13-78
52.2
11.22
47-6
8.67
43-0
6.11
38.4
3-56
56.7
13.72
52.1
11.17
47-5
8.61
42.9
6.05
38.3
3-50
56.6
13.67
52.0
II. II
47-4
8.56
42.8
6.00
38.2
3-44
56.5
13.61
51-9
11.05
47-3
8.50
42.7
5-95
38.1
3-39
56-4
13-56
51-8
11.00
47-2
8.44
42.6
5-89
38.0
3-33
56.3
13-50
51-7
10.95
47-1
8-39
42.5
5-83
37-9
3-28
56.2
13-44
51.6
10.89
47-0
8.33
42.4
5-78
37-8
3.22
56.1
13-39
51-5
10.83
46.9
8.28
42.3
5-72
37-7
3-17
56.0
13-33
51-4
10.78
46.8
8.22
42.2
5-67
37-6
3-11
55-9
13.28
51-3
10.72
46.7
8.17
42.1
5.61
37-5
3-05
55-8
13.22
51.2
10.67
46.6
8.11
42.0
5-56
37-4
3.00
55-7
13-17
51. 1
10.61
46.5
8.05
41.9
5-50
37-3
2-95
55-6
13.11
51.0
10.56
46.4
8.00
41.8
5-44
37-2
2.89
55-5
13-05
50-9
10.50
46.3
7-95
41.7
5-39
37-1
2.83
55-4
13.00
50.8
10.44
46.2
7.89
41.6
5-33
37-0
2.78
55-3
12.95
50.7
10.39
46.1
7-83
41-5
5.28
36-9
2.72
55-2
12.89
50.6
10.33
46.0
7-78
41.4
5.22
36.8
2.67
55-1
12.83
50-5
10.28
45-9
7.72
41-3
5-17
36-7
2.61
55-0
12.78
50-4
10.22
45-8
7.67
41.2
5-11
36.6
2.56
54-9
12.72
50-3
10.17
45-7
7.61
41. 1
5-05
36.5
2-50
54.8
12.67
50.2
10. II
45-6
7-56
41.0
5.00
36.4
2.44
54-7
12.61
50.1
10.05
45-5
7-50
40.9
4-95
36.3
2-39
54.6
12.56
50.0
10.00
45-4
7-44
40.8
4-89
36.2
2-33
54-5
12.50
49-9
9-95
45-3
7-39
40.7
4-83
36.1
2.28
54-4
12.44
49-8
9.89
45-2
7-33
40.6
4-78
36.0
2.22
54-3
12.39
49-7
9-83
45-1
7.28
40.5
4-72
35-9
2.17
54-2
12.33
49.6
9-78
45-0
7.22
40.4
4-67
35-8
2. II
54-1
12.28
49-5
9.72
44-9
7.17
40.3
4-61
35-7
2.05
54-0
12.22
49-4
9.67
44-8
7.11
40.2
4-56
35-6
2.00
53-9
12.17
49-3
9.61
44-7
7-05
40.1
4-50
35-5
1-95
53-8
i 12. II
49-2
9-56
44.6
7.00
40.0
4-44
35-4
1.89
53-7
12.05
49.1
9-50
44-5
6.95
39-9
j 4-39
35-3
1.83
53.6
12.00
49.0
9-44
44.4
6.89
39-8
1 4-33
35-2
1.78
53-5
11-95
48.9
9-39
44-3
i 6.83
39-7
' 4-28
35-1
1.72
53-4
11.89
48.8
9-33
44.2
6.78
39-6
1 4.22
35-0
1.67
53-3
11.83
48.7
9.2S
44.1
6.72
39-5
4-17
34-9
1.61
53-2
11.78
48.6
9.22
44.0
6.67
39-4
4-II
34-8
1.56
53-1
11.72
48.5
9.17
43-9
6.61
39-3
4-05
34-7
1.50
53-0
11.67
48.4
9.11
43-8
6.56 .
39-2
4.00
34-6
1-44
DEPTHS OF THE OCEAN
II. Table for Converting Degrees of Fahrenheit into Degrees of
Centigrade — Continued
°F.
.°c.
°F.
°C.
°F.
°C.
°Y.
°C.
°F.
°C.
34-5
1-39
33-1
0.61
31.8
- 0.1 1
30-5
-0.83
29.2
-1.56
34-4
^■Zl
2,Z-''
0.56
31-7
-0.17
30-4
-0.89
29.1
- 1. 61
34-3
1.28
32-9
0.50
31.6
- 0.22
Z^-Z
-0-95
29.0
-1.67
34-2
1.22
32.8
0.44
31-5
-0.28
30.2
- 1. 00
28.9
- 1.72
34-1
1. 17
32.7
0-39
31-4
-o-ZZ
30.1
- 1-05
28.8
-1.78
34-0
I. II
32.6
0.33
31-3
-0-39
30.0
- I. II
28.7
-1-83 1
33-9
1.05
32-5
0.28
31.2
-0.44
29.9
- i-U
28.6
-1.89
33-8
1. 00
32.4
0.22
3I-I
- 0.50
29.8
- 1.22
28.5
-1-95 1
33-7
0.95
32.3
0.17
31.0
-0.56
29.7
-1.28
28.4
- 2.00
33-6
0.89
32.2
0. II
30-9
- 0.61
29.6
- 1-33
28.3
-2.05 I
33-5
0.83
32.1
0.05
30.8
- 0.67
29-5
-1-39
28.2
- 3. II
33-4
33-3
0.78
0.72
32.0
0.00
30-7
30.6
-0.72
-0.78
29.4
29-3
- 1-44
-1.50
28.1
28.0
-2.17
- 2.22
31-9
- 0.05
33-2
0.67
III. Table showing Decrease of Mean Temperature with
Increase of Depth for the whole Ocean
Calculated from the " Challenger " and all other observations available up to the year 1S95.
Depth.
Temperature.
Fathoms.
Metres.
°F.
°C.
100
183
60°. 7
i5'-95
200
366
50°. I 1 10^05
300
549
44'-7 ' 7 -05
400
732
4i°.8 i 5 .44
500
914
40 .1 4 .50
600
1097
39.0 3°.89
700
1280
38°-i 3-39
800
1463
37°-3 2°.95
900
1646
36°.8 , 2°.67
1000
1829
36^5 . 2^.50
1 100
2012
36°. I 1 2°. 28
1200
2195
35°-8
2 .11 -
1300
2377
35°-6
2 .00
1400
2560
35 -4
i°.89
1500
2743
35 -3
i°.83
2200
4023
35 -2
i\78
Except in the Norwegian Sea and in the North-West Atlantic to the south-east of Greenland,
the temperatures in the North Atlantic at all depths down to the bottom are above the means
for the whole ocean as given in this table. On the other hand, the temperatures in the North
Pacific in the same latitudes and depths are, for the most part, below these means.
DEPTHS OF THE OCEAN
IV. Table showing the Positions of the " Michael Sars "
Observing Stations, 1910
Night Stations where the nets were towed between midnight and dawn are distinguished
by asterisks.
Station.
Date.
Depth in
Metres.
Depth in
Fathoms.
From Plymouth to Gibraltar.
April
9
N.
49' 27'
10
49 30
10
49 32
lo-n
49^ 38'
16
51 24
16-17
50 33
17
49 54
18
48° 53'
18
47° 49'
19-21
45° 26'
21
44 25
21
43 II
22
41 32
22
41 15
22-23
40° 56
23
40° 15
23
38° 20'
29-30
35° 56'
w.
8° 36
9° 42
10 49
II' 35
9° 27
10 42
12 10
11^ 31
10° 52
9 20
9° 18
9° 26
9° 05
8° 54
9° 28
9^ 23
9 43
5 43
146
149
184
923
68
168
[813
4700
166
78
69
154
i860
About 400
80
82
lOI
504
37
92
991
2570
91
42
38
"84
1017
219
From Gibraltar to Gran Canaria.
19
20
21
22
^23
'24
25 A
'25 B
26
27
28
29
30
31
32
33
'34
May
2-3
5
5
5
5-6
6-7
9
9
9-10
10
10
10
II
13-14
36°
5'
35
25
35
31
35
42
35
32
35
34
35
36'
35
46'
36"
53'
36^
31'
36^
0
35
10
34
38'
33
47'
33
27'
31'
17
28°
52'
4 42
6° 25
6° 35
6^51
7 7
7 35
8"2.s
8° 16
6° 48
7° I
7 19
7" 55
8° 22
8° 27
8" 32
10° 6
14° 16'
141
535
835
1215
1615
2300
2055
50
77
292
456
664
883
1258
1124
27
184
lOI
105
57
100
55
170
1187
DEPTHS OF THE OCEAN
IV. Table showing the Positions of the "Michael Sars"
Observing Stations, \()\o— Continued
Station.
Date.
Position.
Depth in Depth in
Metres. i Fathoms.
I
Between Gran Canaria and Cape Bojador (Africa).
35
36
37
38
39 A
'39 B
40
41
^42
May 18-19
27° 27'
14° 52'
2603
1424
„ 19-20
26° 12'
14° 26'
10
5
„ 20
26° 6'
14° 33'
39
21
„ 20
26° 3'
14° 36'
77
42
„ 20-21
26° 3'
15° 0'
214
116
„ 21
26° 3'
15° °'
267-280
146-15
„ 22-23
28° 15'
13° 29'
1197
655
M 23
28° 8'
13 35
1365
747
„ 23-24
28° 2'
14° 17'
From Gran Canaria to Fayal (the Azores).
43
44
*45
46
47
48
49 A
49 B
*49C
50
*5i
52
*53
54
55
*56
57
*S8
May 2 7
28
June I
26-29
29
1-2
4
5-6
6-7
8-9
10
10
lO-II
II
11-13
28°
2'
28"
37'
28"
42
28"
56'
29"
2
28"
54
29
6'
29"
8'
29
7
30
8'
31
20
31
24
34
59
35
37
36"
24
36"
53'
37
20
37
11
37
33
37
33
37
37
37
38
37
42
17
19°
20°
21°
22°
24°
25°
25°
25°
31°
35°
34°
ZZ
30°
29°
29°
29°
29°
29°
29°
29°
29°
29°
5160
3886
2615-2865
• 3185
3239
3239
1700
1510
1735
1235
948
990
2822
2124
1430-1567
1742
1770
1770
930
825
949
675
518
541
DEPTHS OF THE OCEAN
IV. Table showing the Positions of the "Michael Sars'
Observing Stations, igio—Co/ituu/ed
Station.
Date.
Position.
Depth in Depth in
Metres. Fathoms.
From the Azores to Newfoundland.
N.
w.
59
June 17
38° 30'
28^ 37'
225
123
60
„ 20
37° 9'
38° 5'
61
„ 20
37° 7'
38° 34'
...
62
„ 20-21
36° 52'
39° 55'
63
„ 22
36° 5'
43° 58'
5°35
2753
64
„ 24
34° 44'
47 52'
65
„ 25
37° 12'
48^ 30'
66
„ 26
39° 30'
49° 42'
67
„ 27
40° 17'
50° 39'
...
68
„ 28
39° 20'
50° 50'
69
„ 29
41° 39'
51° 4'
'.'.'.
70
„ 30
42° 59'
51° 15'
1 100
602
70 a
„ 30
...
71
„ 30
43° 18'
51° 17'
147-138
80-75
72
July I
44° 35'
51° 15'
75
41
73
„ I
45° 58'
51° 25'
70
38
74
5) 2
47" 25'
52' 20'
156
85
From Newfoundland to Glasgow.
75
July 9
76
9
77
„ 10
78
„ 10
79
„ 10
80
M II
81
„ 12
81 A
,, 12
82
V 13
83
„ 14
84
15
*85
" 15-
86
„ 16
87
,1 17
88
„ 18
88 a
„ 18
88 b
„ 19
16
47°
22'
47°
11'
47°
18'
47
17'
47°
16'
47°
34'
48°
2'
48°
24'
48"
30'
48"
4'
47
58'
47
29
46"
48'
45
26'
49° 16
47° 6
44° 54
44° 2>2
44° 17
43° II
39° 55
36° 53
2,2,' 35
32° 25
31° 41
30° 20
27° 46'
25° 45'
380
171
202
271
2157
3120
66
2^
93
no
147
1094
1180
1706
DEPTHS OF THE OCEAN
IV. Table showing the Positions of the "Michael Sars"
Observing Stations, i<^io— Continued.
Station.
Date.
Position.
Depth in
Depth in
Metres.
Fathoms.
1 "N-
\v.
89 Jul:
^ 20
45° 55
22° 24'
90
21
46^58
19° 6'
91
22
47° 32
16° 38'
4922
2691
*92
23-24
48° 29
13° 55'
93
25
50° 13
11° 23'
1257
687
94
26
50° 13
11° 23'
1565
856
*95
26-27
50^ 22
11° 44'
1797
983
96
27
50° 57
10° 46'
184
lOI
From Qlasg
ow to Bergen.
97 Au^
^ust 4
56° 15
8° 28'
139
76
98
5
56° 33
9° 30'
I 000- I 360
547-744
99
6
57° 45
13° 40'
149
82
100 ,
6
57° 48
'-° 43;
1530
836
lOI ,
, 6-7
57° 41
11° 48'
1853
1013
*I02
, 9-10
60° 57
4° 38'
1098
600
103
, 10
60° 26
2° 34'
159
87
104
, 10
60° 35
3° 20'
234
127
105
, 10
60° 45
3° 50'
670
366
106
, lO-II
60° 54
4° 28'
1 1 40
624
107
5 II
61° 4
5° 5'
730
399
108
) II .
61° 13
5° 47'
249
136
109
) II
61° 22
6° 24'
228
124
no
, 11-12
61° 39
5° 57'
170
93
III
, 12
61° 32
5° 15'
300
164
112
, 12
61° 24
4° 34'
560
306
TI3
, 12
61° 16
3° 50'
1080
591
114
, 12-13
61; 8
3° 16'
1047
573
"5
, 13-14
61° 0
2° 40' .
580
317
116
> 14
60° 52
2° i'
125
69
H.M.S. "Challenger
Shortenins; sail to sound.
CHAPTER I
A BRIEF HISTORICAL REVIEW OF OCEANOGRAPHICAL
INVESTIGATIONS
The phenomena displayed at the surface of the ocean have Development
been the object of observation from the earliest ages, — waves, scjenceTf^^'^'^
currents, winds, tides, and the temperature of the water were oceanography.
matters of very great importance and concern to the earliest
navigators. It was not, however, till about the time of the
famous "Challenger" Expedition, nearly forty years ago, that
any systematic attempts were made to examine the deeper and
more remote regions, or to explore the physical and biological
conditions of the ocean as a whole.
It seems desirable to commence this book by indicating, as
briefly as possible, the various steps by which the present
development of the modern science of oceanography has been
reached. This can best be accomplished by (i) pointing out
some of the scientific observations made previous to the
"Challenger" Expedition, (2) referring to the expeditions
contemporaneous with and subsequent to that expedition, and
{3) referring to the work carried out at marine biological
laboratories, and in connection with international and other
fishery investigations.
B
Early
soundines.
Cusanus"
bathometer.
Puehler's
apparatus.
Alberti's
apparatus.
Hooka's
apparatus.
First sound-
ings laid down
on maps.
First attempt
at deep-sea
sounding.
Magellan.
2 DEPTHS OF THE OCEAN chap.
From time immemorial soundings were taken by hand
with a plummet, always in shallow water near land, but attempts
have not been wanting to sound the ocean without the aid of a
line. Thus about the middle of the fifteenth century Cardinal
Nicolaus Cusanus invented a bathometer, consisting of a hollow
sphere with a heavy weight attached by means of a hook ; on
touching the bottom the weight was detached, and the sphere
returned to the surface, the interval of time from the launching
of the apparatus to the re-appearance of the sphere at the
surface indicating the depth. A century later Puehler improved
on Cusanus' bathometer by adding a piece of apparatus
(clepsydra) to measure the time from the disappearance to the
re-appearance of the float, using for this purpose a clay vase
with a small orifice at the bottom, through which water was
made to enter during the period of the experiment, the amount of
water in the vase indicating the depth. Alberti subsequently
replaced the sphere by a light, bent metal tube. In 1667
Robert Hooke described in the Philosophical Transactions a
similar apparatus, shown in the tailpiece to Chapter IV., with
which experiments were made in the Indian Ocean, but there
was always doubt as to the moment when the float returned
to the surface, and to remedy this Hooke introduced first a
clockwork odometer to register the descent, and then two
odometers — one for the descent and the other for the ascent.
These various forms of bathometers, though interesting historic-
ally, proved of little practical value.
Soundings in shallow water first appeared on a map by
Juan de la Cosa in 1504, and soundings were laid down
on maps by Gerard Mercator in 1585 and by Lucas Janszon
Waghenaer in 1586.
Probably the first attempt at oceanographical research to
which the term " scientific " may be applied is Magellan's
unsuccessful effort to determine the depth of the Pacific Ocean
during the first circumnavigation of the globe. In 1521, we
are told, Magellan tried to sound the ocean between the two
coral islands, St. Paul and Los Tiburones in the Low Archi-
pelago, making use of the sounding lines carried by explorers
at that period, which were only 100 to 200 fathoms in length.
He failed to touch bottom, and therefore concluded that he had
reached the deepest part of the ocean. This first authentic
attempt at deep-sea sounding ever made in the open sea is
historically extremely interesting, though scientifically the result
was negative.
OCEANOGRAPHICAL INVESTIGATIONS 3
The expedition of Edmund Halley, Astronomer-Royal, in Haiiey's
1699, to improve our knowledge concerning longitude and the expedition.
variation of the compass, was a purely scientific voyage, though
it may be said that scientific voyages were really initiated at
the time of James Cook in the second half of the eighteenth
century.
Cruquius introduced bathymetrical contours on a chart of the Bathymetricai
River Merwede published in 1728. Thus contour lines were Jownonmips.
first used on maps to show the depths of the sea and not the cruquius.
heights of the land.
In a map published by Philippe Buache in 1737 we find the Buache.
bottom of the sea again represented by isobathic curves,
intended to show that certain elevations of the sea-floor
correspond to the orography of the neighbouring land. He
develops these ideas in his Essay on Physical Geography,
published in 1752, maintaining that the globe is sustained by
chains of mountains crossing the sea as well as the land,
forming as it were the framework of the globe — a view
previously expressed by Father Athanasius Kircher. His Kirchei.
conception of submarine mountains was a first step towards
founding geography on the real form and relief of each region.
The dredge seems to have been first used by two Italians, First use of
Marsigli and Donati, about the year 1750, for obtaining marine ''^'^^•^^se-
organisms from shallow water, and a modification of this form Doiiatf/^"*^
was introduced by O. F. Muller in 1799, which was known as o. f. Muiier.
the naturalist's dredge.
In the middle of the eighteenth century Dalrymple and Temperature
Davy made observations on the temperature of the equatorial observations.
currents during a voyage to the East Indies. anc/Da?)!^
In 1770 Benjamin Franklin published the first map of the Benjamin
Gulf Stream (see figure in Chapter V.), and in 1776 Charles F'^nkiin.
Blagden was engaged in the study of temperature distribution ^^^g^'*^"-
on the North i^merican coasts, reporting on his results to the
Royal Society of London in 1781.
During Cook's voyages (1772-73), temperature observations James Cook,
beneath the surface were taken by the Forsters, father and son. The Forsters.
but the first use of self-registering thermometers for determining
the temperature beneath the surface of the sea was during Lord
Mulgraves' expedition to the Arctic in 1773 by Dr. Irvine, who Irvine.
seems also to have constructed a water-bottle for bringing up
water-samples from various depths, one sample giving a reading
of 40^ Fahr., while the surface temperature was 55^ Fahr.
I'ullcn.
4 DEPTHS OF THE OCEAN
During this expedition also some of the earhest attempts at
deep-sea sounding were made by Captain Phipps, the deepest
sounding being 683 fathoms, from which depth he brought up a
sample of Blue mud.
In 1780 Saussure determined the temperature of the
Mediterranean at depths of 300 and 600 fathoms by protected
thermometers, and in 1782 Six's maximum and minimum
thermometer was invented, and subsequently made use of by
Krusenstern in 1803, by Kotzebue in 18 15, by Sir John Ross
accompanied by Sir Edward Sabine in 18 18, by Parry in 1819,
and by Dumont d'Urville
in 1826. Slow-conduct-
ing water - bottles were
used by Peron in 1800,
by Scoresby in 181 1, who
recorded warmer water
beneath the colder sur-
face layers in the Arctic
regions, and by Kotzebue
accompanied by Lenz in
1823. Protected thermo-
meters were used for
deep - sea temperatures
by Thouars in 1832, by
Martins and Bravais in
1839, and by Sir James
Clark Ross during his
Antarctic expedition from
1839 to 1843, the last-
mentioned making also
many observations on
the density of the water at various depths. In 1843 Aime-
introduced reversible outflow thermometers, and about 1851
Maury used cylinders of non-conducting material for taking
temperatures in deep water. But it was only when thermo-
meters with bulbs properly protected from pressure came into
use that oceanic temperatures could be recorded with precision.
The first thermometer of this kind seems to have been used in
1857 by Captain Pullen of H.M.S. "Cyclops," and shortly
thereafter improved forms of the Six pattern (Miller-Casella)
and of Negretti and Zambra's reversing pattern were introduced,
and have been largely used ever since, improvements and
modifications being incorporated from time to time.
Captain James Cook.
OCEANOGRAPHICAL INVESTIGATIONS 5
Scoresby in 181 1 recorded some soundings off the coast of Deep
Greenland, and Sir John Ross during his voyage to Baffin's ^^""'^'"ss-
Bay in 181 7-1 8 took some deep soundings by means of an /r*^!^'
apparatus, designed by him and made on board, called " deep-
sea clamms," in depths of 450, 650, 1000, and 1050 fathoms,
bringing up from the last-mentioned depth several pounds of
greenish mud. With the deposit -samples worms and other Deep-sea
animals were brought up, and when sounding in 1000 fathoms ^n""^'^-
a star-fish was found entangled in the line a little distance above
the mud, thus proving that animal life was present in deep
water.
In 181 7 Romme published in Paris a work on winds, tides, Romme.
and currents, and Risso in 1826, Lowe from 1843 to i860, ^^isso.
Johnson from 1862 to 1866, and Giinther from i860 to 1870, ^°'^''-
published important papers dealing with deep-sea and pelagic Jo^"^^"-
fishes. In 1832 James Rennell published an investigation of ^""^^^''
the currents of the Atlantic Ocean, based upon the observations
recorded by sailors up to that time.
During the United States Exploring Expedition in 1839- wiikes and
1842 under Captain Wilkes, accompanied by Dana, several ^^"^■
deep soundings were taken with the aid of a copper wire, and
a few dredgings in shallow water were also made.
Important sounding and dredging work was carried out by
Sir James Clark Ross, accompanied by Hooker, during the
British Antarctic Expedition in 1839 to 1843, the first truly British
oceanic soundings in depths exceedino; 2000 fathoms being^ :^"''^''f5\^
o r^ o ^ <-> li,xpedition.
taken. After many unsuccessful attempts to sound in deep r^^^^^ ^^^.j^
water, due to the want of a proper line, Ross had a line 3600 Ross and
fathoms in length specially constructed on board. It was fitted °°^^''
with swivels here and there, strong enough to carry a weight of
76 lbs., and was allowed to run out from an enormous reel in
one of the ship's boats. With this line the first abysmal Soundings in
sounding on record was taken in 2425 fathoms on the 3rd ^4Ter'^^^'
January 1840, in lat. 27"" 26' S., long. 17° 29' W., and frequently
during the cruise similar and greater depths were sounded.
Such deep soundings could only be attempted in calm weather, introduction
and a note was kept of the time each lOO-fathoms mark left the °i[te,"!^is j,^
reel, a lengthening of the time-interval indicating when the sounding.
weight had reached the bottom. The dredge also was success- Dredgings in
fully used during this expedition in depths down to 400 ^^'^^i^ ^'''^^'^'■•
fathoms, abundant evidence of animal life being forthcoming,
though unfortunately the deep-sea zoological collections were
DEPTHS OF THE OCEAN
Hooker on
Antarctic
diatoms.
subsequently lost to science. In April 1840 the dredge came
up full of coral from a depth of 95 fathoms, and in the following
January dredgings in 270 and 300 fathoms gave abundance of
marine invertebrates in great variety, the deepest dredging in
400 fathoms in August 1841 bringing up some beautiful speci-
mens of coral, corallines, flustrae, and a few crustaceous animals.
Hooker made known some of Ross's results, and drew attention
to the great role played by diatoms in the seas of the far south.
Edward
Forbes.
Audouin and
INIilne-
Ed wards.
Michael Sars.
.Sir James Clark Ross.
In 1839 the British Association appointed a Committee to
investigate the marine zoology of Great Britain by means of
the dredge, the ruling spirit of this Committee being Edward
Forbes, who made many observations on the bathymetrical
distribution of life in various seas. Before this time, it is true,
Audouin and Milne-Edwards in 1830, and Michael Sars in
1835, had published the results of dredgings in comparatively
shallow waters within limited areas along the coasts of Europe.
In 1840-41 Forbes studied the fauna of the yEgean Sea,
OCEANOGRAPHICAL INVESTIGATIONS
7
taking a great majiy dredgings at different depths, and came to
the conclusion that marine animals were distributed in zones of
depth, each characterised by a special assemblage of species.
He divided the area occupied by marine animals into eight
zones, in which animal life gradually diminished with increase
of depth, until a zero was reached at about 300 fathoms. He
supposed that plants, like animals, disappeared at a certain
depth, the zero of vegetable life being at a less depth than that
of animal life. In his Report on the Investigation of British
Marine Zoology by means
of the Dredge (1850), Forbes
suggested that dredgings off
the Hebrides and the Shet-
lands, and between the
Shetland and Faroe Islands,
would throw much light on
marine zoology, thus point-
ing to the scene of the
subsequent important work
carried on by Carpenter
and Wyville Thomson, and
Murray and Tizard.
In 1844 Loven carried
on researches on the distri-
bution of marine organisms
along the Scandinavian
coasts, confirming and ex-
tendine the observations
recorded by Forbes, and m
1845 Johannes Mliller com-
menced to study the pelagic
life of the sea by examining
samples of sea-water and by
means of the tow-net, thus giving a great impetus to the study
of marine biology.
In 1845 Sir John Franklin set sail on his ill-fated North
Polar Expedition, accompanied by Harry Goodsir, who recorded
the results of dredging in depths of 300 fathoms.
In 1846 Spratt took dredgings in the Mediterranean down
to a depth of 310 fathoms; he afterwards brought up shell-
fragments from a depth of 1620 fathoms in the Mediterranean.
In 1850 Michael Sars published the results of his dredgings
off the coast of Norway, giving a list of 19 species living at
Forbes'
observations
in ^^igean Sea.
Marine
animals
distributed
in zones of
depth.
Zero of life
in the sea.
Professor Michael Sars.
John Franklin
and Goodsir.
Spratt.
Michael Sars
and G. O.
Sars.
8
DEPTHS OF THE OCEAN
depths greater than 300 fathoms. He was afterwards assisted
by his son, G. O. Sars, in carrying on this work, and in 1864
they gave a Hst of 92 species Hving in depths between 200 and
300 fathoms, and showed a few years later that marine Hfe was
abundant down to depths of 450 fathoms.
In 1856 Mac Andrew pubHshed the results of his observations
on the marine Mollusca of the Atlantic coasts of Europe and
northern Africa, giving a list of 750 species obtained in his
dredgings, which covered 43 degrees of latitude.
The oceanographical researches of the United States
Coast Survey may be said to date back to 1844, when the
Director, Bache, issued instructions to his officers to preserve
the deposit-samples brought up by the sounding-machine.
J. W. Bailey studied these deposit-samples, and published the
result of his examination in 1851, followed in 1856 by other
papers on deposits and on the formation of greensand in
modern seas.
The name of M. F. Maury, of the United States Navy, was
for a long period associated with the hydrographical work of
the United States. He issued several editions of his Sailing
Directions to accompany the wind and current charts published
by the U.S. Hydrographic Office, the last edition appearing in
1859. About this time the need was felt for an improved and
more trustworthy method of sounding in deep water, and
various attempts were made to devise forms of apparatus to
replace the heavy weight attached to a line which had to be let
down and then drawn up to the surface again, the difficulty
being to know when the weight touched the bottom. This
problem was finally solved by Midshipman Brooke, who
conceived the idea of detaching the weight used to carry down
the sounding lead upon striking the bottom, the sounding tube,
enclosing its deposit-sample, being alone drawn to the surface.
He used a spherical weight (a bullet), with a hole passing
through the centre to receive the sounding tube, suspended by
a cord to the upper part of the sounding tube ; on touching the
bottom the cord was thrown off its support and remained at the
bottom along with the weight. With the aid of Brooke's
sounding apparatus, the records of deep-sea soundings rapidly
accumulated, and enabled Maury to prepare the first bathy-
metrical map of the North Atlantic Ocean, with contour-lines
drawn in at 1000, 2000, 3000, and 4000 fathoms, which was
published in 1854 and is reproduced in Map I. The deposit-
REPRODUCTION OF LIEUT MAURY S MAP OF NORTH ATLANTIC, 1854.
stematic
soundings.
Berryman.
OCEANOGRAPHICAL INVESTIGATIONS 9
samples procured were examined and described by Bailey and romtaies
by Pourtales, the results being of great importance and interest.
Systematic soundings in the North Atlantic were commenced Sy
by Lee in the U.S.S. "Dolphin" in 1851-52, and continued in
the same vessel by Berryman in 1852-53. In 1856 Berryman
on the U.S.S. "Arctic" sounded across the North Atlantic
from Newfoundland to Ireland, with the object of verifying the
existence of a submarine ridge, along which it was proposed to
lay a telegraph cable ; his deposit-samples were described by
Bailey.
In 1857 Pullen and Dayman in H.M.S. "Cyclops" ran a ruiien and
line of soundings along the great circle from Ireland to ^^y"''^"-
Newfoundland, a little to the north of Berryman's line. A
modification of Brooke's sounding-machine was used, in which
the spherical weight was replaced by a cylindrical one suspended
by wire instead of cord, and with a different valve for
collecting the deposit. The deposit-samples were examined
and described by Huxley, who found in the bottles a viscous Huxley,
substance, described by him as BatJiybms, which was subse- Bathybins.
quently shown by the "Challenger" observers to be a chemical
precipitate thrown down from the sea-water associated with the
deposits by the alcohol used in their preservation.
In 1858 Dayman in H.M.S. " Gorgon " sounded across the Dayman.
North Atlantic from Newfoundland to the Azores, and thence
to the south-west of England.
In i860 Sir Leopold M'Clintock on board H.M.S. M'Ciintock
"Bulldog" surveyed the route for the telegraph cable between ^"'^ ^^ ^iii^h.
England and America, in the region previously sounded by
Berryman and Dayman. He was accompanied by G. C. Wallich,
who published in 1862 an interesting account of the very
important observations he made during the cruise on life in
deep water and on the deposits covering the floor of the
North Atlantic.
In i860 a teleo^raph cable laid alone: the bed of the Animals
Mediterranean gave way at a depth of 1200 fathoms, and was subnmrine°
raised for repair by Fleeming Jenkin, who brought up to the cable.
surface portions of the cable about forty miles in length, to
which living organisms were found attached. Corals were
growing on the cable at the place where it broke in 1200
fathoms, and other forms were adhering to the cable where
it had lain in lesser depths, including molluscs, worms, bryozoa,
alcyonarians, and hydroids, thus establishing beyond all doubt
lO
DEPTHS OF THE OCEAN
the fact that members of the higher groups of animals really
lived at great depths in the sea.
Since 1861 Swedish and Norwegian expeditions to the
Arctic regions and the North Atlantic have been numerous,
and during one of these in 1864 many animals were dredged
from depths of 1000 to 1400 fathoms by Otto Torell. In the
same year Bocage published a paper on the occurrence of the
glass-rope sponge {Hyalonema) at depths of 500 fathoms off the
coast of Portugal, which was confirmed in 1868 by Perceval
Wright, who went there for the purpose and dredged up
specimens from 480 fathoms.
From the year 1867 dredgings as well as soundings were
carried out under the auspices of the United States Coast
Survey by Pourtales and Louis
Agassiz off the coast of Florida, and
between Cuba and Florida. Pour-
tales took up the examination of the
deposit-samples after the death of
Bailey, the number of samples
collected up to 1870 being nine
thousand. Louis Agassiz reported
on the results of the dredgings, and
compared some of the dredged
forms with fossil types ; he con-
cluded by stating his conviction that
the continental areas and the oceanic
areas have occupied from the earliest
times much the same positions as at
the present day.
■' Sir C. Wvvili.e ThOxMson.
In 1868 were commenced a series of short cruises in the
North Atlantic and Mediterranean, under the direction of
British naturalists, which may be regarded as preliminary and
leading up to the great "Challenger" Expedition. Thus in
1868 Wyville Thomson and W. B. Carpenter carried out
oceanographical work on board H.M.S. "Lightning," taking
dredgings in depths down to 650 fathoms, and showing beyond
question that animal life is there varied and abundant, repre-
sented by all the invertebrate groups, a large proportion of
the forms belonging to species hitherto unknown, others being
specifically Identical with tertiary fossils hitherto believed to
be extinct, or illustrating extinct groups of the fauna of more
remote periods. The temperature observations seemed to
OCEANOGRAPHICAL INVESTIGATIONS ii
disclose two adjacent regions in which the bottom tern- Peculiar
peratures differed as much as 15° Fahr. (30^ Fahr. in the l-ondSonsTn
one region and 45 Fahr. in the other), and it was con- the Faroe
eluded that great masses of water at different temperatures ^^^""'^'•
were moving about, each in its particular course, maintaining
a remarkable system of oceanic circulation, and yet keeping
so distinct from one another that one hour's sail might be
sufficient to pass from the extreme of heat to the extreme of
cold.
In 1869 Gwyn Jeffreys was associated with Carpenter and h.m.s.
Wyville Thomson in carrying on the work on board H.M.S. "i^o'cupme."
"Porcupine," which made three cruises: (i) to the west of carp'^nter,
Ireland, where dredgings down to 1470 fathoms were taken; and Thomson.
(2) to the Bay of Biscay, where dredgings were taken in depths
exceeding 2000 fathoms; and (3) to the Faroe Channel to
confirm and extend the "Lightning" observations. In 1870
the " Porcupine " carried on work in the Mediterranean and
the Strait of Gibraltar, which was continued in 1871 on board
H.M.S. "Shearwater."
About the same time Leigh Smith made several voyages Leigh Smith.
to the Arctic regions, and, like Scoresby, recorded warmer layers
of water beneath the colder surface waters of the Arctic Ocean. ^
The researches briefly noticed in the preceding paragraphs The
paved the way for the special investigation of the physical, E^J^gdidon^'^
chemical, and biological conditions of the great ocean basins
of the world carried out on board H.M.S. "Challenger" from
December 1872 to May 1876 by a staff of scientific observers.
During this period she circumnavigated the world, traversed
the great oceans in many directions, made observations in
nearly all departments of the physical and biological sciences,
and laid down the broad general foundations of the recent
science of oceanography. The results of the "Challenger"
Expedition were published by the British Government in fifty
quarto volumes, and became the starting-point for all subsequent
observations.
Contemporaneous with the " Challenger " Expedition was The
that of the U.S.S. " Tuscarora," under Belknap, in the Pacific ^^'''^^^'°'^'^'
Ocean, which contributed greatly to our knowledge of the
' Leigh Smith's temperature observations were pubhshed in Proc. Roy. Soc. Loud., vol. xxi.
pp. 94 and 97, 1873, and in Natural Science, vol. xi. p. 48, 1897. In the former paper Wells
(juotes a reading of 64° F. in 600 fathoms and a reading of 42° F. at 300 fathoms near Spitz-
bergen, and argues that they indicate the southward flow of a vast body of warm water from the
circumpolar region, while in the latter paper Leigh Smith refers to a warm undercurrent running
into the Arctic basin between Greenland and Spitzbergen.
The
" Albatross.
12 DEPTHS OF THE OCEAN
distribution of temperature in that ocean and of the deep-sea
deposits covering its floor. Piano wire was first used for
oceanic sounding work on board the " Tuscarora," though for
some years previously Sir WilHam Thomson (Lord Kelvin)
had been experimenting with it on board his yacht.
Also contemporaneous with the "Challenger" Expedition
was the circumnavigating cruise of the German ship "Gazelle,"
during which many
valuable oceanograph-
ical observations were
recorded.
In 1876 the U.S.S.
"Gettysburg" took a
series of deep - sea
soundings in the North
Atlantic, and in the
years 1876 to 1878
the Norwegian North
Atlantic Expedition on
board the S.S. " Vorin-
gen " made important
physical and biological
observations in the seas ;
between Norway and
Greenland, making thus
the first survey of the
Norwegian Sea ; the
scientific results were
published in English
and Norwegian.
From 1877 to 1880
the United States Coast Survey steamer " Blake" explored the
Caribbean Sea, the Gulf of Mexico, and the coasts of Florida,
under the direction of Alexander Agassiz, who published in
1888 a general account of the results. At the same time the
U.S. Fish Commission steamer "Albatross" was engaged in
making observations along the Atlantic coast of the United
States, and later, in 1891, explored the Panamic region of the
Pacific under the direction of Alexander Agassiz.
During the " Challenger" Expedition the naturalists became
convinced, as a result of their observations in different parts
of the world, that a ridge must separate the bodies of cold
and warm water found by the "Lightning" and "Porcupine"
Dr. Alexander Agassiz.
OCEANOGRAPHICAL INVESTIGATIONS 13
Expeditions to occupy the Faroe Channel. On the representa-
tions of Murray and Tizard, H.M.S. " Knight Errant" in 1880, i^iunayand
and H.M.S. "Triton" in 1882, were engaged in re-examining j^^^/i^-j^i^u
the Faroe Channel. The result was the discovery of the Errant."' "
Wyville Thomson Ridge, which separates the warm and cold The "Triton."
areas, and accounts for the great difference in the marine faunas Wyviiie
in the deep water on either side of this ridge. Detailed lists of Rid^.^°"
the animals obtained by these four expeditions were published
in a paper by Murray,^ who shows that 216 species and varieties
were recorded from the warm area, and 217 species and varieties
from the cold area, while only 48 species and varieties were
found to be common to the two areas.
From 1880 to 1883 the French ships " Travailleur " and The
"Talisman" investigated the eastern Atlantic, while from 1881 ;|,Travaiiieur."
to i88s the Italian ships " Washing^ton " and " Vettor Pisani," "Talisman."
the former in the Mediterranean and the latter during a ington." ^^
circumnavigating cruise, were eno-apfed in biologrical and other The"Vettor
. ,-r ^ 1 ^ ^ ^ * Pisani."
scientihc work.
In 1883 J. Y. Buchanan took part in the sounding expedi- ]■ v.
tion of the S.S. " Dacia," belonging to the India- Rubber, ^JJ^ ,^"j^"^j^„
Gutta-Percha, and Telegraph Works Company, of Silvertown,
when surveying the route for a submarine cable from Cadiz to
the Canary Islands, which resulted in the discovery of several
oceanic shoals rising steeply from deep water ; and again in
1885-86 he joined the same company's S.S. " Buccaneer" while The
exploring the Gulf of Guinea, accompanied by a trained natural- "buccaneer. '
ist, John Rattray, when valuable observations as to the depth, john Rattray.
temperature, density, currents, and plankton were made.
During the years 1883 to 1886 the U.S.S. " Enterprise" The "Enter-
brought together a most important collection of deposit-samples p"^^"
taken throughout a cruise embracing all the great oceans.
From 1884 to 1892 Murray investigated the sea- lochs John Murray,
along the west coast of Scotland on board his steam-yacht, the
" Medusa," and discovered in the deeper waters of Loch Etive ^^jg^j^i^^ -
and Upper Loch Fyne remnants of an Arctic fauna. The
physical results obtained were used by Mill in his Memoir on h. r. Miu.
the Clyde Sea Area.-
Since the year 1885 the Prince of Monaco has carried on rrince of
oceanographical work in a systematic manner in the Mediter-
^ "The Physical and Biological Conditions of the Seas and Estuaries about North Britain,"
Proc. Phil: Soc. Glasgow, vol. xvii. p. 306, 1886.
- Trans. Roy. Soc. Edin., vols, xxxvi. and xxxviii., 1891, 1894.
14 DEPTHS OF THE OCEAN
ranean and North Atlantic on board his yachts " Hirondelle,''
'' Hirondelle H," " Princesse Alice," and " Princesse Alice H,"
H.S.H. The Prince of Monaco.
and he has founded and endowed a magnificent oceanographical
museum at Monaco and an oceanographical institute in Pans ;
many important memoirs have been issued from the Monaco
press.
OCEANOGRAPHICAL INVESTIGATIONS 15
From 1886 to 1889 the Russian steamer " Vitiaz," under
Makaroff, made a voyage round the world, during which
valuable observations on the temperature and specific gravity
of the waters of the North Pacific were made, and in 1890
Russian scientists, notably Lebedinzeff and Andrusoff, investi-
gated the physical and biological conditions in the deep water
of the Black Sea.
In 1889 a German expedition on board the S.S. " National"
was despatched to the
The "Vitiaz.'"
Makarofi'.
Lebedinzeff
and Andrusoff
Observations
in Black Sea.
The
'• National.
Plankton
Expedition.
Professor Victor Hensen.
North Atlantic, with the
special object of study-
ing the plankton (hence
called the Plankton Ex-
pedition) by improved
methods, under the
direction of Victor
Hensen, who was ac-
companied by several
other scientific men.
From 1 890 till 1898
the Austrian steamer
" Pola " made observa-
tions in the Mediter-
ranean and the Red
Sea, the chemical work
being in the hands of
Natterer, whopublished Natterer,
someinterestingresults.
In 1890 systematic
observations in the
North Sea and adjacent
waters were commenced
by Swedish investiga-
tors under Otto Petters-
The " Pc
son and Gustav Ekman, important results as to temperature,
salinity, alkalinity, currents, gases, and plankton being achieved,
a summary of which was published by Pettersson in English.^
During the years 1893 to 1896 Nansen made his remarkable
drift on board the " Fram " across the North Polar Sea, during
which valuable oceanographical observations were taken, his
soundings tending to prove that the position of the North Pole
is occupied not by land but by a deep sea, as Murray had
1 Scott. Geogr. Mag., vol. x., 1S94.
O. Pettersson
and
G. Ekman.
Nansen's drift
in the
" Fram.'"
i6
DEPTHS OF THE OCEAN
The
•' Valdi/ia/
Chun.
previously indicated. His scientific results were published in
the English language in six handsome volumes.
During 1895 and 1896 the Danish ship " Ingolf " was
engaged in the investigation of the northerly portions of the
Atlantic, the physical and biological results being published in
English.
From 1897 to 1909 Sir John Murray, associated at first
with F, P. Pullar and afterwards with Laurence Pullar, carried
out a bathymetrical survey of the Scottish fresh-water lochs,
including detailed physical and biological observations, and the
report on the scientific results was published in six volumes in
1 9 10. During these investigations very careful observations
were made by Chrystal on seiches, as a result of which our
knowledge of these oscillations and their causes was widely
extended. Another kind of oscillation was also discovered,
which has been called the temperature seiche. This occurs at
the discontinuity layer, where there is a rapid fall of temperature.
This temperature oscillation in Loch Ness had a period of
about three days, and a maximum rise and fall of about 200
feet. The period of these oscillations is dependent on the
difference in density between the upper warm layer and the
lower cold layer : the smaller the difference in density, i.e. the
smaller the temperature differences in a lake, the longer does the
period of the oscillation become. These observations in the
Scottish lakes have recently been extended by further systematic
work in Loch Earn under E. M. Wedderburn, and have already
suggested explanations of phenomena in the ocean, where long-
period oscillations are observed in various depths, and the
explanation is probably the same as that given for the lakes.
In the years 1897 to 1899 the Belgian Antarctic Expedition
on board the " Belgica " carried on important work. This was
the first vessel to winter in the Antarctic regions, and the
scientific results are necessarily of great interest and value.
In 1898-99 the German Deep-Sea Expedition on board the
" Valdivia" investigated the physical and biological conditions
of the Atlantic and Indian Oceans, penetrating into the
Antarctic as far as the ice would permit. The extremely
valuable scientific results are being issued in a series of
magnificent memoirs under the editorship of Chun, the leader
of the expedition.
In 1899 the U.S.S. "Nero" surveyed the route for a
telegraph cable between the Sandwich and Philippine Islands
by way of Midway and Ladrone Islands, many of the soundings
OCEANOGRAPHICAL INVESTIGATIONS 17
being in very deep water, including the deepest cast hitherto
recorded, viz. 5269 fathoms, in the vicinity of Guam Island in
the Ladrone group. The deposit-samples brought home were
examined by Flint, ^ who records many distinct patches of
Diatom ooze within the tropics, but Murray has examined these
samples, and declares them to be identical with what he has
called Radiolarian ooze ; the frustules of the large Coscinodiscus
rex are, however, very numerous in these deposits.
In 1899-1900 the
U.S.S. "Albatross"
carried on oceano-
graphical observations
throughout the tropical
portions of the Pacific,
under the personal
direction of Alexander
Agassiz,who issued the
scientific results in a
series of profusely illus-
trated memoirs, under
the auspices of the
Museum of Compara-
tive Zoology, Cam-
bridge, Mass.
In 1 899-1 900 the
Dutch steamer " Sib-
oga " investigated the
oceanographical condi-
tions in the seas of
the Dutch East Indies.
Though limited to such
a circumscribed area
the observations are of great value, and the results are being
issued in English, German, or French, under the editorship of
the leader of the expedition. Max Weber of Amsterdam.
Flint.
The
"Albatross,
I 899- I 900.
Alexander
Agassiz.
The
" Siboga.'
Professor Carl Chun.
Max Weber.
During the years 1901 to 1903 the British National The
Antarctic Expedition on board the " Discovery " under Scott, Scott'''"''^'^''
the German South Polar Expedition on board the " Gauss " xhT'' Gauss.'
under von Drygalski, and the Swedish South Polar Expedition
on board the "Antarctic" under Otto Nordenskjold, were The
" Antarctic."
^ "A Contribution to the Oceanography of the Pacific," Bull. U.S. Nat. Mus., No. 55,
Washington, 1905.
DEPTHS OF THE OCEAN
The "Scotia.'
Bruce.
The "Edi."
The
" Stephan."
The
"Planet."
The
"Albatross,
1904.
Alexander
Agassiz.
The
" Nimrod."
Shackleton.
James Murray.
The
" Fran9ais."
The
" Pourquoi
pas ? "
The
" Deutsch-
land."
simultaneously engaged in the exploration of different portions
of the Antarctic regions, and in 1 902-1 904 the Scottish
National Antarctic Expedition on board the "Scotia" under
Bruce was likewise busy in the far south. The results of all
these expeditions have added very largely to our knowledge of
the oceanography of the Antarctic.
Between 1903 and 191 1 the German ships "Edi,"
"Stephan," and "Planet" took many soundings throughout
the different ocean
basins, the last -men-
tioned recording the
greatest known depth
in the Indian Ocean.
In 1904 we find
the U.S.S. "Albatross"
again carrying on
oceanographical work
in the eastern Pacific
under the personal
direction of Alexander
Agassiz, the published
results constituting a
great advance in our
knowledge of the Pacific
Ocean.
In 1907-1909 an-
other British Antarctic
Expedition on board
the " Nimrod," under
Shackleton, was en-
gaged in making scien-
tific observations and
pushing south beyond
anything previously attained. The biological work was under
the direction of James Murray, formerly of the Scottish Lake
Survey, and the results issued under his editorship are excellent
in quality.
Mention may also be made of the two French Antarctic
Expeditions under Charcot, the first from 1903 to 1905 on board
the " Francais," and the second from 1908 to 1910 on board
Dr. Anton Dohrx,
the " Pourquoi pas
Still more recently the German
Antarctic Expedition of 191 1 on board the " Deutschland "
has, during the outward voyage, taken valuable serial
OCEANOGRAPHICAL INVESTIGATIONS
19
temperatures and salinities off the Atlantic coast of South
America.
In addition to the specific expeditions referred to in the
foregoing paragraphs, many British surveying and cable ships
have been busily engaged during the past thirty years amassing
valuable information regarding the depth of the ocean in various
parts of the world. Temperature observations were also in-
cluded in the work carried on by H.M. surveying ships, and British
by some of the cable ships when accompanied by scientific ships.^^"^
men like J. Y. Buchanan and R. E. Peake. The principal
ships and the oceans investigated by them may be here briefly
enumerated : —
H.M.S.
" Egeria "
Atlantic, Indian, and Pacific
1887 to 1899
H.M.S.
" Waterwitch ''
)) ))
1894 ,, 1901
H.M.S.
" Rambler"
?5 !5
1888 „ 1904
H.M.S.
" Penguin "
Indian and Pacific
1890 „ 1906
H.M.S.
"Stork"
Indian and Atlantic
1888 „ 1897
H.M.S.
" Investigator "
Indian Ocean
From 1886 to the
present time
H.M.S.
" Dart "
Pacific Ocean
1888 to 1902
Other ships were engaged in one or other of the great
oceans for shorter periods, including H.M.Ss. " Myrmidon,"
" Marathon," " Flying Fish," "Goldfinch," "Sealark," "Sylvia,"
" Fantome," and " Mutine."
Of British cable ships mention may be made of the British cable
following :— '^'P'-
s.s.
" Britannia "
Atlantic, Indian, and Pacific
1888 to
1907
s.s.
" Great Northern "
Atlantic and Indian
1882 „
1897
s.s.
" Chiltern "
)»
1886 „
1897
s.s.
" Amber "
)) ))
1888 „
1906
s.s.
" Scotia "
1883 „
1898
s.s.
" Seine "
,, ,,
1885 „
1899
s.s.
" Electra "
)) -))
1887 „
1903
s.s.
" John Pender "
1878 „
1901
s.s.
" Duplex "
M ))
1906 ,,
1907
s.s.
" Silvertown "
Atlantic and Pacific
1889 „
1900
s.s.
" Retriever "
M
1880 „
1907
s.s.
" Sherard Osborn "
Indian and Pacific
1888 „
1907
s.s.
" Recorder "
„ ,,
r888 „
1907
s.s.
" Dacia "
Atlantic
1883 „
1905
s.s.
" Minia "
))
1885 „
1907
s.s.
" Norseman "
,,
1893 „
1907
s.s.
" Buccaneer "
„
1886 „
1906
Many other ships were engaged for shorter periods, including
20 DEPTHS OF THE OCEAN
S.Ss. "Westmeath," " Roddam," "Volta," " Mirror," " Viking,"
" Grappler," " Faraday," " Anglia," " Newington," " Henry
Holmes," "Cambria," "International," "Clan McNeil,"
"Patrick Stewart," "Cruiser," " Colonia," "Magnet," etc.
It is quite impossible in this brief review even to mention
the names of all the investigators and authors who have
during the past thirty years made important original contribu-
Professor Ernst Haeckel
tions to the science of oceanography. Among those who have
not taken an active part in extensive explorations and ex-
peditions, but whose influence on the development of the
Ernst science has been very great, the names of Ernst Haeckel
Haeckel. ^^^ Anton Dohm should be mentioned. Through his
voluminous publications on the radiolaria and on other marine
groups in ^the "Challenger" Reports, through his charming
Plankton-Studien, and through his more popular writings,
Haeckel has created a widespread interest in all marine
OCEANOGRAPHICAL INVESTIGATIONS 21
The work of
marine bio-
logical labora-
tories and of
international
and other
fishery investi-
gations.
Anton Dohrn.
investigations among the intelligent reading public of the
whole world.
Although small and more or less permanent marine labora-
tories had been established on various parts of the European
and American coasts previous to 1880, it must be acknowledged
that the foundation of the Zoological Station at Naples in that
year by Anton Dohrn marks an era in all that concerns the
histology and embryology of marine organisms, and these studies
have in turn given a great impetus to the systematic investiga-
tion of many purely oceanic problems.
Similar marine laboratories have since been founded in many
parts of the world, some for researches of purely scientific
interest and others for the
investigation of economic
questions connected with the
study of the habits and
development of the food
fishes.
By far the most import-
ant of these organisations
was that resulting from an
International Hydrographic
Congress held in Stockholm
in 1899, which was largely
brought about by the exer-
tions of Otto PetterSSOn. Pettersson
An International Commis-
sion for the Scientific In-
vestigation of the North Sea
was established, the partici-
pating countries being Great
Britain, Germany, Holland,
Belgium, Russia, Denmark,
Sweden, and Norway. Many important researches have been
undertaken, and many elaborate reports have been issued by the
scientific staffs of each of the countries concerned. This inter-
national work, which has been carried on for over ten years,
and is still in operation, has given a great impulse to nearly all
departments of oceanic science, one result among the many The -Michael
others being the organisation of the " Michael Sars " Expedition i^Jantic eI!^
in the North Atlantic in 19 10, to an account of which this pedition, 1910.
volume is chiefly devoted. J. M.
Hydrographic
Congress,
International
North Sea
Council.
Professor Otto Pettersson.
Michael Sak-
CHAPTER II
THE SHIP AND ITS EQUIPMENT
Importance of
development
of mechanical
aids in deep-
sea work.
It has often been said that studying the depths of the sea is Hke
hovering in a balloon high above an unknown land which is
hidden by clouds, for it is a peculiarity of oceanic research that
direct observations of the abyss are impracticable. Instead of
the complete picture which vision gives, we have to rely upon a
patiently put together mosaic representation of the discoveries
made from time to time by sinking instruments and appliances
into the deep, and bringing to the surface material for examina-
tion and study. Our difficulties are greatly increased by the
fact that it is impossible to watch our apparatus at work. A
trawl, for instance, is lowered to a great depth, and a few .
fathoms below the surface it disappears from view ; later on it
is brought on board and found to be empty. Is this because
there was nothing to catch where it was operating, or has it
somehow or other got out of order, or failed to reach the bottom,
or met with some similar mishap, and so been prevented from
catching anything.'* These questions can only be answered by
examining the trawl when once more on deck, and drawing one's
conclusions accordingly.
Obviously, therefore, the progress of oceanography depends
to a great extent upon the development of mechanical aids, by
which we mean not only the scientific instruments employed,
but also the whole arrangements of the ship itself. To be able
THE
9
Fig. I. — Deck Arrange-
ment ON BOARD THE
" Chai-lenger."
SHIP AND ITS EQUIPMENT 23
to haul in some thousands of fathoms of
line within reasonable time would be quite
out of the question without a steam-winch,
and it is precisely because the use of steam
first made it possible to examine properly
the vast marine areas of the world that
oceanic research is such a comparatively
new science. The cruise of the " Chal-
lenger," the first great expedition specially
fitted out to investigate the ocean, took
place during the years 1872-76. Since
then oceanography has made giant strides,
and we have now many appliances at our
disposal that were unknown to the pioneers
of those days.
It is interesting to compare our modern
methods with those of the "Challenger"
Expedition, for we can then see what great
advances have been made, and realise to
what extent we have availed ourselves of
the scientific inventions of our times. A
critical examination of the mode of work-
ing adopted by the " Michael Sars " will be
of use in this connection.
The "Challenger" was a spar - deck The ;
corvette of 2306 tons displacement, with Ej^'^dulon^'^
an auxiliary engine of 1234 indicated horse-
power. The length of her deck was 226 j
feet, and her greatest breadth was 36 feet.
Almost amidships on her main deck,
and just before the main mast, was a big
steam-winch of 18 horse-power, with a long
axle that extended right across the ship
and carried large end-drums (see Fig. i, 8).
Hemp lines were used, which were hauled
in by being passed round the end-drums.
The sounding-line was operated by two
large reels on the forecastle, 5 feet long
and 2^ feet in diameter (4 and 5), 3000
fathoms of line, one inch in circumference, Methods
to each reel. The breaking strain was ^^p.^^^'^^ °^
about 700 kilos (14 cwt.), and the weight
24 ' DEPTHS OF THE OCEAN
of 3000 fathoms of line in water was roughly 108 kilos. When
heaving the lead the weight used was sometimes 150 and
sometimes 200 kilos. During the whole of the voyage of the
"Challenger" only two temperature lines with eight ther-
mometers, and nine sounding-lines with thirteen thermometers,
were lost ; eleven thermometers collapsed under high pressure
at great depths.
For dredging and trawling they employed hemp lines 2, 2^,
and 3 inches in circumference, with a breaking strain from 1600
to 2550 kilos, spliced together to form a length of 4000 fathoms,
which was coiled on the forecastle (1,2, and 3). An attempt
was made to use swivels to keep the line from twisting, but
this had to be abandoned owing to their being damaged in the
blocks.
It is evident that in the arrangement and working of all the
apparatus account had to be taken of these immense lengths of
line. In the first place, they were extremely bulky, and required
a large amount of deck space for coiling and handling, as the
line had first to be led from the forecastle to the winch, and
frequently from the end-drum on one side of the axle to its
fellow on the other side, when the strain on the dredging rope
was so great that the friction of the revolving drum was not
sufficient to make it bite. This happened sometimes even when
ten or twelve men were holding on abaft the winch. A second
important consideration was the severe strain on the line every
time the big heavy ship lurched, or when the lead or the dredge
stuck fast on the bottom.
The weight of 3000 fathoms of sounding-line in water was,
as already stated, over 100 kilos, and the weights amounted to
200 kilos, so that there was not much margin left for friction in
the water and accidental jerks, when we remember that the
breaking strain was only 700 kilos. Accordingly, when sound-
ing or trawling great care had to be taken to provide against
such contingencies, and large accumulators were used, consisting
of rubber bands 3 feet long and J-inch thick, which could be
extended to 17 feet, and thus counteracted sudden jerks on the
line. For sounding, forty of these were employed, while for
trawling there were as many as eighty, which together could
support 2J tons, or the breaking strain of the line.
Fig. 2 shows the two accumulators, one for sounding
and the other for trawling, attached to blocks high up on a
yard, thus enabling them to expand and contract freely.
Before sounding all sail was taken in, and the ship was
THE SHIP AND ITS EQUIPMENT
25
brought head to wind by means of her engine to keep her from Method of
drifting off too much. With three or four heavy weio-hts of ^°""''^"§-
Fig. 2.— Sounding and Trawling on board the "Challenger."
50 kilos each attached, the sounding-lead was heaved, and the
apparatus was so constructed that the weights slipped off upon
reaching the bottom, thus doing away with the necessity of
hauling the entire mass up again. The Baillie sounding
DEPTHS OF THE OCEAN
Method of
dredging and
trawling.
r"
machine (Fig. 3) was the one in general use on board the
" Challenger."
Time required From the Narrative of the Cruise we get the following
Sje^^v^ale"^'" particulars regarding the time -
required for sounding in deep
water : —
Station 81. Began sounding 5
P.M. ; found bottom at 2675 fathoms ;
finished hauling in at 6.20 P.M.
Station 225. Began sounding
12.30 P.M. ; found bottom at 4475
fathoms ; finished sounding at 3 P.M.
We see, therefore, that sound-
ing in about 3000 fathoms took
nearly an hour and a half, where-
as for about 4500 fathoms two
and a half hours were required,
which must be considered very
quick work. On the same line
and with the same arrangement
as for sounding, series of tem-
peratures were taken and deep-
water samples obtained.
Heavy lines and strong
accumulators were, however,
necessary for the dredge and
trawl, which were each fastened
to a stout 2-inch line, paid out
through a block attached to the
big accumulator (see Fig. 2).
From 300 to 500 fathoms first
ran out, then a weight of about
80 kilos ' was allowed to slide
down the line till it was stopped
just a little in front of the appli-
ance. The weight consequently reached the bottom before
the appliance, with the result that this latter merely skimmed
the ocean floor.
All this time the ship lay with her head to the wind to
enable the appliance to reach the bottom, for which operation
about three hours were required. When all was in readiness
the ship was allowed to drift with the wind abeam, and thus
towed the dredge or trawl along.
Fig.
Baillie Sounding Machine.
The tube (/) was generally made to project
18 inches below the weights {e}.
THE SHIP AND ITS EQUIPMENT 27
Hauling in was done rapidly, as will be seen from the
following extracts : —
Station 79, depth 2025 fathoms. The dredge was lowered at 11 A.M., Time required
and 2800 fathoms of Hne paid out ; at 4 p.m. commenced hauling in, and for dredging
c ' ^ o ' jj^j} trawling.
the dredge came up at 5.45 p.m.
Station 244, depth 2900 fathoms. The trawl was lowered at 4 A.M.,
and 3500 fathoms of line paid out ; commenced hauling in at noon, and
the trawl came up at 3.50 P.M.
Thus in the course of twelve hours it was possible to carry out
a successful trawling at a depth of about 3000 fathoms.
With such means as they had then at their disposal — a
sailing ship with auxiliary engine and hemp lines — it was
scarcely possible to devise a more thorough system of working.
During the whole three and a half years, when trawlings and
dredgings were made at 354 stations, there were only eleven
cases of the parting of the dredge or trawl line. But gear of
this kind necessitated lavish space and a large number of hands,
both of which were generally to be had on the old sailing ships.
It entailed ample space on deck for the coils of line and high
masts for the accumulators, while numbers of men were needed
to coil the lines and to hold on abaft the end-drums of the
winch. A sailing ship, however, required much less coal than (
a steamer, which is a great advantage on a voyage round the •
world.
In the Narrative of the "Challenger" Expedition it is Recent
mentioned that at the time the vessel was being got ready for "methods.
her cruise, Sir William Thomson (Lord Kelvin) was engaged Lord Kelvins
in trying once more to solve the problem of taking soundings on^s^ouSg
with wire instead of with a hemp line, and that a sounding with wire.
apparatus constructed by him was placed on board just before
the ship sailed ; the drum, however, collapsed when first used.
Notwithstanding this Sir William Thomson continued with the
utmost energy, and eventually with complete success, to develop
his method, and it was employed by the American sounding
vessels "Tuscarora" (Captain Belknap) and "Blake" (Captain
Sigsbee). Wire has great advantages over a hemp line, firstly,
because it enables soundings to be taken more quickly, since
the steel wire meets with far less friction in the water ; and
secondly, because it requires much less space.
Fig. 4, which is taken from Sigsbee's excellent book,^ Advantages of
represents sections of the hemp lines used by the "Challenger," hemp Une.
^ Sigsbee, Deep-Sea Soundiiio and Dredging, Washington, 1880.
28
DEPTHS OF THE OCEAN
and of the steel line (piano wire) afterwards adopted for
sounding. It will be obvious at once what a saving of space
is obtained by the use of a steel line. This
will be clear, too, if we look at Sir William
Thomson's sounding machine, the principle
of which is clearly illustrated by the follow-
ing instructive figure from Sigsbee's book
(P'g- 5)- , . , ,
The wire is wound m by a large wheel
consisting of a drum 2 feet 6 inches in cir-
cumference between two thin galvanised iron plates 6 feet in
circumference, the object of making this wheel of such a size
being to enable the line to be paid out and hauled in quickly.
In taking soundings the art consists in getting the wheel
and line to stop the moment the plummet touches the bottom.
00
Fig. 4. — Sounding-Line
AND Wire.
a and l>, Circumference of
the hemp sounding-line of
the "Challenger" ; c, piano
wire. (From Sigsbee.)
The line drifts when free of the lead, as it is, of course, relieved
of the weight as soon as the bottom is reached, but there still
remains the weight of the line itself, while the momentum of
the wheel will cause it to continue revolving for a little while.
The wheel must consequently be made as light as possible, and
a resistance of some sort must be provided, rather stronger at
THE SHIP AND ITS EQUIPMENT
29
/4
any moment than what is necessary to counteract the weight of
the length of line paid out. Thomson obtained this by means
of a brake, a hemp line running in a separate groove at the side
of the big wheel, and passing from there to a block, through
which the brake could be tightened by means of weights.
Sir William Thomson used a plummet weigh-
ing 34 lbs., and commenced his sounding with
a counter-weight of 10 lbs, on it. This was
sufficient to run out the line at the rapid rate of
2000-3000 fathoms in thirty to fifty minutes.
Gradually, as more line was paid out, the
counter-weight was increased proportionately to
the length of wire in the water (12 lbs. for each
1000 fathoms of wire), and this caused the wheel
to stop almost instantaneously when the bottom
was reached. The depth could be ascertained
from the number of revolutions on the register.
1^ If the wheel did not stop instantaneously, an
SL ^ error would result in the determination of the
^K^^K depth, and if the steel line came into contact
SBHb with the bottom, it easily kinked, and the
^^HpF plummet was likely to be lost. To obviate this
^^■^ a few fathoms of hemp rope were inserted be-
^H tween the plummet and the steel line.
^B Obviously this sounding machine is a great
■ advance on the old hemp lines. ^ Economy of
space, smaller weights, greater speed, less fric-
tion in the water (and consequently a more
perpendicular line, resulting in greater accuracy),
are some of the advantages. For this reason
attempts have continually been made to improve
Thomson's machine, and in the course of time
a number of very good sounding machines have
been constructed, amongst others those of Le
Blanc, Sigsbee, and Lucas. Sigsbee's sounding-
tube is shown in Fig. 6. All of them are based
on Thomson's model ; thus Sigsbee says of his own admirable
machine : " The modification or improvement made by me on
the original Thomson sounding- machine lies chiefly in the
employment of a peculiar kind of accumulator, and its adap-
^ It is interesting here to observe that the " Challenger" hemp line could be used for sound-
ing in depths down to 26,000 fathoms before reaching its breaking strain, whereas the wire could
only be used down to a depth of 16,700 fathoms. Depths beyond 26,000 fathoms, should such
depths exist, could not be explored by either method.
Fig. 6.— Sigsbee's
Sounding -Tube.
(From Brennecke.)
Recent
sounding
machines.
30 DEPTHS OF THE OCEAN
tation to the various uses of accumulators, dynamometer, brake,
correct register, and governor."
On board the " Michael Sars " we employed the sounding
machine constructed by Lucas. It was selected originally
because it had been extensively used by the telegraph cable
ships, and because it was the smallest and the cheapest. Weights
used as brakes in Thomson's machine are replaced by spiral
springs, which can be tightened or slackened with a screw,
and can at the same time be relied upon in a high sea as
accumulators (see Fig. 7, which explains the construction).
During the winter of 1877-78 the United States Coast
Survey steamer "Blake" undertook a cruise in the Gulf of
Fig. 7.— Lucas Sounding Machine.
Mexico, under the command of Captain Sigsbee and under the
Wire rope for pcrsonal supcrvision of the late Alexander Agassiz. As it
dredging. ^^g proposed to Carry out investigations with the dredge and
trawl along the bottom, Agassiz suggested the use of a wire
rope instead of hemp ropes. Thanks to Sigsbee's inventive
genius and practical methods, this plan was successfully adopted,
and has since been adhered to by every expedition of any
importance.
Fig. 8 shows sections of the "Challenger" hemp lines,
3 inches, 2^ inches, and 2 inches in circumference (a, d, c), and
of the wire rope, i|- inch in circumference, used by the
" Blake " (d).
THE SHIP AND ITS EQUIPMENT 31
The wire rope consisted of six strands, each made up of
seven wires (like piano wires about 1 mm. in
diameter), or altogether forty-two wires, with
a tarred hemp line in the middle. The
breaking strain of the whole was about 4
tons. Its weight per fathom was 1.12 lbs.
0000
a h c d
Fig. 8.
a, b, c, Circumference of hemp lines used for trawling on board
the "Challenger," and d, of wire rope used for trawling on board
the "Blake." (From Sigsbee. )
n
in the air, and i lb. in the water. We thus
get a breaking strain of about 4000 kilos ;
weight in water of 5000 fathoms 2300 kilos ;
so that with 5000 fathoms out, there were
about 1 700 kilos over for resistance (friction)
in the water, and for strains due to heavy
seas or sticking fast on the bottom. The
great strength of this line made it less
necessary to use accumulators, and they
were only employed occasionally during the
" Blake " expedition.
Fig. 9 shows how Sigsbee worked the Method of
wire rope on board the "Blake.;' It was ^Jf ""^
wound round a big drum (i), driven by a
small steam-winch, and led from the drum
over blocks of considerable diameter (2) to
the large steam-winch (3), which had a large
end-drum 55 centimetres (22.6 inches) in
smallest diameter. From here the line went
to a big boom (4) on the foremast (5).
When dredging or trawling the appliance
was first lowered to near the bottom, while
the ship was stationary, and afterwards the
_ vessel went astern during the process of
Fig. 9.-d^ck Arrange- paying out and dredging. This manner of
MENT OF THE "Blake." working was so successful, and conduced to
(From Sigsbee.) '^
32 DEPTHS OF THE OCEAN
such precision, that it may be considered quite the equal of any
system adopted by subsequent expeditions. Sigsbee relates
that he made one day, off Havana, between 7 a.m. and 5 p.m.,
as many as ten hauls with the dredge at depths varymg from
Fig. 10. — Dredges.
a, Previous model ; fi, Sigsbee's dredge. (From Sigsbee )
SO to 400 fathoms. Although the bottom was unsatisfactory
and the dredge stuck fast every time, he managed to avoid an
accident and made very successful catches. He allowed from
three to five minutes for lowering or for hauling in a line ot a
hundred fathoms, and from ten to thirty minutes for the actual
THE SHIP AND ITS EQUIPMENT ^3
dredging, the time required for dredging depending, of course,
upon the nature of the bottom.
The joint labours of Agassiz and Sigsbee led to a great
Fig. II.— The "Challenger" Trawl. Fig. 12.— Sigsbee's Trawl. (From Sigsbee.)
improvement in the appliances. Previously the dredges had
ploughed into the ocean floor (Fig. 10, a), but the one employed
by Sigsbee (Fig. 10, d) was believed to have skimmed over it,
and so collected the animals which lived upon the surface,
sweeping them up from a wide extent of ground. Both kinds
D
" Challenger
trawl.
34
DEPTHS OF THE OCEAN
of dredge have, however, their advantages, according to the
animals it is desired to procure.
The "Challenger" used a trawl (Fig. 1 1) constructed like
the ordinary beam-trawl, which was employed particularly by
Fig. 13. — Tow-Net fixed at End of Line ("Challenger").
the fishermen in the shallow waters off the flat English coasts.
The beams were of different lengths, 17, 13, and 10 feet,
but the lo-feet length was found to be the best
for deep water. It was, however, difficult to
tell, when the depth was at all great, whether
the trawl had reached the bottom right side up,
and whether it was open while being towed.
Sigsbee solved this difficulty by having tripping
lines on both sides (Fig. 12) ; otherwise the size
of his trawl was identical with that of the
" Challenger," viz. 10 feet between the runners.
Sigsbee's appliances and methods of work-
ing were adopted by the " Valdivia" and other
recent expeditions.
Pelagic During the cruise of the " Challenger" the
of?he"^^^ appliances used for making pelagic captures
"Challenger." cousisted of Small nets resembling long night-
caps, of fine muslin or calico, and 10 to 16 inches
in diameter at the mouth. They were towed
at various depths, even as far down as 800
fathoms, with a weight attached a little in front
of the opening (Fig. 13), or they were some-
times made fast to the line (Fig. 14) and lowered
to a depth of about 2 miles (over 3600 metres),
the object being to ascertain whether or not fi
organisms lived in the deeper layers of water
different from those captured in the surface layers.
Since the time when the "Challenger" conclusively proved
that life was present everywhere in the ocean, not only over
the bottom at the profoundest depths, but also in the inter-
mediate layers of water, much labour has been expended upon
14. — Tow-Net
fixed on the Line
(" Challenger").
THE SHIP AND ITS EQUIPMENT
35
the investigation of the animal Hfe of the sea. The appHances Closing nets
for capturing animals at the bottom have undergone only slight aJewSrr'^'
alterations, whereas many different kinds of contrivances for
capturing the pelagic animals have been tried from time to
time, some of them being of real practical value.
Chun has done more perhaps than any other naturalist in Chun and
the way of studying the vertical distribution of organisms. Jios^ngnet.
Together with Petersen he constructed a vertical net that could
Fig. 15. — Nansen's Closing Net.
16. — Chun's Net. (From Chun.)
be let down closed, then opened, and finally closed again, so
as to catch the smaller organisms existing in a specified layer
of water, say between 400 and 200 metres beneath the surface.
Subsequently other closing nets were constructed on the
principle of this invention. Fig. 15 shows Nansen's closing Nansen
net open (a), and shut (d), the construction of the net itself ^^i^^^^g
and the closing mechanism being easily understood from the
illustrations. It is extremely simple and reliable, and we have
tested it in various ways during the cruises of the " Michael
Chun large
net.
Prince of
Monaco's
pelagic
trawl.
36 DEPTHS OF THE OCEAN
Sars." We have found that if the appliance is sent down open
to a considerable depth, immediately closed and hauled in again,
it fails to capture anything, thus proving that vertical appliances
need not be closed while being lowered.
For studying the vertical distribution of larger organisms
Chun used during the " Valdivia " Expedition a large silk net,
4 metres in length (Fig. 16). By lowering it to different depths
Fig. 17.— Monaco's Pelagic Trawl, (From Steuer.)
and comparing the catches so obtained, he could determine
at what particular depths the animals lived, and he succeeded
in collecting by this means valuable data as to pelagic deep-
water forms.
The Prince of Monaco has also added largely to our
knowledge of the habitats of the larger pelagic organisms by
means of his pelagic trawl (Fig. 17), which is designed for
Petersen
young-fish
trawl.
Fig. 18. — C. G. Joh. Petersen's Pelagic Young-Fish Trawl. (From .Schmidt.)
being towed horizontally through the water. In addition he,
made some remarkable captures of large pelagic animals, chiefly
cuttle-fish, by shooting whales and examining their stomach con-
tents, for the whale is still far more capable of catching living
marine creatures than any scientific appliance hitherto invented.
The young-fish trawl designed by C. G. Joh. Peterser
(Fig. 18) is a considerable improvement on the Prince 01
Monaco's pelagic trawl. It is very easy to construct, and
may be of any size or mesh. For catching young fish, etc., J
THE SHIP AND ITS EQUIPMENT
Zl
he generally uses sackcloth, but a better fine-meshed material
would undoubtedly be more desirable.
Hensen evolved various forms of apparatus for a quantitative
study of the pelagic organisms, that is to say, for estimating
the relative amounts of plankton organisms present in a given
volume of water. He recommends vertical nets of the finest
silk cloth, such as is used in the milling
industry (see Chapter VI.).
In actual practice, however, it has
been found impossible to capture pelagic
organisms of every sort with the same
net ; for the larger forms may escape the
net altogether, while the smallest forms
may pass through the meshes of even
the finest silk. There are other objec-
tions to the method, for it is an almost
impossible task to ascertain the total
quantity of floating organisms in deep
and shallow water where there are
strong currents ; and it is hardly likely
that the larger organisms at any rate,
even though the nets succeed in cap-
turing them, are uniformly distributed
throughout the water- masses over large
areas, so that an estimation of their
total number could not be arrived at
with our present appliances. Still,
Hensen's theoretical analysis of plank-
ton problems has been of great service
to oceanic research, and so, too, has
his plankton net (Fig. 19), whose co-
efficient of capture naturalists have
attempted to calculate. It has been of
the utmost value, for instance, in investigating certain uni-
formly distributed minute species in less extensive areas. The
apparatus consists of a filtration net of miller-silk, with a brass
cylinder at the lower end of the net, and a large conical part
made of canvas, the object of which is to control the amount of
water entering and so enable the silk net to filter it.
Hensen
plankton net.
Fig. 19. — He.nskn's Large
Plankton Net. (From Chun.)
The steamer "Michael Sars " was built in 1900 by the The "Michael
Norwegian Government to undertake researches in connection Sai^."
with the Norwegian fisheries, and to study the natural con-
3^
DEPTHS OF THE OCEAN
Methods
employed
on board.
©"
ditions on which they depend. It was therefore necessary to
have a vessel capable of making investiga-
tions similar to those carried on by oceanic
expeditions, and at the same time suitable
for practical fishery experiments, which are
every year becoming of more and more
importance in the work of scientific re-
search. A ship of this kind, however, had
to be small, otherwise it was impossible to
reckon on sufficient means for its upkeep.
Accordingly the size we selected was that
of a first-class fishing trawler. Her length
is 125 feet between perpendiculars, and
she is of 226 tons burden ; her engines
indicate 300 horse-power, and can give her
a uniform speed of 10 knots; her coal
consumption is small, being about 5 tons
per twenty-four hours when going at the
rate of 9 knots, and she can carry in her
bunkers about 80 tons. As will be seen
from Fig. 20 there is plenty of space on ftUy
deck forward of the engines. The big
winch is placed here just abaft the hatch
of the storeroom, in which there is
cold storage for 10 tons of fish, and
stowage for appliances, instruments, cases
of glass bottles, etc. Forward of this
storeroom are the cabins of the engineers
and mates and the quarters of the crew.
Abaft the engines there is a labora-
tory on deck, and below there are cabins
and a messroom for the scientists. The
deck is perfectly clear on either side
of the deck-house, so that there is ample
room for working with appliances and
instruments.
If we compare Figs. 20 and 21 we
shall get a good idea of the appearance of V^ \Z}
the deck of the " Michael Sars." On the
starboard side there are two small winches,
the forward one of 3 horse-power and the
aft one of i horse-power. The forward fig. 20.— Deck arrange-
winch (2), by means of a long axle (see >.'-,',„- .^^S ™=^
THE SHIP AND ITS EQUIPMENT 39
also Fig. 22), drives a big reel with 6000 metres of wire, 3.5
mm. in diameter, for the hydrographical instruments and the
Lucas sounding machine (6 and 5), and it can also be used
to drive the big centrifuge (10) by means of a hemp line. By
a similar arrangement the aft winch drives two drums with
2000 metres of wire, 3 and 4 mm. in diameter, for the vertical
nets and hydrographical work in moderate depths.
In calm weather and when the currents are slight all the
appliances may be operated simultaneously, provided care be
Fig. 21.— Side View of Arrangement of Gear on board the "Michael Sars."
taken that one appliance, let us say, is lowered while others
are being hauled in. But when there are strong currents there
is always a danger of the appliances colliding, and it is best
in that case to work one at a time from each winch.
For the larger nets and the trawl we use the big winch (i),
which takes tl>e long steel line, 9000 metres in length, increas-
ing from 34 mm. to 44 mm. in diameter. When trawling the
line passes round the big reel {9), on which there is a register,
and from there it is led to the gallows (12 and 13) and paid
out astern. When operating the big vertical nets, the line
is passed round a block in the accumulator, which hangs from
40 DEPTHS OF THE OCEAN
the boom on the foremast, and is then led to the forward
gallows (i i).
Pelagic appliances, to be towed horizontally, are either
fastened to the trawl wire like the trawl itself, or else the wire
is led round a smaller winch (4), situated abaft the deck-house,
and then paid out over the stern.
The vessel may thus tow both steel lines at the same time,
Fig. 22. — The Forward Starboard Winch.
and a number of appliances may be operated simultaneously.
This mode of working differs in many ways from the system
adopted in former expeditions.
Fig. 22 shows the forward starboard winch. The little Lucas
sounding machine may also be seen, fastened quite simply to
the rail of the ship, taking up very little space and requiring
the attention of only one man. The large Pettersson-Nansen
water-bottle, used for hydrographical observations at great
depths, is also in a handy position. What simplifies matters
THE SHIP AND ITS EQUIPMENT
41
very much, and enables us to dispense with the big projecting
structures, or sounding platforms, that were formerly necessary,
is the fact that in our little ship we are so near the surface of
the sea that the
person taking ob-
servations stands
only a few feet
above the water,
and it is conse-
quently much
easier to get the
appliances on
board as soon as
they come up.
It is much easier
also to manoeuvre
with a little
steamer, so as to
humour the appli-
ances and keep
the lines perpen-
dicular whilst be-
ing lowered or
hauled in. Obvi-
ously these are
great advantages,
not merely at the
moment of taking
observations, but
also in our whole
system of work-
ing ; being able to
operate a number
of appliances sim-
ultaneously, for
instance, means a
great saving of
men and time.
In the case of
both sounding machine and hydrographical apparatus we
are able to haul in the line at the rate of 120 metres per
minute, or 6000 metres in fifty minutes. But the forward
starboard winch was unfortunately too weak to keep up this
-The Otter Trawl.
42
DEPTHS OF THE OCEAN
was much line out and the weight was
speed when there
considerable.
Trawling. For trawHng, former expeditions employed the model designed
by Sigsbee, lo feet in breadth. This appliance, notwithstanding
all its good points, is too small for catching large animals.
Modern fishing steamers, which are quite small compared with
the expedition ships of former days, mostly operate trawls 120
feet in length, having a span of about 60 to 80 feet, with a
height at the entrance many times greater than that of the
trawls employed for scientific purposes. Seeing then that a
great many trials have been made in all oceans with the dredge
and with Sigsbee's trawl, it was advisable to try whether a
larger appliance would not yield different species and bigger
catches, and it was natural to select as a model the appliance
supposed to be best adapted for catching fish, namely, the
Otter trawl. Otter trawl in use among fishermen.
Fig. 24.— The Otter Board.
The difference between the otter trawl (Fig. 23) and the
beam trawl (see the "Challenger" trawl, Fig. 11) is that in the
case of the former the appliance is kept distended by means of
otter boards, working on the principle of an otter for trout
fishing or a kite in the air. The otter boards (Fig. 24) are
attached to the line by bridles, and thus have a tendency to
spread when towed along through the water. The regular
trawlers use two steel lines of colossal dimensions, up to 3
inches in circumference and with a breaking strain of 20 tons ;
these are wound round two large drums that are keyed on to
the slow axle of the trawl-winch (see Fig. 25), from which each
line passes to its gallows and then astern, being carefully
fastened with chains during the time that the vessel goes ahead
towing the trawl after it. Sigsbee, it will be remembered, went
astern when trawling, and he had one winch for winding the
wire round the drum and another for the actual hauling in.
It is quite evident that the system adopted by the regular
trawlers economises labour, for it is simple, and space is saved
by using only one winch. The otter trawl, again, has to be
THE SHIP AND ITS EQUIPMENT
43
towed at a good speed to keep the boards in position, and the
vessel skilfully steered, so that the lines
must necessarily be towed from the stern.
It was found very difficult, however, to
adopt this plan to our requirements, the
chief drawback being that everything must
be of the very strongest materials. Sir
William Thomson long ago, when working
at his sounding machine, discovered that
the drums were easily burst, and the
trawlers too have had similar experiences,
in spite of their using drums of cast metal
several inches thick.
The " Michael Sars " could not, of
course, use such large appliances, for if in
addition to overcoming the resistance of
two ponderous otter boards, 6 feet by lo
feet, she had to tow a pair of wires each
many thousands of metres long, she could
obviously not have got over much ground ;
and besides, it would have been next to
impossible to prevent such long lines from
fouling one another. We were compelled
therefore to trust to a smaller size of trawl,
and to substitute a single warp, from the
end of which we led a connecting line, 50
fathoms in length, to either otter board
(see Fig. 26, line and bridle). A similar
arrangement for small otter trawls had
been already successfully tried by C. G.
Joh. Petersen. During previous cruises of
the " Michael Sars " we had operated a
trawl with 50 feet of headrope at a depth
of 1830 metres, and during our Atlantic
expedition we succeeded in working the
same appliance at a depth of 5160 metres.
Our success must be ascribed to the solid
construction of our gear. The drum of
the winch which took the 9000 metres of
wire was of the best cast steel, and the
blocks were made as substantial as pos-
sible, though even then they had to be
changed during the cruise, because
Fig. 25. — Deck Arrange-
the MENTS OF A TRAWLER.
44
DEPTHS OF THE OCEAN
steel wire soon wore deep grooves in them. Our trawlings, too,
took a long time, for the 20 horse-power winch that wound in
Fig. 26.— The "Michael Sars" trawlinc; wi
AND Otter Trawl.
>M-: Wire Rope
the wire directly on to the drum was unable to maintain its full
speed when the load was unduly heavy.
On 31st May, at Station 48, the trawl was shot at a depth of
Fig. 27. — Hauling in Long Lines by means of Line Winch.
5160 metres with 8750 metres of wire ; we commenced lowering
at 5.45 A.M. and started trawling at 11.20 a.m.; hauling in
began at 2.50 p.m., and the trawl was once more on board at
THE SHIP AND ITS EQUIPMENT
45
9 P.M. Hauling in took, therefore, six hours ten minutes, and the
average rate was 24 metres per minute, or about a third of the
speed at which Sigsbee hauled in his little trawl.
In addition to the trawl the "Michael Sars " can use lines Lines and
and drift nets, in which respect she is equipped like an ordinary '^"'"^'^•
fishing steamer. The lines are passed out over the stern and
hauled in amidships by means of the little after starboard winch,
which is really the same as the little winch used for the hydro-
graphical instruments. This is moved forward on the deck,
and the lines are hauled in as in Fig. 27. Herring drift nets are
Fig. 28.— Hauling in Drift Nets.
set from the stern ; when all the nets are out the vessel swings
round on the warp. This warp is hauled in by means of the
large end-drum on the big winch and over the reel in the bows,
and the nets are hauled over the side on to the fore part of the
deck (Fig. 28).
As regards the net constructed by Victor Hensen (Fig. 19),
a great deal of work has been devoted to studying its
"coefficient of capture"; it is suitable for making quantitative
studies of the occurrence of such plankton organisms as copepods,
peridinii, etc., but for other purposes it has little practical value.
Its upper part is furnished with a canvas cone, which allows no
water to filter through, and therefore offers an effectual resist-
Pelagic
appliances.
46
ance to the water, both
hauled in. It is,
besides, quite use-
less for towing, for
which purpose it
was never intended.
In the construction ,
of our nets on the
"Michael Sars" our
idea was to make
the fore part in such
a way that as much
water as possible
might percolate
through. As a rule
they are i metre in
diameter at the
entrance and 4.5
metres long (see
Fig. 29). The fore
part is cylindrical
for a length of ij
metres and of the
same size as the
entrance. There is
first half a metre of
shrimp net, then i
metre of coarse silk
with a mesh of 12.5
mm., and the after
part, consisting of a
cone, 3 metres long,
of finer silk with a
mesh of 0.8 mm.
These filter the
water admirably.
We can tow them
at a great speed and
haul them on board
rapidly, even with
the little after star-
board winch ; and
they capture young
DEPTHS OF THE OCEAN
while being lowered and while being
'-^'^fdj
Fig 29 -The "Michael Sars" Tow-Net.
A, net ; B, coarse silk ; C, finer silk ; D, lead.
THE SHIP AND ITS EQUIPMENT
47
fish almost as well as the trawl itself. The cylindrical fore part
is largely responsible for this, as it retains within its walls the
animals that do not pass immediately into the after part, which,
owing to its great length, lets the water filter easily through.
One great advantage of these tow-nets is that they can be
lowered very rapidly when used as vertical nets. They then
Fig. 30. — Large Vertical Closing Net.
assume the shape depicted on the left in Fig. 29. The net in
the foremost portion of the cylinder is the only part that offers
any resistance, and it too is wide meshed, so that the water
easily passes through it ; the rest descends like a thick rope.
They can also be used as closing nets, and we have actually
employed in that capacity nets J, f , and i metre in diameter at
the entrance.
We further constructed two large closing nets, 3 metres in
48
DEPTHS OF THE OCEAN
Large closing diameter at the mouth and 9 metres long, one of silk and the
"^*^' other of net ; one of these is depicted open on the right and
shut on the left in Fig. 30. They proved to be our most
successful pelagic appliances. We used them sometimes as
vertical nets and sometimes for towing. The closing mechanism
(Fig. 31) was constructed
on Nansen's principle. A
slip-weight sets free the
cords that support the
ring, which falls down
and leaves the whole
hanging by a noose. This
noose draws the net to-
gether so that nothing
more can enter it. Two
sizes of mesh are used in
the construction of these
nets ; in the fore part a
mesh of about i centi-
metre and in the after
part one of almost J centi-
metre from knot to knot.
In deep waters, how-
ever, and especially out
in the open ocean, even
these large appliances, if
merely used as vertical
closing nets, fail to furnish
a representative picture
of the animal life. The
animals can only be cap-
tured by long horizontal
hauls, and therefore to
ascertain what exists at the
different depths we must
tow a large number of
appliances simultaneously.
Fig. 31. — Closing Mechanism.
Method of
using tow-
nets.
Fh
> shows the plan we generally adopted during the
Atlantic cruise of the " Michael Sars." Two lines were used :
a long line from the big winch for the deep-water appliances,
and a shorter one from the after winch for lesser depths.
Silk tow-nets either i metre or f metre in diameter, and
Petersen's young-fish trawls were alternately attached, and to
THE SHIP AND ITS EQUIPMENT
49
the end of the longest line we fastened the large tow-net just
described.
Fig. 32. — The "Michael Sars" towing Ten Nets and Pelagic Trawls.
(Surface net not shown. )
A difficulty which arose when organising this system was
that the cord by which a tow-net or trawl is attached to the
wire becomes easily entangled, in which
case the appliance is rolled round the wire
or else torn off. To avoid this we screwed
a brass knob (Fig. t,^,) on the wire and
Fig. 33.— Brass Knob for Tow-Nets.
fastened the tow-net to a brass ring, which
could be threaded on above the knob (Fig.
34), The appliance is thus kept from
sliding down the wire, and is free to move
in any direction (see also Fig. 32). This
method of working enables one to operate as many appliances as
E
Fig. 34.— Brass Ring
for Tow-Nets.
50
DEPTHS OF THE OCEAN
Centrifuge.
the vessel is able to tow through the water, and by comparing
the catches in the manner described in Chapter IX. one can
ascertain the depths at which the animals lived. It is really a
development of the plan adopted by the "Challenger," which
towed its small nets along at different depths, or else attached
them to the sounding-line (see above, p. 34).
The pelagic investigations of recent years have shown
that a great many marine organisms are so small that they pass
through the meshes of all nets — even the finest silk nets (see
Fig. 35. — Centrifuge dri\e.\ by Electric Motor. (From a catalogue.)
Chapter VI., where these organisms and their occurrence are
described). To catch them in greater quantities we employed
a large centrifuge (Fig. 35) as used by physiologists, which
could centrifuge 1200 cubic centimetres at a time. The centri-
fuge was driven by one of the small steam-winches usually
for a period of seven minutes and at a speed of 500 to 700
revolutions per minute.
This short description of the outfit of the "Michael Sars "
does not claim to be exhaustive. During past years probably
most kinds of fishing gear and scientific instruments available
for the investigation of the sea have been made use of by us.
When undertaking a definite limited cruise, however, a pro-
gramme of the researches contemplated must necessarily be
drawn up in advance and the gear selected accordingly.
Our Atlantic cruise proved that a greater number of
appliances could hardly have been employed during a cruise
THE SHIP AND ITS EQUIPMENT 51
of a few months' duration. But on the other hand a number
of problems arose during the cruise, which we would fain have
had the opportunity of investigating further.
It is especially our knowledge regarding the physical and
biological conditions in the waters of the abyssal regions, and
regarding the large pelagic organisms, that may still be con-
sidered as very imperfect. In order to study these problems
more effectively, still more powerful winches, longer lengths of
wire, and larger and better pelagic fishing gear are the principal
things wanted. Future expeditions will thus have to face a
serious task, not free from technical difficulties.
J. H.
Group of Appliances used on board the "Challenger.
S.S. "Michael Sars" in Plymouth Harbour.
CHAPTER III
THE WORK AND CRUISES OF THE " MICHAEL SARS
In this chapter it is proposed to point out briefly the nature and
extent of the oceanographical work and fishery problems in
which the S.S. "Michael Sars" has been engaged in the
Norwegian Sea during the past ten years. Thereafter we will
turn to the special cruise in the North Atlantic from April to
August 1 910, and will recount the operations of the ship and
the proceedings on board at the observing stations along the
coasts of Europe, Africa, and Newfoundland, and during the
voyages across the whole extent of the Atlantic.
Since the summer of 1900 the " Michael Sars " has made a
great number of cruises in the Norwegian Sea. Fig. 36 shows
the location of the stations occupied during the years 1900-
1904, and a good deal more work has been done there sub-
sequently. In the winter our task has been a particularly
arduous one. We have found that stormy weather nearly
always prevails at that season, and it is light for only a few
hours each day. The temperature of the air is so low that all
the water that falls on the deck and rigging freezes, and the
CRUISES OF THE "MICHAEL SARS "
53
quantity of ice thus formed is sometimes sufficient to weigh
down the ship.
Captain Iversen has given an account of one of the cruises, iversen's
account of a
winter cruise.
Fit,. 36.^The "Michael Sars" Observing Stations during the Years 1900-1904.
that to Jan Mayen in February 1903, and his description
presents such a vivid picture of the difficulties to be encountered
when studying the Norwegian Sea and its fisheries, that it may
well be printed here : —
We came in here {i.e. Lofoten) yesterday with all well on board.
54 DEPTHS OF THE OCEAN
We could not quite keep the course proposed, as the weather took
charge of us a bit sometimes and no mistake. I will endeavour to give
a few particulars of the trip.
We were pretty deep in the water when we left Bergen on the after-
noon of the 9th February, every available hole and corner being crammed
full of coal ; consequently we got a bit of a washing that night. We
had a hard gale dead ahead, but managed all the same to take up three
stations before she refused to look at it about midnight of the loth.
All the nth we lay hove-to, though we were able to take up one station ;
and on the I2th we stopped the engines to save coal, and got sail on
her. Not till the afternoon of the 13th did the sea and wind go down
enough for us to continue our course. During this storm we had
frequent spits of snow and shipped a lot of water. To enable us to take
up our stations we stretched a rope from davit to davit along the whole
of the starboard side where we had to work. We did this to have
something to hold on to, and so save us from being washed overboard.
Koefoed was given a rope to tie round him, which fastened him like a
dog to the davit where he worked. Otherwise everything was all right,
except that the sheet of the mainsail parted so that the sail was damaged
and a couple of thermometers were smashed. An interesting sight was
a school of bottle-nose whales which we observed in lat. 63° 3' N., long.
2° 44' E. They were seven in number, most of them being males,
" barrel hoops."
On the 14th and 15th we had good weather with little snow, so we
made excellent progress northwards and took up a few stations. On
the morning of the i6th we had clear weather and could see the ice-
blink, the water at the same time becoming cold. After taking up a
station during the night just clear of the ice we steamed through ice-
floes all the next morning. We saw Jan Mayen in the distance, but the
ice lay thick all round it. About midday we had to look sharp and get
out again, as the wind increased to a gale, accompanied by severe frost
and remarkable shrouds of mist, which assumed the most fantastic
shapes and were constantly in motion. I have never seen anything like
them before. We shaped our course for Vesteraalen, and got sail on
her to steady her a bit. The whole of the afternoon we were pretty
well cased with ice— hull, spars, and standing rigging — and on running
suddenly into the middle of an ice-floe about nine o'clock that evening
we had a hard job to get the ship round against the wind, her sails
being so stiff with ice that it was impossible to take them in. However,
we managed gradually to get her bows up against a large cake of ice
and brought her round with the help of the engines. There was just
room to turn her and that was all. We then set our course back the
way we had come, and so got clear.
The stations we took up during the severe frost were the reverse of
easy, as the metre-wheels froze up, and we had to keep them warm
with thick, red-hot iron bars that were brought from the engine-room
and held close to the wheel-axles.
On the night of the 17th we ran into another storm, which lasted
till we arrived in port.
On the 19th, at midday, we saw land, but were unable to make it
CRUISES OF THE "MICHAEL SARS " 55
out, as the fog hid everything except a strip along the shore. All that
day we tried to establish our whereabouts, but were compelled to lie to
for the night in a hard south-westerly gale. Next day we found that
we were off Gaukvaer Island and stood in for the land. After burning a
little coal our vessel behaved splendidly, and after we had used up most
of our coal and water, and so were very light, we could run before the
sea in any direction without even having to keep the laboratory door
closed. We wanted all our electricity this journey, for it w^as practically
night the whole time.
The " Michael Sars" has carried out a great many different investigations
kinds of investigations in the Norwegian Sea, viz. : observa- !^4ndiaei
tions on the salinities, temperatures, and movements of the Sars."
water-layers ; observations on the floating organisms of various
sizes and kinds ; observations on the bottom fauna, especially
bottom fishes. We have also made practical fishing experiments
to discover what kinds of fish may be caught in the different
areas of the sea.
To describe all the cruises that have been made would take
too long and lead to much repetition. In the subsequent
chapters of this book the most important results are summarised.
In order to study the movements of the water-layers and the
distribution of floating organisms, cruises were undertaken at
different seasons, as opportunity offered, from the coasts of
Norway to Iceland, Jan Mayen, and Spitsbergen. To ascer-
tain the fluctuations in the water-layers we have run a line of
observations, nearly every year since 1900, and always in the
month of May, from the Sognefjord to the north of Iceland.
This route lies exactly across the axis of the Atlantic water that
streams through the Faroe-Shetland Channel into the Norwegian
Sea, and we have consequently been able to obtain a section of
this layer every year, and to compare its volume in different
years. Besides a great many special studies, measurements of
the velocity of the currents have been made out in the open sea
and in the fjords.
At the time the " Michael Sars" commenced working there investigations
were hundreds of square miles of coast banks where no fishing fi°h1n7^°^ ^^^
had ever taken place, and there was therefore a real fascination industry.
in experimenting in these virgin areas with the appliances in
common use along the coast, more particularly with long lines.
Expeditions were made for several years along the whole coast
for capturing spawning cod on all the banks where the depth was
30-100 fathoms, and for halibut, tusk, and ling on the continental
slope ; drift-net fishing was also undertaken for herring.
In these investigations we have chiefly aimed at ascertaining
56 DEPTHS OF THE OCEAN chap.
the geographical distribution, horizontal as well as vertical, of
the most important species of fish, especially during the spawn-
ing period, when many of them are most sought after, and when
each species may be supposed to congregate at localities where
the natural conditions, such as depth, salinity, and temperature,
acre especially favourable and characteristic. These breeding
places have been discovered partly by searching for the spawn-
ing fish, and partly by charting the distribution of the newly-
spawned eggs, which float immediately above the shoals of
spawning fish.
The development and growth of the fish, and the geographical
distribution of the different stages, formed another important
subject for our scientific studies. By various means it is now
possible to ascertain the age of the different individuals in a
shoal of fish, and we are in consequence able to study the growth
of fishes in different areas.
Some of our fishing experiments have had an immediate
influence on the development of the fishing industry, and have
led to fish being found on hitherto unutilised banks, which have
since turned out to be profitable fishing grounds. The study of
the natural history of fishes may be said to have as its main
object the widening of our knowledge regarding all the physical
and biological phenomena on which depend the life of the fishes
and the fishing industry.
During the winter of 1909-10 a great deal of time was spent
in preparing the " Michael Sars " for an extended cruise in the
North Atlantic, in selecting the route to be followed, and in
preparing instruments and apparatus of the latest and most
approved patterns.
A glance at the depth map is sufficient to make it clear that
the greater part of the North Atlantic is deeper than 2000
fathoms. The coast plateaus off Africa, Spain, and the United
States are very limited, and the continental slope is, as in the
Norwegian Sea, very steep. The bathymetrical curves for 500
and 1000 fathoms lie in close proximity to one another. Only
off Newfoundland and from the Bay of Biscay northwards along
the western shores of Ireland and Great Britain do we find the
continental shelf or coast banks widening out into tolerably
broad plateaus. From the coast banks round Iceland a low
ridge extends in a south-westerly direction, known as the
Reykjanes Ridge. This is continued southwards as the Dolphin
Rise, with deeper water on either side. From this low ridge
CRUISES OF THE "MICHAEL SARS
rise the Azores and St.
57
Paul's Rocks, and other volcanic cones
and islands of small extent
rise from the deeper water,
like the Bermuda, Madeira,
and Canary Islands, and the
Dacia, Josephine, and other
banks.
The route of the " Michael
Sars " from Plymouth to Gib-
raltar (Fig. 37) was selected in
order to find the most favour-
able localities for using the
fishing gear, that is to say,
where the continental slope is
less steep than usual, and
where accordingly the gear
would be working on com-
paratively level ground. We
expected to find the best
ground where the coast banks
are broadest ; for instance, off
Ireland, in the Spanish Bay
(Gulf of Cadiz), south of the
Canaries, and off the New-
foundland Banks. In our
crossings of the ocean we
had particularly to take into
consideration the distance be-
tween the coaling harbours.
All preparations being
complete, the " Michael Sars "
sailed from Bergen on the ist
April, the first port made
being Plymouth, where Sir John
Murray joined the expedition.
While at anchor at Plymouth
the captains of trawlers in-
formed us that the bottom on
the coast banks and on the
continental slope was very
rough in some places, but that
if we took a westerly direction
we should have a good opportunity of using the trawl down to
Route of the
" Michael
Sars."
From
Plymouth to
Gibraltar.
Fig. 37. — The "Michael Sars" Observing
Stations from Plymouth to Gibraltar.
58
DEPTHS OF THE OCEAN
great depths. Our previous cruises had taught us what damage
a rough bottom, especially coral, may do to the fishing tackle.
Fig. 38 shows a piece of such coral brought up by the " Michael
Sars " when fishing on the slope between the North Sea and
the deep water of
the Norwegian Sea.
To avoid the corals
we followed the
advice given us and
took a westerly
course when we left
Plymouth on the 9th
of April, and from
the outermost west-
erly skerry, Bishop's
Rock, we steered
out over the coast
banks to the conti-
nental slope. Every-
thingwas meanwhile
got ready for trawl-
ing and for the
hydrographical and
plankton observa-
tions.
Before leaving
the coast bank we
made observations
at our first three
stations in depths of
T46, 149, and 184
metres, partly to test
the winches and in-
struments and partly
to get a section of
the waters on the
bank. All our
arrangements for
hydrographical and pelagic work were found satisfacftory.
We secured a number of samples, and thoroughly tested the
appliances. It was particularly important to see if the closing
nets were to be relied on, so we lowered them to a depth of
50 metres, and closed them immediately. They came up empty.
38. — Piece of Coral {Lophohelia).
About \ nat. size.
CRUISES OF THE "MICHAEL SARS "
59
showing that they do not catch anything when sent down open.
Successful trawlings at Stations i and 3 resulted in both cases
in catches of over 300 fishes belonging to the ordinary coast-
feN >.>>»">
Fig. 39.— Three Deep-Sea Fishes from Staiion 4, 923 metres (ahout 500 fathoms).
a, Macrm-us cequalis, Gthr. Nat. size, 23 cm.
h, ChimcBra mirabilis, Collett. Nat. size, 71 cm.
c. Mora mora, Risso. Nat. size, 45 cm.
bank species. Even these first hauls, however, made it evident
that the big winch did not run smoothly when paying out line.
On the morning of Monday, nth April, a sounding at Station
4 gave us 923 metres. The big trawl was shot with 2360 metres
of wire. At x p.m. we assumed that it was on the bottom, and
6o
DEPTHS OF THE OCEAN
towed it for three hours till 6 p.m., when hauling in began. It
came up at 7 p.m. with a catch of 330 large fishes [Macrurus,
Mora, Lepidion, CJimicsra, etc. ; see Fig. 39). This haul was
a thorough success. Perhaps never before had so large a
draught of fish been made at such a depth. The trawl itself
worked most satisfactorily, and considering its size hauling in
was done rapidly (about 40 metres per minute). During the
process of lowering, however, the big drum got jammed on the
axle, and in spite of all our efforts we could not move it. There
was nothing to be done, therefore, but to make for the nearest
port to repair it, so we steamed into Cork and had it put right
at the workshop on Wednesday morning (the 13th). We found
after finally getting the drum off the axle that a lot of sand from
the foundry had been left in by mistake, which accounted for its
not working properly. By Friday (15th) the sand had all been
scraped off, and the drum was once more in its place. But in
the meantime a strong north-easterly gale had set in, and it was
not till Saturday (i6th) that we were able to steam westwards
under the lee of the Irish coast. The wind continued strong
and northerly, but for all that we steamed back to Station 4,
occupying a couple of small stations (5 and 6) on our way, and
recommencing our interrupted section, proceeded out to still
greater depths.
On Sunday, 17th April, a sounding at Station 7 gave
us 1 81 3 metres. The trawl was shot with 4000 metres of
wire and towed for two hours. It came up all twisted and
tangled, due to the fact that the swivels for keeping the wire
and bridle from twisting had failed to act. The small steel
balls in the bearings of the swivels had been crushed by the
severe strain or the bend in the blocks. The trawl was got
ready for a fresh attempt, but in the meantime the wind and
sea rose to such an extent that we decided to give up further
work in the deep water. To wait for good weather would have
delayed us too long, so we set our course for the north-west
point of Spain.
The pelagic life of the upper 150 metres was extremely
uniform. Several series of hauls with fine-meshed closing nets
revealed the fact that quantities of the same diatoms extended
down to a depth of over 150 metres. This was particularly
interesting evidence as to the depth at which plant life can
exist, even as far north as about lat. 49' 30' N., under special
conditions. From this and other experiments made later Gran
is of opinion that the same vertical circulation which produces
CRUISES OF THE "MICHAEL SARS
6i
a uniform temperature throughout the deep layer also intro-
duces materials, particularly nitrogenous matter from the
surface — that is to say, indirectly from the coasts — which
are favourable to the development of plant life. The plants
were in consequence extraordinarily abundant. At Station 3
we found great quantities of diatoms, even in a haul with the
closing net from 160 metres up to 100 metres.
On our way southwards from Station 7 we were prevented
by the high sea from attempting any fishery experiments, so
we had to content ourselves with making hydrographical
observations (at Stations 8 and
9), and it was not till we were
well down in the Bay of Biscay
at Station 10 that the sea be-
came calmer and the weather
moderated. We sounded here
and got 4700 metres, so that
we now had an opportunity of
trying our appliances in really
deep water (see Fig. 40).
We commenced at this Vertical hauls.
station, while the ship was still
hove to, by taking a series of
twelve water- samples as far
down as 4500 metres, and
made a number of vertical
hauls with the closing nets
down to 1000 metres. Every-
thing was found to work
splendidly, and all these opera-
tions took only about three
hours.
Temperatures were recorded by means of the best kinds
of reversible thermometers, which give readings exact to
within a few hundredths of a degree even at the greatest
depths. At this station we found the temperature at 3000 Temperatures
metres to be 2.40° C. and at 4500 metres 2.56^ C. It was thus ^n deep water.
apparently warmer near the bottom than 1700 metres (or
nearly 1000 fathoms) above the bottom. It has often been
thought that the water might derive a certain amount of heat
from the sea-bottom, and this may have been the case here,
but there is also another possibility, namely, that the water
at 4500 metres had sunk from the upper layers and had been
Fig. 40.
-The Captain sounding in 4700
Metres.
62
DEPTHS OF THE OCEAN
Trawling in
deep water.
slightly warmed while sinking, just as happens with air that
suddenly sinks from a great height towards the earth. This
rise of temperature has also been attributed to decomposing
organic matter and to radio-active matter in the deposits at the
bottom. Whatever may have been the cause, we certainly
found a similar slight rise in the temperature of the deepest
layer on several subsequent occasions during our cruise.
We next resolved to try the big trawl, and to reach the
bottom at 4700 metres we estimated that it would be necessary
to allow 8000 metres of wire, that is to say, 8 kilometres (Fig.
Fig. 41.— The large Winch.
41). We were engaged in paying out line from 5.30 p.m. to
7.15 P.M., and at midnight we commenced hauling in, which
lasted for about six hours. The trawl contained only two fishes
[Macrzcrus) and a number of lower forms of animals : holo-
thurians, a few worms, a gasteropod, a chalk-coloured crab, some
ascidians, and one or two other things (see Chapter VH.).
This seemed to us such a poor catch that we came to the
conclusion that something had gone wrong. The trawl was
therefore dropped again, and could be seen sinking down in
perfect order. After being towed for three and a half hours,
it suddenly stuck fast and stopped the ship. Hauling in took
CRUISES OF THE ''MICHAEL SARS " 63
eight hours, and the trawl came up (Fig. 42) in perfect order,
containing an enormous mass of perhaps a ton of clay-like
Globigerina ooze, that was as stiff as dough, and looked as if
it might have been dug out of a chalk pit. We carefully sifted
and washed it all with the hose, and found only the following
animals : four actlnians, of which two were growing on hermit
crabs, two cirripeds, a holothurian, some gasteropods, and a
few worms. The question now presented itself — was animal
life really so sparse down at those depths, or did our catch fail
to represent it properly ? Had the trawl perhaps, when dragged
through the ooze, been rendered
incapable of doing its work of
capture? If so, how had we
been able to go on towing for
such a length of time ? This
was a problem that could only
be solved by further experi-
ment. A number of glass
floats, about 3 inches in dia-
meter, were sent down with
the trawl, and were found to
have been reduced to the finest
powder by implosion through
the immense pressure at this
great depth.
One thing at any rate we
had learned. The enormous
weight of 8000 metres of wire,
with a huge trawl at the end,
had worn deep grooves in our
blocks and rollers in a very
short space of time. It was necessary, therefore, to have
rollers in reserve if much of this work was to be attempted.
After a few successful pelagic hauls we resumed our course
on the morning of the 21st April in the direction of Spain,
our intention being to do some trawling at different depths on
the continental slope, where the trawlers had told us the bottom
was good. But when we made the coast of Spain at Cape
Sisargas, an easterly gale sprang up and put a stop to all work,
so after a few hydrographical observations (Stations 11 and 12)
we steered southwards along the coast of Portugal. On the
22nd the weather cleared up, and off the town of Vianna we
saw the first line-buoys, and shortly afterwards the picturesque
Fig. 42.— Otter Trawl coming up.
64
DEPTHS OF THE OCEAN
vith their red lateen-sails came into
Portuguese
fishing
industry.
fishing-boats witn their red lateen-sails came mto view on
the horizon.
One of these came close to us, and we had an opportunity
of learning something of their industry. Their boats were flat-
bottomed, with a deep rudder that acted as a sort of keel.
They were working with nets on a hard bottom, and, as a rule,
in 30-40 fathoms of water. Their catches consisted of the
lobster - like " languste " [Palinurzis vzilgaris), large crabs
{Cancer, Liikodes), skates (Raia clavata, R. circularis), sharks
iyCentrina and Miistelus), and breams {Pagellus centrodontus) ,
They also earned some money
by going on board the trawlers
and getting the small fish (small
whitings, hake, etc.), which are
generally thrown away. We
came across the trawlers them-
selves not long afterwards, and
boarded a boat belonging to
Boston, England. They were
irawling for soles {Soiea V2il-
garis) and large hake ; other-
wise they got, as a rule, only
skates and whitings. We shot
our own trawl to see what
there was on the bank, and
captured the same fishes that
the trawlers had spoken about
(Station 14).
The fine weather tempted
us to try to make a series of
hauls at different depths along the edge of the coast banks.
We accordingly lowered the following appliances in the
evening : a tow-net at the surface and two more at 50 metres
and 100 metres respectively, a young-fish trawl at 150 metres,
tow-nets at 300 metres and 500 metres, and another young-fish
trawl at 750 metres.
We had, however, scarcely begun towing our nets before a
northerly gale sprang up. Hauling in had therefore to be done
in the dark, and the sea became high and broke over the stern,
where the gear was being got in. The result was that the
violent pitching of the ship tore the silk cloth of the nets and
did considerable damage. We lost the tow-nets sent to 100
metres and 500 metres, as well as the young-fish trawl at 750
Portuguese Fishing-Boat.
CRUISES OF THE "MICHAEL SARS
65
metres, and a good deal of harm was also done to the others.
All the same we managed to get some samples of interesting
deep-sea forms, though such catches were of a more or less
fortuitous nature.
Off Lisbon the sea became calm, and we took hydrographical
observations at Station 17, obtaining water-samples from many
depths. Here,
out on the edge
of the continental
slope, and in the
Spanish Bay, the
weather was
beautifully warm,
and the sun shone
brightly. We
now met with
some extremely
interesting forms
of animal life.
Numerous dol-
phins swam
round our bows,
and when stand-
ing in the fore
part of the ship
we saw thousands
of small pelagic
crabs {Poly bins ;
see Fig. 4$),
sometimes as
many as fifty of
them in three
minutes. We
also sighted a
turde.
While steam-
ing along Gran studied the plankton filtered from water dan's inves-
obtained by a pump, and found in every sample more than [IfJ'pfank^on.
forty species of diatoms and peridinii, whereas to the west of
Ireland we had come across a diatom-plankton, rich in indi-
viduals but very poor in species, consisting of the ordinary
North European coast diatoms. This showed that we had now
reached a southern and warmer marine region, with a totally
F
Fig. 44. — Bargaini
66
DEPTHS OF THE OCEAN
distinct assemblage of animal and plant life in the upper
water-layers.
On the morning of
Monday 25th April
we anchored off Gib-
raltar, where we had
our boilers overhauled,
and procured reserve
rollers and blocks, as
well as new swivels
for the trawl line.
Currents in During our stay at
GibfSil''^ Gibraltar we made two
short trips : one to
the Strait to study the
currents, and the other
to the Mediterranean
to test our pelagic
appliances. The
Strait of Gibraltar has
for a long time past attracted the attention of hydrographers.
Through this narrow channel the exchange of water between
Fig. 45.— roRTUGUESE Fisherman.
Fig. 46. — Pelagic Crab [Polyhius henslowi, Leach). Nat. size.
the Atlantic and the Mediterranean takes place, and there are
great fluctuations in the two streams. A knowledge of the
laws that govern the currents of this marine thoroughfare
CRUISES OF THE "MICHAEL SARS " 67
is accordingly of the utmost importance, not merely because
of the light it throws on the question of ocean circulation, but
also because of its value to navigation. As early as 1871 Nares
and Carpenter made a study of these currents, and important
investigations have been made in later days by the Danish
research vessel "Thor" under the direction of Joh. Schmidt.
No direct measurements of the actual velocities of the currents
at different depths and their direction had previously been
undertaken, but current-meters, especially the excellent one
constructed by V. W. Ekman, put it in our power to make the
attempt.
The " Michael Sars " had previously measured currents off
the coast of Norway by anchoring a life-boat fore and aft with
grapnels and a stout hemp line. We endeavoured to work on
the same principle in the Strait of Gibraltar (Station 18), but
were unsuccessful at first ; one line after the other parted, owing
to the velocity of the current. Finally we had to anchor the
ship itself with i|^-inch steel line and a warp anchor, in 400
metres of water on a hard bottom. This held, and she lay at
anchor from 1.30 a.m. till 5 p.m. on the 30th April. During
this time Helland-Hansen worked unceasingly. One current-
meter was used continuously at a depth of 10 metres, and
another was lowered to different depths right down to the
bottom. In addition he took a series of water-samples and
temperatures at different depths.
He found that there were two strong currents in the Strait,
one going east from the Atlantic into the Mediterranean in the
upper layers, and one going west at the greater depths. The
limit between them was for the most part at a depth of about
150 metres, but it varied so much that in the afternoon between
2 and 2.30 P.M. it was at a depth of 50 metres, while between
4 and 5 A.M. even at the very surface the current went westwards.
These variations practically coincided with the tidal movements.
There were high velocities in the upper east-going current ;
at 10 metres the velocity varied between i and 2^ knots, and
at 25-30 metres between 1.7 and 3 knots. At a depth of
100-120 metres the current was always westerly, but the
velocity was only between half a knot and a knot, whereas at
150-200 metres, where the current was also westerly, the
velocity varied from 0.3 knot to as much as 5 knots; close to
the bottom a velocity of ^ knot was measured. Helland-
Hansen's interesting observations are the first reliable figures
regarding the niovements at the different depths, and they are
68
DEPTHS OF THE OCEAN
Pelagic inves-
tigations in
the Mediter-
ranean.
Water strata
in the Medi-
terranean.
Noctihuc
of great assistance towards a proper understanding of the
water circulation in the Strait of Gibraltar.
At Station 19, a few hours' steaming from the entrance to
the Mediterranean, we experimented with different appliances,
to ascertain the best way of arranging our subsequent pelagic
investigations. The big silk tow-net, 3 metres in diameter,
was lowered to a depth of 900 metres and immediately hauled
up again. It was found to work well, and captured a number of
pelagic fish (eight specimens of Argyi^ope/ectis, a. few scopelids,
and some young fish), but our catch seemed to indicate that
vertical hauls were not nearly so productive as horizontal hauls,
and we therefore decided to make long horizontal hauls our
principal mode of catching pelagic fish during the remainder of
the cruise.
At this part of the Mediterranean there was a sharply
defined limit between an upper water-layer, where the temper-
ature was fairly high and the salinity almost identical with that
of the upper layer in the Spanish Bay in the Atlantic, and a lower
water-layer with " bottom-water" of uniform temperature (a little
below 13° C.) and salinity (over ;^S per thousand). Several
series of temperatures and water-samples were taken, and the
limit between the two layers was found at a depth of 150-200
metres, though subject to considerable variation, as in the Strait
of Gibraltar but not to such an extent.
The surface water here was so full of phosphorescent
Noctiluca as to be almost as thick as broth, and when the
contents of the tow-net were emptied into a glass they formed a
sediment a centimetre in thickness at the bottom of the glass.
In the evening the sea resembled a star-spangled sky, and the
wires following the vessel looked like gleaming stripes. During
the day we now saw for the first time the beautiful surface
organisms of the south, such as Velella and the Portuguese
man-of-war [P/iysalia), with which zoologists and sailors in
Mediterranean waters are so well acquainted.
From the
Spanish Bay
southwards
along the
north- west
coast of
Africa.
The region from Spain along the coast of North Africa is
well known to zoologists from the successful labours of the
French " Travailleur " and " Talisman " Expeditions. Series of
trawlings at various depths were undertaken by these two ships
with only small beam trawls, so that we had every hope of
accomplishing something with our large trawl. We were able
besides to turn to good account the information acquired from
the fishermen, large numbers of whom have shot their trawls
CRUISES OF THE "MICHAEL SARS "
69
along these shores in recent years. They had given us to
understand that we could reckon on finding good trawling
grounds as far down as 250 fathoms on many of the coast banks
off Morocco, such as the stretch from Cape Spartel to Casa
Blanca, from Mogador to the bay at Agadir, and south of Cape
Fig. 47. — Depths and Stations in the Spanish Bay.
Juby on the inner side of the Canary Islands. We? also
learned that their catches chiefly consisted of hake {Merhiccius
vu/gaj'is), which, as a rule, made up two-thirds of the whole ;
soles [Solea vulgaris), and different kinds of silvery or brilliantly-
coloured spiny-finned fish (mostly Sparidse), which they call
"salmon."
Our plan was to carry out two series of trawlings from the
coast banks outwards to great depths, one in the Spanish Bay
and one south of the Canary Islands, so as to have a general
idea of the fauna at diff'erent depths in different latitudes. We
70 DEPTHS OF THE OCEAN
wished also to take a thoroughly good hydrographic section
right across the Spanish Bay, with water-samples and tempera-
.^•'
Fig. 48.— Three Shore Fishes from Station 20, 141 meires (about 75 fathoms).
a. De/itex maroccanus, Cuv. et Val. Nat. size, 25 cm.
&. Mullns sunnuletus, L. Nat. size, 29 cm.
c. Peristedion cataphracUim, Cuv. et Val. Nat. size, 30 cm.
CRUISES OF THE "MICHAEL SARS
71
tures from all depths, and we hoped to trace the course of
the salt-water layer that flows out from the Mediterranean to
the Atlantic, which we felt would be interesting to all hydro-
graphers.
We left Gibraltar on 4th May and steamed through the Trawiings in
Strait and past Cape Spartel in perfect weather till we came to ^p^"^^^ ^^y-
the coast bank, where at Station 20 (see Chart, Fig. 47) we saw
seven trawlers at work. Our trawl was dropped in 1 4 1 metres, and
towed for two and a half hours. The resulting catch of 163
fishes was a good sample of the ordinary species to be found
there, namely hake, different kinds of gurnard {Trigla sp.),
Fig. 49. — Two Deep-Sea P'ishes of the Family Ai.epocephalid^.
a. Alepocephalus from Station 23 (1215 metres). Nat. size, 60 cm.
b. Conocara from Station 25 (2055 metres). Nat. size, 20 cm.
mullet [Ahtlhis sttrmuletiis), and silvery or brilliantly-coloured
spiny-finned fishes [Capros, Pagelhcs, Dentex ; see Fig. 48).
The next station (Station 21), in 535 metres, yielded 117
fish, including hake, but all the beautifully-hued fish had dis-
appeared. Instead we found the deep-sea fauna coming into
evidence [Maa^urus, CJiinicErd), and at the three following
trawling stations our catches were made up entirely of true
deep-sea fish (Fig. 49), namely : —
Station 23 at 12 15 metres, 77 fishes.
Station 24 at 1615 metres, 32 fishes.
Station 25 at 2055 metres, 29 fishes.
From a technical point of view these hauls were in every
way satisfactory, as our winch, trawl, and all connected with
them worked perfectly smoothly. The new swivels (Fig. 50)
DEPTHS OF THE OCEAN
Relation
between
Mediter-
ranean and
Atlantic
waters.
r
procured at Gibraltar were a thorough success, and stopped the
twisting in the trawl-warp and bridle. The bottom was every-
where well adapted for trawling.
At Station 23 we towed a small young-fish trawl at 12 15
metres. It touched the bottom and brought up a quantity of
empty pteropod shells which had been sifted out from the
bottom deposit. It is extraordinary to find these deposits of
shells belonging to plankton organisms only at certain relatively
shallow and intermediate depths, for, when
alive, the pteropods float over all depths.
Our trawlings further resulted in a fine
collection of invertebrate animals ; at Station
24, for instance, we found the trawl full of
siliceous sponges.
These waters offer a good field for a
thorough study of the distribution of animal
life, for the nature of the bottom and the gentle
slope permit of trawling at all depths. Our
time unfortunately was too short to permit us
to do more than obtain a general impression.
We next turned our attention to the hydro-
graphical investigations, and steamed to the
north side of the bay near Cadiz (Station 26),
whence we ran a series of stations, at all of
which careful hydrographical observations were
made (Stations 26-30).
At the conclusion of the " Challenger "
Expedition Buchan showed that it was pos-
sible to trace the course of the comparatively
warm Mediterranean water out into the North
Atlantic Ocean, In 1909 the Danish expedition in the " Thor"
under Schmidt made some observations from the Strait of
Gibraltar westwards, and secured extremely accurate determina-
tions of temperature and salinity, showing that the Mediterranean
water (in a very diluted state) makes its way out through the
Spanish Bay, sinking down to a depth of 1000-1200 metres.
In our investigations we aimed at studying more closely the
relation between Atlantic water and Mediterranean water, and
we also endeavoured to become familiar with the currents on
both the Spanish and Moroccan sides of the bay. Unfortun-
ately we had to abandon our current measurements, but the
variations of salinity and temperature from our many adjoining
stations give a fairly good idea of the conditions. It is enough
Fig. 50. — The
Swivel.
CRUISES OF THE "MICHAEL SARS "
n
to mention here that in the neighbourhood of Spain the diluted
Mediterranean water was found at far less depths (as near
the surface, in fact, as 400 metres) than farther south in the
bay. The surface current runs along the Spanish coast in an
easterly or south-easterly direction, and off the Moroccan coast
in a southerly or south-westerly direction (see Chapter V.).
Hydrographical investigations were continued all the way
southwards along the continental edge to the Canary Islands.
We were prevented from attempting any other kind of work, as
near Mogador we encountered a stiff north-east trade-wind, before
which we had to run. Every now and then a heavy sea broke
over our quar-
ter, sweeping
the deck clean.
Not till we
reached the
Canaries did
the wind and
sea go down.
At Lanzarote
we met with
calm weather,
so we did some
pelagic work,
taking vertical
and horizontal
hauls. The
latter resulted
in the capture
of several in-
teresting deep-sea fish, a number of leptocephali, and the beautiful
transparent Plagiisia.
On Saturday, 14th May, we anchored at Porta de la Luz,
the harbour of Grand Canary.
\ ,
, \^ ^\
*"^-- ^^S'lSBtetJP ^
1-?^ll
\>- '-^jliM
'^^^ \
i^m\
^k-
mmm^-
jLJ
fcgMi
■^^gj^^mSk
IP^
..
W
Fi.;. 51.
A Fishing Sen
t'O I'ORTA DE
Luz.
In Porta de la Luz we obtained a good deal of information
regarding the fishing industry from a number of fishing schooners
which work along the African coast, several being in port at
the time of our visit.
Most of them are well -boats, which carry live fish in
addition to the ones they salt. They employ partly hand lines
and partly curious large basket-traps, baited with fish and placed
on the bottom in the position shown in Fig. 52.
74
DEPTHS OF THE OCEAN
African "coast
fisheries.
When the boats arrive in port they transfer the live fish
into big floating- tanks, of which we saw many. We were able
to examine the kinds they caught, and learned from the people
the names in current use. This was a piece of good fortune for
us, because the local guide-books give misleading information.
The fish caught are spiny-finned and silvery, or of brilliant
colours. The following are the commonest species : —
Chiacarone = Dentex vulgaris.
Besugo = Pagrus vulgaris.
Burr oor Chlerne = Diagranwia 7nediierrafieuf?i.
Chopa = Canlharus lineatus.
Saifia = Sargus rotidelettii.
Dorado = Chrysophrys aurata.
Most of them are at present sold alive and eaten fresh, but
some are salted, being first split down the back and sliced.
They are also
occasionally dried,
though this kind
of stock-fish does
not keep long.
The harbour
pilot was thor-
oughly acquainted
with the industry.
He himself owned
one or two
schooners, and
had taken part in
the fishing round
the islands and
off the African
coast. According
to him the best
'A
m' mum
0 ■' J^jfe'- r" ^' ■ ■■ rj i-
f'^lf**^
* V , -
Fio. 52.— A Basket-Trap ox board a Fishing Schooner.
places were on the stretch from Cape Juby and beyond Cape
Bojador to the River Ouro, and down near Cape Blanco. The
trawlers found it too expensive to go so far. Only hand lines
and traps are used at present, and most of the fishing is done
on a hard bottom in about 16-30 fathoms of water. He advised
us to go as far as Cape Bojador, where there was a little bay
sheltered from the trade-winds. We decided to follow his advice,
partly because we hoped to see a little of the mode of fishing
practised in the Canary Islands, and thus learn more about the
animal life than we ourselves could expect to learn in the short
CRUISES OF THE "MICHAEL SARS
75
time at our disposal, and partly with the idea of making a series
of trawHngs like those we had made in the Spanish Bay.
^iG. 53.— "Michael Sars" observing Stations off the Canary Islands and
Coast of Africa.
Accordingly we left Gran Canaria on i8th May, and steamed
for Cape Bojador (see Chart, Fig. 53). On the way we
resolved to try our trawl in deep water, as the weather was fine.
fishinj
76 DEPTHS OF THE OCEAN chap.
We sounded, therefore, at Station 35 and got 2603 metres. The
trawl was dropped with 5200 metres of wire and towed for
about two hours till 6 p.m. At 9 p.m. it was on board again
with an extremely interesting catch, including two baskets of
holothurians and twenty fishes, several of which were remarkable
bottom forms {Harriot fa, Bathysaurus, Halosanrus, Alepoce-
phalus, and different species of Macrurus). There were also
several pelagic fish, including the interesting Gastrostoimis
bairdii, with its huge gullet, which had previously only been
found on the American side of the Atlantic.
At Bojador there were seven fishing schooners and two
smacks at anchor. Some of the people were rowing about in
boats setting traps, while others were jigging from the vessels
themselves. We went on board the " Isabelita." Along the
port-rail stood ten men with hand lines, each furnished with
three hooks, by means of which they hauled up the big grey
"burro" as fast as they could pull. Every now and then they
captured " chiacarone " and smaller silvery fish with red fins and
strong teeth. Their bait consisted of anchovies and sardines,
Seine-net which they secured near the shore by means of a seine net. We
were told that at daybreak next morning they were going close
inshore to use their seine, and we obtained a promise to be
allowed to accompany them. To our surprise we were asked
to bring carbines and revolvers, as the fishermen were very
much afraid of the Arabs.
Before daybreak we rowed towards the shore along with the
fishermen to work the seine. The view was magnificent. For
miles we could see the coast stretching away in a straight,
clear-cut line like a mole, a hundred feet or so above the sea ;
up beyond the cliffs the land apparently was quite fiat, and the
sun rose over this line as it does from the horizon at sea.
Unfortunately the breakers prevented us from landing, and we
had to He a short distance out from the shore. On the heights
above we could see the dreaded Arabs, with their long, thin
firearms ready for use ; but they sat as motionless as statues,
and were probably only thinking of defending themselves.
The Spanish fishermen now made several casts with their
seine (see Fig. 54), but were unsuccessful. They had expected
to catch large quantities of sardines for bait. We got from
them, however, some interesting samples of the small fish that
live in quite shallow water, which it would otherwise have
been difficult for us to obtain. Among them were young fish
(sardines and anchovies), and a number of small spiny-finned
CRUISES OF THE "MICHAEL SARS " tj
fish i^Sargus, Box, Pristipoma), besides fry of the horse-mackerel
[Caranx trachurus), and hake. The fishermen gave us the
whole of the catch and would take nothing for it. On parting
from them we felt that we had made the acquaintance of capable
energetic men, engaged in an interesting industry.
The guide-books sold on the islands state that the fishing
industry is undeveloped, because the island population is
apathetic, and the Spanish Government little interested in it.
This is hardly correct ; their African fishing seems to evince
both enterprise and a power of adaptation to circumstances.
It is no small matter to have to sail in the trade-winds,
which are sometimes very violent off the coast of Africa, and
there is besides an absence of harbours. The fish caught are
best suited for selling alive in the local markets, and it is
Fig. 54.— Uau
extremely doubtful whether it would pay to start a fishery on
a large scale, as has often been proposed, and commence
salting and drying. The kinds of fish may possibly be unsuitable
for curing, and the warm climate is very likely less favourable
than that of northern lands. As long ago as the middle of the
eighteenth century an enterprising man named George Glas
made great efforts to establish a fishery, and maintained that
the Spanish did not need to depend on Newfoundland for their
fish, as they could make their African coast fishery the richest
in the world. He did his utmost to prove the truth of his
assertion, but failed, partly because of the natural difficulties,
and partly owing to various tragic occurrences. Taking every-
thing into account, the conditions under which it is carried on
and the present state of the markets, the fishing industry of the
Canary Islands is quite creditable, and the friendliness of the
fishermen towards our expedition was much appreciated by all
on board.
78
DEPTHS OF THE OCEAN
Our plan after leaving Bojador was to undertake a series of
trawlings over the coast banks and continental edge. This
Fig. 55.— Three Coast Fishes from Station 37, 39 metres (about 20 fathoms).
a. Serranus cabrilla, L. Nat. size, 21 cm.
b. Corisjidis, L. Nat. size, 18 cm.
c. ScorpcETia scrofa, L. Nat. size, 48 cm.
proved, however, a matter of great difficulty. Both at Station
37 (see Fig. 55) in 39 metres of water, and at Station 38 (see
Fig. 56) in "]"] metres, the trawl stuck fast on the hard bottom.
CRUISES OF THE "MICHAEL SARS " 79
Still, we succeeded in making some small catches of the animals
that live on the bank, including soles and megrims [Solea and
Arnoglossus lophotes), gurnard, weevers, monkfish, a large
'm
Mt^
Fig. 56.
a. Pagrus vulgaris, Cuv. et Val. Nat. size, 50 cm.
h. MurcBna helena, L. Nat. size, 102 cm.
[a and b from Station 38, tj metres — about 40 fathoms.)
c. Centrisciis scolopax, L. Station 39, 267-280 metres.
beautifully-coloured muraena i^Murcsna helena), and a number
of skates. At Station 39 (see Fig, 56, c) in 267-280 metres of
water, we were more successful, catching a quantity of spiny-
finned fish (Dentex, Pag^'its, Scorpcrna, Trigla), hake and
skates, and quite a number of deep-water fish. A pelagic haul
8o
DEPTHS OF THE OCEAN
CHAP.
on the edge of the continental slope yielded some interesting
captures, especially several spotted eel larvae (leptocephali).
*(l
Fig. 57. — Two Deep-sea Fishes from Station 41.
a. Sy?iaphobranchus pinnatus, Gron. Nat. size, 31 cm.
b. Bathypterois dubius, Vaill. Nat. size, 17 cm.
Deeper trawlings were impracticable. The captain sounded
in several places to try and find a spot where there was a chance
of trawling along the slope at a fairly uniform depth, but the
Fig. 5S.
Leptocephalvs Co/ign
■'ulgaris.
slope was too steep, and we had to abandon the idea. The
only place where, according to the chart, there was any prospect
of trawling at so great a depth as 1000 metres was between the
CRUISES OF THE "MICHAEL SARS " 8i
coast of Africa and the island of Fuerte Ventura. Here we
Fig. 59.
Ceratias, n.sp. Nat. size, 13 cm. Station 42.
sounded at Station 41 and got 1365 metres. We shot our trawl
with 3400 metres of wire, and towed it for three and a half
hours. Hauling in took an hour
and fifty minutes. Our catch con-
sisted of about fifty deep-sea fishes
(see Fig. 57), several baskets of
holothurians, and a number of in-
teresting invertebrates, including
some beautiful, large, red-coloured
prawns, no less than 30 centimetres
long. This catch was extremely
interesting, as it yielded the same
species of fish that we got in
our hauls to the west of Ireland
(Mo7^a^ Trachyrhyncus, Alepoce-
phalus, Synaphobranchus).
The trade-winds had mean-
while freshened considerably, so
we steamed under the lee ot
Fuerte Ventura, and at Station
42 used our pelagic appliances at
„ ^^_. various depths. The captures Eel larv?
» Ifc J were particularly interesting, in-
«eiS ir eluding as they did nineteen larvae
^" p0^ of eels (leptocephali). One indi-
vidual among these (Fig. 58) be-
longed to the ordinary conger-eel
iyLeptocepIialus Congi'i viclgaris), but the other eighteen were all
of another species closely resembling the conger larva, but
G
\i
Fig. 60. — Spirilla. (From Chun.)
82 DEPTHS OF THE OCEAN
differing from it in the number of muscle segments ; some of
them were only 4.2 cm. long. There were further some remark-
able deep-sea fish, including a curious Ceratias (Fig. 59), and
the little rare cuttle-fish, Spimla (Fig. 60), which is of such
interest to zoologists.
During the night some fiying-fish (Fig. 61) with mature eggs
came on board, and on our way back to Gran Canaria we saw a
quantity of flying-fish near the island. We anchored once more
at Porta de la Luz on Tuesday, 24th May.
From the From Plymouth to the west coast of Africa we had been
Uie^Azores" chiefly cruising over the coast banks and continental slopes.
Fig. 61. — Flying-Fish [Exocaiiis spilopus, Val.). Nat. size, 32 cm.
Now we were to begin a voyage across the Atlantic from the
Canary Islands to the Azores and thence to Newfoundland.
Our task henceforth was therefore to investigate a deep
ocean, the average depth of which may roughly be put at
5000 metres. Everything accordingly had to be so arranged
that we could lower our instruments and appliances to profound
depths.
The experiences of previous expeditions had made it clear
that the larger organisms, at any rate, are sparsely scattered over
the vast ocean depths. We therefore prepared ourselves for
long pelagic hauls of a day's or a night's duration, during the
course of which it would be necessary to employ simultaneously
as many appliances as we could at different depths, partly to
CRUISES OF THE "MICHAEL SARS " 83
accomplish as much as possible in a limited space of time, and
partly to discover what creatures inhabit the various water-
strata.
While on our way to the Azores we hoped to be able to
reach the Sargasso Sea and study its peculiar animal life.
Accordingly before leaving Gran Canaria we interviewed some
Norwegian skippers, who had spent many years in the waters
lying between the Canary Islands and the West Indies, and
were advised by them not to steer direct for the Azores, but
to follow a westerly course as far as the longitude of those
islands and then turn northwards. We followed their sugges-
■-^0^
ohQ
^
40' 67o
O O^Q.
o^'^
68"
d6o~
065
O,
V^.C
6A
53'
a/'
0R£5 ■.
dO'
Fig. 62.
Michael Sars" Stations from Canary Islands to the Azores and
Newfoundland and thence to Britain.
tion, leaving Gran Canaria on 27th May, and, as will be seen
from the chart (Fig. 62), first steered westwards, making some
investigations at Stations 43-52, and then northwards to Fayal,
one of the Azores, occupying Stations 53-58, and arrived at
Fayal on 13th June.
Hydrographical investigations were made all this time, and Uniformity
we took as many as fourteen water-samples at different depths graphical
at each station, from the surface down to 2000 metres, thus conditions and
securing some excellent material from this area. Fig. 63 shows °
a section of the ocean on our westerly route. It is remarkable
how uniform the hydrographical conditions proved to be. The
84
DEPTHS OF THE OCEAN
curves of salinity and temperature lie exactly parallel, both
decreasing regularly as we descend in depth.
The animal life, too, showed everywhere great uniformity.
While on this route we made seven long pelagic hauls, some at
night, with a number of appliances working at different depths
simultaneously. The weather was all that could be desired, and
we had therefore a splendid opportunity of testing even the
very finest of our appliances. As a result we succeeded in
collecting a great variety of forms, a full description of which
can only be given after thorough systematic examination. It
5.lQt
5
1 S
0
■^
e -
6
'^
±
—
-
.18-
SMOloo
L
1
-
}V
3eoQ!i» — 1 — --miin:
Z7Z
.500
--
1
-
-
12!
,\'5 50"„„ 1
- —
1000
'i>: ^
—
'""
31
6°_
—
5S2ilJ- .
' j ~"~^-~.^
-~^
--
il-
~"~
■^.^
Fig. 63. — Hydrographical Section showing the Temperature and Salinity at
Stations 44 to 51.
will suffice here to mention the main features of the catches,
and to describe one or two particularly remarkable forms
(especially fishes) that attracted our attention at the time, or
during our first cursory inspection in the laboratory. In the
following chapters the material collected will be treated in a
more systematic manner.
It was interesting to find that from the corresponding depths
we always obtained catches practically identical in character.
In the appliances towed at the surface and down to 150 metres
there were small colourless young fish of many species, and fish-
eggs of very different sizes, some even as small as 0.5 mm. in
diameter, and leptocephali occurred in considerable quantities.
A profusion of crystal -clear pelagic forms, such as the large
CRUISES OF THE -MICHAEL SARS "
85
transparent amphipod (Cystosoma), Veiella, Cesttmt veneris. Animal life
lanthina, Ptei'otrachea, Physalia, and Glazicus atlanticus, were ^g^^Js*^^"^
also characteristic.
At depths of 300 metres down to 500 metres silvery fishes
were much in evidence. The commonest of them were the flat-
\
Ullf'
Fig. 64.— Two Silvery Fishes from a depth of about 300 Metres.
a. Chauliodus sloanei, Bl. and Schn. Nat. size, 6 cm.
b. Argyropelecus hemigymnus, Cocco. Nat. size, 3.5 cm.
shaped Argyropelectis (see Fig. 64, U) Stoinias, Chauliodus (Fig.
64, a), and Seri'ivovier. The fish which we met with most
frequently, however, was the grey-coloured Cyclothone signata,
hundreds of which were sometimes taken in a single haul (see
Plate I., Chapter X.). Several species of red prawns were
also found here.
Our hauls from 1000 metres down to 2000 metres were
86
DEPTHS OF THE OCEAN
equally interesting. They invariably contained black Cyclothone
microdon (see Plate L, Chapter X.), and different species of
red prawns in abundance. In addition there were many of the
rarer sorts of black-coloured fish, Photostomias, etc., mentioned
in the following pages, and dark brown medusae. Atolla,
Fig. 65. ^Stalk-eyed Fish-larva.
for instance, was especially characteristic, and so were red
chsetognaths, and at some stations red nemertines.
Besides the commonest forms which are almost always found
Fig. 66. — New Species of Leptocephalus.
occurring at the same depths, we obtained something of special
interest at nearly every station. We can best illustrate this
perhaps by a brief description of our most noticeable finds at
Yio, 67.— Two Black Fishes with many Phosphorescent Organs, sometimes found
IN the Upper Layers at Night.
a. Photosiomias gite}-nei, Coll. Nat. size, 17 cm.
/'. Idiacanthi/s ferox, Gthr. Nat. size, 22 cm.
the stations marked on the chart (Fig. 62), remarking only
that in their selection we have been guided by what we consider
the most interesting.
At Station 45 we made a haul with seven appliances during
the night. In the upper 150 metres there was a quantity of
young fish (some of which were stalk- eyed ; see Fig. 65),
CRUISES OF THE "MICHAEL SARS "
^7
pteropods, leptocephali (one of which displayed remarkable
pigment ; see Fig. 66), and cuttle-fish. There were besides a
few black fish {IdiacantJms ferox, Photostomias gtiernei\ see
Fig. 67).
In the deep hauls at 1000 metres and 1500 metres there
were numerous very rare animals. For instance, we secured
specimens of the cuttle-fish Spirnla, and of the fish Melanocetus
krechi, the type of which had been discovered by the " Valdivia "
Expedition in the Indian Ocean, so far removed from the scene
of its recapture. Again,
Aceratias macrorhimts indictts,
a small brown fish (28 mm.
long; see Fig. 68), and Cyema
atrum (Fig. 69), had hitherto
only been met with in the
Pacific and Indian Oceans,
and off the coast of Morocco.
It was extremely interesting to find at one spot all these proofs
of the wide distribution of such " rare " pelagic fishes.
At Station 47 we sounded in 5160 metres. Trawling was
tried, but was a failure, as the trawl got out of order and merely
captured a sea-pen {^Umbelhda gilnthcri). During the night we
sighted a turtle, which was thus about 250 nautical miles from
the nearest land, the island of Palma.
At Station 48 we made another attempt at trawling. The
big trawl was dropped with 8750 metres of wire at 11.20 a.m.
Fig. 68.
Aceratias macrorhinus indiciis, A. Br.
Nat. size, 2.8 cm.
Fig. 69.
Cyema atnim, Gthr. Nat. size.
At 2.50 P.M. we commenced hauling in, and the trawl came up
at 9 P.M. This time everything seemed to have gone right,
for the trawl apparently went down and came up again in Trawling ii
full working order. Strangely enough, the catch was meagre ^^^'^p '''^'^'•
in the extreme, consisting of half a barrel of ooze, a number of
pumice fragments, the earbone (bulla tympanica) of a whale,
two sharks' teeth [Cai'ckarodon and Oxy rhino), a fragment of a
nautilus shell, two holothurians, about ten pteropod shells, an
'antipatharian, a sertularian, Umbellula, six fishes {^AlepocephahiSy
Malacoste2ts indicus, Argyropeleciis, leptocephalus in its transition
stage from the larval form, a new form resembling Ipnops
S8
DEPTHS OF THE OCEAN
murrayi, for which Koefoed and I propose the name Bathy-
microps regis, and an ophidiid not yet determined). All these
fishes, if we except, perhaps, Bat/iymicrops regis, were prob-
ably captured while the trawl was being hauled in. There were
thus no undoubted bottom -fish in this long haul with our
large appliance, and taking everything into consideration,
we had caught
extremely little.
Chapter VII.
deals more fully
with the signific-
ance of this result.
We were interested
to find a fragment
of a sea-pen [Um-
bellula gihitheri.
Fig. 70) which con-
tinued shining
brightly on the
deck, thus furnish-
ing fresh proof of
the well-known
fact that some of
the lower animals
from the profound-
est depths emit
light.
While towing
the trawl we made
some interesting
observations on the
pelagic animal life,
as we put two tow-
nets on the trawl
wire, the one being
towed at about 40
metres, and the other at about 2000 metres, and during the
whole of the day we took samples from the surface.
The tow-net at 40 metres contained a mass of red copepods,
which were not observed at the surface during the daytime, but
suddenly appeared as soon as it grew dark, soon after 6 p.m.
The surface plankton comprised Physalia, a great many molluscs,
such as lanthina and Pterotrachea, one of the remarkable little
Umbelhila giintheri (phosphorescent).
CRUISES OF THE "MICHAEL SARS
fishes called SQ2i-\\ovse.s, (Hippocanipiis, Fig, 71), and the beautiful
belt of Venus {Cestum veneris) ;
very many pelagic foraminifera
were present in the fine nets.
Our deep tow- net caught a
large Alepocephalus, showing that
this fish may be pelagic. So far
as we know it had hitherto been
taken only in the trawl, and this
catch was all the more interesting,
because our trawl at the end of
the same wire also captured a
specimen ; previously one would
have taken it for granted that
this specimen must have been
caught at the bottom.
At Station 49 B we towed seven
appliances in daylight, and no
black fish were captured in the
upper layers. We observed a
number of Portuguese men-of-war
{Physalia), around which were a
great many small fishes — prob-
ably horse-mackerel {Caranx),
which we caught in one of the young-fish trawls — and fry of
Scombresox. A beautiful large transparent amphipod {Cystosovia)
Fig. 71. — Hippotaiiipiis.
Fig. 72.
Opisthoproctus soleatus, Vaillant. Nat. size, 6.5 cm.
was secured at 200 metres, and young Argyropelecus at 500
metres. In the deeper appliances we found large ostracods
90
DEPTHS OF THE OCEAN
{Gigantocypris) with eggs, Opisthoprochis soleatus (a remark-
able little fish, with large telescopic eyes, caught once or twice
,i'' 3
Fig. 73.
Opisthoprodus grimaldii, Zugmayt
Nat. size, 2. 6 cm.
previously ; see Fig. 72), and another species of the same genus,
Opisthopi'ocUis grimaldii (see Fig. ']^, two specimens of which
were taken by the Prince of Monaco off the coast of Portugal.
P
D
\V
rm'*T]7-
^--^^> —
Fig. 74. — Floating Long Lines.
b. Big buoys ; c, drift anchor ; d, leather buoy.
There were also some specimens of the little Aceratias viacro-
rhiniis indicus.
Drift nets We had all along intended to try drift nets and floating lines
and lines. ^^^ j^^ ^^ occan to sce whether big fish were to be caught there,
CRUISES OF THE "MICHAEL SARS "
91
so we now made the experiment. A line was set perpendicularly
with 1300 cod hooks, a fathom and a half apart (see Fig, 74),
and we also put out six cod nets. Only one fish was caught on
the line, at a depth of 550 metres, namely, Omostidis loivei
(Fig. 75), which Lowe captured at Madeira, and is recorded
by GUnther as having been found near the Philippines by the
Fig. 75.
Omosiidis kncei, Gthr, Nat. size, 14.5 cm.
" Challenger." A large ossified spine springs from its gill-cover
and extends right along the side of its body, and it has very
large teeth ; it has a beautiful silvery appearance. Our bait
(sprats) was unfortunately several months old, so that this
experiment cannot be regarded as in any way conclusive.
In the nets there were three pilot-fish {^Naitcrates d2Lcto7%
Fig. 76.
Naucrates diictor, L. Nat. size, 23 cm.
Fig. 76), and under the boat when hauling in the nets a number
of fish were noticed, of which we saw a good many subsequently ;
they seemed to be plentiful near the surface of the sea, and two
species, Lirus ^naculahis (Fig. ']']^ and Lints oralis, were
eventually secured.
At Station 51 we fell in with larger and smaller patches of
drifting Sargasso weed with the ordinary gulf-weed animals
clinging to it, such as small crabs, naked molluscs, and fishes
92
DEPTHS OF THE OCEAN
(Syngnatkus ; see Plates V. and VI., Chapter X.), and in the
open water between the patches were Portuguese men-of-war,
invariably attended by small fishes. This seems to be a
phenomenon corresponding to the association of the cod-fry
with jelly-fishes in the Norwegian Sea.
At this station we made a very successful haul during the
Fic. 77.
Lints maci/Iafus, Gthr. Xat. size, 9.5 cm.
night of 5th-6th June with nine appliances. In addition to the
ordinary surface animals previously referred to, the tow-net at
the surface secured as many as sixty-one leptocephali belonging
Fig. 78. — New Species of Leptocephalus.
to what we have since found to be a new species (Fig. 78),
of which twenty-three specimens were captured at Station 52.
There was also an interesting high leaf-shaped leptocephalus
(Fig. 79), another specimen of which was taken at Station 56.
In the upper appliances there were quantities of fish-eggs
and young fish, another Cystoso7na, and Ceratias couesii, which
had previously been taken by the " Albatross " off the east
CRUISES OF THE "MICHAEL SARS " 93
coast of North America, by the "Challenger" near Japan, and
by the "Valdivia" in the Indian Ocean at the bay of Aden.
At this night-station, too, there were black fish in the upper
layers, such as Ash^onesthes 7iiger (Fig. 80), a dark Dacty-
lostoinias, and some black Cyclothone at 300 metres. An
Fig. 79. — New Spfxies of Leptocephalus.
interesting cuttle-fish with stalk-eyes was taken at 350 metres,
and deeper down we got Serrivoiner, Ahmichthys scoiopaceus,
MalacosteiLS niger, M. choristodactylus.
At this station we were able to try an apparatus for
Fig. 80.
Asironesthes niger. Rich. Nat. size, 3.5 cm.
ascertaining the depth to which the rays of light penetrate.
It was constructed by Helland-Hansen, and is likely to Heiiand
prove useful in the study of the forms of life in deep water. ^^^"J^^^^^^j.
The apparatus shows the intensity of the light both from above and °™^ ^^
and from the sides. By means of panchromatic plates and p^
colour filters it is possible to tell, not merely whether there is
otometric
experiments.
94 DEPTHS OF THE OCEAN
light, but also the proportion of the different prismatic colours
at different depths. At the very first attempts the apparatus
acted perfectly, and as far down as looo metres at any rate
showed light in considerable quantities, whereas at a depth of
1700 metres the plates were unaffected even after an exposure
of two hours. We may assume accordingly that the amount of
light at the latter depth is infinitesimal. The ultra-violet and
blue rays are the ones that penetrate deepest. There were
plenty of these rays at 500 metres, whereas the effect of the red
and green rays there was imperceptible even after an exposure
of forty minutes. At 100 metres the rays were of every colour,
though red rays were least numerous, while there were rather
more green rays, but even at this depth blue and ultra-violet
rays predominated. These experiments are of great assistance
in dealing with such problems as the growth of plants, for
which light is essential, the colours of animals at different
depths, and the remarkable modifications in the organs of sight
and phosphorescent light-organs that are so characteristic of the
higher animal groups in the ocean depths.
Another haul by night was made at Station 52, though only
with four appliances, the deepest of which was at about 600
metres. The catches in the tow-nets at the surface and at 30
metres were particularly interesting, including a quantity of
young fish, amongst which were young fiying-fish and a number
of young Scojubresox, many leptocephali, one of which was
afterwards found to be a small undeveloped larva of the common
eel ; that is to say, a transition stage from the ^gg to the fully
developed leptocephalic larva. It was extremely interesting,
too, to find eggs of the deep-sea fish Trachypterus at the
surface of this deep basin.
In our deepest appliance we found the beautiful Macrostomias
longibarbatus, captured by us at Station 28 in the Spanish Bay,
and previously recorded by the " Valdivia " Expedition from
the Gulf of Guinea and the Indian Oceart. We also captured
a specimen of Opisthoproctns soleatus, as well as a species of
Oiieirodes resembling niegaceros (Fig. 81). The haul with the
trawl resulted in a take of at least two litres of large red prawns.
As we had now reached the Sargasso Sea, at Stations 5 1
and 52, we set our course northwards towards the island of
Fayal, where we intended to coal before crossing over to
Newfoundland. While steaming towards the bank which
surrounds the Azores, we frequently saw sperm whales, some-
times swimming on the surface and easily recognisable by
CRUISES OF THE "MICHAEL SARS " 95
their abrupt heads, and sometimes with their flukes in the air.
A school of other whales, probably the " caaing-whale," was
also seen.
At Station 53 we reached a lesser depth of water, namely
2615 to 2865 metres, and had, accordingly, arrived at the slope
rising from the deep basin of the Atlantic to the plateau of the
Azores. A sample from the bottom showed much pumice,
pteropod shells, and a large percentage of carbonate of lime,
with siliceous spicules of sponges and radiolaria.
We shot the big trawl with 6400 metres of wire, and towed
it from ten in the morning till two o'clock in the afternoon. At
5,15 P.M. it came up with a most successful catch. The greater
abundance of organisms here as compared with profound depths
was surprising. There were at least 500 holothurians belonging
Fig. 81.
Oneirodes sp. Nat. size, 2.5 cm.
to several species, large red crustaceans, fifteen Pagurtts, a
number of actiniae, lamellibranchiates, and sponges, as well as
thirty-nine fishes (different species of Macrtirus, Alepocephalus,
Halosanropsis, Bathysaurits, Benthosaurus, and Synapho-
brancJms). This haul proved again that animal life was
abundant at about 3000 metres (1500 fathoms).
Our pelagic hauls were equally interesting. They were
carried out during the night of 8th June, and nine appliances
were towed simultaneously. The surface tow-net contained a
quantity of the large medusa [Pelagia atlanticd), a number of
what are sometimes called salmon-herrings (scopelids, most of
them Mydophuni coccoi or M. pMiictatiini), and as many as
thirteen black Astronesthes niger. This was the more remark-
able because we had towed appliances on the trawl-wire at a
depth of 30 metres the previous day, for at least four or five
hours, and had not captured a single scopelid or Astronesthes.
A better proof of the vertical wanderings of these animals seems
96
DEPTHS OF THE OCEAN
hard to find. Young fish, too, were nearly absent during the
day, if we except a few specimens taken in a tow-net at 60
metres, but at night we got masses of them at 50 metres.
Among these young fish in the upper layers we found again
five little eel larvae of a size smaller than the grown larvae,
and there were besides a number of interesting young fish
with telescopic eyes, young flying-fish, and different species
of leptocephali. At 150 metres we secured two remarkable
leptocephali with long rostrums (see Fig. 82).
In the intermediate layers, that is to say, from 300 to 500
82. — Two New Leptocephali with Rostrums.
metres, we found stomiatids, there being no fewer than fourteen
specimens of Ckauliodus sloaiiei in a little tow-net half a metre
in diameter. At 800 to 1300 metres there were plenty of
" rare " fishes; for instance, seven specimens of the large-mouthed
Gastrostonius bairdii, a specimen belonging to a new genus of
the Gastrostomidai (Fig. 83), a small fish which has not yet
been described (Fig. 84), one Cyema atrtini, three Aceratias
macrorJiinus indicus, masses of black cyclothones, and several
others of the more common forms. This station may well be
called an El Dorado for collecting zoologists, and instead of a
few days, months might profitably be spent to the south of
the Azores, where we found so many new and interesting forms.
At Station 56, situated about 100 nautical miles from
Fayal, the depth was 3239 metres. Here we lowered nine
pelagic appliances on the evening of loth June, and hauled
CRUISES OF THE "MICHAEL SARS " 97
them ill next morning between 2 a.m. and 4.30 a.m. Our
catches resembled those at the preceding stations. At 50 to
150 metres there were quantities of fish larvae and young fish,
including two small eel larvae and also the young of Macrttrus,
a deep-sea fish, the young stages of which thus occur in the
upper water-layers. Many of the young fish had telescopic
Fig. 83. — Two Gastrostomid.^.
a. Gastros/omiis bairdii, Gill nnd Ryder. Nat. size, 47 cm.
b. New genus. Nat. size, 20 cm.
eyes. The fact that we obtained young flounders showed that
we were nearing land. At greater depths we secured nothing
of any particular note, merely the usual deep-sea forms.
While examining the material from our tow-nets in the
morning, we noticed numbers of small silvery fishes near the
ot turtles.
Fig. 84.
A new species, not classified yet.
surface ; and later on, when we commenced steaming towards
Fayal, we came across one turtle after another. The boat was Great capture
therefore lowered, and a regular turtle-hunt began. Our plan
was to row carefully up to the animals, which lay quite still on
the glassy surface, seize them by the hind leg with our hands,
and heave them into the boat ; in this way we captured as
many as fifteen turtles belonging to the species Thalassochelys
H
98
DEPTHS OF THE OCEAN
corticata. Under the turtles there were often quite a number of
the Httle silvery fish alluded to above, and we caught some of
them in a net and found that they were horse mackerel (Caranx
tracJmi'its, see Fig. 86). Some larger fish too were occasionally
seen below the turtle near the mouth, just where the neck
leaves the carapace.
These swam under the
boat as soon as the
turtle was caught, but
we captured three, and
found them to be wreck-
fish i^Polyprion ameri-
cantis). Quantities of
blue isopods were
seen beneath one or
two of the animals.
Our meeting with tur-
tles was extremely in-
teresting, as we found
Michael that their stomach con-
tents consisted entirely
of medusse and salpae, immense quantities of which floated near
the surface of the sea. In the transparent blue waters we
could perceive thousands and thousands of beautifully-coloured
and iridescent chains of salpae, sometimes as much as 6 to 7
Fig. 85. — T. H. Murray on board the
Sars," iith June 1910.
Nemichthy.
Fig. 86.
Caranx trachurus, L. Nat. size, 10.5 cm.
metres in length, besides siphonophores and floating aurelias,
with little fish in attendance, — a fascinating pelagic animal life.
We made yet one more pelagic haul at Station 58, and
caught a splendid specimen of one of the most remarkable deep-
sea forms \Nemichthys scolopaccus). This is a long fish, with a
long beak like that of a bird, large eyes, quite short body, and
CRUISES OF THE ''MICHAEL SARS" 99
an immense tail. Our specimen was about 125 centimetres
long, of which the beak accounted for 8 centimetres, while the
distance from the corner of the mouth to the anus was 4 centi-
metres, the remainder being thus over a metre long. This
creature has been caught previously in both the Atlantic and
Pacific.
After sounding at Station 58 in 1235 metres, we decided to
shoot our trawl. Hardly was it well out, however, before it
stuck fast, and brought the ship completely to anchor. We
availed ourselves of this circumstance to obtain some current
measurements, hauled in on the trawl-wire, and passed it forward
to the bow, being thus as it were riding on a warp.
We commenced measuring the currents at midnight, and
went on till 3 p.m. next day, when we attempted to haul in the
trawl. Unfortunately, however, the wire parted, so that we
lost the trawl and 1500 metres of line as well. Still we had at
any rate succeeded in taking some measurements, our mode of
working being to have one current-meter constantly recording
velocities at 10 metres, while another current-meter was lowered
to different depths. The movement of the water-masses at
10 metres was a typically tidal one. In deep water, too, there Tidal currents
were relatively strong currents as far down as 800 metres, and "^J^^^ °p^"
distinct indications of tidal movements. Generally speaking,
the currents in deep water had an opposite motion to those of
the surface layers, but a fuller account will be found in Chapter V.
It is sufficient to state here that our expedition succeeded
in measuring currents out in the ocean at considerable depths,
and that we found tidal movements even at profound depths.
We anchored at Fayal on 13th June.
One of the most interesting tasks of our expedition was to From the
take a section across the western basin of the North Atlantic j^ewfoimd-
from the Azores to North America. A section of the Gulf land.
Stream as far south as we could manage would, we felt sure,
be of value, and it would also be interesting to compare the
animal life which we had found in the eastern basin between
the Canaries and the Azores with that of the waters farther
west. Unfortunately the accident by which we lost our trawl
and 1500 metres of wire on the Azores plateau prevented us
from sweeping the greatest depths, but we were still in a
position to carry out pelagic experiments.
It would have been desirable to set our course from the
Azores to the Bermudas, and then on to Boston, finishing with
lOO
DEPTHS OF THE OCEAN
a series of short zig-zag sections between the land and the edge
of the coast-banks, till we reached Newfoundland. We should
in that case have been able to study the remarkable transition
that occurs on passing from the almost tropical conditions of
the Sargasso Sea to those of the icy Labrador Stream, which
creeps southwards along the Labrador coast from Baffin's Bay
to Newfoundland, and even farther south. The short time at
our disposal made this impossible, and we were compelled to
cross from the Azores to the nearest coaling station, namely
Newfoundland, and then make for home.
The mere distance between the
Azores and Newfoundland, between
1 200 and 1300 nautical miles, was a
serious consideration for our little vessel,
for we had to count upon meeting head-
winds and currents, especially when we
reached the Gulf Stream off the New-
foundland Bank ; and there was always
the possibility of fog delaying us. We
resolved accordingly to go westwards
towards the eastern boundary of the
Gulf Stream, and then turn northwards,
which would increase the distance to
1800 miles, but would offer better condi-
tions of wind and current. We should
also be enabled to visit again the Sar-
gasso Sea, the animal life of w^hich we
had found so interesting, and we should
further be able to take a section right
across the axis of the Gulf Stream. To
prepare for all emergencies we not only
filled our bunkers as full as they could hold with the best
Welsh coal, but also piled our decks with as much as we could
find room for. This done, we said farewell to Horta's little
harbour on the afternoon of 17th June.
During the first two or three days of our journey west we
had wind and sea dead against us, so work was limited to
hydrographical observations at Stations 59 and 60 (see Chart,
Fig. 62). The weather afterwards cleared up, and at Station 61
we met with certain fishes, hitherto regarded as extremely
rare, swimming about on the surface of the Atlantic. On lower-
ing a boat to examine a drifting log overgrown with barnacles
(Fig. 87), we found it surrounded by fishes like those observed
Fig. 87.
Lepas anatifera.
hi
CRUISES OF THE -MICHAEL SARS " loi
by us in the Sargasso Sea near Station 50, and we succeeded
in capturing eleven specimens belonging to the species
Pimcleptcj^iLS bos chii 2ind Lirus pei'-ciformis.
At Station 62 we tried nine pelagic appliances at different
depths on the night of 20th June. Our catches were very
satisfactory at all depths, and much
^ resembled those taken between the
I^Sl
Canary Islands and the Azores.
Fir.. 88.-THE SMALLEST LARVA ^^ the Upper kycrs there were
OF THE Common Eel caught some extremely interestmg leptoceph-
"^.'.'™:'.o,'rKa..'tr" aH, including no fewer than eleven
specimens of the common eel larvae Eel
(Fig. 88), 5 to 5.7 centimetres long, showing that the little eel
larvae are to be met with west as well as south of the Azores.
We also found two individuals, only 4.7 and 5.1 centimetres
long, of leptocephali belonging to the deep-sea fish Synapho-
branchus pinnattis. This had previously only been met with
in sizes approximating to the full-grown larva (10-13 cm.), of
which we found several at the different stations ; but it was
most interesting to come across
such small (early) development
stages of the species.
At depths from 300 metres
to 50 metres there were again
the same colourless Cy clot hone
signata as well as silvery
Argyropelecus, Stomias, and
Chaiiliodus. We got, too, a
new species of Ce^'alias. In
the deepest hauls, below 500 \ ' y' — j
metres, the forms were the same "-- >^' A
as in previous hauls. There Vl'
was the little black fish, Cyclo- \
tJione microdon, once more, red ^^^ 89.-LARGE closing net.
prawns (particularly Acanthe-
phyra), red sagittae, dark - brown medusa i^Atolla), large
ostracods {Gigantocypi'is), and the same kinds of " rare " fish:
GastrostoTjms bairdii, Cyema atrum, Gonostoma grande, Dactylo-
stoniias, and several others.
These numerous horizontal hauls accorded so closely with
each other that we now began to feel that there must be a well-
defined conformity in the vertical distribution of the different
forms. Still, to avoid any uncertainty, we considered it desirable
I02 DEPTHS OF THE OCEAN
Vertical to try at the same time some vertical hauls with our closing
oflnimah" nets. Accordingly, at Station 63 we made two series of hauls,
one with a silk net i metre in diameter, and the other with the
large 3-metre silk net {Fig. 89).
These experiments merely resulted in our capturing the
species which occur most commonly, — a fresh proof that it is
difficult to become acquainted with the fauna when only vertical
hauls are made. A great many of the forms are too scarce to
be caught by such means, and can only be taken by long-
continued horizontal towing. In the case of the commonest
species, however, these vertical hauls do give an indication
of the vertical distribution as well as of the quantitative occur-
rence at different depths. It is advisable, therefore, to supply
a few particulars of our experiments with the large net : —
Only 10 fishes were taken in a haul from 4500 metres up to 1500
metres, where we closed the net. All of them belonged to the species
Cydothone inicrodon.
In a haul from 1350 metres up to 450 metres we got 44 fishes; 27
specimens of Cyc/othone mzcjvdon, 3 of C. signata, and 14 young fish
(stomiatids and others).
In a haul from. 500 metres up to 200 metres some small specimens of
Cydothone signata and a number of young fish were caught. From 200
metres to the surface there were only young fish.
This agrees with what we found when making horizontal
hauls. The black Cyclotkone 7Jzicrodon is only to be met with
in deep water, where the light-coloured C. signata is absent,
and C. signata occurs nearer the surface — from about 500
metres up to 200 metres — but has not been taken in depths less
than 200 metres.
It is important to note how much fewer the individuals are
in the deepest hauls. Though we drew the net through 3000
metres (from 4500 up to 1500 metres), we only caught 10
fishes, while in the 900 metres of water from 1350 metres up to
450 metres we got 44 individuals, 27 of them belonging to the
same species as the 10 fishes from greater depths.
Similar conditions appear to prevail in the case of the red
prawns, for in our deepest haul we caught only 1 1 large red
prawns, but in the haul immediately above it there were 35
individuals. This seems to indicate that the deepest water-
layers cannot at all compare in abundance of organisms with
the intermediate layers.
At this station we also recorded a very large series of
hydrographical observations, namely, twenty water-samples and
CRUISES OF THE "MICHAEL SARS " 103
temperature readings down to a depth of 4850 metres. We
were interested to discover that the bottom temperature was
only sHghtly under 2^° C, and thus exactly agreed with what
we had previously found in the eastern basin.
During the night several flying-fish came on board, and in
the morning we again saw small patches of the Sargasso weed. Sargasso
Gran came to the conclusion that these patches must be much ^^^^'
younger, or, rather, that they have drifted for a shorter
time, than the ones found farther east. They had long
vigorous shoots, which reached higher up above the water
than the older growths, and it was easy to tell the top in every
patch. In the older growths, which had been drifting about for
a long time, the shoots in every direction were more stunted,
and the patches became mere tangled masses of weed and lay
deeper in the water. We found on them the ordinary small
crabs {Planes mijiutus), needle-fish {Syngnatktcs pelagicus), frog-
fish [Antennarius), molluscs, compound ascidians, and hydroids
(see Plates V. and VI., Chapter X.).
Station 64 was one of our most successful stations. The
pelagic appliances were lowered in the morning between
6.30 A.M. and 9 A.M., and hauled in from 2.30 p.m. to 5 p.m.,
with excellent results. In the surface layers we secured a
quantity of fish-eggs, including various stages of the eggs of
scombresocids, tiny young fish with stalk-eyes, two small eel
larvae (4.1 cm. and 4.8 cm. long), a number of remarkable
cuttle-fish, and three small leptocephali (1.7 cm., 1.7 cm., and
2.1 cm. in length), all differing in appearance. They cannot
belong to the larvae of the common eel, because they have too
many muscle segments (over 130).
In deep water we got the same familiar forms in unusually
large quantities. The following table shows the numbers of
the species most commonly occurring, belonging to the genus
Cyclotkone : —
Light-coloured, Dark-coloured,
Cyclothone signata. C. nncrodoii.
Young-fish trawl at 500 metres . 1240 214 (small individuals)
„ ,, 1000 „ . 82 448
,, ,, 1500 ,, . 22 322
1344 984
Thus of the two species we were able to preserve more
than 2000 individuals ; we endeavoured to keep all that were
brought on board, but a good many were damaged by the
apparatus, and had to be thrown away.
I04 DEPTHS OF THE OCEAN chap.
These results served to confirm the opinion we had formed
at the previous station (63) that the Hght- coloured species
lives nearer the surface, while the dark-coloured species inhabits
greater depths. Red prawns, sagittse, and other creatures were
found in large numbers in deep water, and we continued to
meet with such forms as G astro sto77ius and Opisthoproctus, and
a new Oneirodes (Fig. 90).
We also discovered a curious little young fish, 4 cm. long,
which we can only suppose to be a transition stage from a
Larval leptocephalus to a Gastrostoimis (probably G. bairdii, which we
so often met with). Its head shows clear indications of the
Fig. 90.
Oneirodes, n.sp. Nat. size, 1.4 cm.
remarkable gullet, the tiny eyes far forward near the snout, and
the small ventral fin. Posteriorly the body much resembles a
leptocephalus, but here, too, there seems to be a commencement
of the strange organ which is situated at the end of the long
tail of Gastrostonuis. What is chiefly interesting about this
find is that it affords fresh proof of the relationship between the
saccopharyngidae and eels. When search is made, as it prob-
ably will be soon, for still younger stages of the common eel
larvae than the ones we found, it will probably be of zoological
interest to seek in these teeming waters for transition stages
between this strange form and the earlier leptocephalid stages.
Another deep-sea fish at this station that deserves mention
was a form, as yet apparently undescribed, which resembles the
undoubtedly blind fish {Cetomimus) found at Station 35 ; the
eyes appear very much reduced, just as in the case of its
relative. Both of them were taken in deep water, at 1000
metres.
CRUISES OF THE "MICHAEL SARS "
105
In addition to the silk nets Gran now commenced using
his big steam centrifuge (Fig. 91) for centrifuging the water
Fig. gi. — The Large Centrifu
samples from difterent depths. Several successful experiments useofthe
had already been made centrifuge.
with it, but it was at this
station that he started to
employ it systematically,
and he continued to avail
liimself of its help until
the end of the cruise. By
means of it he was able
to collect in a little drop
below the microscope all
the most minute organ-
isms, and in spite of the
movements of the little
ship and the vibration
from the propeller, he
was able with his micro-
scope to study the many
hitherto unknown forms
in their living state, to
draw them, and to count the number of the different species
(Fig. 92). A full description of these investigations will be
pp/
p,
i
Fig. 92.
-Gran counting the smallest
Microscopic Plants.
io6 DEPTHS OF THE OCEAN
found in Chapter VI. A few particulars may, however, be
given here.
Among the exceedingly diminutive plants found in the
open sea, calcareous flagellates or coccolithophoridse are the
most important, especially in the w^armer waters. During the
"Challenger" Expedition, Murray discovered that they were
distributed everywhere over the surface of all warm seas, and
he stated that they were plants. These small organisms occur
in far greater abundance, both of species and individuals, than
had hitherto been supposed. In reality they, together with
Great diatoms and other algse, constitute the fundamental source of
cocc"omho-°^ food for all animals in tropical and sub-tropical waters. In the
phorida; in the Sargasso Sea there were in every litre 12 or 15 species and
. argabso -ea. ^qoo to 3000 individuals. In colder masses of water they
decrease very greatly in quantity, yet even on the edge of the
Newfoundland Bank, with a temperature of 2^^ C, we still met
with one or two species numbering 50 individuals to the litre.
In the Arctic and Antarctic Oceans, on the other hand, they
are not found at all.
After occupying Station 64 we were compelled to turn
northwards and steer for our next coaling station, St. John's,
Newfoundland. We had to abandon any idea of following up
in a southerly direction the remarkable finds we had made, and
probably thus lost the chance of making the most interesting
discovery of all, namely, the earliest stages of eels, Gastrostomiis,
and other forms. Still there was the possibility of learning
something about the currents off the coast of North America,
as well as the connection between the different water-layers and
the plants and animal forms existing in them.
Fig. 93 shows a temperature and salinity section from the
Sargasso Sea to Newfoundland. At Stations 64 and 65 we see
the vast layer, with a salinity of over 35 per thousand and high
temperature down to considerable depths, the same as found
by us over the whole distance from away beyond the Canary
Islands.
On our way north from Station 64 on 28th June we saw
patches of Sargasso weed all the morning, and numbers of flying
fish, about 10 centimetres long, started up in front of our bows.
This led us to believe that we should capture the same forms as
before, when we lowered our pelagic appliances in the evening
at Station 66. Great was our astonishment, therefore, to discover
next morning on hauling in our appliances that the catches
CRUISES OF THE "MICHAEL SARS
107
mainly consisted of true "boreal" plankton, that is to say,
animal forms which we were accustomed to get in the so-called
extension of the Gulf Stream in the Norwegian Sea right up
to the very shores of Spitsbergen. There was the amphipod
Etitheinisto, the copepod Eiichceta, and " whale's food " (the
pteropod Clione Iwiacina), large quantities of which are met with
from time to time in the waters between Spitsbergen and the
north of Norway. This last is not an "arctic" form, that is, it
is not associated with polar water in the Norwegian Sea, but
on the contrary is found in Atlantic water to the south of Iceland,
C9 .,, C7 66
see-s-i 96
Fig. 93.— Hydrographical Section from the Sargasso Sea to the
NEWFOrNDI.AM) BAXK.
according to Danish observations. It seems, however, to be
associated with the northern portion of the Adantic and the
Atlantic water that enters the Norwegian Sea. These animal
forms were entirely absent during the whole of our cruise from
the Canary Islands to Station 64, so that their occurrence at
Station 66, where lower temperatures were recorded at no great
depth beneath the surface, is very significant.
We fancied now that we had said farewell to the Sargasso
Sea and its interesting animal life, but at Stations 67 and 69, in
close accordance with the hydrographical conditions depicted in
F^g- 93. we came once more across more southerly forms.
io8 DEPTHS OF THE OCEAN
In the upper layers there were the same young fish, many of
them with stalk-eyes, and leptocephali, while flying fish, Sar-
gasso weed, and the familiar Sargasso animals were all once
more in evidence.
We found a large cluster of eggs, weighing approximately
a kilo, drifting about at Station 69, belonging to the common
angler-fish [Lopkius piscatoritts), the development of which was
studied by Alexander Agassiz ; we hatched out the eggs and
obtained the stages depicted by him. Angler-fish only inhabit
the coast banks, so that our find of slightly developed eggs, that
could not have been drifting many days, indicated that we were
now in the neighbourhood of the American coast bank.
In deep water we found once more at Stations 67 and 69
the deep-sea animals of the Sargasso Sea, that is to say, all
the black fishes and red crustaceans which we have so often
mentioned already. There were not merely the commonest
kinds of small fish, but also large ones (such as three examples
of Gastrosto7}ms), and fishes which are caught in other oceans
(Aceratias, Serrivomer).
While we were hauling in our appliances at Station 67, a
storm got up, which gradually increased to a hurricane, worse
than anything hitherto encountered by the " Michael Sars." It
lasted for twenty-four hours, during which the ship was smothered
in spray. Our engines were kept going full steam ahead, yet
the vessel was driven a whole degree (60 nautical miles) astern.
vStill her buoyancy stood her in good stead, and she did not ship
a single sea.
At Station 70, on the edge of the coast bank, where the
depth was iioo metres, we discovered that we had for the
second time left purely oceanic conditions behind, and once
more the true boreal plankton appeared in the surface layers.
There was the little copepod Cala^ius finmarchicus, the commonest
crustacean in the Norwegian Sea, and we also now met with
EiUhemisto, NyctipJianes, Krohnia hamata, Limacina helicina,^
and Clione limacina, all species that are regarded as specially
characteristic of the Norwegian Sea. Still in the deep water
from 350 metres down to iioo metres we continued to get the
familiar pelagic deep-sea fish Cyclothoiie signata and C. microdon,
as well as the medusa Atolla and other forms ; so that the area
of distribution of these animals extends from Africa to North
America, that is to say, in all the water from the one continental
slope to the other.
^ Limacina was taken in numbers by Ilaeckel and Murray off Scourie in Scotland.
CRUISES OF THE "MICHAEL SARS "
109
Our deepest young-fish trawl was unintentionally towed along
the bottom, and came up full of most beautiful bottom-living
organisms (0///?>/rrt;, asterids, Phormosoma, pennatulids, crinoids,
pycnogonids, lycods, and Macrurtis, as well as many other forms
which need not be detailed here).
We had thus reached the Great Bank of Newfoundland, and
had accomplished our task of taking a section right across the
Atlantic from the shores of Africa. During the transit we had
occupied twenty-nine hydrographical stations, and twenty stations
75
/
fLEHlSH CAP
RE A T
^
Fig. 94.— "Michael Sars" Stations 69 to 80.
where we towed pelagic appliances, and had besides carried out
many other investigations, so that we had every reason to be
satisfied with the results of our venture.
The coasi batik itself (Fig. 94) offered us a totally different Newfoundland
field for study, which no doubt would have proved very interest- ^'''"^''
ing, but unfortunately our time was too short to attempt system-
atic researches ; we had to steam for our coaling station, content-
ing ourselves with one or two shallow stations on the way.
Fig. 95 shows the hydrographical conditions from our last
true oceanic station (69) to a station (74) just off St. John's. It
is extraordinary what a sudden change there is from the warm
salt oceanic water to the cold coast water. The curves of
no DEPTHS OF THE OCEAN
temperature and salinity between Stations 69 and 70 go down
straight like a wall — the well-known "cold wall" of oceano-
graphers. Over the bank there is a surface layer, about 40
metres in depth, with a temperature of over 6° C, similar to
what we get in the boreal portion of the Norwegian Sea along
the coast of Norway. Below that, however, the temperatures
are under 2° C, and even as low as — 1.5° C, that is to say, the
water may be as cold as what Nansen found near the North
Pole. Probably at no other part of the globe are there such
peculiar temperature conditions — conditions comparable with
those in the Arctic regions, though the latitude is the same as
that of Paris. It would have been an agreeable task to trace
these conditions by following up the currents and animal life
Fig. 95. — Hydrographical Section 'across jthe^Great Newfoundland Bank.
both northwards and southwards. Still even our random in-
vestigations furnished interesting results. Thus we discovered
that from Station 70 to St. John's there was the same northerly
plankton already mentioned, and an examination of the young
fish showed that they accorded with what had previously been
found by Norwegian naturalists off the coast of Norway, and
by the Danes south of Iceland.
On the outer side of the coast bank, at Station 71, we met
with larvse of red-fish {Sebastes). At Station 72 there were cod-
eggs and numbers of little cod-fry, besides fully developed eggs of
haddock (Gadus csglefinus) and haddock larvai, 3^ millimetres
in length and upwards, and also young fish of the boreal long
rough dab [Drepauopsettd). At Station ']2i we came across
eggs of this dab (besides a number of eggs that we have not
yet determined), and the shallow-water form Animodytes. At
Station 74 there were neither eggs nor young fish.
CRUISES OF THE "MICHAEL SARS
1 1 1
Similar catches are taken off the coasts of Norway and
Iceland ; near and just beyond the continental edge there are
larvae of red-fish, and on the bank in 30 or 40 fathoms of water
there are larvae and eggs of cod and haddock. It was interest-
ing to find the eggs and larvae of these fish at Station 72, where
the bottom-temperature was between 2' C. and 4.6° C, whereas
nearer land, where the bottom-temperature was o' C, or even
less, they were absent.
'*9f3TE»_-^:-^-
Fig. 96. — French Fishing Schooner.
At Station 72 we sighted the first fishing-boats (Fig. 96). Fishing
They belonged to Frenchmen from the Island of Miquelon, ;j;f^^^"'f°",,d-
south of Newfoundland, and as the weather was good, we paid land Bank.
them a visit, spending a very pleasant time with these hos-
pitable fishermen, who willingly gave us information about their
industry (Fig. 97). They sail from Brittany and Normandy in
April, and reach the Newfoundland Bank in May, at which time
of the year there is ice over the whole northerly portion of the
bank. They commence fishing in the south-eastern portion,
which is probably the only part having warm bottom-water, and
collect their bait by lowering nets with cod-heads in them.
112 DEPTHS OF THE OCEAN
Quantities of gasteropods (most likely a species of Biiccinuni)
creep into the nets, and form a very serviceable bait, just as on
the eastern side of the Atlantic. Afterwards they remove to
the southern portion of the bank, where they were when we met
them. This was, according to the captain, lat. 44° 30' N., and
long. 53° 34' W. The cod spawn here in July, and were just
on the point of doing so. They were from 60 centimetres to
over a metre long, and upon inspecting the catches of several
dories (flat-bottomed boats used for cod-fishing in Norway
also) we found the roes to be quite mature. The fishermen
also catch squid {Gonahis fabricii \ see Fig. 98) with a grapnel
Fig. 97. — -Hand-line Fishing.
— a red piece of metal with hooks all round it — exactly in the
same way as they are caught on the north and west coasts of
Norway.
After July the fishermen work their way northwards,
probably because the cod move northwards along the bank
as the cold water recedes during the course of the summer.
According to their statements, which would justify a thorough
investigation, there are for the most part only small-sized cod
farther south and west on the banks off Nova Scotia and Cape
Breton Island, or on what they call the " Banquereau." Is it
perhaps the case here too, as in Norway and Iceland, that the
larvse and young fish drift with the current and grow into cod
far away from the place where they were spawned }
On the Norwegian coast the cod chiefly spawn between
CRUISES OF THE "MICHAEL SARS
1 1
Romsdal and Tromsoe, but
greatest quantity off Fin-
marken, that is to say, along
the northernmost portion of
the coast, to which they are
carried by the current. Simi-
larly in Iceland they spawn
on the south and west coasts,
but the young fish are chiefly
found on the north and east
coasts. The current there
goes from the south to the
west, and thence round the
north and east coasts, making
a circuit round the island.
The current off New-
foundland runs along the
coast in a south - westerly
direction, towards Nova
Scotia and the United States.
It is possible, therefore, that
it is mosdy young fish that
are found down south, de-
rived to some extent at any
rate from eggs spawned on
the Great Newfoundland
Bank.
Cod spawn on the Nor-
wegian coast banks as far
north as lat. 70° N., and
chiefly during March and
April. Here on the New-
foundland Bank, a little north
of lat. 50^ N., and in the
vicinity of the warm oceanic
water their spawning season
was in July.
The bottom-temperature
on the bank was, as we have
seen, very low — lower indeed
than in the north of Norway
during March — and it was
interesting, therefore, to note
the young fish are found
m
, — Bait ( Goiiatus fahricii).
Nat. size, 27 cm.
foundland to
Glasgow
114 DEPTHS OF THE OCEAN
the summer growth periods and winter stagnation periods in
the scales of cod which we procured from the French fishermen.
Scales (see Chapter X.) illustrate the growth of the cod by
means of " summer-belts " and " winter-rings," Those which we
examined had extremely distinct winter-rings, and although it
was already July, the summer-belt for the year had not yet
commenced. It must therefore have been the winter season
still down in the deep water where the cod were taken — and this
though we were in the latitude of Paris and the month was July.
On 3rd July the "Michael Sars " anchored in the harbour
of St. John's.
From New- It was our Original intention to go from Newfoundland to
Reykjavik in Iceland, as this was the nearest coaling station
on our way back to Europe, and we hardly expected when
starting on our expedition that the little ship would be able
to steam right across the Atlantic without having to put in
anywhere for coal. We had now, however, formed such a
favourable opinion of her seaworthiness, and her coal-con-
sumption had been so small, especially on the voyage from
the Azores to St. John's, that we decided to venture across the
ocean without a stop. The distance from Fayal to St. John's
by the way we had come was about 1800 nautical miles, and
from St. John's to Ireland was roughly 2000 miles, so that the
difference was not so very formidable.
As far as our scientific work was concerned, the direct route
to Ireland was bound to be the more interesting. It is true
that very little is known about the sea leading to Baffin's Bay,
but the physical conditions, and therefore also the animal life,
are presumably very uniform and not likely to differ much from
the conditions prevailing to the eastward of the Newfoundland
Bank. The direct route to Ireland, on the other hand, would
give us a fresh section across the Atlantic, and enable us to
study the varying conditions in the northerly portion of that
ocean. Another reason for selecting this route was the possi-
bility of again studying the remarkable conditions in the Gulf
Stream observed on our southern section between Stations 64
and 70 (see Fig. 93). We therefore filled up our bunkers once
more and piled the deck with the best coal we could procure,
prepared ourselves for as long a cruise as the ship was able to
accomplish, and left St. John's on the 8th July.
The water-masses of the North Atlantic may be roughly
CRUISES OF THE
divided into four principal groups
water, or Gulf ,
Stream water, |
(2) Mediterranean
water, (3) Arctic
polar water, and
(4) the so - called
bottom -water, all
of which we were
able to study on
our voyage across
to Ireland. Fig.
99 shows the posi-
tions of Stations
79-93, and the
vertical distribu-
tionof the different
water -masses in
their relation to
one another on
our route from
the Newfoundland
Bank to Ireland.
Near America, on
the actual coast
bank and just out-
side the edge of
the bank (Stations
75-79), we found
only the cold
Labrador Current,
which descends
from Baffin's Bay,
follows the coast
of Labrador, and
sweeps south-west
past Newfound-
land. Immediately
outside St. John's :
we met several ice- ;
bergsofthekind so ^
familiar to all who \
cross the North
MICHAEL SARS" 115
(i) true Atlantic oceanic
ii6
DEPTHS OF THE OCEAN
Atlantic (Figs, loo and loi), and we had thus an ocular demon-
stration of the origin of the cold water on the Great Bank, as
Jifl^^
Fi<;. loo. — Icebergs outside the Harbour of St. John's.
well as of the dangers which the bank-fishers have to face.
Icebergs, fog, and the great ocean-steamers are the chief perils
Fig. ioi.— Iceberg outside St. John's.
these men have to reckon with, and it was an unpleasant
sensation for us also to have to steam for three whole days over
the bank in fog.
CRUISES OF THE "MICHAEL SARS " 117
At Station 80 we became aware of the influence of Atlantic
water, and at the same time we got clear weather, but, as the
figure will show, it was at Station 81 that we first met with the
real Atlantic or Gulf Stream water with a salinity of about 35.5
per thousand, which extended in a layer 100-200 metres deep
right across to near the coast bank outside Ireland. Below
this layer the salinity and temperature decrease till we come
down to bottom-water, with a salinity of less than 35 per
thousand ; the temperature was the same as what we had found
in bottom-water to the south of the Azores, namely, a little
under 2^° C. Our investigations made it apparent that this
bottom-water is in continuity with the surface water in the
north-west corner of the Atlantic.
Our investigation of the plants of the sea was continued Plants.
during this cruise ; we made collections with silk nets, and
centrifuged water - samples with the big steam centrifuge,
with the result that, in spite of high seas and heavy rolling of
the vessel on the eastern side of the ocean, Gran was able to
proceed with his classification and enumeration of the minute
living organisms that had hitherto eluded observation.
At almost every station he determined the number of
extremely small organisms, chiefly coccolithophoridse, per litre
of sea-water, and ascertained that here, too, on our northerly
route they constituted the greater portion of the plant plankton.
An exception must, however, be made in the case of the coast
banks of Newfoundland and Ireland, where there was also a
very abundant plankton of larger organisms, large enough to
be retained by the tow-nets. One single species (a calcareous
flagellate) at a station just outside the European coast bank
numbered 200,000 per litre, and actually affected the transparency
of the sea.
Gran succeeded in collecting abundant material for the
study of these little-known forms (many of them new to science),
and for a proper understanding of their significance in the total
plant life of the sea. In Chapter VI. he has set down the
chief results of his observations.
We found again a complete accordance between the distri-
bution of the different water-masses and the occurrence of
characteristic "societies" of pelagic animal life. At Stations Pelagic life of
75-79 on the Newfoundland Bank (see Fig. 94) the boreal l^^^;^^
organisms were mixed with arctic forms. Thus there were :
ii8 DEPTHS OF THE OCEAN
Calamis jinmarchicMS and C. hyperboi^eus, Euchcsta, Euthemisto,
Lmiacma, Aglantha, Beroe, Pleurobrachia, Mertensta, Sagitta
arctica, and Krohnia haniata — forms that in the Norwegian
Sea are met with in " Gulf Stream water" or in " Polar water."
At Station 80 — just beyond the continental slope — this
animal life was still typically represented at all depths examined,
but in deep water we found co-existing with it our black fish
and red crustaceans of the southern section. We made a few
hauls here with the closing net, and obtained the following : —
In a haul from 525 metres to 235 metres we got calanids co-existing
with Cyclothom signata.
In a haul from 950 metres to 525 metres w^iowwd^ EucJiceta norvegica,
Calanus Jinjnarchicus, Calanus Jiyperboreus and Clione limacina, together
with Cyclotho7ie inicrodon and the medusa Atolla.
Besides this, our horizontal hauls gave us Gastrostomus bairdii and
large red prawns {Acanthephyrd).
All the arctic forms had disappeared, however, at Station
81, and they did not occur again in our hauls during the rest of
Boreal our section to Ireland. In their place we found the boreal
pelagic h e. ^j^j^iais^ s\\Q}[i as we are familiar with in the Gulf Stream water
of the Norwegian Sea right up to Spitsbergen, strongly repre-
sented, everywhere mingled with true oceanic Atlantic forms,
like those that predominated in the southern section. At Station
81 we secured at the surface a quantity of eggs and young of
scopelids, as well as radiolaria, salpae, small Pelagia, and different
kinds of leptocephali ; of pteropods we got Clio pyraniidata.
In deep water there was the abundant oceanic fauna observed
in the Sargasso Sea previously referred to. If we consider this
short account of the animal life, together with the hydrographical
section (Fig. 99), the accordance will become apparent. It is at
Station 81 that the real oceanic "Atlantic water" or "Gulf
Stream water " occurs, whereas at Station 80 the cold Labrador
Current is still the controlling influence.
