QH90
.H3

Haeckel, Ernst

^lanktonic studies:
A Comparative investi-
gation of the importance
and constitution of
the pelagic fauna
aftd^flAra

V OMMTKSTONER OF

[EXTRACTED FROM TlIK HKl'i, . . '.-i' i mk . . - > .>MMihMt'iN
riSK ANP FISHERIES F( iJ i889 TO 18'.n. l>;u: os 5G5 to Oil.]

PLANKTONIC STli )IES:

A COMPARATIVE INVESTIGATION OE THE IMPORTANCE

AND CONSTITUTION OF THE PELAGIC

FAUNA AND FLORA.

BY

Em^ST H^ECKI..

tTRA.NSI.ATKI3 EY GrKORGE WILTON B^IT:LI3.]

WASHINGTON:

GOVERNMENT PRINTING OFFICE.
1893.

[EXTRACTED FROM THE REPORT OE t\iE U. S. COMMTSSTONEK OE
EiSH AND FISHERIES FOR 1889 TO 1S;)1. Pages 5i« to Gil.]

PLANKTONIC STUDIES:

A COMPAIUTIVE INVESTIGATION OF THE IMPORTANCE

AND CONSriTLlTION OF THE PELAGIC

FAUNA AND FLORA.

BY

EHISTST II.ZECi4l.

[TJa^NSriATED I3Y GEORGE WILX0:N^ EIELD.]

washingto:n':

GOVERNMENT PRINTING OFFICE.

1893.

G-PLANKTOMC STUDIES: A COMPARATIVE INVESTIGATION
OF THE IMPORTANCE xVND CONSTITUTION OF THE PELAGIC
FAUNA AND FLORA.

By Ernst H.eckel.
[Trauslated hy George Wilton Field.]

TRANSLATOR'S PREFACE.

Prof. Haeckers " Plankton Stiulien " first appeared in the Jenaische
Zeitschrift., vol. XXV, first and second parts, 1890. It was immediately
published in separate form by Gustav Fischer, of Jena, and attracted
much attention on the Continent and in England. The subject, "a
comi)arative study of the importance and constitution of the marine
fauna and flora," is presented in Prof. HiTeckel's usual pleasino- style,
and the work can not fail to be of value to all interested in the bio-
logical sciences, to the general reader as well as to the specialist. It
derives especial interest in connection with the work of the Fish Com-
mission, from its broad discussion of those many important elements
which enter into the food supply of all pelagic fishes, such as the
mackerel and menhaden, and, considering the extensive physical inves-
tigations now being conducted in our coast waters by the schooner
Granipiis, its publication at the present time will prove exceedingly
advantageous.

The terminology used by Prof. Haeckel may at first seem formidable,
but this difficulty is more fancied than real. The ^terms are formed
upon correct analogies, and most of them will probably find a perma-
nent place. The definite restriction of the meaning of terms is a funda-
mental necessity in every science, and for the lack of this the branch
of biology here considered is in a very unsatisfactory condition. The
author, first of all, proposes certain terms with a definite meaning.
The word "plankton," from the Greek -Xayxro^, wandering, roaming, was,
I believe, first employed by Hensen in j^lace of the German "Auftrieb,"
to designate all plants and animals found at the surface of the ocean
which are carried about involuntarily in the water. Hteckel adopts this
term, but objects somewhat to the meaning at present attached to it.

Particularly valuable for us is the general review which the author
gives of the discovery and growth of our knowledge of this branch,

565

566 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

which lie names "planktology"; the distinctions which he points out
between the varied constituents and distribution of the plankton; and
finally his extremely valuable suggestions for further work in the field
which he so justly terms "a wonder-land."

In the translation .the liberty of omitting a few personal references
was taken, for the reason that we in this country know very little of
the facts which have called them forth.

In the case of several German words it has been found necessary for
the sake of clearness to use a circumlocution. For instance, I can recall
no English equivalent for '■' Sioffwechsel des Meeres,^'' which would con-
vey its meaning in a single word. The " cycle of matter in the sea,"
i. e., the change of inorganic matter into vegetable and animal organic
matter, and this finally again into inorganic matter, seemed the best
rendering, though even this does not include all which the German term
implies.

I.— HISTORICAL EXPLANATIONS.

For the great progress made in the last half century in our knowledge
of organic life, we are indebted — next to the theory of development — in
a great measure to the investigation of the so-called " pelagic animal
world." These wonderful organisms, which live and swim at the surface
of the sea and at various depths, have long aroused the interest of sea
farer and naturalist, by the wealth of the manifold and strange forms,
as well as by the astonishing number of individuals — these have been
referred to in many old as well as in recent narratives. A considerable
number of these, especially of the larger and more remarkable forms,
were described and figured in the last, or in the first half of the present,
century. The new and comprehensive investigation of the "pelagic
world" began in the fifth decade of our century, and is therefore not
yet 50 years old.

Into this, as into so many other regions of biology, the great
Johannes Miiller, of Berlin, equally distinguished in the realms of
morphology and physiology, entered as a pioneer. He was the first
who systematically and with great results carried on the "pelagic
fishery by means of a fine net." In the autunui of 1845, at Helgoland,
he began his celebrated investigations upon the development of
echinoderms, and obtained the small pelagic larvre of the echinoderms,
and other small pelagic animals living with them, as sagitta, worm
larvje, etc., at first by "microscopical examination of the sea water,
which was brought in" (1). This wearisome and thankless method was
soon displaced by the successful use of the "fine pelagic net." In the
treatise "on the general plan in the development of the echinoderms,"

Note. — Citations inclosed in parentheses which occur in the text refer to the list of
publications at the end of this paper (pp. 040, 641).

PLANKTONIC STUDIES. ^ 567

Miiller compares the different methods of obtaining- them, and chooses,
above all, ''fishing- with a fine net at the snrface of the sea." He
says :

I liave used this method for many years witli the best results; for the advanced
stages of the swimming hirva^. and for the time of maturity and metamorphosis it
is quite indis})ensable, and in no way to be repLaced.

The students who, in 1845-46, as well as in the following years,
accompanied Johannes Miiller to Helgoland and Trieste (Max Miiller,
Busch, Wilms, Wagener, and others) were introduced into this method
of "pelagic fishery'' and into the investigation of "pelagic tow-stuff"
{pelddische Aii/trieh) obtained thereby. It was soon employed at sea
with excellent results by other zoologists — by T. H. Huxley, by Krolm,
Leuckart, Carl Vogt, and others, and especially by the three Wiirts-
burg naturalists, A. Kolliker, Heinrich Miiller, and (3. Gegenbaur,
who in 1852 examined with such brilliant success the treasures of the
Straits of Messina. At this time, in the beginning of the second half
of our century, the astonishing wealth of interesting- and instructive
forms of life which the surface of the sea offers to the naturalist first
became known, and that long series of important discoveries began
which in the last forty years have filled so many volumes of our rapidly
increasing zoological literature. A new and inexhaustibly rich field
was thus opened to zootomical and microscopical investigation, and
anatomy atid physiology, organology and histology, ontogeny and
systematic zoology have been advanced to a surprising degree. The
investigation of the lower animals has since then been recognized as
a wide field of work, whose exploration is of great significance for all
branches of science and to which we owe numberless special and the
most important general conclusions.