Generally speaking, the same pelagic fauna was noted from
here across the Atlantic, though no doubt a closer investigation
may reveal various differences in the different areas traversed.
There is one feature that deserves particular mention, notwith-
standing the incompleteness of our material, namely, the
extraordinary abundance of forms met with from Stations 86 to
8S. These stations lie exactly over the longitudinal ridge that
stretches northivards fro77i the Azores. Just as was the case on
the plateau south of the Azores, so here too we made exception-
ally big catches at all depths, and the surface contained millions
CRUISES OF THE "MICHAEL SARS
119
of chains of salpse the one day and of medusae [Pelagia) the
next.
We caught a large moonfish (Mola rotunda. Fig. 102), Moonfish.
which was moving along near the surface with its dorsal fin
above water ; we harpooned it from a boat, and got it on board
with block and tackle and the steam winch. The length was
2,11 metres, and the height of the body 1.2 metres. A huge
Fig. \02.—Mola rottinda, Cuv. Nat. size, 211 cm.
cuttle-fish, too, was found drifting about. Do these creatures,
like the turtles farther south, feed on the abundant salpee and
medusae, and was that the reason why we found them here ?
Is a richer pelagic life generally to be found just over the ridge,
in the same way that we always find a richer plankton over the
slope of the coast banks ? These problems must be left for
future solution.
On the eastern side of our section, towards the Irish coast
bank, the conditions were again peculiar, especially at the
surface. We found here increasing quantities of young of the
Trawling on
the Mid-
Atlantic rid<r<
I20 DEPTHS OF THE OCEAN
needle-fish Nerophis, Fierasfer, Arachnactis and Lepas fascicu-
laris, as well as young stages of coast -bank forms, stray
specimens of which were also met with just off the slope
(Stations 92 and 94).
It will be an interesting task to compare the western and
eastern portions of this section, as well as the whole of this
northerly section, with the section farther south from the Canary
Islands past the Azores to the Gulf Stream. One thing which
did strike us particularly was that the boreal plankton — the
Gulf Stream forms of the Norwegian Sea — were entirely absent
from the southern section (Stations 45-64), but were everywhere
present in the northern section. It must be remembered,
however, that our pelagic hauls did not reach the very deepest
water-layers, which may have the same plankton in both
sections, including the boreal species known from the Norwegian
Sea. We further noticed in the southern section more of the
remarkable "rare" deep-sea fish that have been found in other
oceans (the Indian Ocean, for instance) than in the northern
section.
The distribution according to size of individuals belonging
to the different larval forms was noteworthy. As previously
mentioned, we came across very small larvae — from 4 cm. to 6 cm.
long — of the common eel to the south and west of the Azores ;
on the northern section also we found larvse of the eel, but
they were all full-grown leptocephali. This distribution does not
seem to be specially characteristic of the eel, for on the southern
section we came across many small larvse and eggs belonging
to other forms, none of which were met with farther north.
Future investigations will doubtless make all this clear, and
may lead to valuable discoveries.
The accident to our trawl on the Azores bank, already
mentioned, prevented us from trawling in very deep water, but
for all that we were able to carry out two successful trawlings at
considerable depths. The first was at Station 88, on the longi-
tudinal ridge north of the Azores, where we shot our trawl in
3120 metres of water. There were numbers of echinoderms of
all kinds (starfish, sand-stars, sea-urchins, and holothurians), as
well as a score of bottom-fish (Macrurits, Synaphobrancktis,
Bathysaurus). The haul was extremely interesting, as it gave
a fresh proof of the abundance of animal life as far down as
3000 metres — not in this case on a continental slope, but out on
a ridge in the middle of the ocean. Off the coast of Ireland we
succeeded in trawling at 1000 fathoms (1797 metres, Station 95),
CRUISES OF THE "MICHAEL SARS " 121
which we had attempted in vain after leaving Plymouth, and we
towed the big trawl for two and a half hours with very satis-
factory results. There were quantities of echinoderms (300 Trawling off
holothurians, 800 ophiuroidse), molluscs, corals, crustaceans, and Jrek^c/
82 fishes [Maci'urus, Antimora viola, A/epocep/tahis, Bathy-
saurns (Fig, 103 a), Notacanthus, Halosauropsis (Fig. 103 b),
i
Fig. 103. — Two Deep-Sea Fishes from Station 95, 1797 metres (about 1000 fathoms).
a. Bathysaiirus ferox, Gthr. Xat. size, 42 cm.
b. Halosauropsis macrochir, Gthr. Nat. size, 60 cm.
and Synaphobranchi). We also found in the trawl a basketful
of stones, coal, and cinders.
The " Michael Sars " anchored at Glasgow on the 29th
July after a passage from Newfoundland lasting three weeks.
Duringthis time we had worked at twenty-two stations, and had
made investigations all the way across the Atlantic. In spite of
having steamed about 2000 miles, and having been three weeks
at sea, we had still nearly ■}^'] tons of coal left, or enough for
another week's work. We had thus proved that a little vessel
may carry out investigations formerly attempted only with large
ships, and this fact is certain to be taken into account when
future expeditions are planned. Taking everything into
consideration, we had made very satisfactory hydrographical
122 DEPTHS OF THE OCEAN
and biological observations over a large part of the North
Atlantic. As previously stated, one of the principal objects
of the expedition was to carry out researches in the North
Atlantic likely to increase our knowledge of the marine area
explored by the " Michael Sars " during the past few years,
namely, the Norwegian Sea lying between Norway, Greenland,
Iceland, and the North Sea. It was important, therefore, to
Fig. 104.-
Michael Sars" Stations from Glasgow to Bergen.
examine the adjoining portion of the Atlantic and to investigate
the inflow of the Atlantic water.
After leaving the vicinity of the Newfoundland Bank, the
Gulf Stream bends sharply eastwards and forms the surface
layer examined by us between Stations 81 and 92 (see Fig. 99).
Off the edge of the Irish coast bank a portion turns northwards
towards the Norwegian Sea. The sea-bottom is here very
complicated, for the deep basins of the Atlantic and Norwegian
Sea are separated by a submarine ridge (see Fig. 104). To the
north-west of Ireland the wide Atlantic plain narrows to a kind
CRUISES OF THE "MICHAEL SARS " 123
of valley, which is bounded on the west by the Rockall bank,
and on the east by the coast bank of Scotland. Farther north
this valley shallows towards the extensive ridge that stretches
from Iceland past the Faroe Islands to Shetland, and separates
the Atlantic Ocean from the Norwegian Sea at all depths
beyond 400 to 500 metres. The part of this ridge between the
Faroe Islands and Shetland is known as the Wyville Thomson
Ridge, which has frequently been examined, first by British,
afterwards by Danish, naturalists ; in fact, it may be regarded
as a classical field for oceanic research (see Chapter I.). The
'tm
■^^^iifeMfcwNi-^
Fig. 105.— Rockall.
" Michael Sars " had made investigations there previously, both
on the Atlantic side south of the ridge and in the Norwegian
Sea to the north of it. In Fig. 104 our former research-stations
are marked with a cross.
It was desirable, however, to re-investigate this area, em-
ploying there the same methods of working as we had adopted
in the North Atlantic, and we felt it necessary to have a
section south of the Wyville Thomson Ridge and another
one to the north of it. The valley between Britain on the one
side and Rockall and the Faroes on the other is really the only
connection between the two deep basins, for it is only through
Glasgow
to Bergen.
124
DEPTHS OF THE OCEAN
this channel that the water of the Atlantic streams into the
Norwegian Sea ; to the west of the Faroes, over the long ridge
that extends to Iceland, the Atlantic water is checked by the
East Iceland Polar current.
Our southern section was from Glasgow to Rockall, with
stations on the British coast bank, on its seaward slope, and on
the Rockall Bank. We had beautiful weather in which to make
tot
li-
,r ,.
-ZZZZZZ-- "_- - z z r - -_-_-------
^z
-
^
' '''''■°
- - - ' ~ i°^ -
7" ^'^l
/ f^-4^-^2;^^^^---
\
1 V.^
6_' 1
J
f500 —
/
2000 .
>5?55%r*'^=i«Lyr
Fig. 106. — Section across the Wvvili.e Thomson Ridge.
investigations, and approached close to the rocky little islet,
which we photographed (Fig. 105). This rock is well known,
Rockall. owing to many a sad disaster (only recently the transatlantic
steamer " Norge " was wrecked there), and shows distinct
traces of the power of the waves. All its brown granite-like
sides are clad with small algse (green-spored algae), kept moist
by the spray, and the top is covered with a thin layer of guano ;
the rock and its surroundings swarm with auks and gulls.
CRUISES OF THE "MICHAEL SARS " 125
After completing this section, we proceeded towards the Wyviik
homs
Lidge.
Wyville Thomson Ridge, and occupied a station (loi) at a Thomson
depth of 1000 fathoms, where we employed the trawl as well as
a number of pelagic appliances, and then concluded our work
by taking two sections on the northern side of the ridge (see
stations in Fig. 104).
The Jiydrographical conditions here have often been de-
scribed. Fig. 106 gives a general idea of what we found at
Station loi south of the Wyville Thomson Ridge, and at
Station 106 to the north of it. South of the ridge salinities
and temperatures are rather lower than what we found in our
northern Atlantic section, but the differences are not very
considerable either in deep water or in the upper layers. The
upper layers extend with little variation down to the level of the
ridge in 500 metres, but the difference in the deep water on the
two sides of the ridge is unmistakable, as the ice-cold bottom-
water of the Norwegian Sea comes close to the northern
margin of the ridge.
These conditions, however, are generally known, and our
attention was chiefly turned in another direction. During our
previous investigations in the Norwegian Sea we discovered
that the hydrographical conditions often varied very consider-
ably within a short distance or in the course of a short period
of time. The variations were not always of the same character.
A number of eddies, both large and small, occurred apparently
during the movements of the water-layers, and there were up
and down movements in the boundary-layers^ — possibly big
submarine waves or something of that sort — as well as distinct
pulsations in certain currents. We resolved, therefore, on our
way over to Bergen to make a careful study of these phenomena
in the Faroe-Shetland channel. To be able to do so, it was
necessary to have our stations very close together and to occupy
them in rapid succession, and also to lie stationary for at least
twenty-four hours at one of them.
Altogether we had fourteen stations north of the ridge in the investigations
Faroe-Shetland channel (Nos. 103-116; see Fig. 104) along two cVan*nrL'°^
nearly parallel sections, the distance from one station to another
being about 20 nautical miles, and the distance between the
sections a little over 25 miles. We found that the hydro-
graphical conditions varied greatly in the different localities,
and that there was an extraordinary difference between the two
sections. At Station 115, on the continental edge to the west
of Shetland, we anchored a buoy, and remained stationary there
126 DEPTHS OF THE OCEAN
for twenty-four hours, taking continuous observations of tempera-
ture and salinity at different depths. It was quite evident that
there were considerable vertical fluctuations, the intermediate
layers showing up and down movements with an amplitude
of as much as 35 metres during a period that corresponded
practically with the tidal period.
Pelagic hauls. After leaving Glasgow we made pelagic hauls with our
silk nets and young-fish trawls on the coast bank, on the slope,
out in the deep channel, near the southern flank of the Wyville
Thomson Ridge (Station loi), and to the north of it (Station 102),
At every depth our catches to the south of the ridge closely
resembled those we made in our northern Atlantic section
between Newfoundland and Ireland, and particularly the catches
made in the eastern portion of that section.
In the upper layers there were all the boreal animals
characteristic of Atlantic water in the Norwegian Sea, as, for
instance, Eiithemisto and Clione liniacina. But there was also a
mass of Atlantic forms that do not occur all the year round in
the Norwegian Sea, though they are known to wander in at
certain seasons of the year, as at the end of the summer or
during autumn. The tow-nets gave a mixture of ^r«^/^;2«^/2i",
Salpa fusiformis, numbers of scopelids, leptocephali (full-
grown larvse of the common eel), the young of Macriirus, and
Nerophis csquorezis.
At a depth of 300 metres we captured the silvery Argyro-
pelecus, and in deep water, from 500 metres downwards, there
was the characteristic fauna of black Cyclothone microdon,
red crustaceans [Acantkephyra), and other forms, which thus
occur right tip to the southern slope of the Wyville Tho^nson
Ridge.
On the northern side of the ridge we towed our appliances
at 50, 100, 150, 200, 300, 500, 700, and 750 metres (Station 102)
without catching a single specimefi of these Atlantic deep-sea
forms ; but in the upper layers there were not merely boreal
forms, but also salpae, the area of distribution of which is
mainly Atlantic.
These results quite accord with our previous observations
during the cruises of the " Michael Sars." Hauls in the deepest
waters of the Norwegian Sea have not yielded any pelagic fish
other than the black Paraliparis bathybii (Fig. 107), which
used to be considered a bottom-fish ; it is interesting to note
that it is black. There was a complete absence of Cyclothone
and the red Atlantic crustaceans belonging to the genus Acan-
CRUISES OF THE "MICHAEL SARS " 127
thephyra, the only pelagic crustaceans found by us north of the
ridge being Hyinenodora glacialis and species of Pasiphcea.
In the upper layers, however, different scopelids have been
found both by us and by others, and on the Norwegian coast
the silvery species of Argyropeleats, which inhabit depths of
about 300 metres in the Atlantic, have occasionally been met
with. It seems tolerably certain, therefore, that the Wyville
Thomson Ridge shuts out the whole of the Atlantic pelagic deep-
sea fauna from the Norwegian Sea, and that it is only in the
superficial layers from the surface down to 400 or 500 metres
that pelagic forms are able to wander in from the Atlantic.
That the bottom -fauna is different on either side of the Benthos of
ridge is well known. Our trawlings, both on this occasion and ch^^ner
previously, have merely helped to confirm the fact ; still we
secured a very large amount of material, which in itself is of
107.
Paraliparis bathybii, Coll. Nat. size, 23 cm.
(Taken in pelagic haul in Norwegian Sea, May 1911.)
considerable interest. At Station loi (south of the ridge), in
1000 fathoms (1853 metres) of water, a haul of two hours'
duration yielded a barrel-full of lower animals, most of which were
echinoderms, and ninety fishes (Alacrurus, Antimo7'a, Alepo-
cephalus, Harriotta, and Synaphobranchi), representing a fauna
that may be said to characterise the north-east Atlantic from
the Wyville Thomson Ridge southwards, far along the coast of
Africa. The remarkable fish, Hari'iotta raleighana, which we
captured at Station loi, a few miles from the deep water of the
Norwegian Sea, had been previously taken by us at Station 35,
to the south of the Canary Islands. On the other hand, fish
that exist only a few miles farther north, on the northern side
of the ridge, never enter the Atlantic, though in the deep water
of the Norwegian Sea they may be met with as far north as
Spitsbergen, and perhaps even still farther north.
The "Michael Sars " anchored at Bergen on 15th August. E.xtent of
During her four and a half months' cruise she had traversed 1 1 , 500 ^^^ '^™'^^'
128 DEPTHS OF THE OCEAN chap. n.
miles, and occupied 1 16 research stations; on a rough estimate we
had lowered and hauled in about 1500 kilometres of wire with
our four winches. Only the greatest attention and energy on
the part of the crew could have made this possible. Thanks to
them we have probably opened up a new way for ocean research,
by showing what a little vessel can accomplish, which is by no
means the least valuable result of our expedition. The follow-
ing chapters aim at giving the results of our scientific observa-
tions from a more general and systematic point of view than
was possible in this brief account of the actual cruise.
J. H.
^4^
S.S. "Michael Sars " towinc. Otter Trawl.
m
("."
^Ni
BATHYMETRICAL CHART Of
THE ©CEAiXS
SHOWING THE DEEPS
According to Sir John Murray
V
SiF"nxG Deposit:
CHAPTER IV
THE DEPTHS AND DEPOSITS OF THE OCEAN
I. The Depths of the Ocean
In the opinion of astronomers the earth is the only planet of The earth as
our solar system which has oceans on its surface. If Mars and ^ p'^"^'-
the moon once had oceans, these have apparently disappeared
within their rocky crusts. Our earth is in what is called the
terraqueous stage of a planet's development. The ocean is less
than the hydrosphere, which is regarded as including all lakes
and rivers, the water-vapour in the atmosphere, and the water
which has penetrated deep into the lithosphere.
If the whole globe were covered with an ocean of uniform
depth, and if there were no differences of density in the shells of
the rocky crust, the surface of the ocean would be a perfect
spheroid of revolution. But, as every one knows, the surface of
the earth is made up of land and water, and at all events the
superficial layers of the lithosphere are heterogeneous. The Figure of
figure of the earth departs from a true spheroid of revolution, ^^^ '^'^'''^'
and is called a geoid. The surface of the ocean is, therefore,
farther removed from the centre of the earth at some points
129 K
I30
DEPTHS OF THE OCEAN
Attraction
of the
land-masses.
Measurements
of depth.
Hand line.
Brooke's
sounding
machine
than at others ; the gravitational attraction of emerged land
causes a heaping-up of the sea around continental and other
coasts. The extent of this heaping-up near elevated continents,
and consequent lowering of the sea-surface far from land, appear
to have been much exaggerated. The difference of level due to
this cause has sometimes been estimated at thousands of feet.
Recent researches indicate that the differences of level at
different points of the sea-surface do not depart more than 300
or 400 feet from a true spheroid of revolution.
The other causes which, in addition to the tides, may affect
the level of the ocean are meteorologic, such as barometric
pressure, temperature, the action of wind, evaporation, precipita-
tion, the inflow of rivers, but in no cases do these affect the
level of the ocean more than a few inches or a few feet.
All depths recorded by the sounding-line in the open sea are
referred to the surface of the ocean, and near coasts to mean sea-
level. The first method of ascertaining the depth of the ocean
was by means of the hand line and lead, armed with tallow, used
by ordinary sailors. A great advance was made when Lieutenant
Brooke, of the United States Navy, devised the apparatus for
detaching the weight or sinker when it struck the bottom, the
line bringing up only a small tube with a sample of the bottom-
deposit. During the "Challenger" Expedition the line used
was a fine hempen rope, and the time when each loo-fathoms
mark passed over the ship's side was carefully noted. When
a great change of the rate was observed, the lead was known to
have reached the bottom. It is believed that even the deepest
soundings taken in this way are correct to within 100 feet.
Another advance was made when fine wire was used for the
soundings, and the machine recorded automatically the moment
when the sinker struck the bottom. There are many types of
wire deep-sea sounding machines now in use, but the most
compact and practical of these is the Lucas sounding machine.
Sounding instruments are referred to in greater detail in another
chapter (see p. 30).
To give the total number of deep soundings recorded by
British and other ships up to the present day, even in depths
exceeding 1000 fathoms, would be difficult. An approximation
has been made by counting the number of soundings in depths
exceeding 1000 fathoms laid down on the latest charts. It
must be remembered that not all the recorded soundings can be
laid down on small scale charts where they are at all numerous.
In 1886 Sir John Murray had three hemispheres drawn on
IV DEPTHS AND DEPOSITS OF THE OCEAN 131
Lambert's equal-surface projection, one to show the Atlantic Equai-smface
Ocean, one the Pacific, and one the Indian Ocean, on which all hemShSes.
the soundings recorded up to that time, in depths exceeding
1000 fathoms, were laid down in position, and contour-lines of
depth drawn in. Since then these hemispheres have been kept
up to date by Dr. Bartholomew by the inclusion from time to
time of new soundings recorded in depths greater than 1000
fathoms, and the contour-lines have been redrawn. The North
Atlantic from one of these hemispheres is shown on Map III.,
where practically all soundings recorded in depths greater than
1000 fathoms are placed in position, the two last figures being
omitted.
The total number of soundings laid down on these charts Number of
is 5969, of which 2500 are in the Atlantic (1873 in the North l^^'^t^l^eater
Atlantic and 627 in the South Atlantic), 2466 in the Pacific than 1000
(1266 in the North Pacific and 1200 in the South Pacific), and f^^^"'^'-
1003 in the Indian Ocean. These figures show that pro-
portionately a great many more soundings have been taken
in the Atlantic than in the Pacific, which covers an area so
much larger. Of these 5969 soundings, 2516 were taken in
depths between 1000 and 2000 fathoms, 2962 in depths between
2000 and 3000 fathoms, and only 491 are laid down in depths
exceeding 3000 fathoms, of which 46 exceed 4000 fathoms, and
only 4 exceed 5000 fathoms. It may be added that though only
four soundings over 5000 fathoms have been laid down on the
charts, in reality seven have been recorded, three in the South
Pacific in the Aldrich Deep, and the other four taken by the
U.S.S. "Nero" in the Challenger Deep in the North Pacific,
near the island of Guam, but in such close proximity to one
another that only the deepest, 5269 fathoms, could be laid down
on the map.
The deepest sounding hitherto recorded is that of 5269 Deepest
fathoms just mentioned. • This is equal to 9636 metres, or ^oundini.
31,614 feet, or 66 feet less than six English miles, and it exceeds
the greatest known height above the level of the sea (Mount
Everest in the Himalaya Mountains, 29,002 feet) by 2612 feet.
The known range of variation in the level of the earth's crust, Range of
from the greatest height above sea-level to the greatest depth i^'evd of'the^
below sea-level, is thus 60,616 feet, or about ii|- English miles, earth's cmst.
but this range is very small when we remember that the
diameter of the earth is nearly 8000 miles ; in fact, on a six-feet
globe a mere scratch one-tenth of an inch deep would represent
the extreme variation in the irregularities of the earth's surface.
Deepest
soundings in
the Atlantic
and Indian
Oceans.
132 DEPTHS OF THE OCEAN
The second deepest sounding on the ocean -floor is 5155
fathoms in the Aldrich Deep in the South Pacific, depths
exceeding 5000 fathoms being Hmited to the Pacific Ocean.
The deepest sounding recorded in the Atlantic is 4662 fathoms
in the Nares Deep to the north of the West Indies, and the
deepest in the Indian Ocean 3828 fathoms in the Wharton
Deep to the south of the East Indies.
Superficial
area of the
earth.
Area of
Antarctic
continent.
Area of land
on the globe.
Area of
water on
the globe.
Areas of the
ocean-floor
at different
depths.
In 1886 Professor Chrystal calculated for Sir John Murray
the supLprficial area of the earth, regarded as a spheroid of
revolution, as equal to 196,940,700 square English miles, of
which the land - surface was estimated at 55,697,000 square
miles, and the water-surface at 141,243,000 square miles.^ At
that time the area of land surrounding the south pole was
estimated at 3,565,000 square miles, but the results of all the
recent south polar expeditions seem to indicate that the
Antarctic continent covers a larger extent than was supposed.
The latest measurements by Sir John Murray give a probable
area of about 5,122,000 square miles for Antarctica, so that
the total land-surface of the globe may now be estimated at
57,254,000 square miles, which may be supposed to include
all lakes and rivers, leaving about 139,686,000 square miles
for the waters of the ocean and seas directly connected
therewith.
Planimeter measurements of the most recent depth hemi-
spheres gave 139,295,000 square English miles for the area
of the whole ocean, and this figure will be adopted throughout
this publication.
The approximate areas between the consecutive contour-
lines drawn in at equal intervals of 1000 fathoms worked out
as follows for the whole ocean : —
Fathoms. | Square English Miles.
Percentage.
0-1000 21,725,000
1000—2000 26,915,000
2000-3000 81,381,000
3000-4000 9,058,000
Over 4000 , 216,000
15-59
19-34
58.42 1
6.50 ,
0.15
' i39j295>ooo
100.00
Scottish Geographical Magazine, vol. ii. p. 550, l<
IV DEPTHS AND DEPOSITS OF THE OCEAN 133
This table shows at a glance that the greater portion of
the ocean-floor is covered by deep water, i.e. by water exceed-
ing 1000 fathoms in depth, equal to more than four- fifths of
the entire superficies of the ocean, two-thirds being occupied by
water exceeding 2000 fathoms in depth, while only one-fifteenth
of the entire sea-floor is covered by water exceeding 3000
fathoms in depth.
Those parts of the ocean in which depths greater than 3000
fathoms have been recorded are called "deeps," and have had "Deeps."
distinctive names conferred upon them, just as mountain ranges
and peaks on the dry land (Mount Everest, for example) are
distinguished by names. These deeps are shown on Map H.,
and will presently be dealt with in some detail.
The table also shows that a comparatively large area, about Areas of the
one-sixth of the ocean-floor, is covered by water less than 1000 SanT^
fathoms in depth, of which by far the greater proportion is continental
covered by still shallower water. Thus if we divide this area ^°p^*
into two portions by the 500-fathoms line, we find that the
area within that line is about 17 million square miles (or
over 12 per cent of the entire ocean) compared with only
4|- million square miles (or 3 per cent of the entire ocean)
beyond that line, i.e. having depths between 500 and 1000
fathoms. Again, of the area covered by less than 500 fathoms
of water, more than one-half is occupied by the continental
shelf or continental plateau lying between the shore-line and
the loo-fathoms line, which has elsewhere^ been estimated at 7
per cent of the whole ocean. The relatively large area covered
by the gentle slopes of the continental shelf in depths less than
100 fathoms, as compared with the relatively small area covered
by the steeper gradients of the continental slope in depths
greater than 100 fathoms, is strikingly shown by these figures,
for while about 7 per cent of the ocean-floor lies within the
lOO-fathoms line, only about 5 per cent occurs within the next
succeeding 400 fathoms (between the 100- and 500-fathoms
lines), and only about 3 per cent within the next succeeding
500 fathoms (between the 500- and looo-fathoms lines).
The position occupied by the junction of the continental Continental
shelf with the continental slope, as indicated by the change nSSne
of gradient, has been called the continental edge (see Fig. 144,
p. 198), and varies in depth according to circumstances, but on
the average all over the world is not far from the lOO-fathoms
1 Sir John Murray, Presidential Address to the Geographical Section of the British Associa-
tion, Dover, 1899.
134
lud-li
DEPTHS OF THE OCEAN
inciding generally with what we have designated the
Area of the
Atlantic
sea-floor at
different
depths.
Continental
shelf and
slope in the
Atlantic.
Let us now consider the distribution of depth in the three
great oceans (the Atlantic, the Pacific, and the Indian Oceans),
regarding them as extending in each case as far south as
the shores of the Antarctic continent.
Atlantic Ocean. — The Atlantic may be looked upon as
including the Arctic Ocean and Norwegian Sea, the
Mediterranean, Caribbean, and Gulf of Mexico, and as being
separated from the Pacific in the south at the meridian of Cape
Horn (long. 70° W.) and from the Indian Ocean at the meridian
of the Cape of Good Hope (long. 20' E.). As thus defined
the Atlantic Ocean covers an area of about 41,321,000 square
English miles, the distribution of depth being shown in the
following table : —
Fathoms.
Square English Miles.
Percentage.
o-iooo
1000-2000
2000-3000
3000-4000
Over 4000
11,388,000
7,531.000
19.539,000
2,848,000
15,000
27.56
18.22
47.29
6.89
0.04
41,321,000
100.00
These figures show that nearly three-fourths of the Atlantic
sea -floor are covered by water exceeding 1000 fathoms in
depth, and over one-half by water exceeding 2000 fathoms in
depth, but the most characteristic feature of this ocean when
compared with the Pacific and Indian Oceans is the large
proportion covered by water less than 1000 fathoms in depth.
The table shows that this shallowest zone (from o-iooo fathoms,
which includes both the continental shelf and the continental
slope) covers about i\\ million square miles, while the succeed-
ing zone (1000-2000 fathoms) covers only 7^ million square
miles. If again we divide the shallowest zone into two portions
by the 500-fathoms line, the predominance of the area covered
by shallow water is still more pronounced, the area less than
500 fathoms being nearly 10 million square miles as compared
1 Murray and Renard, Deep-Sea Deposits Chall. Exp. p. 1S5, 1891 ; Murray, Summary
of Results Chall. Exp. p. 1433, 1895.
IS.C.
IV DEPTHS AND DEPOSITS OF THE OCEAN 135
with i|- million square miles between 500 and 1000 fathoms.
This is due to the large expanses of shallow water in the Arctic
regions and Hudson Bay, on the Banks of Newfoundland, off
the east coasts of North and South America, between Green-
land and the British Isles, around the British Isles, and in
the Baltic.
The most striking feature of the Atlantic Ocean is certainly Mid-Atiamic
the low central ridge (dividing the ocean into eastern and '^''^
western deep basins), which was until recently supposed to be
continuous from Iceland through both the North and South
Atlantic as far as lat. 40° S., but is now known to be discon-
tinuous in the neighbourhood of the equator ; on the other hand,
it has been extended farther south by the soundings taken on
board the "Scotia" in 1904 by Dr. W. S. Bruce, so that the
southern limit of the ridge now extends as far south as lat.
53" S. At the position of the break in the ridge on the equator
the floor of the ocean seems to be more than usually irregular,
for depths less than 2000 fathoms alternate with depths exceed-
ing 3000 and even 4000 fathoms. On this ridge, with the
exception of the Azores group, the only islands are St. Paul's
Rocks, Ascension, Tristan da Cunha, and Gough Island. The
northern extremity of the ridge between lat. 50° and 60° N. is
peculiar because of the number of isolated soundings exceeding
2000 fathoms apparently surrounded by shallower water.
Another point that strikes one in the Atlantic is the gentle Shoie-siopes
slope off the American coasts and off the coasts of the British of the Atlantic.
Isles, as compared with the slopes off Africa and off Spain and
Portugal. This is still more remarkable when compared with
the slopes off the Pacific coasts of America. The wide shore
platform off the coast of the southern half of South America is
especially noteworthy, as well as that off the coasts of the United
States and Newfoundland. The shallow area surrounding
Rockall Bank also attracts attention. The series of banks made Submarine
known as a result of the work of telegraph ships, off the north- A^JlI^nti? ''^^
west coast of Africa to the north of the Canary Islands, is another
striking instance of the irregularity of the floor of the Atlantic.
In the same neighbourhood the area with depths less than 2000
fathoms surrounding Madeira and extending northwards towards
the coast of Portugal is remarkable. In the South Atlantic,
besides the central ridge, three smaller shallow areas should
be noted, two neighbouring ones to the east of the South
American coast in lat. 30° S., and the third midway between
the ridge and the Cape of Good Hope.
136 DEPTHS OF THE OCEAN
The principal area exceeding 2000 fathoms in depth is
continuous throughout the Atlantic, although much broken up
by areas of shallower water ; there are besides in places isolated
areas in which the depth exceeds 2000 fathoms, as in the Gulf
of Guinea, near the Canary Islands, at the northern extremity
of the Mid-Atlantic ridge (as already mentioned), as well as in
the Norwegian Sea, the Mediterranean Sea, the Carribbean
Sea, and the Gulf of Mexico.
The areas exceeding 3000 fathoms in depth (" deeps ") will
be referred to under a later heading.
Pacific Ocean. — The Pacific may be looked upon as extend-
ing southwards from the Arctic circle in Behring Strait to the
Antarctic continent, including the fringe of partially enclosed
seas along its western border, and as being separated from
the Atlantic in the south at the meridian of Cape Horn (long.
70' W.), and from the Indian Ocean at the meridian of Tasmania
(long. 147° E.). As thus defined the Pacific Ocean covers an
area of about 68,634,000 square English miles, the distribution
of depth being shown in the following table : —
Fathoms.
Square English Miles.
Percentage.
O-TOOO
1000-2000
2000-3000
3000-4000
Over 4000
7,174,000
12,214,000
44,633,000
4,412,000
201,000
10.45
17.80
65-03
6.43
0.29
I
68,634,000 100.00
These figures show that nearly nine- tenths of the Pacific
sea- floor are covered by water exceeding 1000 fathoms in depth,
and nearly three- fourths by water exceeding 2000 fathoms in
Continental depth. Unlike the Atlantic, the shallowest zone in the Pacific
hrihe^PactfiT (o- 1 000 fathoms) is smaller than the succeeding zone (1000-2000
fathoms), indicating that the Pacific land -slopes are on the
average steeper than those of the Atlantic, and this is strikingly
shown by the near approach to the land of the deep contours
in certain regions, as off the coasts of South America, North
America, Japan, the Philippine Islands, and South-East Australia.
The ratio between the two areas on either side of the 500-fathoms
line is not so strikino- as in the case of the Atlantic, the area
rv DEPTHS AND DEPOSITS OF THE OCEAN 137
less than 500 fathoms in the Pacific being about 5 million
square miles, as compared with 2 million square miles for the
area between 500 and 1000 fathoms.
The Pacific Ocean differs from the Atlantic in having much shore-siopes
more steeply sloping shores both on the east and west sides, of the Pacific,
greater depths, and very many small islands, chiefly of volcanic
and coral formation. This gives a very irregular appearance to
the depth-map of the Pacific, and shows sharper contrasts in rises
and depressions of the ocean-floor than are found in either of the
other great ocean basins. Along the west coasts of both North
and South America the steep slopes are most remarkable, the
land descending from the great heights of the Rocky Mountains
and the Andes to depths of 2000 fathoms and more in a
comparatively very short horizontal distance. This is par-
ticularly striking off the coast of South America between the
latitudes of 10° and 35° S., where depths of over 3000 fathoms
(in three cases over 4000 fathoms) are found within a very short
distance from the shore-line. It is noteworthy that all the very deep
soundings recorded in depths of over 4000 fathoms are taken com'^arSvei-
comparatively near land, viz. off South America (as just near land.
mentioned), off the Aleutian Islands, the Kurile Islands and
Japan, the Philippines, the Ladrone Islands, the Pelew Islands,
between the Solomon Islands and New Pommerania, and to the
north of New Zealand, east of the Kermadec and Friendly
Islands.
The greater part of the area with depths less than 1000
fathoms lies in the western Pacific, in the fringe of partially
enclosed seas which lie between the continents of Asia and
Australia and the islands fringing their eastern shores, such as
the Behring Sea, the Sea of Japan, the Yellow Sea, China Sea,
Java and Arafura Seas, and around the New Zealand plateau.
The area covered by depths between 1000 and 2000 fathoms Pacific area
lies mostly south of the equator, that part north of the equator beJ^^gtTiooo
consisting of detached areas in the Behring Sea, Sea of Okotsk, and 2000
Sea of Japan, and China Sea, narrow bands round the various ^' °^^^'
island groups and along the western shores of North America,
widening greatly off the coast of Central America, and nine small
areas where the floor of the ocean rises from surrounding depths
of over 2000 fathoms. The area in the South Pacific with depths
between looo and 2000 fathoms was formerly supposed to extend
from the Southern Ocean between Auckland Islands and the
Antarctic continent in a wide band north-eastv/ards towards the
coasts of Central America without a break, but recent investiga-
138 DEPTHS OF THE OCEAN
tions by the late Alexander Agassiz on board the U.S.S.
" Albatross " showed that this rise from the general depth of
over 2000 fathoms was not continuous. This has led to a great
decrease in the figures given for the area with depths between
looo and 2000 fathoms, and a corresponding increase in the
area with depths between 2000 and 3000 fathoms.
Pacific area The area exceeding 2000 fathoms in depth in the Pacific is
SocTfathoms. Connected with the corresponding area in the Atlantic by a
comparatively narrow trench running to the south of Cape Horn
between South Georgia and South Orkney, and is continuous
throughout the Pacific except for detached areas in several of
the fringing seas on the west, one in the Coral Sea, and one
large and six small areas in the South-West Pacific, where the
soundings are very numerous and the contour-lines of depth are
very sinuous.
The areas exceeding 3000 fathoms in depth will be referred
to under a later heading.
Area of the ludiau Oceaii. — The Indian Ocean may be looked upon as
Indian Ocean extendincj southwards from the Bay of Bengfal and Arabian Sea
sea-floor at i a • • • i i • i -r^ ^ c^ i t •
different to the Antarctic contment, mcludmg the Red Sea and Persian
depths. Gulf, and as being separated from the Atlantic in the south at the
meridian of the Cape of Good Hope (long. 20° E.) and from the
Pacific at the meridian of Tasmania (long. 147° E.). As thus
defined the Indian Ocean covers an area of about 29,340,000
square English miles, the distribution of depth being shown in
the following table : —
Fathoms.
Square English Miles.
Percentage.
O-IOOO
1000-2000
2000-3000
Over 3000
3,163,000
7,170,000
17,209,000
1,798,000
10.78
24-44
58-65
6.13
29,340,000
100.00
These figures show that, like the Pacific, nearly nine-tenths
of the Indian Ocean sea-floor are covered by water exceeding
1000 fathoms in depth, while nearly two-thirds are covered by
Continental more than 2000 fathoms of water. The shallowest zone in
inthe^'indiar ^^ Indian Ocean (o-iooo fathoms) is much smaller than the
Ocean. succecdiug zoue ( 1 000-2000 fathoms), indicating that the average
IV DEPTHS AND DEPOSITS OF THE OCEAN 139
land-slopes throughout the basin are, as in the Pacific, steeper
than those of the Atlantic. The ratio between the two areas
on either side of the 500-fathoms line is again much less than
in the case of the Atlantic, the area less than 500 fathoms in the
Indian Ocean being over 2 million square miles, as compared
with less than i million square miles for the area between 500
and 1000 fathoms.
The Indian Ocean, unlike the other two, is completely land-
locked to the north. The area with depths less than 1000 fathoms
forms a zone of varying width along the main land-masses, a fairly
wide zone round the various island groups, and extends into the
Red Sea and Persian Gulf. The area with depths between Indian Ocean
1000 and 2000 fathoms is made up of the greater part of the ^i^p^ti,^''^
Bay of Bengal and the Arabian Sea, a fairly wide belt along between 1000
the east coast of Africa, a much narrower one along the western fathom?"
shores of the Sunda Islands and Australia, a large expanse
between Tasmania and the Antarctic continent which narrows
considerably towards the west, and a large tract extending from
lat. 30" to 55' S. and long. 35° to 94 E., forming a plateau on
which are situated the islands of Prince Edward, Crozet,
Kerguelen, M'Donald, Heard, St. Paul, and Amsterdam, as
well as one or two small isolated areas.
With the exception of a comparatively small area in the Indian Ocean
Southern Ocean, about lat. 60° S. to the south of Australia, the 2000 feAom"^
area with depths between 2000 and 3000 fathoms is a continuous
one, though interrupted by areas of deeper and shallower water ;
it is continuous with the corresponding area of the Atlantic, but
distinct from that of the Pacific, being separated from it by the
rise that runs southwards from Tasmania to the Antarctic
continent.
The areas exceeding 3000 fathoms in depth are referred to
under the next heading.
Deeps. — As already indicated, those areas of the ocean-floor
covered by more than 3000 fathoms (5486 metres) of water
have been called Deeps, and, though occupying a relatively Deeps.
small proportion of the ocean-floor, estimated in the aggregate
at about 9 million square miles, they are extremely interest-
ing from an oceanographical point of view. Map II. shows
the distribution of these deeps throughout the great ocean
basins, according to the present state of our knowledge, and it
will be seen that the total number is fifty-seven, of which thirty- Number of
two occur in the Pacific, five in the Indian Ocean, nineteen in '"°^^" ^^^^'
140
DEPTHS OF THE OCEAN
Largest
deejDS.
Valdivia
Deep.
the Atlantic, and one partly in the Atlantic and partly in the
Indian Ocean. From the point of view of depth the Challenger
Deepest Deep in the North Pacific and the Aldrich Deep in the South
deeps. Pacific are the most important, for only these two include
depths exceeding 5000 fathoms, while in eight other deeps
depths exceeding 4000 fathoms have been recorded. On the
other hand, in some cases the deeps enclose low rises, on which
the depth is less than 3000 fathoms. The deeps vary in form
and size to a most extraordinary degree, and future soundings
may show that some of them should be subdivided into two or
more portions, or that two or more deeps as now laid down
should be united into a single deep.
From the point of view of superficial area, the most im-
portant deeps are the Valdivia, Murray, Tuscarora, Wharton,
Nares, Aldrich, and Swire Deeps, which are estimated to cover
in each case an area exceeding 500,000 square miles. In the
following paragraphs the principal deeps of the world are briefly
characterised, arranged in the order of magnitude : —
Valdivia Deep lies in the far south, partly in the Atlantic
and partly in the Indian Ocean. It is based principally on
soundings taken by the German Deep-Sea Expedition on board
the "Valdivia," and has a maximum depth of 3134 fathoms. It
is estimated to cover a total area of 1,136,000 square miles,
nearly one-half of which (523,000 square miles) lies to the west
of long. 20° E., i.e. within the Atlantic basin, while the remain-
ing half (613,000 square miles) lies to the east of that meridian,
and is therefore in the basin of the Indian Ocean. The outline
of this deep, especially in its western portion, is largely hypo-
thetical, and future soundings may modify the area assigned to
it at present.
Murray Murray Deep, situated in the Central North Pacific between
^'^'^P- lat. 25" and 40° N., is estimated to cover an area of about
1,033,000 square miles, and is founded on soundings taken
partly by the "Challenger" Expedition. The maximum depth
recorded in it is 3540 fathoms, and there is a small area within
the deep in the vicinity of this deepest sounding where depths
of only 2800 and 2900 fathoms are recorded.
Tuscarora Tuscarora Deep lies in the North- Western Pacific, and is of
Deep. elongated form, extending from the Tropic of Cancer north-
eastwards to near the Aleutian Islands in lat. 52° N., approach-
ing to within a comparatively short distance of the shores of
Japan and the Kurile Islands. Its area is estimated at 908,000
square miles, and the maximum depth is 4655 fathoms, recorded
IV DEPTHS AND DEPOSITS OF THE OCEAN 141
by the U.S.S. " Tuscarora" in 1874. A considerable portion of
this deep is covered by depths exceeding 4000 fathoms, includ-
ing one large elongate area founded on eight soundings, and
two small areas founded each on single soundings — one towards
the southern end of the deep and the other in the extreme
north.
Wha7'ton Deep lies in the eastern Indian Ocean, extending wharton
from lat, 10 S. to the Tropic of Capricorn, and is estimated to ^^'^'
cover an area of 883,000 square miles ; it includes the two
deepest soundings yet recorded in the Indian Ocean, viz. 3828
and 3703 fathoms, taken in 1906 by the German ship " Planet"
in what is called by the Germans the " Sunda Graben " at no
great distance from the coast of Java.
Nares Deep is the largest deep lying wholly in the Atlantic Nares Deep.
Ocean, and at the same time the deepest. Its outline is most
irregular, extending from lat. 18° N. to 34° N., and in the
neighbourhood of the West Indies the floor of the deep sinks
to depths exceeding 4000 fathoms over a limited area, the
maximum depth being 4662 fathoms, recorded by the U.S.S.
"Dolphin" in 1902. This deep is estimated to cover an area
of 697,000 square miles.
Aldrich Deep lies in the Central South Pacific, extending Aidrich Deep,
from lat. 15° to 47° S., and is estimated to cover an area of
about 613,000 square miles. It includes seven small areas
lying along its western border in which the depth exceeds 4000
fathoms. In three of these the depth exceeds 5000 fathoms,
viz. 5022, 5147, and 5155 fathoms, recorded by Commander
Balfour on board H.M.S. "Penguin" in 1895. Numerous
soundings have been taken round these* seven deepest areas,
and seem to prove that they are all separated from one another
by ridges covered by water between 3000 and 3700 fathoms in
depth. The outline of this deep is remarkable, and it is
possible that future soundings will show it to be two distinct
deeps, for a rise, on which soundings in 2000 to 2900 fathoms
have been recorded, interrupts the sequence of great depths.
Swire Deep lies in the North-West Pacific in close proximity SwireDeep.
to the Philippines, and extends from about lat. 4° N. to
lat. 25' N., covering an area of about 550,000 square miles. It
is broken up by several rises on the ocean-floor where depths
of 2700, 2800, and 2900 fathoms have been recorded ; on the
other hand, at remarkably short distances from the coasts of
Mindanao and Samar Islands in the Philippines are two areas
with depths exceeding 4000 fathoms, a similar depth being
142
DEPTHS OF THE OCEAN
recorded also at the northern end of the deep. The maximum
depth, which occurs off Samar Island, is 4767 fathoms.
Tizard Deep in the South Atlantic is estimated to cover an
area of about 468,000 square miles, extending southwards from
the equator to lat. 22" S. on the western side of the Mid-
Atlantic ridge. The greatest depth recorded in it is 4030
fathoms, just south of the equator. In the southern portion of
the deep two low rises occur, where depths rather less than
3000 fathoms have been recorded.
Buchanan Deep lies to the east of the Mid- Atlantic ridge in
the South Atlantic, between lat. 6° and 22° S., and covers an
estimated area of 298,000 square miles. This deep appears to
be somewhat flat-bottomed, because the numerous soundings
recorded within it do not reach 3100 fathoms though exceeding
3000 fathoms, the maximum depth being 3063 fathoms.
Brooke Deep lies in the North-West Pacific between the
latitudes of 12° and 19^ N., and covers an area estimated at
about 282,000 square miles. Its greatest depth is 3429 fathoms.
Several elevations of the ocean-floor, rising to within 1400,
1 1 00, and even 1000 fathoms of the surface, are situated close
to the western and northern borders of this deep, separating it
from the Challenger Deep on the west, and from the Bailey
Deep on the north.
Moseley Deep lies in the North Atlantic to the east of the
Mid- Atlantic ridge between lat. 9° and 18^ N., and is estimated
to cover an area of about 279,000 square miles; the deepest
sounding recorded within it is 3309 fathoms.
Bailey Deep lies in the North- West Pacific, between the
Brooke and the Murray Deeps, on the Tropic of Cancer. It is
estimated to cover an area of about 241,000 square miles, and
the deepest sounding recorded in it is 3432 fathoms.
Jeffrey Deep, in the eastern Indian Ocean, extends in
a narrow band round the southern and western coasts of
Australia, and as laid down on the map at present is estimated
to cover an area of about 228,000 square miles. It is based on
nine widely scattered soundings in the southern portion and
four soundings closer together at the northern end, leaving a
long stretch where no soundings have been taken. Further
investigation may show that what is now regarded as one
continuous deep is really two distinct deeps.
Belknap Deep lies in the Central Pacific, extending from
about lat. 12 to 17' N., and covering an area estimated at
about 165,000 square miles. Near the centre of the deep a
,v DEPTHS AND DEPOSITS OF THE OCEAN 143
rise based on a sounding in 2600 fathoms occurs between two
soundings in 3100 fathoms, and the floor of the deep sinks from
this rise towards the east to the maximum depth of 2)ZZ7
fathoms.
C/mn Deep hes in the North Atlantic between lat. 20" and Chun Deep.
29^ N., and is very pecuHar in outhne ; it is estimated to cover
an area of about 159,000 square miles, and the greatest depth
is 3318 fathoms.
Challenger Deep lies to the east of the Ladrone Islands in challenger
the western Pacific, and extends from lat. 11' to nearly 20° N., ^^'"^i"-
covering an area estimated at about 129,000 square miles. In
1875 the "Challenger" recorded a depth of 4575 fathoms
between Guam and the Pelew Islands, and in 1899 the United
States steamer " Nero" took a sounding in 5269 fathoms to the
south-west of Guam, which is the deepest sounding hitherto Deepest
recorded. The 4000-fathoms area extends in a narrow trench bounding.
as far to the north-east of the "Nero" sounding as the
"Challenger" sounding is south-west of it, and a small isolated
area occurs still farther north, based on a single sounding in
4204 fathoms. At a comparatively very short distance from
this deep trench is a pronounced rise within the deep based on
three soundings : one in 1800 fathoms and two in 1000 fathoms ;
another slight rise is based on a sounding in 2900 fathoms.
The remaining deeps are smaller, and need not be referred
to in detail, their position being clearly shown on the accom-
panying map (Map II.). Attention may be drawn, however,
to the great depth of the Planet Deep, situated in the tropical
Pacific between the Solomon Islands and New Pommerania, in
which a sounding in 4998 fathoms was recorded in 19 10 by the
German survey ship "Planet" a short distance to the west of
Bougainville Island.
2. Deep-Sea Deposits
The systematic investigation of deep-sea deposits was first First
undertaken by Sir John Murray during the "Challenger" Ex- sJudy'oV
pedition, and the only standard work dealing with the whole ™_f^^".^^
subject is Murray and Renard's " Challenger''' Report on Deep- '
Sea Deposits, published in 1891. That Report was not based
merely on the deposit-samples brought home by H.M.S.
" Challenger," though the detailed descriptions were limited
to those samples, but included the results of the examination
of samples collected by many other ships, received at the
144
DEPTHS OF THE OCEAN
Number of
deposit-
samples
examined.
Composition
of marine
deposits.
" Challenger" Office from the British Admiralty and from many-
other British and foreign sources. Since the publication of the
" Challenger "Report, deposit-samples collected by H.M. survey-
ing ships and by British cable ships, as well as by many ships
belonging to other nations, have been forwarded to the
"Challenger" Laboratory for study, so that nearly all the
samples of deposits procured from deep water over the ocean's
floor have passed through our hands, and are available for the
preparation of maps showing the distribution of the different
types of deposits, and for the determination of the various
constituents entering into the composition of deep-sea deposits.
How extensive this material is may be surmised from the fact
that nearly 12,000 deposit-samples have been examined in the
" Challenger" Office. Some of these samples were very small,
in a few cases insufficient even to indicate the type of deposit ;
but the great majority sufficed for the determination of the
deposit-type, and of the percentage of calcium carbonate, while
a very large number were available for detailed study and
description. The samples have all been dealt with in a
uniform manner, the methods of examination and description
fully explained in the " Challenger " Report having been adopted
throughout, for, notwithstanding the large amount of sounding-
work carried on since that Report was published, the general
results, the classification, and the nomenclature given therein
have been fully substantiated and found quite adequate in every
respect, no new types having been discovered.
In this place we are dealing only with deep-sea deposits, i.e.
those occurring in depths greater than 100 fathoms, the littoral
and shallow- water deposits found in depths less than 100
fathoms being excluded. It may be stated, however, that these
shallow-water and shore deposits near land are principally made
up of relatively gross materials directly derived from the
adjacent coasts, and from rivers pouring their waters and
detritus into the ocean. Coral sands prevail near coral reefs.
Volcanic sands off volcanic islands, and continental detritus near
the embouchures of great rivers. All these materials become
finer in texture with increasing distance from land, and in the
greater depths of the ocean.
The constituents entering into the composition of deep-sea
deposits may conveniently be divided into two classes : (A)
those of organic origin, precipitated by organisms from the dis-
solved constituents of sea- water, and (B) those of inorganic
IV DEPTHS AND DEPOSITS OF THE OCEAN 145
origin, derived from (i) the decomposition of terrestrial and
submarine rocks, (2) extra-
terrestrial sources, (3) pro-
ducts synthesized at the
bottom of the sea.
Organic remains belong- Materials of
ing to the vegetable kingdom "^g^™'^ ongi"-
are on the whole compara-
tively rare on the sea-floor,
when compared with those
belonging to the animal
kingdom ; still, in the neigh-
bourhood of land, vegetable
matter, branches of trees, piant remains
leaves, fruits, etc., may be
carried into deep water
through the agency of large
rivers, storms, off- shore
winds, etc., along with the
shallow water. Similarly
in marine
deposits.
Fig. 108.
Discosphara thomsoni, Ostenfeld.
From the surface
remains of sea-weeds
in coral-reef re-
gions, the re-
mains of algae
which lived on
the reefs, such
as LithotJiani-
niuin and Coral-
Una, occur in
the deposits in
the vicinity. But
the most con-
stant compon-
ents of vegetable
origin are the
remains of algse,
which secreted
either calcium
carbonate or
silica from the
surface waters
of the ocean to
form their hard
parts, viz. the calcareous coccospheres and rhabdospheres (see
Fig. 109.
Rhabdosphcera claviger, Murray and Blackman.
From the surface ( " "/* " ).
146
DEPTHS OF THE OCEAN
Figs. 108 and 109) characteristic of tropical and sub-tropical
regions, and the siliceous diatoms characteristic of extra-tropical
regions. While the diatom remains are so abundant in the deposits
of the Southern Ocean and of the North Pacific as to form a
distinct deposit-type (Diatom ooze), the remains of the pelagic
calcareous algae are always overshadowed by the abundance of
^^
Fig. no.
Eucoronis challengeri, Haeckel. From the surface (magnified).
the remains of pelagic foraminifera and mollusca in the deposits of
the warmer regions of the ocean. These pelagic calcareous algae
are so fragile in texture, that it is principally their broken-down
parts (coccoliths and rhabdoliths) that occur in the deposits ; in
certain favourable localities coccospheres of small size may be
fairly numerous, but rhabdospheres are practically unknown in
deep-sea deposits, being apparently easily dismembered, and the
same remark seems to apply to the large-sized coccospheres.
DEPTHS AND DEPOSITS OF THE OCEAN 147
Traces of albuminoid orP:anic matter may be found in most Albuminoid
'-* matter.
Fig. III.
Staitracanfha miirrayana, Haeckel. From the surface (magnified).
deep-sea deposits, especially in the neighbourhood of land, and
1
^r^rrrrrr
Fig. 112.
Hexancistra qiiadricuspis , Haeckel.
From the surface (magnified).
Fig. 113.
Lampro7nitra huxleyi, Haeckel.
From the surface (magnified).
may be either of animal or vegetable origin ; a greenish organic
matter is generally associated with the glauconite in the Green
148 DEPTHS OF THE OCEAN
sands. The benthonic deep-sea animals live by eating the mud
or ooze covering the ocean-floor, and appear to find all the
Fig.
Haliomma ivyvillei, Haeckel.
From the surface (magnified).
Animal
remains in
marine
deposits.
Siliceous
remains.
nourishment they require therein. The excreta of these animals
are associated with a certain amount
of slimy albuminoid matter, and in cer-
tain localities these excreta become so
numerous that the term " coprolitic
mud " has been proposed for the
deposits containing them.
The animal remains found in deep-
sea deposits are either siliceous or
calcareous, those of a chitinous char-
acter being extremely rare, if not
entirely absent. The siliceous remains
of radiolaria (see Figs, no to 117)
and the spicules of siliceous sponges
are widely distributed over the ocean-
floor, the radiolarian skeletons being so abundant in certain
regions as to make up a very large part of the deposit, which
Fig. 115.
Lithoptera darwinii, Haeckel.
From the surface (magnified).
,v DEPTHS AND DEPOSITS OF THE OCEAN 149
is then called Radiolarian ooze ; sponge spicules, though present
in nearly every bottom-sample examined by us from deep and
shallow water, very seldom take any considerable part in the
formation of the deposits.
The calcareous remains of foraminifera, corals, alcyonaria, Calcareous
annelids, Crustacea, echinoderms, bryozoa, molluscs, tunicates, '■'^"^^'"^•
and fishes seem to bulk more largely in deep-sea deposits than
the siliceous remains. The Globigerina and Pteropod oozes and
the Coral muds
and sands owe
their names to
abundance in
Fig. 116.
Clathrocaniuin regintv, Haeckel. From the surface (magnified).
Cinclopyra m is infiindi-
hulum, Haeckel. From
the surface (magnified).
them of the re-
mains of pelagic
foraminifera (see
Figs. 1 18 to 121),
of pelagic molluscs (Figs. 122 and 123), or of coral fragments,
while the valves of ostracods (Figs. 124 and 125), the spines
of echinoids, the spicules of alcyonaria and tunicates, and
the otoliths of fishes are among the most constant of the
calcareous remains occurring in the deposits, though rarely
found in any great abundance. Reference may also be made to
the teeth of sharks (see Figs. 126 and 127) and the earbones of
whales (see Figs. 128 and 129) found occasionally in all deposits,
but characteristically in the Red clay areas especially of the
I50 DEPTHS OF THE OCEAN
Pacific Ocean, which have evidently lain there for a long period
Fig. ii8.
Globigerina bulloides, d'Orbigny. From the surface (magnified).
of time, having become much decomposed or deeply impregnated,
and in many cases thickly coated, by the peroxides of manganese
IV DEPTHS AND DEPOSITS OF THE OCEAN 151
and iron. It is remarkable how very few fish bones other than
teeth and otoHths occur in marine deposits.
The inorganic materials entering into the composition of Materials of
deep-sea deposits may be conveniently considered under three o^J'^frT^''^
Fig. 119.
Orbuli?ia utiiversa, d'Orbigny. From the surface (%").
heads: (i) terrestrial, (2) extra-terrestrial, and (3) secondary or
chemical products.
The terrestrial materials are either of volcanic or continental Terrestrial
origin, the former being derived from submarine and subaerial
eruptions, and, by reason of their areolar structure, widely
Volcanic
products.
152
DEPTHS OF THE OCEAN
distributed over the ocean-floor, the latter being derived from
the disintegration of continental land through atmospheric and
physical agencies and distributed in comparatively close proximity
to that land. Of volcanic products the most characteristic is
pumice, which may float for a long time in the surface waters of
Fig. 120.
Hastlgerina pelagica, d'Orbigny. From the surface (\°).
the ocean and may be carried far from its original source before
finally becoming water-logged and sinking to the bottom.
While floating on the surface these stones are knocked against
one another by the waves, and the broken-off fragments fall to
the bottom. Three varieties of pumice have been recognised
among the fragments from the sea-bottom : liparitic, basaltic
IV DEPTHS AND DEPOSITS OF THE OCEAN 153
or basic, and andesitic. After pumice, the most striking volcanic
products are fragments of basic volcanic glass (sideromelan)
nearly always partly, sometimes entirely, decomposed and
altered into palagonite, together with palagonitic tufas, generally
associated with the deposition of the peroxides of manganese
and iron, besides basaltic and other lapilli and volcanic ashes.
Great slabs have been dredged showing sometimes distinct
Fig. 121.
pelagica, d'Orbigny.
From the surface {^x)-
layers produced by showers of volcanic ashes. Minerals of
volcanic origin (volcanic dusts) may be carried great distances
by the winds, and ultimately find a resting-place on the bottom
of the sea.
The continental products consist of fragments of continental Continental
rocks and the minerals derived from their disintegration, the Products.
characteristic mineral species being quartz. The rock-fragments
are usually found only in close proximity to the continental
land-masses, though exceptionally found in deep water far from
154
DEPTHS OF THE OCEAN
Extra-
terrestrial
materials.
land in those regions of the ocean affected by floating icebergs.
The dust from deserts, Hke volcanic dusts, may be carried by
wind to great distances from land, and can be detected in deep-
sea deposits, for instance, off the west coast of Africa.
The materials of extra-terrestrial origin, though extremely
interesting, do
not bulk largely ^'^^^^m ^ h
in marine de- ^' '
posits ; indeed
they are rather
of the nature of
rarities, and are
noticed most
abundantly in
Red clay areas
where, for many
reasons, it is
believed the rate
of deposition is
at a minimum. They consist of minute black metallic spherules
and brown chondritic spherules, which may be extracted by
the aid of a magnet when the Red clay deposit is reduced to
a fluid condition by admixture of water. The black spherules
(see Figs. 130 and 131) sometimes have a shining metallic
V
Canna/'/a lamarckii. Per
of this species are occasionally met with
Fig. 122.
and Les. (From Steuer. )
The fragile shells
deep-sea deposits.
Fig. 123.
Pterotrachea coi'onafa, Forsk. (From Leuckart, after Steuer. ) This species has no shell,
and therefore does not enter into the composition of deep-sea deposits.
nucleus of native iron (or an alloy of iron, cobalt, and nickel),
surrounded by a shell of brilliant magnetic oxide of iron, to
which the magnetic properties of the spherules are due. The
brown spherules (see Figs. 132 and 133) have the lustre of
bronze externally, and have a finely lamellatefd crystalline
structure, with blackish -brown inclusions of magnetic iron,
which account for their extraction by the magnet. A cosmic
IV DEPTHS AND DEPOSITS OF THE OCEAN 155
origin is attributed to both forms of magnetic spherules, which
are supposed to have been thrown off by meteorites, or falHng
stars, in their passage through our atmosphere.
The secondary products entering into the composition of Secondary
deep-sea deposits are (i) clay, (2) manganese nodules, (3) barium P'^°'^"^ts.
and barium nodules, (4)
glauconite, (5) phosphatic
concretions, and (6) zeo-
lites.
The clayey matter in Clay.
the deposits near land
may have been trans-
ported by rivers, etc.,
from the land, but most
of the clayey matter
present in the deposits
far from land is believed
to have been derived from
the decomposition under the action of water of eruptive and
metamorphic rocks and minerals, especially pumice and volcanic
glass. The deep-sea clays, some of which are mostly made up
of these decomposing volcanic materials, are usually coloured
a reddish -brown by the oxides of manganese and iron —
products of the de-
124.
Krithe producta, Brady. From the bottom-deposits
(magnified).
Fig. 125.
From the bottom-deposits (magnified).
composition of the
same rocks that gave
rise to the clayey
matter — and a com-
paratively small
amount of clay may
give a clayeycharacter
to the deposit.
The oxides of iron Manganese
and manganese are "°'^"^^^-
widely distributed in
Cy there dictyon, Brady. , ^ ^ ,.
marine deposits, and
especially in deep-sea deposits. They occur in minute grains,
and act as colouring matter in nearly all deep-sea clays,
and in certain abyssal regions of the ocean they form con-
cretions of larger or smaller size, which are among the most
striking characteristics of the oceanic Red clay. Sometimes
the oxides cover consolidated masses of tufa, fragments of
rocks, portions of the deposit, branches of coral and other
156
DEPTHS OF THE OCEAN
calcareous remains, or form irregular concretionary masses,
though the commonest form is that of more or less rounded
nodules (see Figs. 134 and 135), which at any one station have a
general family resemblance and differ in form and size from
those taken at another station, looking like marbles at one
place, like potatoes or like cricket balls at other places. Gener-
ally the nodules are concretions formed around a nucleus, con-
FiG. 126. — Tooth of Carcharodon megalodon.
"Challenger" Station 281, South Pacific, 2385 fathoms.
sisting of a shark's tooth or whale's earbone, or portions of teeth
or bone, a piece of pumice or fragment of volcanic glass, etc.,
though sometimes no nucleus could be detected. These nodules
of iron and manganese are classed with the impure variety of
manganese known as wad or bog manganese ore, and the
greater part of the manganese and iron is believed to have been
derived directly, along with clay, from the alteration of the rock-
fragments and mineral particles containing manganese and iron,
especially of those of volcanic origin, which are spread over the
IV DEPTHS AND DEPOSITS OF THE OCEAN 157
ocean-floor. Where basic volcanic rocks are in process of
decomposition, manganese nodules may be relatively abundant
in shallow water, and they are never
numerous in Globigerina oozes, ex-
cept where volcanic material is
present in some abundance in the
deposit.
Sulphate of barium has been Barium.
found to be present in most marine
deposits and in manganese nodules
in small quantities ; in terrigenous
deposits up to about o. i per cent, in
manganese nodules slightly more,
and in Red clays up to about i per
cent. Small round nodules have
been trawled off Colombo, in 675
fathoms, containing 75 per cent of
barium sulphate.
-Glauconite occurs in the terri- Giauconite.
genous deposits typically in the form
of minute rounded grains of a green-
ish colour, usually associated with greenish or brownish casts of
calcareous organisms (foraminifera, etc.) ; in fact, the rounded
Fig. 127. — Tooth of Oxvrjj/xa
TRIGODON.
"Challenger" Station 276, Tropical
Pacific, 2350 fathoms.
Fig. 128. — Petrous and Tympanic Bone
of ziphws cavirostris.
"Challenger" Station 286, South Pacific,
2335 fathoms.
Fig. 129. — Section of a Mangan-
ese Nodule, showing a Tym-
panic Bone of Mesoplodon in
the Centre.
"Challenger" Station 160, Southern
Ocean, 2600 fathoms.
trace
green grains are supposed to be casts which have lost all
of the enveloping calcareous chambers. The individual grains
of glauconite do not exceed one millimetre in diameter, though
158 DEPTHS OF THE OCEAN
occasionally they are cemented into nodules, several centimetres
in diameter, by a phosphatic substance ; the grains are always
rounded, often mammillated, hard, dark green, or nearly black,
with sometimes a dull and sometimes a shining surface. Mixed
with the rounded
grains are pale
green, pale grey,
white, yellow and
brownish internal
casts ot the cavities
and chambers of
calcareous organ-
isms, often asso-
FiG. 130. — Black Spherule
WITH Metallic Nucleus
(¥)■
" Challenger " Station 285,
South Pacific, 2375 fathoms.
"iG. 131.— Bla( K Spue
WITH Metallic Nucleus riated with
en
' Challenger " Station 9, North
Atlantic, 3150 fathoms.
amorphous organic
matter of a brown-
ish - green colour.
Glauconite is principally developed in the interior of foramini-
ferous shells and other calcareous structures, the initial stages in
the formation of glauconite being probably due to the presence
of organic matter in the interior of these shells. Glauconite is
Fig. 132.— Spherule of Bronzite
(V).
"Challenger" Station 338, South
Atlantic, 1990 fathoms.
Fig. 133. — -A Lamella of a Spherule
OF Bronzite (highly magnified).
"Challenger" Station 338, South Atlantic,
1990 fathoms.
always associated with terrigenous mineral particles and rock-
fragments, the decomposition of which, under the action of sea-
water, would yield the chemical elements subsequently deposited
•in the form of glauconite in the chambers of foraminifera and
other calcareous organisms. The excreta of echinoderms appear
sometimes to be converted into glauconite.
IV DEPTHS AND DEPOSITS OF THE OCEAN 159
Associated with the glauconite in certain localities, more Phosphatic
especially off the Cape of Good Hope and off the Atlantic coast '^°"'^'^^ti°"^-
of the United States, irregular concretions, largely made up of
phosphate of lime, have been dredged. The concretions vary
greatly in size and form, with a greenish or brownish glazed
external surface, and are made up of
heterogeneous fragments derived from
the deposit containing the concretions
(grains of glauconite and other minerals
or remains of organisms), cemented
by phosphatic material, which consti-
tutes the principal part of the concre-
tions. When the cemented particles
are purely mineral, the phosphatic
matter acts simply as a cement, but
when the remains of calcareous organ-
isms are included in the concretions,
the phosphatic material plays a more
important part, filling the internal
chambers, and often the calcium car-
bonate of the shell is pseudomor-
phosed into calcium phosphate. When
the filling up of a foraminifer, for
example, and the pseudomorphism of
its shell, are complete, the phosphate,
attracted around this little centre con-
tinues to be added at the surface, and
thus a phosphatic granule is formed,
the external appearance of which no
longer recalls that of the organism
around which the phosphate has
grouped itself. These phosphatic con-
cretions occur chiefly along coasts
bathed by waters subject at times to
great and rapid changes of tempera-
ture, which cause the destruction on a
large scale of marine life, the decomposition of the organic
remains, sometimes thickly covering the sea-floor in such locali-
ties, giving rise to the phosphate of lime to be permanently
fixed in the phosphatic nodules.
Just as the silicate glauconite occurs in the terrigenous Phiiiipsite.
deposits, and is supposed to be a secondary product derived
from the decomposition of continental rock fragments, so the
Fig. 134. — Manganese Nodule
with scalpellvm darwinil
growing on it.
" Challenger" Station 299, South
Pacific, 2160 fathoms.
i6o
DEPTHS OF THE OCEAN
silicate phillipsite occurs in the pelagic deposits, and is supposed
to be a secondary product derived from the decomposition of
volcanic rock fragments. Phillipsite is found in the various
kinds of deposits in the deep water of the Central Pacific and
Central Indian Ocean far from land, and is most abundant in
some Red clay areas. It occurs in crystalline form, either as
simple isolated microliths, crossed twins, irregular groups, or
aggregated into spherolithic groups in which these zeolitic
crystals are entangled together so as to form crystalline globules
of sufficient size to be distinguished by the naked eye. The
distribution of these crystals of phillipsite coincides with that of
basic volcanic glasses and basaltic lapilli over the ocean-floor,
the decomposition of which, under
the action of sea-water, would give
rise to the materials afterwards
deposited in a free state as zeolitic
crystals and aggregates.
Radio-active Professor Joly has examined
substances. ^^^ their radium contents a number
of deposit-samples supplied by Sir
John Murray. He finds that the
deep-sea deposits are much richer
in radium than the average terres-
trial rocks. The Red clays and
the Radiolarian oozes, which are
laid down in deep water far from
land, contain much more radium
than the calcareous deposits like the Pteropod and Globigerina
oozes. The radio-activity and percentage of calcium carbonate
in the deposits stand in an inverse ratio to each other, and the
■ Blue muds contain less than the calcareous oozes, though more
than the continental rocks. It seems evident that the quantity
of radio-active substances, of manganese nodules, with earbones
of whales and sharks' teeth, of zeolitic crystals and cosmic
spherules, is greatest where, for other reasons, we believe the
rate of deposition to be least.
Deep-sea In the neighbourhood of emerged land the material derived
deposit types, f^^^^ |.j^^j- \^^^ jg spread over the sea-floor, becoming finer and
finer in texture with greater distance and depth, whereas in
the central regions of the great ocean basins land-detritus may
be almost totally absent from the deposits, while the calcareous
Fig. 135. — Manganese Nodule with
TWO Tunicates and a Brachiopod
attached.
"Challenger" Station 160, Southern
Ocean, 2600 fathoms.
IV DEPTHS AND DEPOSITS OF THE OCEAN i6i
and siliceous shells and skeletons of pelagic or plankton organ-
isms may greatly predominate. This fact affords a ready Classification,
means of dividing marine deposits into two main classes, viz.
Terrigenous Deposits, largely made up of detritus derived
directly from emerged land, with the remains of benthonic
organisms, and Pelagic Deposits, containing little if any land-
detritus, but largely made up of the remains of pelagic organisms.
The former class of deposits must therefore form a border,
varying in extent according to circumstances, around all the
land-masses and islands of the world, while the latter class of
deposits occurs in those regions so far removed from the land-
masses and islands that very little material derived directly
from the land can reach the position where they are found.
The dividing lines between these two classes of deposits, and
between the various types included in them, are not sharply
defined, but the different kinds of deposits merge gradually the
one into the other, so that frequently two names, and in some
cases even three names, might equally well be applied to the
same sample. It is the terrigenous deposits laid down in close
proximity to the land, and in enclosed seas like the Mediter-
ranean, that are represented in the geological series of rocks,
but it is extremely doubtful whether the pelagic deposits laid
down in deep water far from land have any analogues among
the geological strata.
After a careful study of all the available samples, Murray and
Renard gave the following classification of marine deposits : —
Marine Deposits
' Red clay
Radiolarian ooze
Diatom ooze
Globigerina ooze
Pteropod ooze
Blue mud
Red mud
Green mud
Volcanic mud
Coral mud
Shallow - ^^'■ater Deposits, 1 o j i
K^fw^^.. 1..,,. wof«. ^.ovi.. I Sands, gravels,
muds, etc.
Deep- Sea Deposits,
beyond loo fathoms.
I. Pelagic Deposits formed
in deep water removed
from land.
Terrigenous
formed in
Deposits,
deep and
between low water mark
and loo fathoms.
3. Littoral Deposits, between 1 0 ^ 1
, • , J , .1 Sands, gravels,
high and low water \ a \
° 1 muds, etc. •
marks. j
shallow water close to
land-masses.
l62
DEPTHS OF THE OCEAN
Terrigenous
deposits.
Blue mud.
Green mud
and sand.
Red mud.
Volcanic mud
and sand.
Coral mud
and sand.
Pelagic
deposits.
The Terrigenous Deposits are characterised, as already-
stated, by the abundance of land-detritus, and are subdivided
into the following types, viz. : —
Blue Mud. — This is the predominant type of deposit in the
neighbourhood of continental land, and is principally made up
of land-detritus (quartz being the characteristic mineral species),
which becomes less and less abundant with increasing distance
from the land, until the Blue mud passes gradually into one of
the types of pelagic deposits.
Green Mud is a variety of Blue mud, distinguished by the
abundance of grains of glauconite usually associated with
phosphatic concretions, and is found most characteristically on
the continental slopes off high and bold coasts where currents
from different sources alternate with the season, as off the
Cape of Good Hope, off the east coast of Australia, off Japan,
and off the Atlantic coasts of the United States. In the lesser
depths the amount of clayey and muddy matter decreases and
the deposits are called Green Sands.
Red Mud is a local variety of Blue mud found in the Yellow
Sea and off the coast of Brazil, where the great rivers bring
down a large amount of ochreous matter, to which the deposit
owes its colour and its name.
Volcanic Mud occurs off those coasts and islands where
volcanic rocks prevail ; the volcanic mineral particles are larger
and more abundant in the shallower water near the land, and
the deposits there are called Volcanic Sands.
Coral Mud is found in the vicinity of coral reefs and islands ;
fragments derived from the disintegration of the reefs are
larger and intermixed with less fine material in the lesser
depths, and the deposits are then called Coral Sands.
The Pelagic Deposits are characterised by the fact that,
with the exception of Red clay, their composition is largely
determined by the pelagic or plankton organisms, which secrete
hard shells either of calcium carbonate or of silica, the pre-
dominance of the remains of one or other of these classes of
organisms giving the names to the deposits. In fact, the
deposits may be divided into those that are calcareous and
those that are siliceous, the calcareous deposits (Globigerina
ooze and Pteropod ooze) being characteristic of tropical and
subtropical regions, where there is abundant secretion of calcium
carbonate by plankton organisms, the siliceous deposits (Diatom
ooze and Radiolarian ooze) being characteristic of polar and
other regions, where there is a large admixture of clayey matter
IV DEPTHS AND DEPOSITS OF THE OCEAN 163
in the surface waters, and where there is abundant secretion of
silica by the plankton
organisms. Over wide
areas in very deep water,
however, neither cal-
careous nor siliceous
remains predominate ;
the basis of the deposit
then becomes Red clay,
consisting of clayey
matter derived from the
decomposition of vol-
canic materials ; quartz
particles, so abundant
in terrigenous deposits,
are rare or absent.
The pelagic deposits
are subdivided into the
following types, viz. : —
Pteropod Ooze. — In Pteropod ooze.
the shallower waters,
oceanic ridges and cones,
Fig. 136. — Pteropod Ooze.
Valdivia" Station 208, Indian Ocean, lat. 6° 54' N.
long. 93° 28'. 8 E., 162 fathonis (magnified).
on
usually far from continental land
especially within coral
reef regions where
warm water with small
annual range occupies
the surface, almost
every surface organism
which secretes a hard
shell or skeleton is
represented in the de-
posit, the dead shells of
pteropods and hetero-
pods being character-
istic, and the deposit is
hence called Pteropod
ooze (see Fig. 136).
About 35 species of
pteropods and 32
species of heteropods,
as well as pelagic gas-
teropods (see pp. 172-
173), are known to live in the surface waters of the tropics, and
Fig. 137. -Gi.onicERiNA Ooze.
Valdivia" Station 45, Atlantic, lat. 2° 56'.4 N.,
long. 11° 40'. 5 W., 2728 fathoms (magnified).
Globigerina
ooze.
f^^^
Fig. 138.— Globigerina Ooze.
Station 162, Southern Ocean, lat. 43° 44'. 4 S.
Valdivia
long. 75" 33'- 7 E.
1878 fathoms (magnified).
164 DEPTHS OF THE OCEAN
the shells of all these species may occur in the Pteropod ooze,
but the extent of this
type of deposit is not
great. Shelled ptero-
pods, except Lijuacina,
are not found in the
polar oceans.
Globigerina Ooze. —
The average depth of
the ocean is about 2000
fathoms, and the most
widely distributed of
the deposits in these
average depths is Glo-
bigerina ooze (see Figs.
137 to 139), which is
made up largely of the
dead shells of surface
foraminifera, the genus
Globigerina often
greatly predominating,
hence the name. About
twenty species of pelagic
foraminifera (see p. 172)
inhabit the surface
waters of the tropical
oceans, and their dead
shells are found in the
Globigerina ooze ^ and
also in the Pteropod
ooze, but towards the
Arctic and Antarctic
regions only one or two
dwarfed species occur
in the surface and sub-
surface waters. I n very
deep water, even within
the tropics, the calcare-
ous shells do not accu-
mulate on the bottom,
1 The names " Biloculina clay" and ." Orbulina ooze" will lie found in the literature of
marine deposits, but these have been described from samples which had been passed through
fine sieves, the larger shells having been retained while the smaller ones had passed through
the meshes.
Valdivia '
long,
Fi<;. 13M. 1,1^ 'i.^.ij i\ > I )ozE.
Station 154, Southern Ocean, lat. 6
61° 15'. 9 E. , 1940 fathoms (magnified).
45'.2 S.
-f>'
IV DEPTHS AND DEPOSITS OF THE OCEAN 165
being apparently remov^ed through the solvent action of sea-
water, and with in-
creasing depth the
Globigerina ooze
passes gradually into
another pelagic type,
usually Red clay.
Diatom Ooze. We Diatom ooze.
have indicated that in
the colder regions of
the ocean, as in the
great circumpolar
Southern Ocean and
along the northern
border of the Pacific,
diatoms flourish abun-
dantly in the surface
waters, and where de-
trital matters are not
very large in amount
their dead frustules,
falling to the bottom,
make up a large part
of the deposit called
^^>t. I& Diatom ooze (see Fig.
■/// Radio larian Ooze Radioiaiian
;/ (see Fig. 141) has not °°^^-
been recorded from the
Atlantic Ocean, but is
characteristic of deep
water in the tropical
regions of the Pacific
and Indian Oceans,
, where the surface
\:,^' waters have rather a
low salinity and carry
clayey matter in sus-
pension. It may be
Fig. 141.-RA1.10LARIAN Ooze. regarded as a variety
Valdivia" Station 237, Indian Ocean, lat. 4° 45' S. , P-r^ A \ «- ' '
long. 48° 58'. 6 E., 2772 fadioms (magnified). OI KeQ Clay COntammg
Fig. 140. — Diatom Ooze.
Valdivia" Station 140, Southern Ocean, lat. 54°
long. 22° 13'. 2 E., 2207 fathoms (magnified).
' It may be noted that Flint has recorded Diatom ooze from the tropical Pacific, but his
samples have since been examined and classed by us as Radiolarian ooze.
i66 DEPTHS OF THE OCEAN
many radiolarian skeletons. The frustules of diatoms and
skeletons of radiolarians may occur in all deposits, but gener-
ally they do not become characteristic or predominant when
calcareous shells are present in large numbers.
Red Clay is characteristic of great depths, say beyond 2700
fathoms (as Globigerina ooze is characteristic of moderate
depths, between 1000 and 2500 fathoms), and is the most widely
distributed of all the deep-sea deposits, covering a larger area
of the sea-floor than any other deposit type. The basis of the
deposit is the hydrated silicate of alumina, or clay, derived
principally from the decomposition and disintegration of pumice
and other volcanic products long exposed to the action of sea-
water, often associated with secondary products derived from
the same source, such as manganese-iron nodules and phillipsite
crystals. Calcareous remains may be totally absent in the
greatest depths, while in lesser depths the percentage of calcium
carbonate may approach 30, and the deposit then passes gradu-
ally into Globigerina ooze. If the calcium carbonate in a
Globigerina ooze or a Pteropod ooze be removed by weak acid,
the residue resembles closely a Red clay. In other places the
siliceous remains of radiolaria may increase to such an extent
that the Red clay merges gradually into Radiolarian ooze. The
rate of accumulation is evidently at a minimum in the Red clay
areas, for the calcareous shells falling from the surface waters
have been gradually removed in solution either before, or
immediately after, reaching the bottom ; the ear-bones of whales
and teeth of sharks (some of them belonging to extinct species)
are there found in the greatest profusion, impregnated with and
coated by the peroxides of manganese and iron ; and there also
occur in greatest abundance (though always rare) minute
metallic and chondritic spherules supposed to have fallen from
interstellar space, and found there more abundantly simply
because of the sparse deposition of other materials. Radio-
active substances are also found more abundantly in Red clay
than in any other marine deposit, or in any continental rocks.
A few facts relating to the horizontal distribution of marine
deposits may now be Indicated. The terrigenous deposits
include a number of varieties, but as a whole they surround all
continents and islands in all latitudes, and extend to varying
distances from the shore. The Coral muds and sands included
in this class are limited to the coral-reef regions of tropical and
subtropical latitudes, and the presence of the calcareous shells
IV DEPTHS AND DEPOSITS OF THE OCEAN 167
of pteropods and heteropods and pelagic foraminifera in terri-
genous deposits indicates approximately temperate or tropical
latitudes ; in the Arctic and Antarctic regions these shells are
absent from the deposits. Green muds and sands appear to be
limited to regions where there is a wide range of temperature
in the surface waters of the ocean, while Red muds are limited
to those localities where a large amount of ochreous matter is
carried into the sea by rivers, and Volcanic muds and sands are
limited to the neighbourhood of volcanic centres, both subaerial
and submarine. But the most widely distributed of all the
terrigenous types is Blue mud, which occurs in both the Arctic
and Antarctic regions, and along the shores of continents and
continental islands throughout the world, where not displaced
by one or other of the varieties just mentioned.
Broadly speaking, the terrigenous deposits close to land in
shallow water contain more and larger mineral fragments than
those farther removed from the land and in deeper water.
Where great rivers enter the sea the terrigenous deposits may
extend very far seaward, and a Blue mud may occupy the whole
of the continental slope, extending perhaps some distance out
over the deep bed of the ocean. On the other hand, along
high and steep coasts oceanic conditions may approach close to
the shore, and a Blue mud may pass into a Green mud or into a
Pteropod ooze, and finally into a Globigerina ooze along the
continental slope.
Turning to the pelagic deposits, we find that Pteropod ooze
is limited to the tropical and subtropical regions, usually in the
neighbourhood of oceanic islands and on the summits and sides
of submarine elevations ; it is found in relatively shallow water,
and covers a relatively small extent of the ocean-fioor.
Globigerina ooze is much more widely distributed ; in fact, it
covers an area of the entire sea-fioor second only to that occu-
pied by Red clay, extending as far north as lat. 72° N. in the
Norwegian Sea and as far south as lat. 60° S. in the South
Atlantic. A Globigerina ooze from a tropical locality differs
greatly from one taken towards the polar regions, for the
tropical sample may contain the representatives of more than
twenty species of pelagic foraminifera as well as many species
of pelagic molluscs, whereas the polar sample would include
only one or two species of pelagic foraminifera and no pelagic
molluscs. Globigerina ooze is the predominant type of deposit
in the North Atlantic, covering all the deeper parts of that
ocean except for two areas of Red clay, and it is there found
i68 DEPTHS OF THE OCEAN
in much deeper water than in any other of the great ocean
basins.
Diatom ooze occurs typically only in extra-tropical regions,
forming a broad almost circumpolar band in the great Southern
Ocean, outside the zone of Blue mud bordering the Antarctic
continent, and a smaller band along the extreme northern border
of the Pacific Ocean, along the Alaskan and British Columbian
coasts of North America, and the Kamtchatkan and Japanese
coasts of Asia and the intervening Aleutian Islands.
Radiolarian ooze covers the sea-floor in certain portions of
the tropical regions of the Pacific and Indian Oceans, being
apparently entirely unrepresented in the Atlantic ; it occurs in
a band of varying width in the equatorial eastern Pacific,
approaching comparatively close to the shores of Central
America, and in other smaller isolated areas.
Red clay is the most characteristic and most extensive of
the pelagic deposits, occupying the deepest portions of the great
ocean basins except in the polar regions, extending beyond
lat. 50'' N. and S. in the Pacific, and between lat. 40° N. and S.
in the Atlantic. It is the typical deposit of the great Pacific
Ocean, attaining there its maximum development, and being
associated over wide areas with the characteristic manganese
nodules; in the Indian Ocean it is also associated with much
manganese, and therefore usually of a dark chocolate colour,
while in the Atlantic it is generally intermixed with less
manganese and usually of a light red-brown colour.
As regards the vertical distribution of the deposits, we have
already indicated how gradual is the transition between the
various types and classes, so that frequently two or more names
might be used to characterise samples from the border regions.
It is therefore evident that no definite limits of depth can be
assigned to the different types of deposits, but their general
distribution m.ay be broadly outlined.
The terrigenous deposits have for their upper limit the
shore-line, while their lower limit varies according to local con-
ditions. We have already pointed out that in certain localities
Blue mud may be restricted to the continental slope within
depths less than 1000 fathoms, while in other localities it may
extend far into the abysmal area in depths exceeding 2000
fathoms, and in some places approaching 3000 fathoms. Coral
mud may extend into depths approaching 2000 fathoms before
passing gradually into a Globigerina ooze, but sometimes it
merges into Pteropod ooze in depths less than 1000 fathoms.
IV DEPTHS AND DEPOSITS OF THE OCEAN 169
while in the lagoons of coral islands it may be found in a few
feet of water. Volcanic mud may be found extending into very
deep water — in fact, some of the deepest Red clays might be
called Volcanic muds, so abundant are the minute fragments of
pumice and volcanic glass — but in the neighbourhood of volcanic
islands the material from the land is generally masked by the
accumulation of pelagic shells, and the Volcanic mud may pass
into Pteropod ooze in depths of about 1000 fathoms, or into
Globigerina ooze in depths of 1500 or 2000 fathoms. Green
mud and Red mud generally occur in depths less than 1000
fathoms, the seaward limit being about 1300 or 1400 fathoms.
Of the pelagic deposits, Pteropod ooze is found in shallower
water than any of the other types — from about 400 fathoms to
about 1500 fathoms, its seaward limit being reached in about
1700 or 1800 fathoms. Globigerina ooze may be found in all
depths from about 400 fathoms to over 3000 fathoms, but
occurs typically in depths between about 1200 and 2200
fathoms, its deeper limit in the Pacific and Indian Oceans
occurring at about 2800 or 2900 fathoms, while in the North
Atlantic it is known in depths approaching 3500 fathoms.
Diatom ooze occurs usually in depths of about 600 to over
2000 fathoms, but in the North Pacific it is found in depths of
4000 fathoms. Radiolarian ooze is a characteristically deep-
water deposit, hardly known in depths less than 2000 fathoms,
and covers the bottom at the greatest depths recorded by
the "Challenger" and "Nero" in 4500 to over 5000 fathoms.
Radiolarian ooze may, however, be regarded as a mere variety
of Red clay, containing a notable proportion of these siliceous
remains as a result of the favourable conditions in the surface
waters. Red clay is the typical deep-water deposit, and covers
wide areas in depths exceeding 2000 fathoms, occupying the
sea-floor in all the "deeps" except in one or two cases in the
North Atlantic, being displaced in certain parts of the Pacific
and Indian Ocean by its variety, Radiolarian ooze.
The rate of deposition of materials on the sea-floor is Rate of
naturally beyond the range of direct measurement, at all events disposition.
in deep water. The only observations bearing on this point
have been recorded by Mr. Peake, who in 1903 on board the
S.S. "Faraday" raised and repaired a telegraph cable lying in
2300 fathoms in lat. 50^^ N. and long. 31° W. in the North
Atlantic. This same cable had been lifted from a depth of
2000 fathoms about 200 miles to the eastward in 1888 by
ijo DEPTHS OF THE OCEAN chap.
Mr. Lucas on board the S.S. "Scotia," and on portions of the
cable recovered in 1903 being submitted to Mr. Lucas, he was
quite convinced that no deterioration had taken place during the
interval of fifteen years. This is ascribed to the fact that the
cable when lifted in 1888 was covered by Globigerina ooze,
which is believed to act as a preservative upon cables in
contact with it. As in 1888 the cable had been submerged
for thirteen years, this implies a rate of deposition of one
inch of the deposit in some period less than thirteen years ;
but as the deterioration noted in the cable, especially in the
hemp serving, had probably taken some years to effect, it is
perhaps fair to assume a period of ten years for the accumula-
tion of a layer of the deposit one inch in thickness, in the
position referred to. Another cable lifted from the bed of the
equatorial Atlantic (lat. 2' 47' N., long. 30^ 24' W.) from a
depth of 1900 fathoms in 1883, after having been submerged
for nine years, was found to be in much better condition than
the North Atlantic cables examined after having been laid for
a similar period, and this is supposed to be due to the more
rapid deposition of the Globigerina ooze in the warmer waters
of the equatorial Atlantic than in the colder waters of the
North Atlantic, so that the cable became more rapidly covered
over by the Globigerina ooze.^
While, therefore, it may be assumed that the Globigerina
ooze accumulates at the rate of about one inch in ten years in
the central part of the North Atlantic in lat. 50° N., and at a
still more rapid rate in the central part of the equatorial Atlantic,
it would appear from the recent observations of the " Michael
Sars " Expedition that the rate of deposition of sediment may
be almost nil even at depths of 1000 fathoms in certain parts
of the North Atlantic, where glaciated stones have been dredged
in considerable quantities. Possibly, however, these glaciated
stones may have been deeply covered by the ooze since the
close of the glacial period, and may have been subsequently
exposed by the action of deep tidal currents sweeping away the
Globigerina shells from the top of a low ridge perhaps recently
elevated by earth-crust displacements in the deep sea. We
now know that tidal currents prevent the formation of muddy
deposits on the top of the Wyville Thomson Ridge in depths
of 250 to 300 fathoms, while just below the summit of the ridge
on both sides mud is deposited.
1 See Murray and Peake, On Recent Con/rihutions to our A'nozvledge of the Floor of the
North Atlantic Ocean, extra publication of the Royal Geographical Society, London, 1904,
pp. 21 and 22.
IV DEPTHS AND DEPOSITS OF THE OCEAN 171
As to the relative rate of accumulation of the different types
of deposits, it may be assumed that the terrigenous deposits
accumulate at a much more rapid rate than the pelagic deposits.
Of the terrigenous deposits, the Blue muds situated near the
mouths of large rivers may be supposed to accumulate at a
relatively very rapid rate, for the various constituents of the mud
show little trace of alteration, while the rate of deposition in
the case of Green muds and sands must be much slower, since the
mineral particles are generally profoundly altered, and there is
an extensive formation of secondary products, like glauconite
and phosphate of lime ; Coral muds and sands appear to accumu-
late rapidly under certain conditions, and the same may be said
of Volcanic muds and sands in the neighbourhood of active
volcanoes, where the volcanic minerals are fresh and unaltered,
but most of the deep-sea volcanic deposits far from land appear
to accumulate at a relatively slow rate, for the volcanic particles
show abundant traces of alteration accompanied by the deposi-
tion of manganese peroxide.
Of the pelagic deposits, the Globigerina and Pteropod oozes
of tropical regions probably accumulate the most rapidly, from
the greater variety of tropical pelagic species of foraminifera
and molluscs, and the larger and more massive shells secreted in
tropical as compared with extra-tropical regions. Diatom ooze
appears to accumulate at a more rapid rate than Radiolarian
ooze, since in addition to the siliceous remains it usually
contains a considerable admixture of calcareous remains, but
from all points of view it seems reasonable to suppose that the
minimum rate of deposition of materials on the ocean-floor is
reached in those characteristic Red clay areas farthest removed
from continental land and in very deep water. The greater
abundance of cosmic spherules, sharks' teeth, and ear-bones of
whales, some of them belonging to extinct species, in the Red
clays than in any other type of deposit, is ascribed to the fact
that few other substances there fall to the bottom to cover them
up. The state of profound alteration of the volcanic materials
in the Red clay, accompanied by the secondary formation of
clay, manganese nodules, and zeolitic crystals, is ascribed to the
fact that these materials have lain for a long time exposed to
the solvent action of sea-water. The presence of radio-active
substances in this deposit, in much larger quantity than in other
deposits, apparently also points to a very slow rate of deposition.
It may be stated generally, with reference to the horizontal
172
DEPTHS OF THE OCEAN
Distribution
calcareous
remains in
pelagic
deposits.
Pelagic
species of
foraminifera.
of distribution of calcium carbonate organisms, that they are most
abundant both at the surface and at the bottom in warm tropical
regions where the annual range of surface temperature is least.
In the tropics the following genera and species of foraminifera
are known to have a pelagic habitat, three or four of the species
being rather doubtful : —
Globigeruia sacculifera, Brady.
aqicilateralis^ Brady.
conglobaia, Brady.
dubia^ Egger.
rubra, d'Orbigny.
bulloides, d'Orbigny.
i/ijlata, d'Orbigny.
digitata, Brady.
cretacea, d'Orbigny.
dutertrei, Brady.
i>achyderfna (Ehrenberg).
marginata (Reuss).
linncBa?ia (d'Orbigny).
helicina, d'Orbigny.
Orbulina universa, d'Orbigny.
Hastigerina pelagica (d'Orbigny).
Pullenia obliquiloculata, Parker and
Jones.
Sphceroidina dehiscens, Parker and Jones.
Candeina fiitida, d'Orbigny.
Cymbalopora ( Tretomphalus) bulloides
(d'Orbigny).
Fulvmidina ?nenardii (d'Orbigny).
,, tiimida, Brady.
„ canariensis (d'Orbigny).
„ michelmiana (d'Orbigny).
„ crassa (d'Orbigny).
„ patagotiica (d'Orbigny).
The following genera and species of shelled pteropods and
heteropods are pelagic : —
Pteropods
Pelagic species Limacina inflata (d'Orbigny).
of pteropods. ,, triacaiitha {Y\?,z\vQx).
helicitia (Phipps).
antarctica, ^Voodward.
helicoides, Jeffreys.
lesueuri (d'Orbigny).
australis (Eydoux and Soule-
yet).
retroversa (Fleming).
trochiformis (d'Orbigny).
bulinioides (d'Orbigny).
Peradis reticulata (d'Orbigny).
„ bispinosa, Pelseneer.
Clio {C resets) virgida (Rang).
„ ,, cotnca (Eschscholtz).
„ ,, adcula (Rang).
„ ,, duerchice (Boas).
,, {Hyalocylix) striata (Rang).
Clio {Styliola) siibida (Quoy and
Gaimard).
,, andrece (Boas).
„ polita (Craven).
,, balantiimt (Rang).
,, chaptali (Souleyet).
,, ai/stralis (d'Orbigny).
„ sidcata (Pfeffer).
,, pyramidata, Linne.
,, cuspidata (Bosc).
Ciivieri?ia colu7nneUa (Rang).
Cavolinia trispinosa (Lesueur).
,, qicadridentata (Lesueur).
,, longirostris (Lesueur).
„ globidosa (Rang).
,, gibbosa (Rang).
,, tride/data (Forsk^l).
,, iindnata (Rang).
„ i/iflexa (Lesueur).
Heteropods
Pelagic species Carinaria cristata (Linne).
of heteropods. ^^ fragilis, St. Vincent.
,, /a??iardiii, Peron and Lesueur.
Carinaria depressa, Rang.
,, australis, Quoy and Gaimard.
,, galea, Benson.
DEPTHS AND DEPOSITS OF THE OCEAN 173
Carinaria cithara, Benson.
,, punctata, d'Orbigny.
„ gandichaiidii, Eydoux and
Souleyet.
,, atlautica, Adams and Reeve.
„ cornucopia, Gould.
Atla?ita peronii, Lesueur.
„ turriculata, d'Orbigny.
„ lesueurii, Eydoux and Souleyet.
„ involuta, Eydoux and Souleyet.
,, inflata, Eydoux and Souleyet.
„ inclinata, Eydoux and Souleyet.
„ helicitioides, Eydoux and Soule-
_ yet.
„ gibbosa, Eydoux and Souleyet.
Atlanta gaudichaudii, Eydoux and Sou-
leyet.
,, fusca, Eydoux and Souleyet.
,, depressa, Eydoux and Souleyet.
,, rosea, Eydoux and Souleyet.
,, quoyana, Eydoux and Soule-
yet.
„ mediterranea, Costa.
,, violacea, Gould.
,, tessellata, Gould.
,, primitia, Gould.
,, cunicula, Gould.
„ souleyeti. Smith.
Oxy gyrus keraudrenii (Lesueur).
„ rangii, Eydoux and Souleyet.
The gasteropod genus lantkina is also pelagic, while the
species of coccolithophoridse are very numerous.
Sea Surf a
Fig. 142. — Diagram showing gradual disappearance of Calcium Carbonate
WITH increasing DEPTH.
The distribution of the dead shells of these pelagic organisms
in different depths is peculiar and remarkable. If we suppose
a cone to rise from a depth of 4000 fathoms up to within half
a mile of the surface far from land in the warmer regions of
the ocean (see Fig. 142), we shall find on the upper surface of
this cone, and down its sides to about 1000 fathoms, nearly
every shell of pelagic organisms represented in the deposit,
even the smallest and most delicate. At about 1500 fathoms Disappearance
many of the thinnest and smallest shells will have disappeared, carbl!nate\vith
and the Pteropod ooze passes gradually into Globigerina ooze, increase of
At 2000 fathoms there may not be a trace of pteropods, and *^'^^'^'
some of the more delicate foraminifera will also have disappeared.
At 2500 fathoms the larger and thicker foraminifera shells still
remain, and the deposit becomes a Red clay with some carbonate
of lime. At 4000 fathoms not a trace, or little more than a
trace, of these shells can be found, and chemical analysis does
not show I per cent of calcium carbonate.
Now it has been shown by hundreds of observations that
174 DEPTHS OF THE OCEAN chap.
in the surface waters the Hving animals are as abundant over
the Red clay areas, where not a trace of their shells can be
detected in the deposits, as over the Pteropod ooze areas, where
every one of them may be found.
At about 2500 fathoms the percentage of calcium carbonate
in the deposits apparently falls off more rapidly than at other
depths. In some areas, as, for example, in the North Pacific,
calcareous shells are not found in 2500 fathoms, while in
the North Atlantic they are at the same depth sufficiently
numerous for the deposit to be called a Globigerina ooze.
Where the living organisms are most numerous in the surface
waters, the dead shells are to be found at greater depths on the
ocean's floor than elsewhere. Where cold and warm currents
intermingle, shelled organisms are killed in large numbers, and
the dead shells may be found in deeper water than in neigh-
bouring regions.
It must be remembered that while we know the crust of the
earth on the continental areas to the depth of several thousands
of feet, our knowledge of the crust under the oceanic areas is
limited to one or two feet. Only in a few exceptional instances
can we say that the sounding-tube has penetrated more than
eighteen inches or two feet into the deposit. Sometimes, when
the sounding-tube brings up a section over a foot in length,
there are distinct indications of stratification.^ Even in great
depths there may be a Globigerina ooze overlying a Red clay
in the deeper part of the section. This arrangement may be
explained by supposing that the calcareous shells have been
slowly dissolved from the deeper layers, but this explanation
will not suffice when a Red clay occupies the upper and a
Globigerina ooze the deeper layer of the section. This latter
arrangement appears to indicate that a large block of the earth's
crust may have subsided to the extent of several hundreds of
feet — from a depth at which a Globigerina ooze had been formed
in normal circumstances to a depth at which a Red clay is laid
down at the present time.
There are not many cases on record of one type of deposit
being superposed upon another distinct type, examples being
more numerous of differences in colour and in composition in
the different layers of the same type of deposit. Thus, in Blue
1 From his examination of the samples collected during the German South Polar Expedition
on board the " Gauss," Philippi believed that stratification on the sea-floor of to-day is not the
exception but the rule, and that, where it seems to be wanting, the upper layer is probably
thicker than the depth to which the sounding-tube penetrated.
oceanic
areas.
IV DEPTHS AND DEPOSITS OF THE OCEAN 175
muds it seems to be the rule that the upper portion should be
thin and watery and reddish-brown in colour, in striking contrast
with the stiff compact blue lower portion, and this is apparently
due to the ferric oxide or ferric hydrate being transformed into
sulphide and ferrous oxide in the deeper layers. Among our
records there are seven cases of Red clay overlying Globigerina
ooze, eight cases of Globigerina ooze overlying Red clay, thre*e
cases of Globigerina ooze overlying Blue mud, two cases of
Globigerina ooze overlying Diatom ooze, and four cases of
Diatom ooze overlying Blue mud ; in twenty other cases the
percentage of calcium carbonate was considerably higher in
the upper portion of the deposit- samples than in the lower
portion, while in six cases the lower portion was richer in
calcareous remains than the upper portion.
The examples of Red clay overlying Globigerina ooze point Subsidence in
to subsidence in the region where they occur, and, indeed, there
are many reasons for believing that the great earth-blocks in
the oceanic areas for the most part undergo subsidence, while Elevation in
similar earth-blocks on the continents are, on the whole, subject continental
. ' ' J areas.
to elevation.
3. Some Chemical Reactions in the Deep Sea
In Dittmar's well-known analysis of ocean-water^ the acids
and bases are arbitrarily combined, but it is now known that
the dissolved substances in sea-water are not accurately repre-
sented by that table, inasmuch as they are present mainly as
ions. The aggregate degree of ionic dissociation may be cal-
culated from the freezing and boiling points of sea-water to be
about 90 per cent. That is, only one-tenth of the total solids
are present as salts pure and simple ; but these must comprise
not only those named by Dittmar but all the possible combina-
tions of bases with acids, among which calcium and magnesium
sulphates will be relatively in largest proportion. The bulk of
the solutes, however, consists of ions, and it would be more
rational to write the composition of sea-water thus : —
1 Sodium chloride
27.213 grams per litre.
Magnesium chloride .
• 3-807 „
Magnesium sulphate .
1.658 „
Calcium sulphate
1.260 ,, ,,
Potassium sulphate
0-863 ;„
Calcium carbonate
0-123 ,,
Magnesium bromide .
0.076 ,,
35- 000
176
DEPTHS OF THE OCEAN
Dissolved
solids in
sea-water
as ions.
Calcium
sulphate.
Calcium
carbonate.
Parts per 1000.
Percentage.
Na . .
10.722
30.64
Mg
1. 316
3-76
Ca
0.420
1.20
K
0.382
1.09
CI
19.324
55-21
SO4
2.696
7.70
CO,
0.074
0.21
Br
0.066
0.19
35.000
100.00
Dittmar's item CaCO^, which was presumably included in
order to express the fact that there is on the whole an excess
of bases over acids, is obviously incomplete as it stands. From
the most recent measurements we gather that a 3 per cent sodium
chloride solution, in equilibrium, as regards CO„-tension, with
air (which holds good approximately for sea-water), dissolves at
25° C. about 0.07 gr. of calcium carbonate per litre. Hence
there cannot be as much as 0.13 gr. per litre in sea- water. The
surplus base should rather be regarded as a mixture of calcium
and magnesium bicarbonates, existing in equilibrium with a
certain amount of free CO^, and of the products of their hydro-
lytic dissociation, viz. calcium and magnesium hydroxides. It
is the two latter which impart to sea-water its alkaline reaction.
On considering sea-water in its relation to submarine
deposits we note that, of all possible combinations of cation
with anion, there are three which are much less soluble than
any others, and are therefore closest upon saturation and pre-
cipitation : these are calcium sulphate, calcium carbonate, and
magnesium carbonate.
From what is known of the solubility of gypsum in brines,
and allowing for the excess of SO^, one would suppose that
sea-water is very nearly saturated for this salt, and that addition
of, for instance, a sulphate would precipitate it. But gypsum
is unknown as a constituent of deep-sea deposits (unless of
extraneous origin), so that its solubility-limit is evidently never
exceeded under submarine conditions.
Calcium carbonate, on the other hand, occurs, as already
stated, in enormous quantities at the bottom of the sea over
wide areas. All the lime in it has been derived, by the aid of
organic agencies, from the calcium held in solution by sea-water.
IV DEPTHS AND DEPOSITS OF THE OCEAN 177
whilst the carbonic acid owes its origin more or less indirectly
to the atmosphere and to infra-oceanic respiration.
In considering by what agencies calcium carbonate may be
precipitated from the sea, we can at once set aside two which
are of importance in terrestrial geology, viz. removal of solvent
by evaporation and change of temperature ; neither are operative
in adequate degree in the hydrosphere. Turning to chemical
processes we note, in the first place, that the solubility of calcium
carbonate in water is nearly proportional to the cube root of the
COg-tension,^ i.e. the amount of free CO^ present in solution.
Calcium carbonate as such is scarcely soluble at all, but in
presence of CO., the bicarbonate Ca(HC03).3 is formed, and
this is soluble to a considerable extent. Hence, if CO^ be
abstracted, calcium carbonate will tend to come out of solution.
Here we have what seems to be the niodzis operandi of cal-
careous algae. The plant absorbs CO., by way of nutrition,
precipitates calcium carbonate, and thus builds its skeleton.
That this process takes place in fresh water, where the bicar-
bonate is the chief salt of calcium present, may be considered
as established. The mosses Hypiium, Eucladimn, Trichostovia
are cases in point, as also Chara. These plants deposit coral-
like growths, known to mineralogists as tufa and travertine.
Many occurrences have been noted in the Yellowstone Park
and other American localities. In some instances the calcium
carbonate is aragonitic, as at Carlsbad. The calcareous algae,
which are well represented at the surface and at the bottom of
the warmer oceans (coccolithophoridae), no doubt secrete their
skeletons in the same way as the fresh-water algae enumerated.
But there is another far more important agency at work.
Calcium carbonate must separate out if the product of the con-
centrations of its ions Ca"* and CO3" happens to exceed a certain
definite limit. Small increases in the concentration of Ca" ions
may be disregarded, since their concentration is already consider-
able ; but small local accessions of CO3" ions, which, in the shape
of alkaline carbonate, may and do occur, are more effective.
Marine animals generate, as ultimate products of the metabolism
of their proteid food, ammonia and carbon dioxide. These
combine to form ammonium carbonate, which in aqueous solution
is largely dissociated into NH^' and CO3" ions ; thus calcium
carbonate is precipitated with liberation of ammonia, and a shell
or coral growth may be formed. The reaction here described,
1 Schloesing, Coinptes Retidiis Acad. Sci. Paris, vol. Ixxv. p. 70, 1872 ; Bodlander, Zeiischr.
Phys. Cheni., vol. xxxv. p. 23, 1900.
N
178 DEPTHS OF THE OCEAN
which, according to the older chemical notions, was expressed
by the equation
(NH,X,C03 + CaSO^=CaC03 + (NHJ,SO,,
seems to have been first suggested in this connection by
Forchhammer, and was fully proved and worked out experi-
mentally, with respect to marine organisms, by Murray and
Irvine.^ It accounts for the enormous amount of calcium
carbonate at the bottom of the ocean, which once formed part
of the tests or skeletons of living organisms. A limited
amount of purely inorganic precipitation does, indeed, take place
in coral reefs and some shallow-water deposits and in the Black
Sea. In the Mediterranean, for instance, stone-like crusts are
plentiful, consisting of clay cemented by calcium carbonate,
which latter is produced by ammonium carbonate arising from
the decay of organic matter in the mud below bottom-level
meeting with fresh sea-water from above. We have further the
lime-concretions of the Pourtales, Argus, and Seine banks, the
"Challenger" casts of shells from the Great Barrier Reef,^ and
so on. But all these must be regarded as rarities. A great
many of the reactions here referred to are believed to be ruled
by enzymes and catalytic substances.
Whilst a great deal of calcium is thus being taken out of
solution throughout the ocean, conversely the carbonate is
continually being redissolved. Calcium and magnesium carbon-
ates are held in solution mainly as bicarbonates ; but since
these compounds are incapable of existence in the solid state,
questions of precipitation and dissolution, so far as they can be
approached on theoretical grounds, must be decided by the
solubilities of the normal carbonates. The solubility of CaCOg
in water (foreign salts being absent), and the equilibrium of
the various molecules and ions concerned, have been fairly
thoroughly elucidated.^ When MgCOg is also present and
sea-water is the solvent, matters become so complicated that
we cannot calculate, from first principles, how near sea-water
is to saturation for calcium carbonate. . There are, however,
direct empirical data on this point. From the experiments of
Anderson with natural, and of Cohen and Raken with artificial,
sea-water, it would appear that with regard to CaCOg, in the
final stable modification of calcite, sea-water is saturated and
incapable of taking up more, under conditions of stable
equilibrium. Nevertheless the ocean does unquestionably dis-
1 Proc. Roy. Soc. Edin., vol. xvii. p. 79, 1889.
- Deep-Sea Deposits Chall. Exp., pp. 170, 172, 1891. * Bodlander, loc. cit.
IV DEPTHS AND DEPOSITS OF THE OCEAN 179
solve such calcium carbonate as it comes in contact with,
especially dead shells and skeletons. Three reasons for this
may be adduced : —
(i) There may be local accessions of CO2, the dissolving
power of which has already been referred to. The sarcode of
molluscs and the albuminous binding material of their shells are
decomposed, on the death of the animal, to CO2 and ammonia,
the former being much in excess. The solvent thus provided,
in the case of any given shell-forming- organism, can only, how-
ever, be small relatively to the calcareous matter present.
(2) The carbonate may be in a less stable, and therefore
more soluble, form than calcite. This is eminently true of
corals, which are mainly aragonitic. Some shells also are
wholly or partially aragonitic, and marine aragonitic algae
occur, such as Halimeda. Sea-water saturated for calcite
would, needless to say, be unsaturated for aragonite.
(3) It is a familiar fact that freshly precipitated calcium
carbonate is much more soluble than the stable macrocrystalline
modification. The older theory, which supposed the former to
be basic or hydrated CaCOs, seems open to doubt, since there is
no sort of evidence that such compounds exist. More probably
the abnormal solubility is due to the exceedingly small size of
the particles. Above a certain limit of size, the concentration
of saturated solutions of a solid is constant, whether the
particles be large or small ; below this limit the concentration
becomes greater the smaller the particles, these stronger
solutions being in perfectly stable equilibrium with solid
particles of a definite magnitude. Experimental observations
of this phenomenon, which may be an effect of surface-tension
between solid and liquid, have in recent times been made on a
variety of substances.^ The limiting size for abnormal solubility
is about 2/u, diameter for gypsum, and will hardly be very
different for calcium carbonate. It may be that what is called
amorphous calcium carbonate is often merely calcite or aragonite
in a state of extremely fine subdivision, whence the higher
solubility. Abnormal solutions thus produced are of course
supersaturated for larger particles, but there is evidence that
they part with their surplus solute with extreme reluctance.
In all probability, then, the particles of calcium carbonate of
organic origin in the sea, which are protected, during life, by
albuminoid matter, go into solution, in the course of their post-
mortem descent, by virtue of their minute size, and leave trails
^ See Hulett, Zeiischr. Phys. Cketn., vol. xxxvii. p. 385, 1901.
i8o DEPTHS OF THE OCEAN
of sea-water surcharged with Hme. This Hme, though in a
metastable condition, finds no nuclei to deposit upon and
remains in solution, being carried about until it reaches an area
impoverished of lime by precipitation, when its condition
becomes stable, or until it is itself reprecipitated by coming
into the sphere of action of an ammonia-producing organism.
Thus the ocean as a whole remains just about saturated for
calcium carbonate.
Oceanic calcium undergoes extensive circulation between
the dissolved and undissolved states. When calcareous frag-
ments fall on a clayey or muddy bottom, they fall into water
which can take up lime, and are dissolved as the water passes
over them, while on falling on distinctively calcareous deposits
like Pteropod ooze they fall into water-layers, immediately above
the bottom, which can dissolve no more lime. In either case
the lime depends for its redistribution on the slow processes of
diffusion by convection and other currents. In those areas
covered by Globigerina and Pteropod oozes lime is being
steadily withdrawn from the ocean. Over Red clay areas, on
the other hand, lime is being returned to the ocean. From
the state of saturation of sea-water we may infer that the
aggregate accessions of lime to the bottom exactly balance the
aggregate supply from land and from the direct decomposition
of submarine rocks. On the whole, lime at the present time
appears to be accumulating towards the equator.
Another element present in the sea, magnesium, shares the
vicissitudes of calcium, but in a very minor degree. Magnesium,
in contrast with calcium, is very prone to form hydrated and
basic carbonates, ahd when the carbonate is precipitated from '
solutions of magnesium salts, it comes down not in the anhydrous
crystalline form, but mainly as a trihydrate. Now solubility-
determinations in pure water and in salt-solutions indicate that
MgCO., as bicarbonate, in equilibrium with trihydrate, is of the
order of ten times more soluble than CaCOo. Hence the former
is far less likely to be precipitated than the latter, even though
there is about three times as much magnesium in the sea as
calcium. Moreover, it is well known that magnesium carbonate
is not readily brought down in presence of ammonia. Thus we
find that in living shells, corals, and algse the proportion of
MgCOg to CaCOg is usually below i per cent. It is observed,
however, that in dead carbonates, e.g. Coral sands and muds
and calcareous oozes which have been for a long time at the
bottom, there are markedly greater admixtures of magnesium.
IV DEPTHS AND DEPOSITS OF THE OCEAN i8i
This enrichment in magnesium is a famihar phenomenon at
shallow depths, notably in and about coral reefs. It has also been
shown on the basis of the "Challenger" analyses that bottom-
deposits contain more MgCOg in proportion to CaCO,, the less
calcareous they are. Granted that accumulation of magnesium
does take place, there are two explanations which have been
offered, viz. (i) that deposited lime is dissolved away in prefer-
ence to magnesia, and (2) that a kind of pseudomorphosis by
the interaction of calcium carbonate and dissolved magnesium
salts sets in. Both assume MgCOg to be less soluble than
CaCOg, and both may well hold good. Even if MgCOg were
precipitated as trihydrate, it would sooner or later change into
the anhydrous form, or rather into dolomite, that being the most
stable and final form. Perhaps this transformation has already
been effected in the shell. But dolomite is well known to be
less soluble in carbonated water than calcite. As regards
enrichment by accession of magnesia, this could only take place
if sea-water were nearly saturated for MgC03, a matter which
has not hitherto been put to the test ; sea-water is certainly not
saturated for the trihydrate, but it is conceivable that anhydrous
calcium carbonate would determine the deposition of magnesium
carbonate in the anhydrous form, which is relatively very
insoluble. Now when calcium carbonate goes into solution,
the concentration of CO3" ions in its neighbourhood is increased,
whereby the solubility of any other carbonate is lowered ; thus
a precipitation of MgCOg might ensue. However, if this action
were capable of taking place generally, we should expect a far
larger percentage of magnesia in the purer calcareous oozes.
On the whole, therefore, the enrichment in magnesia in deep-
sea deposits proper is rather to be sought in preferential
dissolution of lime.
The total magnesium carbonate at the bottom of the sea
only amounts to a small percentage of the total calcium carbonate.
Since the proportion of Mg to Ca, primarily in rocks and
secondarily in river-waters, is much larger than this, it is clear
that dissolved magnesium is accumulating in the ocean.
Another of the more important constituents of sea-water, Sulphur.
sulphur, suffers transference, on a modest scale, from the sea to
the bottom. Nowhere in the deposits of the open ocean has
sulphur been found to occur as sulphate, but in those very
extensive landward areas where Blue muds form the deposit
there is always a small percentage of ferrous sulphide and
of free sulphur, which are directly or indirectly derived from
i82 DEPTHS OF THE OCEAN chap.
sea-water sulphates. In all deep-sea muds there is a certain
amount of decaying animal and vegetable matter fallen from
the hydrosphere, the proteids of which leave their sulphur, so
far as it escapes oxidation, combined with the iron of the
surrounding mud. But apart from this rather insignificant item,
there are bacteria which, whilst living on sarcodic matter, seize
on the dissolved sulphates of sea-water and reduce them to
sulphides ; the latter react with whatever ferruginous material
is present, and produce the highly insoluble compound ferrous
sulphide. Free sulphur, when found, is to be accounted for by
the partial oxidation of sulphides, either by dissolved oxygen or
at the expense of ferric iron. The retention of sulphur in
bottom-deposits can only occur where there is plenty of decaying
organic matter, where the bottom-waters are stagnant, or nearly
so, and not well aerated, and where there is not a copious hail
of calcareous tests ; that is, mainly in the lower layers of muddy
bottoms at shallow and medium depths. The sea- water
imprisoned below the upper layer of mud becomes poorer in
sulphate and richer in carbonic acid,^ whilst the mud is darkened
in colour by very finely-divided and easily oxidizable ferrous
sulphide. Under suitable conditions the ferrous sulphide may,
as in Black Sea muds,-"' combine with free sulphur and attain a
condition of higher stability in the form of pyrites. The essential
chemical factor which renders possible the retention of sulphur
is the power of the colloidal ferric hydroxide in clay to react
with sulphides. A small quantity of ammonium sulphide added,
in the laboratory, to ordinary Red clay from the deep sea, at
once goes into reaction: the clay is darkened to a tint resembling
that of Blue mud ; the original tawny colour is restored by
atmospheric oxidation ; the darkened clay evolves sulphuretted
hydrogen with dilute acid. At the same time it is well to
remember that many Blue muds owe their colour to quite other
causes than the presence of sulphur.
The reduction of sulphates occurs only where there is a
continuous deposition of detritus, and takes place, in the sub-
marine muds, in the deeper layers. Consequently under
normal conditions precipitated sulphur does not perform a cycle
between bottom and sea, but remains irrevocably buried,
accumulating as the deposit accumulates. No attempt seems
hitherto to have been made to determine the ferrous sulphide
in marine muds, but it is probably very minute in amount.
' Murray and Irvine, Trans. Roy. Soc. Ediii., vol. xxxvii. p. 481, 1893.
- Murray, Scot/. Geogr. Mag., vol. xvi. p. 673, 1900.
IV DEPTHS AND DEPOSITS OF THE OCEAN 183
Free sulphur has been found in a maximum of 0.003 P^^" cent
in oceanic deposits,^ although inland and estuarine deposits may
contain rather more. We may therefore take it that the
aggregate influx of oxidized sulphur into the ocean greatly
exceeds the fixation of reduced sulphur at the bottom.
The elements silicon (as hydrated silica) and phosphorus
(as calcium phosphate) are transported by biological agencies
from the sea to the bottom, the former in large, the latter in
small, quantities. The compounds referred to are capable of
existing in solution in sea-water only to an infinitesimal extent,
so that all the silicic and phosphoric acids carried into the
ocean must eventually find their way to the bottom.
The silica of organic origin in deep-sea deposits, which of sm
course represents but a tiny fraction of the total silica present, is
peculiar in having been derived not only from dissolved, but also
from suspended, silicates.^ It takes the form of tests and skeletons
characterising the important Diatom ooze and Radiolarian
ooze areas, and of sponge spicules, which are ubiquitous but
nowhere concentrated enough to give rise to a definite deposit.
Chemically, this silica is in the hydrated colloidal condition
not unlike opal. By what process the siliceous organisms
convert their intake of dissolved silica and floating clay into
structural silica is not clearly known ; as regards the former, it
is evident that the organisms possess some means of coagulating
to a hydrogel the silica which they receive either as SiO^'' ions
or as a hydrosol of silicic acid ; whilst their argillaceous food is
probably decomposed by some acid juice with elimination of
alumina in solution and eventual deposition of coagulated silica.
During life, siliceous tests are protected from dissolution by
an admixture of albuminoid matter, which rots away after death.
The hydrogel of silica then undergoes peptisation (that is, so
much of it as does not fall to the bottom), probably by virtue of
the free alkali in sea-water, and returns to the dissolved state.
The conditions of dissolution of silica and, for instance, calcium
carbonate are very different. Silica, as being a colloid, has not
a definite solubility ; its existence as a hydrosol is limited only
by the coagulating action of the electrolyte solutes of sea- water
or by its precipitation in combination with a base. As to the
former effect, we have no data except that sodium chloride is
comparatively feeble as a coagulant. It is remarkable that no
silica seems ever to reach the bottom as a chemical precipitate
^ Buchanan, Proc. Roy. Soc. Ediii., vol. xviii. p. 17, 1891.
- Murray and Irvine, Froc. Roy. Soc. Edin., vol. xviii. p. 229, 189 1.
i84 DEPTHS OF THE OCEAN
of calcium or magnesium silicate, although magnesium silicate
is known to be soluble to only i part in 100,000 of sea-water.^
This perhaps indicates that the silica in solution in the sea is
always below saturation-point, so that a local concentration large
enough to determine precipitation never occurs. Or again,
excess silica perhaps combines with what little alumina there is
in sea-water and is deposited as clay ; if that were the case, the
limit of dissolved silica would be set by the solubility of this
substance, which may well be less than that of magnesium
silicate. At any rate, the quantity of silica really dissolved in
sea-water is extremely small. According to the most recent
and trustworthy determinations," there is on the average about
one part, and never more than two parts, per million in North
Sea and Baltic waters.
Although for obvious reasons vastly less silica is produced,
by biological agencies, in the waters of the sea than calcium
carbonate, the former, like the latter, is found in almost all
submarine deposits. When siliceous remains fall into a calcareous
deposit, the silica has little tendency to combine with lime,
since silicic at low temperatures is an even weaker acid than
carbonic ; but, the process of peptisation being accelerated by
the higher alkalinity of the superjacent waters, we should expect
the predominance of lime to favour the dissolution of silica.
This seems to be borne out by the fact that silica is least
abundant in the most calcareous bottoms of the open sea, and
also by the almost total absence of silica in coral reefs and
muds.^ Again, essentially siliceous accumulations (Radiolarian
ooze) are characteristic of the very deepest parts of the ocean,
where calcareous remains have such enormous columns of sea
to fall through that they may fail to reach the bottom. There
is thus a tendency for silica and calcium carbonate to be
mutually exclusive. In terrestrial calcareous deposits (chalk)
we find imprisoned silica going into solution, migrating to
centres of coagulation and forming nodular segregations (flint).
No such phenomenon is observed at the bottom of the sea,
where the silica brought into solution has probably no difficulty
in diffusing into the hydrosphere out of the comparatively loose
deposit.
The soluble silica of the sea is derived ultimately from
felspathic minerals, and the greater bulk is introduced from
1 Murray and Irvine, Proc. Roy. Soc. Edin., vol. xviii. p. 238, 1891.
^ Raben, Wissensch. Meeresuntersiichiingeii, Kiel, vol. viii. pp. 99 and 277, 1905.
^ The Atoll of Funafuti : Report of Coral Reef Committee of the Royal Society ; Chemical
Examination of the Materials from Funafuti, by J. W. Judd, p. 370, 1904.
IV DEPTHS AND DEPOSITS OF THE OCEAN 185
land by means of rivers. Since the ocean cannot retain in
solution more than a trace, all this silica must eventuate as
organic deposits, especially Radiolarian and Diatom oozes.
Furthermore, a certain quantity of suspended terrigenous clay
is being continually converted into the hydrated silica of these
deposits. Neglecting the latter source of biological silica and
the comparatively inconsiderable radiolarian areas, we can say
that the dissolved silica yielded by the continents is tending to
accumulate on the frontiers of the temperate and polar zones,
especially in the Antarctic Ocean.
The amount of phosphorus in sea-water is comparable in its Phosphc
tenuity to that of silica, Raben's determinations for North Sea
and Baltic waters show a seasonal variation ranging from
0.14 to 1.46 parts of PgOj; per million. Phosphorus originates
as calcium phosphate in the form of apatite, passes through the
ionized condition, and is deposited on the bottom of the sea as
calcium phosphate. In the deposits this compound is of
universal distribution ; all samples of whatever character contain
from a trace to about 3 per cent of tricalcium orthophosphate.
The clays and muds no doubt retain traces of undecomposed
mineral phosphate. On the other hand, calcium phosphate is
secreted to a greater or less extent by the living denizens of
the sea, whence its presence in calcareous and siliceous deposits ;
here we have the phosphorus withdrawn from aqueous solution
and partly going through a cycle between the sea and the
bottom, like lime and silica.
If there were no organic life in the ocean, the deposit every- pecompos
where would consist of a mud or clay, composed of mineral m^JJerais.
detritus. As it is, this detritus is nowhere wholly absent, and
large areas consist of little else. Whether the mud be brought
into'the sea by rivers or through the agency of tidal erosion, or
whether it be formed in sittt at the bottom, it is always of a
dual nature. The one ingredient is more or less finely powdered
original mineral matter produced by mechanical comminu-
tion ; the other is a mixture of substances resulting from the
chemical decomposition of rocks. It has not been found
possible to disentangle these components quite satisfactorily by
chemical analysis, but it is safe to state that the proportion of
one to the other ranges from one quarter to three quarters.
In chemically-produced mud we have the result of the action
of water on crystalline silicates without the intervention of any
solute except dissolved gases. Qualitatively, therefore, it is of
i86 DEPTHS OF THE OCEAN
the same composition whether formed in fresh water or in the
sea. Quantitatively, it might be expected to show a difference
for terrigenous and pelagic origin respectively, since the mother-
rocks are in general not the same. Nevertheless, a remarkably
close similarity is revealed by analyses, such as the " Chal-
lenger" analyses of Blue muds and Red clays, or still better, of
Clarke's ultimate analyses of averaged "Challenger" deposits.^
One notable point of difference is brought out, viz. the greater
manganese-content of pelagic deposits.
The action of unlimited water, oxygen, and carbonic acid
on the earth's crust tends to lead to certain definite end-products,
the nature of which is dictated by the abundance and the
affinities of the elements concerned, and by their habit as
regards solubility. All minerals, given time, succumb to these
agencies. Reviewing the chief elements, we find the final con-
ditions of stability under subaqueous influences to be as follows.
The alkalies, being of a highly soluble tendency, go into
solution and accumulate in the hydrosphere. Calcium and
magnesium are rendered soluble by the presence of carbonic
acid and become sea- water constituents, the former being
ultimately redeposited by organic processes. Phosphorus
behaves similarly. Ferric iron is very feebly basic, and therefore
tends to the condition not of a salt but of a hydrated oxide
(FeoOg.Aq) which, being very insoluble, remains in the
residuum. Ferrous iron, which is a much stronger base, is
leached out by the aid of carbonic acid, but is soon oxidized to
ferric iron and rendered insoluble. Much the same holds good
of manganese, which exists in minerals almost exclusively in the
manganous state : it is dissolved as bicarbonate, undergoes
oxidation, and comes to rest as hydrated peroxide (MnO^. Aq).
Aluminium forms only one base, which is very weak, but has
the property of combining with silica to form a highly insoluble
substance, ideal clay (AI0O3. 2510,. 2H2O), which represents its
final stable condition. Silicon exists as a weak acid (SiOo) of
insoluble tendencies, which, after having been brought into
solution, partly joins the residuum as clay and is partly re-
deposited as hydrated silica through organic agency.
The ultimate mineral residuum, then, consists, if we pass
over the rarer elements, of aluminous clay, hydrated ferric oxide,
and hydrated manganese peroxide. In all probability the two
former substances should be considered together and submarine
clay regarded as an ill-defined colloidal compound in which
^ P)Oc. Roy. Soc. Edin., vol. xxxvii. pp. 167 and 269, 1907.
IV DEPTHS AND DEPOSITS OF THE OCEAN 187
silica and alumina play the chief part, but ferric hydroxide and
even lime, magnesia, and alkalies are also represented. These
minor constituents are, at any rate, so combined as to resist
leaching out by dilute acids. Vast areas of the lowest depths of
the sea are covered by such a clay in a state of considerable
mechanical purity, a product of almost exclusively submarine
disintegration, known as Red clay.
The chemical action by which pelagic clay is derived from
its volcanic mother- rocks must proceed, as compared with
subaerial weathering, with the utmost sluggishness. The
fundamental question, indeed, whether fresh or salt water exerts
the more powerful action upon rocks must be regarded as not
yet answered. Great experimental difficulties are encountered,
and we find the results of Thoulet, who concluded that fresh
water is a better disintegrant than salt, diametrically opposed to
those of Joly.^ But several other considerations must be taken
into account, and it cannot be doubted that rock silicates are
degraded more slowly in the sea than on land. For instance,
the clastic action of frost is never brought into play. There is
no comminution of the minerals by moving water. The soluble
by-products are removed, and the supply of oxygen and carbonic
acid maintained, by diffusion only.
At this stage the state of rest of the deep-sea residuum is
not even yet necessarily final, but is capable of being disturbed
locally by organic agencies. Aluminous clay, indeed, is per-
manent once it is at the bottom, but, whilst floating, it is to
some extent decomposed, as we have seen, by siliceous algse for
purposes of nutrition. Iron and manganese oxides are suscept-
ible to reduction by purifying sarcodic matter, whence result the
ferrous iron of the Blue muds, and also many of the concretionary
forms of these oxides.
The Blue mud areas, which are of vast extent, afford a
most important example of the reduction of submarine clay after
deposition. We may indeed divide the floor of the sea, accord-
ing to the relative abundance or paucity of dissolved oxygen
in the bottom-waters, into oxidizing and reducing areas. Re-
ducing conditions will prevail wherever there is a larger excess
of putrefiable organic matter than can be coped with by what-
ever supply of oxygen (depending on the circulation of the
area) may be available. In general, therefore, the coast-lines
of continents are girdled by reducing areas, and it is here that
' It may be mentioned that the methods of leaching adopted by these experimenters are
somewhat dififererit, and that Thoulet measures his effects by loss in weight, whereas Joly deter-
mined the amounts taken up in solution.
i88 DEPTHS OF THE OCEAN
Blue muds characteristically occur. Oxidation of the organic
matter is here effected at the expense of ferric iron, probably
by bacteria] agency. A special case of this, viz, the bacterial
production of ferrous sulphide and free sulphur, has already
been referred to. It may be that sulphur plays an inter-
mediate part in the formation of Blue muds, but the end-
product is simply a clay, in which some or most of the iron
has been reduced to the ferrous state, containing i or 2 per
cent of amorphous black organic substance. To these two
factors the distinctive dark colour is due. The organic sub-
stance is associated with but little nitrogen and hydrogen, and
it no doubt represents the final refuse of bacterial and higher
forms of life. Blue muds are produced out of the deposit from
the top downwards, as is evidenced by the reddish unreduced
layer overlying the deeper Blue ones. Since Blue mud is of
terrigenous origin, the undegraded silicate which it contains
consists of continental minerals.
From the general conditions obtaining in reducing areas it
follows that carbonic acid must be unusually plentiful in the
mud-waters. A consequence of this is that calcium carbonate,
if deposited, is readily redissolved. Hence the Blue muds are
on the whole poor in lime. It further follows that lime is
tending to accumulate in the deposits of the moderate depths
of the ocean, between the reducing areas and the abysses where
it is dissolved before reaching the bottom.
Doubtless the decay of minerals on the floor of the sea
follows much the same course as subaerial weathering. Inter-
mediate products, however, are comparatively rare, since the
general conditions are not (as on land) subject to variation.
The only substances of this category which form in any pro-
fusion are zeolites, especially the one known as phillipsite.
Here and there intermediate products are arrested by being
surrounded with concretions. A notable instance is the mineral
palagonite, which is frequently found at the centre of ferro-
manganic nodules. Basic volcanic glass (an amorphous fused
silicate of calcium, magnesium, and ferrous iron) has the
property of combining with water continuously from the peri-
phery inwards without crumbling, giving what is virtually a
hydrated aluminium-iron silicate in a medium of opal. A
coating of concretionary matter prevents the gelatinous silica
from breaking away and dissolving, but offers no resistance to
the diffusion of calcium and magnesium, which are leached out.
Meanwhile the colloidal silica exerts its absorbing power on
IV DEPTHS AND DEPOSITS OF THE OCEAN 189
the potash and soda of sea-water, and these oxides enter to
the extent of about 4 per cent each. The iron becomes ferric,
and can no longer get away as bicarbonate. The resulting
palagonite is a more or less homogeneous and transparent
amorphous mineral. Exposed naked to the action of bottom-
waters it rapidly breaks down to clay.
Deep-sea conditions are, on the whole, more favourable to Synthetic
the degradation of mineral matter than to the generation of new p'^^'^^'^^^-
minerals. Nevertheless a few syntheses are being continually
carried on in the muddy parts of the bottom and in the
immediately superjacent layers of water; they fall into two
groups, viz. true chemical syntheses of new classes of silicates,
and mineralogical syntheses of concretionary minerals. The
first group comprises glauconite and phillipsite, the second
group ferromanganic and phosphatic concretions.
Glauconite is a hydrous double silicate of potassium and Glauconite.
trivalent iron, occurring in rounded grains said to be composed
of minute felted crystals. The ideal composition (KFe SioO^. Aq)
is claimed for it, but actually the purest marine glauconite
hitherto analysed contains 1.5 per cent of AI0O3, 3.1 per cent
of FeO, and 2.41 per cent of MgO, with only 'j.'] per cent of
K20.^ The chemistry of its genesis is still a complete mystery ;
all that can be said is that it appears to result from a meta-
morphosis of ferruginous clay, and that, in view of its frequent
formation inside the shells of foraminifera (and of its absence
in the Red clay and Red mud areas), decomposing organic
matter probably plays a part in its formation. On the score
of abundance glauconite is a mineral of considerable importance
in bottom-deposits, being the characteristic component of the
Green sands and Green muds. Glauconite is a mineral belong-
ing essentially to the reducing areas of the deep sea.
The most notable geochemical change associated with
glauconite is the withdrawal of potassium out of solution in the
sea. This element has a remarkable tendency to be held in
loose combination in amorphous and colloidal minerals (like
palagonite), and all submarine muds and clays contain a small
amount (less than i per cent) of absorbed potash ; the quantities
thus progressively entangled at the bottom will be roughly
proportional to the aggregate accessions of clayey matter, and
can only be a tiny fraction of the total potassium imported into
the ocean. In glauconite-producing areas, on the other hand,
1 Collet and Lee, Proc. Roy. Soc. Edin., vol. xxvi. p. 238, 1905.
I90 DEPTHS OF THE OCEAN
the fixation of potassium must reach formidable dimensions,
since the purest Green sands may contain 7 to 8 per cent of
K2O. Nevertheless over the whole ocean it is hardly probable
that deposition keeps pace with supply, and potassium may be
regarded as one of those elements which are slowly concentrating
in sea-water.
The zeolite phillipsite is the only substance produced in
well-developed crystalline forms at the bottom of the sea, where
it is peculiar to the deepest Red clay regions. Marine phillips-
ite is a hydrated calcium-aluminium silicate in which the
principal minor bases are potash and soda (4 to 5 per cent each
of KoO and NagO), with insignificant amounts of lime and
magnesia. Like all zeolites, it must have been deposited out of
a solution of its constituents, and it represents an intermediate
stage in the degradation of rock-silicates to clay. Why should
the process of degradation have been arrested at this stage ?
In all probability because solutions containing silica, alumina,
and the other elements in just the right proportions were
imprisoned in interstices of the Red clay, secure from diffusion,
and therefore available for the slow process of crystallisation.
It is worthy of note that in point of percentage quantity the
minor bases of marine phillipsite differ widely from those of the
terrestrial mineral, in which latter calcium plays the chief part.
Taking into account the well-known faculty possessed by zeolites
of exchanging bases with solutions with which they are in
contact we have here (especially in the high percentage of
Na^O) an interesting effect of sea-water as a medium in the
mineralogical world, comparable with its far-reaching biological
effects. Why the crystallographical species phillipsite should
be favoured rather than any other zeolite, we cannot in the
present state of knowledge imagine.
The chief submarine concretionary substances are, in
descending order of abundance, manganese and iron peroxides,
calcium phosphate, calcium carbonate, and barium sulphate.
A tendency to assume concretionary forms argues proneness to
supersaturation and feebly crystalline habit on the part of the
substance concerned. The former property is very characteristic
of the peroxides and of calcium phosphate, and is evidently
connected with the reluctance to come to equilibrium in solution
which so often goes hand in hand with high valencies.'
Wherever concretions are found, we must suppose that there
has at one time been a layer, or a chronological series of layers,
^ See Van t'Hoff, Sitztmgsber. K. Akad. IViss. Berlin, vol. xxxiv. p. 658, 1907.
IV DEPTHS AND DEPOSITS OF THE OCEAN 191
of water surcharged with the substance, whence deposits have
taken place on whatever nuclei offered, forming a hard radial
aggregation, which would continue to grow until either the
solution was exhausted or the supersaturation was relieved by
external causes. The shape of the concretion must depend on
the shape and number of its nuclei and the evenness of concen-
tration in the surrounding solution ; in the ideal case of a small
single nucleus and a uniform supply of substance from all sides,
the concretion becomes an almost perfect sphere, like the
manganese nodules met with in certain localities.
Iron and manganese depend for the formation of super- Concretions
saturated solutions in bottom-waters on the change of valency n\°nganesc.
of which these elements are capable. Iron is brought into
solution as ferrous bicarbonate by the decomposition of minerals;
or again a solution of the bicarbonate may be produced locally
by the action of decaying organic matter on ferric compounds.
Now ferrous oxide is a base of strength comparable to, but
rather less than, that of calcium oxide, and is subject to
analogous conditions of solubility as bicarbonate. If oxygen
were absent, and it the solubility were diminished, e.g. by with-
drawal of carbonic acid, we should expect a deposition of ferrous
monocarbonate (such as has often taken place on a large scale
on land). As it is, the ferrous solution, diffusing out of the
mud, meets with dissolved oxygen, and the change of valency
to ferric iron rapidly supervenes. Ferric oxide, however, is a
much weaker base, and the hydrolytic dissociation of its salts
with a weak acid like carbonic is so complete as to render a
ferric carbonate practically incapable of existence in presence of
water. That is, the substance now in solution is ferric hydroxide.
But this is a vastly less soluble body than ferrous bicarbonate ;
therefore the iron in solution is now supersaturated.
Non - manganiferous ferric concretions are comparatively
rare, and have been reported only from the North Atlantic and
the polar seas,^ where the terrigenous bottoms are poor in
manganese. They attain no great size or hardness, contain
much silica, and are rather balls of clay cemented with hydrated
ferric oxide.
As for manganese, the manner in which supersaturated
solutions come into being is the same, in2itatis imitaiidis, as in
the case of iron. The deposited peroxide has approximately
the composition MnO., in deep-sea nodules, but shows notable
1 Schmelck, Norwegian North Atlantic Expedition, No. IX. p. 52, 1882 ; Eoggild,
Norwegian North Polar Expedition, Scientific Results, vol. v. No. XIV. p. T)%, 1906.
192 DEPTHS OF THE OCEAN
admixtures of lower oxides of manganese when laid down in
landward waters/ where the supply of oxygen is competed for by
much organic matter. The hydration MnOg-^H^O is assumed
by Murray and Renard, and FCgOg. i^Hfi (limonite) for the
accompanying ferric oxide. Deep-sea nodules are never purely
manganic, but contain inclusions of clayey and other matters,
and always a considerable proportion of iron. The mean of
forty "Challenger" analyses works out at 29.0 per cent of
MnO.2 and 21.5 per cent of Fe.^Og, soluble in hydrochloric acid.
As a rule, then, surcharged waters hold both iron and manganese
ready to be deposited simultaneously. The mode of formation
of these nodules and the origin of the manganese from volcanic
minerals have been thoroughly elucidated by Murray and Irvine.^
It should be noted that these oxides need by no means
necessarily assume a concretionary form. They are very
commonly found as thin incrustations on granular and frag-
mentary objects. Furthermore many, if not most, of the pelagic
clays contain intimate admixtures of finely-divided brown
manganese and occasionally of limonitic iron. Here the super-
saturation would seem to have been so high as to transgress the
metastable limit, whereupon the oxides have precipitated them-
selves without the intervention of nuclei ; they certainly must
have been precipitated from solution.
Manganese originates in the form of silicates and comes to
rest exclusively in the form of peroxide. It is imported, on the
one hand, from land as detritus or in solution ; but in the
terrigenous areas of the bottom, where reducing conditions
prevail, as a rule, it tends to exist in the suboxidized, i.e. soluble,
form. Hence much of the terrigenous manganese will be
carried on to the deeper oxidizing waters before it can deposit.
There is thus a constant accession of manganese from land to
the pelagic deposits. In the second place, manganese comes
into the floor of the ocean from certain basic volcanic minerals
of vitreous habit, and these are to be regarded as the principal
source of ferromanganic nodules. These basic glasses are the
only primary minerals in the deep sea which contain important
amounts of manganese. It so happens that they are common
in the Pacific, less common in the Indian Ocean, and rare in
the Atlantic. Consequently the greatest abundance of manganese
peroxide, pulverulent and nodular, is met with in mid-Pacific.
Phosphatic concretions are of very localised occurrence and
^ Buchanan, Trans. Roy. Soc. Edin., vol. xxxvi. p. 459, 1892.
- Trans. Roy. Soc. Edin., vol. xxxvii. p. 721, 1894.
IV DEPTHS AND DEPOSITS OF THE OCEAN 193
are, in the last resort, of biological origin. The phosphoric Phosphatk
acid in sea-water is derived chiefly from the skeletons and concretions.
tissues of the marine fauna. At certain spots great masses of
these skeletons are heaped up at the bottom, and here or here-
abouts phosphatic nodules are presently formed. In order to
explain why the phosphate of decaying bones goes into solution
it is not necessary to postulate exceptional conditions in the
surrounding sea- water. The solubility of tricalcium orthophos-
phate in water is a matter which bristles with complications, and
experimental difficulties have hitherto proved too great for its
exact measurement ; but it seems to be of the order of deci-
grammes per litre. The solubility is much enhanced by the
presence of H' ions, i.e. of acids. The solvent action of carbonic
acid which has been suggested seems, however, to be merely
hypothetical. Carbonic acid is so weak that at best it can
produce only a negligible concentration of H" ions ; moreover,
there is experimental evidence that so long as excess of lime
(as bicarbonate) is present, calcium phosphate is no more
soluble in carbonated than in pure water. In all probability the
rapid dissolution of the calcium phosphate and carbonate in fish-
bones is simply due to the fine state of division. This effect
has already been discussed with reference to sea-shells. The
extreme fineness of the inorganic particles disseminated in the
gelatinous matter of fish-bones is attested by the translucency
of the mass. Or it may even be that the carbonate and
phosphate are present in a colloidal form. In either case they
will readily yield supersaturated solutions when the enclosing
ossein rots away, and as soon as a nucleus presents itself the
formation of concretions is ready to begin. Since phosphatic
concretions usually occur, as already indicated, in positions where
organic remains accumulate on the bottom at a rapid rate, as in
areas having a great range of surface temperature, the trans-
ference of matter from bones to nodules must have taken place
without much delay. Consequently there has been little
opportunity for differentia] diffusion of carbonate and phosphate,
so that these calcium salts are invariably found to have been
deposited simultaneously. The "Challenger" analyses show
i^ to 3 parts of tricalcium orthophosphate to one of calcium
carbonate. Magnesium phosphates being considerably more
soluble than those of calcium, the phosphate of bones is re-
deposited unchanged after its passage through sea-water ; only
a trifling percentage of magnesium is shown by the analyses,
and this is probably present as carbonate.
o
194 DEPTHS OF THE OCEAN
4. Depth and Deposits of the North Atlantic Ocean
The North Atlantic may be called a circumscribed ocean,
being practically land-locked except towards the south. Its super-
ficial area is small compared with the other ocean basins, but
the area draining into it is enormous, since the Arctic Ocean,
the Mediterranean Sea, the Baltic Sea, the Gulf of Mexico, and
the Caribbean Sea all communicate with it. Indeed, it has
been estimated that nearly one-half of the entire world drains
directly or indirectly into the Atlantic Ocean ^ as a whole, or
about four times the area draining into the great Pacific Ocean,
and of this by far the larger portion drains into the North
Atlantic as distinct from the South Atlantic ; the largest river
of South America, the Amazon, enters the Atlantic just on
the equator, and its outflowing waters, with their burden of
sediment, are carried mostly into the North Atlantic. It has
further been estimated that more than one-half of the total
rainfall of the globe falls on the Atlantic drainage area, equal
to more than three times the amount- falling on either the
Pacific or Indian Ocean drainage area.^ Remembering these
facts, and the relatively large area occupied by the continental
shelf and continental slope, it is easy to understand why the
deposits covering the floor of the North Atlantic partake more
of a terrigenous character than those of the other ocean basins,
and this character is further emphasised by the floating icebergs
met with in the northern part of the ocean, and by the
proximity to the southern part of the ocean of the great desert
of the Sahara, the sand grains from which are sometimes
carried far out to sea by the wind. The North Atlantic is also
remarkable for the relatively high temperature of its waters at
all depths from surface to bottom, as compared with the other
oceans, and this is due partly to the influence of the dense
warm water flowing out from the Mediterranean at the Straits
of Gibraltar, and partly to the downward movement of the
dense surface water of the Sargasso Sea. Another characteristic
of the North Atlantic is the permanent anticyclonic area in the
Sargasso Sea region, which largely determines the direction of
the prevailing winds over a large part of that ocean, and hence
of the great surface currents like the Gulf Stream.
The bathymetry of the North Atlantic, according to the
1 Scott. Geogr. Mag., vol. ii. p. 554, 1S86. - Ibid. vol. iii. p. 67, 1887.
DEPTHS AND DEPOSITS OF THE OCEAN 195
present state of our knowledge, is shown in Map HI. On Depths of
the Nortt
Atlantic.
this chart the soundings in depths greater than 1000 fathoms '"^^ ^"""^^
are indicated by the hrst two figures, and they show that the
North Atlantic is now well sounded — in fact, probably the
best sounded of all the ocean basins. The recent soundings
by the "Michael Sars " did not bring to light many new facts
as to depth, and it is not likely that any great changes in the
contour-lines will be revealed by future soundings, though it is
possible that further submarine cones, like the Seine Bank and
Dacia Bank and the Coral Patch, may yet be discovered.
A comparison of this map with the depth map published by Maury's
Maury in 1854, which is reproduced in Map I., brings out ^^P'^^ "^^p-
at a glance the strides that have been made in our knowledge
regarding the depth of the North Atlantic since that time —
a progress from comparative simplicity to great complexity.
Maury's 4000 -fathoms area in the North - West Atlantic,
based upon some doubtful soundings (two of them exceeding
5000 fathoms and another in 6600 fathoms), has disappeared,
though the existence of very deep water in the neighbourhood
is evidenced by the soundings in the Suhm Deep. These deep
soundings laid down by Maury were among the early attempts
at deep-sea sounding, and the records of such depths as 6600
fathoms, no bottom, were due to the uncertainty as to when
the sounding-tube touched bottom. The only part of the
North Atlantic where the depth is now known to exceed 4000
fathoms (in the Nares Deep north of the West Indies) is
blank on Maury's map, but the northern portion of the mid-
Atlantic ridge, on which the Azores plateau is situated, is
correctly indicated, though since modified in outline ; the
continuation southward of this ridge was, however, unknown
in Maury's time.
Reference has already been made to the relatively large area
occupied throughout the world by the continental shelf, which
is equal to about 7 per cent of the entire ocean-floor. The
continental shelf apparently attains its maximum development Continental
in the North Atlantic basin, if we include the tributary seas J^J[i;" ^^^
(x^rctic Ocean, Mediterranean, etc.). The total area of this Atlantic,
basin may be estimated at about 23 million square miles, and of
this area no less than about 6 million square miles (or 26 per
cent) lies between the shore-line and the lOO-fathoms line.
While the gentle gradients of the continental shelf cover such Continental
an extensive area, the continental slope beyond the lOO-fathoms ^T°PtV" * "
line seems, on the other hand, to be relatively very steep, for Ati
in the
th
antic.
iq6
DEPTHS OF THE OCEAN
Abyssal area
of the North
Atlantic.
Deeps of th'
North
Atlantic.
the area between the lOO-fathoms Hne and the 500-fathoms Hne
is only a little over 2 million square miles (or 9 per cent), and
the area between the 500-fathoms line and the looo-fathoms
line is only about i million square miles (or 4 per cent of the
total area). It thus appears that the area with depths less than
1000 fathoms within the North Atlantic basin, as already defined,
is equal to about 9 million square miles (or 39 per cent of the
total area), and of this the continental shelf covered by water
less than 100 fathoms in depth occupies 6 million square miles
(or 26 per cent).
Proceeding into the abysmal region, we find that the area of
the North Atlantic sea- floor covered by water between 1000
and 2000 fathoms in depth is about 5 million square miles (or
22 per cent), the area covered by water between 2000 and
3000 fathoms in depth is about 7^- million square miles (or t,^
per cent), and the area covered by more than 3000 fathoms of
water ("deeps") is about i^ million square miles (or 6 per cent
of the total area). These figures show what a large proportion
of the North Atlantic sea-fioor is covered by shallow water less
than 1000 fathoms (equal to two-fifths of the entire area), and
by deep water between 2000 and 3000 fathoms (equal to one-
third of the entire area).
The deeps of the North Atlantic number fourteen, and cover
an area of about i J million square miles, as already indicated.
The larger and more important of these, Nares Deep, Moseley
Deep, and Chun Deep, have been briefly described on pages
141, 142, and 143. The smaller ones are : Makaroff Deep in the
West Indian seas; Bartlett Deep in the Caribbean Sea; Mill
Deep and Keltie Deep in the sea between Bermuda and the
American coast ; Suhm Deep, Libbey Deep, Sigsbee Deep,
and Thoulet Deep, to the south of Nova Scotia and Newfound-
land ; Peake Deep to the west of Cape Finisterre ; Monaco
Deep to the south of the Azores ; and Hjort Deep immediately
to the east of the mid-Atlantic ridge in lat. 20° N.
The
Norwegian
Sea.
The Norwegian Sea is bounded on the east by Spitsbergen,
Bear Island, the banks of the Barents Sea and the Norwegian
coast ; on the south by the North Sea, the Shetland and Faroe
Islands, and the submarine ridges between the Shetlands and
Faroes and between the Faroes and Iceland ; on the west by
Iceland and Greenland ; and on the north, about lat. 80° N.,
by a submarine ridge supposed to separate the two deep basins
called the Norwegian Sea and the Polar Sea.
IV DEPTHS AND DEPOSITS OF THE OCEAN 197
The Norwegian Sea has a superficial area of 2.58 milHon
square kilometres, nearly two-thirds of which consists of a deep
Fig. 143.— The Norwegian Sea, showing Depths.
200 metres. — • looo metres.
600 ,, — 2000 ,,
3000 metres.
198
DEPTHS OF THE OCEAN
basin (see Fig. 143), more than 3000 metres deep in the central
portion. From this depth the floor rises gradually towards
the continental slope on either side. The main features of the
continental slope and shelf along the coast of Norway will be
grasped by reference to the accompanying diagram (Fig. 144).
The term "coast banks" is usually applied to the higher parts
of the submerged continental plateau or continental shelf, which
are frequented by fishermen ; there is often a marked "edge"
between the plateau and the continental slope.
The continental shelf fringes to a greater or less extent the
whole of the coasts of the Norwegian Sea, and occupies alto-
gether about a third of its entire superficial area. This shelf
is covered by depths down to 200 metres with channels down
to 600 metres. In water shallower than 200 metres there
are only comparatively
small banks, the great-
est being at Lofoten
and Romsdal and
round the Faroes and
Iceland. Deeper than
600 metres the con-
tinental slope is steep ;
the bathymetrical
curves for 600 and
1000 metres lie every-
where in close prox-
imity to one another, and the area of the sea-bottom between
them is no more than 5.4 per cent of the whole extent of the
Norwegian Sea.
G. 144.— Diagrammatic Section off the Norwegian
Coast.
Continental slope ; b, continental edge ; c, continental shelf
or plateau ; d, coast bank ; e, fjord ; f, coast.
Deposits of
the North
Atlantic.
The distribution of the deposit-types over the floor of the
North Atlantic is shown on Map IV., an examination of which
bears out the statement that the terrigenous deposits are
relatively more important in the North Atlantic than in the other
oceans, in correlation with the relatively large area covered by
shallow water. Thus of the total area of 23 million square miles,
one-half, about ii|- million square miles (or 49 per cent), is
covered by terrigenous deposits. This area is to a very large
extent occupied by Blue mud, no attempt having been made to
indicate on the map the small areas occupied by Green mud off
the coast of the United States, off the Spanish and Portuguese
coasts, and in the vicinity of the Wyville Thomson Ridge, nor
the small areas occupied by Volcanic mud in the neighbourhood
,v DEPTHS AND DEPOSITS OF THE OCEAN 199
of the Azores, Madeira, etc. The position of the Coral mud
deposits of the West Indies and Bermuda is, however, indicated
on the map, and these deposits cover an area of about half a
million square miles (or 2 per cent of the total area).
After the Blue mud, the principal type of deposit in the
North Atlantic is Globigerina ooze, which covers an area of
about 9 million square miles (or 39 per cent of the total area).
A glance at the map shows what an extensive area is occupied
by this type of deposit in the open ocean, where it is found in
greater depths than is usually the case in the other ocean-basins
(the "Michael Sars " deepest sounding in 2966 fathoms, for
example, gave a Globigerina ooze with 64 per cent of calcium
carbonate) ; it also occurs in the Caribbean Sea, in the Gulf of
Mexico, and in the Norwegian Sea in lat. 63° N. to 72° N.
Red clay, which covers such an enormous area of the sea-
floor in the great Pacific Ocean, plays a subordinate part in the
North Atlantic, being estimated to occupy about 2^ million
square miles (or 1 1 per cent of the total area) ; it occurs in two
areas on either side of the mid- Atlantic ridge : the larger to the
west of the ridge, surrounding Bermuda and extending from
lat. 13° N. to 40° N., the smaller to the east of the ridge in lat.
8^ N. to 28° N., with a subsidiary area in the Caribbean Sea in
lat. 13^ N. to 15' N.
Pteropod ooze, though widely distributed throughout the
basin, covers in the aggregate a comparatively very small area,
estimated at about 200,000 square miles (or i per cent of the
total area) ; it occurs in the open ocean in the neighbourhood of
the Azores, Canaries, Bermudas, and West Indies, as well as
in the Mediterranean, Caribbean, and Gulf of Mexico. The
other two types of pelagic deposits, Radiolarian ooze and
Diatom ooze, are not represented in the North Atlantic.
Although the "Michael Sars" Expedition did not add "Mic
greatly to our knowledge either of the depth or of the deposits s^ampies!^°''''
of the North Atlantic, still both the soundings and the deposit-
samples are of value, many of the deposit-samples, indeed, being
extremely interesting. A detailed description of all the samples
will be reserved for a later publication, but in this place we may
refer to the more interesting points brought out by a study of
the m.aterial.
In the first place, reference may be made to the stones and
rock fragments brought up from several stations, which form
the subject of a report by Drs. Peach and Home appended to
hael
200 DEPTHS OF THE OCEAN
this chapter ; from another station the ear-bone of a whale and
two sharks' teeth were obtained.
Of the twenty-seven samples submitted to detailed examina-
tion, nineteen were Globigerina oozes, six were Blue muds, one
a Pteropod ooze, and one a Globigerina ooze overlying Blue
mud. The Globigerina oozes occur over the route followed by
the " Michael Sars " as far west as long. 44° W. ; the Globigerina
ooze overlying Blue mud occurred to the north of the Rockall
Bank ; the Pteropod ooze near the Canary Islands ; and the
Blue muds in the Eastern Atlantic from the Faroe Channel to
the Straits of Gibraltar. The " Michael Sars " samples show
that the Globigerina ooze approaches nearer to the coasts of
the British Islands than was previously supposed, having been
found at the following depths along the continental slope off the
European and African coasts: 547 fathoms (Station 4), 1256
fathoms (Station 25 A), 1 122 fathoms (Station 25 B), 1422 fathoms
(Station 35), 746 fathoms (Station 41), 688 fathoms (Station 93),
981 fathoms (Station 95), 742 fathoms (Station 98), and 835
fathoms (Station 100). Globigerina ooze and Pteropod ooze
were found in the neighbourhood of the Canary Islands in
positions where they were previously unrecorded.
An interesting point in connection with the " Michael Sars"
deposits is the number of instances where the sounding-tube
had plunged deeply into the sediment, bringing up sections
varying from two to fourteen inches in length, and in some
cases marks observed on the outside of the sounding-tube
indicated that it had penetrated still farther into the deposit.
Though in most cases the material was apparently uniform
throughout, some of these long sections gave distinct evidences
Stratification, of Stratification. Thus at Station 10 in the Bay of Biscay, at a
depth of 2567 fathoms, the sounding-tube brought up a section
about five inches in length, of which the upper portion to the
depth of about three inches was of a uniform fawn colour,
representing apparently an ordinary Globigerina ooze with
66 per cent of calcium carbonate, while the lower inch or two
had a mottled appearance, with light and dark brown patches,
the dark brown material giving only ;^2> P^^ cent of calcium
carbonate when analysed. At Station 49 C, from a depth of
2966 fathoms, the sounding-tube brought up a section about
fourteen inches in length, showing distinct traces of stratification,
especially towards the upper end, although the lower end
presented a mottled appearance with patches of lighter and
darker brown ; towards the upper end there were small patches
IV DEPTHS AND DEPOSITS OF THE OCEAN 201
of a dark brown colour which proved to be Red clay, with only
25 per cent of calcium carbonate, though the mass of the sample
was a Globigerina ooze with 64 per cent of calcium carbonate.
At Station 100, in 835 fathoms, the sounding-tube brought up a
section about nine inches in length, which was extremely interest-
ing because of the great difference between the upper and lower
portions, the upper portion, to the extent of three or four inches,
being a Globigerina ooze with 58 per cent of calcium carbonate,
while the lower portion was a Blue mud with only 26 per cent
of calcium carbonate. At Station 88, in 1703 fathoms, the
sounding-tube brought up a section about fourteen inches in
length, which showed little difference to the naked eye, although
the colour was darker in the lower portion, the upper portion
being rather lighter in colour, less coherent, and more granular ;
the deposit was a Globigerina ooze, containing 83.79 per cent of
calcium carbonate in the upper portion, 73.66 per cent of calcium
carbonate in the middle portion, and 62.1 per cent of calcium
carbonate in the lower portion. It is curious that at this
station the trawl brought up a large quantity of empty pteropod
shells (chiefly Cavolinia trispinosa), while in the samples from
the soundjng-tube submitted to examination no pteropods were
observed. It is possible that the trawl may have worked
over shallower depths than where the sounding was taken.
Similarly, at Station 23, where the depth was 664 fathoms, the
Petersen net sent down with 820 fathoms of line and towed
throughout the night of 5th and 6th May brought up a large
amount of empty pteropod shells (principally Cavolinia inflexa) ;
indeed, the pteropod shells at this station differ strikingly
in general appearance from those taken at Station 88, ten
degrees farther north. At Station 34, in 1185 fathoms, the
middle portion of the section from the sounding-tube, about six
inches below the upper surface, showed dark-coloured patches
containing a large proportion of volcanic glass splinters, to
which the dark colour was due ; the volcanic glass was quite
fresh and unaltered, as though the products of a volcanic eruption
(probably submarine, since the glassy fragments showed no trace
of friction or decomposition but were perfectly angular) had
been overlain by new material to the depth of six inches.
We append the detailed description of a typical Globigerina
ooze taken by the " Michael Sars " to the south of the Azores: —
"Michael Sars" Station 55. loth June 1910. Lat. 36° 24' N.,
long. 29° 52' W. ; depth, 3239 m. (1768 fathoms).
202 DEPTHS OF THE OCEAN
Description of GlOBIGERINA Ooze — dirty white colour, coherent, granular.
typical deposit Calcium CARBONATE — 78,59 per Cent; pelagic and bottom-living
kcTidVy°the foraminifera, ostracods, coccoliths, and rhabdoliths.
"Michael RESIDUE, 21.41 percent: —
Sars." Siliceous Organisms — 2 per cent ; radiolaria, sponge spicules.
Minerals — 4 per cent, m. di. 0.09 mm., one angular fragment of
volcanic glass exceeded 2 mm. in length ; quartz, plagioclase,
volcanic glass, augite (?), magnetite, mica.
Fine Washings — 15.41 per cent; amorphous clayey matter with
minute mineral particles.
Note. — The sounding-tube brought up a roll about 9 inches in length
of a creamy white colour throughout.
All the rock fragments dredged during the " Michael Sars "
Expedition, as well as those collected by H.M. ships " Knight
Errant" and "Triton" in 1880 and 1882, have been carefully
examined and studied by Dr. B. N. Peach. ^ Drs. Peach and
Home have prepared the folio w^ing note on the general results: —
Rock frag- The materials collected by the " Michael Sars " Expedition fall under
ments dredged |-^q categories: (i) those whose presence on the sea -floor is due to
"\lichael natural agencies, and (2) those distributed by human agencies. The
Sars." materials belonging to the first group consist chiefly of rock fragments,
the remains of floating or swimming organisms that lived at or near the
surface of the sea (such as barnacles and the ear-bone of a whale), and
fragments of wood. The members of the second group are mainly
furnace clinkers and pieces of coal, small pieces of glazed pottery, and
oyster-shells, together with a cannon-bone of a small ox.
By far the most interesting collection of the " Michael Sars" series
was obtained from Station 95, which lies about 230 miles south-west
of Mizen Head, Ireland, at a depth of 5886 feet, or a little over a mile.
The rock fragments, comprising over 200 specimens, included upwards
of 100 of sedimentary origin, 58 of igneous origin, and 40 belonging
to the metamorphic series. Some of the specimens were referred to the
Cretaceous and Carboniferous periods by means of their fossil contents ;
the remainder were grouped with the Devonian or Old Red Sandstone
and Silurian systems solely on lithological grounds.
The fragments regarded as of Silurian age include greywacke-
sandstones, dark shales, and black lydian stone identical in lithological
characters with rocks that floor a large part of the southern uplands
of Scotland and the north of Ireland. Those referred to Devonian
time resemble the Glengariff grits of the Dingle peninsula in the south-
west of Ireland. The carboniferous specimens comprise encrinital
limestones with chert, like those of Galway and Clare. One sandstone
fragment was crowded with ScJiizodus and Edinondia similar to rocks
occurring in places along the Solway shore in Scotland and in London-
derry and Tyrone in Ireland. The specimens of chalk and chalk-flints
are like the rocks in the Antrim plateau.
^ See detailed report in Proc. Roy. Soc. Edin., 19 12.
.V DEPTHS AND DEPOSITS OF THE OCEAN 203
Among the metamorphic series there are representatives of crystalline
o-neisses and schists which could be matched from the Lewisian gneiss
Fig. 145.— Glaciated Stone from "Michael Sars " Station 95.
and Moine schist areas in the North-West Highlands of Scotland.
Associated with these are specimens indicatmg a low grade of meta-
morphism, such as phyllites and sheared greywackes and igneous rocks,
204 DEPTHS OF THE OCEAN chap.
which resemble types to be found along the south-eastern border of the
Highlands and the north of Ireland. Indeed, some may have been
derived from the south of Ireland.
Station 95.
The evidence furnished by the igneous materials is no less remarkable.
The plutonic rocks are represented by granites resembling those of
Lower Old Red Sandstone age in Scotland and the north of Ireland,
and also by a specimen of nepheline-syenite which cannot be matched
IV DEPTHS AND DEPOSITS OF THE OCEAiN 205
with any known rock of this type in the North Atlantic basin. The
lava - form and intrusive types of the basic materials have marked
affinities with the tertiary volcanic rocks of the Inner Hebrides and the
north of Ireland.
Of special interest is the evidence pointing to the conclusion that the
rock fragments from this station must have been transported by floating
ice during some phase of the glacial period. More than half of the
specimens are glaciated, the larger part of the remainder are angular,
and a number are well rounded. A typical example of one of the
glaciated stones is shown in Fig. 145, which is a portion of a larger boulder
broken off before being embedded. Irregular striae appear on this
specimen, but on one surface it is facetted and the striae thereon |are
more or less parallel. It is noteworthy that the glaciated and ice-
FiG. 147. — Surface of Specimen No. 4 in Fic. 146, enlarged to show
" Chatter-marks."
moulded specimens include nearly every rock type represented in the
collection from this particular station. The stones resemble those found
in boulder clay or " moraine profonde," indeed in some instances the
clayey matrix of this deposit has been cemented to some of them by
calcareous matter.
Some of the rounded specimens, consisting of Silurian greywackes,
carboniferous limestone, chalk -flint, dolomite, and vein - quartz, are
shown in Fig. 146. These must have been rounded before they reached
the position from which they were dredged.
An enlarged part of specimen No. 4 in Fig. 146 (chalk-flint) is repre-
sented in Fig. 147, to illustrate the bulbs of percussion or " chatter-marks "
which it displays. Such evidence indicates that the stones had originally
been dashed against each other by torrent or wave action,
A careful examination of the specimens points to the conclusion that
all had been partially embedded in a Globigerina ooze on the sea-floor.
206
DEPTHS OF THE OCEAN
as shown by the attached marine organisms and by a slight coating
of manganese oxide on the exposed parts. In Fig. 148, which represents
a specimen composed of carboniferous Hmestone and chert, the arrow
points to the man-
ganese staining where
the exposed and un-
exposed parts meet.
The average size
of the stones is about
three inches ; only a
very few reach six
inches in length. As
the sounding - tube
brought up from the
sea-floor at this station
a core of ooze nine
inches long, we may
infer that the tube
pierced the deposit to
a greater depth than
that reached by any
of the stones. It is
therefore clear that
none of the stones can
be in situ. They must
have been dropped
from above into the
ooze.
Many of the speci-
mens, as represented
in Fig. 149, must have
stood on end in the
ooze, which is not the
natural position they
would have assumed
if dropped on the
present surface of that
deposit. The infer-
ence seems obvious
that originally they
fell into a soft ooze
in which they were completely buried. The stones would naturally be
arranged along the lines of least resistance to friction, so that many
would be entombed end on or edge on, like those illustrated in Figs.
149 and 1 50. Subsequent current action has removed part of the
material in which they were embedded, and has been powerful enough
to prevent further accumulation of ooze at the spot where they were
dredged. Since the ooze contains IJ per cent of insoluble material, the
theory of the removal of the deposit by solution is improbable.
Among the materials distributed by human agency dredged from
Fig. 148. — Stone with staining ok Manganese, the
arrow showing the position of the surface of
THE DEPOSIT IN WHICH THE SPECIMEN HAD BEEN
EMBEDDED.
IV DEPTHS AND DEPOSITS OF THE OCEAN 207
this station (95) about 200 specimens of furnace clinkers were found, Furnace
together with fragments of unburnt coal, also a portion of an earthen- clinkers, coal,
ware jar and a cannon-bone of an ox. This station lies along the route ^^^'
of the Atlantic Liners, from which these specimens were probably
dropped.
At Station 10, on the south side of the Bay of Biscay, and nearly
200 miles north of Cape Finisterre,
at a depth of over 15,000 feet, an >^>>^ I
assemblage of stones was obtained,
numbering in all 339, most of
which were glaciated and almost
identical in lithological characters
with those just described.
At Station 48, lat. 28° 54' N.,
long. 24° 14' W., in about 2800
fathoms, chalk - flints and ice-
moulded metamorphic rocks were
collected, showing that floating
ice had dropped materials over
that part of the sea-floor. They
were associated with fragments
of pumice carried thither by the
descending branch of the Gulf
Stream. An ear-bone of a finner-
whale was also found at this
locality.
Just outside the Straits of
Gibraltar, at Station 23, in 664
fathoms, a curious assortment of
materials was dredged, comprising
dead lamellibranch shells (some
of them bored by gasteropods),
barnacles dropped from whales,
furnace clinkers, and an American
blue point oyster that had fallen
from a passing ship. The dead
lamellibranch shells point to
subsidence of that part of the
sea - floor in recent geological
times.
The materials dredged at
Station 70, south of the New-
foundland Banks, in 600 fathoms,
indicate that this part of the sea-floor is within the range of the present
Arctic ice-drift.
The rock fragments obtained from Stations 100 and loi, in 835 and
1013 fathoms, seem to point to the conclusion that they were transported
thither by ice that passed over the Orkney and Shetland Isles.
40
so
120
160 MM.
Fig. 149. — Diagrams drawn to scale show-
ing POSITIONS OF Stones embedded in the
DEPOSIT, the shaded PARTS INDICATING
THE PORTIONS PROJECTING ABOVE THE
DEPOSIT.
Important evidence was gathered from the Wyville Thomson Ridge
208
DEPTHS OF THE OCEAN
Rock frag- at depths ranging from 318 to 3420 feet during the expeditions of H.M.
merits dredged ships "Triton" and "Knight Errant." It suggests that the glaciated
stones on the ridge are or have been embedded in a boulder clay. The
stones are composed chiefly of Lewisian gneiss and the Moine schists
lying to the east of the post-Cambrian displacements in the Highlands
of Scotland. A large proportion consists of Caithness flagstones and
other Old Red Sandstone rocks, like those occurring in place in the
Orkney and Shetland
' ^^^ Isles. A considerable
number of Jurassic and
Cretaceous types occur
in the collection, together
with two carboniferous
specimens, the age of
which is determined
by their fossil contents.
The assemblage of fossil-
iferous stones are similar
to those found by Messrs.
Peach and Home in the
boulder clays of Caith-
ness and Orkney.
On the Faroe Banks
the volcanic rocks of the
Faroe Isles are not re-
presented among the
rock fragments dredged,
which would seem to
point to the extension of
the combined Scottish
and Scandinavian ice-
sheets over that part of
the sea-floor during the
glacial period.
Just inside the Rock-
all Bank, at Stations
100 and loi (" Michael
Sars "), only one Old Red
Sandstone boulder was
found in the materials
collected, but the sand
grains occurring in the
ooze are either red or green. The ooze also contained fragments of
brown glass, resembling the slaggy volcanic rocks of Iceland. Such
AO
80
— I —
120
6 //YCHES
160 MM.
Fig.
50. — Diagrams drawn to scale showing positions
OF Stones embedded in the deposit, the shaded
PARTS indicating THE PORTIONS PROJECTING ABOVE
THE DEPOSIT.
distributed by floating ice.
At Station 3 ("Knight Errant"), at a depth of 318 feet, many
dead shells of shallow-water habitat were got, which clearly indicate a
subsidence of the sea-floor since the glacial period. The absence of
raised beaches in Orkney and Shetland, the submerged peat-mosses,
IV DEPTHS AND DEPOSITS OF THE OCEAN 209
the depth and steepness of the sounds between the Faroe Islands, the
great depth at which the seaward extension of the fjords in Iceland cut
the marine shelf, the submergence of shell banks between Iceland and
Jan Mayen referred to by Nansen, all point to the same conclusion. In
all probability there was either land connection with Greenland during
the glacial period, or a confluent ice barrier which prevented the Gulf
Stream from flowing into the Polar basin and deflected it towards
the south.
J. M.
Hooke's Sounding Machine and Water-Bottle, 1667.
(See page 2. )
CHAPTER V
PHYSICAL OCEANOGRAPHY
In the middle of last century the idea of "physical oceano-
graphy " did not exist, but in the course of a few decades it
has become a widespread branch of knowledge, with a copious
literature and bulky text-books. A few figures may serve to
show how important is the study of the sea. The waters of the
globe cover more than two-thirds of its surface, and their
volume is about 1300 millions of cubic kilometres, or thirteen
times that of all the land above sea-level. The mean height
of the land is 700 metres, while the average depth of the sea
is 3500 metres. Sea-water contains various salts in solution,
the total weight of which is nine times that of the earth's
atmosphere.
The reason why the ocean, which plays such an important
part in the economy of the earth, has not been investigated
until recently is because of the special difificulties which are
encountered in making investigations. One great difficulty is,
as has been previously mentioned, that it is impossible to
observe directly what is going on beneath the surface, and it is
necessary to have a special set of apparatus that can be relied
upon. The methods have developed with phenomenal rapidity,
but the observations are still few in proportion to the extent of
the ocean, and consequently it is often difficult to obtain a
complete and true image of the actual conditions. Many of the
results obtained are therefore merely preliminary, and further
study may alter our views on various points ; for the solution of
PHYSICAL OCEANOGRAPHY
sending down
instruments.
many important problems we have not yet sufficiently numer-
ous observations. In a rapid sketch like this, only some of
the principal facts can be dealt with ; we shall first examine
the methods employed in physical oceanography, and then
endeavour to draw some conclusions from the observations
available.
In the first place, one must have a line with which to send Lines for
down the instruments and draw them up again. Formerly
hemp lines were used, but they have now been superseded by
wire ; steel piano-wire is used for sounding, and wire rope
for thermometers, water-bottles, etc. For general use the wire
need not be more than 2 to 3 mm. in
diameter, and it will, nevertheless, bear
the weight of several hundred kilograms
without breaking. The old hemp line
was marked at regular intervals for the
determination of the depth, but this can-
not well be done with the wire, which is
run out over the metre- or fathom-wheel Metre-wheel.
(see Fig. 151), and this is both a con-
venient and accurate method. The
wheel communicates with a clock-work
arrangement with dials and hands, by
means of which the length of wire run
Fig. 151. — Metre-Wheel.
out can always be read off correct to
within a metre. When, however, an
observation is to be taken at a depth of
1000 metres, it is not enough to run out
1000 metres of line. The line must be
"up and down," and this is not always
easily managed, especially in a wind or strong current, when
the ship is drifting. Some manoeuvring is then required, and
the apparatus must either in itself be sufficiently heavy to
straighten the line, or an extra weight must be added. Many Several
of the instruments are so constructed that they may be attached lIsed's'imuK
to the side of the line as well as at the end, and thus several taneousiy.
instruments may be used simultaneously. They are fastened at
certain intervals on the line as it is being paid out, and a
number of observations are made at the same time at different
depths. By this method a comprehensive series of observations
from the surface down to two or three thousand metres may be
taken in a couple of hours. This method was employed during
the "Challenger" Expedition.
212
DEPTHS OF THE OCEAN
7vo/]xyod
When several series of observations have been taken in a
certain region, they are usually represented for diagrammatic
PHYSICAL OCEANOGRAPHY 213
purposes in horizontal plans and vertical sections. It is To show
necessary, in order to be able to see anything in the sections, ^oSfo^g i,^
to exaggerate the scale of depth in comparison with the scale of diagrammatic
horizontal distance. This is shown in Fig. 152, which represents necessary' to
the floor of the Atlantic Ocean along the parallel of 40" N. exaggerate
The upper line (A) shows the section drawn to the same scale scaie.^'^''^^
for depths and horizontal distances ; the variations in the depth
are represented by a thin uneven line, indicating how relatively
small is the depth of the Atlantic Ocean compared with hori-
zontal distances on the earth's surface ; the lower diagram (B)
shows the section with the depths exaggerated 500 times.
Drawing the depth on a larger scale brings out the details of Section across
the relief of the ocean-bed : thus off Portugal there is seen a Atk^dc*
narrow continental shelf, and then a rapid falling-off towards
the deep water (the continental slope) ; farther west (about the
middle of the figure) there is a corresponding slope, on the
summit of which the Azores appear ; then another fall towards
the western basin of the North Atlantic, followed by the
continental slope on the American side, where again a narrow
continental shelf borders the coast. The continental shelf is
seen to be wider on the American side than on the European
side of the section. This exaggeration of the vertical scale
allows of the representation of a number of details, but, of course,
the lines look very much steeper than they really are. One
must not imagine that the continental slopes are so marked as
they appear in the figure, for the angle is usually not so much
as two degrees, the slope being similar to that of our common
roads and railways ; real submarine precipices do occur, but
mostly as rare exceptions.
At a comparatively early date it was known that the The temp^^
temperature^ of _ike_-jseazsuiiace_w^ by ti-,e tureo t esea^
currents. In the beginning of the seventeenth century, for
instance, it was noticed that there was a sudden change of
temperature on passing from the cold Labrador current south
of the Newfoundland Banks to the adjacent warmer waters of
the Gulf Stream. Benjamin Franklin, who made a careful Benjamin
study of the Gulf Stream (see Fig. 153), advised ships' officers Ji^'cuif ""'"^
to use the thermometer in order to find out when they entered Stream.
the Gulf Stream, so that they might take advantage of the
current when voyaging eastward, and steer clear of it when
sailing westward.
The American naval officer M. F. Maury (i 806-1 873), Maury.
214
DEPTHS OF THE OCEAN
one of the founders of physical oceanography, used the surface
temperatures recorded from different places in the sea in his
examination of the currents. He organised an extended
collection of temperature-observations for the benefit of navi-
gation ; he studied the winds and the drift of vessels, and in
the middle of the nineteenth century he published his Ex-
planations and Sailing Directions to accompany the Wind and
Ctwrent Charts. He also wrote an extremely interesting book,
The Physical Geography of the Sea and its Meteorology, which
has appeared in many editions and in several translations.
Maury's work had important consequences, for ship-masters
following his directions shortened the voyage between North
Fig. 153.— Benjamin P^ranklin's first chart of the Gulf Stream.
America and England by ten days, that from New York to
California by about forty-five days, and that from England to
Australia and back by more than sixty days. The profit
derived from the use of Maury's charts by British ship-owners
on the East India route alone amounted to 10 million dollars
yearly.
On Maury's suggestion it was decided, at an international
congress at Brussels in 1853, that numbers of log-books should
be sent out with captains of ships for the purpose of entering
observations of wind and weather, of currents, and of tempera-
tures at the sea-surface. This plan has been followed ever
since, the notes being as a rule entered once every watch, so
that a formidable pile of material has now been amassed. Up
to 1904 the Meteorological Office in London had collected 7
millions of these notes, the Deutsche Seewarte in Hamburg
PHYSICAL OCEANOGRAPHY
215
De Bilt 3J millions, the Hydrographical Bureau in Washington
51^ millions, and so on. Add to this the surface observations
made by scientific and other expeditions, and it will be evident
that in the course of the last sixty years a good deal of know-
ledge regarding the surface of the sea has been gained.
Making surface -temperature observations is very simple Temperature
work. All that is necessary is to haul up a bucket of sea-water observations
dn • /* 1 * 1 ''■ ^LlG suri3.cc
measure the temperature by means 01 an ordmary thermo- of the sea.
meter. It is a far more difficult thing to record the actual
temperature of the deeper layers. In 1749 Captain Ellis Temperature
brought up water from 11 90 metres and from 1645 metres to beneath \h?
the south of the Canaries, and, on measuring the temperature surface.
of the water inside the water-bottle after it had been hauled
up, found it to be 17.2° C. lower than the temperature at the
surface. Some investigators coated their water-bottles with an insulating
insulating substance, so that the temperature might remain water-botties.
unaltered during the process of hauling up. This principle has
recently been developed to a high degree of perfection in one
of the water-bottles now most used, viz. the Pettersson-Nansen
water-bottle, which will be described later.
Attempts were also made to insulate the thermometer itself insulating
by surrounding the bulb with a stout sheath of caoutchouc or thermometers.
wax. This insulated thermometer was lowered to the depth
desired, where it was left for hours to assume the temperature
of the water ; it was then hauled up quickly and the temperature
read off. In this manner de Saussure was able, in 1780, to
determine correctly the temperature in the Mediterranean at
585 metres, finding it to be 13° C. Thermometers made on
this principle have been much used until our own times, but they
have one serious drawback, for the operation takes a very long
time, and this makes them unsuitable for use in expeditions,
where the work must be done as quickly as possible ; they may,
however, do good service in cases where the very greatest
accuracy is not required, and where there is unlimited time at
disposal, as on light-ships.
Nearly a hundred years ago some one thought of employing Maximum
Six's maximum and minimum thermometer for temperature S'-^ermom"""^^^
observations in the sea, various modifications being introduced,
until finally in 1868 it became quite serviceable as made by
Casella under the direction of Dr. Miller. The Miller-Casella Miiier-
thermometer (see Fig. 154) was the one principally used on board Caseiia.
the "Challenger" and during other great expeditions. At the
2l6
DEPTHS OF THE OCEAN
top there are two glass bulbs, united by a bent capillary tube ;
the left-hand bulb is filled with creosote, the capillary tube
contains some mercury, and the right-hand bulb constitutes a
vacuum except for a little creosote. When the thermometer is
heated, the creosote on the left side expands, driving the
mercury through the tube so that it rises in the right-hand
branch ; the mercury lifts a small index, a pin
that is so constructed that it sticks at the place
where the mercury leaves it. When the ther-
mometer is cooled the creosote contracts, and the
creosote-vapours in the right-hand bulb propel
the mercury farther into the left-hand branch,
where there is a similar index. In this way the
index on the right shows the maximum tempera-
ture, and that on the left the minimum tem-
perature. The thermometer is fastened to a
rectangular plate carrying the temperature scale,
and the whole instrument is put inside a protect-
ing tube of copper. The maximum and minimum
thermometer needs about twenty minutes for
adjustment, and is slow enough not to change
appreciably during a rapid hauling up from
moderate depths, but if it has to be brought from
great depths, erroneous results may be recorded,
e.g. in waters where the temperature does not fall
or rise uniformly towards the bottom. In Arctic
and Antarctic seas, for instance, the temperature
generally falls to a minimum at about 50 or 70
metres below the surface, rising to a secondary
maximum at a depth of a few hundred metres,
finally falling again towards the bottom, and this
implies two maxima and two minima. In such a
case Six's thermometer would show only the
highest maximum and the lowest minimum en-
countered, and not the intervening values. This
thermometer has, however, done very good service ; it is,
for instance, astonishing how correct the temperature determina-
tions taken on board the " Challenger" have proved to be. In
the great depths of the ocean the variations of temperature from
year to year are so small that it is possible to verify now the
observations of earlier expeditions.
The French physicist Aime about seventy years ago intro-
duced the reversing thermometer, which is caused — either by a
HlI^SE
Fig. 154.
Miller-Casella
Thermometer.
PHYSICAL OCEANOGRAPHY
217
sliding weight (" messenoer ") or by a propeller-release — to turn
upside down at the depth where the temperature is to be deter-
mined. The temperature is thereby regis-
/^^^^^\. tered, and can be read off at any time after the
(l'i^\\ instrument has been hauled up. Aime's instru- Aime.
ment was, however, rather intricate. In 1878
Negretti and Zambra of London constructed a Negretti and
reversing thermometer, which has played a ^'^"^b''''^-
prominent part in physical oceanography. In
this form there is a narrowing of the tube just
above the bulb ; the mercury fills the tube
above the narrowing to a greater or lesser
extent according to the temperature, and when
the thermometer is tipped over, the mercury
breaks off at the narrowing, the portion which
was above that point sinking down to the end
of the tube (Fig. 155); the scale on the tube
indicates the temperature at the moment of
inversion. The thermometer must be able to
withstand the pressure of the ocean depths,
and is therefore placed inside a strong glass
tube, with some mercury round the bulb of the
thermometer in order to secure a rapid conduc-
tion of heat.
The Negretti and Zambra reversing thermo-
meter has latterly been widely used, but it has
been found that occasionally the mercury broke
off not exactly at the narrowing, but at some
other place in the tube, while sometimes addi-
tional mercury might overflow during the pro-
cess of hauling up. Certain improvements
have therefore been introduced to remedy
these defects, like the recent modifications by
C. Richter of Berlin, who altered the breaking- Richter.
off arrangement so as to render it quite trust-
worthy, and formed the tube in such a way that
no superfluous mercury could enter it during
the ascent (see Fig. 156). The severed
column naturally lengthens or shortens some-
what according to the temperature changes to
which it is subjected : suppose, for instance, the
thermometer to be reversed in water of 2.00'' C, and then
hauled up through warmer water and read off in the air at a
le
H
4yj>
Fig. 155.
Negretti-Zambra
Thermometer,
after reversing.
2l8
DEPTHS OF THE OCEAN
temperature of 20° C,
the mercury - thread
would have expanded a
Httle, giving a reading
perhaps of 2.25° C. in-
stead of 2.00° C. This
secondary change is
easily calculated when
the temperature of the
mercury at the reading-
off is known, and so
inside the protective
tube Richter has placed
a small auxiliary ther-
mometer (d), which
gives the reading tem-
perature, and thereby a
correction for the read-
ing.
In many cases it is
necessary to have the
temperature determined
with the highest possible
degree of accuracy, and
Richter's reversing ther-
mometer is very satis-
factory in this respect.
During the " Michael
Sars" Atlantic Expedi-
tion the temperature
series were taken almost
exclusively by the aid of
these thermometers, and
in most instances two
thermometers were used
simultaneously, so as to
make quite sure of the
determinations. When
the readings were cor-
rected it was found that
the mean difference be-
tween the values given
by the two thermome-
FiG. 156.— Richter's Reversing Thermometer.
The mercury breaks at e ; the figure on the left and the
upper one on the right show the position of the mercury
before reversing. The lower figure on the right repre-
sents part of the thermometer immediately after reversing.
PHYSICAL OCEANOGRAPHY 219
ters in about 600 double determinations was only y-J^" C, so
that the temperature of the greatest ocean depths can now be
determined with great accuracy.
A common form of reversing mechanism is a brass tube Reversing
which can turn over within a frame. A pin retains the tube "mechanism.
(into which the thermometer is placed) in an upright position ;
when the pin is withdrawn, the tube is tipped over by the aid
of a steel spring. The pin is removed either by means of a
propeller or by a messenger. The propeller is so adjusted that
it does not move during the descent, but when the apparatus
is pulled upwards it revolves, drawing out the pin along with
it. Formerly this propeller-release was employed with many
kinds of oceanographical apparatus, but it is not always reliable,
especially in a rough sea, and the apparatus must be hauled
up some distance before the propeller works. It is, therefore,
gradually being superseded by the messenger, a small weight
which is fixed on the line and let down after the apparatus has
reached the desired depth. When the messenger reaches the
reversing mechanism it knocks out the pin and the thermometer
is turned upside down. One of the wa£er-bottles used during
the "Michael Sars " Expedition is reversed together with the
thermometer ; in other words, this water-bottle is a reversing
mechanism for taking a temperature and a water-sample at the
same time.
The Pettersson-Nansen water-bottle has a very high in- Pettersson-
sulating capacity, and the temperature of the water-sample is ^!au?.bottie.
not affected by conduction even when hauled up from a depth
of several hundred metres, though the apparatus may be
drawn through water-layers having very different temperatures.
Pettersson originally used an ordinary thermometer, which was
inserted into the water-bottle after it came up. Then Nansen
thought of fixing a thermometer inside the water-bottle, and
in this way the temperature at any depth was determined more
easily as well as more exactly. The Nansen thermometer is
very delicate, and is protected by a strong glass tube against
the great pressure.
In making temperature-observations, however, one special Effect of great
precaution must be taken. When a liquid is exposed to great P'^'^'^^"'^^-
pressure its volume is slightly diminished, and, some heat being
liberated, the temperature of the liquid rises. Lord Kelvin
studied this question carefully, and arrived at a formula by
which such changes of temperature maybe calculated. Con-
versely, the volume of a liquid released from great pressure
220 DEPTHS OF THE OCEAN
increases, and by this process some heat is taken up which is
drawn from the Hquid, lowering its temperature. When, there-
fore, a water-sample is drawn up in an insulating water-bottle
from a depth of looo metres, the temperature of the water-
sample sinks a little. Nansen first called attention to this fact,
and has drawn up tables for the corrections according to Lord
Kelvin's formula. The corrections prove to be quite consider-
able. When employing an insulating water-bottle, account must
be taken, not only of the alteration of volume in the water-
sample, but also of that taking place in the solid parts of
the water-bottle. A water-sample, for instance, brought up
in an ordinary-sized Pettersson-Nansen water-bottle from a
depth of looo metres in the Norwegian Sea, is cooled 0.06" C.
while being hauled up ; a sample from the same depth in the
Mediterranean is cooled 0.17' C. This difference is due to the
fact that the amount of cooling depends on the temperature of
the water, which at 1000 metres in the Norwegian Sea is about
— 1° C. and in the Mediterranean +13° C.
We are here confronted with a problem of considerable
interest. When a body of water sinks from the surface down
to great depths, its temperature rises a little because of the
compression. The " bottom -water " of the Atlantic Ocean
averages nearly 2^° C. ; supposing that it has sunk from the
surface to a depth of 3000 metres, it has been heated about
0.27° C. in the course of its descent, by reason of the increasing
pressure. If it should appear at the surface again, the reduc-
tion of pressure will have lowered the temperature by the same
amount, — 0.27 C. There are various other conditions which
produce changes in the temperature, as, for instance, mixing
with other bodies of water, in the upper layers absorption of
solar heat, near the bottom possibly a very slight influence
from the internal heat of the earth. It is, of course, difficult
in such a combination of factors to single out the effects of one
of them individually.
During the "Michael Sars " Expedition in the North
Atlantic we made a certain number of observations in the
deeper layers with a Richter reversing thermometer, which
seemed to prove in several cases that the temperature increased
slightly towards the bottom. The following extract from the
" Michael Sars " tables shows the number of the station, the
depth, the temperature (measured in szhi), and the temperature
that the water would acquire — on account of the reduction
of pressure — if it were raised to the surface. The latter
PHYSICAL OCEANOGRAPHY
221
temperature has by the author of the present chapter been Potential
called \\-\^ potential temperature, a term used in meteorology. temperature.
Station.
Depth to the bottom.
Depth of observa-
tion in metres.
Temperature
in situ.
Potential
Temperature.
lO A
4700 m.
3000
4500
2.43° c.
2.55°
2.16° c.
2.08°
49 C
about 5400 m.
3950
4950
2.42°
2.46°
2.03°
1.92°
63
5035 m-
4000
4850
2.35°
2-37°
1-95°
1.85°
From these and many similar observations it is seen that
the temperature in the deepest strata of the North Atlantic is
about 2^° C. (as a rule a little lower). The temperature of the
deepest strata below 2000 fathoms appears to remain almost
constant through long periods of time, the variations probably
not amounting to more than a few hundredths of a degree.
Very delicate instruments are necessary to detect them, and as
yet we have insufficient observations to enable us to study
the details.
It is apparent from the tables that the temperature would
fall several tenths of a degree if the "deep-water" were raised
to the surface without being heated by mixing on the way.