The general belief of zoologists regarding the extent of this rich
pelagic animal world arose as the result of the discovery that a s])ecial
"pelagic fauna" exists, composed of many characteristic forms, funda-
mentally different from the littoral fauna. This pelagic fauna is made
uj) of animals (some floating passively, others actively swimming) which
remain at the surface of the sea and never leave it, or only for a short
time descend to a slight dei)th. Among such true "pelagic animals"
are the radiolaria, peridinia, noctiluca, medusiie, siphonophores, cten-
ophores, sagitta, pteropods, heteropods, a greater.part of the Crustacea,
the larvai of echinoderms, of many worms, etc.

Important changes Avere first made in the prevailing idea of the
"pelagic fauna" by the remarkable discoveries of the epoch-making
Challenger expedition (1873-1870). The two leaders of this, Sir
Wyville Thompson and Dr. John Murray, did not limit themselves to
their chief object, the general physical and biological investigation
of the deep sea, but studied with equal care and perseverance the
conditions of organic life at the surface of the ocean and in zones of

5G8 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

various depths. As the most significant general result Murray, in his
"Preliminary Eeport" (187G), says:

Everywhere we have found a rich organic life at and below the surface of the
ocean. If living individuals are scarce at the surface, below it the tow net commonly
discloses numerous forms, oven to a depth of 1,000 fathoms and more (5, p. 536).

In 1875, on the journey through theKorth Pacific Ocean (from Japan
to the Sandwich Islands), the extremely important fact was established
that the i^elagic organisms in oceanic zones of difi'erent depths belong-
to different species; fine pelagic nets (or tow nets) " on many occasions
were let down even to depths of 500, 1,000, and 2,000 fathoms, and
thereby were discovered many swimming organisms which had never
been captured hitherto, either at the surface of the ocean or at slight
depths (up to 100 fathoms below the surface)" (0, ]). 758). The most
characteristic forms of these zones of different depths belong chiefly to
the class of the Radiolaria^ especially to the order of the Pluvodaria.

Through the investigation of the Challenger radiolaria, which occupied
for ten years the greater part of my time and attention, I was led to
study anew these conditions of distribution; and I reached the con-
viction that the differences discovered by Murray in the pelagic fauna,
at different depths of the ocean, were still more significant than he
assumed, and that they had the greatest significance, not merely for
the radiolaria, but also for other groups of swimming oceanic organisms.
In 1881, in my ^^Enticurf eines Systems der Challenger Radiolarien,^^ p.
422, 1 distinguished three groups: («) jjelagic, living at the surface of
the calm sea; {h) zonary, living in distinct zones of depth (to below
20,000 feet) ; and {c) profound (or abyssal) animals living immediately
above the bottom of the deep sea. In general, the different character-
istic forms correspond (to below 27,000 feet) to the different zones.

In my "General Natural History of the Radiolaria''- (4, p. 120) I have
established this distinction, and have expressed my conviction that it
is i)ossible, by the aid of a suitable bathygraphic net, to demonstrate
many different faunal belts overlying one another in the great deep-
sea zones.

The existence of this "intermediate pelagic fauna," discovered by
Murray, inhabiting the zones of different depths of the ocean between
the surface and the deep-sea bottom, which I have briefly called " zon-
ary fauna," has been decidedly contradicted by Alexander Agassiz.
He claimed, on the ground of "exact experiments" carried on during
the Blal<e expedition, in 1878, that the greater part of the ocean con-
tains absolutely no organic life, and that the pelagic animals go down
no deeper than 100 fathoms. "The experiments finally show that
the surface fauna of the sea is actually limited to a relatively thin layer,
and that no intermediate zone of animal life, so to speak,' exists between
the fauna of the sea bottom and of the surface" (15, pp. 46, 48).

PLANKTONIC STUDIES. 569

Although these negative coiichisious fi-om the so-called " exact ex-
periments" of Agassiz are contradicted by the foregoing results of the
Challenger investigator, yet against the latter, with some show of right,
Agassiz might have raised the objection that the ''tow net" used could
establish no safe conclusion.* This objection could only be finally
removed by the construction of a new tow net, which could be let down
closed to a certain depth, and then opened and closed again. The
merit of inventing such a closible net, and of the immediate successful
use of it, belongs to two distinguished Italian naval officers : G. Pal-
un)bo, commander of the Italian war corvette Vettor Pisaiii, first con-
structed such a closible pelagic net or "bathy graphical zone net;" and
Naval Lieutenant Gsetano Chierchia, who during the three years' voyage
of the Vettor Fisaxi around the world made a very vahiable collection
of pelagic animals, used the new closible net with fine results, even at
a depth of upwards of 4,000 meters (8, p. 83).

Chierchia's first trial with this "deep-sea closible net" was June 5,
1884, in the East Pacific Ocean, directly under the equator, 15° west of
the Galapagos Islands. Fourteen days later, June 19, midway between
the Galapagos and the Sandwich Islands, this closible net was sunk to
4,000 meters. In this and in many other trials these Italian naval
officers captured an astonishing wealth of new and interesting zonary
animals, whose description has for a long time busied zoologists. The
collections brought back to Naples by the Vettor Pisani are, next to
those of the ChaUenger, the most imi)ortant materials from the region
under coi i sideration.

A few faults which pertained to Palumbo's net were soon done away
with by improvements, for which we are indebted to the engineer Peter-
sen and to Prof. Carl Chun, of Breslau. The latter, in 1886, made
trials in the Gulf of Naples with the improved closible net which
showed "a still more astonishing richness of pelagic animals in greater

* The " tow nets " used by the Challenger were the ordiuary Miiller's net (or the
" fine pelagic net" of Joh. Miiller), a round bag of Miilhn- gauze or silk mull, the
mouth being kejit open by a circular metallic ring. This ring is iu ordinary pelagic
fishing fastened to a handle 2 or 3 meters long (like the ordinary butterfly net).
While the boat moves along, the opening of this net is held at the surface in such a
way that the swimming animals are taken into the bag. They remain hanging
in the bottom of this, while the water passes through the narrow meshes of the net.
After a time the net is carefully inverted and the tow stuff (Attftrieb) is emptied
into a glass vessel filled with sea water. If one wishes to fish below the surface,
the ring of the net is fastened by means of three strings, equally distant from one
another, which at a point (about 1 meter distant from the opening of the net) are
joined to a longer line which is sunk by weights to a definite distance, correspond-
ing to the desired depth. When Murray fastened such a tow net to the deep-sea
sounding line or to the long line of the deep-sea dredge, he first obtained the inhabi-
tants of the " intermediate ocean zones," but he could not thereby avoid the objec-
tion that, since this tow net always remained open, the contents might come from
very different depths or even only from the surface. For iu <lrawing up the open
tow net animals from the most different zones of depth might occasionally be taken iu.

570 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

depths, and completely overthrew the assumption that an azoic layer
of water exists between the surface and the sea bottom" (15, p. 2). Chun
embraced the general results of his important bathyi^elagic investiga-
tions under the four following- heads:

(1) The portiou of the Mecliterrauean iuvestigated showed a ric-li pclanio fauna at
the surface as well as at all depths up to 1,400 meters.

(2) Pelagic animals which during the winter and spring a])pear at the surface seek
deep water at the beginning of summer.

(3) At greater depths occur pelagic animals whicli have hitherto beeu seldom or
never observed at the surface.

(4) A number of pelagic animals also remain at the surfjic.' during tlie summer,
and never sink into deep water (15, p. 44).

Among the remarks which Chun made on the vertical distribution of
the pelagic fauna and the astonishing plaiiktouic wealth of the depths
of the sea (at 1,000 to 2,000 meters), he Justly throws out the question,
"Who knows, whether in the course of time our views will not undergo
a complete reversal, and whether the depths will not show themselves
as the peculiar mother earth of pelagic life, from which, for the time
being, swarms are sent out to tlie surface as well as to the sea bottom!
There are only a few forms which can so completely adapt themselves
to the changing conditions of existence at the surface that they no
more seek the deeper levels " {1.% p. 40). In consequence of his obser-
vations on the periodic rising and sinking of pelagic animals, Chun
"can not resist the impression that from the abundance of animal life
in the de])ths the surface fauna represents relatively only an advance
guard of tlie whole, which sometimes to a greater, sometimes to a
less extent, and occasionally completely, withdraws itself into more
protected regions. Facts plainly speak for this, that the periodical
wandering of pelagic animals in the vertical direction is especially
conditioned by the changes in temperature. Only a few pelagic auimal
groups can endure the high temperature of the surface water during
the summer; the majority withdraw from the influence of tliis by
sinking, and, finally, whole groups pass their life in the cool deep
regions without ever rising to the surface" (15, p. 54).

The general ideas which Chun had obtained by this deep-sea inves-
tigation of the Mediterranean he was able to confirm for the Atlantic
Ocean on a trip made in the winter of 1887-88 to the Canary Islands
(10, p. 31). At this time he made the observation that the periodical
wandering of pelagic animals in a vertical direction was influenced in
great part by ocean currents (at the surface as well as in deep wafer),
and that among other things the occurrence of the full moon exerted
a significant action (10, p. 32). Chun's special observation in the sea
of Orotava, upon the poverty of the Canary plankton in November and
December and the sudden appearance of great numbers and many
species of pelagic animals in January and February, agrees completely
with the observations which I myself made twenty years before at

PLANKTONIC STUDIES. 571

the Canary island Lanzarote. I also entirely agree with Chun in
regard to his general views upon the chorology of the plankton, and
consider his investigations upon the pelagic animal world and its rela-
tion to the surface fauna as the most important contribution which
planktology has received since the pioneer discoveries of the Challenger
and of the Vetfor Pisaui.

Entirely new aspects and methods have been introduced into pelagic
biology in the last three years by Dr. Victor Hen sen, professor of phy-
siology at Kiel (9 and 22). He has for a number of years thoroughly
studied the conditions of life of the fauna and flora of the bay of
Kiel, and as a member of the commission for the scientific investigation
of the German Ocean (at Kiel) has endeavored to improve and extend
the fisheries there, and by counting the fish eggs collected to get an
approximate idea of the number of fish in corresponding districts (9,
p. 2). This investigation led him to the conclusion that it was neces-
sary and possible to come nearer to the fundamental food supply of
marine animals and to determine this quantitatively. For solving this
problem Hen sen invented a new mathematical method (2, p. 33). He
constructed a new pelagic net (p. 3), and in July, 18S4, in company
with three other naturalists of Kiel, undertook a nine-day excursion in
the North Sea and Atlantic Ocean, which was extended to the Hebrides
and to the Gulf Stream (57° 42' N. Lat.) (p. 30). In 1887 he publislied
the results of this investigation in a comprehensive work containing
many long numerical tables, "On the Determination of the Plankton,
or the Animal and Vegetable Material found in the sea" (9). He used
the term "plankton" in place of '^Auftrieh,'' the word hitherto com-
monly used, because this name is not sufficiently comprehensive and
suitable (9, p. 1). To be sure, the German term ''Atiftrieh'' or ''pelagi-
Hcher Mulder,'' introduced by Johannes Muller forty years ago, was in
general use and has many times been used in English, French, and
Italian works. But I agTee with Hensen that in this, as in other
scientific terms, a Greek terminus technicus, capable of easier flexion,
is preferable. I ado])t the term Plankton in place of ^^Auftrieh;' and
form from it the adjective planktonic {plauMonisch). The w }iolc science
which treats of this important division of biology is briefly called

])lanktology.

Hensen regards the mathematical determination of the 2)lanlcton us,
the ch ief aim of planktology from a physiological standpoint. By it he
hopes to solve the somewhat neglected question of the cycle of matter
in the sea. For the purpose of solving this, and to make a trial of his
new method on a larger scale, Hensen, in the summer of 1889, arranged
a more extensive expedition in the Atlantic, which was most liberally
supported by the German government and by the Berlin Acadeniy
of Sciences. The German Emperor furnished 70,000 marks; the Berlin

572 REPORT OP COMMISSIONER OF FISH AND FISHERIES.

Academy gave, from tlie income of tlie Humboldt fund, 24,600 marts,
and by further contributions the entire sum at the disposal of the ex-
l^edition was raised to 105,600 marks — a sum never before made avail-
able in Germany for a biological expedition. The new steamer Na-
tional, of Kiel, was chartered for three mouths, and was fitted out " with
all the admirable contrivances for obtaining i)lankton, for deep-sea
fishing, and for sounding." Besides the leader of the expedition. Prof.
Hensen, five other naturalists participated: the zoologists Brandt and
Dahl: the botanist Schlitt; the bacteriologist Fischer; the geographer
Kriimniel; and the marine artist Eichard Eschke. The voyage of
the National lasted 93 days (July 7 to November 15). The course was
westward through the north Atlantic (Gulf Stream, Sargasso Sea),
then southward (Bermudas, Cape Verde, Ascension) to Brazil, and
eastward back by the Azores. JDuring this voyage 400 casts were
made, 140 with the plankton nets, 260 with other nets.

Our German navy has been but little used for scientific, still less
for biological, investigations; much less than the navies of England,
France, Italy, Austria, and the United States. The remarkable serv-
ices which many distinguished German zoologists have rendered in the
last half century for the advancement of marine biology have been car-
ried on almost entirely without government aid. The German govern-
ment has hitherto had very little means available for this branch of
science. Therefore, great was the satisfaction when, by the libei-al en-
dowment of the plankton expedition of Kiel, the first step was taken
for the more extensive investigation, with better apparatus, of the biol-
ogy of the ocean, and for emulation of the results which the English
Challenger and the Italian Ycttor Pisani had latelj' obtained in this
region.

Accounts have been published of the results of the plankton expedi-
tion of Kiel, by Victor Hensen (22), Karl Brandt (23), E. du Bois Eey-
mond (21), and Kriinimel. The essential details of these accounts have
been repeatedly published in the German newspapers, to the general
effect that the i)roposed goal was reached and the most important
question of the plankton was happily solved. I very greatly regret
that I can not agree with this favorable verdict. (1) The most impor-
tant generalizations which the plankton expedition of Kiel obtained on
the composition and distribution of the X)lankton in the ocean stand in
sharp contradiction to all previous experience; one or the other is
wrong. (2) It seems to me that Hensen has incautiously founded a
number of far-reaching erroneous conclusions on very insutticient prem-
ises. Finally, I am convinced that the whole method employed by
Hensen for determining the plankton is utterly worthless, and that tlie
general results obtained thereby are not only false, but also throw a
very incorrect light on the most important problems of pelagic biology.
Before I establish this dissenting opinion let me give an account of my
own i)lanktonic studies and their results.

PLANKTONIC STUDIES. 573

II.— PLANKTONIC STUDIES.