This we have been able to prove in a direct way by means of
the insulating water-bottle, which we used at Station 91 at a
depth of 4750 metres, the temperature inside the water-bottle
after hauling up being only 2.00° C, whereas the water at that
depth was in reality several tenths of a degree warmer. When
ill situ the water has the temperature indicated by the reversing
thermometer, but when brought to the surface it has the
potential temperature nearly indicated by the thermometer
inside the insulating water-bottle. Granted that no other
change has taken place, the bottom-water must have had a
temperature of about 2° C. at the time when it began sinking
down from the surface ; as it sinks the temperature gradually
rises, and at Station to A, for instance, it was found to be
0.12° C. higher at 4500 metres than at 3000 metres. Some
such increase of temperature towards the bottom has long
been suspected as an effect of the internal heat of the earth ;
as early as about 1840 Aime looked for it, but his methods
222
DEPTHS OF THE OCEAN
were not sufficiently accurate. More recently several indica-
tions of a rise of temperature towards the bottom have been
observed. The pressure and the internal heat having the
same effect, it is difficult — at our present stage — to determine
how much is due to the internal heat of the earth. In any case
the bottom-water temperatures would be considerably lower but
for the effect of pressure on the sinking waters.
It may be stated as a general rule that the temperature of
-
?"
0°
r
4"
6° 8° 10°
ir 14" 1
6- /a:
?0"
re
1
f
r
,^^
\/
500
y
•i
^
■^
//
J
/
^
1
/J
^
' J
v/
1
/
{
PE^
<I06 ^fl
.1/
Jl
/OA '^ ^W
'
If
i^
fc
'^^ ^JB
fSOO
if
~~
f
-64
1
j
1
i
1 ^..
^1
?onn
10
Fig. 157. — The distribution of Temperature at four different Stations
IN THE Summer of 1910.
The positions of the Stations are shown in the small inset map.
ocean water is in summer highest at the surface, and decreases
gradually towards the bottom. Fig. 157 shows the distribution
of temperature as observed at four stations during the " Michael
Sars " Atlantic Expedition, the position of the stations being
indicated on the little inset map. Station 64 is situated in the
Sargasso Sea westward of the Azores, Station 87 in mid-ocean
between France and Newfoundland, Station 10 1 between
Scotland and Rockall, and Station 106 in the Faroe-Shetland
Channel north of the Wyville Thomson Ridge. Station 106
belongs to the region of the Norwegian Sea, whereas the other
PHYSICAL OCEANOGRAPHY 223
three belong to the Atlantic proper; Stations 87, loi, and 106
all lie within the precincts of the " Gulf Stream." At all four
stations the temperature is highest at the surface : 22°-23*' C. in
the Sargasso Sea (24th June), over 18° C. at Station 87 (17th
July), 13°- 1 4° C. westward of Scotland (7th August), and 13° C.
at the station west of Shetland (loth August). It is worthy of
note that a temperature of about 13° C. was observed at the
surface near Scotland, while the same temperature occurred at
a depth greater than 500 metres in the Sargasso Sea.
From the surface downwards the temperature falls very
rapidly for the first 50 or 100 metres; at 100 metres it is from
4" to 6° C. colder than at the surface. Beyond 100 metres the
temperature decreases at first much more slowly, then rapidly
again, and then very slowly until the great depths are reached,
where the temperature changes very little. The layers in Discontinuity
which the temperature changes very rapidly are called " dis- ^^y^^^-
continuity-layers" (by the Americans " thermocline," and by
the Germans " Sprungschicht "). They are particularly marked
at Station 106, where there is such a layer immediately below
the surface, and another extending from 450 to 750 metres.
Between the two (from 50 to 450 metres) there is a fairly
uniform stratum, and another one under the deeper layer, from
750 metres to the bottom. At the other three stations the
upper discontinuity-layer is also very strongly marked, but the
lower one is not so sharply distinguished from the adjoining
water-strata.
It will be noticed that the temperatures in the deep strata
(below 800 or 900 metres) were, at the same depths, nearly
identical at the three stations in the Atlantic proper, the differ-
ences not exceeding 1° C, although these stations are situated
far apart ; but at Station 106 in the Norwegian Sea the temper-
ature was 7°-8° C. colder. This is due to the form of the
bottom, the Wyville Thomson Ridge separating the deep layers wyviiie
of the Atlantic from the deep layers of the Norwegian Sea, so ^1^°™^°"
that at a depth of 1000 metres the temperature is 6'-7° C. in
the Atlantic Ocean, and below o" C. in the Norwegian Sea.
That implies two widely different deep-sea regions : a warm
one south of the ridge, and a cold one to the north of it, with
great differences in the deep-sea fauna of the two regions.
The influence of the Wyville Thomson Ridge is very clearly
seen in a section across the ridge (see Fig. 106, p. 124), from
Station loi to Station 106 ; in the upper strata, down to 500
metres, there is little difference, but the deeper strata are like
224 DEPTHS OF THE OCEAN chap.
two different worlds, the Atlantic world south of the ridge, the
Arctic world north of it.
Decrease of The surface-tempcrature is naturally high in the equatorial
temperature Tegious, decreasing toward the poles, where it falls below o° C.
from equator Kriimmel has calculated the mean surface-temperatures for each
to poles. lo-degree zone throughout the great ocean basins, his figures
for the North Adantic being : —
Zone . . o^-io" io°-20° 2o°-30° 3o''-4o"" 40^-50° 5o''-6o" 6o°-7o° N. lat.
Temp. . . 26.83 25.60 23.90 20.30 12.94 8.94 4.26 X.
It is interesting to compare this horizontal distribution of
temperature with the vertical distribution in tropical waters.
The following temperatures, for instance, were recorded by the
German Antarctic Expedition in July 191 1, at a station in lat.
7|-° N. in the middle of the Atlantic : —
Depth .
0
100
200
400
800
1000 metres.
Temp.
. 26.86
18.57
10.71
7.70
5-13
4.81 °C.
At a depth of 100 metres the temperature is seen to be the
same as the average surface-temperature in about 40° N. ; the
mean surface-temperature at 50° N. is the same as that found at
200 metres in the tropics, and the mean surface-temperature at
60° N. corresponds to the temperature at a depth of 700-800
metres in the tropics. In other words, we have a horizontal
distribution of temperature from the equator towards the poles
similar to what we have vertically from the surface towards the
bottom in the tropics. Near the equator one need only send a
thermometer down to 800 metres in order to find the same
temperature that one would have to travel 60° northwards to
find at the surface, but the other physical conditions are widely
different. In the deep water at the equator there is an
enormous pressure and unchanging darkness, but at the surface
far north and south there is a pressure of only one atmosphere
and good light, at least in summer. Thus the physical condi-
tions in the deep layers of the tropical waters are really very
different from those at the surface towards the poles, and in
consequence the conditions of life also differ ; organisms living
in the surface-layers of high latitudes are found in far deeper
water in low latitudes, in so much as they are capable of adapting
themselves to the excessive pressure and the infinitesimal
quantity of light. Some organisms seem to be mainly depen-
dent on the degree of light, the temperature being of less
importance to them. We shall return to the questions of light
PHYSICAL OCEANOGRAPHY 225
and pressure, and the geographical distribution of animals,
later on.
The high temperature at the surface evidenced by the curves Absorption of
in Fig. 157, is principally due to the absorption of heat-rays from surtaceJ!? Ae
the sun. In places the water is heated by contact with warm sea.
air, but this source of heat is of less importance, the temperature
of the surface-water being, as a rule, higher than the temperature
of the air. The sun's rays penetrate into the water and are
absorbed ; the dark heat-rays are absorbed in the uppermost
layers, while the light rays, which also convey a little heat,
make their way down to a depth of several hundred metres
before disappearing altogether. The action of the sun's rays is
strongest in the tropics, declining towards the north and south,
and this in a general way explains the distribution of the surface-
temperature.
A fine example of the heating action of the sun's rays is storage of
afforded by the Norwegian oyster-basins. Along the west jj^nl" ""^""^"^
coast of Norway there are in many places salt-water basins,
separated from the outer fjord by a sill, which is covered only
at high water. At the surface the water of the " poll " — as
such a basin is called in Norway — is comparatively fresh,
and consequently light ; from a depth of about one metre to the
bottom it is very salt and heavy. The sun's rays in summer
penetrate into the water and heat it, mostly at the surface, but
also to some extent down to a depth of a few metres. The
surface-water is cooled during the night, but at a depth of one
or two metres beneath the surface the heat will not be given
off so readily, because the heavy water there does not reach the
surface. When this has gone on for some time, the temperature
at a depth of a few metres may be remarkably high, sometimes
fully 35° C, while the temperature at the surface might be
about 20° C. In these "polls" the surface-layer of relatively
fresh water prevents the layers below from coming into contact
with the cooling air, and such polls may indeed be compared to
hot-houses, the fresh surface-layer corresponding to the fixed
transparent roof, under which heat is stored.^ in these
oyster-basins absolutely tropical conditions are developed in
summer. It is significant that Gran once found in one of them
a small crustacean, which according to G. O. Sars belongs to
the Guinea Coast. Fig. 158 shows the temperatures and salini-
ties in an oyster-basin in the early part of the summer before
1 Compare Murray and PuUar, Bathy metrical Sui~i<ey of the Fresh- Water Lochs of Scotland,
vol. i. pp. 580, 581, and 587, Edinburgh, 1910.
Q
226
DEPTHS OF THE OCEAN
Conduction
of heat.
the maximum temperature has been reached, but already on the
loth June (1903) the water of this poll is seen to be 5° C.
warmer at a depth of 2 metres than at the surface.
To understand how such a high temperature can be preserved
for a length of time at a depth of 2 metres, one must bear in
mind the fact that the conduction of heat plays an altogether
subordinate part in the thermal conditions of the sea. Kelvin
and Wegemann have made some calculations on the trans-
mission of heat in water by conduction ; Wegemann commences
with a sea 5000 metres deep, with a temperature of 0° C.
throughout ; the surface is supposed to be in contact with a
5 n%o 23%.o 24%o 25%o 26%o 17%o Zd%o Zr/oo 30%^ 3/%c
^ t /3° /4° /5° /6° 17° 16- 19" ZOO ^,6 ZZ^''^
1
1
t J
V
^~-
^J
— -__
____
^
.^"^
R
t_
^""^^
\
5
^^^
/_
^
/
Fig. 158.— The Vertical Distribution of Temperature [t) and Salinity {s)
IN THE KvERNE-POLL, IOTH JUNE I903.
source of heat at a temperature of 30' C. No forces inter-
vening other than conduction, no heating effect would be
perceived at a depth of 100 metres after 100 years, and after
1000 years the temperature at 100 metres would only have
reached j.^, C, and at 200 metres 0.6° C. It is thus seen
that transmission of heat by conduction is practically negligible
in the sea. The heat conveyed by the sun to the uppermost
water-layers cannot therefore be propagated into deep water by
conduction, but only through movements of the water — waves,
currents, convection "currents," etc. Where there is no such
motion, and where the sun's rays cannot penetrate, heat cannot
be transmitted by conduction, and hence we find temperatures
as low as 2" C. or less in deep water even under the equator.
PHYSICAL OCEANOGRAPHY
227
In winter, heat will be radiated from the sea-surface to the
colder air, and the temperature will be lowered. In Figs. 159
and 160 two maps of the North Atlantic, one for February and sea.
one for August, are reproduced from Atlantischer Ozean, ein
Atlas, published by the Deutsche Seewarte in Hamburg.
In the February map the isotherm of 25' C. runs from the
Antilles towards the east and a little to the south, in the
direction of Africa, whereas in August this line lies, in the
western part of the ocean, as much as twenty degrees of latitude
Radiation of
heat from the
rface of the
Fig. 159.— Surface Temperature of the North Atlantic in February.
farther north. In the same way the other isotherms have
more northerly positions in summer than in winter. The
difference between the surface-temperature in February and in
August is about 5° C, in some places less, in others considerably
more. Near land the annual variations are much greater, as in
the coast- water within the Norwegian skjsergaard (" skerry-
guard," literally: "fence of islands"), where the surface-
temperature in summer is i5°-20 C, and in winter only a few
degrees above zero. Beneath the surface the variations
gradually decrease, and at a depth of a few hundred metres no
marked seasonal variations can be traced.
Reversal of
seasons at a
depth of 200
metres.
228 DEPTHS OF THE OCEAN chap.
At a certain depth a displacement of the seasons is often
found. Repeated observations have been made by the
"Michael Sars " at a station outside the entrance to the
Sognefjord in different seasons and in different years. In 1903,
measurements were made at this station in the months of
Fig. 160.— Surface Temperature of the North Atlantic in August.
February, May, August, and November, and the following
temperatures were found : —
February.
May.
August.
November.
Surface ....
4.8° c.
7-3° C.
13.8° c.
8.7° c.
100 metres . . .
6.8°
6.4°
6.9°
9-3° '
200 ,, ...
7-9°
7.0°
.6.7°
7-9
300 „ . . .
6.3°
6.5°
6.4°
At the surface it was coldest in February and warmest in
August — the difference being 9^ C. At 100 metres it was
coldest in May and warmest in November, with a difference of
2.9° C. At 200 metres it was coldest in August, warmest in
February and November, the difference being 1.2° C, so that
PHYSICAL OCEANOGRAPHY 229
at this depth the seasons were reversed : it was " winter " in
the water in the middle of the summer, and "summer" in the
middle of the winter. Murray's observations in Upper Loch
Fyne in 1888 gave similar results. At 300 metres at the
" Michael Sars " Station there were hardly any variations at all,
the temperature being very much the same as the mean annual
temperature of the air, as Nordgaard has shown to be the case
with regard to the bottom-water of the Norwegian tjords.
When sea-water is cooled its density increases, and it often vertical
happens in winter that the surface-water becomes heavier than "^'g^^^'wat'erl
the water below. The surface-layer then sinks, and the under-
lying water comes to the surface. By this vertical circulation
the conditions are equalised, so that exactly the same salinities
and temperatures are found as far down as the vertical circulation
extends ; wind and current aid in the process. This takes place
especially from January to March ; in April the weather again
becomes warmer and the temperature begins to rise at the
surface. A very good example of this phenomenon is afforded
by the "Michael Sars" observations taken to the westward of
Plymouth in April 1910 ; at the very surface the temperature
had risen slightly, but otherwise practically the same salinities
and temperatures prevailed at every station down to a depth of
150 metres or more. Later on in spring the surface tempera-
ture gradually rises, and a marked discontinuity-layer is formed.
In many places near the coast, where the salinity is low at the
surface and high beneath the surface, a brisk vertical circulation
cannot be set up ; the comparatively fresh water on top is so
light that, even when considerably cooled, it does not change
places with the salt and heavy water below. But farther out
to sea the vertical circulation may extend down to a depth of
200-300 metres or more.
It is thus not only the surface-water that may give off heat Effect of heat
to the air, but a great body of water extending to several f^eTea.^^^
hundred metres in depth, and hence the great influence of the
sea on winter climates. The capacity for heat of water is very
great compared with that of the air. Supposing that we have
I cubic metre of water giving off enough heat to the air to
lower the temperature of the water one degree, this heat would
be sufficient to raise the temperature of more than 3000 cubic
metres of air by one degree. An example will show the
importance of this. Suppose a body of water, 700,000 square
kilometres in extent and 200 metres deep, to give off enough
heat to the air in winter to lower the water-temperature one
230 DEPTHS OF THE OCEAN
degree, then the heat given off would be sufficient to raise the
temperature of a stratum of air covering the whole of Europe
to a height of 4000 metres on an average ten degrees. This
Gulf Stream, explains how the Gulf Stream renders the climate of northern
Europe so much milder in winter than would be expected from
its northerly latitude. We shall see later on that the oceano-
graphical researches of the last few years give reason to hope
that it will even be possible to predict the winter temperature
of northern Europe from the temperature of the sea some time
in advance.
The salts of
the sea.
Salinity
determined
from water -
samples.
Obtaining
samples from
surface and
shallow water.
Obtaining
samples from
deep water.
Buchanan's
stopcock
water-bottle.
There are many different salts in the sea. Salinity means
the total amount of salts in a given quantity of sea-water, and
is usually stated in parts per thousand (per mille), indicating how
many grams of salt are contained in one kilogram of sea-water.
The salinity of the sea varies considerably both horizontally
and vertically, and its distribution is determined by examining
samples of water from different parts and different depths ; these
samples are secured by means of various water-bottles. From
the surface a sample may be drawn with an ordinary bucket.
For shallow waters down to 30 or 40 metres a common glass
bottle is often employed ; the Hne is bound to the neck of the
bottle and a weight is suspended underneath. The stopper is
fastened to the line a little way above the bottle, and is inserted
when the bottle is lowered. When this simple water-bottle has
arrived at the depth from which the sample is to be taken, the
line is given a sharp pull, so that the stopper is drawn out and
the bottle fills. In hauling up, a little water from the upper
layers may, of course, enter the bottle, but this simple method
does well enough for shallow water
variations are so great as to render
necessary.
Many varieties of water-bottles for investigations in deep
water have been constructed. A few of those most in use, and
most effective in working, may be described, and the different
principles involved explained.
We will begin with an apparatus designed by J. Y. Buchanan
for the "Challenger" Expedition, a so-called stopcock water-bottle
(Fig. 161). It consists of a brass tube (A), which can be closed
at both ends by means of metal stopcocks (B,B) ; the latter are,
through two levers (D,D), connected with a rigid rod (0,0).
When the side-rod is in the upper position, as seen in the left-
hand and central figures, the cocks are open. A tilting plate
near land, where the
extreme accuracy un-
PHYSICAL OCEANOGRAPHY
2.^,1
(E) is hinged on to the rod. In the left-hand figure the plate
is tilted upwards, and it remains in that position while the
C.^^ — ^-
^
Fig. i6i.— Buchanan's Stopcock Water-Bottle.
apparatus is' being lowered. But as soon as it is pulled upwards
the water presses against the plate, tilting it into the position
shown in the middle figure ; the rod is then forced downwards,
232
and
DEPTHS OF THE OCEAN
Pettersson s
insulating
water-bottle.
Pettersson-
Nansen
water-bottle.
along with it the levers, closing both stopcocks simul-
taneously. The plate then falls into the position seen in the
right-hand figure. This simple arrangement allows of enclosing
a water-sample at any depth required. This water-bottle has
done very good service ; it was much used on board the
" Challenger," and has also — with a few small improvements —
been employed a good deal in later times.
In a stopcock water-bottle of this construction the
temperature of the water-sample may alter during the hauling-
up process, and it is impossible to get a record of the temperature
in situ with the water-sample, without having a special apparatus
for the thermometer. Buchanan himself, and later on Nansen,
modified this water-bottle by adding an arrangement for a
thermometer, which would be reversed the moment the cocks
were closed. In the meanwhile Otto Pettersson had adopted
F. L. Ekman's old idea of making a water-bottle which should
be insulating, so that the water- sample would retain its
temperature unchanged, even when drawn up from a great
depth. Pettersson availed himself of the circumstance that the
water itself is an excellent insulator, its power of conduction
being small and its capacity for heat very great. This water-
bottle consisted of a bottom-piece, a cylinder, and a lid ; these
three parts could be separated by lifting up the cylinder and
the lid along two brass rods forming the sides of the encom-
passing frame. The cyHnder is a composite one ; inside a
strong cylinder of ebonite there are various other cylinders of
celluloid and brass, one inside the other like a set of Chinese
boxes. Between these concentric tubes are narrow cylindrical
spaces which fill with water when the apparatus is lowered into
the sea, and in this way a system of excellent water-insulators
is formed. The outer cylinder may alter in temperature con-
siderably in the course of hauling-up, the inner ones less and less,
until in the central chamber the temperature will not change at
all for some time, although the water-bottle be strongly heated
from without. On the bottom and on the lid Pettersson
attached a number of parallel plates, which likewise enclose
insulating water-layers.
Nansen has introduced several improvements, and the latest
model — the so-called Pettersson -Nansen water-bottle — is an
excellent apparatus, which is now very widely used (see Fig.
162). On the left it is seen open, as it is let down into the
water ; the lid is suspended in the upper part of the frame, and
supports the cylinders as well as a weight hanging below the
PHYSICAL OCEANOGRAPHY
233
apparatus. When a messenger is sent down the line and strikes
the water-bottle, the Hd is released, and the weight draws both
lid and cylinders down, clasping the
apparatus together and closing it her-
metically. The right - hand figure
shows the water-bottle closed and
ready for hauling up. The Nansen
thermometer is seen in the left-
hand figure, and is — as mentioned
above — a thin delicate instrument,
fitted inside a strong protective glass-
tube in order to withstand the enor-
mous pressure of the deep sea. The
Pettersson-Nansen water-bottle is so
well insulated that the temperature of
the water-sample is not influenced
from without, even when being hauled
up from a depth of 1000 metres.
But the temperature is lowered
slightly, in consequence of the reduc-
tion of pressure during the process of
hauling up, as has already been men-
tioned. This circumstance asserts
itself quite appreciably in the case of
the insulating water-bottle when used
at great depths. The water-bottle
is, however, fitted with a frame for
carrying a reversing thermometer, so
that a double determination may be
made. During the "Michael Sars "
Expedition we very often employed
the insulating water-bottle, and took
temperatures both with the Nansen
thermometer and with the Richter
reversing thermometer simultaneously.
As an example, an observation made
at Station 10 1 in 1400 metres may
be mentioned : after correction the
Nansen thermometer read 4.45'' C,
the Richter thermometer 4.59° C, that is 0.14' C. lower in the
first case than the second. The water in the water-bottle
should, according to the calculation by Lord Kelvin's formula,
have been cooled 0.12° C. ; granting that the determinations
Fig. 162. — Pettersson - Nansen
Water-Bottle.
Shown open in the left-hand figure, and
closed in the right-hand figure.
234
DEPTHS OF THE OCEAN
are absolutely correct, the cooling of the
solid parts of the apparatus accounts for
the difference of two -hundredths of a
degree, which is a very probable value.
This is an instance chosen at random
from a vast number of observations, and
proves how accurately deep-sea tem-
peratures can now be determined.
V. W. Ekman has constructed an
apparatus to serve as a reversing
mechanism and a water-bottle at the
same time. The apparatus is made of
brass, and consists of a frame carrying
inside a cylinder pivoted on an axle at
the middle of the frame (see Fig. 163).
At either end of the cylinder there is a
lid, to which are attached two pairs of
levers fastened to the frame near the
axle of the cylinder. The cylinder can
be placed in such a position that both
lids are open, and it is kept in this
position by means of a small pin, seen
at the top of the frame on the right.
Thus adjusted the water-bottle is let
down into the sea. A messenger is
sent down after it and knocks out the
pin ; the cylinder is poised in such a
way that it turns over in the frame.
The levers gradually draw the lids
closer, and when the cylinder is wholly
reversed it is held fast by a catch and
encloses the water-sample hermetically.
To the side of the cylinder is attached
a metal sheath for holding a reversing
thermometer, which is consequently
reversed along with the water - bottle.
This apparatus may be fastened any-
where on the line, and a number of
them may be used at the same time, in
which case the messenger - release is
arranged in the following manner : In
the figure a messenger is seen hooked
on to a small bar underneath the water-
'
1
Fig. 163. — Ekman's Reversing
Water-Bottle in process
OF being reversed, and
SHORTLY after BEING RE-
LEASED.
PHYSICAL OCEANOGRAPHY
235
bottle ; when the water-bottle is reversed the bar is withdrawn,
and the messenger is let go. The next water-bottle is knocked
over, releasing in its turn the following messenger, and so on.
It is indispensable with this, as with all other water-bottles, that
when closed it should be absolutely water-tight, otherwise water
might get in from the higher layers and vitiate the sample.^
The water-sample, when brought on board, may be dealt
with at once, and its salinity, etc., determined, but it is generally
the best plan to store the samples for examination in a shore
laboratory. In this case the samples must be preserved Preservation
absolutely air-tight, so that they shall not suffer any change g^nT^^^^s for
in the interval. As a rule, the water may be kept in good glass examination
bottles with lever stoppers, like those used in soda-water bottles. °" ^^°''^-
Cork stoppers will not do, unless capped with paraffin or wax,
as it is difficult to avoid some degree of evaporation which
would invalidate the results.
The chemical composition of sea-water has been very care- Chemical
fully determined. Wellnigh all known elements are found in o?'^ea°^at°en
solution in the sea, but most of them in such small quantities
as to be detected only by the most delicate methods. A
kilogram of sea-water contains about 35 grams of solid sub-
stances altogether ; the quantity varies slightly in different
places, but on an average there are about 35 weight-units of
solids in 1000 weight-units of sea-water (35 per thousand).
According to the results of Dittmar's analyses of the " Challenger"
water-samples there are on an average in 1000 grams of sea-
water : —
Grams.
Percentage on
total solids.
Sodium chloride (NaCl) .
Magnesium chloride (MgCl.,)
Magnesium sulphate (MgSO^) .
Calcium sulphate (CaSO^) .
Potassium sulphate (K2S0^)
Calcium carbonate (CaCOg)
Magnesium bromide (MgBr^) .
Total ....
27.213
3.807
1.658
1.260
0.863
0.123
0.076
77.76
10.88
4-74
3.60
2.46
0.34
0.22
35.000
100.00
^ The highest perfection must be exacted with regard to this point. It formerly frequently
occurred that the instruments leaked a little ; as the knowledge of the sea has grown, many
236 DEPTHS OF THE OCEAN
The numerous other substances in solution are present in
such extremely small quantities that they may be disregarded.
Although the total salinity may vary widely, the composition of
the dissolved solids proves to be practically the same every-
where. Hence if in a sea-water the percentage of any one
component, say chlorine, be known, the total salinity can be
ascertained by calculation.
The direct determination of salinity by evaporating a known
volume of water to dryness does not give accurate results, unless
the amount of chlorine is carefully determined before and after
the evaporation, because in the last stages of evaporation and
in drying the residual salt uncertain amounts of chlorine are dis-
engaged in the form of hydrochloric acid. Such a determination
is very circumstantial, and it is therefore necessary to resort to
indirect methods, which may be physical or chemical.
An old-established physical method consists in determining
the density by means of the hydrometer. This is a glass cylinder
which floats in the water and has a graduated stem, on the scale
of which densities are read off The temperature of the water
must be determined at the same time. Densities so found are
recalculated by means of tables to a standard temperature,
generally 17.5° C. Now, owing to the uniform composition
of sea -salts, a definite density at 17.5° corresponds rigidly
to a definite salinity. Hence by referring to tables the
salinity of a sea-water can be found from its density at standard
temperature.
The hydrometric method is easily applied on board ship,
and may be made to give densities correct to four places of
decimals. Densities can be determined to a yet higher degree
of accuracy by means of the pycnometer, but this method is
practicable only in a laboratory on land, and is not often
employed.
Two other physical methods have been tried by way of
errors have been detected in earlier determinations referable to the leaky condition of the
water-bottles.
When the forms of apparatus described above are to be used, the vessel must be stopped and
hove to as long as the work goes on. Recently several investigators have studied the problem
of constructing a i apparatus to be used while the ship is under way. Water-bottles have been
made which can be let out when the ship is going at full speed, with the line running'freely so
as to allow them to sink. On checking the line the apparatus is closed by a mechanism like
that used by Buchanan in his water-bottle. The water-bottle being insulating, a temperature-
reading is secured together with the water-sample. In such an experiment a metre-wheel
showing how much line has run out is no use ; one must have a special depth-gauge, usually
one to measure the compression suffered by a certain volume of air from the weight of the water.
These new instruments are not in common use as yet, being still in the experimental stage,
but the time is not far off when we shall have automatic water-bottles working with absolute
precision. That will mark an important step forward, as much time will then be saved in
an expedition.
PHYSICAL OCEANOGRAPHY 237
experiment, but are not in general use. The one consists in
measuring the refractivity of the water, i.e. the deflection under-
gone by a ray of monochromatic hght when passing from air to
water ; this quantity, again, stands in definite relation to the
salinity of the sample. The other method is based on the
electrolytic conductivity of sea-water, and has the advantage
that no sample need be brought up, a pair of electrodes being
simply sent down to any required depth and the readings being
taken on board. This method has been applied by Martin
Knudsen with good results in shallow water.
The most convenient, and on the whole the most satis- Chemical
factory, method of determining salinity is a chemical one, and is '"^^^^o^^-
based on the fixed relation between the chlorine contained in
a sea-water and its total salinity.
The amount of chlorine can be determined by a rapid and chlorine
easy method. When a solution of silver nitrate is added to ^^^'^^^'o"-
sea-water, the chlorine is thrown down as a white precipitate of
silver chloride. If a few drops of yellow chromate of potassium
are added it is easy to see when all the chlorine is precipitated,
for the silver nitrate will then act on the chromate so that the
yellow colour is changed into red. When the chlorine content
of a water-sample is to be determined, a certain quantity
{e.g. 15 c.c.) is measured off and poured into a glass; a few
drops of the yellow chromate solution are added as an indicator,
and then nitrate of silver from a burette, that is, a graduated
glass tube with a stopcock (for discharge) at the lower end
(see Fig. 164). When the red colour appears, the burette is
read off to find out how much silver solution has been added,
and it is easy from this value to calculate the amount of
chlorine. From Knudsen's Hydrographical Tables the salinity
or the specific gravity, corresponding to this chlorine-value found
by titration, may be determined. All this can now be done
quickly and accurately ; in fact, the salinity of a water-sample
is determined in less than five minutes to within about j-^ per
iiiille, i.e. i centigram of salt per kilogram of sea- water. The
modern method of chlorine titration is a great improvement on
former methods, and it has been much used in recent oceano-
graphical work, thousands of such determinations being now
made yearly.
The density of sea-water depends both on the salinity and Density of
on the temperature ; the water is comparatively light when ^ea-water.
the salinity is low and the temperature high, and increases
in density with a rise of salinity and a fall of temperature.
DEPTHS OF THE OCEAN
Fig. 164.— Titration Apparatus.
On a shelf there is a large bottle for the silver solution, which can flow through a glass tube into the
burette ; the latter is provided with cocks for regulating the inflow and the outflow of the solution.
Fresh water has its greatest density at 4 C, which is taken
as unity. Salt water becomes heavier the lower the temper-
PHYSICAL OCEANOGRAPHY 239
ature, the density of sea - water with a sahnity of 35 per
thousand and at a temperature of 0° C. being 1.028 13. By
means of Knudsen's Tables the density is quickly found when
both salinity and temperature are known. The value of most
interest to us is the density at the potential temperature (see
above, p. 221) corresponding to the temperature in situ. It has
been found that this density always increases from the surface
downwards to the bottom, even when the compression is left
out of account. If this were not so, in order to attain equilibrium
the heavier overlying water and the lighter underlying water
would have to change places, and this is what actually
takes place in winter, when the density at the surface exceeds
that of the waters below. The layers will always arrange them-
selves in such a way that the lighter water is on the top and
the heavier water underneath.
Salt water freezes at a lower temperature than fresh water ; Freezing-
thus sea-water with a salinity of 35 per thousand freezes at p°"^'"
— 1.9° C, so that temperatures below zero are found in the sea,
— I J° C, for instance, being a common temperature in the polar
currents. When the salinity exceeds 24.7 per thousand the
water becomes heavier on being cooled, until the freezing-point
(below zero) is reached. This implies an essential difference
between salt water and fresh water. In the deep water of lakes
temperatures below 4° C. are never found, while in the bottom-
water of the ocean considerably lower temperatures prevail, as,
for instance, — 1° C. or still lower recorded in the Norwegian
Sea, and about + 2° C. recorded in the Atlantic. Thus it is, as
a general rule, colder in the great depths of the ocean than it is
at the bottom of deep lakes.
We shall now indicate in a general way the distribution of Distributioi
salinity. It must be remembered that the salinity is raised by of^^^™')-
evaporation, and lowered by dilution with fresh water either
from rainfall or from rivers. Where the evaporation outweighs
the supply of fresh water the salinity increases, as is the case,
for instance, in the Mediterranean and in the Red Sea, where
the air is dry and hot, and in the ocean north and south of the
equator, where the warm trade-winds blow, producing a strong
evaporation. In such places a high salinity will be found.
There is a steady inflow of Atlantic surface-water with a salinity Medi-
of about 36 per thousand into the Mediterranean Sea, where the t^rranean.
water removed by evaporation is far greater than the supply of
fresh water, so that the salinity rises to 38 per thousand, accom-
panied by an increase in density, which is accentuated by the
Coastal
districts.
240
DEPTHS OF THE OCEAN
cooling down in winter, and the surface-water becomes so
heavy that it sinks and forms the bottom - water of the
Mediterranean.
On the other hand, there are coastal districts where the
many large rivers constantly carry more water into the sea
than what is evaporated from it. In such places the salinity is
decreased, as, for instance, off the coasts of Scandinavia. A
great part of the rain falling in Northern and Central Europe,
as far south as the Alps, is carried by rivers into the Baltic
and the North Sea, where it is mixed with the salt water,
producing the so-called " coast- water " of comparatively low
salinity. The density of the coast- water is so low that it
-The Sognefjord Section, May 1904.
Salinities above 35.0 per thousand shown by single hatching ; salinities above 35.20 per
thousand shown by cross hatching.
always floats on the top, and often glides along a substratum of
more saline water. Such coast-water forms the Baltic current,
running out of the Baltic Sea through the Kattegat and
Skagerrak, continuing on its way along the coast of Norway,
above the Salter and heavier Atlantic water carried north by the
" Gulf Stream."
Fig. 165 represents a section from the mouth of the Soo-ne-
fjord (near Feje) westwards to a little north of the Faroe
Islands. The Atlantic water is marked by hatching, and we
see the coast-water lying on the top, close to the land on the
right. This section has been examined through a succession
of years in the month of May, and we have measured the coast-
water section in square kilometres. The top curve (I.) in
Fig. 166 shows how this section has varied from year to year.
Now it proves to be the case, as was to be expected, that
these variations to a certain degree correspond to the varia-
tions in the rainfall. The other curves show the divergences
PHYSICAL OCEANOGRAPHY
241
(per cent) from the normal annual rainfall, (H.) for Chris-
tiania, (HI.) for Bergen, (IV.) for Germany; (V.) shows the
divergences in Norway during the months of October, November,
and December. On the whole, the rainfall corresponds well
with the transverse section of the coast-water some time after-
wards. The rainfall was comparatively small in 1902, and the
coast-water had a small transverse section in May 1903 ; the
rainfall was large in 1903, and there was much coast-water in
May 1904, and so on. The effect of the rainfall on the land is
not immediately felt in the coast-current off western Norway ;
there is a delay which
lani tars') /<xnQ zona. /on.^ ^ >
seems to make it possible
to predict some time be-
forehand if there is going
to be much or little coast-
water. This is an ex-
ample of the predictions
likely to be undertaken in
the future, when the sea
and the air have been
more closely studied.
We shall now, after
these introductory re-
marks, examine the ver-
tical distribution of salinity
in some different places,
as found in the cruise
Fig. 166.— Curves showino the Variations in of the " Michael Sars."
I. the transverse section of the coast-water off Feje pTJo- i f\i rp-nrf^cp^ntc fhf^
(May); II., III., IV., the annual rainfall for Chris- ^ ^- , ^y icpiCbCllLb LUC
tiania, Bergen, and Germany respectively; V., the phySICal COnditlOnS a little
. . ^_.-,___ xr ^-.. ._. ^^ ^^^ north of the Sar- Sargasso Sea
gasso Sea, at Station 65, ""^sion.
on 25th June 19 10. In this, as well as in the following
figures, the continuous line indicates the salinity, the broken
line the temperature, and the dotted line the density.^ We
see that the salinity is greatest at the surface, 36.43 per
thousand; this is the result of the strong evaporation. It
decreases downwards, at first rapidly, then more slowly, more
rapidly again, and finally very slowly ; in the deep layers below
1250 metres the salinity is less than 35 per thousand, and
throughout the great body of the deep water 34.9 per thousand.
^ The density is given in abbreviated form, e.g: 25.56 instead of 1.02556, and is indicated by
the Greek letter a (o-j being the density at the temperature zn situ disregarding the compression).
/900
1901 /902 /903 1904 1905
%
120-
/
\^^
HlX
//O-
^
//
\ ^
/
ZOO-
^
^
/J^
K\
V
90-
^^
\ \
A/
SO
'\|/
/ /
V
\^
^ /v
yo
An
\
-^
rainfall in Norway dtu-ing October, November, and
December.
Between
Scotland and
Rockall.
242 DEPTHS OF THE OCEAN chap.
The density increases from the surface to the bottom, but with
varying rapidity ;
through the first
100 metres it in-
creases rapidly,
and also inthedis-
continuity - layer
between 600 and
1 100 metres.
Fig. 168 shows
the conditions on
the 7th August
1910, at Station
loi, between
Scotland and
Rockall, in that
branch of the Gulf
Stream which
flows towards
northern Europe.
The salinity at the
surface is here i
°5
T
25J0
ifSO
0°
0 20 30 4«
2600 2650
3S00 3550
5° 6° 7° 6° 9° 10° 1
2700 2750
ibOO 3650 yoo
" U'U-H" 15''16°17»16''19°20°C.
6O0
1000
1500
9 firm
I
/
/
/
/
f-
/
/
/ ,-'
,•
>r.
-^y
/
/
/;
/
/
i
\
Fig. 167.— Temperature (broken line), Salinity (continu-
ous line), and Density (dotted line) at Station 65,
a little north of the Sargasso Sea (25th June 1910).
Depth in metres.
per thousand lower than at Station 65 near the Sargasso Sea,
^otaiwa 101.
2&S0 ihno
A-no dioo
o' I" 2° 3' 4' S" 6° T
Zbso
iiiO
■ 9" 10' //
dbon 3bSO%o
' /d" /T' /S" /S/" ?U' C
1 '■
1 F 7^. +
Fig. 168. — Temperature, Salinity, and Density at Station ioi, a little
east of Rockall (7th August 1910). Depth in metres.
due to admixture of fresh water ; but from about 900 metres
down to the bottom the salinity, temperature, and density
PHYSICAL OCEANOGRAPHY
243
are all very much alike in these two places, nearly 2000
nautical miles distant from each other. There is thus a
marked difference as far as the upper layers are concerned,
both salinity and temperature decreasing northwards, while in
the deep layers below 500 fathoms the conditions are the same
throughout the middle and north-eastern part of the North
Atlantic. Northwards from Station 65 to Station loi the
decrease of temperature in the upper layers is more marked
than that of the salinity, so that the density of the surface-layer
increases from 1.0254 at Station 65 to 1.0266 at Station loi.
As a general rule, the upper water- layers, on being cooled,
become gradually heavier from the tropics toward the poles.
Fig. 169 shows the conditions at Station 106, loth August Faroe
19 10, in the Faroe- Shetland Channel to the north of the ^^^""^^•
Station 106
t
0°
„
„
' i
2boo
(,' 7' e- s
^
0' 1
r /Z' /3' 1
Zloo
21S0
7' >8^ B'^^'o^^C
^8oo
1
/
r
-
-,
Ix
''
'-'
■"
'{
'^
/'
...
<
!
Lj
Fig. 169.— Temperature, Salinity, and Density at Station 106, in the
Faroe-Shetland Channel (loth August 1910). Depth in metres.
Wyville Thomson Ridge, about 300 miles north-east of
Station loi. At Station 106 some fresher water was found at
the surface, but otherwise the salinity, temperature, and density
were the same at both stations as far down as 500 metres ; the
water had grown slightly colder and heavier in these 300 miles,
but the difference was very small. Below 500 metres, however,
there is a great contrast, the temperature of the deep water
being, as already indicated, much lower north of the Wyville
Thomson Ridge than south of it, and the density is therefore
greater on the north side. The deep water of the Norwegian
Sea is thus colder and heavier than that of the Atlantic, but,
strange to say, there is no difference in the salinity of the
deepest layers of the two regions.
At all three stations the surface -layers are occupied by a
warm, comparatively saline, northerly current. On proceeding
northwards, there is a fall of temperature and of salinity and
244
DEPTHS OF THE OCEAN
an increase of density, but the differences are not so great as
to forbid the inclusion of the three stations in one region with
regard to the upper water-layers ; it is a region with a southern
character.
The conditions are widely different when we come to a
northerly region, like that where the East Greenland Polar
Current and the Labrador Current bring down great water-
masses from the Arctic seas. On our passage to and from
St. John's we sailed across the Labrador Current and took a
number of observations at different places in it. Fig. 170 shows
the conditions at Station 76, due east of St. John's, towards the
eastern margin of the cold current. Here the temperature at
the surface was about 6° C, falling rapidly to —0.35° C. at 55
metres (30 fathoms), rising again, at first rapidly, to 3^ C. at a
M.
/oo
Ji6o
33 0
■ees
33 6
Z" . 3°
g7o
3i.o
4' .5"
J'fS
i'ao
Fig. 170. — Temperature, Salinity, and Density at Station 76, in the eastern part
OF THE Labrador Current, off Newfoundland (9th July 1910). Depth in metres.
little more than 200 metres, and then slowly to 3.4" C. towards
the bottom in about 400 metres. If the depth had been
greater, we should have found that the temperature fell
again as we penetrated into the deep water. This is an
example of the usual conditions in Arctic and Antarctic regions,
where in summer the temperature decreases gradually from the
surface to a minimum at 50 to 70 metres, then rises to a
secondary maximum at 300 to 400 metres, falling again towards
the bottom, and it is in a case like this that the ordinary
maximum and minimum thermometer is inadequate (see p. 216).
At Station 76 the water was warmer through the influence of
the Gulf Stream ; it was much colder, for instance, at Station 75
farther west, where we found -1.43° C. at 55 metres, and at
Station 74, just off St. John's, where the temperature was —1.52°
at 91 metres. As a rule, it may be said that in a polar current
PHYSICAL OCEANOGRAPHY 245
in depths between 50 and 100 metres the temperature is below
zero, and where there are banks at these depths they are
covered wath ice-cold water ; hence the great difference between
such banks and those which lie within the region of the warm
currents. Fig. 95, p. 1 10, represents a section across the New-
foundland Banks from the Gulf Stream (Station 69) northwards
to a point just outside St. John's (Station 74). On the northern
part of the bank it is very cold, for there we are in the middle of
the Labrador Current; on the southern slope it is much warmer,
because of the vicinity of the Gulf Stream. There are accord-
ingly great differences in temperature and salinity in different
parts of the Newfoundland Banks, especially in the deeper
parts.
From Fig. 170 we see that the salinity was below t,t, per
thousand at the surface, that it increased rapidly downwards (to
34.6 per thousand at 200 metres), and afterwards more slowly, but
it nowhere attained the salinity of the " Atlantic water," viz. more
than 35.0 per thousand. This is characteristic of the Arctic and
Antarctic regions, especially in summer. The water brought by
the currents from the North Polar basin is a kind of coast-
water. The great rivers of Siberia and of the north of America
empty volumes of fresh water into the Polar Sea, where it
mixes with the salt water, diminishing the surface salinity,
which is further reduced by the melting of the drifting ice in
summer. The low salinity at the surface renders the density
comparatively small, but it increases rapidly downwards, so
that the water at 100 metres is heavier than at any of the three
stations within the warm water region just mentioned. We
have not in any of these examples taken into consideration the
fact that the density is slightly increased with increase of depth
by the pressure due to the weight of the overlying water.
The pressure in the sea increases by about i atmosphere The pressure
for every 10 metres of depth. Thus there is a pressure of '''^^^^^^■
about 100 atmospheres 1000 metres below the surface, and of
500 atmospheres at a depth of about 5000 metres. When
differences in pressure occur in adjacent areas at the same level
below the surface, various currents arise, just as air-currents
are produced by differences of barometric pressure. The
circumstance that the water is not equally heavy everywhere is
one of the main causes of the ocean currents, and, the water
being easily moved, small differences of pressure will be sufficient
to produce a sensible motion. By the great pressure the water
246
DEPTHS OF THE OCEAN
itself, and all the materials carried into deep water, are com-
pressed. Water is, however, only to a slight extent compressible,
so the effect of pressure is not so great as is popularly supposed.
Tait and Buchanan have shown conclusively that compressi-
bility decreases slightly but sensibly with increase of pressure.
V. W. Ekman has recently made a very careful investigation on
the compression of sea- water, and has published Tables for Sea-
Water under Pre sszcre. From his tables we may easily compute
the actual density with compression, when depth, salinity, and
temperature are known.
Let us take, as an example, the conditions at Station 63,
near the Sargasso Sea, 22nd June 19 10, as shown in the
following table, giving for the depths specified: (i) the
temperature, (2) the salinity, (3) the density disregarding the
compression (calculated by means of Knudsen's Tables), and
(4) the actual density with compression (calculated from
Ekman's Tables) : —
Depth.
Temp.
Salinity
per
thousand.
Density.
■ Metres.
Fathoms.
Without Actual density
compression S. Sj.
0
183
366
549
732
915
1830
3000
4000
0
100
200
300
400
500
1000
1640
2187
22.30
16.71
15.22
^2.35
8.41
5-97
3-54
2.90
2-35
36.44
36.27
36.00
35-54
35-11
35-16
34-94
34-92
34.88
1.02525
1.02658
1. 02671
1.02696
1.02732
1.02770
1. 02781
1.02786
1.02787
1.02525 .
1.02741
1.02835
1.02943
1.03067
1. 03190
1. 03631
I.04171
1. 04621
It is seen that the density is practically identical, for instance,
at 3000 metres and at 4000 metres when leaving compression
out of account, whereas a considerable difference was actually
produced by the compression. At 4000 metres the effect of
the pressure of 400 atmospheres was so great that the density
increased from 1.02787 to 1.0462 1, equal to an increase of
weight of if per cent. As a matter of fact the water at 4000
metres has become only if per cent heavier by reason of the
compression ; a fairly delicate weighing would have been
necessary to detect this increase. The case may also be stated
thus : I litre of water at 4000 metres weighs 1046 grams ; if
PHYSICAL OCEANOGRAPHY 247
this litre were brought up to the surface, it would expand so
that its volume would be increased by 18 cubic centimetres;
subtracting the 18 c.c. and weighing the remaining litre we
find a weight of 1028 grams. Thus even at a depth of 4000
metres the difference caused by pressure is not great.
Now, what is the effect of this increase of density on a solid Sinking of a
body lowered into the sea ? Let us suppose a piece of solid ^^^''^ ^""^y*
iron, weighing 1000 grams in the air, to be sent down to 4000
metres at Station 63. When it is lowered just beneath the
surface it becomes lighter by 131 grams, thus weighing 869
grams. When it has reached a depth of 4000 metres the
buoyancy is 134 grams, so that the piece of iron there weighs
866 grams — a difference in weight of 3 grams for a piece of
iron weighing 1000 grams in air. This is merely 0.3 per cent
of the weight, and consequently quite insignificant. In other
words, metals and other solid substances are practically just as
heavy in deep water as they are at the surface, and will sink as
rapidly there as in shallow water. This may be proved by
direct observation, for if a messenger is sent down to close a
water-bottle at a depth of 2000 metres it will be found to take
four times as long as when sent down to 500 metres.
But suppose that, instead of a massive piece of iron, we take sinking of
a perfectly tis^ht capsule of thin iron filled with air, and lower it ^n air-fiiied
i. J <j X ' C3.DSUIg.
down to 4000 metres ; in the course of the descent the pressure
increases, forcing the walls of the capsule together. The
volume of air within the capsule may be so large that it only
just sinks at the surface, its total specific gravity being then
very little greater than that of the water ; but when it has
reached a depth of 10 metres the air is compressed to half its
original volume, granted that the capsule is collapsible, and the
weight of the iron then acting more freely, the capsule will sink
faster and faster ; when it reaches a depth of 4000 metres it is
exposed to a pressure of 400 atmospheres, and the compressed
air having hardly any buoyancy left, the capsule will sink almost
as fast as if it had been made of solid iron throughout.
Collapsible solid bodies containing air will accordingly sink
faster in deep water than at the surface. A piece of wood
floats at the surface because it contains a large amount of air,
but there is nothing to prevent it from sinking when it is sent
down into deep water ; therefore wood and cork are not
suitable for floats at great depths. It is the same with the dead
bodies of marine animals, etc., for when the air is compressed
they will easily sink.
248
DEPTHS OF THE OCEAN
The penetra-
tion of light
into the sea.
Absorption of
light rays.
Intensity of
light at
different
depths.
Fol and
Sarasin.
When the sun's rays fall on the surface of the sea, some of
them are rejected, and the rest penetrate into the water, though
in a somewhat altered direction. The direction is not much
altered when the sun is high in the heavens, as at noon in the
tropics. When the sun is just above the horizon its rays are
most strongly deflected, the few rays penetrating into the water
forming an angle of about 42" with the surface. As the sun
rises and the light becomes more intense, the deflection from
the course in the air gradually decreases, so that the rays do
not penetrate so deep as might be expected, even if the
angle with the surface increases. When the sun is 60^ above
the horizon, the refraction in the water is about 8°, the angle
between the surface and the penetrating rays then being about
68°, and when the sun is at its zenith, the rays are not bent at
all, but proceed perpendicularly into the water.
The rays making their way into the water are, however,
gradually absorbed, some quickly, others more slowly, accord-
ing to the wave-length of the ray and the limpidity of the water.
The sun's light, of course, consists of many different kinds of
rays : the dark heat-rays, imperceptible to the eye, lie beyond
the red end of the spectrum, and are therefore called ultra-red
rays ; then comes the visible spectrum with the colours in the
well-known order — red, orange, yellow, green, blue, indigo, and
violet ; beyond the violet end are the ultra-violet rays, remark-
able for their chemical action, but having no effect on our
senses. These different rays are refracted and absorbed in
different degrees. The red rays are refracted somewhat less
than the blue and violet rays, and are much more quickly
absorbed. The dark heat-rays are absorbed in the very upper-
most water-layers. The light rays also convey some heat, and
they penetrate deeper before disappearing — the deeper the
nearer the blue end of the spectrum is approached. Light at a
certain depth in the sea has not the same composition as on
the surface of the earth, there being fewer of the red rays
and more of the blue, which proportion becomes gradually more
pronounced with increasing depth.
Attempts have been made to determine the intensity of the
light at different depths, especially in the Mediterranean, by
means of the action of the rays on photographic plates.
Ordinary plates are most influenced by the rays at the blue end
of the spectrum, and by the ultra-violet rays, and only slightly
by the red. Fol and Sarasin, working off the Riviera, traced
an effect on the plate as far down as between 465 and 480
PHYSICAL OCEANOGRAPHY
249
metres ; Petersen found that in the neighbourhood of Capri a Petersen.
plate was influenced by the rays at a depth of 550 metres,
Luksch made some investigations in the eastern part of the Luksch.
Mediterranean, exposing his plate for fifteen minutes, and found
that the limit of the light-rays must be drawn at 600 metres.
In these experiments the influence of the collected rays on an
ordinary photographic plate was studied.
In order to make some investigations on this subject in the
jjy pii
Fig. 171.-
On the left, as it is sent down
-Helland-Hansen's Photometer.
in the middle, open for exposure ; on the right, closed and
ready for hauling up.
'Michael Sars " Atlantic Expedition, the author constructed a Heiiand-
- - - - . . - . . . „. , Hansen's
photometer.
new kind of photometer, which is represented in Fig. 171. In ^^"sens
the centre figure — at the lower part — is seen a brass cube ; the
four sides and the top have square " windows," and on each of
them a small square frame with a similar window (2x2 cm.)
can be screwed fast ; the screws and openings are seen in the
figure. The cube rests on a larger brass plate, or rather on an
india-rubber mat covering the brass plate. The plate and cube
are fastened inside a frame, along which they can be moved up
and down. At the top of the central figure is seen a larger
250 DEPTHS OF THE OCEAN
metal cube without any base ; it is intended to cover tightly
the lower cube to which the photographic plates are fastened.
On the left the apparatus is seen closed, with the cubes suspended
at the top of the frame, the smaller one inside the larger. In
this position the apparatus is lowered into the water. A
small messenger is sent down the line and releases the inner
cube, which drops to the bottom of the frame (see the middle
figure). The plates are thus exposed. After a certain time a
larger messenger is sent down, releasing the large cube, which
falls like a shutter over the plates, as seen in the figure on the
right. The apparatus is then ready for hauling up, and the
cubes are taken out of the frame into the dark-room for develop-
ment and change of plates.
In all previous photometric apparatus for use in the sea the
plates were hermetically closed behind a strong glass pane, in
order to shield them against the great pressure, but in the
photometer here described a totally different principle was
applied. The gelatine-film was covered with a glass plate and
inserted into a small envelope of thin caoutchouc, with a square
opening in front through which the light is admitted. The
envelope with the plate was then placed on one of the sides of
the inner cube, and the corresponding brass frame was screwed
on tightly. The water could penetrate both outside and inside
the cube, so that there was the same pressure on both sides of
the film and the glass cover. The rubber envelope would be
pressed tightly on to the glass plate, so that no water could enter
and spoil the film. By this arrangement the apparatus might
be exposed to any pressure without any special protection, and
it was used at various depths down to 1700 metres without a
single plate being cracked or spoilt by water.
Highly sensitive pan-chromatic plates (4x4 cm.) were
employed in the experiments — the windows being, as mentioned
above, 2x2 cm. In several experiments a gelatine colour
filter was inserted between the photographic plate and the glass
cover. Wratten and Wainwright's three-colour filters (red,
green, and blue) admit respectively only a certain portion of the
spectrum. This made it possible to study the rays present
within the separate fields of the spectrum, as well as the total
intensity of the rays. These investigations were carried out in
the southern stretch of the cruise, and though time and weather
did not allow of many experiments, those that were made gave
interesting results.
Some of the plates exposed are represented in Fig. 172. In
PHYSICAL OCEANOGRAPHY 251
the upper row are seen some results without a Hght-filter at Results at
Station 51. The plate on the left (No. 10), exposed for 40 'j'^p^hTluh
minutes at 500 metres, was strongly influenced by the rays, and without
The next plate (in the middle of the upper row), exposed foj- '^o °"''-*i f^''^-
80 minutes at 1000 metres, was also blackened by the light-rays.
The third plate was exposed for 120 minutes at 1700 metres,
and showed no effect whatever. These experiments were made
at noon on the 6th June with a clear sky, and show that a good
deal of light penetrates to a depth of 1000 metres — considerably
deeper than was previously supposed. The limit of light
Fig. 172.— Photographic Plates exposed at different depths.
The upper row from Station 51, the lower row from Station 55.
sufficient to influence the plate in the course of two hours lies
at a less depth than 1 700 metres.
The lower row in Fig. 172 shows some plates from Station
55, all exposed for forty minutes at a depth of 500 metres. The
plate on the left was used without filter, and shows the same
strong effect as the corresponding plate from Station 51, in the
upper row. The next plate (in the middle of the lower row)
was exposed with the blue filter ; an influence of the blue rays
is visible on the original plate (a faint Roman V), but not so
clearly in the reproduction given here. The right-hand plate
in the figure was exposed with a green filter, and shows no
effect. A plate with the blue filter needs an exposure six times,
and one with the green filter eighteen times, as long as a plate
252
DEPTHS OF THE OCEAN
CHAP.
is therefore difficult to compare the plates
it may at least be maintained that there
with no filter. It
quantitatively, but
must be many blue rays, though hardly any red ones, at a
depth of 500 metres. Series of experiments with and without
filters were also made at a depth of 100 metres ; in forty minutes
all the plates were over-exposed, those with a red filter only a
little, those with a blue one very much, so that there are many
rays of all kinds at 100 metres, though fewest of the red. When
plates without colour-filters were exposed on the top and on
the sides of the cube simultaneously, the plate on the top proved
to be more strongly influenced than the others. This fact is
not without interest, as it shows that the rays in the clear
tropical waters have a distinct direction at 500 metres, not
having yet become altogether diffuse ; shadows should, then,
be thrown even at that depth.
Regnard constructed an apparatus for determining the length
of the day at different depths, in which a clockwork arrange-
ment inside a cylinder causes a photographic film to pass before
an aperture. At the end of March 1889 the Prince of Monaco
made some experiments with Regnard's apparatus in the harbour
at Funchal, Madeira ; the water was not so clear as in the open
sea, so the times recorded may be rather short. At 20 metres
the day lasted eleven hours ; at 30 metres it began at 8.30 a.m.
and ended at 1.30 p.m., the sky becoming overcast ; at 40 metres,
with the sun shining brightly, the film exhibited only a slight
influence of light for a quarter of an hour about 2 p.m. These
and a few other experiments show that the day becomes
gradually shorter, and the intensity of light decreases, as the
depth increases.
The Swiss naturalist, Hermann Fol, has several times gone
down in diving dress off Nice to examine the bottom. At a
depth of 10 metres the solar light disappeared quite suddenly in
the afternoon a long time before sunset. At 30 metres the
light was so bad that it was difficult to gather the animals on
the bottom ; he could see a stone only at a distance of 7 or 8
metres, whereas shining objects in favourable positions could
be discerned at a distance of 25 metres. He also noticed that
dark red animals (like Muriccea placornus) looked quite black,
while the green and green-blue algse appeared lighter in colour.
This is explained by the fact that the red light disappears much
sooner than the blue. A coloured object will always look black
when untouched by rays of its own colour. As the white sun-
light contains all colours, objects display in it their proper tint,
PHYSICAL OCEANOGRAPHY 253
but when the red rays, for instance, are cut off, a piece of red
paper will look black.
The usual method of studying the transparency of the water Transparency
is to lower a large white disc, noting the depth at which it of^ea-water.
disappears from view. The degree of transparency is found
to vary greatly, for in the clear dark-blue water in the middle
of the ocean near the tropics the white disc can sometimes
be seen as far down as 50 metres below the surface, or even
more, while in those places where rivers bring down large
quantities of detritus from the land the disc may occasionally be
invisible a couple of metres beneath the surface. The enormous
quantities of small plankton organisms inhabiting the upper
layers may also render the water relatively opaque. The
penetration of light thus varies according to circumstances, but
few direct observations of the light-intensity have as yet been
made. It would be of the greatest interest to know the amount
of light at different depths in different seas, and thereby gain a
better understanding of the conditions of life, for instance, as
regards the development of the plankton, as the small plankton
algae need light for the processes of assimilation.
Sea-water normally contains oxygen, nitrogen (with argon). Gases in the
and carbonic acid. These gases are absorbed at the surface ^^^•
from the atmosphere, and are carried by currents even into the
deepest parts of the ocean in varying amounts. A study of these
variations is of considerable interest, and may be briefly dealt
with here, although no gas-analyses were made during the
"Michael Sars " Atlantic Expedition. There are several good
methods of analysis. For the three gases named, the method
introduced by Bunsen, and further developed by Pettersson and
Fox, may be employed, the water-sample being boiled at a low
pressure, and the escaping gas collected and analysed. The
oxygen may be determined by a very simple titration, according
to Winkler's method, or Krogh's method of examining the
tension of the several gases in solution may be applied.
Oxygen is not so readily soluble in salt water as in fresh ; Oxygen.
the higher the salinity the less the absorption of oxygen by the
water. It is also a well-known fact that cold water dissolves
more air than warm. This is clearly seen in the following
excerpt from Fox's tables, showing the cubic centimetres of
oxygen in i litre of water at different temperatures and sali
when the water is saturated with this gas : — /C^\
254
DEPTHS OF THE OCEAN
Temperature.
Salinity.
0 per thousand.
20 per thousand.
35 per thousand.
0. in c.c. per litre.
0. in c.c. per litre.
0. in c.c. per litre.
o°C.
10.29
9.01
8.03
10° c.
8.02
7.10
6.40
20° c.
6.57
5.88
5-35
30° c.
5-57
4.96
4-5°
At 30° C. a litre of water which is saturated with oxygen
contains little more than half as much as at 0° C. There is
therefore normally more oxygen in the cold water-masses of the
Arctic and Antarctic regions than in the warm water-masses of
the tropics. The salinity is not such an important factor in the
solubility of oxygen as the temperature.
Marine animals need oxygen for respiration, and therefore
consume some of that contained in the water. By the act of
respiration carbonic acid is produced and dissolved in the water.
The same thing goes on through the respiration of plants.
These are some of the principal oxygen-consuming processes.
But plants assimilate besides breathing ; that is to say, they
make use of the carbonic acid by dissociating it into oxygen
and carbon ; they employ the carbon for building up cells, while
the oxygen is again dissolved in the water. This is the chief
oxygen-producing process, but it is carried on only through the
influence of light-rays. It is doubtful what rays are the most
important for marine plant life, and in what quantity they are
necessary. Experiments have shown that many higher aquatic
plants assimilate much better in yellow light than in blue or
violet light ; this is the case with most adherent green algse,
and hence they are found in the upper water-layers near the
surface, where there is enough yellow light. The red alga^, on
the other hand, assimilate better in blue light than in yellow,
and therefore live in deeper water than the former. We know
nothing of the assimilation by the plankton-algae of the various
light-rays ; we only know that they need light, and that they
are found in the upper water-layers, but not in deep water.
The production of oxygen in the sea is thus limited to the
upper layers, while the consumption of oxygen takes place
wherever there are living organisms (excepting certain bacteria).
Now, supposing the processes of assimilation and of respiration
PHYSICAL OCEANOGRAPHY
255
balanced, the quantity of oxygen in the water is not altered
however many or-
ganisms are pre-
sent. But if there
is an excess of
animal life the
amount of oxygen
decreases (as it
always does in the
dark) ; if there is
an excess of plant
life the amount of
oxygen increases,
provided there is
light enough.
Knudsen a n d Knudsen and
Ostenfeld made o^t<^"f^>d's
?, \
>
I
f
^.
.£•
1
/
X
\
A
\
)\
i
-, \
VA "^^^
sv
1^ ^
^ /
\\\\-
^ /
\ \.
^ ^^
c;:^o3 ■f.-t^.
^ \
V
' ^
\\
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\ .
y ,
r: Q
O ^
experiments.
some expermients
g ;S to prove this.
3 S. They filled some
'^ S bottles with a
K I capacity of i litre
z § with sea-water, and
z J into one they put
t \ some living crus-
o ^ tacea (copepods).
0 o After three hours
§ ^ there was 3.88
^ I cubic centimetres
1 & less oxygen in this
S I bottle than in the
y I' others, while the
^ £ quantity of car-
l bonic acid had
" increased. They
'i filled two litre-
bottles with sea-
water, and intro-
duced equal quan-
tities of vegetable
plankton (dia-
toms), covering
one
of them with tin-foil so as to shut out the light.
After
256 DEPTHS OF THE OCEAN chap.
three hours it was found that the diatoms had consumed
2.34 cubic centi-
metres of the
oxygen in the dark '^•
bottle (the amount
of carbonic acid
being shghtly in-
creased), whereas
in the uncovered
bottle thequantity
of oxygen had
increased by i i.oo
c.c. (the amount of
carbonic acid
being decreased).
Brennecke has
compared the
results of a num-
ber of oxygen-de-
terminations from
the Atlantic
Ocean, and in
Figs. 173 and
174 his two sec-
tions showing the
vertical distribu-
tion of oxygen in
the Atlantic (from
the surface to a
depth of 1 500
metres) between
lat. 60° N. and 50
S. are reproduced.
The first section
shows the quan-
tity in cubic centi-
metres per litre.
A little north and
south of the equa-
tor the value is ^
only 1-2 c.c. per
litre in the water
between 200 metres and 600 or 700 metres ; on the equator,
PHYSICAL OCEANOGRAPHY 257
where the cold water from below comes comparatively near the
surface, it is a little more ; the highest value, over 6 c.c.
per litre, is found in high northern and southern latitudes.
The second section shows the deficiency from saturation in
cubic centimetres per litre at the temperature and salinity
ill situ. In the upper 50-100 metres the water is nearly
saturated all over the Atlantic, while in greater depths the
oxygen is deficient, especially in tropical waters^ at a depth
of about 500 metres in lat. 10" N. and S. the deficit amounts to
five or six cubic centimetres per litre. This is explained by the
abundant supply of oxygen in the surface-layers, through absorp-
tion from the atmosphere, and through assimilation by the rich
plant life, while the oxygen is being constantly consumed at
greater depths, where plant life is scarce and animal life in
excess. As a rule, where there is a great deficit of oxygen the
water is characterised as " stale," a long time having elapsed since
it was aerated at the surface or purified through the action of
plants.
The disappearance of the oxygen is not, however, due only
to the respiration of animals, but may also be caused by various
hydro-chemical processes. In the Black Sea oxygen is found
only in the upper 150-200 metres (about 100 fathoms) of water ;
below this it has disappeared totally, whereas sulphuretted
hydrogen is present in increasing quantities down towards the
bottom. The Black Sea is separated from the Mediterranean Black Sea.
by the Bosphorus ridge, so that the water in its deep basin lies
stagnant, unrenewed by the influx of other water. Similar con-
ditions prevail in several Norwegian " threshold fjords," or on a Norwegian
smaller scale in the oyster-" polls." In such places the bottom fj^JS^aSi
is thickly covered with organic matter ; a slimy black mud is oyster- ^
formed, swarming with bacteria that produce sulphuretted ^° ^'
hydrogen, which spreads through the water, combining with
the oxygen to form various sulphates. This causes the oxygen
to decrease and finally to disappear altogether, when the
sulphuretted hydrogen begins to appear free in solution. It
gradually spreads upwards, until the water is devoid of oxygen
and contains free sulphuretted hydrogen, at a depth of only
100 fathoms in the Black Sea, and in the oyster-basins in
autumn often at merely a couple of metres below the surface.
In summer the "bottom-water" of the oyster-" polls " lies
stagnant, but in the course of the autumn and winter it is
generally renewed by the supply of comparatively heavy water
from without ; then the sulphuretted hydrogen disappears and
258
DEPTHS OF THE OCEAN
the oxygen returns, producing thus an annual change in the
gaseous conditions of the deeper parts of the oyster-" polls.'*
In autumn the state of things may become critical for the oysters,
which are suspended in baskets at a depth of i-J-2 metres ; it
happens occasionally that the animals all die at this time by
suffocation through want of oxygen or by sulphur poisoning.
The water may, on the other hand, become over-saturated
with oxygen, as occurs sometimes in the Kattegat, or in spring
in some parts of the oyster-" polls," where plant life is particularly
luxuriant.
Carbonic acid. Carboiiic add occurs combined as carbonates and bicar-
bonates, and only in very small quantities as a free gas. The
quantity varies considerably, among other things because of the
activity of plants and animals, as above mentioned. Usually
there is about 50 c.c. of carbonic acid in i litre of sea-water,
but of this only a few tenths of a cubic centimetre is free gas in
solution.
Carbonic acid has probably been present from the formation
of the primitive ocean, together with the salts of the sea, but
the quantity varies from place to place and from time to time,
depending on the number of plants and animals, on the com-
position of the bottom, and more especially on atmospheric
conditions. At times considerable quantities of carbonic acid
gain access to the water through submarine volcanic activity,
but this has probably less influence on the variations than the
atmospheric conditions. August Krogh has made some very
valuable investigations on this point, and has arrived at the
conclusion that the sea is a sort of regulator for the amount of
carbonic acid in the atmosphere. When there is much carbonic
acid in the air, much will be absorbed by the sea ; this is the
case near land, and especially where there is a dense population
and extensive industrial activity, or near active volcanoes. The
tension of carbonic acid is everywhere small, but it is on the
average greater over the land than over the sea. Now, if the
tension in the air over a certain portion of the sea is smaller
than it is in the sea, the latter will give off carbonic acid to the
air. The sea thus has a regulating influence on the variations
in the carbonic acid of the atmosphere. Many important
questions arise with regard to these relations, but we cannot
enter into further detail here ; investigations on the subject
are few.
Nitrogen. NUrogeu is SO inert a gas that it is of little importance in
oceanography. It is absorbed from the atmosphere in con-
Krogh's
investigations.
PHYSICAL OCEANOGRAPHY 259
siderable quantities, i litre of water at a temperature of 10° C. and
with a salinity of 35 per thousand, for instance, containing when
saturated 12 c.c, of nitrogen. It is possible that marine bacteria
partly dissociate nitric compounds so as to liberate nitrogen,
and partly bind free nitrogen in various salts. These variations
are always small, and not easily demonstrable. As a rule,
though not without exception, the surface-water is saturated
with nitrogen from the air, and when the water leaves the
surface it carries down with it practically the same amount of
nitrogen.
A vessel running a certain course at a speed measured by Currents ii
the log often proves to have arrived at another point than that ^^^ ^^^'
which would be expected from the reckonings. This will be
the case when there is a strong wind, but even in a calm a dis-
placement is frequently experienced, which is then caused by a
current, and when the calculated position is compared with that
actually arrived at, the difference will indicate the effect of the
current on the ship. In sailing across the Gulf Stream off the*
east coast of North America, for instance, the ship is carried
north or north-east of its latitude according to the compass and
the log. The deviation is then an expression of the direction
and velocity of the current, and much information with regard
to the set of the currents has been obtained in this way. But
the method is not trustworthy when there is a wind acting on
the ship. The drift of various objects floating on the sea. Drift of
wreckage for example, has also been studied. When wreckage ^'^eckage.
belonging to the *' Jeanette," which foundered in the Arctic Sea,
was found in the North Atlantic, Nansen concluded that a
current must run from the polar basin between Greenland and
Spitzbergen into the Atlantic Ocean, and on this supposition
he planned the " Fram " Expedition. In the Atlantic Ocean
wrecks are often encountered drifting about with wind and
current. These are reported, and from such reports one can
follow the movements of wrecks for a long time. Fig. 175 shows
some such wreck-courses ; many of the wrecks have drifted
from North America towards Europe, thus showing the effect
of the Gulf Stream ; others have been carried eastward in the
direction of the Azores, then south, and finally west back towards
America again. But in these cases the wind always plays an
important part, so that it is difficult to form a correct idea of the
movements of the water. In the far north and far south we Floating
can follow the drift of the icebergs ; one, for instance, breaking ''^^^^''g^-
26o DEPTHS OF THE OCEAN chap.
loose far north on the west coast of Greenland would float
towards the south along the coasts of Labrador and Newfound-
land, and even farther south, thus proving the existence of the
Labrador Current. An iceberg lies deep in the water, a fraction
only of its bulk rising into the air, so that the wind will have
little influence on its motion, which will practically express the
aggregate effect of the currents through which the foot of the
iceberg stretches.
It has occurred more than once that vessels have been
locked up in the ice east of Greenland, and have been carried
Fig. 175. — Drift of Wreckage in the North Atlantic. (After Kriimmel.)
along with the drifting ice far towards the south. In the year
1777 a number of whalers were caught in the ice north of Jan
Mayen, and all their efforts to free themselves were in vain,
many of the ships being crushed, while most of the men
perished; when the last ship was lost it had drifted iioo
nautical miles in 107 days, or an average of 10 miles per day.
On the second German Arctic Expedition one of the ships, the
" Hansa," was locked up in the ice in lat. 74° 6' N. and long.
i6j^ W. on the 6th September 1869, and was carried southwards
until it was crushed on the 19th October. The crew took
refuge on an ice-floe, and drifted on till the 7th May 1870,
when they were able to land in Greenland in lat. 61° 12' N.
PHYSICAL OCEANOGRAPHY 261
They had been carried 1080 nautical miles in 246 days, that is,
4,4 miles per day on an average.
Information about the currents is also obtained from objects
found drifting along with them. At Lofoten golf-balls have
been found which must have come across from Scotland. In
the Norwegian Sea drift-wood from Siberia is occasionally met
with ; once we came across the trunk of a Siberian tree thickly
covered with littoral diatoms, which had thus travelled right
through the polar sea, so that the log had come from the
northern coast of Asia with the same current that carried the
" Fram " through the northern waters.
In order to study the currents, drift-bottles have often been Drift-bottles.
employed, in which are enclosed slips of paper with directions
to the finder to send the note to the address given, with ■
information about when and where it was found. Fig. 176
shows the results of some of the bottle-experiments made in the Fulton's
North Sea by Fulton, who has in this way been able to give a ^"-p^"'"^" ^•
more complete account of the currents of the North Sea than
was previously possible. In this case the method gave quite
trustworthy results, because there were shores all round where
it was comparatively easy to recover the bottles within a short
time. As regards the great oceans, the method often gives
rather doubtful results. In the first place, one cannot know the
route followed by the bottle from the time it was thrown over-
board till the time it was found, and then it may lie for years
on the shore before it is found, so that no one can tell how long
it has been on its journey.
These methods give a certain amount of information about
the motion of the superficial layers, but none about the deeper
currents. We can also study the set of the water-masses
by means of their physical or chemical qualities, especially
temperature and salinity and gaseous contents. It is, for
instance, known that the Gulf Stream carries much salt water
(with a salinity above 35 per thousand) from the Atlantic into the
Norwegian Sea, and the course of this salt water can be traced
farther north ; it forms a band along the coast of Norway, and
branches off in several places. The position of this salt water
indicates the course of the current itself, not at the surface only,
but also in the deeper layers.
From a study of the distribution of salinity and temperature
the average direction of the drift of the water-masses may be
deduced, and an idea of the velocity obtained by calculation, ^j^j^,^
Mohn, and more recently especially Bjerknes, have greatly Bjerknes.
262 DEPTHS OF THE OCEAN chap.
aided oceanographical work by giving the mathematical basis
Fig. 176. — Results of Dr. Fulton's Drift-Bottle Experiments in the North Sea.
for these investigations. This method, however, is indirect,
and is in many cases insufficient for obtaining an exact know-
PHYSICAL OCEANOGRAPHY 263
ledge of the motions of the sea, for which purpose direct
current-measurements are necessary.
Measuring the currents at different depths in the sea is
much more difficult than might appear at first sight, and re-
Ekman's Current-Meter.
quires good apparatus. Many excellent current-meters have
been constructed, the one made use of during the cruises of
the " Michael Sars " being that invented by V. W. Ekman, Ekman's
represented in Fig. 177. The apparatus consists ot a double
wing (A), that points in the direction of the current. In front
current- meter.
264 DEPTHS OF THE OCEAN
is a propeller which is moved by the current, the velocity-
determining the number of revolutions in a certain period.
The propeller works some small cog-wheels connected with
hands showing on a dial the number of revolutions. The
mechanism for indicating the direction of the current is very
ingenious. Some small shot are inserted into a tube leading
to one of the cog-wheels, which is provided with notches each
holding one little ball. The balls are carried round by the
wheel, and after half a revolution are discharged through
another tube into the centre of a metal box, in which is poised
a magnetic needle with a groove along the top of one branch.
As the shot fall, they roll along the needle and drop off its point
into the box. Their path may be traced in the figure. The
bottom of the box is divided into thirty-six small partitions, and
the balls fall into one or other of these according to the position
of the needle. The position of a ball in the box thus indicates
the angle between the axis of the apparatus and the magnetic
meridian, that is, the direction of the current. When the
apparatus is lowered into the water, the propeller is set and
fixed, and is subsequently released by a small messenger so
as to spin with the current ; when desired, a larger messenger
is sent down to arrest the propeller before hauling up. With
this current-meter a great number of observations have now
been made, many of which have given very important results.
In order to obtain good results it is necessary that the
apparatus should hang practically still, without being carried
along by the ship or the water, or — if this be unavoidable —
that the drift should be perfectly well known. The boat
from which the work is done must be very firmly anchored.
In the Norwegian investigations we have, as a rule, worked
from a small boat with anchors fore and aft, and it was possible
in this way to hold the boat, even when more than 500 metres
over the bottom, the most exact bearings showing that the
boat did not drift sufficiently to influence the current-meter ;
one anchor alone is usually not sufficient, for the boat may
swing, thus affecting the apparatus. When measuring the
currents in the Straits of Gibraltar, we tried double staying
with the life-boat, using a strong hemp line about one inch in
circumference, but the current was so strong that the line broke
again and again, and we had to give it up. When the current
(or the wind) is very strong, good results may be obtained by
means of a single anchor forward, so we dropped one of the
large anchors of the "Michael Sars," and the steamer lay so
PHYSICAL OCEANOGRAPHY 265
still that we could work with the current-meters from deck, but
the strain on the wire was enormous. Double staying is much
too difficult at great depths, although a single line may some-
times do. At Station 58, south of the Azores, we had the
trawl out in about 900 metres of water, when it caught on
something and stuck fast on the bottom, holding the ship
practically still (the compass was carefully observed the whole
time) ; we improved the occasion by making a series of current-
observations, and the results, which will be discussed farther
on, prove the drift or the swing to have been insignificant, so
that the observations are fairly reliable.
In the deep ocean, where current-measurements would be
of special interest, it is impossible to anchor the ship on the
bottom, but the drift of the vessel may, when exactly known,
be allowed for, and measurements may be made at any depth.
We tried this two or three times. At Station 19, in the Medi-
terranean, all the nets and young-fish trawls were towed at the
same time. The speed of the vessel then just balanced the
surface current ; the motion appeared to be quite steady, and
some observations were made at different depths to determine
the deeper currents in comparison with the surface current.
Again, at Station 49 C, west of the Canaries, we employed the Current-
large bag-net (3 metres in diameter) with the wire as a drift- "o?he w^st^of
anchor. The net was lowered to a depth of 1000 metres and the Canaries,
held there for many hours ; the drift of the vessel was fairly
steady, and the compass showed the swing to be trifling. The
depth of water was about 5000 metres, and measurements were
made at different depths down to 1830 metres (1000 fathoms)
with two Ekman current-meters, the results being indicated
in Fig. 178. It may be interesting to see how an attempt at
determining the currents above so great a depth turned out.
The cardinal points of the compass are shown by dotted
crosses, and arrows are used to indicate the velocity and
direction according to the current- meters sent to different
depths, a broken line for 915 metres (500 fathoms) and 1830
metres (1000 fathoms), and a thin line for 10 metres. Now,
we know nothing directly about the currents in deep water in
the open ocean between 500 and 1000 fathoms, but we must sup-
pose the movements to be comparatively insignificant when the
depth to the bottom is very great, say more than 2000 fathoms.
Supposing there were no current at these depths, the apparatus
would act as a log, showing the velocity and direction of the
drift of the vessel. Granting this to have been the case, the
266
DEPTHS OF THE OCEAN
lo-metre arrow will represent the resultant of the two com-
ponents : the actual current at lo metres and the actual motion
IOtti
915 772y
10171 z.^izi.'^.o^ani
Fig. 178.— Current-Measurements at Station 49 C (ist-2nd June 1910).
of the ship, as indicated by the deep-water measurements.
The actual current at 10 metres is then easily determined ; it
PHYSICAL OCEANOGRAPHY 267
is here indicated by the thick arrows. Two measurements
were made at 1830 metres (Nos. I. and IV. in the figure), and
two at 915 metres (Nos. II. and III.), and at the same time
observations were made at 10 metres with another apparatus.
The time by the watch is noted in the figure. The arrows
in V. show the currents thus found at 10 metres after allowing
for the assumed drift of the vessel, and it is seen that the
variations both in velocity and in direction are large. This
method is, however, uncertain so long as the currents in deep
water are unknown ; if these are considerable, the thick arrows
in Fig. 178, v.. do not give the actual currents at 10 metres,
but only the relation between these currents and those in deep
water. Still one thing is at least clear from the figure : the
thick arrows alter their direction regularly, and the change is
counter-clockwise. A continuous alteration of set is one of
the characteristics of tidal currents, and the conclusion is in all
probability admissible that our measurements at Station 49 C
prove the existence of tidal currents in the Atlantic Ocean,
even where it is very deep.
Tidal motion in the sea is due to the attraction exercised Tides and
by the sun and moon on the water-masses, which varies from ^'^^^ currents.
place to place. It would take us too far to enter into the
theories of the tides here, and besides, we have not yet a clear
solution of the problem, because, among other reasons, we have
no observations from the open sea, but only those from the
coasts. The rise and fall of the surface, known as tides, are
accompanied by currents, and the study of these currents in
the open sea would be of great importance for the comprehen-
sion of tidal phenomena. In the "Michael Sars " Expedition,
as mentioned above, we made a number of current-measure-
ments, the principal object being to find out if it were possible
to make trustworthy observations of the veldcity and direction
of tidal currents in the ocean. This has not been done
before in deep water. Buchanan in 1883 made some interest- Buchanan.
ing measurements on the Dacia Bank, off the west coast of
Morocco, and found marked tidal currents during the couple
of hours the observations lasted. Afterwards R. N. Wolfenden Woifenden.
discovered tidal currents on the Gettysburg Bank. Beyond
these and a few other observations, we have no observations
from the open ocean far from land and none at all in deep water.
We usually figure to ourselves the attraction of the moon Tidal waves,
and the sun producing a tidal wave which can develop freely
in the Southern Ocean, where a zone of water encircles the
268
earth
DEPTHS OF THE OCEAN
This wave has a very great length, with high - water
at the crest and low- water in the trough. Its form remains,
fettered by the moon, while the earth revolves beneath it.
Passing the opening between Africa and South America, it
gives rise to a lateral wave moving from south to north through
the Atlantic. This tide-wave reaches the coasts of northern
Fig. 179. — The Currents on the Ling Bank in the North Sea (7th-8th August 1906).
Europe, producing tidal effects there. But besides this wave
coming from the Southern Ocean there is formed an Atlantic
tide-wave following the movement of the sun and moon from
east to west. As already remarked, these things are somewhat
enigmatical, but as there is a connection between tidal waves
and tidal currents, we may hope that careful current-observations
will contribute to the unravelling of these problems.
PHYSICAL OCEANOGRAPHY
269
In August 1906, a series of current-measurements was made c
by the "Michael Sars "
the Ling Bank in the North Sea,
Sea. Fig. 179 shows the
currents at depths of 2, 20,
and 75 metres (the depth of
water being 80 metres). In
the lower row the direction
j- and velocity of the current
^ are indicated by arrows for
^ every hour from 5 p.m. on the
? 7th August to 6 A.M. on the
? 8th August. It is seen how
I the water moved at the differ-
^ ent depths, varying in direc-
j tion and velocity ; in the
I course of twelve or thirteen
^ hours the direction of the
5 current had passed through
I all the points of the compass.
I In the top row all the arrows
5 are joined, thus forming a
^ line which shows roughly the
I motion of the water during
^ the period of thirteen hours.
I The course proved to be
'^ somewhat elliptic, the water
S returning very nearly, but
^ not quite, to its point of
J departure. This is a typical
^ case, for tidal currents are, as
]* a rule, characterised by this
g turning, the water arriving at
": its Starting-point again after
^ a period of about twelve and
a half hours. The displace-
ment in the course of this
time, as exhibited by the
current-lines, is attributable
to a general motion of the
water, towards the east at
2 metres, north-east at 20
metres, and north - north - east at 75 metres. But this
measurements
n the North
270
DEPTHS OF THE OCEAN
general motion is quite insignificant compared with the tidal
current.
In Fig. 180 we see some current-lines of a totally different
form, the results of a number of measurements made on
Storeggen, westward of Aalesund, on the 12th and 13th July
1906. A line is drawn for each of the following depths below
the surface: 2, 20, 50, 100, and 200 metres (the depth of water
being 260 metres). It is seen that the current on the whole
flowed in a north-easterly direction at all depths, but the
Stat 58
12 VI
to meters
1910
Fig. 181. — Result of Current-Measurements at io metres at Station 58,
SOUTH OF THE AZORES (i2th June 1910).
direction was not constant, as implied by the bends in the lines.
The variations of direction were due to the tides, but here the
tidal current was weak compared with the general motion of
the water-masses. In this place the coast-current of the upper
75 or 100 metres, and that portion of the Gulf Stream which
traversed the layers below, both ran towards the north-east ;
had there been no tide-motion on the bank, the lines would
probably have been straight, not sinuous.
The measurements at these two stations give an idea of the
movements of the water -masses in the sea, and show that
current-lines may have very different courses, largely determined
PHYSICAL OCEANOGRAPHY
271
by the relation between the tidal current and the general drift of
the water.
We have already mentioned that the observations made at
J ^einf25f.)
JT -^Sdmfioof)
jn: 732/72 f9^6?y^J
\i
7.1 2 ant,
'%.
0 iO 20 50
Fig. 182.— The Currents at different Depths at Station 58,
SOUTH OF the Azores (12th June 1910).
Station 49 C lead us to infer that tidal currents exist even in
the deep sea. Again, at Station 58, south of the Azores, we
made a number of current-measurements from the ship at
anchor throughout one complete tide-period. With one of the
measurements
to the south
of the Azores.
272 DEPTHS OF THE OCEAN
Current- current-metcrs we took regular observations at 10 metres, 70 in
all, from i a.m. till 2.45 p.m. on the 12th June. Fig. 181 shows
the variations at this depth, which recall the current-lines on the
Ling Bank. The tidal current predominated, attaining a maxi-
mum velocity of 38 cm. per second (0.7 knot per hour) ; there
was also a general drift of the water towards the south-east, with
a mean velocity of 8-9 cm. per second (0.2 knot per hour).
Simultaneously another apparatus was employed to determine
the current at different depths down to 732 metres (400 fathoms),
the depth of water exceeding 900 metres. Some of the results
are represented in Fig. 182, which shows the current at different
depths: I, at 46 metres (25 fathoms); H. at 183 metres (100
fathoms) ; and HI. at 732 metres (400 fathoms). At all depths
the velocity and direction varied constantly,^ the changes in
direction being clockwise, and it is notable that the direction
shifted about 180'' in the course of half a tide-period. In this case
there is no doubt that tidal currents prevailed throughout the
whole body of water from the surface to the bottom ; they were
unmistakable even at 732 metres ; at this depth a velocity of
more than 27 cm. per second (more than ^ knot. per hour) was
once measured, showing that the tide can make its influence felt
down to considerable depths. This is particularly the case
where a plateau or ridge obstructs the passage of the tidal
wave ; in such places the current near the bottom is probably
increased. This would explain the remarkable fact that on
many submarine slopes and ridges no fine mud is deposited,
because the strong current sweeps the bottom clean.
Another interesting result of these measurements is repre-
sented in Fig. 183, where the arrows show the currents at several
depths simultaneously: I. at 3.35 a.m., and II. at 7.12 a.m. on
the same date. We see that the currents set in different
directions at the different depths. In the upper layers the
direction shifted more and more to the right with increasing
depth, but from 100 fathoms (183 metres) down to the bottom
the direction was reversed. Thus the current at 500 metres ran
in the opposite direction to that of the upper layers, which again
approached that of the currents at the greatest depths. At a
certain moment the currents are, then, arranged in the fashion
of spiral staircases, the whole system turning in clockwise
direction from top to bottom.
These observations in the Atlantic give rise to many inter-
esting ideas about the currents in the sea, and show that there
PHYSICAL OCEANOGRAPHY
27:
is still much to be done in this line. But the fluctuations of the
ocean-currents are determined by more influences than tides,
for many other forms of motion supervene, rendering the whole
picture highly complicated. A careful analysis of the measure-
ments made on Storeggen in 1906, led to the conclusion that
there were certain regular variations which took the form of
3, 55a.77t.
JT 772 a.m.
Fig. 183. — The Currents as determined by simultaneous measurements
(3.35 A.M. AND 7.12 A.M.) at different DePTHS AT STATION 58.
pulsations in the current. When the effect of the tide was Puis
subtracted it appeared that the ordinary current at lo metres "^ ^^
ran for some time with considerable velocity (up to ^ metre
per second) ; then the velocity decreased during seven or eight
hours until it approached zero, increasing again during the next
seven to eight hours, and so on. The fluctuations had thus a
period of about fifteen hours, but we are as yet ignorant of the
particular cause, though it may be a usual phenomenon in the
T
274
DEPTHS OF THE OCEAN
Wind-
produced
currents.
Boundary-
waves.
sea. Supposing the coexistence of two different periodical
variations, one with a period of about twelve and a half hours,
the other with one of about fifteen hours, an infinite number of
variations would ensue, to which might be added the more
casual influence of the wind and other factors, causing among
other things incessant dislocations of the boundaries between the
different water-layers or currents.
The wind may produce a current, particularly in the surface
layers, thus altering the direction and velocity of the existing
current. We know very little, however, about the relation
between wind and current, through lack of detailed observations,
although the question is naturally of the first importance from
an oceanographical point of view, as well as from its bearings on
the conditions of everyday life. This is one of the principal tasks
for the oceanographer of the future ; such observations are
diflicult to make, no
doubt, but with modern
methods much can be
done.
A wind blowing over
the sea will carry the
surface water along with
it. In the open ocean
the current thus pro-
duced is generally somewhat deflected from the direction of the
wind itself. During the drift of the " Fram " over the North
Polar Sea, Nansen found that the ship, as a rule, was carried to
the right of the wind's course. V. W. Ekman has studied the
question theoretically, arriving at the conclusion that such a deflec-
tion is a result of the earth's rotation. Later, Forch, by extracting
the records from a number of ships' journals, found the same
deflection to the right in the Mediterranean and in the North
Atlantic, while, as might be expected, there is a deviation to
the left in the southern hemisphere. Now, as the surface-water
is carried along by the wind, the deeper layer will approach the
surface at the place of origin of the wind-current. In Fig. 184,
which represents one of Sandstrom's experiments, we see how
the wind may raise the boundary between the upper and lower
water-layers. When the wind ceases this rise again subsides,
producing a boundary-wave which will proceed farther. A wave
like this may attain a considerable height, without being
perceptible at the surface ; its dimensions will depend on the
distribution of density. A boundary-wave in the Norwegian
Fig. 184.— Sandstrom's Experiment for producing
A Submarine Wave by a gust of wind.
water.
PHYSICAL OCEANOGRAPHY 275
Sea 100 metres in height would manifest itself as a surface-
wave about 5 cm. high, that is, practically imperceptible, as the
wave is very long and proceeds slowly. Several of the
"Michael Sars " investigations indicate such boundary-waves,
but here also precise observations are lacking. They are, "Dead
however, known in one particular form, viz. as the boundary-
wave producing "dead water." When a comparatively fresh
and light water-layer, 2 or 3 metres thick, rests on a salt
and heavy layer, a passing ship may give rise to a boundary-
wave between the two layers. This wave may stop the ship,
so that it lies in dead water hardly able to move at all. Ekman,
who has investigated these phenomena, has demonstrated the
dead-water wave by the following experiment (see Fig. 185).
He put salt water, coloured dark, into a long basin, and on the
top he poured a thinner layer of fresh water ; when he slowly
towed a small model of a ship through the upper layer, a
Fig. 185.— Ekman's Experiment to show the wave producing Dead-water.
boundary-wave arose, as seen in the figure, which, when strongly
developed, checked the speed considerably.
Naturally when a wave like this passes a certain spot on the
sea, the undulating boundary between the two water-layers will
at one moment be vertically nearer to that spot, at another
moment farther down. Similar vertical oscillations may
arise in other ways, as we shall now briefly indicate before
describing some observations made during the cruises of the
" Michael Sars," which prove that such undulations do exist
in the sea.
We may first mention one of the effects of the rotation of Effect of the
the earth. By reason of the earth's rotation a body moving rotation
freely in the northern hemisphere in any direction will
be deflected to the right, and with great velocities this de-
flection is quite considerable. There are many examples of
it : a swinging pendulum constantly turns ; the wind does not
blow straight towards a cyclonic area, but in a spiral direction,
bending to the right in the northern, and to the left in the
southern, hemisphere ; the effect of the earth's rotation is also
276
DEPTHS OF THE OCEAN
seen in the direction of the trade-winds, monsoons, etc. The
rivers of Siberia flowing northwards to the Polar Sea, eat into
their eastern beaches as an effect of the rotation of the earth.
It is the same influence which directs the course of the great
ocean-currents. In the North Atlantic the warm currents from
the south bend in general to the right, that is to the east, and
the cold currents from the north likewise bend to the right, that
is to the west ; thus the Gulf Stream flows across to Europe,
and the polar currents to Greenland and Labrador. Let us
now suppose that we take observations at a couple of stations
right across a current. This may be represented roughly by a
vertical section, as in Fig. 186 ; we must here imagine that the
motion takes place in the direction from the eye through the
paper, that the motion is swiftest at the top, and that we are in
the northern hemisphere. The rotation imparts to the water
A ^ 3 A _^ B
'^ — "^^r
--^ t
M
Fig. 186.
(represented by the horizontal arrows) the water-layers
acquire a slanting position, determined by the difference of
velocity and density in the different layers.
mass a tendency to
move to the right ;
J there will be a pressure
in that direction (indi-
cated by the arrows),
forcing the layers down
at Station B, raising
them nearer to the
surface at Station A.
By reason of the deflecting influence of the earth's rotation "FU.'c rr\\Te'c tVio K/->iir>.-1
i^^r^^^^^^tc^A K„ ^^r.^ i,„,-w„„toi ovK,^,.,e\ ti.a ,.,oto,- io„^.-c ^ ^ib ^ives loe UOUnQ"
ary-layers a slanting
position, as shown by
the broken lines, the incline being slight if the surface-
current is slow (I.), and strong if the current is rapid
(II.). Consequently the light water will go deep at B, the
station situated to the right in the current, while at Station A,
on the left, the heavy water from below will come nearer to the
surface. Wherever there is a strong current in the upper
water-layers the following rule will apply in the northern
hemisphere : on the right-hand side the water is comparatively
light, on the left-hand side comparatively heavy ; the conditions
are reversed in the southern hemisphere. There are many
examples illustrating this. Off the west coast of Norway the
current runs north, and the water to the right, near the coast, is
light, while that to the left, in the middle of the Norwegian
Sea, is heavy. In the Gulf Stream off the east coast of North
America the water is light (warm) on the right side of the
current, and cold (heavy) on the left. The southern hemisphere
PHYSICAL OCEANOGRAPHY
277
affords many other examples ; the distribution of temperature in
the remarkable Agulhas Current, for instance, is explained in
this way.
The Norwegian coast-current presents a good example of
the effect of the earth's rotation on the inclination of the water-
zoo .
/S03
MAY.22-25.
Fig. 187.— The Sognefjord Section in May 1903.
(Fig. 165 shows the same section in May 1904.)
layers. Fig. 187 shows the conditions in May 1903 along a
section through the Norwegian Sea from the mouth of the
Sognefjord to the west ; on the right, close to the land, the
coast- water attains a depth of about 100 metres. By heating
in the course of spring and summer this water becomes lighter
Om.
zoo :
Fig. I
The Sognefjord Section in August 1903.
and acquires a greater tendency to spread over the surface.
This tendency counteracts the deflecting force of the earth's
rotation, and finally causes the surface-layers to extend towards
the west, becoming less thick in proportion. Fig. 188 shows the
conditions along the same section in August 1903, when we
repeated the investigations. The coast- water now lay much
farther from the land than in May, reaching only to a depth of
278
DEPTHS OF THE OCEAN
60 metres near the coast, the water naturally having become
lighter and its tendency to spread westwards having overcome
the effect of rotation acting eastwards. When the coast-water
is cooled down in autumn it becomes heavier again, is not then
so much lighter than the Atlantic water, and has consequently
not such a great tendency to spread westwards over the surface
as in summer ; it is then forced towards the land (to the right)
again by the rotation of the earth. Thus there are in the
course of the year periodic lateral movements of the coast- water,
which are of importance, for instance, in their effect on the
distribution of the young fish.
The water-layers, then, slant differently according to the
strength of the surface-current and the vertical distribution of
density. Supposing the surface-current to run sometimes fast
and sometimes slow, the layers will respectively be lowered or
raised. Again, regarding Fig. 186, the layers that in I. are
comparatively deep at Station A, by an increase of the surface-
current (as in II.) will rise considerably higher. Thus vertical
oscillations are set up as a consequence of the fluctuations of
the current ; at a certain fixed point the movement will be like
that of a submarine wave. Such vertical oscillations may be
imagined to arise in other ways. It is, for instance, highly
probable that there exist in the sea standing waves with one or
more nodes, similar to the undulations of a violin string. Forel,
Chrystal, and others have found these standing waves in
lakes, the Japanese have shown them to be present in their
seas, and we have several indications of their existence in the
Norwegian Sea.
We cannot dwell any longer upon this question, but will
now examine some observations made during the "Michael
Sars " Expedition, which show marked vertical oscillations of
one kind or another. We made a number of careful measure-
ments in the course of twenty-four hours at Station 115, in the
eastern part of the Faroe-Shetland Channel, near the slope west
of Shetland, in 570 metres of water. Here we anchored a buoy,
near which the steamer kept as long as the observations lasted.
We made continuous observations of temperature and salinity
at the same depths, and were thus able to see whether or not
the conditions at a certain depth varied. At the same time
similar measurements were made by the Scottish research
steamer, the "Gold-Seeker," on the Faroe side of the channel.
By these simultaneous investigations we hoped to determine
PHYSICAL OCEANOGRAPHY
2/9
whether the variations were due to a progressive wave, or to
fluctuations in the current, or to standing waves. The results
have not yet been worked out, so we can only discuss some of the
" Michael Sars " observations. Unfortunately it was impossible
to make direct current-measurements, as the weather was too
rough.
During the twenty-four hours we made 86 observations at
the buoy, care being taken that the line was absolutely vertical.
Surface-observations apart, most of the measurements were made
at a depth of 300 metres (19 observations). The temperatures
found at this depth are noted in Fig. 189 along the vertical scale,
while the hours are put down along the horizontal scale. There
were considerable variations : on the 13th August at 5.8 p.m the
temperature was 5.60° C, and on the 14th August at 12.25 a.m.
l3 Vllt /9/0
\
\
/■
/
1
\
^•
^
/
\
\
-
/
V,
"
^
*\
^-
/
^
Fig. 189. — Temperature Variations at 300 metres at Station 115
(13th- 14th August 1910).
it was 4.73" C. — a difference of 0.87° C. When the mean
temperatures of the different water- layers are calculated and
represented in curves, it is easy to see how much the tempera-
ture altered for each metre of depth. At about 300 metres the
temperature decreased with increase of depth to such an extent
that a difference in temperature of 0.87° C. corresponded to a
difference in depth of about 35 metres. In the other layers
there were similar variations, indicating vertical oscillations of
between 15 and 35 metres. These observations go far to prove
the presence of such undulations of the water-layers, which is
indicated also by the form of the curve in the figure, among
other things. But these variations are not comprised in one
single period, as if they were due to an ordinary progressive
wave, or an ordinary standing wave alone. The shape of the
curve points to complicated fluctuations of the velocity as the
cause of the variations, but it is possible, nay probable, that we
28o DEPTHS OF THE OCEAN
are here confronted with an inter-play of several different factors.
It is, by the way, worthy of notice that there is an interval of
twelve or thirteen hours between the two principal maxima of
temperature ; this agrees with the tide-period, and we know that
the velocity of the current varies with the tide.
In previous investigations in the Norwegian Sea we have
several times encountered variations which are most naturally
explained by supposing that there are great undulatory move-
ments of the water-layers, and the investigations just described
strongly corroborate this supposition. The problem is one of
the greatest importance, and its solution will, in more ways than
one, lead to a fuller comprehension of the science of the sea, in
the first place with regard to the dynamics of the water-masses,
and in the second place with regard to certain biological
questions. The discontinuity-layer is often a boundary between
two different worlds of living organisms, and it is a point of
interest for the study of these to know if this boundary is
moving up and down, for this would probably imply that the
organisms themselves (possibly even shoals of fish) were also
being moved up and down. On the continental slope, just
below the edge, there live multitudes of marine animals, the
warm water having one characteristic fauna, and the deeper
cold water another. Now, if the fairly definite boundary
between the two water-masses swings up and down, one must
expect that there is a comparatively broad transitional region,
where the particularly hardy individuals of either of these
characteristic domains would live together. Where the change
of temperature is slow and regular the effect upon the organisms
would be of little importance ; not so, however, where there is
a marked discontinuity-layer, as for instance in the Norwegian
Sea. The proof that there are such oscillations would also be
of very great importance for our methods of studying the sea.
Let us look, for example, at Fig. 190, showing a section from
Shetland to the Faroe Islands, taken during the " Michael
Sars" Expedition on the loth and nth of August. The
positions of the stations are shown in Fig. 104, p. 122.
Isotherms are drawn at intervals of two degrees Centigrade ;
single hatching indicates salinities between 35.00 and 35.25 per
thousand, and cross-hatching salinities above 35.25 per thousand ;
in the deep layers the salinity was below 35 per thousand.
The lines both for temperature and salinity are strikingly wave-
like in the intermediate water-layers. The saltest water has
come from the Atlantic in the south, and the cold deep water
PHYSICAL OCEANOGRAPHY 281
from the Norwegian Sea ; the boundary between these layers
hes deeper at Station 106 than at the neighbouring stations, the
difference of level amounting to 200 metres. In order to get
as true a picture of the conditions as possible the stations were
placed at short intervals of only 20 nautical miles ; there may
be great differences within 20 miles, as from Station 105 to
Station 106, and fewer stations at longer intervals might have
given a totally false representation. Knowing the distribution
of salinity and temperature, we may now draw conclusions as
'06 /05 /04 /03
200
300
400
500
Fig. 190.— The Southern Section in the Faroe-Shetland Channel
(loth-iith August 19 10).
to the nature of the currents, their direction, breadth, and depth.
Our section has a rather irregular look, suggesting complicated
conditions ; it seems, for instance, as if the Gulf Stream were
divided into two branches, one close to Shetland, and one in
the middle of the channel. In the present case the variations
from one station to another are probably in part caused by
the vertical oscillations mentioned, but they are evidently in
part due also to another important phenomenon, viz. vortex
movements.
One of the objects of our joint-research with the Scottish Vortex
investigators in the Faroe-Shetland Channel was to throw light '"ovements.
282
DEPTHS OF THE OCEAN
on possible vortex movements. Four parallel sections were
made, the two in the middle by the " Michael Sars," the
southerly one being represented in Fig. 190, and the northerly
one in Fig. 191. In the map of the stations (Fig. 104, p. 122) the
position of the sections is seen, the distance between them being
20 to 25 nautical miles. Although the sections were so close
together they differed greatly. In the northern section the
lines are fairly regular; high salinities of more than 35.25 per
thousand are found only in the neighbourhood of Shetland, not in
^00
600
600
Fig. 191
-The Northern Section in the Faroe-Shetland Channel
(nth- 14th August 1910).
the middle of the channel. Vertical oscillations may have had
great influence on the appearance of the section. The two
sections might not have presented such great differences if the
observations had been taken at other times, but in any case they
point to other irregularities, in the first place to vortices with
vertical axes, similar to those known in rivers, only very much
larger. These vortices have rendered the motion of the water
highly complicated. The "Atlantic water" has moved towards
the north, having a breadth of 50 or 60 miles in the neighbourhood
of Shetland; between Stations 105 and 106 the water of the
upper layers has probably moved southwards, between Stations
106 and 107 to the north, and so on. Previous investigations
PHYSICAL OCEANOGRAPHY
28-
have shown that there are great vortices in several places in the
Norwegian Sea. Fig. 192 shows the distribution of salinity at
a depth of 100 metres in the southern part of the Norwegian
Sea and the northern part of the Atlantic in May 1904. The
arrows mark the probable direction of the movements. There
are several vortices of different dimensions, one being drawn in
Pio. 192. — The DioTribltion of Salimiy in the ^ORrHERN part of the Atlantic
Ocean and the southern part of the Norwegian Sea at a depth of ioo
METRES (May 1904).
the Faroe-Shetland Channel ; similar conditions prevailed in
this place in August 19 10.
Nansen and the writer have discussed^ at some length the Currents and
oceanographical conditions of the Norwegian Sea on the basis J,°onvegkV^'^
of earlier investigations. Fig. 193 shows the currents and Sea.
vortices in the Norwegian Sea. We arrived at the conclusion
that there must be many forms of motion of great and far-
reaching importance, though hitherto hardly known at all,
^ The Norwegian Sea, Bergen, 1909.
284
DEPTHS OF THE OCEAN
among them vertical oscillations of the water-layers and vortex
movements. Many things go to prove that these are phenomena
of general occurrence. We must picture to ourselves great
^Ihi"
■^^'i©
v_>
.y
-, 11////
Fig. 193.— The Currents of the Norwegian Sea.
submarine waves moving through the water-masses, alterations
of depth in the layers according to changes in the velocity of
the currents, standing waves, and great vortices. We must
further conceive of constant fluctuations in the velocity, pardy
PHYSICAL OCEANOGRAPHY 285
also in the direction, of the great ocean currents, not only by
reason of the tides and as the effect of the wind, but also because
the currents are subject to a sort of pulsation, the nature and
origin of which are as yet unknown. There is an interplay of
many different forces, producing an extremely variegated picture ;
the sea in motion is a far more complex thing than has hitherto
been supposed. Physical oceanography is confronted with a
host of new problems, the solution of which will be a matter of
the highest interest. It was to attack a few of these general
problems that the physical and chemical investigations of the
"Michael Sars " Atlantic Expedition were undertaken.
We shall now consider the investigations made during the
" Michael Sars " Atlantic Expedition into the physical conditions
in the Straits of Gibraltar. At the current-measurement station current-
(Station 18) on the 29th and 30th April we obtained a series of "jj'^th^e StS^
observations from different depths throughout one complete tide- of Gibraltar.
period. Some of the results are represented in the accompany-
ing three figures. Fig. 194 shows the direction and velocity of
the movement at different depths on the 30th April : (i) at 10
metres (about 5 fathoms), (2) at 46 metres (25 fathoms), (3) at
91 metres (50 fathoms), (4) at 183 metres (100 fathoms), and
(5) at 274 metres (150 fathoms). The arrows are drawn in the
true directions ; the velocities are seen by the scale. The
current 10 metres below the surface (i) had a westerly set on the
30th April between 2 and 4 a.m., afterwards — until 4 p.m. at
least — running without interruption eastwards (between south-
east and north-east), that is into the Mediterranean. The
velocities were at times very considerable, being greatest about
9 A.M., when we measured velocities up to 118 cm. per second,
corresponding to 2.3 knots per hour ; velocities of about i metre
per second, or 2 knots per hour, were found during the whole
time from 7 to 1 1 a.m. Later in the day the current slowed
down ; at noon it was only 40 cm. per second (0.8 knot per
hour), increasing a little later; at 4.30 p.m. it was 70 cm. per
second (1.4 knot per hour) ; then the observations were broken
off, but it was ascertained that the velocity was decidedly on
the increase. The current thus ran into the Mediterranean
with no very fixed set, the uncertainty of direction being pardy
due to the formation of vortices on the sides of the strait.
Early in the morning the current set from the Mediterranean
into the Atlantic, as mentioned above ; the velocity at 2 a.m.
was 47 cm. per second (0.9 knot per hour), but it was then
286
DEPTHS OF THE OCEAN
Ji- s.
Fig. 194.— The Currents in the Straits of Gibraltar on the
30TH April 1910 at different depths.
1 at 10 metres, 2 at 46 metres, 3 at 91 metres, 4 at 183 metres, and 5 at 274 metres.
PHYSICAL OCEANOGRAPHY 287
decreasing. These periodic changes, between a strong current
running east and a much weaker one running west, are caused
by the tides, which are strong enough to reverse the current.
The tide-period being nearly twelve and a half hours, one might
expect the turning of the current about 2 in the afternoon ; at this
time it was, however, still setting east, though with comparatively
small velocity. It was thus only once in the day that the
current at 10 metres ran out of the Mediterranean; in other
words, there was a difference between the two tide-periods in the
same day. It is probably connected with the so-called "daily
difference " of the tide, well known in many places, which
manifests itself by each alternate high-water being conspicuously
greater than the intervening one. We must, however, bear in
mind that these results, of course, only apply to the particular day
on which the observations were made, and we must therefore
beware of drawing general conclusions until observations during
a longer period and at different times of the year are available.
On the preceding afternoon (29th April) we obtained from
the life-boat some measurements of the velocity of the current
at a depth of 5 metres. At 5,15 p.m. the velocity was 113 cm.
per second (2,2 knots per hour), and was then on the increase,
being more than 150 cm, per second (nearly 3 knots per hour)
at 6 P.M., and the current then set eastwards. This corresponds
to the increasing velocity eastwards at a depth of 10 metres half
a day and a whole day afterwards. Some observations in the
deeper strata were also made from the life-boat about 6 p.m. on
the 29th April, the velocity at 25 metres being 124 cm, per
second (2,4 knots per hour), and at 50 metres 138 cm. per
second {2.7 knots per hour) ; at both depths the current set in
a north-north-easterly direction. Unluckily the observations were
then interrupted for many hours by the breaking of the anchor-
cables, otherwise we should have had continuous observations
during two whole tide-periods.
On the 30th April we obtained some series of measurements
from the steamer down to the bottom in about 200 fathoms of
water. The current often ran so fast that the wire with the
apparatus was brought into a slanting position, and the first
messenger was not sent down for some minutes to allow time
for adjustment. This rendered the determination of depth
somewhat uncertain ; the depths quoted refer to the length of
wire out, and may sometimes exceed the actual depth, but it
was useless to apply corrections, as we did not know the lie of
the line in the water. Fig, 194, 2, shows the current at 46
288 DEPTHS OF THE OCEAN chap.
metres (25 fathoms) below the surface between 6 a.m. and 2.20
P.M. In the forenoon the current ran east in the same manner
as at a depth of 10 metres ; about 8 a.m. the velocity was more
than 90 cm. per second (1.8 knot per hour); about 11 a.m. it
was slackening considerably, and at 2.20 p.m. it was merely
9 cm. per second (0.2 knot per hour) ; the current then set to
the north. The variations in velocity correspond to those
found at 10 metres.
Similar results (Fig. 194, 3) were obtained at 91 metres (50
fathoms), where the current ran into the Mediterranean in the
forenoon with velocities attaining 105 cm. per second (2 knots
per hour) ; but between 2 and 3 p.m. it turned to the north-west,
that is, mainly towards the Atlantic and contrary to the current
at 10 metres.
Fig. 194, 4, shows the results obtained by sending down the
current-meter with 183 metres (100 fathoms) of wire. The
observations were made between 6.40 a.m. and 11.26 a.m., and
all this time the current ran out from the Mediterranean in the
direction opposite to that of the higher layers, the greatest
measured velocity being rather more than 40 cm. per second
(0.8 knot per hour). The transition from the current running
into the Mediterranean to that running out must have been
somewhere above 100 fathoms.
The observations with the apparatus out with 274 metres
(150 fathoms) of wire are particularly interesting (see Fig.
194, 5). They were made from 2.15 a.m. to 3.30 p.m., and
the current all that time ran west, from the Mediterranean into
the Atlantic. At 2.15 a.m. the enormous velocity of 227 cm.
per second (4.4 knots per hour) was observed ; at this time the
current at 10 metres had also a westerly set. Then the velocity
decreased ; at 8.49 a.m. — half a tide-period later — a velocity of
only 17.5 cm. per second (rather more than 0.3 knot per hour)
was measured ; at this time the current in the opposite direction
at 10 metres ran its fastest. Later on, the deep current
increased in velocity, running at 3.27 p.m. — after another half-
tide period — 83 cm. per second (1.6 knot per hour). There
was a similar difference between two successive tides at
274 metres and at 10 metres. These observations gave this
important result : that when the surface current ran fastest to
the east the under current setting west was at its slowest, and
vice versa.
At 12.22 P.M. one of the current-meters was sent down with
366 metres (200 fathoms) of wire, but after working for ten and a
PHYSICAL OCEANOGRAPHY 289
half minutes it was hauled up in a wrecked condition. The wings
were battered and bent, and the compass was gone ; it was
clear that the apparatus had been bumping against the stones
on the bottom. The propeller had made 280 revolutions,
implying a velocity of 1 1 cm. per second (0.2 knot per hour), so
that the water had moved along the bottom at that rate at
least, probably faster, as the propeller must have revolved too
slowly after being injured. This separate measurement gives
the interesting result that there may be an appreciable current
even along the bottom.
Now, in what relation do these currents stand to high and
low water ? The tide-tables show that at Cadiz and Algeciras
high water and low water on 30th April 19 10 occurred at the
followinp- hours :
High Water.
Low Water.
Cadiz
Algeciras .
4.51 A.M., 5.16 P.M.
5.15 A.M., 5.40 P.M.
11.04 A-J^I-
11.28 A.M.
In the straits high water may with sufficient accuracy be
referred to about 5 a.m., low water to a little after 11, and the
next high water to about 5.30 p.m. It follows that the water ran
fastest into the Mediterranean about four hours after high
water, i.e. at falling tide, and that it ran fastest out from the
Mediterranean three or four hours after low water, that is, with
a rising tide.
In Figs. 195 and 196 the current-conditions between the sur-
face and the bottom are shown, in the first for the 30th April at
9 A.M., when the current into the Mediterranean was running at
its maximum, and in the second the mean for the movements at
2 A.M. and at 3 p.m., when the current out of the Mediterranean
attained its greatest velocity. The velocities at the different
depths have been calculated with regard to the longitudinal
direction of the strait, the varying directions of the current
having been taken into account ; the actual velocities are shown
in Fig. 194. The two diagrams give a good picture of the
relation between the upper and the lower current in the middle
of the straits, the former about four hours after high water, the
latter three or four hours after low water. It is seen that the
boundary between the two currents lay at a depth of about 160
metres when the inflow into the Mediterranean was greatest, and
u
290 DEPTHS OF THE OCEAN chap.
that it approached the surface when the inflow was least,
wo
Fig. 195. — The Motions in the different layers in the Straits of Gibraltar
(calculated for the longitudinal axis of the straits) when the current
WAS SETTING INTO THE MEDITERRANEAN AT ITS STRONGEST (30th April I910).
SO
\
1 Z Z I
^__^
_ — — _ _
-
— — — —
1
^^^
Fig. 196. — The Currents along the longitudinal axis of the Straits of Gib-
raltar ON the 30TH of April 1910, when the current set strongly towards
the Atlantic.
moving 100-150 metres up or down in the course of half a
tide-period.
PHYSICAL OCEANOGRAPHY
2QI
Together with the current - measurements four series of Temperatures
water-samples and temperatures were taken
efiven in the following: table : —
the results are
ind salinities
in the Straits
of Gibraltar.
Depth.
Metres.
Station 18 A.
29 IV. 114 A.M. -
12^ P.M.
Station 18 B.
29 IV. 2-2i P.M.
Station 18 C.
29 IV. 11-12 P.M.
Station 18 D.
30 IV. 9i-ioi A.M.
Temp.
Salinity.
Temp.
Salinity.
Temp.
Salinity.
Temp.
Salinity.
o
17.0
36.12
16.6
36.14
16.6
36.02
17.4
36.17
25
15.16
36.19
14.89
15.6
16.18
50
13.29
37.80
13-35
15.09
36.20
15-39
100
12.92
38.30
12.92
38.33
14.38
36.28
14.09
200
12.91
38.39
13.II
37-97
12.94
38.36
300
12.87
38.39
12.89
38.39
Here also we see considerable variations from time to time
at the different depths, variations corresponding to a difference
2800
•28-50
2900
38-50%,
Fig. 197. — Temperature (broken line), Salinity (continuous line), and Density
(DOTTED line) AT STATION I9, IN THE MEDITERRANEAN (2nd May I910).
of level between the layers of 100-150 metres. On the 29th
April, about 2 p.m., the current running in must have been
feeble and that running out must have been strong, judging
from the later current-measurements, and the salt Mediterranean
under current extended up towards the surface, whereas on the
30th April, between 9.30 and 10.30 a.m., the upper current was
very strong and the undercurrent from the Mediterranean very
feeble in comparison, and the salt water from the Mediterranean
lay about 100 metres deeper. The vertical distribution of
salinity and temperature is seen to accord with the currents.
Two days after these observations in the Straits of
Observations
in the Medi-
terranean.
292 DEPTHS OF THE OCEAN chap.
Gibraltar, the "Michael Sars " entered the Mediterranean, and
took observations at Station 19, the hydrographical conditions
being shown in Fig. 197. The surface temperature varied from
1 6° to 1 7' C, and the salinity was nearly 36.4 per thousand. The
temperature decreased and the salinity increased downwards,
until we struck the Mediterranean deep water at a depth of
about 160 metres ; from this point downwards we found exactly
the same temperatures and salinities as in the undercurrent in
the straits. This was on the 2nd May, between 10 a.m. and
I P.M. ; the observations in the uppermost 300 metres were
made between 10.30 and 11. 30 a.m. Judging from the previous
measurements the in-
flow in the straits
should then be about
its strongest. Be-
tween 5 and 6 p.m.
some of the observa-
tions were repeated,
and the boundary be-
tween the surface-
layers and the deep
water then lay some-
what higher; it might
be a matter of 10 or
15 metres. The
under current setting
out of the straits was
then very strong and
the surface current
comparatively feeble.
So there were fluctua-
in the Mediterranean
the fluctuations in the
^^^^^i^H
■1
^^^^^^1
^^^^^^^^^^v
27. ^H
^^
^^^^m
19a^
m ""•' ^?.J^
'—v-^^i |k,
/' ^^ ' 20^Kk
^
29, •^'^^H
^^^^^^^
^^^^
^^^^^I^^^^H
^^^^^^^H
^^^^^^^^^^H
30^ ^^^k
^^H
.^^^^^^^^1
^^^^^H
^^H
J2^^^^^H|
^1
Fig. 198. — "Michael Sars" Stations in the Spanish
Bay between Spain and Morocco in May 1910.
The lines indicate the positions of the two sections represented
in the two following figures.
tions in the position of the boundary
eastward of the straits corresponding to
straits, only considerably smaller, because the current-velocities
naturally would be much smaller where the basin was broad.
A few days later a number of observations were taken in
the Spanish Bay westward of the straits. The positions of the
stations are indicated in Fig. 198, and the salinities and tempera-
tures are shown in the two sections: Fig. 199, in an east and
west direction, and Fig. 200, in a north and south direction. In
the east to west section the salt Mediterranean water with a
salinity exceeding '}y^ per thousand is seen stretching out through
the Straits of Gibraltar, its salinity, however, soon decreasing
PHYSICAL OCEANOGRAPHY
293
to little more than 36 per thousand. Agreat mixing process must
be going on here, as might be expected with the mighty sub-
marine current rolling its saline waters into the strata occupying
the Spanish Bay. By admixture with the somewhat colder and
considerably less saline water, the temperature is slightly, and
the salinity greatly, reduced ; thereby the density also decreases,
becoming lower than that of the deepest layers of the Atlantic
region, although higher than that of the surface layers. This
294
DEPTHS OF THE OCEAN
PHYSICAL OCEANOGRAPHY
295
({ id 60
5 d550
t
5tatLoa 17
0 2750
3600 3650%,
mixed water enters like a wedge between the other water-
masses at a depth of about 1000 metres, as clearly shown in the
two sections. In this part of the Atlantic Ocean the salinity
and temperature first decrease for some hundred metres below
the surface ; then both increase a little through the influence of
the outflow from the Mediterranean, below which they again Outflow of
decrease. The admixture of water from the Mediterranean can fj^ter^^jo"^^"
be widely traced over the eastern part of the North Atlantic, as the North
already pointed out by Buchanan and Buchan. It is also ^'^^"^^'^•
evident from our ob-
servations at a number
of stations, for instance
at Station 17, off the
coast of Portugal, as
shown in Fig. 201. In
the map showing the
physical conditions at
the depth of 500
fathoms (given in Fig.
202), we can trace it
by the comparatively
high salinities and
temperatures reaching
north towards Ireland
and west towards the
Azores. This ad -
mixture is far more in
evidence along the
coasts of Europe than
along those of Africa ;
this signifies a drift
towards the north,
which might be ex-
pected as an effect of the earth's rotation and the consequent
deflection to the right. It appears, however, that some of this
mixed water is carried far to the south-west by the great
currents running between Madeira and the Azores.
This wedge of mixed water from the Mediterranean is not
met with near the surface nor in the greater depths. Thus it
is not seen in the map (Fig. 203) showing the physical condi-
tions at a depth of 200 fathoms (366 metres). At this level the
saltest water (with a salinity above 36 per thousand) is found in the
south-western part of the North Atlantic (excluding the fresher
1000
1500
)° "
a gc go IQO ,10 1^, jy ,
If" 1
yc-
(
y
S
/■
1
\
\
1
1
\
\
y
1
;
;
/
/
f
y
J
^
\
^
'■^
Fig. 201.— Salinity, Temperature, and Density at
Station 17, west of Portugal (23rd April 1910).
296
DEPTHS OF THE OCEAN
American coast-water). Farther north the salinity decreases,
being a little more than 35.5 per thousand off the south-western
coasts of Europe, and between 35.0 and 35.5 per thousand farther
north off the British Isles towards the Faroe Islands and Iceland.
In the northern part of the ocean the saltest and warmest
water is found on the European side, the Gulf Stream making its
influence felt there, whereas the less salt and much colder water-
masses south of Greenland are derived from the polar currents.
PHYSICAL OCEANOGRAPHY
297
In this map (200 fathoms) the lines south and east of the
Newfoundland Banks have a peculiar form. The warm and
Alternating
currents off
Newfound-
land Bank.
ON
salt water-masses appear to be cleft in two by a colder wedge
from the north-east. This indicates a current towards the
south-west, forcing its way between the other water-masses
flowing in the opposite direction. Now, it is quite possible
298
DEPTHS OF THE OCEAN
that the Hnes in the map are wrongly drawn, because had
there been many more stations the Hnes might have formed a
number of vortices, Hke those mentioned above, p. 282. How-
ever that may be, it is a fact that we fell in with a current
running south-west, in the midst of the water-masses following
the direction of the Gulf Stream towards the north-east, and
this singular circumstance may be dealt with in greater
detail.
The section shown in Fig. 204 stretches from the Sargasso
Sea along: the track of the " Michael Sars " northwards to the
Newfoundland bank
Stal 72 71 70
3 7 2-3A 95
Fig. 204. — Section from the Sargasso Sea to the Newfoundland Bank.
Newfoundland Bank. At Stations 64 and 65 the conditions
were uniform, resembling those found during the cruise from
the Canaries westwards (see Fig. 63, p. 84). All this part of
the Atlantic in and about the Sargasso Sea belongs to an
oceanographically homogeneous region, but at Station 66 we
suddenly met with very different conditions, for it was much
colder in all the layers above the deep water, and the salinities
were much lower. On proceeding farther north we again
found, at Station 67, the same warm and salt water-masses
as farther south at Stations 64 and 65. There was a decided
difference also as regards the pelagic flora and fauna, which
had a more northern facies at Station 66 than at Stations
PHYSICAL OCEANOGRAPHY 299
65 and 67. Now, when we consider the position of the
water-layers and the effect of the earth's rotation, as treated
above (p. 276), we come to the following conclusion : the
current in the upper water-layers sets towards the north-east
between Stations 65 and 66, another current runs tow.ards the
south-west between Stations 66 and 67, then a current runs to
the north-east again towards Station 70.
As we were working at Station 67 on the afternoon of the
27th June, a gale arose, increasing in the course of the night
to a hurricane from the south-west, veering later on to the
west. There was a rough sea with choppy waves, as is usual
with the wind blowing against the current. We kept the
ship's head to the wind all night, and it was as much as we
could do under heavy steam pressure to stem the storm with-
out drifting off. Next morning the wind fell somewhat ; it was
fresh from the west when we occupied Station 68. When the
captain got an observation, it proved that we had been carried
southwards about fifty nautical miles from Station 67 to
Station 68. This agrees excellently with our conclusions from
the distribution of temperature and salinity, and it is established
beyond doubt that in this place there was a strong current
running towards the south-west. The west wind caused the
ship to drift more to the south than the course of the current.
Peake and Murray^ and Schott tell us that a current running
south-west has been met with before in the same region ; thus,
the cable - steamer " Podbielski," in May 1902, drifted 53
1 " The climate of the British Isles being influenced to such a large extent by the warm water ot
the Gulf Stream, the movements of this great body of water, the course of its main current, and
the manner in which this spreads itself over a very large portion of the North Atlantic, should
be a subject of special interest to the inhabitants of these islands. Among those who have not
carefully studied the observations that have been made on this subject, a general impression
obtains that after leaving the American coast the Gulf Stream consists of a body of warm water
moving steadily across the North Atlantic in the direction of the Irish coast. An increasing
number of observations tend more and more to show that this is not the case ; the movement of
this great mass of water is more probably somewhat in the form of bands of current which
curve and recurve on one another, forming swirls of large area whose strength and direction
change almost daily. A glance at the current charts shows how the Gulf Stream in its passage
across the Atlantic spreads itself out at the surface like a fan, and forms what is known as the
Gulf Stream drift.
" It will also be noticed that on the line of observation given herewith, an easterly current was
met with considerably farther to the westward than would have been expected from the
Admiralty current charts ; this, however, merely exemplifies the variations which occur in the
course of even the main body of the stream at the surface, the course as shown on the Admiralty
current charts being its average direction.
" In the appended list of observations the total ' sets ' are given, and these are again corrected
for the pressure of the wind and the force of the sea, leaving a ' set ' due to current only.
The correction for wind and sea is necessarily only an approximation, but the result approaches
more nearly to the current effect than would have been the case had no correction been
attempted. The direction of the current as observed between the Azores and North America
is shown on the accompanying map by arrows " (Peake and Murray, " On the Results of a Deep-
Sea Sounding Expedition in the North Atlantic during the Summer of 1899," extra publication of
the Roy. Geog. Soc. London, 1901, pp. 13-14).
.^oo
DEPTHS OF THE OCEAN
miles to the south-west in the course of twenty-four hours in
lat. 40' N. and long. 55' W. It would be interesting to know
whether these conditions are constant in this region, as it
might then be of importance for navigation, or whether there
may be certain irregularities, perhaps one or more progressing
vortices.
As a matter of fact, the general current was here split into
two branches. Whether it proceeds as two separate currents
or not is difficult to judge from our investigations, as we had
too few stations in the neighbourhood, and there are no
previous observations. Our section from Newfoundland to the
Bay of Biscay (Fig. 99, p. 115) has a suggestion of a similar
division at Station 85, but it is too
slight to base any conclusions upon.
It is, however, known that farther
south there occur " bands " of water
with comparatively low temperatures
in the surface - layers of the Gulf
Stream. But we are on many points
deficient in our knowledge of this most
important ocean current, among other
things also with regard to the yearly
variations to which it is subject.
/^K^
^ \
:. /I ^\ \\\ 1 1
' 1
L \ \
"r \^4
^ X
I ^ 2 t
v_ ^
.^^ t
V
\,
I t
^
3
I ~i
v_
• ^ i -
A
>^Ji -J
Fig. 205. — AlR-rEMPERATURE AT
THE Faroe Islands
G, when the wind blew from the
"Gulf Stream" region; and P,
when the wind blew from the East
Iceland Arctic-current resfion.
It is a well-known fact that the
climatic conditions of northern
Europe are influenced by that branch
of the Gulf Stream which flows north-
wards along the shores of the British
Isles into the Norwegian Sea. In places with such a maritime
climate as that of the Faroe Islands this influence is especially
felt. Martin Knudsen has examined some meteorological
observations from the Faroe Islands, and has found (see Fig.
205) a conspicuous difference between the temperature of the
air when the wind blew from the Gulf Stream region in the
south and west, and when it blew from the north, over the
Arctic East Iceland current. The difference was greatest in
winter (as much as 6V C.) and least in summer (smallest
difference ij" C). Pettersson at an early period entered on
the study of questions regarding oceanic influence on the
climate of Scandinavia, and his work on this subject has
been more conducive than anything else to the establishment
of the international investigations of North European waters.
PHYSICAL OCEANOGRAPHY 301
Figs. 206 and 207 show some of his results. At that time (in
the nineties) no systematic investigations of the Norwegian Sea
through any length of time had been carried on, so he could
only study the surface-temperatures noted at three Norwegian
lighthouses.
In Fig. 206 we see the variations in the surface-temperature
off the west coast of Norway (indicated by the thick line) and
in the air-temperature at Orebro in Sweden (indicated by the
thin line), both for January during the years 1874 to 1892. The
vertical scale indicates the deviation from the mean temperature,
which for the coast-water is 5.3° C. and for the air 3.4" C.
On the whole the curves agree well, a high temperature in the
74 7S 76 77 76 yjj 80 01 az ,yj {If 65 iih d7 6d dV 90 91 9^,
M
0
3°
\
/
1
'i°
\
/
\
J°
\
1
/
\
Z°
\
1/
/
^
/
\
\ ,
^
;
\
/
J
1
/
^
n\
/
/
^1
Ocean 5^'C
V
w
^
\\
/
r
\
^
Htmoiph.i ^
\
\
/i\
1
-r
"6°
\
\
Fig. 2o6.
The thick line shows the variations in January of the surface temperature off the west coast of Norway
from year to year ; the thin line the variations of the air-temperature at Orebro (Sweden).
surface-water corresponding to a high temperature in the air.
Pettersson further pointed out that a certain deviation from the
normal temperature of the air, as a rule, lasts for a length of
time ; a cold period, for instance, often lasts for weeks, or
even months. Now, there are many relations on the land
which are influenced by the deviations of the air-temperature
from the normal, among other things, the duration of the snow-
covering, the time of blossoming of many plants, the time for
beginning field-labour in spring. Pettersson found the varia-
tions in some of these particulars to agree with the variations
in the temperature of the air and of the surface-water off the
west coast of Norway some time before. Fig. 207 shows an
example of this agreement ; the lower curve gives the variations
302 DEPTHS OF THE OCEAN
in the temperature of the sea-surface off the Norwegian light-
houses for the month of February, while the upper curve shows
the variations of the date at which the coltsfoot {Ttissilago far-
fara) began to blossom in central Sweden (Upsala). This plant
begins to blossom, on the average, about the 9th April, the
exact date varying in different years from the i8th March to
the 28th April. The two curves agree in many points ; when
the water off the lighthouses was relatively warm in February
the flowering commenced early, and when it was cold the
blossoming was late.
Pettersson had at his disposal only observations from the
water in the immediate vicinity of these coast stations, but since
7^ 75 76 77 7a 79 SO 61 82 83 8H 85 86 87 68 89 90 9/ 92 93 9^ 95 96
^
13 -
9 —
30mrf5
zo —
6'
Fig. 207.
The upper curve shows the time of blossoming of Tz/ssi/ago /ar/ara at Upsala during a series of
years. The lower curve shows the surface-temperature of the sea off the west coast of Norway,
in the month of February of the same years.
regular investigations were started in the Norwegian Sea in
1 900, we have excellent series of observations during a succession
of years, not only in the coast-water, but also in that branch of
the Gulf Stream which flows into the Norwegian Sea. Nansen
and the writer have found, by going through all the observations
made in the years 1900 to 1905, that there are great variations
in the temperature-conditions of this Atlantic current, and that
these variations are apparently followed by corresponding
variations in many other conditions ; for example, the temper-
ature of the air, the year's harvest, the growth of the trees, and
various circumstances touching the appearance of great shoals
of fish. One or two instances may be referred to here.
During the Norwegian investigations a section was run
PHYSICAL OCEANOGRAPHY
303
from the mouth of the Sognefjord westwards, in the middle of
May, every year from 1901 to 1905. One of these series is
figured on p. 240. Nansen and the writer have calculated the
mean temperatures in the Atlantic water of this section, both
for the surface and for the deeper water. The variations in the
surface-temperature are represented in curve L, Fig. 208, curve
H. showing the variations in the growth of the pine in eastern
Norway during the following year. The low surface-temperature
in May 1902 corresponded to the small growth of the pine in
the succeeding year, 1903, and the high temperatures in the
surface of the Gulf Stream in May 1905 corresponded to a
great addition to the height of the pine trees in the year 1906.
This is explicable by the fact that the annual growth of the pine
is not determined by the meteorological conditions of the same
year, but by those of the year
before, when the bud was
formed, the growth mainly
depending on the formation
of the bud. Continued inves-
tigations will prove whether
the agreement strongly sug-
gested by the figure is really
a general rule, in which case
it may be possible, on the
basis of investigations in the
Norwegian Sea, to predict
with a high degree of probability how much the Norwegian pine
will grow in the following year.
By calculating the mean temperature of the Atlantic water-
masses below the surface in the Sognefjord section, and
multiplying the ascertained value by the area of the transverse
section of these water-masses, an expression is obtained for the
amount of heat in the northern branch of the " Gulf Stream."
This has been done from the observations made during the
May cruises, and the results are exhibited in curves I. and II. in
Fig. 209 ; the two curves are obtained by two different methods
of calculation which need not be discussed here. The lower
curve shows the variations in the mean temperature of the air
in Norway during the winter months from the ist November to
the 30th April. The coincidence is striking ; when, for instance,
the amount of heat in the Gulf Stream was great in the
month of May, the air-temperature in Norway was high in the
following winter. This holds good throughout six years,
X
1901
1902
t90i
190^
1905
JL 1902
/903
190^
J905
/906
'
a ■
\
V
J"^
-y
/'
7°-
v/
Fig. 208.
mean temperature of the surface of the ' ' Guh
Stream " in the Norwegian Sea (Sognefjord
section, May) ; II., mean growth of the pine
in eastern Norway.
304
DEPTHS OF THE OCEAN
but, of course, that is too short a period from which to draw
definite conclusions. Anyhow, these preHminary results point
to possibilities of no little importance, and we may in the future
be able to predict, months beforehand, whether the coming
winter will be warmer or colder than the normal. Many
similar relations could be pointed out between the conditions in
the sea and facts of interest bearing upon our daily life, but the
above examples give an indication of the problems to be faced
in modern oceanography.
The Atlantic current flowing northwards over the Norwegian
Sea, which in our waters
/SOO /so/ t902 /S03 /S04 /SOS . ' , >-> i r
IS also called the Gulf
Stream, is thus subject to
considerable variations in
temperature and total
amount of heat. This cur-
rent is, however, a mixture
of water from the Atlantic
proper with water from the
northern currents penetrat-
ing intothe Norwegian Sea,
north of the Faroe Islands,
and the character of the
" Gulf Stream " will de-
pend on the conditions of
mixture, and on the indi-
vidual temperature of each
of these currents, factors of
It
is highly probable that the
Gulf Stream of the Atlantic also shows annual variations,
and, though they may not be of much importance in their
effect on the small branch in the Norwegian Sea, they may
prove to be of great climatological significance for the
countries on both sides of the Atlantic Ocean ; a thorough
study of this current in the immediate future is therefore
looked forward to with great expectations. That there are
large annual variations in the caloric conditions of the huge
water-masses of the North Atlantic was suggested by the
observations of the "Challenger" nearly forty years ago, and
has been confirmed during the recent cruise of the " Michael
Sars," these two vessels having made investigations in the
Fig. 209.
I. and II. , the annual variations in the amount of
heat in the "Gulf Stream" (Sognefjord section,
May); III., variations in the air- temperature of which WC knOW little.
Norway (November to April).
PHYSICAL OCEANOGRAPHY
305
same oceanographical region. In July 19 10 observations were Comparison of
made bv the " Michael Sars" at Stations 60 to 6s in the vicinity " ^^^^l^,"^v." ','
r 1 ./j—-i 11 M r- • ^ r T o in. t i "^ ^"^^ "Michael
ot the " Challenger Station 65 ot June 1873. Now, the temper- Sars"
atures of the great depths beyond 1000 fathoms prove to be oSvSont
identical in these two years, showing that the thermometers
worked properly, but in the upper layers it was much colder in
1 9 10 than it was thirty-seven years before, the difference in
TEMPERATURE °C
0 ^*
€
8' 10'
12" 14- 16° 18° 20"
22°
100
fr^
^^
200
I J
300
^^y /
400
,
.4^ /
500
y^
^/"^
1
t 600
^^
5
1
'/
•CHALLENGER' -21 6.1873 36' 33 N. 47" 58 W.
700
/
1
/
x'MICHAEL sars' 25. 6. I9IO 37° Is'N 4a" 30'w.
eoo
/
/
900
/
1000
i
Fig. 210.— Comparison of the Temperatures taken by the "Challenger"
IN 1873 AND BY THE " MiCHAEL SaRS " IN I9IO.
some cases amounting to about 5' C. at a depth of 700-800
metres (400 fathoms). Fig. 210 shows the temperature-observa-
tions at the "Challenger" Station 65 and the "Michael Sars"
Station 65, between the surface and a depth of 1000 fathoms.
Observations were taken at the " Michael Sars" Station 51
in June 1910, in the vicinity of the "Challenger" Station 354
in May 1876. Fig. 211 shows the conditions at these two
stations, which varied only to a slight extent ; at certain depths
X
3o6
DEPTHS OF THE OCEAN
it was a little colder in 1876 than in 19 10, at other depths a
little warmer, but no general difference appears between the two
series of temperatures — one series taken thirty-four years after
the other. There have probably been many variations in the
course of these years of which we have no knowledge. In this
TEMPERATURE C
10' 12° 14"
'CHALLENGER 6.5. 1876 32° 41 N. 36 6' W
("MICHAEL SAR5' 6 6. 1910 3l' 20N 35°7'W
Fig. 211 — Comparison of the Temperatures taken by the "Challenger"
IN 1876 AND BY the " MICHAEL SaRS " IN I9IO.
and in many other respects the Atlantic Ocean calls for further
and more detailed investigation ; as we said at the beginning of
this chapter, very much more work will have to be done before
we shall be able to solve the many interesting and important
problems relating to the great ocean waters.
B. H.-H.
CHAPTER VI
PELAGIC PLANT LIFE
Not many years have elapsed since the scientific world became Historical
aware that the sea contains plants in abundance floating on and introduction.
beneath its surface, and that they build up the organic sub-
stances upon which marine animals depend. In the open sea
the plants are too minute to be detected without the microscope ;
so that, until this instrument came to be regularly employed by
biologists, it was impossible to know anything about them.
The first to use the microscope for studying unicellular
organisms in the sea was the celebrated Danish zoologist,
O. F. Mtiller, who, in 1777, described one of the most important o. f. Muiier.
plants of our northern waters, namely, Ceratimn tripos. He
was succeeded by the microscopist Ehrenberg, who laid the Ehrenberg.
foundation of our knowledge regarding the multiplicity of forms,
their wide distribution, and their significance in the economy of
nature ; and also discovered the coverings of diatoms together
with coccoliths and the skeletons of various unicellular animals
(radiolaria, foraminifera) in deposits on the sea-bottom and in
geological strata from previous ages. Ehrenberg aroused
interest by pointing out the wonderful structure of these
coverings, and improvements in the microscope have resulted
in fresh wonders being disclosed, which have induced quite a
number of capable amateurs to take up the study of diatoms.
Classification of these algae dates from about the middle of the
nineteenth century. It is based on the shape and structure of the
cell-wall, less attention having been given to the living contents
and to the biology. The pelagic forms have as a rule thinner
coverings, and a more indistinct structure, than the robust species
nearer the coast, and have therefore been less studied. How-
ever, occasional samples have now and then been collected from
the surface with nets, and researches have been carried out by Bailey.
J. W. Bailey in the waters off Kamchatka, by Brightwell along Brightwdi.
307
3o8 DEPTHS OF THE OCEAN
Lauder. the shorcs of England, by Lauder at Hong-Kong, and by Cleve
cieve. in the North Polar Sea and at Java. A regular gold mine in the
Waiiich. way of rare pelagic forms was found by Wallich in the intestinal
canals of salpse, and this source has subsequently been utilised
for procuring forms that our apparatus could not capture.
Pelagic algae which have no skeletons of durable mineral
constituents, such as silicic acid or lime, were in those days
neglected. A few, no doubt, of the larger peridinese were
Nitsch. described by Nitsch, Ehrenberg, Bailey, Claparede, and
ciaparede. Lachmaun ; but there was very little progress made, and it
Lachmann. ^as uot till 1 883 that T. R. von Stein published his first
Stein. comprehensive monograph, a great deal of the material for
Bergh. which had been taken from the stomachs of salpse. R. S. Bergh
had already issued, two years previously, a text- book on the
organisation of these algse.
Since 1870 important expeditions have been undertaken,
one object of which was to study the pelagic organisms
" chaiiengei •' systematically. The "Challenger" Expedition, in particular,
Expedition. collected quantities of material from all the seas of the world ;
though attention was still chiefly directed to those forms whose
coverings are met with in deposits on the sea-bottom, that is to
say, diatoms with their silicious coverings, and the remarkable
little organisms forming the microscopic calcareous bodies which
Ehrenberg had already designated coccoliths and rhabdoliths.
John Murray. Murray pointed out that coccospheres and rhabdospheres, as
they were termed, are really self-existent organisms in the
surface-layers. He could obtain them by allowing a glass of
sea-water to stand for a few hours, so that they sank to the
bottom and attached themselves to threads placed there for
purposes of experiment ; and he also found numbers of them in
the stomach-contents of salpse, of which they often formed an
essential part. It was possible, too, by noting the occurrence
of their coverings in the bottom-samples, to obtain definite
information regarding their geographical distribution. He
observed that, while they are abundant in all tropical and sub-
tropical waters in the open ocean, they are not found in arctic
and antarctic waters having a temperature below 45° F., nor are
they to be found in the deposits of the polar oceans. Murray
further ascertained that diatoms are irregular in their occurrence,
and that they are more numerous in coastal areas than out in
Castracane. the oceau. Unfortunately Castracane, when examining the
diatoms collected by the expedition, was unable to find any
conformity in the distribution of the different species.
PELAGIC PLANT LIFE 309
The other expeditions that were sent out about the same
time as the "Challenger" carried out their investigations on
similar lines. G. O. Sars, who was a member of the Norwegian g. o. Sars.
North Atlantic Expedition in 1 876-1 878, made a study on
board ship of the luxuriant plant life near the ice-limit, and re-
marked, like QErsted before him, that plants are really the basis CErsted.
upon which the nutriment of animals is founded. It was not,
however, till twenty years afterwards that an examination was
made of the algae in the comparatively small number of samples
then collected.
Soon after 1880 Hensen commenced a physiological study Hensen.
of the sea, and essayed principally to estimate its production of
nutritive substances at different seasons. As a result the plants
came more into notice than they had previously done ; and it is
significant that Hensen found it necessary to introduce the new
name of " plankton " to designate generally all pelagic organisms, "Plankton
both plants and animals, regarded as one universal community.
The term "plankton" is now used for all floating organisms
which are passively carried along by currents, while "nekton" "Nekton."
— a term introduced by Haeckel — is used to designate all
pelagic animals which are able to swim against currents.
During Hensen's Plankton Expedition in 1889 Schlitt made Schutt.
the first investigations regarding the general biology of the
plankton - algse. His ingenious descriptions and admirable
drawings explained the different ways in which the alga; adapt
themselves to their floating existence.
An endeavour was made by Hensen to find a method of Qu;
calculating the quantity of pelagic organisms occurring in
different localities. He constructed nets to be drawn up for
certain distances through the water, that were supposed to
filter the whole column of liquid through which they passed, and
to retain all the organisms existing therein. The total amount of
these organisms was then measured by determining the volume,
and a most careful enumeration was made of the number
of individuals belonging to each species. The nets were drawn
vertically through the whole zone where plant plankton is abund-
ant, that is to say, from a depth of 200 metres to the surface ;
and Hensen attempted to utilise the results for measuring the
production of life in a column of water whose superficial area is
one square metre. He tried at the same time to solve import-
ant problems, such as the rate of augmentation of algse, or what
proportion of individuals disappears owing either to consump-
tion by other organisms or unfavourable conditions of existence.
uantitative
estimations.
lO
DEPTHS OF THE OCEAN
Aurivillius.
Pettersson.
Hensen's work must not be disparaged because his aspirations
have been more difficult to reaHse than he at hrst imagined.
The difficulties are far from insurmountable, while Hensen
himself will be always looked upon as one of the founders of the
science of marine physiology.
In the biology of the sea we have also to consider the
geographical distribution of the different species and their
dependence upon ocean currents. The Swedish scientists,
Cleve and Aurivillius, brought these two questions into special
prominence, though no doubt they had been previously con-
sidered by others. But with the hydrographical investigations
of Otto Pettersson and others the whole subject assumed a
new aspect. Thanks to improved methods they succeeded in
following the movements of the water-layers, by determining
their salinity, temperature, and other hydrographical character-
istics ; and from this time forward the plankton was also
enlisted as a supplemental means of characterising water-
masses of different origin. Cleve with his marvellous power
of distinguishing forms was able in a short space of time to
determine numbers of species, animals as well as plants, and
it is to him we owe the foundation of our knowledge regarding
the distribution of plankton-algaj.
Since the international marine investigations were commenced
nvestigations. ^bout ten years ago, researches have been carried out in the
Northern Atlantic, North Sea, and Baltic ; and specialists from
the different countries of North Europe have gradually extended
our knowledge, as far as northern species are concerned.
Simultaneously great improvements have taken place in our
methods of studying plankton. Lohmann has made it clear that
the catches in the silk nets originally used incompletely repre-
sented the flora of the sea, owing to the fact that whole series of
the most diminutive organisms slip through the meshes of even
the finest straining-cloth. He devised methods for catching them
by means of the filter and the centrifuge, and could thus estimate
their numbers in a given quantity of sea-water. Coccolitho-
phoridse, which the " Challenger " Expedition claimed to have
discovered, but which Hensen refused to recognise as self-
existent plankton organisms, because he did not capture them
himself, were now investigated, and Lohmann was able to
declare confidently that they really are algae, furnished with
brown pigment granules, the physiological equivalent of
chlorophyl, thus confirming the ecrlier discoveries of Sir John
Murray, George Murray, Blackman, and Ostenfeld. Lohmann
International
Lohmann.
G. Murray
Blackman.
Ostenfeld.
PELAGIC PLANT LIFE 311
has further, by his quantitative investigations of the variations in
the plankton of Kiel Bay and off Syracuse, taught us the value
of exact studies of this description.
Our future investigations will have to be conducted on three
main lines : —
(i) In the first place, much study must be devoted to the
biology, in the restricted sense of the word, of the algae. We
will have to learn how the forms adapt themselves to their
conditions of life, and in particular to their floating existence.
Here, however, a great advance should most certainly be made,
now that W. Ostwald has shown us a new factor affecting their Ostwaid.
floating power, namely, the varying viscosity of sea-water, and
since the instructive writings of Wesenberg-Lund have directed Wesenberg-
our attention to the seasonal modifications which the species ^""^•
adopt to suit variations in viscosity.
(2) In the second place, the distribution of the species
throughout the seas of the world requires further investigation
at different seasons, and this must be founded on a careful
characterisation of the different species. In recent years the
peridineae, after a long period of neglect, have received due paviHard
attention at the hands of Ostenfeld, Ove Paulsen, Pavillard, jorgensen.
Jorgensen, Broch, and Kofoid. A great deal, however, still Broch.
remains to be accomplished. Kofoid.
(3) In the third place, we will have to deal with the laws of
production in the sea. This great physiological question calls
for observations on a very comprehensive scale, if we are to be
in a position to discuss the interesting theories put forward by ^^^^^^^
Brandt, Nathansohn, and Putter. A brief discussion of their Nathansohn
theories will be found at the end of this chapter. piuter.
During the Adantic Expedition of the " Michael Sars " we
were able to make observations on all these three aspects of
the subject ; and in what follows I shall endeavour to summarise
our results, and to consider, while doing so, the attitude at
present taken up by the scientific world with regard to these
three lines of investigation.
Most of the ocean plants exist in countless myriads of General bio-
minute individuals, though they are invisible to the naked eye. p°e^g°c aiga.
Still, small as they are, they are in a way highly organised,
and their organisation is in strict accordance with the particular
conditions of life. On land' a higher plant consists of a
community of separate cells, each of which has a special function
to perform in the service of the whole. It establishes an under-
312
DEPTHS OF THE OCEAN
ground system of roots to collect moisture and nourishment
from the soil, and its leaves are raised aloft on slender stems
to derive benefit from the rays of light and build up organic
substance out of carbonic acid and water. Ocean plants have
no such point cTapptii \ they find their nourishment dissolved in
sea-water and distributed uniformly all around them, and they
get most benefit from the sunlight when they are regularly
spread throughout the whole bulk of the water in the photic
zone. Their diffusion is also their best defence against their
enemies, for, while animals have no great difficulty in
finding and consuming the larger plants, these creatures,
scattered everywhere like dust amidst the immeasurable
water-masses, are not so easily available. The majority of
the floating plants pass their lives as single cells, though they
are frequently far more highly organised than the single cells
that go to form a higher plant.
As pelagic algse have generally a greater density than the sea-
water in which they live, they would sink out of range of the
rays of light, and perish, if it were not for the fact that they are
kept from descending either by their own exertions or by
suspension organs which act as a parachute. The most notice-
able features in their organisation are their different forms of
structure, which are directly connected with the floating existence
they lead. In what follows I shall describe the most important
types, belonging to a limited number of classes, most of which
have variously shaped pigment granules or chromatophores,
consisting of brown colouring matter instead of green chlorophyl.
Comprised in their number are diatoms, peridineae, and brown
flagellates, amongst which last we also include calcareous
flagellates or coccolithophoridse. In addition there are a few
pelagic representatives of the green and blue-green algse, which
I will discuss separately.
A diatom can be distinguished from other algse by its
silicated cell-wall. This is composed of two quite similar
halves, or valves as they are called, that are united to one
another like the top and bottom of a pill-box (see Fig. 212).
Inside the valves the protoplasm lines the wall like a thin sort
of bladder, while the nucleus is frequently in the very centre
surrounded by a denser mass of protoplasm connected to the
bladder by bridges or strings. The rest of the cavity is full of
a clear cell-fluid. The pigment granules, which are organs of
nourishment, enable the diatom to collect rays of light and build
PELAGIC PLANT LIFE 313
up' organic substance out of carbonic acid. They usually
lie in regular order along the cell-wall (Fig. 213, <?) ; but if the
light becomes too strong for them, they are able to huddle
more closely together, either in the middle of the cell or
Fig. 212. — Cell-wall of a Diatom {Coscinodiscus subbuluens), ^i"*.
(7, External view ; b, vertical section ; c, section in cell-division.
at some point where they can mutually protect each other from
the harmful effects of the rays (Fig. 213, ^ and c). This has been
demonstrated by Schimper. The assimilation of carbonic acid
produces a fat oil, which may form into comparatively large drops.
Cells are produced by
r^^i division. The nucleus and
protoplasm divide into two
parts, the valves are pushed
a little apart, and two new
valves develop within the old
ones. Thus each of the
daughter-cells gets one of the
valves from the mother-cell
and a new valve that joins on
to it (see Fig. 212, c). When
once the valves have acquired
their shape they seem incapable
of expanding, so that the cell
generations will gradually be-
come contracted in the plane
in which division takes place.
It follows that the cavity of
the cell will also be dimin-
ished, though at the same time
the perpendicular axis of the plane of division is frequently
slightly prolonged. Algse can, however, regenerate their
original size, by throwing off their old valves, growing into a
larger bladder with a thin expansible skin, and forming within it
new valves that are two or three times as large as the old ones.
This is the so-called auxospore development (see Fig. 214).
Diatoms occur in quantities over the whole world in both
Schimper.
Cell division.
Fig. 213.
b, Lauderia annnlata. a, Cell with the pig-
ment granules (chromatophores) in normal
position, collected early in the morning ; b,
chain from the surface of the sea, 3 P. M. ,
chromatophores congregated at the ends of
the cells ; c, Detonula schrxderi in the same
condition. All ^\^.
Auxospore
development.
314
DEPTHS OF THE OCEAN
fresh and salt water, and they are found not merely as floating
forms, but also along the coasts, some of them attached to the
bottom or to other algse and animals ; some are capable of
motion, gliding over the mud in enclosed bays or among grains
of sand near the seashore. The coast forms, however, are
essentially different from the pelagic forms in their structure.
Littoral diatoms are apt to have a comparatively thick and
extremely silicated cell-wall with the characteristic patterns,
ribs, and pores, that have made them such an attractive object
of study to amateur scientists. Bilateral symmetry prevails,
especially amongst forms that are capable of motion, which are
as a rule pointed at the ends like the bows of a boat. Diatoms of
Fig. 214.— Auxospore-formation of Thalassiosira gravida.
a. Showing in the centre a newly-formed auxospore, the old cell-walls still lying outside (-y-) ; b,
showing on the left a cell before auxospore-formation, succeeded by an auxospore during its
first cell-division, the chain of five cells having originated from an auxospore (-"^-).
this kind have a highly organised locomotion apparatus, which
is differently constructed in the different genera, such as
Navicula and Nitzschia. Attached forms show more variation.
Symmetry with them depends upon the mode of attachment.
LicmopJio7'a and Gomphonema are fastened at one end to a
gelatine-like stalk, and their cells are wedge-shaped, narrow at
the bottom and widening out towards the top. Others, like
Epit hernia, are convex on the one side and straight on the
other, the straight side being the one by which they are attached.
And there are others again that consist of more or less highly
organised and often ramifying colonies, composed of series of
cells, or sheaths of mucilage, within which the cells are able to
move past one another.
PELAGIC PLANT LIFE 315
Pelagic forms usually have thinner cell-walls, and the f
characteristic ornamentations on their silicated valves are not
so prominent, though in their case too a high magnifying power
will nearly always render them visible. The families that are
endowed with locomotion organs are very scantily represented,
and even amongst the few that are thus favoured, several species
make use of them for quite a different purpose, employing them
as organs to secrete mucilage and thus keep the cells united in
chains. Most of the pelagic diatoms belong to families that
lack organs of locomotion, though by way of compensation
various types have highly developed suspension organs, which
increase their superficies and consequently their friction against
the surrounding water-masses. It is possible, too, that these
algae are able to reduce excess weight by evolving specifically
lighter matter, such as fat, within the cells or air-bladders outside
them, but this has not yet been properly investigated.
The suspension organs, however, have been most carefully
studied, especially by Schlitt, who was one of the members of Schutt.
Hensen's Plankton Expedition in 1889, and the different cell-
forms, with their numerous contrivances for maintaining a
floating existence, may be grouped under four heads : —
(i) TJie Bladder Type.— In these the cell is comparatively large, p'our types of
while the cell-wall and protoplasm are merely thin membranes round a suspension
big inner cavity which is filled with a cell-fluid of about the same specific °''S'^"^-
gravity as sea-w^ater. Among diatoms the best instances of this type
are species of the genus Coscinodiscus, whose structure resembles
cylindrical boxes, sometimes fairly flat-shaped, and sometimes more
elongated and rounded at the top and bottom. In most forms the cell-
wall is quite thin, though it is strengthened by means of a fine mesh-
work of more or less regular hexagons. One of the biggest, Coscinodiscus
rex {Et/unodiscus rex, Antelinine/lia gigas), is over a millimetre in diameter,
and is quite a common form in "the warmer parts of the Atlantic (see Fig.
215). A series of species with stouter structure, and more distinct orna-
mentations on the cell-wall, occur especially in the deeper water-layers,
at about the lowermost limit of plant-life (lOO to 200 metres), and
belong to a characteristic twilight-flora, of whose existence Schimper
became aware during the " Valdivia " Expedition.
(2) The Ribbon Type. — The surface is enlarged owing to the cell
being flattened down into a plane, which is often bent or twisted to a
certain extent. Diatoms of this type (see Fig. 216) are scarce. We
have, along the coasts especially, a few species with flat cells, which are
associated in ribbon-shaped colonies, such as Fragilaria and Climacodimn.
The cell-walls of these species are extremely thin, and not of a particularly
distinct structure.
(3) The Hair Type.— The cells are very much prolonged in one
direction, or else they are united in narrow, elongated colonies. Diatoms
i6
DEPTHS OF THE OCEAN
furnish many varieties of this type. Sometimes the length axis is situated
in the division-plane of the cells, as, for instance, in Thalassiothrix
longissivia, one of the characteristic forms in colder seas ; at other times
division takes place across the elongated cell, as in the genus RJiir:osolenia,
of which there are many species (see Fig. 217). Hair-shaped cells of this
kind create a great deal of friction when horizontal, but would sink
rapidly when perpendicular, if it were not for the fact that they are
either slightly curved, or else their terminal faces are sloping ; so that
jO '
0 ;
[0 '
■01
La.
<>J
[O '
1^
fa
' «J
Fig. 2\^.~Coscixodisc.us rex (-'V')-
Fig. 216. — Pelagic Diatoms of the
ribbon-type {-^?^).
Chain of Navicula vanhoffeni, the cells con-
nected by a band of mucilage ; b, part of a
chain of Frasrilai-ia oceaiiica.
the resistance of the water soon restores them to an almost horizontal
position, and they sink slowly in long spiral sweeps.
(4) The Branching Type. — The surface of the cell is enlarged by
various kinds of hair-shaped or lamelliform outgrowths. To this type
belongs the genus CJicetoceras with its numerous species (see Fig. 218)..
j5^«fe«>
Fig. 217.— Pelagic Diatom of the hair-type, Rhizosolenia hebetata-semispina.
a, Entire cell (^oo) ; b, end of a cell (^f «).
Every cell has four long setiform outgrowths, and the cells are besides
nearly always associated in chains, so that these setae radiate in every
direction. When the chain is straight and stiff it is frequently furnished
with special terminal setae, which are stiffer than the others, and act as
a sort of steering apparatus.
In addition to the actual outgrowths from the cell many
diatoms can secrete long filaments of mucilage from special
PELAGIC PLANT LIFE
317
secretion pores. These filaments act as an effective suspen-
sion-apparatus (see Fig. 219). During unfavourable conditions
Fig. 218.— Chain of Ch.f.toceras decipiens ('f-").
of existence, especially when there are considerable changes in
the salinity, sufficient mucilage is secreted to form a protecting
Fig. 219. — Chain of Thalassiosira gravida (-f")-
Showing on the right five cells with filaments of mucilage. (Mangin. )
sheath round the cells. This I have myself observed in the
case of species of Thalassiosira on the Norwegian coasts.
Adjustment of their organisms to the conditions of their
3i8 DEPTHS OF THE OCEAN chap.
floating existence affects the whole structure of these alg^,
though it is not always carried out to the same degree in the
different genera and species. If we examine into their distribu-
tion we shall find that no particular region is distinguished by
specially well -equipped species. Genera with the greatest
numbers of species have their representatives in both the
warmest and the coldest areas of the sea, and no essential
difference in the development of their suspension-apparatus is
to be found between the species of ChcEtoceras and Rhizosolema
which live near the confines of the polar sea, and their relatives
in the tropics. The greatest abundance of forms is to be met
with in coastal waters, where, too, the majority of the species
have their home. I shall return later on to the special biology
of these coast-forms.
Many species of diatoms show variations indicating that
within certain limits the algae can adapt their floating power to
the demands made on them. Their tendency to sink increases
with a rise of temperature, and decreases with an increase of
salinity. It is not alone the specific gravity (density) of
sea-water that is here the determining factor; no doubt we
must bear specific gravity in mind also, but its variations are
comparatively small. Ostwald has shown that the internal
friction or viscosity of sea-water is the most important con-
sideration, and this diminishes with an increase of temperature.
Other things being equal, sea-water at 25° C. offers only half the
resistance that it would at freezing-point. Salinity, on the
other hand, is of less account. A rise of i per cent in the
salinity will produce no more than an increase of 2 to 3 per
cent in the internal friction, and as salinity in the open sea is
subject to what are after all quite inconsiderable variations, it
follows that it is really temperature which indirectly affects the
development of the suspension-organs. In areas of the sea
where there is a big difference in temperature between summer
and winter, we find a number of species with distinct summer
and winter forms, that have sometimes even been supposed to
belong to totally different species. And the same variation
occurs also in species with a wide distribution, the warm-water
types corresponding to the summer forms, and the cold-water
types to the winter ones. The summer forms have usually
thinner cell-walls, and a more slender structure ; their excess
weight appears to be reduced, though at the same time
their surface is comparatively larger. As, however, diatoms
vary greatly in their dimensions throughout their life-cycle,
PELAGIC PLANT LIFE
319
their cells diminishing by being divided and increasing again
owing to the formation of auxospores (see Fig. 220), it is
Fig. 220.— Colonies of Thalassiothrix nitzschiowes (^f^).
(/, With long cells shortly after auxospore formation ; b, with shorter and thicker cells.
difficult to show in the case of many species to what extent
variations are due to adaptation and regulation of their floating
power, though in the case of some chain-forming species it is
Fig. 221. — Parts of two chains of Chmtoceras decipiens (^f^).
a. From the Atlantic off the coast of Spain, April 1910 ; b, from Christiania-Fjord, March 191 1.
evident enough. Chcetoceras decipiejis, one of the commonest
species in the northern Atlantic, consists of straight chains
of flattened, almost rectangular cells, every one of which is
,20
DEPTHS OF THE OCEAN
furnished with four long setse. Each of these setae is attached
at the root to its fellow from the neighbouring cell, the result
being the formation of the chain. The terminal faces of the
cells are otherwise separate, so that there are openings between
them. In the winter and spring Chcetoceras decipiens is furnished
with thick cell-walls and stout setae, and the interstices between
the cells are quite inconsiderable (see Fig. 221,^); but in summer
the walls are thin and the setae extremely fine, and the openings
in the chain between the cells then become large, round or
oval gaps, which are almost as big as the cells themselves (see
Fig. 22\,d). Corresponding variations occur in other species
of Chatoce7'as, and in other diatoms, such as Biddulphia
aitrita. Along the arctic coasts, for instance, BiddzilpJiia has a
rather gross structure, and is almost cylindrical, with short
conical projections at the corners, but off the south of Norway
it has a comparatively much larger surface, and the corners
develop into long, slender outgrowths.
We find a variation of a different nature in the case of
Fig, 222. — Cell of Rhizosolenia hebetata-semispina {^^^).
One end of the cell belongs to the typical arctic hebetata (on the right), the other
to the Atlantic form semispina.
Dimorphism. Rhizosoletiia hebetata. It occurs in two perfectly distinct forms,
that were formerly regarded as good species. The first, which
belongs to arctic waters, is thick-walled and gross, and is the
true R. hebetata. The second, R. semispina, has thinner walls
and is proportionately longer, and it is furnished with a long
hair-like point at each end. Its distribution extends over
practically the whole Atlantic, though it is chiefly to be found
in the neighbourhood of the cold currents. These two
" species " can originate from one another reciprocally as the
result of one cell-division. During the course of transition a
cell may be hebetata at the one end and semispina at the other
(see Fig. 222). Dimorphism of this kind is known, moreover,
in the case of other species.
Still, in the open sea conditions of existence are compara-
tively uniform compared with what we find in coastal waters,
where the temperature and salinity vary considerably. Most
of the diatoms which belong particularly to the coastal waters
Resting- have a special adaptation, the so-called resting -spores, which
spores. must be regarded as a means of protection against such altered
conditions. The contents of the cell can shrink into a denser
PELAGIC PLANT LIFE 321
mass in the middle, and become enwrapped in a new thick wall
of characteristic shape within the old cell-wa
carded as soon as the resting-spore
is completely developed (see Fig.
223). The spores have now ac-
quired an increased specific weight,
as compared with their original cell,
and sink down into deep water,
where they may be found months
after they have disappeared from
the surface-layers. The majority of
them, however, rest on the bottom
in shallow coastal waters, until con-
ditions of existence again occur
which induce them to make a fresh
start.
The germination of the resting-
spores has not yet been described,
though Hensen states that Lohmann
has observed the first stages on
several occasions. It will be a great
advantage when we can follow their
development-history through all its
stages, and study the conditions of
existence that lead to germination.
Resting-spores are unknown in the
true oceanic species ; but, as already
stated, they are found in most of
the species belonging to coastal seas,
not aware of them till quite a short
^hich
Fig. 223. — Chain of Chmtoceras
constrictum, with three rest-
ing - spores and one normal
cell (the end - cell of the
CHAIN) {*-r-).
In some cases we were
time ago. It is only
recently that they have
been discovered in Lep-
tocylindrus danicus (see
Fig. 224), in which the
cylindrical cells are
broken across in the
Fig. 22af.—LEPTocYuxDRus danicus, WITH RESTING- process of spore-forma-
sFORE(i"/^). ^j^^^ g^ ^^^^ ^^^ spores
are liberated, and in Chcetoceras pseudocrinitum, in which the
resting-spores originate in auxospores.
So far as we are able to ascertain, the auxospores of pelagic
diatoms are always formed without any sexual act. There is,
however, another kind of organ, the so-called microspores, Microspores.
Y
,22
DEPTHS OF THE OCEAN
Bergon.
Karsten.
Peridineae.
which, according to Bergon's investigations^ would seem to be
zoospores, and which Karsten assumes to be sexual cells.
Karsten has observed the formation of microspores in an
antarctic diatom, Corethroii valdivicE (see Fig. 225), and in the
same microscopic preparations found amalgamations of small
cells resembling microspores. We cannot yet, however, consider
this conclusively settled. We do not know the life-history of
the numerous small spores after they have emerged from the
mother-cell. We can only hope that the centrifuge will enable
us to study the
most diminutive
andsensitivecells
immediately after
capture, and that ^ ^ ¥ } II ^
we shall thus suc-
ceed in solving
this problem in
the biology of
diatoms.
H
Fig. 225.— Microspore-formatio.\ 01 Cokethron valdivi.e
in different development stages (="-1").
Ripe microspores in the cell to the right. (Karsten.)
Peridinese are
mobile algae fur-
nished with two
cilia. Several
species can pro-
duce brilliant
phosphorescence.
Their cells are
highly organised,
with adistinctdif-
ference between
the anterior and
posterior ends, and between the dorsal and ventral faces.
The cell-wall is built up entirely of organised matter, which
dissolves soon after the death of the cell. Peridinese are
therefore not noticeable in the deposits of the ocean -bottom,
which is one of the reasons why, until quite recently, they were
but slightly and imperfectly known. A number of laminae,
characteristic in shape and position, compose the cell-wall. On
the posterior side there is a characteristic furrow, with a pore
for one of the cilia, which can be withdrawn spirally into a
sheath (see Fig. 226). The ventral furrow is often protected
by curtain-membranes. Another furrow encircles the cell, and
PELAGIC PLANT LIFE 323
is known as the ring -furrow. It is guarded by projecting
borders on the anterior and posterior sides, called ring-borders.
It is in this furrow that the second cilium lies and vibrates.
These principal organs appear in a great variety of shapes.
The genus Ceratmm has the anterior end drawn out into a long Ceratmm.
horn, which is open at the top ; its posterior end has also nearly
always two horn-like projections, which in most species bend in
a forward direction. The species of Ceratmm are well supplied
with brown pigment granules, and they occur in the upper
water-layers, where they constitute an essential part of the plant
life. The horns must be regarded
as suspension-organs, even though
the mobility of the cell makes an
adaptation of this kind less indis-
pensable. We frequently find
them, especially in the species
of tropical seas, transformed into
very consummate suspension -
organs. Sometimes they are
decidedly long and hair - shaped,
sometimes flattened, and in a
few species actually terminate in
radiating branches. Kofoid has Kofoid.
shown that the species of Cera-
tmvi can regulate their floating
power, and that when, owing to
the movement of the water
masses, they enter colder or
Yio. 2z(y.-PERiDiNiuM DEPREssvM {^\^). warmcr layers of water, they can
(Schlitt.) .^ r u • u
shed portions 01 their horns or
prolong them at will (see Fig. 227). They have also still
another mode of improving their floating power. The cell wall
grows in thickness during the whole life of the algse, and
simultaneously ribs and pores are constantly developing ; but
as soon as the cell gets too heavy, one or even several laminae
peel off from the cell armour, and new extremely thin plates
take their place.
The species of Ce^^atiimi are also formed by division, and
with them, too, the daughter-cells each retain half of the
membrane of the mother-cell, the other half being new. This
does not, however, take place within the cell- wall of the mother-
cell, and there is therefore no gradual diminution in the bulk of
the individual. Sometimes the cells hang together in chains.
>24
DEPTHS OF THE OCEAN
and it is then quite evident that the direction and shape of the
horns may vary considerably from one generation to another.
Fig. 22-J.—CERATIUM TRICHOCEROS.
Showing progressive and proportionate reduction of the horns in autotomy (^ f-). (Kofoid. )
0.0
0.2 0-3 mm. U
Fig. 228. — Ceratium platycorne.
, Forma cojnpressa ; 2, 3, forma normalis.
In other cases, where the cells separate immediately after
division, it is more difficult to tell which variations are due to
hereditary dissimilarities and which are the result of direct
PELAGIC PLANT LIFE
325
adaptations from one generation to the othier. Still, now and
then even this, too, is possible. I found during the Atlantic
expedition of the " Michael Sars " that the subtropical Ceratium
platycorne, both of the posterior horns of which are developed
ordinarily into flat wing-like suspension-organs, changed gradu-
ally into a form with cylindrical horns belonging to the Gulf
Stream in the Norwegian Sea, that I
had myself previously described under
the name of Ceratium compresstnn (see
Fig. 228).
Discontinuous variations have been
found as well as continuous ones in the
species of Ceratitim. Lohmann has Lohmann.
shown that the ordinary Baltic form,
C. tripos, can set up an intermediate
generation of a totally different type,
much smaller and with short, straight
horns, corresponding to the forms de-
scribed under the name of C. lineatttm.
Kofoid has met with similar variations
in American species (see Fig. 229). The
signification of these development forms
has not yet been discovered. Jorgen- jcirgensen.
sen, who has recently published a mono-
graph on the genus, is inclined to
regard them as degenerate forms that
have been produced under abnormal
conditions of existence. It seems to
me, however, more probable that these
Only one cell IV. I shows the charac- , , i -i n 1
ter of the type, the others (I. -III.) Small, extrcmely mobile, cells are normal
belonging to the type of pm//««/ formations, which have a definite func-
cali forii tense {^\"). (Kotoid. ) . - . , . _ , -
tion to perform m the imperfectly known
development - cycle of the species of Ceratium. It is still
questionable whether peridinese propagate sexually, even though
Zederbauer claims to have discovered sexual propagation in the Zederbauer.
ordinary fresh-water form [Cei^atium hirundinella\ But, a
priori, it is quite possible that the above described inter-
mediate generation may be a sex-generation. Just as little as
these "mutations" do we understand the significance of the
gemmation which Apstein has lately described in Ceratium Apstein.
tripos, nor do we know what conditions of existence cause
gemmation instead of normal cell-division.
Another important genus with many species, Peridirmtm, Peridinium.
Fig. 229.
Ch.vin of Ceratium tripos.
¥.
326 DEPTHS OF THE OCEAN
differs in various ways from Ceratittm, though systematically it
is not far removed from it. The cells, however, lack the brown
pigment-granules (at any rate, this is so in the case of marine
species), and the contents are pale yellow or pink. It is im-
probable that it can assimilate carbonic acid, and it must there-
fore somehow or other obtain organic matter for its nourish-
ment. Unfortunately nothing is known regarding its mode of
nourishment. These forms do not live so close to the surface
as the species of Ceratiuvi, but all observations made hitherto
indicate that they belong exclusively to parts of the sea to
which light penetrates, where they exist along with the other
algae. Their cells are much grosser than
those of the species of Ceratmm, and the
projections corresponding to the horns of
Ceratiuin are short or entirely wanting.
The membrane-curtains along the furrows
are only slightly developed, and the cell
itself is much more globular. The species
of Peridiniu77i, and some other genera
{Goiiymilax, Goniodoina), have thus at
best only imperfect suspension-organs,
but the mobility of the cells makes up for
„ this deficiency. The way they are formed.
Fig. 230. • y-rr [ u
GoNYAULAx poLYGRAMMA. too, IS dinerent from what we notice m
The cell-contents form a zoo- Ceratium. There is no proper cell -
spore, shed out from the burst- ,. . , , , 11 1 •
ing cell-wall (^1 2). (Schiitt.) Qivision, but the Cell changes its contents
to one, two, or four naked spores, which
are shed out from their original covering (see Fig. 230). Each
spore afterwards gradually evolves a new cell-wall for itself,
within which it develops as the wall expands, and bands, due to
accession of growth, intervene between the laminae composing
the structure. This has been demonstrated by Broch. The
genus Peridinmiu includes a large number of species distributed
throughout all the seas of the world, but the systematic arrange-
ment of the species is extremely difficult, and has not so far
been sufficiently investigated. A large amount of material has,
however, been brought home by our expedition, and it is to be
hoped that we shall now be able to ascertain the characteristics
to which we can ascribe chief systematic importance. A good
beginning, at all events, has been made by Kofoid and Broch.
The family Dinophysidae possesses the most remarkable
suspension-organs of all the peridineae. In northern waters
its representatives are limited to a number of species all
PELAGIC PLANT LIFE
327
resembling one another and all belonging to the same genus,
namely, Dinophysis. The commonest of these, D. acuta (see Dinophyi
Fig, 231), has a small tongue-shaped mobile cell without particu-
larly well-defined suspension -organs. Its ring- furrow and
protecting borders are situated at
the forepart of the cell, and its
sides are flattened to such an
extent that the ventral furrow is
on quite a sharp edge, where it is
guarded by two membrane-cur-
tains. The cell is formed by
division, which takes place per-
pendicularly to the ring- furrow.
Within the cell are several brown
chromatophores, showing that
Dinophysis is one of the peri-
dineae that assimilates carbonic
acid.
In warmer waters this funda-
FiG. 2-^1.— Dinophysis acuta.
From the west coast of Norway (-?--)•
(Jorgensen. )
Fig. 232.
a, Amphisolenia globosa ;
b, Amphisolenia tenella, n.sp. {^\^
mental type shows strange variations. Amphisolenia (see Fig. Amphisolenia.
232) has its w^hole cell drawn out to a hair, the ring-furrow is
situated right in front on a little head, and the ventral furrow
is on a narrow neck with slightly developed membrane-curtains
like a kind of collar. The cell widens out slightly like a spindle
in the middle, and posteriorly ends in a globular knob by way
of balance, or in two or three ramifications. Triposolenia (see Triposoienia.
Fig. 233) has a similar anterior structure, but the middle part is
,28
DEPTHS OF THE OCEAN
more expanded, and the two bent legs which issue from it do
not lie in quite the same plane, with the result that in sinking
the cell describes very long sweeps. Besides these we get other
genera, where the suspension-organs are not formed by the
Oniithocercus. Cell itself, but by the membrane-curtains. In Ornithocei^cus
splendid2is the ring - borders are transformed into an un-
mistakable parachute, stiffened by a network of ribs (see Fig.
234, a), and in some species, such as O. steinii and O. qtiadratus,
the membrane-curtains are ventrally or posteriorly most highly
developed (see Fig. 234, b). The
majority of these more different-
iated forms are without chromato-
phores, but some of them by way
of compensation are in almost
constant symbiosis with small
brown naked cells that are prob-
ably immobile stages of brown
flagellates. In Oriiithocercus
7nagniJicuSy for instance, we find
these naked cells in the space
between the ring-borders, where
they are well protected against
harm (see Fig. 235) ; and in a
series of species of the remarkable
Histioneis. tropical genus Histioneis this
home of theirs is expanded pos-
teriorly into a cavity which may
be of considerable dimensions
as compared with the cell. In
Citharistes. Citkaristes the cavity takes up
the whole of what should be the central portion of the cell, and
the cell-membranes are merely the outer skin like the shell of
a guitar (see Fig. 236).
A remarkable subdivision of the peridinese is the genus
Pyrocystis. Pyvocystis, which Sir John Murray discovered during the
"Challenger" Expedition. Pyrocystis noctihica (see Fig. 237) has
large globular cells with a thin layer of protoplasm along the
cell-wall, a denser mass round the nucleus, and brown pigment
granules. Murray stated that the genus was abundant in all
tropical and subtropical waters, where the temperature exceeds
68° F., and where the salinity at the surface is not lowered
by the presence of coast or river water. The cells have
no organs of motion, but belong to the most brilliantly phos-
■Triposolenia b/cora'is m^).
(Kofoid.)
PELAGIC PLANT LIFE
329
phorescent of the algae ; biologically they are of the "bladder-
type." Other species are elongated (see Fig. 238), straight,
or crescent-shaped. Within their cells they form big zoo-
^r^f -rr T^
Fig. 234.
a, Ornithocercus splendidus [-\-) ; b, Ornithocercus steinii (^-f^). (G. Murray and Whitting. )
Spores, built up exactly like the peridinese type with a ring-
furrow and two cilia, for which reason the species of Pyrocystis
are included among the peridinese, though their fully-developed
cells are really of a quite different type.
'■'"'%.
M^mK
330 DEPTHS OF THE OCEAN
Besides these highly-organised forms, which I have given
as instances, the peridineae include many with a far more simple
structure. There are, especially in the samples collected by
means of the centrifuge, numerous series
of small forms, both coloured and colour-
less, and often with very poorly de-
veloped cell -walls. These, too, have
already got or will shortly be given
names, although many of them are prob-
ably nothing more than development-
stages of the larger forms. We can
recognise the whole series by their char-
acteristic ring-furrow, so that we are
seldom left in doubt as to the classifica-
tion of even the simplest types. Still a
good deal remains to be done before we
With brown flagellate cells in the cau claim a thorough acquaintance with
^4^0^ ^""jr^" ^f'"^"'^"'''^*'" their development-history and systematic
' ' '^ " ' arrangement.
The third series of pelagic algae consists of brown flagellates,
the chief place amongst which is occupied by calcareous
flagellates or coccolithophoridse (see Fig. 239). Their cells are
Fig. 235
Ornithocercus magnif/ccs.
>:^^/^:
Fig. 236.
a, Citharistes apsteini (^-) ; b, Histioneis gubernaiis {-\^), both with cells of
brown flagellates in special chambers. (Schiitt. )
generally nearly globular, with one or two cilia and one or two
brown chromatophores, and they are protected by remarkable
shields of lime which unite into a complete defensive covering,
though sometimes with a big opening in front. The cell does not
PELAGIC PLANT LIFE
331
always occupy the whole internal space, but lies sometimes, as
it were, at the bottom of a hollow hemisphere or up at the
mouth-opening in a conical sac. The shields of lime can be
dissolved by the weakest acids, and the cell then remains as
an insignificant mass with undefined boundaries. Still, these
shields are very characteristic, and have been found in such
enormous quantities in the deposits on the ocean-bottom that
they aroused the attention of scientists
long before the algae themselves were
known. The commonest forms {Cocco-
lithophora, Pontosphcera) have an almost
globular lime-covering, and are there-
fore without special suspension-organs,
though their surface is big in proportion
to their bulk, if we consider their extra-
ordinarily minute dimensions (5 to 20 \x
if'
Fig. zyj.—PvKOCYSTis noctilvca. (From Chun.)
Fig. 238.
pvrocvstis fusiform is (^j").
( From ' ' Challenger " Narrative. )
in diameter). But in forms like Rhabdosphcsra the calcareous
shields have each a more or less large spike in the middle. In
Discosph(^ra we find trumpet-shaped spines, in Scyphosplicsra
barrel-shaped outgrowths, and during the "Michael Sars" Expedi-
tion I succeeded in discovering even stranger forms. Ophiaster
has a tuft of slightly spiral flexible calcareous filaments.
Michaelsarsia carries in the front of its cell a sort of parachute
or pappus of hollow jointed calcareous tubes arranged in a
332 DEPTHS OF THE OCEAN
wreath. Calciosolenia 7nurrayi resembles, to some extent, the
shape and structure of Rhizosolenia, as the shields of lime are
not rounded like those of most other species, but rhomboid and
spirally bent, so that between them they form a cylindrical tube,
pointed at either end, and furnished at the extremities with one
or two fine calcareous setae.
Notwithstanding their small dimensions these microscopic
calcareous algae oc-
C\^ \ I cupy a very important
place in the economy
of the sea, and their
shields of lime, which
may be met with in
geological deposits
dating from as far
back as the Cambrian
period, show that they
have retained their
shape practically un-
altered through im-
measurable ages.
They are almost en-
tirely oceanic, and
mostly belong to the
warmer seas. In
coastal waters, where
the salinity is lower,
they are scarcer, but
the commone st
species, the little
Pontosphcera ktixleyi,
has been found even
in the Baltic, and
there were such immense quantities of it in the inner parts of
the Christiania fjord during the hot summer of 191 1 (5 to 6
million cells per litre) that the calcareous cells with their strong
refraction gave the sea quite a milky appearance.
The naked flagellates in the sea are still only imperfectly
known, though, no doubt, the part they play is quite a consider-
able one. In coastal waters they occur sometimes in such
abundance that we have actually been able, even with our present
defective methods, to discover and describe a number of species.
In the open sea we are best acquainted with the passive and
Fig. 239.
-Different Types of Coccolithophorid.^i.
Mickaeharsia elegans ; 2, Ophiaster formosi/s ; 3, Rhabdo
spheera claviger ; 4, Syracosphcsra frolongata ; 5
leriia murrayi ; 6, 7, Coccolithophora leptopora ;
sphcera ktixleyi.
Calcioso-
, Portio-
PELAGIC PLANT LIFE
usually almost globular development-stages that live in symbiosis
with various animals, and, in particular, with radiolaria. Of
these radiolaria, which would seem from Brandt's investigations Brandt.
to derive special benefit from the assimilation-products of algae,
we occasionally get the colony-forming species and Acantho-
metridae in such myriads among the surface-layers, that they
contribute a very large proportion of the organic substance
produced. I have previously stated that the brown algae also
regularly associate with a whole series of Dinophysidae. Another
family of brown flagellates includes the species of Phceocystis,
which form large colonies visible to the naked eye, and enveloped
in a loose slime (see Fig. 240). In cold waters these have actually
been known to occur in sufficient
numbers to stop up the mieshes of
silk nets, and render them ineffec-
tive in working.^
It is the brown algae that,
properly speaking, characterise the
plant-world of the sea. Still there
are two other important series, the
cyanophycese and the chloro-
phyceae, which preponderate in
fresh water, and are, no doubt, re-
presented in salt water also, though
by only a few species.
The Cyanophyceae are chiefly Cyanophyce^.
to be met with in warmer seas, if
we except the brackish water forms
that may be found along the coasts
of North Europe in the height of the summer. The genus
T7Hchodesmmm appears as clusters of threads, composed of Tnchodes-
brownish-yellow or red cells, which are either parallel to one """'"'
another, or twisted together, or matted and tangled, and
radiating in all directions. Wille, who described these forms wnie.
collected by the German Plankton Expedition in 1889, showed
that all the types may belong to the same species, Tricho-
desinium thiebaulti, under different development-forms. The
clusters may be seen sometimes when they collect near the
surface in calm weather, and resemble yellowish-brown snow-
flakes. Like the different kinds of fresh-water forms, they can
raise themselves in the water by means of vacuoles that, accord-
ing to Klebahn, contain air. When abundant they sometimes Kiebahn
^ See Summary of Results Chall. Exp., p. 499, 1895.
Fig. 2^0.— PiiyEOCYSTis povcheti.
(Lagerheim.)
134
DEPTHS OF THE OCEAN
cover the surface in one unbroken layer, a phenomenon which
CErsted. CErsted observed in 1849, and which led him even then to
look upon microscopic plants as the basis of production in the
sea. Besides the species of TricJiodesmi2Lm we have another
Katapiymcne. gcuus, Katagjty 7716116, with Spiral series of cells in sheaths of
slime. Mention must also be made of
Riciieiia. the remarkable little alga, Richelia
iiiti^acellulai'is, described by Jobs.
Schmidt. Schmidt, which lives in cells belonging
to various species of Rhizosole7iia (see
Fig. 241). These diatoms appear to
have no difficulty in accommodating
their guest, which apparently repro-
duces itself within the cell, and is thus
transferred to new generations of the
hospitable plant. The riddle is, how
did it originally manage to get in ?
Most likely this happened at a stage
when the Rhizosoleiiia had not yet
developed the silicated cell-wall of the
hermetically sealed chamber with which
we are acquainted.
The green colour which predomin-
ates in plants on land is practically
only to be found at sea in the globular
Haiospiuzra. HalospIicE7'a vi7'idis (see Fig. 241).
Schmitz. This has been described by Schmitz
from Naples, where the people call it
" punti verdi," that is to say, green
spots. It is or may be lighter than
sea-water, so that it floats quite close
to the surface. On the other hand,
Hensen's expedition found it at pro-
found depths, even at 1000 metres,
away down near the limit of the pene-
tration of sunlight, but if this denotes anything in its life-
history, it must be at any rate in a state of resting. HalospJi(E7'a
is reproduced by zoospores, though we do not know how they
proceed to form the small globular cells that little by little
grow up to the normal size. The cell-wall is so firm and
thick that its outer part is burst at last in the course of
growth and discarded, and the inner elastic parts are thus
cieve. enabled to expand. Cleve has also observed thick -walled
Y\G. 241. — Chains of Richelia
INTRACELLULARIS WITHIN THE
CELLS OF RHIZOSOLENIA STVLI-
FORMIS. (Karsten.)
PELAGIC PLANT LIFE 335
resting - cells. Halosphcsra occurs over the whole Atlantic
Ocean, and follows the Gulf Stream to its farthest ramifica-
tions in the north near the coasts of Norway and Spitzbergen.
In the North Sea there are quantities, especially in the winter,
and they form their zoospores in May, and thereby commence
their new generation.
Just as HalosphcEra differs from all the rest of the pelagic
algae in having a pure green colour, so, too, it has its own special
mode of reproduction. The other forms, whose development-
history we know, are reproduced by division, and this goes on
incessantly, the rate of increase depending upon different
conditions of existence. Halosphcera does not undergo division,
but continues to grow for a comparatively lengthy period, and
then finally transforms all its contents,
as has just been stated, into a great
number of zoospores.
In addition to Halosphcera viridis
there are one or two similar species
that have been described, but they do
not call for any particular discussion.
In the foregoing I have sketched
the most important types of pelagic
algae and their biology, but the picture
Fig. 2ifi.—HALospHMRA VIRIDIS, would not be complete if I omitted to
™a1m?T''''^"'°''''''^''''" describe the drifting species of sea- Floating sea-
weed. These do not really belong '''^^^^•
to the open sea. They grow along the coasts in the littoral
zone, and their gas - filled bladders assist them in main-
taining their position whatever be the state of the tide.
The violence of the waves finally tears them loose, and then
these same gas-bladders keep them for a long time floating
on the surface. These patches of-- seaweed are to be met
with in every coastal sea, the chief kinds along the coasts
of North Europe being Fuais vesicidosus and Ascophyllum
nodosum, and in the Mediterranean species of Cystosira.
They may also drift right out into oceanic waters, and in
the Sargasso Sea we have an immense eddy where the
patches of weed often collect in enormous quantities. The
prevailing weed is Sargassuni baccifertivi, but one fre-
quently gets patches of AscophyllMm nodosimi as well, the
whole being derived from the coasts of Central America.
The Sargasso weed is easily recognisable, owing to its
136
DEPTHS OF THE OCEAN
side branches
(see
berry - like bladders on special small
Fig- 243)-
One cannot help being struck by the fact that the drifting
Sargasso weeds are destitute of the ordinary organs of repro-
duction. This seems to be invariably the case with attached
algae that have been torn loose from their support. They con-
tinue to grow vegetatively, but are deprived of all power of
forming new reproduction organs, until they can attach them-
selves afresh. The same holds good, too, with those strange
broken-off masses of
algae that one finds
drifting about along
the bottom in bays, the
constant movement of
the water-masses pre-
venting them from
attaching themselves
to the soft mud or
sand.
The Sargasso
weed continues to
grow as it drifts, but
the gas -bladders are
not formed in the
same proportion as
on the ordinary
branches, the result
being that one finds
newly detached
patches close up to
the surface, whereas
the older patches with
a greater specific
weight have sunk lower down. These last have, moreover,
thinner branches and a lighter olive-brown colour. Finally,
the power of floating ceases altogether, and the patches sink
into deep water and perish. Their disappearance is, however,
quite imperceptible, since fresh patches of weed are constantly
arriving from the coast.
It is quite usual to find smaller algae fastened to the Sargasso
weed, and there is, besides, a characteristic animal-life amidst its
branches, but none of these organisms properly belong to
the ocean, notwithstanding their being found there so invariably.
Fig. 243.
-Branch of Sargassum bacciferum.
(From Kerner.)
PELAGIC PLANT LIFE 337
This is true also of the attached algae, which develop upon
driftwood, vessels, and other large objects. They show that
germs of littoral organisms abound in the open sea, and are far
more numerous than our random samples would seem to
indicate. In May 1904, when cruising in the Norwegian Sea,
in lat. 67° N., where the bottlenose whales are annually shot,
we came across some wadding from a whaler's gun drifting in
the sea, the lower side of which was thickly overgrown with
attached forms of littoral diatoms.
Castracane, after examining the first big collection of pelagic Geographical
diatoms from all the seas of the world made by the " Challenger " offhe^^gia'^c
Expedition, came to the conclusion that there was no essential aigje.
difference between the flora of the different areas. In this,
no doubt, he was right to a certain extent, since many species
are very widely distributed ; still a closer study has shown us
that there are definite marine areas and conditions of existence
in which they develop in vast numbers, whereas in other localities
they occur perhaps in such small quantities that only their
skeletons in the bottom-samples furnish evidence that they have
actually been present. Besides, we often find that species with
a wide distribution have different forms in the different areas,
though we have not yet the means of deciding whether these
forms diverge from the main type by virtue of hereditary
characteristics, or whether they merge into one another through
constant modifications. But in any case these forms are
characteristic of the flora of a given locality, and any one
who examines plankton-samples will become aware that it is
nearly always possible to determine the area from which they
have come. During the German Plankton Expedition under
Hensen in 1889, Schiitt convinced himself that the different Schutt.
currents had their characteristic flora, and he was at a loss
to understand how it is that local boundaries of distribution
can continue, seeing that the currents are ever carrying off the
microscopic plant-life from one part of the ocean to another,
and it might consequently be expected that all differences would
be obliterated.