My own investigatious on the organisms of the plankton were begun
thirty-six years ago, when I got my lirst conception of the wonderful
richness of the marine fauna and iiora in the North Sea. Accepting
the kind invitation of my ever-remembered teacher, Johannes Miiller,
I accompanied him in the autumn of 1854 on a vacation trip to Helgo-
land, and was introduced by him personally into the methods of plank-
ton fishery and the investigation of the pelagic fauna. There, during
August and September, I accompanied him daily on his boating trips,
and under all conditions of the rich planktonic captures I received from
him the most competent instruction, and pressed with corresponding
eagerness into the mysteries of this wonderful world. Never will I for-
get the astonishment with which I first beheld the swarms of pelagic
animals which Miiller emptied by inversion of his "fine net" into a glass
jar of sea water— a confused mass of elegant medusae and glistening
ctenophores, swift-darting sagittas and snake-like tomopteris, copepods
and schizopods, the pelagic larvre of worms and echinoderms. The
important stimulus and instruction of the founder of planktonic inves-
tigatio^n has exercised a constant infiuence on my entire later life, and
has given me a lasting interest in this branch of biology.*

Two years later (in August and September, 185G), while at Wiirtz-
burg, I accepted the invitation of my honored teacher, A. Kolliker, to
accompany him to Mzza, and, under his excellent guidance, became
acquainted with the zoological treasures of the Mediterranean. In
ct)mpauy with Heinrich Miiller and K. Knpfifer, Ave investigated espe-
cially the rich pelagic aninnil life of the beautiful bay of Villafranca.
Tliere, for the first time, I met those wonderful forms of the pelagic
fauna which beh)ng to the classes of the siphonophores, pteropods, and
heteropods. I also there first saw living polycyttaria, acanthometra,
and polycystina, those phantasmic forms of radiolaria, in the study of
which I spent so many later years.

Johannes Miiller, who was at this time at Nizza, and had already
begun his special investigation of this latter order, called my attention
to the many and important questions which the natural history of
these enigmatical microscopical organisms present. These valuable
suggestions resulted some years later in my going to Italy and spend-
ing an entire year in pelagic fishing on the Mediterranean coast. Dur-

* When at Helgoland, investigating the wonders of the plankton with the micro-
scope, Johannes Miiller, pleased with the care and patience Avith which his zealous
students tried to study the charming forms of meduste and ctenophores, spoke to me
the ever-memorable words, "Tliere you can do much; and as soon as you have
entered into this pelagic wonderland you will see that you can not leave it."

574 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

iDg the summer of 1859, at Naples aud at Oapri, I endeavored to gain
as wide a knowledge as possible of the marine fauna. In the following
winter, at Messina, I devoted my entire attention to the investigation
of the radiolaria, and thus obtained the material which forms the
basis of my monograph of this class (1802). Daily boat trips in the
harbor of Messina made me acquainted with all the forms in the
pelagic fauna which make this classic spot, in consequence of the com-
bination of uncommonly favorable conditions, far richer for planktonic
study and investigation than any other point on the Mediterranean
(3, pp. v, 25, 166, 170).

For a full generation, since that time, the study of plankton has
remained my most i^leasant occupation, and I have haidly let a year
pass without going to the seacoast and, by means of the j)elagic net,
getting new material for work. Various inducements were offered to
me in addition ; on the one hand the radiolaria, on the other the siphouo-
phores aud medusie, to which I had already given some attention while
at Mzza in 1864. The results of these studies are given in my mono-
graphs of these two classes (1870 and 1888). In the course of these three
decades I have by degrees become acquainted with the entire coast of
the Mediterranean and its fauna. I have already made reference, in
the preface to my "System of Medusae," p. xvi, to the places where
I have studied this subject. In addition to the Mediterranean I iave
continued my planktonic studies on the west coast of Norway (1869) ; on
the Atlantic coast of France (1878); on the British coast (1876 and
1879); at the Canary Islands (1866-67); in the Eed Sea (1873), and in
the Indian Ocean (1881-82).

By far my richest results and my deepest insight into the biology of
the plankton were vouchsafed me during a three months' residence
at Puerto del Arrecife, the seaport of the Canary island Lanzarote
(in December, 1886, and in January and February, 1887). The pelagic
fauna in this part of the Atlantic is so rich in genera and species;
the fabulous wealth of life in the wonderful "animal roads" or Zain
currents (18, p. 309) is, every day, so great, aud the opportunities for
investigation on the spot are so favorable that Lanzarote afibrded
me greater advantages for planktonic study than all the other places
ever visited by me (excepting perhaps Messina). Every day the
pelagic net brought to me and to my companions (Prof. Eichard Greeff"
and my two students, N. Miklucho-Maclay and H. Fol) such quanti-
ties of valuable tow-stufi' {Auftrieh) that we were able to work up only
a very small part of it. At that time I concentrated my chief inter-
est on the medusae and siphonophores, and the larger part of the
new material which is worked up in my monographs of these two
classes was collected at Lanzarote. All my observations "On the
Development of the Siphonophores" (1869) were made there.

PLANKTONIC i^TUDIES. 575

The excursiou to the coral reefs of the Red Sea (1873), which is
recounted in my ''Arabic Corals," and the trip to Ceylon, about which
I have written in my "Indian Journal" {Indische Eeisehriefe, 1882),
were extremely valuable to me, because I thereby gained an insight
into the wonders of the Indian fauna and flora. On the journey from
Suez to Bombay (in Js^ovember, 1881), as well as on the return from
Colombo to Aden (in March, 1882), I was able to make interesting
observations on the pelagic fauna of the Indian Ocean, as well as dur-
ing a six weeks' stay at Belligam and in the pelagic excursions which
I made from there, I obtained thereby a living picture of the oceanic
and neritic fauna of the Indo-Paciflc region, which differs in so many
respects fi'om that of the Atlantic-Mediterranean region. The special
results of my experience there are, with the kind consent of Dr. John
Murray, for the most part embraced in my report on the Radiolaria
(1887), and on the Siphonophora (1888), which form parts xviii and
XXVIII of the ChaUemjer Report. These two monographic reports also
contain many observations on plankton, which I had made in earlier
journeys and had not yet published.

The extensive experience which I had gained through my own obser-
vations of living plankton during a period of three decades was well
filled out by the investigation of the large and well-preserved planktonic
collections placed at my disposal from two different sources by Capt.
Heinrich Rabbe, of Bremen, and by the Challenf/er directors of Edin-
burgh. Capt. Rabbe, with very great liberality, turned over to me the
valuable collection of pelagic animals which he had obtained on three
different trips (with the ship Joseph Raydn, of Bremen) in the Atlantic,
Indian, and Pacific oceans, and which he had carefully preserved
according to my directions and by approved methods. This extraor-
dinarily rich and valuable material, contained in numerous bottles,
embraced planktonic samples from the most diverse localities of the
three oceans, chiefly in the southern hemisphere. Like the nuich more
extensive collection of the ChaUemjer, it gives (though to a smaller
degree) a complete summary of the complexity of the composition of the
plankton and the difference in its constituents. Rabbe's collection
supplements that of the Challenger in a most welcome manner, since the
course of the Challenger was southward from the Indian Ocean through
the Antarctic region, and between the Cape of Good Hope and Mel-
bourne was always south of 40° south latitude. The course of the Joseph
Haydn, on the other hand, on the repeated voyages through the Indian
Ocean, was much more northerly, and between Madagascar, the Cocos
Islands, and Sumatra included a number of points where the pelagic
net obtained a very rich and peculiarly constituted capture. I hope
to be able to publish soon in detail the special results which I have
obtained by investigation of Rabbe's plankton collection, with the aid
of the ^carefully kept journal which Capt. Rabbe made of liis observa-
tions. The discoveries of new radiolaria, medusie, and siphonophores

576 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

which I owe to these are ah-eady embraced in my monographs on these
three classes in the Challenger Eeport, and in the preface I have ex-
jiressed to Gapt. Eabbe my sincere thanks for his very vahiable aid.

Of all expeditions which have been sent out for investigating the
biology of the ocean, that of the Challenger was, without doubt, the
greatest and the most fruitful, and I recognize it with additional grati-
tude since I was permitted for twelve years to take part in working up
its wonderful material. When, after the return of the expedition, I was
honored by its leader. Sir Wyvillc Thompson, by being summoned to
work up the extensive collection of radiolaria, I believed, after a hasty
survey of the treasures, that I could complete their investigation in the
course of three to five years; but the further I proceeded in the inves-
tigation the greater seemed the assemblage of new forms (4, p. xv), and
it was a whole decade before the report on the radiolaria (part xviii)
was completed. Three other reports were also then finished — on deep-
sea horny sponges (part lxxxii), on the deep-sea medusiT3 (part xii),
and on the siphonophores (part xxviii) collected by the Challenger.
The comparative study of these extremely rich planktonic treasures
was highly interesting and instructive, not only on account of the daily
additions to the number of new forms of organisms in these classes,
but also because ray general ideas on the formation, composition, and
importance of the plankton were enriched and extended. I am sin-
cerely thankful for the liberality with which Sir Wyville Thomi^son,
and after his untimely death (1882) his successor. Dr. John Murray,
placed these at my entire disposal.

A record of the 168 stations of observations of the Challenger ex-
pedition, whose soundings, plankton results, and surface preparations
I have been able to investigate, has been given in § 240 of the report
on the radiolaria (4, p. clx). The number of the bottles containing
plankton (from all parts of the ocean) in alcohol amounts to more than
a hundred, and in addition there are a great number of wonderful
preparations which Dr. John Murray finished at the different obser-
vation stations, stained with carmine and mounted in Canada balsam.
A single such preparation ^for example, from station 271) contains
often 20 to 30 and sometimes over 50 new species. Since the material
for these preparations was taken with the tow net, not only from the
surface of all parts of the sea traveled by the Challenger, but also from
zones of different dej^ths, they make important disclosures in morphol-
ogy as well as in jihysiology and chorology. To the study of these
station preparations I am indebted for many new discoveries. I have
been able to examine over a thousand (4, p. 16).

If I here refer to the development and extension of my own plankton
studies, it is because I feel compelled to make the following brief sum-
mary of results. I am not now in a position to give the proofs in detail,
and must defer the thorough establishment of the most weighty

PLANKTONIC STUDIES. 577

series of observations for a later and more detailed work. But since,
to my regret, I am compelled to decidedlj' contradict the far-reacliing
assertions made by Hensen (22), it is only to justify and prove these
that I refer to my extended experience of many years. I believe I do
not err in the assumption that among living naturalists I am one of
those who by extensive investigation on the spot have become most
thoroughly acquainted with the conditions of the plankton and have
worked deepest into these intricate problems of marine biology. If I
had not for so many years hud these continually in mind, and at each
new visit to the sea begun them anew, I would not dare to defend with
such determination the assertions expressed in the following pages.

III.— CHOROLOGICAL TERMINOLOGY.

The science of the distribution and division of organic life in the sea
(marine chorology) has in the last decade made astonishing progress.
Still this new branch of biology stands far behind the closely related
terrestrial chorology, the topography and geography of land-dwelling
organisms. We have as yet no single work which treats distinctly
and comprehensively of the chorology of marine plants and animals in
a manner similar to Griesbach's <' Vegetation of the Earth" (1872) for
the land jilants, and Wallace's "Geogra])hical Distribution of Animals"
(187G) for the land animals.

How much there is still to be done is shown by the fact that not one
of the simplest fundamental conceptions of marine chorology has yet
been established. For example, the most important conception of one
subject, that of the pelagic fauna and flora, is now employed in three
different senses. Originally, and through several decades, this term
was used only in the sense in which Johannes Miiller used it, for ani-
mals and plants which are found swimming at the surface of the sea.
Then the term was extended to all the different animals and plants
which are found at the surface of fresh- water basins. It was so used,
for example, by A, Weismann in his lecture upon " the animal life at
the sea-bottom" (1877), in which he "distinguishes the animal world
living on the shore from the 'pelagic or oceanic company living in the
open sea.'" To a third quite different meaning has the conception of
the pelagic living world been widened by Chun (1887), who extends it
from the surface of the ocean down to the greatest depths (15, p. 45).
In this sense the conception of the pelagic organisms practically agrees
with the "plankton" of Hensen.

Errors have already arisen from the varied use of such a funda-
mental conception, and it seems necessary to attempt to clear this up,
and to establish at least the most important fundamental conception
of marine chorology. In the use of words I will, as far as possible,
conform to the usage of the better authors.
H. Mis. 113 37

578 REPORT OF COMMISSIONER OF FISH AND FISHERIES.
MARINE FLORA AND FAUNA.

Since the old mooted question about "the limits of the animal and
vegetable kingdom " comes anew into the foreground in the planktonic
studies, a few words must first be devoted to its consideration. In the
plankton, those organisms (for the most i)art microscopic) which stand
on the boundary liue and which may be regarded as examples of a
neutral "Protista realm," play a conspicuous part — the unicellular
diatoms and murracytes, dictyochea and palmellaria, thalamophora and
radiolaria, dinoflagellata and cystoflagellata. Since it is still asserted
that for replies to this boundary question we need new researches,
"more exact observations and experiments," I must here express the
opposing belief, that the desired answer is not to be obtained by this
empirical and inductive method, but only by the philosophic and deduct-
ive method of more logical definite conception {logisclier Begriff-Bestim-
mung). Either we must use as a definite distinction between the two
great organic realms the physiological antithesis of assimilation, and
consider as "plants" all "reducing organisms" (with chemical-synthetic
functions) and as "animals" all "oxidizing organisms" (with chemical-
analytical functions) or we may lay greater weight on the morphological
differences of bodily structure and place the unicellular '■'■Protista'''' (with-
out tissues) over against the multicellular Histona (with tissues).*

For the problem before us, and with more particular reference to the
important questions of the fundamental food suj)ply ( Urnahrung) and
the cycle of matter in the sea {Stoffwechsel des Meeres), it is here more
suitable to employ the first method. I regard the diatoms, murracytes,
and dinoflagellates as Protoplujtes^ the thalamophores, radiolarians, and
cystoflagellates as Protozoa.

For a term to designate the totality of the marine flora and fauna,
the expre>ssion halohios seems to be suitable, in opposition to Uunwbios
(the organic world of fresh water) and to geohios (as the totality of the
land-dwelling or terrestrial plant and animal world). The term hios
was applied by the father of natural history, Aristotle, "to the whole
world of living " as opposed to the lifeless forms, the ahion. The term
biology should be used only in this comprehensive sense, for the
whole organic natural science, as oi)posed to the inorganic, the abiology.
In this sense, zoology and botany on the one side, and morphology
and physiology on the other, are only subordinate parts of biology,
the general science of organisms. But if (as is frequently done to-day
even in Germany) the term biology is used in a much narrower sense,
instead of(»co/o;7^, this narrowingleads to misunderstandings. I mention

^ rrotlsta aud Hiaiona may both again be divided into two groups, on the ground
of the different assimilation, into an auimial and a vegetable group, the Protista into
Protophrita and Protozoa, the Histona into Metaplnjta aud Metazoa. Compare my
"Natural History of Creation" (XatUrliche Schopfungsijeschichte), 8th edition, 1889, pp.
420 aud 453.