Schutt has also given a good description of the character of
the plant-life in different parts of the Atlantic, but the honour
of being the first to systematically investigate the distribution of
all the different species, and the influence exerted upon them
by ocean currents, must be assigned to the Swedish biologist cieve.
Cleve. A chemist by profession, he had for many years made a
z
33<
DEPTHS OF THE OCEAN
special study of diatoms before he commenced co-operating about
1890 with the well-known hydrographers, Otto Pettersson
and Gustaf Ekman. They commenced their labours in the
Skagerrack, that remarkable little sea where so many different
water-masses meet and pass each other ; and it very soon became
clear that different currents might each possess synchronously its
own particular flora, and therefore there was the possibility of
ascertaining where the water-masses came from, by determining
their flora.^ All that was requisite was to know the distribution
of the different species in contiguous parts of the sea. The
investigations were accordingly extended, and samples were
collected by ordinary steamers in the North Sea, the Norwegian
Sea, and the Northern Atlantic, in addition to the collections
that were gradually formed chiefly through the efforts of
Swedish, Norwegian, and Scottish scientific expeditions.
Cleve also studied the annual changes in the plankton, and had
weekly collections made at selected stations on the Swedish
coast. The scope of his investigations was further enlarged,
for his unique knowledge of forms enabled him to determine,
not merely all pelagic plants, but also little by little, a whole
series of animal-families which proved no less useful than the
algse as " guiding forms " to determine the character and origin
of the plankton.
Cleve believed that he could distinguish a series of plankton-
types characteristic of defined marine areas. Particular species
were therefore assigned by him to one or other of these main
types. But whereas outside the Skagerrack each of the plankton-
types had its own characteristic distribution, within this sea the
same types were found to predominate, each in its own character-
istic season. From February to April there were the same
species that we have learnt to connect with the coasts of Green-
land and Spitzbergen in the Polar Sea, and from May to June
there was a plankton resembling that of the Western Baltic.
During the course of summer and autumn there were, first of all,
species like those belonging to the southern part of the North
Sea, and afterwards Atlantic and more northerly forms. Cleve
was led to conclude that these changes in the Skagerrack were
due to the fact that it is supplied during the course of the year
1 " While passing through the Japan Stream the tow-net observations indicated water from
two different sources. When in the colder streams there were very many more small diatoms,
Noctilucce, and Hydromedusse than in the warmer streams, where the same pelagic animals that
were obtained all the way from the Admiralty Islands prevailed. Many similar instances
occurred during the cruise, where the approach to land or the presence of shore water was
indicated by the contents of. the tow-nets" (Narrative of the Cruise, Chall. Exp., vol. i.
p. 750, 1885 ; see also Summary of Results Chall. Exp., pp. 893 and 895, 1895).
PELAGIC PLANT LIFE 339
in regular rotation with water-masses from the marine areas
to which these plankton-types belong.
Subsequent investigations have shown that Cleve's view,
which he endeavoured to apply even more widely, was pre-
conceived. His eagerness to discover how far the distribution
of particular species depended on sea currents, made him apt to
forget that algae are living organisms which are incessantly in
process of formation. Accordingly, when the conditions of
existence in the flowing water-masses gradually alter, it is the
new conditions of existence that decide the character of the
flora, since the species best qualified to endure them will very
soon get the upper hand over the others. When, therefore, in
a sea like the Skagerrack we find northern and southern forms
alternating during the course of the year, we are not compelled
to assume that the flora is being periodically recruited from
different areas. The periodic alterations in the conditions of
existence, and particularly in temperature and sunlight, which
in our latitudes follow the course of the seasons, sufficiently
explain why at one time northerly species predominate and
thrive in low temperatures, and why southern forms succeed
them and benefit by the warmth which they find necessary for
their proper development. Of course it is absolutely essential
that germs should be present ready to develop whenever the
conditions of existence become favourable. A certain proportion
of these, no doubt, may be introduced by currents from else-
where, but there is nothing to prevent them from remaining in
a particular area, even though the water-masses are in constant
motion. Recent hydrographical researches have shown us that
eddies are far more common than was at one time believed.
Even in areas where huge masses of water are constantly
streaming in one direction, which one might naturally suppose
would carry away with them all germs belonging to a local flora,
these eddies act as a retaining factor, preventing any complete
replacement till germs sufficient to maintain the local flora have
been transferred to the supplanting water-masses. In coastal
seas, moreover, many of the species are able to evolve resting
bottom-stages, which lie waiting to reproduce the local flora, as
soon as the conditions of existence are congenial.
Still Cleve's investigations have been of great value, and
his plankton-types provide us with a biological division of
species which is yet in the main quite serviceable. All that
we have to say by way of qualification is that Cleve looked
upon his types as representing communities of species limited
340 DEPTHS OF THE OCEAN chap.
to definite marine areas, whereas in reality the areas of distri-
bution of the different species encroach so upon each other,
that a division of this kind is hardly practicable. This is true,
not merely of the altering flora of ocean-currents, but also of
the attached flora along the coasts and on land. Unless the
areas are exceedingly remote from one another, the forms
common to the areas usually exceed those peculiar to each
area. Cleve's types, on the contrary, have no species in
common, and therefore do not record the species in any
definite area, but merely group them in accordance with their
conditions of existence. If we adopt his principles we can
certainly obtain a biological division of the species that is
satisfactory in the main ; but when we come to details it will,
in some cases, be difficult to decide whether a species is to be
assigned to this or to that type.
Biogeographically, the pelagic alga; may be divided, firstly
according to the latitudes in which they are distributed, which
is generally tantamount to saying according to their need of
warmth and light, and secondly according to their occurrence
along the coasts or in the open sea. This latter classification
gives us the most distinct boundaries, and we will therefore
consider it first. There is a whole series of species which
unmistakably belong to coastal waters, and occur there in
myriads at definite seasons of the year. Out in the ocean we
do not find them, except when salinities or other physical
properties indicate that they must have drifted from the coast.
iiaeckei. These have been termed neritic on the suggestion of Haeckel.
Opposed to them are the oceanic species, which belong to
the ocean and float over profound depths, from which
occasionally they are swept by the currents into coastal seas
and there usually perish.
Neritic It is possible to imagine various reasons why the neritic
species. species keep in the vicinity of the coasts. Some may derive
benefit from the low or fluctuating salinities, which enable them
to outstrip the more easily affected forms. Others, perhaps,
require the abundant supply of nourishment from the land
in order to grow and multiply as fast as such organisms should
do. There may be other species, again, whose development-
history makes it necessary for them to remain on the bottom
at one stage of their existence, like the hydroid medusae and
all pelagic young-stages of littoral animals. Most of the neritic
algae have a bottom-stage, in so far as they form resting-spores
PELAGIC PLANT LIFE 341
that sink to the bottom in the shallow coastal seas, where they Resting
rest until conditions of development become favourable again, ^p^""^^-
This has been observed by many naturalists since Schlitt first
noticed in the Western Baltic that a species which begins to
form resting- spores disappears shortly afterwards from the
surface-layers. He showed, too, that the resting-spores sink
down to the bottom, and, although their germination has not
been carefully studied, we may be sure, all the same, that it
does take place ; further, when we subsequently find the same
species once more in abundance, we have every reason for
surmising that the resting-spores on the bottom were the
principal source from which these forms have been derived.
Ability to form resting-spores must be of the utmost
importance for the existence of the species in coastal waters.
The chief difference between coastal seas and the ocean, so
far as hydrographical conditions are concerned, lies in the
extreme and rapid changes in such fundamental conditions
of existence as salinity and temperature in coastal waters,
Resting-spores, therefore, must be the means by which many
species continue in coastal seas, notwithstanding the fact that
there conditions of existence are only favourable for a limited
portion of the year. The arctic diatoms, for instance, which
are sometimes to be found in the plankton of the Skagerrack,
are very easily affected by a rise in temperature, but their
development takes place during the winter months from
February to April, when the temperature is at its minimum.
In the summer they are not to be seen, but their resting-spores
are then most probably on the bottom. In the same way a
whole series of warmth-loving species pass through the winter
as resting-spores, and are to be found along our shores only
in the warmest months of summer and autumn.
The neritic species may often be met with a long way Neritk
out at sea, still continuing to increase, though they are ^i^t°i"-
• -y^ rir- 1 P^ ^^'
seldom m any great quantity. One of the few mstances that
I know of, where we regularly find an immense production of
neritic diatoms in the open sea, is in the Gulf Stream north
of Shetland and the Faroe Islands during May. I made this
discovery as long ago as 1895, and it has often been confirmed
since then during the international investigations. When the
snows begin to melt in the spring, the surface-layers of water
are carried far away out from the land, and the neritic algae are
taken with them. I shall presently show that it just happens
to be in the spring that conditions of nourishment favourable
diatoms in the
342 DEPTHS OF THE OCEAN
to an abundant plant-life exist in the Northern Atlantic, and
the somewhat exacting neritic species benefit accordingly.
This explanation, at any rate, seems to me the most reason-
able one.
Another well-known instance is in the Polar Seas during
the summer. Close to the melting polar ice, where it meets
the warmer water- masses, a rich flora of neritic diatoms
sometimes develops, while littoral species form a brown layer
over the floes and broken lumps floating between them.
Blessing, who took part in Nansen's expedition during 1893-
1896, has given a good description of this latter phenomenon.
We must look upon the Polar Seas as coastal waters in
the biological sense. They have the extreme variations of
temperature and salinity, and probably also the abundant
supply of nourishment, that we would expect to find in a
coastal sea. The resting-spores are enclosed in the ice, as
I was able to show after examining the material collected
by Nansen.
In the warmer parts of the Atlantic there are neritic
diatoms nearly everywhere, but never in any great quantity,
except where rivers enter the sea in the tropical regions. As
a rule, too, they are smaller and weaker in structure than
those we meet with in coastal waters under similar conditions
of temperature. The cell -walls are very often only slightly
silicated, and the form itself is so indistinct that it is difficult
to distinguish species, which in their properly developed
condition have unmistakable characters. It is not easy to
tell whether this degeneration is merely a sign of insufficient
nourishment, or whether other causes are also responsible.
Certainly in one case want of nourishment is not entirely to
blame. Out in the water-masses of the Atlantic to the south
of Iceland we get a community of neritic diatoms that occur
especially in the spring and autumn. Most of them are species
of Chcetoce7'as. The prevailing forms have been long ago
determined, and are undoubtedly C. schilttii and C. /aciniosum.
Still they are so dwarfed in structure, and so much the reverse
of typical, that one might very well say that they were separate
species (see Fig. 244). During this last expedition of ours we
succeeded in finding this diatom-flora again, though in smaller
quantities, in the Gulf Stream off the east coast of North
America, so that it is practically certain that the neritic diatoms
of the Atlantic south of Iceland are derived from the American
coastal sea. As they are borne passively northwards towards
PELAGIC PLANT LIFE
143
the shores of Iceland, they commence to develop at a great
rate, with the result that the plankton in those parts frequently
yields abundant though monotonously uniform samples of these
degenerate forms. The altered conditions of existence, which
obviously must have supervened, have thus resulted in an
extensive production of algse, though without investing them
with their normal robust appearance. The strings of cells
are of much smaller diameter than usual, so that the formation
of auxospores cannot have taken place at the stage that is ^^^^^^^^^
usual elsewhere. Wesenberg-Lund has told us that pelagic Lund.
Fig. 244.
la, ChcBtoceras laciniosum : ifi, forma pela^ica ; 2a, C. schiittii : zb, forma oceanica.
fresh - water diatoms, such as Asterionella gj'-acillinia and
Fragilaria crotonensis, keep on reducing their dimensions in
the Danish lakes for months, sometimes even for over a
year, and then suddenly return to their maximum measure-
ments, and that this is undoubtedly due to the formation of
auxospores. All are not, however, affected alike by such a
change, and the species occur thereafter in two different sizes,
making it necessary to express the measurements of their
cell-dimensions by means of divergent curves. This goes on
uninterruptedly, moreover, and the smallest forms diminish
and seem to degenerate more and more, until in Wesenberg-
Lund's opinion they lose all power of regaining their normal
344 DEPTHS OF THE OCEAN
dimensions and of reproducing their kind. The degenerate
forms of neritic diatoms met with in the open sea appear to
me to lack the stimulus which in some unknown manner leads
to the formation of auxospores ; consequently their ultimate
extinction is only a matter of time, even though they may
continue reproduction through a whole succession of genera-
tions. This is, of course, merely an unsupported surmise, for
the few random investigations we have hitherto made do not
afford sufficient material to settle questions of this nature at
all definitely ; but my idea is that the hypothetical views of an
author are of more value than the enumeration of solitary facts
that have no apparent connection.
Resting-spores When the neritic diatoms evolve resting-spores out in the
sea^^^°^^^" open sea, which occurrence w^e have been able to observe on
more than one occasion, it might be supposed that the spores
would be destroyed after sinking down to profound depths.
This is not, however, necessarily always the case, since they
appear to sink slowly, and remain within the region of light
for weeks if not for months. The spores after leaving their
cells are so minute that they are rarely caught in silk nets,
so that little has been done as yet to throw light upon this
question. But now that we have adopted the centrifuge-
method it is possible to collect them, and we discovered numbers
of resting-spores of species of Chcstoceras in our centrifuge-
samples from the Atlantic. In a litre of sea-water from Station
87 (lat. 46° 48' N., long. 2f 46' W.), from a depth of 100
metres, I secured altogether. 1 160 resting-spores belonging to
three different species of ChcBtoceras, though the forms them-
selves were not present at that time in a vegetative state either
in the surface-layers or deeper down. Most probably what we
got were representatives from the last remnants of the diatom-
masses that throng the surface-layers there during the spring.
Distribution. Nentic species include a very large number of diatoms —
a class by far the most characteristic in coastal seas. In the
majority of these neritic diatoms we have now been able to
prove the existence of resting-spores. The peridinece, on
the other hand, are mainly oceanic, especially the species of
Ceratmni. One of the best-known neritic peridineae is the
comparatively low species Prorocentrimi micans ; but there are
probably, too, whole series of small forms, as yet imperfectly
known, which prefer the neighbourhood of the coasts. The
coccolithophoridse, again, are undoubtedly oceanic, whereas
most of the naked flagellates are most likely domiciled in
PELAGIC PLANT LIFE 345
shallower waters, Halosphara is oceanic, and so also are the
species of Trichodesmium ; but there are several blue-green
species that are brackish-water forms, and they must of course
be accounted neritic [Anabcsna baltica, Nodtilaria spumigena,
Aphanizoinenon flos-aqiics).
Several of the neritic algai practically only occur locally.
Detonida cystifera, for instance, appears in the Limfjord in
Denmark and along the south coast of Norway, while Litho-
desinium juidulatuniy Coscinodiscus granii.Navicula memb^^anacea,
and Streptotheca thamensis belong to the English Channel and
to the southern portion of the North Sea. I could mention
additional examples, but the greater number of them are far
more widely distributed. It has been found possible to allocate
all the species along the coasts of the Northern Atlantic to
three comprehensive main groups, namely, the arctic, temperate,
and tropical. This is perhaps rather an arbitrary arrangement,
as these groups encroach to a very great extent upon one
another ; so that we get northern forms a long way south in
the winter, and in the autumn the southern forms extend
northwards. Further researches, too, might result in a stricter
classification, while it is known that there are species which,
biologically speaking, unite the groups, and might with equal
reason be assigned to the one or to the other.
(i) Arctic neritic species are mainly those which Cleve termed Sira- Arctic neritic
plankton, and consist principally of diatoms. The characteristic forms species.
are the species of Thalassiosira from which this name was derived.
They are composed of long strings of short cylindrical cells united by
a central thread of slime. Thalassiosira hyalina has its southernmost
limit off the north of Norway, while T. gravida and T. nordenskioldii
occur in winter as far south as Central Europe. A series of species
belonging to the genera Fragilaria, Achnantes, Navicula and Amphiprora
are also distinctly arctic forms, and are characterised by having their
cells bound together like ribbons. These include Fragilaria oceanica,
F. islandica and F. cylindrus, Achnantes tceniata, Navicula septentrionalis,
N. vanJwffenii and A", granii, and Amphiprora liyperborea. The
usually predominant genus Chcetoceras is only represented by two
purely arctic species, namely, Chcetoceras furcellatum and C. mitra.
We must likewise add the well-known Biddulphia aurita. Besides
these diatoms, there are the peridinean Gonyaulax triacatttha, and the
brown flagellate PhcEocystis poucheti, with its naked cells in large slimy
round or lobate colonies.
(2) Temperate neritic species are even more numerous. The warmth- ^J^^I^Pf^'^^^^g
loving species fall under Cleve's designation of Didymus-plankton, with "*-» ^c species.
CJicBtoceras didymum as the most characteristic form. It is, however, a
better arrangement, perhaps, to associate with them a series of other
species with a sUghtly more northerly character, that cannot be really
346
DEPTHS OF THE OCEAN
called arctic. Here, too, diatoms predominate, and CJicetoceras takes
first place. The commonest forms include : —
{a) Northerly : Ch(£toceras teres, C. constrictuin, C. diadema, C. debile,
C. crinitum, C. pseudocrinitum, C. scolopendra, C. sociale, C. simile,
Rhizosolenia setigera, TJialassiosira decipiens, CosciJiosira polychorda,
Leptocylindriis daniciis.
ip) Southerly : ChcBtoceras weissflogii, C. contortiim, C. didymuvi,
C. laciniosmn, C. schnitii, C. curvisetum, C. cinctum, C. afiastoinosans,
C. radians, Laiideria anmdata, Ceratatdina bergonii, Biddidphia mobi-
liensis and B. regia, Eucampia zodiacus, Dityluni brightzvellii, Guinardia
fiaccida, Asterionella japonica, the peridinean Prorocentruvi inicans, and
the brown flagellate Phceocystis globosa.
Tropical (3) Tropical neritic species have had far less study devoted to them ;
neritic species, g^ii} ^yg j^^y denote by this term a whole series of species that have
their northernmost limit on the coasts of the Mediterranean. Of these
we may mention : —
Chcetoceras furca, C. diversum, C. femur, Hemiaulus hauckii and
H. heibergii, Detonula scJirdderi, Asterionella notata, Rhizosolenia
cylindrus.
The neritic flora off the coasts of the Atlantic in the southern
hemisphere has also been comparatively little studied as yet.
Still we are justified in saying that the neritic diatoms of the
antarctic, from the ice barrier northwards, differ in the main
from species belonging to the northern hemisphere. The
difference indeed is so great, that hardly a single species is
common to both arctic and antarctic waters. The investiga-
tions of Cleve, Karsten, and Van Heurck show that the
following neritic diatoms may be considered characteristic of
the antarctic : — -ChcEtoceras radiculum, Moelleria a^itarctica,
Eucampia balatistitun, jFi'agilaria antardica, Thalassiosira
anlarclica, and probably several others whose biology is as yet
only slightly known.
Neritic dia-
toms in the
Antarctic.
Oceanic
species.
Oceanic plankton algai are much more widely distributed
than neritic algae, and it would almost seem from our material
that each species may be met with in all the seas of the world,
wherever there are favourable conditions of existence. The
diatoms are apt to occur irregularly. Sometimes we find
enormous quantities of them, and at other times they may
be so scarce that it is difficult to detect them. The peri-
dinese are more evenly distributed, and this is true especially
of the species of Ceraliuni, which are fairly abundant and hardly
ever absent from oceanic-samples, unless perhaps in arctic
waters. They may well be used as guiding forms to express
the character of the plankton. It is possible that the different
PELAGIC PLANT LIFE 347
species and varieties of the genera Peridinium and Gonyaulax
might be employed with equal advantage, but they are more
difficult to determine, and so little studied as yet that the
determinations of Hensen and Karsten are unserviceable.
Owing to so little being known about their distribution, I have
decided to ignore them for the present.
The oceanic species may also be divided into three main
groups : —
(i) Arctic forms, corresponding to Cleve's Tricho-plankton and Arctic oceanic
Chaeto-plankton. Most of them occur also in antarctic waters. species.
Diatoms : Thalassiothrix longisshna, Coscinodiscus subbulliens, CJiceto-
ceras criopJnlum, C. boreale, C. convolutum, C. atlanticum, C. decipiens,
Rhizosolenia hebetata {seuiispina), Nitzschia seriata.
Peridineae : Ceratimn arcticum, C. longipes, DinopJiysis gramdata.
(2) Temperate- Atlantic forms, corresponding to Cleve's Styli-plankton Temperate
and Tripos-plankton. The latter of these two designations comprises a oceanic
small community of species, which are less exacting as regards salinity, *P^"^^-
and are therefore produced in quantities along the coasts of North
Europe.
Diatoms : Rhizosolenia styliformis, R. acuminata, R. alata, Coscino-
discus radiatus, C. centralis, C. stellaris, Chcetoceras densum, C. dichata,
Corethron criophilum, Dactyliosolen antarcticus, Thalassiosira subtilis,
Coscinosira cestrupi, Asteromphalus Jieptactis, Bacteriastrum delicatulu^n,
B. elongatum.
Peridineae : Ceratium tripos, C. bucephalum, C. azoricum, C. niacroceros,
C. interjuedium, C. lamellicorne, C. reticulatum, C. fusus, C. furca,
C. lineatuni, Dinophysis acuta, D. hastata, D. hommiculus.
Coccolithophoridae : Coccolithophora pelagica, PontospJicsra Jiuxleyi.
Chlorophyceae : HalospJicsra viridis.
(3) Tropical-Atlantic forms, corresponding to Cleve's Desmo-plankton, Tropical
and comprising a series of species, especially peridineae and coccolitho- oceanic
phorids. Cleve's guiding form is the blue-green alga Trichodesmium
tJiiebaultii. The following are some of the commonest : —
Diatoms : Coscinodiscus rex, Planktoniella sol, Gossleriella tropica (see
Fig. 245), Rhizosolenia castracanei, Chcetoceras coarctatum, Asterolampra
marylandica, A. rotula.
Peridineae : species of Ceratium of all groups {prcelongum, cephalotum,
gravidum, cajidelabrum, pennatum, extensuvi, palmatum, massiliense,
carriense, and several others), species of Oxytoxuvi and Podolampas,
Ceratocoiys horrida, species of Phalacroma, Dinophysis schiittii and
D. uracantJia, species of Amphisoletiia and Ty-iposolenia, Ornithocercus
magnificus, O. quadratus, O. steinii and O. splejididus, Pyrocystis
noctiluca and P. fusiformis.
Coccolithophoridae : Coccolithophora leptopora, species of Syracosphcera,
Calciosolenia murrayi, Michaelsarsia elegans, and many others.
The boundaries of the areas populated by these communities
of species are as variable as the limits of distribution for the
348
DEPTHS OF THE OCEAN
species themselves. Our investigations at different seasons,
both in coastal waters and in the North Atlantic, have shown
us that the flora of each locality is constantly changing. One
species succeeds another as month follows month, and different
societies predominate in the same locality at different seasons.
Along the west coast of Norway, for instance, we find a
flora during the winter, from December to February, scanty in
numbers, but consisting of many species, and mainly composed
of true Atlantic forms (Styli-plankton), which reach their northern-
most limits in the dark months of the year. About March or
April the temperature attains its minimum, and great quantities
Fig. 245.
a, PlanktoTiiella sol, and b, Gossleriella tropica, from the Atlantic. (Schiitt. )
of diatoms are then produced, which are mainly arctic. Some-
times these are almost entirely neritic, and sometimes there is a
considerable addition of oceanic species. As often as not it
is the species of Thalassiosira and Coscinodiscus which first
appear, and then comes Chcetoceras, C. debile being usually the
form found on the west coast, C. constiHctum preferring the
Skagerrack. In May the predominant form is generally
Leptocylindrus daniciis. We next get a period in June when
the prevailing forms are oceanic, Ceratimn longipes at that time
attaining its maximum development and characterising the
flora. In August the warmth-loving peridineae begin to be
more and more numerous, Ceratuim fusus, C. furca, and
C. tripos being then much in evidence, and continuing to increase
until October. Finally, in November we get a comparatively
PELAGIC PLANT LIFE 349
large amount of southern neritic species (Didymus-plankton),
made up to a great extent of forms of distinctly foreign origin.
As the dark months of winter approach, however, their numbers
rapidly decline.
In the open sea, too, our investigations appear to indicate Flora of the
that the southern forms reach farthest north in the autumn, say °pensea.
about November, while during the months of spring, from
April to May, northern forms extend very far south. We have
not as yet made investigations at different seasons in the tropical
parts of the Atlantic ; consequently we cannot say whether there
is an annual cycle of plant-development in a region where the
conditions of existence seem to vary so little. It would be an
excellent thing if researches of this nature could be undertaken.
Supposing that the ocean -currents do exercise a direct Ocean-
influence upon the character of the plankton in the tropics, it is J^hrpSnkton
fair to imagine that it must be in the direction of periodicity.
Lohmann has put forward the suggestion that the changes in
pelagic animal life near the coasts of South Europe are connected
with a cyclic movement of the water-masses. When these
reach their northernmost point the conditions of existence will
affect the organisms, so that the water-masses that pass through
this region in the winter are likely to have a different fauna
from that of the water passing through in summer. Elsewhere
it is very difficult to tell what changes in the plankton are
due to the direct influence of ocean-currents, and what changes
are the result of altered conditions of existence partly due
to ocean -currents and partly to other causes. It has often
been observed, not only by Cleve and Hensen, but also
during previous researches made by the " Michael Sars " and
during the "Challenger" and " Valdivia " Expeditions, that the
plankton changes its character the moment one passes the
boundary between two currents. Thus an examination of the
plankton may serve as a check on purely hydrographical
investigations, which aim at ascertaining the boundaries of
currents by means of observations of their temperatures and
salinities. Perhaps the best guiding forms are the species of
Ceratiwn, and strangely enough it is very often the species
that systematically are the nearest related, which replace each
other as we pass from one area to another. Many of them
are so closely related that it is only for the sake of con-
venience that we regard them as distinct species, and there
is always the possibility that they may be able to pass directly
from one form into the other, even if we cannot actually prove
350
DEPTHS OF THE OCEAN
that they do so. There is a series of closely related species,
for instance, grouped round Ceratiuvi macroceros. Ceratium
arcticum is the farthest outpost in the direction of the polar
sea, and shows the greatest variation. Its three horns are
extremely divergent ; the centre one, which points forward,
is slightly bent, and so also are the other two. Near the
southern limit of the species there are more and more instances,
in a series of transition forms, where the two posterior horns
bend forward, till we get to Ceratium longipes, the characteristic
form of the Norwegian Sea and North Sea during the first half
Fig. 246. — Species of Ceratium belonging to the type of C. macroceros,
northern species.
a, C. arcticum; b, C. longipes ; c, C. macroceros ; d, C. infermediitm (-J-). (Jorgensen.)
of summer. In this case, the posterior horns are bent quite
forward, so that their extremities are parallel with the frontal
horn. In the Gulf Stream we get C. intei'-niedium, which has a
straight frontal horn, like the other members of this type, and
all three of its horns are much longer and more slender than
those of the two northern species. At the eastern limit, where
fresh water from the Baltic and the coasts of North Europe
reduces the salinity, and where, too, the high summer temperatures
diminish the viscosity of the surface-layers, there is a species
with an even better suspension-apparatus, namely C. macroceros
(see Fig. 246). Its frontal horn is particularly long and thin,
and the posterior horns first bend a little backwards, and then
PELAGIC PLANT LIFE
351
sweep round to the front, sometimes in a direction parallel to
the frontal horn, and sometimes with a moderate amount of
divergence. We have already mentioned that C. ardicum and
C. longipes belong to the Tricho-plankton and that C. inter-
medium and C. macrocej^os are Styli-plankton. We have finally
a whole series of variations belonging to the tropical Desmo-
plankton, namely C. vultur, C. paviliardii, C. trickoceros, and
C. tenue, which we reproduce from Jorgensen's excellent mono-
graph (see Fig. ^^ ^,
247), and many
others. They
illustrate the dif-
ferent tendencies
to variation. In
similar fashion
there are series of
variations which
group themselves
round the other
main types of the
genus.
Guiding forms
like these are of
very great assist-
ance in defining
the boundaries of
adjacent currents
which have a
different biological
character. But
we need to exer-
cise the utmost
care in drawing
conclusions as to
the origin of ocean-currents from the composition of their
pelagic flora, and it must not by any means be taken for
granted that areas where the same species occur are neces-
sarily united by a continuous stream connection. We have
repeatedly made discoveries which go to indicate that most
plankton-species of any consequence are to be found scattered
about here and there outside their proper domain, so that
these stray individuals might easily originate an abundant
flora whenever conditions of existence became favourable.
Fig. 247.— Species of Ceratium belonging to the type
of c. macroceros, tropical species.
a, C. paviliardii (\*-) ; b, C. trickoceros (-\4) ; c, C. vultur, var.
Japonica (\*-) ; d, C. tenue, var. buceros {-\^). (Jorgensen. )
352 DEPTHS OF THE OCEAN
Cleve, who looked upon the dispersal of organisms by currents
as the chief factor in affecting the character of the plankton,
was at first of opinion that he could fix the north-western
boundaries of the Gulf Stream by noting the distribution of
Rhizosolenia styliformis, the guiding form in his Styli-plankton.
But he, too, found that its area of distribution extends northwards
in the course of spring and summer, and that the swarms of
Rhizosolenia actually outdistanced the speed of the current.
The wider distribution of the algae was evidently, therefore, due
not alone to the increased volume of the current, but also to a
rapid propagation produced by summer warmth outside the
influence of the current, the algae apparently having been already
present in this area in small quantities.
I may further instance the close agreement between oceanic
species in arctic and antarctic waters. Thalassiothrix longissima
and Rhizosolenia semispiiia [hebetata) are the two most character-
istic forms among algae along both the polar boundaries of the
Atlantic, though they have also been found in small quantities
at various localities in the tropics. I personally came across them
on several occasions during the "Michael Sars " Expedition,
and it requires, in my opinion, no special theories to account
for this " bipolarity." There is quite sufficient connection
between the two oceans to enable a few germs which are
exceptionally tenacious of life to pass from the one to the other,
and this would amply explain the agreement. Characteristically
enough there is no similar agreement between arctic and
antarctic waters when we come to the neritic forms, and this is
probably because they are less adapted to travel over such
immense distances. It may be, too, that their tendency to evolve
resting-spores is an obstacle to long passive wanderings.
As a means of determinino^ the direction and velocity of
currents pelagic algae will be found of very little use. Their
continued existence during the progress of the current must
always depend upon their persistence in reproduction, and this
again is dependent upon conditions of existence and competition
with other species. It is not mere coincidence that the
microscopic flora of the warm Atlantic extends farthest north
during the dark winter months, when no other species are much
inclined to develop, and there is therefore no competition of
any consequence, the character of the flora consequently
remaining for a long time unaltered. Large animals, such as
medusae and salpae, or the larvae of bottom-animals like Phoronis,
will be found far better indicators of the currents. Ostenfeld
PELAGIC PLANT LIFE
353
has, however, encountered one solitary case where plankton
algae could be employed for this purpose. Biddulphia sinensis
(Fig. 248), a neritic diatom from the coasts of the Indian Ocean,
was met with in the North Sea for the first time in 1903, to
begin with in the southern parts, and then gradually farther
and farther north, until at last it was discovered on the west
coast of Norway at Bergen. Its travelling rate corresponds
to the values which have been otherwise obtained for the
velocities of the current along the coasts of Denmark and
Norway. Latterly, it has found a fixed distribution-centre in
the north-eastern corner of the North Sea, whence it extends
still farther northwards every
autumn. The velocity of the
current could hardly be deter-
mined from the observations of
these last few years, as there is
always the possibility that this
diatom has more than one
centre of distribution, but its
annual wanderings clearly in-
dicate the direction of the
current.
A large quantity of plankton
algae has been collected during
the "Michael Sars " Expedi-
tion along the whole route, and
will contribute valuable infor-
mation regarding the distribu-
tion of the different species. We have been particularly
successful in our study of the coccolithophoridae, owing to the
improved methods we were able to adopt. I shall deal
separately with their distribution in what follows, and at the
same time give some particulars of their quantitative occur-
rence. Part of the material is still incompletely examined.
The difficult species of Peridinium in particular, and of a few
other genera, will require a separate monograph for their special
treatment ; we have secured immense numbers of these forms.
In other respects our observations practically confirm the
views regarding the distribution of species that we owe chiefly
to Cleve.
I shall now give a preliminary description of the character of
the plankton along our route, founded upon an examination of
Fig, 248. — Biddulphia sinensis (^
(Ostenfeld.)
Phytoplank-
ton collected
during the
" Michael
Sars " Ex-
pedition.
354 DEPTHS OF THE OCEAN
material from representative stations, and upon observations
of the living organisms on board ship.
The coast All our first stations about the middle of April, with the
No'nh Europe, ^xception of Stations i and 5, that were close in to land
(Stations i-io, and had a less abundant flora, had an extremely plentiful
Aprfu^ diatom-plankton, such as we only get in the waters of North
Europe during the spring. Our experiments with the closing-
net, which, thanks to the fine calm weather, were made with
the utmost exactitude at Stations 3 and 10, showed that by far
the larger number were to be found between the surface and
a depth of 100 metres, though even at a depth of 100 to 150
metres there were still quite considerable quantities. The
character of the flora was mainly northern, especially in the case
of the oceanic species. Among the principal forms we got
Rhizosolenia hebetata forma se7nispina and Nitzschia seriata.
Neritic diatoms were also numerous, and some had resting-
spores. They are of a distinctly southern character compared
with the species which occur, for instance, along the coasts of the
North Sea ; further, they belong to a local flora, which does not
seem to have any direct connection with the North Sea. On
the whole, these neritic diatoms are so small in their dimensions
that they show signs of an "oceanic degeneration."
Besides them, there was an addition of subtropical species,
especially in the deeper layers, and especially at the southern-
most stations, Nos. 9 and 10, consisting of both diatoms and
peridinese, not in any great quantity, but still occurring regu-
larly. These are the northernmost outposts of the Desmo-
plankton, including such species as Planktoniella sol, Ceratmm
gibberuni, Dinophysis schuttii, and D. uracantha}
The coast Throughout the stretch of sea along the coasts of South
Europe anT Europe and North Africa our investigations were carried
North Africa, on Comparatively close to the coast, and the plankton was
4i,Vi°srAprii- generally found to be poor both in quality and quantity as soon
22nd May.) as we stood at all far out from the land. It was then 'composed
^ As representing this area, I here give a list of species from Station 7, depth 0-20 metres : —
Oceanic diatoms : ChcBtoceras decipietis, C. densum, C. convolutum, C. periivianum,
C. atlatiticum, C. dichceta, Coscinodisctts centralis, C. margutatus, Euodia cuneiforniis, Thalassio-
stra subtilis, Asteromphalus heptactis, Rhizosolenia alata. A', seinispitia, E. stolterfotkii,
R. shrubsolei, R. acuminata, R. amputata, Dactyliosolen antarcticus, Nitzschia seriata,
Thalassiothrix longissinia.
Neritic diatoms : Chcetoceras diadema, C. schiittii, C. contortum, C. coronatum, C. scolo-
pendra, Bacteriastrum varians, Eucampia zodiactis, Thalassiothrix nitzschioides, Cerataulina
bergonii, Dattyliosolen tenuis, Thalassiosira decipiens, T. excentrica, T. tiordenskioldii.
Peridineae : Ceratium tripos forma atlantica, C. lamellicorne forma compressa, C. azoricum,
C. furca, C. arietinum, and several others.
Coccolithophoridffi : Distephanus speculum, Coccolithopkora pelagica.
PELAGIC PLANT LIFE 355
of oceanic species, that we subsequently met with in the central
parts of the ocean, though there was not more than a mere
selection of the very commonest forms. It was here that we
first became aware of the immense contrast between the scanty
plant life and the teeming animal life. Sir John Murray and I
examined the stomach contents of the salpee abounding in the
Strait of Gibraltar, and could see that they lived almost entirely
on small forms like coccolithophoridse and tiny peridinese,
which were too diminutive for our silk nets to capture.
Radiolaria, however, both Acanthometridae and colony-forming
species, in symbiosis with brown flagellates, were present
sometimes in such quantities that their assimilation of carbonic
acid played no small part in proportion to that of the scanty
plant plankton. Close in to the shore, on the other hand, there
was abundance of plankton, and we got quantities of neritic
diatoms off Lisbon, in the Strait of Gibraltar, and at several
places on the coast of Morocco down to Cape Bojador. Different
species predominated in the different samples, but Laiideria
aimulata was the commonest form everywhere.
No one accustomed to the plankton algae of northern waters,
with their numerous dark-brown chromatophores, could fail
to be struck by the fact that the species never had more
than a few small chromatophores, and thus had a pale
appearance. In the diatoms the strong light frequently had
the effect of making the chromatophores group themselves in
the centre of the cell, or in Lmtderia annulata at the terminal
faces where the cells in the chain touch each other. This was
invariably the case in plankton near the surface, though deeper
down the position of the chromatophores might be normal.^
On this cruise we made acquaintance with the tropical The Central
Atlantic plankton in all its abundance. For a northerner it ;A^tia'itic from
V • • -11 r ' • 11 "^"^ Canaries
was most tascmatmg to study the many strange forms, especially to the Azores,
of peridineae. Every fresh batch disclosed species that were A^oresTo^he
new or rare, or else remarkable stages of development. The Newfoundland
1 The following list is from a sample pumped up from the surface, off the south coast of gg 28th May
Portugal, on 24th April 1910 :— 29th Tune.)'
Diatoms : Lauderia anmilata (the prevailing form, found with auxospores), Thalassiosira
subtilis, T. gravida, Stephanopyxis turris, Paralia sulcata, Coscinodiscus concinnus, Lepto-
cylindrus danicus, Rhizosolenia alata, R. shrubsolei, R. styliformis, R. stolterfothii,
R. delicatula, R. robusta, Chatoceras densum, C. schiittii, C. didymu))i,C. curvisetum, C. decipiens,
C.'lorenzianum, C. diversum, Eucanipia zodiacus, Hemiaulus hauckii, Biddtdphia mobiliensis,
Bacteriastrujn varians, Nitzschia seriata.
Peridineee : Ceratium lineatttm, C. macroceros, C. fusus, C. furca, C. candelabrum, species
of Peridinium, Gonyaulax spinifera, Diplopsalis leiiticula, Dinophysis acuminata, D. rotundata,
D. acuta; Coccolithophora pelagica.
356 DEPTHS OF THE OCEAN
multitude of species was surprising, though none of them was
very numerously represented. Every day one might sit and
examine some unique microscopical form, which might be lost
only too easily, and consequently had to be drawn there and
then. And whereas in the north there are large quantities of
every species, so that it is easy to investigate them in all their
stages of development and variation, this multiplicity of forms
in the tropics renders it incomparably harder to find out what
stages of development belong to the same species, or how the
boundaries between the different species are to be fixed.
The various stations did not differ much from one another,
if we except Station 59, near Fayal in the Azores, where there
were numbers of neritic diatoms, and Station 66, close to the
Newfoundland Bank, where there was an addition of arctic
forms. On the whole, the multiplicity of species increased as
we went westwards. Possibly considerable differences may
be revealed when the material has been completely treated, but
all the species occur too sparsely in these samples to justify
one in drawing conclusions from negative results.^
The Tropical Atlantic flora much resembles the plankton
flora of the Indian Ocean observed by Karsten. In the Pacific
there would seem, according to Kofoid, to be an even greater
multiplicity of species, but I found several of the new species
obtained by him during the "Albatross" Expedition, and it is
probable that more and more of these rare Pacific species will
gradually be found within Atlantic waters also.
In conclusion, it should be stated that, as far as quantity
is concerned, the smallest plankton organisms, Lohmann's
Nanno-plankton, play a far more important role than the whole
of the other species caught in our silk nets, which will be
subsequently discussed in their proper order.
^ To show the character of the flora I append a list of species found at Station 64, lat. 34°
44' N. , long. 47° 52' W. , in a closing-net sample from a depth of 2CX) metres to the surface : —
Diatoms : Coscinodiscus rex, C. Hneatus, Euodia cuneiformis, Planktoniella sol, Gosslenella
tropica, Thalassiosira stibtilis, Asterolatnpra tnarylandica, Rhizosoleniacastracanei, R. acuminata,
R. styliforinis, Bacteriastrum elongatuin, HemiaulKS sp., Chatoceras diclmta, C, tetrastichon,
C. peruviaman, C. coarctattiiii, C.furca.
Peridinese : Ceratium pentagonum, C. teres, C. candelabrum, C. gravidum, C. fusus,
C. extensuin, C. pennattmi, C. gibberutn, C. buceros, C. platycorne, C. azoricum, C. ienue,
C. pavillardi, C. karsteni, C. declinatuin, C. gracile, C. arietinum, C. macroceros, C. massiliense,
C. arcuatum, C. ca}-riense, C. reticulatum, C. trichoceros, C. pahnatum, C. limidus, C. pulchellum,
species of Peridinium, Diplopsalis lentictda, Blepharocysta splendor maris, Ceratocorys horrida,
Goniodoma polyedricum, G. Jlvibriatum, Gonyatilax polygramma, G. joliffei, G. pcuifica,
G. fragilis, G. mitra, Protoceratium retictdatum, Podolampas elegans, P. palmipes, P. bipes,
Oxytoxum scolopax, 0. retictdatum, O. cristatum, O. milneri, O. tesselatum, Dinophysis
uracantha, D. schiittii, D. schrdderi, PJialacrotna argus, P. doryphorum, P. cuneus, P. rudgei,
Amphisolenia palmata, and another new species, Ornithocercus quadratus, O. magnificus,
O. steinii, O. splendidus, Pyrocystis lunula, P. noctiluca, Hexasterias problematica.
CyanophyccEe : Trichodesmium thiebauUi.
PELAGIC PLANT LIFE 357
The plankton of the cold water on the Newfoundland Bank The Nc
was very poor in species, Ceratijim arcticum and Peridinmm g^^k^^
parallelum being the commonest forms. There were, besides, (Stations 70
9, 3(
loth July.)
a few diatoms, such as Chcetoceras atlanticum, C. criophihim, 79, 30th June
and Rhizosolenia seynispina, all well-known species in the
Norwegian Sea. In the harbour of St. John's, on the other
hand, we found the plankton quite abundant, consisting of
northern forms, both neritic and oceanic : the species of Chce-
toce7'as {decipiens, debile) predominated.
to our
ir northern section across the Atlantic contributed largely
knowledge of the distribution of species, since it showed
Atlantic
section.
(Stations 8i-
92, I2th-24th
July.)
Fig. 2^().—Chmtoceras perpusillum (^f^).
US that a great many tropical forms are still to be found in lat.
45-50^ N. These particular waters had been very little studied
previously, and it was extremely interesting to follow all this
Atlantic flora on its passive journey northwards. On the whole,
its character remains unchanged, though of course the number
of species becomes considerably reduced. During the first half
of the section, on the western side of the mid-Atlantic ridge,
there were a few small degenerate neritic diatoms belonging to
the species which occur in the Atlantic water-masses south of
Iceland : namely Chcutoceras schiittii, C. laciniosimi, and others.
It seems unquestionable that they are derived from the American
coast, and follow the current as far as Iceland. At Station 85 I
also came across a remarkable little ChcEtoceras, that Cleve found
in 1897 ^^ ^^ Skagerrack and named ChcBtoceras perpusillum
358
DEPTHS OF THE OCEAN
(Fig. 249), which had not been met with subsequently. The
whole structure of this diatom shows that it, too, is most
probably a neritic form, and it must therefore have a wider
distribution than was commonly supposed.^
As we neared the coast banks of Europe we found the
number of species growing distinctly less, though on the other
hand the quantity of the plankton increased.
The plants of the sea like those of the land build up all the
organic substance which forms the chemical foundation of life.
If we wish to know clearly when and how and under what
^^^' conditions vigorous production takes place, or what prevents
the development of an exuberant plant-life, we must first
acquire the means of estimating the amount of vegetation in the
different parts of the sea.
Hensen. Hcnsen was the first to take up this problem, the solution
of which depends on three assumptions: (i) it is absolutely
essential to have apparatus that can capture all the organisms
living in a specified quantity of water, (2) the plankton must
be supposed to be uniformly distributed in the sea, so that the
catch represents a reasonably extensive area ; and (3) a scientific
examination of the catch must supply a really correct picture of
the amount of plants and their capacity of production.
Hensen'snet. The apparatus employed by Hensen and his assistants
consisted of extremely fine straining-cloth, with meshes 0.04 to
0.05 mm. in diameter. He made the mouth of his net small in
proportion to the filtering silk surface, to ensure as far as
possible the immediate filtering of all water that came in through
the opening, his object in this being to ascertain approximately
how much water was filtered, when the net was drawn through
the sea for a calculated distance. Experiments showed that in
^ As illustrating a haul on this section I append a list of the species found in the closing net
at Station 8i (lat. 48° 2' N., long. 39° 55' W. ), from a depth of 50 metres to the surface : —
Diatoms : Coscinodisciis excentrictis, Euodia c2ineifor»ns, Planktotiiella sol, Coscinosira
(Estrtipi, Thalassiosira subtilis, Corethron C7-iophilum, Rhizosolenia styliformis, R. shrubsolei,
R. fragillima, R. alata, R. semispina, Baderiastruni delicatulum, B. elongatum, Chatoceras
atlanticum, C. boreale, C. mediterraneiim, C. peruvianum, C. criophilum, C. decipiens,
C. contoftuiii, C. schiittii, C. curviseium, C. lacmiosum, C. furcellatum (a resting-spore),
Thalassiothrix longissitna, T. nitzscktoides, Nitzschia seriata.
Peridinese : Ceradum lineatu7n, C. candelabruvi, C. pe,7itagonum , C. gravidum, C. fusus,
C. pennattim, C. tripos, C. azoricum, C. gibberum, C. plat y come, C. arcticiim, C. intermedium,
C. macroceros, Protoceraiium reticnlatum, Peridinium oceanicum, P. depressum, P. divergens,
P. conicum, P. ovatjim, P. tristylum,z.nA some others, Diplopsalis leiitictda, Pyrophactis horologium,
Goniodotna polyedricm/i, Gonyaulax polygram ma, Podolampas elegaiis, P. palmipcs, Oxytoxum
scolopax, O. diploconus, Ptychodiscus carinatus, Dinophysis acuta, D. schiittii, D. rotundata.
Flagellates : Phceocystis poticheti.
Silicoflagellates : Dictyocha fibtda.
Chlorophycese : Halosphcera viridis.
Cyanophycere : Trichodesmium thiebaulti.
PELAGIC PLANT LIFE 359
practise his net could not filter the whole of the water which
ought to pass through ; it was possible, however, to work out a
coefficient for each size of net, namely a fraction indicating
what proportion of the total quantity of water had actually been
filtered. Hensen trusted chiefly to vertical hauls, since he was
anxious to know definitely the exact distance through which
the net had passed. He lowered his apparatus open, but with
a heavy weight attached, so that it went down end-first and
therefore caught nothing until hauling in began. Initial investi-
gations aimed at ascertaining the total quantity of plankton in
the photic zone, and accordingly the net was drawn in one haul
from a depth of 200 metres right up to the surface, or from the
bottom to the surface in water shallower than 200 metres, the
idea being to find out the quantity of plankton in a column of
water of known depth i metre square.
It is not, however, sufficient merely to compare the total
quantity of plankton present in different localities ; it may be
just as important to know what there is at different depths, not
only because we have to consider the effect of light, let us
say, upon plant production, but because there may be layers of
water, such as we find especially in coastal areas, totally distinct
in hydrographical characters, and with different conditions of
existence. Hensen made vertical hauls from different depths,
and had recourse to subtraction when estimating the plankton
of the deeper layers, but since that time closing-nets have been
introduced, and we are able now to get samples from any layer Petersen's
we wish to study. C. G. J oh. Petersen constructed a closing- fp'^'Jft^,,
apparatus to go with Hensen's vertical net, and Nansen also
designed a vertical closing net which was invariably used by the Nansen's
'' Michael Sars," and found to be handy and reliable. Provided ^i^^i^g"^^.
only the bag be long enough in proportion to the opening, it
will act successfully from a quantitative point of view, though
we did not employ it much for this purpose, as we had better
methods of our own for estimating quantity. Otto Pettersson Pettersson's
obtained his estimates of quantity by attaching silk nets a^faching^nets
to a large current-meter, which recorded the velocity of the to current-
current, and thus indirectly supplied approximate figures de- "^^^^^'
noting the amount of water filtered. A series of very interest-
ing determinations, from samples secured in this way, has
been described by Broch. Broch.
The net-method was found unreliable as time went on. In
the first place, it does not fairly represent the total quantity of
plankton, since many of the smaller forms pass altogether, or to
360
DEPTHS OF THE OCEAN
Lohmann's
pump method
a very great extent, through the meshes ; and, secondly, the
meshes become gradually clogged with the slimy little algae, or
animals, so that the coefficient of filtration does not remain con-
stant. Even during the course of a single haul we occasionally
noticed that everything worked well to begin with, but that the
cloth became more and more stopped up, until at last filtration
ceased entirely. In other words, it is sometimes impossible to
tell how much water has been filtered, and consequently the
catch is practically valueless from a quantitative point of view.
An endeavour was made to overcome this last difficulty by
filtering a quantity of water, previously measured, either through
silk nets, or through an even less porous filter-material, such as
taffeta, or hardened filter-paper, or sand, an additional advantage
being that by this means the very smallest organisms could be
retained. Water-samples were secured by water-bottles or by
pumps. Lohmann, who did much to perfect the pump-method,
was not only able to get his water-samples from any depth
desired, but could obtain samples representing a column of
water from the surface down to a specified level. The pump
was made to work in connection with a long, flexible hose, the
mouth of which was lowered as far down as considered necessary,
and then drawn gradually up towards the surface as pumping
proceeded. The pumped-up water thus represented propor-
tionally the whole distance through which the hose passed
before reaching the surface. These samples were afterwards
filtered by Lohmann, and the results compared with catches
obtained by vertical hauls with the silk nets.
The methods of capture had thus been greatly improved,
and it was possible to obtain the smallest organisms, but for
practical reasons it was necessary to limit the quantity of water
filtered on each occasion. This forced us to turn our attention
to the second question, namely the regularity with which
Distribution of organisms are distributed in the sea. Fortunately, the
?!!!?™„?1^"^^ researches of Hensen and his assistants, as well as those of
Lohmann and myself, have all gone to show that the distribu-
tion of the pelagic plants, at any rate, is extremely regular.
The samples from adjacent localities with similar life-conditions
have yielded very concordant results. I do not consider it
any exception to this statement that in tropical waters dense
masses of Trichodesntium sometimes collect as water- bloom
in certain areas and not in others, or that diatoms near
the edge of the polar ice occur in more or less local swarms,
for I consider it more than probable that these irregularities
extremely
regular
PELAGIC PLANT LIFE 361
arise because the conditions of existence vary in closely
adjoining areas. Lohmann has found that at certain seasons
10 to 15 c.c. of sea- water amply suffice to give a representative
sample of the total plankton, but it is evident that only the
commonest organisms floating in the sea in any locality do
occur so densely and regularly that we can be sure of securing
them, or even of catching enough for ascertaining their com-
parative frequency, in a water-sample consisting of only a few
litres of water or less. The more scattered or mobile the
individuals are, the larger masses of water must we examine to
get a knowledge of the quantity present in any locality.
It follows, therefore, that we must abandon all thought of a No universal
universal method. Fine silk nets give us complete collections "sUmatin^
of the larger Ceratia and diatoms, but are of no use for the quantity of
smallest species, for which we are obliged to have recourse to p^^"^'°"-
more delicate methods of filtration, and to the centrifuge. The
larger forms, too, will be found in our silk nets in sufficient
quantities, if they are at all abundant, but where they are
scarcer than, say, fifty specimens to the litre, the centrifuge
cannot be depended on. Besides amongst these larger organisms
some species are so scanty that even a vertical haul with the
big net yields insufficient material, so we have been compelled
to adopt the special methods described in this volume.
Various methods have been employed for estimating the
quantity of plankton on the basis of catches made. We can Determina-
allow the whole sample to sink to the bottom of a measuring tionsof
, 1 . ^ . • 1 • 1 •! 1 volume and
glass, and appraise its volume, or we can weigh it while the weight.
organisms are saturated with water or spirit, or we can weigh
the dry substance. Such determinations of volume and
weight give us our first rough idea of the variations in the
quantity of plankton, but there are many sources of error
which it is unnecessary to discuss here. The worst fault is that
measurements of this kind group into a whole the most diverse
values, such as plants and animals, producers and consumers,
one-celled organisms that are constantly reproducing themselves,
and multicellular animals with a longer duration of life, or, again,
organisms with slow and others with rapid metabolism. If we
want to know a litde about the conditions of development of
organisms, we must have a method of investigation that allows
us to trace the growth and retrogradation of each of the different
species by itself, and counting then becomes the only method counting
possible, as Hensen has continually asserted. Counting is a necessary.
method that requires much time, and also absolute accuracy in
362
DEPTHS OF THE OCEAN
determining the species whose development we desire to trace ;
consequently most of those who endeavour to work at these
interesting questions will be forced to confine themselves to
definite problems, and content themselves with tracing the
growth of a limited number of species. No doubt a man like
Lohmann may be able to know all the species within certain
limits, and may actually calculate by counting what each of
them contributes to the total plankton volume, but speaking
generally a " uni-
versal method " that
will give us the total
quantity of all the
plants and animals
of the sea in curves
and tables is un-
attainable.
During the
" Michael Sars "
Expedition our
quantitative investi-
gations yielded really
remarkable results.
Lohmann had suc-
ceeded by means of
a centrifuge in de-
termining the quan-
tity of plankton in
quite small samples
of Baltic water, and
we felt confident,
therefore, that this
excellent method
ought also to prove
serviceable in the
open sea. We very soon found, however, that the algae there
were too scarce for our little hand-centrifuge (Fig. 250) to be
of much utility ; there was so little to be found at the bottom
of the centrifuge glasses (Fig. 251) that we obtained a hope-
lessly inadequate idea of the plant life, whereas in the
stomachs of salpse we might, perhaps, get a quite abundant
flora of small forms. Fortunately, we had taken with us a
big centrifuge to be worked by steam (see Fig. 91, p. 105),
and in its six glasses we could centrifuge at one time as much
Fig. 250. — Lohmann's Hand-centrifuge.
PELAGIC PLANT LIFE
3^3
as 1 200 c.c. of sea-water. It made 700 to 800 revolutions per
minute, and after eight minutes the plants were all collected at
the bottom of the glasses. Our next proceeding was to pour
away the clear water, and after rinsing the deposit, to put it
in a smaller glass with a tapering
bottom, where it was subjected to
the action of a small hand-centrifuge.
In this way we collected all the con-
tents of, say, 300 c.c. of sea-water in
one drop, which we examined in a
counting chamber beneath the micro-
scope, and noted carefully each single
organism. As a rule we had to
centrifuge the whole 300 c.c, but, if
the plankton was very abundant, 150
c.c. or even 100 c.c. might suffice.
Examination with the microscope is
always more difficult when the or-
ganisms in the counting chamber lie
close together.
These investigations were carried Smallest
out all the way from the Canaries to Zo£m
Newfoundland, and thence to the in the open
Irish coast banks, and resulted in
our discovering that the smallest
organisms which pass right through
the silk nets are far more abundant
than the others in the open sea,
while the larger diatoms and peridineae
would appear to be so scanty that
the total of all their species together
only amounts to about ten per litre.
Despite this fact, however, we found
in the samples taken with our nets
that there were at least fifty species
Glasses of these larp-er forms at every station,
SO that as far as species go the flora
is exceedingly rich.
We were also able in this way to determine the occurrence Amount of
of algae at different depths. Samples from the surface, and §Jj-"Jejjf "^^
from 20, 50, 75, and 100 metres were taken regularly, and depths.
we also examined samples now and then from still greater
depths. We found, invariably, however, that the plant life
Fig. 25
. — Centrifuge
AND Pipettes for use with
Lohmann's hand-centrifuge.
364
DEPTHS OF THE OCEAN
below 100 metres was extremely scanty. The maximum in
the ocean nearly always lay at about 50 metres, which is
what Lohmann also found in the case of the Mediterranean
coccolithophoridse. At the surface there was less than down
in the 20 to 50 metres zone, though the plankton nearly always
approached its maximum value as soon as we reached a depth
of 10 to 20 metres. At 75 metres the quantity diminished
to about half of that found at 50 metres, and at 100 metres it
had dwindled to at most a fifth. These were the values on our
southern section. On the northern crossing the quantity of
plankton fell away even more rapidly as we went deeper down ;
at Station 92, where there was a slight admixture of coast-
water near the surface, and the lighter surface layer was
separated from the pure Atlantic water somewhere between 25
and 40 metres, there were upwards of 250,000 plant cells per
litre in the surface layer ; whereas at 50 metres the plankton
was less abundant than at any of our previous stations, and only
amounted to 2213 cells per litre.
These results quite bear out the most valuable investigations
so far made regarding the vertical distribution of algse in the
ocean, namely Schimper's observations in the Antarctic during
the " Valdivia" Expedition. He found that the entire produc-
tion was practically limited to the uppermost 200 metres, that
the bulk was to be found above 100 metres, and that the
maximum lay between 20 and 80 metres, or to be more precise,
between 40 and 60 metres. We were able to confirm this, after
comparing the volume of the samples taken with nets on those
few occasions when there was a sufficiently large quantity of
plankton at our stations to make such volume-measurements of
any real value. There was, however, a different vertical dis-
tribution everywhere along the coasts where diatoms abounded,
for then the exuberant plant production was limited to the
surface layer, which was mixed with fresh water from the
land.
As illustrating our investigations at a station in the warmest
part of the Atlantic, I give particulars of what I found at
Station 64 (lat. 34° 44' N., long. 47" 52' W.) in water-samples
from 50 metres (150 cc.) and 75 metres (300 c.c). The figures
denote the number of individuals per litre.
PELAGIC PLANT LIFE
365
Coccolithophoridae : —
PontosphcEra huxleyi, Lohm.
SyracosphcBra echinata, n.sp.
,, spinosa, Lohm. .
„ ampulla, n.sp.
,, IcEvis, n.sp.
„ blastula, n.sp.
„ pulch7-a, Lohm. .
„ robusta, Lohm. .
Calyptrosph(e7-a oblonga, Lohm.
Coccolithophora leptopora, Murr. and Blackm.
,, pelagica, \Vallich
„ wallichii, Lohm.
,, lineata, n.sp.
RhabdosphcEra styliger, Lohm. .
„ daviger, Murr. and Blackm.
DiscosphcBra fiibifer, Murr. and Blackm.
Scyphosphcera apsteini, Lohm. .
Calciosolenia murrayi, n.sp.
Ophiaster for7nosiis, n.sp.
Undetermined coccolithophoridfe ^ .
Total coccolithophoridse .
Pterospermataceai : —
Pterosperma disci/liis, n.sp.
Peridineae : —
Protoditiium .
Amphidiniuni gracile
Oxytoxum scolopax .
,, hjorti, n.sp.
Di/iophysis, sp.
Exuvicel/a, sp.
Other peridineae
Total peridineae
Diatoms : —
Nitzschia seriata
sp.
Rhizosolenia calcar avis .
Thalassiothrix frauenfeldi
Silicoflagellates : —
Didyocha fibula
Other plant-cells
Total plant-cells
Cells per
50 m.
300
287
193
93
147
160
80
593
33
73
7
7
33
107
3007
57ii
litre.
75 m-
173
123
33
40
83
3
100
67
370
7
53
37
7
93
23
13
7
497
[729
853
1007
33
37
7
3
3
7
3
300
350
1403
7
33
14
43
7
43
93
147
377
3708
I have previously given a list from this station of the species
found in a vertical haul with the silk net. The number of
1 Mainly young stages, which could not be determined with certainty; to a great extent
they belong no doubt to Coccolithophora leptopora.
366
DEPTHS OF THE OCEAN
Plankton less
abundant in
the open sea
than in coastal
waters.
species is very considerable, yet the total quantity of individuals
is surprisingly small compared with what we might find, for
instance, off the coasts of Europe. In the Skagerrack one
often gets plant- cells in tens of thousands or even hundreds
of thousands in every litre of sea-water from the upper layer,
and, what is more, they are much larger and more nutritive
than the stunted forms which make up the bulk of this ocean
plankton.
It cannot be denied that our investigations are as yet too
incomplete to justify us in framing laws for plant production in
the ocean. Still the great expeditions which have made
researches in the open sea have given us a general conception
of the conditions prevailing over wide stretches of water at
certain seasons ; on the other hand, careful investigations of the
variations in the plankton throughout the year have been
carried out at a number of coast stations, while our international
researches have resulted in a great deal of material being
collected at all seasons from the North Sea and adjoining
areas. Though these investigations have not all been devoted
to studying quantity, they have nevertheless enabled us to
form some idea of the annual variations.
One thing at any rate we may learn even from this in-
complete material. The development of the plankton is much
more irregular than it would be if merely such simple factors as
warmth and light controlled production. It is not in the
warmest waters that the greatest amount of organic substance
is to be found. On the contrary we get larger masses of plants
in temperate seas than we have ever yet come across in
tropical or subtropical areas,^ at any rate so far as the open
ocean is concerned. Even when we come as far north as
the coast of Norway we find that it is not in the hottest months
of summer that the plankton attains its maximum, but in the
early part of the spring or the end of autumn. Now it is
certainly true that the quantity of vegetable matter present at
any given moment is no direct measure of production. Ac-
cording to the law of Van 't Hoff, metabolism always takes place
quicker ceteris paribus at a high temperature than at a low
temperature, and a plant-cell in the tropics may perhaps produce
more organic matter than a similar cell would do in the North
Sea in the same space of time. The small tropical plants may
^ The "Challenger " met with diatoms in the Arafura Sea in as great abundance as in the
Antarctic regions, but neritic in character (see lists of species in Summary of Results,
Chall. Exp., pp. 515 and 733).
PELAGIC PLANT LIFE 367
pass more rapidly through their life-cycle, and their numbers may
be more drawn upon by the abundant animal life ; consequently
considerable additions to their apparent total may be necessary,
if we wish to estimate properly the importance of plant life
in the tropics, as compared with that in higher latitudes. We
must remember, moreover, when dealing with observations
made in coastal waters all the year round, that the different
species have a natural periodicity that may be connected
with unknown internal factors in their cycle of life, as well
as with the influence of currents which at one time carry the
surface - layers away from the coast and at another time
towards it. All the same there are many irregularities which
cannot be explained as being solely the result of the actual
physical conditions of existence. Besides light and warmth we
might perhaps be apt to think of salinity, which, in the course of
its variations, influences both the density and the osmotic tension
of the sea-water. Though we are aware that a low or greatly
varying salinity is injurious to many pelagic organisms, there
are others which thrive remarkably well and multiply exceed-
ingly under such conditions, as for instance the diatom
Skeletoneina costahmi and the peridinean Ceratiurn tripos forma
subsalsa. Results, in fact, are often the reverse of what one
might expect. The flora of brackish - water bays, which is
poor in species, may develop into even greater masses than we
find synchronously in the open sea, where no osmotic changes
have disturbed the vital activity of the numerous species
belonging to the community of oceanic algse.
We cannot get away from the view, which was first con- Brandt.
fidently put forward by Brandt, that certain indispensable
nutritive substances occur so sparsely that, according to Liebig's Liebig's
minimum law, they act as factors which limit production. ™™'"""^ ^^•
Liebig found that the growth of plants on land depends on the
amount of the requisite nutritive substances present, the deter-
mining substance being the one of which at any moment there
is least in proportion to the needs of the plant. As long as
a particular nutritive substance occurs " in minimum," plant
production will be proportionate to the available quantities of it,
even though there be a superabundance of all other essentials.
If this law is made to include all necessary conditions of life,
it will be found to apply universally to all organisms both on land
and in the sea, in which case that condition of existence, whether
it be physical or chemical, which occurs " in minimum," will be the
factor of limitation. We must remember, however, that produc-
368 DEPTHS OF THE OCEAN chap.
tion at a given moment need not necessarily be proportionate
to the conditions of existence prevailing. There may be after-
effects of a previous set of conditions. Indeed it is possible to
point to places totally destitute of vegetation, owing to former
unfavourable circumstances having destroyed all germs, while
new germs have not yet found their way there. Still this is the
only reservation we need to make, when asserting the universality
of this natural law.
The necessary nutritive substances which are most likely
to occur "in minimum" in the sea are nitrogen, phosphoric
acid, and, in the case of diatoms, silicic acid ; all others occur
even to superfluity. Brandt in his works on metabolism
in the sea discusses at some length the importance of nitrogen,
phosphoric acid, and silicic acid, and his assistants at Kiel
have carried out a number of tests to ascertain the extent
to which these substances are present in sea- water. Not
only the nitrogenous compounds (organic compounds, ammonia,
and nitrates), but also phosphoric acid and silicic acid, occur in
extremely minute quantities, so that it is particularly difficult
to get accurate values representing them. We have therefore,
unfortunately, no proper conception as yet of the way in which
these substances vary in different parts of the sea. According
Raben. to Rabcn's latest investigations the total quantity of combined
nitrogen (ammonia, nitrates, and nitrites) in true North Sea
water varies between o. no mg. and 0.314 mg. per litre, of
which 0.047 to 0.124 mg. is saline ammonia, the whole being
reckoned as free nitrogen. Even if we assume that the quantity
of nitrogen in the Atlantic is considerably less, these values are
high compared with the quantity of nitrogen to be found
combined in the cells of the plankton -algs. It seems,
therefore, hardly possible that the nitrogenous compounds are
entirely consumed by thealgse. It is, however, quite conceivable
that the variations in the total quantity of nitrogen, or in the
quality of such compounds as are easiest to absorb, may hasten
or retard the augmentation of the algse. The same is the case
with silicic acid, which Raben found to vary between 0.30 mg.
and 1.03 mg. per litre in thirty samples from the North Sea.
The quantity of phosphoric acid, according to Raben's investi-
gations, is as a rule below i mg. per litre, though it slightly
exceeds the quantity of nitrogen.
Brandt starts by discussing the occurrence of nitrogenous
compounds in the sea. He calculates that large quantities of
combined nitrogen are carried out from the land by the
PELAGIC PLANT LIFE 369
rivers, as organic nitrogenous compounds, ammoniacal salts, and
nitrates. The result would be a constant increase, until at last
the sea became poisoned, were it not that it is continually being
absorbed by living organisms, or else being restored in some
form or other to the atmosphere. We now know that there is
very little combined nitrogen in the sea, so that it must evidently
be used up as fast as it arrives. The consumers of nitrogen
are first and foremost the seaweeds growing along the coasts,
and the floating algae of the open sea, but besides them there
are also bacteria, which exist in all sea-water, as shown by
Fischer. Their competition with the algae for the nitro- Fischer.
genous compounds is not of any great consequence, so long
as they do not interfere with the circulation of nitrogen other-
wise than by disintegrating organic compounds so as to form
ammonia, or by binding ammonia and nitrates in their cells
as albumen.
From the bacteria-life of the soil, however, we are acquainted Nitrifying and
with another kind of nitrogenous metamorphosis produced by bacterS?"^
bacteria. There are nitrifying species which oxidise ammonia
into nitrites and nitrates, without requiring organic substance to
enable them to live ; there are further whole series of other
species which can reduce nitrites and nitrates, and give off
nitrogen in a free state. Their action drives out of the natural
circulation larger or smaller quantities of this valuable nutritive
substance, scarce enough already, which all plants generally
utilise to the uttermost. How great the loss is, as compared
with the metamorphosis in other respects, and under what
conditions it takes place, are questions that require our most
careful attention before considering anything else.
Baur, and others after him, succeeded in finding several Baur.
kinds of these denitrifying bacteria in the sea, where they
appeared to be widely distributed. It was found, too, that
they produced free nitrogen with greater rapidity when the
temperature was high (20° to 30° C.) than when it was low.
Brandt, accordingly, put forward the hypothesis, that to the
activity of these bacteria is due the fact that the abundance of
plant life does not increase as we approach the tropics, but
on the contrary very often decreases. This theory has now
for some years been considered the only explanation of the
irregular distribution of the plankton, but recent researches
have shown that it is untenable.
The denitrifying bacteria require organic substance for their
existence. If they are to give off free nitrogen, they must have
2 B
370 DEPTHS OF THE OCEAN chap.
nitrates or nitrites, though denitrification is as little a vital
necessity for them as alcoholic fermentation is for the fermenta-
tion fungi. Feeding them with sugar and ammoniacal salts will
result in their multiplying to an unlimited number of generations,
without exhibiting their power of denitrification. They can
attack nitrates whenever met with, utilise their oxygen, and
give off nitrogen, but denitrification is not of any particular
importance, provided the bacteria find sufficient free oxygen in
their surroundings. It is only when this fails that they attack
nitrates to any great extent. Given the requisite quantity of
oxygen they will enter the regular circulation, and no nitrogen
worth mentioning will be produced even where denitrifying
bacteria are living and multiplying.
This is the case at any rate in the soil, where denitrification
is of no importance, unless nitrates are brought into contact
with considerable quantities of easily disintegrated organic
substance. In the sea the quantity of organic substance is
generally so small that a cubic centimetre of salt-water from the
open sea rarely contains more than 50 to 100 living bacteria
cells, while the nitrogenous compounds occur for the most part
as ammonia or inorganic compounds, and not as nitrates or
nitrites. It is more than likely that nitrates are not formed to
any great extent in sea- water. Nitrifying bacteria are met
with occasionally in the mud along the coasts, but they have
not been proved to exist in the open sea ; in any case they
have not the same importance there that they possess on land,
where numbers of them are present in every single gram of
cultivated earth. So it is probable that the small quantities of
nitrates and nitrites in the sea-water are brought either from
the land, or in a minor degree from the atmosphere as the
result of electrical discharges. Most of the combined nitrogen
of the sea occurs as organic compounds or as saline ammonia,
neither of which can be reduced by denitrification. Supposing
then that denitrification does play any noticeable part, it will
only be in more or less enclosed bays and fjords, where
there is a comparatively large amount of organic substance,
a plentiful supply of nitrates from land, and so little circulation
that there may be a lack of oxygen. In the open sea it is
negligible.
N.ithansohn. We must look for other conditions to explain the apparent
irregularities in the distribution of the plankton. Nathansohn
was the first to notice that vertical currents are bound to
exercise considerable influence. If it be true that one or
PELAGIC PLANT LIFE 371
several of the necessary nutritive substances may be present in
such small quantities as to act as factors that limit the develop-
ment of the vegetation, then the more or less considerable
exchange taking place between the illumined surface -layers
and the vast water-masses of the deep is certain to produce a
great effect. All the forms of animal life inhabiting the sea
below 200 metres live solely upon organic substances which are
due to plants in the surface layers ; that is to say, they either
feed directly upon the plant-cells which sink downwards, or
upon the inanimate remains or excrements of the animals living
up above, or else upon other animals which, in their younger
stages, have inhabited the surface-layers and fed on the plants
they found there. A large proportion of the produce of the
surface-layers must thus be continually descending into the
deep sea, and these nutritive substances are therefore with-
drawn from their regular circulation in the photic zone. Down
in deep water, no doubt, the destructive metabolism of animals
will set free these nutritive substances, so that eventually
carbonic acid and ammonia will be produced ; still these gases
can only regain the photic zone by very slow degrees if
diffusion is their sole means of conveyance. If, however. Ascending
whole masses of water are brought up from the deep sea to <^""e"^s-
the surface, the nutritive substances contained in them will
once more enter into circulation, and cause an abundant plant
life to develop. Nathansohn has pointed out that marine areas
where such ascending currents occur, and where the surface-
layers are replaced by water from the deeper layers, are well
known to be extremely prolific, not merely in plankton, but
also in larger organisms. In anticyclonic systems like that
of the Sargasso Sea, on the other hand, where, conformably
to the laws of ocean-currents, the water-masses cannot ascend
from the deep sea, but where the surface -layers sink down-
wards, the plankton is much less plentiful than in any other
similar area where investigations have been made. Our
researches in the Atlantic during the summer of 19 10 have
done a great deal to settle this question. I shall first of all,
however, refer to a series of investigations which bring quite
another light to bear upon the question, and show what
difficulties we have to face.
In 1907 Professor Nathansohn and I commenced to study Pelagic aigos
the Christiania fjord, and subsequently I continued these in- f/oS"^*'''"''
vestigations alone. My previous observations had taught me
that the pelagic algae in this fjord attain their maximum between
372 DEPTHS OF THE OCEAN chap.
March and May, and that they occur in rather smaller quantities
from June to August. From September to October there is
again a maximum, but from then onwards they decrease rapidly
and reach their minimum between December and January. It
is not surprising that the plankton is scanty during the dark
period of the year, but the unmistakable secondary minimum
in the summer months must be due to some special cause,
which it should be possible to discover by studying carefully
the whole year round the variations in quantity and the
fluctuations in the outward conditions of existence. It struck
me that the factors at work might be analogous to those which
cause the differences in production met with in different regions
of the great oceans.
Method of To ascertain the quantity of plankton present we employed
^uant?"ff'^^ the method introduced by Sedgwick and Rafter for drinking-
piankton. water tests in North America, which has been described by
Whipple. A litre of water is filtered through a fine grade of
sand, and the algse that collect on its surface are rinsed off".
To the rinsed-ofT water containing the algae, filtered water is
added until the whole comes to exactly lo c.c. We then transfer
I c.c. of this with a pipette to a counting-chamber 5 cm.
long, 2 cm. broad, and i mm. high, which exactly holds it. For
examination we use a microscope which magnifies to 40 or 50
times the natural size. A thorough knowledge of the species
is requisite to enable us to enumerate them correctly. When
counting species represented by many individuals we require
a micrometer, with a larger or smaller number of millimetre
squares marked off by lines, placed in the eyepiece of the micro-
scope.
We soon found that our task was more difficult than we
had at first imagined. The quantity of plankton fluctuated
greatly in the course of short periods of time, yet the variations
could not be ascribed directly to conditions of existence, since
these remained fairly constant. The temperature in the surface-
layers rose steadily during March to May from 1.5° C. to 6.3° C,
the quantity of chlorine was about 16 per thousand, and according
to Nathansohn the quantity of free ammonia in filtered samples
of sea-water was between 0.0175 mg. and 0.031 mg. per litre,
and of ammonia in organic combined form between 0.105 ^S-
and 0.217 mg. per litre. Of nitrates and nitrites he only found
infinitesimal quantities up to 0.009 ^ig-. set down as ammonia.
Chcetoceras constrictum, one of the commonest diatoms in the
spring plankton of the Christiania fjord, furnished the following
PELAGIC PLANT LIFE
Z7?,
figures, denoting the number of living cells in every litre of
surface-water near Drobak : —
1907.
27/111.
■30/111.
2/lV.
9/n'.
15/iv.
20/iv.
4/\'.
6/v.
l/VI.
19/VI.
ChcEtoceras
constrictum
20,850
45=850
12,750
59.730
760
44,425 192,500
95,480
1280
0
A quite satisfactory explanation presented itself, however,
for the variations turned out to be closely connected with the
direction of the winds and currents. The outflowing current
in the surface-layers might reduce the quantity of plankton to
a mere fraction of the normal amount in the course of a day
or two, while the inflowing current might perhaps double the
quantity in a few hours. The current exerts so great an
influence because the abundant plant life is limited to a thin
surface-layer which is sharply differentiated both in salinity and
temperature from the water-masses below. On 28th March
1907, for instance, the temperature from the surface down to
20 metres was 2.6'^-3.6° C, and the quantity of chlorine worked
out at 16.74-17.62 per thousand ; from 40 metres down to the
bottom at 80 metres the temperature was 6.2^ C, and the
quantity of chlorine was 18.73 P^^ thousand. The outflowing
current carries the surface-layers with their algse out of the fjord,
and the infertile deep water may be sucked up to perhaps
5 metres below the surface. The inflowing current, on the
other hand, heaps up the fertile surface-waters. We found, on
examining the plankton at different depths, that the bulk of the
plants was limited to a very thin surface layer, say 5 metres in
depth, after the current had set outwards, whereas subsequent
to the inflow of the current they were as abundant down to
30 or 35 metres as at the surface.
At a place like this it was difficult to trace any regular
connection between the local conditions of existence and the
development of plankton-algae, in view of the fact that currents
caused variations of even greater extent than those actually due
to^conditions of existence. We had therefore to conduct our
investigations on other lines. Supposing it were possible to
determine the rate of growth of the algae we should get a better
measure of production, and probably also of the influence due
to vital conditions, than variations in the total amount could
give us. The number of individuals at any given moment
depends not merely upon the rate at which production has
374 DEPTHS OF THE OCEAN
taken place, but also upon how many have perished or been
carried away ; and the causes bringing about diminution, which
we may perhaps term factors of loss, may vary without being
in any way directly connected with the conditions of existence
of the plankton. There is one genus, at any rate, whose rate
of augmentation can be approximately determined. The
species of Ceratmin only divide their cells at night, so that
if we make our investigations early in the morning we can tell
which cells have been divided during the night and which
remain entire. In a sample of surface-water on loth September
1907 we found 300 whole cells and 161 half cells of CeratitLvi
tripos, the latter consisting of 79 anterior parts and 82 posterior
parts. The number of cells, then, had in twenty-four hours
increased from 300 -I = 380.5 on 9th September to
300 -|- 161 =461 on loth September. The addition is accordingly
= 80.5 individuals, and the percentage of the total amount
10 1 1 100 X 80.5
on 9tn September works out at — ^ ^ = 21.2 per cent.
This was the plan we adopted for calculating the augmenta-
tion of the species of Ceratimn at Drobak during the whole
of their vegetation period in 1907, and we also recorded the
average number per litre at different depths during the whole
year.^ The following tables show our chief results : —
^ Similar investigations in the case of Ceratiuni tripos were carefully carried out during
1908-1909 by Apstein in the Baltic. The values he obtained for percentages of augmentation
on the whole accord as nearly with mine as might be expected.
[Table
PELAGIC PLANT LIFE
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3/6 DEPTHS OF THE OCEAN
The figures in the tables clearly indicate that, though the
rate of increase is highest in August, the number of cells of
Ce^-atiiini in the fjord makes no great advance before October.
Throughout the whole summer the number continues at about
the same level, in spite of a comparatively rapid production.
This affords a further indication that in the Christiania fjord
variations in the current and other factors of loss exert a greater
influence than the variations in the conditions of existence
which affect rate of increase.
The fact that we find in the Christiania fjord, and assuredly
also in many other places along the coasts of North Europe,
that the plankton is less abundant in the summer months than
in spring, does not necessarily imply any unfavourable change
in the conditions of existence due to summer. It may be caused
by the melting of the snow in spring, and by the river water all
through the summer driving the surface-water and its plant-
life away from the coast, so that the production near land
barely replaces the loss. In the autumn it would seem as
if the prevalent sea-winds heap the surface -layers together
along the coast, and thereby accumulate large quantities of
plankton.
What effect these movements of the surface-water have
upon the occurrence of the plankton we are as yet unable to
say definitely, but they must be taken into consideration. We
were obliged, therefore, to abandon our original intention,
which was to ascertain the importance of such conditions of
existence as dissolved nutritive substances, and particularly
nitrogenous compounds.
I made a series of cultivation experiments, however, under
experiments, conditions of existence resembling the natural conditions as
nearly as possible. Stoppered glass bottles holding two and a
half litres were kept just floating at the surface, by being filled
with about two litres of sea-water ; the amount of plankton
present was carefully checked in advance, and then one bottle
was left in its original state, while in the other two small
quantities of chloride of ammonium or calcium nitrate were
placed. After an interval of 3 or 4 days the plankton in all the
bottles was once more examined, and it was generally found
that most of the species had augmented best when nitrogenous
nutriment had been added. The addition had naturally to be
made with the utmost care, since anything over 0.5 mg. per
litre generally had a poisonous effect. The following table
shows the result of one of these experiments : —
Cultivation
PELAGIC PLANT LIFE
Number of Cells per Litre.
Z11
1
Before experiment
on 21/viii.
Three Days Later (24/viii).
In Original
State.
With addition of 0. 5 mg.
NH4CI per litre.
Ceratiinn tripos . 583
„ fusus . 543
„ furca . 155
Prorocentrum micans , 1052
Dinophysis acmiiinata 219
„ rotundata 33
Rhizosolenia alata . 157
Cerataulina bergonii 2840
640
649
149
548
107
30
232
3381
696
833
196
1464
226
42
345
7214
Experiments with pure cultures of different plankton-
diatoms, made by Allen and Nelson at Plymouth, show that
they do not thrive without a regular supply of nitrogenous
compounds. The plan of working which they adopted may
also be employed with advantage when we wish to ascertain
what concentration of dissolved nitrogenous compounds induces
the plankton-algae to augment most rapidly. This is the
first thing to find out if we desire to know whether a want of
dissolved nutritive substances is the limiting factor of production.
It is quite possible that augmentation diminishes from lack of
nitrogen long before the total amount of this essential has been
fully consumed ; yet augmentation must not fall below a certain
minimum if the species is to hold its own, because of the larger
or smaller number of individuals that are constantly perishing.
Questions like these can only be settled by experiment, so that
the cultivation method of Allen and Nelson is bound to be of
great assistance to us eventually. But in the meantime our
comparative investigations over large areas of the sea are also
of considerable value.
I have already stated that plant life in the Christiania fjord
was limited to a very thin surface-layer, which, owing to its
lesser density, was differentiated from the deeper infertile
water-masses, and this was practically the case along all
the coasts where plankton-algse were plentiful. Out in the
open sea, on the other hand, where there are not such
marked differences in salinity, temperature, and density be-
Allen and
Nelson.
Plankton
extends
deeper, but
is less
abundant, in
the open sea
than in
coastal areas.
378 DEPTHS OF THE OCEAN
tween the surface water and the deep water, the pelagic
algse extended deeper ; at 50 metres, for instance, the quantity
was still near the maximum, and even as deep as 100 metres
or more the number was considerable. This, at any rate,
was what we found in the case of the diatoms that abounded at
our first stations off the Irish coast-banks and in the Bay of
Biscay, and this too was what Schimper discovered in the
Antarctic. It is also a regular rule that plankton is far more
plentiful along the coasts than in the open sea, and, judging
from investigations hitherto made, the proportion between what
is produced in a typical coastal area and what is developed in
typical oceanic water-masses would be more accurately expressed
by 100 : I than by 2:1. For this the best explanation which I
can give is that the open sea generally suffers from a want of
one or more nutritive substances required by the plants, for
though these are brought down to the sea in comparatively
large quantities by the rivers, they are almost entirely consumed
by the plant life of the coastal areas.
This is why the abundant plant life of the coastal seas is
confined to the surface-layers, since the water-masses lying
below remain separated, and consequently cut off from the
plentiful supply of nutritive substances which regulate the
augmentation of plants. But out in the open sea there is
another important source of nutriment to be taken into account.
Nathansohn has pointed out that pelagic animals are constantly
taking nutritive matter down into deep water, and that for
the time being it is accordingly withdrawn from the plants,
even though the metabolism of the animals and the action
of bacteria liberate it once more in inorganic form. These
nutritive substances may rise to the surface-layers again by
diffusion, but the process will require a long time. They may
also accompany the ascending water-masses where off-shore
winds bring about up-welling, in cyclonic current systems, and
where the surface-layers, becoming chilled, sink and make
Vertical room for warmer layers from below. Wherever vertical
circulation takes place, and it is assisted in its action by storms
and waves, the temperature and salinity will be extremely
uniform from the surface down to a depth where the water-
masses have such a high salinity that their greater density sets
a limit to circulation. Conversely uniformity in temperature
and salinity may be taken as a sign that vertical circulation has
just taken place. This was the condition of affairs at our
stations to the south-west of Ireland (see Fig. 252), where we
circulation.
PELAGIC PLANT LIFE
79
Stat. 4 a
106 55-50
found abundance of plankton in April 1910, algae being present
in large quantities as deep down as they have been known to
occur, that is to say as far down as sufficient light penetrates.
We can appreciate the difference between these conditions and
the conditions in coastal areas like the Christiania fjord, if we
remember that the nutritive substances in the first case may rise
up from the deep water, while in the second they are derived
from the surface through the admixture of fresh water.
Vertical circulation is regulated by differences in tempera-
ture at the surface, due to summer and winter, which are
sufficient to in-
crease the density
of the upper
layers till it equals
the density lower
down, and if cir-
culation is to have
any effect in the
open sea, the sur-
face-layers must
be able to sink to
a depth of at least
200 to 300 metres.
The greater the
difference in tem- ^^°
perature between
summer and win-
ter, the more
effective will ver-
tical circulation
generally be.
Assuming, then, that our view is correct, namely that plant
production in the sea is mainly regulated by the amount of
dissolved nutritive substances, we must expect to find plankton
produced in abundance in coastal areas to which large rivers
convey nourishment from the land, and in oceanic areas where
vertical circulation takes place on a large scale, or where
ascending currents bring up the deeper water-masses. Where
vertical circulation is the controlling influence, the greatest
profusion will be at seasons when the temperature of the
surface reaches its minimum ; that is to say, generally in
winter, or in higher latitudes in the early months of spring. It
would be possible to test the truth of this theory if we could
Hydrographical Section off the Irish Coast
(April 1910).
Temperature and salinity nearly uniform from the surface down
to a depth of 250 metres.
38o DEPTHS OF THE OCEAN chap.
carry out systematic quantitative plankton investigations all
through the winter, in combination with hydrographical re-
searches, in parts of the Atlantic like the sea round the Azores,
where the plankton is known to be scanty during the summer,
but where during the course of winter vertical circulation
might be expected to create different conditions of existence.
Whipple. In this connection it should be mentioned that the influence
of vertical circulation upon the production of plankton-algse
in fresh water has long been known to biologists. It has been
pointed out by Whipple, who showed that the maxima of
diatoms in particular coincide with the seasons when vertical
circulation takes place, namely autumn and spring. And in
the sea, too, it seems that diatoms, with their power of rapid
augmentation, are the first to respond to improved conditions of
nourishment.
Which of the essential nutritive substances are the chief
limiting factors in the sea, it is impossible to say as yet. Prob-
ably, however, nitrogen is the most important, and next to it,
perhaps, more especially in the case of diatoms, we may put
silicic acid. Brandt and Nathansohn have both discussed
the occurrence of these substances, but we need further and
more conclusive information than what we now possess.
Nathansohn has likewise considered the possibility of carbonic
acid occurring "in minimum." This seems paradoxical, of
course, since there are comparatively large quantities of it in
sea-water. Still the greater part is combined in the form of
carbonates, and only a very small portion is set free by dis-
sociation at any given moment, so as to become available for
the plants. How much there is in this form will depend on the
alkalinity of the sea-water and on the temperature. When
the free carbonic acid is used up by the plants, fresh quantities
will gradually be absorbed from the atmosphere, though this
may take place so slowly that there need not necessarily be any
equilibrium between the carbonic acid tension in the atmosphere
and at the surface of the sea. It is accordingly quite conceiv-
able that the shortage may for a time be considerable enough
to stop the algae from assimilating carbonic acid. When the
temperature is high the quantity of free carbonic acid in the
sea-water will ceteris paribus be less than when it is low, and
this also may help to explain the relatively poor production in
warm seas. Variations in the tension of carbonic acid, how-
ever, have not as yet been sufficiently studied.
The organic substances built up by pelagic algae unquestion-
PELAGIC PLANT LIFE 381
ably form the chief basis, and in the open sea practically the
sole basis, of nutriment for all the pelagic animal life, as well
as, through their pelagic forms, for the fauna of the sea-bottom.
It is not, however, quite so certain that all the different algae
are equally useful as food to the animals which live on plant
stuffs. Brandt's chemical studies of plankton organisms have
distinctly shown that nutritive value does not necessarily
correspond to volume. Diatoms, with their long silicated
setae, or with big bladder-shaped cells that merely enclose a
thin layer of protoplasm along the inner side of the wall, have
little nutritive value compared to the majority of the peridineae,
in which most of the cell -chambers are full of protoplasm.
The dry substance of diatoms, according to Brandt's analyses Chemical
of plankton samples, chiefly ChcEtoceras, contains 10 to 11.5 per o? plankton
cent albumen, 2.5 per cent fatty matter, 21.5 per cent carbo- samples.
hydrates, and as much as 64.5 to 66 per cent ash, 50 to 58.5
per cent of this last being silicic acid. Another sample, largely
consisting of Ceratium tripos, had a totally different composition,
the dry substance containing 13 per cent albumen, 1.3 to 1.5
per cent fatty matter, 80.5 to 80.7 per cent carbohydrates
(half of which was chitin), and not more than 5 per cent ash.
We are still without systematic studies of the nutriment of
plankton animals, and consequently do not know for certain
whether some families of plants are preferred to others. The
contents of the intestinal canals of salpse make it evident that ^ooAoi Saipa.
these animals at any rate collect all the different small organisms
to be found in their neighbourhood. In warmer waters the
greater part of. their stomach-contents consists of coccolitho-
phoridae and other tiny forms, but we find besides representatives
of all the plankton-algae. Small peridineae, for instance, like
Gonyaulax poly gramma, are seldom wanting. In fact, Stein, the
well-known specialist on protozoa, who had no plankton-catches
to aid him in his researches, got the best part of his material
from the stomachs of salpae, and was thus able to write his valu-
able initiatory monograph on peridineae. And this, too, was the
plan adopted at first for studying diatoms, so that our knowledge
of pelagic genera like Asteroinphalus and Asterolampra is largely
due to the examination of the stomachs of salpae. During
the cruise I invariably examined the stomach-contents of
salpae, and obtained thereby plenty of small forms, coccolitho-
phoridae especially, for comparison with the material in the
centrifuge samples. As we approached the coast of Europe,
however, the contents took on another character, for at Station
382
DEPTHS OF THE OCEAN
Food of
Appendicu-
laria.
Food of
Copepods
Proportion of
plants and
animals in
the plankton.
97 most of the forms were diatoms, and to a great extent con-
sisted of Rhizosolenia alata. Generally speaking we discovered
that salpse do not trouble to make any selection. Lohmann's
studies of Appendicular ia have shown us t^t these animals get
their nutriment by means of a filter apparatus, which allows only
the minutest organisms, coccolithophoridse in particular, and
small peridineae, to enter the digestive canal.
The chief consumers of plants in the sea are undoubtedly
copepods. Their conditions of nutriment, however, have so far
been principally studied by means of their excrements, which sink
down in the shape of small elongated lumps, and are often brought
up in numbers by the silk nets. Still, in these excrementa all
the softer components have been digested, and the shells that can
be identified do not necessarily always belong to species which
are an indispensable part of their nutriment. Undoubtedly the
calcareous shields of coccolithophoridse occur too frequently for
their presence to be ascribed to chance, indicating, moreover,
that the digestive juices of copepods cannot have an acid
reaction. In addition we very often meet with more or less
bent and distorted coverings of peridineae, and in northern
waters the excrements contain stiffer forms like the little
Dinophysis gi'amilata in a practically unchanged condition. In
localities where diatoms predominate, the excrements consist
largely of bent and broken bits of species like Rhizosolenia
semispina and R. alata. Even if Hensen's view be right
that diatoms supply far less nutriment comparatively than the
other classes of plants in the plankton, it is at any rate quite
certain that the animals do feed on them, and especially when
they are plentiful. In the Norwegian Sea I have several times
observed that where diatoms abounded there might perhaps be
only a few copepods and other plankton animals ; still the
copepods were there, and In large numbers too, just below the
diatom zone, and their excrements consisted to a great extent
of the silicious coverings of diatoms.
Hensen noticed that the plants in the sea are often
so scanty that it is hard to understand how all the animals
get enough nourishment, and this is even more difficult to
comprehend when we consider that the plants have directly
or indirectly to support every single animal from the surface
right down to the bottom. In many cases, perhaps, the plants
may be more abundant than a cursory examination would seem
to indicate ; and the most diminutive forms, which are still
practically unknown to us, undoubtedly exist in sufficiently
PELAGIC PLANT LIFE 383
large numbers to play a momentous part in the general economy.
Still careful study distinctly reveals the fact that the plants
of the sea are in striking disproportion to the animals. The
most reliable results so far obtained are those due to Lohmann's
researches in Kiel Bay. He studied the quantities of all the
plankton organisms for a whole year with great thoroughness, and
calculated the volume of the various groups in the plankton of the
different water-masses at all seasons. To us his most interesting
discovery is that the plants on an average made up 56 per cent
and the animals 44 per cent of the total plankton. In the
winter months the plants were easily outnumbered by the
animals, and from December to February they formed scarcely a
third of the total plankton. In the summer, on the other hand,
they predominated, and made up sometimes even as much as
three-quarters of the whole. Plants which are reproduced by
division must necessarily decrease rapidly whenever vigorous
augmentation ceases, if animals are constantly consuming
numbers of them.
The life-cycle of animals, with its growth-period in youth Life-cycle of
and propagation in maturity, is more complicated than that of ^""^^^'^•
plants, and gives them a better chance of withstanding unfavour-
able conditions of existence. A lower temperature necessarily
reduces their intensity of breathing, and thus diminishes their con-
sumption of nourishment, and it may be also that they can go
without feeding for a comparatively long time, during which they
live upon reserve matter that they have accumulated at more
favourable seasons. Damas made some interesting studies of
the life-cycle of the larger copepods, and found that propagation
may require a higher temperature than what is necessary for
conserving vital energy, and that therefore these forms can
delay their propagation until the conditions of existence become
more favourable, so that the young animals may have the rich
nutriment required for their growth. Calamis finmarchims, the
commonest large copepod of the Norwegian Sea, abounds
wherever the temperature is over 2° C, in both its half-grown
and full-grown stages, but propagation does not begin till the
temperature rises to 4" C, either owing to warmer water-masses
arriving from the south, or to heating at the surface from the
atmosphere.
Lohmann has endeavoured to calculate the relation between Relation
the augmentation of the algse and their consumption by animals production
throughout the year in Kiel Bay. He assumes that there is a and consump
daily accession of 2>'^ per cent to the volume of the algse, and '°" ° ^^^'
384 DEPTHS OF THE OCEAN chap.
that this can be consumed by the animals without harm to the
plant aggregate. He further assumes that copepods and other
multicellular animals require per day a quantity of nutriment
equal to a tenth of their own volume, whereas protozoa need
half their own volume. In view of what I have previously
stated regarding the variations in the rate of production of
Ceratiitm, I have no hesitation in declaring that the augmenta-
tion of the algae varies within wide limits, and the same is
undoubtedly also the case with the nutriment-requirements of
the animals. Still I am quite ready to concede that Lohmann's
assumptions may apply to the average conditions. The follow-
ing table compiled by him, and showing values in cubic milli-
metres of plankton per 100 litres of sea- water, will doubtless be
of interest : —
Organic
matter in
sea-water.
Daily Augmentation
Daily
Surplus
of Producers
Nutriment-requirement
or
available for Nutriment.
of Animals.
Deficiency.
August
35
6
+ 29
September
27
8
+ 19
October
14
5-5
+ 8.5
November .
9
4-5
+ 4-5
December .
3-5
2-5
+ i.o
January
3
1.8
+ 1.2
February .
I
1.8
-0.8
March
3
2.4
-t-0.6
April .
13
2.0
+ 11
May .
14
5-5
+ 8.5
June .
20
4.0
+ 16
July . .
17
4-5
-f 12.5
August
16
4-3
-f 11.7
According to this table the surplus plant substance is not
large, and in February there was actually a deficiency. It is
possible, too, that Lohmann's assumptions are on the optimistic
side, and that he has put the production-capacity of the plants
too high, and the nutriment requirements of the animals
too low.
Putter, after studying the quantities of oxygen consumed by
different marine animals, both benthonic and pelagic, considers
that the augmentation of the plant aggregate by no means
suffices as nutriment for the animals. If his view is correct, there
must, of course, be other sources of nutriment, both to replace
the loss of organic substance which the animals incur by
PELAGIC PLANT LIFE 385
breathing, and also to supply building material for their growth
and propagation. Putter has endeavoured to find out whether putter.
organic matter dissolved in the sea-water does not provide this.
He investigated its amount, and got surprisingly high values.
Improved methods have enabled Raben to check his experi-
ments ; in water from Kiel there were 10.9 to 13.9 milligrams,
or on an average 12.25 milligrams, of organic combined carbon
per litre of sea-water, and at a station in the Baltic 3 milligrams.
These are really high values, if we compare them with the
quantities of organic substance we are able to point to in the
form of living organisms. Lohmann's studies show that the
total amount of the organic combined carbon in the plankton at
Laboe in Kiel Bay varied during the year between 12.7 mg.
and 1 89.8 mg. per 1000 litres of sea- water. According to Raben's
investigations at a place close by, the mean value of organic
combined carbon in dissolved form is 12,250 mg. per 1000 litres,
or in other words about sixty times as much.
Too little is known, unfortunately, about the occurrence of
organic matter, and there are many difficulties to be overcome
before we can look for conclusive results. Perhaps the most
discouraging thing is that even the best filters allow a good
many organisms to pass through them. The water-samples
to be examined ought possibly to be freed from all suspended
insoluble matter by means of the centrifuge, but even this
method will not always give entirely satisfactory results, since
some of the algae (cyanophycese, Halosphcp.ra) are lighter than
sea-water, while the nimbler animals will swim up from the
bottom before one can separate the clear water from the
deposit. Putter's hypothesis, however, certainly deserves to
be further tested. If it be really true that in the salt-water of
the open sea there is organic substance in sufficient quantities
to be compared with what is combined in plants and animals,
then this substance must be due to the production of plants.
We will accordingly be forced to conclude that the pelagic
algse distribute to their surroundings through their surface
comparatively large quantities of organic substance, and that
their production is thus in actual fact much more consider-
able than we are led to believe, when we merely measure what
they store up in their cells during growth and augmentation.
Even if it seems strange biologically that they should evince
such want of economy in regard to valuable nutritive matter,
it would be unwise to reject the hypothesis, and the best plan
is to await the results of continued investigations. Some
2 c
386 DEPTHS OF THE OCEAN chap, m
biologists favour the theory and others oppose it ; some of
them have pubHshed the results of special studies, particularly
of the nutrition-processes of animals, all of which have been
of service to the cause of science, though they have not
succeeded in deciding this question.
Lohmann and C. G. J. Petersen have maintained that
organic detritus may be of intrinsic importance for the nutriment
of animals, as well as plants, and they have demonstrated that
organic detritus from the land is present in fairly large quantities
in waters like the Baltic or off the coasts of Denmark. We
have reason, therefore, to expect extremely interesting results
from the work of the Danish biologists on organic detritus in
the water and in the deposits at the bottom of the sea. But out
in the open sea this detritus is only met with in inconsiderable
quantities, as our centrifuge-samples showed us on board the
" Michael Sars." I do not, of course, include inanimate organic
substances, such as excrements or the empty chitin-coverings
of copepods, which form a part of the circulation of nutritive
substances through the pelagic organisms. Organic fragments,
not actually derived from pelagic organisms, either do not occur
at all in the open sea, or, if they do, are not worth taking into
consideration.
H. H. G.
CHAPTER VII
FISHES FROM THE SEA-BOTTOM
Zoologists on both sides of the Atlantic have long been
engaged in collecting facts regarding the occurrence of fishes
and other organisms which inhabit the Northern Atlantic and
adjacent waters. In recent times special expeditions have
offered opportunities of collecting according to definite plans,
and the American expeditions in the " Blake " and the
"Albatross," and the European ones in the "Challenger," in
the " Travailleur," the "Talisman," and the " Princesse Alice"
have added essentially to our knowledge. As a consequence
a very large amount of material has been accumulated, but as
yet this material has not been utilised for the purpose of
drawing up a general account of the distribution of the
different animal-communities.
Any attempt to review our knowledge, or to summarise the
voluminous literature on this subject, would extend this book
beyond all reasonable limits, and I shall therefore restrict
myself to certain important and characteristic main lines in the
distribution of Atlantic fishes and other animals, relying
principally on the captures made during the cruises of the
" Michael Sars." The material gathered during these cruises
is so large that a representative view may now be obtained,
and while confining myself to our own observations I hope to
give some information of real value. My aim, then, will be to
describe the geographical distribution of the fishes, as this
group has been made the special object of our researches ;
other groups of animals will be mentioned only in order to
illustrate the surroundings and the animal-communities associ-
ated with the different fishes.
In dealing with animal geography one must always pre-
suppose a knowledge of a vast number of animal forms. The
animals inhabiting the depths of the sea are strange to all but
387
collected by
the " Michael
Sars."
388 DEPTHS OF THE OCEAN chap.
a few specialists, and are known only by Latin names, of
which most zoologists even are ignorant. Nevertheless these
names must be used if the reader desires to penetrate into the
general laws which govern the distribution of animals in the
ocean. In order to overcome this difficulty I commence this
chapter with systematic lists recording the different species of
fishes, and the details of their capture, accompanied by outline
drawings of the most important species. By means of these
lists the reader may easily obtain information as to what group
in the system a certain fish belongs, and further details will be
found in the literature of the subject.^
Bottom-fishes During the many cruises of the "Michael Sars" probably
all the species of fish which live in the Norwegian Sea and
the North Sea have been captured, but only the commonest
species will be treated of here. Nearly all the fish caught
during the Atlantic cruise in 19 10 will, however, be mentioned,
or at all events as many as the present state of the work
will permit.
The following list includes all the forms captured by us in
the Atlantic which, according to our experience, must be con-
sidered as living mainly along the bottom.
I. List of Fishes caught by the "Michael Sars"
ALONG THE SeA-BoTTOM IN THE NoRTH ATLANTIC
This list includes 138 different species belonging to almost all the
most important groups of bottom-fishes. Thirty-two species belong
to the order Plagiostomi, fishes with a cartilaginous skeleton, and 106
to the order Teleostei, fishes with an ossified skeleton.
The Elasmobranchii. — Our list includes of the order Plagiostomi
the two sub-orders, Selachii (sharks) and Batoidei, with the family Raiidae
(rays), besides the order Holocephali with the Chimaeridae.
Seventeen species are sharks (Selachii), including the large Atlantic
Notidamis, the small but numerous Scylliidas, which also go into the
Norwegian Sea. Of the large group of the Spinacidae, Acanthias -vulgaris
is caught by the nets of the fishermen in the North Sea ; it follows the
herring shoals, and is therefore called dog-fish by the fishermen.
The two genera CentropJiorus and Spinax include deep-sea fishes living
on the slope. CentropJiorus is confined to the Atlantic only, and so is
CentroscylliuDi ; Spinax niger is caught in the Norwegian fjords also.
Two teeth of extinct species of sharks, CarcJiarodon and Oxyrhina, were
' See, for instance, A. C. L. G. Giinther, An hitroduciion to the Study of Fishes, chap,
xxi., Edinburgh, 1880 ; Francis Day, The Fishes of Great Britain, Edinburgh, 1880-84 ;
Boulenger and Bridge, Fishes, in the Cambridge Natural History, 1904. The lists are arranged
according to the system proposed by Boulenger.
FISHES FROM THE SEA-BOTTOM 389
found in deep water by the " Michael Sars," similar to those found in
such great numbers by the "Challenger" in the Pacific,
Twelve species are rays (Raiidae). Raia niicroocellata and R. miraletus
are true Atlantic species, caught by the "Michael Sars" only south of
the Canaries. The other species are caught also in the Norwegian
Sea.
Of the family Chimseridae, CJiimcEva monstrosa is recorded from the
Norwegian Sea, from the extreme north of Norway, from the whole of
the Atlantic down to the Cape of Good Hope, from Sumatra and Japan.
C. viirabilis was discovered by the " Michael Sars " in 1902, south of
the Faroe Islands, in deep water. Hariotta raleighana, in appearance a
most remarkable deep-sea fish, was previously known from the Atlantic
slope off the United States.
The Teleostei are represented in our list by no less than eight
sub-orders.
The Malacopterygii include salmon-like fishes ; two species of the
genus Argentina live near the continental edge or the deepest part of
the coast-banks of the Norwegian Sea and the Atlantic. The family
Alepocephalidae includes true deep-sea fishes, black in colour, known
from the greatest depths of the ocean, but not recorded from the
Norwegian Sea. They are salmon-like in form, and attain the dimen-
sions of a small salmon.
The Apodes, or eel-like fishes, include a great number of deep-sea
fishes belonging to the family Synaphobranchidas. SynapJiobrancJius
pinnatus is known from all the oceans of the world, and was caught
in deep water by the " Michael Sars " at many stations. The family
Mursenidae includes shore -fishes ; the splendid Murcena helena was
caught off the African coast.
The Haplomi and the Heteromi include true deep-sea fishes, the
genera being BatJiysauriis, Bathypterois, the new genus BatJiyniicrops,
Halosauropsis, and NotacantJnis. None of them are known from the
Norwegian Sea, but some have a world-wide distribution, and have been
caught at the very greatest depths where trawlings have been taken.
The Catosteomi and Percesoces are only represented by one species
each ; both coast-fishes. Centriscus scolopax is a brightly-coloured little
coast-fish with a pipette-like rostrum.
The Anacanthini are represented in our list by no less than 36
different species, 19 of Macruridae, and 17 of Gadidae. These two
families are very nearly related. The Macrurids include the most
important and numerous bottom-fishes on the continental slopes and
over the abysmal areas of the ocean. The Gadidae are the most numer-
ous and economically the most important food-fishes in northern and
subtropical waters. The Macruridae have representatives which live in
very deep water only, others which are confined to certain geographical
areas of the slope, and so on ; these will be treated in greater detail later.
Of the Gadidae the genus Gadus has a number of species (for instance,
the cod, the haddock, the whiting, the pollack, the saithe) which are
characteristic of different parts of northern waters, while the genus
Merluccius is the most important food-fish on subtropical coast-banks.
The genera Molva (ling) and Brosviius (tusk) inhabit the deepest parts
390 DEPTHS OF THE OCEAN
of the coast-banks, and the genera Mora, Lepidion, and Halargyreiis the
uppermost part of the continental slope.
The Acanthopterygii.- — Fifty-one species belong to this very important
and large group of highly developed fishes, most of which are true coast-
bank fishes, only a few of them being known from the uppermost part
of the slope.
Most of these fishes, the Serranidae, Sciaenidae, Pristipomatids,
Sparidae, Mullidae, Caproidae, Labridae, Scorpaenidae, Triglidae, Trachi-
nidai, Uranoscopidae, and Callionymidae, are brightly-coloured fishes, with
hard ossified scales and spines of moderate size, living in shallow water,
or deeper, on the coast-banks, with a maximum distribution in warm
subtropical waters. The northern limit of their distribution differs for
different species, several extending even to the southern warmer parts of
the bays and fjords of Scandinavia; other families, e.g. Cottidae and
Blenniidae, have representatives in the Arctic {Triglops, Lumpenus).
None of these families have, however, any economical importance in
the Norwegian Sea or North Sea.
The family Pleuronectidae, or flounders, includes very important
food-fishes. The plaice, flounder, sole, dab, megrim, halibut, all belong
to this family. Hippoglossus, Pleuronectes, and Zeugopterus are northern
genera ; Solea is the most important genus in the Atlantic, Solea
vulgaris being of importance also in the southern parts of the North Sea.
The Scombriformes, to which belong the genera Trachurus or
Caranx, Scomber, Thynnus, are mostly pelagic, but are also caught very
near to the shore. The mackerel, the tunny, the horse-mackerel are
all economic species of great importance.
Class— PISCES
Sub-Olass— ELASMOBRANOHII
Order — PL AGIOSTOMI
Sub-Order— SELACHII
NOTIDANID^
Notidanus griseus, Cuv. (six-gilled shark), 1902, Faroe-Shetland channel (Fig.
253)-
Fig. 253.
Notidanus griseus, Cuv. (After Bonaparte.)
FISHES FROM THE SEA-BOTTOM
391
SCYLLIID^
Scyllium canicula, Cuv. (rough hound), 1910, Stations 3, 14, 20, 39.
Pristiurus melanostomtis, Bonap. (black-mouthed dogfish), 1902, Faroe-Shetland
channel; 19 10, Stations i, 21.
Pristiurus murifius, Coll., 1902, Faroe-Shetland channel, 11 00 to 1300 metres.
CARCHARIIDyE
Mustelus vulgaris, Miill. and Henle (smooth hound). 19 10, Station 13.
Lamnid^
Carcharodon, fossil tooth, 19 10, Station 48 (see Fig. 254).
Oxyrhina, fossil tooth, 19 10, Station 48.
Fig. 254.
Carcharodon mrgalodon. Fossil Tooth. Station 48. (After Zittel. ) This figure shows a Car-
charodon tooth from Tertiary deposits ; those dredged from the deep-sea deposits have never
the base preserved (see Fig. 126, p. 156).
Spinacid^
Cenirina salviani, Risso, 19 10, Station 13.
Acanthias vulgaris, Risso (dog-fish), 1902, Faroe Bank, 390 metres; Faroe-
Shetland channel; 1910, Stations i, 3, 20, 39 (see Fig. 255).
Fig. 255.
Acanthias vulgaris, Risso. (After Smitt.
192
DEPTHS OF THE OCEAN
Centrophorus crepidater, Boc. and Cap., 1902, Faroe Bank, 750 metres.
Cetitrophorus squamosus, Gmel., 1902, Faroe Bank, 390 to 750 metres (see Fig
256).
Fig. 256.
Centrophorus squamosiis, Gmel. (After Jensen. )
CeJitrophoriis ca/cei/s, Lowe, 1902, Faroe Bank, 750 metres.
Centrophorus coelokpis, Boc. and Cap., 1902, Faroe Bank, 750 metres.
Spinax niger, Bonap., 1902, Faroe Bank, 426 metres; 1910, Station 21.
Spinax (Etmopterus) prificeps, Coll., 1902, Faroe-Shetland channel and Faroe
Bank.
Centroscyllium fabricii (Reinh.), 1902, Faroe-Shetland channel and Faroe Bank.
RhINID/E
Rhiiia squatina, Dumeril, 1910, Station 39.
Sub-Order— BATOIDEI
Raiid^e
Ram clavata, L. (thornback ray), 1902, Faroe Bank, 130 metres; 1910, Stations
I, 3, 13, 14, 20, 39 (see Fig. 257).
Fig. 257.
Eaia clavata, L. (After Smitt. )
Raia punctata, Risso, 1910, Stations 37, 38,^39.
Rata mkroocellata, Montagu, 1910, Station 37.
FISHES FROM THE SEA-BOTTOM
393
Raia alba, Lacep., 1910, Station 37.
Raia miraletus, L., 1910, Station 39.
RaiafyllcB, Ltk., 19 10, Stations 25, 95.
Raia circularis, Couch, 19 10, Stations 3, 13,
;9 (see Fig. 258).
Fig. 258.
Raia circularise Couch. (After Smitt. )
Raia batis, L. (skate), 1902, Faroe Bank, 130 metres; Faroe-Shetland channel.
Raia vomer, Fries, 1902, Faroe Bank, 750 metres ; 19 10, Station 3.
Raia /lidrosiensis, Coll., 19 10, Station 4.
Raia fullonica, L., 1902, Faroe Bank, 390 metres; 1910, Station 21.
MyliobatidtE
Myliobatis aqiiila, Cuv. (whip-ray), 1910, Station 36.
Order— HOLOCEPHALI
Chimverid^
Chimcvra monstrosa, L., 1902, Faroe Bank, 435 metres; 1910, Station 21.
Chimcera mirabilis, Coll., 1902, Faroe-Shetland channel; 1910, Station 4 (see
Fig. 259).
Fig. 259.
Chimcera mirabilis. Coll. Nat. size, 76 cm.
394 DEPTHS OF THE OCEAN
Hariotta ra/eigha?ia, G. and B., 1910, Stations 35, loi (see Fig. 260).
Fig. 260.
Hariotta 7-aleighana, G. and B. (After Goode and Bean.
Sub-Class— TELEOSTOMI
Order— TELEOSTEI
Sub-Order— MALACOPTERYGII
Salmonid^
Argentina sihts, Nilss., 1910, Station 39 {see Fig. 261).
Argentifia sphyrcena, L., 19 10, Stations i, 3.
Fig. 261.
Argentina stilts, Nilss. (After Sniitt. )
Alepocephalid^
Alepocephalus giardi, Koehl., 1902, Faroe-Shetland cliannel ; Faroe Bank, 750
to 840 metres (see Fig. 262).
Fig. 262.
Alepocephaliis giardi, Koehl. (After Collett. )
Bathytroctes rosfmtus, Giinth., 19 10, Stations 29, 56.
Conocara macroptera, Vaill. (G. and B.), 1910, Station 25 (.see Fig. 263).
FISHES FROM THE SEA-BOTTOM
395
Fig. 263.
Coiiocara 7nacroptera, Vaill. Nat. size, 20 cm.
Sub-Order— APODES
SYNAPHOBRANCHIDiE
Synaphobi-anchus pintiatus, Gron., 1902, Faroe-Shetland channel; Faroe Bank,
750 metres; 1910, Stations 4, 24, 41, 53, 88, 95, loi (see Fig. 264).
Histiobranchus sp., 19 10, Station
Fig. 264.
Synaphobranchus pinnaiits, Gronov. Nat. size, 31 cm.
MUR/ENID.^
Miirana helena, L., 1910, Station 38 (see Fig. 265).
Fig. 265.
Miircena helena, L. Nat. size, 102 cm.
396
DEPTHS OF THE OCEAN
Sub-Order— HAPLOMI
SCOPELID^
Bafhysaiirus ferox, Giinth., 1910, Stations 25, 35, 53, 95 (see Fig. 103, a).
Bathypterois longipes, Giinth., 1910, Station 53.
Bathypterois dtibius, VailL, 1910, Stations 23, 41 (see Fig. 266).
Fig. 266.
Bathypterois diibiiis, VailL Nat. size, 17 cm.
Benthosaurus grallator, G. and B., 19 10, Station 53.
Bathymicrops regis, n.g., n.sp., 1910, Station 48 (see Fig. 305).
Sub- Order— HETEROMI
Halosaurid^
Halosaiiropsis macrochir, Giinth. (Coll.), 1910, Stations 35, 53, 88, 95 (see Fig.
103, b).
NOTACANTHID^
Notacanthus bojiapartii, Risso, 1902, Faroe-Shetland channel; Faroe Bank, 840
metres (see Fig. 267).
Polyacanthonotus sp., 1910, Stations 53, 95.
®
Fig. 267.
Notacatithus botiapartii, Risso. (After Goode and Bean. )
Sub-Order— CATOSTEOMI
Centriscid^
Centriscus scolopax, L., 19 10, Station 39 (see Fig. 268).
FISHES FROM THE SEA-BOTTOM
397
Fig. 268.
Centi-iscjis scolopax, L. Nut. size, 16 cm.
Sub-Order— PERCESOCES
Atherinid^
Atherina p7-eshyter, Cuv. and Val., 19 10, Station 36.
Sub-Order— ANACANTHINI
Macrurid^
Trachyrhynclms trachyrhynchus^ Giinth., 1910, Stations 4, 23.
Trachyi-hyiichiis mtirrayi, Giinth., 1902, Faroe-Shetland channel ; Faroe Bank,
840 metres (see Fig. 269).
Fig. 269.
Trachyrhynchits miirrayi, Giinth. (After Giinther. )
Macrurus {Cxlorhynchus) talismani, Collett, 1902, Faroe Shetland channel
1910, Stations 4, 24, 41.
Macrurus {Ca'Iorhynchus) ca'lorhyiichus, Risso and Bonap., 19 10, Station 21.
Macrurus sclerorhynchus, Val., 1910, Stations 25, 41, 88, 95, loi.
Macrunis cequalis, Giinth., 1902, Faroe Bank, 750 metres; 1910, Stations 4, 23,
25> 35> 41 (see Fig. 270).
Macrurus zaniophorus, Vaill., 1910, Stations 4, 41.
Macrurtis guntheri, Vaill., 1902, Faroe-Shetland channel.
Macrurus {Coryphee noides) rupestris, Gunn, 1902, Faroe - Shetland channel
Faroe Bank, 750 to 840 metres.
DEPTHS OF THE OCEAN
Fig. 270.
Macrurus aqualis, Giinth. Nat. size, 23 cm.
Macriirus {Coryphcenoides) asperrimus, Vaill., 19 10, Station 41.
Macrurus {Cetotiurus) globiceps, Vaill., 19 10, Station 41 (see Fig. 271).
Fig. 271.
Macrurus (Cetonurus) globkeps, Vaill.
(After Vaillaiit. )
Macrurus {Chalinura) bj-evibarbis, G. and B., 19 10, Station 10.
Macrurus {Chalinurci) murrayi, Giinth., 1910, Stations 25, 95.
Macrurics {Chalinura) swtulus, G. and B., 1910, Station 53.
Macrurus {Ma/acocephalus) lewis, Lowe, 1910, Station 21.
Macrurus {Ne?}iatomirus) armatus, Hect., 19 10, Stations 10, 35, 53,
Fig. 272).
(see
P'iG. 272.
Macrurus [Neviatonurus] armatus, Hect. (After Giinther.)
FISHES FROM THE SEA-BOTTOM
Bathygadus lo?tgifilis, G. and B., 1910, Stations 23, 24, 41 (see Fig. 273).
Bathygadus melanobranchus, Vaill., 19 10, Stations 23, 41.
;99
Fig. 273.
Bathygadus longijilis, G. and B. (After Brauer. )
Gadid.®
Gadits ca/larias, L. (cod), 1910, Rockall (see Fig. 274).
Fig. 274.
Gadus callarias, L. (.\fter Sniitt. )
Gadus ceglefimis, L. (haddock), 1902, Faroe Bank, 130 metres; 1910, Station 3.
Gadus merlangus, L. (whiting), 19 10, Station 14.
Gadus luscHS, L. (bib), 19 10, Station 14.
Gadus esmarki, Nilss., 1910, Station i.
Gadus poutassou, Risso, 19 10, Stations i, 3.
Gadiculus argenteus, Guichenot, 1910, Stations 3, 21, 96.
Merluccius vulgaris, Flem. (hake), 1910, Stations i, 3, 14, 20, 21, 2)^, 39 (see
Fig. 275).
Fig. 275.
Merluccius vulgaris, Fleni. (After Smitt.)
400 DEPTHS OF THE OCEAN
Phycis l)k?tntoides, Briinn, 1910, Stations i, 3, 21 (see Fig. 276).
Phycis ble
Fig. 276.
ides, Briinn. (After Smitt. )
Molva jnolva, L. (ling), 1902, Faroe-Shetland channel; Faroe Bank, 350 to
440 nietres (see Fig. 277).
Fig. 277.
Molva molva, L. (After Smitt. )
Molva byroelange, Walb., 1902, Faroe Bank, 840 metres.
Molva elongata, Risso, 19 10, Station 21.
Brosmius brosine, Ascan (tusk), 1902, Faroe-Shetland channel ; Faroe Bank,
550 to 440 metres.
Mora mora, Risso, 1902, Faroe Bank, 750 metres; 1910, Stations 4, 23, 41 (see
Fig. 278).
Fig. 278.
Mora mora, Risso. Nat. size, 45 cm.
Antimora viola, G. and B., 1910, Stations 4, 95, loi (see Fig. 279).
Lepidion eques, Giinth., 1902, Faroe-Shedand channel; Faroe Bank, 750 metres;
1 910, Station 4 (see Fig. 280).
FISHES FROM THE SEA-BOTTOM
401
Halargyreus affinis, Coll., 1902, Faroe-Shetland channel ; Faroe Bank, 750
metres (see Fig. 281).
Fig. 279.
Antimora viola, G. and B. (After Giinther. )
Fig. 280.
Lepidion eqites, Glinth. (After Giinther. )
Fig. 281.
Halai-gy reus affi fits, Coll. (After Collett.)
Sub-Order— ACANTHOPTERYGII
Division— PERCIFORMES
Berycid^e
Hoplostethus mediterraneum, Cuv. and Val., 1910, Stations 4, 21 (see Fig. 282).
2 D
402
DEPTHS OF THE OCEAN
Fig. 282.
Hoplostethus mediterraneum, Cuv. and Val. (After Goode and Bean.
ACROPOMATIDyE
Epig07itis tekscopiis, Risso, 1902, Faroe Bank, 750 metres.
Serranid.^
Serramis cabrilla, Cuv. and Val., 19 10, Station 37 (see Fig. 283).
Fig. 283.
Serranus cabrilla, Cuv. and Val. Nat. size, 21 cm.
SCI^NID^
SdcBna aquila^ Risso, 1910, Station 36 (see Fig. 284).
Ufnbrina roiichus^ Val., 1910, Station 36.
FISHES FROM THE SEA-BOTTOM
Fu;. 284.
Sciceiia aquila, Risso. (After Smitt. )
Pristipomatid/e
Pristipoma bennettii, Lowe, 19 10, Station 36.
Diagramma i7iediterra)ieum, Guichenot, 1910, Canary Islands.
Sparid^ (Sea-Breams)
Dejitex vulgaris, Cuv. and Val., 19 10, Canary Islands (see Fig. 285).
Dentex macrophthalmus, Cuv. and Val., 19 10, Stations 20, 38, 39.
Dentex Jtiaroccatms, Cuv. and Val., 19 10, Stations 20, 37 (see Fig. 48, a).
Fio. 285.
Dentex -i'lilgaris, Cuv. and Val. (After Cuvier and Valenciennes.) (The teeth, after Day.)
Cantharus Htieatus, Montagu (White), 1910, Canary Islands, Station 37.
Box vulgaris, Cuv. and Val, 1910, Station 36.
Sargus rondeletii, Cuv. and Val., 1910, Canary Islands.
Sargus annularis, Cuv. and Val., 1910, Station 36 (see Fig. 286).
Chrysophrys aurata, Cuv. and Val., 1910, Canary Islands.
Pagrus vulgaris, Cuv. and Val, 1910, Canary Islands, Stations 38, 39 (see Fig.
287).
Pagellus centrodontus, Cuv. and Val., 1910, Stations 13, 20 (see Fig. 288).
Pagellus acar7ie, Cuv. and Val., 19 10, Station 20.
404
DEPTHS OF THE OCEAN
Fig. 286.
Sargi/s annularis, Cuv. and Val. (After Cuvier and Valenciennes.)
Fig. 287.
Pagriis vulgaris, Cuv. and Val. Nat. size, 50 cm.
Fig. 288.
Pagellus cenfrodoufus, Cuv. and Val. (After Smitt. )
MULLID/E
Muilus surtmtktus, L. (red mullet), 19 10, Stations 20, 37, 39 (see Fig. 289).
FISHES FROM THE SEA-BOTTOM 405
Fig. 289.
Mullus siininiletiis, L. Nat. size, 29 cm.
Caproid/e
Capros aper, Lacep., 19 10, Stations i, 3, 20, 39 (see Fig. 290).
Fig. 290.
Capros ape)-, Lac^p. Nat. size, 9. 3 cm.
Labrid^
Coris Ji/lis, L., 1910, Station 37 (see Fig. 291).
Fig. 291.
Coris Julis, L. Nat. size, 18 cm.
4o6
DEPTHS OF THE OCEAN
Division— SCOMBRIFORMES
CARANGIDit:
Caranx trachurus, L. (horse-mackerel), 1910, Stations i, 3, 14, 20, 36, 39 (see
Fig. 292).
Temnodon saltator, Cuv. and Val., 19 10, Station 36.
Fig. 292.
Cara?ix i?-achuri/s, L. Nat. size, 1 1 cm.
Fig. 293.
Zeusfaber, L. Nat. size, 26 cm.
FISHES FROM THE SEA-BOTTOM 407
Trichiurid^
Lepidopiis caudatus^^w^hx., 1910, Station 43 (Gomera).
Division -ZEORHOMBI
ZeiD/E
Zeusfal/er, L. (dory), 19 10, Stations i, 20 (see Fig. 293).
Pleuronectid^e
Hippoglossus vulgaris, Flem. (halibut), 1902, Faroe-Shetland channel ; Faroe
Bank, 130 to 450 metres (see Fig. 294).
Fig. 294.
Hippoglossus vulgaris, Flem. (After Smitt. )
Pleuronecies /imanda, L., 1902, Faroe Bank, 130 metres.
Arnoglossus laterna, Walb., 19 10, Station 3.
Arnoglossus lophotes, Giinth., 19 10, Stations 3, 37, 38.
Ar?ioglossus gro/wiafini, Bonap., 19 10, Station 38.
Zeugopterus niegastoma, Donov. (megrim), 1902, Faroe Bank, 130 metres; 191c,
Stations i, 3, 96 (see Fig. 295).
Fig. 295.
Zeugopterus mtgasioma, Donov. (After Smitt.)
4o8
DEPTHS OF THE OCEAN
Zeugopterus boscii, Risso, 19 lo, Station 21.
Solea vulgaris, Quensel (common sole), 1910, Stations 20, 38 (see Fig. 296).
Fig. 296.
Solea vitlgaris, Quensel. (After Cunningham. )
Soka lufea, Bonap., 1910, Stations 36, 38.
Solea variegafa, Flem., 1910, Station 3.
Division— SCLEROPAREI
SCORP/ENID^
Sebastes dactylopterus, Nilss., 1910, Station 21 (see Fig. 297).
Scorpcena scrofa, L., 1910, Stations 37, 38 (see Fig. 298).
Fig. 297.
Sebasfes dactylopterits, Nilss. ( After Moreau. )
Scorpcena ustulata, Lowe, 19 10, Stations 37, 39,
Scorpana cristtilata, G. and B., 19 10, Station 4.
FISHES FROM THE SEA-BOTTOM
409
Fig. 298.
ScorpcEna scrofa, L. Nat. size, 48 cm.
Triglid^ (Gurnards)
Trigla pini, Bl., 19 10, Stations 3, 20.
Trigla hiriindo, Bl., 1910, Station 20.
Trigla gurnardiis, L., 1910, Stations i, 3.
Trigla cuculus, BL, 19 10, Station 20.
Trigla fyra, L., 1910, Stations 3, 20 (see Fig. 299).
Trigla obscnra, L., 19 10, Station 38.
Fig. 299.
Trigla lyra, L. (After Day. )
Lepidotrigla aspera, Cuv. and Val. (Giinth.), 1910, Stations 20, 39.
Peristedion cataphractiim, Cuv. and Val., 19 10, Stations 20, 39 (see Fig. 300).
4IO
DEPTHS OF THE OCEAN
Fig. 300.
Peristedion cataphractum, Cuv. and Val. Nat. size, 30 cm.
Division— JUGULARES
Trachinid.^ (Weevers)
Trachiiius draco, L., 19 10, Station 38.
Trachinus vipera, Cuv. and Val., 1910, Station 14 (see Fig. 301).
Fig. 301.
Trachinus vipera, Cuv. and Val. (After Cuvier. )
■ Uranoscopid^
Uranoscopus scaher, L., 19 10, Station 37.
Callionymid^
Callionymiis maculatus, Bonap., 19 10, Station 3.
ZOARCID/E
Lycodes ferrcB novce, Coll. (?), 19 10, Station 70 (see Fig. 302).
Fig. 302.
Lycodes terrce ?iovcs. Coll. (?) Xat. size, 11 cm.
FISHES FROM THE SEA-BOTTOM 411
Sub-Order— PEDICULATI
LOPHIID^
Lophhis piscatorius, L., 1910, Station 3 (see Fig. 303).
Fig. 303.
Lophins piscatorins, L. (After Smitt. )
Malthid^e
Dibranchus hystrix, Garm., 19 10, Station 70.
Sub-Order— PLECTOGNATHI
Tetrodontid^
Tetrodon speiigleri^ Bl., 19 10, Station 37 (see Fig. 304).
Fig. 304.
Tctrodon spengleri, Bl. (After \'alenciennes. )
412 DEPTHS OF THE OCEAN
2. The Geographical Distribution of Bottom-Fishes
IN the North Atlantic
The Fishes of the Abyssal Plain ^
In Chapter IV. the areas of the ocean-floor at different
depths are given, the percentages being as follows : —
reas shallower than loo
fathoms
= 7-o%.
„ between loo and 500
= 5.6 %, or 1.4 % per 100 fathoms
„ „ 500 „ 1000
= 3.0 %, or 0.6 % „ 100
„ „ 1000 ,, 2000
= 19-3 %, or 1-9 % .> 100
„ „ 2000 „ 3000
= 58.4 %, or 5.8 % „ 100
„ deeper than 3000
= 6.7 %.
About two-thirds of the sea-floor is thus covered by more
than 2000 fathoms (or 3600 metres) of water, forming an abyssal
plain 90J millions of square English miles in extent, or nearly
half the surface of the earth.
What organisms inhabit this abyssal plain ? When studying
the literature of deep-sea expeditions, we must remember that
all the hauls hitherto made in the abyssal area have been effected
by means of trawls or dredges, which function not only while
being towed along the bottom, but also while being lowered
and raised, filtering the immense column of water from bottom
to surface. Therefore only organisms like worms, molluscs,
holothurians, starfishes, corals, and all sessile forms may safely
be considered as having been captured at the bottom. In the
case of crustaceans and fishes, however, it may be doubted
whether they were really caught at the bottom or in intermediate
waters. Lists recording the catches of deep-sea expeditions at
great depths cannot therefore be accepted as representing the
animal-life on the ocean-floor, for in such lists we often find
forms which are now known to live quite close to the surface.
Although we have now a much more precise idea of the vertical
distribution of pelagic fishes than was previously possible, some
surprising facts are occasionally brought to light. Thus, as
mentioned in Chapter HI., the "Michael Sars " at Station 48,
between the Canaries and the Azores, brought up an Alepo-
cephalus in the large trawl towed at the bottom in 5000 metres,
just as these fishes have been captured by most deep-sea
expeditions ; on the trawl-rope a small tow-net was fixed in
^ The mean sphere level, which lies at a depth of about 1700 fathoms, has hitherto been
regarded as the depth at which the abyssal plain of the ocean commences, but it will be seen
that Dr. Hjort places this depth at 2000 fathoms. — J. M.
FISHES FROM THE SEA-BOTTOM 413
such a way that it was towed about 1000 metres above the
bottom, and in this net an Alepocephalus was also captured.
Such facts warn us against hasty conclusions. Many fishes
may, like the fishes in the Norwegian Sea (Gadidse, Sebasies),
occur in midwater above considerable depths as well as on the
coastal banks and the continental slopes. A single record of
a species from intermediate waters does not necessarily entitle
us to consider the species as entirely pelagic. As in most
biological questions, we have to judge from the available
evidence, and, in dealing with the captures of fishes by deep-
sea expeditions ^ in depths exceeding 2000 fathoms {3600 metres),
I have endeavoured to eliminate all those species which are
apparently pelagic, having been frequently captured at inter-
mediate depths. In this way I have attempted to ascertain Fishes from
how many species and individuals have really been captured on d^pth°"ovTr^"
the bottom of the abyssal plain of the oceans, and the result is 2000 fathoms.
given in the following table, which comprises 35 individuals
belonging to 2 1 species in all : —
^ The excellent lists given by Brauer in his Report on the Deep- Sea Fishes of the
" Valdivia " Expedition, the list by Vaillant in his Report of the French deep-sea expeditions,
Carman's Report of the "Albatross" expeditions, Goode and Bean's Oceanic Ichthyology,
and Murray's splendid Summary of the "Challenger" Expedition, have greatly facilitated
this task.
[Table
414 DEPTHS OF THE OCEAN chap
Bottom-Fish taken at Depths exceeding 2000 Fathoms (3600 metres).
Greatest
Number
Species.
Taken by.
Depth
(Metres).
of Indi-
viduals.
Locality. Other Localities.
ALEPOCEPHALID/E.
Aleposomus copei
"Albatross"
5317
I
East of North
America
/'Between the Morocco, the
Alepocephalus rostratus .
"Talisman"
3655
J Azores and : Azores, the
Bathytrodes attritus
"Talisman"
3655
1 France | Canaries,Medi-
\^ terranean.
SCOPELID^.
■
Bathysaurus mollis .
"Challenger"
4360
I
Mid- Pacific 1
5)
" Talisman"
3655
Cape Verdes ;
Bathypterois longipes
"Challenger"
4844
East of South
America
Mid-Pacific
„ longicaudata
"Challenger"
3761
Ipnops murrayi
"Challenger"
3931
North of Celebes i Brazil, Tristan
' da Cunha.
Halosaurid/e.
Halosaurus rostratus
"Challenger"
5027
Mid -Atlantic
Macrurid^.
Macrurus sclerorhynchtis .
"Talisman"
3655
Cape Verdes Whole eastern
slope of North
Atlantic.
,, liocephalus
"Challenger"
3747
Japan, Mid-
Pacific
South and Mid-
„ armatus .
"Challenger"
4432
Pacific, New
Zealand
„ Sis-as
"Talisman "
4200
Between the
Azores 'and
France
, , filicaiida .
"Challenger"
4843
East and West of
South America,
Antarctic
ZOARCID/E.
Neobythites crassus .
"Talisman"
4255
Between the
Azores and
France
Mixonus laticeps .
"Challenger"
4570
Mid-Atlantic
Lycodes albus .
"Talisman"
3975
Between the |
Azores and
France
Bassozetus tania
"Challenger"
4570
Mid-Atlantic
Typhlonus nasus
"Challenger"
4460
~
North of Australia |
and Celebes
Alcockia rest rat a
"Challenger"
3888
North of Celebes
Synaphobranchid^.
Htstiobratichus infernalis
"Albatross"
4062
East of North
America
,, bathybhis .
Number of species . 21
"Challenger"
3749
Mid-Pacific Japan.
35
It is doubtful whether ail these came from the bottom.
Thus the three Alepocephalidae, the six Scopelidse, the one
FISHES FROM THE SEA-BOTTOM 415
Halosaurus, and the two Synaphobranchidse may be suspected of
pelagic habitat. Less doubt may be entertained about the 15
Macruridae and the 8 Zoarcidae, and the probability is that these
(some 20 individuals) constitute the total result of the attempts
of all the deep-sea expeditions to capture bottom-fish on the
abyssal plain beyond the 2000-fathoms line. Most of these
fishes were taken by the "Challenger" in 57 hauls with the
dredge or trawl in depths exceeding 2000 fathoms. In these
hauls 22 individuals were captured, and the French expeditions
caught 1 1 bottom-fish in eight hauls, giving an average of i
fish to two hauls.
The 35 individual fishes enumerated belong to 21 species,
15 genera, and 6 families. On the average not even two
individuals of each species have been captured. The genus
Macrurus preponderates, 15 of the 35 individuals belonging to
this genus, and of deep-sea fishes the Macruridae may most
safely be regarded as bottom-dwellers. The impression of Scantiness of
scantiness conveyed by these facts, only one or two individuals greTdepOis.^
of each species of fish being known from the immense area of
the abyssal plain, agrees with the scarcity of the lower orders
in the same barren region. A perusal of the "Challenger"
Reports astonishes us by the fact that large numbers of species
of lower animals are known only from a single locality, and
often from one solitary specimen.
These facts suggest that the bottom-fishes of the abyssal
region are very local in their occurrence, but, considering the
small number of individuals recorded, it seems risky to come to
that conclusion, as the want of material for comparison tends to
weaken our power of discriminating between the species. In
certain problems of geographical distribution, the question may
be vital whether two individual fishes caught in widely separated
parts of the world are to be referred to one species or not.
The systematic study of these deep-sea species leaves a strong wide dis-
impression that many of them differ very slightly from one Jj^^p!^"^ °^
another. Thus, for instance, my collaborator, Mr. E. Koefoed, forms.
and myself have not been able to convince ourselves that there
is any specific difference between the two species, Macrurus
armatus and M. gigas, mentioned in the above table, and this
circumstance alone leads to far-reaching conclusions, M. armatus
having been caught in the Pacific and M. gigas in the North
Atlantic (see Fig. 308).
The collections of the " Michael Sars " throw much new
light on these questions. In the following table I give the
4i6
DEPTHS OF THE OCEAN
distribution of the most important forms taken in the abyssal
plain and the bordering intermediate zone. The localities of
special importance are the Southern Ocean for Halosauropsis
macrochir, and the Pacific for Macrurus armalus.
Species.
Localities where Captured.
By the " Michael
Sars."
By other Expeditions.
Hariotta raleighana .
Bathypterois lotigipes .
Halosauropsis macro-
chir
Macrui'us cequalis
„ siinulus
„ brevibarbis
„ armatus
globiceps .
Synaphobranchus pin-
natus
Stations.
35, loi
41, 53
35, 53, 88, 95
25, 35, 41
53,88
10, 88
10, 35, 53, 88
41, 88
24, 41, 53, 88,
95, loi
Off the east coast of North America.
Off the east coast of South America.
Between South Africa and Kerguelen,
off east coast of North America,
Gibraltar, Morocco, the Azores.
From Faroe Islands to Cape Verdes.
Off the east coast of North America,
Denmark Straits.
Off the east coast of North America,
Denmark Straits.
Pacific.
Bay of Biscay to the Azores.
Japan, Philippines, Arabian Sea, off
east coast of North America, Faroe
Islands to Cape Verdes, off Brazil.
Besides these we caught at Station 48 an Alepocephalus and
the new form Bathymic7'ops regis (see Fig. 305), which may both
be pelagic.
Excepting the Hai'iotta, which has only been taken at some-
what lesser depths (Station 35, 2603 metres), all these species
Fig. 305.
Bat hyfiticrops regis, n.g. , n.sp. Nat. size, ii cm.
belong to the genera recorded by previous expeditions from
the abyssal plain. Of the nine species, three \Halosa2iropsis
mac7^ockir, Macrurus armatus, and Synaphobranchtis pinnatus)
have previously been taken in other oceans. Of special interest
is the fact that M. armatus has been found in so many new
FISHES FROM THE SEA-BOTTOM
417
localities, and this species is now known to have the widest
distribution on the abyssal plain, and on this only. Another
Fig. 306.
Macrurus {Liomtrus) Jilicaiida, Giinth. (After Giinther. )
Fic. 307.
Hariotta ralcighana, G. and B. Xat. size, 30 cm.
Fig. 30S.
Chart showing the localities where Macrurus armatus % and M. Jilicauda 0 have been taken.
Temperatures in Centigrade.
species, M. jilicauda, also shares this wide distribution (see
Fig. 306, and Chart, Fig. 308).
Highly interesting also is the fact that no less than four of
these deep-sea forms, viz. Hariotta raleighana (see Fig. 307),
2 E
4i8
DEPTHS OF THE OCEAN
Species found
on both sides
of the North
Atlantic.
Abyssal forms
have a con-
siderable
vertical
distribution.
"Challenger'
hauls in the
deep water
of the North
Atlantic.
Bathypterois longipes, Macrti^nis simulus, and Macrtcnis brevibar-
bis, are now known from both sides of the Atlantic. The three
last-mentioned species were also caught near the Azores, and we
must therefore conclude that their habitat stretches right across
the Atlantic. Macrurus csqualis was previously known only
from the eastern side, Macrurus globiceps also from the Azores,
and during the cruise of the " Michael Sars " it was taken a
little north of the latter locality (Station 88). If the above
table is compared with the list of " Michael Sars" stations, it
will be noticed that these fishes from the abyssal region have
a considerable vertical distribution, occurring also on the
continental slopes.
Sir John Murray has, in his excellent "Summary," given
lists recording all the different animals captured at each of the
" Challenger " stations, and in a final chapter he endeavours to
lay down some of the most important laws governing the distri-
bution of animals in the ocean. At twenty-five stations where
the depth exceeded 2500 fathoms the "Challenger" took with
dredge and trawl 600 individual animals of all kinds ; this gives
24 individuals per haul. Now, firstly, many of these were
pelagic (most of the crustaceans and some of the fishes), and
secondly, many of them were very small (hydroids, bryozoa).
As examples I give a list of the bottom-forms (protozoa
excluded) obtained at some of the "Challenger" stations
between the Canaries and the West Indies.
Station 5. Depth, 2740 fathoms. Three living mussels {Leda, Limopsis, Area),
and some dead shells.
„ 13. Depth, 1900 fathoms. Some bryozoa and brachiopods (10 Tere-
bratiila).
„ 14. Depth, 1950 fathoms. Some bryozoa.
„ 16. Depth, 2435 fathoms. Sharks' teeth {Oxyrhina, Lamna\ valves of
Scalpellum, 2 mussels {Area).
„ 20. Depth, 2975 fathoms. Dredge came up half full of clay, containing
half a dozen tubes of serpulids, some of these with the worms
living.
,, 61. Depth, 2850 fathoms. Trawl captured some ophiuridte (6^////^^/)7^//rt'),
2 holothurians, 7 Sealpellum.
„ 63. Depth, 2750 fathoms. Trawl captured some fragments of worms, 3
Scalpelhim, i fish {Halosaiirus rostratus).
This list is representative of most deep-sea hauls, and their
uniform poverty is only broken by rare exceptions, as in a note-
worthy haul taken by the " Challenger " in the Pacific, between
Japan and Hawaii, at Station 244, in 2900 fathoms, which
gave :—
FISHES FROM THE SEA-BOTTOM 419
I sponge, I antipatharian, 6 actinians, 2 corals, i hydroid colony, 2 crinoids,
3 starfish, i sea-urchin, 5 holothurians, many worms, 7 or 8 mussels, and a
brachiopod.
This is, as far as I have been able to ascertain, the richest
haul in depths exceeding 2000 fathoms on record, but never-
theless the impression created by the results of the many deep-
sea hauls of the " Challenger " is that animal life is poorly
developed in the abyssal region.
During the cruise of the "Michael Sars " I therefore con- "Michael
sidered it an interesting object to ascertain if our large otter i^^Jhe^er'*
trawl could catch more, and possibly larger, animals on the water of the
abyssal plain. As stated in Chapter HI., technical success Atlantic.
attended our attempts at great depths, and the catches were
certainly somewhat larger than those previously taken in the
North Atlantic, but nevertheless they were very poor, as shown
by the following list :^
Station 10. Bay of Biscay, 2567 fathoms (4700 metres). Trawl dragged for
five hours gave : Some sponges, 3 actinians, some holothurians
{Elpidia), 2 starfish {FrugeUa, Dorigona), a few worms, ascidians,
and bryozoa, i gasteropod, and 2 fishes, presumably bottom-fish :
Macrurus armatus (Hector), i individual 70 cm. in length, and
M. brevibarbis (G. and B.), i individual 25 cm. in length.
Same Station. Duration of haul, 3J hours. Cod-end full of ooze, and in the meshes
3 ophiurids [Ophiopkura, Ophioglypha, Ophiocte?t}) ; washing the
ooze produced 4 actinians (one of them growing on a hermit
crab), I holothurian {Elpidia), worms in clay tubes, and some
gasteropods.
Station 48. Between the Canaries and the Azores, over 5000 metres. Duration of
haul, 4I hours. Trawl contained a large quantity of ooze, the
washing of which produced : 30 pieces of pumice-stone, i shell of
Argonaufa, i ear-bone of a whale, 2 sharks' teeth {Carcharodon
and Oxyrhina), 10 large shells of pteropods {Cavolifiia), 1 umbel-
\\i\ax\dix\ {Utnbellula gihitheri), i sertularian, 2 holothurians {Lcet-
■mogone violacea, Elpidia sp.). Besides these there were 3 pelagic
fishes {Malacosteus indicus, Argyropekciis sp., and a Leptocepha-
lus), and 3 fishes which may be surmised to have lived at the
bottom {Alepocephalus, a new genus related to Ipnops : Bathy-
microps regis, see Fig. 305, and a specimen not yet determined).
These hauls of the "Michael Sars" thus entirely confirm
the idea of the poverty of the abyssal plain, a confirmation
especially valuable on account of the size of the trawl employed
and the technical success attending its use in great depths.
The proof afforded by these results of the " Michael Sars," like
that from all other expeditions, suffers from the inherent weak-
ness attached to all negative proofs. The barrenness of the
abyssal plain may be only apparent, owing to imperfections in
420 DEPTHS OF THE OCEAN
the methods of capture, the technical difficulties of operating
dredges and trawls at great depths being of considerable
moment, but I do not attach great importance to this, because
the same appliances, when used in deep water on the continental
slope, gave large catches.
If we fix the boundary of the abyssal plain at the 2000-
fathoms line, we may consider the area between the 2000-
and 1500-fathoms lines as an intermediate zone between the
abyssal plain and the continental slope. In this zone the
"Challenger" made 25 hauls with trawls and dredges, with the
result that three times as many fishes per haul, and twice as
many invertebrates, were captured as on the abyssal plain. The
"Michael Sars " made 3 hauls with the trawl in such depths,
which, compared with our results from the abyssal plain, are
very interesting, and invite inspection of their details : —
Station 35. South of the Canaries, 1424 fathoms (2603 metres). Trawl dragged
two hours. Result of haul : Many silicious sponges (including
Hyalonetfia), hundreds of holothurians, large prawns {Benthesicymus,
n.sp.), 18 bottom-fish (9 Macrurids, i Bathysmirus, 2 Halosau-
ropsis, 5 Alepocephalus, i Hariotta).
„ 53. South of the Azores, 1430 to 1570 fathoms (2615 to 2865 metres).
Trawl dragged three or four hours. Result of haul : 2 large and
many small sponges, 3 mussels, 5 cirripeds {Sca/pellum), 30 large
prawns {Aristeopsis), 15 hermit crabs, 5 Pentacheles, i large white
decapod {Mutiidopsis, n.sp.), 500 holothurians, 39 bottom-fishes,
(17 Macruriis, 5 Halosauropsis, 2 Benthosmirus, 2 Bathysaurus,
2 Bathypterois, 6 Alepocephalus, 5 Synaphobranchus).
„ 88. North of the Azores, 1700 fathoms (3120 metres). Result of haul :
a great number of holothurians, sea-urchins, starfish, ophiurids,
some crustaceans {^Polycheles, Mti?ndopsis, Farapagurus), 2 1 bottom-
fishes (17 Macrurus, i Bathysaurus^ 3 Histiobranchus\
These hauls plainly show that the appliances of the " Michael
Sars" were excellently suited for the capture of bottom organisms,
fish as well as invertebrates. Indeed in one single haul (Station
53) we caught nearly as many individual bottom-fishes as the
" Challenger " captured in its twenty-five hauls in depths between
1 500 and 2000 fathoms. I think we are justified in concluding
that the vast difference between our captures on the abyssal plain
and these three hauls in 2600 to 3200 metres represents an
actual difference in the abundance of animal life in the two
regions. The fauna of the abyssal plain must be very poor
compared with the more abundant life met with, at all events
in the Atlantic, in depths of about 3000 metres and less, where
the fauna is infinitely richer in number of species as well as in
number of individuals. Perhaps the most striking contrast is
FISHES FROM THE SEA-BOTTOM 421
obtained when we consider the enormous difference in the
number of animals brought up by the trawl from the two regions
in question.
The Fishes of the Continental Slopes
The angle of the slopes rising from the abyssal plain
towards the coast varies in different parts of the globe, being
in some places steeper than in others. The percentages of the
ocean-floor given on p. 132 show that the steepest angle
occurs between 500 and 1000 fathoms, while the slope between
1000 and 2000 fathoms is much steeper than in the upper 100
fathoms. Between the shore-line and the loo-fathoms line the
angle of the slope is low, and this area is regarded as a special
region, generally termed the coast -plateau, or the continental
shelf or platform (see Fig. 144, p. 198). The fishermen's term
for this section of the sea-bottom is " the banks," and the narrow
intermediate belt between the coast-plateau and the continental
slope is by the fishermen termed " the edge."
One of the objects of the " Michael Sars" Expedition was
to make a number of trawlings on the continental slopes of the
Atlantic in different latitudes, in order to study the fish-fauna at
different depths and under varying conditions. We succeeded "Michael
in making quite a number of good hauls, and, taken together onThe*^^"^^
with the captures of other expeditions (especially those of the continental
French deep-sea expeditions), they give a good representation ^^°p^'
of the different fish-faunas. Our stations along the slope may
be divided into three groups : —
1. West of Great Britain (including some hauls from
localities south of the Faroe Islands in the year 1902).
2. Spanish Bay, west of Morocco.
3. South of the Canaries.
First of all, we will consider the number of fishes caught in
these hauls at different depths, as recorded in the following
table, and next we will investigate the vertical and horizontal
distribution of the species : —
[Table
422
DEPTHS OF THE OCEAN
West of Great Britain.
Spanish Bay, west of
Morocco.
South of the Canaries.
Station.
Depth
(metres).
Number
of
Fishes.
Station.
Depth
(metres).
Number
of
Fishes.
Station.
Depth
(metres).
Number
of
Fishes.
I
3
Faroe slope
4
Faroe slope
95
lOI
146
184
831
923
1060
1073
1797
1853
308
332
300
332
76
127
82
90
20
21
23
24
25
141
...
535
1215
1615
2055
161
117
77
32
29
39
41
35
280
1365
2603
about 300
about 80
18
The French deep-sea expeditions made in all 106 hauls at
different depths down to 5000 metres, mostly in the same part
of the Atlantic examined by the " Michael Sars," the fishing
results being very interesting : —
4 hauls between 0
and
100
metres
gave
224
fishes,
or
56
per
haul
9
, 100
200
,,
323
36
6
, 200
500
„
1275
212
28
500
1000
„
1044
37
29
, 1000
2000
„
905
31
20
, 2000
2900
„
115
6
4
2995
4000
„
61
IS
6
„ 4000
5000
„
10
2
Both these tables show clearly that the number of bottom-
fish decreases from land towards the abyssal plain. This
decrease is, however, far from uniform. Even down to 500
fathoms the "Michael Sars" obtained just as many fishes as
on the bank, viz. about 300 fishes in one haul, and these were
not small. At the same time the trawl was also crammed with
other animals. In depths greater than 500 or 600 fathoms we
no longer obtained anything like that number, but even down
to 1000 fathoms (1853 metres) we still got as many as 90 fishes
in one haul. Beyond 1000 fathoms fishes seem rapidly to
decrease in number, for neither the " Michael Sars " nor the
French expeditions got more than a score, or exceptionally
nearly two score of fishes in depths exceeding 1000 fathoms.
The richest haul of fishes known from a great depth is one
taken by the "Michael Sars" at Station 53, in 2865 metres,
viz. 39 fishes, of which some were large.
FISHES FROM THE SEA-BOTTOM
423
If we now consider what species of fish we obtain in our
trawlings along the continental slopes, we immediately recognise
different strata, each characterised by its peculiar fish-community.
It will be of interest to define the extent of these communities
by means of the species found most abundantly at different
depths, though there are no sharp limits between them, as it is
difficult to find even two kinds of fish (or other animals) having
in every respect the same distribution. It is thus obvious that
on the borders of the different communities recognised by us,
we shall find species belonging to neighbouring communities.
We have already mentioned that the " Michael Sars "
caught some of the abyssal species along the continental slopes,
and the French deep-sea expeditions also gathered similar
information. We may then first consider the bathymetrical Bathymetricai
range of some of these peculiar bottom -fish living at the seali^shes?^^^'
greatest depths : —
Bathymetrical Range.
Macriirus sckrorhynchus . . . from 540 to 3655 metres.
„ talismani,
globiceps .
Ahpocephalus rosiratus .
Halosauropsis macrochir .
Synaphobranchus pinnatus ^
We see here a group of species which may occur in very
deep water as well as along the continental slope ; the upper
limit seems to be about 800 or 900 metres (about 450 fathoms),
although stray individuals have been caught in somewhat
shallower water.
The main body of the fishes peculiar to the continental slopes
consists, however, of other species, which have not been captured
in the abyssal plain, though they have a wide distribution, like
the denizens of the abyssal plain, and resemble them also in
shape. Such are the following : —
460 ,
, 2220
"39 ,
, 2995
«3o >
, 3655
1183 ,
> 2995
201 ,
, 3250
Bathymetrical Range.
Macrunis cequalis . . . .
from 460 to 1319 metres.
„ zaniophorus ....
„ 830 „ 1590
Bathygadus melanobranchus
,, 830 „ 1590 ,,
„ longifilis ....
„ 1374 „ 1635 „
Mora mora
„ 614 „ 1367
Lepidion lepidion .....
„ 631 „ 1097 „
Chimcera monstrosa ....
„ 535 >» 1257
Different species of Centrophorus (sharks)
„ 1230 „ 1853 „
^ The fact that this form has been taken within such wide limits must, in my opinion, give
rise to the suspicion that it may really be caught in midwater ; perhaps it never actually occurs
in the abyssal area.
424 DEPTHS OF THE OCEAN chap.
These appear to be representatives of the fauna peculiar to
the steepest part of the slope, from 700 to 1500 metres (400 to
800 fathoms).
The " Michael Sars " captured on the Atlantic slope, in
depths between 800 and 2600 metres, over 1200 fishes, the
relative abundance of the different forms being as follows : —
569 fishes, or about 47 per cent, belonged to Macruridse.
393 „ 33 ., ,, Gdid\<l2d{Mora,Anti?nora, Lepidio?i,
Halargyreus).
66 ,, 6 ,, ,, Alepocephalid^.
47 „ 4 ,, „ Sharks {Cefttrophortts, Chimcera,
Etmopterus).
The remaining 10 per cent consisted offish represented by
only a few individuals (Notacantktcs, rays, and others).
In about 400 to 500 fathoms (700 to 900 metres) we meet
with forms having their lower limit in this region, which live in
greatest abundance at 200 to 300 fathoms. As instances may be
mentioned : —
Bathymetrical Range.
Sebastes dactylopterus . . . from 75 to 975 metres.
Motella macrophthalma . . . „ 146 ,, 987 „
Hoplostethus mediterranettm . . „ 140 ,, 1435 ,,
In about 300 to 350 fathoms (550 to 650 metres) we meet
with real representatives of the fauna of the coast banks. The
following are some of these species, found in deep water by the
French expeditions, with their bathymetrical range : —
Bathymetrical Range.
Merluccius vulgaris (hake) . . from 65 to 640 metres.
Gadici/lus argenieiis . . . ,, 411 „ 550 „
Zeugopferus megastoma . . . „ 60 ,, 560 ,,
Dentex macrophthalmus . . . „ i2o„46o „
In these depths we thus find in the same hauls representa-
tives of two entirely different faunas, and we must therefore
consider this region as an intermediate belt.
Before attempting to describe the fauna of the coast banks, I
wish to discuss some questions of general importance arising
from the examination of animal life on the continental slopes.
In his report on the deep-sea fishes of the " Valdivia "
Expedition, Brauer gives a very able and interesting review of
the general laws governing the geographical distribution of
these fish, particularly the Macruridae. While the genus
Macruriis is found in all the oceans, he considers most of the
species to be local. Of 116 species of Macruridae he has so far
FISHES FROM THE SEA-BOTTOM 425
only found one (^M. parallelus) which is common to the Indian,
Atlantic, and Pacific Oceans. All the 19 species taken at the
Sandwich Islands are known only from that locality. Some
species, like M. ar77iatus and M. filicmtda, have a wide distribu-
tion, but these are exceptions from the rule. Thus, in his
opinion, there are no species common to both sides of the Atlantic.
The only exceptions then known i^M. siimtlus, M. goodei,
M. berglax, and M. rupestris) are explained by him as being due
to these species following the cold Labrador current from their
normal habitat, the eastern side of the ocean.
Brauer attempts to explain the peculiar distribution of the
Macruridae. He considers that the Macruridse have originated
from coast-fishes, and only commenced to migrate towards the
abyssal region after a great variety of coast-forms had been
developed. ** The fact," he observes, "that only a few species
have penetrated into the abyssal plain, while the main body of
the species still remains on the slope, tends to show that in
most cases the migration towards the abyssal plain is still going
on, that it is very slow, and that it has not yet reached the
borders of the abyss ; or else it indicates that the abyssal plain
tends to limit further distribution, acting as an almost in-
surmountable obstacle."
We have seen that all the deep-sea expeditions, prior to the
"Michael Sars," captured only 35 individual "bottom-fishes,"
and that these belonged to twenty-one species. Our present
knowledge must therefore be very imperfect. We have not yet
learnt to fish to perfection at 2000 or 3000 fathoms, and we
have as yet made too few fishing experiments at such depths.
The short cruise of the "Michael Sars" in the Atlantic has
essentially altered Brauer's ideas of the distribution of deep-sea
fishes, and it appears desirable to give the interesting question
raised by him a fresh trial, in view of the large amount of
information which we now possess regarding the migrations
of many fishes. When, for instance, we find the cod of the
Norwegian Sea at one season spawning near the coasts of
Norway, at another season migrating to Spitzbergen, or to
the slopes of the coast - plateau, we must conclude that
fishes may undertake horizontal as well as vertical migrations
of enormous extent in a short space of time. Seeing that
Macrurus sclero^'-JiyncJms has the enormous bathymetrical range
of from 540 to 3655 metres, we can hardly suppose that the dis-
tribution of deep-sea fishes down the slope and on the abyssal
plain could have been prevented by "lack of time." We have
426
DEPTHS OF THE OCEAN
every reason to believe that the physical conditions in these
depths have been essentially the same at least for thousands of
years.
We possess, of course, no information as to the time required
for the distribution of a species into oceanic depths. In shallow
waters we know quite well that new physical conditions may
permit a species to migrate into new areas and to multiply
enormously in a short space of time (as an instance may be
mentioned the immigration of cod into the Liimfjord after
the North Sea broke through at Thyboroen). At all events it
seems reasonable, first of all, to look for factors in operation at
the present day, the influence of which may be investigated,
before we fall back on the hypothetical conditions prevailing in
a previous geological period.
In his " Challenger " Summary, Sir John Murray has
attempted an explanation of the quantitative distribution of
organisms in different depths, which not only throws much
light on these important geographical questions, but also possesses
the great advantage of containing in itself a whole programme
of future research. He found that many deep-sea animals — the
hydroids, for example — had developed special apparatus for
catching the minute shells and particles of food that fall from the
surface waters, and the holothurians and other echinoderms —
the most abundant of deep-sea animals — had their intestines
always crammed with the surface layers of the deposit on which
they were captured, either Blue mud, Diatom ooze, Globigerina
ooze, Pteropod ooze, or Red clay.
We have seen in Chapter IV. that marine deposits may be
separated into two main groups : terrigenous deposits and
pelagic deposits, the former occurring in deep and shallow
water around all continents and islands within an average
distance of one hundred or two hundred miles from the coast,
and the latter occurring in the deeper water towards the central
parts of the great ocean basins.
It is a well-known fact that the detrital matter which is
carried into the sea by rivers is rapidly deposited on meeting
salt water, but in shallow water, where currents and wave-action
produce their maximum effect, these fine detrital matters are not
allowed to settle on the bottom, but are moved along till they
reach the lower limit of wave-action. In enclosed seas this may
be at a depth of only a few fathoms, but along coasts facing the
great oceans the waves are so long and so high that to a depth
of several hundred fathoms minute particles of sand may be dis-
FISHES FROM THE SEA-BOTTOM 427
turbed, as, for instance, off the north of Scotland. Murray has
termed the Hmit of wave-action the mud-lme, and the average
depth in the open ocean at which mud commences to be laid
down he places at about 100 fathoms.
Beyond the mud-line the physical conditions become more
and more uniform, and for a few hundred fathoms below this
limit animal life is exceedingly abundant. This region, accord-
ing to Murray, is the "great feeding ground" of the ocean,
especially around continental shores ; the organic particles from
the continents and from the shallow waters there slowly come to
rest on the bottom and supply food to the wealth of crustaceous
forms which are captured in such situations (Calantis, Bzickcsta,
PasiphcEa, Crangon, Calocaris, Pandahcs, Hippolyte, Pagitmis,
Amphipoda, Isopoda, and Mysida).
The surface layers of the organic deposits which are Decreasing
situated in moderate depths towards the central parts of the food"on°pro-
ocean basins (Diatom ooze, Globigerina ooze, Pteropod ooze), ceedinginto
yield an abundance of food for benthonic animals, but all '^^^p^'^^"-
investigations go to show that where the organic oozes pass
with increasing depth into Red clay, the quantity of food for
bottom-living animals rapidly diminishes, and the number of
animals captured on Red clay bottoms likewise diminishes very
greatly. The poorest hauls during the whole of the " Challenger "
Expedition were those taken in the stretches through the
central Pacific from Japan to Valparaiso, and Alexander Agassiz's
investigations on board the "Albatross" gave similar results.
He calls the central South Pacific a "barren region."
This short statement will make it obvious, that the condi-
tions of life offered to organisms may vary greatly in different
depths. Murray's theory on the importance of the deposits to Relation
the distribution of animal life is of special value, because it df^^rent kinds
opens up to science the possibility of finding certain definable of deposits
reasons for the differences observed in the specific composition, Hvfng^on^""^
and in the abundance, of animal life from place to place. them.
This study has, however, been somewhat neglected as far as
the oceans are concerned. Most of the deep-sea expeditions
have been so absorbed in faunistic research, that the problems of
the economy of the ocean have been very little attended to,
and the strong interest taken in theoretical plankton-research
peculiar to recent times has drawn attention away from the
bottom-life of the ocean and the importance of the deposits as
food for the bottom fauna, but Lohmann and C. G. J. Petersen
have recently turned attention again to Murray's point of view.
42;
DEPTHS OF THE OCEAN
During his plankton work in the Liimfjord, Petersen
arrived at the conclusion that the plankton played a very
unimportant part in the food of bottom-animals (as, for instance,
the oyster). He commenced therefore to study the finely
granular mass found in the gut of the bottom animals. He
discovered that the uppermost layer of mud on the fjord bottom,
2 or 3 mm. in thickness, consisted of detritus containing minute
remains of organisms, mainly of decayed plants from the
littoral region, and that only this upper layer of the mud has
any nutritive value, the deeper blue-black layer not occurring
in the gut of the bottom animals. Starting from these re-
searches, Petersen studied the organic (nutritive) constituents
of the mud, especially of the upper layer, and investigated the
abundance of bottom-animals over different kinds of deposits.
For this purpose he constructed an apparatus (see Chapter X.)
for cutting away from the sea-bottom a square foot of its
surface. When this large "bottom sample" is sifted the
animals contained in the mud can be counted, and by com-
paring the quantities of mud-eating animals thus found per
square foot of bottom, the yielding power of different areas
may be estimated, much on the same principle as the productive
value of agricultural land is estimated.
The "Michael Sars " had, during the Atlantic cruise, some
of Petersen's apparatus on board, but owing to difficulties in
using them in deep water, we did not succeed in obtaining
material of any value, a fact all the more regrettable, as there
is no doubt that Petersen's method gives far more exact results
as regards the quantities of certain animals living on the bottom
in shallow water than hauls with dredges and trawls. Neverthe-
less, the material at hand may be used to illustrate the question.
The most stringent quantitative science is in the first stages of
a new study satisfied to dispense with the demand for absolute
exactness, and contents itself with relative values — in other
words, with a comparison between different localities.
Sir John Murray long ago attempted to compare the number
of animals taken in the dredge or trawl on different deposits,
based on the results of the " Challenger " Expedition, and I
reproduce some of his figures f^pm the second volume of the
" Challenger " Summary : —
[Table
FISHES FROM THE SEA-BOTTOM
429
Specimens per Haul.
Trawlings.
Dredgings.
On Red Clay-
In the Atlantic ....
„ Pacific ....
„ Southern Ocean .
On Globigerina Ooze —
In the Atlantic ....
„ Pacific ....
„ Southern Ocean .
On Terrigeftous Deposits —
In the Atlantic ....
Pacific ....
„ Magellan Strait .
„ Southern Ocean .
40.0
20.3
50.0
21. 1
56.5
96.7
108.5
71.4
lOO.O
4.2
5-2
7.0
5-0
55-3
59-0
93-0
These figures plainly show that animal life was found most
abundantly on terrigenous deposits, though the Globigerina
ooze was also, especially in the Southern Ocean, very rich in
organisms.
At the two deepest stations of the " Michael Sars " (Station
10, 4700 metres, and Station 48, over 5000 metres) the trawl
was dragged for hours along the bottom, and brought up great
quantities of ooze, which on being sifted yielded only a few
holothurians (one individual at Station 10 and two at Station
48). Of other mud-eating animals we found none at Station
48; and at Station 10, in two hauls, a gasteropod, two ophiurids,
and a few worms.
These hauls are comparable with those made by the
"Challenger" between the Canaries and the West Indies (see
p. 418), in depths between 2000 and 3000 fathoms.
Different conditions are encountered on the slopes in
shallower water, the slopes of both continents and submarine
ridges. From the " Michael Sars " journal the following results "Michael
of trawlings on the continental slope west of the British Islands frawiin son
may be quoted : - • the continental
Station loi, 1853 metres (about 1000 fathoms). Besides 90 fishes, great wesTof
numbers of invertebrates, mainly echinoderms, ophiurids and starfish being Britain,
especially abundant.
Station 95, 1797 metres (981 fathoms). Besides 82 fishes, 300 holothurians,
800 ophiurids, starfish, Fhormoso/fia, etc.
430
DEPTHS OF THE OCEAN
Station 4, 923 metres (547 fathoms). Besides 332 fishes, quantities of star-
fish, sea-urchins {Brissopsis, Fhormoso?na), etc.
South of the Faroe Islands, 831 metres (460 fathoms). Besides 300 fishes,
large numbers of invertebrates.
In Chapter IV. Sir John Murray has stated that the bottom-
samples collected during the cruise of the " Michael Sars " show-
that Globigerinaooze approaches nearer to the coasts of the British
Islands than was previously supposed, having been found at
Station 4, 547 fathoms; Station 93, 688 fathoms; Station 95,
981 fathoms; Station 98, 742 fathoms; and Station 100, 835
fathoms.
While the fishes of the continental shelf all live on terrigenous
deposits, like Blue mud, the " MichaeliSars " results prove that
in the eastern Atlantic, at any rate, most of the fauna of the
continental slope live on Globigerina ooze. Circumstances may
be quite different on other slopes, as, for instance, the Atlantic
slope off the United States, or off Newfoundland, where terri-
genous deposits seem to have a much wider distribution. But
the very important question of the limits between the terrigenous
and the pelagic deposits requires further careful study by means
of series of hauls with the trawl and series of samples of the
deposits from shallow water down the slope to the abyssal plain.
The results given above show in any case that . the
Globigerina ooze in depths of 550 to 1000 fathoms may be a
rich ground for animal life, since we got such good hauls at
the stations quoted, and this is corroborated by the hauls taken
on this type of deposit in deeper water, far from continental
land, as at Stations 53 and 88.
At Station 53, south of the Azores, 2615 to 2865 metres
(1430 to 1570 fathoms), the trawl captured in one haul, besides
39 fishes, about 500 holothurians, and abundance of different
crustaceans, actinians, etc.
At Station 88, in 3120 metres (about 1700 fathoms), the
trawl brought up a wealth of animals, especially sea-urchins,
starfish, ophiurids, holothurians, etc.
We thus see that it is not terrigenous deposits alone wJiich
harbour an abundant bottom fauna ; in fact, on true pelagic
deposits, like Globigerina ooze, we may have the conditions
necessary for abundant life. The percentage of carbonate of
lime gives no indication of the suitability of the conditions for
animal life, for the terrigenous deposits with abundant fauna, as
well as the barren Red clay, both contain very little calcium
carbonate. The important item is the organic stcbstance con-
tion of fish.
FISHES FROM THE SEA-BOTTOM 431
tained in the deposits, which fertilises the surface layers of the importance
Blue mud as well as of the Globigerina ooze. maufr^?n^he
Petersen has shown that only the uppermost layer of the deposits.
mud contains organic detritus, but the quantity of organic
substance deposited is not always the most important factor.
Where the water is in motion at the bottom, a fine cloud of influence of
organic matter is swept along, and in such localities the mud- ^^H'^^^l ^^
eaters thrive in great quantities. The fishermen have for a the distribu
long time profited by this fact, for they do not seek those places ' ^""^
(as in pits and channels on the bottom) where mud is laid
down, but choose rather the spots where the bottom is covered
with coarser particles, and where the finest mud cannot settle.
In these places the fish find most food, and the fishermen most
fish.
Perhaps conditions like these prevail on the eastern Atlantic
slope, as, according to the current-measurements of the
" Michael Sars," considerable currents extend down to great
depths. All such conditions call for further examination,
especially in the open ocean, and it may be affirmed that studies
of this kind will be essential for an understanding of the
quantity of life along the bottom.
Returning to the question of the geographical distribution of
different species of fish, we may now examine some of the
conditions which influence that distribution, according to the
present state of our knowledge.
We have seen that the species Macrttrus arniatus is known
from the abyssal plain in the Pacific as well as in the Antarctic
and Atlantic Oceans. The chart (Fig. 308) indicates the
localities of capture and also the temperature, and shows at a
glance that, notwithstanding the immense geographical range of
this species, it is taken only where the range of temperature
is very small (1° to 3^ C). The species is not local ; it is not
limited by distance, but by certain physical conditions, which in
this case prevail over an immense geographical area.
Temperatures in abyssal depths are, as we have seen in
Chapter V., on the whole very uniform. It is therefore interest-
ing to note that it is especially the abyssal forms that are known
from wide areas ; thus, for instance, Macrurtis filicatida, known
from the Pacific and Antarctic, has a bathymetrical range from
2515 to 4843 metres. Macrnrns parallelus, known from New
Zealand, Japan, Ceylon, South-west Africa, ranges down to 1300
metres. Halosauropsis 7nacrochir, known from the Southern
Distribution
of different
species of fish.
432 DEPTHS OF THE OCEAN
Ocean, between South Africa and Kerguelen, and from the
" Michael Sars " Stations 35, 53, 88, and 95, was taken down to
2995 metres.
As regards the North Atlantic in particular, the distribution
of the deep-sea fauna and the hydrographical conditions show in
many instances a marked and interesting correspondence. The
rule just discussed holds good also in this ocean : the deepest
living forms have a wide distribution. Thus three forms
[Macrtirits brevibarbis, M. simulus, and Hariotta raleighana),
previously known from the American side of the Atlantic, were
found by us on the eastern side, as well as on the ridge in Mid-
Atlantic. These forms were only taken at the deepest stations.
In Fig. 99, p. 115, a section is given from Newfoundland
to Ireland, showing the vertical distribution of salinities and
temperatures, and we see from this that on the eastern side
of the Atlantic high temperatures go far deeper than on the
western side, where the isotherms take an upward turn along
the slope. In intermediate depths, for instance between 500
and 800 fathoms, it is therefore much colder on the western side,
while at depths of 1000 to 2000 fathoms similar temperature
conditions prevail on both sides. Special interest thus attaches
to the fact that representatives of the deepest living forms were
found on both sides of the ocean, while the faunae of the slopes
in 500 to 800 fathoms are, on the whole, distinct. From this
latter rule exceptions may be noted, some forms being also at
these depths common to both sides, like Antimora viola, found
first on the eastern side by the " Michael Sars," Macrurus
7'upestris, and M. ccElo^'hynchus ; these forms, however, appear
to be allied to the fauna of the coast banks, and they can hardly
be counted among the forms characteristic of the intermediate
depths on the slopes.
Among the Macruridse the following species may perhaps be
considered as characteristic of the two sides of the North
Atlantic : —
Western Side. Eastern Side.
Macrurus carminatus. Macrurus zaniophorus.
„ bairdii. „ cEqualis.
„ goodei. „ sclerorhynchus.
„ sulcatus. Bathygadus melanobra/ichus.
„ longifilis.
Fishes from We will here only discuss the fauna of the eastern side,
the eSern° where trawHngs as well as hydrographical investigations were
Atlantic. made by the " Michael Sars." The most important fish caught
FISHES FROM THE SEA-BOTTOM
433
are recorded in the following table, arranged according to the
three series of trawlings taken: (i) west of the British Isles,
(2) west of Morocco, and (3) south of the Canaries : —
West of the British Isles.
West of Morocco.
South of the Canaries.
South of Faroe Islands,
831 metres.
73 Lepidion eqiies.
94 Halargyn-etis affinis.
Station 21, 535 metres.
Merhiccius, Gadiculus ar-
genteus, Molva, Phycis,
Zeugopterus boscii, Sebastes
dactylopterus, Chimcera vion-
strosa, Spinax niger, Hoplos-
tethus mediterraneum.
20 Macrurus, mostly hevis and
ccelorhynchus.
Station 39 B, 2S0 metres.
400 to 500 fishes, mostly
Sparidre.
74 Macrurits mostly rupestris
and (vqiialis.
I Trachyrhynchtis niurrayi.
I Alepoccphalus giardi.
15 Notacantlms bonapartii.
I Synaphobranchus pinnatus.
Station 41, 1365 metres.
4 Mora mora.
18 Macrurus {talismani, sclero-
rkynckus, zaniophorus,
aqualis, asperrimus ;
Centrophorus, Chinntra
mirabilis, and several
others.
Station 23, 1215 metres.
36 Mora mora.
II Macrurus, mostly aqualis
and Bathygadus longifilis.
5 Alepocepkalus.
3 Halosaurus.
I Bathypterois.
3 Synaphobranckus pinnatus.
Batky gadus melano-
branckus).
6 Alepocepkalus.
12 Bathypterois.
Station 4, 923 metres.
15 Sytiaphobranckus pinnatus.
I A)itinio)a viola.
70 Mora mora.
31 Lepidion eques.
200 Macriirus, mostly talismani,
aqualis, zaniophoriis.
16 Trachyrhynchus.
9 Alepocepkalus giardi.
I Halosauriis.
3 Hoplostethus mediterraneutn.
3 Siorptma cristtilata.
3 Synaphobranchus pinnatus.
8 Chinuera mirabilis.
I Rata nidrosicnsis.
Station 35, 2603 metres.
6 Macrurus [armatus and
ceqtcalis).
Station 24, 161 5 metres.
12 Macrurus, mostly talisniajii,
Bafkygadus longifilis.
12 Alepocepkalus.
3 Synaphobranckus pi)inatus.
5 Alepocepkalus.
2 Halosauropsis.
I Hariotta raleighana.
Station 25 B, 2055 metres.
9 Macrurus {sclerorkynckus
and tcqualis).
16 Alepocepkalus.
I Bathysaurus.
I RaiafyllcE.
Station 95, 1797 metres.
16 Atttimora viola.
36 Macrurus, mostly sclero-
rhynchus, murrayi.
5 Alepocepkalus.
2 Bathysaurus.
3 Notacantkus.
2 Synaphobranchus pinnatus.
2 Kaiafylhe.
Station ioi, 1853 metres.
16 Antimora viola.
66 Macrurus, mostly sclero-
rhynchus.
3 Alepocepkalus.
3 Synaphobranchus pinnatus.
2 Hariotta raleighana.
From this list we see that the fish fauna of the slope is very
uniform all the way from the Faroe Islands to south of the
Canaries ; no less than six species are common to the northern
2 F
434 DEPTHS OF THE OCEAN
and southern series. The hydrographical conditions prevailing
along the east side of the Atlantic at these depths are well seen
in the chart for 500 fathoms (see Fig. 202, p. 296), which shows
that the temperature at 500 fathoms to the south of the Faroe
Islands is above 7.0° C, and south of the Canaries, 8.0° C.
Only outside of the Mediterranean do we find a higher tempera-
ture. On the western side of the Atlantic the temperature at
the same depth is only 4.0" C. These facts seem to me to
throw much new light on the geographical distribution of the
deep-sea fauna.
The conditions in the deep basin of the Norwegian Sea, which
has been described in Chapter IV., are no less interesting. In
the little chart (Fig. 309) the contour-lines for 600 and 2000
metres are shown. The 2000 metres isobath encloses the
abyssal plain of the Norwegian Sea, the central parts of which
are covered by 3000 and 3500 metres of water. The area
between the 2000 and the 600 metres isobaths shows the region
of the slopes, which are steep all the way from Spitzbergen to
the Wyville Thomson Ridge, a deep channel (the Faroe-
Shetland channel) running from the deep basin right down to
the ridge. The hydrographical conditions in the Norwegian
Sea are indicated in the vertical section (Fig. 310), which runs
through the points a, b, <;, from the east coast of Greenland
across Jan Mayen to Vesteraalen in Norway. In this section
the "Atlantic water," with a salinity above 35 per thousand, is
shaded, and is seen to be limited to the eastern side, the
depth of the layer not exceeding 600 to 700 metres (or 350
to 400 fathoms). All the water to the west, and beneath this
" Atlantic water," is quite cold, most of it below 0° C, the
abyssal plain itself being covered by water having a temperature
below — 1° C.
The fauna of this cold deep basin has been extensively
studied during the Norwegian expeditions on board the
" Voringen " and the "Michael Sars," during the Danish
expeditions on board the " Ingolf" and the " Thor," and also by
Swedish and French expeditions (Duke of Orleans, etc.). On
the chart (Fig. 309) small circles denote localities where
Norwegian expeditions have employed dredges or trawls, the
captures everywhere being remarkably poor in species.
The abyssal plain and the slopes of the Norwegian Sea do
not show a single species in common with the Atlantic. While
in the Atlantic the genus Macrurus plays an important part in
FISHES FROM TH^: SEA-BOTTOM
435
the fauna of the abyssal area, not one species of this genus
has been found in the cold water of the Norwegian Sea, where
the genus Lycodes (of the family Zoarcidae) predominates. But
Lycodes is not limited to the Norwegian Sea, being represented in
Fig. 309. — -The Norwegian Sea.
Continuous line-— 600 metres. Broken line =2000 metres.
Section through a, b, c, shown in Fig. 310.
the abyssal depths as well as on the slopes of the Atlantic, though
no species has been found common to the Atlantic and the
Norwegian Sea. To the Danish scientist Adolf Jensen we owe
our knowledge regarding this interesting biological fact.
436
DEPTHS OF THE OCEAN
The principal "cold-water" fish of the deep Norwegian Sea
belong to the following species : —
ZoARCiD/E — Lycodes mitrcB/m, L. flagellicauda, L. fn'gidus, L. palHdus,
L. similis, L. eudipleurostictus, L. seminudus.
OPHiDUDiE — Rhodichthys reglna.
Li PAR I D^ — Careproctus reinhardi, Paraliparis bathybii.
CoTTiD^ — Cottunculus microps, C. stibspinosus.
Sharks — Sonmiosus inicrocephalus (the Greenland shark).
Rays — Raia hyperborea.
Excepting the Greenland shark these species have been
Fig. 310. — Section across the Norwegian Sea from Greenland to Norway in
Position shown in Fig. 309. (Drawn by Helland-Hansen.)
taken in cold water only, below 0° C, and mostly in small
numbers, though occasionally they are more numerous.
Thus a haul made by the " Michael Sars " to the north of
the Faroe Islands, in 975 fathoms, with a trawl similar to the
one used in the Atlantic, gave in two hours : 34 Paraliparis
bathybii, i Rhodichthys regina, and 17 Lycodes. East of
Iceland, in 467 fathoms, where the temperature was -0.6°
C, the Danish research steamer "Thor," on a line of 225
hooks, obtained 4 Raia hyperborea, i Greenland shark, and 20
black halibuts (Hippoglossiis hippoglossoides) ; the latter two
species are not, however, exclusively cold-water fish.
FISHES FROM THE SEA-BOTTOM 437
Previously all these fishes of the Norwegian Sea were
generally believed to live only along the bottom, but, as
mentioned in Chapter HI., the "Michael Sars " in May 191 1
obtained in a pelagic haul in the cold layers of the Norwegian
Sea a specimen of Paraliparis bathybii. In the cold water
layer there are thus fishes which at least occasionally occur in
midwater.
On the coast banks off Greenland, Jan Mayen, and the Arctic
most northerly coasts of Spitzbergen dwells a genuine Arctic Juia ofThe^''
fauna. Of these shallow cold-water species the following are Norwegian
most important : Icebis kamatics, Triglops pingelii, Ltwipenus
niactilatits, L. viedius, and L. lampetriformis, besides Gadtis
saida (the polar cod).
On the east and south side of the Norwegian Sea, from
Spitzbergen along the coast of Norway and the North Sea
banks, and also at Iceland, the cold water does not occur on the
slopes in depths less than 600 or 700 metres, and the change
from the cold water to "Atlantic water" is very marked. The
deep-sea fauna and the fauna of the coast banks are for this
reason much more sharply separated than in the Atlantic. At
most seasons the limit is determined by the vertical distribution
of the Atlantic water, and this limit may oscillate according to
changes in the current, though this point has not yet been
thoroughly examined.
The fishing experiments of the " Michael Sars " have some-
times in a very striking way shown how sharp the limit is
between the two faunce. In June 1902, for instance, a long line
of 1200 fathoms was shot on the northern slope of the North
Sea bank towards the deep water, one end of the line being in
217 fathoms, where the temperature was 6° C, and the other end
in 300 fathoms, where the temperature was — 0.2° C. In the cold
water we obtained cold-water fish {Raia hype^'borea), while near
the upper end of the line (in warmer water) the fish belonged to
the coast bank species [Sebastes, Macrurus fabricii). Rata
hyperborea has been taken from North Spitzbergen down to the
slope of the North Sea plateau ; Macrurus fabricii is known
from the Bay of Biscay, from the ocean off the east coast^of
North America, and from other localities.
The Fishes of the Coast-banks
The " Michael Sars " has now had the opportunity of
investigating the coast-banks from Spitsbergen to a little south
438 DEPTHS OF THE OCEAN
of the Canaries, a stretch of more than 40 degrees, or 2400 miles,
A survey of the animal life on this long stretch of sea-floor is
very interesting. As the temperature gradually falls toward the
north the fauna changes. Some species are hardy, and are dis-
tributed over a greater part of the area ; others can only live
under more uniform conditions, and therefore have a more
limited area of distribution.
Zoological oceanography has long recognised this, and
zoological literature contains much information regarding the
distribution of animals within our area of investigation. I will
mention only one example, for which purpose I choose the
excellent survey of the mollusca of Arctic Norway by G. O.
Sars, recording the geographical distribution of 1 74 species of
lamellibranchs and 366 species of gasteropods.
Of the 174 lamellibranchs no less than 128 or 74 per cent
were known also from Great Britain ; 119 or 70 per cent from
the Mediterranean, and 56 or 32 per cent from boreal North
America.
Of 366 gasteropods found in Norway, 225 or 62 per cent
were also known from Great Britain ; 133 or 36 per cent from
the Mediterranean, and ']^ or 23 per cent from the coasts of
boreal North America. A great many species of molluscs have
been taken in the Mediterranean as well as in Norway, and
quite a number of forms are common to the faunae of Norway
and of North America.
Examining the conditions in various parts of the coast of
Norway, we see that the Mediterranean species rapidly decrease
in number as we go north from western Norway, for instance,
from the latitude of Bergen towards the North Cape. While
119 lamellibranchs and 133 gasteropods are common to the
Mediterranean and Southern Norway, Northern Norway and the
Mediterranean have only 49 lamellibranchs (28 per cent) and 35
gasteropods {10 per cent) in common. Also south of the
Mediterranean we find a similar decrease in the number of
species common to both areas ; thus only 5 species of lamelli-
branchs and 4 species of gasteropods are common to Madeira
and Northern Norway.
1^ A thorough understanding of the distribution of different
animals, or of the different animal-communities, is, however, not
obtainable by m.eans of records of this kind, for it makes a
world of difference whether a few specimens of a species have
been found in a certain locality or whether it lives there in
great quantities. A complete knowledge of the distribution of
FISHES FROM THE SEA-BOTTOM
439
a species would be based on material containing information
as to how many individuals of the species live in different
sections of the area, and a complete knowledge of an animal-
community would be to have information as to the exact
relative occurrence of the animals.
In regard to no species, however, does our present knowledge
comply with this ideal demand. As regards the fishes we have
Fir,. ^11. — Steam-Trawlers laid up in Grimsby during Engineers' Lock-out.
most information on the species of economic importance, for In
recent years many fishing experiments have been made with the
object of ascertaining what quantities of fish occur in different
waters. In co-operation with the International Council for the Fishery
study of the sea, the fishery statistics of several countries have ^^^^'^^^^^
also been so far improved, that the quantities of fish landed are
now separated in regard to species and areas where caught.
The quantities landed are certainly not on the whole repre-
440 DEPTHS OF THE OCEAN chap, vn
sentative of the quantities living in the sea. For instance, it is
clear that the intensity of fishing is not only determined by the
abundance of fish, the prices and the distances to fish markets
being (among others) very important points. But notwith-
standing these drawbacks, we possess at the present time hardly
any better means of judging of the abundance of fish in different
areas than the information regarding the capture of edible fish
contained in the fishery statistics of recent years. An enormous
fleet of modern fishing steamers (see Fig. 311) is now dis-
tributed from Cape Kanin, at the mouth of the White Sea,
down to Morocco, that is to say, over the area investigated by
the " Michael Sars."
From the statistics published by Dr. Kyle of the Inter-
national Bureau for the Study of the Sea, we have compiled
two tables recording the capture of bottom-fish in 1906. One
(Table A) shows the catch of each species in each fishing area
expressed in percentages of the quantity of the species landed
from all areas ; the other (Table B) shows the catch of each
species expressed in percentages of the aggregate quantity
landed from each area. The tables deal with nearly a million
tons of fish of all kinds from all waters, the quantities varying
greatly in different areas. First of all is the North Sea with
nearly 400,000 tons, or nearly 40 per cent of the total quantity ;
then comes the coast of Norway, north of Stat, with 28 per cent,
Iceland with 18 per cent, the Faroe Islands with 4 per cent, the
region north-west of the British Isles with 5 per cent, the Bay
of Biscay, Portugal, and Morocco with less than ^ per cent
each. Among the different bottom-fish the cod plays the most
important part with no less than 44 per cent, next comes the
haddock with 25 per cent, plaice with 6|- per cent, saithe with
3|- per cent, ling 3 per cent, and hake with a little above
2 per cent, of the total quantity.
Considering now the abundance of each species in each of
the nine areas recognised by the fishery statistics, we first
observe that most of the species have their maximum abundance
in the North Sea. This applies principally to the haddock,
the whiting, the species of Bot/ms, the plaice, the lemon sole,
and the dab. The intensity of the fishing in the North Sea
is, of course, to some extent responsible for this. But never-
theless we find several exceptions. Thus the Norway haddock
(Sebastes), the cod, the saithe, and the tusk are taken in the
greatest quantities off the coast of Norway, the halibut at
Iceland. On the other hand, we find in regard to dog-fish.
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CHAP. VII FISHES FROM THE SEA-BOTTOM 443
bream (Pagelhts), pollack, hake, megrim i^Zetigopte^^us), and
conger-eel, that the greatest quantities are taken south-west of
the British Isles in the Atlantic.
We can thus distinguish northern species which are mainly Northern and
taken north of the North Sea and in the North Sea, and ;°^'^^^';^^ ^j^^
southern species, which are chiefly derived from the Atlantic, easteni
notwithstanding the fact that comparatively little fishing is '^^^^"*^'^-
carried on in this area. The percentages of each species in the
aggregate quantities landed from each area confirm these facts.
In the area between the mouth of the White Sea and the
west coast of the British Isles we find the cod constituting at
least 20 per cent of all the fish caught, on the coast of Norway
even 81 per cent, at Iceland 60 per cent, and at the Faroe Islands
48 per cent. South-west of the British Isles the quantity of
cod dwindles to 4|- per cent, and farther south it disappears.
The haddock also constitutes a large proportion of the quantities
landed from the area between the White Sea and the north-
west of the British Isles (excepting off Norway, where the
bottom is unsuitable for haddock-fishing) ; in the North Sea even
45 per cent of all the fish caught are haddock. The quantities
of this fish also dwindle and finally disappear south-west of
the British Isles. The same applies to plaice, halibut, ling, and
tusk.
The percentages of southern fish, on the other hand, increase
west of the British Isles. The hake [Alerhiccius) practically
does not occur north of the North Sea, where it constitutes
only about J per cent of the total quantity ; south-west of the
British Isles it reaches 32 per cent, in the Bay of Biscay even
65 per cent, and all the way southward it constitutes at least
30 per cent of the total quantity. Similar conditions apply to
the pollack, sole, sea-bream [Pagelhts), the monk or angler, the
gurnards, and others.
On the coast banks of the western side of the Atlantic we Northern and
meet with similar groups of northern and southern forms, JpedeT^n the
the change between these groups occurring about the New western
England states. We give some instances of quantities of fish
landed in the New England states, the middle Atlantic states,
and the south Atlantic states, taken from the fishery statistics
for the year 1906, the figures signifying tons : —
[Table
444
DEPTHS OF THE OCEAN
Northern States.
Middle States.
Southern States.
Cod . . .
40,000
1,400
Haddock
21,000
200
Saithe .
7,900
50
Flounder
2,150
1,400
350
Halibut
5.500
Hake .
15,000
200
Mullet .
150
18,500
Sci^nidas
3>3oo
11,400
4,300
Sparidse
30
6,100
Influence of
temperature
fishes.
The northern forms — cod, haddock, saithe, flounder, and
hahbut — disappear along the coast of the southern states, as does
also the hake. On the other hand mullet, ScisenidEe, and
Sparidae, i.e. the southern forms, increase as we go south, just as
they do on the eastern side from the Bay of Biscay towards the
coast of Morocco.
If, with these facts in mind, we look at the chart (Fig. 312)
,.,. recording: the temperature at a depth of 100 metres (about 50
conditions on p ,11, -ii 1 r 1 1 tm •
distribution of fathoms), we shall be astonished at the tact that the distribution
of different species curiously coincides with certain temperatures.
The southern limit of northern boreal species everywhere
coincides with the isotherm for lo^ C. On the west side this
isotherm just reaches the border between the northern and
middle states of North America, while on the east side, on the
coast of Ireland, this isotherm just separates the two areas
termed respectively areas north-west and south-west of the
British Islands.
The areas of the northern species correspond on both sides
of the ocean to the area between 2° and 10" C, the maximum
frequency of the species occurring between 6^ and 8° C. These
latter temperatures are found on the Newfoundland banks, on
the southern and western banks of Iceland, in the North Sea,
and along the entire coast of Norway. The uniformity of the
fauna peculiar to all these localities compares well with the
uniform conditions of temperature. South of the 10° isotherm
we have on both sides of the ocean belts with temperatures
between 10' and 18° C. ; that on the west side ranges from
Cape Cod to Florida, and that on the east side from Iceland to
south of the Canaries.
A peculiar feature is that all the isotherms on the west side
are quite close together, the water layers being squeezed
FISHES FROM THE SEA-BOTTOM
445
between the oceanic sub-tropical waters from the south and the
arctic Labrador current from the north. All changes in
temperature are therefore on the western side very sharp. On
the eastern side the layers are spread out fan-wise, and as a
consequence we may at a depth of lOO metres find the same
temperature prevailing from north to south over wide areas, as,
Fig. 312. — Distribution of Temperature in the North Atlantic at a Depth of
100 metres. (Drawn by Helland- Hansen.)
for instance, along the coast of Norway from the North Sea to
the North Cape.
We may now discuss the distribution of the southern and
northern species.
Comparing the percentages of the different species noted in The southern
the quantities landed from different geographical areas (see ^p^"^^-
446 DEPTHS OF THE OCEAN chap, vn
Table B), we observe that northern (boreal) forms decrease
enormously to the west of the British Isles, We may say that
there is a sharp southern limit to the distribution of these
species west of the Channel ; the cod, saithe, tusk, and halibut
here quite cease to play any part in the captures.
The northern limit for the southern forms is essentially
different. Of the species recorded in the systematic list of
bottom-fish captured by the " Michael Sars " in the Atlantic, 63
species were previously known from the Mediterranean, and are
found there in abundance. Of these only a few are genuine
southern forms; 10 species have their northern limit on the coast
of France, 19 on the coasts of the British Isles, and 23 occur
in varying numbers even on the coasts of Scandinavia. As we
shall show in Chapter X., this wide range of certain species is
probably due to the fact that the water- layers in the North
Atlantic run north, and transport especially the young stages of
certain southern species, which may as a consequence pass their
youth very far from the localities where they were born. This
is why the boreal fish-fauna is more or less mixed up with
southern forms, especially in the southern part of the boreal
region, for instance in the southern North Sea, in the areas
west of the British Isles, in the Kattegat, and along the coast of
the Skagerrack, in which localities high summer temperatures
prevail in the upper layers.
To the south-west of the British Isles, from the Bay of Biscay
towards Morocco, we enter the real area of the southern fauna.
This is shown by the table containing the fishery statistics, as
well as by the record of the captures made by the " Michael Sars "
in the Atlantic. In the following list the captures made during
the cruise down to about 500 metres, or 300 fathoms, are
recorded and arranged in three groups : (i) West of the British
Isles, (2) West of Morocco, and (3) South of the Canaries.
[Table
Fishes from the Atlantic Coast Banks.
West of British Isles.
West of Morocco.
South of Canary Islands.
Off Faroe Islands,
130 metres (trawl and long-line).
2 Gadus aglefimis.
1 2 Hippoglossus vulgaris.
6 Plettronectes limanda.
I Zetigopterus niegastoma.
I Raia clavata.
9 Raia bat is.
Off the Coast of Portugal,
Stations 13-14, 70-80 metres,
(trawl and line).
8 Gadus merlangus.
36 ,, luscus.
22 Merluccius vulgaris.
I Pagellus centrodontus.
I Caranx track urns.
3 Trachinus viper a.
I Mustelus vulgaris.
I Scyllium canicula.
I Centrina salviani.
I /"a/a clavata.
I j?a/« circularis.
Station 36, 10 metres.
5 Merluccius vulgaris.
1 .SW^a /z^/^a.
Many Sargus annularis.
Many Pristipoma beniiettii.
2 Sciczna aquila.
2 Umbrina ronchus.
2 .5(?.r vulgaris.
32 Atherina.
77 Caranx trachurus.
I Temnodon saltator.
73 Clupea pilchardus.
I , , «/^ja.
26 Engraulis encrasicholits.
I Myliohatis aquila.
Station i, 146 metres.
2 Gadus esviarkii.
2 ,, poutassoH.
2 Phycis blennioides.
20 Merluccius vulgaris.
4 Zetigopterus niegastoma.
Station 20, 141 metres.
52 Merluccius vulgaris.
I ^o/cja vulgaris.
7 Pagellus centrodontus.
1 , , acarne.
3 Dentex maroccanns.
5 ,, niacrophthalinus.
1 1 Mullus surmuletus.
8 Caranx trachitrus.
4 Zeus faber.
30 Capros aper.
1 Trigla hiriindo.
16 ,, /j'ra.
3 , , cuculus.
2 , , //;;/.
20 Lepidotrigla aspera.
I Peristedion cataphractum.
4 Acanthias vulgaris.
6 Scyllium canicula.
I ^a/a clavata.
184 Caranx trachwus.
I Zeusfaber.
52 Capros apcr.
18 Trigla guniardus.
5 Argentina sphyncna.
20 Acanthias vulgaris.
I Pristiurus melanostonius.
7 /'a/a clavata.
Station 37, 39 metres.
I Artioglossus lophotes.
1 Dentex maroccatius.
2 Cant'harus lineatus.
3 Serranus cabrilla.
I Coris julis.
1 Mullus surmuletus.
2 ScorpcEna scrofa.
2 ,, ustulata.
1 Uranoscopus scaber.
2 Tetrodon spengleri.
2 Raia punctata.
2 ,, microocellata.
I „ a/^a.
Station 3, 184 metres.
I Gadus czglefinus.
8 , , poutassou.
40 Gadiculus argenteus.
5 Merluccius vulgaris.
1 Phycis bleiinioides.
170 Zeugopterus megastoiiia.
2 Arnoglossus latema.
2 ,, lophotes.
3 vSi^/^a variegata.
2 Caranx track icr us.
Station 38, 77 metres.
2 .S^/fa vulgaris.
2 „ /i^/^a.
2 Arnoglossus lophotes.
I ,, grohmanni.
I Pagrus vulgaris.
1 Dentex macrophthalmus.
2 Trigla ohscura.
I Scorpicna scrofa.
I Trachinus draco.
I Lophius piscatorius.
1 Miimna helena.
2 i?a«'a punctata.
2 Capros aper.
12 Trigla gurnardus.
29 ,, /j'ra:.
I ,, //wz.
5 Callionymus maculatus.
4 Lophius piscatorius.
4 Argentina sphyncna.
8 Acanthias vulgaris.
5 Scylliuii! canicula.
Station 21, 535 metres.
14 Gadiculus argenteus.
8 Merluccius vulgaris.
12 Phycis blennioides.
1 Molva elongata.
9 Malacocephalus lisvis.
9 Ca-lorhynchus calorhynchus.
2 Macrurunger.
6 Zeugopterus boscii.
10 .Se bastes dactylopterus.
30 Hoplostethus mediterraneum.
2 Chimcera monstrosa.
1 1 P7-istiurus melanostonius.
2 Spinax niger.
I RaiafuUonica.
25 /'«;« clavata.
I , , vomer.
I , , ciirularis.
Station 39 B, 280 metres.
10 Merluccius vulgaris.
I Pagrus vulgaris.
250 Dentex macrophthalmus.
1 Mullus surmuletus.
2 Caranx trachurus.
I Capros aper.
Many Centriscus scolopax.
I Trigla lyra.
]\Iany Lepidotrigla aspera.
I Peristedion cataphractum.
I Scorpcena ustulata.
5 Argentina silus.
5 Acanthias vulgaris.
1 Scyllium canicula.
2 Rhina squatifta.
20 /v'az'a miraletus.
I , , clavata.
4 ,, punctata.
I , , circularis.
Off Faroe Islands,
442 metres (long-line).
8 J/(?/z'a ;«^/z;rt.
40 Brosmius brosme.
2 Hippoglossus vulgaris.
2 ChimcEra inonstrosa.
40 Pristiurus melanostonius.
I Spinax niger.
3 Ceiitrophorus 'squamosus.
448 DEPTHS OF THE OCEAN chap.
In the lists from the stations west of the British Isles we find
the northern forms : haddock, halibut, and tusk, but also forms
which never occur in the Norwegian Sea or the North Sea,
such as Capros aper and Centrophorus squamosus. The hake
(Merhiccitcs), the gurnard (Trigld), and southern flatfish
\Arnoglossus lophotes, A. laterna) also occur.
To the west of Morocco the hake and the southern cod
{Gadus luscus), besides a few whiting, are the only representa-
tives of the cod family. Here we find no less than five
species of gurnards in one haul, mullets (Midlus surmiiletzis) ,
and Sparidse [Pagellus centrodontus, Dentex maroccanus, and
D. macrophthalmus). In the deep haul in 535 metres we
observe the southern ling [Molva elongatd), Sebastes dactylop-
terus, and different Macruridse, along with Merliicmis (hake),
and Gadiculus argenteus.
To the south of the Canaries the acanthopterygian fish
decidedly predominate. We find Sparidse {Dentex, Pagrus,
Sargiis, Box, Serranus, Scorpcsna, Mullus, Trachinus, Trigia).
There are also soles [Solea, Arnoglossus), hake, and anglers.
In shallow water we also meet with the young of different
herrings, such as pilchards, Clupea alosa, and anchovy.
Thus the three series of hauls show the changes encountered
in the fauna, from the mingled community of boreal and
southern forms west of the British Isles to the entirely southern
fauna on the west coast of Africa.
These records also serve to illustrate the catches of fishing
vessels on the European and African banks of the Atlantic.
As is well known, the trawling industry was developed in the
North Sea. When it was carried farther south along the Bay
of Biscay, along the coast of Portugal, and along the coast of
Morocco, the hake and the sole were first and foremost the main
objects of capture. These two species are still of first import-
ance to the trawlers. From Table B, page 442, we learn
that in the Bay of Biscay the hake constitutes 65 per cent, and
farther south 36 per cent, of all the fish caught. The valuable
sole constitutes no less than 16 per cent of the weight of all
the fish caught in the most southerly areas. The rays play an
important part (in the Bay of Biscay 15 per cent, farther south
2 1 per cent), but also the acanthopterygians (Pagel/ns, Mullus,
Dentex, etc.) are of great importance. I have obtained some
information on their catches off the Moroccan coast-banks from
trawlers, who tell me that the hake constitutes two-thirds of the
catch. The acanthopterygians very often make up one-fourth.
FISHES FROM THE SEA-BOTTOM
449
and farther south, near the Canaries, off Agadir, they may
even amount to two-thirds of the total catch. Soles are also
numerous. South of the Canaries we saw during our cruise
(see Chapter HI.) a considerable handline fishery for acanthop-
terygian fish {Dentex, Diagranwia, etc.) carried out on hard
stony and gravelly bottom. The trawl cannot be worked there,
where the acanthopterygians were present in enormous shoals,
outnumbering all other species. We had there a fauna entirely
different from the boreal fauna, lacking all the northern forms.
All the way from western Ireland to the coast banks of
Morocco, fishing is carried on down to deep water, at least to
300 fathoms (500 to 600 metres). West of Ireland the trawlers
in April capture two kinds of ling (Molva violva and M. eiongata),
hake and breams (Pagelhis), down to 300 fathoms, and west of
Morocco they get large hake down to 200 or 300 fathoms. Fish-
ing thus goes on as deep as the fauna of the coast banks extends.
As we have seen already, the Macruridae peculiar to the
fauna of the slopes, commence at about 500 or 600 metres.
Will this fauna of the slopes, particularly the Macruridae, Mora,
etc., ever be the object of a fishing industry.^* This question
is important, and the possibility of such an industry cannot
a priori be denied. If we consider that the " Michael Sars " in
one haul, with a comparatively small trawl, at Station 4 took over
300 fishes, some of which, as for instance the Mora, seemed just as
fit for the market as the tusk, it does not seem improbable that
improved technical appliances may render fishing profitable
even down to 500 fathoms and more.
It is very interesting to note, as shown in the following
table, that the temperature in 300 fathoms (the limit of the
coast fish) is 10° C. — a temperature which we have previously
referred to as marking the southern limit of the northern forms
to the west of Ireland, where the southern forms commenced to
increase in abundance : —
Depth limit
of fishing on
Atlantic slope.
Depths in Fathoms.
Station 43,
South of the Canaries.
Station 93,
West of Ireland.
50
16.8°
10.8°
100
15-7°
10.4
200
I3-I
10.3
250
11.7°
10.2
300
lO.O
350
9-5°
400
9.2
2 G
450 DEPTHS OF THE OCEAN
Vertically as well as horizontally the fauna termed by me the
southern one appears to exist within the same limits of tempera-
ture. The different species appear to be at liberty to move
within these limits and to be independent of depth. Thus
there are many observations showing that the southern species
occur in deeper water on the Atlantic slope than they do in
the North Sea. This is easy to understand, because in the
North Sea only the shallow upper layers are affected by high
summer temperatures. Nevertheless the records of such species
from deeper water available from the results of the "Michael
Sars " and other expeditions are quite surprising. Thus the
French deep-sea expeditions found : —
Solea vulgaris
in 235 metres.
Solea variegata
Arnoglossits grohmanni
Gobius 7ninutns
„ 306 „
„ 175 »
„ 118 „
Callionymus lyra
Trachhius draco
>, 175 ,,
Lophius piscatorius hoXw^tQn 2 1() 3.nd 668 „
Merluccius vulgaris ,, 99 „ 640 „
Motella tricirrhata „ 112 „ 640 „
Phycis albidus „ 40 „ 460 „
These instances are quite sufficient to show that in the
southern part of our area the fishes tend to migrate vertically
within considerable bathymetrical ranges. Evidently tempera-
ture here plays a dominant part, and perhaps also other factors
come into play, above all the deeper penetration of light in
southern waters.
The Northern We have previously seen that the northern species in North
(boreal) European waters rano^e from the Barents Sea in the north to
west of the British Isles in the south. But within this wide area
we meet with many variations in detail, even though the fish
fauna of the whole area in a broad sense may be said to be
homogeneous. Thus some species belong mainly to the most
northerly part of the area, while others are taken in quantities
worth mentioning only in the far south of the region. The
abundance of a species does not alone depend on latitude or
conditions of temperature, but the extent of the area of bottom
suitable to the species is also of great importance.
An analysis of this question cannot, however, be restricted to
a search for the geographical limits of the species. As regards
the northern forms, information as to their bathymetrical dis-
tribution is very important. The English fishery statistics
FISHES FROM THE SEA-BOTTOM
451
recording the catches of trawlers in the North Sea contain the
most ample details on the vertical distribution of certain northern
species. Within this area information has been gathered Fishes taken
separately for certain smaller areas, the limits of which coincide depthJ'in"the
with isobaths of the North Sea. Thus one area comprises all North Sea.
the banks between the coast and the 20 metres line, i.e. all the
coast banks and the Dogger Bank ; another area occupies the
space between the 20 and the 40 metres lines, etc. In the
following table we have reproduced a record of the occurrence
of the principal food fishes at different depths compiled from
these statistics, the figures indicating the percentage of each
kind of fish landed from each of the seven areas : —
Percentages of Fish taken at Different Depths in the North Sea
Over
Species.
0-20
20-40
40-60
60-80
80-100
IC0-200
metres.
metres.
metres.
metres.
metres.
metres.
metres.
I
Dogfish
Acanthias vulgaris .
16.3
64.0
II. 0
3-5
5-2
2
Skates and Rays
RaiidK ....
3-2
36.8
319
10.4
8.8
8.5
0.2
3
Monks
Lophius piscatorhis .
o.S
17-3
20.7
28.6
15-2
17-5
0.3
4
Gurnards .
Trigla sp. . . .
0.7
25.1
31.0
18. 1
10.9
14.0
O.I
5
Catfish
Anarrhicas hipus .
7-7
26.1
39-1
15.2
II. 8
O.I
6
Cod, large .
Gadus callarias
0.7
19.9
2g.g
28.7
12.4
8.3
0.2
7
,, medium
,, ,, . .
I.O
41.8
29.4
13-3
8.9
5-5
8
,, small .
,, ,, . .
0.6
36.1
259
31-7
3-9
1.9
9
Coalfish
,, virens .
3-9
6.1
19.7
21.6
48.4
0.3
10
Haddock, large .
,, aglefinus
0.4
18.6
SO. 2
20.6
5.6
4.8
II
,, medium
,, ,, . .
O.I
19.9
27.2
17.2
21.5
13-6
0-3
12
,, small .
,, ,, . .
8.6
16.6
25-2
19.6
29.9
0.3
13
Pollack
,, pollachius
12.0
31-7
14.2
17.9
23.6
0.6
14
Whiting .
,, merlangiis .
0.3
29.2
40.3
9-3
7-4
13-4
0.1
15
Hake, large
Merhtccius vulgaris
O.I
5-7
15-3
4-7
4.1
68.3
1-7
16
,, medium .
jj J)
iS-4
26.3
4.6
5.0
46.2
2.3
17
,, small
26.5
3^-4
2-5
4.2
30.7
47
18
Ling .
Molva molva .
5-6
14.9
25-3
20.3
33-S
0.3
19
Tusk .
Brosinius brosme
0.4
7-9
7.9
82.5
1-3
20
Soles, large
Solea vulgaris
6.4
64.3
27.8
1-3
21
,, medium .
,, ,, . .
5-2
Si.o
43-6
0.3
22
,, small
,, ,, . .
8-5
S6.7
35-4
0.2
23
Brill .
Bothus rhombus
3-3
63.2
32-7
0.6
0.1
24
Turbot
,, maximus
2.6
40.0
48.2
5.6
1.6
1.4
25
Plaice, large
Pleuronectes platessa
0.6
48.5
42.8
6.3
1-3
0.3
26
,, medium .
,, ,, . .
2.8
49-8
43-3
2.9
1.0
27
,, small
,, ,, . .
13-9
59-5
25.8
0.3
0.2
28
Lemon soles
,, viicroccphalus
0.4
317
18.2
32-9
12.4
4.3
29
Flounders .
,, flesus .
7-1
67.2
24.7
0.9
0.2
30
Dabs .
,, limanda
3-4
81.7
5-5
6.7
2.7
0.2
31
Witches .
, , cynoglossus .
0-5
1.4
12.3
21.2
64.2
0.4
32
Halibut . .
Hippoglossus vulgaris
0.1
2.4
7-3
24.7
33 -o
32.5
0.2
33
Megrims .
Zeugopterus me gas to ma ,
0.8
3-3
8.1
87.2
0.7
34
Conger eels
Conger vulgaris
0.6
37-8
SO. 8
7-5
1-7
1-7
On the shallow banks between the shore and a depth
of 40 metres (about 20 fathoms) the flat-fish — sole, brill, plaice,
452
DEPTHS OF THE OCEAN
flounder, and dab — are the most characteristic, but young stages
of cod, rays, and dog-fish (Acantkias) also occur plentifully.
In medium depths, from 40 to 100 metres (25 to 50 fathoms),
the gadidae — haddock, large cod, pollack, and whiting — pre-
dominate, but we also meet with flat-fish, turbot, lemon sole
{P/eiironectes microcep/ialiis), and young halibut, and with some
southern forms : hake, gurnards, anglers, and conger eels.
Below 100 metres (50 fathoms) we meet with the saithe,
ling, tusk (see Fig. 313), large hake, besides witch, megrim, and
large halibut.
Fig. 313.— The "Michael Saks fishing Ling and Tusk in the deep part of
THE North Sea.
Different physical conditions accompany these characteristic
differences in the distribution of the fish ; for instance, the
depths from o to 40 metres are the ones mainly influenced by
summer temperatures ; on the shallow coast banks and on the
Dogger Bank the temperature at the bottom rises to at least
12° C. in the summer season. The sole may thus find here
temperatures similar to those off the Atlantic coast of Europe,
though in somewhat shallower water. Below 40 metres the
summer temperature is not much higher than the temperature
during winter, viz. between 6° and 7" C.
The species inhabiting the deeper areas of the plateau
extend out towards the deep basin of the Norwegian Sea until
FISHES FROM THE SEA-BOTTOM 453
the cold bottom water with a temperature below o'' C. is reached,
where they are gradually replaced by the cold water fauna pre-
viously described.
The same laws which regulate the distribution of different
species in the North Sea apply also in the main to other boreal
waters where these species live. Scientific fishing experiments,
and above all the mass of information gathered from the fishing
industry, have in recent years vastly contributed to our know-
ledge on these points. If on the basis of this knowledge we
want to compare the actual conditions in different boreal waters,
we must compare areas of corresponding depth. In this way
we may possibly form an idea as to the part played by the
extent of the sea-bottom, and by physical conditions, in regard
to the distribution of our northern species. Some examples
may illustrate this point.
In the North Sea the shallow banks in depths less than 40
metres cover large areas, while off the coast of Norway there
are hardly any such banks, the coast sloping steeply into
greater depths. Shallow banks occur off the south and west
coast of Iceland, and far north and east in the Barents Sea,
as well as round Cape Kanin. Of the fish inhabiting the
shallow areas of the North Sea, only the plaice and the cod
occur in great quantities on these northern banks of Iceland and
Cape Kanin. Sole, brill, and other flat-fish might also find suit-
able conditions of depth here, but the temperature is too low.
Off the coast of Norway none of these fiat-fish, neither the
plaice nor the sole, occur abundantly. Thus we plainly see
the important parts played by depth as well as by temperature
in respect of the occurrence of various species.
While the haddock in the North Sea constitutes nearly half
of the total weight of bottom-fish landed, the same species
constitutes only 3 per cent off the coast of Norway. This is
not because Norway is too far to the north, nor because the
temperature of the water is too low, since at Iceland and in the
Barents Sea, where conditions are similar, haddock amounts to
20 per cent of the catch, but because off the coast of Norway
there are no great areas of suitable depth and with the soft
bottom preferred by the haddock. On the contrary we here
meet with great areas of "cod-bottom" (sand, stones, shingle,
or rocks overgrown with kelp), and therefore the cod makes up
over 80 per cent of all the bottom-fish taken off northern
Norway.
Thus the extent of the area, and the captures made therein.
454
DEPTHS OF THE OCEAN
of the North
Atlantic
Food-fishes are closely correlated. If we know the area where a vessel
Sfferen't parts hshes, we Can predict the nature of the catch, and on the other
hand we may judge of the extent and nature of the area from a
knowledge of the fish caught in that area. This fact may be
illustrated by the following table giving the quantities of
important food-fish in millions of kilograms landed from
different areas of the North Atlantic : —
Cod.
Haddock.
Plaice.
Halibut.
Hake.
White Sea, Barents Sea.
Norway, north of Stat .
Iceland ....
Faroe Islands
North Sea .
Atlantic coast of Europe
Total .
3
221
io6
i8
73
9
2
8
37
II
174
II
lO
i
45 1
3 2
2
I
o
o
o
o
2
20
43°
243
88
14
22
Boreal fishes
on the slope
of the
Norwegian
Sea.
According to this table the North Sea proves to be the
richest of all in plaice and haddock, just as it includes the
greatest area of shallow sandbanks and fiats with muddy bottom.
The sea of Norway is richest in cod, just as it represents the
greatest stretch of rocky coast with temperatures between 6°
and 8° C.
Below lOO metres (50 fathoms) and down to 300 fathoms,
we find on the northern slope of the North Sea plateau the
following species to be the most important : saithe, ling, tusk,
and halibut (see Fig. 314). During the summer we also find the
cod in such depths, especially to the north of Lofoten, and on
the slopes from the Faroe Islands to Lofoten. A little higher up
on the bank these species are mingled with large hake, witch
iyPleuronectes cyjtoglossus), and megrim iyZeugopterus megastonia).
Lower down on the slope below 200 metres we find Norway
haddock [Scbastes), blue ling, black halibut (Hippogiossus
hippoglossoides), Macrurus fabricii, Argentina sihis, and Green-
land sharks. This latter group of species has been found during
the Norwegian fishery investigations along the " edge " of the
continental platform all the way from Spitzbergen and Bear
Island along the coasts of Norway, the North Sea plateau, the
Faroe Islands, and along the Faroe-Iceland ridge.
If we follow the 600 metres line in the chart (Fig. 309) from
Spitsbergen and round the southern part of the Norwegian Sea
FISHES FROM THE SEA-BOTTOM 455
to Iceland, we shall at the same time trace the limit between
the cold-water fauna of the deep basin and the boreal fauna of
the slope of the coast plateau. Within this boreal region we
may discern different areas of distribution. The ling, for
instance, is caught off the coast of Norway in abundance as far
north as Lofoten ; north of Lofoten, between the Faroe Islands
and Iceland, and at Iceland, the ling is only poorly represented,
A. i
■■■■ /
B^/ /^
m<
rr
1
W^^l^k
>.
ii
1
Fig. 314.— The "Michael Sars" fishing Halibut on the Slope.
while the cod there plays an important part in the "edge"
fishery during the summer. Large halibut, from 50 to 1 50 kilos
in weight, on the other hand, occur on the slope from west of
Bear Island, round the North Sea plateau, the Faroe Islands,
and on to Iceland. The Norway haddock has a similar distribu-
tion to that of the large halibut.
The fauna of the eastern and southern slopes of the
Norwegian Sea thus proves to be very uniform for a distance of
456
DEPTHS OF THE OCEAN
1 200 or 1500 miles, in accordance with the uniformity of the
physical conditions. As we have previously seen, uniform
physical conditions of a different character are met with along
the slopes of the Atlantic from the Wyville Thomson Ridge down
to south of the Canaries, the forms peculiar to this region being
entirely different to those inhabiting the slopes of the Norwegian
Sea.
J. H.
CHAPTER VIII
INVERTEBRATE BOTTOM FAUNA OF THE NORWEGIAN SEA
AND NORTH ATLANTIC
The topography of the Norwegian Sea has been briefly noticed
in Chapter IV. and the hydrography in Chapter V.
The distribution of forms in the Norwegian Sea agrees
with the hydrographical conditions, and we can distinguish two
great regions, the boreal and the arctic, each of which has its
own appropriate fauna. All those parts of the ocean-floor Boreal region
covered by Gulf Stream water or by coast-water make up the jlJ^'^w j^n
boreal region, while the arctic region is covered by water with Sea.
polar characteristics. The temperature and salinity in boreal
areas vary greatly in the different water-layers, and are much
affected by the seasons. What chiefly distinguishes the boreal
region from the arctic region is the higher temperature, which
never falls below o C, and over large areas never sinks below
6° C. The uppermost water-layer may form an exception, for the
temperature may occasionally at the very surface and for a com-
paratively short time fall below o' C. High summer temper-
atures are characteristic of the upper water-layers, and exercise
a considerable effect upon the fauna. The boreal region of the
Norwegian Sea includes the North Sea with the Skagerrack and
Kattegat, the Norwegian coast plateau as far as the North
Cape, the coast plateau of the Faroe Islands, and the south and
west coasts of Iceland.
In the arctic region the temperature and salinity are much Arctic region
more uniform than in the boreal region : the temperature is jfor^^gian
usually below o° C, though in summer the actual surface may Sea.
show higher temperatures under the influence of the sun, but
the sun's heat does not penetrate so deeply as in the boreal
region ; the salinity varies greatly at the surface, but at the
depth of a few metres it is rarely less than -t^o per thousand.
The arctic region comprises the coast plateaus of Greenland
457
458 DEPTHS OF THE OCEAN
north of Denmark Strait, Spitsbergen, Franz -Josef Land,
Novaya Zemlya, the coast between the White Sea and the
Kara Sea, as well as the plateau of Jan Mayen and the
deep central basin of the Norwegian Sea,
In addition to these purely boreal and purely arctic areas
there are transitional areas, designated boreo - arctic, which
may be found wherever boreal and arctic water-masses meet
Such areas occupy more or less extensive tracts, and exercise
a distinct influence upon the distribution of the fauna. The
temperature is not so high as in the boreal region, except
perhaps at the surface, varying between o" C. and 3° or 4 C,
though in the shallower parts a far higher temperature is found
in summer, due to the heat of the sun, and as a result there
are certain boreal littoral forms that occur also in the boreo-
arctic region.
The following are boreo-arctic areas : the south - western
portion of the Barents Sea, from the East Finmark and Murman
coasts to the White Sea, where a branch of the Gulf Stream,
flowing eastwards, is gradually blended with arctic water ; the
north and east coasts of Iceland, where branches of the Gulf
Stream unite with the East Iceland Polar Stream^ ; the Iceland-
Faroe ridge, where the East Iceland Polar Stream meets the
Gulf Stream ; the Wyville Thomson Ridge, over which the Gulf
Stream passes into the Norwegian Sea, where a mixture of
the two waters undoubtedly takes place, but this boreo-arctic
area is of small importance compared to the others ; and the
continental slope on the eastern side of the Norwegian Sea,
where there is a narrow area of mixture between Atlantic
water and arctic water, resulting in temperatures slightly higher
than o" C. A weak branch of the Gulf Stream flows along the
west coast of Spitsbergen, giving rise to a very limited boreo-
arctic belt, though, generally speaking, the west side of
Spitsbergen must be considered purely arctic. The shallower
parts of the coastal waters, as well as the inner portions of the
fjords, from Lofoten to the North Cape, are boreo-arctic.
North The topographical conditions in the North Atlantic are
Atlantic, rnych like those of the Norwegian Sea, but the hydrographical
conditions are dissimilar. On the eastern side the coast banks
of both Europe and North-West Africa are bathed by much
warmer water than those of corresponding parts of the Nor-
' I ought to state, however, that owing to the influence of the East Iceland Polar Stream
the north-eastern coast must perhaps be considered a purely arctic area.
INVERTEBRATE BOTTOM FAUNA 459
wegian Sea, and the littoral fauna naturally accords with its
surroundings. This is true also of the archibenthal area (that
is to say, the steep continental slopes) and the abyssal region.
The temperature at 1000 metres may be as high as 6' or 8' C,
and 2^ or 3° C. at still greater depths. Here, again, the fauna
conforms to its surroundings. In addition to the vast central
abyssal plain, the boreal region of the Atlantic includes the
coast plateaus off Europe and North -West Africa, and the
southern slopes of the ridges extending from the Shetlands to
Greenland, that is to say, practically the whole of the eastern
portion of the Atlantic. Arctic currents, on the contrary,
prevail in the western portion of the Atlantic, and cause
hydrographical, and therefore faunal, dissimilarities at different
parts of the coast. In the coastal areas south of Cape Cod
(about lat. 42" N.) we find Gulf Stream water and a character-
istic warm-water fauna ; but north of Cape Cod we meet with
an icy polar current descending from higher latitudes, so that the
stretch of coast from Cape Cod to the north of Newfoundland
must be looked upon as boreo-arctic. More genuinely arctic
conditions prevail off the coasts of Labrador and Greenland.
Boreal Region of the Norwegian Sea
The boreal coastal area may be divided into three vertical The coastal
zones, distinguished by different physical, topographical, and bo*rea°iVeg1on
biological conditions. The uppermost is the littoral zone, which of the
extends from the shore down to a depth of 'X)'^ or 40 metres — sea."^^^'^"
that is to say, almost as far down as there are sea-weeds. The
physical and topographical conditions characterising the littoral
zone are : periodic changes in temperature and salinity (the
temperature of the water being directly affected by that of the
air), strong light, and a great variety in the materials at the
bottom, such as loose stones, solid rock, sand with or without
coarse or fine fragments of different kinds of shells, mud,
and " mixed mud " — that is to say, sand, mud, and stones all
mixed together. Here we find the whole vegetation collected,
consisting of fucoids, green and red algae, Laniinaria, and
Zostera, all of which, as a rule, form big interdependent com-
munities that are very often arranged in belts.
The lower limit of the sttblittoral zone on the west coast
of the Scandinavian peninsula may be put at about 150
metres. It differs from the preceding in being without
vegetation, as well as in having more uniformity in the bottom-
46o DEPTHS OF THE OCEAN
deposits, higher and more constant salinities, and less pro-
nounced differences in temperature. The bottom consists
either of solid rock or sandy clay, or else of a rather coarse
mixture of shells and sand, which is often found on the slopes
of rocky portions in particular, together with large stones
and pebbles. On the other hand, we do not get the fine
mixture of shells and sand which is so characteristic of the
littoral zone out among the skerries. The lower limit of this
zone practically coincides with the lower limit of the coastal
water, the salinity of which is lower than that of the Atlantic
water lying beneath it.^ The temperature does not vary more
than a few degrees in the different seasons, being lowest during
the summer in the deeper portions, but it is, for part of the year
at any rate, higher than that of the Atlantic water.
Below the sublittoral zone we come to another zone, dis-
tinguished by more uniform and more constant topographical
and physical conditions, which we may call the continental
deep-sea zone (ranging from 150 to 1000 metres or more). The
bottom consists mainly of rock or a fine mud, which may
perhaps be mixed with a little sand in the uppermost portions.
In its upper parts, near the borders of the sublittoral zone,
temperatures and salinities vary to a slight extent, but in the
deeper parts both are constant, the salinity being 35 per
thousand or a little over, and the temperature between 6° and
7^ C. all the year round.
We propose to discuss the coastal area of the boreal region
under three headings: (i) the islands of the Norwegian west
coast, where the littoral zone alone is represented ; (2) the
fjords, where all the zones are represented ; and (3) other
northern boreal areas.
(i) Islands of the Norwegian West Coast i^' Skj(:(^rgaard''\ —
We may divide the littoral zone among the islands of the Nor-
wegian west coast into different areas. There is first a low-tide
area, subject to changes of tide, and accordingly dry for certain
portions of the twenty-four hours. Here we can distinguish
three " facies" with different bottom-conditions, namely (i) rocky,
either bare rock or very scantily overgrown ; (2) a fucoid belt ;
and (3) sand. Each of these has, as a rule, several forms pecu-
liar to it, though unquestionably a good many species of the
littoral fauna are common to all. The dissimilarity in the com-
' It must, however, be stated that the Hmits between the coastal water and Atlantic water
vary with the seasons.
INVERTEBRATE BOTTOM FAUNA
461
position of the fauna of the different " facies " depends to a great
extent on the structure of the animal-forms, inasmuch as some
forms must have a vegetable or hard solid foundation, while
others require loose material. Littoral gasteropods, as a rule,
require a solid foundation, and they are therefore generally absent
from the sandy bottom ; but there are certain burrowing forms
which can only live where the bottom is incoherent. Other
forms, again, like the crab, are able to live on nearly every
kind of bottom.
Fig. 315.
Balaiius ba/anoidcs, L.
Below the low-tide area, with its fucus vegetation, we find
on hard bottom a Laminaria belt beginning immediately below
the fucoid belt, and always covered by water.^ We find also a
Zostera belt, hard bottom, and sandy bottom.
On the bare or scantily overgrown rocks near high-water Low-tide
mark we find a white belt of barnacles {^Balamis balanoides, see ^'^'^^•
Fig. 315); when examined at high tide we notice these little
creatures extending and contracting their lash-like limbs to set
^ Only at very low ebb-tides and in certain places do we find certain species of Lamiuaria
also laid bare.
462 DEPTHS OF THE OCEAN chap.
the water in more rapid motion, and so bring nourishment to
their mouths inside their shells, but when exposed at ebb-tide the
shells are closed and
the animals remain
concealed within
them. Immediately
below the barnacle-
belt we frequently
find a belt consist-
ing of dense masses
of mussels {Mytilus
edit lis, see Fig. 3 1 6),
though the individ-
uals in such locali-
ties never attain
any considerable
size. On the rocks
we find everywhere
four species of gasteropods, which are very characteristic of this
area, namely, the limpet {Patella vulgafa,
see Fig. 317), two periwinkles {Littorina
Fig. 316.
Mytilus edulis, L.
Fig. 317.
Patella vulgata, L. a. From the side ;
from beneath.
Fig. 318.
Littorina littorea, L.
littorea, see Fig. 318, and L. rudis), and the purple snail
(Purpura lapillus, see Fig. 319), this last being
often plentiful in the barnacle -belt, where it
feeds on these crustaceans. These forms live
chiefly on the naked rock, but, except the limpets,
also often on the algae in the tidal area. But
when the belt of fucoids is exposed at ebb-
tide, especially in sheltered places where a
good current runs, we see that the algae, the
species of Fucus in particular, have their special
Fig. 319. fauna, consisting chiefly of attached forms.
Purpura iapiiius,\.. -j^j^^ majority of them are hydroids, the com-
monest species being Dynamena puniila (see Fig. 320),
INVERTEBRATE BOTTOM FAUNA
463
Laomcdea flex2wsa, and Clava squamata (see Fig. 321). There
are several bryozoans ^ here too, and the fucoids are often densely
thronged by small white spiral-shaped tube-worms [Spirorbis).
Amongst the un-
attached forms as-
sociated with the
algae I may mention :
Littorina obtusata,
which keeps mostly
to little bays shel-
tered from the action
of the waves ; L.
littorea, which is very
common ; and our
smallest shelled snail
Skene a planorbis,
which is met with in
favoured spots under
stones and upon algae
of different species.
More local in
their occurrence,
though generally numerous
of Actiniae
Fig. 320.
Dynamena pmnila, L. (After Hincks.
where found, are certain species
the red Actinia equina (see Fig. 322), the yellow
or brownish MetiHdiuvi dianthus (see Fig.
323), and Urticina crassicornis being the
commonest forms. The first of these is
generally found in quiet bays where the
shore is covered with large stones and
pebbles, the individuals being sometimes
attached to these and sometimes to cracks
in the rock. As this species produces its
young fully developed, and the newly-born
actiniae are able to attach themselves easily,
it is frequently met with in fairly large
colonies.
Another remarkable mode of propaga-
tion, namely schizogony, is to be seen in Metridium diantJms
in its younger stages. From the foot-disc of the animal small
pieces unwind and form new organs, such as new tentacles, new
mouth, etc. In this way colonies are formed, which may be
widely distributed over the rock or the roots of the laminaria.
^ Chiefly Alcyonidiuin hirsiitum, Fliistrella hispida, Bowerbankia i?/ibricata.
Fig. 321.
Clava squamata, Miill.
(After Hincks.)
464
DEPTHS OF THE OCEAN
The fully developed individuals of Metriduuu are usually found
in places where there is a strong current.
Off the coasts of Scandinavia the sandy bottom of the
low-tide area is not so extensive as along other coasts of the
North Sea, but it is interesting to note that the fauna inhabiting
this region is much the same everywhere, and that burrowing
forms predominate. There is first the sandgaper i^lMya
Fig. 322.
Actinia equina, L.
arenaiHa), and then the cockle [Cardmm ediile, see Fig. 324),
and also different species of Tapes, though these are not so
universally distributed. The lugworm [Arenicola piscatorum,
see Fig. 325) is another burrowing form, and its presence can
easily be detected by little heaps of string-like excrements.
In addition to these forms, which are adapted for life in
the low-tide area at those parts of the coast where the ebb-tide
recedes a long way, we also get the common shore crab
{Carcimis moeiias), often to be found under fucus that has been
left exposed. This is the case also with the common starfish
[Asterias itibens), and occasionally, too, with the common
INVERTEBRATE BOTTOM FAUNA
465
sea-urchin {Echinus esaUentus), the hermit crab' {Pagiirus
bernkardiis), and a few other forms. Their occurrence is,
however, really due to their being surprised by the receding
of the tide, and they are not, strictly speaking, adapted to a
life in this area.
There are some forms characteristic of the low-tide area
Fig. 323.
Metridiitm diaiifkus. VA\. (After Andres. ) '~
which cannot be regarded as belonging solely to any particular
facies. Perhaps the commonest are the sandhoppers (Gam-
marids), which have a wonderful knack of hiding themselves
quickly in holes and cracks, when the stone or other object,
under which hundreds may be sheltering, is removed. One
of the most abundant is Orckestia littorea, which, although a
true marine form, is able to exist for a long time out of the
water. I have found quantities of them during summer living
2 H
466
DEPTHS OF THE OCEAN
perfectly happily with true land-animals, such
as centipedes and woodlice, in places that
were very rarely covered by the sea, so that
they had to depend upon the slight moisture
retained beneath the stones ; individuals
found living under these conditions on being
Fig. 324.
Cardiiim cdule, L.
transferred directly to sea-water showed not
the least sign of being inconvenienced by
the sudden change. Another equally com-
mon sandhopper ( Gaminartis locusta, see Fig.
Fig. 326.
Gammarus locusta, L. (After Bate and \\'estvvood. )
326) is also a littoral form, but it never quits
the sea for any length of time.
Unexposed
area.
Laminaria
belt.
In the unexposed portion of the littoral
zone of the skerries we may distinguish four
"facies": (i) Laminaria belt, (2) Zostera
belt, {3) hard bottom, and (4) sand.
The Laminaria belt begins immediately
below the fucoids, and alone the west coast of
Fig. 325.
Arenicola piscatorum, L.
INVERTEBRATE BOTTOM FAUNA
467
Norway there are three common species : Laniinaria hyperborea,
L. digitata, and L. saccharina. The first of these occurs in
great thickets in open bays or places where the play of the
waves is felt, whereas the other two grow in more sheltered
localities. The fauna varies accordingly. On the stalks of
Lanimaria hyperborea we
chiefly hydroids, bryozoans,
^et numbers of attached forms,
synascidians (see Fig. 327), and
calcareous sponges. Halichondria
panicea, one of the few siliceous
sponges of the littoral zone, also
Fig. 327.
Synascidian : Polycycli/sficscus,
Huitfeldt Kaas.
Fig. 328.
Obelia ge7iiculata, L. (After Hincks. )
frequently forms a thick covering over long pieces of the stalks.
On the blades of the laminaria two forms are very common,
namely the bryozoan Membranipora nievibranacea, which makes
a white covering over large portions, and the little hydroid
Obelia genicidata (see Fig. 328). An unattached form, the
gasteropod belonging to the Patellid family [Nacel/a pelhicida),
is very conspicu-
ous, owing to its
handsome blue-
striped shell, and
lives exclusively
on the laminaria.
Besides the fig. 329.
I 1 c Caprella linearis, L.
attached lorms,
that often completely cover the lower parts of the laminaria,
there are unattached species in great abundance existing upon
or among them. The best way of observing them is to shake
a thickly overgrown laminaria stalk, placed in a large glass of
sea-water, when we may perceive swarms of amphipods, worms,^
tiny mussels and snails, little starfishes, and other creatures.
The most noticeable of the amphipods are the elongated and
strangely built caprellids, of which Caprella linearis (see Fig. 329)
^ A species of Nicolca is common.
468 DEPTHS OF THE OCEAN
is the commonest. With their prehensile claws they climb
about among the hydroids and red algae, hooking themselves
on by their hind limbs, swaying to and fro for a time, and then
catching hold of another branch with their front claws and
climbing farther. In fairly sheltered localities we often get
among the branches of the hydroids and algse little tube-
shaped dwellings constructed out of various materials and
inhabited by different species of amphipods,^ and here, too,
we meet with some kinds of pycnogonids.^ Beautifully coloured
,.y, nudibranchs (usu-
^"^^; ''^^'^"-' " ~^ ally species of
V^T y^olis, and especi-
^■^^^^^^^ ^ . s ^jj^ yEolis inifo-
* branc hialis, see
Fig. 330- Fig. 330) crawl
^olis rufobranclualis, Johnst. (After Alder and Hancock.) slowlv aboUt and
feed like the pycnogonids upon the hydroids ; certain kinds of
nudibranchs (especially some species of Doris, see Fig. 331,
Polycera, etc.) occur chiefly in the winter. Animal groups
that are very numerously represented in the algse -vegeta-
tion of the littoral zone, though they must be very carefully
searched for, are rhabdocoelous turbellaria and several species
of Halacarids. There are, in addition, quantities of the young
of Myfilus, asterids,
etc. Among the
" roots " of the lamin-
aria we frequently get
Nereis, Ophiopholis
aculeata, and borer
mussels [Saxicava).
I n contradistinction ^^^.^ tuberculata, Cm^'V^ftJ; Alder and Hancock. )
to Laniinaria hyper-
borea, which prefers the most exposed situations, where there
are waves or strong currents, as well as hard bottom to which
to attach itself, we find the eelgrass [Zostera marina) in
enclosed sheltered localities (pools, estuaries, etc.) and upon
soft muddy bottom. The fauna of the eelgrass is not nearly
so rich in species as that of the laminaria, still there are several
characteristic forms living mainly, and perhaps exclusively, in
its vicinity. There is, for instance, a small whitish semi-trans-
^ Especially species of the family Podoceridre, characterised by the extremely hairy antennte.
- N'yniplioi brevirostre, Phoxichilhihtin fentoi-aii(ni, Phoxichilns spinosus, etc.
INVERTEBRATE BOTTOM FAUNA 469
parent snail [Rissoa), which may often be found in enormous
quantities ; often also there are great numbers of another snail
(Akei^a biillatd), and in the mud, even where there is no zostera
vegetation, we frequently find species of Philine. A species
of attached ascidian {Ciona intestmalis, see Fig. 332), which,
however, is also found on laminaria, especially when growing
in sheltered or rather deep places, is one of the most prominent
animal forms of the eelgrass. Hydroids and synascidians are
also occasionally met with. Swim-
ming amongst the blades of the -^ ;, (?»',**
eelgrass we further find various crus-
taceans, of which two species of
prawns [Pandalics animlicornis and
Palcumoii) are the most noticeable.
They are not limited to the eelgrass,
however, but occur also in places
where zostera does not grow. The
list of forms to be found here is
far from exhausted, for I have men-
tioned only some of the chief ones.
The zostera belt is not of so much
importance along the Atlantic and
North Sea coasts of Scandinavia, as
it covers a very limited area in com-
parison with the other subdivisions of
the littoral zone, and it is negligible
indeed, when compared with the im-
mense tracts in the Kattegat which
are literally overgrown with this plant. ^--^^i
Such in general is a picture of the
fauna to be found in the algat and ^. ^.^^'•^^";. ,
111 Ciona mtestinalis, L,.
zostera vegetation of the strand-belt; (After Aider and Hancock. )
though it must be understood that
when speaking of this fauna as associated with the plants I
do not imply that these animal -forms can exist only upon
them. This is only exceptionally the case. The relation-
ship between them depends on the fact that, as a rule, the
algse afford an excellent foundation for the attached forms,
which find favourable conditions of nourishment wherever
the alg^e flourish. For we must remember that these attached
forms are obliged to obtain their nourishment from such
organisms as chance to come within their reach, and since
currents and waves furnish the necessary assistance, we
470
DEPTHS OF THE OCEAN
generally find the most abundant animal life among the algse
in localities where wave-action is most effective. Most of the
non-attached forms are in no way directly dependent upon the
algae-vegetation.
It will be evident that attachment to fucus and laminaria
is not biologically essential, if we bear in mind that the same
animal forms which attach themselves to these plants occur
also on rocks and stones. The vegetation merely increases
the area available for the attached forms. Nor is any particular
plant essential for any particular species of animal. No doubt
on the Norwegian west coast
Laomedea flexuosa and Clava
sqiianiata nearly always attach
themselves to Ascophylhmi, while
Obelia o-eniculata and some others
prefer laminaria, but this is chiefly
owing to the tides. On the
Skagerrack coasts, where tides
are inconsiderable and irregular,
we find even in the fucus belt
forms like Coryne (see Fig. '^ZZ)>
Tubularia, and Obelia geniculata,
though on the west coast of Nor-
way they grow only among the
laminaria and at a lower depth.
These forms cannot stand exposure
for any length of time, and they are
therefore not to be found in places
where the ebb regularly goes back
a long way. The forms met with
in the tidal area cannot, however, be in any way dependent
upon the ebb-tide for their existence, seeing that they occur
numerously also on the coasts of the Skagerrack, where tides
are scarcely felt. Instances of this are furnished by Clava,
Campanularia Jlexuosa, and Dynamena pumila, but the fact that
these forms are able to withstand exposure for considerable
periods of time makes it possible for them to occupy a far
more extensive area than would otherwise be the case.
So far as the structure of their organs is concerned, the
unattached forms in the algae-fauna are particularly well
equipped for gripping, climbing, or creeping about among the
hydroids and the red bushy alg^e that usually grow in quantities
upon the laminaria. The crustaceans (caprellids and amphipods)
Fif5. 33.
Coryiic pusilla, Gaertn.
(After Hincks.)
INVERTEBRATE BOTTOM FAUNA 471
have extremely bent legs and claws, the naked snails have their
flexible foot-discs and the planarians their rhabdites, so that
these creatures furnish excellent examples of adaptability to
external conditions. A bodily structure of this kind is necessary
for these forms, or when exposed to the action of the waves
or currents they would run the risk of being torn from the
objects to which they cling.
The marine algse are known to be rather particular about
the localities they select. Some species grow high up on the
Fig. 334.
Asterias glacialis, L. (After Ludwig. ) ,
rocks so as to be covered only at high tide, while others choose
the lowest limit of ebb-tide ; some prefer sunlight, while others
thrive only away from it ; some grow best amidst the waves and
breakers, while others need sheltered places. This is, to some
extent, true also of the animal forms of the upper littoral zone,
many of which prefer the open parts of the coast, while others
live in sheltered localities, and others again where the currents
are strong. The three bryozoans Alcyonidiuni, Flustrella, and
Bowerbankia, for instance, seem to prefer shelter and a good
current, whereas Membranipora pilosa flourishes best in the
laminaria belt, in exposed places where Laminaria hyperborea
472
DEPTHS OF THE OCEAN
grows. Litto7'ina littorea and L. obtusata again are found in
greatest abundance wherever there is shelter, while Nacella
pelliicida generally lives on the blades of Laminaria hyperborea.
In the sheltered haunts of Lmnmaria saccharina and L.
digitata, particularly on the first named, we find the brittle-star
OpJiiothrix fragilis, while the localities with L. hyperborea have
evidently no attractions for it ; the blades of L. saccharina, too,
are much patronised by the bryozoan Aetea. Asterias glacialis
(see Fig. 334) also prefers sheltered localities. Why there
should be these apparently capricious affections is as yet un-
known, but it may be that in undisturbed waters there are
higher temperatures during the summer, and that consequently
various influences are brought to bear upon the organisms at
one stage or another of their
lives.
The most typical localities
of this kind are met with as
portion of the a rul.e in sounds amongst the
skerries, where there is a more
or less strong current, which
carries away the finer particles
of mud that would otherwise
settle, and leaves only large
fragments of shells and similar
debris. On the hard bottom
there are usually numbers of
both attached and unattached
forms, chiefly consisting of bryo-
zoans, hydroids, especially the
genus Ttibitlaria, and ascidians. The coral Alcyoniiim digitatiim
too is often plentiful,^ generally attached to large empty mussel
shells or stones. The empty mussel shells are also patronised
by big colonies of the serpulid Pomatoceros triqueter, which
however is just as much at home on the rocks up to the very
shore. There are, besides, Anoinia ephippittm, Chiton cinereus,
Tectura virginea, Buccimun nndatiwi, and several others, some
sedentary, and others, like the chitons and Tectiira, able to
move about from one place to another ; as well as Mytilus
77todiolus, though this mussel is far more plentiful inside the
fjords, and Gonactinia prolifera.
Fig. 335.
OphiopJiolis aculeaia, L.
^ This form may even be found up to hiw-tide mark, where there are strong currents, as for
instance in narrow shallow sounds.
INVERTEBRATE BOTTOM FAUNA
47;
Several echinoderms occur numerously wherever there are
currents. There are quantities of the brittle-stars : Op/iiop/iolis
aciileata (see Fig. 335), Ophiocoma nigra, and Ophiura albida.
Two species of sea-urchins that live on the hard bottom in the
littoral zone are very common among the skerries on the west
coast of Norway, namely Echiims esculentiis and Strongylocen-
trotiis drdbackiensis. On the other hand, Echinus acittiis and
Parcchinus miliaris^ have a different local distribution, to which
I shall allude later. All four species
may be found up to low tide mark. _ t 1%^
This is true also of the big dark-
brown holothurian Cuciimaj^ia fron-
dosa (see Fig. 336), large numbers of
which live on the hard bottom among
the skerries, and in the outer parts
of the fjords, especially where there is
a strong current. They fasten them-
selves to the rock by means of their
suckers, and often have their tentacles
stretched out in order to capture pe-
lagic organisms, which are afterwards
licked off, the animal sticking one
tentacle at a time into its mouth.
Together with the above forms
we find a mussel, Lima hians, which
is very characteristic of these localities.
It is of interest biologically, because
it lives within a nest constructed with
the assistance of its byssus out of
bits of empty mollusc shells, frag-
ments of echinids or serpulids, and
similar materials ; in fact, no loose
substances appear to come amiss.
Two starfishes are always present, namely Asterias rubens
and A. miilleri. There are other species as well, of course,
such as worms and serpulids, but they cannot be called particu-
larly characteristic.
Here, too, the lobster {Homartts vidgaris) is equally at home,
and may be met with under rocks and stones, occasionally
venturing on to sandy bottom. It is distributed throughout the
whole littoral zone from a depth of about one metre downwards,
a certain proportion of individuals migrating vertically, descend-
^ In a few localities all these species may be found together.
Fig. 336.
Cucumaria frondosa. Gun.
474
DEPTHS OF THE OCEAN
ing- to greater depths in winter. The spawning females usually
repair to shallow places in the summer, the higher temperatures
being better suited to the development of the eggs and larvae.
Several of the strange mask crabs {Hyas, see Fig. 2)2)7 >
Stenorhyncktis, Inachus) also inhabit the littoral zone, chiefly
where the bottom is overgrown with algae, bryozoans, and
hydroids, being rarely met with upon sandy bottom. They
are supplied with small hooks on the carapace and extremities,
by which they attach to themselves the algae or animal-colonies
around them. These crabs are extremely sluggish and inactive,
and they derive an advantage from this remarkable habit, since
they are difficult
todistinguish from
their surround-
ings, and conse-
quently they can
conceal them-
selves from their
prey as well as
from their ene- V
The bottom
here chiefly con-
sists of what has
been called shell-
sand, made up Hyas arar,eus, L.
entirely of shell-
fragments of molluscs, echinoderms, balanids and other creatures ;
it is usual to make a distinction between the coarse and the fine
shell-sand. This detritus is practically only met with in the
littoral zone of the skerries, and is undoubtedly due to the action
of the waves and breakers. Burrowing forms, for the most part
mussels, spatangids, clypeastrids, and worms, predominate.
The lancelet {Ampkioxtis) also makes this its principal home.
The loose formation is burrowed into quite easily, and a
lancelet can work its way down in the course of a few seconds.^
We must also include the sand-eels i^Am.modytes) amongst the
vertebrate forms that burrow in this sandy bottom, though they
are somewhat local in their occurrence.
Fig. 337.
' This form burrows in a curving direction beneath the surface of the sand, finally pro-
truding its head very slightly a short distance from where it went in, and remaining stationary
in this position.
INVERTEBRATE BOTTOM FAUNA 475
Several families of burrowing mussels inhabit the shell-sand,
the most important being Veneridse, Tellinidse, Astartidae,
Cardiidse, and Solenidee. The most characteristic species
are Venus casina, V. fasciata, Timoclea ovata, the species of
Tellina and Psainmobia, Nicaitia banksi, Solen ensis and
Cardiiivi fasciatuin. The common cockle, Cardhmi edule, on
the other hand, never occurs here. Solen ensis is generally so
deeply embedded that an ordinary dredge brings up merely
fragments instead of the whole animal. The small species of
Lunatia belonging to the gasteropod family Naticidse, and par-
ticularly Lunatia intermedia, also burrow some distance down, as
they feed on little mussels, boring through their thin shells to get
at the animals within. Antalis entalis is often common here.
Spatangids are represented by Echinocardium fiavescens (see
Fig. 338), the commonest of
all, Spatangits purpureus, and
Echinocyainus pusillus, the last
named being the only clypeastrid
in northern seas. Except perhaps
Spatangus piupuretis, they are
not confined to the shell-sand of
the skerries, but may be found
also in the clay of the sublittoral
zone. All of them burrow deeply.
Another deep-burrowing form is fig. 338.
// / / / • 1 • U ■ 1- Echinocardiiini fiavescens, O. F. Miill.
Asti'opeden irregularis, which ■'
also lives in the clay bottom of both the skerries and fjords.
This creature has conical legs (without suckers) particularly
well adapted for digging, though they compel it to procure its
food in a different way from Asterias riibens, which preys on
large mussels by placing its foot-suckers on their shells and
pulling the valves apart till the muscles relax and the shell is
opened, whereas Astropecten swallows whole little worms,
mussels, the young of Echinocardium, and other small animals.
The worms are chiefly those belonging to the genera
Glycera and Nepktkys, and the family Ophelidse {Ophelia lima-
cina and Travisia forbesi). They live down in the sand, where
they make long passages that are kept open by having the
walls lined with a film of slime.
All these animals are variously equipped for living buried
in the sand, which naturally forms a splendid protection against
their enemies. The burrowing mussels are provided with two
more or less elongated movable siphons, the openings of which
476
DEPTHS OF THE OCEAN
are always raised above the level of the sea-floor, the one being
for supplying food and water, and the other for voiding excre-
ments. The Spatangids get their nourishment down in the
sand by means of their remarkably shaped mouth-feet, and
through the rapid vibrations of the spines, some of which are
specially adapted for the purpose, they keep the water circulat-
ing in the holes where they lie, and so obtain oxygen for breath-
ing. Astropecten has a row of small spines along its arms, which
vibrate in similar fashion, and cause a circulation of water round
its body. The tubes of the worms are almost invariably directly
connected by an opening with the level of the sea-floor.
Among the higher crustaceans inhabiting the sandy bottom
we get one or two
species of swimming
crabs {^Portumts, see
Fig- .339)- They har-
monise in colour with
the variations in the
colour of the bottom,
and are thus enabled
to escape notice when
motionless. Their
name is derived from
the terminal joint of
the fifth pair of swim-
merets, which is ex-
panded and paddle-
shaped, so that they are able to swim upwards. During the
cruises of the " Michael Sars " in the North Sea one of these
swimming crabs {Porttnuis depiLrator^ was found hanging in
the drift-net, and numbers of young crabs of the same species
were captured in the plankton net. These forms must,
nevertheless, be regarded as genuine bottom animals ; I have
observed that they can even burrow down into the sand for
a short time, but never remain there long.
One of the most characteristic forms of the littoral zone is
the common edible crab. Cancer pagiirus, which is not so
particular as the lobster regarding the nature of the bottom,
being as much at home on sand as on rocks. Cancer pagiiriLS
goes farther up the fjords than the lobster does, but they both
are undoubtedly littoral animals, occasionally found close up to
low-tide mark, and occurring exceptionally below the lower
limit of the littoral zone.
Fig. 339.
Portiaius depurator, L.
After Bell. )
INVERTEBRATE BOTTOM FAUNA 477
(2) The Fjords. — We have seen that the fauna of the Littoral zone.
Httoral zone among the skerries, especially in the tidal area and
laminaria belt, is abundant both in species and individuals.
There is a diminution, however, as we penetrate farther into
the fjords. In the tidal area of the inner fjords, and at greater
depths also, we miss the limpet and the purple snail, while the
hydroids to be found on the fucus in the skerries become less
and less abundant, until even Dyna77iena piunila disappears/
This change in the fauna is mainly due to the decrease in
salinity, since the surface of the inner fjords, for a great part of
the year at any rate, is occupied by a layer of less saline water
in which these forms cannot thrive. Far up the fjords, however,
in the tidal area, we get the barnacle, the mussel Mytiliis, and the
black periwinkle, which seem to be less affected by a difference
in salinity, though even they require a certain percentage of salt,
since they disappear, for instance, from the tidal area in the more
enclosed parts of the fjords, where, owing to the great accession
of fresh water, the salinity is particularly low. The mussel and
black periwinkle, it is true, may sometimes occur even here
also, but only in fairly deep water. We also find the horse
mussel in the fjords. The great thickets of Laniinaria hyper-
borea, which are so characteristic of the skerries, are absent
from the inner fjords, and so are most of the forms associated
with them. In their place, however, we get Laminaria digitata
and L. sacckarina, but in comparatively small quantities.
The difference between the inner fjords and the skerries is
not so marked when we descend to greater depths, since a
good many forms are equally at home in both. Some of the
littoral fauna, like the lancelet, appear to avoid the fjords
altogether.^ Two forms, which rarely ascend far up the fjords
of West Norway, are the lobster and the common edible crab ;
but the common shore crab {Carcimts moenas) penetrates to
their inmost recesses. The big black sea-slug i^Cucumaria
frondosa) is another form which abounds among the skerries
and in the outer parts of the fjords, but very exceptionally
penetrates far in. No doubt their absence is due to the feeble
currents, or the greater or less accessions of fresh water
prevailing in the fjords — local conditions that are bound to
affect the distribution of the fauna.
The distribution of the two sea-urchins Echinus escnlcnttts
1 It is interesting to note that Dynamena piimila is also found in the estuary of the Elbe as
far up as Cuxhaven.
^ The reason for this may perhaps be that the lancelet requires pure sand or shell-sand to
live in, while the bottom of the fjords generally consists of mud.
478 DEPTHS OF THE OCEAN
and Echimts acutus (forma flemingi) is curious. The former is
very common out among the skerries, while E. aczUus confines
itself to a few localities, but on ascending the fjords E. escidentiLs
becomes scarcer, and descends to greater depths, whereas
E. acutus occurs in the greatest abundance. A similar distribu-
tion characterises the sea-urchins Pai^echinus miliaris and
Strongylocentrotus drobacJiiensis, which much resemble one
another in outward appearance, and are both exceedingly
plentiful in their different localities. Strongylocentrotus lives in
the more open estuaries and bays of the skerries, whereas
Parechinus miliaris keeps to sheltered waters, and especially to
pools. For instance, in a pool south of Bergen (the Inderoe
Poll) I found Pai'echimis miliaris literally in thousands, but there
was not a single specimen of Strongylocentrotus ; in the neigh-
bourhood of Bergen again I collected from another pool of a
rather less typical character, sixty-three specimens oi Pai^echinus,
and only three specimens of Strongylocentrottis. This difference
has not been explained, though most probably the cause is to be
found in the difference in temperature. Pools contain water
of a much higher temperature than the sea outside, and most
likely Pai^eckinus miliaris requires for its reproduction warmer
water than Stro7igylocentrotus. It is interesting to note that,
according to Petersen, there is the same diversity between these
two forms in the Kattegat.
The foregoing is not meant to be even an approximately
complete account of the forms inhabiting the skerries and the
fjords, my sole object having been to show that the dissimilarity
in physical conditions (temperature, salinity, etc.) and in the
nature of the bottom, between the skerries and the inner parts
of the fjords, determines the difference in their biological
conditions.
Those areas of the littoral zone which have been called
Pools, pools, or "polls" (see p. 225), are salt water basins connected
with the sea outside by a shallow channel. The pools vary in
depth, the deepest not exceeding 30 metres. One feature
which they all have in common is that their channels to the sea
are far shallower than their basins. The surface is always
covered by a layer of more or less fresh water derived from the
land, having a lower temperature than the salt-water layer
underneath. About i^ or 2 metres below the surface the
temperature in some summers may rise to 30° C. or even more,
while that of the surface-layer does not rise above 18° or 20° C,
INVERTEBRATE BOTTOM FAUNA 479
though the conditions vary in different years. Below 2 metres
the summer temperature decreases as we approach the bottom,
but late in autumn and in winter the temperature is highest at
the bottom.
In the intermediate warm salt water layers we get a fauna
abounding in individuals that form a distinctive feature of the
pools. There is, first of all, the oyster, Ostrea edtdis, which
finds its principal home here, and there are also quantities of
Pecten operailaris attached to the rocks all round. The
ascidian fauna is represented by several species, which are all
exceedingly plentiful, the commonest being Ascidia vientttla,
Ascidiella aspersa, Ciona intestinalis, and Clavellina lepadiformis}
The most abundant of the bryozoans is Aetea, while a species
of Botigainvillia appears to be the commonest hydroid. The
principal sea - anemones are Metridium diantJms, Urticina
crassicornis, and a species of Sagartia. Parechinus miliaris is
the only echinoid, but it occurs in great numbers. Ostrea,
Pecten, and Pai'ecJiinus indicate the decidedly southern
character of the fauna, and it may not be out of place to
mention that among the plankton forms we get a copepod
{Paracartia grani) belonging to a genus not met with again till
we reach the west coast of Africa.
In addition to the forms having a southern distribution and
of southern origin, however, we find eurythermal and euryhaline
forms. Asterias rubens, Carcinus i?icenas, and Mytilits edzilis
are nearly always present, the last named in particular being in
great abundance, frequently attached to the lines stretched
across the oyster-pools for carrying the bundles of twigs or the
baskets to which the oyster spat attaches itself. Mingled with
this assemblage of mussels, ascidians, etc., we get enormous
quantities of smaller animal forms, the crustacean family Tanaidae
being invariably represented.
Among the forms described as characteristic of the littoral vertical
zone, there are very few that do not occur in all its depths, that fije^iuorar °^
is to say, only a few forms are restricted to the actual strand- fauna.
belt. These few, however, include most of the forms that
characterise the tidal area." No doubt even these may
occasionally be met with at a depth of a few fathoms, but
1 In enclosed places, though not actually in pools, Corclla paralldogya»ima is also common.
- For instance, Patella vulgata, Piu-pura lapillus, Littorlna littorea, L. rudis, and L. obtiisata ;
besides Balanus balanoides, Mytilus edulis, Oixhestia littorea, Campaiiiilaria flexiiosa, Clava
squatjiafa. Actinia equina, Alcyoniditwi hirsutum ; and among the burrowing species Alya
arenaria, Carditim edtile, and Arenicola piscatornm.
48o DEPTHS OF THE OCEAN chap.
the tidal area is their proper home. On the other hand,
those forms which have been described as passing their
hves in the vicinity of low-water mark are not limited to
this situation, but may be met with throughout the whole
littoral zone, sometimes on sand, sometimes on rock, and
sometimes impartially on either hard or soft bottom. Further-
more, on the coasts of Norway the majority of the forms which
characterise the littoral zone either never, or only to an
inconsiderable extent, pass below its lower limit, though there
are some that go down to perhaps about lOO metres, and a very
few that descend to greater depths. But forms which on the
Norwegian west coast are exclusively littoral, may be met
with in deeper water in other northern areas, as I shall show
later on.
It would hardly be possible in a short account like this to
give even an approximately complete description of the fauna
along the coasts in the sublittoral zone, seeing that this is the
abode of most coastal species living below the littoral zone. As
a rule, the soft bottom is of a different character from that in
the deepest parts of the fjords. Instead of viscous gray clay or
mud, a coarser clay, more sandy in character, covers the Hoor
in the medium depths of the sublittoral zone, which in the case
of the fjords is near the sides or on submarine banks. Where
there are plateaus sloping gradually down from the sides we
also get rocks and stones and bits of shells, and there is thus
accommodation for forms that naturally live on hard bottom.
We often get, for instance, quantities of brachiopods and
bryozoans, as well as a certain number of hydroids, ascidians,
etc. Generally speaking, the character of the bottom here is
more favourable to animal life than in the deep water, for while
the mud harbours chiefly burrowing mussels, for instance, the
medium depths accommodate, in addition, a large number of
creeping snails,
A good many forms which occur in the continental deep-
sea zone ascend to the sublittoral, and some even as high as
the littoral ^ zone. Still for most of them we may put the upper
limit of distribution at lOO to 200 metres. Probably, however,
their vertical distribution is affected to some extent by the
variations in the vertical distribution of the Atlantic water,
which may be higher or lower according to the different seasons
1 For instance, Paguriis ptibcscens, Ophiopholis aculeata, and Terebellides siromi.
INVERTEBRATE BOTTOM FAUNA 481
of the year.^ Other sublittoral species again are plentiful every-
where throughout the whole sublittoral zone, but rarely descend
below its lower limit, so that we find at a depth of 100 to 200
metres a mixed fauna, consisting partly of forms that have here
reached their upper or lower limit of vertical distribution, and
partly of forms which find here the most favourable conditions
of life. The sublittoral zone accordingly ranks first in number
of species.
The continental deep-sea zone for all practical purposes The
coincides with the deeper parts of the fjords, whereas out among deep"efz^one
the skerries, with their comparatively shallow water, we either
do not find it at all or else meet with it merely in very limited
areas. A feature of the fjords is their very great depth, usually
increasing as we proceed inwards, and in their deepest parts, so
far as the nature of the bottom and the physical character of
the water are concerned, we get what are practically Atlantic
conditions.
In the fjords the greatest depth is met with along the
middle and in the innermost portions, and may be put on an
average at 400 to 800 metres." The sides of the fjords descend
in some places practically perpendicularly into deep water, in
other places forming more or less extensive submarine plateaus
and terraces. At various depths, especially in the seaward
portions, there are cross ridges, which frequently consist of hard
bottom. The material covering the floor in deep water is
almost invariably a soft, viscous, grayish clay or mud. It is
the animal life existing upon and in this mud which I shall now
describe.
The mud-fauna of the deeper parts of the fjords resembles the
sand-fauna in the littoral zone, inasmuch as it consists mainly of
burrowing forms, or at any rate of forms which to some extent
burrow into the mud to obtain their nourishment. When we
sift the mud brought up by the trawl or dredge, we obtain a
number of curious little bodies (round, star-shaped, rod-like,
conical, etc.), composed of sand or particles of mud. These
creatures are rhizopods (foraminifera). By putting out
extremely fine thread-like prolongations of their protoplasm
through one or more openings in their covering, they attract to
themselves small organic particles in the mud which furnish
^ Thus Helland-Hansen has fixed the summer limit along the coasts at 75 metres, and the
winter limit at 150 metres.
'■^ In some fjords, such as the Sogne and Hardanger fjords, the depth is in places 1000 metres
or more.
2 I
482 DEPTHS OF THE OCEAN
them with nourishment — an operation that under favourable
circumstances can actually be observed/ Of larger forms, the
numbers of which render them characteristic of these depths, two
sea-slugs deserve mention : a red one {Stichopus treimilus, see
Fig. 340), and a gray one i^Mesotlnuna intestmalis). They belong,
however, to a division different from the sea-slugs found in the
littoral zone, the distinction consisting inte7' alia in a different
structure of the tentacles.
Other characteristic forms are: the brittle star AvipJiiura norvegica,
the sea-slugs Cuciiuiaria Jiispida and BatJiyplotes ticardi. Of higher
crustaceans we have the genus Munida, with the two species M. rugosa
and M. tenuimana, of which the latter in particular is to be met with in
the deepest parts of the fjords, and the prawn PontopJiilus norvegicus.
The mussels come next to the rhizopods in number of species, the forms
Fig. 340.
Stichopus tremulus, Gunn. Reduced. (After O. F. Mtiller. )
most frequently found being Malletia obtusa, Portlandia hidda, P. tenuis,
and P.frigida, Abra longicallis and A. nitida, Kelhella miliaris, Axinus
flexuosus and A. ferruginosus, Ntccula tiimidula, and the species of
Necera. Scaphopods include three characteristic forms, namely Antalis
striolata, Siplwnentalis tetragona, and Cadulus aubfusifonnis, which last
becomes more abundant as the depth increases. Worms are represented
by the families Maldanidae and Terebellidse, of which latter Terebellides
stromi is very common, and there are also Luvibrinereis fragilis, Nephthys,
Aricia, etc.
The coelenterates are represented on the mud of the deeper parts of
the fjords by the group of pennatuhds or sea-pens, a kind of unattached
coral animal. The commonest forms are Kophobeknmoii stellifeTum (see
Fig. 341) and Fiiniculina quadrangiilaris, though they are not so regularly
or abundantly distributed as the two sea-slugs already referred to, which
are found practically everywhere. Two species of sea -anemones
{Actinostola callosa and Bolocera tiiedicB) - are also universally distributed,
1 The following are a few forms which are characteristic owing to their numbers and size :
the globular Saccammitia spluzrica, the rod-like ramifying Rhabdatnmma abyssoruin, and the star-
shaped Astrorhiza m-enaria, the test of which consists of particles of sand, the rod-like non-
ramifying Bathysiphon fdifo7-mis, etc. In addition there are other large forms of which I may
mention the species of Cristellaria, the shells of which are calcareous and consist of several cells.
- Both these forms are found in the deep parts of the fjords, but I am not certain whether
they live on the mud or on the patches of harder bottom which occur here and there.
INVERTEBRATE BOTTOM FAUNA
483
:%^i
and so is the sponge TJienea inuricata (see Fig. 342), which adheres to
the mud by means of long outgrowths, and the worm-like gephyrean
Sipunculiis priapuloides.
Thus the majority of the mud-fauna in the deep parts of
the fjords, owing to the nature of the bottom,
consists of unattached animal forms, most of
the sponges, corals, hydroids,^ bryozoans,
ascidians (including the unattached molgulids),
and brachiopods being absent ; in other words,
the nature of the bottom gives the fauna its
character. Still even here it is possible for
certain attached forms to occur normally, and
very often abundantly. There are frequently
great quantities of the little mussel [Area
pectiuiciLloides), which fastens itself by its
byssus-filaments sometimes to the larger for-
aminifera, sometimes to slag from steamers,
or any other hard substances which it happens
to come across in the mud. There are also
numbers of the white semi-transparent Peden
abyssorimi, which occurs, according to Sars,
also in the deepest parts of the Christiania
fjord, where it attaches itself to rotten bits
of sea- weed.
I shall now turn to the faunal conditions
in the fjords where there is hard rocky
bottom, i.e. the more or less steep sides of
the fjords and the submarine ridges or emin-
ences. These latter are sometimes isolated
raised portions of the floor surrounded on
all sides by softer bottom, and sometimes
spurs running out from the walls of the fjord.
The slopes of the ridges and eminences are
frequently covered with coarse sand and
stones, as are also the sides of the fjords
where not too steep. In many cases, how-
ever, the walls go down so steeply that no
loose deposits occur till we reach. a depth of
several hundred metres.
The fauna here is quite different from that on the muddy
bottom, consisting mostly of attached forms of various groups,
^ Only a little form {Perigoniimis abyssi) is common here, attached to mussel shells,
■especially those of Nticula tuviidula.
Fig. 341.
Kophobelevinonstelliferum,
O. F. Miill. (After
Asbjornsen. )
484
DEPTHS OF THE OCEAN
especially sponges, coelenterates, bryozoans, brachiopods, and
tube - worms, with a few unattached forms, of which the
crustaceans are the most important. Most of the species of
attached forms belong to the sponges, coelenterates, and
bryozoans, though the brachiopods and tube - worms exceed
the others in number of individuals. The sponges are nearly
Fig. 342.
Thejiea muricata. Bowerbank.
all silicious, whereas in the littoral zone they are chiefly
calcareous. The principal coelenterates are attached coral
animals, especially gorgonians,^ alcyonarians, and hydroids.
We commonly get, for instance, one or two species of alcyonaria
of the genus Paraspongodes, the larger specimens of which
resemble cauliflowers ; in the same way we find Alcyonium
1 Paramuricea placomtis, Primnoa lepadifera. In the same localities we also find two sea-
anemones {Phellia abyssicola and Bolocera ttiedia:), of which the latter also occurs on muddy
bottom in the deep parts of the fjords (see p. 482).
INVERTEBRATE BOTTOM FAUNA 485
digitattun, belonging to the same group, upon hard bottom in the
Httoral zone. We must also include among the alcyonaria the
sea-tree, Paragorgia ai'borea (see Fig. 343), which is taller than
a man and has many branches. Of true corals we may mention
Lophohelia prolifcra and AinpJiihelia raviea, though the coral
fauna is not regularly distributed over the hard bottom, but is
more or less local ; still
there are often numbers
of individuals where
hard bottom does occur.
Several species of hy-
droids, such as Lafoea
ditmosa, Sertularella
gayi, ' etc., are very
common ; and of the
bryozoans, Retepora
beaniana, easily recog-
nisable owing to its
trellis-like structure, is
both widely distributed
and plentiful. So, too,
are the brachiopods,
Terebratulina capiit-
serpentis and Wald-
heiuiia a^anmin, and
the two tube - worms,
Placostegus tridentahis,
the tube of which divides
into three tooth - like
processes, and Serpiila
verinicularis (see Fig.
344). Both these worms,
it may be added, have
calcareous tubes, in
contradistinction to the „ ^ , J^^' ^^^: , .
Branch of Paragorgia arborea, L.
tube-worms of the mud
which inhabit tubes of mud or sand. There is, besides, a species
of barnacle ( Verruca strmni) on the stones, which is frequently
nearly as abundant as Balamis balanoides in the tidal area.
It would take too long to give a full description of the
unattached fauna associated with the hard bottom. I will
therefore merely point out that some free forms occur only
upon the attached forms, and seem accordingly to be dependent
486 DEPTHS OF THE OCEAN
upon them. The most noticeable of these is medusa's head
{Gorgonocepkalus linckii, see Fig, 345), a brittle-star with ex-
tremely branching arms that lives upon the larger gorgonians
and sea-trees. A crustacean, GalatJiodes tridentatus, appears
also to be intimately connected with the corals, and large
quantities are occasionally found upon them. As for the
remaining higher forms of crustaceans the fauna consists chiefly
of prawns, though they are
, >• different from the ones in
the littoral zone,^ but other
groups are not entirely
wanting.-
The large mussel, Lima
excavata, is extremely character-
istic of the rocky bottom, attach-
ing itself by means of its fine
silky byssus-filaments. We may
further mention a sea-slug {Psolus
sqiiajiiatus, see Fig. 346), easily
recognisable owing to its abruptly
truncated disc with suctorial feet,
by which it adheres to stones,
shells, etc. ; a crinoid {^Antedon
petasus) occurring locally, though
often in abundance, especially
where there are sponges ; several
star -fishes, Pentagonaster granu-
laris, Porania pulvillus^ Hippa-
sterias phrygiana {plana), which
last seems to prefer places where
the hard bottom is covered with
coarse sand ; a brittle - star
{Ophiopliolis aculeata) ; molluscs,
as, for instance, species of Pecten ;
ascidians, particularly of the family
Styelidae ; sea-spiders {NyuipJion strdmi\ etc. At considerable depths
there is also the remarkable starfish Brisinga endecacnemos. Some of
these are exclusively deep-sea forms, and rarely leave the deeper
parts of this zone. Munida te7iuiniana, BatJijplotes tizardi, Brisinga
endecacnemos, and Lima excavata do not occur in depths less than 300
or 400 metres.
(3) Other Northern Boreal Coastal Areas. — There are
several areas where the littoral zone has been but little studied,
^ Pandalus pj-opinquus, P. brevirostris, Hippolyte polan's, and H. securifrons.
- Thus a hermit-crab {Pagurus ptibescetts), which occurs, too, in the littoral zone, is quite
common, and so are Munida rugosa, which also inhabits soft bottom, and the stone-crab
{Lithodes maja).
Fig. 344-
Serpula verinicttlaris, Mtil
INVERTEBRATE BOTTOM FAUNA 487
and the information received from Iceland and the Faroe
Islands is not as yet sufficiently comprehensive to enable one
to speak with confidence regarding the composition of the
littoral fauna there. In Iceland, however, if we may judge
from our knowledge of the hydroid fauna in the boreal coast
areas, the conditions are very similar to those on the Scan-
dinavian coasts, and the same is true also of the North Sea
coasts of Britain.
If we compare the North Sea coasts with the Skagerrack
coasts of Scandinavia we find many points of resemblance, the
littoral fauna for the
most part living under
similar natural con-
ditions in both areas.
The tides of the
Skagerrack, however,
are inconsiderable and
irregular, and in conse-
quence forms, which
on the North Sea
coasts belong to the
low-tide area, can un-
doubtedly live here in
shallow water and on
thesame kind of bottom,
but they are not left
regularly exposed by
the ebb. A good
instance of this may be
seen in the case of the
hydroids Clava squa-
mata and Laomedea flexuosa, which are quite common on the
fucoids in spite of the fact that the ebb-tide only on rare
occasions leaves them exposed. On the other hand, certain
species, which are not met with in the low-tide area of the
North Sea, and consequently do not patronise the fucus there,
attach themselves to these algae on the Skagerrack coasts. It
is evident from this that it is not the actual foundation but
the natural conditions and the ability to adapt themselves to
these conditions which determine the distribution of the animals
in the strand-belt.
Although the littoral faunas of these two coastal areas bear
a very strong resemblance to each other, there are yet
Fig. 345.
Gorgonoccplialiis linckii, M. and T.
^'ar. Reduced.
488
DEPTHS OF THE OCEAN
some differences between them. Thus several forms that
abound on the west coast of Norway are absent from the
Skagerrack coast, if we may judge from my observations at
Risor in Norway compared with the researches of Theel at
Kristineberg in Bohuslan.^ For instance, Cuctunaria froiidosa,
a littoral echinoderm common on the North Sea coast, has
not been met with in the Skagerrack, and Ophiocoma nigj^a is
very rarely found in the latter area. Echiims acutiis occurs in
enormous quantities on the North Sea coast, but is extremely
Fig. 346.
Psoitis squamatus, Koren.
rare on the Skagerrack coast, while the mussel, Lima kians,
has not been met with on the Bohuslan coast of Sweden,
though in certain localities of the Norwegian west coast it is
one of the most characteristic forms of the littoral fauna. On
the other hand, the Skagerrack coast is the home of certain
littoral forms which occur but rarely on the coast of the North
Sea. Thus on the west coast of Norway Echmocardium
cor datum is seldom found, and then only in a few special
localities, whereas in Bohuslan it seems to be one of the
^ Theel, " Om utvecklingen af Sveriges zoologiska hafsstation Kristineberg och om djurlifvet
i angrjinsande haf och fjordar," Arkiv. f. Zoologie, Bd. iv., 1907.
INVERTEBRATE BOTTOM FAUNA 489
commonest forms. Ophhtra ciliaris, too, is far more plentiful
in the Skagerrack, and the gasteropod, Nassa reticidata, occurs
in quantities in the littoral zone of the Skagerrack, but is
comparatively rare on the North Sea coast.
I have noticed also a difference between the fauna which
patronises Laminaria hyperborea and the fauna associated with
the two other species oi Laminaria. It is only the first named
with its stiff thick stalks which is densely crowded with attached
forms, whereas the comparatively thin pliant stalks of the other
two are either entirely neglected or only made use of to an
inconsiderable extent, with the result that there are nearly
always far more individuals in the L. hyperborea belt than in
either of the other two laminaria communities.
I have already stated that the natural conditions prevailing
on the different coasts affect the character of the fauna much
more in the littoral zone than at greater depths. Where, for
instance, there is nothing in the way of foundation for attached
forms, we must expect to find a fauna more suited to another
kind of environment. Thus on many North Sea coasts, where
the long shallow shores consist merely of sand, like the "vader"
of Schleswig and Holland, upon which the waves do not break
with any violence, there are immense stretches where practically
the sole inhabitants are the lug-worm [Arenicola), a tunnelling
amphipod [Corophium grossipes), and one or two other forms.
In such sandy stretches the fauna differs entirely from that
found along rocky coasts, and only occasionally do we get
attached forms where piles, stone quays, or other suitable
foundations happen to occur. The animal life differs again on
the sandy Danish coasts, which are unprotected by a line of
outer islands, and are therefore exposed to the full force of the
breakers, where the constant disturbance produced by the waves
upon the sandy bottom is distinctly unfavourable to plant and
animal life ; consequently the upper littoral zone on such coasts
rarely harbours many forms. On the other hand, at slightly
greater depths, and in fjords or similar enclosed areas, we get
the conditions requisite for the development of Zostera vege-
tation with its special fauna. We may see how much the
topography of the bottom affects the development of animal life
by studying the conditions on the Kattegat coast of Denmark ;
wherever reefs, overgrown by algae, occur amidst the eelgrass,
we may be certain of finding a fauna consisting of chitons, snails,
bryozoans, and hydroid polyps.
The littoral fauna in the southern portion of the North Sea
490 DEPTHS OF THE OCEAN chap.
comprises quite a number of shallow-water forms that are
otherwise foreign to northern regions — Mediterranean immi-
grants which make occasional visits or have effected a
permanent lodgment in comparatively limited tracts. Some of
them I shall refer to later on, when dealing with the shallower
portions of the North Sea. Their presence may be ascribed to
hydrographical conditions, and in no way depends upon the
topography of the bottom. To some extent the English
Channel acts as a boundary between two littoral faunal areas, a
fairly large number of Mediterranean forms living in the
Channel but not venturing into the North Sea ; while on the
other hand several northern forms do not enter the Channel,
these last being especially forms of Arctic origin. Many or
probably most of the species are common to both areas, since the
majority of the boreal species of the North Sea were originally
immigrants from southern waters.
So far as the coasts of the boreal region are concerned the
sublittoral zone does not vary much, though certain species from
the continental deep-sea zone, which ascend to the sublittoral
zone along the North Sea and Atlantic coasts of Scandinavia, are
absent from large portions of the Skagerrack and Kattegat as well
as from other coasts of the North Sea. They would seem to be
forms whose distribution follows the Gulf Stream, and are there-
fore found mainly along the eastern coasts of the North Sea
and Atlantic. They include the holothurian Psohis sq2ianiatus,
the asterid Pentagonaster granularis, the gephyrean Bonelha
viridis, the brachiopod Waldheimia cranium, and some mussels.
Munida rugosa, which is one of the most characteristic decapods
belonging to the sublittoral and deep-sea zones is, according to
Theel, seldom met with on the Bohuslan coast of Sweden ; the
true corals and gorgonids of the deep-sea fauna, which else-
where patronise the sublittoral zone, are much restricted in
their distribution throughout the Skagerrack and wide tracts of
the North Sea, and seem to be absent from the fjords of the
Bohuslan coast. Certain forms, which along the coasts are
chiefly sublittoral in their distribution, occur sometimes quite
commonly in one area, whereas in another area they may be
scarce or even entirely absent. For instance, on the Swedish
and Norwegian coasts of the Skagerrack the spatangid
Brissopsis lyrifera is generally met with in the sublittoral
zone, but on the west or North Sea coast of Norway it is
comparatively rare. The converse is the case with the
INVERTEBRATE BOTTOM FAUNA 491
spatangid Schisasier fragi/is, y^h'ich is plentiful in the North
Sea, but not found in the Skagerrack/
We propose now to discuss the fauna of the continental
plateaus within the boreal region, dealing firstly with depths less
than 100 metres, "-^ and secondly with depths greater than 100
metres.
I. Continental Plateaus covered by less than 100 Metres (?/ The southern
Water. — In the portion of the North Sea to the south of ^"^'^J^J'/JJg
the Dogger Bank, where the waters are shallow and the North Sea.
summer temperature is high, there are southern forms unknown
farther north, though this exclusively southern element in the
fauna is very inconsiderable compared with the remaining
boreal forms, some of which are more abundantly developed
than in more northerly latitudes. During the cruise of the
" Michael Sars " in 1904, I was able to carry out investigations
with the dredge at a series of stations from the Danish coast
to Scotland, in lat. 56° to 58° N. in depths between 14 and 100
metres, an area not previously systematically examined.
The floor of the North Sea is for the most part covered with
soft materials (sand, sandy mud, and clay), with areas of stony
bottom in places, though even here the rocks and stones are
nearly always mixed with softer materials. In some localities
the soft materials contain masses of empty shells, which are
invaluable to the animal life, acting as a foundation for the
hydroids, bryozoans, and other attached forms. This mixed
bottom supports a greater variety of forms than the soft bottom,
offering suitable conditions to unattached forms, whether they
burrow or not, as well as to attached forms.
The abundance of echinoderms characterises to a great extent
the fauna of the North Sea. Among the star-fishes Asterias
rubens occurs at all depths and upon every kind of bottom,
though it seems less partial to soft clay bottom at considerable
depths. Astropecten irregularis is met with everywhere, and the
sea-mice Echinocardium and Spatangus purpureus ^ are equally
common. Ophiura ciliaris (see Fig. 347) may be described as
the brittle-star of the North Sea, for we found well-developed
specimens everywhere on mixed bottom down to a depth of about
100 metres, and at temperatures varying from 7° to 12° C, but
1 The continental deep-sea zone not being represented, or only in very limited tracts, in the
coastal areas of the Skagerrack, Kattegat, western and southern North Sea, a good many forms
characteristic of that zone are absent here.
- As the type for this area we take the southern and central parts of the North Sea, those
parts being the best explored.
•' In a trawling at 96 metres we found 500 specimens of the last named.
492 DEPTHS OF THE OCEAN
not on soft clay bottom ; all the individuals from stations in the
open North Sea at considerable depths were very much lighter
in colour and much larger than those taken along the Norwegian
and British coasts. A good idea of the enormous quantities in
which this form sometimes occurs was afforded by a haul with
the dredge off Aberdeen, in 25 metres of water (temperature
10.26° C), where they must have literally covered the bottom,
and the same remark applies to the west coast of Jutland. In
some localities we met with numbers of Brissopsis lyrifera,
which prefers as a rule clay bottom in deep water at a tem-
FiG. 347-
Ophiura ciUaris, L. Reduced.
perature of 6° or 8^ C, though occasionally specimens may be
found on sand. Everywhere, throughout the whole area
examined, there were the two brittle-stars Ophiopholis aculeata
and Ophiothrix fragilis, as well as the starfish Liddia sarsi,
which are numerous here and there, but cannot be called
characteristic forms. More local, though plentiful in places,
were sea-slugs {Cucumaria elongatd), which were met with at
two stations, together with Brissopsis, on muddy bottom in
about 50 metres, at a temperature of approximately 8° C.^
^ Of other echinoderms found at a few stations, in smaller quantities, I may mention Ophiura
albida (only at one or two stations in the neighbourhood of the Danish coast and one station off
Aberdeen in 25 metres) and O. sarsi, Aniphiiira filiformis {chiajeil), Ophioden sericeum (many
young-stages in young-fish trawl east of Aberdeen in 62 metres, temperature 8'4° C, and also
from the Norwegian depression), Asterias 7iiiillcri, Solaster papposus (only from the edge of the
INVERTEBRATE BOTTOM FAUNA 493
Special mention must be made of specimens of our common
sea-urchin Echimis esculentiis from two stations in the North
Sea: two specimens from ']'] metres, temperature 7.1° C, and
eight specimens from 96 metres, temperature 6.15° C. The
species generally varies very little, and individuals from our
littoral zone scarcely differ at all. Normally the shell is high
and of a reddish colour, while the spines are violet. The ten
specimens from the North Sea, however, all differed from the
typical form, having a flattened shape and varying considerably
in colour. The shell itself shows variations from the typical
red hue to a chocolate brown, and the spines assume every
intermediate shade from the most beautiful vermilion (like what
we find in E. elegans) to pure green. Many specimens have
in consequence an outward resemblance to Strongylocentrotus
or Echimis miliaris. Mortensen has described from the
North Sea (40 fathoms) two specimens of flattened shape with
unusually long bright red spines (like those of E. elegans).
Norman tells of a variety from deep water near the Shetlands
that had very fine spines and an exceptionally high shell, and
Sars has described a similar variety from the Great Edge.
These facts appear to justify the conclusion that, whereas in
shallow water and along the coasts the species is of a fairly
constant type as regards both shape and colour, it has a marked
tendency to variation at greater depths, although the normal,
or almost normal, form is to be found also in deeper water, as
on the Faroe banks. The deeper portions of the North Sea
in particular appear to produce very striking variations.
Of shell-bearing snails there are two forms which characterise
the area investigated, namely Nephmea antiqiia and Sipho
gracilis, both species being met with everywhere from Denmark
to the Scottish coast, and sometimes in great numbers.^
Judging by our investigations Nephinea extends into shallower
water than Sipho, though both species exist plentifully side by
side at considerable depths. One biological peculiarity worth
recording was that every individual of Sipho in the haul referred
to had a sea-anemone {Chondi^actinia digitata) on its shell, and
at other stations, too, they were found living together in
symbiosis. These sea-anemones were likewise found on the
Norwegian depression, from the Danish coast, and east of Aberdeen in 62 metres), Eckmaster
sangumolenius, Sti'ongylocentrotus drobachiensis (only from the Danish coast, one specimen with
Stylifer tiirtoni on its shell), Echinus esculent us var., Echinocyamus pusillus (only east of
Aberdeen in 62 metres), Cucwnaria lactea.
^ We secured 130 specimens of Neptunea and 375 of Sipho at one haul from a depth of 96
metres (temperature 6.15° C. ).
494 DEPTHS OF THE OCEAN
shells of Neptunea, and on several specimens of this large snail
two other large actinians {Urticina crassicornis and Met7ndm7n
dianthus) had attached themselves. Our common whelk
[Buccininn iindatum, see Fig. 348) occurred over the whole area
down to a depth of 100 metres, as a rule along with the two
snails referred to, though never in such great abundance.^
Nudibranchs yielded, with one or two exceptions, only a
very few specimens, and this was particularly the case with
Tritonia, Doris, and Doto. At certain stations, however, re-
markably enough from muddy bottom where there were no
hydroids, the young -fish trawl brought up quantities of
yEolis, which had
i \^' ^ ' most probably located
J #. themselves upon
I Virgiilaria and Alcy-
, Ij- oniiun, although their
'^ \^?. usual home is among
'^Wr- hydroids. Chceto-
dei'ma, a worm -like
.::.Z,^'^'h form belonging to the
y " ^ /-' "-^^ molluscs, was repre-
^' ^ ^ .%.^ sented by only a few
^^ '*!/ ^^'-'.V.i* specimens (depth 47
^"'1^*»^ -^^ to 80 metres, tempera-
' ' / * ture f to 8" C.) ;
^' cuttle-fishes by some
Fig. 348. specimens of Lolio^o
Buccinuin imdatinn, L. r i ■ •
joroesi at one station
(depth 38 metres, temperature 10° C), and a little Sepiola from
94 metres. The almost complete absence of species of Chiton,
^ Of more or less regularly distributed mollusc-forms we may further mention : Pecten
opercidaris (large), Mytilus modiolus (from a depth of 96 metres about 70 specimens were taken,
averaging 11 or 12 cm. in length and often with Urticina attached), Modiolaria nigra, Cardium
echinatnin, Cyprina islandica, Venus gallina, Mactra elliptica (very numerous off the coast of
Jutland, 14 metres, temperature 12.5° C), Solen ensis, Cultellus pelhtcidus, Aporrhais
pes-pelecani, Antalis entalis. At some stations we came across Niictda tenuis, Leda tninuta,
Kellia suborbicularis, Coj-btda gibba, Dosinia lincta, Cylichna cylindracea, all on mud in about 50
metres and at a temperature of 8° C. Astarte sidcata was extremely numerous at one station
(depth 86 metres, temperature 8.4° C), but otherwise very scattered. Aho Nicania banksi,
Peclunculus glycimei'is, Mactra stidtoriim, Psatnmobia ferroensis, Panopcea norvegica (large
specimen, 80 mm. long, 55 mm. high), Saxicava arctica, Pholas crispata (in pieces of timber on the
bottom, depth 32 metres, temperature 10.9° C), Abra sp., Montacuta (on Spatangus), Philine sp.,
Velutina hcvigata, Lunatia intermedia (in enormous quantities at Jammer Bay off the coast of
Jutland, 14 metres, together with Mactra elliptica, on which latter, judging from the many
shells with holes bored in them, it feeds), Lunatia montagui, Natica catena (strings of eggs were
found in large quantities on the north slope of the Dogger Bank, though the animal itself was
rarely captured), Boi-eofusus berniciensis, Scalaria trevelyana, Volutopsis norvegica (only at one
station, depth 96 metres, temperature 6.15° C, though in fairly large quantities— about 30
specimens).
INVERTEBRATE BOTTOM FAUNA 495
notwithstanding the apparently suitable bottom of stones and
shells, is very remarkable, a few specimens of Lepidopleztriis
{Chiton) cinereiLS at one station (57 metres, temperature 7.9'" C.)
being all that we met with.
The bottom of the North Sea abounds, as already stated,
in empty shells, particularly of mussels. The commonest forms
are Cardium echinatinn, Cyprina islandica, Venus gallina,
Dosinia lincta, Mactra, Psanwiobia ferroensis, So/en, etc., all
of which were likewise taken alive. Lucina borealis, on the
other hand, though shells were met with here and there at a
depth of 38 to 98 metres, sometimes even in fairly large
quantities, was not captured alive out in the North Sea by
us, and the "Pomerania" Expedition obtained only empty
shells on the Dogger Bank ; it is not included by Heincke
amongst the molluscs of Heligoland, but we do find it along
the coasts of Britain and in the Skagerrack. Empty shells of
Alya truncata forma typica were also found in two localities,
one at a depth of 14 metres off the north-west coast of Jutland,
and the other midway between Jutland and Scotland at a depth
of 68 metres.
The higher crustacean fauna is comparatively poor in species,
most of them being restricted in distribution and few in numbers.
The hermit crabs Pagm^us bernkardns and P. p2ibescens are
exceptions, as they are pretty generally distributed over the
whole area, though only the first named is met with in shallow
water, at or below 40 metres ; at greater depths both species
occur, as in some other areas of the North Sea. Of crabs Hyas
coarctattts is common in both deep and shallow water, whereas
Portunus depiLrator (or holsatics^) and P. pusillus are more
limited in their distribution, and occur mainly in the lesser
depths. Other forms are more local, though frequently met
with in considerable numbers, like the little Porcellana longi-
cornis ; as a contribution to its biology I may mention that we
found large numbers at two stations (depth 32 metres and 42
metres, temperature 10.9° C. and 8.7° C), where in one case
it had crept into the holes made by the borer-mussel (Pholas
crispata) in sunken pieces of timber and in the other it occu-
pied cavities in the large clotted lumps of sand constituting the
colonies of the tube-worm Sabella^Ha alveolata. At greater
depths it was absent, Porcellana being to a great extent a
littoral form.^
^ We also found two other crabs in shallow water west of Jutland (32 metres) : the ordinary
edible crab {Cancer pagiirus) and Hyas araneus. Single specimens of two species of Ebalea
496
DEPTHS OF THE OCEAN
The stone crab {Lithodes maja, see Fig. 349) was met with
only in the deeper parts where the temperature was lower (^j
metres and 96 metres, temperature 7.1' C. and 6.15° C), as in
the deep parts of the Norwegian tjords. The whole central
portion of the North Sea proved remarkably poor in shrimps
(caridids) though the few species present were frequently in
considerable numbers.^
The ordinary wide-meshed appliances (trawls and dredges)
undoubtedly give a good idea of the larger bottom-forms
composing the fauna, but are less satisfactory when the fauna
consists mainly of small crustaceans, for which we found the
young-fish trawl extremely useful, as by its means we secured
the large numbers of young crangonids already referred to,
besides quantities of lower forms of crustaceans, especially
amphipods, cumaceans, etc., and larvae of higher crustaceans,
particularly hermit crabs. Even these, however, occur locally,
{E. cranchi and E. tuberosd) were obtained at depths from 47 metres to 86 metres, with
temperatures of 8° to 8.4° C. W^e also obtained specimens of the crabs Inachiis dorsettensis
and Stenorhynchtis rostraius, and a single specimen of Atelecydus septemdetitattis was taken
in the neighbourhood of the Scottish coast in 62 metres at a teinperature of 8.4" C. At one
station on the coast of Jutland (32 metres, temperature 10.9° C.) the crab Corjsles cassivelamis
was common, but it was quite absent in the central portions. Galathea dispersa and G. inter-
media were got at some stations.
^ We found, for instance, numerous specimens of a little crangoriid {Ckeraphilus nanus) at
a depth of 78 metres, temperature 7° C, a number of individuals belonging to a form related to
the common shrimp, Crangon alhnanni, and Pandalus anmdicornis. At a station near the
Scottish coast, that is to say in the western portion of the North Sea, at a depth of 86 metres,
temperature 8.4" C, we found in addition to small specimens of the two last-mentioned forms,
of which Crangon was in myriads, several specimens of another shrimp {Hippolyte secitrifrons),
which is also met with on the eastern side, but not at corresponding depths in the central
portion.
INVERTEBRATE BOTTOM FAUNA
497
being extremely numerous in certain localities and absent in
others ; no doubt the currents at the bottom are responsible for
this, seeing that the depth and temperature are in themselves
entirely favourable. These enormous quantities of small
crustaceans must have an appreciable influence upon the shoals
of fishes, and in particular upon the young fishes, and this I have
been able to confirm by direct observation. On the northern
slope of the Dogger Bank we captured a number of young
whitings and flounders with the trawl at a depth of 38 metres
(temperature 10^ C), and their stomachs at first sight seemed
to contain only sand, but closer
investigation revealed small amphi-
pods (sand- hoppers) which thus
formed their principal nourishment,
the sand being swallowed simul-
taneously with them ; the stomachs
of the larger fishes generally con-
tained hermit crabs and swimming
crabs (Portunus). The caprellids
seemed to be especially associated
with a bottom overgrown with
Fig. 350.
Macrocliymm pomum, M. Sars.
hydroids, and were found only
exceptionally where hydroids were
absent.^
The central portion of the
North Sea is poorly supplied with
pycnogonids (sea- spiders), there
being only one widely distributed
form [Pyaiogonum littorale), and
it was only found in deep water (80 to 100 metres) at low
temperatures (6°-7° C), where I sometimes found it, as
described by Sars, clinging to large sea-anemones [Urticina
crassicornis and Metridium diantkus), into the skin of which
it bores its proboscis for sucking ; a solitary specimen of
Nyniphon stromi was the only other pycnogonid found in deep
water.
The ascidians (sea-squirts) are also poorly represented ; the
monascidians (simple sea-squirts) were not very conspicuous any-
where in the area examined, but we got large and well-developed
specimens of Ciona intestinalis in about 80 metres (tempera-
1 The commonest is Caprella linearis (it seems difficult to discover any invariable difference
between this species and C. septenirionalis), but stray specimens occur o{ Proto pedata, mainly
found along the edge of the Norwegian depression, at a depth of about lOO metres, and one
individual o{ Protella phasma was captured at 77 metres, temperature 7.33° C.
2 K
498
DEPTHS OF THE OCEAN
ture about 7' C), whereas along the Norwegian coasts it is
chiefly found in quite shallow water, where it attains its fullest
development. Asciciiella virginea and Styela loveni were
fairly widely distributed. A large globular compound ascidian
{Mac7'oclinum pomiun, see Fig. 350), although very local, was at
times very plentiful.
The attached fauna, which, properly speaking, includes the
sea-squirts, is mainly represented by three groups : sponges,
hydroids, and bryozoans, the two last forming occasionally
regular little forests. On the northern slope of the Dogger
Bank (depth 'i^'^ metres, temperature 10° C.) there were con-
siderable quantities of large bush-like colonies of two species
of bryozoans (Fhtstra securi/rons, see Fig. 351, and Alcyonidium
gelatinosiim\ which, ^'whFlustra
foliacea, are the most character-
istic of the North Sea bryo-
zoans ; they vary in relative
abundance, but on the Great
Fisher Bank Flustra foliacea
appears to be the predominant
form. Small bryozoans, some-
times occurring in large quan-
tities, are found growing on the
bigger species or on other
substances.
Hydroids are distributed
over the whole area examined
wherever the bottom is suit-
able, especially where it is covered with empty shells or
stones. They sometimes form " communities," but are as
a rule scattered about here and there. Tuhilaria larynx is
occasionally met with in enormous quantities, and there
are sometimes "communities" of Tlmjaria thuja (see Fig.
352), Hydrallmannia falcata, Campamilaria longisshua, and
C. verhcillata. The species of Dicoryne and Hydractinia are
very often found on shells inhabited by hermit crabs. ^ The
hydroids in the central portion of the North Sea differ to a
certain extent from those found in the northern portion or
on the other plateaus. Tkujaria and Hydrallmannia are, how-
ever, common to both areas.
Among coelenterates there are really only two forms, if we
Fig. 351.
Flustra sectirifrons , Pallas.
' Dicoryne conferta, Hydractinia echinata ; other species commonly found in the North Sea
are Campanidaria johnstoni, Plumularia pinnata, Lafoea diimosa.
INVERTEBRATE BOTTOM FAUNA 499
Fig. 352.
Thujaria thuja, L. (After Hincks. )
500 DEPTHS OF THE OCEAN
except the sea - anemones already referred to/ which are
universally distributed over the central portion of the North
Sea, namely dead-men's fingers {Alcyonmin digitatuni) and the
sea-pen Virgidaria mirabilis. The former generally consists
of irregularly shaped ramifying masses attached by the base to
other substances, but in the area examined by the " Michael
Sars " during 1904, in depths between 2)^ and 96 metres,
temperature 10° to 6.15° C, there was an interesting variation
in its relation to its foundation. An annelid [Sabel/a pavonid),
commonly met with here, inhabits an upright muddy tube
attached at the lower end. The whole length of this tube was
covered by the dead-men's fingers, which in some instances grew
out from the lower end of the tube into the usual irregularly
ramifying masses. This symbiosis was no fortuitous occurrence,
but was invariable throughout the whole of the central portion
of the North Sea where these two forms are everywhere to be
found." On the coasts of Scotland and Jutland, on the other
hand, Alcyoniwn occurred in its ordinary form. The common
Virgularia mirabilis, found at depths of 50 to 100 metres,
with a temperature of 7°-8° C, was the only sea-pen met with
in the area examined, but we obtained a fairly large number
of individuals.
Sponges constitute a group of attached forms abounding
in individuals, though remarkably poor in species ; they cannot
be said to be regularly distributed, but are more or less local.
On the north side of the Great Fisher Bank in particular
we got enormous quantities of a ramifying whitish form
[Halickojidria panicea van bibitla)} The different variations of
Ficulina {^Siiberites) fiats are, however, the most prevalent.
The commonest of these variations, where the sponge grows
round shells and gives shelter to the hermit crab Pagiiriis
pubescens, are comparatively scarce in the central portion of
the North Sea, and we came across them at only one or two
stations, but in the more northern parts of the North Sea
plateau they were plentiful. Another variety, attached to
empty shells of the sea-tooth [Anfa/is entalis) which as a rule
shelter the gephyrean Phascolosoma strovibi, was abundant at
^ Urttcina crassicornis, Metridiuin dia>it/uis, chiefly found on large shells of Mytihis modiolus
and NepUinea, Boloccra tuedia and Chondradinia digitata on shells of Neptunea and Sipho ; at
one or two stations (depth about lOO metres, temperature slightly over 6° C. ) we got Zoatithns.
^ Several of these overgrown tubes were empty, which looks as if the worm benefited least
by the symbiosis.
^ Thanks to information kindly sent me by Professor Plate, Berlin, I can add H. panicea
forma typica as being common on the Great P'isher Bank ; this form was also abundant on the
northern slope of the Dogger Bank.
INVERTEBRATE BOTTOM FAUNA
501
several stations, for instance on the northern slope of the Dogger
Bank (38 metres) and north-west of the Great Fisher Bank
{']'] metres).
The Httle tube - worm Filigrana implexa, whose slender
white irregular tubes are associated in trellis - work colonies,
was met with over a large portion of the area examined, but
only in the deeper parts. Another common form is Tkeieptts
circi7tnaius, whose sinuous, parchment-like tube, covered with
fragments of shells, grains of sand, etc., is attached to foreign
substances such as empty
mussel - shells, Flustra, etc.
The annelid Aphrodite acu-
leata is characteristic of the
North Sea, but is as a rule
limited to the deeper parts
with soft or "mixed" bot-
tom, though nowhere found
in any great quantity. I
have already stated that
Sabella pavonia is common,^
and, speaking generally, we
may say that as far as worms
are concerned the central
portion of the North Sea
does not differ typically from
the boreal portion of the Nor-
wegian Sea.
One peculiarity of the
deeper parts of the central
North Sea is that on soft
bottom there is an absence
of the foraminifera so plenti-
ful in the Norwegian fjords
very minutely the contents of the fine sieves through
bottom-material was passed.
It has been mentioned that in the southernmost portion of
the North Sea, off the coasts of Belgium, Holland, and south-
eastern England, there are many forms of southern origin,
which are absent in more northerly latitudes ; some of them,
however, find their way farther north than the others, though
all keep to shallow waters with high temperatures. ^' ' '
Fig. 353-
Cory5tescassivelanus,Wo\\l. ,5 Reduced. (After Bell.)
this I can assert after examining
which the
This is, for
1 On deep soft bottom we found representatives of the MaldanidK, as well as Eiimenia
crassa, Trophom'a glauca, Lnmbrinereis, and N'ephthys, which we also find on the coasts.
502 DEPTHS OF THE OCEAN
instance, the case with the crab Corystes cassivelanus (see Fig.
353), the mussel Mactra stultorum, the shelled snail Natica
catena, and the tube-worm Sabellaria alveolata, all of which were
found west of Jutland to the north of lat. 56' N. The last
mentioned was met with at only one station (depth 41 metres,
temperature 8.7" C), but in large quantities and big colonies;
while the other three were taken in shallow water (less than
40 metres) with the highest temperatures observed during the
cruise (10° to 12^ C). The characteristic ribbon-like egg-clusters
of Natica were found as far out as the northern slopes of the
Dogger Bank, where the animal itself had been previously
captured. According to Professor Plate both Natica catena and
Mactra stultorum occur on the Great Fisher Bank, which shows
that these forms do sometimes leave the coast region. On the
other hand, Corystes seems exclusively to follow the coasts of
Britain and Denmark, since we did not capture it with our
trawl on the Dogger Bank, though depths and temperatures
appeared to be favourable, and it has not been recorded at any
great distance from the coast. These forms are found along
the shores of Britain, and penetrate into the northern part of
the Kattegat, but, if we except Mactra stultoru7n, they do not
reach the coast of southern Norway.
Our knowledge regarding the faunal character of the North
Sea may be briefly recapitulated as follows : In the southern-
most portion, at depths down to 40 or 50 metres, where the
water-layers in summer attain a temperature of 13°-! 5' C, but
in winter are cooled down to 4 or 5 C, the fauna consists
partly of northern elements capable of adapting themselves to
variations of temperature, and partly of a special southern
contingent that has wandered in through the English Channel
and requires high temperatures for at any rate part of the year.
Most of these latter forms are limited to the southernmost
portion, though a few follow the coasts towards the north,
penetrating on the east side even to the Skagerrack, and on the
west side to the coasts of Northumberland or perhaps still
farther, but avoiding the deeper parts of the central area. The
northernmost portion of the plateau, where the depths exceed
100 metres, but where, notwithstanding, the waters are warmer
than in the central parts, is characterised in similar fashion, as
we shall presently show, partly by special southern deep-water
forms that have wandered in past Shetland and only very rarely
get as far as the coast of Norway or the Skagerrack, and partly
by forms which may either have arrived originally from the
INVERTEBRATE BOTTOM FAUNA 503
south, or else are true natives, nowadays at any rate widely dis-
tributed throughout the northern seas. Most of the forms met
with in the central portion are also to be found along the
coasts, but numbers of forms frequenting the coasts, especially
shallow-water forms, do not inhabit the plateaus.
We have not at present sufficient information to describe in
detail other plateaus in depths less than 100 metres. The
" Michael Sars " occupied two stations in 50 to 100 metres, off
south-eastern and south-western Norway, where the fauna did
not appear to differ from that in the outer part of the fjords and
in the island belt. Certain forms (for instance Balanoglossus,
taken off Risor on the south-east coast) have, however, not
been taken in the western fjords nor in the central North Sea,
but they have been recorded from the west coast of Sweden
(Bohuslan). At the localities mentioned we were able to
observe the remarkable fact that certain forms (for instance
Echinus esculentus, Asterias rudens, Ophiothrix fragilis) occur
in comparatively deep water, while in the fjords and island
belts they generally occur in the littoral zone only.
The investigations of C. G. J. Petersen in the Skagerrack
show, as far as we can judge from his short statements, a marked
similarity to the conditions prevailing in the North Sea. At
present it is impossible to enter into a detailed account, and we
can only state that along with the similarity there are certain
discrepancies : thus, for instance, the pennatulid Pennatula
phosphorea has not been captured by the " Michael Sars " in the
central North Sea, but it is frequent on the Norwegian North
Sea plateau and in the Kattegat.
2. Continental Plateaus covered by more than iog Metres of
Water. — The different lands bounding the Norwegian Sea and
North Sea form the emerged portions of larger or smaller
submarine plateaus. The bottom on these plateaus varies con-
siderably, though, generally speaking, it may be described as a
mixture of stones and rock together with fine or coarse sand ;
only exceptionally, and in the deeper portions, is it composed of
mud. The character of the bottom renders investigations
extremely difficult, and the fauna is therefore not so well known
as that of the fjords. Where the bottom is covered with
softer material the fauna resembles that of the fjords. This
is particularly the case in the Norwegian depression or gut, Norwegian
running parallel to the Norwegian coast from the latitude of ^^^p^^s^^""-
Stat to the Skagerrack. The depth in the middle averages
504 DEPTHS OF THE OCEAN chap.
approximately 300 or 400 metres, till we come to the inner
portion of the Skagerrack where it increases to about 700
metres. The bottom consists of soft mud throughout, except
for a long narrow strip of stones and rock that penetrates its
north-eastern portion. On the one side the depression is
bounded by the Norwegian coast-plateau, which is here only a
few miles wide, and on the other side by the plateaus of the
North Sea and Skagerrack.
During the cruise of the " Michael Sars " in 1902 investiga-
tions were made with the trawl and dredge in its northern
portion, the principal forms found being as follows : —
Echinoderms : SticJiopus tremiihis (in quantities), Bathyplotes tizardi^
Cucinnaria hispida, MyriotrocJms vitreus, A mphiura norvegica, Ophioscolex
glacialis, OpJiiura sarsi, Aster onyx loveni (on Funiculind), ScJiizaster
fragilis, Bj'issopsis lyrifera, Spatangus rascJii, Psilaster andromeda,
Pontaster tenuispiniis.
Crustaceans : PontopJiilus norvegicus, Pandalus bonnieri.
Ascidians : Ascidia obliqua.
Molluscs : Abra longuallis, Malletia obtusa, Portlandia lucida,
Axiniis flexuosus, Pecten septeinradiatus, Sipho islandicus, Scaphatider
punctostriatus, Antalis agzlis, SipJionentalis tetragona, Caduliis
subftcsiforni is. ^
Worms : Lumbrinereis fragilis, LcEtinonice filicornis, Aricia sp.,
Terebellides str'dmi.
Gephyreans : Sipunadus priapuloides.
Ccelenterates : Bolocera ttiedzce, Actinostola callosa, KopJwbelemnon
stelliferuiii^ Fiinicidina quadrangularis , UlocyatJius arcticiis.
Sponges : Thenea muricata.
Also the foraminifera AstrorJiiza and RJiabdamniina, though these
are not numerous.
These animal forms make it tolerably certain that the fauna
in the Norwegian depression is practically identical with the
Atlantic fauna in the boreal region of the Scandinavian
peninsula, and closely resembles the fauna of the western
fjords of Norway. Petersen's researches have revealed
similar conditions in the deepest portion of the Skagerrack.
But along with the fjord forms, which exceed the others in
numbers, there is a fauna in the Norwegian depression composed
of forms seldom or never occurring among the skerries and in the
fjords, but having their home on the plateaus of the open sea.'^
^ On the other hand, Mesothuria intestinalisYiz.'i not been found by the "Michael Sars"
nor by other Norwegian and Danish Expeditions.
^ This species was found by the Norwegian North Atlantic Expedition.
3 To this fauna I assign the following forms : — Echinoderms : Spatangus raschi, Pontaster
tenuispimis •■, Molluscs: Sipho islandicus, Antalis agilis ; Crustaceans: Pandalus bonnieri;
Coelenterates : Ulocyathus {Flabelliim) arcticus.
INVERTEBRATE BOTTOM FAUNA 505
In the depression these are all common enough to be regarded
as an essential part of the fauna. Spatangus rascki, for
instance, appears never to approach the coasts or to enter the
fjords, but keeps to the deeper parts of the plateaus where it
takes the place oi Spatangus pttrpuretts ; it has also been found
by the " Michael Sars " on the continental slopes south of the
Faroe Islands. Pontaster te^iiiispimts only exceptionally enters
the fjords of West Norway to the south of Stat, though it is
found now and then in the Trondhjem fjord, and during the
cruise of the " Michael Sars " in 1902 it was found at the mouth
of the Sulenfjord near Aalesund.^ Antalis agilis and Pandalus
bonnieri are only met with occasionally in the fjords,^ and
Ulocyatlms arcticus belongs to the forms which do not enter
our more southerly enclosed fjords, but may be met with in the
more open northern fjords as far as the North Cape ; it has
also been found, according to Norman, on the Shetland
plateau.
All or most of the forms enumerated as belonging to both
the fjords and the plateaus, as well as those which chiefly or
exclusively belong to the plateaus, may be met with as far north
as Lofoten, and probably extend to the North Cape. The
Norwegian North Atlantic Expedition came across many of
the forms that inhabit the Norwegian depression and fjords in
deep muddy hollows on the plateau north of Stat, and some of
the forms occur on muddy bottom upon the outer slopes of the
continental edge wherever the temperature is above 0° C.
One peculiarity of the Norwegian depression still remains to
be mentioned, namely that a deep trench extends along the north-
eastern side to about the latitude of the Sogne fjord, approxi-
mately 400 metres deep, where experiments with lines revealed
a true hard-bottom fauna of corals (Paragorgia, PrijJinoa) and
sponges ; the "Michael Sars" found this to be the case in several
places in the trench.^ It is strange that this deeper portion is not
full of mud like the adjoining shallower parts, since usually we
find a reversed state of things, hard bottom rising up out of the
^ Pontaster tenuispimis is found in two variations of colour, namely a rather pale form of
weak structure, which belongs exclusively to the warm area, and a deep-red form much more
stoutly built, which as a rule seems to belong to cold areas, though reddish individuals of weak
structure occur also in warmer waters.
'^ A good many individuals of Pandahis bonnieri, which used to be regarded as rare, have
lately been found in the Norwegian depression and in the fjords north of Stat. It is of
interest to state that the Danish research vessel "Thor" has found large quantities off
South Iceland. It has also been discovered in the fjords near Bergen during certain years in
varying quantities.
* Large well -developed colonies oi Lophohelia prolifera were found on the plateau near Stat>
together with other forms that are characteristic of such localities.
5o6 DEPTHS OF THE OCEAN
surrounding mud, and we can only conclude that the bottom
here must be scoured by the action of currents.
Some very interesting discoveries were made by the
"Michael Sars " in 1904 in a southern part of the depression
between lat. 58° and 59^" N., at a depth of 292 metres, the
temperature being 5.83° C, where the young-fish trawl brought
up a quantity of amphipods, cumacea, Euchcsta norvegica,
etc. Among these forms there were two that were particularly
noticeable, namely Epimeria loricata, of which there were
many specimens, full-grown as well as young, and Acanthozone
cuspidata, of which there was one young specimen. Both these
species were hitherto only known to exist in more northern
latitudes, the former not having been met with to the south of
the Malangen fjord, and the latter not south of the Trondhjem
fjord, where several other arctic forms have their southern
limit. ^
The faunal conditions on hard bottom and on sand at the
upper part of the Norwegian depression, from about 100 metres
down to considerable depths, are very like those in the Nor-
wegian fjords, but differ in many respects from those of the
central parts of the North Sea. The sponges resemble those
taken on hard bottom in the deep parts of the fjords. Among the
hydroids there was S er hilar e lla gay i, a form that is absent from
the central portion of the North Sea, but is one of the com-
monest deep-water hydroids of the fjords. Crangon alhtanni
and Pa7idalus aftmilicornis again were represented only by young
individuals in the central portion, whereas at the edge of the
depression our appliances brought up numbers of full-grown
specimens. Other forms that we failed to find in the central
area, but which occurred on the edge of the Norwegian
depression, were : Hippasterias plana, Solaster endeca and
S. papposus, Antedon sp., Psoitis squamahis, Nymphon stromi (of
which we secured only one solitary specimen in the central
portion, in spite of repeated trawlings and dredgings, though
quite common on the edge of the depression), Crania anomala
(common), Porella (characteristic of hard bottom in the fjords),
as well as one or two other bryozoans, Scaphander punctostriatus,
^ The following are a few of the other forms taken at the same time, showing that the boreal
fjord and plateau forms occurred together ; several of them are met with in the arctic region,
and may perhaps be of arctic origin : — Amphipods : Epimeria cornigera, Pardalisca abyssi (in
quantities), Lilljeborgia Jissicornis, Khachotropis (two or three species). Cumacea : Eiidorella
emarginata, Canipylaspis verrucosa and C. horrida, Hemilamprops cristata. Isopods : Apseudes
spinosus, Munnopsis typica, Rocinela dammoniensis. Decapod crustaceans : Pontophilus
norvegicus, Pandalus bonnieri, Hippolyte polaris, Bythocans siinplicirostris, Caridion gordoni.
Molluscs : Rossia sp., Torrellia vestita, Portlandia tenuis, Pecten hoskynsi, Cardium jnininnun.
Echinoderms : Ophioscolex glacialis, Aniedon tenella. Worms : Filigrana implexa (in quantities).
INVERTEBRATE BOTTOM FAUNA 507
etc. It must, however, be clearly borne in mind that there were
many forms common to both areas, — partly those which belong
to the entire boreal region, and partly those which are ex-
clusively or nearly always found on the plateaus.
As already stated, the bottom on the plateaus rarely, and Fauna of the
as a rule only in deep hollows, consists of soft mud, being for
the most part coarse or fine sand, sandy mud, stones, and rocks.
The stony bottom usually predominates near the outer limits of
the plateaus, or continental edge. Investigations by Rasch in
1844 and by Sars in 1871 made it clear that large round stones
and pebbles are to be met with on the Great Edge to the west
of Aalesund at a depth of about 200 metres, and the " Michael
Sars " also found round stones and pebbles there, as well as on
continental
edge.
Fig. 354.
Dorocidaris papillata, Leske. Reduced. (After Diiben and Koren. )
the rather less sharply defined edge of the Faroe plateau ; in
the latter locality the dredge brought up from a depth of about
400 metres a mass of loose round stones.
The character of the fauna on the edges of the boreal
plateaus, judging from what we have found on the Faroe and
the Norwegian plateaus, is fairly uniform. Owing to the nature
of the bottom we meet with attached forms, particularly sponges
(for instance Oceanapia robusta), hydroids, corals, brachiopods,
and bryozoans, together with a number of unattached forms,
of which the echinoderms are the most characteristic. Among
brachiopods we get Crania anotnala, Terebratulina caput-
serpentis, Waldheimia cranitwi, and W. septaia, the last of
which inhabits the plateaus of the open sea and never or
only exceptionally enters the fjords. The same is the case
with several echinoderms: Dorocidaris papillata (see Fig. 354),
5o8 DEPTHS OF THE OCEAN
for instance, easily recognisable owing to its long thick spines,
is one of the most characteristic forms of the plateaus and
especially of the edges, but hitherto not found within the
fjords ; a characteristic brittle-star, Gorgonocephalus lamarcki,
is also a plateau form, represented within the fjords by
Gorgonocephalus linckii. One species of Echmus {E. acutiis
forma norvegiciis) is often found in quantities, and far exceeds
the fjord form in size. There are also the following brittle-stars,
some of which are found in large quantities : Ophiacantha
abyssicola and O. bidentata, Opkiactis abyssicola, all three of
which are pure coast forms that do not go far up the fjords,^
Ophiopholis acideata, Ophiura sarsi, Ophioscolex glacialis, and
O. purpurea, which are commonly found on the edges and are
also fjord forms. During a cruise of the " Michael Sars " in
1902, the lines on the Faroe Edge yielded a large number of
molluscs {Sipko glaber, or a very similar form), which attached
themselves to the bait, but they seem to occur in such abundance
only in a few localities. The tubeworm Placostegus tridentatus
is frequently found attached to the stones, and a deep-
water barnacle (Verruca stromi) also, both of them being
characteristic of the rocky bottom in the deep parts of the
fjords ; and on the spines of Dorocidaris there is now and then
a Scalpelhun. There are large quantities of the little mussel
Anomia, which is also commonly found in the fjords. Corals,
too, are found locally on the edges just as much as in the fjords,
and the species are the same.-'
The spaces between the stones are filled with sandy mud,
so that the forms accustomed to soft bottom may be found
there. How many of the characteristic species occur on the
edges cannot be stated with certainty, but probably many, if
not most, of the forms belonging to the soft bottom of the
plateaus inhabit the edges also, though not in such great
abundance.^
My reason for mentioning the fauna of the plateau-edges
separately is, not that the forms constitute a separate faunal
^ This is true of the Norwegian fjords south of Stat, though these species, like several others,
have been found in the Trondhjem fjord.
'^ The dredge brought up branches of Primnoa, Paragorgia, Paraspongodes, Lophokelia, and
Amphihelia ; also Sertularella gayi, Allopora, sponges, masses of Ophiacantha hidentata,
Ophiacantha abyssicola, Ophioscolex purpurea, Ophiactis abyssicola, Gorgonocephalus. V)^^-^-
sea individuals of jS'it/^/w^/j- £j-,^///£«/?« were found both by Sars and by the "Michael Sars "in
1906, though as a rule they differed in shape from those found in the middle of the North Sea.
^ Of the forms found by G. O. Sars, by the Norwegian North Atlantic Expedition, and by
the "Michael Sars" on the Great Edge and its northerly continuation, as well as by the
"Michael Sars" on the Faroe Edge, we may mention Stichopus tremulus, Spatangus raschi,
Echinocyamus pusillus, Schizaster fragilis, Astarte sulcata, Porowya granulata, Liiiiopsis utinitta,
Onuphis, Nephthys, and other annelids, etc. ; all these forms belong to soft bottom.
INVERTEBRATE BOTTOM FAUNA 509
region, — though, probably owing to the influence of currents,
forms Hke Dorocidaris and Waldheimia septata seem to find
their most favourable conditions of existence there, and con-
sequently are extremely abundant, — but because the plateau-
edges are the limits of distribution between the fauna inhabiting
the plateaus and the totally distinct fauna of the deep central
basin of the Norwegian Sea known as the "cold area." To
avoid misunderstanding I may repeat that on the steep slope
below the actual edge, and down to a depth of 600 or 800
metres, that is to say, to a depth where the temperature does
not fall below 0° C, forms belonging to the boreal fauna may
be met with. Still these slopes are as a rule so precipitous in
comparison with the wide plateaus that, topographically, one
is almost entitled to look upon the edges as a boundary region.
The bottom of the slopes below the edge itself seems to consist
nearly everywhere of soft mud dotted over with large-sized
stones, thus providing a home for both mud-bottom forms and
hard-bottom forms.
I have stated that we are still only imperfectly acquainted Fauna of the
with the fauna on the bottom of sand and stones upon the p'^*^^"^-
plateaus, as only a few systematic investigations have been
undertaken here and there. But we know enough to conclude
that from a zoo-geographical point of view it is similar to that
of the muddy bottom, consisting partly of forms that are common
to both the plateaus and the fjords, and partly of forms peculiar
to the plateaus which do not enter the fjords. The latter,
however, like the corresponding forms of the muddy bottom,
are comparatively few. This is confirmed by some dredgings
made by the "Michael Sars " in 1906, when researches were
carried out on several parts of the Norwegian plateau.
Without attempting a full description of the lower animal-
forms on the plateaus, we may refer to a few of the principal
ones. Several hauls by the " Michael Sars " with the trawl in
1902 and 1906 showed an abundance of animal life in the
northern portion of the North Sea Plateau, on hard sandy
bottom (probably mixed with small stones) at depths of 150
to 200 metres, belonging to both fjord forms as well as
plateau forms : —
There were numbers of Spatangus (especially vS. rascJii in the greater
depths), Echinus acutus forma norvegicns, and Dorocidaris papillata,
forms characteristic of the edges, also considerable quantities of Asterias
rubens, Porania pulvilhis, Goniaster borealis (?), Echinaster sanguinolentus,
Pontaster tenuispinus, Stichaster roseus, Hippasterias phrygiana {plana),
5IO
DEPTHS OF THE OCEAN
Ophiopholis aculeata, OphiotJirix fragilis, Nephrops norvegicus, Pagurus
bernJiardus and P. Icevis, Rossia macrosoina, Pecten septemradiatus and
P. opercular! s, Oceanapia robusta, Ficulina ficus (with Pagurus pubescens)
as well as many other sponges. Occasionally we got Sipho islandicus,
Natica sp., Neptunea antiqua (with Chondr actinia digit atd), Bolocera
tuedics, Halipteris christi, Atelecyclus septemdentatus, Inachus dojynchus,
Portunus tuberculatus, Galathea nexa, Pagurus vieticulosus, Onuphis
tubicola. Nereis sp., Stichopus treniulus, Brissopsis lyrifera, Luidia ciliaris,
Ophiura ciliaris, Ascidia
venosa, etc.
This list shows that
several forms found in
the Norwegian depres-
sion and on the deep
muddy bottom occur
here also. Two crus-
taceans [Hyas coarctatus
and Munida rzigosa, see
Fig. 355) should be
noticed in particular, as
they inhabit the plateau
in large numbers, and
seem to furnish an
important supply of
food to the larger kinds
of fish ; they were both
also taken by the trawl
in 200 metres on the
Norwegian coast - bank
off Stat. In addition we
secured a couple of star-
fishes [Pout aster tenui-
spinus and Astropecten
irregu I arts), while
brachiopods, bryozoans,
chitons, etc., were attached to the stones. Among the
amphipods we noticed species of the genus Hoplonyx, immense
numbers of which sometimes collect on dead fish or baited
lines.
British investigators have made the plateau round the
Shetland islands, to a depth of about 200 metres, one of the
most familiar.^ Most of the Shetland forms are identical with
those occurring in the Norwegian boreal region, but we do
^ For details see Report of the British Assoc, 1868, pp. 232-342.
Fig. 355.
MiDiida rugosa, Fabr.
INVERTEBRATE BOTTOM FAUNA 511
not find there many of the forms that on the west coast of
Norway are chiefly distributed in the great depths of the fjord ; ^
there are also certain forms living in deep water at the Shetlands
having a southern distribution, Atlantic or Mediterranean
forms which find their northern limit there. These differences
may to some extent be due to the warm Atlantic water which
flows over the Shetland plateau ; thus the " Michael Sars "
found a temperature of 9, 12° C. on the western edge at a depth
of 300 metres, and captured with a line a southern shark
(Hexanchus griseus), frequently taken by British fishermen,
which has never been caught farther north in the Norwegian
Sea, It is interesting to remark that some of the forms, though
no doubt only stray individuals, make their way eastwards along
the northern portion of the North Sea plateau as far as the
edge of the Norwegian depression, beyond which, however,
they never pass, like the crab Portunus tuberculatus ' and the
starfish L7iidia ciliaHs, which were captured on the northern
slope of the Viking Bank. Others penetrate even into the
Norwegian fjords, like the hermit crab Pagurus meticidosus
{tricarinatus), and the crab Atelecyclus septemdentatus, small
individuals of which were captured on several occasions in the
Bergen fjord. Some of the southern forms occurring off the
Shetlands wander down along the east coast of Scotland and
England, though without spreading farther eastwards, and we
find the same faunal agreements and dissimilarities between
the east coast of Britain and the west coast of Norway as in
the case of the Shetlands.
Certain parts of the plateaus, at a depth of 100 to 1 50 metres,
seem to be favourite abodes of the hydroids, which form regular
forests on the bottom, and are plentifully represented by both
species and individuals. Just as with the hydroid fauna in the
laminaria tracts, so here, too, an assemblage of other animal
groups, especially lower crustaceans and naked molluscs, live
upon and among these hydroids.^
The hydroids appear to occupy comparatively large tracts
of the plateaus, though not regularly distributed over their
^ For instance, Stichopus treinitlus, Bathyplotes tizardi, Amphiura norvegica, Pandalus
propinquns, Mimida temdniana.
^ A specimen of this species was also taken on the deeper part of the slope, in 275 metres,
with a temperature of 7-94° C.
^ Characteristic and common forms of hydroids were : Thujaria thuja, easily recognisable
owing to its verticillate branches, Hydrallmannia falcata, Diphasia abietina and D. fallax,
Sertularellatrkuspidata, Lafoea s])., Canipmiidana volubilis. Among the lower crustaceans it
is especially the caprellids {.-Eginella spinosa) and the arcturids {Astacilla longicornis and
Ardiirus sp.) which climb about among the hydroids by means of their specially adapted feet.
/Eolids too creep about here in great numbers.
512
DEPTHS OF THE OCEAN
Fig. 356.
Rhizocrinus lo/otensis, G. O. Sars. Magnified.
(After Wyville Thomson.)
whole extent. They thrive
well apparently on sandy
bottom, wherever it is covered
with fragments of shells, to
which they may attach them-
selves, and this is even better
seen in the central portion of
the North Sea. The " Michael
Sars " found hydroid-bottom,
of the kind described, on the
northern portion of the North
Sea plateau, on the Faroe
plateau east and west of those
islands and on the large bank
to the south of them, on the
Iceland-Faroe ridge, and on
the south-eastern Iceland
plateau.
A number of species be-
longing to different groups,
which among the skerries and
in the western fjords of Nor-
way are littoral forms, or at
any rate only occasionally
descend below the lower limit
of the littoral zone, occur at
greater depths out on the
plateaus, where they are some-
times very plentiful.
During the cruise of the
"Michael Sars" we found on the
eastern Faroe plateau, at a depth
of 1 10 metres, on sandy shell-
strewn bottom : Cucumaria fron-
dosa, Strongylocentrotus droba-
cktensis, Pandalus atmulicornis,
Pagurus bernJ tardus, Asterias
rubens, Mytilus modiolus, Bucci-
nuin undatuin, Alcyoniuvi digi-
tatum, and on the Faroe Bank,
south-west of the Faroe Islands,
at about 125 metres, Echinus
esculentus and OpJiiura albida.
On the banks around the Faroes
beyond the lOO-metres line there
INVERTEBRATE BOTTOM FAUNA 513
were : Spatangus purpureus, Echinocardium, Echinaster sangtiinolentus,
Liiidia sarsi, Hippasterias plana, Ophiopholis aculeata, Ophiothrix
fragilis, Scaphander, Hyas coarctatus, Pagiirus pubescens, Inachus
dorhynchus, Stenorhynchus longirostris, the annelids Thelepus circinnatus
and Leodice norvegica (both very common), etc. Some of these
are mainly littoral forms on our coasts. Inachus dorJiynchus and
Stenorhynchus longirostris seem to have a more westerly distribution than
the rest, the former being very rarely, and the latter never, found near
the Scandinavian coasts, though two , other species {Inachus dorsettensis
and Stenorhynchus rostratus) do occur there ; these four forms are
all met with on the North Sea coasts of Great Britain. From the deep
part of the plateaus we may mention the comparatively rare RJiizocrinus
lofotensis (see Fig. 356), which is fixed in the mud by root-like off-shoots.
One locality examined by the "Michael Sars" in 1902 is Sheii-covered
entitled to special notice, viz. the extensive Faroe Bank to the ^^"^^*
south-west of the Faroes, v^here the bottom at a depth of 100
to 300 metres is peculiar, being quite covered with an enormous
quantity of empty shells of different mussels,^ with a few living
specimens among them.- The empty shells were pure white,
and it was interesting to see how this white colour affected the
other bottom-animals, fishes as well as invertebrates. A couple
of species of Raia, for instance, had large white spots, and a
flounder i^Plezironectes Imianda) had assumed the light colour of
the bottom ; Ophiiira albida, which on our coasts and elsewhere
is of a blackish-brown colour, was here perfectly white, and the
spines of Echi7ius esculentus were far lighter in colour than
usual. Astacilla longicornis, which climbed about among the
hydroids, had on the other hand assumed their green hue.
The geological significance of these shell-covered banks
(there are several round the Faroe islands, and fossil shells are
also found on the Norwegian coast-banks) has been discussed at
considerable length by Professor Brogger.^ They are generally
believed, like the Norwegian coast-banks and the plateaus
round the Shetlands, etc., to have stood at a higher level during
the glacial and inter-glacial periods, forming part of the littoral
region of the sea-floor, and to have since subsided. The fossil
remains of animals that along our coasts nowadays appear to be
able to live, or at any rate to thrive, only in shallower waters
are taken as proof of subsidence, it being assumed that with the
subsidence of the bottom this shallow-water fauna became
extinct.
1 Pecticnculus glycimeris, Venus casina, Tellina crassa. Area tetragona. Tapes eduHs.
2 Pedunculus glycimeris, Venus casina, Tellina crassa, Mactra elliptica, Psatit7Hobia iellinella,
and Dosinia.
^ " Oni de senglaciale og postglaciale nivaaforandringer i Kristianiafeltet (Molluskfaunaen),"
Norges geoL Undersogelse, No. 31, pp. 106, etc., Kristiania, 1900-1901.
2 L
514 DEPTHS OF THE OCEAN chap.
That there must have been considerable alterations in the
physical conditions of the sea on these banks appears evident
from the large decayed shells of an arctic form, Pecten islandicus,
and the remains of other arctic molluscs. The enormous
quantities of empty shells of more southern forms may indicate
that special forces have been at work, resulting in the destruc-
tion of these animals in vast numbers. But, on the other hand,
I consider it too hasty an assumption from a biological point of
view to maintain that, because these forms are in other localities
solely or mainly littoral forms, their extinction must have been
due to subsidence of the ocean-floor. As already mentioned,
the " Michael Sars " dredged from the bank large living
specimens of several of the species represented by empty shells
in such abundance, showing that there is still a possibility of
finding the necessary conditions of existence there. And there
were also some characteristic littoral forms, like Echinus
esculentus, Opkiiira albida and Alcyonhmi digitahtm, of which
the first named was in too great abundance to have been
merely the result of chance.
The occurrence of these forms may perhaps be explained
by the high temperature (9.33°C.) at these depths in the middle
of August 1902 — a temperature differing very slightly from
that prevailing at the same season along the Norwegian coast
in the shallower depths principally inhabited by these forms — for
temperature and salinity more than depth regulate distribution.
An extinct fauna of forms like these at a spot somewhere
out on the plateaus does not necessarily imply subsidence of
the bottom, but more likely physical changes in the sea-water.
Oysters and many other forms are examples of this. A further
instance may be cited from the North Sea cruise of the
" Michael Sars" in 1904. At Jammer Bay, on the north-west
coast of Jutland, at a depth of 14 metres, the dredge brought up
great quantities of Mactra elliptica, Lunatia intermedia,
Ophtura ctliaris, Echinocardiiim, etc., along with a very large
number of empty shells belonging to the mussel Venus gallina,
of which only two living specimens were found. It would be
absurd to assert in this case that mortality was due to changes
of level, as this form is found elsewhere in quantities at such
depths, but the numbers of empty shells point to an encroach-
ment of unfavourable conditions. Another factor must be
kept in view, namely bottom-currents, that may possibly, under
certain circumstances, accumulate bottom-material such as piles
of empty shells at particular localities, which would not
INVERTEBRATE BOTTOM FAUNA
515
necessarily indicate mortality from extraordinary circumstances,
but merely an accumulation, from a considerable area, of
individuals whose deaths were due to natural causes. Although
certain indications along the coasts of our own and other lands
would appear to justify us in regarding currents as a means of
conveyance, we know far too little about the matter to be able
to discuss it with any profit.^
In my remarks regarding the edge of the Norwegian
depression I endeavoured to show that the fauna of this part
of the North Sea differs from that in its more central parts (see
p. 506) ; for this difference, however, the depth, nature of the
Fig. 357.
Nephrops tioti'egicus, L. Reduced. (After Bell. )
bottom, and temperature cannot be held solely responsible.
This difference holds good also for the continental plateau beyond
the 100 metres curve. The " Michael Sars " captured in 1 10 to
150 metres : the crustaceans Nephrops norvegicus (see Fig. 357),
Geryon tridens, Sabinea sarsi, Pontophilus spinosus, Pandalus
brevirostris, Hippolyte pusiola, Caridion gordoni\ the pycnogonids
Nymphon stroiui and N. mixtitm ; the echinoderms Hippasterias
plana (according to Plate rarely found on the Great Fisher
Bank), Solaster endeca, Pteraster viilitaris (two small specimens),
Ophiocten sericeimi (quantities of young specimens) ; the snail
Scaphander punctostriatiis, etc. None of these forms (except
one individual of Nyynphon stromi) were met with in the central
portion of the North Sea. Three of them in particular
1 Compare Heincke, "Die Mollusken Helgolands," Wissensch. Meeresttnterstich. Komni. f.
Untersuchimg Deutsch. Afeere, Neue Folge, Bd. i, pp. i^o et seq.
5i6 DEPTHS OF THE OCEAN
{Nepkrops norvegicus, Nymphon stromi, and Hippasterias plana)
furnish unmistakable evidence of the dissimilarity of these areas,
for they are widely distributed over the North Sea, occurring
even on the coasts of Great Britain in depths both greater
and less than lOO metres, and if they existed in the central
portion of the North Sea, where we frequently towed our
big trawls, they could hardly have avoided capture. Then
why should a considerable part of the central area of the
North Sea be closed to a number of forms more or less widely
distributed elsewhere ? We must, I think, conclude that in
this central area there are special hydrographical conditions
which exclude these forms and their larvae. As a matter
of fact, Helland- Hansen has shown that in the deeper layers
there is a circular current of Atlantic water in the North
Sea, a branch of the Gulf Stream following the east coast of
Scotland, turning north-east just before reaching the Dogger
Bank, and afterwards sweeping northwards on reaching the edge
of the Norwegian depression. As a result, the periphery of the
central portion of the North Sea is bathed by water of much the
same composition as the warmer water of the Atlantic, enclos-
ing an area covered by more stagnant and on the whole colder
water, having a fauna of its own.^ Repeated investigations
will be necessary to ascertain whether this faunal dissimilarity
observed in the summer of 1904 is permanent or not,
Arctic and Boreo-Arctic Regions of the Norwegian Sea
When we speak of an arctic and a boreal fauna it must be
clearly understood that there is not always a distinct line of
demarcation between the two, either in regard to topographical
boundaries or to forms. There are undoubted intermediate
areas, where boreal and arctic forms meet, and many forms
are as much boreal as arctic, being impartially distributed
over either region, and able to thrive amidst very different
natural conditions. It is interesting to note, however, that the
same species sometimes occurs in two distinct varieties, usually
connected by transition forms, and that the varieties conform
to the region in which they occur, a fact indicative in all prob-
ability of the influence of physical conditions upon organisms.
A circumstance that has especially attracted the attention
of arctic investigators is that some animal forms are apt to
^ I must add that the entire northern part of the North Sea plateau is also covered by Atlantic
water.
INVERTEBRATE BOTTOM FAUNA 517
flourish in some localities in such immense quantities as to
displace all others, a phenomenon that may certainly be seen
also now and then in the boreal region, though not to such a
marked extent. Even when several species occur together the
specimens appear to be more numerous than is the case in
the boreal region. On one occasion in the Barents Sea the
" Michael Sars " brought up in a single trawling over a ton of
big sponges [Geodea), and near Jan Mayen at another time
more than a barrelful of Pecten gronlandictis. The prawns
again are sometimes in myriads, and Sars relates that during
the Norwegian North Atlantic Expedition the trawl came up
positively full of the feather star, Antedon eschrichti. One Direct
reason for such enormous quantities of individuals is that many development.
of the arctic animals produce their young fully developed, without
any free pelagic stage, so that in all probability a large proportion
continue to live where they were born.^ Currents, the nature
of the bottom, and conditions of nourishment must also be
taken into account. '''
Nowhere perhaps do we find such a marked contrast between
the boreal and arctic faunas as when we pass from one of the
boreal coast plateaus out into the cold area of the Norwegian
Sea. If we trawl on the plateaus, where the temperature does
not sink below 6° or 7 C, we find a boreal fauna consisting to a
great extent of forms which have migrated into the Norwegian
Sea from southern latitudes. As soon, however, as we come to
the slope of the deep basin (the cold area), at a depth of say
600 to 800 metres,-' where the temperature falls below 0° C,
the exclusively arctic element begins to predominate, and we
meet with species that are almost entirely foreign to the banks
and coasts of the boreal region.
There is the remarkable Umbellula encrinus (see Fig. 358), Arctic fauna
a form belonging to the pennatulids, that may grow several p^Jt^ofX'"'
metres high, with large rosette-like polyps at the upper end of cold area of
the stalk. Of star-fishes we have the beautiful purple Pontaster ^J^egJ^n'^sea.
1 Romer and Schaudinn, Fauna antka, Einleitung, p. 48 ; see also Murray, Trans. Roy.
Soc. Edin., vol. xxxviii. p. 492, 1896.
2 At one locality in the North Sea we captured large numbers of snails ( Sipho gracilis and
Nepttmea antiqiid) and of a sea-mouse (Spatangits purpureus). The first named deposits its
eggs in capsules, from which the young emerge fully developed, a circumstance sufficient to
explain their plentifulness, but Spatangus has floating larvae, so that other factors must have
come into operation. There may be an aggregation of individuals in a limited area without
direct development, provided the larvre are not carried away by currents ; thus our common
ascidian {Ciona intestinalis) often forms large congregated masses owing, as far as I could make
out, to the fact that the eggs sink in large quantities by the mother's side, and develop in a
comparatively short space of time.
^ The depth at which the temperature falls below 0° C. is liable to variation ; north of
Tampen the " Michael Sars" found such temperatures in 1902 at about 550 metres.
5i8
DEPTHS OF THE OCEAN
tenuispimcs, also found on the plateaus and in the Norwegian
depression, the whitish-yellow Bathybiaster vexillifer (see Fig.
359, which in the cold area takes the place o^ Psilaster andro7neda,
^\ :^%''^.
",;i^-??-'
^^teia«^^
its relative of the plateaus and coasts), and in smaller quanti-
ties the semi-transparent Hymenastcr pellucidus (see Fig. 360).
Among brittle-stars the big light-coloured Ophiopleura borealis
and the smaller gray Opkiocten sericeum (also found along the
coasts, though in a slightly different variety) are in greatest
INVERTEBRATE BOTTOM FAUNA
519
^^pr '"^^^^
abundance. The sea-slugs Stichopus tremulits and Mesothuria
intestinalis so charac-
teristic of the deep
parts of our fjords, are
entirely absent, but in-
stead of these forms
with foot-suckers we
have a footless genus
TrocJiostonia (see Fig.
361). The sea-mice
are represented by
Pourtalesia (see Fig.
362), a very remark-
able genus that in
some respects re-
sembles forms long
extinct, but Spatangus,
Ech in oca rdui ;?z and
Brissopsis (character- fig. 359.
istic of our fiords and BathyHastervexillifer,^y.Thoms. Reduced. (After Bell. )
coast-banks), and the ordinary sea-urchins are no longer to be
found. Huge sea-
lilies or feather-
stars [Antedon
esckrickti, see Fig.
363, and A. pro-
/za'rt;), and quantities
of the medusa's
head [Gorgono-
cephalus eiicnemis),
are attached most
likely either to Um-
belhda or to the
numerous sponges,
Cladorhiza sp.,
whose hard central
axis and tree -like
ramifying shape
make it so conspic-
uous, someof which
sometimes form
regular thickets
There are gigantic representatives of the
Fig. 360.
Hytnenasier pellitcidus, Wy. Thorns,
Michael Sars,
along the bottom.
520 DEPTHS OF THE OCEAN
pycnogonids or sea-spiders, Colossendeis proboscidea in particular
Fig. 361.
Trochostotna boreale, M. Sars. Reduced. (After Danielssen and Koren. )
being immense, though Nyfuphon robusttwi (see Fig. 364) is the
most numerous and characteristic
species of the cold area, and is
easily recognisable by its semi-
circular prehensile organs, resem-
bling fingers which incline towards
one another. The higher crus-
taceans consist entirely of shrimp-
like forms, such as Sclerocrangon
Fig. 362.
Pourtalesia Jeffrey si, Wy. Thoms.
(After Wyville Thomson. )
ferox{sQ.e. Fig. 365), Bytkocaris, and
Hymenodora glacialis (the last of
which is also found pelagic in the
deeper water-layers), whereas crabs
are very poorly represented in the
arctic areas. On the other hand,
the lower crustaceans, especially
isopods and amphipods, occupy a
very prominent position among
the fauna of the Norwegian Sea
deep basin, as there are numbers
of species, and several attain to considerable size,
Fin. 363.
intedon eschrichti, ]. Mliller.
(After Stuxberg. )
One of the
INVERTEBRATE BOTTOM FAUNA 521
most characteristic of the amphipods is Amathillopsis spinigera
(see Fig. 366), which has an extremely spinose body.^ The
cold area, moreover, like the plateaus and coasts, has its caprel-
lids climbing about among the sponges and hydroids, the most
numerous and common being Caprella spinosissima, whose body
is covered with dense strong spines. Among isopods we get
the remarkable Etcrycope gigantea belonging to a group with
very long legs that easily drop off; it has a relation not nearly
Fig. 364.
Nymphon robusfum. Bell. (After Wyville'Thomson. )
SO big [Mti7inopsis typica) in the greater depths of the boreal
region and widely distributed throughout the arctic seas.
The isopod fauna is further represented, often in consider-
able quantities, by the genera Arcturus (A. baffini, see Fig.
367) and Astacilla (A. granulata).
A sea- anemone, Allantadis parasitica, is another of the
most characteristic forms, attaching itself to the shells of snails
belonging to the species of Sipho and Neptunea.
1 Other amphipods conspicuous owing to their size are Stegocephalus inflalus, the extremely
thick forepart of whose body makes it easily recognisable, Cleippides quadricuspis, with long
spines along the dorsal portion of its posterior segments, Anonyx sp. , etc.
522
DEPTHS OF THE OCEAN
Hydroids are little in evidence ; the vast thickets of these
animals found on the plateaus are absent.^ Alcyonaria are
chiefly represented by the genus Paraspongodes, with its
cauliflower-like colonies, numbers of which also flourish in
tsf;^:?^^
Fig. 365.
Sclerocrangon ferox, G. O. Sars. (After G. O. Sars. )
warmer waters ; apparently the same species occur in both
areas, the most widely distributed being P. fritticosa.
The commonest molluscs are shelled snails of the genera
Fig. 366.
Amat/iillopsis spinigera, Heller. Slightly magnified. (After G. O. Sars.)
Nephmea and Sipko. There are cuttlefishes of the genus
Octopus, though never in any great quantity, and another very
remarkable form is the rare Cirroteuthis miti/eri, one of the
eight-armed group, whose members diff"er from the other in
' The most characteristic representatives of this group, belonging to the family Myriotiielicla-
(genus Lampra), are rare.
INVERTEBRATE BOTTOM FAUNA
523
S^.
having tins ; its arms are united to each other throughout their
whole length by a skin attachment. The sea-tooth (scaphopod),
Sip hono dent alium vitrezcm, is also a very widely distributed form.
In the Norwegian Sea deep basin beyond 2000 metres the
conditions seem as a rule to be less favourable for the develop-
ment of an animal-life abounding in species, as already alluded
to by Sars in his report on the first cruise of the Norwegian
North Atlantic Expedition. The bottom at these great depths
consists of Globi-
gerina (or Bilocu-
lina) ooze, offering
no foundation for
attached forms.
Only a few species
are limited to
these profound
depths, as the
majority occur
also in the shal-
lower areas of the
Arctic region, or
are met with on
the slopes of the
Norwegian Sea
deep basin.
One of the
most character-
istic deep-sea
forms is a sea-lily,
Bathycrinus car-
pent eri, that at-
taches itself to
the soft bottom
by means of the root-like ramifications issuing from its stalk
(this form has a near relation, Rhizocrinns lofotensis, which
occurs in the deeper parts of the boreal region). Another
characteristic echinoderm is a sea-slug, Kolga hyalina, which is
never found in depths less than 2000 metres. Elpidia glacialis
(see Fig. 368), too, must be considered a characteristic sea-slug
of the Norwegian Sea deep basin, though it may from time to
time be met with in the north at lesser depths. These two
holothurians belong to a remarkable group, with few though
very large feet arranged in rows on either side ; they
Fig. 367.
Arctiirus baffi?ii. Sab. With young.
(After Wyville Thomson. )
Fauna of the
abyssal area
of the
Norwegian
Sea.
524
DEPTHS OF THE OCEAN
«-:
occur occasionally in immense quantities. Crustaceans are
represented by a characteristic deep-sea form, namely the
isopod Glyptonotiis megaluriis, nearly related to a form that occurs
in the arctic region in shallower waters ; pycnogonids by
Ascorhynchus abyssi; and molluscs by
Pecten frigidus (see Fig. 369), Nephmea
mohni, Natica batJiybi, etc. There are
also some deep-sea sponges, prominent
amongst which are the Hexactinellids;
although not regularly distributed over
the Norwegian Sea, they are found in
great quantities to the north of Spits-
bergen at a depth of 1000 metres,
where they and another group (Tetrax-
onia) constitute the most characteristic
portion of the fauna. Outgrowths on
their under sides enable them to hold
fast to the soft bottom, which is littered
with silicious spicules from dead
sponges.^ Romer and Schaudinn have
doubted whether the deep-sea fauna
of those northern latitudes is to be
considered zoo-geographically as a part
of the fauna of the Norwegian Sea deep basin, or whether
it belongs to a separate faunal area, the deep polar basin ; deep-
sea sponges have, however, been subsequently found in
quantities farther south (lat. 72 23' N., long.
13 50' W.) at a depth of 2000 metres.-
The forms limited exclusively to the abyssal
region, or at any rate only very exceptionally
occurring in shallower waters, are not the only
ones which characterise the Norwegian Sea deep
basin, for we find regularly also a number of other
forms met with on the slopes in the cold area.^
Just as the Norwegian Sea deep basin has
its own (even though rather few) character-
istic forms, which do not ascend to the arctic plateaus but con-
stitute a typical deep-sea fauna, so, too, the plateaus have a
^ Romer and Schaudinn, op. cit. p. 49.
^ Kolthoff, Till Spetsbergen och 7iord'6stra Gronland, igoo, pp. 212-213.
'^ The "Michael Sars" found at about 2000 metres the echinoderms : Bathybiaster
vexillifer, Ophiocien sericetim, and Pourtalesia ; the mollusc : Siphonodentaliiiin vitretim ; the
crustaceans : Bythocaris leucopis and Hymenodora glaciaUs ; tlie pycnogonid : Nymphon
robustum ; the worm : Lwtibrinereis, etc. The tube-worm, Myriochele, with its fine sand-tube,
belongs to the forms which occur in quantities in the depths of the Norwegian Sea.
Fig
Elpidiaglacialis, Thfel. Magnified
(After Stuxberg. )
Fig. 369.
Pccte?i frigidus,
Jensen. ' ' Michael
Sars," 1900.
INVERTEBRATE BOTTOM FAUNA 525
series of species that do not descend to the profound depths.
These latter may be designated arctic shallow-water forms, or, Arctic
to use a different zoo-geographical description, arctic continental £0^^,^°^"^^^^"^
forms, though it is as well to remember that the depth on the
plateaus averages about 400 metres. As in the case of the
boreal plateaus, so here, too, we can distinguish between forms
that keep entirely to less depths and those which chiefly
inhabit the deeper portions. The bottom conditions of the
plateaus are quite different from those that prevail in the
abyssal region, since hard bottom is to be found as well as soft,
whereas the floor of the deep basin consists almost entirely of
soft materials ; consequently the plateaus have a far greater
abundance of attached animal forms.
Currents, owing to the increased abundance of nourishment
they bring with them, are likewise responsible for the greater
profusion of attached forms on the arctic plateaus. To what
extent they affect the distribution of animal-life may be seen by
comparing the fauna of the west and east coasts of Spitsbergen.
Romer and Schaudinn, who made careful researches in 1898,
found that on the western side non-attached forms, especially
echinoderms, were most in evidence, while on the eastern side,
where strong currents flow through the sounds, attached forms
predominated. Of this latter area Romer and Schaudinn
write as follows : " Most of the rocks and large stones are
covered with barnacles, while monascidians and synascidians
form populous colonies on the bottom. Sponges, which are
scarce on the western side, are represented by numerous
species, and alcyonids inhabit the deeper channels. The
shallower rocky localities accommodate large congregations of
actiniae. The animals, however, which, so to speak, hall-mark
the fauna, and are developed in almost fabulous fashion, are
hydroids and bryozoa. So dense are the thickets formed in
some places by these organisms that the heavy dredge failed
to reach the bottom, and merely brought up animals instead of
bottom-material." Amongst these attached forms, moreover,
there is, just as in the boreal region, a rich fauna of non-
attached forms like worms, crustaceans, and molluscs. Romer
and Schaudinn drew attention to the fact that the worms,
crustaceans, and molluscs, in particular, did not show such a
striking difference in their distribution around Spitsbergen as
other groups, but were, on the contrary, fairly equally distributed
between east and west. Nor are echinoderms absent on the
eastern side, where in fact there are actually more species than
526 DEPTHS OF THE OCEAN
on the west, but in regard to individuals they are very much
exceeded by the attached forms.
A great difference between the arctic region in high
latitudes, where the Gulf Stream has lost its warming influence,
and the boreal region, is to be found in the littoral, or more
correctly in the strand, zones. The luxurious growth of fucus
and laminaria which covers the rocks along the coasts in the
boreal region, both above and below low-water mark, is wanting
in depths less than about 6 metres. This is due to the ice
blocking up the shore for a great part of the year and prevent-
ing the development of animal and plant life. The strand
zones in high arctic latitudes accordingly exhibit nothing but
naked rock, in contradistinction to the rocks of the boreal
region, where we find numbers of attached animal-forms right
up to high-water mark. As soon, however, as we descend
below the limit of the baneful effects of the ice, we meet
with a profusion of both plants and animals, sometimes even
in greater abundance than in the boreal region.
Though we are thus unable to speak of an actual strand-
fauna in high arctic latitudes, we can distinguish, to a certain
extent, between the littoral, or rather sub-littoral, and the deeper
non-littoral forms. The former, however, appear to be compara-
tively few in number, taking 40 metres as the lower limit as we
did in the boreal region, while on the other hand most of the
non-littoral forms reach nearly up to or actually pass the littoral
limit. Generally speaking, the limits between a littoral and
non-littoral zone seem to be less clearly defined in the arctic
than in the boreal region.^ The reason for this is obvious
enough, if we remember that temperature largely controls
distribution. In high arctic latitudes the difference in tempera-
ture between deep and shallow waters is inconsiderable
compared with that at corresponding depths in boreal areas.
As a result the forms find favourable conditions of existence,
so far as temperature is concerned, at very different depths, and
the vertical distribution of most of the arctic forms is far more
extensive than that of boreal forms. A few instances may be
cited : Hymenaster pellticidus in the Norwegian Sea deep
basin is found even below 2000 metres, while on the east side
of Spitsbergen it occurs at 27 metres; Antedon eschrichti v(\2.y
be met with in the cold area of the Norwegian Sea at very
considerable depths, whereas at Spitsbergen it flourishes in
^ Cf. Stuxberg, "Evertebratfaunan i Sibiriens ishaf," Vega-exped. vetenskap. iakttagelser,
Bd. i. pp. 730, etc.
INVERTEBRATE BOTTOM FAUNA 527
18 metres of water, and the same is the case with Ophiocten
sericeum ; Nymphon rohishmi, which even at depths of 2000
metres is the most characteristic pycnogonid of the Norwegian
Sea deep basin, can actually thrive at a depth of 6 metres in the
arctic littoral zone ; Gorgonocephahis eucneniis occurs in the Nor-
wegian Sea deep basin and yet finds itself at home in the arctic
littoral zone. Many similar examples could be adduced, but
special works on the different groups, indicating the depths at
which the various forms have been found, furnish the clearest
evidence. The character of the water in different arctic areas
must also be taken into consideration. Species which almost in-
variably live in water at a temperature below 0° C. will not be
met with in shallow depths except where truly polar water pre-
dominates ; thus on the west coast of Spitsbergen there are
echinoderms found only in deep water, which on the east side
occur very much nearer the surface, owing to the fact that on
the west side the Gulf Stream makes its influence felt to a con-
siderable depth, while on the east coast the water is everywhere
polar. I shall return to the influence of warm currents upon
animal life in arctic tracts.
It must not be supposed, however, that the vertical distribu-
tion in arctic tracts is entirely devoid of system. No doubt there
are a great many forms with a far more extensive distribution than
would be possible in the boreal region, still the arctic plateaus
shelter numerous forms that do not descend into the Norwegian
Sea deep basin, and apparently therefore are unable to thrive in
such deep water. In their case it is evidently not temperature
but other factors that regulate distribution, and besides it is
actually possible to point to a purely littoral arctic fauna, although
its representatives are far from numerous.
Hard bottom as well as soft are to be found in the
deeper parts of the arctic plateaus ; where the bottom is of
mud it differs from the brownish Globigerina (or Biloculina)
ooze of the Norwegian Sea deep basin, being of a grayish
colour like what we find in the Norwegian fjords and on
the boreal coast banks ; in the Barents Sea, however, we get
greenish-gray mud. The arctic mud, like the boreal, contains
many foraminifera, though the species differ to a certain extent.^
We may divide the species composing the arctic fauna into
^ The species named by Kiier {Norwegian North Atlantic Expedition, Thalamophora,
p. 12) as characteristic of the gray mud in northern arctic areas are : Astrorhiza crassatina,
Lagena apiciilata, Ptdvinulina karsteni, Globigerina pacliyderma. Biloculina IcEvis, Globigerina
bulloides 3.nd G. pachy derma, Haplopliragmium latidorsatuiii , Truncatidina wullerstorji, Rotalina
orbicularis, and Lagena apiculata are common in the Globigerina (or BilocuHna) ooze of the
Norwegian Sea deep basin ; some of them belong also to boreal areas.
528 DEPTHS OF THE OCEAN
Purely arctic three catcgories. The first category may be termed purely
forms. arctic, occurring in water having a low temperature all^the year
round. ^ Allowing for slight variations it is safe to assert
that the majority of them require a temperature considerably
below what prevails in the deeper parts of the boreal region
(6° to 7' C), though a few coast and shallow-water forms are able
to exist at higher temperatures for a short portion of the year ;
this is particularly the case with those arctic forms that come
as far south as the Lofoten, Murman, and Finmark coasts.
Still even within the purely arctic areas we find faunal differ-
ences that are due to temperature. Some forms are never, or
very rarely, found in water having a temperature above o° C,
others appear to thrive impartially throughout the whole arctic
region in whatever temperatures prevail, while others again
avoid the coldest water and
keep as much as possible to
temperatures slightly above
o° C.
As regards horizontal dis-
tribution within the arctic
region we may assume that
most of the species are wide-
spread, even if they have not
yet been met with everywhere,
^^^°- 37>3- for we are still only imper-
1 oldia arctica. Gray. (After Stuxbers;. ) r i • i • i i
tectly acquamted with the
fauna over a large portion of the arctic plateaus, especially that
off East Greenland. Some species, however, will undoubtedly
prove to be more or less local, judging from what we have
found in the boreal region.
A few of the larger forms that characterise the arctic coasts
•and plateaus are given in the following list : " —
Molluscs : Margarita cinerea, Onchidiopsis glacialis, Nat tea clausa,
Amauropsis islandica (rarely found on the Norwegian west coast), Nep-
tunea despecta, SipJio curtus, S. turgidulus, S. kfbyeri, S. glaber, Buccinum
glaciale, B. hydrophanuin, B. grdnlandicum, and a few other species of
Buccinum^ species of Beta, Sipho7todentalium vitreuni. Nucula tenuis var.
expansa, Yoldia hyperborea, Y. {Portlandia) arctica (see Fig. 370) and Y.
limatula, Area glacialis, Pecten gronlandicus, P. islandicus, Astarte
{Nicanid) banksi van, A. borealis, and A. crebricostata, Axinopsis
orbiculata, Axinus gquldi, Tellina calcarea (rarely found alive on the
Norwegian west coast, though extremely abundant in the arctic region),
1 There are a few exceptions, for instance, Pecten islaitdkus, Ctenodiscus crispatus,
Onchidiopsis glacialis, which are more boreo-arctic than arctic (see p. 534).
^ In this list I deal only with the molluscs, echinoderms, crustaceans, and ascidians.
INVERTEBRATE BOTTOM FAUNA 529
and a few other species of Tellina, Verms fiucttwsa, Cardium ciliatmn,
C. grojilandicum, Thracia trwicata (rarely found in the boreal region),
Pandora gladalzs. Brachiopods : Rhynchonella psittacea (see Fig. 371),
TerebraUdina spitsbergensis. Echinoderms : Asterias lincki, A. panopla,
A. gr'bnlandica, A. Jiyperborea, SticJiaster albulus, Ctenodiscus crispatus,
Ophiopleura borealis, OpJiiura nodosa, Amphiura sundevalli, Ophiopus
arcticus, Gorgonocephalus eucneniis and G. agassizi, Antedon eschrichti,
A. prolixa, Cuciimaria niinuta, C. glacialis,
Eiipyrgus scaber, Trodwstoma boreale, Ankyro- . — ' -i>.^
derma jeffreysi, Chirodota Icevis, Myriotrochus
rinki. Decapod crustaceans : Sclerocrangon ^
ferox, S. boreas, Sabinea septemcarinata, Hippo- ^^^^^^^ -^-^ V\
lyte turgida and H. spinus, BytJwcaris payeri,
Idotea entonion. Two species of pycnogonids,
Ny nip] ion robustuni and N. Jm'tipes, are very ^ig. 371.
abundant in the arctic region ; the former is Rhynchonella psittacea, Chemn.
largely a deep-sea form, which descends far (After G. o. Sars. )
down into the cold area of the Norwegian Sea
deep basin, whereas N. liirtipes belongs more to the banks and plateaus.
Both species were trawled by the "Michael Sars" on the Jan Mayen
plateau, showing that they may be abundant in shallow waters also.
The largest pycnogonid of the Norwegian Sea is Colossendeis proboscidea,
found both on the slopes of the deep basin and on the banks.
There are also several other species of Nyniphon, such as N. elegans,
N. macronyx, and N. gracilipes, which are
common arctic forms. The hydroids have
comparatively few purely arctic species,
though the magnificent large Tubularia
regalis is one that deserves special notice ;
in congenial localities like the Bear Island
shoal and the banks of Jan Mayen it forms
regular thickets on the bottom. Among
ascidians Dendrodoa {Styela) aggregata (see
Fig. 372) is a very characteristic arctic form,
and is often found in little colonies com-
^^^ , ,5 posed of a number of cohering individuals.
l&^jl,^^' Another characteristic though rarer species
*jj*B* jg Chelyosoma madeyanum, easily recognis-
iG. 372. ^]_jjg owing to its extremely flattened shape
Dendrodoa a^pre^ata, Rathke. 1,1 • . 1 • 1 •. r •
N^t. size. ^"" the squares mto which its surface is
divided. Ciona intestinalis, one of our com-
monest boreal forms, occurs in the arctic tracts as a distinct variety
{longissinia\ The compound ascidians are represented by several
species, amongst which the tuberous Synoicmn incrustatuin, whose
surface is encrusted all over with grains of sand, may be easily recog-
nised. Other forms are Molgula retortiforinis, Amarouciuni niutabile
(tuberous and of a reddish-violet colour), and Sarcobotrylloides aureuni.
The second category of forms in the arctic region is made Arctk-boreai
up of those which are at the same time extensively distributed ^°''""-
k.
530 DEPTHS OF THE OCEAN
over the boreal parts of the Norwegian Sea, and are thus just
as much boreal as purely arctic ; I append a short list : —
Molluscs : Lepeta ccBca, Margarita grdnlandica and M. Jielicina,
Lnnatia grdnlandica, Littorina rudis, CylicJma alba, Leda pernula,
Modiolai'ia Icevigata and M. nigra, Astarte {Nicania) banksi with
varieties, Astarte compressa, L. ( = elliptica, Br.), Mya truncata (chiefly
arctic, whereas ilf. arenaria is the typical boreal form), Saxicava
arctica, Pecten hoskynsi, Portlandia frigida. Echinoderms : Strongylo-
centrotus drdbachiefisis, Pont aster tenuispinus, Echinaster {Cribrelld)
sanguinolentus, Solaster papposus (occurs as a rule in the arctic region
as a distinct variety, ^. affinis), Pteraster inilitaris, Ophiura sarsi and
O. robusta, Ophiocten sericeuni, OphiopJiolis aculeata, OpJiiacantha
bidentata, Ophioscolex glacialis, Cucuinaria frondosa, P solus phantapus.
Decapod crustaceans : Pandalus borealis, Hippolyte gaimardi, and
H. polaris, Pagurus pubescens, Hyas araneus and H. coarctatus.
Isopods : Munnopsis typica. Pycnogonids : Nymphon grossipes (and a
few other species of Nymphon). Ascidians : Pelonaia corrugata, Styela
rustica and 5. loveni, Styelopsis grossularia, and Ascidia prunmn. Worms :
a number of species of HarmotJioe, Lumbrinereis fragilis, Onuphis
conchy lega, Nereis pelagica, Arenicola piscatoruni {marina), Owenia
assimilis, Nicolea zostericola, Thelepus circinnatus, and Terebellides str'bmi.
These forms are very interesting biologically, as they show
to how great an extent the same species is able to adapt itself
to different natural conditions. Many of them ^ are quite
common in the littoral zone of the boreal region, where during
a large portion of the year the temperatures are comparatively
high, and yet they are also to be found in arctic tracts, where
temperatures are all the year round below o C, or at any
rate not more than a few degrees above o*" C. during a very
short period. Others, again, are more consistent, as they
inhabit only the greater depths of the boreal region, where
throughout the whole year the temperature is fairly uniform and
comparatively low (though never sinking below 6^ or 7 C),
whereas in the arctic region they exist in shallow water ; thus
on the Norwegian west coast we find the mussel Porllandia
frigida, the brittle-star Ophiacantha bidentata, and the prawn
Hippolyte polaris (see Fig. 373) only as a rule beyond 100
metres, whereas in high arctic latitudes they may be met with
at a depth of about 10 metres. The species included in this
second category do not all by any means show the same dis-
tribution throughout the arctic region ; some forms occur every-
^ Margarita grdnlandica and M. helicina, which both occur in the boreal laminaria belt,
Saxicava arctica, Strongylocentrotus drobachiensis, Echinaster sanguinolentus, Ophiopholis
aculeata, Cucumaria frondosa, Hippolyte gaimardi, Pagurus pubescetts, Hyas, Styela rustica,
Nereis pelagica, Arenicola, Nicolea, etc.
INVERTEBRATE BOTTOM FAUNA 531
where in both the arctic and the boreal regions, while others are
generally limited within the arctic region to water having
temperatures just about or above o' C. These last are inter-
mediate forms between this and the following category, and
include, for instance, the prawn Pandalus borealis.
A third category of species composing the arctic fauna con- Boreal forms
sists of boreal forms that are able to enter the arctic region a^-cJlc'^"'^"
owing to the warmth introduced by various branches of the distribution.
Gulf Stream, which counteracts the chilling effects of the icy
coastal and polar currents. On the coasts of East Finmark
and on the Murman coast these are particularly in evidence.
These boreo-arctic intermediate areas occupy that portion of
the Norwegian Sea where the waters of the Gulf Stream and
polar currents intermingle, or where the shallow coast waters
(r^^
FUJ. 373.
Hippolyte polaris, '^ah. Reduced. (After Parry. )
acquire a high summer temperature in consequence of the
comparatively milder climate produced by the proximity of the
Gulf Stream.
This boreo-arctic area contains certain forms of truly arctic
origin, less sensitive in regard to temperatures above o'' C, and
attaining here the extreme limits of their advance in a boreal
direction. It also contains genuine boreal species, which may
range as far south as the Mediterranean, and have their
northern limit within this area.
,. Along the north-west coast of Norway from Lofoten to the Boreo-arctic
North Cape (West Finmark) the character of the fauna is very ^''^^^•
complicated, owing to the diversified hydrographical conditions,
especially in the deeper places of the coastal area compared
with those in the inner basins of the fjords. Many of these
north-western fjords are open to the ocean for part of their
length, so that their seaward portions may fairly be regarded
532 DEPTHS OF THE OCEAN
as inlets, while their landward portions are cut off by submarine
barriers which are often comparatively shallow. As a con-
sequence the warm water of the Gulf Stream flows along the
bottom of the fjords till it reaches the barriers, but is unable to
penetrate into the inner basins, which are therefore greatly
affected by climate, their water-masses at comparatively shallow
depths being stagnant and at a low temperature. We find
accordingly an arctic fauna predominating in the inner basins,
while the boreal forms met with on the coast and in the sea-
ward portions of the fjords in corresponding depths are for the
most part absent.^ Still there are arctic forms in these latitudes
along the coast in the shallow waters of the littoral (and sub-
littoral) zones, where climatic conditions occasion low tempera-
tures for at any rate part of the year. The fauna at greater
depths along the coast, on the other hand, is purely boreal
owing to the influence of the Gulf Stream. We are accord-
ingly justified in regarding Lofoten as the southern limit of the
boreo-arctic area, so far as the coast tracts are concerned,
even though the boreal element preponderates there, and
similarly we are entitled to call the inner basins of the fjords
boreo-arctic, although in their case it is the arctic element that
predominates.-
The coastal areas and fjords east of the North Cape (East
Finmark) are altogether boreo-arctic. The fjords here are open
arms of the sea, in which there is no distinction between the
fauna of the outer and of the inner portions, and, owing to the
intermingling of Gulf Stream and polar waters, the purely boreal
character of the fauna predominating in West Finmark is absent
even in the deeper parts. Moreover, the farther east we go and
away from the influence of the Gulf Stream the more do these
conditions assert themselves, the fauna becoming gradually
more and more purely arctic. A comparison between this area
and large parts of one of the best-known areas in high arctic
latitudes, namely Spitsbergen, shows how perfectly justified we
are in calling it boreo-arctic, for we find a fauna on the Murman
coast which, in addition to purely arctic species, includes littoral ^
^ G. O. Sars, " Some Remarks on the Character of the Marine Fauna along the Northern Coasts
of Norway," Tromsd Museums Aarshefter II., 1879, p. 60; Nordgaard, Hydrographical and
Biological Investigations in Norwegian Fjords, Bergen, 1 905.
^ It must be distinctly stated, however, that this fauna is made up mainly of forms which,
although undoubtedly of arctic origin, are distributed over both the boreal and arctic regions ;
whereas the purely arctic forms are comparatively few. These Qord areas are entitled to be
characterised as boreo-arctic owing to the presence of a small number of purely boreal forms
with boreo-arctic distribution otherwise.
^ Purpura lapilhis, Littorina littorea, Nacella pellucida, Mytilus edulis, Tellina baltica,
Asterias rubens, Balaiius balanoides, Crangon vulgaris, Dynamena puinila.
INVERTEBRATE BOTTOM FAUNA 533
and deeper-living ^ boreal forms that are never met with at
Spitsbergen.
Another boreo-arctic area lies in the south-western portion
of the Norwegian Sea on the ridge connecting Iceland and the
Faroes. The crest of the Wyville Thomson Ridge between the
Faroes and Shetland has not been examined by the "Michael
Sars," but undoubtedly it may be included. On the broad ridge
between the Faroes and Iceland we took up several stations
in 1902, at a depth of 450 to 480 metres, the temperature varying
between 3.12° C. and 3.98° C. ; the greatest depth on the top of
this ridge is about 500 metres. Here we came across the same
mixed fauna already described as characteristic of the north-
eastern boreo-arctic area, the "Michael Sars" securing
distinct arctic forms,- together with boreal forms ^ which
penetrate into the boreo-arctic portion of the Barents Sea. If
we remember that the polar and Atlantic currents meet about
the middle of the Iceland-Faroe ridge, it will be easy to
understand the boreo-arctic character of the bottom fauna. It
is remarkable that such distinctly cold-water forms as Hyme7iaster
and Nymphon robtistum were found in water with a temperature
of 3° or 4° C. ; no doubt the individuals were few (only one
specimen of Nymphon robushim, for instance, being taken), still
their occurrence seems to show that the bottom-water on the
ridge has not always the high temperatures we recorded — the
temperatures must often be considerably lower, perhaps even
below 0° C. at times.* Boreal deep-water forms are furthered in
their advance occasionally by warm currents, and yet they can
endure low and varying temperatures ; the converse probably
holds good with various purely arctic forms, which owe their
distribution to the cold arctic water, but can endure the higher
temperatures when that is displaced by Gulf Stream water.
In spite of this Hymenaster and Nyuphon robusttwi are just as
much arctic forms 2isHippasterias, Pentagonaster, diwd Pontophilus
are boreal forms.
^ Antalis entalis, Schizaster fragilis, Hippasterias plana, Pentagonaster granularis.
Verruca strovii, Hippolyte securifrons, Crangon alhnanni, Nephrops norvegicus (?), Fottiophilus
norvegicus, Munida negosa, and several others. The hydroids, on the other hand, are very widely
distributed, as most of the species met with in these tracts are commonly distributed throughout
the boreal region ; some species of hydroids seem able to adapt themselves to all temperatures
(eurythermal forms).
- Hymenaster pellucidus, Solaster squamatus, Antedon esckrichti, Rhachotropis aculeata,
Epimeria loricata, Nymphon robustum, Lampra purpurea.
^ Hippasterias plana, Pentagonaster granularis, Schizaster fragilis, Antedon tenella,
Gorgonocephalus lincki and G. lamarcki, Pontophilus 7wrvegicus, Sabinca sarsi, and amongst
hydroids Thujaria thuja and Hydrallmanuia falcata, although not in any great quantities.
•* The Danish " Ingolf " Expedition recorded a temperature of +0.5° C. at about 510
metres.
534 DEPTHS OF THE OCEAN chap.
I have already stated that the north and east coasts of
Iceland are boreo- arctic areas. Even as far south as lat.
64° 17' N. and long. 14° 44' W., that is to say, quite close in to
the coast, the " Michael Sars " found purely arctic forms at a
depth of 75 metres, namely, the prawn Sclerocrangon boreas and
the ascidian Molgula retortifoinnis, together with forms that are
either widely distributed throughout both regions, or are boreal
with a boreo-arctic distribution.^ Here again, therefore, the
character of the fauna was evidence of the meeting of the
two great currents, the
East Iceland Polar
Stream and the At -
lantic Stream.
Before leaving the
arctic fauna I have
still to mention a few
characteristic forms,
which penetrate for a
short distance into the
boreal region along the
coast of Norway. The
starfish Ctenodiscus
crispatus is found as
far south as Christian-
sund, where it occurs
in enormous quanti-
ties; and another star-
fish, Leptoptychaster
arctictisi' has its south-
ern limit in the Trondhjem fjord. A very characteristic arctic
species of mussel, Peden islandiais (see Fig. 374), is very
numerous and of large size in the Trondhjem fjord, and may
be met with even farther south, while the same fjord is the
southern limit for the molluscs Onchidiopsis glacialis, Dendro-
notus velifer, and a few others. We have thus another instance
of the difficulty in fixing definite boundaries for the different
regions. The Trondhjem fjord shelters too many forms which
^ I append tlie names of a few forms : — Ascidians : Ascidia obliqiia, Peloiiaia roryugata,
MacrocUnum poinunt (numerous), Distoma aystallimim. Crustaceans : Hyas coairtaitis,
Pagurus, Pandaliis atimdicornis, Hippolyte polaris, Crangon allnianni, Arciurus sp. Echino-
derms : Asterias ricbens, Echiuaster sanguinolentus. Pycnogonids : Pycnogonum littorale,
Nytnphon mixtum, N. hirtipes. Coelenterates : Metridium dianthus, Cory7norpha glacialis,
Ttibularia indivisa (common), Hydrallmannia falcaia, and a few other hydroids. Also some
sponges and worms.
^ The peculiarity about this form is that it lives mainly in boreo-arctic areas, and is thus
neither purely arctic nor purely boreal.
Fk;. 374.
Pecten islandicus, L. Reduced.
\fter G. O. Sars. )
INVERTEBRATE BOTTOM FAUNA
535
Fig. 375.
Tridoiita borealis, Chemn.
(After G. O. Sars. )
do not enter the boreo-arctic area to be designated an inter-
mediate area. Possibly both Ctenodiscus crispatiis and Leptop-
tychaster arcticus Hve chiefly in isolated basins, where the tem-
perature for part of the year sinks lower than in the other parts of
the fjord, though I do not know that
this has actually been confirmed.
Occasionally too we find in far
more southern areas a few forms
that must be considered purely
arctic, although they are quite accli-
matised and plentiful. They are
survivals (relicts), and date from the
glacial age when the northern seas
were inhabited by an arctic fauna.
The milder climate which succeeded
the glacial period brought about the
elimination of all those species that are now purely arctic, and
such forms are at present practically limited to arctic tracts.
Only a few were able to adapt themselves to the altered con-
ditions,^ and are to be found to this day
in isolated areas, located outside the
range of this chapter, though owing to
the interest attached to them, they
may be briefly alluded to.
There is, for instance, the mussel
Astarte {Tridonfa) borealis (see Fig.
375), large quantities of which are
found in the arctic tracts from Lofoten
northwards. In the south we do not
find it till we come to Oresund, The
Belts, and the Western Baltic, where
it is very plentiful. In the interven-
ing waters it is merely a stray guest,
having been found once or twice in
the neighbourhood of Bergen. The
survival forms include also a few crus-
taceans, for instance, the isopod Idotea entoinon (see Fig.
376), some worms, and a sea scorpion {Cothis quadricorms),
which are mostly to be found in the Baltic, and in a few lakes
of North Europe that were connected with the sea in the
glacial age.
^ On the other hand there are, as already stated, a number of forms from the glacial age
which became thoroughly acclimatised, and, in contradistinction to the relict-forms, are
widely distributed throughout both regions.
Fig. 376.
Idotea entomon, L. (After Stuxberg. )
536 DEPTHS OF THE OCEAN
Deep-Water Fauna of the North Atlantic
It is easy to see how much the configuration of the bottom,
and the hydrographical conditions associated with it, affect the
distribution of animal-forms, if we compare the fauna of the
Norwegian Sea north of the submarine Iceland - Faroe -
Shetland and Iceland-Greenland ridges, with the fauna of the
Atlantic Ocean to the south of these ridges. Thanks to the
painstaking researches of the Danish " Ingolf" Expedition,
and the subsequent investigations of the " Michael Sars " in
Fig. 377.
Calvcria hystrix, Wy. Thorns. Reduced.
(After Wyville Thomson.
1902, we are now acquainted with the principal characteristics
of both. The chief hydrographical differences in these two
marine areas are due to the intervening ridges, covered on an
average by 550 to 600 metres of water, which prevent the icy
bottom water of the Norwegian sea from entering the Atlantic,
and conversely the warm Atlantic water from flowing over the
floor of the Norwegian Sea.^ Two temperature-readings are
sufficient to make this clear : in 1902 the " Michael Sars" found
a temperature of -0.41" C. in the Faroe-Shetland channel at
^ On the other hand, the Atlantic and Tolar currents meet, as already stated, over the
Iceland -Faroe ridge.
INVERTEBRATE BOTTOM FAUNA 537
a depth of 11 00 metres, while at a similar depth hardly a
^1
^^
,k
degree farther south the temperature was as high as + 8.07"^ C.
538 DEPTHS OF THE OCEAN
Such great temperature differences produce a corresponding
dissimilarity in the fauna (see pp. 13 and 661). We have trawled
in the cold Norwegian Sea deep basin and captured more or less
familiar arctic forms, and then only a few hours steam farther south
we have trawled again on the southern slope of the Wyville
Thomson Ridge, and taken forms, fishes as well as inverte-
brates, which one would expect to find in quite southern areas.
Among the deep-water forms of the Atlantic that are
present in large quantities on the southern slopes of the ridges
and plateaus we have first some species of sea-urchins belonging
to the remarkable family of the Echinothuridae (see Fig. 2>77)-^
They differ from all other sea-urchins in the structure of their
shells, for, instead of having continuous plates of lime, their plates
are connected by non-calcareous attach-
ments of skin, so that their shells are
flexible and more or less like leather.
One species of holothurian, Lcstmogone
violacea, is very abundant. It belongs
to the same division as the forms Elpidia
and Kolga, which are so plentiful in the
Norwegian Sea. The " Michael Sars "
also found large numbers of the star-
fish Zoroaster fic/gens (see Fig. 378).
The following are a few other
forms met with on the southern slopes
of the ridges : —
Regular sea-urchins : Echinus alexandri
and E. affinis, Porocidaris purpuvata. Irre-
gular sea-urchins : UrecJdmis naresianus, Pourtalesia wandeli, Echinosigra
pldale, Hemiaster expergitiis. Starfishes : BatJiybiaster rolmstus (a species
which outwardly resembles B. vcxUlifcr of the Norwegian Sea, though
the structure of its skeleton is different),- Plutonaster bifrons, Benthopecten
spinosus (see Fig. 379), Pentagonaster perrieri, Solaster abyssicola.
Ophiurids : Ophiopleura aurantiaca, OpJuomusium lymani, Amphiura
denticulata. Coelenterates : EpizoantJius paguripJnhis (in symbiosis with
Parapagurus pilosimanus, see Fig. 380), the ^enmXuYids Ant hoptdum mur-
rayi and UmbeUula lindaJdi, the true corals StephanotrocJms diadema (see
Fig. 381) and Flabelluin sp. (see Fig. 382), the \iOX\\-zox7>\'s, Acanthogorgia
annata and Strophogorgia challengeri. Decapod crustaceans : Lispogna-
tJms tho7nsoni, ScyramatJna carpenteri^ Geryon affinis, Cymonomus normani,
Neolithodes griinaldi, Parapagiirus pdosimanus, Munida microphthalma,
Munidopsis curvirostra, Uroptydius rubro-vittatus, Polycheles sculptus and
Fk;. 380.
Epizoanthus paguriphilus, ii
osis with Parapagurui
manus. Reduced.
Sars," 1902, 750 metres
I symbi-
pilosi-
Michael
^ The species occurring here include Phormosoina placenta, Calveria [Asthenosoma) hystrix,
and Sperosoma grinialdii.
^ According to J. A. (irieg, Conservator of the Bergen Museum. .
INVERTEBRATE BOTTOM FAUNA
539
P. nanus, NepJiropsis atlantica. Molluscs: Dentaliuni caudani and others.
Sponges : Pheronema carpenteri (see Fig. 383).
Fig. 381.
S/epkanotrochus diadema, Moseley. " Michael Sars," 1902, 750 metres.
This list is very far from complete, but it shows what a number
of forms there are which do not belong to the Norwegian Sea.
ir
|.i4.iif
Flabellum sp.
Fig. 382.
Michael Sars," 1910, Station loi, 1853 metres.
Besides these specifically Atlantic forms, the fauna on the
southern slope of the ridges and plateaus comprises others
familiar to us from the boreal region of the Norwegian Sea,
and from the North Sea, where they occur either on the plateaus
or in the deeper parts of the fjords. Including : —
540 DEPTHS OF THE OCEAN chap.
Sea-slugs : Stichopus tremulus, Bathyplotes tizardi, and Cucumaria
hispida. Starfishes: Psilaster andromeda, Astrogonium pareli, Pteraster
multipes, Peltaster nidarosiensis, Brisinga coronata and B. endecacnemos.
Pheronema carpenteri, W's. Thorns. Reduced. (After Wyville Thomson. )
Brittle-stars : Ophiacantha abyssicola, Ophiactis abyssicola, Ophiocten
sericeum, Asteronyx loveni (on Funiculina quadi'angularis), Gorgono-
cephalus lincki. Sea-mice : Spatangus raschi, Schizaster fragilis. Sea-
lily : Rhizocrinus lofotensis. Crustaceans : Munida tenuimana, Pasiphcea
INVERTEBRATE BOTTOM FAUNA
541
Fig. 384.
Deima fastosum, Th^el. " Michael Sars,
Station 48.
tarda, Pontophilus norvegicus, Pagurus pubescens, Calocaris macandrece,
Geryon tridens. Worms : ApJwodite aculeata, Lcetnionice filicornisy
Lumbrinereis fragilis. Brachi-
opod : Waldheiniia septata (in
large quantities).
This list also might
easily be extended. We
see, therefore, that the
fauna in the continental
(archibenthal) deep - sea
area of the Northern At-
lantic consists partly of
species peculiar to it, and
partly of others that regu-
larly belong to the con-
tinental deep-sea fauna of
the Norwegian Sea. Two
questions arise : How is
the Atlantic archibenthal
(and abyssal) fauna distri-
buted outside the Nor-
wegian Sea.'^ Is there any real resemblance between this fauna
and its counterpart
in the cold area of
the Norwegian
Sea?