TLANKTONIC STUDIES. 579

this here because iu plauktology the interesting- and complex vital
relations of pelagic organisms, their manner of life and economy, are
very often called biological instead of cecological problems.*

PLANKTON AND BENTHOS.

If under the term Halohios we embrace the totality of all organisms
living iu the sea, then these, in (ecological relation, fall into two great
chief groups, benthos and pJc.nkton. I give the term lenthos] (in opposi-
tion to plankton) to all the nou-swimining organisms of the sea, and to
all animals and plants which remain upon the sea bottom either lixed
(sessile) or capable of freely changing- their place by creeping or run-
ning (vagrant). The great ojcological differences in the entire mode of
life, and consequently in form, which exist between the benthonic and
planktonic organisms, justify this intelligible distinction, though here
as elsewhere a sharp limit is not to be drawn. The hentJios can itself
be divided into littoral and abyssal. The littoral-benthos embraces the
sessile and vagrant marine animals of the coast, as well as all the
plants fixed to the sea-bottom. The ahyssal-benthos, on the other
hand, comprises all the fixed or creeping- (but not the swimming) ani-
mals of the deep sea. Although as a whole tlie morphological char-
acter of the benthos, corresponding to the i)hysiological peculiarities
of the mode of life,, is very different from that of the plankton, still
these two chief groups of the halobios stand in manifold and intimate
correlation to one another. In part these relations are only phylo-
genetic, but also in part at the i^resent day of an ontogenetic nature, as,
for example, the alternationof generations of the benthonic polyps and
the planktonic medusiL\ The adai)tation of marine organisms to the
mode of life and the organization conditioned thereby may in both
chief groups be primary or secondary. These and other relations, as,
well as the general characteristics of the |)elagic fauna and tlora, have
already been thoroughly considered by Fuchs(lL') andMoseley(7).

PLANKTON AND NEKTON.

The term fiankton may be used in a wider and in a narrower sense;
either we understand it as embracing all organisms swimming in the
sea, those floating passively and those actively swimming; or we may
exclude these latter. Hensen comprehends under plankton " every-
thing which is in the water, whether near the surface or far down,
whether dead or living." The distinction is, v>hether the animals are
driven involuntarily with the water or whether they dis])lay a certain
degree of independence of this impetus. Fishes in the form of eggs

* The terms biology and cecology are not intercliangeable, because the latter only
forms a part of physiology. Comp. my " Generelle Morphologie," 1866, Bd. i, j). 8,
21; Bd. II, p. 286; also my ''Ueber Etwickelungsgang und Aufgabe der Zoologie/''
Jena. Zeitsch. fur Med. u. Nat., Bd. v, 1870.

t/ieVQo?, the bottom of the ocean; hence the organisms living there.

580 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

and young belong in the highest degree to the plankton, but not when
mature animals. The copepods, although lively swimmers, are tossed
about involuntarily by the water, and, therefore, must be reckoned in
the plankton (9, p. 1). If, with Henseu, we thus limit the conception
of 2)Ianldon, then we must distinguish the aetirely swimming nelcton
from the passivehj driven iilanldon. The teiin thus loses its firm
hold, and becomes dependent on quite variable conditions; upon the
changing force of the current in which the animal is driven, by the
momentaiy energy of voluntary swimming movements, etc. A pehigic
fish or copepod, which is borne along by a strong current, belongs to
the plankton ; if he can make a little i)rogress across this current, and
if, besides this, he can voluntarily and iudependently define his course,
then he belongs also to the nekton. It therefore seems to me advisable,
as jireliminary, to regard the term plankton in the wider sense, in oi)j)0-
sition to benthos.

Still, for the chief theme which Hensen has set up in his plankton
studies, for the physiological investigation of the cycle of matter in
the sea {Stofffwechscl des 3Ieeres), this limitation of the plankton con-
ception will not hold; for a single large fish which daily devours hun-
dreds of i)teropods or thousands of coi)epods exerts a greater intluence
on the economy of the sea than the hundreds of small animals which
belong to the i)lankton. I will return to this in speaking of the
vertebrates of the i)lankton. If with Hensen we could, on practical
grounds, separate those animals of the plankton which are carried
involuntarily from those following their own voluntary swimming
movements (independent of the current), we might distinguish the
former as ploteric* the latter as nccferic*

HALIPLANKTON AND LIMNOPLANKTON.

Although the swimnung population of fresh water shows far less
variety and i)eculiarity than that of the sea, still among the former as
among the latter similar conditions are develoi^ed. Already the study
begins to take a joyous flight to the pelagic animals of the mountain
lakes, etc. Therefore, it will be necessary here also to fix limits,
as has been already done for the marine fauna; but since the term
"pelagic" should only be used for marine animals, it becomes advis-
able to designate as limnetic the so-called "pelagic" animals of fresh
w\ater. Among these we can again distinguish auioJimnetic (living only
at the surface), zonolimnetic (limited to certain depths), and haihylim-
netic (dwellers in the deep waters). The totality of the swimming and
floating population of the fresh water may be called Jimnoplanldov, as
opposed to the marine liaUpJanMon (9, p. 1), Avhich we here briefly
<-A\\\pJ(tnldon.

* Tl/io>-//p = drifting ; vtiktij^ = swimming,

PLANKT0^^1C STUDIES. 581

OCEANIC Ai^D NERITIC* PLANKTON.

The manifold differenees wliicli the character of the plimlcton shows
according to its distribution in the sea, lead first, with reference to
its horizontal extension, to a distiuction between oceanic and neritic
plankton. Oceanic pkmlion is that of the open ocean, exclusive of the
swiinniing" bios of the coast. The rejiion of oceanic plauktou may froui a
zoological point of view be divided into five great provinces : (1) the Arc-
ticOcean; (2) the Atlantic; (.3) the Indian; (4) the Pacific; (5) the Ant-
arctic. In each of these five great provinces the characteristic genera
of the plankton are apparent through the different species, even if the
differences in general are not so significant as in the different provinces
of the neritic and still more of the littoral fauna.

The neritic i)lankton embraces the swimming fauna and fiora of the
coast regions of the continents as well as the archipelagos and islands.
This is in its composition essentially different from the oceanic plank-
ton, and is quantitatively as well as (|ualitative]y richer. For along
the coast there develop, partly under i)rotection of the littoral bios, or
in genetic relation with it, numerous swimming animal and vegetable
forms which do not generally occur in the open ocean, or there quickly
die; but the fioating organisms of the latter may be driven by currents
or storms to the coast and there mingled with the neritic plankton.
Aside from this the richness of the neritic plankton in genera and
species is much greater than that of the oceanic. The complicated and
manifold relations of the latter to the former, as well as the relations of
both to the benthos (littoral as well as abyssal), have been but little
investigated and contain a fund of interesting problems. One could
designate the neritic plankton also as "littoral plankton" if it were not
better to limit the concei)tion of the littoral bios to the non-swimming
organisms of the coast, the vagrant and sessile forms.

PELAGrIC, ZONARY, AND BATHYBTC PLANKTON.