There seem to Limits of the
be some reasons for ^^j;;^^'"'^"'
fixing the lower
limit of the archi-
benthal fauna at
about 2000 metres,
and the upper limit
at about 800 or
_ ^ 1000 metres. The
^jt^ \| \| V V - charts of the area
's^^^^l^Sr south of the ridges
Kj^ published by the
Danish " Ingolf "
Expedition show
that beyond 2000
metres the slope of the bottom becomes less steep downwards
to the vast abyssal plain whose upper limit may be put some-
j^-M^jV"^^
Fig. 385.
Peniagone tvyvillii, Thfel. " Michael Sars," 1910, Station 53,
2615 to 2865 metres.
542
DEPTHS OF THE OCEAN
where between 2000 and 3000 metres ; the temperature at the
same time falls to about 2-^° C, which prevails everywhere in
Fig. 386.
Oneirophanta sp. "Michael Sars," 1910, Station 10, 4700 metres.
the abyssal tracts of the Atlantic and other non-arctic waters.
The upper limit certainly presents greater difficulties, but I
^^,.
4C
Fig. 387.
Freyella sexradiata, Perrier. "Michael Sars," 1910, Station 10, 4700 metres.
believe that a great many of the forms which characterise the
archibenthal belt do not as a rule extend into depths less than
INVERTEBRATE BOTTOM FAUNA 543
800 metres, though it is quite possible that certain forms may
be met with at 600 metres. We have not yet acquired sufficient
knowledge of the factors regulating vertical distribution to be
able to divide the different parts of the Atlantic into vertical
zones, and a division of this kind will, I fancy, always be more
or less a matter of personal opinion. Besides, it is undeniable
that forms which properly belong to the abyssal fauna may find
their way to the lower parts of the archibenthal zone, and that
Fig. 388.
Salenia hastigera, Agassiz. Reduced. "Michael Sars," 1910, Station 88, 3120 metres.
archibenthal forms may go down into the abyssal region, while,
given favourable conditions, certain littoral and sub - littoral
forms may descend below the upper limits of the archibenthal
belt. In any case there is no clearly defined boundary between
archibenthal and abyssal areas.
Real abyssal forms are, for instance, the following : Deima Abyssal forms.
fastosum (see Fig. 384), Peniagone wyvillii (see Fig. 385),
Oneirophmtta sp. (see Fig. 386), Freyella sexradiata (see Fig.
387), and Salenia hastigera (see Fig. 388), the last mentioned
being found, however, also in the archibenthal zone.
I have already stated, with regard to the horizontal dis-
544 DEPTHS OF THE OCEAN
tribution of the Atlantic deep-sea^ fauna, that some of the
forms occur likewise in the deeper parts of the boreal areas of
the Norwegian Sea. This, however, refers only to a small
proportion, since the majority consist of specifically Atlantic
forms which do not cross the boundaries of the Norwegian
Sea. As to the distribution of this specifically Atlantic fauna
opinions differ. One very prevalent view is that, throughout
the North Atlantic at any rate, temperatures, salinities, and
other external physical conditions are extremely uniform, and
that consequently the various forms have a correspondingly
extensive distribution. Certain facts seem to me to contradict
this, for instance, in such well-known groups as the echinoderms
and decapod crustaceans, of which there are numbers of species.
Mortensen's work on the North Atlantic echinids, and Koehler's
description of the material collected by the Prince of Monaco,
show that the West African coastal seas shelter 28 species of
echinids, and that immediately to the south of the ridges 21
species of the same group have been trawled by the " Ingolf "
and "Michael Sars." In all these two areas yielded 39-
species, but not more than 10 of them are common to both.
We find much the same position of affairs when we compare
the deep-sea fauna of the European or African Atlantic
side with its counterpart on the West Atlantic (American)
side.^ Merely taking the echinids, which may be regarded as
specifically belonging to the archibenthal-abyssal fauna on both
sides, there are altogether 74 species, but only 24 of them are
common to both areas. The other groups of echinoderms
have not yet been so carefully studied, but we know enough
to show that in their case, too, a similar difference exists between
these archibenthal-abyssal areas of the Northern Atlantic.
If we take decapod crustaceans the result is still the same.
The northernmost portion of the European Atlantic area
immediately south of .the ridges has been examined by Danish
and Norwegian expeditions at many stations, and 15 archi-
benthal-abyssal species of Brachyura and Anomura have been
discovered at depths of 1000 to 2000 metres, while the
researches of the Prince of Monaco, and the " Travailleur '" and
" Talisman " Expeditions, have resulted in 40 species being
found at the same depths in West African Atlantic waters ;
1 I wish to make it clear that in what follows no distinction will be made between the archi-
benthal and abyssal faunas, unless expressly stated, but would merely remark that the bulk of
the species belong to the archibenthal zone.
- I have omitted one or two species that have a very extensive bathymetrical distribution,
inasmuch as they occur also in the littoral and sub-littoral zones of the coastal areas.
* No account has here been taken of pelagic deep-water forms.
INVERTEBRATE BOTTOM FAUNA 545
there are altogether 45 species in the two areas, 10 oi which
are common to both. A comparison between the West
Atlantic (American) and the East Atlantic (European- African)
deep-sea crustaceans shows an equally small number of common
forms.
These instances show that, in spite of temperatures and
salinities appearing identical in widely separated localities, it is
possible to distinguish between the faunal communities of the
deeper tracts of the ocean, and we perceive accordingly that
temperature and salinity are not the only factors which regulate
the distribution of species. Unquestionably there are other
physical conditions which are of considerable importance, and it
must further be remembered that biological factors, such as
competition between species, exert a decided influence.^
Murray showed in 1895 that the results of the " Challenger "
Expedition afforded no confirmation of the opinion that a
universal deep-sea fauna was spread all over the floor of the
ocean ; he compares the catches at six deep-water stations
scattered over the Atlantic, Pacific, and Southern Oceans,
the total number of species recorded being 290, but not a
single species was common to the six stations."^ At the same
time we must remember that whole groups of forms, showing
common characteristics in bodily structure, and belonging to
types quite distinct from the littoral ones, belong either entirely
or principally to the deep sea. These types are as a rule
very extensively distributed, even if their species and genera
may be limited to more circumscribed areas. Among fishes,
for instance, we have the Macrurus-type, which is to be found
in all the greater depths of the oceans of the world, although
particular species have a comparatively limited distribution.
The big group of holothurians known as Elasipoda is a
particular type, separated in all essentials from the littoral and
sub-littoral forms of holothurians. They belong almost entirely
to the archibenthal and abyssal tracts of the different oceans,
and are often abundant enough to give a distinct character
to the deep-sea fauna. The same is true also of the Echino-
thuridae, though in their case there are littoral and sub-littoral
species ; some species, however, have a comparatively limited
distribution. Among crinoids we find survivals from remote
ages of the earth, namely, the stalked genera [Rkizocrimis,
Bathycrinus, Pentacrinus, etc.), as typical inhabitants of widely
^ I must, however, point out that in all probability some faunal groups show a greater
uniformity in widely separated localities than others.
- See Summary of Results Chall. Exp., p. 1438.
2 N
546
DEPTHS OF THE OCEAN
separated areas of the deep sea. And so, too, we could mention
deep-water types of particular structure in the case of most of
the invertebrate classes.
Now as these types are distributed over a large portion
of the great oceans, and occur there sufficiently generally to
give the deep-sea fauna its character, it is fair to assert that
this fauna is more uniform than the fauna of the littoral and
sub-littoral zones. As is well known, we get great differences
in the physical conditions of the different areas of both littoral
and sub-littoral zones, consequently we find there greater varia-
tions of the fauna than in the deep sea, where physical conditions
are uniform, or, in other words, there are more coastal faunal
areas than there are deep-sea faunal areas.
We may briefly characterise the deep-sea fauna as follows :
It is largely composed of groups of forms, which morphologically
differ in many essentials from the types of the littoral fauna.
These groups are distributed over very extensive tracts of the
deep sea, but the different species (genera, families) within
the groups may be limited to more circumscribed areas. It is
evident, therefore, that we can distinguish between the various
faunal areas of the deep sea, though we may not yet be able to
fix their boundaries.^
The second question is how far the deep-sea fauna of the
Atlantic resembles that of the Norwegian Sea, or in other
words whether the Atlantic area with its higher bottom-
temperatures shares many species with the " cold area " of the
Norwegian Sea. As indicated on p. 13, Murray in 1886
summarised the results obtained in the Faroe Channel by the
" Lightning," " Porcupine," " Knight Errant," and " Triton "
Expeditions, and showed that of 385 species recorded from the
"warm" and "cold" areas, only 48 species (or 12J per cent)
were common to both areas. ^'
The Lycods are especially characteristic of the cold area
of the Norwegian Sea, whereas the Macrurids are typical
of the deeper parts of the Atlantic, and Jungersen has drawn
attention to the abundant horn-corals and joint-corals (Gorgonids
and Isids) as well as the "star-corals" {Octilina, Amphihelia)
and other corals of the Atlantic deep water, none of which occur
in the Norwegian Sea deep basin.
The finding of such differences in the general character of
i.
^ In regard to the boundaries, however, the cold area of the Norwegian Sea forms an ex-
ception, and the same may possibly be true of the Antarctic deep sea (Chun, Atts der Tiefe des
WelUne.eres ; Mortensen, Echinoidea of the " Tngolf" Expedition).
'^ See also Murray and Tizard, Proc. Roy. Soc. Edin., vol. xi. p. 638, 1882.
INVERTEBRATE BOTTOM FAUNA 547
the two faunas led to a closer examination of certain forms
which had formerly been looked upon as common to both areas,
and as a result the Danish zoologist Jensen came to the con-
clusion that not a single species of Lycodes belonging to the
cold area occurs in either the Atlantic or the boreal parts of the
Norwegian Sea. He further succeeded in showing that one of
the most characteristic mussels of the cold area, formerly
designated Pecten fragilis and included as such among the
fauna of the Northern Atlantic, is in reality a form peculiar to
the cold area of the Norwegian Sea, and he has accordingly
named it Pecten frigidus. Other naturalists have made similar
discoveries in the case of a number of other forms. Thus, the
irregular sea-urchin of the Norwegian Sea, P ourt ale sia Jeffrey si,
is quite distinct from the Atlantic forms of the same genus.
The characteristic starfish of the Norwegian Sea, Bathybiaster
vexillifer, was formerly said to be distributed throughout
the Atlantic, but it is now known to be different from the
Atlantic form, which is Bathybiaster robiistzis. Another starfish,
Pontaster temcispinus, is represented by different varieties in
the two areas, and the same is true of the ophiurid Ophioden
sericetuji. The one characteristic pennatulid of the Norwegian
Sea, Unibellula encrintis, is not found outside that sea, though
there is a species closely related to it in the Atlantic, namely,
Umbelhtla li?tdak/i. Further evidence of the difference in the
two areas is supplied by a pycnogonid belonging to the genus
Colossendeis. A form in the Norwegian Sea deep basin,
Colosseiideis ano^usta, is said to occur also in the Northern
Atlantic, but if we compare Atlantic and Norwegian Sea speci-
mens we immediately recognise considerable differences in
their structure, the latter being much more robust and furnished
with shorter legs and claws. Any one seeing the two forms
side by side would be able to tell the respective areas from
which they came, though it may be difficult to find sufficient
dissimilarities to designate them separate species.
^hese are merely a few instances. It must be admitted Coidarea
that nothing like a complete comparison of the species has yet Norwegian
been made, but we know enough to justify us in looking upon Seaanarctic-
the cold area of the Norwegian Sea as a distinct deep-sea faunal ^ ^^^^ ^'^^^'
region, which with Mortensen and Jungersen we may term the
arctic abyssal.^ No doubt, this arctic-abyssal region owes its
1 In my description of the fauna in the cold area on pp. 517-524, I have made a distinction
between the continental slopes and the abyssal region below 2000 metres, but no such distinction
has been made here, for in instituting a comparison between the fauna of the cold area and the
fauna of the Atlantic, I have included everything below 800 metres.
548 DEPTHS OF THE OCEAN chap.
distinctive character chiefly to the low temperature of its bottom
water, and to its isolated position due to the submarine ridges,
which are responsible for the low temperature.
Though the cold area of the Norwegian Sea must be re-
garded on these grounds as a separate faunal region, it un-
doubtedly had formerly more direct connection with the deep
water of the Atlantic. The many closely allied species in both
Sea and North areas point to a common origin. Most probably the fauna was
Atlantic. ^^ ^^^ ^j^^ homogeneous in both areas, and the bottom water
of the Norwegian Sea had then the same temperature as we
-find in the Atlantic nowadays. When physical conditions
changed in the Norwegian Sea, either owing to the formation
of the submarine ridges or from other causes, the fauna re-
sponded in two ways. Some of the warm water forms, including
a number of present Atlantic forms, died out, while others were
able to adapt themselves to the altered physical conditions and
survived. Their adaptation, however, led to morphological
alterations in the species, and in some cases these alterations
were considerable enough to produce distinct species differing
from the primitive Atlantic forms. Naturally, the isolation
brought about by the submarine ridges had much to do with
the development and establishment of their characteristics. In
fact, it seems like an experiment carried out by nature herself
on a large scale, and shows that external conditions can probably
alter the bodily structure of a species, and consequently give
rise to the formation of new species and varieties.
To understand properly the composition of the fauna in the
Norwegian Sea at the present time we must go back to the
Glacial Age, when uniform arctic conditions prevailed, and the
fauna was everywhere arctic. This is confirmed by the marine
deposits of the Glacial Age, containing exclusively arctic animal
forms, met with in what are now boreal areas. When sub-
sequently the ice melted, and the climate became milder, southern
forms were able to immigrate, gradually distributing themselves
throughout the boreal (and boreo-arctic) waters.
The question as to what happened to the arctic fauna of the
Glacial Age admits of a thoroughly satisfactory answer. In
areas which at the present day are arctic, we still find arctic
species, but in boreal areas the changes have been great.
Some of the arctic forms which formerly inhabited what
are now boreal areas have gradually died out from failure
to adapt themselves to the new conditions ; their remains may
INVERTEBRATE BOTTOM FAUNA 549
be seen in glacial deposits, though they no longer live in the
neighbourhood. Considerable numbers of the arctic species
have succeeded in adapting themselves to the altered conditions,
and constitute at the present day a regular portion of the
boreal fauna, being at the same time distributed throughout the
arctic region ; these are the arctic-boreal forms.
The present-day fauna of the Norwegian Sea thus consists
of two elements of different origin: (i) an endemic arctic
element, and {2) a southern element derived from the littoral,
sub-littoral, and the deeper parts of the Atlantic and Medi-
terranean. Thus we may divide the present-day fauna into
groups, as follows : —
(i) One group consists of two categories of endemic arctic
forms, viz. the purely arctic species, and the arctic-boreal species
widely distributed throughout both arctic and boreal waters.
Both categories existed everywhere in the Norwegian Sea
throughout the Glacial Age, but only species of the last-named
category have since been able to adapt themselves to the boreal
areas. These species, therefore, in contradistinction to the
remaining boreal forms, are of genuine arctic descent ; that is to
say, when a species occurs normally in both arctic and boreal
areas, it is as a rule arctic in its origin.
The purely arctic species are not generally limited to the
arctic region of the Norwegian Sea, but are usually widely
distributed over the other arctic seas as well. Very frequently
they inhabit all the areas round the pole (European, Asiatic,
and American), and are in that case designated cir'ciimpolar
species. The arctic-boreal species have precisely the same
arctic distribution, but within the boreal region their southern
boundaries have strict limitations ; the bulk of them on the
European side never leave the Norwegian Sea, being absent
from the coast banks south of the British Islands and deeper
parts of the Atlantic,^ owing to the physical differences of the
sea-water. A great many of the arctic-boreal forms, in boreal
areas at any rate, inhabit the littoral or sub-littoral zone along
the coasts and in the North Sea, and it is precisely in these
zones to the south of the English Channel that the hydro-
graphical conditions (and especially the temperature) differ
^ There are, however, a few exceptions to this rule in the case of archibenthal and abyssal
forms, some arctic-boreal deep-water species being distributed throughout the northern Atlantic
as far as the Azores, including among others the echinoderms Cribrdla sangidnolenta, Pontastef-
tenuispimis var. , and Ophiacantha bidentata. An explanation may perhaps be found in the
fact that the temperatures in the deeper boreal areas of the Norwegian Sea and Atlantic are fairly
alike and uniform.
550 DEPTHS OF THE OCEAN
most from those of the Norwegian Sea. It seems, then, that
the arctic-boreal species have not been able to adapt themselves
to such conditions, or in other words that their power of
adaptation is limited.
Outside the Norwegian Sea the species of this group
have another area of distribution on the western side of
the Atlantic, north of Cape Cod. The cold polar current
sweeps down over the shallow parts of the American coast, and
produces conditions that vary from arctic to boreo-arctic. As
a result we find there arctic species, such as normally occur in
the boreo-arctic areas of the Norwegian Sea and similar waters,
and also the majority of the arctic-boreal species of the
Norwegian Sea, a few of the latter being found as well a
little to the south of Cape Cod, where conditions are more
boreal.
(2) The second group consists of the boreal species, that is
to say, those species which are limited to boreal areas within
the Norwegian Sea, and those which are able to penetrate as
well into boreo - arctic areas, though not into arctic tracts.
Most of them are widely distributed over the northern
Atlantic, either in its littoral and sub-littoral or in its deeper
zones. We find their southern limit accordingly in the Medi-
terranean or at the Azores and the Canary Islands, while the
deep-sea forms also go a long way south on the American side.
Very few of the shallow-water forms, however, which extend
southwards along the coasts of Europe are to be met with on
the American side of the Atlantic, either because they cannot
pass across the profound depths separating the two continents,
or because they are debarred from advancing over the shallow
northern parts of the Atlantic by the arctic conditions prevailing
there. No satisfactory explanation can, therefore, be given for
the presence of the very few boreal shallow-water forms which
are common to both sides.
I have already stated that most of the species of this group
have migrated into the Norwegian Sea in post-glacial times,
and their present distribution is evidence of this ; but there are
some species nowadays confined on the eastern side to the
boreal and boreo-arctic areas of the Norwegian Sea, and on
the western side occurring to the north, and in some cases
also a little to the south, of Cape Cod. As to their origin it is
difficult to form an opinion, but most probably a number of them
have been developed from arctic species after the ice-period
came to an end, and have adapted themselves to their boreal
INVERTEBRATE BOTTOM FAUNA 551
environment without any considerable changes in their bodily
structure, as for example the decapod crustaceans Hippolyte
seciirifj-ons (boreal) — Hippolyte spiims (arctic), Sabinea sarsi
(boreal) — Sabinea septenicarinata (arctic). These forms are so
alike that I cannot help thinking they must have had some
phylogenetic connection in a geologically not very remote past.
Other forms of the same category have no near relations in the
arctic region, and cannot, therefore, be of arctic origin. That
these species lived in the Norwegian Sea in late glacial times,
when more boreo - arctic conditions prevailed, seems evident
from their normal distribution nowadays in boreo-arctic areas,
but it is impossible to decide whether they migrated into the
Norwegian Sea from the American or the European side, or
are derived possibly from southern species which have become
morphologically so altered in their new home that the specific
differences are unmistakable.
There are other species in the Norwegian Sea which, so
far as is known, are strictly confined to the boreal and boreo-
arctic areas, extending neither southwards nor to the coasts
of North America in the west. They are, however, not very
numerous. Like the forms just mentioned they could not
have lived in the Norwegian Sea during the Glacial Age,
and have probably originated there in post-glacial times,
through development from southern immigrants that have been
morphologically altered by adaptation to their environment.
Several of them are closely allied to species known outside the
Norwegian Sea. In some cases there would seem to have been
a variation from the immigrated species, and we find inhabiting
the Norwegian Sea both the primitive form and its descendant,
like the crustaceans Pag2Lrus chir'oacanthus (a purely boreal
endemic species) — Pagurus l(svis (immigrated primitive form),
Cheraphilus (purely boreal endemic) — Crangon or Pontophilus
(immigrated primitive form), Virbius fasciger (purely boreal
endemic) — Virbiiis varians (immigrated primitive form). We
may take it for granted, in view of what we know nowa-
days regarding the larger invertebrate forms, that the majority
of these species have not a widespread distribution either
southwards or westwards, and this might give grounds for
believing that they had immigrated in their present form.
I have already mentioned that the littoral and sub-littoral Distributional
faunas differ greatly in different areas of the Atlantic, and we ^'^^^•
find similar differences when we compare the Atlantic and
552 DEPTHS OF THE OCEAN
Norwegian Sea. Certainly, many species are common to
both, but there are far more pecuHar species, the difference
becoming more pronounced the farther south we go. The
British Isles and the English Channel, the shallow-water fauna
of which has been thoroughly studied, may be taken as the
boundary where the northern and southern forms meet, both
categories having reached their respective southern and
northern limits of distribution. Along the British coasts and
the Channel we get, accordingly, a kind of coalition territory,
which has often been considered a separate faunal "province,"
and has actually been termed Lusitanian, though in my opinion
without sufficient justification. The shallow - water faunas of
Iceland and the Faroe Islands are so little known that it is
impossible to say whether they are coalition territories or not.
We must remember that it is much more difficult for shallow-
water forms to find access to insulated areas like these, cut off
as they are by profound depths and special conditions of
temperature, than to the British coasts.
It is now admitted that faunal resemblances and dis-
similarities between different marine areas are chiefly due to
the physical conditions of the sea-water, but we must not
regard them as the sole factors that regulate distribution. Two
marine areas may have similar physical conditions and yet
differ greatly faunistically. The Northern Pacific and Northern
Atlantic have in many cases similar hydrographical con-
ditions, but their faunas are on the whole quite distinct.
There are other factors at work, and isolation probably
does more than anything else to cause faunal differences.
Two areas may be isolated from each other owing to
the topographical character of the bottom, or because the
physical properties of the water prevent any faunal connection,
and consequently their faunas develop in different directions.
Temperature is another of the chief physical conditions
affecting distribution, and this explains why the British coasts,
the Mediterranean, the Azores, and the Canary Islands, not to
mention tropical coastal areas, shelter many forms which do not
occur in the Norwegian Sea, although there do not seem to
be any obstacles of a topographical character in the long
connected coast of western and northern Europe.
We often see the limit of the arctic fauna in the Norwegian
Sea put at about lat. 67" N., it being apparently forgotten
that, owing to the hydrographical conditions, a large arctic area
(part of the arctic-abyssal) extends as far south as lat. 60" N.,
INVERTEBRATE BOTTOM FAUNA 553
while a purely boreal area (the deeper parts of the plateaus)
extends to lat. 71 N. How little latitude affects faunal marine
areas is evident when we compare the conditions on either side
of the northern Atlantic, for on the American side the southern
limit of the arctic shallow-water area lies about lat. 42' N.,
whereas on the European side it lies about lat. 67° N.
It has already been mentioned that intervening areas of a
different hydrographical character can always prevent connec-
tion between two, marine areas. The northernmost parts of
the Pacific and Atlantic are arctic, and so also is the sea
between them lying to the north of America. As a result the
arctic faunas of the two areas have an uninterrupted connection
and resemble each other. It is otherwise with the temperate
parts of these oceans, for their boreal forms are isolated by the
arctic tracts which intervene, though they share a few boreal
species like Crangon vulgaris, as well as some others that are too
closely allied for any one to doubt that they have formerly been
identical. This probably arises from hydrographical changes in
what are now arctic areas, which caused an isolation of specimens
belonging to the same species in both areas, for there are
indications that higher temperatures prevailed during post-glacial
times in the coast-waters of some of these arctic tracts, and we may
assume that the boreal species now occurring normally in boreo-
arctic areas could exist then in what have since become purely
arctic waters, and that by way of the shores of Canada and Alaska
they had uninterrupted connection from ocean to ocean. When
subsequently arctic conditions set in, the individuals of these
boreal boreo - arctic species were compelled to retire south-
wards either to the Atlantic or to the Pacific, and all connection
between them ceased. There is, of course, the possibility that
these species lived as long ago as the tertiary age — in which
case their present distribution can be easily explained — for
tertiary fossils make it perfectly certain that a warm climate
existed at that time in these latitudes.
The theory of a warmer post-glacial period is based upon .
the sub-fossil boreal molluscs found in certain arctic areas, like JTenod. ^^"^
those from the south-west coast of Greenland described by
Adolf Jensen, comprising shells of present-day boreal species
no longer found there (Anornia ephippium, Cyprina islandica,
ZirphcFa crispata). In the Gulf of St. Lawrence, too, where
conditions are nowadays arctic or boreo-arctic, we get quantities
of empty mussel-shells belonging to undoubtedly southern forms.
In the purely arctic waters of Spitsbergen there are sub-fossil
Warm climate
554 DEPTHS OF THE OCEAN
shells of Mytiliis edit lis, Littorina liitorea, and Cyprina islandica,
all boreal forms requiring a higher temperature and not living
there now. Again, in northern boreal areas there are sub-
fossil deposits of molluscs which require greater warmth than
.generally prevails in the boreal region {Tapes deaissatiis in
Denmiark, Isocardia cor in Norway, etc.), and it is held in
some quarters that they could only have existed there when
the temperature of the sea was higher.
Without criticising this theory, I should like to point out
that we ought not always to take these finds of sub-fossil shells,
belonging to species no longer inhabiting the adjoining seas,
as evidence that great hydrographical changes have necessarily
taken place in these areas. Tapes deaissahts, for instance, which
is now quite extinct along the coast of Denmark, is still to be
found at various places along the west coast of Norway, from
Bergen down to the south coast, but only in restricted localities
where there are special natural conditions, that is to say, in
shallow, well-sheltered, sandy bays, dry at low water, but afford-
ing full access to the salt water of the sea. These bays differ
greatly from the " pools," which have a layer of fresh water
at the surface and a muddy bottom smelling unpleasantly of
sulphuretted hydrogen, but one feature they do possess in
common, namely, that the sun raises their temperature consider-
ably above the normal, so much so, in fact, that I have sometimes
recorded 23"' or 24° C. in the shallow water of these " Tapes
bays " during the summer. Beyond question this high summer
temperature, in combination with favourable bottom-conditions
and the salt water, enables Tapes deciLSsatus to thrive, and,
what is still more important, to reproduce itself It is not
difficult to imagine that these rather limited localities may have
been silted up, or cut off from the inflowing of salt water in
some way or other, thus giving rise to sub-fossil deposits of Tapes
shells. Nevertheless, in the case of boreal forms found fossil
or sub-fossil in arctic areas, it seems to me that the warmer sea-
water theory is the only reasonable one, since there is nothing
to indicate that other important factors have been instrumental
in their extinction.
Effect of It is important to ascertain how changes of temperature
*^^^"^Suue ^ff^ct ^ species, whether they influence chiefly the development
u^i^n animal and growth of the young stages or the full-grown animals through
''^'^" other physiological processes. This question has not been
deeply studied, though we have acquired sufficient knowledge
to enable us to draw one or two conclusions. We know, for
INVERTEBRATE BOTTOM FAUNA 555
instance, that a high temperature is required for the develop-
ment of the oyster larvae, and that along the Scandinavian coast
it is only in the so-called pools that reproduction on any large scale
takes place. Most probably the same is the case with many
other inhabitants of the pools. The eggs and larvae of the lobster
are only developed during the warmest part of the year, though
the female often carries spawn in winter, and it has been found
by experiment that a fall of a few degrees in temperature is
sufficient to retard the development of the larvae several weeks.
We can understand, therefore, why these forms do not live in
arctic or boreo-arctic areas. Even though the fertile eggs or
larvae of boreal forms do not demand a higher temperature
for their development, additional warmth may nevertheless be
absolutely essential for the production and development of the
ova within the mother's body. This, again, limits the dis-
tribution of many forms. The converse naturally holds good,
and the development and other physiological processes of forms
living exclusively in arctic waters can only take place at a low
temperature.
We have already seen that many species are common to
both boreal and purely arctic areas, and we must ascribe their
widespread distribution to their power of adapting themselves
to very different temperatures. Most likely we are dealing
here with physiologically distinct species, even though the
differences do not appear in corresponding morphological altera-
tions in bodily structure. Not that differences of this latter
kind are by any means excluded, as I have previously shown
how a species may vary morphologically in certain directions,
according as it occurs in arctic or boreal tracts. Future
researches regarding the time when reproduction begins in
these widespread forms in the respective areas will possibly
show that the temperature at which development takes place
varies a good deal less than the temperature prevailing in the
different areas seems to indicate. For forms which live in
boreal deep water, where the temperature is comparatively low all
the year round, the difference is in any case not particularly
great, and if it should prove that the widespread shallow-
water forms develop during the winter in boreal areas, the
difference there again is relatively small. Now we find that two
of our typical littoral animals, the sea-slug Cuannaria frondosa
and the starfish EcJiinaster {C^'ibrelld) sanguinolentus, both of
which inhabit arctic tracts, deposit their eggs in boreal waters
early in March when the upper water-layers have a low
556 DEPTHS OF THE OCEAN
temperature. Experiments have taught us that the eggs of
CuctLmaria, which float near the surface, are so much affected
by the surface-temperature of the coast-water in summer, that
they are destroyed before a single larva is hatched, and it
follows that the existence of this form in the littoral zone of the
boreal region depends upon its period of reproduction being in
the coldest months of the year ; this is probably true also of
Echinaster. Again, in the case of another arctic-boreal species,
Hippolyte gamzardi, which along the west coast of Norway
lives only in the littoral zone, the eggs develop during the cold
months of the year, and the young are hatched in April. On the
other hand, the lobster and the oyster, which are typical boreal
forms inhabiting the littoral zone, have their period of repro-
duction in the months between June and August.^ It must be
admitted, however, that too few researches have been made upon
which to base any general conclusions, and that the conditions
in arctic tracts are quite unknown."
Little is known as yet regarding the power of withstanding
variations of temperature in different species, though most of
the littoral animals, which are eurythermal and exposed to
extreme variations, are astonishingly hardy. The Swedish
zoologist Aurivillius has found, from observations made on
the coast of Bohuslan in Sweden, that the barnacle (Balanus
balanoides), the periwinkle i^Littorina littorea), the sandgaper
{Mya), the cockle {^Cardiuvi), and the lugworm [Arenicold) are
able to endure for a considerable period a temperature below
freezing point, and that the barnacle after being quite a
long time in the ice had actually got vigorous young.^ Other
littoral forms can protect themselves by descending into deeper
water or by burrowing downwards into the mud. Still we
cannot expect every species to be equally hardy, and wholesale
destruction sometimes takes place under specially unfavourable
circumstances, as, for instance, when the ice lasts too long or
when the bottom freezes to too great a depth. That many of
our littoral animals are able to live in boreo-arctic areas at a
^ The German naturalists Samter and Weltner have published an interesting account
of several arctic survival forms in North German lakes, illustrating their mode of life and
reproduction. One crustacean, Mysis relicta, lives during the summer in the depths of cold
lakes, and migrates landwards during autumn and winter, reproduction chiefly taking place at
a temperature of 3° C. With another crustacean survival-form, Pontoporeia affiftis, also, repro-
duction takes place m winter at temperatures varying between 0° and 7° C.
- It will be interesting to find out whether the boreal forms which penetrate into boreo-arctic
areas with high temperatures for a short portion of the year have a short period of reproduction
there, seeing that farther south their reproduction is known to extend over several months.
^ Aurivillius, " Littoralfaunans furhuUande vid tiden fiir hafvets islaggning," Cfvers. Kgl.
Vet. Akad. Forhandl., 15^95.
INVERTEBRATE BOTTOM FAUNA 557
low temperature depends upon their finding the conditions
necessary for reproduction, namely, higher temperatures during
a portion of the year.
With regard to vertical distribution, it should be noted stenothermal
that the deeper a species lives the more uniform is the tempera- ^°'^'^^^'
ture to which it is exposed (stenothermal forms). This is true
especially of the boreal areas, whereas in arctic tracts there is,
as a rule, less difference between the temperatures in deep and
in shallow water. It is not so much the depth as the tempera-
ture which regulates the distribution of animals. Another
factor affecting distribution is salinity. Many forms, particularly Euryhaiine
the littoral ones, can stand a considerable variation of salinity Jafine^fo°ms,
(euryhaiine species), while others are limited to water varying
little in salinity (stenohaline species) ; the former includes
those littoral forms which are as much at home among the
skerries as far up the fjords or even in the mouths of the rivers,
while the latter are only to be found off the coast or at
considerable depths.
I have already tried to make it clear that no arrangement of
vertical faunal zones applies to the whole of the Norwegian Sea.
Forms which near the coast inhabit the littoral zone may be met
with, normally apparently, out on the plateaus, in the sub-littoral
zone, or perhaps in the deep-sea zone. Thus in the northern
portion of the North Sea the trawl brought up from a depth of
180 to 190 metres Ophiothrix fragilis and large specimens of
Ejipagnrus bei'nhardiis — forms which are distinctly littoral along
the Norwegian coast, and on the Faroe plateau we found these
and a number of others at no metres. When we compare the
North Atlantic with the Norwegian Sea we find still more strik-
ing differences, some of the species belonging to the Norwegian
Sea occurring at far greater depths in the Atlantic. Now if we
remember that the physical conditions in the medium in which
a species lives are largely responsible for its vertical distribution,
we may assume that in the littoral zone of the coastal waters and
in the deeper parts of the Norwegian Sea and Atlantic there are
at any rate certain identical conditions — temperature is most
decidedly not one of them — which permit these species to live
impartially in these areas. If it were merely a question of
adaptation to quite different conditions, we might expect them
to adapt themselves also to the deeper water-layers along the
coasts.
Light is unquestionably one of the principal factors affecting Effect of light.
vertical distribution. During the Atlantic Expedition of the
currents.
558 DEPTHS OF THE OCEAN
"Michael Sars " in 1910 tests were made at various depths,
and it was found that the Hght was far stronger south of the
Azores than in the northernmost portion of the Atlantic at
corresponding depths. But whether light is in itself sufficient
to explain the different vertical distribution of a species in
different marine areas, or whether there are other contributing
factors, are matters yet to be decided. So far the question has
not been sufficiently studied.
Effect of The animals of the ocean-floor owe their distribution mainly
to the agency of currents, since these serve to transport their
pelagic larvae, and perhaps also carry along full-grown bottom-
forms like the amphipods and most of the prawns, which creep
almost as much as they swim. It is through transportation of
larvae that the Norwegian Sea acquired most of its southern
forms, and to this day these forms are still being disseminated
in similar fashion throughout its component parts. We must
bear in mind that most bottom-animals are attached, or, if
we except a few crustaceans, very limited in their locomotion,
and that consequently distribution by direct migration is all
but impossible. The distribution of larvae is subject to
physical laws, and is dependent on the occurrence of the adult
animals, and on the hydrographical conditions that prevail.
Larvae of arctic forms which inhabit only polar areas will, as
a rule, only be transported by polar currents, so that the
bottom they will reach, when their development is completed,
will lie within the arctic region. In the same way the species
belonging to Gulf Stream areas will be retained in boreal
waters.
In addition to the two main currents of the Norwegian
Sea there are several others consisting of blended layers, such
as mixtures of the Gulf Stream, polar water, coast water,
North Sea water, and bank water in various combinations.
Probably every one of these plays its own particular part in
distributing the larvae, and consequently the bottom-animals,
but we do not yet know to what extent. It seems absolutely
certain, in view of what we have learnt regarding pelagic
animals, that the larvae in an area bordering on two currents
may be swept away by one or the other, and so conveyed to
a strange area. This, I fancy, explains why a coast-form like
our common sea-urchin, Echinus esciilentits, may be exceptionally
met with in deep water out in the North Sea and Atlantic, where it
succeeds in existing as a somewhat different variety. The occur-
rence of the arctic amphipods, Epimeria loricata and Aca7ithozone
INVERTEBRATE BOTTOM FAUNA 559
mspidata, far south in the Norwegian depression, is probably
also due to the same cause, as they have most likely been
carried there by one of these blended currents and have
managed to adapt themselves to more boreal conditions.
That larvae may be transported in quantities to areas where
they are unable to develop was proved during the autumn
of 1903, when the fjords near Bergen were found to be full
of Actinotrochae. (larvae of P/ioronis, a form related to the
bryozoans, which occurs in the south parts of the North Sea
and other southern waters), but in the following year repeated
dredgings failed to reveal a single full-grown animal either
there or anywhere else on the coast of Norway,
Currents also carry nourishment to the bottom-animals and
sweep away the finer particles of mud and other soft substances,
leaving, in sounds especially, nothing but the bare rock, or
perhaps a slight covering of coarse sand and shells. This
enables attached forms to thrive, since the current prevents
their being buried, and at the same time supplies them with
the nourishment they require.
It is strange that a few boreal forms are peculiar to the
plateaus and do not enter the fjords, for the fjords and plateaus
have most of their forms in common. Whether it is due to
the fact that these peculiar forms develop at a time when the
Atlantic water, in which they probably live during both their
larval and full-grown stages, does not penetrate into the fjords,
or whether the physical conditions of the fjords are in some
way uncongenial, is unknown. Similarly we are unable to
explain why a number of boreal forms, which are widely dis-
tributed elsewhere, avoid the North Sea and Skagerrack, or
why some plateau-forms enter fjords north of Stat, like the
Trondhjem fjord, but are absent from fjords farther south.
Distribution is of course very much affected by the character Effect of
of the sea-floor, since whole groups of animals are limited by their j°p°s,"s
structure or mode of living to some particular kind of bottom.
No doubt there are forms which appear to be equally at home
everywhere, but there are others again which are extremely
exacting in their requirements. This is especially the case with
burrowing forms, like the lancelet and numbers of mussels and
worms, and as a result we find, when conditions are favourable,
that extensive stretches of the bottom are occupied by one or
more of these. Some forms like sponges and corals, belonging
to groups most of whose members are attached and therefore
confined to rocky bottom, have developed special organs in the
56o
DEPTHS OF THE OCEAN
way of root-like outgrowths, by means of which they adhere
to soft bottom and can accordingly reside there normally.
Plant-growths have much to do with the distribution of bottom-
animals, providing foundations for attached forms ; some few
species appear to be associated solely with one particular kind
of plant, whether it be eelgrass or laminaria or some other
conorenial alofa.
A. A.
"■3^*'
CHAPTER IX
PELAGIC ANIMAL LIFE
In the "Challenger" Summary, Sir John Murray writes as
follows: "The tow-net experiments carried out on board the
" Challenger " during several years in all parts of the world led me
to the conviction that these intermediate regions were inhabited,
although with a much less abundant fauna than the waters near
the bottom or those near the surface of the ocean. Thousands
of hauls of the tow-nets were taken in the surface and sub-
surface waters, and the contents were daily submitted to
microscopic examination ; the forms present in these waters
became quite familiar to the naturalists. When, however, the
tow-nets were sent down to deep water, and dragged in depths
as nearly as possible of 500, 1000, and 2000 fathoms, organisms
— such as the Tuscaroridse among the Radiolaria — were nearly
always observed in the gatherings in addition to the usual
surface organisms. Organisms from these intermediate layers
of water appear to have a much wider horizontal distribution
than the surface fauna or flora. These oft-repeated experiments
produced a strong belief that all the intermediate zones of
depth were inhabited. I am not aware that the Tuscaroridse
have ever been taken in the surface or sub-surface waters. It
is probable that the animals in the intermediate zones of depth
obtain their food by the capture of the dead organisms continu-
ally falling from surface to bottom. It is well known that the
deposits at the bottom are in most regions chiefly made up of
the dead shells and skeletons of surface organisms." ^
During the cruise of the Italian ship "Vettor Pisani," Captain
G. Palumbo constructed a closing-net with which Lieutenant
Gaetano Chierchia collected animals from accurately determined
depths. At the zoological station at Naples this work was
continued by Eugen von Petersen and Professor Carl Chun.
^ Summary of Results Chall. Exp., p. 1455) 1^95'
561 2 O
562 DEPTHS OF THE OCEAN
When Chun in 1898 fitted out the "Valdivia" Expedition,
special arrangements were made for the purpose of obtaining
an accurate knowledge of the animal life in " mid-water."
Hundreds of hauls with closing-nets and with other large nets
were taken at various depths, the material procured proving
that the main conclusions drawn from the " Challenger" Expedi-
tion were quite correct. Even in hauls between 5000 and 4000
metres living crustaceans as well as larvae of the same animals
were captured — a sufficient proof that these organisms not only
live but also breed at these depths.
The conception of a " pelagic " mode of life, originally
associated with the animal-life of the ocean-surface, thus
gradually proved to hold true for life in mid-water also, and to
apply to floating or drifting organisms as well as free-swimming
animals. The main characteristic of pelagic life is its independ-
ence of the bottom. The term " bottom- animals " is applied
not only to the animals fixed to or creeping along the bottom,
but also to those animals which, like certain crustaceans and
bottom-fishes, swim and feed along the bottom. But it is im-
possible to draw a perfectly sharp limit between these migrating
bottom-dwellers and some of the deep-living pelagic animals,
which have been called " bathypelagic." In accordance with the
varying conditions in deep and shallow water and in different
parts of the ocean, the pelagic animals have been subdivided into
groups : thus Ernst Haeckel ^ introduced the idea of " Holo-
pelagic " (wholly pelagic) to distinguish those forms leading an
entirely pelagic life from those forms having a bottom-stage
like the Hydromedusae, which he called " Meropelagic " (partly
pelagic) ; he further distinguished those forms found only in
coastal waters by the term " Neritic " from those found only in
the open sea, which he called "Oceanic."
As in all geographical comparisons of animals we may
divide the pelagic organisms into tropical, subtropical, boreal,
arctic, and antarctic forms. It has also been proposed to
arrange the pelagic fauna in certain bathymetrical zones,
distinguishing between those forms living in profuse light, or
in the region of twilight, or in the dark abyssal waters, but
such distinctions are arbitrary, because our knowledge of the
bathymetrical distribution of animals is limited, because
the laws of distribution are imperfectly understood (for
instance, the effects of light), and because the bathymetrical
1 Ernst Haeckel, Plankton-Siudien, ]Qndi, 1S90. Haeckel used the words " holoplanktonic "
and " meroplanktonic," but I prefer " holopelagic " and "meropelagic," as the word
" plankton" is not so clearly defined, and is used in different ways (see Chapter X).
PELAGIC ANIMAL LIFE 563
occurrence of certain species is subject to great variation in
different regions. We shall, therefore, dispense with the many
Latin and Greek terms employed to define such groups of
pelagic organisms, and simply use the term " bathypelagic "
to denote those animals that live deep in the intermediate
layers. Hensen proposed the term " plankton " to denote
every kind of organism floating or drifting in the water, either
shallow or deep, "dead or living," and Haeckel applied it so
as to include all pelagic animal and plant life as a whole, in
contrast to bottom-life as a whole, which he terms " benthos."
In this chapter I propose to consider only the different
species or communities of pelagic animals, not the pelagic life
as a whole. Pelagic forms occur in all classes of the animal
kingdom from the unicellular Protozoa to the fishes ; to mention
them all would be to write a text-book on zoology. The chief
aim of this book is however to give some of the general and
special results of the cruises of the " Michael Sars," A discussion
of the results relating to pelagic animals (as with the bottom-
fish) calls for some information about the principal forms, so I
commence with a short review of pelagic animals.^ In the
absence of descriptions of the animals, the illustrations will give
the reader an idea of some of the forms referred to. Their
geographical distribution, as known from previous expeditions,
is briefly indicated, and in a later section I shall deal with the
distribution of the most important animals in their communities
in the different areas of the North Atlantic and the Norwegian
Sea.
I. Short Review of Pelagic Animals
Among unicellular animals the Foraminifera and the Radiolaria may-
be given prominence. Being exceedingly rich in species, as well as
individuals, they play an enormous part in the economy of the ocean,
and their shells constitute an essential portion of the deposits on the
ocean-floor.
The pelagic foraminifera have shells of carbonate of lime, usually Foraminifera.
divided into several chambers communicating with each other, allowing
the protoplasm to penetrate the whole shell, which is perforated by
innumerable small apertures (foramina), through which the finest threads
of the protoplasm (the pseudopodia) may pass. In Chapter IV.
p. 172, a list is given of all the species known to be pelagic, and certain
important forms are figured. The list embraces eight genera and
twenty-six species, fourteen of which belong to the genus Globigerina,
also represented by an enormous number of individuals. During the
^ A very useful review of the results of modern (especially German) investigations is given in
Steuer's PlanMonkiinde (Leipzig and Berlin, 1910), with extensive lists of literature.
564 DEPTHS OF THE OCEAN
cruise of the " Challenger " Sir John Murray captured them from a boat
in calm weather floating at the surface of the ocean, where they were
just visible to the naked eye. On the ocean-floor in moderate depths in
tropical and sub-tropical regions the dead shells occur in such enormous
numbers that the deposit is called Globigerina ooze. The species and
individuals decrease in number as we go north or south from the tropics,
and in the Norwegian Sea only one species, viz. Globigerina biilloides
(see Fig. 118, p. 150), occurs in any abundance either at the surface or in
the bottom deposits.^
Radiolaria. The Radiolaria occur in a profusion of species. The cell possesses a
central capsule containing the nucleus or nuclei and an outer layer of
protoplasm capable of throwing out very thin threads (pseudopodia).
The skeleton is developed in various ways and facilitates the dis-
crimination of an enormous number of sharply separated forms (see Figs,
no to 117 in Chapter IV.). In his report on the "Challenger" Radio-
laria, Haeckel described no less than 20 orders, 85 families, 739 genera,
and 4318 species, taken partly from the deposits and partly in the tow-
nettings ; in one single bottom sample from 4475 fathoms in the Pacific
338 species were found. The Radiolaria are wholly pelagic, and occur
in all oceans where the salinity is not too low (as it is in the Baltic),
over deep water as well as over shallow water, attaining their maximum
development in the Pacific.
In order to discuss their distribution we may mention some of the
typical groups :■ — ■
The Acantharia are mostly spherical ; the perforations of the central
capsule are regular. The skeleton consists of acanthin, a peculiar elastic
organic substance, in the form of twenty needles radiating from the
centre of the sphere. The majority of the species occur in tropical
waters and in the upper layers of the ocean. They are divided into two
groups, Acanthometra and Acanthophracta.
In a vertical haul in the Atlantic Popofsky- found no less than
75 species of Acanthometra alone, and a haul in the Indian Ocean
procured a similar number. North and south from the equator the
number of species decreases, the majority living between lat. 40° N. and
40° S. The different regions of this warm belt have many species in
common. According to Popofsky the total number of known species
is 179, of which only 18 have been found in the Atlantic to the north of
lat. 50° N., and 10 of these are known only as casual or seasonal visitors.
The commonest forms in northern waters are Acanthochiasmafusiforme,
Acanthometron pellucidiim (Fig. 389), AcantJionidium ecJiinoides (Fig. 390),
Phyllostaurus quadrifolius, Acanthostaurns nordgaardi {¥\g. 391).
It is generally supposed that the temperature limits the bathy-
metrical distribution of the Acantharia, just as it is known to limit their
horizontal occurrence. In the Atlantic the German Plankton Expedition
found the deepest living species at a temperature of 9.4° C. In the
Mediterranean, where high temperatures occur deeper, they have been
^ See Murray, "On the Distribution of the Pelagic Foraminifera at the Surface and on the
Floor of the Ocean," Nattiral Science, vol. xi. p. 17, 1897.
"^ Popofsky, " Acanthometriden," Ergeb. Plankton-Expedition, Bd. iii. , 1904; "Die nor-
dischen Acantharien," Nordisches Plankton, No. xvi.
PELAGIC ANIMAL LIFE
565
taken down to a depth of 1200 metres. In northern waters several
species have been taken just at that time of the year when the
temperature is highest.
The Aulacanthidae, the Challengeridae, the Tuscaroridae, and the
Medusettidae have siHcious skeletons and prefer mainly cold water.
Fig. 389.
Acanthometron pelluciduvi, J. Miiller.
(After Hertwig, from Steuer. )
Fig. 390.
Acanthonidium echinoides, Claparede and
Lachmann. (From Popofsky. )
The Aulacanthidae are spherical, the skeleton consisting of numerous
isolated hollow needles, some of which radiate from the centre while
other smaller ones are arranged along
the surface of the sphere. The great
majority of the Aulacanthidae have
been found in the north-western
corner of the Atlantic (the Irminger.
Sea and Davis Straits), and also
south of the Cape Verdes, but
several species are very widely dis-
tributed, for instance Atilographis
pcmdora (Fig. 392) taken in the
Mediterranean, Indian Ocean, Paci-
fic, and also in the Atlantic north
and south of the Equator. This
species occurs between 400 and 1000
metres, and is considered specially
characteristic of these depths. One
of the best-known species, A ulacantha
scolyinantJia (see Fig. 393), is found,
like several other radiolarians, in
two races distinguished by their
difference in size. One is a pygmy 0.6 to 1.8 mm. in diameter, the
other a giant about 3 millimetres in diameter. At Naples, and during
the cruise of the " Valdivia," Haecker^ studied the bathymetrical
^ V. Haecker, "Tiefsee-Radiolarien," Wiss. Ergeb, " Valdivia''' Expedition, Bd. xiv. (Jena, 1908).
Vv
Fig. 391.
Acantliostaurus 7iordgaardi, Jorgensen (^J-)-
(From Jorgensen.)
566
DEPTHS OF THE OCEAN
Fig. 392.
A ulographis pandora, Haeckel (about '/')
(From Haecker. )
distribution of these forms, and found the small one (var. typica) occur-
ring in all depths, the large one (var. bathybia) in depths between 400
and 1000 metres ;
^ .J. the giant form
V , occurs very rarely
i n N o r w e g i a n
fjords.
The Challenger-
idae have an q%^ or
lentil-shaped silici-
ous shell of most
delicate structure,
the aperture being
provided with a
collar or tube-
shaped moulding
(see Fig. 394).
They occur in all
oceans, but some-
times their distribu-
tion is very peculiar,
for some species live
only in abyssal
depths under the
equator, others at
both poles, others only in Antarctic waters ; some species live in the sur-
face waters, others between 50 and 400 metres, others between 400 and
1000 metres, others again
between 1500 and 5000
metres. From Haecker's
report on the Radiolaria
of the " Valdivia " Expedi-
tion we reproduce some of
these species. Protocystis
{Challengeri a) tridens
(Figs. 394, 2 and 3) occurs
in the northern and south-
ern cold zones, having
been taken as far north
as Spitsbergen, in the
Norwegian fjords, the
Skagerrack, round Green-
land, in the Labrador cur-
rent, and also in Antarctic
waters by the " Valdivia " ;
in Norwegian waters it has
been taken in deep water
up to 50 metres below the surface. P. swirei (Fig. 394, 1) has been
taken only in the Antarctic from the surface down to a depth of 4000
and 5000 metres. P. tJwmsoni (Fig. 394, 4) belongs to a group of
Fig. 393.
Aulacantha scolymantha, Haeckel. a, var. typica ; b, var.
bathybia, deep-sea form. (After Haecker, from Steuer. )
PELAGIC ANIMAL LIFE
567
large forms, of which the
species P. naresi is the
largest. These forms have
been taken in abundance only
at the greatest depths, as is
the case with the giant race
of A ulacantha scolyinantJia.
Among Norwegian Sea forms
we may mention Protocystis
bicof'nis and P. harstoni, Chal-
lengeria xipliodon^ and Poros-
pathis Jiolostoma, the three
latter being found in the
Atlantic as well. P. holostoina
has been taken at great depths
in the Norwegian Sea and in
the Sargasso Sea.
The Tuscaroridae are
genuine deep-sea forms,
having a bottle - shaped shell
provided with large strong
spikes arranged in rings
around the main axis (see
Fi!
195).
In hauls with
closing nets they have never
been taken in less than 400
metres of water ; some species,
for instance Tiiscaretta tubulosa,
occur in all oceans.
Remarkable deep - sea
forms, as well as certain
small surface forms, belong
to the Medusettidae. Medu-
s etta arc ife ra has been
taken in the Norwegian
fjords.
On the basis of his
study of the Radiolarians of
the " Valdivia " Expedition,
Haecker distinguishes the
following bathymetrical
regions : —
IW
(i) An upper Acanthometra-
layer.
(2) A Challengeria-layer (50 to
400 metres). Fig. 394.
(3) A Pandora - layer (from Challengeridas (-f). i, Protocystis swirei, John
A i/lographis pandora, 400 to 1000 Murray; 2 and 3, Protocystis tridens, Haeckel ;
metres), in which the Tuscaroridse
are also found.
Protocystis ihomsoni, John Murray.
Haecker. )
(From
568
DEPTHS OF THE OCEAN
(4) An abyssal layer (1500 to 5000 metres), in which the large Challengeridse
{Frotocystis fiaresi, P. thomsoni) are found.
The multicellular animals are all represented among the pelagic
forms, from the medusae to the fishes.
Commencing with the Coelenterates we may mention the Medusae,
the Siphonophores, the Ctenophores, and the larval Actiniae.
Medusre. The Medusae are generally bell-shaped or globular, with a more or
less transparent jelly-like body. On the edge of the bell some forms
have a band-shaped fold or moulding (" craspedon "), and accordingly
the medusae are divided into two main groups : Craspedota with a
craspedon, and Acraspeda without a craspedon.
The Craspedota comprise four groups : Anthomedusae, Leptomedusae,
Fig. 395.
Tiiscaretta globosa (Borgert), subsp. chiini, Haecker (about "^).
(From Haecker. )
Trachymedusae, and Narcomedusae, of which the first two are mero-
pelagic and the last two holopelagic. The meropelagic forms pass
through an " alternation of generations," i.e. the eggs produced by the
medusae develop into larvae which attach themselves to the bottom and
grow into hydroid polyps or zoophytes ; by " budding " the zoophytes
produce small medusae, which lead a swimming pelagic life and produce
eggs. Fig. 396 shows a colony of hydroids with different stages of
medusae developing, and Fig. 397 shows one of the medusae just after
leaving the colony. The Craspedota are therefore termed hydroid
medusae or hydromedusae, although they include two groups with no
alternation of generation and no bottom stages, which are supposed
to be descended from neritic forms. The hydromedusae having an
alternation of generations are represented by a vast number of species in
the surface waters off all coasts where the temperature is not too low.
They do not occur far from land nor in deep water. Their pelagic life
PELAGIC ANIMAL LIFE
569
is short and they die unless they reach the bottom within a certain
Hmited time.
Damas and Koefoed ^ mention as the most important forms in
Scandinavian waters the following species : Sarsia tubulosa, S. eximia,
Euphysa aurata, Cojymorpha nutans, Hybocodon prolifer, Bougainvillia
superciliaris var., Dysmorphosa octopunctata, Tiara pileata, Limneandra
norvegica, Melicertidiinn octocostatiim, different species of Obelia and
Fig. 396.
Hydroid colony of Syncoryne pulchella.
(From Allman. )
Fig. 397.
Medusa, just after leaving
colony.
Phialidiiim, Mitrocoinella fiilva, Tiaropsis viulticirrata, and Lutonia
socialis. From the Arctic plateau between Spitsbergen and Bear
Island they mention Sarsia flammea, Codoniuvi princeps, Catablema
campanula, Hippocrene superciliaris (see Fig. 398). These forms do not
play any part in the fauna of the open ocean.
The Trachymedusae have a direct development without a hydroid or
bottom stage. In northern waters we meet with only one species in such
numbers, and so frequently, that it may be considered truly northern
^ Damas et Koefoed, " Le Plancton de la Mer de Greenland," Due d'Orleans' Croisiere
occanogyaphique (Bruxelles, 1905).
570
DEPTHS OF THE OCEAN
Fig. 398.
Arctic Medusae : i, Hippocrene supercili-
aris, Ag. ; 2, Codonium princeps,
Haeckel ; 3, Catablema campanula,
Haeckel. (From Vanhoffen. )
Fig. 399.
Aglantha digitalis, O. Fabr. [\
(From Vanhoffen. )
Fig. 400.
Liriope tetraphylla, Chamissoand Eysen-
hardt (about f). (From Vanhoffen. )
Fig. 401.
Crossota bnninca, Vanhoffen [\
(From Vanhoffen. )
PELAGIC ANIMAL LIFE
571
(boreal), viz. Aglantha digitalis (see Fig. 399), which sometimes plays an
important part in the pelagic life of the Norwegian Sea ; in the North
Sea Hensen fell in with a shoal of these medusae which he estimated at
23^7 billions of individuals. As mentioned by Haeckel, it is character-
istic of this form that it suddenly appears in enormous quantities for
some days and then suddenly disappears for some months.
As rare visitors in the north may be mentioned, Pantachogon
haeckelii, Pectyllis arctica, and Crossota norvegica} Other species are
strictly limited to the warm zone of the ocean, which may be said to
f^. _.,..._
Fig. 403.
Halicreas rotiindatum, Vanhoffen (^').
(From Vanhoffen.)
Fig. 402.
Agliscra ignea, Vanhoffen (f ).
(From Vanhoffen. )
reach the 40th or 50th degree of latitude, where we Hnd some small
forms living entirely in the upper layers of the Atlantic and Indian
Oceans, as for instance RJiopalonenia velatuni, Aglaura hemistoma,
and Liriope tetraphylla (Fig. 400) ; they are devoid of colour or
only faintly tinted, some of them being only a few millimetres in
diameter. Others are genuine deep-sea forms, found only below 600 or
1000 metres. Crossota brunnea (Fig. 401) is dark brownish, Agliscra
ignea (Fig. 402) is a flaring red, and Halicreas rotundatum (Fig. 403) is
distinguished by bright red markings.
The Narcomedusa; are oceanic forms, including some small colourless
surface forms and strongly tinted (brown) deep-sea forms.
1 This species was taken by me in a deep haul in the Norwegian Sea, and Vanhoffen placed
it very near to the tropical species Crossota brunnea, see Wiss. Ergeb. " Valdivia" Expedition,
Bd. 3, 1902 ; and "Die Fauna und Flora Gronlands," Grdnland Expedition (Berlin, 1897).
572
DEPTHS OF THE OCEAN
The Acraspeda include the common jelly-fish, and excepting the
genus Pelagia they all go through an alternation of generations. The
free-swimming medusae produce eggs, the larvae fixing themselves to the
bottom and developing a zoophyte differing from the hydroid-zoophyte
in that it produces only one kind of bud ; the division is transverse, the
medusae not being'produced, as in the hydroida, by evagination (Fig. 404).
In northern waters, for instance on the coast banks and in the fjords
of Scandinavia, the brown stinging jelly-fish Cyanea capillata and the
transparent jelly-fish Aurelia aurita are the most important species ; in
the southern part of the North Sea we find the blue Cyanea lamarckzana,
which annually drifts up to the Skagerrack and the west coast of Norway.
Distantly related to these is Rhizostoma octopus, which is similarly dis-
Fig. 404.
Development of Aurelia aurita froni the o\um. The upper series shows the development of the
larva (planula) into Scyphostoma ; the lower series shows stages in the formation of small
medusas by division. (After Hatscheli, from Hertwig. )
tributed and occurs in Scandinavian waters as a visitor. The oceanic
genus Pelagia, as already indicated, has a direct development, and is
thus holopelagic (see Fig. 405). Of certain smaller groups resembling
the Trachymedusae, I may mention the gehera Atolla, PeripJiylla (Fig.
406), and Nausithoe, which are wholly oceanic forms widely distributed
mainly in deep water.
During the cruises of the " Michael Sars " the distribution of medusae
in the Norwegian Sea and in Norwegian coast waters has for years
been investigated, and Damas, who is working up the material, has
found 64 species, of which 14 are new to science ; some are shallow- water
forms, and others belong to the deep fauna of the fjords. In 1900 I
noted the occurrence of Cyanea capillata all over the warm part of the
Norwegian Sea, and later on the drift of this form from the coasts has
been traced, as also the drift of Cyanea lamarckiana from the North Sea to
the west coast of Norway (see Chapter X.).
PELAGIC ANIMAL LIFE
573
During the Atlantic cruise in 1910 a large collection of medusae was
obtained, of which only the Acraspeda have been determined by Broch,
who records the following forms from the stations specified : —
Fig. 405.
Pelagia perla, Slabber.
(After McAndrevv and Forbes, from
Steuer. )
Fig. 406.
Periphylla hyacmthiiia, Steenstrup.
About nat. size. (From Vanhoffen.
Periphylla hyacinthina, Steenstrup, Stations 10, 19, 34,
56, 58, 62, 64, 66, 67, 70, 80, 81, 82, 84, 88, 92, 94,
lOI.
P. regina., Haeckel, Stations 19, 49, 56, 62, 63, 64, 84, 92.
Naiisitho'e atlatitica^ n. sp.. Stations 56, 90, 92.
„ globifera, n. sp.. Stations 10, 88, 90, 98, loi.
Atolla wyvillei, Haeckel, Station 62.
„ hairdii^ Fewkes, Stations 10, 23,
51. 53> 56, 62, 64, 66, 67, 70, 80, ^
92, 94, 98, lOI.
Pelagia perla, Slabber, Stations 10, 25, 51, 52, 56, 81, 82, 84,
86, 87, 88, 90, 92, 94.
Chrysaora mediterranean Peron et Lesueur, Algeciras.
Poralia sp. {rufescens}), Station 85.
Aurelia solida, Browne, Station 56.
:5, 29, 35> 42, 45,
, 82, 84, 87, 88,
42, 45> 51, 5-
./
Fig. 407.
Diphyes arc tic a,
Chun (f ). (From
Vanhoffen. )
This list shows that Periphylla hyacintJiina and
Atolla bairdii are so widely distributed in the North Atlantic that they
may be said to occur everywhere ; they are, as we shall see later, both
574
DEPTHS OF THE OCEAN
-^.4
'V
deep-living forms. Among surface forms only Pelagia perla was taken
abundantly, and its distribution was peculiar, the species being most
numerous along the line of stations crossing the Azores in a north and
south direction, coinciding
with the submarine ridge \\
on which these islands are : 'W^..
situated (see Map III.).
Siphono- The Siphonophores are i
phorae. an interesting group, .. - -^
sometimes referred to the i ^^
hydromedusae, but entirely I
independent. They are
oceanic, and have no
bottom - stage, their de-
velopment being a direct
one. This class of animals
is exceedingly rich in
species, and we can only
mention some North
Atlantic forms.
Only three species are
wholly indigenous to
northern waters : Diphyes
arctica (Fig. 407), peculiar
to the Gulf Stream north
of lat. 59° or 60'^ N., ex-
tending to Spitsbergen in
lat, 81° N., and Galeolaria
biloba and Cupiilita cara,
which are less common. In
the Atlantic we find a
wealth of both deep - sea
and pelagic forms, some of
the latter being known as
visitors in the North Sea
and the Norwegian Sea, a
few having being found on
the west coast of Norway
and described by Michael
Sars as long ago as the
'thirties, like Agalmopsis
elegans and Physophora hydrostatica (Fig. 408) ; in the Sognefjord
Haeckel also found Circalia stephanomvia. These forms have numerous
swimming bells and long tentacles, and are interesting as immigrants
from the Atlantic into the North Sea and the Norwegian Sea, Among
forms peculiar to the warm surface layers we may mention the
" Portuguese man-o'-war," Physalia aretJmsa (Fig, 409), and the " By
the wind sailor," Velella spiralis (Fig, 410), which belong to the regions
south of the 40th degree, but have occasionally been found as visitors on
the shores of the British Islands.
Physoplu
Fig. 408.
■a hydrostatica, Forskal.
About half iiat.
(From M. Sars.)
PELAGIC ANIMAL LIFE
575
Together with these forms we often find Cestus veneris, one of the Ctenophc
Ctenophores, a class including many pelagic forms, both surface and deep
sea. Four species of Ctenophores have been observed in the arctic
region : Mertensia ovum, Pleurobrachia pileiis, Bolina mfundibulmn, and
Beroe cuaimis. After studying the collections of the "Belgica" and
the "Michael Sars," Damas and Koefoed state that Pleurobrachia pileus
..M^'-pff^
Fig. 409.
Physalia. (I-'roni Steuer. )
is a coast form occurring from the channel
infundibuluin and Beroe cucumis have a
occur in deeper water, for instance, in the
fjords ; Mertensia ovum is an arctic form,
wegian fjords. -
to Spitsbergen ; Bolina
far wider distribution, and
deep waters of Norwegian
also found in deep Nor-
all the higher groups of Pelagic larv«.
• pelagic, from the medusae to
forms of the latter the general
lead a bottom life while the
among the medusae the mature
swimming or floating, young
Pelagic larvae are encountered among j
animals either holopelagic or mero-
the fishes. Among the higher organised ■>'
rule seems to be that the mature stages j;'
eggs and larvae are pelagic, whereas
stages are generally pelagic. Pelagic,
stages are found in the echinoderms '"'^ (starfishes, holothurians,
etc.), annelida, bryozoa, and in various '"' crustaceans from the sessile
cirripeds to the lobsters and crabs ; snails and mussels also have pelagic
young.
In spring especially the coast-waters teem with the larvae of all
these animals, the larval forms very often differ from the adult, and an
enormous amount of work has been devoted by zoologists to the
description of all these forms. Some of these larvae seek the bottom
after a lapse of only a few days, but many species lead a long pelagic
life and during this period go through metamorphoses, among the most
576 DEPTHS OF THE OCEAN
remarkable being the larvae of starfishes, ophiuridae, and sea-urchins. In
the larvae of the ophiuridae (see Fig. 411) the skeleton consists of rigid
^--
Fig. 410.
Velella spiralis, Esch. (From Steuer. )
Larva of Ophiothrix fragilis, O. F. Mtiller (about -\-). (From Mortensen.)
P^lG. 412.
Arachnactis albida, M. Sars. Nat. size. (FromSars. )
rays of carbonate of lime, with a belt of cells provided with whip-like
hairs, by the aid of which they swim ; these larvae go through wonderful
metamorphoses before finally attaining the adult form.
PELAGIC ANIMAL LIFE
577
The larval Actiniae are biologically of great interest, especially Actiniaria.
AracJinactis albida, first described by Michael Sars (Fig. 412). The north-
eastern corner of the Atlantic is its main area of distribution, principally
between the Hebrides and the Faroe Islands, but at certain seasons it is
carried into the North Sea and the Skagerrack, and to the west coast of
Norway, where Sars found it (see Fig. 480).
A description of the larvae peculiar to the different groups would lead
us too far, but in order to prepare the reader for the next chapter
some of the forms have been mentioned.
r
The Worms are comparatively rare among the pelagic forms. Of Vermes,
the lowest worms (platyhelminthes) the pelagic Nemertines are of
interest. Nearly all Nemertines live along the
bottom, but a pelagic genus {Pelagonemertes) was
described by Moseley in the " Challenger" Reports.
Subsequently several species have been described,
all represented by isolated specimens. These re-
markable forms are red or orange coloured, and
their digestive tract is extremely ramified. Accord-
ing to Brinkmann, who is examining our material,
most of the previously known species, as well as
some new species, have been taken during our
Atlantic cruise, and prove that several species
hitherto regarded as distinct are really identical :
thus Nectoneinertes grimaldi^ N. lobata, and
N . pelagica are all identical with N. mirabilis. The
genus Nectonemertes with N. mirabilis, and also
the genus Hyalonemertes with H. atlantica, were
established by Verrill. The two forms (see Fig.
413) differ, as shown by later investigations, only
in one single character, N. mirabilis having two
long appendages on the head, which are lacking
in H. atlantica. The abundant material collected
by the " Michael Sars" has enabled Brinkmann to
show that all the individuals of N'. mirabilis are
males, while all the individuals of H. atlantica are
females, and he concludes that both belong to the same species, the
difference between them being only a sexual one.
Very interesting were some gigantic specimens belonging to this
group secured during the cruise. One form, Dinonemertes investigatoris
(see Fig. 414), was 20.5 cm. long, and when living was of a bright red tint
and nearly transparent, all the ramifications of the digestive tract being
plainly visible. As we shall see when reviewing the captures of the
" Michael Sars," all these Nemertines are deep-sea forms with a very
characteristic vertical distribution. Several of the species are very widely
distributed, Nectonemertes mirabilis, for instance, being known from
Davis Straits, from the Pacific off California, and all through the Atlantic ;
Dinonemertes investigatoris is known from the Atlantic as well as from
the Indian Ocean.
The most abundant group of pelagic worms as regards number of
2 P
Fig. 413.
Nectotieme rtes mirabilis,
Verrill. Slightly enlarged.
a, male ; b, female.
578
DEPTHS OF THE OCEAN
individuals is the Sagittidee or Chsetognaths, which,
along with copepoda, salpaj, pteropoda, and radiolaria,
everywhere constitute the bulk of the small pelagic
organisms captured by our fine-meshed tow-nets. They
are perfectly transparent, of slender build, and swift of
motion. On the head are some bristle-like gripping
appliances, and an elastic film-like rim, reminding one
of the fin of a fish, runs along the
body and the "tail "(see Fig. 41 5).
The Sagittidae comprise only
a few genera, the most prolific in
species being the genus Sagitta,
which is represented in all
oceans ; some of the species are
very widely distributed, such as
Sagitta hexaptera, S. serratoden-
tata^ S. bipiinctata. In northern
waters Krolmia hamata, Sagitta
arctica, and Sagitta gigantea are
characteristic forms, the last men-
tioned having been taken by the
"Michael Sars" in deep hauls
in the Norwegian Sea, while
Sagitta inflata is a form peculiar
X I to warm waters. All these
I I species are perfectly transparent,
I I but during the Atlantic cruise
we found specimens of a bright
red colour, precisely like that of
the pelagic Nemertines, belong-
ing to Sagitta niacrocephala and
Eukrohnia foivleri; they were
very abundant, and occurred,
like the Nemertines, only in
deep hauls.
The very numerous families
of higher worms, especially the
Annelida, contribute very little
to the pelagic fauna of the ocean.
Among the best known is the genus Tornopteris, which
has many beautiful surface forms, some of these (like T.
septenti'ionalis) being boreal, some belonging to warm
waters. In his narrative of the cruise of the " Valdivia,"
Chun tells us that nearly every haul from deep water in
the Antarctic brought up beautiful specimens of Tomop-
teris, as long as the finger, transparent, and with rose-
tinted feet (parapodia). Individuals belonging to the
genus Tomopteris were taken in several of the deep
hauls and also in the surface hauls of the " Michael
Sars," but the material has not yet been worked up.
Fig. 414.
Dinonemertes investigatoris ,
Laidlaw. Half nat. size.
d'Orb. {\). (From
Hertwig. )
PELAGIC ANIMAL LIFE
579
No class of multicellular animals in the ocean is represented by any- Crustacea,
thing like such countless forms and individuals as that of the Crustaceans ;
in the life of the ocean they play, according to Haeckel, a part corre-
sponding to that of the insects in the land fauna. The Entomostraca
include the most important groups, first the Copepoda, then the
Ostracoda, and the Cladocera. Among the larger Crustacea, the
Schizopoda, the Amphipoda, and the Decapoda are also very important,
but in abundance and specific variation they can never be compared to
the groups of smaller crustaceans.
The Copepoda, as a rule, attain only a few millimetres in length, and Copepoda.
are adapted to feed on the small plants of the oceanic flora in the upper
layers of all oceans. It may safely
be asserted that they are the chief
consumers of these minute plants,
and in turn serve as food for
larger animals.
Giesbrecht ^ discusses the geo-
graphical distribution of 299 species
of Copepoda, and divides the area
of their distribution into three
regions: (i) a warm region between
47° N. and 44° S., (2) a northern
region, and (3) a southern region.
The warm region comprises all the
oceans, the warm - water species
throughout the world being more
alike than the species of warm and
cold regions in the same ocean.
Of the 299 species, no less than
254 belong exclusively to the
warm region ; there are besides
a few widespread forms and others
peculiar to the northern or southern region. About 85 per cent of
the species belong to the warm region, 5 per cent to the northern, and
2 per cent to the southern region.
As characteristic of the warm region Giesbrecht mentions the follow-
ing genera: Augaptilus, Calocalanus, Copilia, Euchirella, Heviicalanus,
Monops, Pleuromina, Pontella, Pontellma, Sapphirma. Peculiar to the
northern area are : Acartia bifilosa, Calanus hyperboretis, C. cristatus,
Centropages Jiamatus, EuchcEta norvegica, Pseudocalanus elongatus, and
perhaps Teviora longicornis. Some forms are common to the warm
region and one of the cold regions, such as Anomalocera patersoni and
Centropages typicus, while Calanus fitimarchiciis and Oithona similis
occur in all the three regions.
The warm and cold water forms differ in structure, the body, legs,
and antennae of the warm water forms being generally provided with
wonderful feather or fan-shaped attachments, which greatly enlarge the
Fig. 416.
Calanus Jinmarchicus, Gunner.
After G. O. Sars, from
Steuer. )
1 Giesbrecht, " Systematik und Faunistik d. pelag. Copepoden," Fauna nnd Flora
des Golfes von Neapel, Bd. 19, 1S92.
58o
DEPTHS OF THE OCEAN
surface of the animals and facilitate their floating, while in northern
waters the species are devoid of such appendages. It is thus interesting
to compare the widespread species Calanus finmarchicus (Fig. 416),
which occurs in greatest abundance in boreal areas, with the tropical
Augaptiliis filigeriis (Fig. 417), which has elaborate appendages, reminding
one of peacocks' feathers. We find the same difference between
Oithona plumifera and Oithona similis, and between EiicJiczta marina
and Euclmta norvegica (Fig. 418). We find in these cases a perfect
analogy with what Gran has
described among the peridineae
in Chapter VI. ; for instance,
Ceratiuni platycorne (see Fig.
228, p. 324) in warm water en-
FiG. 417.
Augaptilus filigerus, Claus.
(After Zacharias, from Steuer. )
Fig. 418.
/ iichata norvegica, Boeck.
( From Sars. )
larges its surface, while in cold
water the horns are much more
slender, the lower specific gravity
caused by the higher temperature
rendering floating appliances
necessary for both animals and plants (see also Chapter X.).
The Copepoda occur in all depths, and some authors have attempted
to define certain bathymetrical regions, each with its own characteristic
forms, but the observations available are insufficient to enable us to
form definite ideas on the subject ; much new light will' doubtless be
thrown on the matter when the reports of the " Valdivia" and " Michael
Sars " Expeditions come to be published. The discussion as to whether
the surface forms of cold regions are found in the deep water of warm
regions is interesting.
The " Valdivia " Expedition captured EucJiirella venusta and Calanus
finmarchicus in a haul with a closing net between 1600 and 1850 metres
PELAGIC ANIMAL LIFE
581
in subtropical seas where the surface temperature is very high, and
Dahl mentions this latter form as living in deep water in the Sargasso
Sea.
Numerous investigations on the Copepoda of the Norwegian Sea have
in recent years been made by the " Michael Sars," the material having
been worked up mainly by Damas, whose results will be mentioned in
the sequel. From the Atlantic cruise of 1910 the " Michael Sars" also
brought home a large collection of Copepoda captured both in horizontal
hauls and in closing nets, and this material is at present being described
by Nordgaard and Lysholm, but their results are not yet ready for dis-
cussion. G. O. Sars has, however, been good enough to determine the
Copepoda for me in a few selected samples, and these determinations
are so interesting that I give in the following table the number of
species found at various depths : —
Number of Species of Crustaceans, chiefly Copepoda, taken in
Closing Nets at the Stations specified
Depth of the Hauls.
Station
SO-
Station
63.
Station
80.
Station
92.
Station
113.
0 to 200 or 300 metres
200 or 300 to 500 metres .
500 to 1000 metres .
22
22
51
25
27
16
27
34
18
12
33
21
18
II
The most northerly station (113) is relatively poor in species, especi-
ally in the deep cold layers, the richest station being the most southerly
one (50), and remarkably enough the richest sample is the deepest one
in 500 to 1000 metres, which contained twice as many species as the
surface sample.
The Ostracoda are considered by Haeckel to be the most important Ostracoda.
group of Crustacea next to the Copepoda, being represented by a great
number of species. The "Challenger" collected 221 species, of which
52 were taken in depths greater than 500 fathoms, 19 beyond 1500
fathoms, and 8 beyond 2000 fathoms. Many ostracoda possess the
power of emitting intense phosphorescent light, and Haeckel narrates how
on his voyages to Ceylon he saw the entire sea like a continuously
twinkling ocean of light as far as the eye could reach ; the microscope
proved most of these luminous animals to be ostracoda, with some
medusae, salpae, and worms.
Some of the surface ostracoda are very widely distributed, like
ConcJicecia elegans, which occurs all the way from the Norwegian Sea
to the Antarctic. In northern waters we may find also C. borealis and
C. obUisata. In Antarctic waters we find C. antipoda, closely resembling
C. obtusata of the north. As abyssal forms we may note the large
individuals (attaining i cm. in length) of the genus Gigantocypris
(see Fig. 419), recorded by the " Valdivia " from the Indian Ocean
and from the Atlantic between lat. 14" N. and 42° S., previously
582
DEPTHS OF THE OCEAN chap.
took this genus in deep
known from the Pacific.^ The " Michael Sars
water at several stations in the North Atlantic,
The Cirripedia are the only group of crustaceans which in the adult
stage abandon the pelagic life of youth and become sessile, fixing them-
selves to the bottom like many other invertebrates. Some are fixed to
the rocks of the littoral region (the balani), or to pumice stones and
nodules from the great depths of the ocean, while others are attached to
whales and turtles, or (like the Lepadidae) to floating objects carried
along by currents. One species {Lepas fascicidaris) forms considerable
floating clusters composed of several individuals. A peculiar group
(for example, Sacculina from the tail of decapod Crustacea) is entirely
parasitic and transformed to
such a degree that the crusta-
ceous nature of the animal is
hardly recognisable.
The Cirripedia from the
Atlantic cruise of the " Michael
Sars " have been examined by
P. P. C. Hoek, who found the
following species of the genus
Lepas : —
Lepas anatifera (see Chapter III.,
p. loo, Fig. 87), taken at Station
61 (on a floating log), and off
St. John's.
Lepas anserifera, Station 67 (on
Sargasso weed), Station 69 (on
a small log).
Lepas pectinata^ Stations 10, 25, 31,
69, 86, 91 and 92 (fixed to birds'
feathers, cork, fucus, pumice-
stone, and to L. fascicularis).
Lepas hii/i, Station 56 (on a turtle).
Lepas fascicularis, Stations 25, 91, 92.
All these species are known from other oceans, especially the Pacific,
and are principally warm-water forms. Of other Cirripedia the following
species were captured : —
Fcvcilasma carinatmn, Station 53 (on the bottom).
Conchoderma virgatum, Station 56 (on a turtle).
Scalpelliim vehitinum, Stations 24 and 53 (on the bottom).
„ dicheloplax, Station 10 (on the bottom).
,, atlanticiim, Station 23 (on the bottom).
G. O. Sars described 57 species of Schizopoda from the " Challenger "
Expedition,^ of which 32 were taken only at the surface, 6 between 32
and 3CX) fathoms, 4 between 300 and 1000 fathoms, 11 between 1000
and 2000 fathoms, and 4 beyond 2000 fathoms. Most of these were
1 See G. W. Miiller, Wiss. Ergeb. " Valdivia" Expedition, Bd. 8, 1906.
2 See Zool. Chall. Exp., Part XXXVII., 1885.
Fig. 419.
Gigantocypris agassizii , G. W. Miiller (|)
(From Miiller. )
PELAGIC ANIMAL LIFE
583
represented by few specimens, though widely distributed. Hardly any
of the " Challenger " species described by G. O. Sars are found in the
Norwegian Sea.
The Schizopoda play a great part in northern waters, where the
numerous species occur in enormous numbers, sometimes near the bottom
and sometimes near the surface ; the fishermen term them " Kril." They
Fig. 420.
Meganyctiphanes notvegica, M. Sars {\). This form has
highly phosphorescent organs on the under side of the
are mostly colourless, transparent, with large red spots around the mouth,
and have generally the appearance of small prawns with black stalked
eyes. The most important species are Meganyctiphanes norvegica (Fig.
420) and Thysandessa longicaudata. The closing-net samples determined
by Sars included some Schizopoda,
Amphipoda, and Isopoda (see list, pp.
654-655)-
The great majority of the species of Amphipoda.
Amphipoda inhabit the warm oceans,
where they occur mostly in the upper
400 metres of water. Woltereck has
described some very remarkable deep-
water forms belonging to the genera
Lanceola and ScypJiolanceola (Fig. 421).
The members of the latter genus have
light-reflecting eyes, the retina of which is entirely transformed and
provided with peculiar cornet-shaped reflectors. They were previously
considered rare, but according to Woltereck, who is describing our
material, they were taken in great quantities during the cruise of the
" Michael Sars." Another deep-sea form is the large transparent
Cystosoma with splendid red eyes, which was taken in both our
southern and northern sections in depths exceeding 500 metres (Fig.
422). One of the most striking types is the genus PJironima, of the
family Hyperidae. Most of the Hyperidae make themselves a house of
the empty mantle of a Salpa or Doliohini, and lay their eggs in the
Fig. 421.
Scypholanceola agassizii, Woltereck.
(From Woltereck.)
584
DEPTHS OF THE OCEAN
barrel-shaped abode (see Fig. 423). Phronima was taken in great
quantities in the surface waters during our southern and northern sections
across the Atlantic.
In the Norwegian Sea two forms are very important : ParatJieviisto
oblivia (Fig. 424), which lives in the open sea, frequently even in very cold
water, and also in the Norwegian fjords ; and Euthemisto libellula, which
sometimes attains a length of 4^ cm., and lives in the icy waters of the
Fig. 422.
Cystosoma neptuni, Gu^rin-M^n6ville. (After Wyville Thomson.)
Polar Sea. Both these forms were taken also in the Atlantic, but only
in boreal areas (see list, pp. 654-655). A form which lives at great
depths in the Norwegian Sea is Cyclocaris giiilelmi, taken by the Prince
of Monaco off the Lofotens and described by Gran.
While capturing turtles at Station 56 we observed a great number of
deep-blue Isopoda belonging to the species Idotea metallica.
Decapoda. The Decapoda include nearly all the large types of crustaceans, like
prawns, lobsters, crayfish, crabs, etc. The first deep-sea expeditions
captured a considerable number of decapod crustaceans in the trawls at
PELAGIC ANIMAL LIFE
585
Phronima.
■ 4^3-
(From Steuer. )
great depths, and they were consequently supposed to be bottom-dwellers.
Subsequently the Prince of Monaco, and later the " Valdivia," took in
pelagic tow-nets a number of forms belonging chiefly to the family
Sergestidae, and to the genera AcanthepJiyra, Notostomus, and Eryoneicus,
all of which were thus proved to lead a pelagic life. The " Valdivia "
took Sergestes in a haul with a closing net from 5000 to 4000 metres, and
Chun states in his narra-
tive of the cruise that
whenever the vertical nets
reached deep water this
genus never failed to
appear in the hauls.
During the Atlantic
cruise of the " Michael
Sars " we obtained large
red prawns in such abund-
ance (several litres per
haul) as to prove that
these animals play a more
important part in pelagic
life than was previously
supposed. Our catches are
also of special interest, be-
cause their study has thrown new light upon the vertical distribution
of the different species. We may here mention some of the most
important forms recorded by Oscar Sund, who is describing this group.
Of pelagic decapoda more than forty species were taken during our
expedition, but the great bulk is made up of about a dozen species, each
of which has a wide geographical range, being regularly caught at all
stations over vast areas. Most of these
common species, which will be dealt
with later on, present peculiarities in
their biology and distribution.
Most of the pelagic decapoda be-
long to the more primitive divisions of
the group, viz. Sergestidae, Peneidae,
Pasiphaeidae, and Hoplophoridae, but
a truly pelagic Pandalid {Plesionika
nana, n. sp.) was taken at most of
the stations from Spain to Newfound-
land.
The genus Acanthephyra of the Hoplophoridae (see Plate III.
Chapter X.) includes large red prawn-like forms, of which no less than
eight different species were taken. On the section between Newfoundlarid
and Ireland the two species A. purpurea and A. multispina were m
special abundance.
Before the cruise of the "Michael Sars" only fifteen individuals
belonging to the genus Notostomus, representing no less than thirteen
species, had been recorded. We procured nineteen individuals in the
North Atlantic belonging to five species, of which four are new to
Fig. 424.
Parathemisto oblivia, Kroyer (f ).
(From Sars. )
586
DEPTHS OF THE OCEAN
science. One of these new species is represented by a specimen 17 cm.
long (see Fig. 425) — one of the largest pelagic prawn ever taken. Noto-
stomus was taken only in the deepest hauls, which only extended down
to 1500 or 2000 metres ; perhaps hauls in still deeper water might have
Fig. 425.
Notostomus, n. sp. Nat. size, 17 cm.
yielded more of them. Still larger are the bottom-living Peneidas, of
which a whole tubful were taken south of the Canaries in our trawl
(Station 41, 2605 metres),
some of them 30 to 40 cm,
long, with feelers 4 or 5 feet
long.
One of the most remark-
able genera is Eryonezcus, of
which twelve species are
known, easily recognisable
by their inflated balloon-like
bodies (see Fig. 426). They
are allied to Pentacheles,
Polycheles{¥\g. 427), etc., and
Sund, after examining the
twenty - four specimens col-
lected by the " Michael Sars,"
expects to be able to show that
they are really the larvae of these abyssal bottom-living decapoda. Thus,
what might be regarded as a new species of Eryoneiais is in reality a
larval stage of a previously known decapod, PolycJieles sculptus.
During the first cruise of the " Michael Sars " in the Norwegian Sea I
succeeded in capturing the two species PasiphtEa pj'inceps and Hymenodora
glacialis (Fig. 428; in deep hauls. PasipJicea probably lives sometimes
on the bottom, sometimes in midwater, and is common in Norwegian
Fig. 426.
Eryoncicus Circus, Spence Bate.
Faxon. )
PELAGIC ANIMAL LIFE
587
fjords along with numerous species of Pandalus, "the deep-water prawns,"
which are now the object of import-
ant fisheries. Hymenodora is known
/ / Vk even from the ice-region, and was
met with by Scoresby during his
arctic voyages.^
Though the Mollusca are widely
distributed and represented by a
vast number of different forms on
the ocean-floor, the pelagic forms
are comparatively few, but as re-
gards abundance of individuals few
groups of pelagic animals can com-
pare with the winged snails or
Pteropoda, which are divided into
two groups : Thecosomata (or shelled
pteropods) and Gymnosomata (or Pteropoda.
naked pteropods).
The Thecosomata are important
on account of the part they play
both in the plankton and in the
bottom-deposits (see Chapter IV.).
They include the family Limacinidae
having a spiral shell, of which the
well-known Liinadna Jielicina occurs
in immense quantities in the Arctic
(the seas around Spitsbergen and
Greenland), while Liniacina balea,
the " Flueaat " of Norwegian
fishermen, is a boreal species, and
Liniacina retroversa (Fig. 429) is a
more southern form occurring also in
the Norwegian Sea. The shell is about the size of a pin's head, and can
Fig. 427.
Polycheles sculptus pacijicus, Fax. (From Faxon.)
Fig. 428.
Hymenodora glacialis, Buchholz. (From G. O. Sars. )
^ In the pelagic life of the ocean the Insecta are represented only by several species of
Hemiptera {Halobates and Halobatodes), which are found skimming over the surface in the
tropical regions.
588
DEPTHS OF THE OCEAN
barely be seen in the sea with the naked eye. The two last-mentioned
forms are found in warm currents on the coast of Norway, and their
presence is feared by the fishermen, because they very often spoil the
herring which feed on them ; the shells are very slowly digested and the
stomach-contents putrify when the her- ^__^
rings are salted, and then the whole herring ( .
decomposes. Among the many warm- ^
water species Liniacina biilimoides is
characteristic. The Cavolinidse include
numerous forms with cornet-shaped shells.
Clio pyramidata (Fig. 430) and Diacria
trispinosa are very important forms,
occurring in vast numbers, and their shells
are very numerous in the deposits. Creseis
Fig. 429.
Lhnacina retroversa, Fleming.
(From Sars. )
Fig. 430.
Clio pyra m id a ta, L
(From Boas.)
acicula (Fig. 431) and Cavolinia gibbosa
(Fig. 432) are characteristic forms.
The " whale's food," Clione liniacina
(Fig. 433), is specially abundant in north-
ern waters, and is better known than most
of the Gymnosomata. It is 3 or 4 cm.
long, perfectly transparent, with red shad-
ings and black stomach. In the Polar
Sea it may be seen swimming among the
ice-floes, but it occurs also in the Nor-
wegian Sea, in the Norwegian fjords, and
in the Atlantic south of Iceland.
The majority of the pteropoda (both
species and individuals) are restricted to
warm water : in the Atlantic the northern limit for the warm-
water forms may be roughly drawn from the Bay of Biscay to New
York, and the southern limit from Brazil to the Cape. This area
is the real home of Clio pyramidata, C. aispidata, Creseis aciada, the
Cavolinidae, the Cymbulidae, Pneumoderma violaceum, Liniacina infiata,
L. lesueuri, L. biilimoides. As with the radiolaria and copepoda, many
Fig. 431.
Creseis acicula, Rang.
(From Meisenheimer. )
\_.. /
PELAGIC ANIMAL LIFE 589
of these warm-water species of pteropoda are also known from the
Indian and Pacific Oceans, where their geographical distribution is
similar to that in the Atlantic. North of lat. 45"
or 46° N. we meet with only a few of the warm- ,/y'^^^~~'^:
water forms, Creseis acicula and Clio cuspidata
having been taken in isolated specimens up to \
60° N. Typical denizens of this region are Clio / ^
pyraniidata and Diacria trispinosa, which appear '
to be as numerous as under the equator. The
northern forms Liviacina lielicina and L. balea, as
well as Clione limacina, also occur in the northern
part of the Atlantic. In the Antarctic we find
species which are very similar to the northern
ones.
Meisenheimer,^ who reported on the pteropoda
of the " Valdivia" Expedition, isof opinion that the \y
horizontal and vertical distribution of the ptero- ^
poda depends mainly on the temperature. Most ^ ,. .^^^'.^}'^' ^
^,. ^. . 1-1, , ir Cavohma ginbosa. Rang.
of the species require a high temperature, and for (prom Meisenhdmer. )
this reason the majority live in the surface layers.
Only exceptionally do they occur as deep as lOOO metres, and this is
specially the case in the Mediterranean, where high temperatures prevail
to very considerable depths. During
our Atlantic cruise we found some real
deep-sea forms : Peraclis diver sa^ Lima-
cina helicoides, and Clio falcata, which
occurred only between 500 and 1500
metres.
During the Atlantic cruise of the
" Michael Sars " pteropoda were taken
in thousands, and this material has been
examined by Bonnevie, who records the
following species : —
The Thecosomata include: — Limacinidse:
Limacina balea, L. retroversa, L. buli-
moides, L. infiata, L. lesueuri, L. helicina,
L. helicoides, Peraclis reticulata, P. triacanfha,
P. diversa, and Procymbulia sp. Cavolinidae:
Clio pyraniidata, C. cuspidata, C. falcata,
Creseis acicula, Sty Ho la subula, Hyalocylix
striata, Cuvierina columnella, Diacria tri-
spinosa, D. quadridefitata, Cavolinia infiexa,
C. gibbosa, C. loigirostris, C. tridentata.
Fig. 433. C. uncinata. Cymbulidse : Cymbulia
Clione limacina, Ph'\^Y>^. (FromlVanhoffen.) peronii.
The Gymnosomata comprise, besides
Pneumodermopsis macrochira 'and Clio/ie limacina, several new species not yet
described.
Of other Mollusca I may mention the beautiful surface forms :
^ Meisenheimer, Wiss. Ergeb. '■'■Valdivia'' Expedition, Bd. 9, 1905.
><
DEPTHS OF THE OCEAN
1
lanthina, Carinaria (see Fig. 122, p. 154), Pterotrachea (see Fig. 123,
p. 154), and Glaucus, which were taken in abundance in the southern
section of our Atlantic cruise.
Of the large group of Cephalopoda (squids
and cuttle-fishes) previous expeditions ob-
tained very few in their small tow-nets, those
captured being generally taken in the bottom
trawls, and it was uncertain whether they
lived at the bottom, or in intermediate
depths, or near the surface. It has long
been recognised, however, that many Cepha-
lopoda are true pelagic animals, and in the
sixties of last century Japetus Steenstrup
applied the term " Decapodes pelagici " to
the group CEgopsidae. The Prince of
Monaco not only captured Cephalopods in
his pelagic trawls, but also obtained them
from the stomachs of whales which he shot,
his material being reported on by Joubin.^
During the " Valdivia " Expedition the large
vertical nets captured a wealth of new forms
belonging especially to small types, and
Chun in his narrative draws attention to
the remarkable Cranchiidae and the little
Spirula. Chun has recently published the
first part of his report on the " Valdivia "
collections of Cephalopoda, dealing with the
CEgopsidae."
It was a special pleasure to me that
Chun undertook to describe the Cephalopoda
obtained during our Atlantic cruise, and his
report, which has just been completed, is
available for this preliminary record of the
results. His determinations are given in the
list on pp. 595-597, and comprise 43 species
in all, 3 or 4 of which are new to science,
besides some larval forms, the identity of
which is uncertain.
The Cephalopoda are generally divided
into two groups according to the number of
tentacles, those with ten arms or tentacles
being termed Decapoda, and those with
eight tentacles Octopoda ; the Decapoda are
subdivided into CEgopsidae and Myopsidae.
the Octopoda have a membrane covering the eye, but in the CEgop-
sidae this is perforated.
^ Joubin, " Cephalopodes provenant des campagnes de la Princesse- Alice," Campagnes
scientifiques du Prince de Monaco, Fasc. xvii., 1 900.
2 Chun, Wiss. Ergeb. " Valdivia" Expedition, Bd. 18, 1910.
Fig. 434.
Pterygioteuthis giardi, Fischer (f ).
( From Chun. )
The Myopsidae and all
PELAGIC ANIMAL LIFE
59:
Most pelagic squids belong to the CEgopsidse, which present a wealth
of forms ranging from minute fantastically shaped deep-sea species to
the giant squids.
The Enoploteuthidae obtained by us are small forms previously
known from the Atlantic and Indian Oceans.
The general occurrence of PterygioteutJiis giardi
(see Fig. 434) seems to justify the conclusion
that it is a very common pelagic species, inhabit-
ing the open ocean far from land ; it is provided
with light-organs. The larvae belonging to this
**'
Fig. 435.
Larva of Enoploteuthidae (^x)- (From Chun. )
family are very abundant in the North Atlantic
(see Fig. 435).
Of the family Onychoteuthidae many unde-
termined larvae have been taken by the " Michael
Sars," which are of great interest as proving the
occurrence of this group ; a larval form taken by
the " Valdivia " is shown in Fig. 436. Onyclio-
teutJiis banksii occurs from the Mediterranean
to the Kattegat and Skagerrack and along the
entire coast of Norway. Octopodoteuthis sicida
and CalliteutJns reversa are minute forms, the former known from
the north-eastern part of the Atlantic, while the latter is widely dis-
tributed in the surface waters of the Indian and Pacific Oceans, and has
Fig. 436.
of Teleoteuthis caribtpa.
.(f). (From Chun. )
Fig. 437.
Calliteuthis reversa, Verrill (f ).
(P'rom Chun.)
light-organs (see Fig. 437). Ctenopteryx siculus, Brachioteiithis riisei, and
the three species of Doratopsis are small and live presumably in the
upper water-layers. Doratopsis exophthalmica (Fig. 438) is noticeable
on account of its remarkable eyes (see Fig. 439).
The families Ommatostrephidae, Gonatidae, and Chiroteuthidae
592 DEPTHS OF THE OCEAN
include mostly large forms, belonging to a biological group of squids
(comprising the family of giant squids, Architeuthidae), the members of
which are among the pirates of the ocean, and in their turn fall a prey to
the large squid-hunting whales. Illex illecebrosus and Onimatostrephes
todarus are northern forms, of great importance on the banks of New-
foundland, and along the coasts of Iceland and Norway, as Gonatus
fabricii (see Fig. 98, p. 113) is the squid of the "bottle-nose grounds"
in the Norwegian Sea. Todaropsis eblancz and OmmatostrepJies sagittatus
extend nearly as far north as the southern borders of the Norwegian Sea.
Fig. 438.
Doratopsis ex ophthalmic a, Chun (f). (From Chun.)
Mastigoteuthis, Grimalditeuthis, and CJiiroteiitJiis are large squids, some of
which were captured by the Prince of Monaco around the Azores,
Madeira, and Canaries. Grimalditeuthis ric/iardi described by Joubin,
proves to be identical with G. bonplandi (see Fig. 440) taken by the
" Michael Sars." A new species is described by Chun under the name
of Mastigoteuthis hjorti. We succeeded in catching adults as well as
larvae of the Ommatostrephidae and Gonatidae ; Chun has described the
interesting larva of OinmatostrepJies (see Fig. 441), taken in the southern
««3ae^^
\^'
Fig. 439.
Head oi Doratopsis lippula, Chun.
section of our Atlantic cruise, in which the two long tentacles are united
into a tube.
In the Cranchiidae we have an entirely different group of wonderful
deep-sea forms, which probably undertake extensive vertical migrations ;
some of these, for instance Corynovima speculator, Toxeimia beloue (Fig.
442), and BathotJiauma lyroinma (Fig. 443), were taken in the Indian
Ocean by the " Valdivia."
Among the Myopsidae I mention first the interesting form Spirula
australis (see Fig. 60, p. 81), of which only three specimens had
previously been taken : one in the Pacific by the " Challenger," one off
North America by the " Blake," and one in the Indian Ocean by the
PELAGIC ANIMAL LIFE 593
^^*iw^.._ \ i ^ J
)
f »
Fig. 440.
Grimalditeuthis bonplandi, V(?rany. Half nat. size. (From Joubin. )
2 Q
594 DEPTHS OF THE OCEAN
" Valdivia." The " Michael Sars " captured no less than seven specimens,
ki
m^
\'^
m
i-lu. 441.
Larva of Ommatostrephes (\"-). (From Chun. )
Fig. 442.
Toxeuma belone, Chun. About
nat. size. (From Chun.)
Fig. 443.
Bathothauma lyromma, Chun. Two-thirds nat. size.
(P'rom Chun.)
in different interesting stages of development, around the Canaries and
PELAGIC ANIMAL LIFE
595
on the track to the Azores. In all probability this form is bath}'pelagic.
Of other Myopsidae the genera Sepiola, Rossia, Loligo, and Sepia have
been captured only in trawls along the bottom. The same remark
applies to the genera Octopus and Cii'voteutJiis, belonging to the Octopoda.
A large new species, named by Chun Octopus {Polypus) lothei, was taken
in the trawl south of the Canaries in 2600 metres of water. Interesting
pelagic forms of Octopoda were also met with ; for instance : Treinoctopus,
Eledonella, Bolitcsna, Optsthotcut/ns, Vampyi-oteutJiis, and CirrotJiaunia.
The two last mentioned are probably the most interesting. Vainpyroteuthis
infernalis, a fantastic deep-sea form, had previously been taken by the
Fig. 444.
Cirrothauma murrayi, Chun. About half nat. size. (From Chun. )
" Valdivia." CirrotJiaunia murrayi (Fig. 444) is a new species taken at
great depths in our northern section. It is as fragile as a Ctenophore, and
of a jelly-like consistency, its structure being exceedingly interesting and
unlike that of any previously known squid. It is, besides, the only
blind squid known, and has therefore been exhaustively treated by Chun
in his report on our material.
I. CEPHALOPODA DECAPODA
A. (EGOPSID.a;
Enoploteuthid.«
Abraliopsis morisii, Verany, Station 23.
Pterygioteuthis giardi, Fisch., Stations 15, 29, 35, 45, 49, 51
64, 67, 81, 87.
Larvje of Enoploteuthidte, Stations 45, 47, 48, 51, 53, 56, 58,
, 52, 53. 54, 56, 62,
62, 67, 81, 82, 84.
596 DEPTHS OF THE OCEAN chap.
Onychoteuthid/e
Larvae of CEgopsidge, mostly Onychoteuthidas, Stations lo, 29, 32, 49, 51, 52, 57,
64, 82, 88.
Veranyid^.
Octopodoteuthis sicu/a, Riippell, Station 90.
HiSTIOTEUTHID/E
Calliteuthis reversa, Verrill, Stations 42, 49, 51, 52, 58, 62, 70, 80, 81, 82, 84, 92.
Ommatostrephid/E
IHex illecebrosus, Les., Stations 33, 39, Newfoundland Bank.
Todaropsis eblance^ Bal., Station 33.
Ojftmatostrephes sagiftatiis, Lam., Station 115.
Larvae of Ommatostrephidae {Rhynchofei/fhis), Stations 48, 56, 67.
GONATIDyE
Gonatus fabricii, Lichtenst., Stations 70, 80, 81, 94.
BATHYTEUTHIDyE
Ctowpteryx sicuius, Riippell and Verany, Stations 56, 88.
Tracheloteuthid/e
Bradiioteuthis riisei, Steenstrup, Stations 45, 51, 52, 53, 62, 64, 67, 84, 88.
ChIROTEUTHID/E
Mastigoteuthis flammea, Chun, Stations 29, 64.
Larvae probably of the preceding, Stations 35, 51, 53, 84.
Mastigoteuthis grimaldii, Fisch. (Joubin), Stations 64, 67, 81, 82.
Mastigoteuthis hjorti, n.sp.. Stations 52, 62, 63 (?).
Grimalditeuthis bonplandi, Verany, Station 53.
Doratopsis vermicularis, Verany, Station 64.
Doratopsis lippula^ Chun, Station 51.
Doratopsis exophthai/nica, Chun, Station 90.
Young stages probably of the preceding, Stations 53, 88, 94.
Young stages of the genus Doratopsis, Stations 23, 53, 56, 58, 81, 90.
Cranchiid^
Cranchia scabra, Leach, Stations 51, 52.
Leachia cyclura, Les., Stations 23, 64.
Desmoteiithis peUiicida, Chun, Stations 10, 45, 67, 98, loi.
Corynomnia speculator, Chun, Stations 51, 64.
Teuthowenia mega/ops, Prosch., Stations 10, 45, 51, 58, 63, 64.
Toxeuma belone, Chun, Stations 49E, 51, 53, 67.
Galiteuthis suhmii, Hoyle, Station 64.
Bathothauma lyromma, Chun.
PELAGIC ANIMAL LIFE 597
B. MYOPSID^
SPIRULIDyE
Spirilla aiistralis, Lam., Stations 34, 35, 42, 44, 45.
Sepiolid/E
Heteroteuthis dispar, Riippell, Stations 42, 56, 58.
Sepiola rondelettii^ d'Orbigny, Stations 39, 96.
Rossia caroii, Joubin, Station 70.
LOLIGINID^
Loligo media, L., Stations 14, 20.
Loligo forbesi, Steenstr., Station 39.
Sepiid/E
Sepia d' Orbignyi, Ferussac, Station 33.
Sepia officinalis, L., Station 37.
II. CEPHALOPODA OCTOPODA
Philonexid^
Tremoctopus atlafificus, d'Orbigny, Stations 51, 53, 62.
Argonaiita sp.. Stations 45, 49B.
Larvffi, either of Tremoctopus or Argonaula, Stations 95, 98, loi.
POLYPODID/E
Octopus {Polypus), n.sp., Station 58.
Octopus {Polypus) lothei, n.sp.. Station 41.
BOLlT^NIDvE
Eledonella pygmcea, Verrill, Stations 45, 53, 62.
Bolitana diaphana, Hoyle, Stations 35, 53, 56, 64, 92.
C1RROTEUTHID.E
Opisthoteuthis agassizii, Verrill, Station 4.
Cirroteuthis umbellata, Fischer, Stations 25, 53, 70.
Vampyroteuthis infertialis, Chun, Stations 51, 57.
Cirrothauma murrayi, n.sp.. Station 82.
The Tunicata have been so termed from the gelatinous mantle or tunic Tunicata.
surrounding their body, which is composed of a peculiar substance,
*' tunicin," supposed to be closely related to cellulose. All Tunicata have
pelagic larvae, which have long attracted the interest of zoologists,
because their central nervous system (medullar tube), sense organs, and
axial skeleton present a striking likeness to the lower vertebrates or to
the early embryonal stages of the vertebrates. Among the Tunicata
there is a large group, the Ascidians, which at the close of larval
598
DEPTHS OF THE OCEAN
life fix themselves to the bottom and become sessile, like the Hydro-
medusae, forming colonies by budding. They are
thus meropelagic, whereas all other Tunicata are
holopelagic and perfectly independent of the
bottom. These latter are the only ones to be dealt
with here, viz. Appendicularians, Salp^e, and the
genera Dolioluui and Pyrosonia.
The Appendicularia resemble greatly the larv«
of Ascidians, and present a remarkable likeness to
early vertebrate types. As a rule they are trans-
parent and perfectly devoid of colour. Their body
(see Fig. 445) is clumsy in shape and contains all
the organs of nutrition and propagation, with a
long elastic tail which serves solely the purpose of
locomotion. Lohmann has studied the biology of
this group,' and his results will be referred to later.
The Appendicularians live mostly in the upper 200
metres of the ocean, though in tropical waters they
occur deeper ; in fact in the Sargasso Sea the
German Plankton Expedition found more of them
below than above 200 metres. As with most sur-
face forms the species are most abundant in warm
waters, like Appendicularia sic2ila,Fritillaria ve^iusta,
and Oikopleura parva, while Oikopleura vanJioffeni
and O. labradoriensis are northern forms.
The Salpae are free-swimming, barrel-shaped,
transparent animals, well-known to all sea-faring
people (Fig. 446), They are often seen crowding
the surface-waters of the ocean in countless num-
bers. Among investigations of recent years we
may cite the report on the " Valdivia " collection
by Apstein.^ In hauls with closing nets the
" Valdivia" found the majority of Salpae in depths less than 200 metres.
Fic. 445.
Oikopleura labradoriensis
Lohm (about Y")-
(From Lohmann.)
Fk;. 446.
Salpajusiformis forma aspera, Cham. Nat. size.
Lohmann, Ergeb. Plati kton- Expedition , Bd. 2, 1896.
Apstein, IViss. Ergeb. '^Valdivia" Expedition, Bd. i;
[906.
PELAGIC ANIMAL LIFE
599
Only exceptionally, and chiefly in the Antarctic, forms were found be-
tween 1500 and 1000 metres that in warm waters live at the surface.
The Salpae are individually most abundant in warm water, and in the
Atlantic we do not find a single species which is peculiar to the area
north of lat. 45° N. Apstein tells us that three species have been found
in the northern region, viz. Salpa fusifoi-mis, S. mucronata, and
5. :::onaria, but they really belong to warm waters and have been carried
north by currents (see Fig. 447). The genus Cydosalpa comprises
typical warm-water forms.
The genus Dolioliiin is also, according to Neumann's ^ treatise on
the " Valdivia " collection, chiefly a warm-water form exceedingly
sensitive to changes of temperature. Dolioliim kroJini, D. tritonis.
Fig. 447. — Distribution of Salpa fcsiformis.
(From Apstein.)
D. mulleri, and D. gegenbaiiri are the species which go farthest north in
the Atlantic.
The genus Pyrosoma (Fig. 448) has from the earliest days of
oceanography attracted the interest of man, to a great extent on
account of the strong phosphorescent light emitted, the name meaning
" fire-animal." The individuals are aggregated into cylindrical colonies,
which may attain an enormous size (several yards long). Some occur in
the surface-waters, some in deep water.
In the narrative of the "Challenger" cruise, Sir John Murray,
describing the voyage from the Bermudas to the Azores, writes as
follows : — " On the 25th (of June) a very large colony of a new species of
Pyrosoma was captured in the trawl. The cylinder was 4 feet 2 inches in
length and 10 inches in diameter, closed at one end, and as in the
Neumann, Wiss. E7-geb. Valdivia-Expediiion, Bd. 12, 1906.
6oo DEPTHS OF THE OCEAN
smaller forms, the colony was spotted with red, the red spots being the
visceral nuclei of the several animals. The specimen was kept in a tub
of water till after dark, when it gave off brilliant phosphorescent light on
being disturbed. The officers amused themselves by writing their names
along this living cylinder with one finger, the track of which remained as
a bright line of light for some seconds. Salpae were the commonest
animals in the surface waters ; there were several kinds, and many long
bands of them in the chain form were taken in the surface nets. Brilliant
phosphorescence was observed at night during calm weather."^ During
the Atlantic cruise of the "Michael Sars" great quantities of Salpae,
Dolioliuii and Pyrosoma, were captured. The collections have been
examined by Bjerkan, to whom I am indebted for the following list,
which shows that many of the species are widely distributed in the
North Atlantic. Excluding the Appendicularia, which have not yet been
Fig. 448.
Pyrosoma spinosu7n, Herdman. Nat. size.
investigated, seventeen species were taken during the cruise, of which seven
were taken to the north as well as to the south of the Azores.
Cydosalpa pi7inata, Forsk., Stations 56, 57, 58, 59, 86, 88.
Cyclosalpafloridana, Apstein, Stations 22, 25, 29.
Salpa maxima, Forsk., Stations 29, 33, 34, 35, 42, 43, 52, 56, 62, 66, 86, 88.
Salpafusiformis, Cuv., Stations 10, 19, 31, 39, 51, 52, 53, 56, 58, 67, 81, 82, 84,
86, 87, 88, 90, 92, 94, 97, 98, 100, loi, 102.
Salpa fu sif or m is {ormdi aspera, Cham.,- Stations 10, 15, 19, 24, 25, 29, 32, 51,
58, 62, 67, 84, 87, 88, 90, 92.
Salpa amboinensis, Apstein, Stations 19, 23, 49, 56, 58.
Salpa mucronata, Forsk., Stations 32, 43, 44, 45, 50, 56, 57, 58, 59, 67, 83, 87.
Salpa confcederata, Forsk., Stations 31, 40, 42, 43, 51, 69, 81, 84, 86, 88.
Salpa zonaria, Pall., Stations 10, 15, 22, 23, 25, 29, 42, 43, 56, 62, 66, 67, 71, 80,
81, 82, 84, 88, 97, 102.
Salpa tilesii, Cuv., Station 10.
Salpa henseni, Traustedt, Stations 56, 58.
Doliohim tritonis, Herdman, Stations 88, 90, 92, 94, 98, 100, loi.
Doliolum sp., Stations 23, 25, 29, 32, 34, 44, 48, 49, 56, 67, 84.
Pyrosoma spinosu?fi, Herdman, Stations 10, 39, 51, 62, 64, 67, 81, 84, 87, 88, 90.
Pyrosoma gigantei/m, Lesueur, Stations 29, 48, 87, 88.
Pyrosoma atla)iticiim, Peron, Stations 42, 47, 56, 58.
Pyrosoma, n.sp.. Stations 49, 56, 88.
1 Narrative Chall. Exp., vol. i. p. 170, il
2 Previously forma ecliiuata (Herdman).
PELAGIC ANIMAL LIFE 6oi
i\s indicated in Chapter VII., zoologists have until lately been un- Fishes,
able to decide what species of fishes live along the bottom, and what
species belong to the intermediate and surface waters. In recent years
our knowledge has greatly increased. The " Valdivia " Expedition
took no less than 151 species in pelagic fishing appliances.^ Many of
these have raised considerable interest on account of their curious shapes,
especially the so-called " deep-sea fishes," which were supposed to live
in the great depths of the ocean.
During the cruise of the " Michael Sars " probably about 10,000
specimens of pelagic fishes were taken, exclusive of the many larvse and
young stages. This abundant material has not yet been worked up,
and complete lists, even of the adult fishes, are not available. Of the
Scopelidas (including the genus MyctopJiuni), the genus MelampJides
and different Stomiatidae, only a limited number of species have
been dealt with, many of the species being new, while the larvae
and young fish have as yet only been divided into certain groups.
Nevertheless, the following- list is of interest, as it indicates a great advance
Fig. 449.
Pet7-omyzon mariniis, L. (From Goode and Bean.)
in our knowledge of the fishes of the North Atlantic ; though the
collections of the " Michael Sars " are deficient as regards the coastal
and northern waters of the Atlantic, much information has been gained
regarding the pelagic fishes of the Norwegian Sea and the North Sea.
The present list records 95 species, all, except one specimen of the
lamprey, Petrotiiyzon viarinus (see Fig. 449), taken on the banks of
Newfoundland, belonging to the Teleostei, or bony fishes.
The sub-order Malacopterygii comprises many of the most important
forms from coastal waters as well as from the ocean.
The Clupeidae (or herrings) are economically the most important of
all pelagic fishes, and belong wholly or chiefly to the coast waters
(neritic). In southern waters (Bay of Biscay, off the coasts of Spain,
Portugal, and Africa) the principal species are the anchovy {Engraulis
encrasicholus, see Fig. 450), Clupea alosa, and the sardine or pilchard
{Clupea pilchardus, see Fig. 451), while in northern waters the herring
{Clupea Itarengus) and the sprat {Clupea sprattus) predominate.
The Salmonidae have many pelagic representatives. The light-
coloured salmon and sea-trout are generally considered to be pelagic
when away from the rivers and the coasts. The list of bottom-fish in
1 Brauer, IViss. Ergeb. '■'■ Valdivia'' Expedition, Bd. 15, 1906.
602
DEPTHS OF THE OCEAN
Chapter VII. includes the deep-sea genera Argentina and Alepocephaliis,
and it is somewhat surprising to find the small curious forms of the
pelagic genus Opisthoprodiis referred to the same family ; but there are
Fig. 450.
Eiigraiilis encrasicfiolus, Cuv. (From Day.)
really certain features connecting it with AlepoccpJialus. The Opistho-
proctidae are small fishes, only a few centimetres long, laterally com-
FiG. 451.
Chipea pilchard us, Walb. (From Sniitt. )
pressed, with large thin scales, telescopic eyes, a remarkable flattening of
the belly, forming a peculiar sole, and with a small adipose fin as in all
Fig. 452.
Opisthoproctiis griinaldii, Zugmayer. Nat. size, 2 cm.
Other Salmonidae. One species, OpistJioproctiis solcatus, was taken pre-
vious to our cruise in the Atlantic, and the other species {O. grimaldii,
see Fig. 452) was taken subsequently near Gibraltar.
PELAGIC ANIMAL LIFE
60-
The families Stomiatidae and Sternoptychidae present many points of
resemblance, and comprise many fishes which were previously looked
upon as genuine deep-sea forms. They vary greatly in shape, some
being long and slender, others short and laterally compressed, and the
Fio. 453-
Sfomias boa, Risso. Nat. size, 16 cm.
mouth is large with a great number of teeth. Both families are
characterised by abundant light-organs, the only difference between
them lying in the fact that the Sternoptychidae have only one kind of
Fig. 454.
ChauUodus sloanej , Bl. and Schn. Nat. size, 6 cm.
light - organ, while the Stomiatidae have below or behind the ^eye
large and powerful light-organs, very often coloured, quite different in
structure from the small ones on the bodv.
Fig. 455.
Photostotnias guernei , Coll. Nat. size, 17 cm.
The Stomiatidae occurring most commonly in the Atlantic are
Stoniias boa (see Fig. 453) and ChauUodus sloanei (see Fig. 454), both
taken in the tow-nets of the " Michael Sars " at nearly all oceanic
stations. They both occur in all oceans, and some of the rarer forms,
like Macros toiiiias longibarbatus, Malacostetis indicus, and Astronesthes
niger, are also known from other oceans. An interesting species.
6o4
DEPTHS OF THE OCEAN
Photostojiiias guernei, is shown in Fig. 455. The Hst includes several
new forms, which have not yet been described, showing that the Stomia-
tidas are more abundant in the Atlantic than was previously supposed.
Fig. 456.
Gonostoma deniidatum, Ratiii. Xat. size, 3.5 cm.
The Sternoptychidae occur in vast numbers, some of the forms
being among the most abundant of all pelagic fishes in the ocean, like
Fig. 457.
Vinciguerria liicctia, Garm. Nat. size, 3.9 cm.
the genus Cydothone ; in the North Atlantic the two species C. viicrodon
and C. signata (see Plate I. Chapter X.) are specially abundant. Nearly
Fig. 458.
Argyropelectts heinigymnus, Cocco. Xat. size, 3. 5 cm.
allied to Cydothone is the genus Gonostoma, the species Gonostoma grande
and G. rhodadenia'^ being biologically very interesting (see Plate II.
^ On Plate II. this species is named G. eloiigatuiii.
PELAGIC ANIMAL LIFE
60:
Chapter X.). Gonostoma denudatuui is shown in Fig. 456. The genera
Vi7iciguerria (see Fig. 457), IcJitJiyococcus, and Valenciennellus resemble
each other considerably, and have large and numerous light-organs ;
their geographical distribution is very wide. Very peculiar are the
compressed silvery forms of the genera Argyropelecus (see Fig. 458) and
Sternoptyx, which have highly-developed light-organs. Most of them
occur in all oceans, the species in the list having been taken at many
stations in the North Atlantic, while some of them are also known from
the Norwegian Sea.
The sub-order Apodes includes the eel-like fishes devoid of ventral
Fig. 459.
Gastrostonius bairdii, G. and R. Nat. size, 47 cm.
fins. From coastal waters the eel, the conger, and the Muraenidae are
best known. In deep waters the Synaphobranchidae, included in the
list of bottom-fishes, are very important ; some of them are perhaps
deep-living pelagic fish, but our knowledge on this point is still
imperfect. The three species of the Nemichthyidae and the two species
of the Saccopharyngidae are undoubtedly pelagic forms. Gastrostoinus
bairdii is shown in Fig. 459. Serrivomer sector was taken at numerous
stations, one specimen of the large and remarkable Nemichtliys
Fig. 460.
Cyema atritm, Gtinth. Xat. size, 11.5 cm.
scolopaceus was captured south of the Azores, and the peculiar Cyema
atriiin (see Fig. 460) was taken at three stations in the southern part of
our track. To this sub-order belong the larval forms termed Leptocephali,
which are all larvae of Anguillidae, Muraenidae, Nemichthyidae, Synapho-
branchidae, and Saccopharyngidae.
The sub-order Haplomi includes the Scopelidae, one genus of which,
Myctophuin, is represented by numerous species (Brauer mentions
more than seventy) ; these play a greater part in the surface fauna of the
ocean than all other pelagic fishes. Our list records only those species
determined up to the present time, and there are doubtless many more.
Of greatest interest to us are Myctop/mm glaciale, M. punciattcin, which
6o6
DEPTHS OF THE OCEAN
(together with ]\I. eJongaiuin) are known from the Norwegian Sea, but
most of the species belonging to this genus are warm -water forms.
M. rafinesquei is shown in Fig. 461. Several genera belonging to the
Scopeliclae are recorded in the list of bottom-fishes, Bathysanriis,
Fig. 461.
Mycfophtivi (Diapkiis) rafinesquei, Cocco. Nat. size, 7 cm.
BatJiypterois, etc., which will probably prove to be bathypelagic forms, but
the present state of our knowledge renders this merely a conjecture. Of
interest is the remarkable iormOinosudis /ozvez taken on a long line between
the Canaries and the Azores (Station 49 ; see Fig. 462). This sub-order
Fig. 462.
Omosudis lowei, Glinth. Nat. size, 15 cm.
includes the Cetomimidae, one genus of which was previously known
and one was discovered by us ; both genera contain blind forms (see
Chapter X.).
The sub-order Catosteomi contains the Syngnathidae, the needle-fish
rr^m nmf» mi u mrrrmmmM ) ( JUiildLO If
mfwm
Fig. 463.
Syngnathus pelagiciis, Osbeci<. Nat. size, 12 cm.
and the pipe-fish. The pipe-fishes {Siphonostonia typhle and SyiignatJius
acus) are common along the coasts of Northern Europe. Of the needle-
shaped species, SyngnatJius pelagicus (see Fig. 463) is a typical Sargasso
form (see Plate V. Chapter X.), while Neropliis cequoreus lives mainly in
the north-eastern part of the Atlantic, where it occurs in all the hauls
PELAGIC ANIMAL LIFE
607
with surface tow-nets. The beautiful Httle Hippocavipus (see Fig. 71,
p. 89) was taken between the Canaries and the Azores.
The sub-order Percesoces contains several important and interesting
surface-fish. To the family Scombresocidae belong the gar-pike {Belone),
the genus Scombresox, and the flying-fish of the genus Exocoetus.
Sco7nbresox sauriis attains a length of 50 cm., and resembles the gar-
pike, but does not approach so near the coasts, nor does it extend so far
north ; it is known from the Atlantic coasts of North America, Northern
Europe and Africa. Day records a capture of icxD,ooo individuals in
one haul off the British shores. Only very young specimens were taken
by the " Michael Sars" (see Chapter X.), but these are very interesting,
because they prove that the species occurs pelagically right across the
Atlantic. Flying-fishes were constantly observed on our southern
Fig. 464.
datus, Giinth. Nat. size, 9. 5 cm.
track, and some of the specimens w^hich flew on board have been
referred to Exocoetus spilopits. Between 40 and 50 species of this genus
are known from tropical and sub-tropical waters. Very interesting are
our captures of minute young flying-fish (see Chapter X.). The only
fish belonging to the sub-order Percesoces from great depths is
Chiasmodus niger (see Fig. 514, p. 721), taken by the "Michael Sars" in
the Sargasso Sea. It was previously known from the eastern and west-
ern sides of the Atlantic, and from the Indian Ocean. The fish has very
powerful teeth, and can swallow a fish much larger than itself, the diges-
tive tract being marvellously tensile (see Chapter X.). Lirus maculatus
(see Fig. 464) and L. ovalis belong to the family Stromateidae. Along
with Acanthopterygians, like Polyprion aviericamis, these fishes gather
around wreckage and other floating objects. They live in tropical
or sub-tropical surface waters, and biologically resemble the large lump-
fish or sun-fish. All the forms mentioned were captured from a boat,
either with a hoop-net or, in the case of Mola rotunda, with a harpoon.
6o8 DEPTHS OF THE OCEAN
The sub-order x-\canthopterygii does not play the important part
Sis,
Fig. 465.
Naiicrates drictor, L.
Fic. 466.
Ceratias couesi, (Jill. Nat. size, 3 cm.
Flc. 467.
O/ifirodcs, n.sp. No. 2. Nat. size, 3 cm.
among the oceanic pelagic fish that it does among the bottom-fishes (see
Chapter VII.)- One group, however, is very important, viz. the Scombri-
PELAGIC ANIMAL LIFE
609
formes or mackerels. The Scombridae are represented by many species
in tropical and sub-tropical waters, the most important in the North
Atlantic being the mackerel {Scomber scomber), the tunny {T]iynnus
thynnus), the bonito {TJiynnus pclamys), and Pelamys sarda. The adult
fishes are widespread, but most of them probably seek the coasts in
spawning time. The natural history of all these important and interest-
ing species has been very little investigated, and very little material was
obtained during the cruise of the " Michael Sars." We obtained far
■odes, n.sp. No. 3. Nat. size, 2
more information concerning the Carangidae or horse-mackerels, of which
young individuals were taken abundantly so far from land that their
oceanic habitat may be considered as proved. To this family also
belongs the famous pilot-fish {Naiicrates ductor, see Fig. 465), some
specimens of which were taken. Allied forms are Zeus fab er and Capros
aper, of which only adult individuals were taken in our trawls, but which
nevertheless must be supposed to be capable of living in mid-water. The
Fig. 470.
Aceratias macrorhi/ites iiidicus, A. Rr
Nat. size, 2.8 cm.
Fig. 469.
Melauocetus johnsoni, Giinth. Nat. size, 4.5 cm.
young of Capros aper and of several other Acanthopterygians were taken
in the surface waters far from land. Bathypelagic forms are very scarce
among the Acanthopterygians, Our list records only two species of the
genus Melamphaes, but many of our specimens have not yet been
determined. M. mizolepis shows a wide distribution in the North
Atlantic, and is known from the Indian Ocean.
The sub-order Pediculati is well known from shallow water through
the angler {Lophius piscatorius), the eggs of which we found floating off
the banks of Newfoundland. Genuine deep-sea forms are the members
of the Ceratiidse, containing the genera Ceratias, Otieirodes, Melanocetus
2 R
6io
DEPTHS OF THE OCEAN
(see Figs. 466-469). They are small, generally black, forms, with a mouth
of gigantic size provided with powerful teeth. They have attracted
special attention from the nasal tentacle carrying at its end a peculiar
Antennariiis
Fig. 471.
irmoraius, Giinth. Nat. size, 3.3 cm.
lantern-like light-organ. Of the eight species of Ceratiidae taken during
our crui.se, no less than five are supposed to be new to science ; one
species {UTelanocettis krecJii) is represented by a single specimen
Fig. 472
Moitacanthtis. Nat. .siz
from the Indian Ocean. Such facts show that our knowledge of the
fauna of the ocean still leaves much to be desired. Remarkable small
forms of the genus Aceratias (see Fig. 470) al.so belong to this sub-order.
One of these was previously known from the Indian Ocean only ; the
PELAGIC ANIMAL LIFE 6ii
other was taken off the Congo. Ante7tnarius viannoratus (see Fig. 471)
presents in its shape some Hkeness to the Ceratiidae and to Lophius,
ijut is in fact a small surface form peculiar to the Sargasso Sea (see
Plate V. Chapter X.), where the genus Monacant/ms, belonging to the
sub-order Plectognathi (see Fig. 472 and Plate V.), also occurs.
PELAGIC FISHES
Taken bv the "Michael Sars" in 1910 in the Atlantic
north of lat. 26° n.
Class-CYCLOSTOMATA
Order— PETROMYZONTES
Petromyzontid^
Petromyzou marinus, L., 1910 (see Fig. 449).
Class PISCES
Sub-Class— TELEOSTOMI
Order— TELEOSTEI
Sub-Order— MALACOPTERYGII
ClUPEIDtE
Engraulis e/icrasichoiiis, Cuv., 1910, Station 36 (see Fig. 450).
Clupea alosa, L., 19 10, Station 36.
Clupea pilchardus^ Walb., 19 10, Station 36 (see Fig. 451).
Salmonid.e
Opisthoprodus soleatus, Vaill., 1910, Stations 49, 52, 64 (see Fig. 72, p. 89).
Opisthoprocti/s grivialdii, Zugmayer, 1910, Stations 23, 49 (see Fig. 452).
Stomiatid^
We give here Brauer's ^ classification of the Stomiatida^ and Sternoptychidje.
Stomias boa, Risso, 1902, Faroe-Shetland Channel; 1910, Stations 10, 19, 29,
34, 42, 51, 53, 56, 62, 63, 64, 67, 80, 82, 84, 87, 88, 90, 92, 94, 98, loi
(see Fig. 453).
Chaidiodus sloanei, Bl. and Schn., 1910, Stations 10, 25, 29, 34, 35, 42, 45, 49,
50, 51, 52, 53, 56, 62, 63, 64, 80, 81, 82, 84, 88, 90 (see Fig. 454).
Photostomias guernei. Coll., 1910, Stations 34, 45, 49, 51, 53, 58, 81, 82 (see
Fig- 455)-
Eustomias obscurus, Vaill., 1910, Station 29,
1 " Die Tiefsee Fische," IViss. Ergeb. Valdivia- Expedition, Bd. 15, 1906.
6i2 DEPTHS OF THE OCEAN chap.
Eustomias, n.sp., 1910, Stations 45, 81.
Macrostomias longibarhatus, A. Br., 1910, Stations 23, 52.
Melanostomias, n.sp., 1910, Stations 49, 87.
Dactylostomias, n.sp., 1910, Stations 42, 45, 49, 51, 52, 53, 56, 58, 62.
Echiostoma (species undetermined), 19 10, Station 62.
Idiacanthus ferox, Giinth., 1910, Stations 34, 42, 45, 49, 51, 53 (see Fig. 67, b,
p. 86).
Malacosteus tndicus, Giinth., 1910, Station 48.
Malacosteits niger, Ayres, 19 10, Station 51.
Malacosteus choristodactyhis, Vaill., 1910, Stations 45, 51, 58.
Asironesthes fiiger, Rich., 1910, Stations 51, 52, 53, 64, 67 (see Fig. 80, p. 93).
Astronesthes (species undetermined), 1910, Stations 42, 87, 88.
StERNOPTVCHID/E
Gonostoma r/iodade?iia, Gilb., 19 10, Stations 49, 51, 52, 53, 58, loi.
GoHostoma grande, Coll., 1910, Stations 45, 53, 56, 62, 64, 81, 88, 92, 94, 98.
Gonostoma denudatiwi, Rafin., 1910, Stations 58, 62 (see Fig. 456).
Cydothone signata, Garm., 1910, Stations 10, 22, 25, 27, 28, 34, 35, 40, 42, 45,
47, 48, 49, 50, 51, 52, 53, 56, 62, (i2)i 66, 67, 80, 81, 82, 88, 90, 92, 94, loi.
Cydothone sig?iata allm, A. Br., 1910, Stations 34, 52, 56, 62, 64, 66, 67, 81, 92,
lOI.
Cydothone livida, A. Br., 1910, Stations 34, 35.
Cydothone microdon, Giinth., 19 10, Stations 10, 19, 25, 27, 29, 34, 35, 42, 45,
47, 48, 49, 50, 51, 52, 53, 56, 62, 63, 64, 67, 80, 81, 82, 90, 92, 94, lOI.
Cydothone microdon pallida^ A. Br., 1910, Stations 28, 35, 56, 63, 81, 98, loi.
Cydothone acdinidens, Garm., 1910, Stations 51, 67.
Vindguerria lucetia, Garm., 1910, Stations 20, 29, 34, 39, 42, 45, 50, 51, 52, 53,
56, 62, 64, 69, 81, 88 (see Fig. 457).
Ichthyococcus ovatus, Cocco, 19 10, Stations 23, 58.
Valendennellus tripimdidatus, Esm., 1910, Stations 23, 29, 34, 35, 42, 45, 48, 51,
52, 53' 56, 58, 62.
Argyropelecus affi.ms, Garm., 19 10, Stations 34, 45, 48.
Argyropelecus he?}iigy?fimis, Cocco, 1910, Stations 10, 15, 19, 23, 29, 34, 35, 42,
45> 49, 51, 52, 53. 56, 58> 62, 64, 66, 67, 88, 92, 98 (see Fig. 458).
Argyropelecus olfersi, Cuv., 1910, Stations 10, 23, 56, 58, 88, 92.
Argyropelecus aculeatus, Cuv. and Val., 1910, Stations 23, 29, 34, 42, 52, 53, 58,
62, 67.
Sternoptyx diaphana, Herm.. 1910, Stations 23, 29, 34, 45, 48, 49, 51, 52, 53,
56, 62, 66, 67, 81, 82.
Sub- Order— APODES
Nemichthyid^
Serrivomer sector, Garm., 1910, Stations 45, 49, 51, 52, 56, 64, 67.
Nemtchthys scolopaceus, Richards, 19 10, Stations 51, 58.
Cyema atrum, Giinth., 19 10, Stations 45, 53, 62 (see Fig. 460).
SACCOPHARYNGIDyE
Gastrosto7nus bairdii, Gill and Ryd., 1910, Stations 35, 53, 62, 64, 67, 80, 81
(see Fig. 459).
New genus, 1910, Station 53 (see Fig. 83, b, p. 97).
PELAGIC ANIMAL LIFE 613
Sub-Order— HAPLOMI
SCOPELID/E
Omosudis loivei, Giinth., 1910, Station 49 (see Fig. 462).
Myctophum {Myctophum) rissoi, Cocco, 1910, Stations 29, 56.
Myctophum {Myctophum) glaciate, Reinh., 1902, Faroe-Shetland Channel, Faroe
Bank; 1910, Stations 10, 15, 19, 70, 80, 82, 90, 102.
Myctophum (^Myctophum) benoiti, Cocco, 1910, Station 28.
Myctophtcm {Myctophu??i) benoiti hygoffii, Liitk., 1910, Stations 29, 49.
Myctophum {Myctophum) punctatum, Rafin., 1910, Stations 25, 29, 53, 80, 92.
Myctophum {Myctophum) affi/ie, Liitk., 1910, Stations 52, 53.
MyctophujH {Myctophum) humbotdti, Risso, 1910, Stations 20, 53.
Myctophum {Myctophum) coccoi, Cocco, 1910, Stations 20, 25, 29, 53, 56, 58, 62,
' 64. '
Myctophum {ATyctophum) chxrocephalum, Fowl., 19 10, Stations 50, 53.
Myctophum {Diaphus) gemellari, Cocco, 1910, Stations 49, 53, 56.
Myctophum {Diaphics) rafitiesquei, Cocco, 1910, Stations 62, 84 (see Fig. 461).
Myctophum {Lampanyctus) maderense, Lowe, 19 10, Station 34.
Myctophum {Lampanyctus) warmingi, Liitk., 1910, Station 51.
Myctophum {Lampanyctus) micropterum, A. Br., 1910, Stations 51, 62.
Myctophum {Lartipanyctus) gemmifer, G. and B., 1910, Station 58.
Cetomimid/E
Cetomimus storeri, G. and B., 1910, Station 35 (see Fig. 497, p. 681).
New genus, 1910, Station 64 (see Fig. 498, p. 682).
Sub-Order— CATOSTEOMI
Syngnathid^
Syngnathus pelagicus, Osbeck, 1910, Sargasso Sea, Stations 51, 53, 64 (see
Fig. 463)-
Ahrophis cequoreus, L., 1910, Stations 10, 56, 58, 84, 86, 87, 88, 90, 92, 94, 98.
Llippocainpus ramulosus, Leach, 1910, Station 48 (see Fig. 71, p. 89).
Sub-Order— PERCESOCES
SCOMBRESOCID/E
Scombresox saurus, Walb., 1910, Stations 25, 27, 37, 46, 47, 48, 49, 50, 51, 52,
56, 64, 66, 90.
Exocoetus spi/opus, Val., 1910 (see Fig. 61, p. 82).
Chiasmodontid/e
Chiasjuodus niger, Johns., 1910, Station 52 (see Fig. 514, p. 721).
SXROMATEIDrE
Lirus ??iedusophagus, Cocco, 1910, Stations 23, 25.
Lirus 7naculatus, Giinth., 19 10, Station 49 (see Fig. 464).
Lirus ovalis, Cuv. and Val., 1910, Stations 49, 56.
Lirus perciformis, Mitchell, 19 10, Station 61.
6i4 DEPTHS OF THE OCEAN
Sub-Order— ACANTHOPTERYGII
Division— PERCIFORMES
Bervcid/e
Melamphaes mizoiepis, Giinth., 1910, Stations 67, 80, 81, 82, 92.
Melamphaes, n.sp., 1910, Stations 51, 67.
Cyphosid/e
Cyphosus doscii, Lacep., 19 10, Station 61.
Serranid^
Polyprion americatius, Bl, and Schn., 19 10, Station 56.
Caproid/e
Capros aper, Lacep., 1910, Stations i, 3, 20, 39, 56, 58.
Division— SCOMBRIFORMES
CARANGIDyE
Caranx trachuriis, L., 1910, Stations i, 3, 14, 20, 36, 39, 49, 52, 56, 58 (see
Fig. 86, p. 98).
Temnodon saltator, Cuv. and Val, 19 10, Station 36.
Seriola, sp.juv., 1910, Station 66.
Naucrates ductor^ L., 19 10, Station 49 (see Fig. 465).
TRICHIURIDyE
Lepidopus caudatus, Euphras., 19 10, Station 43.
Division— ZEORHOMBI
Zeid^
Zeus faber, L., 1910, Stations i, 20.
Division— SCLEROPARE I
SCORP^NID^
Sel'astes dactylopterus, de la R., 191 o, Station 21.
Sub-Order— PEDICULATI
Ceratiid^
Ceraiias couesi, Gill., 1910, Station 51 (see Fig. 466).
Ceratias, n.sp., 1910, Station 42 (see Fig. 59, p. 81).
Oneirodes, n.sp. No. i, 1910, Stations 64, 81, 84 (see Fig. 90, p. 104).
Oneirodes, n.sp.. No. 2, 1910, Station 29 (see Fig. 467).
Oneirodes, n.sp. No. 3, 1910, Station 53 (see Fig. 468).
Oneirodes megaceivs, Holt and Byrne, or n.sp. No. 4, 19 10, Stations 52, 62 (see
Fig 81, p. 95).
Melanocetus johnsoni, Giinth., 1910, Station 53 (see Fig. 469).
Melanocetiis krechi, A. Br., 19 10, Stations 45, 53.
IX PELAGIC ANIMAL LIFE 615
ACERATIID^
Aceratias mollis, A. Br., 1910, Stations 45, 49, 51, 64.
Aceratias macrorhinus indiats, A. Br., 1910, Stations 45, 49, 51, 56, 67 (see
Fig. 470).
Antennariid^
Anteniiaritis iiiarmorali/s, Giinth., 1910, Stations 64, 66, 67 (see Fig. 471).
Sub Order-PLECTOGNATHI
Division— SCLERODERMI
Balistid^
Mo/iacanfhiis sp., 1910, Station 67 (see Fig. 472).
Division— GYMNODONTES
Tetrodontid.e:
Tetrodon spengleri, Bl., 1910, Station 37.
MOLID/E
Mola rotunda, Cuv., 1910, Station 87 (see Fig. 102, p. 119).
2. Distribution of Pelagic Animals
The foregoing remarks and lists show that our knowledge
of the distribution of pelagic animals in the ocean is now
considerable, especially as regards small forms, which are
easily captured in closing nets, and whose habitat may therefore
be localized with accuracy. As to larger organisms the difficulties
increase in proportion to their size. Thus only five of the 151
pelagic species of fishes taken during the " Valdivia " Expedition
were captured in closing nets, but the bathymetrical distribution
of certain species was approximately determined by lowering
large vertical nets to different depths and comparing the
catches. By studying the material thus obtained, Brauer^
succeeded in ascertaining the bathymetrical distribution, or at
least the upper limit, of several common species.
In Chapter II. I have described our methods of capturing
pelagic animals by means of large closing nets and by simul-
taneously towing eight or ten nets at different depths, and in
Chapter III. I have given particulars of some of the catches
thus secured. My object in this chapter is to show in some
detail the knowledge now available as to the vertical and
horizontal distribution of pelagic animals and animal-communities
^ Brauer, loc. cit.
6i6
DEPTHS OF THE OCEAN
in the waters examined by the " Michael Sars," viz. the North
Atlantic and the Norwegian Sea.
To commence with, it will be advisable to consider the details
of our fishing methods. The method of simultaneously towing
many appliances at different depths cannot be supposed to give
such exact results as hauls with closing nets, because the tow-
nets function not only while being towed along, but are also
liable to do so while being lowered and raised. To counteract
the errors arising in this way we generally towed our nets all
night long, or for lengthened periods sometimes extending to
twelve hours. The distance thus covered in towing the nets
was infinitely greater than the distance traversed by the nets
in being lowered and raised, and the sources of error were
presumably proportionally diminished.
In order to judge of the results obtained in this way we
may examine the catches of individuals belonging to a definite
species at all depths and at all stations. Of the well-known
species Argyropelecus kcmigyinmis we took during our cruise a
total of 286 individuals, at the various depths indicated in the
following table : —
Vertical Surface
distribution of At a depth of 50 metres
Argyropelecus. ^^ 100
150
300
500
750
1000
1250
1500
2000
The bulk occurred at depths between 150 and 500 metres;
no individuals were caught above 150 metres, and only about
7 per cent were taken at depths lower than 500 metres. If we
assume, then, that these 7 per cent were captured during the
process of hauling in the appliances, and that none of them
live at depths below 500 metres, we will have an idea of the
accuracy of our method.
We see, further, that by far the greater number were caught
at a depth of 300 metres, where we generally had out a |-metre
silk net, whereas at 150 metres and at 500 metres the appliance
used was, as a rule, a young-fish trawl, that would have had a far
greater capacity for catching these fishes. It seems, accordingly,
that a preponderating majority of the individuals of this species
0
indi
viduals
0
0
62
155
48
0
6
0
II
4
PELAGIC ANIMAL LIFE 617
are very strictly limited to an intermediate layer situated at
a depth of about 300 metres. A closer investigation showed
that the individuals captured at a depth of 150 metres
were all caught at night. This may be due either to an upward
nocturnal wandering or to chance, though on this question the
small amount of our material makes it unsafe to hazard an
opinion ; in subsequent investigations, however, it will be
worth while taking this fact into consideration. Among the
individuals captured at 500 metres there must, at any rate, be
a few that were taken in the process of hauling in the young-
fish trawl through the intermediate layer above, though the
majority probably lived at that depth — a deduction supported by
the fact that far fewer specimens were found in the young-fish
trawl towed at 1000 metres, which may have been captured
while hauling in.
This instance is a good illustration ot our method with its
advantages and deficiencies. Clearly the method is trustworthy
only in cases where many specimens have been caught. At
the same time, it is the only effective method of capture known
at present, and it is therefore interesting to inspect the results
obtained.
The distribution of different animal - communities in the
ocean rarely coincides with what seem to be natural distribu-
tional areas. The fact is that the occurrence of animals is
largely influenced by such conditions as depth and temperature.
In Chapter VII. we have seen that the limit between the
southern and the northern bottom-fishes did not coincide with
the border-line between the Atlantic Ocean and the Norwegian
Sea, but ran from Ireland or the Channel to Iceland, and
thence to the coast of the United States. In the case of
pelagic animals we may also distinguish between southern or
Atlantic communities and northern communities, the border-
line between these two communities very nearly coinciding
with the line separating the corresponding communities ol
bottom-fish.
A. The Atlantic Pelagic Communities
There is a striking difference between the pelagic faunas of
the open ocean and of the coast banks. In the open sea we
find different pelagic communities according to the different
conditions presented at various depths, and by way of introduc-
tion it may be useful to inspect the aggregate catches of a
6i
DEPTHS OF THE OCEAN
definite group of pelagic animals taken at a genuine oceanic
station far from land in deep water. I have for this purpose
prepared the following list recording all the fishes taken at
Station 53, to the south of the Azores, during the night of the
8th - 9th of July, but 1 regret being unable in the case of
the young fish to indicate the species, which would have added
greatly to the interest of the list : —
Pelagic Fishes, Station 53
Surface, tow -net : Scopelidae : Myctophmn coccoi, M. pu?ictatum, M. charo-
cephalum, M. affine, M. hitmholdti, etc.; Stomiatidse : Stomias boa, 13
Astronesthes niger.
50 metres, tow-net: Great numbers of larvae and young fish, some with
telescopic eyes, 4 small larvae of the common eel {Leptocephalus brevirostris,
4.8-5.7 cm. long); many Scopelidae: 12 Stomias bwa, Chauliodus
s/oanei, 3 Dactylostomias n.sp. No. i, Idiacanthus ferox.
100 metres, tow-net: Scopelidae: Myctophmn {Diaphus) gettiellari, 3 Stomias
boa, Vincigiterria lucetia, Argyropelecus.
150 metres, young-fish trawl: a few fish-larvs, 2 Leptocephalus n.sp., some
Argyropelecus, 2 Stomias boa, Fhotostotfiias giiernei, Go)iostoma rhodadetiia,
new genus of Saccopharyngidae.
300 METRES, young-fish TRAWL : Young fish with telescopic eyes ; Scopelidae
{Myctophum coccoi, etc.) ; 5 Cyclothone signata, Cyclothone 7nicrodofi, 10
Vinciguerria lucetia, 13 Valenciennellus tripunctulatus, 16 Argyropelecus he?ni-
gymnus, Argyropelecus aculeatus, Sternoptyx diaphana (young fish from
8.5 cm. in length).
550 METRES, TOW-NET: 14 Cvclotliofie signata, 7 Cyclothone microdon, 14 Chauli-
odus sloanei, 3 Ster?ioptyx diaphana.
800 METRES, YOUNG-FISH TRAWL: 2 2 Cyclothone signata, 121 Cyclothone microdon,
Gonostoma rhodadenia, Gonostoma grande, Stomias boa, 2 Vinciguerria
lucetia, 2 Idiacanthus ferox, Astronesthes tiiger, 4 Gastrostomus bairdii.
1300 METRES, LARGE NET: Leptocephalus, 16 Cyclothone signata, 357 Cyclothone
microdon, 7 Gonostoma grande, Photostomias gtiernei, 5 Chauliodus sloanei,
2 Idiacanthus ferox, Cyema atrum, 3 Gastrostofnus bairdii, Melatiocetus
johnsoni, Melanocetus krechi, Oneirodes n.sp. No. 3, 3 Aceratias macro-
rhinus indicus.
These catches may be classified into three main regions : —
(i) a region extending downwards from about 500 metres,
characterised by the occurrence of Cyclothone and various black
or dark coloured fishes, and of many peculiar invertebrates,
red prawns being prominent ; (2) a region ranging between
150 and 500 metres, characterised by a peculiar community of
silvery or grayish fishes, belonging to the families Sternoptychidse
and Stomiatidee ; and (3) the surface region comprising the
upper 150 metres, characterised by transparent or blue coloured
animals and juvenile forms, especially the members of the large
family Scopelidae.
PELAGIC ANIMAL LIFE 619
In describing the pelagic communities of the open Atlantic
it is therefore natural to treat each of these three regions
separately, and to consider the pelagic communities of the coast
banks as a fourth biological region.
Bathypelagic Comuiiinities in Depths greater than §00
Metises. — The most abundant fishes in this region are two
Sternoptychidse of the genus Cyclothone, viz. C. signata and
C. luicrodon.
Of these two species we caught altogether over 7500 Vertical
individuals, which were all measured and arranged according cj^/w!
to their length and the instrument in which they were captured,
so as to obtain information regarding the occurrence of the
different sizes at different depths. Fig. 473 shows, in the
case of both' species, the results of the catches made between
Newfoundland and Ireland.
Cyclothone niicrodon was found during the cruise of the
" Michael Sars " in the North Atlantic at every station where
an appliance was towed in depths below 500 metres. Above
500 metres it was met with only occasionally, and at a depth of
300 metres we came across only one individual. In depths
from 500 metres down to 1500 metres its quantitative occurrence
appears to be fairly uniform.
In our northern as well as in our southern section we found
approximately the same number of individuals in each of
the three young- fish trawls which we towed simultaneously
at depths of 500 metres, 1000 metres, and 1500 metres. At
depths below 1500 metres we made only a few hauls, though,
on the other hand, we carried out some vertical hauls, which
allow of a comparison between the quantity met with above
and below 1500 metres. At Station 63 (in the northernmost
portion of the Sargasso Sea) we secured ten individuals in a
haul from a depth of 4500 metres up to 1500 metres, and
twenty-seven individuals in a haul from 1350 metres up to 450
metres. Accordingly, seeing that the first haul was made
through a distance more than three times as great as the
second, we get the result that there were nine times more
individuals in the intermediate layer from 1350 metres up to
450 metres than below 1500 metres. A more complete
analysis of the different depths from 1500 metres down to the
bottom of the sea (about 5000 metres) would have been very
desirable, but unfortunately we were unable to spare time for
it. It may be that there is a layer at the lowest depths where
there are no individuals, and I, for my part at any rate, cannot
620
DEPTHS OF THE OCEAN
Cycksthone microdon.
J300 Indii/iduals from Stations 80- 101
Newfoundfand to Ireland.
Cvclothone sign
780 Ind from Stations
Newfoundland to li
Fig. 473.
PELAGIC ANIMAL LIFE
621
help believing that the profoundest deep is far more poorly
supplied than the intermediate layer.
If we next examine the size-distribution at the different
depths, we shall see that it is perfectly clear that the smaller
sizes are met with much higher up than the larger ones,
which latter are mainly to be found at a depth of 1 500 metres.
In the northern section we find that at a depth of 500 metres
the greatest number of individuals were 30 mm. in length,
Cyclothone microdon
Cyclothone Signata.
Average lengths in various depths
Average lengths in various depths.
» Stations. 80 - 101
» Stations. 80- 101
0 51 - 67
X
0 51 - 67
-so /o
/ /
-50
-40
-30 "" 0-^
- 30 ^' ^^^>f-^^/
/
^. .0 0
/
-20 °
-20 0'
lengths in mm.
lengths in. mm
-10 1
1 ) Hppths in M
1.1,1
-10 1
1 J depths in m
1 1 1 . 1
500 1000 1500
500 1000 I5O0
Fig. 474.
whereas at 1500 metres the majority attained 60 mm. At a
depth of 500 metres we came across only two that were over
50 mm. in length. The smaller and younger individuals of
a length of 20-30 mm. live, accordingly, to a preponderating
extent, 1000 metres higher up in the water-layers than the
majority of the largest and oldest individuals.
Another remarkable fact which strikes us when we study
our catches is that the average size of the individuals is much
less in the southern than in the northern section at the same
622 DEPTHS OF THE OCEAN
depth, as shown by the graph (Fig. 474). We see, for
instance, that in the southern section, if we want to get
individuals of an average size of 30 mm., we must fish 250
metres farther down than we would in the northern section.
The vertical distribution of Cyclothone signata is very
different from that of C. microdot. We have captured many
individuals at a depth of 300 metres, at any rate, in our southern
section. The bulk, however, were found at a depth of 500
metres. In the hauls made at greater depths, the quantity
diminished so rapidly that we may assume that a large portion
of the fishes were caught during the process of hauling
in, and that there is only a comparatively thin layer below 500
metres in which they live. In a vertical haul from a depth of
4500 metres to 1500 metres we caught no individuals of this
species, but, on the other hand, we secured three individuals
in a haul from 1350 metres to 450 metres.
Cyclothone signata is, accordingly, found in an intermediate
layer with a maximum in the number of individuals at about
500 metres. In the case of this species, too, we note that the
younger individuals are mainly to be found high up in the water
(notice particularly the southern stations), and that the same
size is to be found deeper in the southern section than in the
northern (see Figs. 473 and 474).
Vertical We have a remarkable parallel to the vertical distribution
distribution of q{ these two species of fish in the case of the species of
'y"-- j.g^ prawns. These latter, along with the black fishes, form
a populous and characteristic "community." We have come
across no fewer than about forty species of pelagic prawns, of
which we shall here refer only to Aca^tthephyra inu/tispina and
A. purpurea.
Acanthephyra nuiltispina shared with Cyclothone niicrodon
the peculiarity that the largest and oldest individuals were found
in the nets towed at the greatest depths, say, at 1000- 1500
metres (see Fig. 475). At depths between 500 and 750
metres we met with medium-sized specimens, and in the upper
layers, from 50 to 150 metres, we found the larvae. These
larvae were taken in quantities, whereas formerly only a single
individual collected by the Prince of Monaco, described by
Coutiere as Hoplocaricyphus similis, but now identified as a larva
of Acanthephyra multispma, was known.
Acanthephyra purpurea resembles Cyclothone signata, in
that its' distribution is chiefly confined to an intermediate
layer between 500 and 750 metres in depth. Our appliances
PELAGIC ANIMAL LIFE 623
captured so few individuals at greater depths that we may
safely assume that even these were caught during the
process of hauling in. A vertical haul at Station 63, from a
depth of 4500 to 1500 metres, yielded five individuals of A.
multispijia, but none of A. purpurea ; while another haul from
1350 to 450 metres gave us two A. multispina and thirty-three
A. pzirpurea. The larvae of the latter occur in the higher
layers of water, just as is the case with A. multispina.
Acanthephyra A.M. E.dw.
lultispina { Coutiere \ purpurea A. M. Ed«
Scale refers to length of Carapace.
Fig. 475.
What has just been said illustrates the conditions on the
northern section from Newfoundland to Ireland, and if we
examine the material from the stations farthest south in the
Sargasso Sea, we are confronted with exactly the same difference
that we encountered in the case of the species of Cyciothone,
namely, that the same forms descend to greater depths in
the south than they do in the north ; the larger individuals
ot Acanthephyra purpitrea, for instance, occur at depths
624 DEPTHS OF THE OCEAN chap.
between 500 and 750 metres in the northern section, whereas
in the south they were seldom captured by the net towed at 500
metres, though present in large numbers at a depth of 1000
metres.
The results of these investigations clearly show that the
dark-coloured fish, the deep-red prawns, and other organisms
are limited to the deep parts of the ocean beyond 500 metres.
This bathypelagic region may, however, be subdivided into
various layers. We thus recognise a layer varying according
to geographical position between 500 and 800 metres contain-
ing the light-coloured species of Cyclothone and the bright-red
prawn with orange-coloured eggs [Acantkephyra purpurea).
The layer from 800 or 1000 metres downwards may require
to be still further subdivided, for certain forms like the larger
Acanthephyra with red eggs i^A. midtispina). Notostomus and
several fishes and squids have been taken only in the deepest
hauls at 1500 or 2000 metres, but we must point out that the
deeper parts of the Atlantic were not investigated by us, our
efforts being devoted mainly to the upper layers between 1500
metres and the surface. We shall, therefore, consider the layers
below 500 metres as a whole, referring to some characteristic
forms from this bathypelagic region, examining their horizontal
and vertical distribution, and discussing the laws which seem to
govern their occurrence.
We have seen that Haecker, in dealing with the vertical
distribution of the Radiolaria, recognised a Pandora region
from 400 to 1000 metres, and an abyssal region from 1500 to
5000 metres ; and this division coincides very well with the
two regions characterised, respectively, by the occurrence of
Cyclothone signata and C. microdoii and by the two species
of prawns.
Among the medusae a similar correlation is found, Periphylla
hyacinthina being most abundant at 500 metres, and Atolla
bairdi at 1000 metres.
No nemertines were taken in depths less than 700 or 800
metres, and the fifteen specimens belonging to the genus
Planctonemertes, taken at five separate stations, were taken
beyond 1500 metres.
The ostracod Gigantocypris was taken at eleven stations,
but only one individual occurred at 500 metres, the remainder
occurring in deeper water. Pyrosoma spinoswn was always
taken beyond 750 metres, most of the specimens coming from
1500 metres.
PELAGIC ANIMAL LIFE 625
Three species of pteropoda [Peraclis divcrsa, Limacina
helicoides and Clio falcata) live below 500 metres, but accord-
ing to Bonnevie, the first of these seems to avoid the cold
bottom water, while the second species seems to prefer this
water and the third seems indifferent. All three forms are
dark -coloured, and their structure differs from that of the
surface forms, being of a more archaic type.
All the large groups of squids include bathypelagic species,
of which the following may be mentioned : —
CEgopsidge : Calliteuthis reversa, Mastigoteuthis flammea, M. grhnaldi and
M. hjorti, Grivialditeuthis bonplandi, Toxeuma belone.
Myopsidas : larvje of Spirula.
Octopoda : Ekdonella pygmcBa^ Vampyroteuthis infernalis, Cirrothauma murrayi.
Many peculiar species of fish were found at and beyond 750
metres, for instance : Malacosteus indicus and M. niger,
GastrostomiLS bairdii, Cyema atrum, Gonostoma grande,
Melainphaes mizolepis, Cetomimus storeri and a closely allied
new genus. Of eight species of Ceratiidae seven have been
taken only beyond 500 metres. Acei^atias inacrorhinus indicus
may also be mentioned.
Proceeding to consider the horizontal or geographical dis- Horizontal
tribution of these forms, we commence with the most abundant
species of fish, Cyclothoiie signata and C. microdon. The chart
(Fig. 476) shows the localities where these species have been
taken previous to and during the " Michael Sars " Expedition,
and it is seen that the records are so numerous that these
fishes may be said to occur all over the area examined, wherever
a fishing appliance was lowered to a depth of 500 metres.
They are found everywhere, from the Wyville Thomson Ridge
in the north to beyond the Azores in the south, and from the
slopes of Africa and Europe to the slopes of America ; but the
distribution of the two species is not identical. Cyclothone
microdon has been captured by previous expeditions ^ on both
sides of Greenland, in Davis Straits, in Denmark Straits, and
also south of Iceland, whereas C. signata is unknown in these
localities ; and outside the Atlantic C. microdon occurs in the
Pacific, in the Indian Ocean, and in the Antarctic south
of lat. 50° S., whereas C. signata is much more restricted in
its southern distribution, having been taken at only one locality
to the south of lat. 40° S.
The peculiar vertical and horizontal distribution of the two
^ This information is derived from a chart in Brauer's paper on the deep-sea fishes of the
" Valdivia " Expedition.
2 S
distribution of
Cyclothone.
626
DEPTHS OF THE OCEAN
forms in question seems explicable when compared with the
distribution of temperature. In Chapter VH. we noted that
the temperature along the ocean -floor is very uniform, and
consequently the abyssal bottom-fish, like Macriirus armatus
and M. filicauda, have a very wide distribution. Throughout
the abyssal region of the Pacific, Atlantic, and Indian Oceans
the temperature varies only between i' and 3° C, and only
far south in the Antarctic do we meet with temperatures below
0° C. The water-layer from 5000 or 6000 metres up to 1500
vious catches cf
C. microdon
■\- Previous catches of
C. signata
10 L.Wot G. 0 L E of G. 10
OCyclothone Signata and microdon
caught bv "Michael Sars"
Fig. 476.
metres is practically homogeneous as to temperature, and if it
were possible for a fish to swim so far, keeping constantly at
a depth of 1500 metres, it might travel from India to Australia,
then westwards past the Cape, and northwards through the
Atlantic as near to Iceland as the depth would permit,
encountering all the way no greater variations in temperature
than from 3 to 5° C. Even at a depth of 1000 metres con-
ditions are very uniform, for only in the Indian and North
Atlantic Oceans do the temperatures rise to 7° or 8^ C,
PELAGIC ANIMAL LIFE 627
neglecting the somewhat higher temperatures found off the
entrances to the Red Sea and the Mediterranean, but the
temperatures at 1000 metres usually vary only from 4° to 6° C.
The habitat of CyclotJione viicrodon is below 1000 metres, the
temperatures generally varying between 3' and 6' C, and the
wide range of this species must evidently be directly connected
with the wide areas occupied by these temperatures. On the
other hand, the area of distribution of C. signata at about 500
metres shows great differences in temperature in different
parts of the ocean. In the Indian and Atlantic Oceans, where
C. signata is found, temperatures at this depth are generally
above 10° C, sometimes even above 15° C. In the sea
between Newfoundland and Iceland, as well as south of lat.
40^ S., temperatures are below 5° C, and in these localities
C. siznata is absent.
These facts, especially the conditions touching the wide
distribution of the bathypelagic C. niicrodon, assume more
general importance considering that we found many bathy-
pelagic species in the North Atlantic, which have been taken in the
deep water of other oceans. As instances of such forms I may Bathypelagic
mention the widely distributed medusae Atolla and Periphylla, ^°™^-
which were taken by us in the Northern Atlantic at nearly all
the localities and depths where C. microdon and C. signata were
taken. The genus Gigaiitocypris , taken at three stations in
our southern and at six stations in our northern section,
had previously been captured by the " Valdivia " in the Indian
Ocean. Three species of squids, taken by us in deep hauls
in the North Atlantic, were caught by the "Valdivia" in the
Indian Ocean, viz. Callitcnthis revcrsa, Mastigoteuthis flamniea,
Toxeuma belone. Bathypelagic fishes common to both these
oceans are : Malacosteus indicus, Cyema atrum, Mclamphaes
inizolepis, Cetomintus storeri, Melanocetus krec/ii, Ceratias cotiesi,
besides Aceratias macrorhinus indicus. These squids and
fishes are, however, represented by very few specimens, in
some cases only one from each ocean. The fact that we
caught several new species of the family Ceratiidse, as well
as such interesting forms as Gastrostomns bairdii and Gonostoma
grande, proves that a great field of research is still open to
systematic zoologists. The chart (Fig. 477) shows the dis-
tribution of Gonosto77ia grande.
All the forms mentioned live, as far as we know, always in
deep water, except perhaps the early stages, which in some
cases occur closer to the surface, but certain cold-water
62;
DEPTHS OF THE OCEAN
species found in depths below 500 or 1000 metres may in
other locaHties nearer the polar regions reach the surface.
During the Atlantic cruise of the " Michael Sars " numerous
arctic or northern forms were found in deep water in company
with the genuine or permanent deep-sea animals, especially in
our northern section from Newfoundland to Ireland. We
succeeded in proving the continuous occurrence of such forms
from the cold water-layers off the Banks of Newfoundland
down to great depths, just as these cold water-layers have
Qbnostoma grande
Fig. 477.
proved to be directly connected with the deep layers of the
ocean (see pp. 658-659).
Pelagic Commttnities in Depths between 1^0 and 500
Metres. — At the upper limit of the bathypelagic region in
about 500 metres certain fish, entirely different from the
bathypelagic species, make their appearance along with
CyclotJione signata. These fish are as a rule laterally com-
pressed, with a mirror-like silvery skin ; when coloured, the
back is generally blackish brown, and the resplendent mirror-
like sides of the body blue or violet. The eyes are large,
PELAGIC ANIMAL LIFE 629
very often telescopic, and the body is provided with a number
750
1000
1250
Slomias Boa 154 Ind
Chaufiodus Sic
anei 95 Ind.
Stallones 3m. sa
1350- 450 m.1 Ind
Station 63
3 3 cm 3m.sn 1350- 400
3 Ind ca. 3c
Station 50 1 s
1000m-500m 1 In
ca3
cm
Valenciellus
tripunctula-
tus771nd.
Ichthvo^
coccus
ovatus
5 Ind
Vihetguer
ria lucetia
61 Ind
Station 50
1 sn. 1000-
500 1 1nd
21 mm.
Station 691 srL 1500-300"
1 Ind 19mm.
Argyropelecus hemigyn
nnus 286 Ind
Arg. alfersi
Arg.acule
Arg. afTinis
Sternoptyx Diapha-
53 Ind.
atus50lnc
3 Ind.
na 101 Ind
150
-
o
300
'
'
750
.
1000
-
O
-
1500
-
-
2000
■
O
-
Fig. 478.
of light-organs varying in size. These forms have their lower
630 DEPTHS OF THE OCEAN
limit at about 500 metres, where they are found together with
the upper representatives of the bathypelagic fauna, just as on
the continental slopes the Macrurid bottom-fauna is mingled
with the deepest living species belonging to the coast banks.
Fig. 478 shows the vertical distribution of certain of these
pelagic fishes, and we see that Sternoptyx diaphana, Stomias
boa, and Chauliodus sloanei were taken most abundantly at
500 metres, while the species of the genera Argyropelectis,
Valenciennellus, and Vinciguerria were mostly taken at 300
metres ; the upper limit for all these species seems to be about
150 metres below the surface. As regards the geographical
distribution of these species, we find that, excepting Stomias boa,
they occur in the Indian Ocean to the north of lat. 40° S., and in
the Atlantic between lat. 44^ N. and 40° S., though Argyropelecus
olfersi, A. actileatus, and A. kei7iigymnus have been found on
the coasts of Norway, and Stomias boa has been taken in
the Faroe-Shetland channel during one of our cruises in the
" Michael Sars."
During our Atlantic cruise in 19 10, Argyropelecus affinis
and A. actileatus, Valenciemielhis tripunctiilatus, IchthyococciLS
ovatuSy and Serrivomer sector were only taken at our southern
stations, and did not appear at any of the stations between
Newfoundland and Ireland, while Argyropelecus hemigymnus,
Sternoptyx diapha^ia, Stomias boa, and Chauliodus sloanei were
caught both at northern and southern stations, but only Stomias
boa occurred in numbers of any consequence at the northern
stations. Thus, of 286 specimens oi Argyropelecus hemigymnus
taken during the cruise only 1 7 were captured on our northern
track; of loi specimens of Sternoptyx diaphana only 2 were
taken north of the Azores ; of 95 specimens of Chauliodus
sloanei ow\y 10 were taken north of the Azores. On the other
hand, out of our total of 154 specimens of Sto7nias boa 91 were
taken on the northern track, and this species appears to be
the only abundant one north of lat. 45" N.
The temperature throughout the region occupied by these
fishes, between lat. 40^ S. and 45° N., and between 500
and 150 metres, exceeds 10° C. We found the distribution
of the fishes of the Atlantic coast banks to be limited by this
temperature in a northerly direction as well as vertically. A
limit of this kind can only be roughly fixed, and is subject to
variations, but the isotherm of 10" C. seems on the whole to
coincide with the localities where the organisms in question
occur in numbers of importance. Within the region great
PELAGIC ANIMAL LIFE 631
variations apparently occur, for at a depth of 200 metres the
temperature exceeds 1 7" C. in the Sargasso Sea, in the
Mexican Gulf it is above 20'' C, in the Indian Ocean it varies
between 13° and 20° C., while in the southern Atlantic it is
only a little above 10' or 12" C. The fauna living at this
depth is thus subject to temperatures varying between 10"
and 20"^ C, corresponding with what we found in the case of
the fishes of the Atlantic coast banks from south of the Canaries
to the south-western coast of Britain.
All the silvery fishes of the region between 150 and 500
metres are small, and the same remark applies to all the other
organisms of the community. They consist almost exclusively
of small crustaceans (copepoda, ostracoda, amphipoda), sagittidse,
pteropoda, and small medusae. Besides these we commence
to find the larvae of squids and fishes, which, however, become
more numerous in the layer above 150 metres.
Pelagic Comm^utities in Depths less than 150 Metres. — In
reviewing the pelagic oceanic forms I mentioned that they
belong mainly to the warm belt on both sides of the equator
between lat. 40° N. and 40° S., where both species and
individuals are most numerous. Foraminifera, radiolaria
(acantharia), copepoda, medusae, siphonophora, pteropoda,
and salpae all occur in abundance, and the number of species
rapidly decreases as soon as we leave tropical waters. This
is also the case with the typical and most abundant surface
fishes, the scopelidae, which occur in numerous tropical and sub-
tropical forms, while only a few species are found in the
northern part of the North Atlantic.
The beautiful siphonophores Physalia and Velella were first Distribution
seen by us during our short visit to the Mediterranean and in pj^^^P °"°"
the Spanish Bay. On the way from the Canaries to the Azores
and thence westward to Station 64 they were frequently seen,
sometimes accompanied by Agalmopsis and Cestus veneris,
besides various surface mollusca. On the other hand, none of
these forms were observed on our northern track between
Newfoundland and Ireland.
The shelled pteropods (Thecosomata) are vertically limited Distribution
to a comparatively thin layer, extending in our northern section ° *^''°p° ^'
down to only 50 or 100 metres, and in the southern section to
250 metres, four-fifths of all the individuals taken occurring
within these limits. No less than 3500 individuals comprising
22 species were preserved by us, and of these only about 500
specimens comprising 16 species came from the northern section.
632
DEPTHS OF THE OCEAN
In the southern section, again, the majority were taken in the
western half towards the Sargasso Sea, west of the longitude of
the Azores, where these forms occurred in great abundance.
The distribution of salpae is somewhat different. Certain
forms occur only in the south, for instance, Cyclosalpa floridana,
Salpa amboinensis, and S. henseni ; but the majority were taken
to the north and south of the Azores, for example, Cyclosalpa
pinnata and Salpa inaxwia. The medusa Pelagia perla is
similarly distributed. All these surface animals occur in this
central region of the North Atlantic in such countless numbers
as to be immediately noticeable, and it struck me at the time that
this peculiar distribution north and south of the Azores might
be correlated with the submarine ridge on which these islands
are situated. The currents are probably influenced by the
configuration of the bottom, and the distribution of the pelagic
organisms, even in the surface waters, may possibly be thereby
affected, as we have often observed during previous cruises of
the " Michael Sars " in the Norwegian Sea. A third group of
salpae, viz. Salpa fusifonnis, S. mucronata, S. confcederata, and
S. zonaria, while certainly most abundant north and south
of the Azores, occurred frequently in other localities, especially
in our northern section. Salpa fusiforviis was doubt-
less the principal form among these, and was the only one
observed. at all the stations to the south-west of Ireland, between
Rockall and the west coast of Scotland, and towards the Faroe-
Shetland channel. Fig. 479 illustrates the distribution of Salpa
zoiiaria, which was found abundantly in the northern part of
the Atlantic.
Most of the squids taken at the surface occurred south of
the Azores, especially larval forms, and included larvae of
Onychoteuthidae, Octopodoteuthis sictda, Cranchiidae (Cranckia
scabra, Teuthowenia megalops, GalitetUhis sukniii), Heteroteuthis
dispar, Tremoctopus atlaiiticiis, and Argonauta. Certain north-
ern forms like Gonatiis may be supposed to be wholly boreal.
Among oceanic surface fish the Scopelidae are probably
most abundant. They were taken in thousands, but only a
few have as yet been determined. Of these, Myctopkum
rissoi, M. benoiti, M. affine, M. humboldti, M. coccoi,
M. ckcerocephahi7n, M. gemellari, M. maderense, M. warmingi,
M. 77iicropterum, and M. gemmifer were taken only in the south ;
while M. glaciale, M. punctatuvi, and M. rafinesquei were also
taken in our northern section. The Scopelidae were usually
accompanied by numerous young fish, of which I may mention
PELAGIC ANIMAL LIFE
^33
the fry of the horse mackerel, the young of Scombresox saurus
(a near relation of the gar-pike), and of the flying fish {Exocoehts).
These forms were with one exception observed only in our
southern section.
A peculiar group of fishes are the Sargasso fish, which live Sargasso
on or around the Sargasso weed. We found Antennarius
inarmoratus, SyngnathiLS pelagicus, Hippocampus ramulostis, and
MonacantJms, together with a peculiar Sargasso fauna, including
small crabs {^Plmies minutus) and small prawns of several kinds
Fig. 479. — Distribution of Salpa zonaria.
(see Plates V. and VI., Chapter X.). But besides the Sargasso
fish various remarkable forms occur in the surface waters of
the ocean, such as the " wreck-fish," Liriis 7nedttsophagus and
L. ovalis, Polyprion americanus, and the pilot fish {Nazccrates
ductor), taken by us to the south of the Azores, where salpse
and large medusae were present in such numbers, as well as the
enormous sunfish i^Mola), harpooned due north of the Azores.
A community nearly as peculiar as the Sargasso fauna exists
in the north-eastern corner of the area investigated by us,
extending from the Azores to Ireland and thence to Rockall
634 DEPTHS OF THE OCEAN chap.
and the Faroe-Shetland channel. Johs. Schmidt first drew
attention to this community. Salpa fusiforjuis, the larval
actinia Arachnactis albida (the distribution of which is shown
in Fig. 480), the barnacles Lepas pectmata and L. fasciathiris,
young stages of the thread-like fish Fierasfer, Nerophis cEquoreiis,
larvae of the common eel and scopelidse iyMyctophum glaciale
and M. pitnctatum) ozQMX here in great numbers. Excepting
the salpse, the barnacles and the leptocephali, which also
occur in the warm Atlantic, all these forms live in what may be
Fig. 480. — DiSTRTBUTION OF Arachx
called a transitional area between the Atlantic and the Nor-
wegian Sea.
The conditions of temperature in this bathymetrical region
are shown in Figs. 159, p. 227, and 160, p. 228 (surface
temperature for February and August), and In Fig. 312, p. 445
(temperature at 100 metres). Comparing these charts with the
current chart in Chapter X., we obtain a good impression
of the currents of the North Atlantic. The warm Gulf Stream,
originating in the Gulf of Mexico, follows the east coast of the
United States towards the Banks of Newfoundland, where it
divides into several branches. A northern branch appears to run
towards Davis Strait, partly as an undercurrent. An eastern
branch runs towards the Azores and, spreading out like a fan,
PELAGIC ANIMAL LIFE 635
merges finally into the Canary stream and the enormous whirl-
pool of the Sargasso Sea. A North European branch, after
reaching the British Isles, continues to the Norwegian Sea and
the North Sea. We may consequently distinguish various
surface regions in the North Atlantic: (1) the genuine
Gulf Stream ; (2) the eastern Azores current ; (3) the Canary
current; (4) the Sargasso Sea; (5) the North European Gulf
Stream.
The last mentioned, which we crossed on our northern track,
receives a certain admixture of cold water from the Labrador
current, besides many animals from northern waters. It
appears from these considerations that the limit to the genuine
warm-water forms of the Atlantic follows a line parallel to the
axis of the true Gulf Stream water, the faunas to the north and
south of this line differing to some extent.
Pelagic Commimities on the Coast Banks of the Atlantic. —
The chief aim of our cruise was to examine the pelagic life of
the open ocean, and our catches on the coast banks were there-
fore casual. On the coast of Africa, at Cape Bojador, quite Fishes of the
close to the shore we caught the young of the anchovy ^^^"'^^^ '^°^^^-
[Bngraulis encrasickohis), Clupea alosa, the sardine [Chipea
pilckardus), the horse mackerel {Caranx trac/mrus), and
Scombi'esox saurus. Together with the mackerel, the bonito,
the tunny, and the gar-pike, these fish are the most important
pelagic species on the coast banks. To these may be added
the great sharks : the blue shark {Carckarias glazccits), probably
the species most commonly captured by sea-faring people ; the
hammer-head [Zygcsna 77ialleus), which the trawlers get among
the hake on the coast of Morocco ; and several others.
As far as we know, these fishes belong mainly to the coast
waters ; at all events the herring, mackerel, tunny, and gar-
pike spawn in the coast waters or their vicinity. On the other
hand, we found on our cruise the eggs and young of Sco7nbresox
so far from land that they may safely be said to spawn in the
open ocean, as is probably the case with Caranx. Many of
these fishes are probably widespread in the ocean, even if they
do appear in the coast waters.
When journeying some years ago on the west coast of Fishery m the
France I was informed that a peculiar bonito and tunny fishery op^" o"^"^-
had recently originated in the Atlantic, carried out with deck
cutters which went as far as 150 miles off the coast of
France, the voyages lasting eight to twelve days. The fishing
commences in July and continues all the autumn, and is a kind
636 DEPTHS OF THE OCEAN
of harling, like the mackerel fishery in the North Sea. It is
carried on only during the day, some of the fish weighing over
thirty pounds. This is the only fishery I know of in the open
ocean over deep water and away from the coast banks, and the
species captured visit the coast banks, at all events, some time
during the year.
Among pelagic fishes, however, the sardine is the most
important to the fisheries on the Atlantic coast banks, and it is
captured in the same area as the Atlantic bottom fish, i.e. from
the Channel along the coasts of Spain and Portugal and Africa.
The sardine, the bonito, and the tunny are here probably the
only Atlantic pelagic species of economic importance.
B. The Northern Pelagic Communities
In the ocean we find no sharply defined border between the
animal-communities belonging respectively to the tropics and
the polar seas ; on the contrary, there are numerous transitions
between the extreme conditions of life peculiar to the tropics
and the polar regions. It is therefore difficult to classify the
communities, and this difficulty is intensified by the fact that
most records note merely the occurrence or non-occurrence of
certain organisms and not their quantitative occurrence — a vital
point in discussing questions of distribution. If I attempt to
separate the genuine Atlantic from the northern pelagic animal-
communities, it is because I feel that in this way we shall
actually gain a better conception of their main features. I
believe that a division of this kind will coincide generally with
the limit drawn between the areas of distribution peculiar to
the southern and northern bottom fish on the Atlantic coast
banks, viz. the isotherm of 10° C. at 100 metres, running from
the Channel, south of Ireland, skirting the south coast of Iceland,
and thence to the United States.
Among northern communities it is impossible to separate
oceanic and coastal communities so sharply as among Atlantic
communities, probably because northern communities are chiefly
restricted to comparatively small areas, and the substances
carried from the land vary in quantity and quality, giving rise
to corresponding variations in the food supply. Neither is the
vertical distribution so easily defined as in the Atlantic, certain
species having a very different vertical distribution in different
areas.
It is extremely important for a true conception of the
PELAGIC ANIMAL LIFE 637
communities of northern waters to distinguish between the
various types of areas of distribution. In accordance with all
previous descriptions of the animal life of northern waters, we
may recognise three typical faunas, viz. (i) the arctic, (2) the
boreal, and (3) the temperate Atlantic.
The arctic communities include those forms which are
propagated and attain their maximum abundance in waters
belonging to the ice - covered area at temperatures below
2 'C.
The temperate Atlantic communities comprise those forms
which occur mainly in the warm layers of the Atlantic, and only
at certain seasons or in small quantities occur in the north.
Most of these forms are entirely oceanic.
The boreal communities include those forms having their
maximum frequency in waters at temperatures between 4° and
8° C. It is the boreal region which specially interests us, but
the nature of boreal communities can only be fully grasped
when we know the " strange elements " — the Atlantic and arctic
"visitors."
The boreal region includes several areas, each limited by
natural borders, one of which lies between the west coast
of Britain and South Iceland, extending to the Faroe-Shetland
channel, the upper layers being occupied by the North
European branch of the Gulf Stream. Another area is the
Norwegian Sea, separated from the first-mentioned by the
submarine ridges between Shetland and Faroe and Iceland ;
a third area is found round Greenland, Davis Straits, and the
Newfoundland banks.
We will discuss the Norwegian Sea first, because this area
has been most thoroughly investigated.
The Noi'zuegian Sea. — The borders of the ice may be con- Arctic animal
sidered as indicating roughly the limits of distribution of pelagic communities.
arctic communities. It is therefore interesting to examine the
ice-limits as shown by the charts published by the Danish
Meteorological Institute. Fig. 481 represents some of these
ice-limits for different months of the years 1902, 1903, and 1906,
showing considerable variations from season to season and
from year to year. Vast areas of the Barents Sea and White
Sea are closed in winter and open in summer, as also the sea
off Spitsbergen, and the Greenland Sea between Jan Mayen
and Greenland. The Polar Sea north of Spitsbergen is in
certain years ice-covered all the year round, but sometimes a
Fig. 481.— Ice boundaries from the Charts of the Danish
Meteorological Office.
CHAP. IX PELAGIC ANIMAL LIFE 639
bay of open water runs for an unknown distance towards the
north.
The vertical distribution of the cold water in the Norwegian
Sea along a line from Greenland past Jan Mayen to Vesteraalen
is shown in Fig. 310, p. 436, which indicates that the great
body of water in the Norwegian Sea has a temperature below
2° C., and that warm water is found only in the eastern part of
the sea towards Norway to a depth of 500 or 600 metres.
The investigations of the " Michael Sars " have been
limited mainly to the area covered by this warm water, but a
thorough investigation of the arctic Greenland Sea has been
made by the Duke of Orleans in his expeditions on board the
" Belgica," in which Koefoed took part, and had the oppor-
tunity of making collections with the same appliances as were
employed on board the " Michael Sars." The " Belgica" and
" Michael Sars " material has been dealt with jointly by
Koefoed and Damas, upon whose treatise ^ I have drawn for
information about some of the most important arctic forms.
Damas and Koefoed divide the Copepoda of the Greenland
Sea into several biological groups : (i) forms which live
mainly in the surface waters, such as Calanus finmarchicus and
C. Jiype7''boreus, Pse^idocalanus elongatus and P. gracilis, Onccsa
conifera and O. notopiis, Oithona similis \ (2) forms living
mostly in mid-water, but occasionally appearing at the surface,
atypical form being EuchcEta norvegica \ (3) mid -water forms
which never occur at the surface, especially Eiichceta glacialis ;
and (4) deep-sea forms, like Euchceta barbata, Chiridiella
7nacrodactyla, and others.
At the surface the commonest form is Calanus kyperboreus, caiatms
one of the largest of copepods, attaining a length of 9 mm. h'perboreus.
At the ice it is found 5 to 10 metres below the surface in
enormous numbers. Thus in July a few hauls with closing nets
in lat. 75° 55' N, long. 9° W., depth 1275 metres, gave: —
In a haul from lo to o metres, tooo specimens.
,, ,, 100 to 20 ,, 2 ,,
,, ,, 400 to 210 ,, 4 ,,
It is mainly an arctic form, and occurs in the Polar basin,
in the Greenland Sea, and in the colder parts of the Norwegian
Sea. Its propagation takes place principally in the shallow parts
of the Greenland Sea, on the coast banks and not where the
water is deep, whence the young are carried out into deeper
water by currents. The wealth of animal life in the Arctic is
1 Damas and Koefoed, loc. cit.
640
DEPTHS OF THE OCEAN
largely due to the enormous abundance of this species, which
constitutes the food of the arctic whales.
Vertical In the boreal parts of the Norwegian Sea most of the arctic
distribution of species occur in the deeper layers in accordance with the hydro-
Copepocia in ^ , . , ,. , ^1 •' ■, 1 r n • 1 r
the Norwegian graphical conditious, as shown by the ioUowmg abstract trom a
^^f- table given by Damas and Koefoed : —
0-50
50-100
100-200
200-500
500-1000
metres.
metres.
metres.
metres.
metres.
Calanus finmarchicus
X
X
X
X
X
Calanus hyperboreus .
X
X
X
Pseudocalanus elongatus
X
X
X
X
X
Microcalanus pusillus
X
Euchata norvegica
X
X
X
Euchceta glacialis
X
Chiridius armatus
X
X
X
Chiridius obtusifrons
X
X
AinaUopho7-a magna
X
Ojiccea conifera .
X
X
Oithona plumifera
X
X
X
Oithofia similis .
X
X
X
X
X
According to this table a peculiar bathypelagic fauna appears
to exist in the Norwegian Sea, whether the surface layers be
warm or cold. We find, however, many transitions between
the typically arctic and the typically boreal forms, and the
most intimate knowledge of their distribution and life-history
is necessary to enable us fully to characterise the various
species.
Among the pteropoda Limacina helicina is typically arctic ;
it spawns on the coast banks of Greenland at a temperature of
0° C, and between the ice-floes, the young being gradually
distributed into deeper water.
As already indicated, there are certain medusae which must
be considered as arctic coast forms (see Fig. 398, p. 570), such
as Hippocrene superciliaris, Codonium princeps, Catablevia
campanula. Of oceanic medusae Aglantha digitalis is found
in the upper layers, and Crossota norvegica in the deepest layers
of the Norwegian Sea, both being characteristic forms.
The siphonophore Diphyes arctica, the sagittidae Krohnia
kamata, Sagitta gigantea and S. arctica, the ostracod Conchcecia
borealis, the schizopoda Meganyctiphanes norvegica, Boreophausia
inennis and Thysanocssa longicaitdata, the amphipoda Euthetnisto
PELAGIC ANIMAL LIFE 641
libellula and Paratheniisto oblivia, the prawns Hymenodora
glacialis and Pasiphcea princeps are partly arctic, partly boreo-
arctic, and partly boreal in their occurrence, but in the present
state of our knowledge it is impossible to define sharply the
general laws of their distribution. In the year 1900 I made a
number of closing- net hauls in the Norwegian Sea, which
showed that there was a peculiar pelagic fauna in the deep
cold layer below the Gulf Stream, including the following large
forms : Cyclocaris guilelmi, Hy^nenodora glacialis, PasipJicea
princeps, and large Sagittae (.S". giganted).
Of holopelagic fish there is not a single arctic species.
The coast fishes of Greenland, Spitsbergen, and other Arctic
shores may certainly be captured in the surface waters above
the coast-banks, but their life-cycle is not wholly pelagic. In
regard to one species only, Gadus saida (the polar cod), there
may be some doubt, for it lives everywhere along the ice
independent of depth, but it seems most feasible to classify it
among the Arctic shore-fishes. In the case of this fish the ice
apparently replaces the shore, a condition peculiar to many
other arctic forms.
Highly important is the Capelan or Caplin [Mallohis villosus),
which lives in the Arctic or in the extreme north of the boreal
area, where it appears at all events once a year to deposit its
spawn on the coast banks. We may thus term it a meropelagic
fish of " boreo-arctic " character.
The black Paraliparis batliybii has been taken by the
"Michael Sars " in mid-water in the Norwegian Sea, but
whether this species is mainly a bathypelagic or a bottom fish
cannot be decided from the available records.
It has long been known that Atlantic species sometimes Atlantic
appear in the coast waters of Norway, and Nordgaard^ ^^s ^"JJJJ^Jj^ijjgg^
published an interesting review of historical details of
this kind. Thus in 1821 salpae were observed by a certain
Norwegian priest, and between the 'twenties and 'forties of
last century when Michael Sars was engaged in his pioneer
work on the west coast of Norway, he found many Atlantic
forms, like Salpa nmcronata and S. fusiformis, well known by
the fishermen and termed " Silderaek," a portent of successful
herring fishery. Sars described from the west coast of Norway
some new species of Siphonophores and a larval Actinian
having their main distribution in the Atlantic, such as Galeolaria
^ Kgl, Videnskapers selskaps skrifter, Trondhjem, 1910.
2 T
642 DEPTHS OF THE OCEAN chap.
biloba and G. tnincata, Agalmopsis elegans, Physophora
hydrostatica {borealis), and Arachnactis albida. Since then
many records of Atlantic forms occurring on the coast of Norway-
have been pubHshed, and Collett ^ has collected many such
records referring to fishes. Similar information has been
gathered in Sweden, Denmark, and Germany. I give here
some of these records, without any claim to completeness.
Oi Foraminifera, the majority of which are oceanic forms,
Globigerina bulloides is always found in the Gulf Stream off
the coast of Norway.
Surface Radiolarians (Acantharia), and also Atlantic deep-
sea species of the same group, sometimes occur, for instance,
Challengeridae, Medusettidae, and Arachnosphseridse. Jorgen-
sen has greatly contributed to our knowledge on this group
of animals. In the Skagerrack, Atlantic Radiolarians have also
been found by Aurivillius.
As prominent among Atlantic Medusa taken in the
Norwegian Sea and fjords we may mention Atolla bairdi and
Periphylla hyacinthina. In May 191 1 I investigated the
Sognefjord, having a depth of 1000 to 1200 metres, towing
simultaneously a number of pelagic fishing appliances at various
depths, and captured more than 1000 Periphylla hyacinthina
of all sizes ; they occurred at all depths below 75 metres, 100
large and 300 small individuals being taken at 750 metres.
Of southern jelly-fish Cyanea lamarcki and Rhizostovia octopus
have been taken on the Norwegian coast ; the former is a
coast form and probably came from the southern North Sea.
Among the Siphonophores Physophora hyd^'ostatica is most
abundant, but the other forms recorded by Michael Sars also
occur." Damas has drawn attention to the importance of this
immigration.
Arachnactis albida is frequently found and is a characteristic
Atlantic species.
Nordgaard has recorded Atlantic Copepoda from Lofoten
(Pleuro7}wia robusta), and the barnacle, Lepas fascicularis, has
frequently been found. The southern pteropod Clio pyra7nidata
also occurs. Salpa fusiformis and S. mucronata occur on the
coast of Norway, having been recorded by many observers
from the south-west coast to Trondhjem fjord (Nordgaard).
Regarding the squids some interesting information is on
record. Steenstrup collected information about colossal squids
^ Collett, Meddelelser om Norges Flske (Kristiania, 1902- 1905).
^ See Damas in Report on Norwegian Fishery and Marine Investigations, vol. ii. No. i,
1909.
PELAGIC ANIMAL LIFE 643
from the Northern Atlantic stranded on various North European
coasts, which he described as Architeuthis dux. The stranding
of such giant squids is recorded from Nordland (where Collett
heard of a specimen 12 feet long) and from Trondhjem. In my
opinion it is an open question whether certain smaller squids
do not passively invade the Norwegian coasts in enormous
quantities from the Atlantic. During the cruises of the
" Michael Sars " in the Norwegian Sea we never found the
larvae of the abundant Gonatus fabricii, but on our Atlantic
cruise we caught them between Newfoundland and Ireland.
Our knowledge is, however, most exhaustive on the subject
of the Fishes, and from Collett I have compiled the following
list of Atlantic species found in Norwegian waters with their
relative frequency : —
ScOMBRIDvE (mackerels)
Auxis thazardus, 2 specimens.
Thynnus thynnus (the tunny), annually.
Euthynnus alliteratus, 3 specimens.
Sarda sarda, almost annually.
Stromateid^
Centrolophus ponipilus, 2 specimens.
ZEIDiE
Zeus fab er (John Dory), about 16 specimens, between Christiania and Bergen.
Lamprid^e
Lampris giitfatus, annually one or more specimens.
Bramiid^
Bra7?ia rati, i specimen.
Pterycombus bra??ia, 14 specimens.
Trichiurid^
Trichiurus lepturus, i specimen.
XiPHIIDiE
Xiphias gladius (the swordfish), 30 or 40 specimens during the last twenty years,
Christiania fjord to Fin mark.
Trachypterid^
Trachypterus arcticus, annually one or more specimens stranded.
Regakcus glesjie^ 12 specimens during sixty years.
STERNOPTYCHID.E
Argyropelecus olfersi, about 20 specimens observed as far as Finmark.
Argyropekcus acukatus, i specimen.
Argyropekcus hemigynmus, i specimen in Finmark.
644 DEPTHS OF THE OCEAN chap.
SCOPELID^
Mydophum g/acia/e, 4 or 5 specimens in one hundred years.
Myctophum elongatiim, shoals observed during certain periods in the Trondhjem
fjord.
SCOMBRESOCID^
Scombresox saurus (skipper or saury pike), found now and again as far as Finmark.
Exocoetiis voliians (flying-fish), i specimen, Christiania fjord.
Clupeidte
Clupea pilchardiis (sardine), since 1871 no specimen on record.
Clupea a/osa, 30 specimens.
Clupea finta, 10 specimens recorded.
Engraulis encrasichohcs (anchovy), insignificant numbers.
Syngnathid^
N^erophis cequoreus, sporadic, as far as Tromso.
MOLID/E
Mola mola (sunfish), stranded now and again ; in Christiania fjord 20 specimens
since the 'seventies.
Besides these several southern sharks have been found,
for instance, the blue shark {Carcharias glaucus), which, how-
ever, is rare. Petromyzon marimis, which we took in the
surface waters off the banks of Newfoundland, has been found
up to Finmark.
These carefully gathered records show that many Atlantic
fishes occur in the Norwegian seas only as very rare visitors,
and seldom in great quantities. That these fishes are scarce
is shown by the fact that in all the hauls made by the " Michael
Sars " in the Norwegian Sea only Myctophun glaciale and
Nerophis were observed. On the other hand interesting
information as to the occurrence of Atlantic invertebrates has
been gathered.
This list of Atlantic fish from the Norwegian Sea is of
general interest because none of the species recorded are
known to live in the deep region of the Atlantic below 500
metres, but are forms belonging either to the surface layers,
or silvery forms from the " intermediate " layers about 300
metres. The Sternoptychidae and the Trachypteridae belong
to the latter, while the others are typical surface forms. Not
a single Cyclothone has as yet been captured in the Norwegian
Sea.
Boreal animal In the Norwegian Sea the boreal region is essentially
communities, lin^ite^j by f^g prcscncc of arctic water, which in the Greenland
PELAGIC ANIMAL LIFE 645
Sea in the west, at Spitsbergen in the north, and in deep water,
even close to the banks of Norway and the North Sea, excludes
all boreal species (see Fig. 310, p. 436).
In the boreal area, as thus limited, we find not a single
species of tish, perhaps not even a single animal-form, which
may be said to be entirely oceanic.^ The only oceanic com-
munity in the Norwegian Sea would perhaps be the arctic deep-
sea fauna. Among the boreal species, however, we find several
gradations between the purely oceanic and the purely coast
forms of life.
Of all invertebrates the minute crustacean Calanzcs Caianus
finmarchicus is undoubtedly the most important in the boreal /«"'«''^'^"'"«^
community. If during spring or summer a hoop-net is towed
along the surface in the warm part of the Norwegian Sea off the
coast banks, a practically uniform catch is obtained, consisting
almost exclusively of this species, indicating a "monotonous"
pelagic life, as Haeckel calls it. G. O. Sars, in his reports on
the " Voringen " Expedition, drew attention to this fact and to
the wealth of life peculiar to the open ocean, and this monotonous
fauna has recently been investigated by Gran and Damas during
the cruises of the " Michael Sars." Calamis fiimiarchiais occurs
both above the coast banks and in the fjords, but in these localities
its preponderance is less pronounced than in the open sea.
In the coast waters we notice many pelagic forms belong- Coast water
ing to various groups, along with many larval forms of bottom ^°™^"
animals, thus introducing a strange variety into the pelagic life.
Want of space prevents a full discussion of this animal com-
munity, and in regard to the various groups I refer the reader
to my preceding review. Besides Calamis finmarchicus there
are many other Copepoda, especially the genera Centropages,
Ternora, Acartia, Anoinalocera, and Enchcsta. Of Schizopoda
Thysanocssa, Meganyctiphanes , My sis, and of Decapoda Pasiphcsa
and Pandahis, occur. Vast numbers of Medusae are found at the
surface and in the deep water of the fjords, in the Norwegian
depression or gut, and in the Skagerrack. Two species of jelly-
fish, the brown stinging jelly-fish Cyanea capillata, and the trans-
parent Aurelia aurita, are frequent. Of Pteropoda we meet with
Clione liniacina, Limacina retroversa, and L. balea. The most
important squid is Ommato strep lies todarus. Of fish the follow-
ing species may be noted : mackerel [Scomber scomber),
sprat [Clupea sprattus), herring (Chpca karengzts), salmon
^ According to Damas even Calamis finmarchicus is to some extent dependent on the
configuration of the bottom (in the spawning time).
646 DEPTHS OF THE OCEAN
{Salmo salar), sea trout (Salvia trtitta), capelan (Mallohis
villosus).
In the southernmost part of our boreal region certain
Atlantic pelagic forms are found in such numbers that they
may be considered as belonging to the boreal area, though in
the main they are Atlantic ; so far the occurrence of these
species resembles that of certain bottom fish, like the sole,
the turbot, and the brill. The principal forms are : the horse
mackerel [Caraitx trachttrus), Clupea alosa, and the anchovy
(Engraitlis encrasichohts).
Certain bottom fishes are often found in mid-water, such as
the sharks which pursue the herring shoals, the common dog-fish
{Acantkias vulgaris)^ the herring-shark (Lamna cormibica) and
the large Selache maxiiiza. Many fishes of the cod family lead a
partly pelagic life, especially the saithe, and sometimes also the
cod, haddock, and others. A specially remarkable type is the
Norway haddock [Sebastes marinus). The pelagic eggs, larvae,
and young of economically important fishes, chiefly the cod and
flounder families (Gadidse and Pleuronectidae) form another very
important section of the pelagic communities.
When in the year 1900 I commenced my investigations
with the newly built " Michael Sars," one of my main objects
was to find out to what extent the fishes of the coast banks
occurred in the deep mid-water of the Norwegian Sea. A large
amount of information regarding this question has been accumu-
lated, and we may now classify these animals in four groups : —
1. Larvae and young organisms which have been carried out
by currents, mainly of jelly-fish and cod, saithe and haddock.
2. Adult coast fish which have migrated ; they spawn
on the coast banks, but not over the deep water of the
Norwegian Sea, the species observed being herring, cod,
haddock, and saithe ; also the squid, Ommatostrepkes todarits.
3. Adult forms which spawn and occur in all stages of
development in the coast waters, and also spawn over the deep
Norwegian Sea ; the only species of this kind observed is the
Norway haddock (Sebastes viarinus).
4. Atlantic animals : besides those previously mentioned we
have also found the squids, GonattLS fabricii and Architeuthis
dux, and the " Atlantic " whales, the " Bottle-nose " (Hyperoodon
diodon) and the cachalot (Pkyseter macrocephahis).
Of these groups I will discuss the three last, leaving the first
to be dealt with in the next chapter.
On the chart (Fig. 482) I have denoted all the localities
PELAGIC ANIMAL LIFE
647
from which we possess definite information as to the occurrence The herring.
of herrings, gadids, and Sebastes over deep water. Most of the
"^t!
f'
0
0 ^,
° ^\ :b|
<.^:i 3 an May en O
8^3^ oLO ..^*P
'
0
'^ --,^
/'/' 0/''^
^ ^ ^>
-•^..J'^-OT^ ^
^!$;:.
'"^ /
f- ?T ^
J ;'°
1' 1
«. ( !f ^
(
<^-\
Ji- ■y^''$^^ 0
'; '
W ^
\ /'
.-:--' / >i>et'lancL y^'
.,;&5^
" V "'
'■::■••>>■■■' i
^'m^
Fig. 482.— Animals caught over great depths in the Norwegian Sea.
The isobaths represent depths of 100, 200, and 500 fathoms.
(•) Cyclopterus.
X Herrings.
+ Cod.
/\ Gadus vireris.
O Sebastes.
0 Cephalopoda
^\ Lamna.
^ Acanthias.
rn Haddoclc.
J Aiiarfhicas.
C Greenland sharl<.
^ Macl<erel.
herrings occur from the northern slope of the North Sea towards
Iceland. Only in two places elsewhere, between the Lofotens
and Jan Mayen, did we succeed in capturing herrings, and
648
DEPTHS OF THE OCEAN
though the individuals are few they are very interesting
because the localities are no less than 240 miles distant from
any shore. As the herring spawns on the bottom comparatively
near the shore, and the young are consequently born there,
these captures illustrate the actual migrations. Several of the
records obtained near the slopes of the coast banks of the North
Sea, the Faroe Islands, and Iceland are specially interesting,
because the fishermen always report that herrings occur in the
stomachs of ling and cod captured on the slopes of the banks in
summer. It will be an interesting object for future research to
ascertain if herrings may be captured along the bottom on the
slopes. This might be possible now that the trawl has proved
a fit appliance for the capture of herrings along the bottom, and
if successful would confirm the hypothesis of Sir John Murray
that this part of the sea bottom, the " mud-line," is a feeding
ground for these fishes.
The Gadidae (cod, haddock, and saithe) have been taken in
the surface waters over the deep parts of the Norwegian Sea
far from the coast banks, but not in great numbers. The
species most numerously represented in these parts seems to
be the Norway haddock [Sebastes marimis). As will be noticed
from the chart it has been taken in many localities, and these
have been added to by recent investigations. Sebastes occurred
mostly at depths of 100 to 200 metres, and we captured them
by means of floating long lines, as shown in Fig. 74, p. 90,
in numbers bordering on the abundance necessary for com-
mercial fishing. Thus on one occasion we captured 65 fishes
on 600 hooks with salted bait. Two young specimens of this
fish were captured during the " Voringen " Expedition, and
during our cruises we have found the fry in thousands all over
the Norwegian Sea — a fact pointing to the existence and propa-
gation of a large stock of Sebastes in these intermediate layers.
Among the squids Ommatostrephes todanis plays the most
important part in the animal community of the Norwegian
Sea. In his book on the Mollusca of Northern Norway,
G. O. Sars, referring to this form, says : "It is the commonest
squid on our coasts, and among the fishermen is generally
termed ' Akker,' ' sprut,' etc. They generally appear in enormous
shoals, coming from the open ocean in pursuit of the herring
shoals on which they gorge themselves greedily. In pursuing
the herring they often run up on the beach in their excitement,
and long sandy beaches are sometimes said to be covered with
the carcases of stranded squids. At Lofoten they have been
PELAGIC ANIMAL LIFE 649
fished and salted in barrels for bait in the cod-fisheries, being
usually captured at dusk or during the night by the aid of
minute grapnels, several large hooks tied around a cylindrical
piece of lead, baited with a herring and lowered to a suitable
depth. The species is known outside Norway from the Skager-
rack, the Faroe Islands, and Iceland, as well as from the west
coast of France and the Mediterranean."
While fishing on the slopes of the coast banks one often
finds this squid in the stomachs of cod, and repeatedly I have
had occasion to make most interesting notes as to the occurrence
of this species in the open sea far from land. One night we
were hauling long lines on the Faroe slope, working with an
electric lamp hanging over the side in order to see the line,
when like lightning fiashes one squid after another shot
towards the light ; on the same occasion the beaks of these
animals were found in the stomachs of the captured fish. In
October 1902 we were one night steaming outside the slopes
of the coast banks of Norway, and for many miles we could see
the squids moving in the surface waters like luminous bubbles, re-
sembling large milky white electric lamps being constantly lit and
extinguished ; with a hand-line we captured several specimens.
The existence of such numbers of squids in the open sea must
undoubtedly be considered a very important item in the fauna.
Squids occur very abundantly also in the western part of
the Norwegian Sea, where the small "bottle-nose" whale is
captured by whalers during spring and summer. I have tried The"bottk
to obtain reliable information as to where this whaling goes on, '^"^'^ ^^^^^
and on the basis of this information I have prepared a chart
(Fig. 483); each dot signifies a place where several whales
have been observed or shot. The chart brings out the peculiar
fact that all the localities are situated on the western side of
the Gulf Stream water in the Norwegian Sea, i.e. in the transi-
tion belt between the Arctic and Atlantic currents. We gather
from this chart that in April and May the "bottle-nose" is
widely distributed over this part of the Norwegian Sea ; in July
the whaling ceases, and in September the inhabitants of the
Faroe Islands get their last " bottle-nose." These whales are
never, or only on extremely rare occasions, observed or shot on
the coast banks, and thus they do not enter the Barents Sea, but,
according to an experienced whaler, they follow the 800-fathoms
line.
I have succeeded in obtaining information as to the stomach-
contents of the "bottle-nose"; these consist mainly of the
650
DEPTHS OF THE OCEAN
remains of squids, not Om^natostrephes todartcs, but Gonattis
fabricii, which must consequently occur in great numbers in
Fig. 483. — Distribution of " Bottle- nose " Whale {Hyperoodon diodon) in the
Norwegian Sea.
IV. -Vn. indicate the months April-July.
the western part of the Norwegian Sea ; farther south, in the
vicinity of the Faroe Islands, herrings are also found in the
stomachs. As previously mentioned, numerous larvae of Gonatus
PELAGIC ANIMAL LIFE
651
fabricii^^r^ taken on our Atlantic cruise between Newfoundland
and Ireland (at Stations 70, 80, 81, and 94, covering a wide
expanse of ocean) ; such larvae have never been taken by us in
the Norwegian Sea. As a working hypothesis we may suppose
that in spring and summer Gonatus migrates into the Norwegian
Sea from the Atlantic, just as the " bottle-nose " is universally
believed to do.
The same remark probably applies to the interesting giant
squid, ArchiteutJiis dux, a specimen of which (see Fig. 484) was ArchUeuthis.
found floating at the surface to the north of the Faroe Islands
during a cruise with
the " Michael Sars "
in 1902. This speci-
men was not large,
but in 1903 in Ice-
land I had the oppor-
tunity of making an
interesting observa-
tion, showing the
gigantic dimensions
of these squids. On
the 15th of August
the " Michael Sars "
arrived in Mofjord
on the east coast of
Iceland, and visited
the local whaling sta-
tion. On the shore
were two freshly
caught whales, one a
north-caper,the other
a cachalot. Inspecting the cachalot I saw around its enormous
jaws several long parallel stripes (see Fig. 485), consisting, as
closer scrutiny revealed, of great numbers of circular scars or
wounds about 27 mm. in diameter; Fig. 486 shows a piece of
the skin with these scars. It occurred to me that these scars
must have been left by the suckers of a giant squid, and
following up this idea I found in the whale's mouth a piece
of a squid - tentacle 17 cm. in maximum diameter. In the
stomach of the whale many squid-beaks of various sizes were
found, the largest measuring 9 cm. in length, besides some
fish bones, and the men who had shot the whale told me that
in its death-flurry it disgorged the arm of a squid 6 metres
Fig. 484.-
-Architeuthis, found dead north of the
Faroe Islands.
652 DEPTHS OF THE OCEAN
long. Similar observations have been recorded from the
Azores by the Prince of Monaco.
The Boreal Area outside the Norwegian Sea. — The northern
North Atlantic has previously been investigated by Danish
expeditions on board the " Ingolf," " Thor," and " Tjalfe " in
the waters of western Europe, Iceland, and Greenland, by a
German expedition on the west coast of Greenland and by
British expeditions west of Britain, while Hensen's Plankton
Expedition also crossed this area. On the other hand, the
Fig. 485. — Cachalot wiih i.ung mrji'es from struggle with Architeuthis.
exceedingly interesting waters between Davis Strait and the
United States have been very little examined.
The results of all these expeditions prove the northern
North Atlantic to contain the same pelagic animals as the
Norwegian Sea. According to the various bodies of water,
however, the animal life varies in composition in different parts
of the ocean. Thus to the west of Britain pelagic life is
temperate Atlantic, mingled to some extent with boreal forms ;
to the south of Iceland the boreal forms predominate, though
the Atlantic admixture is very important ; in Davis Strait the
character of the fauna is mainly Arctic, though some boreal forms
still appear (the capelan, for instance, seems very characteristic).
Proceeding from Labrador to the Northern States the purely
PELAGIC ANIMAL LIFE
653
Arctic, the boreal, and the subtropical Atlantic forms are met
with in succession, their distribution changing according to
seasons and local conditions ; the boreal waters are here
squeezed between bodies of Arctic and Atlantic water, and the
transitions between the different bodies of water and between
the different animal-communities are very sudden.
"Ipii
Fig. 486 — Skin of Cachalot with marks from struggle with Architeuthis.
Nat. size.
The tow-nettings made by the "Michael Sars " in 1910
between the Sargasso Sea and Newfoundland and thence 'to
Ireland are particularly interesting, because they comprise
Arctic, boreal, and Atlantic forms mingled together in the same
oceanic area, and afford a rare opportunity for observing to
what extent the distribution of different forms depends jon
certain physical conditions.
G. 0. Sars' list of Crustacea referred to on
PP.
656-7.
Station 50. 1
Station 63.
Station 80.
Station 92.
Station 113.
0
210
500
2
900
0
235
525
Q
200
500
Q
100
300
500
Limits of vertical haul (metres)— 5>
t
t
rot
t
T
t
t
t
t
L
t
t
t
t
t
t
200
500
200
500
rooo
235
525
950
^°°
500
1000
100
300
500
1000
Decapoda
mppolyte
+
Acanthephyra ....
+
Hymenodora ....
+
Sergestes
+
D
+
0
+
Pandalus, larvae .
D
Munida rugosa, juv.
0
SCHIZOPODA
Stylocheiron longicome .
n
Euphausia krohni .
0
+
0
0
+
gibba .
+
0
+
„ tenera .
+
,, larvae
D
0
D
D
Thysano'essa neglecta
n
, , longicaudata
0
+
0
0
+
„ minor .
+
Parva .
+
T/tysanopoda acutifrons .
0
, , obtusifrons
+
Meganyctiphanes no^-vegica .
0
Netnatoscelis microps
+
,, 7>iegalops .
+
0
+
Neniatobrachion boops .
0
Amphipoda
Oxycephalus sp. . . .
D
Scina borealis ....
+
0
+
Scyphocaris anonyx
+
Phronima sedentaria
D
0
D
0
+
D
Hyperia 7nedusaru}n
0
+
Parathemisto oblivia
0
0
Eutkeviisto Ubellula
n
0
+
Lyca;a%x>
D
D
Platyscelis sp
+
0
ISOPODA
Eurycope gigantea .
+
Munnopsis sp. .
+
Calanoida
Calanus minor
n
0
„ Jinmarchicus . .
□
0
+
D
0
0
+
„ helgolandicus .
+
D
+
„ hyperboreus
0
+
0
+
„ gracilis .
n
0
+
n
0
+
n
a
,, robustus
n
Eucalanus eiongatus
D
0
+
n
0
+
D
+
D
0
+
,, attenuatus
n
„ comutus
0
+
n
0
„ nasutus .
+
n
+
+
D
0
+.
D
„ monac/ius
+
n
+
Nauplii, etc.
D
+
Pseudocalanus eiongatus
D
0
+
Spinocalanus magnus
+
Scottocalanus securi/rons
+
Onchocalanus rostratus _ .
+
Megacalanus longicornis
+
Euchata norvegica .
D
0
+
+
D
0
0
+
„ barbata
+
+
„ marina .
glacialis .
n
0
+
„ sp. juv. .
D
+
D
,, acuta
+
0
0
Undeuchceta 7ninor .
+
„ ma/or .
0
,, sp. . . .
' +
Chirundina stressi . .
+
+
Euchirelia jitessinensis .
+
+
„ rostraia
n
+
Di
0
+
„ venus
„ venus ta
n
0
,, brei'is .
n
Lophothrix frontalis
+
latipes .
+
Cephalophaties refulgens
+
Pleuromma xiphias
0
+
0
+
0
„ abdominal is
0
+
D
0
gracilis
0
D
0
+
0
0
+
,, robusta
0
0
+
0
0
Metridia curticauda
+
„ lucens .
„ normani .
+
+
0
+
+
D
+
+
n
0
0
,, longa
0
+
n
0
0
+
654
G
. 0.
Sai
vS' LIST
OF Crustacea
continued).
Station 50.
St
ition 63.
Station 80. ,
Station 92.
Station 113.
Q
210
500
2
200
900
Q
235
525
0
200
500
Q
100
300
500
Limits of vertical haul (metres)— >
i
t
t
L
t
t
t
t
t
t
t
t
1
t
t
L
500
1000
—
500
1000
235
525
950
200
500
1000
300
500
Calanoiba, contimted—
Lucicutiajiavicornis
D
+
a
0
0
+
„ curt a
+
+
brevis
+
,, atlantica
+
Atnallophora affinis
+
+
+
,, magna
+
„ obtusi/rons
+
0
Mtideus giesbrechti
D
0
□
„ ar?natus .
D
+
Mtideopsis multiserrata
+
Gaidius tetucisphius
0
+
+
0
„ notacantha
+
Gai-tanus miles
0
0
„ kruj,/>i .
+
+
„ caudani .
+
, , tatifrons .
+
, , minor
+
0
,, armiger .
0
laticeps .
+
Haloptilus longicortiis
D
0
+
0
D
,, fiuicronaius
D
,, acutifrons
+
0
„ omatus .
0
0
Augaptilus sguamatiis
+'
+
+
,, longicatidatu
i-
+
c
, , palutnboi
+
0
,, oblongus
+
,, gibbus .
+
/iligerus
0
,, laticeps .
+
sp. juv. .
n
H eterorhabdus norvegicus
+
0
+
0
+
Dl
0
+
0
„ brevicaudatus
+
„ vipera
+
papHliger .
0
+
„ longicornis
0
D
0
+
„ spini/rons
0
0
+
Scolecithrix dana; .
a
Scoiecit/iricel'/a"sp. '.
„ minor
0
D
D
0
+
0
Acartia dants .
D
0
D
D
0
Centropages typicus .
D
Candace sp.
Dl
Disseta palutnboi .
+
Chiridius poppei .
0
, , armatus .
0
+
+
Phaenna spini/e>-a .
0
0
Phyllopus bidentatus
+
+
+
Bathypontia minor .
+
+
Other Copepoda
Oithona similis
D
n
+
D
0
„ plumifera .
+
sp. .
n
0
+
D
0
Onci^a coni/era
0
+
+
'• ^P- .• . •
a
0
+
D
. 0
Lubbockia squillimana
+
Microsetella norvegica
n
j^gisthiis mucronatus
0
Mormonilla minor .
+
Corycaus sp. . .
D
0
0
Copilia sp.
n
Sapphirina sp.
n
OSTRACODA
Conchcecia elegans .
0
0
0
sp. .
,, maxima
n
c
+
D
0
+
0
+
D
0
0
+
„ bore alls .
+
,, obtusata
D
0
+
+
0
Halocypris <.p. .
„ globosa .
n
n
0
+
n
D
Conchoecilla sp.
0
+
+
,, lacerta .
+
0
Concluecissa sp.
+
„ armata
32
16
27
34
18
12
+
33
9
18
11
Number of species
22
22
51
25
27
655
656
DEPTHS OF THE OCEAN
Our collections of minute crustaceans, especially Copepoda,
are very extensive, but their examination will take a long time.
In order to give some information about the distribution of
these interesting forms, I asked G. O. Sars to determine the
species contained in some of our closing-net hauls, and selected
samples from certain stations (see Fig. 487), which I believed
to be specially characteristic, viz. two stations in the Sargasso
Fig. 487. — Positions of Stations from which lists of Crustacea have been
DRAWN UP. [Station 6o should be 63.]
Sea (50, 63), one station off the Newfoundland banks (80), one
station off Ireland (92), and one station in the Norwegian Sea
north of the Wyville Thomson Ridge (113). Before referring to
Sars' determinations (see list, pp. 654-5) I may indicate the tem-
peratures at the various depths where the nets were towed : —
Station 50.
Station 63.
Stat
on 80.
.Sta
ion 92.
Station 113.
Depths.
Temp.
Depths.
Temp.
Depths.
Temp.
Depths.
Temp.
Depths.
Temp.
'C.
Metres.
°C.
Metres.
°C.
Metres.
°C.
Metres.
°C.
Metres.
200 to 0
17.7° to 20. 3°
200 to 0
16.7° to 27.3°
200 too
7.6° to 11.8°
200 to 0
11° to 16.5°
loo too
8.3° to 11.6°
500 to 200
13.7° to 17.7°
500 to 200
13.8° to 16.7°
5C0 to 200
4.6° to 7.6°
500 to 200
10° to 11°
300 to 100
6.4° to 8.3°
100010500
9.7° to 13.7°
100010500
6" to 13.8-
1000 to 500
3.3° to 4.6°
1000 to 500
8.6° to 10.2°
500 to 300
1000 to 500
,.i°to6.4°
-0.5° to 1.1°
PELAGIC ANIMAL LIFE 657
From a study of the list on pp. 654-5 we note the follow-
ing points : —
(i) A certain number of genuine warm-water forms occur
only in the upper hauls (200 to o metres) in the southern
stations (50 and 63), such as : Eucalanus attemmhis, Euchceta
marina, Euchirella brevis, Haloptilus vmn'onatus, Scolecithrix
dancE, Acartia dams, Candace, Copilia, Sapphirina.
(2) Some Atlantic deep-sea forms do not occur at the
surface either in the Sargasso Sea or along our northern track ;
they do not enter the Norwegian Sea and are consequently
distributed like the Atlantic bathypelagic fauna. Such are :
Amallophora affinis, Augaptihts squamatus, Phyllopus bidentahis,
Bathyp07itia minor.
(3) Some forms have a large vertical range in warm waters,
like Calamis gracilis and Plcuromma gracilis.
(4) Other forms have a large vertical range in the southern
as well as in the northern stations, like Eucalanus elongatus
(see Stations 50, 63, 80, and 92).
(5) A peculiar group is composed of forms having at the
boreal stations a large vertical range, but occurring at the
warm southern stations only in deep water such as : Calamis
Jinmarchicus (Stations 80 and 113 at all depths); Euchceta
noruegica (Stations 80 and 113 at all depths, Station 92 only
between 1000 and 500 metres, also, according to Nordgaard,
Station 64, in 1250 metres, Station 62 in 1000 metres) ; Metridia
longa (Stations 80 and 113 in all hauls); Psetidocalanus
elongatus (Station 80 at all depths) ; Scolecithricella 7ninor
(Station 80 at all depths) ; Hetcrorhabdus non^egicus (Station
92 at all depths, and in deep water at Stations 50, 63, 80 and
113). All these forms occur in the Greenland Sea, where they
also have a large vertical distribution (Damas and Koefoed).
(6) Certain forms recorded only from the deep hauls at
Stations 80 and 113, where the temperature is lowest, such as
EuchcBta barbata, E.glacialis, Calajms kyperboreus, Amallophora
magna. None of these occur in deep water at Stations 50 and
63, but, according to Nordgaard, Calamis kyperboreus and
Euchceta barbata have both been taken at Station 62 in the
Sargasso Sea in a horizontal haul at 1000 metres in great
numbers, 65 specimens of Calamis hyperbo^^eus being counted
in a small part of the sample. These forms belong to the
Arctic region in the Norwegian Sea, where according to Damas
and Koefoed they are also deep-sea forms, except the surface
species Calamis kyperboreus.
2 u
6s8
DEPTHS OF THE OCEAN
The general results may be summarised as follows : —
In the northern North Atlantic we find Atlantic, boreal, and
Arctic forms. On our track from Newfoundland to Ireland we
met chiefly Atlantic species at the surface (see Station 92,
0-200 metres). In deeper water we find certain Atlantic
deep-sea species which nowhere in the ocean reach the surface,
mingled with boreal species. At Station 80, situated in an
area where the cold waters of the Labrador current communicate
directly with the deep bottom layers, the boreal forms occur at
all depths (Group 5), as they do in the Norwegian Sea; but to
the east of Station 80, where the warm layers are thicker, we
meet only the boreal forms in the deeper water, and in the
Sargasso Sea at depths
Thus
®
©
DISTRIBUTION OF CLIONE LIMACINA
BETWEEN Newfoundland and the Sargasso Sea.
The encircled figures denote the number of individuals
captured.
of 1000 metres.
EuchcEta
taken at all depths at
Stations 80 and 113; at
' (7y^_ /<?_" Station 92 only from
1000 to 500 metres, and
at Station 62 only at
1000 metres.
The genuine Arctic
forms (Group 6) occur
in waters with tempera-
tures below 5 or 6 C.,
thus Caiantis hyper-
bore us was taken on
the Newfoundland
banks at the surface,
at Station 80 only below 200 metres, and at Station 62 at 1000
metres.
As shown in Chapter III., this conformity appeared even
during the cruise, and was obvious not only in regard to these
small crustaceans, but for quite a number of other boreal
and Arctic animals as well (see pp. 106-108 and 11 7- 11 8).
The most important boreal and Arctic forms encountered
between Newfoundland and Ireland, besides the Copepoda
previously mentioned, were : the medusa Aglantka, the
Ctenophores Bero'e, Pleurobrac/iia, and Mertensia, the worms
Sagitta arctica and Krohnia kamata, and the pteropods Liinacina
helicina and Clione limacina.
During our voyage from the Sargasso Sea to Newfoundland
and thence to Ireland, Clione limacina was, according to
PELAGIC ANIMAL LIFE
659
Bonnevie, taken at the depths indicated by circles in Figs. 488
and 489. At Newfoundland it lived at the surface, but all the
way from Newfoundland to Ireland it was taken only below
750 metres. Its occurrence in only 50 metres on the coast
banks off Ireland is remarkable and important, showing that
this form occurs in shallow water, both on the eastern and
western sides of the North Atlantic, in cold and in warm water.
This distribution seems to be shared by Aglantha digitalis,
81 83 S/f 65 86 67 as 89 W 91 92 93 9fc
6° ■.. .. iO"
0 -Qj- (I) ., ^^<. ...
7\G. 4S9. — Vertical distribution of Clione limacina between Newfoundland
AND Ireland.
The encircled figures denote the number of individuals captured.
which was taken on the Newfoundland banks at the surface, at
Station 80 in vertical hauls from 950 to 525 metres, at all the
deep stations farther east (for instance Station 92) at 1000
metres, but close to the slope of the coast banks of Ireland it
was taken only 100 metres beneath the surface.
In the deep water of our northern section our pelagic
fishing appliances at, for instance, 1000 metres gave bathy-
pelagic Atlantic forms like Cyclothone inicrodon, Atolla bairdi,
Gigantocypris, Pelagonemertes, Pyrosoma, Acanthephyra, besides
boreal forms like Etick^sta norvegica, Aglantha digitalis, and
Clione limacina.
J. H.
CHAPTER X
GENERAL BIOLOGY
About the beginning of the nineteenth century many dis-
tinguished men of science seem independently to have developed
the idea that the structure of animals and their occurrence in
various localities are determined by external conditions.
Lamarck in his Philosophie zoologiqtte (1809) writes as
follows : " The external conditions always and strongly exert
their influence on all living beings. This influence is, however,
difficult to ascertain, because its effects only appear, and may
be recognised, after a very long time."
Goethe's zoological works all testify to his strong belief
that "all living beings possess the faculty of adapting them-
selves to the manifold conditions presented by external
influences, without, however, resigning a certain hard-earned
and decided independence." In his Skeletons of Rodents he
says that " the difference of forms is a consequence of their
necessary dependence on the outer world." In his introduction to
comparative anatomy he attempts to show the various influences
exerted by certain climatic conditions, by water, and by air upon
the shape of animals, which become altered on passing from one
group of conditions to another. This again explains the fact
that " no organism intended to live is conceivable without a
perfect organisation." Goethe was full of such ideas, but felt
the danger of following them up, and of "losing oneself in the
infinite " {^Principles of Zoological PJiilosophy\
Kant's view is still clearer as regards the idea of adaptations
to surroundings. He endeavoured to show that all biological
investigations had to take for granted that living beings are
fitly organised in relation to their natural surroundings. But
no definite human idea of the fitness of adaptations is of any
value as knowledge. No more does any human idea necessarily
correspond to the reality occurring in nature. The idea is only
660
GENERAL BIOLOGY 66i
valuable as stimulating the investigator to seek realities. And
reality, in the scientific sense, means a definite positive
mechanism, existing in the organism itself or in the surrounding
medium. The object of investigation is to understand these
mechanisms ; the leading idea may often prove an empty fancy
beyond the world of realities.
In the second half of last century the investigations on the
history of the development of animals disclosed many organs
(for instance, rudimentary organs), the function of which in the
life of the organism could not be understood. According to
the Darwinian idea the development of species consisted in
innumerable minute changes. These changes were conceived
as being due to "chance," which to a certain extent seemed to
contradict the idea of " fit adaptations."
The historical way of explaining the structure or occurrence
of organisms is, however, at present not considered contradictory
to the ideas of adaptation. Even Lamarck, as mentioned above,
thought that a species must exist for a very long time before
the effects of the influence of surroundings appear or disappear.
As to the origin of variation it is now more and more
recognised that a comprehension is only to be gained by studying
the reaction of organisms against the influence of surroundings.
One may endeavour to ascertain these reactions by experiment,
by observing the changes taking place in the organisms when
subjected to altered conditions. In nature we may also observe
how the shape of individuals alters in various surroundings, and
how similar shapes reappear in similar environments.
In recent times we note an increasing tendency to observe
animals in their natural surroundings, and during frequent ex-
peditions the influence of this tendency has been predominant.
In recent literature we may find many investigations and many
opinions, which remind us of the interest attached to these
problems about a hundred years ago.
In the history of oceanic research nothing has possibly con-
tributed so much to the awakening of this interest as the
discovery of entirely different animal -communities living, on
either side of the Wyville Thomson Ridge (see Fig. io6, p. 124).
Atlantic forms occur to the south and Arctic forms to the north
of the ridge, corresponding to the very different thermal
conditions on either side.^
1 See Murray and Tizard, " Exploration of the Faroe Channel, during the summer of _iS8o,
in H.M.'s hired ship 'Knight Errant,'" Proc. Roy. Soc. Ediii., vol. x. p. 638, 1882 ; Tizard,
" Remarks on the soundings and temperatures obtained in the Faroe Channel during the summer
662 DEPTHS OF THE OCEAN
Another series of investigations in this field were those
of C. G. J. Petersen, regarding the distribution of mollusca in
the Kattegat. In The Cruises of the '' Haitch,'' Petersen^ has
employed the only empirical method of investigating the
distribution of animals, viz. to analyse the distribution of species
in relation to various external conditions, as for instance, high
or low salinity, high or low temperature, great changes in
temperature or salinity, etc. It proved possible in the Kattegat
to define areas of distribution of certain species, coinciding with
areas where characteristic physical conditions prevailed.
Similar methods have been employed by Chun for the study
of pelagic organisms. An important branch of this science has
the object of studying the changes occurring in the physical
conditions of the ocean, and the influence of these changes on
the occurrence or abundance of organisms. By means of a
continually increasing co-operation between hydrography and
biology, both equally necessary in the study of such problems,
oceanography has made great progress, especially during the
international investigations in the study of the sea.
The additions which during the cruises of the " Michael
Sars " it has been possible to make to these branches of science
consist mainly of information regarding the vertical and
horizontal distribution of animals, accompanied by physical
observations of various kinds. These, biological and physical
investigations place us in a position to test certain ideas regard-
ing the adaptations of animals, and thus acquire knowledge on
certain important mechanisms of life.
The following review of some of our principal results can
by no means claim to be complete. The literature referred to,
the various fields of biology discussed, and even the selection
made from the material collected by our recent expedition, have
all been limited for the purpose of this review. Still I hope to
indicate some new contributions to science, and at the same
time to convey some idea of the general methods and aims of
biological oceanic research.
Colours of Marine Animals
From time immejnorial seafaring men have possessed a
certain amount of knowledge as to the colours of marine animals.
of 1882 (H.M.S. 'Triton')," Proc. Roy. Soc. Loud., vol. xxxv. p. 202, 1883; Murray, "The
physical and biological conditions of the seas and estuaries about North Britain," Froc. Phil.
Soc. Glasgow, vol. xvii. p. 306, 1886.
1 Petersen, Det videtiskabelige Udbytte af Kanonbaaden '' Haiuhs" togier, Kjobenhavn, 1893.
GENERAL BIOLOGY 663
Sailors know well the sky-blue colours peculiar to the tropical
surface forms. Herring-fishermen also know that the blackish-
brown back of the herring is almost invisible from above, and
only when occupying a slanting position or making a sudden
turn does the herring become visible, its mirror-like sides
emitting a silvery flash. The deep-sea fishermen are equally
acquainted with the dark, black, brown, violet, or red colours
peculiar to deep-sea animals. No scientist can claim the dis-
covery of these phenomena, which are as well known as the
colours of the ocean itself.
When considering the peculiar colours of marine animals,
and their variation in different surroundings, many naturalists
concluded that the colouring was due to their attempts to adapt
themselves to the colours of their surroundings, in order to
make themselves invisible or to protect themselves against
enemies, just as is supposed to be the case with the land fauna.
This idea requires confirmation by acquiring more exact
knowledge as to the conditions of light and the colours of animals
from similar depths. Our knowledge regarding the penetra-
tion of light in the ocean has been as deficient as our knowledge
of the vertical distribution of the animals, and the whole subject
has thus been a matter of suppositions and ideas rather than of
actual knowledge.
During the Atlantic cruise of the "Michael Sars " we
investigated the intensity of light at different depths and also the
colours of the animals. The results obtained by the photometer
at a few stations in the Sargasso Sea are referred to on
pp. 251-2. On a sunny day when the water was perfectly clear Penetration
and transparent, light-rays of all colours, but very few red rays, °f^'§^'-
were observed at a depth of 100 metres. At 500 metres the
light acted strongly on the photographic plates, especially the
blue rays, but the green rays were absent ; even at 1000 metres
the influence of the sunlight could be traced on the plates, but
at I 700 metres no influence was noticeable.
As we have seen in Chapter IX. the different water-layers Animals of
in the Sargasso Sea contain animals of very different colouring, t^he^ Sargasso
certain general features in the colouring being easily recognisable
in certain regions. In the hauls from 500 to 750 metres and
deeper we found only black fishes and red crustaceans (prawns).
At 300 metres we found the laterally compressed Sterno-
ptychidse with silvery sides and brownish backs. In the upper
layers we met with transparent young fish, for instance lepto-
cephali, or silvery ScopelidiDe and blue flying-fish.
664 DEPTHS OF THE OCEAN
Plates I. -VI. show certain forms found in the Sargasso
Sea, representing a small selection from the numerous
coloured drawings by Rasmussen. Plate I. shows the black
Cyclotkone microdon from deep water and the light coloured
C. signaia, which has its lower limit just at the upper limit of the
black fish. Other black fish and some red prawns from depths
beyond 500 metres are represented in Plates H. and HI.
The black and red colours are easily seen in strong sunlight.
The theory of protective colours must therefore assume that
these colours only appear in dark surroundings. In this con-
nection it is very interesting to note that the upper limit to the
occurrence of these black and red deep-water animals, which
according to latitude varies between 500 and 750 metres, is also
the limit within which most of the sun's rays are absorbed, and
it is important also to note that the red rays belong to that part
of the spectrum which is most rapidly absorbed by the water.
In connection with the question of the Colouring of these
bathypelagic forms we may refer to some observations made
during the cruise regarding the vertical migrations of such
dark-coloured forms, as shown in Fig. 490. Three species,
Gastrostoinus bairdii, Cyema ati^uvi, and Gonostoma grande have
been taken only at 750 metres or deeper, while two species,
Gonostoma rhodadenia^ and P/iotostoniias gtcernei, have been
taken also at lesser depths, even at 150 metres. I have already
mentioned several instances (see p. 93) where forms like
Asti^onesthes and Idiacantlms have been taken at the surface,
but only at night. In the case oi Photostomias and Gonostovia
rhodadenia I have denoted the night-captures with a dark disc,
while a ring denotes day-captures. These catches seem explic-
able only by supposing vertical migrations to take place, and
as these occur in the darker part of the twenty-four hours they
probably coincide so precisely with the disappearance and re-
appearance of daylight that the dark colouring may be of no
danger to the animals in their nightly migrations towards the
surface of the sea.
The occurrence of dark colours thus coincides with the
region where the intensity of the sunlight is greatly diminished.
Another circumstance seems to confirm this, viz. that in
different waters the upper limit to the black fish and the red
crustaceans seems to coincide with the same low intensity of
light.
^ The specimens which in Fig. 490 are referred to Goiiosioina eloiigatwn have, on closer
investigation, proved to be the closely allied Gonostoma rhodadenia.
Depths of the Ocean.
Plate 1.
.^-^^m^^^^'^^:
^^
^
2.7 cm.
CYCLOTHONE SIGNATA.
5 cm.
CYCLOTHONE MICRODON.
DeptKs of the Ocean
Plate II.
ARGYROPELECUS AFFINIS, GARM^
>X
GONOSTOIvIA GRANDE, COLLETT.
rONOSTOMA ELONGATUM, GTHR.
Bale &L DamslssoTi.L'^^^lili..
Depths of the Ocean
Plate III
1. Acanthephyra multispina (Coutiere), Sund
2. Acanthephyra purpurea, A. M.- Edwards
3. Systellaspis debilis, A. M. -Edwards
GENERAL BIOLOGY
665
We have seen that the upper Hmit for Cyclothone ^nicrodon
and the red crustaceans, in the northern section from Newfound-
land to Ireland, or about lat. 50° N., was approximately 500
metres below the surface, and we have also noticed that the
limit of depth for the same forms at the southernmost stations,
or about lat. ■^■^^ N., was some 200-300 metres deeper. In the
Norwegian Sea I have previously investigated the intermediate
Depths
Gaslrosto
Cvema
Gonostoma
Gonostoma
Photostom-
m.
mus Bairdii.
atrum
grande.
elongatum
las Guernei
150
•
•
300
a •»
500
• e
0
750
-0000
00000
0
1000
000
000
• 0
I250
000
0
000000
0
•
1500
000000
00
00000000000
0 0
0 0 0 •
2000
■0
•
490.
-Vertical distribution of black-coloured Pelagic Fishes.
pelagic fauna, and found pelagic red prawns as well as the dark-
red fish, Sebastes norvegictts, at depths of about 200 metres
below the surface. Sebastes was taken, for instance, with float-
ing long lines in considerable quantities on a course from Jan
Mayen to Lofoten — that is to say, in about lat. 67° N., — at a
depth of 200 metres, and it was found, though in decreasing
quantities, in even less depths. Along the Norwegian coast, in
the fjords and sounds, we have a particularly rich fauna of red
crustaceans (especially Pandalus borealis), occupying depths
666
DEPTHS OF THE OCEAN
whose upper limit in the north, at any rate, may be put at
above lOO metres.^ Now, if we calculate the depth to which
the rays of the sun penetrate, after passing through the same
distance in the water, assuming always that the rays are direct
and that the rate of absorption is the same, we find that the rays
will have passed through the same distance to reach a depth of
500 metres in lat. 50 N,, that they will pass through to reach
650 metres in lat. 33° N., or 300 metres in lat. 67^ N.
The transparency of the water, however, varies greatly in
different regions. If we take the results of previous observa-
tions during different expeditions, we may set down the visible
depth in the open sea as being roughly 50 metres in lat. ;^2>" ^m
40 metres in lat. 50° N., and 25 metres in the Norwegian Sea
in lat. 67° N. Taking this into consideration, we find that
there will be the same intensity from the rectilinear rays —
In lat. 33° N. at about 800 metres.
,, 67° ,, 200 ,,
The red and black animal forms, therefore, as has been
found in the investigations I have just described, have an upper
limit in the different waters which corresponds everywhere with
the same intensity of light.
Very interesting also is the fact that certain dark bathy-
pelagic forms appear as varieties differing in the intensity of
their colours. Broch from his study of the "Michael Sars "
collections thus recognises four varieties of the deep-sea medusa
Atolla bairdi: (i) stomach alone containing pigment; (2)
peripheral muscular belt also pigmented ; (3) the brown pigment
distributed also on the lower side of the bell, while gonads are
^ Sir John Murray reports that in Upper Loch Fyne, in Loch Etive, and in some other sea-
lochs of the west coast of Scotland, which are cut off from the ocean by submerged barriers, red
prawns and other red crustaceans are very numerous in depths of 50 to 70 fathoms (about 270
to 310 metres) ; for example Nyctiphaiies {Megaiiyctipliattes noi-vegica), both adult and young,
can always be captured in these lochs by dragging nets one or two fathoms above the bottom.
This species possesses ten phosphorescent organs : one pair in the eye peduncle, two pairs on
the under side of the thorax, and the remaining four in the median line of the abdominal seg-
ments. Sir John believes that these organs are used as a kind of " bull's eye lantern," and
enable the Nycliphanes to see and pick up the minute particles of organic matter which are
settling on the bottom-deposits. Many specimens of this species were kept in aquaria for a
considerable period, and were observed to light up and shut off their phosphorescent organs at
will. The surface layers of water in these Scottish lochs are much less saline than the deeper
layers, and contain much suspended matter, so that the penetration of light is much obstructed.
Besides Nydiphanes other red or red and transparent crustaceans are always to be captured in
the deeper water-layers of the Scottish sea-lochs, such as Calainis Jinniarchicus, Eticha-ta
norvegica, Conckaria elegans, Boreophatisia raschii, Pandalus anniilicornis, Pasiphcea sivado,
Cratigon allniani, Hyppolyte securifrons, etc. (see Murray, Scot. Geogr. Mag., vol. iv. pp. 353-6,
1888 ; Coiitptes rendits des Seances dii jine Congres international de Zoologie, Leyde, 1895,
p. 107).
GENERAL BIOLOGY
667
when
still visible ; and {4) gonads also concealed by pigment
viewed from above.
For each of these varieties Broch has recorded the vertical
distribution observed, as represented in the following table, the
figures denoting the number of specimens found in each
layer : —
Depth.
No. I.
No. 2.
No. 3.
No. 4.
Surface .
100 metres
250 „
1 I
500 ,>
1 17
4
750 .>
I
17
14
7
1000 „
5
33
19
3
1250 ,,
I
2
4
1500 ,,
I
9
6
4
2000 „
I
Even if the difference between Nos. 2, 3, and 4 is not strongly
marked, the increase in dark pigment following the increase
in depth is still very perceptible.
Another instance of this is afforded by the following table,
showing the vertical distribution of eleven species of pelagic
decapod Crustacea, according to the results of Sund's examina-
tion of the " Michael Sars " decapoda : —
[Table
H op
o -t:
s
Atnalopenceus
alicei
Scarlet and
orange,
no blue
9
: : : - f:^ ? -
0 M N M
^
0
Hynienodora
gracilis
Orange
2
1 1 '■
1 ^
o ■
• ; ") *1. <b >^ -a-
o>
Parapasiphcea
sulcati/rons
Red.
Eggs red
1
1 , ■
Q
00
Acanth ephyra
multispina
Red.
Eggs red
^
OS g
Q
"
-
Amalopcnipus
elegans
Coralline,
blue patches
2
OS g
: : N
r*^ ;^ ^ -0 O- ./^ ^
A vialopeneeus
valens
Coralline,
bright-blue
patches
'^ *
n- . ^ . OJ
-
A vtalopentrus
tinayrei
bright-blue
patches
1
2
1
"" '^ ^
•^ . . ■> l^ ^, .
Acanthephyra
purpurea
Red.
Eggs orange
K
CO ."ai :
r
: § S
'^ '^ ^ %. " °- :
Systellaspis
debilis
Red, vvith blue
luminous
patches
- ^ : ^ C; X
§
tv, t^ . c», r^ fV) n.,
g g^ : " " " :
Plesionika
nana
Transparent
and red
1
0 ■
■" s 1m
-
Funchalia
ivood'wardi
Transparent
with pinkish
tint
^ z
1 : . . :
N >, . CV, . .^ .
1
1
1 1
I 1
o
-s
2c. -S _
i
Ratio of Cj
pace to eye
Time of Cat
Surface .
50 metres
100 ,,
150 „
■ ■ p
8 § S 8 1 M
CHAP. X GENERAL BIOLOGY 669
The close correspondence between the development of
pigment and the vertical distribution is very striking. Nos,
I and 2 live above 150 metres, and are nearly transparent.
Nos. 3 to 7 are distinguished by deep red colours with blue
patches, and were taken above 500 metres during the night,
iDut in the daytime have their maximum distribution at 500
metres or deeper. Nos. 8 to 1 1 have no blue pigment, but
only red and yellow colours, and live deeper than 500 metres,
not having been taken in less depths even at night.
As indicated in Chapter IX. the deep layers contain a great Dark-coloured
variety of animals, and in all these groups we repeatedly find jee^^gr kVrs^
the same dark colours. In the medusae Atolla, Periphylla,
Crossota we find dark-brown colours or, as in Agliscra and
others, red colouring. Among the Sagittidae we meet red
colours [Sagitta macrocephala, Ezikrohnia fowleri). All the
crustaceans are red [Buchtrta, Cyclocaris, Gigantocypris, Schizo-
poda, Decapoda) ; in the Pteropoda the colours are dark violet
{Pe7^aclis diversa, Limacina helicoides, Cliofalcatd). The squids
are red, the fishes black or blackish violet.
In the Atlantic gray, mirror-like, and silvery colours are Silvery and
characteristic of the fishes between 150 and 500 metres. The
silvery sheen is very often iridescent with dark green, shallower
violet, and blue tinges (see Argyropelectis affinis in Plate II.). ^^^^"^^^
The backs of these animals are brown or black.
These colours correspond to those of the herring in boreal
waters, and as previously mentioned they have been well
known and recognized as protective colours. From above
the fish are not easily seen because from this point of view
the ocean looks dark or black. On the other hand, the light
rays from above are reflected by the mirror-like sides of the
body. From a position below the fish an eye would have great
difficulty in distinguishing the outlines of the fish because of the
rays coming directly from the source of light. This can only
be understood when examining the fish in a living condition,
for preserved fishes lose their silvery sheen very soon, generally
turning black, and losing their original appearance. Most
Scopelidae have generally been represented as black, but many
of them are really quite silvery (see Fig. 491, which, however,
is not very good, because the silvery sheen does not come out
well in this kind of reproduction).
These remarks apply not only to the animals of this inter-
mediate layer, but to many surface forms having a similar
arrangement of colour. During our Atlantic cruise this was
light-coloured
animals in the
670 DEPTHS OF THE OCEAN
especially conspicuous in the case of the minute young of
Sconibi^esox living at the very surface, the sides of which are
mirror-like, while the back is not black, but intensely blue. This
seems to correspond well to the fact that the uppermost
layers of the ocean, viewed from above, appear blue. A similar
arrangement of colour is met with in boreal waters, for instance
Colourings of in the colouring of the surface fish, the mackerel. The colours
adLpTadonsto secm SO intimately adapted to certain conditions, and the
advantages they offer for the purpose of eluding observation
are so obvious, that we can hardly avoid the conclusion that
these colours must be considered as the result of adaptation
to surroundings.
In the surface layers most animals are colourless. The eel
larvae (leptocephali) are specially interesting, being indeed so
environment.
Fig. 491.
Myciophum (Diaphus) rafinesquei, Cocco. Nat. size, 7 cm.
transparent that when sorting them out of the living material
captured, one can only see their small black eyes ; even their
blood is transparent and perfectly devoid of haemoglobin.
The surface fishes are so well known that I may merely
refer the reader to Plates IV. and V. One group con-
taining sea -blue forms is represented by the flying -fish.
The pilot-fish are also blue, but with some darker trans-
verse bars. Is this because biologically it approaches another
group of surface- forms, which live in the immediate vicinity
of drifting or floating objects ? To this group belong the
wreck - fish (Lirtts, Polyprion). We captured such fishes
swimming around a log covered with barnacles, and the
similarity between the colours of the fish and those of
the log and its Inhabitants was marvellous. The most
intimate adaptations to life among drifting objects are met
with among the animals of the Sargasso Sea (see Plates
t)epths of the Ocean
1. Naucrates ductor, L.
2. Exocoetus spilopus, Val.
Depths of the Ocean
Plate V
W^
*»»««trMi«Ei*t^.t«*itft1
fljiliiiiPiiiPlill'^iii " .^^i^s^^'
<^>^ ^^-r
^msgifr
1. Antennarius marmoratus, Giinth. 4. Seriola, juv.
2. „ ,, 5. Syngnathus pelagicus, Osbeck.
3. Monacanthus, juv. 6. Cyphosus boscii, Lacep.
Depths of the Ocean
Plate VI
%
#^
Planes minutus (L.)
Depths of the Ocean
Plate VII
^^^v
W^
1. Dentex maroccanus, Cuv. & Val.
2. Pagrus vulgaris, Cuv. & Val.
3. MuUus surmuletus, L.
O -2
U Q
V
a S
Depths of the Oct
Plate IX.
V H
0.9 cm.
1. 2 cm.
5.2 cm.
BATHYTROCTES ROSTRATUS.
GENERAL BIOLOGY 671
V. and VL). The small fishes [Aiitennariiis marmoTatus,
MonacantJnis, Seinola, Syngnatkzcs pelagicus), the crabs {Planes
minutiLs), the prawns {Latreutes ensifei^us and Palcemon nalator),
and also the naked snails, in fact all the animals of the Sargasso
Sea, seem in regard to colours, shape (see for instance the
remarkable prehensile organs of the pectoral fins oi Antennarms),
and size, to be intimately adapted to life among the drifting
tufts of the Sargasso weed. The idea of the utility of these
adaptations is here unavoidable. The occurrence of blue fins
appeals to me as most striking, and this feature is specially
noticeable in Hippocampus (the sea-horse). The specimen
captured by us (see Fig. 71, p. 89) was reddish-brown, only
the fins, which have to be freely moved in the blue water,
being deep blue. Plate VL shows five different specimens of
the crab Planes ininiUuSy exhibiting all the varieties of colour-
ing presented by the Sargasso weed. This species ought to
be a splendid object for experiments in order to test the
possible effects of variation in the colour of the surroundings ;
AntennaiHus might possibly also be employed for this purpose,
but on an expedition like ours the idea of performing such
experiments had to be abandoned.
What I have said here refers mainly to the Sargasso Sea,
which was examined by us in regard to the light-conditions at
different depths, as well as the vertical distribution and the
colouring of the animals. As to the animals of the coastal
waters and those of the bottom of the ocean I have much less
to say. In coastal waters the light-conditions are undoubtedly
very different from those in the open ocean. The large amounts
of suspended substances reduce the transparency of the water
and prevent the light rays penetrating so far as they do in the
clear tropical or subtropical ocean. Hermann Pol's interesting
experiments at Nice have already been referred to (see p. 252) ;
he went down in a diving dress as far as 30 metres, at which
depth red animals appeared black.
Are the red, yellow, and blue colours of the coast-fish
(as shown on Plate VII.) to be explained as protective colours.'*
Are they adaptations to the red of certain algse and other
colours of the sea-bottom, like the gaudy paintings of the
coral-reef fishes ? Or are they to be considered like those
adaptations which Darwin has ascribed to sexual selection ?
Still more difficult is it to frame any idea as to the laws of
colour in the abyssal region. Plate VIII. shows two bottom
fishes from deep water, just on the limit where the traces of
672 DEPTHS OF THE OCEAN chap.
sunlight disappear, viz. Chwicera mirabilis and Alacrurus cequalis.
Brown, blue, and violet are the principal colours of the abyssal
fishes ; very often the pupil of the eye is yellow, as in Chim^era.
But has any eye at all the power of perceiving colours in the
abyssal region? Is any other light present there than the light
produced by the animals themselves ?
In what has been said above I have compared the
conditions of light and the colours of animals at various depths,
and in every case we have had to acknowledge that there is
some connection between the colours of the fauna and the
light-intensity in the surrounding water. On the other hand it
is in many cases difficult to show that the colours are actually
protective colours, and many scientists have relinquished the
idea that the colours are protective. The indisputable
connection between light-intensity and peculiarities of colouring
has been explained as resulting from a purely physiological
process of assimilation. An interesting attempt in this
Pigmentation ^ direction has been made by Doflein,^ who says : " In normal life
certain gland-shaped organs in the higher decapod Crustacea
form pigments. The formation of these pigments is influenced
by light. Feeble light is sufficient for the formation of red
pigment. Under the influence of light and of still unknown
processes of assimilation, the red pigment may be transformed
into yellow or even into white pigment. Very little is known of
the nature of the yellow and white colour substances, which may
perhaps arise from a union of the pigment and other con-
stituents of the body of the crustacean, for instance, the lime
salts. The blue pigment is derived from the red under the
influence of light, and dissolving passes into the tissues where
it becomes colourless and disappears, evidently through the
chemical processes into which it enters. The destruction of
blue pigment occurs also under the influence of light, this
substance thus being of a temporary nature, visible only
when produced in great quantities, but under other conditions
destroyed as soon as formed. This would explain the presence
of red pigment in crustaceans living in deep water, and the
lack of pigment in many pelagic Crustacea, as well as the blue
colours of oceanic forms. In the surface layers of the ocean
the formation and destruction of pigment, under the influence of
light, are in equilibrium. Small quantities of pigment indeed
prove to be present in nearly transparent forms, but in the
^ F. Doflein, " Lcbensgewohnheiten und Anpassungen bei Decapoden Krebsen," Festschrift
fa r Richard Hertwig, Bd. iii. , Jena, 19 lO.
GENERAL BIOLOGY 673
blue oceanic species, living in the intense light of the surface,
the formation of blue pigment is so vigorous that it exceeds
the destruction. Light is thus a very important agent in all
these processes, bearing on the formation and transformation of
pigment in the bodies of crustaceans, but it is not the only one.
Other powers may equally influence the conditions of pigmenta-
tion. Experiments thus prove that when subjected to low
temperatures blue colour developed in the animals ; this was in
my opinion due to the prevention of the destruction of the blue
pigment in the tissues, thus causing an accumulation of this
pigment."
I have quoted Dofiein's theory because it opens up very
interesting questions for future experimental research, though it
hardly explains all the colour adaptations presented by the
oceanic animals, for instance the mirror-like forms with dark
backs and silvery sides, from intermediate layers, nor does it
explain the profuse variation in the Sargasso animals and their
peculiar conformity with the various colour-shades of the ocean
and of the Sargasso weed. I fail to see any necessity for con-
troversy over the two theories, one claiming the colours as due
to adaptation serving the purpose of protection, the other
explaining them as being due to peculiar processes of assimila-
tion. Perhaps the latter theory alone may in many 'cases be
sufficient, but may it not possibly signify the very mechanism
by the aid of which the organisms adapt themselves in order to
obtain protection ?
A more perfect understanding can only be obtained from
an increased knowledge as to the habitats of animals, as to the
physical conditions there, and as to their life-history generally.
The influence of various physical factors on the animals may be
studied by experiment, and several interesting experiments
have already been made. Gamble and Keeble, for instance,
have proved the variations in colour of Hippolyte varians to
correspond to variations in the colours of the surroundings.
But the significance of such influences in the life of the animals
can in my opinion only be understood by studying the life of the
animals in nature.
Light-Organs
That many organisms possess the power of emitting light Phosphor-
has been known from earliest times. The Norwegian fisher- ^^'^^"^ ^'^^^"
men distinguish two kinds of phosphorescence: "dead
phosphorescence" and "fish phosphorescence." The "dead
2 X
674 DEPTHS OF THE OCEAN
phosphorescence " resembles the stars in a clear sky, myriads of
minute nearly invisible points emitting a scintillating light, now
increasing, now decreasing, in intensity. The " fish-phosphor-
escence" appears like great dull bubbles of light which
suddenly flare up, as if a dull electric lamp had been turned
on and then extinguished, and is produced by large animals,
fishes or squids, rushing through the water, sometimes, by the
impetus of their movements, causing all the minute phosphor-
escent organisms to flare up intensely in response to the
irritation produced. That the "dead phosphorescence" is also
caused by living organisms has been recognised since time
immemorial by fishermen and others who haul ropes or nets
through the water at night. Very often small phosphorescent
creatures, especially minute crustaceans, are captured and
furnish proof that the light is not emitted by the water
itself. But scientific men have not always recognised this,
for Franklin believed that the phosphorescence of the sea was
due to electric sparks caused by friction among the salts of
sea-water. According to Steuer, the abbot Dicquemare is
supposed to have filtered the sea-water and in this way proved
that the water emitted no light. Later on microscopic ex-
amination of the minute organisms of the sea has finally proved
that the emission of light is inseparable from living substance,
and that it is restricted to certain organs built for the sole
purpose of this peculiar function of life.
The power of emitting light is found in most groups of
marine animals and plants, beginning with the bacteria.
Among plants the peridineans and the remarkable ball-shaped
flagellates, Noctiluca viiliaris and Pyi^ocystis noctihica, are
noted for their power of emitting light. In animals this
power is always attributed to certain structures, which may be
said to represent all conceivable forms of glandular develop-
ment, from simple epithelial membranes to more or less
complicated tubular or lobular glands. These organs secrete
a slimy luminous substance. As a rule a layer of black
pigment is arranged around the gland, acting as a reflector.
Very often the light is projected through a transparent lens-
shaped organ. The light - organs thus very often resemble
minute eyes, and were previously supposed to perform the
function of perceiving instead of emitting light. As we
reach the more highly organised groups in the animal kingdom
the structure of light- organs exhibits an increasing complexity.
In minute crustaceans (see Fig. 492) we very often find only a
GENERAL BIOLOGY 675
single row of luminous cells in the usual epithelium, and a
lens formed by the cuticula or chitinous layer of the epidermis.
In squids and fishes the organs are very complicated, as we
shall presently see.
The object of the " Michael Sars " Expedition being mainly
the investigation of the distribution of animals, the examination
of the collections has necessarily been limited to the determina-
tion of the species, and my contributions to this fascinating
section of the science of marine life will largely consist in dis-
cussing the distribution of animals possessing light- organs,
which occur in salt water only, for no luminous animals are
known from fresh water and no phosphorescence occurs there.
Glandular, clearly defined, and localised light-organs are Light-organs
found mainly in pelagic animals. Among bottom animals principally
from the coast banks luminosity is exceed- in pelagic
ingly rare, but on the other hand, many ' — ammas.
bottom animals have been brought up
from the abyssal region in a luminous
condition, and have continued to emit
light when placed in dark surroundings ^
on board (see Fig. 70, p. 88, representing
a luminous umbellularian). No special
luminous structure has been found in fi^ 4^2
these cases, the luminosity being attached Light-organ of sergestes chai-
to the surface epithelium. As regards irl";„«:ie'rrl„le:
fishes, Giinther has drawn attention to lens ; </, glandular ceiis ;
the fact that many deep-sea forms secrete HaLen,°from' st'euer. )
a large amount of slime. The heads of
many deep-sea Macruridae exhibit certain pits and channels,
which produce great quantities of slime. This slime is supposed
to be luminous, and to perform the function of ordinary glan-
dular light-organs, which last are found only in a few fishes sup-
posed to live along the bottom, for instance, sharks (Spinacidse,
Spinax niger), and even in these they occur only as isolated
organs, not in such numbers as in the genuine luminous fishes.
Among the pelagic fishes of the coast banks no species is
known to possess light-organs ; neither the herrings nor the
mackerels have any representatives with light- organs. As
shown in Chapter IX. there is not a single independent pelagic
fish-species in the northern boreal waters, and as a consequence
no boreal pelagic fish-species possesses light-organs.^ A minute
examination of the lower forms has never been made, and at
^ I regard the Scopelidse in the Norwegian Sea as visitors, and not as true boreal forms.
676
DEPTHS OF THE OCEAN
Luminous
fishes.
present it is probably impossible to lay down any rules relating
to them.
If we take into account the exceptions here mentioned, we
arrive at the result that in the higher groups, viz. squids and
fishes, special light-organs are known mainly in oceanic forms
belonging to warm areas.
Among the fishes the luminous forms are mostly found in the
families Stomiatida:, Sternoptychidse, Scopelidae, and Ceratiidae.
Fig. 493.
1. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone
signata, Garm. , and C. signata alba, A. Br.
2. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone
microdon, Giinth. , and C. microdon pallida, A. Br.
3. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone
livida, A. Br.
4. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone
acclinidens, Garm.
5. The largest photophore from the ventral series between the isthmus and the ventral of Cyclothon^
signata, Garm.
6. The smallest photophore from the ventral series between the isthmus and the ventral of Cyclothone
signata, Garm.
7. Reflector cells of a photophore from the ventral series of Cyclothone microdon pallida, A. Br.
(After Brauer. )
After carefully examining the specimens belonging to these
groups captured by the " Valdivia," Brauer pointed out that a
certain regularity in the arrangement of the light-organs seems
GENERAL BIOLOGY
677
to correspond with different depths, and that the light-organs are
not peculiar to the deepest and darkest water-layers. Previously
this belief was generally adopted because the light -organs
were looked upon as a means of illuminating the dark abyssal
region. Brauer indicates that of the six species of Cyclothone
five are black and live in deep water, while one species
(C signata) is grey, lives in much shallower water, and has by
far the largest light-organs (see Fig. 493, showing the small light-
organs of the dark forms and the large ones of C. signata). Of
the Scopelidae, the surface forms of the genus Mydophum (s.s.)
possess the largest light -organs,
while the sub-genus Lampanydus,
taken in closing- net hauls by the
"Valdivia" between 800 and 600
metres, has very small light-organs.
If now we consider the captures
of the "Michael Sars," and the
vertical distribution of the fishes
previously described, we see that
our experience confirms Brauer's
views. Cyclothone mi c to don with
small light-organs was found much
deeper than C. signata (see Plate
I., showing these two forms, the
difference between their light-
organs being easily observed). Of
special interest is Fig. 490, showing
the vertical distribution of five
black fish-species, two of which
iGastrOStomUS bairdii^ and CyeUia Go?iosto?na rhodadenia, GWh. Photophore
, \ 1 1 • 1 , from upper lateral series (\^-).
atrunt) have no light - organs ;
Gonostojna grande has very small light-organs, while those of
Gonostoma rhodadenia and Photostoviias guernei are large (see
Plate II., showing the two species of Gonostoma, Fig. 67, a, p.
86, representing Photostomias giternei, and Fig. 494, showing
a light -organ of Gonostoma rhodadenia magnified). Besides
these we found in our deepest hauls many forms without light-
organs, for instance, species belonging to the genera Aceratias,
Melampha es, Cetom im us.
Light-organs are, therefore, specially characteristic of fishes
belonging to the upper 500 metres in warm oceanic waters.
^ On the tip of the tail this species is provided with an organ, the function of which is un-
known ; it has been regarded as a light-organ, but this does not alter our view.
Fig. 494.
678 DEPTHS OF THE OCEAN
Our contribution to the knowledge of this subject consists
mainly in determining the vertical distribution of the silvery
Fig. 495.
ria lucetia, Garm. Nat. size, 4 cm.
luminous Sternoptychidee and Stomiatidse more exactly than had
previously been done (see Fig. 478, p. 629, showing the vertical
distribution of some
of the most peculiar
luminous fishes).
Fig. 495 represents
one of these, Vinci-
guerria hicetia with
its numerous power-
ful light-organs, the
structure of which,
according to Brauer,
is shown in Fig.
496, where we see
the black pigment
behind the reflector,
the gland, and the
lens (see also Fig.
493' 7' which shows
a section through the
light-organ in Cyclo-
thone).
Splendid light-
organs have also
been discovered in
squids, and Chun
has described them
in many species (see
Fig. 434, p. 590). These forms are entirely pelagic. The
Octopoda, being bottom animals, possess no light-organs. In
the large group of squids light-organs have also been found in
Fig. 496.
Light-organ of Vinciguerria lucetia, Garni., from
of body (about ~\-). dr, glandular cells ; /,
fleeter; p, black pigment. (From Brauer.)
central series
lens ; r, re-
GENERAL BIOLOGY 679
species which live in intermediate depths, and are now and
again, like the ScopeHdae, captured at the surface (see p. 649).
The function and importance of the h'ght-organs in the hfe Function of
of animals have been subjects of controversy in the world of i^ght-organs.
science. The production of light has been explained as a
simple consequence of metabolism, and it has been supposed
that the light itself serves no purpose. Comparisons have
been drawn between the accumulation of mucous substance
and the mucous secretion of the light - organs, and it has
been pointed out that these organs occur particularly in
pelagic animals, which in order to float in the water are
supposed to need the mucus for the purpose of reducing
their specific gravity. Brandt, who has studied the adapta-
tions of animals to pelagic life, is perhaps right in supposing
that metabolic factors have played a part in the history of
the development of light-organs, but a closer scrutiny of the
structure of these organs, and particularly the discovery of
reflectors and lenses, seem to place it beyond doubt that the
light-organs serve the function of projecting light in definite
directions. This is the function for which the higher animals
use their light-organs, but for what purpose do they project
light ? Is it in order to illuminate the surrounding water, to
avoid foes, or to recognise their own kind } These questions
are not easy to answer with any certainty. At all events the
answers would probably tend to show that the many different
kinds of light-organs serve different purposes. For instance,
the large light-organs carried on the tentacles of the Ceratiidse
are probably used for other purposes than the smaller organs
found in Vinciguerria on the side of the body.
Brauer has examined the position of light-organs in relation Light-organs
to body segments in different species, and has found them chaSfrs.
to be arranged in exactly the same manner in all individuals
belonging to the same species, and consequently the number
and position of the light-organs are specific characters. He
advocates the idea that in the ocean the light-organs replace the
specific colour-markings of terrestrial animals.
Is it possible to explain the peculiar geographical distribution
of luminous animals, for instance, fishes ? The fact that light-
organs are found only in marine animals has been explained by
supposing the salt to be necessary for the production of light.
Experiments have shown that luminous bacteria develop and
emit light only when sodium chloride or calcium chloride is
present. As regards those organisms which secrete a slime
68o DEPTHS OF THE OCEAN
that only becomes luminous on the surface of the animal, the
phosphorescence seems to present an analogy or likeness to
certain chemical reactions, for instance, the slow oxidising of
organic compounds (grape sugar, etheric oils), which are accom-
panied by a feeble emission of light. In higher specialized
organs chemical processes of a more complex nature probably
take place. From the structure of the organs we may be
induced to believe that the development of the organ must
have depended on the fact that its function was intended to be
seen by an eye. The light emission must evidently be of
vital importance to the life of the animal and to the maintenance
of the species. The discussion of these questions must there-
fore be postponed until we have mentioned the eyes of the
different animals.
Eyes
Nothing has appeared more hopeless in biological oceano-
graphy than the attempt to explain the connection between the
development of the eyes and the intensity of light at different
depths in the ocean. In a trawling from abyssal depths in the
ocean we may find fishes with large eyes along with others with
very small eyes or totally blind. Nowhere would a more perfect
uniformity be expected than in the dark and quiet depths of the
ocean, Brauer, who has given a valuable contribution to our
knowledge of the eyes of deep-sea fishes, remarks in his treatise
on the fish collections of the " Valdivia " Expedition: "If the
surroundings really acted directly on the organisms, and were
the only agents which could produce alterations, their influence
would be much more uniform and general. Instead of this we
find the greatest variation. Thus we find the eyes now
altered or permutated, now highly differentiated even in closely
related forms,"
The conditions, however, where these different forms live,
are not so uniform as was supposed, or rather, these forms do
not really live under the same conditions. First of all it made
a great difference when we learnt that certain fishes were bottom
dwellers and others pelagic in their habits.
Most, if not all, bottom dwellers from abyssal depths have
large eyes, very often larger than those of bottom fish living
in the strong light of the coast banks. Perhaps there is a
maximum in the development of eyes in bottom fish at a certain
depth followed by a decrease in size as we proceed still deeper.
But even the deepest living forms, which must be supposed to
GENERAL BIOLOGY 68i
migrate all over the abyssal plain of the oceans, have very large
eyes, the diameter of the eyes in Macrin^us armatus, for
instance (see p. 417, and Fig. 272, p. 398), being equal to one-
fifth of the length of its large head.
As regards pelagic fishes we must remember that light
penetrates to far greater depths than was previously supposed,
for, as already stated, in the Sargasso Sea photographic plates
were strongly acted upon by light at 500 metres, and at 1000
metres traces of light were clearly perceptible, so that at least
certain components of the sunlight penetrate to that depth.
If we now review the size of the eyes of the fishes in
relation to their vertical distribution, we notice a strange
change just about the bathypelagic limit often referred to in
this book, viz. 500 to 750 metres, varying according to latitude.
Fig. 497.
Cetotnimiis storeri, G. and B. Nat. size, 12 cm.
In the fish taken between 150 and 500 metres the diameter of
the eye compared to the length of the head is, according to
Brauer, as follows : —
Stomias about 1:4 Argyropelecus about i : 2
Chauliodus „ 1:4 Sternoptyx „ 1:2
Ichthyococcus „ 1:2.6 Opisthoprocttis „ 1:4
VincigKerria ,, 1:3
If we consider Cyclothone and other fish which live deeper
than 500 metres we find the following relations : —
Cyclothone signata 1:12 (see Plate 1.)
,, microdon 1:12 (see Plate I.)
,, obsaira i : 15 or 20,
and if we inspect the figures representing Gastrostomus bairdii
(Fig. Z'x^ ^' P- 97)' Cyema atrufn (Fig. 69, p. 87), and Gonostoma
(Plate II.), we obtain a still stronger impression of the small
size of the eyes. Finally our deepest pelagic hauls contained
blind forms which have never been taken in the upper layers ; I
reproduce two of these blind fishes (Figs. 497 and 498), of
682 DEPTHS OF THE OCEAN chap.
which Cetomimus storeri has been taken before, while the other
form will probably have to be referred to a new genus. It is
"?
Fig. 498.
New blind fish, resembling Cetomimus, from Station 64. Nat. size, 6 cm.
also interesting in this connection to note that the only blind
squid known was taken
during our cruise at
Station 82 in 1500
metres. Chun has
called it CirrotliaiLma
mtirrayi and has shown
that its eyes are entirely
concealed below the
skin (see Fig. 499).
There is conse-
quently no doubt that
as far as fishes are
concerned, there is in
the ocean a limit be-
in ^ tween an upper region
down to 500 metres,
where the pelagic fishes
have large and well-
developed eyes, and a
lower region where im-
perfect organs of vision
are typical. The only
exception to this rule I
can think of is that a
few fishes, mainly be-
longing to the genus
'■rayi. (From Chun.) Melampha'eS 2iX\A\i2.V\n^
large eyes, were taken
in our deepest hauls beyond 1000 metres. Brauer remarks
that in M. mizolepis he has found great variation in the relation
of the diameter of the eye to the length of the head (from
cphl-h.
oph.
ophrh.s.
V ophrh
Fig. 499.
Rudimentary eye of Cirrothauma n
GENERAL BIOLOGY 683
I : 5.2 to I : 7), and he imagines this to be due to differences in
age. In the other species of this genus at all events the
relation is usually 1:7 or 8. Further investigations are
necessary to explain these relations.
Malacosteus also has a relatively large eye, but in this
genus as well as in other Stomiatidae we must suppose that
important vertical migrations occur. Thus we see from the
table (Fig. 490) that Photostomias guernei has been captured
at night in comparatively shallow water, and its eyes are
considerably larger than those of the fishes which constantly
live at great depths (see Fig. 67, a, p. 86).
The pelagic decapod Crustacea show a similar correspond-
ence between the development of eyes and vertical distribution
(see table, p. 668). In the two species living above 150 metres
the ratio of carapace to eye is 5-7, and in the five species with
a maximum distribution about 500 metres the ratio is 6-1 1,
while in the four species living below 500 and mostly beyond
1000 metres the ratio is 9-20.
Although in fact many cases as yet seem inexplicable, there
seems to be reason for supposing that the efficiency of the eyes
decreases with the decreasing intensity of light as we descend
into deep water. That we cannot fully explain all cases seems
to be a natural consequence of the fact that our knowledge of
the vertical distribution of pelagic fishes is still imperfect, being
based mainly on the closing-net hauls of the " Valdivia " and
the long horizontal hauls of the " Michael Sars," and both these
expeditions were of very short duration. Further investiga-
tions will probably furnish many interesting details as to
differences within the regions recognised by us, for we are
aware that various kinds of eyes occur in the region above
500 metres, such as stalked eyes, telescopic eyes, as well as
eyes built on the principles of the common type of fish eye.
Stalked eyes seem to be peculiar to larval stages, stalked eyes.
and in certain cases are known to develop into normal eyes
even during the larval stage (Lo Bianco). They seem to
occur only in the uppermost layers, where all transparent fish
larvae live. Considering the insufficiency of our knowledge of
the development of pelagic fishes, I do not venture to guess
to what species our stalk-eyed larvae belong.
Telescopic eyes are found only in fishes from depths less than Telescopic
500 metres. We have observed them in Argyropelecus. in a ^^^^'
new genus closely related to Dysomnia (see Fig. 540, p. 746), in
Opisthoproctus, and also in leptocephali. Fig. 500 represents
684
DEPTHS OF THE OCEAN
an Argyropelecus seen from above, and we see that the eyes
point upwards, which is probably the case in most fishes
possessing telescopic eyes, even if exceptions occur.
Two interesting facts go to explain this peculiar adaptation.
Firstly, these telescopic eyes occur only in fishes which are
very bad swimmers, fishes which practically only float in the
water-layers. Secondly, the light-measurements in the Sargasso
Sea showed that the light-rays acted more strongly on the
top plate than on the side plates ; for fishes possessing small
swimming capacity the telescopic eyes seem to be most
perfectly adapted to receive the faint rays
of light which penetrate to these dusky
depths.
Among eyes built on the general
principle the difference in size first com-
mands attention when the vertical pene-
tration of light and the vertical distribution
of each species come to be investigated.
As regards the upper layers, an interest-
ing subject will also be found in the
detailed study of the anatomy of dif-
ferent eyes. In the retina of the human
eye two special kinds of sensory cells
are known to occur, viz. "rods" and
"cones." These cells occur also in the
eyes of fish from the surface layers.
From Brauer's investigations we know
that in all deep-sea fishes, as well as in
silvery fishes from about 300 metres, only
the " rods " are found in the retina of the
eye. According to an old maxim of Max
Schultze, nocturnal animals possess only
"rods" while diurnal animals have both
It has therefore been generally believed that the "rods" alone
possess the faculty of observing light-intensity, light and shade,
while only the "cones" perceive colours, quality of light.
Further, an interesting difference has been found in the
colour-substance or pigment of the retina by day and by night.
Brauer has also found that these conditions in the eyes of deep-
sea fishes signify that their eyes are constantly adapted to
nocturnal conditions. The deep-sea fishes are "nocturnal
animals" and "day-blind." But the gradual development of
these peculiarities from the surface to the bottom, from the
Fig. 500.
A rgyropelec u s hemigymnus,
Cocco. Head seen from
above, enlarged.
" rods " and "cones."
GENERAL BIOLOGY 685
larval stages living at the surface to the adult fishes of the deep
sea, presents a vast field for future research and opens up a
vista of possibilities, which may explain the adaptation to special
surroundings peculiar to each species.
Investigations in the deep regions below 500 metres
should evidently, first of all, attack the questions whether a
regular decrease in the size of the eye occurs with increasing
depth, and whether the number of blind species and blind
individuals is not far greater than is generally supposed. Our
pelagic hauls only exceptionally went below 1500 metres,
but nevertheless we found in the deepest hauls no less than
three species of blind fishes, of which two were new to science,
besides one blind squid. In the deep oceans, where the depth
exceeds 5000 or 6000 metres, we might perhaps expect inter-
esting discoveries if large and efficient appliances were towed
after the vessel with 5000 or 6000 metres of wire out.
But if it be the case that the size of the eyes in pelagic Large eyes in
fishes decreases vertically with the decreasing intensity of light, fromTheS-^
how can we explain the fact that the bottom-fishes, like Alacrtci^us bottom.
arniatus, living in abyssal depths possess large and apparently
well-developed eyes? In order to explain this, the possible
existence of a source of light other than sunlight has been
sought for, but nothing has so far been discovered beyond the
light produced by the organisms themselves. We shall therefore
have to consider at the same time the power of emitting and the
power of perceiving light possessed by the animals, so that we
must take their light-organs as well as their eyes into account.
From what has been said we see that a remarkable
coincidence exists between the development of light - organs
and eyes in pelagic fishes. The Scopelidae, Sternoptychidse,
and Stomiatidae, which live above 500 metres, possess well-
developed light-organs and eyes, while from 500 metres down-
wards light-organs and eyes both decrease in size.
Along the sea-bottom, however, the fishes possess only eyes Abyssal
and no special light-organs. We have previously seen that h°"°e'es^b?t
the invertebrates are luminous even in abyssal depths, and at no light-
present the large eyes of the bottom fishes cannot be explained °''§^"^-
otherwise than by supposing that the light emitted by the
invertebrate bottom animals is so strong that objects on the
bottom may be seen by the eyes of fishes. As regards most of
the bathypelagic fishes we may, on the other hand, suppose that
they have little use for eyes, because pelagic life in great depths
is scanty, and not so definitely localized as on the sea-bottom.
"»j<9»e/i3«H!>Mr5=-.-r
686 DEPTHS OF THE OCEAN
These are the explanations offered at present, but they open
up new questions. How is it possible, for instance, for the
bathypelagic fishes to find their food in the dark, sparsely popu-
lated, water-layers ? Clearly we can advance no farther in this
field without more knowledge
gathered from new and ex-
tensive investigations. Even /-
with our present knowledge, ^
and accepting the explanations
given as perfectly correct, many
questions arise in regard to de- ', ^
tails. I will mention one very i^^^' ^'
interesting instance. ^ ^"
During the "Challenger"
Expedition some specimens
were captured of a certain
blind fish i^Ip7iops murrayi),
which was taken in the trawl
only at great depths, between c^^r
3000 and 4000 metres. As y
already mentioned, the
"Michael Sars " also captured
a small blind fish, apparently a
near ally of Ipnops, which we ^^e^
have called Bathymicrops regis ^ >y i
(see Fig. 305, p. 416). Ipnops ^
and Bathymicrops both belong
to the family Scopelidee, and
among allied forms we find a
remarkable series in respect V
to the development of the eyes.
This series has been repre-
sented in Fig. 501, a to e : —
a represents the head of
Chloropkthalmus prodiichis, Gthr., taken at Fiji in 575 metres.
b represents the head of Bathypterois dubius, Vaill., taken
by the " Talisman " at the Canaries, and by the " Michael Sars "
at Station 41 between 843 and 1635 metres,
c shows the head of Benthosaurus grallator, G. and B.,
taken off America, and by the "Michael Sars" at Station 53
in about 3000 metres,
^ shows the head of Bathymicrops regis, n.g,, n.sp., taken by
the " Michael Sars " in about 5000 metres.
Fig. 501.
Development of Eyes in Scopelids.
GENERAL BIOLOGY 687
e represents the head of Ipnops vmrrayi, Gthr., taken by
the " Challenger" in about 3000 metres.
a shows a "normal" eye like the eyes of bottom-fishes on
the slopes of the coast banks ; b and c exhibit very small
eyes; finally, d and e are perfectly blind. In Bathymicrops
the whole head is covered with scales, including the eyes,
which are only faintly visible through the covering as minute
black dots. In Ipnops the head is covered with filmy bony
plates, and eyes are entirely absent. A peculiar organ, which
has been regarded as a light-organ, is situated below the
plates, and supposing this interpretation to be correct it is the
only light-organ known in these forms, ^
How is this series of remarkable forms to be arranged con-
formably to the biological classification of the fishes accord-
ing to their light - organs attempted above } They have all
been taken only in the trawl, but are they really bottom fish ?
Why then (if we may be allowed the expression) do they not
all possess large eyes, like other bottom fish living at similar
depths .^ On the other hand, we must admit that they all differ
from pelagic fishes in appearance. Most bathypelagic fishes
are black, and their scale covering is but poorly developed.
As a " working hypothesis " I would suggest that these
fishes belong to the deepest water-layers near the ocean-floor,
and for this reason they unite qualities characteristic of both
bottom fishes and pelagic fishes. The fact that they belong
to the family Scopelidae seems to strengthen this view,
as this family comprises such a wealth of pelagic forms.
Several of these fishes, as for instance Benthosaiirus grallator
(Fig. 502), are also provided with long filaments or whip-
like appendages indicating pelagic habits ; to the south of the
Azores we took some splendid specimens, in which these
appendages, really transformed fin-rays, were intact, as seen in
the figure.
Another problem attaches to the remarkable fact, previously peiagic fishes
mentioned, that li2:ht-orQ:ans are lackino^ in all pelagic fishes o{°^^^^'^^
o& fc> rfc) waters and
the coast waters and also of the boreal area. Neither are they of the
found in the fishes of tropical coast waters, where the temperature ^^"^^^^ '^'■''''•
cannot be supposed to prevent their development, nor do they
occur in those of the Norwegian Sea, where the depth is sufficient
^ Sir John Murray and Professor Moseley at first described these organs as modified eyes, —
without lens or vitreous humour, and with only rods arranged in hexagonal bundles in the retina.
Later Moseley stated they were certainly not eyes, but phosphorescent organs (see Manchj
Science Lectures, Dec. i8, 1877, P- 132 ; Narr. Chall. Exp., vol. i. p. 239, 1885 ; Zool
Exp., Part LVII. Appendix A, 1887).
688
DEPTHS OF THE OCEAN
to enable us to find all degrees of light-intensity, at all events
during summer. Pm^a/iparis bathybii,
the large black bathypelagic fish found
by us in the Norwegian Sea (see Fig.
107, p. 127), possesses well-developed
eyes, although it lives in deep water
and undoubtedly in surroundings just
^ as devoid of daylight as does Cyclo-
^ tJione microdon. The same remark
I applies to RJiodichthys regina.
'^ Is it the rich phosphorescent pel-
E agic fauna peculiar to the coast waters
^ and the boreal area which renders
« light-organs useless and eyes useful to
? the fishes of these regions? Is it the
* case that the peculiar light-organs and
I the wonderful eyes can develop only
0 in warm oceanic waters of low specific
I" gravity ? Are all these features only
Z special adaptations to special and
1 1 definite conditions, like the splendid
^'^ colours of animals in tropical lands .f*
I ;f Are the small light -organs and the
° minute organs of vision peculiar to the
^ deep, dark, and cold oceanic waters
1 only rudimentary organs, which are no
. longer of vital importance to the fishes?
■a Are they to be considered as evidence
'^ that these fishes are descended from
^- ancestors living under entirely different
I conditions in lesser depths ?
I Floating and Organs of Floating
I If organisms did not possess the
c^ power of floating, thus preventing them
from sinking into deep water, the ocean
would become a lifeless desert, be-
cause in the surface layers of the ocean
live the minute plants which form the
source of nourishment for all animals
in the various depths of the ocean.
In order to understand the faculty of floating possessed by
GENERAL BIOLOGY 689
various organisms, we must first of all become acquainted
with the external conditions governing floating and sinking ;
mainly owing to the investigations of Chun and Ostwald our
knowledge on this point has increased greatly in recent years/
First and foremost among these conditions is the specific Specific
gravity of ocean water. If an organism has the same specific fhg'^^^JJr^
gravity as the sea-water it floats, because, according to the law
of Archimedes, it displaces a volume of water equal to its own
weight. When the specific gravity of the organism is greater
than that of the water it has a surplus gravity and may possibly
sink. If nothing counteracts its sinking, the velocity will be
proportionate to the value of the surplus gravity (equal to the
specific gravity of the organism minus the specific gravity of
the water).
Experience shows, however, that all objects of the same viscosity of
specific gravity do not sink with equal velocity. Fine sand ^^^ '''^^"'•
particles float much longer in water than large pebbles, although
they have the same specific gravity. This is due to a
property more or less peculiar to all liquids, called the viscosity
or the internal friction of the liquid, but in a liquid with a
definite viscosity objects sink with varying velocity, which
depends on what has been termed the surface resistance of
bodies.
An object has a great surface resistance, and sinks slowly. Surface
when its surface is largfe compared with its volume, and when "resistance
r 1^ ^., 1 ,,., of bodies.
Its surface presents a large area at right angles to the direction
of the sinking.
Surplus gravity and surface resistance are the two properties
in sinking bodies which determine the velocity of their sinking.
The greater their surplus gravity and the smaller their surface
resistance the greater is the velocity of their sinking. High
specific gravity and great viscosity of the water counteract the
sinking and require lower specific gravity and less surface
resistance on the part of the organisms in order to keep them
floating.
We will first consider the two " external conditions," the
specific gravity and the viscosity of the water, and then discuss
the faculty of regulating the surplus gravity and surface
resistance possessed by the organisms, enabling them to adapt
themselves to their surroundings. The importance of the two
elements, specific gravity and viscosity, anywhere in the ocean
1 See, for instance, Chun's Reisebericht {loc. cit.); W. Ostwald, " Theoretische Plankton-
studien," Zoologische Jahrbiicher, Abtg. Systematik, etc., Bd. i8, Jena 1903 ; " Zur Lehre vom
Plankton," Naturwissenscliaftliche Wocheiischrift, N.F., Bd. 2, Jena, 1903.
2 Y
690
DEPTHS OF THE OCEAN
depends hrst of all on the salinity and temperature, but the
influence of salinity and temperature is essentially different in
regard to specific gravity and to viscosity. This fact is easily
seen from the following table, compiled from Knudsen's
tables for specific gravity and from Ostwald's measurements for
viscosity : —
Viscosity,
Specific
Gravity.
Temperature
C.
30 %„ Salinity.
35 %„ Salinity.
30 %„ Salinity,
35 %o Salinity.
0 °
102
103
24.11
28.13
5°
87
88
23-75
27.70
10°
75
76
23.09
26.98
15°
66
66
22.16
26.00
20
58
59
20.99
24.79
25
52
53
19.61
23-37
30
47
47
18.02
21,76
We see from this table that within the common limits of
salinity, 30 to 35 per thousand, the salinity influences viscosity
very little ; in other words, viscosity is almost entirely dependent
on temperature. If the viscosity of pure water at o C, is placed
at 100, ordinary sea-water at 0° C. has a viscosity of 102-103 ;
at lo"" C. it has decreased by one-fourth,' and at 25" C. by one-
half. Sea-water at 25^ C. is only half as viscous as the same
water at 0° C, that is, the same body sinks twice as rapidly
at 25'' as at o'^ C. Variations in salinity alone, it will be
observed, influence the specific gravity as well as variations
of temperature. In the ocean specific gravity and viscosity
therefore do not run parallel, but they run in the same direction.
Thus a body, which can maintain its specific gravity in-
dependent of changes in temperature and salinity, will have its
velocity of sinking increased with falling specific gravity and
viscosity of the sea-water, and its floating faculty will be
augmented when viscosity as well as specific gravity increase.
Osmotic Temperature, and especially salinity, influence the floating
pressure, faculty of Hving bodies, through changes in osmotic pressure.
If the salinity of a cell is higher than that of the surrounding
water, the cell will, if not surrounded by an impermeable
membrane, give off salt and absorb water. The volume of
the cell will then increase, but although the cell actually
increases in weight, its specific gravity will decrease. In
GENERAL BIOLOGY 691
Salter water, on the other hand, such a cell will give off water ;
its volume will decrease, and it will attain a higher specific
gravity. These alterations will, however, react on the surface
resistance of the cell and influence its relations to the
viscosity of the water, as we shall subsequently see.
These three elements — specific gravity, viscosity, and
osmotic pressure — constitute the external conditions governing
the faculty of floating at different depths. Ostwald has in
various ways attempted to explain many of the peculiar
features of pelagic organisms. He cites instances from
interesting experiments made by Chun, Verworn, and Brandt,
showing how organisms decrease in size and volume with
increasing salinity, when sea-water evaporates in open vessels.
The animals sink when the sea-water is diluted with fresh
water, and rise towards the surface when the salinity in-
creases. After some time the difference in osmotic pressure
becomes adjusted, so long as the difference between the cell
and its surroundings has not been too great. These ideas
due mainly to Chun and Ostwald have, during recent years,
largely stimulated the scientific world to study the influence
upon organisms of variations in the external conditions.
All groups of pelagic plants and animals are now known Floating
to have a wonderful power of adaptability pertaining to their ^^^'<^^^-
faculty of floating in surroundings of varying specific gravity,
viscosity, and osmotic pressure. As regards the pelagic plants,
Gran has in Chapter VL mentioned some important and
characteristic instances of the alterations in shape to which certain
plants are subject in various waters. When dealing with the
various groups of pelagic animals I mentioned a few instances
of the differences in the general characters of the animals as to
shape, size, and appearance in warm and cold waters.
The various means adopted by different organisms in order
to increase their faculty of floating may perhaps be classified as
follows : —
(i) Certain organisms seek to diminish their specific gravity Secretion
by secreting and depositing specifically light substances in °^^^''
their cells. A very important part is here played by the fats
and oils, which are also of enormous importance as a reserve
food for the animals in question. From the radiolarians to the
whales, the fats are of great significance to pelagic life. In the
crustaceans, for instance the northern Calanus finmarchicus,
in fish eggs, which frequently possess oil-globules, in fishes and
in pelagic mammalia, the fats are specially important.
692
DEPTHS OF THE OCEAN
Specific
surface.
Numerous forms absorb water to such an extent that their
water-contents may amount to 90 per cent of the whole organism,
as in the medusae, ctenophores, and many fish eggs. In fish
eggs chemical analysis shows how the amount of water decreases
during development, and how this decrease continues as the
larvae seek deeper water and finally settle on the bottom.
Salpse and Pyrosomidae with large soft integuments also contain
a high percentage of water.
All the forms living in the surface waters of the sea, which
have developed special floating devices in the shape of air-
bladders or bells, may also — at all events in order to avoid a
too formal classification — be ranged into this group. These
remarkable devices are specially noticeable in the wonderful
group of the siphonophores. The air-filled lungs of whales and
seals and the air-bladders found in most fishes are also instru-
mental in diminishing the specific gravity of these animals.
(2) A reduction of the specific gravity of the kind mentioned
above must necessarily reduce or abolish the surplus gravity,
which tends to make the animals sink. But even if a surplus
gravity is present they will float, if they can offer a sufficient
amount of surface resistance, which may be effected either
actively by swimming, or passively as a consequence of the
shape of the body.
In order to understand the various and complicated adapta-
tions within this field, we should have .to compare the various
types of shape found in pelagic animals. I will at present
limit myself to pointing out the main laws as laid down by
Ostwald and Chun. In considering surface resistance two
points are essential : (i) the size of the organism, and {2) the
shape of the organism.
If we take two bodies, for instance two balls, consisting of
the same substance but with different diameters, and let them
sink in the same fluid, the larger one, that is, the ball in which
the relation between surface and volume is smallest, will sink
the faster ; thus the smaller the body the slower will it sink.
Ostwald terms the relation between surface and volume the
" specific surface," and gives the above-mentioned fact in the
following words : "small bodies sink slower than similar large
bodies which have the same surplus gravity, because their
specific surface is greater."
Next it is important to take into account the diameter of
organisms transverse to the direction in which they sink. A
thin plate sinks much faster in a vertical than in a horizontal
GENERAL BIOLOGY 693
position. Ostwald terms this relation the "size of projection," Size of
and has asserted that the velocity of sinking decreases in P'^oJ^ction.
proportion to the increase in the size of projection.^
These two principles of "specific surface" and "size of
projection " have in a most wonderful manner been employed
by organisms for the purpose of developing their faculty of
floating. First of all, in organisms which cannot lower their
specific gravity by depositing fats or absorbing water, we find a
dominant tendency to develop minute forms in specifically light
waters. In this connection we may note that small radiolarians
are found in shallow water, and large ones much deeper, as
Fig. 503.
Calocaianus />avo, Dana. '^ (about -\"-). (From Giesbrecht. )
mentioned in Chapter IX., and in Chapter VI. Gran refers to
the minute coccolithophoridae of the light oceanic surface-layers.
A large " size of projection " is found in countless numbers of
crustaceans, especially in warm oceanic waters. The copepoda,
for instance, show magnificent devices for enlarging their
surface, developing feather, plate, or rod -shaped appendages
(see Fig. 503). The surface resistance of these appendages
depends on their position in the vertical line, and thus they
serve the purpose of vertical locomotion as well.
Ostwald next points out the necessity of studying in nature
1 Since this was written Sandstrom has published a paper, " Hydrometrische Versuche,"
Meddelaiiden frail hydrografiska byraii, Stockhohn, 1912, showing that the velocity of sinking is
not exactly proportional to the size of projection, other circumstances, which are not yet clearly
understood, also influencing the process.
694
DEPTHS OF THE OCEAN
the specific gravity and viscosity of different waters, and
comparing them with the distribution and structure of the
animals. In this way I shall presently attempt to compare
various areas of the waters investigated by the " Michael Sars."
For this purpose Mr. Einar Lea has, on the basis of the
observations made by Dr. Helland- Hansen on our cruise,
worked out the three sections representing temperature, specific
Fig. 504.— Distribution of Temperature from the Sargasso Sea (Station 63)
TO Lofoten (Norwegian Sea).
Depth in metres ; temperature Centigrade.
gravity, and viscosity from the Norwegian Sea, west of Lofoten,
to the Sargasso Sea (see Figs. 504, 505, and 506).
Temperature, As to these sections, I wish to remark that they must not be
Savky, and Considered as representing the direct continuity of the water-
viscosity along masses from the Sargasso Sea to the Norwegian Sea. The
currents do not run directly between the two terminal stations,
and perhaps it would be more correct to represent each of the
stations separately without connecting the curves. With this
reservation in mind, however, it should prove very instructive
to compare the conditions as shown in the sections.
We see from the little chart (Fig. 62, p. 8^) that Station 63
GENERAL BIOLOGY
695
is situated in the Sargasso Sea, Station 86 on our northern
track, Station loi to the south of, and Station 113 to the north
of, the Wyville Thomson Ridge, while Station 46 from the
year 1900 is west of the Lofotens.
Figs. 504 and 505 show that just on the verge between
the two seas, between Stations loi and 113, a marked drop
occurs in the temperature and specific gravity. In the Nor-
wegian Sea (Station 46 of 1900) a specific gravity of 1.0278 is
St.6d
too
66
101
115
46
i — •
y
/^
/
/
- -"' s^"^
^^-' ^
^ ^
^^
y^ ^
/
'C-"
X
//
C
//
'?l
/
/
/I
/l
/I
/
/
1
1500
Fig. 505.— Distribution of Specific Gravity from the Sargasso Sea (Station 63)
TO Lofoten (Norwegian Sea).
28 = 1.028.
found only at 100 metres, and towards the Wyville Thomson
Ridge even at 1500 metres. A specific gravity of 1.028 does
not occur in the Atlantic at all at the depths here treated of,
while the entire deep layer in the Norwegian Sea is of a
specific gravity even higher than 1.028. In the Atlantic the
curves all fall away towards deep water and as we approach the
tropics. In the Sargasso Sea we find the same specific gravity
at 600 or 800 metres as occurs in the Norwegian Sea at 50
metres. The densely gathered curves at the surface denote
water of low specific gravity.
696
DEPTHS OF THE OCEAN
The viscosity exhibits, as shown in Fig. 506, a similar course.
We find a much greater viscosity in the waters of the Norwegian
Sea than in those of the Atlantic. The conditions of viscosity at
a depth of 50 metres in the Norwegian Sea correspond to the
conditions at about 800 metres in the Atlantic, where at the
surface we meet water-layers of small viscosity : " thin water."
If now we compare the distribution of animal life, as
46
Fig. 506. — Distribution of Viscosity (see text) from the Sargasso Sea (Station 63)
TO Lofoten (Norwegian Sea).
100 = the viscosity of distilled water at 0° C.
described in Chapter IX., with these facts, we may clearly
understand many of the peculiarities of distribution.
Warm-water From the distribution of specific gravity and viscosity it
oceanic life. fQ^Q^g l-j^g^j- jj^ light, thin, and warm oceanic waters only those
animals are found which have lowered their specific gravity by
the aid of light substances (fats, water), or have increased their
surface resistance by reducing their size or by developing
special organs for floating. To the first type belong the
Siphonophores [Pkysalia, PJiysophoi'a, Agahnopsis, and many
others), besides Medusae, Salpse, Doliolum, Pyrosoma, and
GENERAL BIOLOGY
697
large fishes which, like the sunfish, have a layer of blubber
round their body, and may be seen floating at the surface, the
dorsal fin above the water (see Fig. 507).
The organs of floating have previously been described and
Fig. 507.
Mola rottmda, to show the thick fat covering under the skin.
figured (see the Copepoda in Figs. 416-418, and the radiolaria
and foraminifera with siliceous and calcareous spines and filiform
pseudopodia, pp. 146-153).
Of special interest to us, however, is the oceanic fauna, the
members of which are remarkable for their small size, and in
this fauna the fishes especially appeal to us. The whole tauna
698 DEPTHS OF THE OCEAN chap.
of typical surface fish (Scopelidse, young fish), besides the
silvery fishes of the intermediate layer, the Sternoptychidse and
the Stomiatidae found mainly between 150 and 500 metres, live
just in the specifically light and thin water-layers (see Fig.
526, representing an adult Argyropeleais heinigyinmis, only 34
millimetres long, but with almost ripe ovaries). Excepting the
long ribbon-like Trachypteridse, Regalectts gles?ie, etc., these
minute fishes are, as far as we know, the principal if not the only
ones peculiar to these light water-layers. In the surface-layers
it is possible to recognise three distinct types: (i) the minute
Scopelidae ; (2) the larger oily fish like the sunfish ; and (3) the
species which live near solid floating objects, such as the
Sargasso fish.
One meets exceedingly few large fish in the ocean belonging
to the good swimmers, for instance, mackerels, pilot fish, sword-
fish, and sharks. Little is really known about the distribution
of all these, but several of them spend at least some part of their
lives in coast waters.
Boreal A comparison of the fauna of the Norwegian Sea and that of
pelagic life. |-}^g Atlantic is very interesting. We have seen in Chapter IX.
that numerous fishes which live mainly in the Atlantic have
been found in the Norwegian Sea as very rare visitors. From
the notes of Professor Collett, covering many decades, I have
given a list (see p. 643) recording the frequency of the
occurrence of these Atlantic forms. The most remarkable
feature is the fact that most of them have been found at
the very surface, or have drifted ashore and have been found
stranded on the beach. Among these fishes there are several
species, for instance those belonging to the genus Argyropeleais,
which live at 300 metres in the Atlantic and have not been
captured at these depths in the Norwegian Sea. Figs. 504-506
show that the lines of temperature, specific gravity, and viscosity
situated in 300 to 500 metres in the Sargasso Sea rise up to
the very surface as we approach the Norwegian Sea. In this
direction the Gulf Stream runs, at all events in the northern
part of the section.
The facts pertaining to the occurrence of boreal species in
the Atlantic are just the reverse. In Chapter IX. we have
learnt that on our track from Newfoundland to Ireland we found
boreal species, Clione limacina, Aglajttha, Calan7cs, Euchc^ta, and
several others, at depths between 750 and 1000 metres, while
in the Sargasso Sea we took Calanus hyperboreus and E2ich(sta
at 1000 metres. At these depths we find the same specific
GENERAL BIOLOGY 699
gravity and viscosity as in the Norwegian Sea, and also the
same temperatures. These Boreal species are essentially larger
than the warm-water forms belonging to the Atlantic surface-
layers, and have far smaller organs of floating. This applies
equally to the genuine deep-sea forms of the Atlantic in whose
company the boreal forms are found (see, for instance, what I
have previously said about the radiolarians, the trachymedusse,
and the crustaceans). A parallel is also found in fishes and
squids, of which some larger forms commence to appear in the
deeper layers, their size apparently increasing as we descend
towards the bottom (compare the measurements of Cyclothone
signata and C. micj^odon, Fig. 473, p. 620, and the two figures
representing ripe Cyclothone, Figs. 527 and 528). The bathy-
pelagic Gastrostomus dairdii, one of our deepest-living pelagic
fishes, was found to attain a length, including its long tail,
of 75 cm. In these regions we also find large prawns, which
appear to increase in size with increase of depth [Acantkepkyra,
Notostomiis). The squids seem to be arranged in two
groups, a number of small forms living in the upper layers
and the larger species living in deeper water. Although our
captures from a systematic point of view may be characterised
as exceedingly rich, they are not satisfactory for a study of the
vertical size-distribution of squids.
The peculiar agreement between size, form, and distribu- coast waters.
tion of species and the occurrence of a certain specific gravity
and viscosity of the water seems entirely absent in coast waters,
where the specific gravity of the water is lower than in the ocean,
because the inflow of fresh water from continental rivers lowers
the salinity. The viscosity, mainly dependent on temperature,
should, as a rule, be similar to that of the open ocean outside.
One would therefore expect to find, for instance on the coast
banks of Africa, similar oceanic forms, or the same faunistic
characters on the whole, as in the Atlantic Ocean, On the
contrary, we find that the fauna as well as the flora have
entirely different features. For unicellular plants as well as for
animals, the rule holds good that all forms are much larger
than those in the open ocean. Among plants the minute cocco-
lithophoridae are replaced by peridineae ; instead of the minute
oceanic scopelidse we meet with pelagic herrings and mackerels,
animals of quite another size and character.
As to the northern part of the Atlantic we perceive that
several boreal forms (among others Clione Ih?iacina), which in
700 DEPTHS OF THE OCEAN
the open ocean are found from 750 to 1000 metres, ascend
not only to the coast banks of Ireland, where the water is warm
and the specific gravity low, but also to the coast banks of
Newfoundland (see Fig. 489, p. 659, showing the vertical dis-
tribution of Clione on our northern track).
How is this remarkable distribution to be explained ?
First of all it shows that our conclusions as to the distribu-
tion of animals must be drawn with great caution. Except the
single occurrence of Clione to the west of Ireland, all the
captures agree as to temperature, specific gravity, and viscosity,
both in deep water as well as on the Newfoundland banks.
We require further information regarding the physical and
biological conditions in order to understand the difference
between the coast banks and the ocean. The biological con-
ditions, especially the great difference between the food supply
on the coast banks and in the ocean, will be discussed after
touching upon certain physical conditions.
As previously mentioned, Ostwald has pointed out the
influence exercised by salinity on the size of organisms ; in
surroundings of low salinity certain organisms absorb water and
increase in volume, while in high salinities they diminish in
volume. To what degree this fact may entail a difference
between the size of organisms belonging to the salt oceanic
waters and the size of organisms in the fresher coast waters, can
only be decided by future investigations. Possibly the richer
nourishment offered by coast waters affords the organisms a
better chance to store up fatty substances {^Clione as well as
Noctilitca store up fat), which increase the power of floating.
Finally, we may raise a question which seems to be worthy of
future investigation. Is the viscosity of the water influenced
by the number of organisms suspended in it } That this
may be so is conceivable when we think of china ink, for
instance, which is more or less viscous according to the amount
of substance dissolved in the water. Investigations as to the
actual facts occurring in nature have not yet been made.
Those who have observed the extent to which coast water
may be filled with suspended substances, detritus as well as
living organisms, may perhaps find this question worth con-
sideration.
Migrations
We have considered how far and in what manner the
appearance, shape, size, and also the several organs of different
GENERAL BIOLOGY 701
organisms may be supposed to have been adapted to certain
external conditions prevailing in the water-layers which surround
them. But these water-layers are not stationary, and the con-
ditions in a certain water-layer may change in many different
ways from time to time. These changes alter the habitat of
the animals and cause active or passive migrations. The
study of these migrations is specially interesting as showing
the influence of physical conditions acting upon the animals.
From time immemorial it has been known that many Daily vertical
animals ascend at night to the surface of the ocean. Fisher- '"^srations.
men have during ages turned this knowledge to advantage in
setting their drift-nets at night at the surface of the sea to
capture the herring. Recently it has proved possible to trawl
successfully for herring along the sea-bottom, but only during
the daytime. All sailors can tell us that at night great
numbers of animals gather in the surface waters, which are
never seen there in the daytime. An interesting instance of
this was mentioned in Chapter IX. While fishing with long-lines
on the Faroe banks our lines were set for cod along the bottom
in about 200 fathoms ; the lines were hauled at night, and the
stomachs of the cod contained squids, which had been eaten
during the day, while at night numerous squids were seen at
the surface darting into the glare of our electric lamp hanging
over the side. Most fishermen have had similar experiences.
A certain amount of information has also been gathered as
to the vertical migrations of minute pelagic organisms moving
towards the surface at night. Chun especially has investigated
the extent of these migrations, and found that the majority
of small pelagic organisms migrate generally within a vertical
range of 30 to 50 metres. Steuer draws attention to the fact
that vertical migrations very rarely involve all the pelagic forms
of a locality ; at all events they do not migrate in the same
manner, for there are many transitions between forms which
only retreat vertically during a few hours in the daytime, and
forms which rise only during the darkest nocturnal hours. If
the forms were large enough to be seen in the water, we should
"by day as well as by night be able to observe a continuous
rise and fall of organisms. Only during the day we should
see a larger congregation in deeper water, and at night at
the surface." ^
Some instances of the difference plainly observable in our
catches by day and by night have already been mentioned
1 Steuer, op. cit.
702 DEPTHS OF THE OCEAN
(see p. 95). Specially striking were the fishes Astronesthes
and Idiacanthiis occurring at the surface only at night. It was
also very interesting to note the remarkable coincidence between
the vertical migrations of the fishes and the development of their
light-organs. Fig. 490 shows the vertical occurrence of five
black fishes, each mark denoting the capture of one individual ;
in the case of Gonostoma rhodade^iia and Photostoniias guei-nei,
a black dot denotes a specimen captured at night, while a ring-
shaped dot denotes a specimen taken during the day. In
Gastrostomus, Cyema, and Gonostoma grande only slightly
developed light-organs, if any, are met with. In Gonostoma
rhodadenia and Photostomias guernei particularly large light-
organs are present (see Fig. 494 and Plate II.). Specially
interesting is a comparison of the two species of Gojiostoma,
the light-organs along the side of the body in G. rhodadenia
having a length of 2.5 mm., while in G. grande they are only
0.5 mm. long. Evidently we have here a type of deep-sea
fishes, living in deep water, but with the power of migrating
towards the surface. These forms have retained their well-
developed light-organs, which in other black fishes of the deep
sea must be considered as extremely reduced, perhaps even
quite rudimentary, organs. A perfect analogy is found in the
decapod Crustacea. The deepest living species (see table on
p. 668, Nos. 8-11) have no light-organs and make no vertical
migrations. Light-organs, or organs which are believed to
produce light, are found only in species living between 150 and
500 metres with a maximum distribution at about 500 metres.
These species have been found much higher up in the water
during the night than during the day, as is brought out quite
clearly by the table.
During our southern cruise we might have had a good
opportunity of making an exact study of vertical migrations
by the aid of precise closing-net hauls, but time did not permit,
though our isolated observations are very interesting, for
instance those made at Station 48. While towing our big
trawl all day at this station, we were continually taking hauls
with surface tow-nets, the catches during the day consisting
only of the common surface forms : lant/iina, Pterotrackea, fish
eggs, pteropoda, radiolaria, etc. ; but between 6 and 7 p.m.
the nets suddenly captured a mass of small red copepoda, which
during the day had been taken at about 70 metres. At
Station 53, during the day, we captured only radiolarians at the
surface ; at 30 metres there were a few copepoda, no young
GENERAL BIOLOGY
703
fish or scopelidse, while at 60 metres there were several
copepoda, and no scopelidae. In the same place, during the
night, we obtained at the surface a rich collection of copepoda,
numerous scopelidae, and thirteen black fishes {Astronestkes
niger). These instances furnish conclusive proof of vertical
migrations of considerable extent.
Ostwald, after studying the variations in the viscosity of the
water from time to time, has made an attempt to explain the
vertical migrations as due entirely to physical laws. During the
twenty-four hours certain changes occur in the temperature of
the ocean surface, and the viscosity of the water is, as we have
seen, largely dependent on temperature. According to Buchan,
the mean diurnal fluctuation of the surface temperature, as
shown by the "Challenger" observations, was in mid North
Atlantic 0.8' Fahr., in mid South Atlantic also 0.8' F., in mid
North Pacific 1.0° F., and in mid South Pacific 0.9° F, ; near
the equator both in the Atlantic and Pacific the diurnal range is
only 0.7° F. The mean daily range deduced from the whole of
the "Challenger" observations during the three years and a
half is 0.8° F.^
According to Krlimmel ^ the daily range of temperature
occurring in the surface waters of the open ocean amounts to
about 0.5° C. ; in the North Atlantic 0.59° C. Although several
investigators, like Aime and Hensen, tackled the problem we
have very little knowledge regarding the daily changes at
different depths. From Krlimmel I give the following differ-
ences found by Aime between evening and morning at different
depths in the Mediterranean : —
Depth.
Temperature.
Difference.
Metres.
Evening.
Morning.
0
15.1° c.
14.6 °c.
0-5
2
15-1° C.
14.6 ° c.
0-5
4
15.0° c.
14.5 ° c.
0-5
6
14.8° c.
14.5 ° c.
0-3
10
14.6 °c.
14.4 ° c.
0.2
14
14-4° C.
14.3 ° c.
0.1
18
14.3 °c.
14.3 ° c.
0.0
22
14.3 ° c.
14.2 ° c.
0.1
1 Phys. Chem. Chall. Exp., Part v. p. 6, 1889.
Otto Kriimmel, Handbuch der Ozeanographie , Bd. I, Leipzig, 1907.
704 DEPTHS OF THE OCEAN
From this it does not seem that such migrations as those
mentioned above are due to changes in temperature and
viscosity alone. We must, for the present, suppose that the
animals have the power of actively altering their level in the
water-layers. Ostwald's observations on the viscosity of sea-
water, and on the floating capacity of organisms, should render
these questions easier of solution, and their further investigation
should form a very interesting object for future expeditions.
Effect of The currents of the ocean exert a very strong influence on
Q^^lhT ^^^ distribution of many animals. All seafaring men and the
distribution inhabitants of all shores have known for ages that drifting
objects are carried very far by the currents of the sea, and that
"rare " and strange animals are stranded on the coasts. Along
the entire coast of Norway, even up to the Barentz Sea, drifting
objects and stranded fish are found, which really belong to the
distant warm Atlantic. Numerous accounts of the passive
migrations of animals through currents are to be found in
literature, many of them valuable notwithstanding the fact that
these conditions have only exceptionally been made the subject
of systematic investigation.
Looking at the current-chart (Fig. 508), we see that the
central part of the North Atlantic, south of a line drawn from
the Bay of Biscay to the northern United States, forms a
separate current-system. The branch of the Gulf Stream
flowing north-east towards the coasts of northern Europe
receives an admixture of cold water from the Labrador current,
and also large volumes of water, as well as numerous organisms,
from the main body of the Gulf Stream. Entering the
Norwegian Sea this branch of the Gulf Stream runs through
the Faroe-Shetland Channel, sending off one branch to the
North Sea and another branch along the coast of Norway right
up to the Barentz Sea. This current system enables us to
understand many of the laws governing the distribution of
pelagic forms as referred to in Chapter IX. Thus the warm-
water fauna of the North Atlantic belongs mainly to the
central current system ; isolated specimens belonging to this
fauna not only occur in the north European Gulf Stream, but
are found in the Norwegian Sea, and on the northernmost
coasts of Norway (see the discussion of the distribution of
pelagic fishes in depths between 150 and 500 metres in the
Atlantic, and the occurrence of Atlantic fishes in the Norwegian
Sea, p. 644). The distribution of the animals of the coast banks
GENERAL BIOLOGY
705
is peculiar in so far that southern species of molluscs, for
instance, occur as isolated specimens even far north in the
Norwegian Sea, while northern species have a sharp southern
limit (see Chapter VII.). Vast numbers of small pelagic
organisms are introduced into the Norwegian Sea from the
Atlantic.
As the water-masses of a current are carried along, the
vr/ f'^J'
Fig. 50S.— Currents of the North Atlantic. (From Schott's " Valdivia" Report and
Helland-Hansen and Nansen's memoir on The Norwegian Sea.)
conditions of existence for certain animals change, and as a
consequence the fauna gradually changes in character. This
change of fauna from place to place in the same expanse of
water has always presented interesting problems in oceanic
research. Sir John Murray writes upon this point as follows :
"Where cold and warm currents meet at the surface of the Effect of large
ocean, there is a rise of temperature for the animals of the cold ff"^!.°H,-„
/* 1 •tz-i LCnipcrutUl c
current, and a fall of temperature for the animals of the warm in the surface
current, which results in a plentiful destruction of organisms. ^^^^^'^^•
2 z
7o6 DEPTHS OF THE OCEAN
The tow-net collections during the ' Challenger ' expedition
gave frequent illustrations of this fact by the dead animals
collected in such positions off the coast of North America, off
the Cape of Good Hope, in the North Pacific, and elsewhere.
Dr. O. Fischer records a remarkably large number of bacteria
on the borders of such meeting currents. This destruction of
life is not limited to minute pelagic organisms, but occasionally
affects animals which live at the bottom of the sea. Some
remarkable instances of this kind have been observed between
depths of 50 and 100 fathoms off the eastern coast of the United
States.
" Lieutenant-Commander Tanner, commanding the United
States Fish Commission steamer ' Albatross,' reports that ' on
the morning of July 20, 1884, in lat. 37 47' N., long. 74' 15' W.,
near the loo-fathom line, we passed numerous dead octopods
floating on the surface. This unusual sight attracted immediate
notice and no little surprise among those who knew their habits,
as it was not suspected at first that they were dead. We
lowered a boat and picked up three or four specimens, which
we were unable to identify, but in general appearance they
resembled Alloposus mollis (Verrill) of unusually large size.
These dead cephalopods were seen frequently on the 100-
fathom line and outside of it, from the position given above to
the meridian of Montauk Point, a distance of 180 miles.
They were less numerous, however, as we went to the north-
ward and eastward. Several dead squid were seen also, and
two specimens were picked up with a scoop-net.'
" A still more remarkable instance of this kind is furnished
in the well-known case of the destruction of the tile-fish
[Lopkolatilus ckajucsleonticeps) in the same locality in the spring
of 1882. In the months of March and April 1882, vessels
arriving at Philadelphia, New York, and Boston reported
having passed large numbers of dead or dying fish scattered
over an area of many miles, and from descriptions and the
occasional specimens brought in, it was evident that the great
majority of these were tile-fish. Naturally, these fish were not
evenly distributed over all the area in which they were seen,
some observers reporting them as scattering, and others as at
times so numerous that there would be as many as fifty on the
space of a rod square. As one account after another came in,
it became apparent that a vast destruction of fish had taken
place, for vessels reported having sailed for forty, fifty, and
sixty miles through floating;- fish ; and in one case, the schooner
GENERAL BIOLOGY 707
' Navarino' sailed for about 150 miles through waters dotted Destructive
as far as the eye could reach with dying fishes. Computations rfiigl of^'''^''
made by Captain J. W. Collins seem to indicate that an area temperature.
of from 5000 to 7500 square statute miles was so thickly
covered with dead or dying fish that their numbers must have
exceeded the enormous number of one billion. Since there
were no signs of any disease, and no parasites found on the
fish brought in for examination, their death could not have been
brought about by either of these causes ; and many conjectures
were made as to the reason of this wholesale destruction of
deep-water fishes, such as would ordinarily be unaffected by
conditions prevailing at the surface, submarine volcanoes, heat,
cold, and poisonous gases being variously brought forward to
account for the loss of life. Professor Verrill has noted the
occurrence of a strip of water having a temperature of 48 to
50' Fahr., lying on the border of the Gulf Stream slope,
sandwiched between the Arctic current on the one hand and the
cold depths of the sea on the other. During 1880 and 1881
Professor Verrill dredged along the Gulf Stream slope, obtaining
in this warm belt, as he terms it, many species of invertebrates
characteristic of more southern localities. In 1882 the same
species were scarce or totally absent from places where they
had previously been abundant ; and this, taken in connection
with the occurrence of heavy northerly gales and the presence
of much inshore ice at the north, leaves little doubt that some
unusual lowering of temperature in the warm belt brought
immediate death to many of its inhabitants. This is the more
probable, as it is a well-known fact that sudden increase of cold
will bring many fish to the surface in a benumbed or dying
condition." ^
From the Barents Sea we know many instances of a similar
destruction of animals on a large scale. The case of the boreo-
arctic fish, the capelan [Maliotus villosns), is specially striking,
millions of this fish having occasionally been found drifting dead
at the surface. In the Barents Sea very sudden changes of
temperature occur, and it is natural to conclude that the death
of the fish is caused thereby. The greatest destruction of this
kind probably occurs among the young stages, eggs and larvae of
fishes. As we shall see later, these young stages may be removed
by currents very far from the places w^here they are capable of
developing, and in all probability they are also liable to
1 Sir John Murray, "On the Annual Range of Temperature in the Surface Waters of the
Ocean," Geogr. Jouni. vol. xii. pp. 128-130; 1898.
7o8
DEPTHS OF THE OCEAN
encounter catastrophes which sweep them off in enormous
numbers. I come to this conclusion because our investigations
on the age-composition of various fish-species have proved the
frequency of the different year classes to be so variable (see
section on age and growth).
As the Gulf Stream flows northwards its waters are
gradually cooled, partly because they give off heat to the cold
air, and partly because of the admixture of cold water. With
the cooling the southern forms disappear, and their place is
taken by entirely different boreal species ; very little is known
about the actual stages of this change.
During the cruise of the "Michael Sars " from the west
coast of Scotland to Rockall, and north to beyond the Wyville
Thomson Ridge we found vast numbers of Salpa^ {S.foisiformis),
the great majority of which were wholly degenerated. Bjerkan,
who is examining our collection of Salpae, informs me that the
mantle and the muscular system of the specimens were generally
in a very ragged condition, in many cases only the intestine
being distincdy recognisable. Here then, on the border
between the Atlantic and the Norwegian Sea, it appears that
certain forms die in large numbers, while others degenerate.
Gran refers to the degeneration of certain coast diatoms found
drifting far out at sea (see p. 342).
When organisms cannot within a certain time regain condi-
tions necessary for them, or to which they can adapt themselves,
they invariably die sooner or later. The isolated specimens of
such fishes as Argyn-opelecus found in the northernmost parts of
the Atlantic undoubtedly represent a few survivors of the
change.
The boreal fauna which in northern waters replaces the
genuine Atlantic forms also belongs to a great current-cycle.
If we look at the current charts (Fig. 193, p. 284 and Fig.
508), we observe that the Gulf Stream receives admixtures
from boreal and boreo-arctic currents, which consequently carry
boreal organisms. As we have previously seen, we meet with a
wealth of boreal forms in deep water even in the Sargasso Sea,
and probably much farther south, living below the warm-water
fauna of the surface.
The velocity of ocean currents is subject to many varieties
of periodical and non-periodical changes (see pp. 284-5). T^^e
annual changes are of peculiar interest, and are very noticeable
in northern waters, though also important in the Atlantic,
If we compare the two charts (Figs. 159, p. 227, and 160, p. 228)
GENERAL BIOLOGY
709
we see that the surface temperatures of the North Atlantic
change very considerably from February to August. In
February the isotherm of 15" C. follows approximately the 40th
degree of latitude, while in August it reaches the north-western
corner of Iceland, north of the 50th degree. The isotherm of
10' C. has in February a course approximating to that of the
15 isotherm in August, when the isotherm of 10° runs far
north in the Norwegian Sea, where the seasonal difference is
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ISO
Yic. 509.— Variation of Temperature according to Depth during different
Seasons, off the Norwegian West Coast.
Still more pronounced. Fig. 509 shows the vertical distribution
of temperature during approximately fifteen months, as observed
by me in the 'nineties of last century while making repeated
investigations in one locality off the west coast of Norway.
We perceive that during the summer months warm temperatures
occur in the upper 50 metres, temperatures which during
winter we can find in the Atlantic only south of the 40th degree
of latitude (see Fig. 159, p. 227). During autumn high
temperatures (8° C.) pass down through the water column, so
that towards the close of the year the warmest water is found
at 250 metres. At the same time the surface -layers cool
7IO
DEPTHS OF THE OCEAN
interest attaches to the fact that the immigra-
into
Norwe
rapidly and the lower temperatures gradually descend towards
deep water during early spring and summer. Great changes
in specific gravity, viscosity, and light-intensity accompany
these changes in temperature ; in the very magnitude of
these changes we must look for the essential difference between
the tropical and subtropical conditions on the one hand, and the
arctic-boreal conditions on the other.
The greatest
tion of Atlantic forms
season when the condi-
tions in the latter are
most similar to those of
the Atlantic. The in-
ternational investiga-
tions have contributed
to our knowledge on
this immigration.
Schmidt,^ for instance,
in the Danish investiga-
tion-steamer " Thor,"
had the opportunity of
studying the immigra-
tion of Salpae from the
Atlantic into the Nor-
wegian Sea, and writes
as follows : —
" The organisms
concerned were the dis-
tinctly Atlantic Salpse
(especially Salpa fusi-
fornns), which are so
characteristic and which
were taken often in hundredweights in each haul of our
pelagic apparatus in the Atlantic beyond the looo- metres
line. The year 1905, during which we several times crossed
the North Sea, made two cruises to and from Iceland and the
Faroes, following approximately the looo-metres line, then
sailed southwards west of the British Isles to the Bay of
Biscay, was thus specially well suited to give light on these
conditions, as I have endeavoured to delineate on the accom-
panying Chart [reproduced in Fig. 510]. The shaded lines
1 Jobs. Schmidt, "The Distribution of the Pelagic Fry and the Spawning Regions of the
Gadoids," etc., Rapports et proces verbatix dii Conseil International, vol. x., Copenhagen, 1909.
Fig.
510.— Drift ok Salp^ {Salpa fusiformis)
1905. (From Schmidt.)
GENERAL BIOLOGY 711
(single or double) on this Chart represent the regions where the
Salpse occurred. As will be seen, up to the end of May the
Salpae were limited to the Atlantic, where the northern boundary
was found on the voyage of the ' Thor ' southwards to lie to
the west of the Hebrides, and absolutely none were found in
the Norwegian Sea or North Sea. Towards the end of July
the conditions had quite changed, a fact of which I was able to
convince myself on a cruise from Scotland to Bergen and from
Bergen to the Shetlands, the Faroes, and Iceland. From the
chart, on which the places where we found the Salpae are
marked by black spots, we see how the northern boundary has
moved to the east and north. Thus a large tongue of the
Salpae had pushed its way north of the British Isles in a north-
easterly direction, far towards the Norwegian coast, and in a
northerly direction we see now that the Salpae reached as far as
north-west of the Faroes. And it was not a matter of small
quantities. Thus at our station (Station 121, 1905) north of the
Shetlands we took many hundred litres per half-hour haul ; and
in the quiet, calm weather we could see under the clear surface
how the water was quite thick with the Salpae which occurred
here and, it is to be remarked, over small depths (less than 200
metres), along with other distinctly Atlantic oceanic forms, in
almost as large quantities as we had found them anywhere,
even in the Atlantic over deep water where they really belong.
At the end of August, when the 'Thor' was coming south-
wards from Iceland, the northern boundary had moved some-
what, yet not very much. We see also that the south-eastern
boundary in the North Sea had spread out farther, correspond-
ing to a greater development of the large tongue in July."
Similar experience has also been gained during the
Norwegian investigations. Thus in the survey of the " Michael
Sars " investigations on pelagic organisms in the years 1900-
1908, Damas writes as follows: —
" In the middle of the summer the invasion of oceanic forms
from the Atlantic commences in the Faroe-Shetland channel.
There we find an imposing array of species that are entirely
absent from the Norwegian Sea, and that certainly do not
belong to the fauna appropriate to that sea-basin. Among the
most characteristic we may name : Lepasfascic2ilaris,Physophora
borealis, Cupulita sarsi, Sohiiaris coj'ona, Salpa fusij^ormis,
S. i^iincinata, and ^. irregularis, Arachnactis albida, Clio
pyrarnidata and C. tmcinata. These forms do not enter en bloc,
and the water-masses which convey them do not seem to have
712 DEPTHS OF THE OCEAN
a homogeneous composition. Their approach is heralded by
an immense swarm of Lepas fascicular is, which at the beginning
of May and June float passively on the surface of the northern
portion of the North Sea. Arachnactis albida follows soon
afterwards, as does also Physophora borealis. The salpse and
doliolids, which with Cipitlita sarsi, constitute the bulk,
generally make themselves visible in July, August, and
September."
We know that these warm surface forms approach the coast
of western Norway, and as far north, for instance, as the
Trondhjem fjord.^ Even within the Norwegian Sea such
seasonal migrations occur, the warm water layers from the
eastern part spreading out over the deeper areas during summer.
The foregoing remarks refer only to the passive migrations
or drift of pelagic forms with the currents of the sea. Fisher-
men have, however, long recognised the vast active migrations
of the powerful swimmers, especially fishes, generally supposed
to be undertaken in order to reach definite localities. The
first to submit these migrations to scientific investigation
was probably G. O. Sars. As to the herring fisheries on
the coasts of Norway he was struck with the fact that
while herrings of all sizes are captured along the entire
coast from the Skagerrack to the Barents Sea, spawning
herrings are only caught in large quantities on a definite
restricted portion of the coast, viz., from Stavanger to Romsdal
(the Norwegian North-Sea coast), and he concluded that the
herrings must necessarily migrate to these places to spawn,
enormous spawning-migrations entering as a necessary link in
the life-history of the herring.
Numerous instances of such migrations are known from the
fishing industries, on the coast of Norway principally in the case
of herring and cod, and in Iceland of cod and plaice. I refer
the reader to my description of the migrations of the capelan
(Ma/lotics villosus) In the Finmark Sea^ (Barents Sea). This
small boreo-arctic fish spawns in spring on the coast banks of
Finmark, and during summer it migrates far north into the
Barents Sea towards the Ice-limit. In March 1901, when many
miles off the Finmark coast and over deep water, I could observe
and fish the capelan, the shoals being followed by millions of
auks, fulmars, kittlwakes, and gulls, the stomachs of which
contained capelan.
^ See Nordgaard, loc. cit.
' \l]ox{, Fiskeri og Hvalfatigsi i det iiordlige Norge, Bergen, 1902.
GENERAL BIOLOGY
71,
The exact experimental proofs as to migrations obtained
during recent years from the marking of fish are also of great
value. Marking experiments on marine fishes were started in the
'nineties of last century by C. G. J. Petersen, during his studies of
the life-history of the plaice. During the international investiga-
tions they have been carried out on a large scale, especially by
Heincke, Garstang, Trybom, and Schmidt, the investigations
by the last named on the migrations of cod and plaice at Iceland
having perhaps yielded the clearest results. The Iceland plaice
Fig. 511.— Schmidt's marking Experiments showing the Migrations of Plaice in
Icelandic Waters. (From Schmidt. )
spawn during spring south and west of the island, but at other
times they migrate to the north and east coasts. Schmidt
marked a number of plaice in Skjalfandi Bay on the north coast,
and a number in Vapnafjord on the east coast (see chart, Fig,
511). He got a great many of these back from the west and
south coasts, where they were taken in the spawning season.
From the North Sea interesting results from marking experi-
ments are also available, but the fishes do not appear to migrate
to such an extent as in Icelandic waters.
While investigating the fisheries and the whaling in northern
Norway, I was successful in obtaining similar conclusive
714
DEPTHS OF THE OCEAN
ir
evidence as to the migration of whales.
With the aid of Captain Sorensen I
obtained the two harpoons or bomb-
lances which in the years 1888 and 1898
were found in the bodies of blue whales
{Balcmoptera miisculus) killed in the
Barents Sea (see Fig. 512). Such har-
poons were never used there, being
employed only by the whalers of the
Atlantic, for instance, off the coast of
North America, and they bear the stamp
of the American patent-holder, testifying
to their American origin. They must,
therefore, be considered as proving
enormous migrations on the part of the
whales in which they were found.
G. O. Sars attempted to show that
some migrations were undertaken in
order to obtain food, and others for the
purpose of reproduction, and he thus
distinguishes between feeding-migrations
and spawning- migrations. When the
capelan gather in millions on the coast
banks of Finmark, when countless
numbers of cod approach the banks of
Lofoten, and when the herrings flock to
western Norway, they migrate to spawn.
The fat-herring collecting off the coast
of Nordland, and the cod gathering
around the shoals of capelan in the
Barents Sea, are examples of feeding-
migrations. Such were the ideas of
Sars. A more detailed discussion could
only be given by reviewing the whole
natural history of each species.
An attempt at explaining a vast
migration of fishes by means of mechan-
ical laws has recently been made by
Otto Pettersson.^ Each year during
late autumn large numbers of herrings
gather off the island belt at Bohuslan fi^- 51^— -^^iericax "Bomb-
Lances " taken in Blue
^ Otto Pettersson, Stiidien iibcr die Bewegtingen des Whales in Northern
Tiefeiiwassers und ihren Eiiifiiiss aicf die IVanderuiigen der Norway, Finmark, 1888
fferinge, Fischerbote, 191 1. and 1898.
GEiNERAL BIOLOGY
715
(on the west coast of Sweden), and are captured in the
deep channel of the Kattegat, or in the fjords of Bohuslan.
Pettersson discovered that the regular occurrence of these
herrings in several cases coincided with certain large sub-
marine waves which he could register in the Gullmar fjord,
and he sets up the hypothesis that there is a certain connec-
tion between these two phenomena. Fig. 513 shows curves
denoting different salinities in the Gullmar fjord in November
and December 19 10, and it is seen that the deep salt layers
rose several times during November, like huge waves, up
towards the surface. Extensive investigations off the coast
in the Kattegat proved the occurrence of similar deep-sea waves
Bomo.
Kov Dec, 7910,
17 19 Z1 Z3 Z5 17 19
^
Xf
^
^
>^
T
-~~^
K
^
^
,^
//
J
\
f
9-
\
\
f^r
\
i
P
'^
I
/
J.
r
r
s
\
\ )
1
%
4
/
\
^
/
/
^
/
\
\V
\
10
100 ? 2'tOOO 30000 HL.
Fig. 513. — Submarine Waves in the Gullmar Fjord in November and
December 1910. (From Pettersson.)
in the latter locality. These waves, according to Pettersson,
carried the water of the Jutland coast banks (bank-water with
a salinity of 32 to 34 per thousand) like a torrent into the
Kattegat and its fjords, forcing the fresh surface water out.
The herring shoals dwelling on the Jutland coast banks were
literally, Pettersson says, sucked into the fjords of the Swedish
west coast as by an enormous vacuum pump. This inflow,
Pettersson points out, takes place periodically and coincides
with the phases of the moon (see Fig. 513). One wave, on
the 15th of November, occurred at full moon, when the moon
was nearest to the earth (perigee), another wave on the 28th
of November occurred at new moon, when the moon was
farthest from the earth (apogee). Coinciding with the last
wave the herring shoals appeared, and between the 23rd and
24th of November 24,000 barrels of herring were taken.
7i6 DEPTHS OF THE OCEAN
Pettersson's observations made by the aid of his ingenious
self-registering appHances are of very great interest, but it must
be pointed out that the relations between the phases of the
moon and the waves are not very well marked. Further, it is
well known that similar oscillations in the water-layers of the
Scottish lochs are produced by the varying winds that blow
over the surface.^
Nordgaard has compiled an account recording the
months of the year when southern Atlantic fish-species are
stranded on the coasts of Norway, and has found that such
strandings generally occur from January to May. On this
subject he remarks : " It is hardly accidental that so many
specimens of these pelagic deep-sea fishes arrive on the coast
during the first months of the year, during the time of the cod
fisheries (when the shoals of cod appear in order to spawn).
It is obvious that during this season especially the deeper
layers move towards the land, probably as a compensation
current in deep water caused by the off-shore winds forcing
the surface layers out to sea." If we look at Fig. 509, show-
ing the annual changes of temperature in the sea off western
Norway, we shall see that towards the new year and during
spring a marked drop in temperature occurs in the surface
layers. We must take it for granted that the organisms con-
sequently tend to move towards the surface, the specific gravity
and viscosity of the water increasing enormously compared
with the conditions in warmer seasons.
These conditions and their influence upon animal life are
to a great extent mere guess-work, but they open up a vast
field for future oceanic research.
Nutrition
Sir John Murray divides marine deposits (see p. 161) into
two main groups: (i) Terrigeno2LS deposits formed in deep
and shallow water close to the land masses ; and (2) Pelagic
deposits formed in deep water remote from land.
Corresponding to this division we may define the nourish-
ment of marine animal life as derived from two main sources :
(i) Organic detritus carried into the sea from land or formed by
disintegration of the plants of the coast belt and the animals
living upon them ; and (2) Pelagic plants.
As a third source, Putter has suggested the organic com-
1 See Murray, Scott. Geogr. Mag., vol. iv. p. 345, 1888, and vol. xiii. p. i, 1897.
GENERAL BIOLOGY 717
pounds dissolved in sea-water, which must be formed, however,
when all is told, either by dissolution of the detritus or as
excreta from living organisms.
It has long been recognised that the dust-like detritus plays Organic
an important part in the nourishment of certain bottom-animals ^^'"^^1^-
(see Chapter VII. and the reference to Murray's "mud-line").
Investigations on the food of the oyster by Redeke and
American investigators have proved that detritus forms the
main contents of its stomach and intestines. Zoologists know
that great numbers of bottom forms (holothurians, worms,
and many others) are " mud-eaters," which live by passing
the soft mud of the sea-bottom through their digestive tract.
Lohmann and Rauschenplatt have lately shown that detritus
also plays an important part in the nourishment of pelagic
forms. Our ideas on this subject have recently been
advanced by the systematic investigations of C. G. J. Petersen.^
In the Limfjord Petersen studied how detritus was formed
by the disintegration of the dead plants along the coast, how it
was found suspended in the water, and finally settled on the
bottom as a soft layer 2 or 3 millimetres in thickness. In every
respect this fine mud was similar to that found in the digestive
tract of mussels and other animals. Petersen has proved this
phenomenon to be of general importance in all the waters
examined by him, and it will be necessary to examine the
conditions in various areas of the sea in a very extensive way
before we can arrive at a more perfect knowledge as to the
nutrition of animals. In the open ocean conditions are still
practically unexplored, and I will here only draw attention to
some points worthy of examination in the future.
How far out to sea is the organic detritus carried ?
During our Atlantic cruise Gran was continually looking for
detritus, centrifuging water- samples for this purpose, but as
he tells us in Chapter VI. only insignificant quantities were
found in the open ocean. If we may draw conclusions from
bottom -deposits like Blue mud, there are vast differences in
various areas of the ocean. In Chapters IV. and VII. we
have seen that the terrigenous deposits on the eastern side
of the Atlantic are limited to the African and European coast
banks, while on the western side they extend far into the
ocean beyond the coast banks of America (see Map IV.).
These facts may obviously be explained as being due to
currents (see current-chart, Fig. 508), which on the western side
^ Report of the Danish Biol. Statioti, No. XX. Copenhagen, 191 1.
7i8
DEPTHS OF THE OCEAN
run off-shore and on the eastern side run towards the land.
The distribution of the Sargasso weed also furnishes evidence,
for, wherever found it has actually been derived from the shore,
and, as we know, the Sargasso weed covers a vast area of the
western part of the Atlantic. Even the Sargasso weed must
become detritus. Hensen has shown that the tufts of this weed
gradually become overgrown with heavy bryozoa, which causes
them to sink, and then they are gradually disintegrated, being
transformed into detritus while sinking, and furnishing nourish-
ment for the animals in deep water. During the cruise of the
" Michael Sars " the deep waters of the western part of the
ocean proved to contain a far more abundant animal life than
the corresponding depths in the eastern part. We have seen
from Chapter IX. that by far the greater number of the
Pteropoda collected, about 3500 or 4000 specimens, were
taken in the south-western portion of our track, that is in the
Sargasso Sea, and the same remark applies to the pelagic
fishes, for instance Cy clot hone 7nicrodon. In giving some
figures in support of this, I wish to point out that these figures
must only be looked upon as relative values, and are therefore
only suited for a comparison between different localities.
I choose for comparison two stations east of the Sargasso
Sea, between the Canaries and the Azores (Stations 42 and 49),
and two stations in the Sargasso Sea (Stations 62 and 64), and
indicate the number of specimens taken at corresponding depths
with the same fishing gear : —
East of the Sargasso Sea.
In the Sargasso Sea.
Station 42.
Station 49.
Station 62.
Station 64.
Young - fish trawl,
1000 metres
Large tow-net, 1500
metres
6
9
8
14
90
76
448
332
In northern boreal waters, like the Norwegian Sea, the
water-layers of the coast banks cover nearly the whole of the
deep area ; we know this because many of the animals which
are born on the coast banks are found to have drifted out into
the waters above the deep area. Are also the detritus and
dissolved substances carried so far from the shore ? How far
is the abundant life peculiar to boreal waters due to supplies
GENERAL BIOLOGY 719
of nutriment derived from the shore ? These questions must
be left to future research.
In Chapter VI. Gran has described the vertical distribution Pelagic
of pelagic plants. In the open Atlantic he found that the p^^^^^^-
great majority of the plants occur in depths between 10 and 50
metres ; at 75 metres the numbers decrease to about one-half,
and at 100 metres to one-tenth, of the numbers found in the
upper layers. The whole of the animal life in the oceans,
5000 or 6000 metres deep, thus mainly depends on the pelagic
plants suspended in the uppermost 100 metres of water. The
animals frequenting this upper layer feed partly on plants,
partly on other animals, while in deeper water only animal
food is available, besides the dead plants and animals sinking
from the surface. Nutrition in the upper " plant "-region must
therefore be different from that in the deeper layers.
Many animals of the plant-region are typical plant-eaters,
and their bodies are organised for this purpose. This is
especially the case as regards appendicularians and salpse, the
foremost part of their digestive tract, the so-called branchial sac,
being provided with a grating of the finest and most delicate
structure, retaining even the most minute plants (the cocco-litho-
phoridse). Many of these minute plant- forms were indeed first
discovered by examining the stomach-contents of salpse (Stein,
Sir John Murray, Lohmann), and during the Atlantic cruise- of
the " Michael Sars " Gran also collected salpae in order to secure
material for comparison with our tow-net captures of minute plants.
The coelenterates (medusae, ctenophores, siphonophores) are
well adapted to capture minute plants by the aid of their tentacles,
and so are the unicellular animals (foraminifera and radio-
laria) by the aid of their long thin plasm threads (pseudopodia).
The most important of all plant-eaters are, however, the small
crustaceans, particularly copepoda, which seem specially adapted
for feeding on the microplankton of the ocean. Gran has
examined the excrements of copepoda, which sink through the
water in the shape of minute sausage-like lumps, and are very
often taken in considerable quantities in the silk nets. All the
soft parts have been digested, but the shells of the plants eaten,
the calcareous shells of the coccolithophoridse, the armour of
peridinese and the silicious shells of diatoms, can be identified.
In the Norwegian Sea Gran observed that the copepoda were
present in enormous numbers just below the layers containing a
wealth of diatom plant-life, but nevertheless the excrements of
these copepoda consisted of the frustules of the diatoms. The
720
DEPTHS OF THE OCEAN
Abundance
of minute
Crustacea in
various areas
and depths.
food of copepoda in deep water has not yet, as far as I know,
been made the subject of systematic investigation, although this
point is essential to a more complete understanding of marine
biology. Nordgaard, who is describing the copepoda from our
Atlantic cruise, has at my request been kind enough to examine
the stomachs of a large number of copepoda from our deepest
hauls in the Sargasso Sea, but has not been able to find any-
thing morphologically definable in their stomach-contents. Do
these copepoda there feed on detritus formed by the dead and
disintegrating organisms falling from the surface of the ocean ?
Along with other small animals (foraminifera, radiolaria,
sagittidae), the copepoda and other Crustacea form the main
food -supply for the majority of the somewhat larger oceanic
animals. Thus the stomach-contents of the pteropods Clio
falcata and Lmiacina helicoides taken at depths between 500
and 1500 metres consisted of foraminifera and radiolaria. In
the stomachs of large prawns, Acanthephyra purpurea and
A. multispma taken below 500 metres, Sund found the remains of
copepoda, sagittidae, and fragments of minute fishes (Cyclotkone).
Koefoed has examined numerous stomachs of Cyclotho7ie without
finding any contents, but their guts contained organic remains,
mainly the jaws of minute crustaceans. The stomach of the
fish Gonostoma grande from deep water was found to contain a
mysid [E?t-copia austi^alis), and in Gonostoma rhodadenia were
found five euphausidse i^Nematosceiis, Siylockeiron, Eiphausia,
Thysanopoda), seven sagittae, five copepoda (Btuhceta, Buca/amis),
and some lumps consisting of radiolaria.
Many of the pelagic fishes are extremely voracious.
Repeatedly other fishes have been found in their stomachs of
a size nearly equal to that of the devourer. Thus a small
Astronesthes niger had a scopelid in its stomach, and a
Chauliodus had eaten a Stomias boa. The record for voracity
is held by the remarkable Cliiasmodus niger (of which we
took three specimens in the Atlantic), which is known to
swallow fishes several times its own size. Fig. 514 shows a
specimen with only slightly extended abdomen; Fig. 515
shows a specimen that has swallowed a fish much larger than
itself, and most strangely one of the same species.
Generally speaking, the very minute animals, especially the
minute Crustacea, play an exceedingly important part as
nourishment for other and larger animals. These minute
crustaceans are constantly taken in the fine silk tow-nets, and
in nets with a somewhat larger mesh they constitute the bulk
GENERAL BIOLOGY
721
of the catches. If we compare such catches at different depths
and in different waters, we generally get a fair idea of the relative
amount of nourishment present, and it may be of interest to
examine some catches of this kind from the Atlantic and the
Fig, 514.
Chiasmodus ?iiger, Johns. Nat. size, 9.5 cm. From Station 52.
Norwegian Sea, where the " Michael Sars " employed the same
silk hoop-nets, i metre in diameter, with J millimetre mesh.
To commence with, we will consider the same hauls from the
*>
Fig. 515.
Chiasmodus niger, Johns. This specimen had swallowed a larger specimen of the same species.
Nat. size, 5.7 cm. From Station 56.
Atlantic which in Chapter IX. we have discussed from a
systematic point of view, noting the volume of small pelagic
animals captured, compared with the temperature, specific
gravity, and viscosity of the water at corresponding depths.
722 DEPTHS OF THE OCEAN chap.
During the first cruise of the "Michael Sars " in the
Norwegian Sea in 1900 I was convinced that in deep water a
great quantity of food would accumulate wherever a rise in the
specific gravity occurs, and where, consequently, all sinking
bodies either stop or have their sinking velocity reduced,
forming as it were a "bottom" in mid-water. In my report on
the cruise^ I mentioned the matter, and the following observa-
tions appear to confirm this hypothesis.
In the Sargasso Sea series of hauls with closing-nets were
taken at Stations 50 and 63, the net employed at Station 50
St 63.
GtZS2i ^ 5 J ;> ,g 9 26o ; z i i, s h 1 a .9 27o / z j .', 5 t, y s .9 28o
f.^^yix-kr ^p°/9°/^° /r /(,'■/$-■ iJ,- li- iz" >/" 10' 9" e° 7° 0° ■?' &' 3°
1>
\
X,
"\
Fig. 516.— Curves of Temperature {t") and Specific Gravity (a,), Station 63.
(Sargasso Sea.)
being i metre in diameter, and at Station 63 half a metre in
diameter, made of very fine silk. At Station 50 hauls from
200 to o metres gave 3 c.c, containing 22 species of Crustaceans.
500 to 200 „ 1.5 „ 22 „
1000 to 500 „ 6 „ 51 „
At Station 63 hauls from
100 to o metres gave 1.6 c.c.
200 to 100 ,, 0.5 „
500 to 200 „ 1.6 ,,
^ Hjort, Die ersle Nordmeerfahrt des norwegischen Fischereidampfers ^'■Michael Sars"
igoo, Petermann's Mitteilungen, Bd. 47, 1901.
GENERAL BIOLOGY
72.
These figures show a minimum below 100 metres, and a
maximum between 500 and 1000 metres. Comparing this with
the curves for specific gravity at these two stations (Figs. 516
and 517), we notice a pronounced rise in specific gravity in the
upper 100 metres (the plant region), followed by a very slow
rise and then a rapid rise towards 1000 metres, beyond which
the specific gravity becomes very uniform. The temperature,
which greatly influences the viscosity, falls gradually, correspond-
ing to the rise in specific gravity, and in consequence the
viscosity increases towards deep water.
t" = ZO' 19° 18" IT
St SO
S 9Z7o
li' IZ" 11" ,
Fig. 517. — Curves of Temperature (/°) and Specific Gravity (o-,), Station 50.
(South of the Azores.)
Off" the banks of Newfoundland we took the following series
at Station 80 :
235 to o metres gave 5 c.c. containing 16 species of Crustaceans.
525 to 235 „ 45 „ 27
950 to 525 „ 28 „ 34
The curve of specific gravity here (see Fig. 518) is
essentially different from those in the Sargasso Sea, for a rapid
rise occurs down to about 500 metres, beyond which the specific
gravity becomes practically uniform, and at this station no
minimum quantity of organisms is noticeable between 500 and
200 metres, but on the contrary a considerable rise.
724
DEPTHS OF THE OCEAN
The abundant plankton peculiar to boreal waters in summer
(August) apparently accumulates in those layers where the
highest specific gravity occurs, the volume thence decreasing in
the deep uniform layers below 500 metres. A series of hauls
taken close to the Wy ville Thomson Ridge in the southern part
of the Norwegian Sea at Station 113 gave the following
results : —
100 to o metres gave 10 c.c. containing
300 to 100 ,, 5 „
500 to 300 „ 12 ,,
1000 to 500 „ 140
species of Crustaceans.
5Ldo
.5 6 r £
90 a- yo 60 5»
9 n.o .1 J. Ji
2° /»
^ .5 ^ .7 .G.
'N.
\
Fig. 518. — Curves of Temperature (t°) and
Specific Gravity (cr,), Station 8o.
(Off Newfoundland Bank.)
The curve for specific gravity shows here (see Fig, 519) a
rapid rise down to 100 metres, then a slow rise down to
about 300 metres, and finally a rapid rise down to about 600 or
700 metres. A pronounced minimum in the volume of Crustacea
occurs between 300 and 100 metres, and an enormous increase
is found between 1000 and 500 metres, where the volume is
fifty times larger than the volume in the surface layers of the
Sargasso Sea.
In my opinion these facts prove the correctness of the
hypothesis that minute pelagic Crustacea (and consequently
nourishment suitable for larger organisms) tend to accumulate
at those depths where a pronounced rise in the specific gravity
GENERAL BIOLOGY 725
and viscosity occurs. Especially convincing is the fact that
although this rise occurs at very different depths in the three
localities mentioned, the increase in the volume of small
organisms captured in the nets in every case coincides with the
rise in the specific gravity.
An important point for our conception of the animal life of
the Atlantic is that the greatest volume of pelagic Crustacea has
never been found in the upper 100 or 200 metres, where the
production of minute plants takes place ; the great majority of
small pelagic Crustacea live everywhere in the deeper inter-
mediate layers. The examples cited above show further that
the volume of organisms captured differs greatly in correspond-
ing depths at the different stations, being strikingly small
in the Sargasso Sea com-
pared with the boreal waters
off Newfoundland and the
southern part of the Nor-
wegian Sea.
All these investigations
indicate the quantity of
organisms present only at
the moment of examination.
We cannot, from our results,
conclude that similar condi-
tions always prevail, nor that Fig. 519.— Curves of temperature (O and
the a^^reaate quantities of Specific gravity {<r,), station 113.
r 1 ^ • *i I'll- 1 (North of Wyville Thomson Ridtre.)
iood-animals which live and
die during the year are proportionate to the quantities found
at a given moment in the different localities. The quantity
of food-animals changes first according to seasons and second
according to the intensity of production, but very little is
known about these two Important factors. Only in restricted
areas of the coastal waters have attempts been made to
investigate these questions systematically at different seasons,
and at present we can only compare the conditions found in
different localities. Such comparisons have led us to recognise
a vast difference between boreal and subtropical conditions,
which we may with advantage consider separately.
The boreal waters are mainly characterised by great seasonal Seasonal
changes. We have previously noted the great seasonal abundance [If^
changes in temperature principally in the surface layers where minute
pelagic plants are produced. A no less important part is ""^^^^ea.
played by the changes in light intensity from summer to winter
t, -
2(xa sZTo ./ z 5 ." i 6
/?» //" 10- 9° 8° T 6° 5' If"
7 « 9 l&fO ,
JO x" r o'-^i^
100
500
I
726 DEPTHS OF THE OCEAN
and from winter to summer. Any one who has examined
the quantity of organisms obtainable in silk nets at different
seasons in boreal waters will know the magnitude of these
changes. I may cite some of my own results from the coast
waters of Norway.
During my winter cruises in the sea between northern
Norway and Spitzbergen and 240 miles west of Tromso, the
sea was everywhere found to be so poor in organisms from the
surface down to 100 fathoms that we had to drag our nets for i|-
or 2 hours before we perceived any organisms at all on the silk
cloth of the nets. In February I made a haul in the Westfjord
(Lofoten) with an 8-feet hoop-net from 200 metres to the
surface, and caught only 380 specimens of Calanus Jinmarchicus,
although perhaps 1000 tons of water were filtered by
the net. On the loth of April a haul was made on the
bank off Tromso (Svendsgrund), with the same net and from
100 metres to the surface, when 2356 specimens of Ca/anus
were taken. Another haul yielded 16,420 specimens of
Calanus, and a third about one litre of Calanus. This obvious
increase in their numbers continued during spring, and on the
ist of June in the Altenfjord a lo-minutes' haul with a i-metre
net at the surface yielded so many individuals of Calamts, that
their weight, after squeezing off the water, amounted to o*8
kilogram, — a weight corresponding to at least two millions of
individuals. In July some hauls with the 8-feet net were made
in the Norwegian Sea, generally from 200 metres to the
surface, and as a rule 200 or 250 c.c. of Calarms were taken,
mainly consisting of Calamts finmarchiais. These hauls
indicate the characteristic features of the occurrence of minute
crustaceans in boreal waters : the poverty of winter, the
abundance of summer.
Gran and Damas have continued these investigations during
the cruises of the " Michael Sars," at the same time taking up
the study of the life-history of Calamts JimnarcJiiats. Gran
arrived at the conclusion, now confirmed by more recent
investigations, that the life-cycle of this species is annual.
During winter only adult animals are met with. They breed
in spring, and the young pass through five larval stages ; in the
sixth stage they assume the shape of the adults. From a detailed
study of the material collected in the nets Damas attempted to
draw a chart showing the spawning places, arriving at the con-
clusion that spawning does not take place to any important extent
in the fjords, nor on the coast banks, but principally above the
GENERAL BIOLOGY 727
continental slopes of the Norwegian Sea. From these localities
the young stages spread over the whole sea, including the coast
banks and the fjords of Norway. During summer only young
individuals are met with, immediately recognizable by the
presence of large oil-globules. These minute calani constitute
the main nourishment upon which more or less directly the
animal life of the Norwegian Sea depends. Even the enormous
whalebone whales feed on calani. During the last months of
the year the number of calani decreases enormously, and in
winter only a few adult individuals remain.
In Chapter VI. Gran gives an account of Lohmann's
attempts at calculating the relation between the increment in
pelagic plants and the consumption of plants by animals in the
fjords at Kiel during the course of a year. According to
Lohmann's calculations the volume of plants increases daily by
30 per cent, which increase may be used up by animals without
endangering the existence of the plant-stock. Copepoda and
other multicellular animals are supposed to need a daily supply
of food equivalent to about one-tenth of their own weight.
Starting from these assumptions Lohmann attempts to calculate
the relation between production and consumption in the course
of the year, and arrives at the conclusion that there is generally
a surplus of plants except in the winter. For details I refer to
the table on p. 384, recording the daily increment of various
food producers during the year, which varies greatly from summer
to winter, the relation amounting sometimes to 35 : i.
In tropical and subtropical waters no seasonal changes of Conditions
this kind appear to take place. At least all the tow-nettings ^l^'^""^^^
taken in the tropics by various expeditions have always yielded
remarkably uniform catches in the upper layers, which are the
ones most thoroughly examined, these catches being very small
compared with similar catches during summer in boreal waters.
As instances of this I may mention that the closing-nets of the
" Michael Sars " when hauled from 200 metres to the surface in
the Sargasso Sea yielded on the average 3 c.c. of plankton,
while in the Norwegian Sea from 85 to 225 c.c. were obtained
in numerous similar hauls.^ Similar results were obtained
during the German Plankton Expedition.
It is, however, at present impossible to form any idea
whether the volumes thus obtained really tell us anything what-
ever about the annual production. First of all in boreal waters
we have to deal with the enormous seasonal changes. Secondly,
^ Damas and Koefoed, /oc. cit.
728 DEPTHS OF THE OCEAN
we know nothing whatever about the "daily increment" in the
producing organisms of the open ocean, and therefore the
futility of every attempt at comparison is evident. The small
volume of plants and animals peculiar to the upper strata of the
warm regions of the ocean cannot, in consequence, justify the
conclusion that the production is small. The abundance of
animals found in the deeper layers of the open ocean seems to
indicate rapid production associated with rapid consumption in
the upper plant region of the sea.
Although it is as yet quite impossible to form an opinion on
the absolute magnitude of the production in certain regions, it
has been supposed that the relative amount of nutriment
contained in various waters might be compared. As mentioned
by Gran on pp. 367-381, botanists are of opinion that in the open
ocean, far from land, certain of the nutritive substances essential to
plant life, especially nitrogen, are present in very small quantities
(the minimum of Liebig), and consequently the plants cannot
develop as profusely as they otherwise would do. Pelagic
plant life draws its principal supply of dissolved or undissolved
nitrogen either from the coasts (see remarks on detritus), or
from localities where cold and warm currents meet. In these
latter localities the conditions may suddenly become favourable
for the development of life, just as development in boreal
waters begins in spring, when the rays of the sun raise the
temperature of the surface water. The organic substances
contained in the cold waters become transformed into inorganic
salts through the action of bacteria, and these salts are used by
the microscopic plants to build up new protoplasm. Murray
and Irvine^ first drew attention to the importance of this
process in the ocean, which plays a great part wherever large
sheets of cold and warm water are mixed,-
The boreal waters should, accordingly, present favourable
conditions for developing an abundant animal life during the
warm season, the coast waters carrying detritus spread out
over the whole oceanic area, while arctic currents mix with
the warm Atlantic Gulf Stream, for instance in the Barentz
Sea, north and east of Iceland, and off the coast banks of
Labrador and Newfoundland.
^ " On Coral Reefs and other Carbonate of Lime Formations in Modern Seas," Proc. Roy. Soc.
Edin., vol. xvii., 1890.
2 Similar ideas have been expressed by Nansen, "The Oceanography of the North Polar
Basin," N'orwegian North Polar Expedition, Christiania, 1902.
GENERAL BIOLOGY
729
Propagation
During autumn and the last months of the year thermal
conditions alter greatly in boreal waters, high temperatures
retreating from the surface down to 200 or 300 metres (see
Fig. 509). At the same time the sexual organs develop in most
boreal food fishes : the cod family, the herrings, the tiat-fishes
and others, and during the three or four first months of the
year they spawn. Most
of these edible fishes
possess large ovaries
containing enormous
numbers of eggs, the
cod, for instance, having
apparently on the aver-
age no less than five
million eggs.
Late in the 'sixties of Develop-
last century, G. O. Sars ZT^T'
commenced his investi-
gations on the famous
cod fisheries in the
Lofoten Islands. He
found that the eggs of
the cod were pelagic,
floating in the surface
layers of the sea, and
he carefully studied the
development of these
eggs, making a number
of excellent drawings,
which I regret to say
have never been pub-
lished. These original
drawings foreshadow much of the knowledge gained in recent
years on the early development of the cod, and I consider it
interesting to reproduce some of them illustrating certain
stages. The characters distinguishing these stages are just
as law-bound as those of the adult individuals. One stage
(see Fig. 520) is characterised by dark transverse bars of
black pigment, which subsequently dissolve into fine longi-
tudinal bands, following the dorsal and ventral side of the
body, a fine stripe running along the lateral line. Later on the
O. Saks.
730
DEPTHS OF THE OCEAN
^-^^^
::^
8
Fig. 520.
Development of the cod (Gadus callarias) from the egg to the young-fish stage.
(From drawings by G. O. Sars. )
(General biology
731
pigment is arranged in a chequered colour pattern, resembling
the squares of a chess-board. So regular and characteristic are
these stages that, once knowing them, we can separate a young
cod from every other young fish, and define its stage of develop-
ment or even its age.
Since Sars discovered the eggs of the cod to be pelagic, a
great many other species have been found to possess floating
eggs and larvae, for example all the cod-species and flat-fishes,
the sprat, the mackerel, and many others. A voluminous
literature recording the investigations has accumulated, Agassiz,
Fig. 521.
Diagrammatic figures to show the arrangement of the postanal pigment in the eariiest stages of
CaJiis ca//arias, G. virens, G. pollachius. (After Schmidt. )
Ehrenbaum, Heincke, Hensen, Holt, M'Intosh, Masterman,
Petersen, and Schmidt having made valuable contributions
to our knowledge of the eggs and larvae of various fishes.^
From Schmidt - I reproduce some outline drawings (see Fig. 521)
of the pigment arrangement in a corresponding larval stage of
three closely related cod-species, viz. Gadus calla7^ias, G. virens,
and G. pollachius (the cod, saithe, and pollack). Although
these larvae closely resemble each other, the arrangement of
the pigment is different.
^ Ehrenbaum gives an excellent summary in " Eier und Larven von Fischen," Nord.
riaiiktoii, Lfg. 4, 1905, Lfg. 10, 1909.
- Schmidt, he. cit.
732 DEPTHS OF THE OCEAN
This power of distinguishing the different species in early
stages has been of great advantage to oceanography. By
securing the eggs and larvae floating in the surface waters, we
can decide what species spawn in a definite area. We capture
in our silk nets a profusion of different eggs and larvse, and
can with certain limitations separate them as belonging to
various species, just as we assort the catches of adult fishes
Spawning from 3. haul with the trawl. The spawning area of a species
can thus be determined by merely taking numerous tow-nettings,
and ascertaining the presence or absence of the eggs belonging
to the species in question.
To catch the adult spawners is very often difficult, and takes
a long time. The floating eggs can, on the other hand, be
taken with the greatest ease, and the simple appliance of the
tow-net furnishes an excellent means of ascertaining where the
fishes spawn, for most species remain some time underneath
the recently spawned eggs. In April 1901- I followed up this
reasoning on the coast banks off northern Norway, and
succeeded in finding enormous shoals of cod on certain
banks, where no fishing was carried on, and where, as a con-
sequence of our discovery, millions of cod were afterwards
taken. ^
Stimulated by this experience I advised the International
Council for the Study of the Sea to effect a systematic survey
of the spawning areas of the cod family. My proposals were
adopted, and an enormous amount of material relating to the
natural history of the cod family was accumulated, thanks to
the exertions of those on board the Danish, Belgian, English,
Scottish, Dutch, Norwegian, Swedish, and German investigation
steamers.
The Danish steamer " Thor," under the leadership of
Schmidt, investigated certain parts of the Atlantic and the
waters round Iceland. The Norwegian steamer " Michael
Sars" examined the Norwegian Sea and the northern portion of
the North Sea, while the steamers of the other countries worked
mainly in the North Sea. The results obtained through this
organisation of the work proved that even closely related
species presented certain peculiarities as regards the situation
and extent of their spawning places," as shown in the following
table : —
^ Fiskeri og Hvalfangst i det nordUge Norge, Bergen, iqo2.
^ "Rapport sur les travaux de la commission A dans la periode 1902-1907," Rapports et
Proces verba iix dit Conseil iuteniatioiial, vol. x. Copenhague, 1909.
GENERAL BIOLOGY
7Z2,
I. Spawning in the Atlantic, in the
North Sea, and in the Norwegian
Sea.
A. On coast banks in depths less than
100 metres.
Gadus vierlangiis, Optimum 20 to 60 metres.
„ callarias,^ ,, 40 to 80 ,,
,, cBgleJinus, ,, beyond 60 ,,
,, esi7iarki, ,, ,, 80 ,,
B. On the slopes of the coast banks.
Molva molva, Optimum 60 to 200 metres.
Gadus virens, ,, I GO to 200 ,,
C. On the edge of the coast banks.
Brosmius brosine, Optimum 100 to 500 metres.
II. Spawning entirely, or almost
entirely, in the Atlantic.
A. On coast banks beyond 100 metres.
Gadus liiscus.
,, mi nut us,
„ pollac hilts.
B. On the slopes towards the edge.
Alerluccius vulgaris. Opt. 100 to 200 metres.
C. On the edge of the coast banks.
Gadiculus argenteus,^^
Gadus poutassou, \ Optimum from
Molva byrkelange,^ j" 200 to 1000 metres.
,, elongata j
floating eggs.
From the point of view of general biology it is interesting
to note from this table that species, which in shape and general
anatomy are very similar, present such pronounced differences
as to their habitat during this most important process of life
(see the chart, Fig. 522, showing the spawning area of the three
ling species).
C. G. J. Petersen" was one of the first to draw attention Effect of
to the influence exerted by currents on pelagic eggs. After '^^^"■entson
his investigations in the Lesser Belt (Faenoe Sund) he sums
up as follows : " It is one of the facts that have astonished
me most during these researches that the fry of pelagic eggs,
which were sometimes found in such huge numbers in
Faenoe Sund, was not hatched there, or at any rate was
only to be found there quite exceptionally. This condition did
not only apply to the cod, but indeed to all species which
possess floating eggs, in contrast to the fishes which deposit
their eggs on the bottom." It has proved very important to
investigate the drift of pelagic eggs, and this study has yielded
important results regarding the different species. The drift of
the eggs depends on physical as well as biological condi-
tions. The direction and velocity of the currents, the tem-
perature, the duration of the hatching and development, the
actual duration of the pelagic life which varies in different
species, all these are important points. Finally, the specific
gravity of the eggs and larvae is of great importance in
determining the depth at which they float. From my investiga-
tions on the distribution of cod eggs, larvae, and pelagic fry in
1 Also spawn in the Norwegian fjords. ^ Report of the Danish Biol. Station, 1893.
734
DEPTHS OF THE OCEAN
northern Norway I reproduce Fig. 523, in which the different
curves denote : —
I. The outer limit of pelagic cod eggs during the spring of 1901.
II. „ minute larvae and young, June- July, 1901.
III. „ large pelagic fry, August 1900.
Fig. 522. — Spawning Regions of the three Species of the genus Molva.
Vertical lines, Molva byrkelange ; horizontal lines and black portions, .1/. molva ; dots,
M. elongata.
(From International Reports, vol. x.)
In northern Norway there is plainly a movement along the
coast and away from land. During development the minute fish
are carried hundreds of miles away from the spawning places.
GENERAL BIOLOGY
735
The direction of the movement will, of course, depend on the
currents, and on other conditions peculiar to various localities.
In the district of Romsdal Damas made some excellent
investigations on board the " Michael Sars," and ascertained
that spawning took place almost exclusively on the coast
banks, that in the fjords being quite insignificant (see Fig. 524).
The young fry, however, were later found in vast quantities in
the fjords, having been carried in by currents. Schmidt has
Fig. 523.— Distribution of Pelagic Eggs and Young-Fish of the Cod at
different seasons.
I. Outer limit of pelagic eggs in the spawning time, January to April 1901.
II. Outer limit of pelagic young-fish, June to July 1901.
HI. Outer limit of pelagic young-fish, August to September 1900.
given an account of the spawning of different cod-species off
Iceland, the occurrence of pelagic eggs and their subsequent
fate (see Fig. 525). Most cod species and flat-fishes spawn on
the south and south-west coasts of Iceland, the northern and
north-eastern sides of the island being encircled by cold waters
during winter and spring. The freshly spawned eggs drift
from the south to the west coast, and farther to the north and
east coasts, the current running in this direction. The duration
of the pelagic stage is, however, different in different species of
the cod family ; their spawning seasons also differ. As a con-
73^
DEPTHS OF THE OCEAN
sequence the distribution of the first bottom-stages is different,
for instance, in cod and saithe, as shown in Fig. 525. The
young saithe, having a comparatively short pelagic life, occur
mainly on the south and west coasts, and only to a small extent
on the north and east coasts. The eggs and fry of the cod are
pelagic for a longer period, and consequently the majority of
them drift round to the north and east coasts.
Fig. 524. — Distribution of Eggs and Larv^ of Gadoids in the Romsdal District.
Dots denote that less than 500 eggs were taken ; small circles, that 500 to 10,000 eggs were
taken ; large circles, that 10,000 to 100,000 eggs were taken (March to April 1906) — all in
hauls of five minutes' duration. Small triangles denote that less than 100 pelagic fry were
taken, large triangles, that 100 to 10,000 pelagic fry were taken per hour in May to June 1906.
(From Damas' investigations with the " Michael Sars.")
When currents run off-shore, the direction of the current
and the extent of the influence of the coast-water in the open
ocean can be ascertained by studying the distribution of
organisms born on the coast banks. As we have seen, this
study is also very important for our ideas as to the amount of
nutriment carried from the land to the open ocean. Fish fry
are actually such current indicators, and in the Norwegian Sea
they are accompanied by stinging medusae {Cyanca capillata),
GENERAL BIOLOGY
m
which have also a bottom stage on the coast banks. In August
1900 their distribution was identical with that of the pelagic
cod fry, and was limited by curve III. in chart, Fig. 523.
Similar instances might be quoted in profusion, especially from
recent Danish and Norwegian investigations. Of special
interest is the great number of observations of larvae and young
fish drifting from the Atlantic coast banks off the west coast of
Scotland into the North Sea and the Norwegian Sea (compare
the drift of Salpse).
We will now proceed to review our knowledge as to the
Fig. 525.— Relative numbers of the earliest Bottom-Stages of Gadus virens
AND G. CALLARIAS AROUND ICELAND IN THE SUMMER OF I904. (P^rom Schmidt.)
conditions of the Atlantic, referring, for want of space, mainly
to our own investigations.
It is not an easy matter to examine the reproduction of
animals in the open ocean. Very few studies have, there-
fore, been made on the development of the oceanic fishes,
and little is known as to their characters in early stages.
Valuable information has been gathered and drawings have been
made, especially by Giinther and by Danish naturalists, Lutken
and others, but complete series, showing the development of the
species, are only available for a very limited number of species.
Every expedition must, therefore, in the present state of our
knowledge, make a laborious systematic study of the collections
7Z^ DEPTHS OF THE OCEAN chap.
brought home. As regards our own expedition we have as
yet been able to accomplish only a small part of this work,
and at present I am unable to pass a definite opinion on our
material as a whole, nor to say what this material does not
contain.
Spawning Do our Collections of fish eggs and fry from the Atlantic
indicate any definite spawning seasons in the Atlantic, as there
are in the Norwegian Sea? It is generally known that in the
tropics many animals propagate at all times of the year. Thus
Carl Semper writes as follows : " During my stay in the
Philippines nothing struck me as being more peculiar than the
seasons.
Fig. 526.
Argyropelecus hemigymnus, Cocco. Nat. size, 3.4 cm.
evident lack of periodicity in the life of the animals, peculiar
even to insects, land mollusca, and other terrestrial animals.
I could always find eggs, larvae, and adult individuals of a
species at the same time, during winter as well as in summer."
It is quite evident that a short voyage in a steamer, passing
over enormous stretches of ocean in the course of a few
days, offers no opportunity of studying the conditions of
propagation all the year round. I can only point out how
desirable it is that the Atlantic should be examined at all
seasons of the year, for only by this means can the conditions
be fully understood.
Although we could effect no reliable quantitative analysis, it
struck me on our cruise that the number of fish larvae and fry
GENERAL BIOLOGY
739
seemed far to exceed that of the pelagic fish eggs ; this also appears
to have been the case with the catches of ^
the German Plankton Expedition, but these
catches were very small. The scarcity of
fish eggs and the abundance of pelagic fish
fry might appear to indicate a continuous
production of rapidly hatching eggs, the
larval and post-larval stages being of much
longer duration, but a study of the ovaries
of the adult fishes does not favour this sup-
position. In Cyclothone, for instance, the
eggs seem to be equally developed in every
portion of the ovary, and to ripen through-
out the entire length of the ovary at the
same time. During our cruise the ovaries
were found to be ripest at Stations 53 and
64 on the southern section.
Any observer previously acquainted only
with the spawning of large boreal fishes
must be strongly impressed by the appear-
ance of the minute, sexually mature, oceanic
fishes. Figs. 526 to 529 represent some
ripe fish of genuine oceanic types and their
ovaries. In the laterally compressed Argy-
ropelecus hcmigyvinus (Fig. 526), the ovaries,
containing only a few hundred eggs, lie
wholly or partly above one another, and the
full-grown individual, the ovaries of which
approach ripeness, is only 3.4 cm. long.
Cyclothone signata (Fig. 527) becomes sexu-
ally mature when 3 or 3.5 cm. in length,
the aggregate number of eggs contained in
both ovaries being about 1000. Cyclothone
microdon (Fig. 528), on the whole a larger
species, becomes mature when about 6 cm.
in length, the ovaries containing a total of
about 10,000 eggs. A specimen of Photo-
stoniias guernei 10.8 cm. in length had,
according to Collett, about 400 eggs in
each ovary. Gonostoma grande had, accord-
ing to Collett, 2798 eggs. On the other
hand, the larger pelagic fishes from deep water, like Gastro-
stonius bairdii (see Fig. 529), have many eggs, but they
Fig. 527.
Cyclothone signata, Garm.
Nat. size, 3.5 cm.
740
DEPTHS OF THE OCEAN
are very small (according to Gill and Ryder 0.7 mm. in
diameter).
An important question is : Where does the spawning take
place .-* I do not believe in any general vertical spawning
migration among deep - sea pelagic animals, even if the
eggs develop in the upper strata of the ocean ; the eggs
themselves must rise to the surface. If this were not so, we
Fig. 528.
Cydothonc viicrodon, Giinth. Nat. size, 6.3 cm.
should undoubtedly have taken, in the upper layers, many
more of the pelagic fishes peculiar to deep water, whereas
we took them with ripe eggs in deep water. The eggs
captured and examined by us vary greatly in size and
Size of fish appearance; Fig. 530 shows the relative size of some of
them.
lall
^^Z
ittle
than
mm. m
Fig. 529.
Gastrostomiis bairdii. Gill and Ryder. Nat. size, 76 cm.
diameter, taken between the Canaries and the Azores ; B
and C are nearly ripe eggs from Cyclothone signata and
C. microdon (0.46 and 0.56 mm. in diameter) ; D is the ^^^ of
Gastrostomus bairdii. It is interesting to compare these with
the cod &^^ (E), especially when we consider the number of
eggs produced by this fish. Cyclothone signata, the eggs of
which are perhaps only one-tenth of the volume of the cod
eggs, has only 1000 eggs compared with the five million eggs
of the cod.
GENERAL BIOLOGY
741
This great contrast in the conditions of propagation is
obviously a very characteristic feature. At this point, however,
we encounter the same difficulty met with in discussing the
reproduction of the miniate plants and food animals of the ocean,
for we are ignorant as to how often these small fishes reproduce
their kind during the year.
Figs. 531 and 532 represent the eggs of Scombresox and
Trackypterus, and show that oceanic eggs are not all small.
The large e^g of Trackypterus (2.8 mm. in diameter) was
captured at Station 52, south of the Azores, and plainly shows
that the large and remarkable Trachypteridse propagate in
Fig. 530.
A. Egg from the surface, Station 48.
B. Ovarian egg of Cyclothone signata, Garm.
C. Ovarian egg of Cyclothone niicrodon, Giinth.
D. Ovarian egg of Gastrostofnus bairdii. Gill and Ryd.
E. Egg of Gadus callarias, L.
(All^fA.)
entirely oceanic conditions. Judging from their appearance
they probably live at similar depths as Argyropelecus and the
Stomiatidse.
During the whole of our Atlantic cruise we constantly Vertical dis-
captured young fish, in fact many thousands in all. According young°fi"h.^
to their vertical distribution these young fish may be divided
into two groups. Fig. 533 shows that the majority of the 3604
young fishes examined were taken in the uppermost 150 metres
of the sea. Most of the young fishes taken in appliances used in
deeper water have, in all probability, been taken while hauling
in the gear, and nearly all the peculiar large leptocephali have
also been taken in the upper layer. But there is a certain
group of young fishes which show a maximum frequency about
742 DEPTHS OF THE OCEAN
300 metres, mainly those of the genus ArgyropekciLs, the adults
Fig. 531.
Egg of Sconibresocid. Diameter, 2. 2 mm. Station 64.
of which live at these depths. A third group containing larvae
and young of Alepocephalidse has only
been taken below 500 metres. We
see from Fig, 474, p. 621, that even the
small stages of Cyclothone are found
at 300 and 500 metres.
It is interesting to note that the
young stages of pelagic fishes are sub-
ject to the same laws regarding the
development of colouring and light-
organs as the adults. In the upper-
most 150 metres the young are quite
transparent, and many of them pos-
sess light-organs in very early stages.
Early stages of Argyropelecus (see Fig. 534) develop the silvery
Fig. 532.
Egg of Trachypterus.
Diameter, 2.8 mm. Station 55
GENERAL BIOLOGY
743
sheen peculiar to the adults, and the young Alepocephalida;
(see Plate IX.) have the black pigment peculiar to the fish-
fauna of deep water. The genus Gonostonia is in this respect
specially interesting, for the young of the deepest living species,
744
DEPTHS OF THE OCEAN
Gonostoma grande (see Chapter IX. and Plate H.), occur in
deep water, and even when only 3 or 4 centimetres long are of
■'^^li
Fig. 534.
ArgyropelecHS, sp. juv. Nat. size, 0.8 cm.
i
/ '/P- [ ^
Fig. 535-
Gonostoma grande, Collett. Nat. size, 3. 7 cm.
»-
Fig. 536.
Aceratias 7nacrorhinus indicus, A. Br., juv. Nat. size, t.8 cm.
a deep black colour (see Fig. 535), while the young of Gono-
stoma demidatwn are colourless and live in the surface waters.
Fig. 536 represents the young of the dark species, Aceratias
GENERAL BIOLOGY 745
macrorhinus indictis, 1.8 cm. long. So few of these were
captured that I cannot attempt to define their vertical dis-
tribution.
These instances suffice to show that in the ocean the
vertical distribution of young stages varies greatly in different
species. Certain forms pass the whole of their life-cycle in
deep water beyond 500 metres ; others live in deep water only
in the adult stage, or at least spend their early life in the upper
water-layers ; others, again, pass the whole of their life in certain
clearly defined intermediate layers ; while others live in the
surface waters all their lives. All these groups are holopelagic
forms, but we meet with a group of genuine deep-sea fishes,
Fig. 537.
YoMr\g oi Macrurus. Nat. size, 4.6 cm. Station loi.
which in the adult stage live along the ocean-floor, while the
eggs and fry occur in the water above, at depths varying in
different species. These forms remind us of the fishes ot the
coast banks, from which they have probably been derived. Of
special interest is the fact that we found the pelagic young of
Macruridae (see Fig. 537) south of the Azores and at Station
loi, between Rockall and the west coast of Scotland, though
we have been unable to determine the species.
The majority of the young fish collected by us belong
to the biological group of transparent surface forms, but some
of the minute stages may have escaped our notice or may
have been damaged beyond recognition by the coarse cloth
employed in some of our gear. The various forms contained
in our collections have yet to be systematically examined, so
746
DEPTHS OF THE OCEAN
that I can here only with great reserve say something about
my prehminary impressions. It seems as if most of the
specimens belong to the family Scopelidse, which is repre-
sented in great num-
.-^^^ bers. Even young
stages develop light-
organs (see Fig. 538),
the arrangement and
numbers of which,
according to Brauer,
are so regular that
specific distinctions
may be based upon them. Secondly, there are many inter-
esting and peculiar forms, stalk-eyed larvse (see Fig. 539) of
Fig. 538.
Myctophum rissoi, Cocco. Nat. size,
1.5 mm.
Fig. 539.
Stalk-eyed fish larva. Nat. size, 0.9 cm.
various species being present. We have also excellent series
of perfectly transparent forms with large telescopic eyes (see
Fig. 540.
New fish, resembling Dysomma. Nat. size, 8.5 cm.
Fig. 540, representing one of a series of stages belonging to a
near ally of the genus Dysornmd).
I was very anxious during our cruise to see If the pelagic
appliances would yield any widely distributed young fish
GENERAL BIOLOGY 747
belonging to the large edible types of pelagic fishes known Geographical
' ' ' distribution
of young fish.
from the coast banks, such as the mackerel, but our preliminary <^'stribution
examination has not revealed many of these. At Station 42
one young individual belonging to the genus Scomber was
taken, but this station is not far from the Canaries. The only
young belonging to larger fishes of any economic importance
taken by us in great numbers were those of the Saury pike
{Scovibresox satLrus; see Fig. 541) and of the horse mackerel
[Caraiix trachurus). The young of both these forms have
obviously a wide distribution, occurring abundantly in the
open ocean even at the greatest possible distance from the
coast ; the eggs of Scombresox sauriis were taken in the
Sargasso Sea.
The list of pelagic fishes in Chapter IX. shows that the
majority were taken on our southern track, which agrees with
the results of previous expeditions. Liitken says in his Spolia
Fig. 541.
Scombresox saiirus, Walb. Nat. size, 6.2 cm.
Atlantica that the young of Scovibresox were the most numerous
fishes in his collections from the open Atlantic, having been
obtained from no less than ninety different localities situated
in two belts between latitudes ii° or 12 and 40" on both sides
of the equator. They are typical surface forms, distinguished
by a dark-blue colour on the back, while the sides are silvery
and mirror-like. They pass through a typical metamorphosis,
like the young of the gar-pike, the long jaws appearing only at
a more advanced age (see Fig. 542, reproduced from Liitken).
Related to Scombresox is the genus Exocoehts, which includes
the typical flying fishes; I have indicated in Chapter III. that
the young of these flying fishes (see Fig. 543) were taken by
us at several localities in various stages. Scombresox, Caranx,
and Exocoetus were thus the most important young fish belong-
ing to large surface forms taken in our Atlantic cruise. In the
chart (Fig. 544) I have indicated the quantities of young fish
captured by us in various localities, though these quantities have
in my opinion no other value than showing that great numbers
of larvae may be captured during summer in the open ocean as
748
DEPTHS OF THE OCEAN
well as near the coast banks. Our methods of capture were
not designed for the purpose of obtaining detailed information
h
Fig. 542.
a-/i, heads of Scornbresox saurus in different stages of development ; /;, a young fish. The younger
stages somewhat enlarged, the older somewhat reduced in size, a-e, heads of Belone
vulgaris. (From Liitken.)
as to the quantities occurring in different areas of the ocean ;
but in the present state of our knowledge it is very interesting
^-^S^-"
Fig. 543.
Young flying fish {Exocoetus). Nat. size, 2 cm.
to note that such large numbers of larvse and young fish really
occur all over the ocean.
Eei-iarvK I will here restrict myself to giving some information as to
(leptocephah). ^^ isolated group, viz. the larvae of the eel-like fishes (lepto-
GENERAL BIOLOGY
749
cephali). We see from Fig. 533 that about 200 individuals of
this group were taken by us, belonging to some 20 species,
and I have represented in Chapter III. some of the most
peculiar new forms. Like most Atlantic fish-larvae these forms
are difficult to classify, because our knowledge of the different
developmental stages is deficient, and also because these larvae
pass through a remarkable metamorphosis before assuming the
ultimate shape of the adult. In a number of cases we are
therefore quite ignorant as to what larval forms develop into
O < 100 Q 100 —250 p>250 Youngfish
Fig. 544. — Distribution of Young Fish.
the various known species belonging to the group of Apodes.
Our material is being examined by Einar Lea, and will prob-
ably help to clear up some of the difficulties mentioned above.
The stages belonging to Gastrostoinus bairdii (repeatedly
mentioned in Chapters III. and IX.; see Fig. '^:^, a, p. 97)
form a very interesting series, the stages a and b (see Fig. 545)
obviously being the transition stages between leptocephalus
and adult ; figure a plainly exhibits characters peculiar to the
leptocephalus as well as to the adult, and evidently forms a
more advanced stage of the transition. Another interesting
transition stage in leptocephali is exhibited by the form repre-
750
DEPTHS OF THE OCEAN
sented in Fig. 546, taken at Station 53 in 1300 metres. The
head has been much transformed, but the body still retains
much of the leptocephalous character, while on the ventral side
pigment has been developed.
Fig. 547 shows the number of leptocephali of every descrip-
tion taken during our cruise, and we see that the majority were
taken south of a line from Newfoundland past the Azores to
Fig. 545.
a. Larva of Gastrostomiis bairdii (?). Nat. size, 4 cm. Station 64.
b. Gastrosfomus bairdii. Gill and Ryd. Nat. size, 7.5 cm.
North Africa. The ones taken north of this line belong,
according to Lea, to the following species : —
Leptocephalus hrevirostris, the larva of the common eel.
Leptocephalus Congri vulgaris^ the larva of the conger eel.
Leptocephalus Synaphobranchi phinafi, the larva of Synaphobranchus pinnatiis.
Leptocephalus amphioxus, larva of an unknown species.
Transition-stage from leptocephalus to " j'oiing fish." Station 53, 1300 metn
Only one specimen of the last mentioned was taken at
Station 8i off Newfoundland, so that we may say that the three
first mentioned are the only ones observed north of the line
indicated. The majority of individuals as well as of species
were thus taken south of the Azores.
The interest attached to this peculiar distribution of the
leptocephali is greatly increased when we examine their dis-
GENERAL BIOLOGY
751
tribution according to size and consequently according to age.
We then find that the earliest stages of all the leptocephali
Fig. 547.— Number of Leptocephali of all species caught at each Station.
'*%^-.
Fig. 54S.
Young Leptocephalid, only 1.7 cm. long. Station 64.
Fig. 549.
Leptocephalus Syyiaphobranchi pinnati. Nat. size, about 5 cm. Station 62.
captured were also taken in our southern section, south of the
Azores. As mentioned in Chapter IH. we took, in the Sargasso
Sea at Station 64, very small leptocephali between i and 2 cm.
752 DEPTHS OF THE OCEAN
long (see Fig. 548). In this locality we also captured small
Fig. 550.
Stages of development of the common eel [Anguilla vulgaris, L. ). (-j*-)
(The five lower figures from Schmidt. )
stages of leptocephali belonging to the common eel and to
Sy7iaphobranchus pinnatus (see Fig, 549). North of the line from
GENERAL BIOLOGY
753
Newfoundland to the Azores and Morocco only essentially larger
(and older) stages of these species were taken, as shown in the
case of the larvae of the common eel {^Leptocephalus brevirostris).
It has long remained a mystery where the common eel spawns.
No sexually mature individual has ever been found among the
millions of eels annually captured in the waters of Europe,
nor have the eggs or minute larvae ever been found. The
autumnal migration of the eel has, however, been known for
ages. During this migration the eels leave the rivers, lakes,
and closed waters of the sea
and make for open water, and
certain naturalists, like C. G. J.
Petersen, concluded that the
eel was actually an oceanic
deep-sea species. This idea
seemed all the more obvious
as the Italian scientist Grassi
had, in the Mediterranean,
proved Leptocephalus breviros-
tris to be the larva of the eel.
A marked advance in the solu-
tion of this mysterious problem
was made when Jobs. Schmidt^
succeeded in capturing quanti-
ties of leptocephali along the
Atlantic slope of the coast
banks of western Europe.
Schmidt here found the fully
developed larvae, mostly ex-
ceeding 6 cm. in length, and all
the transition stages before the
leptocephali become " glass eels"
or elvers, which in spring invade
all the coasts of northern Europe, where they are well known.
During our cruise we found essentially smaller stages,^ down
to 4 cm., long, and we have thus been able to trace the series
shown in Fig. 550. In this figure the five lower stages are
taken from Schmidt's excellent account, the upper four stages
having been drawn from specimens captured by the " Michael
Sars," all magnified 1.4 time. The three upper figures
^ See Schmidt, " Contributions to the Life-History of the Eel," Rapports et Proces-verbaux
dii Conseil international, vol. v., 1906.
- See Hjort, " Eel-larvce from the Central North Atlantic," Nature, vol. Ixxxv. p. 104, 1910.
% C
Length
in mm.
Mumber of
JndividuQlb
AD-
0
Southern Group
21 <3ndii/idualb
AS'
0
0
50-
0
0
0
0
0
0
0
0
0
0
0
55-
0
0
0
0
0
0
60
0
65
0
0
northern firoup
0
0
ih individuals
70
0
0
0
0
0
0
0
0
0
0 0
0
75-
0
0
0
0
0
0
80-
0
85-
LarvK of the
common eel.
Fig. 551. — Measurements of Larvae of
THE Common Eel {Anguilla vulgaris).
754
DEPTHS OF THE OCEAN
represent stages prior to the fully grown leptocephalus, the five
lower figures representing stages of the " metamorphosis."
Without entering into the voluminous literature of the subject,
we may state that we found a certain regularity as regards the
geographical distribution of the various stages. Measuring the
forty-four specimens taken by the " Michael Sars," and arranging
them according to size (see Fig. 551), we see that they may be
divided into two groups, one ranging from 41 to 60 mm., and
P'iG. 552.— Number of Larv./e of the Common Eel caught during the Expedition.
O full grown larvae ; + smaller larvae.
the other exceeding 60 mm., in length. All the individuals of
the former group were taken south of the Azores as denoted
by crosses in Fig. 552, while all the specimens longer than 60
mm., i.e. the full-grown leptocephali, were taken north of the
Azores as denoted by circles.