I keep the original meaning of the pelagic planJdon as given forty -five
years ago by Johannes Miiller, and used since by the great majority
of authors. I also limit the meaning of the pelagic fauna and flora to
those actively swimming or passively floating animals and plants, which
are taken swimming at the surfiice of the sea, no matter whether they
are found here alone or also at a variable depth below the surface.
These are the superficial and interzonary organisms of Chun (15, p. 54).
On the other hand, I distinguish the zonary and bathybic organisms; I
call zonary planldon those organisms which occur oidy in zones of defi-
nite depths of the ocean, and above this (at the surface of the sea) or
below (at the sea bottom) are only found occasionally, as for example
many phajodaria and Crustacea; also the deep-sea siphonophores dis-

* Nr/piriji, sou of Nereiis.

582 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

covered by Chiercliia, wliicli were taken by him in great numbers and
in great vertical and horizontal extension, but never higher than 1,000
meters below the surface and never deeper than 1,000 meters above
the sea bottom (8, p. 85). The deepest part of this zonary fauna forms
the haihyhic planMon (or the profound tow-stuil", A<(/ifWe6), i. e., animals
of the deep sea, which only hover over the bottom but never touch it,
whether they stand iu definite relation to the abyssal benthos or not.
One might also call them ^' abyssal planT<ton,^^ if it were not more prac-
ticable to limit the term " abyssal" to the (vagrant and sessile) benthos
of the deep sea. To the bathybic plankton belong many phfpodaria,
some inedusie and siphonophores, many deep-sea Crustacea, Tomopteris
euchwta, Megalocereus ahyssorum, etc. (15, pp. 55-57).

In each of these vertical parts of the plankton, distinctions may be
made which apply to the horizontal distribution. We may also dis-
tinguish oceanic and neritic forms in the pelagic fauna as in the zonary
and bathybic fauna.

AUTOPELA.GIC, BATHYPELAGIC, AND SPANIPELAGIC PLANKTON.

If, following the old custom, we limit the term "pelagic hios''^ to those
organisms wliich, at some time, swim or float at the surface of the sea —
if we do not with Chun (15, p. 45) extend this term to the zonary and
bathybic animals — it still is necessary to further distinguish by differ-
ent terms those forms of life which constantly, temporarily, or only
exceptionally live at the surface of the sea. I suggest for these the
terms autoj^elagic, bathypelagic, and sijanipelagic. Autopelagic are
those animals and plants which are constantly found only at the sur-
face (or iu stormy weather at slight depths below it), the "superficial"
of Chun (15, pp. 45, 60). To this "constant superficial fauna" belong,
for example, many polycyttaria (most sphiierozoids), many medusae (e. r/.,
Encoplda'), and many sii^honophores {e. g., ForsJcalicIa'); further, the
lobate ctenophores {Eucharis, BoUna), particular species of Sagitta {e. </.,
hipunctnta)^ and many copepods [e. </., Fontellma, 15, p. 27).

I call hathypelagic all those organisms which occur not merely at the
surface, but also extend down into the dei)ths, and often fill the deei)
layers of the ocean in not less astonishing multitudes than the surface
layers. Chun d. signates such bathypelagic animals as "interzonary
pelagic animals" (15, p. 45). Here belongs properly the chief mass of
the j)lankton; for through the agreeing researches of Murray (5, 6),
Moseley (7), Chierchia (8), and Chun (15, 16), as well as from my own
wide experience, it becomes highly probable that the great number of
pelagic animals and plants only pass a part of their lives at the surface ;
swimming at different depths during the other part. Among the
bathypelagic animals there are farther to be distinguished: (a) Kycti-
2)elagiCj which arise to the surfiice only at night, living in the depths
during the day; very many meduste, siphonophores, pyrosoma, most

PLANKTONIC STUDIES, 583

pteropods, and licterupods, very many Crustacea, etc. ; (/>) Chimopekujic,
whicli appear at tlie surface only in winter and in summer are bidden
in the depths — radioiaria, medusa', siphouophores, ctenophores, a part
of the pteropods and heteropods, many Crustacea, etc.; (c) Allopehujic,
which perform irregular vertical wanderings, sometimes appearing at
the surface, sometimes in the depths, independently of the changes of
temperature, which condition the change of abode of the nyctipelagic
and chimopelagic animals; the final cause of these wanderings ought
to be found in different oecological conditions, as of reproduction, of
outogeny, of food supply, etc.

Finally one may call spanipelagic those animals which always live
in the ocean dejiths (zonary orbathybic), and come to the surface only
exceptionally and rarely. This does not apply to a few dee])-sea ani-
mals which once every year ascend to the surface, but only for a short
time, for a few weeks or perhaps I'or a single day, c. g., Athoryhia and
PhysopJiora among the siphonophores, Charybdea und Per ijjhylla among
the medusie. The final cause of this remarkable spanipelagic mode
of life must lie chiefly in the conditions of reproduction and ontogeuy.
These animals must be much more numerous than present appearances
show.

HOLOPLANKTONIC AND MEEOPLANKTONIC OEGANISMS.

Numerous organisms pass their whole life and whole cycle of devel-
opment hovering in the ocean, while with others this is not the case.
Tliese rather pass a ]>art of their life in the benthos, either vagrant or
sessile. The first groiip we call holoplanldonic^ and the second mero-
pJanMonic. To the holoplanktonic organisms, which have no relation
whatever to the benthos, belong* the greater part of the diatoms and
oscillaria, all murracytes and peridinea; further all radiolaria, many
globigerina, the hypogenetic medusie (witliout alternation of genera-
tions), all siphonophores and ctenophores, all chsetognatha^, pteropods,
the copelata, pyrosoma, and thalidia„etc. Among these we find '^purely
pelagic, zonary, or bathybic*' forms.

The meroplanlctonic organisms, on the othei- hand, which are found
swimming in the sea only for a part of their life, passing the other
part vagrant or sessile in the benthos (either littoral or abyssal), are
represented by the following groups: A x:)art of the diatoms and oscil-
laria, the planktonic/?/con7,9, the metagenetic medusre {Cras2)edotawit]i
hydroid nurse, Acraspeda with scyphistoma nurse), some turbellariaus
and annelids, etc; further, the "pelagic larva;" of hydroids and corals,
many helminths and echinoderms, acephala and gasteropods, etc.

584 REPORT OF COMMISSIONER OF FISH AND FISHERIES.
IV.— SUMMARY OF THE PLANKTONIC ORGANISMS.

A. — riionjPllYTKS OK TIIK PLANKTON.

The vniceUnJiir plants {Protopliyta*) have very great importance
ill the physiology of the phinktoii and the cycle of matter in the
sea {^ioffweclisel des Meercs), for they furnish by far the greater part
of the fundamental food {Uniahrung). The inconceivable amount of
food which the countless myriads of swimming marine animals consume
daily is chiefly derived, directly or indirectly, from the planlctonic flora,
and in this the unicellular protophytes are of much greater importance
than the multicellular metaphytes. Nevertheless the natural history
of these small plants has thus far been very much neglected. As yet
no botanist has attemi)ted to consider the planktonic flora in general,
and its relation to the planktonic fauna. Only that single class, so rich
in forms, the diatoms, has been thoroughly investigated and .systemat-
ically worked up; as regards the other groui>s, not a single attempt at
systemization has been made; and many simple forms of great impor-
tance have lately been recognized for the first time as unicellular plants.
I must, therefore, limit myself here to a brief enumeration of the most
important groups of the plankton flora. Its general extent and quanti-
tative development have in my opiniou hitherto been much under-
valued, and with reference to the cycle of matter in the sea {Staff wecJtsel
(les Meeres) deserve a thorough consideration. I find masses of various
protophytes everywhere in the plankton, and suspect that they have
been neglected chiefly because of their small size and inconspicuous
form. ]\rany of these, indeed, have been regarded as protozoa or as
eggs of planktonic metazoa.