I presume that this peculiar distribution can only be ex-
plained by supposing that the eel spawns south of the Azores,
and that the eggs and larvae pass through their early stages
there, being later carried into the northern North Atlantic and
towards the coasts of northern Europe by the Gulf Stream. If
this be correct, the majority of the young eels found in Europe
GENERAL BIOLOGY 755
have been carried there by the currents from distant spawning
grounds, just as the herrings are carried to the coasts of
northern Norway from distant spawning grounds on the
North Sea coast, or as the young cod of northern Iceland have
drifted from the south coast of that island. This result is in
itself of great importance, contributing to our knowledge of the
mysterious life-history of the eel, especially when viewed
together with similar facts pertaining to other leptocephali
(conger, Synapkobrancktis), and to forms like A7'gyropelecus,
Scopelidae, etc., which were far more numerous on our southern
than on our northern track. Just as all the tropical and warm
water forms, from foraminifera and copepoda to fishes, occur
mainly south of the 40th degree, so also is the spawning of
warm water fishes limited to this same area. I therefore
believe that the eel probably belongs to this " intermediate "
group, of which one is reminded by the large eyes and the
silvery sheen of migrating "ripe" eels (compare, for instance,
Serrivomer).
I am inclined to explain the fact that we did not obtain
many of the remarkable larvae and young fish collected by
other expeditions from the surface of the ocean, as recorded for
instance by Llitken in his Spolia Atlantica, by supposing
that we did not go far enough south. Llitken states that his
small young swordfish were all captured in tropical localities, and
in regard to the mackerel he quotes Captain Andrea thus :
"The Bonito is the oceanic fish which I have most frequently
seen and captured; it is seen everywhere in the North and South
Atlantic between the tropics, increasing in abundance as one
approaches the equator. In the Indian Ocean I have not seen
it south of lat. 26^ S. nor east of long. 70° E. In the Java Sea,
the China Sea, the Yellow Sea, and the Japan Sea I have
never observed it."
In this place I have limited my remarks to the fishes alone,
but similar results would probably appear in most animal groups
if their vertical and horizontal distribution were studied ; this
must be reserved for the future, when the material collected by
the expedition has been examined in detail.
Age and Growth
It has long been recognised that there is a certain correlation
between the size and the age of animals belonging to the same
species, and that a definite increment in size takes place within
756
DEPTHS OF THE OCEAN
Fish measure-
ments.
a certain law-bound space of time, which varies in different
species. These facts form the basis of an important branch of
marine research, which possibly more than any other will help
us to understand the life conditions of animals. The foundation
of this branch of science is mainly due to C. G. J. Petersen^
and H. Heincke.
In his first investigations Petersen aimed at defining the
age of the fish-species occurring in a restricted area, and for
this purpose he selected
a small Danish fjord,
the Holbaek fjord,
where he attempted to
capture all sizes of the
various fishes, and
measured the length of
each one ; he then
tabulated these length-
measurements for each
species in order to
study the frequency of
the various sizes. Fig.
553 shows the results
of his measurements of
the common vivipar-
ous blenny (Zoarces
vivipariis). The scale
is in Danish inches,
and each dot denotes a
specimen measured ;
males and females were
measured separately,
T. Petersen. i_ ^i_ i j
where the sexes could
be distinguished. I quote Petersen's description of this graphic
representation : " If we now consider the females, we undeni-
ably find remarkably few of a length between 8 and lo inches ;
also there is a marked gap between the largest of the fry and
the smallest females. Something similar is seen though less
plainly in the males. The latter are, however, too few to let
the gaps appear quite plainly. Alternating with these gaps
certain sizes occur as it were in heaps, where many fish have
almost the same length. The blennies may, to put it shortly,
C. G
1892.
C. G. J. Petersen, Beretiiing fra deit danskc hiologiske Station, No. i, 1890, Kjobenhavn,
GENERAL BIOLOGY
757
in three groups: (i) the large ones, (2) an inter-
and (3) the small ones or fry, and when fishing
2 cf
be classified
mediate group
we will very seldom be un-
certain as to which group
we may refer the fishes
captured. It is impossible
to apply the rule to both
sexes, but the males seem
on the average to be
somewhat smaller than
the females, and also less
numerous. Among the
larger sizes of the blen-
nies, the longest ones
seem to be sparingly re-
presented. Notwithstand-
ing all my exertions in
various localities, I have
never been able at this
time of the year (summer)
to find blennies of less
length than the ones re-
corded under the head of
fry, that is, about 3 to 4
inches. As the fry, when
born, are actually ij inch
long, I cannot doubt that
the group of small blennies,
which at this time of the
year differ so considerably
in size from the large
ones, really are the fry of
the year, which during the
last six months have grown
to this size, that is, have
added a couple of inches
to their length. It appears
equally natural to consider
the intermediate group of
blennies, between 6 and 8
inches, as the fry of the previous year. The direct conse-
quence is that all the large blennies between 10 and 12 inches
are of an age exceeding one year and a half by one year at
13
12 .
11 •
10 •
9 •
8 .
• •
7 . .
6 .
"
Fig. 55:
-Petersen's Measurements of
ZOARCES VI VI PAR us.
758
DEPTHS OF THE OCEAN
least, and as only very few individuals grow to a large size, this
group must be considered as 'full-grown' blennles. In other
words, it takes the blennies 2^ to 3 years to become 'full-grown.'"
This account contains the foundation of this branch of
science and a programme for further investigations, which
have been employed in many recent researches, and will in
future be employed
along with more
modern methods.
Another important
series of investigations
was inaugurated by
Heincke, who endea-
voured to employ the
methods of anthro-
pology by recording
various dimensions of
the organisms in order
to characterise varia-
tions in growth pecu-
liar to a species in
different areas of the
sea. Heincke mea-
sured the length and
height of body, length
of head, etc., in a great
number of herrings
from various marine
areas, and he found the
relations between these
dimensions to be so
characteristic that he
supposed the herring to be subdivided into various races, each
constituting a peculiar type of growth.
These two methods are, however, useful only as long as one
can operate with great numbers of measurements according to
the principles of the statistical method, and it proved in many
cases impossible to determine the age and the type of growth
of each individual by these methods. As regards the study of
age alone this proved a great obstacle, especially in regard to
the older animals. It was therefore very important to find a
method which would give the age of each individual and define
Its particular type of growth.
H. Heincke.
GENERAL BIOLOGY 759
It has been discovered that in various boreal fishes the
seasonal changes in their growth leave certain traces in all the
osseous structures, such as vertebrae, gill-covers, otoliths, and
scales, a difference being plainly seen between the parts formed
during rapid growth (in summer), and the parts formed during
feeble growth (in winter). In this way visible rings or zones Age and
are formed in the structures mentioned, varying according to Ish^s ae°noted
summer and winter, thus enabling us to count the number of by their
winters and summers passed by the fish in question, and to^'^^^^'
ascertain its growth in various phases of life. This was first
discovered by Hoft^bauer in the scales of the carp (1899), ^"^
has also been observed to hold good in the case of the otoliths
of the plaice (Reibisch), and of the scales of gadoids (Stuart
Thomson), while Heincke and others have proved various
bones to be good indicators of growth. A voluminous
literature ^ has accumulated as the result of these methods,
which assumed greater importance when in 1904, upon the
recommendation of Heincke, the international fishery investi-
gators adopted them and applied them to many special
and general problems. In recent years during the fishery
investigations of several countries the growth and age of
various commercial species have been subjected to analysis.
In Norwegian fishery work the scales have mostly been
employed for age assessments, and in this way a number of
species belonging to the cod family have been treated by
Damas, while Sund has studied the age of the sprat, Broch,
Dahl, and Lea the age and growth of the herring, and Dahl
of the salmon and trout.'
Fig. 554 represents a series of scales of saithe, ranging from
17 to 67 cm. in length, taken on the west coast of Norway.
They have been represented in proportion to the size of the
1 See Knut Dahl, " The Assessment of Age and Growth in Fish," Internationale Revjte der
ges. Hydrobiologie 21. Hydrographie, Bd. II., 1909, containing review of literature.
- Desire Damas, "Contribution a la biologic des Gadides," Rapp. et Proc.-verb. de la
coin. perm, pour Texpl. de la mer, vol. x., Copenhague, 1909.
Hjalmar Broch, " Norwegische Heringsuntersuchungen wahrend der Jahre 1904-1906,"
Bergens Miis. Aarbog, 1908, No. i.
Oscar Sund, " Undersokelser over Brislingen i Norske farvand," Aarsbcretning vedk. Norges
Fiskerier igio, Bergen, 191 1.
Knut Dahl, "The Scales of the Herring," Report on Norwegian Fishery and Marine^
Investigations, vol. ii. No. 6, Bergen, 1907 ; " Age and Growth of Salmon and Trout in Norway,"
Salmon and Trout Association, London, 191 1.
Johan Hjort, "Report on Herring Investigations until Jan. 1910," Publications de
Circonstance, No. 53, Copenhague, 1910.
Johan Hjort and Einar Lea, "Some Results of the International Herring Investigations,
1907-1911," Picbl. de Circonstance, No. 61, 1911 ; " Einige Resultate der internationalen
Heringsuntersuchungen," Mitteihlngen des Deiitschen Seefischerei- Vereins, No. i, 1912.
Einar Lea, "On the Methods used in the Herring Investigations," Pitbl. de Circonstance,
No. 53, 1910 ; " A Study on the Growth of Herrings," Publ. de Circonstance, No. 61, 191 1.
76o
DEPTHS OF THE OCEAN
fish, and we therefore easily see how the number of annual
rings increases proportionately with the growth of the fish.
By counting the winter-rings we can ascertain how many
winters each fish has lived, and by examining a great number
Fig. IV
Fig I Dm Bergen April 1907
FigNVVi Bredsund Juli 1907
fig vn Hauqsholmen Mars 1907
Gadusvirens
Fig. 554.
Scales of saithe [Gad us virens) of different sizes (size of the fish noted below each scale).
(From Damas. )
of individuals from a definite catch we may ascertain the
number of individuals belonging to each annual class. In
this way we may obtain an idea of the age-composition of the
catch. The next step is to examine a large number of catches,
and to form an estimate regarding the age-composition of the
GENERAL BIOLOGY
761
fish-stock. Fig. 555 represents an analysis of the age-composi-
tion of a catch of saithe ; it is of course not representative of
22
r\
so-
1 \
1 \
la-
1 \
lb-
\ ,.-^
.
1 \ '' ^v
'V-
.
/ / >
fZ
/ / '»
:
' / ' \
10.
/ ' \ V'''-^
8-
6-
/
/ ET / \ Y /\ "H ^x2II IZIir
HS
50
65
6C
5S 60
Fig. 555.
Age distribution of the saithe [Gadus virens) from an examination by Damas of the scales of 654
fishes caught in Sondmor (Norway) in July 1907. The age-groups that were poorly repre-
sented have been left out.
16
0
IS
°
0 °
• /•
-^^^
14
y
/^
~""\
/
/\°
13
s
^
\
° ^s
12
X
^
" N
\
/^
\
\ /
10
\ \
\
^ /
9
\ \
\
/
8
\ \
\
J
7
\ \
\
t
b
\ \
1 °
\
1
5
XN-
^^^y^
4
-
i
■
2
1908
1909
1910
12 I 2 3 4-5
7 8 9 10
12
3/^5
the
the
Fig. 556.
° Percentage of fat in sprats caught off the Norwegian west coast in different months.
K Average temperature of the surface of the sea, off Bergen, in each month of the year.
(From Sund. )
saithe-stock, but might perhaps have been so in regard to
special shoal of saithe from which it was taken.
762
DEPTHS OF THE OCEAN
Some of the general results obtained by these investigations
are of great interest ; for instance, the growth of fishes has
proved to be largely dependent on the temperature. Some
chemical investigations corroborate this. Fig. 556 shows the
fat-contents of the sprat as determined by H. Bull, compared
by Sund with the surface temperature of the sea off western
Norway in various seasons of the year. The fat-contents of
the sprat increase during summer, when there is a rise in temper-
ature, while both decrease towards the end of the year ; it
follows from this that the growth of the fish must be influenced
by the prevailing temperatures in different waters.
The investigations on the scales of
fishes have now given us numerous
facts confirming and elucidating this.
Thus Damas says that the age of first
maturity in the cod undoubtedly varies
greatly according to local conditions.
Generally the growth of cod -species
flliin'lllllliiiil^l^^J^^'^^fiiflilllllliiiij "^^y be said to decrease, and the age of
pS'V#E|^^i^^^^^^ first maturity to increase, the farther
te»;^^^^^ north we go. Thus on the Skagerrack
\Um>^y>-^^W/o'.!,!iiliA ^^^3, ^ 3^i^j^^ ^^y be 30 cm. long at the
end of its first year, while a saithe of
corresponding age in northern Norway
is not, as a rule, more than 10 cm. in
length. In northern waters, therefore,
the winter-rings in the scales are much
more marked than in more southern
waters, for instance, in the North Sea.
The duration of the warm season also
differs in different waters, and the time when it sets in
varies in different localities as well as at different depths (see
Fig- 509- which shows that at 200 or 300 metres the highest
temperatures do not occur in the summer, but late in the
autumn). An examination of cod scales from the Barents Sea
proved that in August summer growth had not yet commenced
in that area, where the winter season is of very long duration,
while the summer is short. It is interesting to compare this
with certain observations which we had the opportunity of
making during our Atlantic cruise on the banks of Newfound-
land, where, as mentioned on pp. 109- 114, the cod spawn in
July. We here observed cod with large ripe ovaries and found
the recently hatched larvae at the surface. The scales of these
llSiiiiiiiii
iil
Fig. 557.
Scale of Gadus callarias, L. Nat.
size of fish, 55 cm. Station 72.
GENERAL BIOLOGY 763
cod (see Fig. 557) plainly show winter-growth along their
edges, that is to say, vigorous summer-growth had not yet set
in, and as a matter of fact the temperatures were low (between
2 and 4 C, see Station 72, Fig. 95, p. 1 10) just where the cod
were taken.
These variations of growth put their stamp on the fish, the
shape of which depends on its growth-history. And in waters,
like those off the Norwegian coast, subject to great variation
and extending south and north through so many degrees of
latitude, an infinite variety in growth-types appear as a natural
consequence. Some of these types may perhaps, through
generations, be subjected to the accumulating influence of
surroundings, thus possibly giving rise to races. Other and
minor variations in growth may perhaps be considered as
A B
Fig. 558.
Interoperculum of plaice {Pleiironectes platessa). A,$ 21 cm. long, North Sea, three years old;
/), 9 21 cm. long, Baltic Sea, si.\ years old. (From Heincke. )
temporary or individual variations due to surroundings only,
and not subject to the laws of heredity.
The way in which individuals vary according to surroundings
might profitably be studied by experiments in transplantation
and marking of various types. Heincke^ has made some very
interesting investigations on the growth of the plaice, and
found that in waters so widely different as the North Sea and
the Baltic the growth of the plaice varied greatly. Fig. 558
shows the gill covers of two plaice of the same size, both 21
cm. long ; the North Sea plaice is only 3 years old, while the
Baltic plaice is no less than 6 years old. Similar distinct types
of growth have been discovered in the herring during the
international investigations, Dahl having first drawn attention
to the existence of such types ; Lea continued these investiga-
tions with a large amount of material, and claims that among
others two growth-types may be recognised, one belonging to
the north-eastern part of the North Sea (the Norwegian
west coast), and the other to the Kattegat (see Fig. 559).
^ Die Beteiliguug Dent schlaiids an der intenmlionaleii Meeresforschiing, IV.- V. Jahresbericht,
Berlin, IQOS.
764
DEPTHS OF THE OCEAN
Both the scales represented belong to herrings six winters
old and represent true averages of growth, which has obviously
been very different in the two types.
While studying the growth of Gadidae, Damas conceived
the idea that by examining the growth -history of single
individuals, as depicted in their scales, one should be able to
determine the localities, or at least the conditions, in which the
individuals had grown up, in other words that this study
should afford a key to the migrations of the fishes ; thus he
considers it probable that a certain saithe captured on the west
coast of Norway may be recognised as having spent its
infancy on the north coast of Norway. Similar ideas have
Fig. 559.
Diagram of herring scales of average growth. A, from the north-eastern part of the North Sea ;
B, from the Kattegat.
been expressed by Lea after studying the scales of herring.
He discovered that among the fat-herrings of northern Norway
the ones born in 1904 could be seen to have had an exceedingly
poor growth during their third year, the summer-belt in the
scales being strikingly small in that year (see Fig. 560). This
peculiar feature was in that year limited to a certain part of
the coast. The individuals thus " marked " were, however, in
subsequent years when increasing in age found to have a much
wider distribution, extending to the west coast of Norway and
other localities. He considers this as significant of migration,
and even attempts to calculate the percentage of the herrings
taken on the west coast that had spent their infancy in
northern Norway.
GENERAL BIOLOGY 765
The study of numerous samples taken from the fish-stock Age-com-
of a certain area may aim at ascertaining the age -com- tSock^of
position of that stock, and from the results the follow- fishes.
ing main points in the natural history of the fish may be
elucidated: (i) the age at which maturity occurs; (2) the
A B
Fig. 560.
Two scales of fi\'e-year-old herrings. A, growth under normal conditions ; B, abnormal growth
in the third zone.
duration of life ; and {3) the variations in the age-composition
and magnitude of the fish-stock.
Studies of this kind have shown us that various species
A B
Fig. 561.
Scales of .4, herring [Clupea hareng/is) ; B, sprat {Cliipea sprattus). Both fishes i6 cm. long.
are distinct even in this respect. Nothing shows this
more clearly than a comparison between the two closely
related species : the sprat and the herring. Fig. 561 represents
scales of a herring and of a sprat, both 16 cm. long, the
herring being only \\ year old and the sprat 4 years. The
^66
DEPTHS OF THE OCEAN
age-composition of spawning shoals in the two species appears
from the following examples :
Annual Class.
^
3
4
5
6
7
13
8
19
9
3
2
2
12
I
I
14
...
Percentage of sprat .
Percentage of herring
30
42
2
19
22
8
19
15
Sund found that the majority of sprats spawn when two to four
years old, while Dahl found that the herrings spawn from the
3rd to the 14th year, the majority between four and eight years
old. This difference is fundamental in the life-history of the two
species. The life-cycle of the sprat is rapid, indicating a rapid
renewal, while the herring lives much longer, spawns for a great
number of years, and spawning commences two years later than
in the sprat. The herring is a typically boreal fish, its southern
limit to the south-west of Britain conforming to that of all
the boreal bottom-fishes (see Chapter VH.). Herrings live,
at least sometimes, at considerable depths, depositing their
eggs on the bottom of the coast banks during winter and
spring, now in shallow, now in deeper water.
The sprat is distributed far south in the Atlantic, occurring,
according to Day, round the Iberian Peninsula. It is a
surface fish occurring in boreal waters mainly where high
summer temperatures prevail ; it spawns during summer, the
eggs being pelagic.
From the study of the age of fishes I was induced to
hope that the variations in the magnitude of the fish-stock
might be estimated, and my collaborators have made very
extensive investigations with most important results. This
applies to the cod family as well as to the sprat and the
herring. I will here only review some of our results from the
herring investigations.
For a number of years samples for age-analysis have been
collected during the various herring fisheries on the coast of
Norway, the analysis of which has proved that the age-com-
position of immature herrings, as well as the shoals of spawning
herrings, vary considerably from year to year. These variations
are mainly due to the fact that certain annual classes are
exceedingly prolific, while others are very poorly represented.
The following table records the results of an analysis of
GENERAL BIOLOGY
767
samples representing immature fat - herrings from northern
Norway in the years 1907-1910,^ the frequency of each annual
class being given in percentages of the total sample for each
year : —
Annual Classes.
7
I
2
3
4
5
6
1907 .
11-5
36.8
51.3
0.4
1908
0.4
51-4
10.3
37.8
1909 .
3-1
61.0
^3-3
5-0
16.9
0.7
0.2
I9I0
0.2
50-7
42.0
0.9
1-7
4.5
0.1
This table shows that the fat-herrings in 1907 consisted
mainly of fish two and three years old, in 1908 they were mainly
two and four years old, and in 19 10 again the majority were
two and three years old. This apparent irregularity has an
enhanced interest when we remember that the herrings, which
in 1907 were three years old, in 1908 were four years old, and
so on. The annual classes born in 1904 and in 1907 are
printed in heavy type, and the table shows a decided regularity
in the abundance of certain annual classes. The same regularity
appeared when older herrings were studied. When four years
old the fat-herrings begin to " migrate " away from the shoals
of immature herrings, and mingle with the "spring-herring"
shoals (the spawners). In such spawning shoals from western
Norway the year class born in 1904 proved to have the
occurrence shown in the following table in percentages of the
total sample analysed each year, comprising sixteen annual
classes : —
Among the great number of annual classes composing the
^ J. Hjoit and E. Lea, "Some Results of the International Herring Investigations, 1907-
[911," Pul>L de Cinonstance^ No. 61, Copenliague, 191 1,
768 DEPTHS OF THE OCEAN chap.
herring stock, one single annual class may thus be enormously
prolific, the individuals exceeding in number those of all other
annual classes taken together.
These facts naturally lead to the following conclusions
touching questions of interest to general biology as well as to
practical fisheries. The age-composition of a fish-stock varies
exceedingly ; there are good and bad years, producing annual
classes rich or poor in individuals. Favourable and unfavour-
able conditions must thus vary in nature, and seem to affect
specially the earlier phases in the life of the fish, inasmuch as
we perceive that in advanced years the numerical preponderance
of an annual class is equally perceptible for a number of years.
The variations caused by the influence of one year will
therefore not always perceptibly influence the number of
individuals of the total stock, and in practical fishery its influence
will as a rule only be felt some years later, when the annual
class in question plays an important part in the catches of
fishermen. If favourable years have occurred just before or
after the birth of the class in question its influence may perhaps
not be felt at all. All this of course applies only to species
with many annual classes of spawners, for where few annual
classes spawn (or perhaps only one) conditions will be diff"erent.
The influence of one year may, however, appear in the
quality of the whole stock, for instance in the fat-contents (see .
Fig. 556 representing the growth of the sprat).
Wherever there is a good opportunity of obtaining repre-
sentative samples showing the age-composition of a fish-stock,
it should be possible to predict the composition of that stock
for the following years. We may thus, for instance, count upon
the possibility of annual classes containing a marked abundance
of young individuals reappearing, after the lapse of a definite
time, as equally abundant shoals of older and more valuable fish.
The results here mentioned have been obtained through
laborious investigations occupying many years, involving the
study of the fishes at all seasons, in order to prove that the
various growth-rings of the scales really correspond to seasonal
changes.
As far as I know, no systematic investigations as to growth
have ever been made in the open ocean, but I may point out
that in tropical waters and at all depths in the ocean the same
biological problems, which we have just described from boreal
waters, present themselves for study and solution. In this
connection I consider it interesting to cite some instances from
GENERAL BIOLOGY
769
our preliminary investigations, showing that periodic growth
may be traced even in the ocean, but as to the nature of this
periodicity I dare not at present express an opinion.
Fig. 562 represents a scale taken from the abyssal fish
Macrnrus {^Nematomu^us) arviatus. As indicated in Chapter
VIL this species lives in depths beyond 2000 fathoms, and at
^ Vu
1^
'h
Fig. 562.
Scale of Macriirus [Nematonurus) armatus, Hect. (about -^ ).
Fish from Station 88. Length, 52 cm.
Fig. 563.
Scale of Bathygadus melanobranchus, Vaill.
Nat. size of fish, 42 cm. Station 41,
1365 metres.
a temperature of \" to 3 C. The specimen from which this
scale was taken was captured at Station 88 in 3120 metres,
and was 52 cm. long. The figure shows the presence of rings,
which remind one of the rings found in the scales of the cod
family, but they do not continue round the entire area of the
scale. The number of rings present appears to be more than
ten, but I am unable to decide this with accuracy.
Fig. 563 shows a scale from Bathygadus vielanobranclms,
^ D
770 DEPTHS OF THE OCEAN
42 cm. long, taken at Station 41 in 1365 metres. We see here
a great number of rings, perhaps twenty m all, but these rmgs
are in many respects
_ ■""' essentially different
,^^^>o from the annual rings
' ;^ :' '; in the scales of boreal
/'■ ; fish. In the latter the
V . central rings are as a
\ rule very large, the
^v subsequent rings be-
coming narrower as the
fish grows older. If
the rings in the scale
of Bathygadus signify
periods of growth,
these wouldseem to be
of a peculiar character,
cm. in length from the
Fig. 564.
Scale of Canthariis lineatus, Montagu (White).
Length of fish, 42 cm.
Fig. 564 is the scale of
coast banks of Africa,
Cantharus lineatus,
taken in shallow water
at a high temperature.
This scale also shows
rings which are very
distinct, especially to-
wards the periphery of
the scale.
In Fig. 565 I have
represented a scale
from a surface fish,
Polyprioii americanus,
49 cm. in length,
taken in the surface
waters at Station 56.
In the scales of
all these fishes, taken
under such various
conditions, we observe
peculiarities of struc-
ture, resembling the • 1 1 r
rings produced by the periodicity of growth m the scales ot
fish from boreal waters. There seems thus to be every reason
for subjecting the growth of the scales and other organs of
Fig. 565.
Scale of Polyprion atnoHcatins, Bl. and Schn.
Length of fish, 49 cm.
GENERAL BIOLOGY 771
warm-water and oceanic fish-species to a closer investigation,
and for studying them at various seasons. As a means of
control and comparison, measuremejits on a large scale, accord-
ing to Petersen's method, would be very important. Although
our material is very abundant, it is insufficient for the purpose
of distinguishing various size-groups among the fishes. That
such groups occur among the deep-sea fishes is plainly indicated
by our measurements of Cyclothone (see Fig. 473, p. 620), which
show a binodal curve for individuals of Cyclothone signata from
500 metres, and a multinodal curve in the case of C. microdon.
At 500 metres the average size is about 35 mm., and at 1500
metres about 60 mm. Perhaps there is another group in
depths between the two mentioned. Regarding the meaning
of the nodes in these curves I must confess myself ignorant.
From the coast banks of Africa we have a series of measure-
ments of Dentex macropktkalnms, which for the sizes between
17 and 24 cm. show a very regular size-distribution of the fish
captured.
Future investigations of the fish-fauna of the coast banks
may lead to good results by starting from the study of such
forms as occur also in the North Sea, for instance the hake
i^Merhcccius vulgaris). Their growth might then be subjected
to a comparative study on a long stretch of coast through many
degrees of latitude and under exceedingly various conditions.
The same method might also be applied in the case of the southern
pelagic clupeidae : the sprat, the pilchard, and the anchovy.
Abundance of Marine Animals
On dry land we can, to a large extent, examine the yield of
the soil, weighing and measuring the crops, and keep count
of animals of economic importance. As regards the yield of
the sea our experience is merely of a relative kind. From
generation to generation a certain amount of knowledge has
been accumulated as to the quantities of various fish that have
been captured, but the number of animals actually living in
the sea is unknown.
Many scientists have undoubtedly often had to acknowledge
that biology would be raised to an essentially higher level, if it
were possible to arrive at absolute figures denoting the numbers
of individuals inhabiting the sea, instead of merely the relative
figures which are now obtained through the study and com-
parison of various catches.
estimations of
organisms in
the ocean.
7/2 DEPTHS OF THE OCEAN chap.
A first attempt in this direction was made by Sir John
Murray during the cruise of the "Challenger," by calculating
the amount of calcium carbonate in the form of living organisms
per square mile of the ocean by lOO fathoms in depth.
Quantitative No one has devotcd more time and thought to this problem
than V. Hensen, who has been indefatigable in his endeavours
to devise methods for an absolute determination of the quantities
of organisms contained in the ocean, his avowed intention
being to ascertain the quantities of "primitive food for
marine animals." ' From theoretical considerations he con-
cluded that the primitive food of marine animals necessarily
consisted of the microscopic plants living in the surface waters
of the ocean, and that the effect of currents would be to
distribute these minute plants quite regularly and uniformly.
He held the idea that a hoop-net hauled vertically from bottom
to surface would filter a column of water with a diameter very
nearly corresponding to the diameter of the net, and that in
this way it was possible to calculate the catch per square metre
of surface. The volume of the catch might be measured,
and the number of individuals belonging to all the species
might be counted. Definite figures might thus be obtained
representing the abundance of each species per square metre
of surface, and the area of the water being known, the
aggregate quantities might be calculated. In order to count
all the micro - organisms he invented a method based on
the principle employed in physiology for the purpose of
counting blood corpuscles, viz. to dilute a sample of known
volume with a known volume of liquid in which the organisms
become evenly distributed. With a specially devised instru-
ment a small sample (say i c.c.) is taken out and its contents
counted.
This method has added greatly to the practical working of
biological ocean research, and will undoubtedly increase in
importance in future. Like all other means of research it
must be employed with judgment, and the special nature of the
investigations must decide whether it may be applied and at
what stage with advantage. The application of the method has
led to much discussion, the enthusiastic advocates of the
method considering it imperative that it should be used in all
"truly scientific" investigations on the micro-organisms of the
ocean, while its opponents have looked upon it as a means of
' V. Hensen, " Uber die Bestimmung des Planktons," F. Bericht der Coiitniission zitr wiss.
Untersuclnmg der detitschen Meere in Kiel, 1887.
GENERAL BIOLOGY ^^^
investigation to be applied, like all other means, according to
circumstances.
Hensen invented his method for the purpose of investigating
the floating or suspended life in the sea, which he termed
" plankton." This plankton is, however, very difficult to define,
for among the profusion of organisms, ranging from the
minutest plants, the coccolithophoridae, to large crustaceans
and fishes, there is an enormous variety in size, in activity,
and consequently in the faculty of avoiding the appliances of
capture. In many investigations, therefore, the word plankton
may be taken to signify practically " the catch made in the
hoop-net constructed by Hensen, when new and in perfect
working order." But does this selection among the organisms
of the sea correspond to an arrangement peculiar to the
organisms in nature ? All our experience shows that the
catching power of the Hensen net is restricted, firstly,
because, as shown in Chapter VI,, an important group of plants
(the coccolithophoridae) may pass through the meshes of even
the finest silk nets, and secondly, because the selection of
animals actually taken is very limited, consisting of unicellular
animals, minute crustaceans, sagittidae, etc., while the large
crustaceans, schizopoda, decapoda, and even small fish-fry,
mostly avoid the net. This limited power of capture alone is
apt to affect our ideas of marine life in a perfectly arbitrary
manner ; but another objection to the universal application of
the Hensen method arises from the fact that in large areas
the conditions do not correspond to the theoretical condi-
tions on which the method is based, for in theory the dis-
tribution of the organisms is regarded as something like the
even distribution of the molecules of a gas encased in a box or
aquarium.
In 1885 Hensen made an expedition in the " Holsatia" and
in 1889 another in the " National," during which vertical hauls
were made with his nets in shallow water from bottom to
surface, and in the ocean mostly from 200 metres to the
surface. The volumes of organisms taken during these cruises
have been represented graphically in Fig. 566, reproduced
from Steuer's text-book. In this figure the track of the cruise
has been used as horizontal axis, and lines have been drawn
vertically (as ordinates) to show the relative volumes taken per
square metre of surface. These volumes are very great
in the Irminger Sea and in the North Sea (amounting to
166.9 c.c), and very small in the Sargasso Sea as well as in
774
DEPTHS OF THE OCEAN
the open ocean on the whole. In all or most of these samples
the numbers of individuals have been counted after the return
of the expedition, — a laborious and painstaking piece of work,
i23J
Fig. 566. — Volumes of "Plankton" in the Atlantic and in the North Sea,
ACCORDING TO THE INVESTIGATIONS OF THE " HOLSATIA " IN 1885 AND THE
" National "^IN 1889. (AfterjHensen, from Steuer.)
which has added greatly to our knowledge of marine biology.
In Chapter IX. I have had occasion to refer to many important
facts for which we are indebted to these expeditions, but I
GENERAL BIOLOGY 775
doubt whether the method of work adopted has resulted in a
correct idea of the quantities of organisms which these hoop-
nets can capture per square metre of surface, and whether this
method recommends itself for adoption in the present state of
our knowledge.
It is evident that the quantity of organisms present at any
given moment does not afford any gauge as to the " primitive
food" contained in the ocean. The quantity of such food
depends on the intensity of reproduction, which is entirely
unknown, from coccolithophoridae to fishes. For this reason
the volumes of plankton shown in Fig. 566 convey no idea of the
actual production of the ocean, a fact of which Hensen was
fully aware. The abundance in boreal waters only lasts a short
time, and during that time production is probably not by any
means so rapid as in the warm ocean. While the Hensen nets
thus capture only an arbitrary selection of organisms, the depths
from which the nets were hauled were also chosen in an
arbitrary manner. Hensen^ himself says, when describing the
copepoda : " The figures show that the copepoda usually live
still deeper than 200 metres, their density being, however,
insignificant." The results seem to have given rise to some
doubt in his mind as to the latter opinion.
In Chapter IX., and when speaking of nutrition, I have
mentioned some of the investigations made on board the
" Michael Sars " regarding the capture of minute crustaceans in
closing-net hauls from various depths. The catches have been
classified in regard to number of species as well as to
volume, and the characteristic feature was that the greatest
number of species and the greatest volumes of these
crustaceans did not occur in the upper water-layers, but at
certain intermediate depths. In the Sargasso Sea the greatest
volumes were captured between 1000 and 500 metres, off
Newfoundland between 500 and 200 metres, and in the
Norwegian Sea (Station 113) between 1000 and 500
metres. In the Sargasso Sea a greater number of species (51)
was found in the deep hauls between 1000 and 500 metres
than in the "surface" hauls between 200 metres and the
surface (22). Certain species occurred at all depths, others only
in the deepest hauls. Our horizontal hauls showed that besides
these minute forms taken by the closing-nets there is a prolific
community of large crustaceans, prawns, etc., in deep water,
where many litres could be taken in each haul, while higher up
^ "Das Leben im Ozean," Erg. d. Plankton-Expedition , Bd. v., Kiel, 1911.
776 DEPTHS OF THE OCEAN chap.
these animals are absent, and the volume is obviously at a
minimum.
We may therefore assert that the small nets actually capture
a purely accidental selection of the animals present, and that
the use of the nets only above 200 metres gives a merely
casual selection, which is by no means a characteristic gauge as
to the quantity of organisms living beneath a square metre of
surface even at the moment.
Is the idea of a certain quantity per square metre of
surface on the whole of any value whatever as regards the
ocean ? We may speak about the quantities produced per
hectare or per square metre of soil, and we may also classify
the production of a pond ; but is there in the ocean any connection
whatever between the different layers of a column of water 5000
or 6000 metres deep by i metre square in regard to the
vertical exchange of nutritive substances? Is it not probable
that this exchange takes place in an oblique direction and at
various angles at different depths ? At the surface of the North
Atlantic the Gulf Stream in many places runs with great
velocity, but how deep this current extends, or, to put it more
correctly, at what depths it runs in the same direction and
with the same velocity, is indeed as yet almost unknown.
Below this current there are perhaps in places powerful
reaction currents, running in opposite or other directions,
probably with a considerable vertical range (see current
measurements described in Chapter V.), and these would
have to be passed through before reaching depths where the
water layers move very slowly or not at all. Bodies sinking
from the productive plant-stratum at the surface must, therefore,
be supposed to be carried far away in a horizontal direction
before reaching deep water. The nutriment of the deep layers
of any locality is thus not derived from a point situated exactly
above it, but has probably come from some very distant point,
and the fact that boreal forms are found in deep water below
the warm waters of the south may be a corroborative proof of
this.
Notwithstanding my admiration for Hensen's methods, I
have always held that before these methods can be applied in
nature we must make a qualitative investigation, to be followed
by an investigation as to the relative quantities of the organisms
present, in order to define the selection which must be made if
we wish to determine the absolute quantities. To define the
quantity of something perfectly casual is indeed of little
GENERAL BIOLOGY ^^^
importance, but to determine the exact quantity of something
clearly defined, as, for instance, the number of individuals of
certain definite species living in a sharply limited water-layer,
is of the highest interest.
When planning the Atlantic cruise of the " Michael Sars " I
considered it our first duty to investigate in a qualitative way
what organisms live at the various depths. For this purpose
we made many determinations of quantity (see Chapter IX.),
for instance, in order to illustrate the abundance of certain
species in each of the appliances towed at different depths.
This method made no pretence of giving absolute figures, but
it gave us certain ideas regarding the relative quantities of
organisms living at different depths, and the figures obtained
by counting the fishes in our trawlings are of a similar kind.
My opinion is that these estimates represent the natural
conditions better than the ideas regarding animal life in the
Atlantic gained by the German Plankton Expedition ; this
ocean, being inhabited by organisms at all depths, is very far
from being as poor as shown by the nettings of the Plankton
Expedition. At the surface reproduction must be exceedingly
rapid, or else it would be perfectly inconceivable that so
many animals could live in the deeper water, unless, indeed,
their nourishment were derived from distant localities, a
question that future investigations must answer. Further, the
peculiar difference between the quantities of organisms
occurring in the deep water of boreal and of warm oceanic
waters will have to be more closely studied. In the ocean we
find first a minimum just below the surface, then a pronounced
maximum, with probably a minimum again in the deeper waters
(see Chapter IX. on capture of Cyclothone in closing-nets at
Station 63). I suggest as a working hypothesis that this is
due to the peculiar distribution of specific gravity and viscosity,
which is quite different in boreal and in warm oceanic waters.
When speaking of floating, I mentioned how the distribution
of temperature, and consequently of specific gravity and viscosity,
affected the geographical distribution of species, and in Chapter
IX. I drew a limit between boreal and warm - water forms,
which on the whole, horizontally and vertically, coincided with
the isotherm of 10° C. In thus employing temperature alone
as a means of dividing animal-communities my idea has only
been to consider the temperature as an indicator of certain
climatic conditions on which animal life is dependent. From
this point of view let us inspect a section of the Atlantic along
778
DEPTHS OF THE OCEAN
the 30th meridian west (Fig. 567). We see that the water-
layer limited by the isotherm of 10° C. is relatively thin in
proportion to the depth of the ocean. The genuine warm-
water layers with temperatures exceeding 15° C. reach only
to 30° south and north, and are only 200 to 300 metres
thick. The whole layer above 10° C. has a thickness
varying between 300 and 700 metres (or between ^^ and ^
of the depth of the ocean). Now it was only a part of this
small layer which was examined by Hensen's expeditions,
and consequently the results must necessarily be incomplete.
Lat.S
Equator.
10° rf 10°
Lat.N.
50° 60°
2500
Fig. 567.— Distribution of Temperature in the Atlantic along the thirtieth
Meridian of West Longitude. (From Schott.)
In order to understand the abundance of animal life in
various parts and at various depths of the Atlantic, it is very
useful to review our knowledge of the distribution of whales in
that ocean. I agree with Eschricht in dividing the whales
into different biological groups according to the food on which
they live. One group feeds on " plankton," another on both
plankton and fishes, and a third group on squids.
Genuine " plankton whales " are the arctic " right " whale
(the Greenland whale, Balcena mysticetus, see Fig. 568), and
the boreal blue whale i^BalcEnoptera nmsculus, Fig. 569). By
the aid of their enormous tongues they press the water out of
their mouths between the whalebone lamellae, thus filtering the
water and retaining the minute organisms (see Fig. 570).
GENERAL BIOLOGY
779
Another group of whalebone whales, the fin -whale
[Balcsnoptera p/iysalus), the humpback whale {Megaptera boops,
Fig. 568.
Greenland whale {BalcEtia viysticetus). (From Scoresby.
Fig. 569.
/hale [Balcenoptera mnsculus). (From G. O. Sars.)
!|\\
I' I
'-v.
■■V^.-jX1/!^Via.-
Fig. 570.
Cross-section of head of a fin-whale {Balieiioptera). (From Boas.)
h, Head ; tt, lower-jaw ; b, whalebone ; fit, tongue ; f, furrows of the skin.
Fig. 571), and the " saithe " whale i^B alcenoptera borealis) feed
on plankton as well as on pelagic fishes, mainly capelan and
herrings, which also constitute the main food of the small tooth-
whales of the porpoise description.
/So
DEPTHS OF THE OCEAN
The cachalot or sperm - whale {Physeter inacrocephalus,
F^g- 572) and the bottle-nose {^Hyperoodon diodon) feed mainly
on squids.^
Howard Clark- has published an interesting chart recording
the various whaling areas, in which he has separated areas
fished in 1887 from areas previously fished but then abandoned.
The whales fished in various areas are denoted by letters : —
B. = Greenland whale.
R. = Other Right whales (Balsena).
F. = Fin-whales (Balsenoptera).
H. = Humpback whales (Megaptera).
S. = Cachalots or Sperm-whales.
Fig. 571.
The Humpback [Megaptera boops). (From G. O. S;irs. )
Cachalot or Sperm-whale {Physeter inacrocephalus). (From drawing in the Bergen Museum.)
The Chart (Fig. 573) gives his records from the Atlantic, and
at the same time the temperature at 100 metres has been
entered, from Fig. 312, p. 445, and from Schott's report on the
"Valdivia" Expedition. The dense hatching shows areas
where whales were fished in 1887, the open hatching areas then
abandoned. In northern boreal waters, north of the isotherm
of 10' C, only or mainly the Greenland whale, fin-whales, and
humpbacks are found, the right whale of the North Atlantic
(north-caper or Biscayan whale, Balcsna biscayensis, Fig. 574)
being a rare visitor. In antarctic waters, where the thermal
^ See Turner, /onrn. Anat. and Phys., vol. xxvi.
- 7^he Fisheries and Fishery Industries of tlie United States, Section V., Washington, 1887.
GENERAL BIOLOGY
781
conditions correspond to those of boreal waters, right whales
predominate ; in recent years, however, large numbers of Hn-
100° 90° 80' 70° 60° 60° 40° 50° 20° 10° 0° 10° 20° iO° 40°
100° 90" 30° 70" 60° SO" 4.0" JO" 20° 10° 0° W 20" JO" ^Q^
Fig. 573. — Distribution of Whales, and Temperature at 100 metres (see text).
whales and humpbacks have also been found there. In coast
waters right whales and humpbacks predominate. In the
open ocean between the parallels of lo north and south,
782 DEPTHS OF THE OCEAN chap.
the cachalot is the principal, if not the only, large species
which has been the object of man's exertions in these
parts.
The distribution of whales, here roughly outlined, seems to
agree very well with what I have previously stated in regard
to the distribution of pelagic animals. In boreal, and probably
also in antarctic, waters the abundance of minute pelagic
animals (plankton) in the upper layers is particularly character-
istic of certain seasons of the year, and for this reason the
whalebone whales have their habitat in these waters. In coast
waters the plankton is equally rich in many places, along with
quantities of small pelagic fishes, herrings, sprats, pilchards,
etc., which are the food sought by humpback whales.
Whether the various right whales, like BalcEna biscayensis, in
Fig. 574.
Balcrna biscayensis. (From Guldberg. )
southern waters eat the small herring species besides the
plankton is unknown to me ; in boreal waters I am only aware
that plankton has been found in their stomachs.
In the open ocean the plankton is scarce in the upper layers,
but the deeper layers contain multitudes of large crustaceans
and squids, and here only squid-hunting whales like the cachalot
are found in numbers. Enormous diving power is peculiar to
the cachalot and its ally, the bottle-nose. One of our most
experienced bottle-nose whalers has told me how the whale
"sounds" when struck by the harpoon, very often diving
straight down, taking out as much as 400 fathoms of line in a
perfectly vertical direction. It is very interesting to note that
on our Atlantic cruise we found many proofs of the existence
of quantities of squid in vast areas of the open ocean, partly
belonging to the same species as the Prince of Monaco found in
the stomachs of sperm-whales. The occurrence of these whales,
and the importance of the sperm-whaling carried on in the open
GENERAL BIOLOGY 783
oceans, seem to indicate that the oceans are not quite so poor
as Hensen's results would imply. But the nature, reproduction,
and vertical distribution of the " plankton " differ entirely in the
warm part of the ocean and in boreal waters. The only thing
we can do at present is to compare these two classes of
conditions, and to compare the groups of phenomena regarding
adaptation found in the ocean.
Generally speaking, 1 think our experience justifies the
opinion that the scientific investigation of an ocean must
commence with observations of a qualitative kind. A chemist,
intent upon the investigation of a complex chemical compound,
sets to work in the same way, first endeavouring to make out
the nature of the single components of the compound, and in
many cases he will find it practicable to make preliminary,
merely relative, estimates as to the quantity of each component
present before entering into an absolute quantitative analysis.
Hensen himself has shown how to make a definite
selection in the case of the complex " plankton "-problem by
taking up for quantitative investigation the occurrence of one
single organism, viz. the pelagic egg of the plaice. In this Pelagic
case, of course, an infinitely more clearly defined and sharply '^^^■«^g§^-
limited problem presented itself, and Hensen endeavoured to
solve it for certain areas of the North Sea and the Baltic,
developing the very interesting idea that the number of
spawning plaice might be arrived at by studying the number
of pelagic eggs within a restricted area, and ascertaining the
number of eggs spawned by the average female plaice. While
studying the cod eggs of the Norwegian Sea I have very often
had occasion to consider the same problem, but I have never
ventured to attempt its solution. Even in this case I con-
sidered it necessary, first of all, to make qualitative investiga-
tions, commencing with a detailed study of the areas where the
eggs of each species occur.
The Norwegian waters are peculiar in varying greatly in
depth : in the course of a few miles one may find depths
ranging from a few to a couple of hundred fathoms ; they
are very instructive although, compared with the North Sea or
the Baltic, they exhibit extreme conditions.
Another point to be considered is the fact that eggs, as
soon as spawned, are carried away by currents, the distance
which they travel depending on various local conditions. The
influence of these currents must, therefore, be ascertained, as
the eggs cannot be considered as stationary.
784
DEPTHS OF THE OCEAN
A third and important point is that all the individuals of a
species do not spawn at the same time. Hensen himself
thinks that each fish spawns several times within a short period,
and besides the spawning season of each species varies from place
to place. At a definite moment it is thus impossible to find all
the eggs in the earliest stage, for as a matter of fact in the
Norwegian coast waters the same haul includes eggs in various
stages as well as larvse and more advanced young. As regards
Norwegian waters it is therefore, as far as 1 can see, at present
impossible to realise Hensen's idea of counting the fishes of the
sea, or to cope with the problem of calculating the stock arising
from the developed larvae.
It is well known that in many countries a considerable
amount of work has been devoted to so-called artificial fish-
hatching, which consists in keeping the eggs until the minute
larvae have escaped. Hopes have been entertained of increas-
ing the fish-supply by means of this hatching, the idea having
prevailed that these larvae had a better chance of growing up
than the eggs. But when these minute larvae are placed in
the sea, where there are already great numbers of them, they
disappear from view in a few minutes, and their subsequent
fate is entirely unknown. All calculations as to how many of
them grow up must be based on unknown and uncontrollable
factors, and become all the more doubtful considering there
is now ample proof that the abundance of different annual
classes varies enormously in nature.
Quantitative investigations of an entirely different kind have
in recent years been started by C. G. J. Petersen,^ who
constructed a bottom-sampler, or kind of gripper (see Fig. 575),
which, like a dredging apparatus, brought up a large sample
from the surface of the sea-floor. The bottom-sampler is
intended to cut out a sample of one square foot from the
bottom, which is passed through sieves, the sand and mud
being sifted off, leaving the animals to be classified, measured,
counted, weighed, and finally submitted to chemical analysis.
These investigations on the abundance of bottom animals are
simpler than those dealing with the pelagic organisms, which
move so freely in a horizontal as well as in a vertical direction.
Petersen has also attempted to solve the problem of the
quantity of fishes by experiment. "-' He captured great numbers
1 Report of the Danish Biol. Station, No. xx., 191 1.
^ " The Labelling of Fish in the Sea," Fishery Report for the Years i8SS-i88g, and Report
from the Danish Biol. Station, No. iv., 1893.
GENERAL BIOLOGY
785
of plaice, marked them, and let them go again. He then kept
account of the percentage of marked plaice subsequently
recaptured, and comparing this percentage with the total
catch according to the fishery statistics he hoped to arrive
Fn;, 575.— C. G.J. Petersen's Bottom-Collector.
approximately at the proportion between the number of plaice
caught by the fishermen and those living in definite regions.
In restricted areas, where immigration and emigration are
insignificant, his interesting experiments have yielded very
good results, providing probably the only accurate knowledge
at present available regarding the abundance of fishes in the sea.
J. H.
3E
INDEX OF PROPER NAMES
Agassiz, Alexander, 12,^17, 18, 30, 33, 138,
731
Agassiz, Louis, 10
Aime, G., 4, 216, 221, 703
Alberti, L. B., 2
Allen, E. J., 377
Anderson, W. S., 178
Andrea, A. F., 755
Andrusoff, Nicolaus, 15
Appellor, Adolf, vii
Apstein, Carl, 325, 374, 598, 599
Audouin, J. V., 7
Aurivillius, C. W. S., 310, 556, 642
Bache, A. D., 8
Bailey, J. W., 8, 9, 307, 308
Balfour, A. F., 141
Bartholomew, J. G., 131
Baur, E., 369
Belknap, G. E., 11, 27
Bergh, R. S., 308
Bergon, P., 322
Berryman, Lieut., 9
Bjerkan, Paul, vii, 600, 708
Bjerknes, Vilhelm, 261
Blackman, , 310
Blagden, Charles, 3
Blessing, H. G., 342
Bocage, Barboza du, 10
Bodliinder, G., 177, 178
Boggild, O. B., 191
Bonnevie, Kristine, vii, 589, 625, 658
Boulenger, G. A., 388
Brandt, Karl, 311, 333, 367, 368, 369, 380,
381, 679, 691
Brauer, August, 413, 424, 425, 601, 605,
611, 615, 625, 676, 677, 678, 679, 680,
681, 682, 684, 746
Bravais, A., 4
Brennecke, Wilhelm, 256
Bridge, T. W., 388
Brightwell, Thomas, 307
Brinkmann, August, vii, 577
Broch, Hjalmar, vii, 311, 326, 359, 573,
666, 667, 759
Brooke, T- W., 8, 130
Bruce, W. S., 18, 135
Buache, Philippe, 3
Buchan, Alexander, 72, 295, 703
Buchanan, J. Y., 13, 19, 183, 192, 230, 232,
236, 246, 267, 295
Bull, Henrik, 762
Bunsen, R. W., 253
Carpenter, W. B., 7, 10, 67
Caspari, W. A., viii
Castracane, Francesco, 308, 337
Charcot, Jean, 18
Chierchia, Gaetano, 561
Chrystal, George, 16, 132, 278
Chumley, James, viii
Chun, Carl, viii, 16, 35, 546, 561, 562, 585,
590, S92, 595, 662, 678, 682, 689, 691,
692, 701
Claparede, Edouard, 308
Clark, Howard, 780
Clarke, F. W., 186
Cleve, P. T., 308, 310, 334, 337, 338, 339,
340, 345, 346, 347, 349, 352, 353, 357
Cohen, E., 178
Collet, L. W., 189
Collett, Robert, 642, 643, 698, 739
Collins, J. W., 707
Cook, James, 3, 4
Cosa, Juan de la, 2
Coutiere, H., 622
Cruquius, , 3
Cusanus, Nicolaus, 2
Dahl, Knut, 581, 759, 763, 766
Dalrymple, Alexander, 3
Damas, Desire, 383, 569, 572, 575, 581,
639, 640, 642, 645, 658, 711, 726, 727,
735, 759, 761, 762, 764
Dana, J. D., 5
Darwin, Charles, 661, 671
Davy, , 3
Day, Francis, 388, 607, 766
Dayman, Joseph, 9
Dicquemare, Abbot, 674
Dittmar, W., 175, 235
Doflein, F. J. T., 672, 673
Dohrn, Anton, 18, 20
Donati, V., 3
787
788
DEPTHS OF THE OCEAN
Dons, Carl, viii
Drygalski, Erich von, 17
d'Urville, T. S. C. Dumont, 4
Ehienbaum, Ernst, 731
Ehrenberg, C. G., 307, 308
Ekman, F. L., 232
Ekman, Gustav, 15, 338
Ekman, V. W., 67, 234, 246, 263, 274, 275
Ellis, Henry, 215
Eschricht, D. F., 778
Fischer, Alfred, 369
Fischer, Otto, 706
Flint, J. M., 17, 165
Fol, Hermann, 248, 250, 671
Forbes, Edward, 6, 7
Forch, Carl, 274
Forchammer, J. G., 178
Forel, F. A., 278
Forster, J. G. A., 3
Forster, J. R., 3
Fox, C. J. J., 253
Franklin, Benjamin, 3, 213, 214, 674
Franklin, John, 7
Fulton, T. W., 261, 262
Gamble, F. W., 673
Garstang, Walter, 713
Giesbrecht, Wilhelm, 579
Gill, Theodore, 740
Glas, George, 77
Goethe, J. W. von, 660
Goodsir, Harry, 7
Gran, H. H., v, vi, 60, 65, 103, 105, 117,
225, 645, 691, 693, 708, 717, 719, 726,
727, 728
Grassi, G. B., 753
Grieg, J. A., vii, 538
Giinther, A. C. L. G., 5, 91, 388, 675, 737
Haeckel, Ernst, 20, 108, 309, 340, 562, 563,
564, 571, 574, 581, 645
Haecker, Valentin, 565, 566, 567, 624
Halley, Edmund, 3
Heincke, Friedrich, 495, 515, 713, 731, 756,
758, 759, 763
Helland- Hansen, Bjorn, v, vii, 67, 93, 249,
283, 303, 481, 516, 694
Hansen, Victor, 15, 37, 309, 310, 315, 321,
334, 337, 347, 349, 358, 360, 3S2,
563, 571, 652, 703, 718, 731, 772,
773, 775,776, 77^, 783, 784
Heurck, H. van, 346
Hjort, Johan, viii, 412, 712, 722, 759, 767
Hoek, P. P. C, viii, 5S3
Hoffbauer, C, 759
Holt, E. W. L., 731
Hooke, Robert, 2
Hooker, J. D., 5, 6
Home, John, 199, 202, 208
Hulett, , 179
Huxley, T. H., 9
Irvine, Robert, 178, 182, 183, 184, 192,
728
Irvine, William, 3
Iversen, Thor, v, 53, 61
Jeffreys, J. Gwyn, 1 1
Jenkin, H. C. Fleeming, 9
Jensen, Adolf, 435, 547
Johnson, J. Y., 5
Joly, John, 160, 187
Jorgensen, Eugen, 311, 325, 350, 351, 642
Joubin, Louis, 590, 592
Judd, J. W., 184
Jungersen, H. F. E., 546, 547
Kant, Immanuel, 660
Karsten, Gustav, 322, 346, 347, 356
Keeble, , 673
Kelvin, Lord (Wm. Thomson), 12, 27, 29,
43, 219, 220, 226, 233
Kiffir, Hans, 527
Kircher, Athanasius, 3
Klebahn, H., 333
Knudsen, Martin, 237, 239, 246, 255,300,690
Koefoed, Einar, v, vii, 54, 88, 415, 569, 575,
639, 640, 657, 720, 727
Koehler, Rene, 544
Kofoid, C. A., 311, 323, 325, 326, 356
Kolthofi", Gustaf, 524
Kotzebue, O. von, 4
Krogh, August, 253, 258
Kriimmel, Otto, 224, 260, 703
Krusenstern, A. J. von, 4
Kyle, H. M., 440
Lachmann, Johannes, 308
Lamarck, J. B. de, 660, 661
Lambert, J. H., 131
Lauder, H. S., 308
Lea, Einar, vii, 695, 749, 763, 764, 767
Lebedinzeff, Arsenius, 15
Lee, G. W., 189, 759
Lee, S. P., 9
Lenz, H. F. E., 4
Liebig, Justus von, 367, 728
Lo Bianco, Salvatore, 683
Lohmann, Hans, 310, 321, 325, 349, 356,
360, 361, 362, 363, 364, 382, 383,
384, 385, 3S6, 427, 598, 717, 727
Loven, S. L., 7
Lowe, R. T., 5
Lucas, ¥. R., 29, 30, 39, 40, 170
Luksch, Jos., 249
Llitken, C. F., 737, 747, 755
Lysholm, , 581
MacAndrew, R., 8
M'Clintock, Leopold, 9
INDEX OF PROPER NAMES
789
M'Intosh, \V. C, 731
Magellan, Ferdinand, 2
Makaroff, S., 15
Marsigli, , 3
Martins, C. F., 4
Masterman, A. T., 731
Maury, M. F., 4, 8, 195, 213
Meisenheimer, Johannes, 589
Mercator, Gerard, 2
Mill, H. R., 13
Milne-Edwards, Henry, 7
Mohn, H., 261
Monaco, Prince of, 13, 90, 252, 544, 585,
590, 592, 622, 652, 782
Mortensen, Theodor, 493, 544, 546, 547
Moseley, H. N., 577, 687
Mulgrave, Lord, 3
Miiller, G. W., 582
Miiller, Johannes, 7
Miiller, "O. F., 3, 307
Murray, George, 310
Murray, James, 18
Murray, John, v, vi, vii, viii, 7, 13, 15, 16,
17, 57, 106, 108, 130, 132, 133, 134,
143, 161, 170, 178, 182, 183, 184, 192,
225, 229, 299, 308, 310, 355, 413, 418,
426, 427, 428, 430, 517, 545, 546, 561,
564, 599, 64S, 661, 662, 666, 687, 705,
707, 716, 717, 719, 72S, 772
Nansen, Fridtjof, 15, 1 10, 209, 219, 220, 232,
259, 274, 283, 302, 303, 342, 359, 728
Nares, G. S., 67
Nathansohn, Alexander, 311, 370, 371, 372,
378, 3S0
Natterer, Konrad, 15
Nelson, E. W., 377
Neumann, Giinther, 599
Nitsch, Roman, 308
Nordenskjold, Otto, 17
Nordgaard, Ole, viii, 229, 532, 581, 642,
657, 712, 716, 720
Norman, A. M., 493
CErsted, A. S., 309, 334
Orleans, Duke of, 434, 639
Ostenfeld, C. H., 255, 310, 311, 352, 353
Ostwald, Wolfgang, 311, 31 S, 6S9, 690, 691,
692, 693, 700, 703, 704
Palumbo, G., 561
Parry, W. E., 4
Paulsen, Ove, 3 1 1
Pavillard, Jules, 3 1 1
Peach, B. N., 199, 202, 208
Peake, R. E., 19, 169, 170, 299
Peron, F., 4
Petersen, C. G. J., 36, 43, 359, 386, 427,
428, 431, 503, 504, 662, 713, 717, 731,
733> 753, 756, 771, 784,785
Petersen, Eugen von, 35, 249, 561
Pettersson, Otto, 15, 20, 219, 232, 253, 300,
301, 302, 310, 338, 359, 714, 715, 716
Philippi, Emil, 174
Phipps, Captain, 4
Plate, Ludwig, 500, 515
Popofsky, A., 564
Pourtales, L. F. de, 9, 10
Puehler, Christoff, 2
Pullar, F. P., 16
Pullar, Laurence, 16, 225
Pullen, Captain, 4, 9
Piitter, August, 31 1, 384-386
Raben, E., 184, 185, 368, 385
Rafter, G. W., 372
Raken, M., 178
Rasch, Halvor, 507
Rasmussen, Thorolv, vii, 664
Rattray, John, 13
Rauschenplatt, E., 717
Red eke, H. C, 717
Regnard, Paul, 252
Reibisch, Johannes, 759
Renard, A. F., 134, 143, 161, 192
Rennell, James, 5
Richter, C, 217
Risso, J. A., 5
Romer, Fritz, 517, 524, 525
Romme, , 5
Ross, J. C, 4, 5, 6
Ross, John, 4, 5
Ryder, J. A., 740
Sabine, Edward, 4
Samter, , 556
Sandstroin, J. W., 274, 693
Sarasin, Edouard, 248
Sars, G. O., viii, 8, 225, 309, 438, 493,
507, 508, 517, 523, 532, 581, 582,
583, 645, 64S, 654, 655, 656, 712, 714,
729, 731
Sars, Michael, 6, 7, 574
Saussure, H. B. de, 4, 215
Schaudinn, Fritz, 517, 524, 525
Schimper, A, F. W., 313, 315, 364, 378
Schloesing, T., 177
Schmelck, Ludwig, 191
Schmidt, Jobs., 67, 72. 334, 634, 710, 713,
731, 735' 753
Schmitz, Fr.. 334
Schott, Gerhard, 299, 780
Schultze, M. S., 684
Schlitt, Fr., 309, 315, 337, 348
Scoresby, William, 4, 5, 1 1
Scott, R. F., 17
Sedgwick, , 372
Semper, Carl, 738
Shackleton, E. H., 18
Sigsbee, C. D., 27, 29, 30, 31, 32, ^^
Smith, B. Leigh, 11
Sorensen, Gerhard, 714
790
DEPTHS OF THE OCEAN
Spratt, T. A. B., 7
Steenstrup, Japetus, 590, 642
Stein, T. R. von, 30S. 381, 719
Steuer, Adolf, 563. 674, 701, 773
Stuxberg, Anton, 526
Sund, Oscar, vii, 585, 667. 720, 759, 762, 766
Tait, P. G., 246
Tanner, Z. L., 706
Theel, Hjalmar, 488, 490
Thomson, C. Wyville, 7. 10
Thomson, J. S., 759
Thomson, William {sec Kelvin)
Thouars, A. D., 4
Thoulet, T., 187
Tizard, f. H., 7, 13, 546, 661
Torell, Otto, 10
Trybom, Filip, 713
Turner, William, 780
Vaillant, A., 413
Van Heurck, H., 346
Vanhoffen, Ernst. 571
Van 't Hoff, J. H., 190, 366
Verrill, A. E., 577, 707
\'erworn. Max, 691
Waghenaer, L. J., 2
Wallich, G. C., 9, 308
Weber, Max, 17
Wedderburn, E. M., 16
Wegemann, Georg, 226
Wells,;. C, II
Weltner, Wilhelm, 556
Wesenberg-Lund, C, 311, 343
Whipple, G. C., 372, 380
Wilkes, Charles, 5
Wille, J. N. F., 333
Winkler, L. W., 253
Wolfenden, R. N., 267
Woltereck, R., viii, 583
Wright, E. P., 10
Zederbaur, E., 325
INDEX OF GENERA AND SPECIES
Abra, 494
loiigicallis, 482, 504
ftitida, 482
Abraliopsis morisii, 595
Acanthepliyra, lOl, 1 18, 126, 127, 5S5, 622-
624, 654, 659, 699
multispina, 585, 622-624, 668, 720
purpurea, 585, 622-624, 668, 720
Acanthias, 452, 647
vulgaris, 391, 441, 442, 447, 451, 646
Acanthochiasma fusifoniic, 564
Acanthogorgia armata, ^38
AcantJionietron pelhicidum, 564, 565
Ai-aiithonidium echinoides, 564, 565
Acanthostauj-us nordgaardi, 564, 565
Acaiithozone cuspidata, 506, 558, 589
Acartia, 645
bifilosa, 579
clausi, 655
^i2;/^j, 655, 657
Acerafias, 108, 610, 677
macrorhiuus iiiduiis, 87, 90, 96, 609, 615,
618, 625, 627, 744, 745
7tiollis, 615
Achnantes, 345
tcvniata, 345
Actinia equina, 463, 464, 479
Actinostola callosa, 482, 504
Aigitiella spinosa, 5 1 1
^gisthus nntcronattis, 655
ALolis, 468, 494
rtifobj-anchialii, 468
^^/^a, 472, 479
Aifideus armatus, 655
giesbrechti, 655
Agalmopsis, 631, 697
elegans, 574, 642
Aglantha, 1 1 8, 658, 698
digitalis, 570, 571, 640, 659
Aglaura hemistoma, 571
Agliscra, 669
ignea, 571
Akera bullata, 469
Alcockia rostrata, 414
Alcyonidiuiii, 471
gelatinosum, 498
hirsutum, 463, 479
Alcyonium, 494, 500
digitatum, 472, 4S4, 500, 512, 514
Alepocephaliis, 71, 76, 81, 87, 89, 95, 121,
127, 412, 413, 416, 419, 420, 433, 602,
743
^^°7«n//, 394, 433
7-osfratus, 414, 423
Aleposomus copei, 414
Allantactis parasitica, 521
Alloposus mollis, 706
Amallophora affinis, 655, 657
magna, 640, 655, 657
obtusifrons, 655
AiiialopencEus alicei, 668
elegans, 668
tinayrei, 668
Amarouciuni viutabile, 529
Amathillopsis spinigera, 521, 522
Amauropsis islandica, 528
Amniodytes, no, 474
Amphidinium gracile, 365
Amphihelia, 508, 546
ramea, 485
Aviphioxus, 474
Aviphiprora, 345
hyperborea, 345
Amphisolenia, 347
globosa, 327
palmata, 356
tenella, 327
Amphiura chiajei, 492
denticulata, 538
filiforniis, 492
no>-Z'egica, 482, 504, 51 1
sundevalli, 529
Anabivna baltica, 345
Anarrhicas, 647
lupus, 441, 442, 451
minor, 442
Anguilla vulgaris, 752, 753
Ankyroderma jeffreysi, 529
Anomalocera, 645
pater sofii, 579
Anomia, 508
ephippium, 472, 553
Anonyx, 521
Antalis agilis, 504, 505
791
792
DEPTHS OF THE OCEAN
Antalis enfa/is, 475, 494, 500, 533
striolata, 482
Antedon, 506
eschrk/it/, 517, 519, 520, 526, 529, 533
petasus, 486
prolixa, 519, 529
tenella, 506, 533
Antelmiiicllia gigas, 3 1 5
Antomariiis, 103, 671
viar»!oraiiis, 610, 611, 615, 633, 671
Anthpptihim mnrrayi, 538
Afitiinora, 127, 424
viola, 121, 400, 401, 432, 433
Aphanizotnenonflos-aqiKT, 345
Aphrodite aculeata, 501, 541
Aporrhais pes-pelecaiii, 494
Appendicularia, 382
sictila, 598
Apseudes spinosus, 506
Arachnactis, 1 20, 126
a/(5?'^rt, 576, 577, 634, 642, 711, 712
^;ra, 418
glacialis, 528
pecttiucidoides, 483
te/ragoiia, 513
Architeuthis, 651, 652, 653
^MX, 643, 646, 651
Arcturus, 51 1, 521, 534
baffini, 521, 523
Arenicola, 489, 530, 556
marina, 530
piscatormn, 464, 466, 479, 530
Argentina, 389
«/«-r, 394, 447 > 455
sphyrana, 394, 447, 449
A7-gonauta, 419, 597, 632
Argyropelecus, 68, 85, 87, 89, loi, 126,
127, 419, 605, 616, 618, 630, 6S1,
683, 684. 698, 708, 741, 742, 743, 744,
755
aciileatus, 612, 618, 630, 643
affinis, 612, 629, 630, 669
hemigyjnnus, 85, 612, 616, 618^629, 630,
643, 684, 698, 738, 739
olfersi, 612, 629, 630, 643
Aricia, 482, 504
Aristeopsis, 420
Arnoglossics, 448
grohmanni, 407, 447, 450
laterna, 407, 447, 448
lophotes, 79, 407, 447, 448
Ascidia incnlula, 479
obliqua, 504, 534
prumiui, 530
venosa, 510
Ascidiella aspersa, 479
virginea, 497
Ascophyllum, 470
nodosum, 335
Ascor/iynchiis abyssi, 524
A St ac ilia, 521
Astacilla gramilata, 521
longicoi-nis, 511, 513
Astarte banksi, 528, 530
Iwrealis, 528, 535
compressa, 530
a-ebricostata, 528
elliptica, 530
sulcata, 494, 508
A sterias glacialis, 471, 472
gronlandica, 529
hyperhorea, 529
lincki, 529
miilleri, 473, 492
panopla, 529
r//(5f;w, 464, 473, 475, 479, 491, 503,
509, 512, 532, 534
Asterionella gracilliiiia, 343
japonica, 346
notata, 346
Asterolatnpra, 381
Diarylandica, 347, 356
rottila, 347
Asteroniphalits, 38 1
heptactis, 347, 354
Asteronyx loveni, 504, 540
Asthenosoma hystrix, 538
Astrogoitium pareli, 540
Astronesthes, 95, 664, 702
wz'fer, 93, 95, 603, 612, 618, 703, 720
Astropecten, 475, 476
irregidaris, 475, 491, 510
Astrorhiza, 504
arenaria, 482
crassatina, 527
Atelecychis sepfenidcntafns, 496, 510, 511
Atherina, 447
presbyter, 397
Atlanta ciinicjila, 173
depressa, 173
///i-ra:, 173
gaudichatidii, 173
gibbosa, 173
helicinoides, 173
inclinata, 173
z'^/ai-a, 173
invohita, 173
lesueurii, 173
mediterranea, 173
peronii, 173
priinitia, 173
qtioyana, 173
rosea, 173
soitleyetii, 173
less el lata, 173
turriculata, 173
violacea, 173
Atolla, 86, loi, 108, 118, 572, 627, 669
bairdi, 624, 642, 659, 666
loyvillei, 573
Augaptilus, 578, 655
filigerus, 580, 655
INDEX OF GENERA AND SPECIES
793
Aiigaptihts gihbus, 655
■ laticeps, 655
longicaudatus, 655
oblongiis, 655
palumboi, 655
sqitaiiiatiis, 655, 657
Aitlacantha scolyniantha, 565, 566, 567
var. bathybia, 566
var. typica, 566
Aulographis paiido)-a, 565, 566, 567
Aurclia, 98
,?;/r//«, 572, 645
so/ida, 573
Aifxis thazardtis^ 643
Axinopsis orbiculata, 528
Ax in lis ferriiginosus, 482
Jlexuosus, 482, 504
,^(7///a'/, 528
Bacteriastruiii delicatiihiin, 347, 35S
elongatum, 347, 356, 358
varians, 354, 355
Bahrna biscayeiisis, 780, 782
my St ice ins, 778, 779
Bahrnoptera, 779
borealis, 779
7) til sen his, 714, 77S, 779
physaliis, 779
Balanoglossiis, 503
Balanus balanoides, 461, 479, 485, 532, 556
Bassozetiis tivnia, 414
Bathothatima lyromma, 592, 594, 596
Bathybiaster robusius, 538, 547
vexillifer, 518, 519, 524, SjS, 547
Bathybiiis, 9
Bathycrinus, 545
carpe7tteri, 523
Bathygadus, 770
lojigifilis, 399, 423, 432, 433
vielanobraiichiis, 399, 423, 432, 433, 769
Bathymicrops, 389, 686, 687
rd^/j-, 88, 396, 416, 419, 686, 687
Bathyplotes tizardi, 482, 486, 504, 51 1, 540
Bathypontia minor, 655, 657
BatkyJ>te)-ois, 389, 420, 433, 606
diibius, 80, 396, 686
longicaudata, 414
loiigipes, 396, 414, 416, 418
Bathysaurus, 76, 95, 120, 121, 389, 420,
433> 606
ferox, 121, 396
viollis, 414
Bathysiphon filiformis, 482
Bathytrodes, 394
attritiis, 414
^f/a, 528
Be /one, 607
vulgaris, 748
Benthesicymiis, 420
Beuthopecten spinosiis, 537, 538
Benthosauriis, 95, 420
Beuthosatiriis grallator, 396, 686, 687, 688
i9tvw, 118, 658
aicumis, 575
Biddtilphia atirita, 320, 345
mobiliensis, 346, 355
7r^«-/a, 346
sinensis, 353
Biloculitia Icevis, 527
Blepharocysta splendor mai-is, 356
Bolina infiindibitiiim, 575
Bolittrna, 595
diaphana, 597
Bolocera tiiedice, 482, 484, 500, 504, 510
Bonellia viridis, 490
Boreofusiis bernicieiisis, 494
Boreophausia ineniiis, 640
raschii, 666
Bothns, 440
maximus, 441, 442, 451
rhombus, 441, 442, 451
Bougainvillia, 479
siiperciliaris, 569
Bowerbankia, 471
imbricata, 463
i?^x, 77, 448
vulgaris, 403, 447
Brachiotenthis riisei, 591, 596
Brama raii, 643
Brisinga coronata, 540
cndecacnenios, 486, 540
Brissopsis, 430, 492, 519
lyrifera, 490, 492, 504, 510
Brosmiiis, 389
/;;wwf, 400, 441, 442, 447, 451, 733
Bticcimim, 112, 528
glaciale, 528
gronlandicum, 528
hydrophanum, 528
undatum, 472, 494, 512
Bythocaris, 520
leucopis, 524
payeri, 529
simplicirosiris, 506
Cadiilus iubfiisi/orinis, 482, 504
Calanus, 427, 698, 726
cristatits, 579
finmarchiius, 108, 118,383, S79> 580,639,
640, 645, 654, 657, 666, 691, 698, 726
gracilis, 654, 657
helgolandicus, 654
hyperboreus, 1 18, 579, 639, 640, 654, 657,
658
minor, 654
robustus, 654
Calciosolenia nnirrayi, 332, 347, 365
Callionymiis lyra, 450
maculatus, 410, 449
Calliteuthis reversa, 591, 596, 625, 627
Calocalantis, 579
/«7W, 693
794
DEPTHS OF THE OCEAN
Calocaris, 427
macandrecF, 541
Calve}-ia hystrix, 536, 538
Calyptrosphara oblonga, 365
Cavipaiiularia flextiosa, 470, 479
johnstoni, 498
lo7toissima, 498
verticillata, 498
vohibilis, 5 1 1
Canipylaspis horrida, 506
verrucosa, 506
Cancer, 64
pagurus, 476, 495
Candace, 655, 657
Candeina nituia, 172
Cantharus liiieattts, 74, 403, 447, 770
Caprella linearis, 467, 497
septentrionalis, 497
spinosissima, 521
Capros, 71
a/e";-, 405, 447, 448, 609, 614
Caranx, 89, 370, 635, 747
Irachuriis, 77, 98, 406, 447, 614, 635,
646, 747
Carcharias glaticus, 635, 644
Carcharodon, 87, 388, 391, 419
megalodon, 156, 391
Carcintts nianas, 464, 477, 479
Carditim, 556
ciliatuni, 529
echinatum, 494, 495
^flSf^/^, 464, 466, 475, 479
fasciattwi, 475
gronlandicu/H, 529
minimum, 506
Careproctus reinhardi, 436
Caridion gordoni, 506, 515
Carinaria, 590
atlantica, 173
cithara, 173
cornucopia, 173
cr is fat a, 172
depressa, 172
fragilis, 172
^^(7/m, 172
gaudickaudii, 173
lainarckii, 154, 172
punctata, 173
Catablema campanula, 569, 570, 640
Cavolinia, 419
gibbosa, 172, 589
globitlosa, 172
i7iflexa, 172, 201, 589
longirostris, 172, 589
quadridentata, 172
tridetitata, i^z, 589
trispinosa, 172, 201
uncinata, 172, 589
Centrina, 64
salviani, 391, 447
Centriscus scolopax, 79, 389, 396, 447
Centrolophus pompilus, 643
Centropages, 645
Centropages hamatus, 579
////a<j, 579, 655
Centrophorus, 388, 423, 424, 433
calceus, 392
coelolepis, 392
crepidater, 392
squamosns, 392, 447, 44S
Centroscyllium fabricii, 392
Cephalophanes refulgens, 654
Cerataulina bergonii, 346, 354, 377
Ceratias, 81, 82, loi, 609, 614
couesii, 92, 608, 614, 627
Ceratium, 323, 325, 326, 344, 346, 349,
374, 376, 377, 384
a;r//a/w, 347, 350, 351, 357, 35S
arctiatum, 356
arietimim, 354, 356
flsor/fww, 347, 354, 356, 358
biicephalum, 347
buceros, 356
candelabrum, 347, 355. 356, 358
carriense, 347, 356
cephalotum, 347
compressum, 325
declinatiiin, 356
extettsum, 347, 356
>rra, 347, 348, 354, 355, 375, 377
>««, 347, 348, 355, 356, 358, 375, 377
gibberjim, 345, 356, 358
gracile, 356
gravidum, 347, 356, 358,
hirtmdinella, 325
intermeditim, 347, 350, 351, 358
karsteni, 356
lamellicorne, 347, 354
limulus, 356
lineatum, 325, 347, 355, 358
longipes, 347, 348, 350, 351, 357
war-mww, 347, 350, 351, 355, 356, 358
massiliense, 347, 356
pahnatzim, 347, 356
pavillardii, 351, 356
pennatum, 347, 356, 358
pentagonnm, 356, 358
platycorne, 324, 325, 356, 35S, 580
prcelongum, 347
pulchellum, 356
reticulatuin, 347, 356
/t';;«^, 351, 356
var. buceros, 351
/67-£j, 356
trichoceros, 324, 351, 356
/;v>j-, 307, 325, 347, 348, 354, 367, 374,
375, 381
vultur, 351
vox. japonica, 351
Ceralocorys, 347
horrida, 356
Cesium veneris, 85, 89, 575, 631
INDEX OF GENERA AND SPECIES
795
Ceiomimus, 104, 677, 682
storeri, 613, 625, 627, 681, 682
Chatoceras, 318, 342, 344, 345, 346, 348,
357, 381
anastomosans, 346
atlantiaun, 347, 354, 357, 35S
boreale, 347, 358
cinctum, 346
coarciatiiin, 347, 356
constrictiim, 321, 346, 34S, 372, 373
contorhnn, 346, 354, 358
cotivolutum, 347, 354
coronatuni, 354
crinjtuiii, 346
criophihim, 347, 357, 35S
curvisetum, 346, 355, 358
debile, 346, 348, 357
decipiens, 317, 319, 320, 347, 354, 355,
357, 358
densHiu, 2,^7, 354, 355
diadenia, 346, 354
diclmta, 347, 354, 356
didymum, 345, 346, 355
diverstim^ 346, 355
femur, 346
>;ra, 346, 355
furcellatum, 345, 358
laciftiosum, 342, 343, 346, 357, 358
lorenziamini, 355
mediterranewii , 358
wzVra, 345
perpusillum, 357
peruvianutn, 354, 356, 35S
pseudocrinituni, 321, 346
radians, 346
radicuiuin, 346
jf/«///«, 342, 343, 346, 354, 355, 357, 35S
scolopendra, 346, 354
simile, 346
sociale, 346
^er^j, 346
tetrastichon, 356
weissjlogii, 346
ChcBloderma, 494
Challengeria trideiis, 566
xiphodon, 567
Chara, 177
Chaidiodits, 85, loi, 681, 720
sloaiiei, 85, 96, 603, 611, 618, 629, 630
Chelyosoma macleyamiiii , 529
Cheraphilus, 551
nanus, 496
Chiast?iodus niger, 607, 613, 720, 721
Chimara, 71, 424, 672
mirabilis, 59, 389, 393, 433, 672
7nonstrosa, 389, 423, 447
Chiridiella macrodactyla, 639
Chiridius armatiis, 640, 655
obtiisifrons , 640
poppei, 655
Chirodota Icevis, 529
Chiroteuthis, 592
Chirundina stressi, 654
Chiton, 494
cinereus, 472, 495
Chlorophthalmus productus, 686
Chond7-actinia digitata, 493, 500, 510
Chrysaora i?iediferranea, 573
Chrysophrys aurafa, 74, 403
Cinclopyramis infundihiiliini, 149
Ciona intestinalis, 469, 479, 497, 517, 5^9
longissima, 529
Circalia stephanomma, 574
Cirroteuthis, 595
fnulleri, 522
umbellata, 597
Cirrotkatttna, 595
murrayi, 595, 597, 625, 682
Citharistes, 328
apsteini, 330
Cladorhiza, 519
Clathrocaniiim regince, 149
Clava, 470
squamata, 463, 470, 479, 487
Clavellina lepadiformi s , 479
Cleippides quadricuspis, 521
Cliinacoditim, 315
C//t) andrece, 172
australis, 172
balantiitm, I'JZ
chaptali, 172
cuspidata, 172, 5S8, 589
falcata, 589, 625, 669, 720
polita, 172
pyramidafa, 118, 172, 588, 589, 642, 711
sulcata, 172
uncinata, 711
[Creseis) acictila, 172, 588, 5S9
chierchicE, 172
conic a, 172
virgula, 172
{Hyalocylix) striata, 172, 5 89
{Styliola) snbula, 172, 589
Cliojte, 701
limacina, 107, 108, 118, 126, 588, 589,
645, 658, 659, 698, 699
Clupea alosa, 447, 448, 60 1 , 6 1 1 , 635, 644, 646
Jiuta, 644
harengns, 601, 645, 765
pilchardus, 447, 601, 602, 61 1, 635, 644
sprattiis, 601, 645, 765
Coccolith oph or a, 331
leptopora, 332, 347, 365
I i neat a, 365
pelagica, 347, 354, 365
wallichii, 365
Codonium princeps, 569, 570, 640
Colossendeis, 547
atigiista, 547
proboscidea, 520, 529
Conchoderma virgatum, 582
Conchcecia, 655
796
DEPTHS OF THE OCEAN
Conckcecia antipoda, 581
borealis, 581, 640, 655
elegans, 581, 655, 666
maxima, 655
obiusaia, 581, 655
Conchcccilla, 655
lacerta, 655
Conchcecissa, 655
armaia, 655
Conga- V7ilgaris, 441, 442, 451
Conocara, 71
mac7-optera, 394
Copilia, 579, 655, 657
Cor alii na, 145
Corbula gibba, 494
Corella parallelogramma, 479
Corethron criophiliwi, 347, 358
valdivicB, 322
Coris julis, 78, 405, 447
Corophiiim grossipes, 489
Cory cans, 655
Corymorpha glacialis, 534
nutans, 569
Coryne, 470
pus ilia, 470
Corynomma speculator, 592, 596
Corystes, 502
cassivelanus, 496, 501, 502
Coscinodiscus, 348
centralis, 347, 354
concinnus, 355
excentricus, 358
^ra:«», 345
lineatus, 355
viarginatus, 354
radiatns, 347
;rjr, 17, 315, 316, 347, 356
stellaris, 347
subbulliens, 313, 347
Coscinosira ccstrupi, 347, 358
poly chorda, 346
Cottunculus microps, 436
sttbspinosus, ^2^
Cottus quadricornis, 535
Crane hia scab r a, 596, 632
Crangon, 427, 496, 551
allinanni, 496, 506, 533, 534, 666
vulgaris, 532, 553
Crania anomala, 506, 507
Creseis acicula, 588, 589
Cribrella sanguinolenta, 549
Cristellaria, 482
Crossota, 669
brtinjiea, 570, 571
norvegica, 571, 640
Ctenodiscus crispatus, 528, 529, 534, 535
Ctenopteryx siculus, 591, 596
Ctuumaria, 556
elongala, 492
frondosa, 473, 477, 4S8, 512, 530, 555
glacialis, 529
Cucutnaria hispida, 482, 504, 540
lac tea, 493
Diinutn, 529
Cidtellus pellucidus, 494
Cupulita car a, 574
jflri-/, 711, 712
Ctivierina columnella, 172, 5 89
Cyanea capillata, 572, 645, 736
lamarckiana, 572, 642
Cyclocaris, 669
guilelmi, 584, 641
Cyclopterus, 647
Cyclosalpa, 599
jloridana, 600, 632
pinnata, 600, 632
Cyclothone, 93, 96, 103, 126, 604, 618, 619,
623, 624, 625-627, 644, 677, 678, 681,
699, 720, 739, 742, 771, 777
acclinidens, 612, 676
livida, 612, 676
jiiicrodon, 86, lOl, 102, 103, loS, 1 18,
126, 604, 612, 618, 619-622, 624, 625-
627, 659, 664, 665, 676, 677, 681, 688,
699, 71S, 739, 740, 741, 771
microdon pallida, 612, 676
obscura, 681
signata, 85, lOi, 102, 103, 108, 118,604,
612, 618, 619-622, 624, 625-627, 62S,
664, 676, 677, 681, 699, 739, 740, 741,
771
signata alba, 612, 676
Cyema, 702
atrum, 87, 96, loi, 605, 612, 618, 625,
627, 664, 665, 677, 681
Cylichna alba, 530
cylindracea, 494
Cymbalopora (Tretoiitphalus) bulloidcs, 172
Cymbulia pcronii, 589
Cymonomus norniani, 538
Cyphosus boscii, 614
Cyprina islandica, 494, 495, 553, 554
Cystosira, 335
Cystosoma, 85, 89, 92, 583
neptuni, 584
Cytiiere dictyon, 155
Dactyliosolen antarctictis, 347, 354
tenuis, 354
Dactylosfomias, 93, lOl, 612, 618
Deima fastosiun, 541, 543
Dendrodoa aggregata, 529
Dendronotus velifer, 534
Dental ill m caudani, 539
Dentex, 71, 79, 448, 449
macrophthalmus, 403, 424, 447, 448, 771
maroccanus, 70, 403, 447, 448
vulgaris, 74, 403
Desmoteuthis pellucida, 596
Detonula cystifej-a, 345
sclircederi, 313, 346
Diacria quadridentata, 589
INDEX OF GENERA AND SPECIES
797
Diacria frispiitosa, 588, 589
Diagranwia, 449
mediterra7ieum, 74, 403
Dibranchus hystrix, 41 1
Dicoryne conferta, 498
Dictyocha Jibula, 358, 365
Dinonemertes investigaforis, 577, 578
Dittophysis, 327, 365
acuminata, 355, 377
acuta, 327, 347, 355, 358
gramilata, 347, 382
hastata, 347
hoinunculus, 347
rotundata, 355, 358, 377
schrdderi, 356
j^/»-<y/«, 347, 354, 356, 358
uracantha, 347, 354, 356
Diphasia ahictina, 511
fallax, 5 1 1
Diphyes arctica, 573, 574, 640
Diplopsalis lenticula, 355, 356, 358
Discosphcera thomsoni, 145
tubifer, 365
Disseta palumboi, 655
Distephanus speculum, 354
Distoma crystallinum, 534
Dityliim brightwellii, 346
Doliolum, 583, 598, 599, 600, 696
gegenbauri, 599
krolmi, 599
miilleri, 599
tritonis, 599, 600
Doratopsis, 591, 596
exophthalmica, 591, 592, 596
lippula, 592, 596
Dorigoiia, 419
Doris, 468-494
tuberculata, 468
Dorocidaris, 508
papillata, 507, 509
Dosinia, 513
lincta, 494, 495
Z)o/i?, 494
Drepanopsetta, 1 1 0
Dynainena pumila, 462, 463, 470, 477, 532
Dysniorphosa octopunctata, 569
Dysomma, 683, 746
Ebalea cranchi, 495, 496
tubcrosa, 495, 496
Echinaster, 556
sauguinoleutus, 493, 509, 513, 530, 534,
555
Echinocardium, 475, 491, 513, 514, 519
cor datum, 488
flavescens, 475
Echinocyamus pusillus, 475, 493, 508
^c/i inosigra ph iale, 538
Echinus aculiis, 473, 478, 488
iormvijleiningi, 478
forma norvegictis, 508, 509
Echinus affinis, 538
alexandri, 538
clegans, 493
escukntus, 465, 473, 478, 493, 503, 508,
512, 513, 514, 558
miliaris, 493
Echiostoma, 612
Eledonella, 595
pygmtca, 597, 625
Elpidia, 419, 538
glacialis, 523, 524
Eng7-aulis encrasicholus, 447, 601, 602, 611,
635, 644, 646
Epigonus telescopus, 402
Epimeria cornigcra, 506
loricata, 506, 533, 5 58
Epithemia, 314
Epizoanthus paguriphilus, 538
Eryoneicus, 585, 586
ccectis, 586
Ethmodiscus rex, 315
Etmopterus, 424
Encalamis, 720
attenuatus, 654, 657
cornutus, 654
elongatus, 654, 657
monachus, 654
nasutus, 654
Eucanipia balaustium, 346
zodiacus, 346, 354, 355
Euchceta, 107, 118, 427, 645, 654, 669,
698, 720
acuta, 654
batbata, 639, 654, 657
glacialis, 639, 640, 654, 657
marina, 580, 654, 657
norvegica, 118, 505, 579, 580, 639, 640,
654, 657, 658, 659, 666
Euchirella, 579
(5r^zv>, 654, 657
messinensis, 654
r OS t rat a, 654
venus, 654
venusta, 580, 654
Eucladium, 177
Eucopia australis, 720
Eucoronis challengeri, 146
Eudorella emarginata, 506
Eukrohiiia fozvleri, 578, 669
Eumenia crassa, 501
Euodia cuneifonnis, 354, 355, 358
Eupaguj-us benihardus, 557
Euphausia, 654, 720
^z'3(Ja, 654
krohni, 654
tenera, 654
Euphysa aurata, 569
Eupyrgus scaber, 529
Etirycope gigantea, 521, 654
Eustomias, 612
ohscurus, 611
798
DEPTHS OF THE OCEAN
Euthemisto, 107, 108, 128, 126
libellula, 584, 640-641, 654
Euthynnus alliteratiis, 643
Eutonia socialis, 569
Exocoetus, 607, 633, 747, 748
spilopus, 82, 607, 613
volitans, 644
Exuvicella, 365
Ficulina Jifiis , 500, 510
Fierasfer, 120, 634
Filigrana implcxa, 501, 506
Flabellum, 538, 539
arctiiiis, 504
Flustra foliacea, 498
seciirifroiis, 498
Flustrella, 471
hispida, 463
Fragilaria, 315, 345
antarcHca, 346
crotonensis, 343
cylindrus, 345
oceanica, 316, 345
Freyella sexradiata, 542, 543
Fritillaria venusta, 598
Frugella, 419
Fuais, 462, 464, 470, 487, 526
vesiculosus, 335
Fiinchalia woodwardi , 668
Funiculina, 504
quadrangularis, 482, 504, 540
Gadiculus argenteus, 399, 424, 433, 447,
448, 733
Gadus, 389
cEglefinus, no, 399, 441, 442, 447> 45i.
733
callarias, 399, 441, 442, 451, 730, 731,
733. 737, 741, 762
esmarkii, 399, 447, 733
/z««/r5, 399, 447, 448, 733
merla7tgus, 399, 441, 442, 447, 451, 733
minutus, 733
navaga, 441, 442
pollachius, 441, 442, 451, 731, 733
poiitassou, 399, 447, 733
jiz/ifo, 437, 641
»zmw, 441,442, 451, 647, 731, 733, 737,
760, 761
Gactaniis anin'gcr, 655
catidani, 655
/t;7////, 655
laticeps, 655
latifrons, 655
miles, 655
mmor, 655
Gdidius notacantha, 655
teniiispmus, 655
Galathea dispersa, 496
intermedia, 496
«e;f«, 510
Galathodes tridentatiis , 486
Galeolaria biloba, 574, 641-642
truncata, 642
Galiteuthis suhtiii, 596, 632
Ganimartis lociista, 466
Gasirost07nus, 104, 106, 108, 702
baird/i, 76, 96, 97, loi, 104, 118, 605,
612, 618, 625, 627, 664, 665, 677, 681,
699, 739, 740, 741, 749, 750
Geodea, 517
Geryon affinis, 538
tridens, 515, 541
Gigantocypris, 90, loi, 581, 624, 627, 659,
669
agassizii, 582
Glaiiais, 590
atlanticus, 85
Globigerina, 164, 563
(Eqtdlateralis, 172
bulloides, 150, 172, 527, 564, 642
conglobata, 172
cretacea, 172
digit at a, 172
dubia, 172
dtitertrei, 172
helicina, 172
inflata, 172
linjtcBana, 172
marginata, 172
pachyderm a, 172, 527
7-jtbra, 172
sacczilifera, 172
Glycera, 475
Glyptonotns megalurus, 524
Gobius mimitus, 450
Gomphonema, 314
Gonactinia prolifera, 472
Gonattis, 632, 651
fabricii, 1 12, 113, 592, 596, 643, 646,
650, 651
Goniaster borealis, 509
Goniodoma, 326
Jimbriatum, 356
polyedricum, 356, 358
Gonostoma, 604, 677, 681, 743
deniidatum, 604, 605, 612, 744
elongatiim, 604, 664, 665
grande, loi, 604, 612, 618, 625, 627,
628, 664, 665, 702, 720, 739, 744
rhodadenia, 604, 612, 618, 664, 665, 677,
702, 720
Gonyaulax, 326, 347
fragilis, 356
y^'^i^^^, 356
mitra, 356
pacijica, 356
polygramf/ta, 326, 356, 358, 381
spini/era, 355
triacantka, 345
Gorgonocephaliis, 508
agassizi, 529
INDEX OF GENERA AND SPECIES
799
Gorgonocepkahis eiiciieiitis, 519, 527, 529
lamarcki, 508, 533
linckii, 486, 487, 508, 533, 540
Gossleriella tropica, 347, 348, 356
Grimalditetithis, 592
bonplandi, 592, 593, 596, 625
richardi, 592
Gniiiai-dia Jlaccida, 346
Halargyreus, 370, 424
affinis, 401, 433
Halichondria panicea, 467
forma typica, 500
var. bibula, 500
Halicreas rotundatttvi, 571
Halimcda, 179
Hal ion una -wyvillei, 148
Haliptcris christi^ 510
Halobates, 587
Halobatodes, 587
Halocyp}-is, 655
globosa, 655
Haloptihis aciitifrons, 655
longicornis, 655
miicronatus, 655, 657
ornatus, 655
Halosauropsis, 95, 121, 389, 420, 433
macrochir, 121, 396, 416, 423, 431
Halosaiatts, 76, 415, 433
rost rains, 414, 418
HalosphcEra, 334, 335, 345, 3S5
Z7r/r/?>, 334, 335, 347, 358
HaplopfuagmiiiDi latidorsatuin, 527
Hartnotho'c, 530
Harriotta, 76, 127, 416, 420
raleighana, 127, 389, 394, 416, 417, 432,
433
Hastigerina pelagic a, 152, 153, 172
Hemiaster expergitus, 538
Hemiaulus, 356
hauckii, 346, 355
heibergii, 346
Hemicalanus, 579
Heinilamprops cristata, 506
Heterorhabdiis brevicaiidaius, 655
longicornis, 655
noi-vegicus, 655, 657
papilliger, 655
spinifrons, 655
viper a, 655
Heteroteidhis dispar, 597, 632
Hexanchus griseus, 510
Hexancistra quadricttspis, 147
Hexasterias probleiiiatica, 356
Hippasierias, 533
phrygiana, 486, 509
//«««, 486, 506, 509, 513, 515, 516, 533
Hippocamptis, 89, 607, 671
raimdosus, 613, 633
Hippocre7ie superciliaris, 569, 570, 640
Hippoglossiis, 370
Hippoglossiis hippoglossoides, 436, 455
vulgaris, 407, 441, 442, 447, 451
Hippolyte, 427, 654
gaiinardi, 530, 556
polaris, 486, 506, 530, 531, 534
pusiola, 515
securifrons, 486, 496, 533, 551, 666
spi7ius, 529, 551
tu7'gida, 529
varians, 673
Histiiobranchus, 395, 420
bathybitis, 414
inf emails, 414
Histioneis, 328
giibernans, 330
Homarus vulgaris, 473
Hoplocaricyphiis siinilis, 622
Hoplonyx, 510
Hoplostethus iiiediterraneicin, 401, 402, 424,
43 3 > 447
Hyalocylix striata, 589
Hyalonei7ia, 10, 420
Hy alone merles, 577
atlantica, 577
i^l/rtj, 474, 530
araneiis, 474, 495, 530
coarctatus, 495, 510, 513, 530, 534
Hybocodon prolifer, 569
Hydractinia echinata, 498
Hydrallviannia, 498
/a/^a/a, 498, 511, 533, 534
Hymenaster, 533
pellucidzis, 518, 519, 526, 533
Hyrnenodora, 587, 654
glacialis, 127, 520, 524, 5S6, 587, 641
gracilis, 668
Hyperia inedusaruni, 654
Hyperoodon diodon, 646, 650, 780
Hypnum, ITJ
lanthina, 85, 88, 173, 590, 702
Icelus hainatus, 437
Ichthyococcus, 605, 681
ovatns, 612, 629, 630
Idiacanthits, 664, 702
y;?r^x, 86, 87, 612, 618
Idotea eiitoinoii, 529, 535
nietallica, 584
///^jc illecebrosus, 592, 596
Inachus, 474
dorsettensis, 496, 513
dorynchtis, 510, 513
Ipnops, 419, 686, 687
mtirrayi, 87, 414, 686, 687
Isocardia cor, 554
Katagnyniene, 334
Kellia suborbicularis, 494
Kelliella miliaris, 482
A'^/^rt, 538
hyalina, 523
8oo
DEPTHS OF THE OCEAN
Kophobelemnon stellifenu/i, 482, 4S3, 504
Krithe pi-odtuta, 155
Kroknia hamata, 108, 118, 578, 640, 658
Lcetmogoneviolacea, 419, 538
Lcetinonice filiconiis, 504, 541
Lafoea, 5 1 1
dtimosa, 485, 498
Lagena apiailata, 527
Laminaria, 459, 461, 467, 470, 489, 526
530, 560
digitata, 467, 472, 477
hyperborea, 467, 468, 471, 472, 477, 489
saccharina, 467, 472, 477
Lamna, 418, 647
coniubica, 646
Laiiipra, 522
purpurea, 533
Laiiipris gtittatiis, 643
LainproDiitra huxleyi, 147
Lanceola, 583
Laomedeajiexuosa, 463, 470, 487
Latreictes ensiferus, 671
Laiideria amiulata, 313, 346, 355
Leachia cyclura, 596
Z^d/a, 418
viinuta, 494
pernula, 530
Leodice norvegica, 5 1 3
Zi?/a^, 582
anatifera, 100, 582
anserifci-a, 582
fascicularis, 120, 5S2, 634, 642, 711,
712
/^?7//, 582
pectinata, 582, 634
Lepeta ccsca, 530
Lepidion, 60, 370, 424
tY«^.i-, 40O) 401, 433
lepidion, 423
Lepidopleuriis cinereus, 495
Lepidopus caudatus, 407, 614
Lepidotrigla aspera, 409, 447
Leptocephahis, 618
amphioxus, 750
brevirostris, 618, 750, 753
Congri vulgaris, 80, 81, 750
Synaphobtanchi pinnati, 750, 751
Leptocylindrus danicus, 321, 346, 348, 355
Leptopty chaster anticiis, 534, 535
Licinophora, 314
Licodes albus, 414
Lilljeborgia fissicomis, 506
Lima excavata, 486
hians, 473, 488
Liiiiacina, 118, 164
antarctica, 172
aus trails, 172
<Ja/£a, 587, 589, 645
btdimoides, IT 2, 588, 589
helicina, 108, 172, 587, 5S9, 640, 658
Limacina helicoides, 172, 589, 625, 669, 720
inflata, 172, 588, 589
lesuetiri, 172, 588, 589
retroversa, 172, 587, 588, 589, 645
triacantha, 172
trochifortnis, 172
Limneandra norvegica, 569
Limopsis, 418
minuta, 508
Lii-iope tetraphylla, 570, 571
Lints, 670
inaculatus, 91, 92, 607, 613
mediisophagiis, 613, 633
ovalis, 91, 607, 613, 633
percifonnis, loi, 613
Lispognathus thoi/isoiii, 538
Lithodes, 64
/iiaja, 486, 496
Lithodes?niiiiii it/idulatii/n, 345
Lithoptera darwinii, 14S
Lithothamnium, 145
Littorina littorea, 462, 463, 472, 479, 532,
554, 556
obtttsata, 463, 472, 479
rudis, 462, 479, 530
Zo/i^,?, 595
/(7r^fj-/, 494, 597
media, 597
Lophius, 611
piscatorius,\oZ,d^\ 1,442.447, 450,451,609
Lophohelia, 58, 508
p rotifer a, 485, 505
Lopholatiliis chainicleonticeps, 706
Lopkothrix frontalis, 654
latipes, 654
Lubbockia squillimaiia, 655
Lucicutia all aula, 655
brevis, 655
curta, 655
flavicornis, 655
Lucina boreal is, 495
Luidia ciliaris, 510, 511
jar^?', 492, 513
Lumbrinereis , 501, 524
fragilis, 482, 504, 530, 541
Lumpemis, 370
lampetriformis, 437
inaculatus, 437
inedius, 437
Lunatia, 475
gronlandica, 530
intermedia, 475, 494, 514
montagni, 494
Lyaia, 654
Z7C(7^«j-, 435, 436, 547
eudipleurostictus, 436
flagellicauda, 436
frigidus, 436
JHurana, 436
pallidus, 436
scntimidiis, 436
INDEX OF GENERA AND SPECIES
80 1
Lycodes similis, 436
terra: nova, 410
Macrocliiniin pomum, 498, 534
Alacrostomias longiharbatus, 94, 603, 612
Alacriirunger, 447
Macriirus, 60, 62, 71, 76, 95, 97, 109, 120,
121, 126, 127, 415, 420, 424, 434, 745
cequalis, 59, 397, 416, 41S, 423, 432,
433, 672
arinatus, 685
bairdii, 432
berg/ ax, 425
carmi)iattts, 432
fabricii, 437, 455
^'^[^aj, 414, 415
goodei, 425, 432
glint her i, 397
liocephalus, 414
parallelus, 425, 431
sulcatus, 432
zaniophortis, 397, 423, 432, 433
(Cetonurus) globiceps, 398, 416, 4 1 8, 423
{Chalinura) brevibarbis, 398, 416, 418,
4I9> 432
vturrayi, 398, 433
simuhis, 398, 416, 418, 425, 432
(Ca^lorhynckus) CKlorhynchiis, 397, 432, 433
talismatti, 397, 423, 433
{Co7ypkiznoides) asperrimus, 398, 433
rupestris, 397, 425, 432, 433
(Lioniirus) JUicauda, 414, 417, 425, 431,
626
(Macrurtcs) sclero7-hynchus, 397, 414, 423,
425, 432, 433
{Malacocephalus) lewis, 398, 433, 447
{Nematomirus) artnatus, 398, 414, 415,
416, 417, 419, 425, 431, 433, 626, 769
Mactra, 495
elliptica, 494, 513, 514
stultorum, 494, 502
Malacosteus, 683
choristodactyhis, 93, 612
indicus, 87, 419, 603, 612, 625, 627
niger, 93, 625
Malletia obtiisa, 482, 504
Mallotiis villosus, 641, 646, 707, 712
Afargarita cinerea, 52S
gronlaiidica, 530
helidna, 530
Masfigofeuthis, 592
Jiain/nea, 596, 625, 627
grimaldi, 596, 625
/z/or^?, 592, 625
Medusetta a7rifera, 567
Megacalanns longicornis, 654
MeganyctiphMies, 108, 645
norvegica, 583, 640, 654, 666
Megaptera boops, 779, 780
Melamphacs, 601, 609, 614, 677, 682
7nizolepis, 609, 614, 625, 627, 682
Mela/ioce/iis, 609
johiisoiii, 609, 614, 618
k7-echi, 87, 610, 614, 618, 627
Melanosio/ziias, 612
Melicertidimii octocostattu/i, 569
Me77ib7-a7iipora memb7'a7iacfa, 467
pilosa, 471
Merliicciiis, 389, 433, 443, 448
vulgaris, 69, 399, 421, 441, 442, 447,
450. 451, 733> 771
Merte/isia, 118, 65 8
ovufH, 575
Mesoplodon, 157
Afesothjiria intestinalis , 4S2, 504, 519
Metridia ciu-ticauda, 654
lo/iga, 654, 657
lnce72s, 654
tior//ia/ii, 654
Metridiu7n, 464
dia7ithus, 463, 465, 479, 494, 497, 500,
534
Michaelsarsia, 331
elegans, 332, 347
Microcala7tii5 pusillus, 640
Microsetella 7i07~vegica, 655
Mit7-oco7neUa fulva, 569
Mixoims laticeps, 414
Modiolaria hzvigata, 530
7iigra, 494, 530
Moelleria a7ita7-ctica, 346
yJ/^i/rt:, 633
;«(?/«, 644
rotu7uia, 119, 607, 615, 697
Molgiila retorliforiiiis, 529, 534
i]/^/z'a, 389, 433, 734
byrkcla/ige, 400, 733, 734
elongata, 400, 447, 448, 449, 733, 734
w^/ra, 400, 441, 442, 447, 449, 451, 733,
734
Mo7iaca7ithus, 610, 611, 615, 633, 671
Mo/iops, 579
Mo7itacufa, 494
Mo7-a, 60, 81, 370, 424, 449
7nora, 59, 400, 423, 433
Mo7']iionilla 7niiior, 655
Adotella 7nac7-ophthalma, 424
triciri-hata, 450
Mtilltis, 448
sur7imletits, 70, 71, 404, 405, 447, 448
Mu7iida, 482
w ic7-ophth ahna, 5 3 S
7-ugosa, 482, 486, 490, 510, 533, 654
teniii/7ia7ia, 482, 4S6, 540
Munidopsis, 420
ai7"vi7-ostra, 5 38
Mn7mopsis, 654
/j///Va, 506, 521, 530
MiD-icna helc7ia, 79, 389, 395, 447
Muricu-a placo/mis, 252
Mus/elus, 64
7Wi^«;-/.f, 391, 447
3F
802
DEPTHS OF THE OCEAN
My a, 556
arenaria, 464, 479, 530
truncata, 530
forma (ypica, 495
Myttophum, 601, 605, 677
{Diaphtis) gemellari, 613, 618, 632, 670
rafinesqiiei, 606, 613, 632
{Lampaiiyctiis), 677
elongatum, 606, 644
gemmifer, 613, 632
maderefise, 613, 632
micropterum, 613, 632
warmingi, 613, 632
{Myctophum) affine, 613, 61 S, 632
benoiti, 613, 632
hygomi, 613
chcerocephaluiu, 613, 618, 632
(r<?(:c^/, 95, 613, 618, 632
glacialc, 605, 613, 632, 634, 644
hzimboldti, 613, 618, 632
pundatiim, 95, 605, 613, 618, 632, 63^
rwj(7z, 613, 632, 746
Alyliobatis aqtiila, 393, 447
Myriochele, 524
Myriotrochus rinki, 529
vitrc'us, 504
My sis, 645
relict a, 556
My til lis, 468, 477
ediilis, 462, 479, 532, 554
fiiodioliis, 472, 494, 500, 512
Nacella pellucida, 467, 472, 532
Nassa reticulata, 489
Natica, 502, 510
bathybi, 524
catena, 494, 502
clausa, 528
Naucrates diictor, 91, 608, 609, 614, 633
Nausitho'e, ^J2
atlantica, 573
globifera, 573
Nautilus, 87
Navicula, 314, 345
^-a«?Y, 345
membranacea, 345
septentrionalis, 345
vanhdffe7ii, 316, 345
Necera, 482
Nectonemertes griinaldi, 577
/^(5a/a, 577
mirabilis, 577
pelagica, 577
Nematobrachion boops, 654
Nematoscelis, 720
microps, 654
Nemickthys scolopaceus, 93, 98, 605, 612
Neobyt kites crassns, 414
Neolithodes grivialdi, 538
Nephrops tiorziegiciis, 510, 515, 516, 533
Nephropsis atlantica, 539
Nephthys, 475, 482, 501, 508'
Nepttmea, 493, 494, 500, 521, 522
antiqua, 493, 510, 517
despecta, 528
7/iohni, 524
Nereis, 468, 510
pelagica, 530
Nerophis, 120, 644
czquoreus, 126, 606, 613, 634, 644
Nicania banksi, 475, 495, 528, 530
Nicolea, 467, 530
zostericola, 530
Nitzschia, 314, 365
i-^;-M/a, 347, 354, 355, 358, 365
Noctiliica, 68, 338
miliaris, 674
Nodularia spiimigena, 345
Notacanthns, 121, 389, 424, 433
bonapartii, 396, 433
Notidanus, 388
griseus, 370
Notostomzts, 585, 586, 624, 699
Nucula tenuis, 494
var. expaitsa, 528
iumidula, 482, 483
Nyctiphanes, 666
(Meganyctiphanes) noi-vegica, 666
Nymphon, 529, 530
brevirostre, 468
elegans, 529
gracilipes, 529
grossipes, 530
hirtipes, 529, 534
macronyx, 529
mixtuvi, 515, 534
robtistum, 520, 524, 527, 529, 533
st7'oini, 486, 497, 506, 515, 516
Obelia, 569
getiiculata, 467, 470
Oceanapia robusta, 507, 510
Octopodoietithis sicula, 591, 596, 632
Octopus, 522, 595
{Polypus), 597
/^M^/, 595, 597
Oculina, 546
Oikopletira labradoriciisis, 598
parva, 598
vanhoffeni, 598
Oithona, 655
pluinifera, 580, 640, 655
siinilis, 579, 580, 639, 640, 655
Ommatostrephes, 592, 594
sagittatus, 592, 596
todarus, 592, 645, 646, 64S, 650
Otnosudis lowci, 91, 606, 612
Onccea, 655
conifera, 639, 640, 655
notopus, 639
Onchidiopsis glacialis, 528, 534
Onchocalanus rostratus, 654
INDEX OF GENERA AND SPECIES
803
Oneiivdes, 94, 95, 104, 608, 609, 614, 61 S
inegaceros, 94, 614
Oneirophanta, 542, 543
Oniiphis, 508
conchylega, 530
Hibicola, 510
Onychotetithis haiiksi, 591
Ophelia limachia, 475
Ophiacantha abyssicola, 508, 540
bidentata, 508, 530, 549
Ophiactis abyssicola, 508, 540
O pinaster, 331
formosiis, 332, 365
Ophiocoina 7iigra, 473, 488
Ophiocten, 419
^«-/«z<w, 492, 515, 518, 524, 527, 530,
540, 547
Ophioglypha, 418, 419
Ophiomiisiutn lyniani, 538
Ophiopholis actileata, 468, 472, 473, 4S0,
486, 492, 508, 513, 530
OpJiiopleiira, 419
aurantiaca, 538
borealis 518, 529
Ophiopus arcticus, 529
Ophioscolex glacialis, 504, 506, 508, 530
purpurea, 508
Ophiothrix fragilis, 472, 492, 503, 510, 513,
557, 576
Ophiura, 109
a//«-./a, 473, 492, 512, 513, 514
ciliaris, 489, 491, 492, 510, 514
nodosa, 529
robusta, 530
jflrw, 492, 504, 508, 530
Opisthoprochis, 104, 681, 683
grimaldii, 90, 602, 61 1
soleatus, 90, 94, 602, 611
Opisthoteitthis, 595
agassizii, 597
Orbulina universa, 151, 172
Orchestia littorea, 465, 479
Ornithocercus, 328
magnificus, 328-330, 347, 356
qttadratus, 328, 347, 356
splendidus, 328, 329, 347, 356
jA'/;/??, 329, 347, 356
Ostrea, 479
edulis, 479
Owenia assimilis, 530
Oxycephalus, 654
Oxygyrus keraudrenii, 173
rangii, 173
Oxyrhina, 87, 388, 391, 418, 419
trigodon, 157
Oxytoxum, 347
cri statu)?!, 356
diploconus, 358
>^>;-/2", 365
milneri, 356
reticulatutn, 356
Oxytoxum scolopax, 356, 358, 365
tesscUatitiii, 356
Pagellus, 71, 441, 442, 443, 448, 449
acariie, 403, 447
centrodontus, 64, 403, 404, 447, 448
Pagrus, 79, 448
vulgaris, 74, 79, 404, 447
/"a^^/zr/w, 95, 427, 534
bernhardus, 465, 495, 510, 512
chiroacanthus, 551
/«T'/j-, 510, 551
ineticulosus, 510, 511
pubescens, 480, 4S6, 495, 500, 510, 513,
530, 541
tricariuatus, 5 1 1
Pahciiion, 469
natator, 671
Palinurus vulgaris, 64
Pandalus, 427, 587, 645, 654
annulicornis, 469, 496, 506, 512, 534, 666
bonnieri, 504, 505, 506
borealis, 530, 531, 666
brevirostris, 486, 515
propiuquus, 486, 5 1 1
Pandora glacialis, 529
Panopica norvegica, 494
Pantachogon haeckelii, 571
Paracartia grani, ^"jg
Paragorgia, 505, 508
arborea, 485
Par alia sulcata, 355
Paraliparis bathybii, 126, 127, 436, 437,
641, 688
Paramuricea placovius, 484
Parapaguriis, 420
pilosimamis, 538
Parapasiphcca sulcatifrons, 668
Paraspongodes, 484, 508, 522
fruticosa, 522
Parathemisto oblivia, 584, 5S5, 641, 654
Pardalisca abyssi, 506
Parechinus, 478, 479
miliai-is, 473, 478, 479
Pasiphcea, 127, 427, 5S6, 645
princeps, 540-541, 5 86, 641
sivado, 666
Patella vulgata, 462, 479
Pecten, 479, 486
abyssorum, 483
frigidus, 524, 547
grdiilandicus, 517, 528
hoskynsi, 506, 530
islandicus, 514, 528, 534
opercularis, 479, 494, 510
septemradiatus, 504, 510
Pecttmculus glycimeris, 494. 213
Pectyllis arctica, 571
Pelagia, 118, 119, 572
atlantica, 95
/,'/-/«, 573, 574, 632
8o4
DEPTHS OF THE OCEAN
on emeries, 577, 659
Pelaviys sarcia, 609
Pelonaia corrugata, 530, 534
Peltaster nidarosiensis, 540
Peniagone wyvillii, 541, 543
Peniiatida phosphorea, 503
Pentacheles, 420, 586
Pejitaa-iniis, 545
Pentagonaster, 533
granularis, 486, 490, 533
perrieri, 538
Per ac lis bispinosa, 172
diversa, 589, 625, 669
reticulata, 172, 589
triacantha, 589
Peridinium, 326, 347, 353, 355, 356
conicum, 358
depressum, 323, 358
diveigefis, 358
oceaiiiciim, 358
ovatum, 358
parallelum, 357
tristylum, 358
Perigonimus abyssi, 483
Periphylla, 572, 627, 669
hyacinthi)ia, 573, 624, 642
r<^/«a, 573
Peristedion cataphractm/i, 70, 409, 410,
447
Petromyzoit niarintts, 601, 611, 644
Phaemia spiuifera, 655
Phceocystis, 333
globosa, 346
poucheti, 333, 345, 358
Phalacroiiia, 347
«^'A''«^, 356
alliens, 356
doryphortim, 356
rudgei, 356
Phascolosoma strombi, 500
Phellia abyssicola, 484
Pheronema carpenteri, 539, 540
Phialidiinu, 569
PJiiline, 469, 494
Pholas crispata, 494, 495
Phormosoma, 109, 429, 430
placenta, 538
Pkoronis, 352, 559
Photostomias, 86, 664
gtternei, 86, 87, 603, 604, 611, 61S, 664,
665, 677, 683, 702, 739
Phoxichilidium fcnioratiini, 468
Phoxichilus spinosiis, 468
Phrotiivia, 583, 584, 585
sedentaria, 654
/•/y^/j-, 433
albidus, 450
blennoides, 400, 447
Phyllopus bidentatjis, 655, 657
Phyllostajiriis (jitadrifoliiis, 564
Physalia, 68, 85, 88, 575, 631, 696
Physalia arethusa , 574
Physeter macrocephahis, 646, 780
Physophora, 696
borealis, 7 1 1 , 712
hydrostatica, 574, 642
Pitnelepteriis boschii, 10 1
Placostegus trideiitafiis, 485, 508
Plagusia, 73
Planctonemertes, 624
Planes minutus, 103, 633, 671
Planktoniella sol, 347, 348, 354, 356, 358
Platyscelis, 654
Plesionika nana, 585, 668
Pleurobrackia, 1 18, 658
pileus, 575
Pletiromma, 579
abdoniinalis, 654
gracilis, 654, 657
robnsta, 642, 654
xiphias, 654
Pleiironectes, 390
cynoglossus, 441-442, 451, 454
/(^j-z/j, 451
limanda, 407, 441, 442, 447, 451, 513
niicrocephalus, 441-442, 451, 452
platessa, 441-442, 451, 763
Pliimularia pinnata, 498
Plutonaster bifrons, 538
Pneumoderma violaceum, 588
Pneutnodermopsis macrochira, 589
Podolampas, 347
^?/!i£j', 356
elegatts, 356, 358
palmipes, 356, 358
Pcecilasma carinatiim, 582
Polyacaiithonotus, 396
Poly bins, 65
henslo7ui, 66
Polycera, 468
Polycheles, 420, 586
Jianus, 539
sctdptus, 538, 596
pacificiis, 587
Polycyclus fuscus, 467
Poly prion, 670
americanus, 98, 607, 614, 633, 770
Pomatoceros triqueter, 472
Pontaster tenuispinus, 504, 505, 509, 510,
517-518, 530, 547, 549
Pontella, 579
Pontellina, 579
Pontophilus, 533, 551
norvegicns, 482, 504, 506, 533, 541
spinosus, 515
Potitoporeia affinis, 556
PontosphcBra, 331
huxleyi, 332, 347, 365
Poralia, 573
rtifescens, 573
Porajiia pnlvilliis, 486, 509
Porcellana, 495
INDEX OF GENERA AND SPECIES
805
Poncllana longicornis, 495
Forella, 506
Forocidaris purpiirata, 538
Poroiiiya granulata, 508
Porospathis holostoma, 567
Portlandia frigida, 482, 530
liicida, 482, 504
tenuis, 482, 506
Portuniis, 476, 497
depurator, 476, 495
holsatzis, 495
pusilhts, 495
tuberculatus, 510, 511
Pourtalesia Jeffrey si, 520, 547
wajideli, 538
Priinnoa, 505, 508
lepadifera, 484
Pristipoma, 77
beimettii, 403, 447
Pristiurus melanostomns, 391, 447
II I II rill lis, 391
Procymbulia, 589
Prorocentnnit inicaiis, 344, 346, 377
Protella p has ma, 497
/';'(7/'o pedata, 497
Protoceratium reticidatum, 356, 358
Prolocystis bicornis, 567
harstoni, 567
tiaresi, 567, 568
swirei, 566, 567
thoinsoni, 566, 567, 568
tridens, 566, 567
Protodiniuin, 365
Psaiiimobia, 475
ferroensis, 494, 495
tellinella, 513
Pseudocalanus eloiigatus, 579, 639, 640, 654,
• 657
gracilis, 639
Psilaster androineda, 504, 518, 540
Psoitis phantapus, 530
squamatus, 486, 488, 490, 506
Pterasier militaris, 515, 530
iitultipcs, 540
Ptcrosperma discitlus, 365
Pterotrachea, 85, 88, 590, 702
coronata, 154
Pterycombus brania, 643
Pterygioteuthis giardi, 590, 591, 595
Ptychodisciis carinahis, 358
Pulleitia obliquiloculata, 172
Pulvinulina caiiariensis, 172
, crassa, IT 2
karsteni, 527
menardii, 172
micheliniana, 172
patagonica, 172
tiiiiiida, 172
Purpura lapillus, 462, 479, 532
Pycnogoiiuin littorale, 497, 534
Pyrocystis, 328, 329
Pyrocystis fiisiforiiiis, 331, 347
lunula, 356
nociiluca, 328, 331, 347, 356, 674
Pyrophacus horologiuiii, 358
Pyrosoina, 598, 599, 600, 659, 696
atlanticuiii, 600
giganteuiii, 600
spiiwsuiH, 600, 624
Kaia, 513
rt/(J^, 393, 447
/5a//j-, 393, 447
circularis, 64, 393, 447
clavata, 64, 392, 447
fiillonica, 393, 447
/>//«-, 393, 433
hypcrborea, 436, 437
iiiitroocellata, 389, 392, 447
iniraletus, 389, 393, 447
iiidrosieiisis, 393, 433
punctata, 393, 447
vomer, 393, 447
Regal ecus glesne, 643, 698
Retepora beaniana, 485
Rliabdanimina, 504
abyssorum, 482
Rliabdosphizra, 331
claviger, 145, 332, 365
styliger, 365
Rhachotropis, 506
aculeata, 533
Rhiiia squatina, 392, 447
Rhizocrinus, 545
lofotensis, 512, 513, 523, 540
Rhizosolenia, 316, 318, 332, 334
acuminata, 347, 354, 356
rt/rt/rt, 347, 354, 355, 358, 377, 382
ampittata, 354
calcar avis, 365
castracanei, 347, 356
cylindriis, 346
delicatiila, 355
fragillima, 358
hebctata-semispina, 316, 320, 347, 352,
354. 357> 358, 382
robusta, 355
semispina (see i?. hcbetaia)
setigera, 346
shrubsolei, 345, 355, 358
stolterfothii, 354, 355
styliformis, 334, 347, 352, 355, 356, 358
Rhizostoma octopus, 572, 642
Rhodichthys regina, 436, 688
Rhopalonema velatum, 571
Rhynchonella psittacea, 529
Rhyncoteuthis, 596
Richelia intracellularis, 334
Rissoa, 469
Rocinela dammoiiiensis, 506
Rossia, 506, 595
8o6
DEPTHS OF THE OCEAN
Rossta caroli, 597
macrosoma, 510
Rotalina orbicularis, 527
Sabella pavonia, 500, 501
Sabellaria alvcolata, 495, 502
Sabiiiea sarsi, 515, 533, 551
septevicarinata, 529, 551
Saccavimina splucrica, 482
Sacculina, 582
Sagai-tia, 479
Sagitta, 578
ardira, 118, 57S, 640, 658
bipuiictata, 578
gigantea, 578, 640, 641
hexaptera, 578
iiiflata, 578
macrocephala, 578, 669
serratodentata, 578
Salenia kastigcra, 543
Sabiio salar, 442, 646
trutta, 442, 646 ^
5a//a, 381, 583, 710 i'fS
amboiiiensis, 600, 632
confaderata, 600, 632
fusiformis, 126, 599, 600, 632, 634, 641,
642, 708, 710, 711
forma aspersa, 598, 600
forma echiiiata, 600
henseni, 600, 632
irregularis, 7 1 1
maxima, 600, 632
miicronata, 599, 600, 632, 641, 642
riincinata, 7 1 1
tilesii, 600
zonaria, 599, 600, 632, 633
Sapphirina, 579, 655, 657
Sarcobotrylloides aureum, 529
Sarda sarda, 643
Sargassiun bacciferum, 335, 336
Sargus, 77, 448
annularis, 403, 404, 447
rotidelettii, 74, 403
Sarsia eximia, 569
Jlammea, 569
tubulosa, 569
Saxicava, 468
arctica, 494, 530
Scalaria trevelyana, 494
Scalpellum, 418, 420, 508
atlanticum, 582
dar-juinii, 159
dicheloplax, 582
velutinum, 582
Scaphander, 513
pjinctostriatus, 504, 506, 515
Schizaster fragilis, 491, 504, 50S, 533, 540
Sciccna aquila, 402, 403, 447
Sciiia bor calls, 654
Sclerocrangon boreas, 529, 534
^;ur, 520, 522, 529
Scolecith ricella, 655
minor, 655, 657
Scolecithrix dance, 655, 657
minor, 655
Scomber, 370, 747
scomber, 609, 645
Scombresox, 89, 94, 607, 635, 670, 741, 747
j-az^riw, 607, 613, 633, 635, 644, 747, 748
Scorpczna, 79, 448
cristulata, 408, 433
scrofa, 78, 408, 409, 447
ustulata, 408-447
Scottocalanus sccurifrons, 654
Scyllium canicula, 391, 447
Scyphocaris ano7iyx, 654
Scypholanceola, 583
agassizi, 583
Scyphosphara, 331, 347
apstei^ii, 365
Scyramathia. carpenlcri, 538
Sebastes, no, 437, 440, 441, 442, 455, 647,
648, 665
dactylopierus, 408, 424, 433, 447, 448,
614
marinus, 646, 648
norz'egicus, 665
Selachc maxima. 646
^t:/^;Vr, 595
d^orbignyi, 597
officinalis, 597
Sepiola, 494, 595
rondeletlii, 597
Serges tes, 585, 654
ckallengeri, 675
Seriola, 614, 671
Serpula vermicularis, 485. 486
Serranus, 448
cabrilla, 78, 402, 447
Serrivomer, 85, 93, 108, 755
j^c^r, 605, 612, 630
Sertularella gayi, 485, 506, 508
iricuspidata, 511
^z)*/^^, 493, 500, 521, 522
curlis, 528
glaber, 508, 528
gt-acilis, 493, 517
islandiciis, 504, 510
kroyeri, 528
turgidulus, 528
Siphoncntalis teiragona, 4S2, 504
Siphonodentalium vitreum, 523, 524, 528
Siphonostoma typhlc, 606
Sipunculus priapuloidcs, 483, 504
Skeletonema costal um, 367
Skenea planorbis, 463
Solaster abyssicola, 538
rt/^ww, 530
endeca, 506, 515
papposus, 492, 506, 530
squamatus, 533
-Wfrt, 79, 370, 448
INDEX OF GENERA AND SPECIES
80:
Solea hitca, 40S, 447
vulgaris, 64, 69, 370, 408, 441, 442, 447,
450. 451
Solen, 495
ensis, 475, 494
Solinaris corona, 7 1 1
Soinniosus fiiicrocep/ialns, 436
Spatangtis, 494, 509, 517, 519
picrpurem, 475, 491, 505, 513, 517
raschi, 504, 505, 508, 509, 540
Sperosoma grimaldii, 538
Sphcvroidina dehiscens, 172
Spinax, 388
niger, 388, 392, 433. 447, 675
(Etniopterus) princeps, 392
Spiiiocalamis magnus, 654
Spirorbis, 463
Spirilla, 81, 82, 590, 625
aiistralis, 592, 597
Stattracantha niiirrayaita, 147
Stegocephalus iujiatiis, 521
Stenorhynicluis, 474
longirostris, 513
rostrahds, 496, 513
Stcphanopyxis iitrris, 355
Stephanotrochus diadenia, 538, 539
Stei-noptyx, 605, 681
diaphana, 612, 618, 629, 630
Stichaster alhultis, 529
roseus, 509
Stichopiis tremuhis, 482, 504, 50S, 510, 511,
519. 540
Stomias, 85, loi, 681
<^ofl, 603, 611, 618, 629, 630, 720
Streptotheca thamensis, 345
Strongylocentrotus, 478, 493
drdbachiensis, 473, 478, 493, 512, 530
Strophogorgia challenger i, 538
Styela aggregata, 529
loveni, 498, 530
rust tea, 530
Styelopsis grosstilaria, 530
Stylifer turtotii, 493
Styliola subula, 589
Stylocheiron, 720
longicorne, 654
Suberifes ficus, 500
Synaphobranchus, 81, 95, 120, 420, 755
pinnatus, 80, loi, 389, 395, 416, 423,
433. 750, 75i> 752
Syncoryne piikhiila, 569
Syngnafhiis, 92
«c«j-, 606
pelagicus, 103, 606, 613, 633, 671
Synoiciim incrustaliaii, 529
Syracosphcera ampulla, 365
blasiula, 365
echinata, 365
Icevis, 365
prolongata, 332
////r/^ra, 365
Syracosphicra robitsta, 365
spina sa, 365
Sysfellaspis deb His, 668
7«/£j, 464, 554
dectissatus, 554
ediilis, 513
Tectura, 472
virgiuca, 472
Tclcoteufhis carilnca, 591
Tellina, 475, 529
ballica, 532
calcarca, 528
(vvm«, 513
Te/iniodon saltafor, 406, 447, 614
Tetnora, 645
longicornis, 579
Terebellides strcvni, 480, 482, 504, 530
Tercbratiila, 418
Tercbratulina caput-scrpcntis, 4S5, 507
spitsbcrgensis, 529
Tetrodon spengleri, 411, 447, 615
Teitthowenia viegalops, 596, 632
Thalassiosira, 345, 348
antarctica, 346
decipiens, 346, 354
excentrica, 354
gravida, 314, 317, 345, 355
hyalina, 345
nordenskioldii, 345, 354
W;////.f, 347, 354, 355, 356, 358
Thalassiothrix frauetifeldi, 365
longissima, 316, 347, 353, 354, 358
nitzsckioides, 319, 354, 358
Thalassochelys corticata, 97
Thelepus circinnatns, 501, 513, 530
Thenea mtiricata, 483, 484, 504
Thracia truncata, 529
Thiijaria, 498
///?//«, 498, 499, 511, 533
Thynnus, 370
pclamys, 609
thynmis, 609, 643
Thysanocssa, 645
longicaudaia, 583, 640, 654
711 i nor, 654
neglect a, 654
parva, 654
Thysanopoda, 720
aciitifi'ons, 654
oblusifrons, 654
Tiara pileata, 569
Tiaropsis multicin-ata, 569
Timoclea ovata, 475
Todaropsis eblarnx, 592, 596
Toinopte7-is, 578
scptentrionalis , 578
Torrellia vestita, 506
Toxenma belone, 592, 594, 596, 625, 627
Trachiniis, 448
a'rfft-^, 410, 447, 450
8o8
DEPTHS OF THE OCEAN
Trachinus vipcra, 410, 447
Trachurus, 390
Trachypterus, 94, 741, 742
arcticiis, 643
Trachyrhynchus, 81, 433
mtcrrayi, 397, 433
trachyrhynchus, 397
Travisia forbesi , 475
Tremoctopiis, 595, 597
atlanticus, 597, 632
Trichodesmium, 333, 334, 345, 360
(kiebauUi, 333, 347, 356, 358
Trichostoiiia, 177
Trichiurus lepturtts, 643
Tridonta borealis, 535
7>i;?-/a, 71, 79, 441, 442, 448, 451
cucultis, 409, 447
giirnardus, 409, 447
hirundo, 409, 447
/>';'«:, 409, 447
obscura, 409, 447
/?«?, 409, 447
Triglops, 370
pingelii, 437
Triposolenia, 327, 328, 347
bicornis, 328
Tritonia, 494
Trochostoma, 5 1 9
boreale, 520, 529
Trophonia glauca, 501
Truncatulina wullcrstorfi , 527
Tubularia, 470, 472
indivisa, 534
larynx, 498
regalis, 529
Tuscaretta globosa subsp. chnni, 568
tubidosa, 567
Tussilago farfara, 302
Typhlonus nasus, 414
Ulocyathtis arcticus, 504, 505
Umbellula, 87, 519
encrimis, 517, 518, 547
giintheri, 87, 88, 419
lindahli, 538, 547
Umbrina ronchus, 402, 447
Undeuchata major, 654
minor, 654
Uranoscopus scaber, 410, 447
Urechinus naresianus, 538
Uroptychus rubro-vittatus, 538
Urticifia, 494
crassicornis, 463, 479, 494, 497, 500
Valenciennellus, 605, 630
tripunctulatiis, 612, 618, 629, 630
Vatnpyroteuthis, 595
infernalis, 595, 597, 625
F6'/f//fl, 68, 85, 631
spiralis, 574, 576
Velutina kcvigata, 494
Venus casina, 475, 513
fasciata, 475
Jluctuosa, 529
gallina, 494, 495, 514
Verruca slromi, 485, 508, 533
Vinciguerria, 605, 630, 679, 681
lucetia, 604, 612, 618, 629, 678
Virbius fasciger, 551
varians, 551
Virgularia, 494
mirabilis, 500
Volutopsis norvegiia, 494
Waldheimia cranium, 485, 490, 507
septata, 507, 508, 541
Xiphias gladiits, 643
Yoldia hypcrborea, 528
li??iatula, 528
(Portlandia) arctica, 528
Zcugopterus, 370, 443
boscii, 408, 433, 447
megastoma, 407, 424, 44 1 ,
Zewj- faber, 406, 407, 441.
614, 643
Ziphius cavirostris, 1 5 7
Zirphaa crispala, 553
Zoanthus, 500
Zoarces vivipartis, 756, 757
Zoroaster ftilgens, 537, 538
Zostera, 459
marina, 468
Zygicna malleus, 635
442,447,451,454
, 442, 447, 609,
GENERAL INDEX
Abundance of marine animals, 771-7S5
Abyssal fauna of the Norwegian Sea, 434-437,
547-54S
forms of the Atlantic, 543
plain, boundary of, 420
plain, fishes of, 412-421
Acantharia, 564, 631, 642
Acanthin, 564
Acanthometra, 564
Acanthometrid;e, ^^^, 355, 564, 567
Acanthophracta, 564
Acanthopterygii, 390, 401-410, 44S-449,
607-608, 609, 614
Accumulators, 24, 26, 27, 29, 31
Aceratiida", 615
Acraspeda,_568, 572, 573
Acropomatidne, 402
Actiniaria, 63, 95, 419, 430, 463, 494,
525, 577
larval, 634, 641
Actinotrochse, 559
.-Eolids, 5 1 1
African coast fisheries, 74
Age and growth of fishes, 755-771
Age-composition of the stock of fishes, 765
Agulhas current, 277
" Akker," 648
"Albatross," The, 12, 17, iS, 92, 138, 387,
706
Albuminoid matter in deep-sea deposits, 147
Alcyonaria, 9, 149, 484, 485, 525
Aldrich Deep, 131, 132, 140, 141
AlepocephalidK, 71, 389, 394-395> 4i4, 424^
742, 743
Algre, 106, 124, 145, 462, 463, 469, 470,
474, 487, 489, 530, 560
calcareous, 145, 146, 177
green, 459
pelagic, 307-386
red, 459, 468, 470
Alkalinity of sea-water, 176
Alternation of generations, 568
" Amber," The, 19
Ammonia in relation to plant life, 36S, 369,
370, 372
in sea-water, 177, 178
Amphipoda, 85, 89, 107, 467, 468, 470,
489, 496, 497, 506, 510, 520, 521, 558,
579, 583-584, 631, 640, 654
Anacanthini, 389, 397-401
Anchovies, 76, 448, 601, 635, 646, 771
Anemones, 479
Angler, 443, 448, 452 {see also Monk)
eggs of, 108
" Anglia," The, 20
Anguillidiv, 605
Animal life at different depths, 85, 95, 415,
557-558
remains in marine deposits, 14S
Annelida, 149, 500, 501, 508, 575, 578
Anomura, 544
" Antarctic," The, 17
Antarctic continent, area of, 132
expeditions, 5, 6, 16, 17, 18
regions, 244, 245
AntennariidLie, 615
Anthomedusie, 568
Anticyclonic area of North Atlantic, 1 94
Antipatharia, 87, 419
Apatite, 185
Apodes, 389, 395, 605, 612
Appendicularians, 382, 598, 600, 719
Arabs at Cape Bojador, 76
Arachnospharidte, 642
Aragonite, 177, 179
Archibenthal area, 459
fauna of the North Atlantic, 538-546
Archimedes, law of, 689
Architeuthidx', 592
" Arctic," The, 9
Arctic alg«, neritic, 345
oceanic, 347
Arctic currents, 115, 459, 707
expeditions, 7,10,1 1,15, 259, 260, 261, 274
fauna, 13, 517-523, 52S-529
abyssal, 547-548
boreal, 529-531
littoral, 526-527
shallow-water, 437, 525-526
ice, 207, 638
regions, 11, 244, 245, 274, 457
and boreo-arctic regions, 516-535
809
8io
DEPTHS OF THE OCEAN
Arcturids, 5 1 1
Areas of the ocean-floor at different depths,
412
Argus Bank, 178
Ascidians, 62, 103, 419, 469, 472, 479, 483,
486, 497, 49S, 504, 517, 51S, 529, 530,
534, 597, 598
Astartidce, 475
Asterids, 109, 468, 490
Atherinid?e, 397
Atlantic Ocean, area draining into, 194
area of, 134.
area of, at different depths, 134, 136
continental shelf and slope in, 134
deepest sounding in, 132
deeps of, 140- 143
depths of, 131, 132, 134-136, 140-142
number of soundings in, 131
shore-slopes of, 135
submarine banks of, 135
North, abyssal area of, 196
area of, 195
anticyclonic area of, 194
archibenthal fauna of, 538, 546
continental shelf in, 195
continental slope in, 195-196
deeps of, 196
deep-water fauna of, 536-548
deposits of, 9, 194, 198-209
depths of, 56, 194, 195
hydrographical conditions of, 295-300,
458-459
temperature of, 194, 221, 222, 224, 227,
228, 295, 305
Atlantic ridge, 118, 120, 135
Attraction of land-masses, effect of, 130
Auks, 124, 712
Aulacanthida;, 565
Austrian expeditions, 15
Auxospore development, 314, 314-319, 343,
344
Azores current, eastern, 635
Bacteria, 182, 188, 259, 369, 370, 674, 72S
denitrifying, 259, 369, 370
nitrifying, 259, 369, 370
sulphur-reducing, 182, 188
Bailey Deep, 142
Baillie sounding machine, 25, 26
Balanids, 474, 582
Balistida}, 615
Baltic Sea, phosphorus in water of, 185
silica in water of, 184
" Banks," 421
" Banquereau," 1 12
Barium nodules, 157
sulphate, 157, 190
Barnacle belt, 461-462
Barnacles, 100, 200, 207, 477, 508, 525, 556,
634, 642, 667, 668, 669, 670, 672, 683
Bartlett Deep, 196
Bathometers, 2
Bathymetrical contours first shown on maps, 3
range of deep-sea fishes, 423
Bathypelagic animals, 562, 563, 624-628
Bathyteuthidre, 596
Batoidei, 388, 392-393
Belgian Expeditions, 16
" Belgica," The, 16, 575, 639
Belknap Deep, 142
Belt of Venus, 89
Benthos of the Faroe Channel, 127
Berycidse, 401-402, 614
" Besugo," 74
Biloculina clay, 164, 523, 527
Biological laboratories, marine, 20
Biology, general, 660-785
Bipolarity of oceanic diatoms, 352-353
Birds following shoals of capelan, 712
on Rockall, 124
Black Sea, 15, 178, 1S2, 257
Bladder type of suspension organs, 315,
329
"Blake," The, 12, 27, 30, 31, 387, 592
Blennies, 756, 757, 758
BlenniidjE, 390
Blind fishes, 104, 6S1, 682, 685, 686, 687
squid, 682
Blue mud, 160, 161, 162, 167, 168, 171,
175, 181, 182, 187, 188, 19S, 199, 200,
201, 426, 431, 717
Bog manganese ore (see Manganese nodules)
Bolitsenidae, 597
Bomb-lances taken in blue whales, 714
Bonito, 609, 635, 636, 755
Boreal pelagic life, 107, 108, 118, 120, 126
region of the Norwegian Sea, 457, 459-516
Boreo-arctic region of the Norwegian Sea,
458, 531-535
" Bottle-nose grounds," 592
"Bottom-water" in Mediterranean, 68
in North Atlantic, 115, 117, 220
in Norwegian Sea, 125
Boulder clay, 205, 208
Boundary-waves, 274, 715
Brachiopoda, 160, 418, 419, 480, 483, 484,
485, 490, 507, 510, 529, 541
Brachyura, 544
Bramiidce, 643
Branching type of suspension organs, 316
Bream, 64, 441, 442, 443, 449
Brill, 441, 442, 451, 453, 646
" Britannia," The, 19
British Antarctic Expeditions, 5, 17, 18
Association Dredging Committee, 6
cable ships, 19
surveying ships, 19
Brittle-stars, 472, 473, 482, 486, 491, 492,
508, 518, 530, 540
Bronzite spherules, 154, 158
Brooke Deep, 142
Brooke's sounding apparatus, 8, 9, 130
GENERAL INDEX
8ii
Bryozoa, 9, 149, 418, 419, 463, 467, 471,
472, 474, 479, 4S0, 4S3, 4S4, 4S5, 489,
491, 498, 506, 507, 510, 525, 559, 575,
718
" Buccaneer," The, 13, 19
Buchanan Deep, 142
Buchanan's stopcock water-bottle, 230, 231
" Budding," reproduction by, 568
" Bulldog," The, 9
" Burro," 74, 76
" By-the-wind sailor," 574
Cables, telegraph, 9, 169, 170
Cachalot, 646, 651, 652, 780, 782
Calanoida, 1 18, 654-655, 727
Calcareous deposits, 162
sponges, 467
Calcite. 178, 179
Calcium carbonate, 145, 159, 173, 174, 175,
176-180, iSi, 1S4, 186, 1S8, 190, 193,
430
phosphate, 159, 171, 183, 185, 190, 193
sulphate, 175, 176, 179
Callionymidre, 390, 410
"Cambria," The, 20
Canary current, 635
Capelan, 641, 646, 652, 712, 714, 707, 779
Caprellids, 467-468, 470, 497, 511
Caproidae, 390, 614
Carangidce, 406, 609, 614
Carbon dioxide, 176, 177, 179, 186, 188,
193, 253, 254, 255, 256, 258, 327, 355,
3S0
Carbonic acid (see Carbon dioxide)
Carchariida;, 391
Cardiidse, 475
Caridids, 496
Carp, 759
Catfish, 441, 442, 451
Catosteomi, 389, 396-397, 606, 613
Cavolinidse, 588
Centrifuge, 50, 105, 117,310,361, 362,363,
386
Centriscid:e, 396-397
Cephalopoda, 590-597, 632, 647
Ceratiida?, 609-61 1, 614, 625, 627, 676, 679
Cetomimidoe, 606, 613
Chittognaths [see Sagittidre)
Chseto-plankton, 347
Challenger Deep, 131, 140, 143
"Challenger," The, i, 9, -lo, 11, 12, 23-27,
34, 50, 72, 91, 93, 106, 130, 140, 143,
211, 215, 216, 230, 232, 305, 306, 308,
309, 310, 337, 349, 366, 389, 413, 415,
418, 419, 420, 427, 428, 429, 545, 561,
562, 564, 581, 582, 592, 686, 687, 703,
706, 772
ChallengeridK, 565, 566, 568, 642
" Chatter-marks," 205
" Chiacarone," 74, 76
Chiasmodontid;Te, 61^5
" Chierne," 74
"Chiltern," The, 19
ChimasridjE, 388, 389, 393-394
ChiroteuthidiT?, 591, 596
Chitons, 472, 489, 510
Chlorine titration for determining salinity,
237, 238
ChlorophyceEe, 333, 347, 358
" Chopa," 74
Christiania fjord, pelagic alga: of, 371-376,
377, 379
Chromatophores, 312, 355
Chun Deep, 143, 196
nets, 35, 36
Circulation, oceanic, 11, 229, 310, 378-380
Cirripeds, 63, 420, 575, 582
Cirroteuthidae, 597
Cladocera, 579
"Clan McNeil," The, 20
Clays, deep-sea, 155, 166, 185-188
Clinkers dredged by " Michael Sars," 202,
207
Closing nets {see Nets)
Clupeidx, 601, 611, 644, 771
Clypeastrids, 474, 475
Coaltish, 441, 442, 451
Coast banks, 55, 198, 354, 437, 456
plateau, 421, 425
" Coast- water," 240, 241, 278
Coastal area of the boreal region of the Nor-
wegian Sea, 459-460
Coccolithophoridse, 106, 117, 173, 177, 310,
330-332, 344, 347, 353, 354, 355, 364,
365, 381, 382, 693, 699, 719, 773,
775
Coccoliths, 146, 307, 308, 332, 382
Coccospheres, 145, 146, 308
Cockle, 464, 556
Cod, 9, 55, 112, 113, 114, 122, 440, 441,
442, 443, 444, 446, 448, 451, 452, 453,
454, 456, 641, 646, 647, 648, 649, 712,
714, 716, 729-732, 735, 755, 762, 763,
766
Cod-eggs, no. III, 783
Cod-fry, 92, no, in, 734, 735
Cod-larvas, 646, 731-738
Coelenterates, 482, 484, 498, 504, 534, 538,
719
"Colonia," The, 20
Colours of marine animals, 662-673, 729,
731, 742, 743, 744
Coltsfoot, 302
Compressibility of sea-water, 246
Concretionary substances in deep-sea deposits,
190-193
Conduction {see Heat)
Conger-eels, 441, 442, 443, 451, 452, 605,
755
Continental deep-sea zone, 460, 481-486
edge, 133, 198, 421, 456, 507-509
products in marine deposits, 153-154
8l2
DEPTHS OF THE OCEAN
Continental shelf, 56, 133, 134, 136, 13S, 195,
198, 421, 430
slope, 55, 133, 134, 136, 138, 195, 198,
213, 420-437
Contour lines of depth first used on maps, 3
Convection currents, 226
Copepoda, 88, 107, 108, 382, 384, 479, 578,
579-581, 588, 631, 639-640, 642, 645,
655, 658, 693, 697, 702, 703, 719, 720,
727, 755. 775
Coprolitic mud, 148
Coral mud, 149, 161, 162, 166, 168, iSo,
199, 200
reefs, 181
sand, 144, 149, 162, 166, 180
Coral Patch, 195
Corals, 9, 58, 121, 149, 419, 483, 484, 485,
486, 490, 505, 507, 508, 538, 546-559
Cosmic spherules, 154, 158, 160, 166, 171
Cottidie, 390, 436
Crabs, 62, 63, 64, 65, 66, 91, 103, 420,
461, 464, 474, 476, 477, 486, 495, 496,
497, 498, 500. 502, 511, 520, 575, 584,
633' 671
Cranchiidas, 592, 596
Cranyonids, 496
" Craspedon," 568
Craspedota, 568
Crayfish, 584
Crinoids, 109, 419, 486, 545
"Cruiser," The, 20
Crustacea, 95, 108, 1 18, 121, 126, 127, 149,
225, 418, 420, .430, 469, 470, 476, 479,
482, 486, 496, 497, 504, 510, 511, 515,
520, 524, 525, 528, 534, 540, 545, 551,
556, 558, 562, 575, 579, 581, 582, 584,
631, 645, 656,658,663, 665, 666,669,
672, 673, 674, 691, 699, 719, 720-727,
773> 775, 782 {see also Decapods)
Ctenophorce, 575, 595, 658, 692, 719
Cumacea, 496, 506
Current, Agulhas, 277
Canary, 635
Eastern Azores, 635
East Iceland Polar, 124, 300, 534
Labrador, 100, 115, 118, 213, 244, 260,
635, 658, 704
Current-meter, 67, 263-264, 359
observations, 13, 66, 67, 73, 99, 264-306
Currents, oceanic, 5, 66, 67, 113, 174, 244,
245, 259-306, 310, 349-352, 370-374,
431, 514, 517, 525, 527, 531, 533, 534,
536, 558-559, 634-635, 704-710, 717-
718, 733-738
reaction, 776
tidal, 170, 267-272
Cuttle-fish, 82, 87, 93, 103, 1 19, 494, 522, 590
Cyanophyce^ii, 333-334, 356, 358, 385
" Cyclops," The, 4, 9
Cyclostomata, 611
Cyphosidte, 614
Dabs, no, 441, 442, 451, 452
Dacia Bank, 57, 195, 267
" Dacia," The, 13, 19
Danish Expeditions, 16, 67, 72
"Dart," The, 19
" Dead-men's fingers," 500
" Dead water," 275
Decapod Cephalopoda, 590
Crustacea, 420, 506, 529, 530, 538, 544,
551, 579, 582, 584-587, 585,654,702, 773
Deeps, 133, 139-143, 169
Deep-sea deposits {sec Deposits)
fauna, 415, 536-54S
Denitrification, 369, 370
Density observations, 13, 236, 237, 238, 239,
246
Deposits, marine, 8, 9, 10, 143-175, 427-431,
559, 560, 784
Depth of the Ocean, 129-143, 164
Desmo-plankton, 347, 351, 354
Deutsche Seewarte, 214, 227
"Deutschland," The, 18
Development, direct, 517
Diatom ooze, 17, 146, 161, 162, 165, 168,
169, 171, 175, 183, 185, 426, 427
Diatoms, 6, 60, 61, 65, 106, 146, 312-322,
341-344, 345, 346, 347, 352, 353, 354,
355, 356, 357, 358, 360, 361, 363, 365,
366, 378, 380, 381, 382, 70S, 719
Didynms-plankton, 345, 349
Dimorphism in diatoms, 320
Dinophysidpe, 326, 333
Discontinuity layers, 16, 223, 280
" Discovery," The, 17
Dog-fish, 440, 441, 442, 451, 452, 646
Doliolids, 712
Dolomite, 181, 205
"Dolphin," The, 9, 141
Dolphin Rise, 56
Dolphins, 65
" Dorado," 74
Dory, 441, 442
Dredging, 3, 5, 6, 10, 11, 24-27, 30-32
Drift-bottles, 261, 262
Drift nets, 45, 55, 90, 91
of vessels in the ice, 260
of wreckage in the North Atlantic, 260
" Duplex," The, 19
Dutch Expeditions, 17
Meteorological Institute, 215
Earbones of whales, 87, 149, 156, 157, 160,
166, 171, 202, 207, 419
Earn, Loch, temperature observations in, 16
Earth, area of the, 132
Earth's crust, variation in level of the, 131
Earth's rotation, effects of {see Rotation)
Echinoderms, 120, 121, 127, 149, 158, 429,
473, 474, 488, 491, 492, 504, 506, 507,
515, 523, 524, 525, 527, 528, 529, 530,
544, 575
GENERAL INDEX
13
Echinoidea, 149, 473, 544, 546
Echinothurida.', 545
" Edge" (see Continental edge)
"Edi," The, 18
Eelgrass, 468, 469, 4S9, 560
Eel larva;, 80, 81, 94, 96, 97, loi, 103,
104, 120, 126, 618, 634, 670, 748-755
Eels, 104, 605, 753, 755
conger, 441, 442, 443, 451, 452, 605, 755
sand, 474
Effect of light on distribution of organisms,
224, 557, 558
" Egeria," The, 19
Ekman's reversing water-bottle, 234
Elasipoda, 545
Elasmobranchii, 3S8-389, 390-394
" Electra," The, 19
Electrolytic conductivity of sea-water, 237
Elevation in continental areas, 175
Elvers, 753
Enoploteuthidce, 591, 595
"Enterprise," The, 13
Entomostraca, 579
Etive, Loch, Arctic fauna in, 13
Euphausidas, 720
Euryhaline forms, 479, 557
Eurythermal forms, 479, 533, 556-557
Everest, Mount, 131, 133
Extra-terrestrial materials in marine deposits,
154
Eyes of different animals, 680-688
" Fantome," The, 19
"Faraday," The, 20, 169
Faroe Islands, 300, 513-515
Faroe-Shetland Channel, 7, 11, 13, 55, 123,
125, 126, 127, 222, 243, 278-283
Feather-stars, 517, 519, 523, 540
Ferrous sulphide in deep-sea muds, 181, 182,
188
Fish-eggs, 84, 92, 94, 103, 108, no, in,
691, 692, 702, 707, 729-741, 745, 747,
784
Fish-fry, 97, no, ni, n2, 618, 631, 707,
736, 738, 739, 740, 741-748, 749, 757,
773, 784
as current indicators, 736
Fish-hatching, artificial, 784
Fish measurements, 756-758
otoliths in marine deposits, 149, 151
remains in marine deposits, 149
teeth in marine deposits, 151
Fishery in the open ocean, 635-636
on African coast, 73
on Newfoundland Bank, ni-n4
investigations, 20
statistics, 439-444
Fishes, African coast, 74, 635
age and growth of, 755-771
bottom, 387-456
pelagic, 601-615
Fishes, Sargasso Sea, 633
Fishing, depth limit on Atlantic slope, 449
Fjords, 460, 477-486
Flagellates, 106, 117, 312, 330, 332-335,
344, 358, 674
Flat-fishes, 448, 451, 452, 453, 731, 735
Floating and organs of floating, 688-700
Flounders, 97, 444, 451, 452, 497, 513, 646
" Flueaat," 587
" Flying-Fish," The, 19, 663, 670
Flying-fish, 82, 94, 103, 106, 108,607, 633,
747, 748
Food of marine animals, 427, 772, 775
Foraminifera, 89, 146, 149, 164, 167, 171,
172, 173, 307, 481, 501, 504, 527, 563-
564, 631, 642, 697, 719, 720, 755
Fossil mollusc shells, 553-554
"Fram,"The, 15, 237, 259, 261, 274
" Fran9ais," The, 18
Freezing-point, 239
French Expeditions, 13, 18, 68
Frog-fish, 103
Fucoid belt, 461, 462, 466
Fucoids, 459, 463, 487
Fulmars, 712
Fyne, Loch, Arctic fauna in, 13
temperature observations in, 229
Gadidce, 399, 413, 424, 452, 646, 647, 648,
736, 737, 759, 764, 766
Gar-pike, 633, 635, 747
Gases in the sea, 253-259
Gasteropods, 62, 63, 112, 163, 164, 173,
419, 429, 438, 461, 462, 467, 475, 489
Gastrostomidre, 97, 97
" Gauss," The, 17, 174
" Gazelle," The, 12
Geoid, the earth as a, 129
Gephyrea, 483, 490, 500, 504
German Expeditions, 15, 16, 17, 18, 140,
224, 260, 727, 739
Gettysburg Bank, 267
" Gettysburg," The, 12
Gibraltar Strait, n, 66, 67, 72, 264, 285-
290, 291, 293
Glacial period, 535, 54S, 549
Glaciated stones dredged by " Michael Sars,"
203, 205, 207
"Glass eels," 753
Glauconite, 147, 157-158, 159, 162, 171,
189, 190
Globigerina ooze, 63, 149, 160, 161, 162, 163,
164-165, 166, 167, 168, 169, 170, 171,
173, 174, 175, 180, 199, 200, 201, 202,
426, 427, 429, 430, 431, 523, 527, 564
" Goldfinch," The, 19
" Gold-Seeker," The, 278
Gonatidse, 591, 592, 596
"Gorgon," The, 9 *
Gorgonians, 484, 4S6, 490
" Grappler," The. 20
8i4
DEPTHS OF THE OCEAN
Gravitiilional attraction of land-masses, 130
"Great Northern," The, 19
Greenland Polar current, 244
Green mud, 161, 162, 167, 169, 171, 1S9,
198
sand, 8, 148, 162, 167, 171, 189
Growth of fishes, 755-771
Gulf Stream, 3, 100, 107, 114, 115, 117,
118, 120, 122, 124, 194, 207, 213, 214,
223, 230, 240, 242, 244, 259, 261, 270,
276, 281, 296, 298, 299, 300-306, 457,
458, 459, 531, 532, 534, 574, 634, 635,
641, 69S, 704, 707, 708, 72S, 776
Gulf- weed fauna, 91
Gulls, 124, 712
Gurnard, 71, 79, 441, 442, 443, 448, 451
Gymnodontes, 615
Gymnosomata, 587, 588, 589
Gypsum {sed Calcium sulphate)
Haddock, 440, 441, 442, 443, 444, 448, 451,
452, 453, 454, 455, 456, 646, 647, 648
eggs, no. III
larva;, no, 1 1 1, 646
Hair type of suspension organs, 315-316
Hake, 64, 69, 71, 77, 79, 440, 44i, 442,
443, 444, 448, 449, 451, 452, 454,
635
Halacarids, 468
Halibut, 55, 440, 441, 442, 444, 446, 448,
451, 452, 454, 455, 456
Halosaurida;, 396, 414
Hand-line fishing (see Line-fishing)
" Hansa," The, 260
Haplomi, 389, 396, 605, 613
Hardanger fjord, 481
Harling fishing, 636
Harpoons taken in blue whales, 714
" Hauch," The, 662
Helland-Hansen's photometer, 93, 94, 249-
252
Hemiptera, 587
Hemp lines for apparatus, 23-31, 21 1
" Henry Holmes," The, 20
Hensen's plankton net, 37, 45, 358, 359
Hermit crabs, 465, 486, 495, 496, 497, 498,
500
Herrings, 55, 448, 635, 645, 646, 647-648,
663, 699, 712, 714, 715, 716, 755,
758, 759, 764, 765, 766, 767, 76S, 779,
782
Heteromi, 389, 396
Heteropods, 163, 164, 167, 172-173
Hexactinellida, 524
" Hirondelle," The, 14
Histioteuthida;, 596
Hjort Deep, 196
Holbaek fjord, 756
Holocephali, 388, 393-394
Holopelagic forms, 562
Holoplanktonic forms, 562
Holothurians, 62, 63, 76, 81, 87, 95, 120,
121, 418, 419, 420, 429, 430, 473, 490,
523, 538, 545, 575, 717
" Holsatia," The, 773, 774
Ilooke's sounding-machine and water-bottle,
2, 209
HoplophoridK, 5S5
Horse-mackerel, 77, 89, 98, 609, 633. 635,
646, 747
Hydrographical Bureau, Washington, 215
sections, 84, 107, no, 115, 124, 240,
277, 379, 694, 695, 696
Ilydroid polyps [see Zoophytes)
Ilydroids, 9, 103, 418, 419, 426, 462, 467,
468, 469, 470, 472, 474, 477, 479, 483,
484, 485, 487, 497, 491, 494, 498, 506,
507, 511, 512, 513, 521, 522, 525, 529.
534, 568
HydromedusK, 338, 562, 568, 574, 598
Hydrometer, 236
Hydrosphere, 129
Hyperida;, 583
Icebergs, 115, 116, 154, 205, 207, 208, 259
Ice boundaries, 638
Ice-drift, 207
Iceland Polar current, 124, 300, 534
Indian Ocean, area of, 138, 139
continental shelf and slope of, 137
deepest sounding in, 18, 132
deeps of, 139, 140, 141, 142
depths of, 131, 132, 138, 139, 141, 142
number of soundings in, 1 3 1
"Ingolf," The, 16, 434, 533, 536, 541, 546,
652
Inorganic materials in marine deposits, 151
Insecta, 587, 738
" International," The, 20
International Council for the exploration of
the sea, v, 20, 300, 310, 439, 440,
732, 759
Invertebrate bottom fauna, 457-560
" Investigator," The, 19
Ionic dissociation of sea-water, 175
Iron in sea-water, 150, 153, 154, 155, i^^,
175, 186, 187, 188, 189, 190, 191, 192
concretions in marine deposits, 19 1
and manganese nodules (see Manganese
nodules)
" Isabelita," The, 76
Islands of the Norwegian West Coast, fauna
of, 460-476
Isopoda, 506, 520, 521, 524, 530, 535, 583,
584, 654
"Jeanette," The, 259
Jeffrey Deep, 142
Jelly-fish (see Medusce and Siphonophonv)
"John Pender," The, 19
Josephine Bank, 57
Jugulares, 410
GENERAL INDEX
15
Keltic Deep, 196
Kelvin's sounding machine (set' Thomson)
Kittiwakes, 712
" Knight Errant,"' The, 13, 20S, 546, 661
•• Kril," 583
Labrador current, 100, 115, 118, 213, 244,
260, 635, 658, 704
Labridce, 390
Lakes, survey of Scottish, 16, 225
temperature of, 239
Lamellibranchiata, 95, 207, 438
Laminaria belt, 461, 466-468, 471, 489, 51 1
Lamnidffi, 391
Lampreys, 601
Lampridoe, 643
Lancelet, 474, 477, 559
" Languste," 64
Le Blanc's sounding machine, 29
Lemon sole (see Sole)
Lepadida;, 582
Leptocephali, So, 81, 84, 86, 87, 92, 93, 94,
96, loi, 103, 104, 108, 118, 120, 126,
605, 634, 663, 670, 683, 741, 743,
748-755
Leptomedusre, 568
Libbey Deep, 196
Liebig's minimum law, 367, 728
Life-cycle of animals, 383
Light, effect on the distribution of organisms,
224, 254, 557-558
Light-intensity, 248-253, 710-725
Light-organs of animals, 673-680, 702, 742
Light-penetration, 93, 94, 248-253, 450, 663,
664, 666, 681
" Lightning," The, 10, 11, 12, 546
Limacinidse, 587
Lime {sw Calcium carbonate)
Limpets, 462, 477
Lines for sending down instruments, 211
Ling, 55, 440, 441, 442, 443, 448, 449,
451, 452, 454. 455
Ling Bank, current measurements on, 268,
269, 272
Liparidne, 436
Littoral deposits, 161
zone, 459, 460-461, 472-478, 486-490
Lobsters, 473, 476, 477, 555, 556, 575, 584
Lochs, Scottish, 13, 16, 225
Loliginidce, 597
Lophidce, 41 1
Low-tide area, 461-466
Lucas sounding machine, 29, 30, 39, 40, 130
Lugworm, 464, 489, 556
Lump-fishes, 607
Lusitanian faunal area, 552
LycodidK, 109, 436, 546
Mackerel, 609, 633, 635, 643, 645, 647,
670, 698, 699, 747, 755
eggs and larva?, 731
MacruridK, 389, 397-401, 414, 415, 420,
424, 425, 432, 448, 449, 545, 546, 630,
675> 745
Magnesium carbonate, 178, 179, 180-181,
186, 193
phosphate, 193
sulphate, 175, 176
" Magnet," The, 20
Makaroff Deep, 196
Malacopterygii, 394-395, 601, 611-612
Maldanida;, 482, 501
Malthidte, 411
Manganese in marine deposits, 150, 153, 155,
166, 168, 171, 186, 187, 190, 191, 192
nodules, 155, 157, 159, 160, 166, 168,
171, 188, 189, 190, 191-192
"Marathon," The, 19
Marine biological laboratories, 20
deposits (sM Deposits)
Mask crabs, 474
Mean sphere level, 412
Mediterranean, 7, 11, 13, 15, 68, 71, 72,
115, 178, 194, 220, 239, 248, 249, 252,
292, 293, 295
"Medusa," The, 13
MedusK, 86, 92, 95, 98, loi, 118, 119, 352,
568-574, 581, 624, 627, 631, 632, 633,
640, 642, 645, 658, 666, 669, 692, 696,
719. 736
larvK, 646
"Medusa Head," 486, 519
Medusettida?, 565, 567, 642
Megrim, 79, 441, 442, 443, 451, 452, 454
Meropelagic forms, 562
Meroplanktonic forms, 562
Messengers, 217, 219, 234, 235
Metabolism, 177, 366, 378
Meteoric spherules, 155
Meteorological Institute, De Bilt, 215
Office, London, 214
Metre-wheel for sounding, 211
"Michael Sars," The, 20, 22, 30, 37, 38,
45, 46, 47, 48, 49, 52, 53, 55, 56-128,
305, 306
deposit-samples, 199-202
Microspores, 321-322
Mid-Atlantic ridge, 118, 120, 135, 632
Migrations of animals, 700-716, 764, 767
Mill Deep, 196
Miller-Casella thermometer, 4, 215, 216
Minerals in marine deposits, 151- 154
" Minia," The, 19
Minimum law, Liebig's, 367, 728
" Mirror," The, 20
Molgulids, 483
Molidie, 615, 644
Mollusca, 8, 9, 88, 91, 103, 121, 146, 149,
167, 171, 438, 473, 474, 486, 494, 495,
504, 506, 508, 511, 514, 522, 524, 525,
528, 530, 534, 539, 553, 554, 587, 589,
631, 662. 738
8i6
DEPTHS OF THE OCEAN
Monaco Deep, 196
Monaco, oceanographical museum at, 14
pelagic trawl, 36
Monascidians, 525
Monkfish, 79, 441. 442, 443, 448, 451, 452
Moonfish, 119
" Moraine profonde," 205
Morocco fishery, 69
Moseley Deep. 142, 196
Mud-eaters, 717
"Mud-line," 133, 134, 426-427, 648, 717
Muds, deep-sea, 185-188
Mullet, 71, 444, 448
Mullidse, 390
Mursenidse, 79, 389, 395, 605
Murray Deep, 140
Mussels, 418, 419, 420, 462, 467, 468, 472,
473, 474, 475, 477, 479> 480, 482, 483,
486, 488, 490, 495, 501, 502, 508, 513,
514, 530, 534, 535, 547, 553,559,575,71?
"Mutine," The, 19
Myliobatidre, 393
Myopsidae, 590, 592, 595, 597, 625
Myriothelidse, 522
" Myrmidon," The, 19
Mysids, 720
Nannoplankton, 356
Nansen's closing net, 35, 359
Nansen thermometer, 233
Naples Zoological Station, 20
Narcomedusa;, 568, 571
Nares Deep, 132, 141, 195, 196
Narratives of " Michael Sars " cruises, 52-128
Naticidas, 475
" National," The {see " Plankton " Expedition)
Nauplii, 654-655
"Navarino," The, 707
Needle-fish, 103, 120
Negretti and Zambra thermometer, 4.217
Nekton, 309
Nemertines, 86, 577, 57S, 624
NemichthyidK, 605, 612
" Neritic," 562
Neritic algx, 344-346
diatoms, 354
peridinea;, 344
plankton alga;, 340-346
"Nero," The, 16, 131, 143
Ness, Loch, temperature oscillations in, 16
Nets attached to current-meter, 359
Chun's, 35, 36
closing, 58, 59, 61, loi, 102
drift, 45
Hensen's, 37, 45, 35^, 359
"Michael Sars," 46, 47, 48, 49, loi, 102
Nansen's, 35, 359
Petersen's, 359
Newfoundland Bank, 106, 107, 109, no,
111-114. 115, 116, 117. 213, 244, 245,
297-300. 357
" Newington," The, 20
Night - hauls by "Michael Sars," 92, 93,
94, 95
" Nimrod," The, 18
Nitrates, 368, 369, 370, 372
Nitrites, 368, 369, 370, 372
Nitrogen in sea-water, 253, 258-259, 368-
370, 377, 380, 728
Nodules, manganese (see Manganese nodules)
phosphatic (see Phosphatic nodules)
" Norge," The, 124
"Norseman," The, 19
North Atlantic (see Atlantic, North)
North Sea, current observations in, 268, 269
fauna of, 491-503
phosphorus in water of, 185
silica in water of, 184
Norwegian Depression, 503-507
Expeditions, 10, 12, 15, 309. 504, 505.
517, 523
fisheries, 37, 55, 56
fjords (see Fjords)
Norwegian Sea, 12, 55, 122, 124, 125, 167,
196-198, 220, 222, 223, 239, 240, 243,
261, 274, 275, 276, 277, 278, 280, 281,
282, 283, 284, 302, 303, 304,457, 516-535
fauna of, 92, 107, 108, 118, 120, 126, 127,
434-437,517-525,546-551,637-641,647
Notidanidte, 390, 396
Nudibranchs, 468, 494
Nutrition of marine animals, 716-728
Ocean, area of the, 132
" Oceanic," 562
plankton alga;, 346-349
Oceanographical Institute at Paris, 14
Museum at Monaco, 14
Oceanography, physical, 210-306
Octopoda, 590, 595, 597, 625, 678, 706
CEgopsida;, 590, 595-596, 625
Ommatostrephida;, 591, 592, 596
Onychoteuthida;, 591, 596, 632
OphelidK, 475
Ophidiid, 88
Ophiuridoe, 121, 418, 419, 420, 429, 430,
436, 538, 547, 576
Orbulina ooze, 164
Organic matter in marine deposits, 42S, 430-
431, 716, 717-719
remains in marine deposits, 145
substances in the sea, 358-370, 381, 385,
_ 386, 717, 728
Origin of the present-day fauna of the Nor-
wegian Sea, 548-551
Osmotic pressure in the cells of animals, 690-
691
Ostracoda, 89, loi, 149, 579, 581-5S2, 624,
631, 640, 655
Otoliths of fishes in marine deposits, 149, 151
of the plaice, 759
Otter board, 42
GENERAL INDEX
817
Olter trawl, 41, 42, 63
Ox bone dredged, 202, 207
Oxidizing areas in the ocean, 187-188
Oxygen in sea-water, 253-258
Oyster "polls," 225, 226, 257-258, 478-480,
554, 555
shells, 202, 207
Oysters, 479-514. 555, 556
Pacific Ocean, area of, 136, 137, 13S
continental shelf and slope in, 136
deepest sounding in, 17, 131
deeps of, 139-143
depths of, 131, 132, 136-138, 140-143
number of soundings in, 131
shore-slopes of, 137
Palagonite in deep-sea deposits, 153, 188-
189
Pandalids, 585
Pasiph?eid9e, 585
Patellids, 467
" Patrick Stewart," The, 20
Peake Deep, 196
Pediculati, 411, 609, 614
Pelagic animals, 561-659
Arctic communities, 637-641
Atlantic communities, 617-636
boreal communities, 637, 644-656
northern communities, 636-659
appliances, 34, 45
deposits, 161, 162-163, 167, 171, 426,
430, 716
Peneidae, 585, 586
" Penguin," The, 19, 141
Pennatulids, 109, 482, 503, 517, 538, 547
Percesoces, 389, 397, 607, 613
Perciformes, 401-405, 614
Percussion, bulbs of {see "Chatter-marks")
Peridinete, 65, 322-330, 346, 347, 348, 354,
355, 356, 358, 363, 365, 381, 382, 580,
674, 699, 719
neritic, 344
suspension organs of, 323
Periwinkles, 462, 477, 556
Permanence of oceanic and continental areas,
10
Petersen's pelagic young-fish trawl, 36
bottom-collector, 785
Petromyzontes, 611
Petromyzontidoe, 611
Pettersson's insulating water-bottle, 232
Pettersson-Nansen water-bottle, 40, 215,
219, 220, 232, 233
Phillipsite, 159-160, 166, 190
Philonexidae, 597
Phosphates {see Calcium phosphate)
Phosphatic concretions, 159, 162, 189, 192,
193
Phosphorescence, 68, 86, 88, 94, 329, 673,
674, 675, 680
Phosphoric acid, 368
Photometer, Helland-Hansen's, 93, 94, 249-
252
Regnard's, 252
Photometric observations, 94, 248-252
Physical oceanography, 210-306
Phytoplankton, 60, 61, 94, 117
Pigmentation {see Colours of marine animals)
Pilchards, 448, 601, 771, 782
Pilot-fishes, 91, 609, 633, 670, 698
Pipe-fishes, 606
Pisces {see Pishes)
Plagiostomi, 388, 390-393
Plaice, 440, 441, 442, 443, 451, 453, 454,
712, 713, 759, 763, 785
eggs, 783
Planarians, 471
Planet Deep, 143
" Planet," The, 18, 141, 143
Plankton, 13, 37, 45, 65, 107, 108, 309-
311, 338-340, 357, 358-366, 370-3S3,
562-563, 772-776, 779, 782, 783
alga;, neritic species of, 340-346
oceanic species of, 346-349
"Plankton" Expedition, 15, 309, 315, 333,
337, 564, 598, 652, 773, 777
Plant life, 60, 94, 254-256, 305-386, 727-728
remains in marine deposits, 145
Plateaus, fauna of continental, 491-516
Platyhelminthes, 577
Plectognathi, 411, 611, 615
Pleuronectidfe, 390, 407-408, 646
" Podbielski," The, 299
Podoceridce, 468
"Pola,"The, 15
Polar currents, no, 117, 118, 124, 244,
245, 276, 300, 458, 531, 533, 534
Pollack, 441, 442, 443, 451, 452, 731
" Polls" {see Oyster "polls ")
PolypodidK, 597
" Pommerania," The, 495
Pools {see Oyster "polls")
" Porcupine," The, 11, 12, 546
" Portuguese man-of-war," 68, 89, 92, 574
Potassium, 189-190
Potential temperature {sec Temperature)
" Pourquoi Pas?" The, 18
Pourtales Bank, 178
Prawn larvae, 622, 623
Prawns, 420, 469, 482, 486, 517, 530, 531,
534, 558, 583, 584, 585, 586, 587, 618,
622, 624, 633, 641, 663, 664, 665, 671,
699, 720, 775
red, 81, 86, 94, loi, 102, 104, 118
Pressure in the sea, 24, 219, 224, 245-247
" Princesse Alice," The, 14, 387
Pristipomatidge, 390, 403
Propagation of marine animals, 729-755
Protozoa, 563
Pteropoda, 72, 87, 107, 118, 163, 164, 167,
172, 201, 419, 578, 587-590, 625, 631,
640, 642, 645, 658, 669, 702, 7 1 8, 720
8i8
DEPTHS OF THE OCEAN
Pteropod ooze, 149, 160, 161. 162, 163-164,
167, 168, 169, 171, 173. 174, iSo,
199, 200, 426, 427
Pterosperniatacea;, 365
Pulsations in currents, 273
Pumice, 152-153, 155, 156,166,169,208.419
Pump method of capturing plankton, 65, 360
" Punti verdi," 334
Pycnogonids, 109, 468, 497, 515, 519, 524.
527, 529, 530, 534, 547
Pycnometer, 236
Pyrosomidse, 692
Qualitative investigations of marine organisms,
776-778
Quantitative estimations of marine organisms,
772-776
of plankton, 37, 309-310, 358-366, 372-
377, 772-776
with bottom-sampler, 784-785
Quartz, 153, 162, 163, 205
Radio-active matter in marine deposits, 62,
160, 166, 170
Radiolaria, 118, 148. 307, 355, 561, 563,
564-568, 578, 588, 624, 631. 642, 691,
693, 697, 699, 702, 719, 720
Radiolarian ooze, 17, 149, 160, 161, 162,
165-166, 168, 169, 171, 183, 184, 185
Raiidie, 388, 389, 392, 393, 424, 436, 441,
442, 448, 451, 452
"Rambler," The, 19
Rays {see Raiidae)
*' Recorder," The, 19
Red clay, 149-, 154, 155, 160, 161, 162, 163,
165, 166, 168, 169, 171, 173, 174, 175,
180, 182, 186, 187, 189, 19c, 199, 200,
426, 427. 429, 430
Red -fish larviE, no, in
Red mud, 161, 162, 167, 169
Reducing areas in the sea, 187-188, 189
Refractivity of water in relation to salinity,
236-237
Regnard's photometer, 252
Resting spores, 320-321, 341, 342, 344
" Retriever," The, 19
Reykjanes Ridge, 56
Rhabdoliths, 146, 308
Rhabdospheres, 145, 146, 308
Rhinidas, 392
Rhizopods, 481, 482
Ribbon type of suspension organs, 3 1 5
Richter's reversing thermometer, 217, 218,
220, 233 v^
Rofkall, 123, 124
J Rock fragments in marine deposits, 155, 156,
^ 157, 163, 166, 170, 171, 185-188, 202-
209
" Roddam," The, 20
Rotation, eftects of the earth's, 274-278, 295,
299
Saccopharyngida;, 104, 605, 612, 618
Sagittidcv, 86, loi, 104, 578, 631, 640, 641,
669, 720, 773
" Saifia," 74
Saithe, 440, 444, 446. 452, 454, 646, 648,
649, 731, 736, 759, 760, 761, 762, 764
larvEC, 646
Salinity of sea-water, 230, 236, 237, 238,
239.245, 318
" Salmon-herrings," 95
Salmonidre, 69, 394, 441, 442, 601, 602,
611, 645, 759
Salpidre, 98, 118, 119, 126, 308, 352, 355,
381, 382, 578, 581, 598, 599, 600, 631,
632, 633, 634, 641, 692, 696, 708, 710,
711, 712, 719
Salts of the sea, 230-245
Sandgapers, 464, 556
Sandhoppers, 465, 466, 497
Sand-stars, 120
Sardines, 76, 601, 636
Sargasso fishes, 633, 698
Sargasso Sea, 83, 94-99, 100, 106, 107, 108,
118, 194, 222, 223, 241, 242, 246, 298,
371, 598. 619, 623, 631, 632, 633, 635,
656, 657, 658, 663-664, 670-671, 673,
681, 684, 694, 695, 698, 708, 718, 720,
722, 723, 724, 725, 727, 747, 773, 775
weed, 91, 103, 106, 108, 335-337. 671,
673. 718
Saury pike. 747
Scales of fishes as indicators of age and growth,
114, 759-765
Scaphopoda, 482, 500, 523
"Schizogony," 463
Schizopoda, 579, 582-583, 640, 654, 669,
773
Scii>;nidie, 390, 402-403, 444
Sclerodermi, 615
Scleroparei, 408-410, 614
Scombresocidse, 607, 613, 644
eggs of, 103, 742
ScombridEC, 609, 643
Scombriformes, 390, 406-407, 609, 614
Scopelidoe, 68, 95, 126, 127, 396, 414, 601,
605, 606, 613, 618, 631, 632, 634, 644,
663, 669, 675, 676, 677, 679, 685, 686,
687, 698, 699, 703, 746, 755
eggs and young of, 118
Scorp£enid?e, 390, 408-409, 614
" Scotia," The,' 18, 19, 135. 170
Scottish lochs, investigations in, 13, 16, 225
Scottish Antarctic Expedition, 18
Scyllidre, 388, 391
Scyphostoma, 572
Sea-anemones, 482, 484, 493, 497, 500, 521
■Sea-bream {see Bream)
Sea-horses, 89, 671
" Sealark," The, 19
Sea-lilies {stjc Feather-stars)
Sea-mice, 491, 517, 519, 540
GENERAL INDEX
819
Sea-pens, 87, 88, 482, 500
Sea-scorpion, 535
Sea-slugs, 477, 482, 486, 492. 519, 523. 540,
555
Sea-spiders, 486, 497, 520
Sea-squirts, 497, 498
Sea-tooth [see Scaphopoda)
Sea-trees, 485, 486
Sea-trout, 646
Sea-urchins, 120, 419, 420, 430, 465, 473,
478, 493. 519. 538, 547, 558, 576
Sea-water, chemical composition of, 175, 176,
235
compressibility of, 246
ionic dissociation of salts in, 195
transparency of, 253, 666, 671
samples, methods of obtaining. 230
preservation of, 235
Sea-weeds, 145, 335-337, 3^9
Seals, 692
Seiches, 16, 278
Seine Bank, 178, 195
" Seine," The, 19
Seine-net fishing, 76. 77
Selachii, 388, 390-392
Sepiidse, 597
Sepiolidae, 597
Sergestidas, 585
Serpulids, 418, 463, 473
Serranida;, 390, 402, 614
Sertularians, 87, 419
Shad, 448
Sharks, 64, 424, 436, 455, 635, 644, 646,
647, 698
blue, 635, 644
Greenland, 647
hammer-head, 635
herring, 646
Sharks' teeth, 87, 149, 156, 157, 160, 166,
171, 418, 419
" Shearwater," The, 11
" Sherard Osborn," The, 19
Shoals, oceanic, 13
Shore slopes, 135, 137, 139
Shrimps, 496
" Siboga," The, 17
Sideromelan, 153
Sigsbee Deep, 196
Sigsbee's dredge, 32
method of trawling, 31, 42, 45
sounding machine, 29
trawl, 33, 42
" Silderaek," 641
Silica, 145, 183-185, 1S6, 187, 188. 36S
Silicates, 185, 187, 189. 190
Siliceous deposits, 162
remains in marine dejiosils, 14S, 149
sponges, 467
Silicic acid (see Silica)
Silicoflagellates, 358, 365
" Silvertown," The, 19
Sinking of air-filled capsule, 247
of solid body, 247
Siphonophora, 98, 574, 631, 640, 641, 642,
692, 696, 719
Sira-plankton, 345
Six's thermometer, 4, 215
"Size of projection," 693
Skate, 64, 79, 441, 442, 451
" Skjasrgaard," 227, 460
Snails, 462, 467, 469, 471, 477, 480, 489,
493, 494, 502, 517. 521, 522, 575, 671
Sogne fjord, 55, 22S, 240, 277, 303, 481,
574
Solenidte, 475
Soles, 64, 69, 79, 440, 441, 442, :443, 448,
449, 451, 452, 453, 646
Sounding by bathometer, 2
by hand, 2, 130
by hemp-line, 23, 24, 25, 26, 27, '28, 29.
' 130
by wire, 5, 12, 27, 28, 29, 130
deepest, 17, 131
first abysmal, 5
first attempt at deep-sea, 2
Sounding machine, Baillie's, 25, 26
Brooke's, 8, 9, 130
Hooke's, 2, 209
Le Blanc's, 29
Lucas's, 29, 30, 39, 40, 130
Sigsbee's, 29
Thomson's, 28
Soundings first shown on maps, 2
Spanish Bay, 57, 65, 68, 69, 72, 292-295
Sparidaj, 69, 390, 403-405, 433, 444, 448
Spatangids, 474, 475, 476, 490, 491
Specific gravity of sea-water, 689, 690, 691,
692, 694, 695, 696, 698, 699, 700, 710,
716, 721, 722, 723, 724, 725, 777 (see
also Density)
surface, 692, 693
Spheroid of revolution, the earth as a, 129, 132
Spinacidte, 388, 391, 675
Spirulidis, 597
Sponges, 10, 72, 95, 419, 420, 483, 484,
486, 498, 500, 504, 505, 506, 507, 508,
510, 517, 519, 521, 524, 525, 534, 539,
559
Sponge spicules in marine deposits, 148, 183
Sprat eggs, 731
larvK, 731
Sprats, 91, 601, 645, 759, 761, 762, 765,
766, 771, 782
" Sprungschicht " (see Discontinuity layer)
" Sprut," 648
Squid larvce, 631
Squids, 112, 113, 590, 591, 592, 624, 625,
627, 632, 642, 643, 645, 646, 648-649,
650, 651, 669, 674, 675, 676, 678, 682,
685, 699, 706, 782
" Stale" water, 257
Stalk-eyed fishes, 86, 103. 108
820
DEPTHS OF THE OCEAN
Stalk-eyed cuttle-fish, 93
fish-larva, 746
Standing waves, 278, 284
Starfish, 120, 419, 420, 429, 430, 464, 467,
486, 491, 492, 510, 511, 517, 534, 538,
540, 547, 555, 575, 576
Stenohaline forms, 557
Stenothermal forms, 557
" Stejjhan," The, 18
Sternoptychida% 603-605, 611-612. 618, 619,
643, 644, 663, 676, 678, 685, 698
StomiatidLx;, 96, 102. 601, 603-604, 611, 618,
676, 678. 683, 685, 698, 741
Stones dredged by the "Michael Sars," 121,
170, 202-209
Storeggen, current observations on, 269, 270,
273
"Stork," The, 19
Stratification in marine deposits, 174, 200, 201
Stromateidre, 607, 613, 643
Styelidse, 486
Styli-plankton, 347, 348, 351, 352
Sub-littoral zone, 459-460, 480-481, 490-491
Submarine banks, 135
waves, 714-716
Subsidence in oceanic areas, 174, 175, 207,
208, 209
Suhm Deep, 195, 196
Sulphates in marine muds, 181, 182, 188
Sulphides in marine muds, 175, 181, 182, 188
Sulphur, 1 81-183, 188, 258
Sulphuretted hydrogen, 257, 554
" Summer-belts " in fish-scales, 114, 764
" Sunda Graben," 141
Sunfishes, 607, 633, 697, 698
Surface resistance, 689-690, 692
Surplus gravity, 689, 692
Suspension organs, 312, 315-320. 323, 327.
328, 350 .
Swedish Expeditions, 10. 15, 17
Swire Deep, 141
Swordfish, 698, 755
"Sylvia," The,' 19
Symbiosis, 328, 334, 355, 493, 500
Synaphobranchiidre, 121, 127, 389, 395, 414,
4i5> 605
Synascidians, 467, 469, 525
Syngnathidre, 606. 613, 644
"Talisman," The, 13. 68, 387, 544. 686
Tanaida;, 479
Teeth of fish in marine deposits, 1 5 1
Teleostei, 388, 389, 394-411, 601, 611-615
Teleostomi, 394-411, 611-615
Telescopic eyes, 90, 96, 97, 746
Tellinidre, 475
Temperate neritic species of pelagic alga,
345-346
oceanic species of pelagic algoe, 347
Temperature conditions as affecting, animal
life. 431-437- 444-445< 554-556- 705-706
Temperature observations, 3, 4. 11. 13, 61.
68, 70, 72, 84, 103, 106, 107, no.
Ill, 113, 117, 125, 126, 213-230. 239,
246, 305. 306, 694, 709, 722, 723. 724,
778
oscillations in lakes, 16
potential, 221, 239
seiche, 16
TerebellidiTS, 482
Terraqueous stage of the earth's evolution, 129
Terrestrial materials in marine deposits, 1 5 1
Terrigenous deposits, 161, 162, 166, 167,
171, 426, 429, 430, 716, 717
Tetraxonia, 524
Tetrodontidce, 411, 615
Thalamophores, 527
Thecosomata, 587, 589, 631
Thermocline (see Discontinuity layer)
Thermometers, 3, 4, 24, 215, 216, 217. 219.
244
Miller-Casella, 4, 215, 216
Nansen, 233
Negretti and Zambra, 4. 217
Richter, 217, 21S, 220, 233
Six, 4, 215
" Thin water," 696
Thomson sounding machine, 28
"Thor," The, 67, 72, 434, 505, 652, 710,
711, 732
Thoulet Deep, 196
Tidal currents, 67, 99, 170. 267-272. 289
Tile-fish, 706
Tizard Deep, 142
"Tjalfe," The, 652
Tow-nets, 34, 35, 36, 37, 45. 46, 47, 48.
49, 68
Tracheloteuthida, 596
Trachinidre, 390, 410
Trachymedusa, 568, 569, 572. 699
Trachypteridie, 643, 644, 698, 741
Transparency of sea-water, 253. 666, 671
" Travail leur," The, 13, 68, 387, 544
Travertine, 177
Trawling and dredging, 24, 26. 27, 30, 31,
32, 36, 41, 42, 49, 62, 68, 71, 87, 99,
120, 121
Trichiuridre, 407, 614, 643
Tricho-plankton, 347
Triglida, 390, 409-410
Tripos-plankton, 347
"Triton," The, 13, 208, 546, 662
Tropical neritic species of pelagic alga. 346
oceanic species of pelagic alga, 347
Trout, 441, 442, 759
Tubeworms, 502, 508, 524
Tufa, 153, 155, 177
Tunicata, 149, 160, 597-600
Tunicin, 597
Tunnies, 609, 635, 636
Turbellaria, rhabdoccelous, 468
Turbot. 441, 442, 451, 452, 646
GENERAL INDEX
821
Turtles, 65, 87, 97, 98, 119, 582, 584
Tuscarora Deep, 140
"Tuscarora," The, 11, 12, 27, 141
TuscaroridK, 561, 565, 567
Tusk, 55, 440, 441, 442, 443, 446, 448,
449, 451, 452, 454
Umbellularia, 419
Uniformity of hydrographical conditions and
of animal life, 83, 84
United States Coast Survey, 8, 10, 12
Exploring Expedition, 5
Fish Commission, 12
llydrographic Oflice. S
UranoscopidK, 390, 410
" Vader," 489
Valdivia Deep, 140
" Valdivia," The, 16, 34, 36, 87, 93, 94, 140,
163, 164, 165, 315, 349, 364, 413. 424.
562, 565, 566, 567, 571, 580, 581, 585,
589. 590, 591. 592. 594, 595» 59S, 599,
601. 605, 625, 627, 676, 677, 680, 683,
780
Venerida?, 475
VeranyidK, 596
Vermes (see Worms)
Vertical circulation of ocean waters, 229, 378,
379, 380
oscillations of ocean waters, 275, 278, 279-
281, 282, 715
migration of organisms, 89, 93, 95, 96, 664
"Vettor Pisani," The, 13, 561
" Viking," The, 20
Viscosity of sea-water, 311, 318, 689, 690,
691, 694, 696, 698, 699, 700, 703, 710,
716, 721, 723, 725. 777
" Vitiaz," The, 15
Volcanic ashes, 151, 152, 153
glass, 153, 155, 156, 160, 169, 188
mud, 161, 162, 167, 169, 171, 198
sand, 144, 162, 167, 171
" Volta," The, 20
" Vdringen," The, 12, 645, 648
\'ortex movements, 281-285, 298, 300
Wad {see Manganese nodules)
"Washington," The, 13
Water-bottle, Buchanan, 230, 231
Ekman, 234
Hooke, 209
Pettersson, 232
Pettersson-Nansen, 40, 215, 219, 220, 232,
233
Water-bottles, 4, 215, 219, 220, 230-236
" Waterwitch," The, 19
782
Waves, boundary, 274
standing, 278, 284
submarine, 714-716
Weevers, 79
Weights used for sounding, 25, 29
"Westmeath," The, 20
Whales, Atlantic, 646 —
Biscayan, 780
bottle-nose, 54, 646, 649, 650. 651, 780,
782
blue, 714, 778
caaing, 95
cirripedia attached to, 582
distribution of, 778-783
earbones of {see Earbones)
fin-, 779, 780, 781
floating devices of, 691, 692
Greenland, 778, 779, 780
humpback, 779, 780, 781,
migrations of, 714
north-caper, 651, 780
plankton, 778
right, 778, 780, 78 1
saithe, 779
sperm, 94, 780, 7S2
squid-hunting, 592. 7S2
tooth-, 779
whalebone, 727, 779, 782
" Whale's food, " 107, 588
Wharton Deep, 132, 141
Whelks, 494
Whiting, 64, 440, 441, 442, 448. 451, 452, 497
Wind-produced currents, 274
"Winter-rings" in fish-scales, 114, 760
Wire for sounding, etc., 5. 12, 27-31, 130.
211
Witch, 441, 442, 451, 452, 454
Worms, 9, 62, 63, 418, 419, 464, 467, 482,
484, 485, 489, 501, 502. 504, 506, 508,
524, 525, 530, 534, 541, 559, 577-579,
581, 658, 717
Wreck-fish, 98, 633, 670
Wyville Thomson Ridge, 13, 122-127, 170,
207, 208, 223. 243. 456. 458, 533, 538,
625, 656, 661, 695, 708, 724
Xiphiidce, 643
Zeidte, 407, 614, 643
Zeolites, 159, 160, 171, 18S, 190
Zeorhombi, 407-40S, 614
Zoarcidse, 410, 414, 415, 435
Zoophytes, 489, 568, 572
Zooplankton {see Plankton)
Zoospores, 322, 329, 334, 335
Zostera belt, 461, 468-472, 489
Prinfed ly R. S; R. Clark, Limited, Edhth
A SELECTION OF WORKS FOR NATURALISTS
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