As a foundation for a most important province of botany, the classi-
fication of the protoi)hytes, we must kee]) in the foreground the follow-
ing considerations: (1) The kind of reproducticm, whether by simple
division {Schizophyta) into two, four, or many parts, or by formation
of motile swarm-spores, Ma.stigopln/fa: (2) the constitution of the i)hy-
tochroms, of yellow, red, or brown pigment, which is distributed in the
protoidasm of the cell (usually in the form of granules), and has great
significance in assimilation (chlorophyll, diatomin, erethrin, i>h;eodin,
etc.); (3) the morphological and chemical constitution of the cell-mem-
hrane (cellulose, siliceous, capsular, or bivalvular, etc.). So long as we
hold to the present view of the vegetable physiologists, that for the
fundamental process of vegetal assimilation, for the synthesis of proto-
plasm and amylum, the presence of the vegetal pigment matter is nec-
essary, we can regard as true protophytes only such unicellular organ-
isms as are provided with such a phytochrom, but we will have to

* The separation of tlie Protopliyta from the Metaphyta is as justifiable as that of the
Protozoa from the Metazoa. The latter form tissues, the former do not. (Compare
Natiirl. Sc'ho])fungsgesohichte, viii Aufl., 1889, jtp. 420-453.)

PLANKTONIC STUDIES. 585

include here a great number of protista, which have hitherto been
reckoned as protozoa, e. //., the Murraci/tea', Diciyochew, Fcridinea'.
As characteristic and important protopliytes of the plankton I here
mention seveiii groups: (1) Chromacea', (2) Calcocytea'j (3) Ifnrracytecv,
(4) iJiatomea', (5) Xanthellea', (G) Dictyochea', (7) Feridinea'.

1 . Chromacece (30, p. 452). — In this lowest vegetable group is probably
to be placed a number of snmll "unicellular alg.e" of simplest form,
which occur in great abundance in the jjlankton, but on account pt
their minute size and simple spherical shape have for the most part
been overlooked, or possibly regarded as geiin cells of other organisms.
They may here be i)rovisionally distinguished as FrocyteUa 2)>'imordi((Us.
The diameter of the spherical cells in the smaller forms is only about
.001 to .005 mm., in the larger .008 to .012 mm, seldom more. Usuallj^
each cell contains only one phytochrom granule of greenish color,
sometimes approaching a yellow or red, sometimes a blue or brown.
Whether there is also a diminutive nucleus is doubtful. Increase takes
l»lace simply by division into two or four parts, and appears to go on
with excessive rapidity, but swarm si^ores do not appear to be formed.
Hundreds or thousands of such green spheres may be united in a mass
of jelly. The decision whether these simplest Chromacece belong to the
Chlorcoccecv or Frotococcea', or to some other primitive protophytic group,
nmst be left to the botanist for further investigation, as well as the
(|uestion whether these diminutive FrocyteUw are actually true nucleated
cells or only unnucleated cytodes. For our plankton studies these are
of interest only so far as they develoj) in astonishing quantities in manj-
(the colder) regions of the ocean, like the diatoms; and with the latter
form a great part of the fundamental food {Uniahrung). Over wide
areas the sea is often colored brown or green, and they form the chief
food (described as Frotococcus marinus) of inconceivable myriads of
copepods, as Kiikenthal has mentione<l in his " Contributions on the
Fauna of Spitzbergen."

2. Calcocytew. — In the eighth edition of the ^'- Naturliche Scliopfnngs-
geschichte''^ (30, p. 437) I have designated as Calcocytew or "unicellular
calcareous algie " those imj^ortant minute organisms which, as " Coc-
cosplmra^ Cyathosphcera, and Bliahdospltwra, play a great role in oceanic
life. They are found abundantly in the plankton of the tropical and
sul)tropical seas, less abundantly in colder zones, and are never absent
where pelagic Thalamophora occur in great numbers. Like the latter,
they arebathypelagic. Theball of protoplasm which completely fills the
interior of the small calcareous-shelled plastid seems, when stained red
with carmine or brown with iodine, to be unnucleated, and therefore a
cy tode. The beautiful calcareous plates which comj^ose the shell ( Cocco-
litha, Cyatholitha, Bhahdolitha), and which in the RhahdosplKera bear a
radial spine, fall apart after death and are found in great numbers in all
parts of the warmer oceans and in the globigerimi ooze of the bottom.
Murray (5, p. 533; G, p. 939) and Wyville Thompson (14, i, p. 222)

586 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

were the first to demonstrate tlie wide distribution and innumerable
abundance of this unicellular calcareous alga, and I agree with them
in tlie supposition that these play a significant part in the biology of the
ocean and in the formation of its globigerina ooze.

3. Murracytecv.—TJBcler this name I may here refer to tlie very im-
portant but hitherto neglected group of planktonic protophytes, which
were first discovered by John Murray and described under the name
Pyroeystis (5, p. 533, plate xxi; 6, pp. 935^938). These '^ unicellular
algcT3"are transparent vesicles, from 0.5 to 1 or 1.5 millimeters in di-
ameter, and spherical, oval, or spindle-shaped in form. Their simple
continuous cell membrane is veiy thin and fragile, like glass. It is
stained blue by iodine and sulphuric acid, and seems to contain a small
quantity of siliceous earth. The contents of the vesicle is a vacuolated
cell, whose protoplasmic network contains many yellow granules of
diatomin. The spherical form {Pyroeystis noctiluca Murray) is very
similar in size and form to the connnon NoGtiluca miliar is and probably
is very often mistaken for it. I saw these thirty years ago (1860) at
Messina, and later (1866) at Lanzarote, in the Canary Islands.

AVhen John Murray published in 1876 the first figures and careful
description, he at first placed them with the diatoms, but later (6, p.
935) he has, with justice, separated them. He there says of Pyroeystis
noctiluca :

This organism is everywhere present, often in enormous masses, .at the surface of
the tropical and subtropical oceans, where the temperature is not more than 20^ to 21°
C and the specific gravity of the oceanic water is not diminished by the presence
of coast and river water. Pyroeystis shines very brightly ; the light comes from the
nucleus and is the chief source of the diffuse phosphorescence of the equatorial oceans in
calm Aveather.

Since tliese unicellular vegetable organisms do not have the char-
acteristic bivalve shell or siliceous case of the diatoms, but their cell
membrane forms a completely closed capsule, they can not be reckoned
with the latter, but must lie regarded as representatives of a different
group of protophytes, for which I propose the name Murracytecv or
"glass bladders" {Murra, a name given by the Eomans to a glasslike
mmeral-fluospar(?)— from which costly articles are made.)*

nn the Atlantic and Indijin oceans I h'^i^^seen great masses of M^^^^^^Zy^^a^i
have dis inguished many species, which may be regarded as representatives of four
genera: (1) P^,.ocv.s/is „oe/l/«,ca Murray; spherical. (2) Fhotoc„stls elllpsoldes Hkl-

Bhrer\4?\ r^T''-^'"'-^"''"" "^'^ (pyroeystis fuslformls Murray); spindle:
shaped, (i) ^eetacyst,s .H»rm.,««« Hid; cylindrical. The Murracytes mnltLy as

dWided heie f 1 "r"' '^f ^ eccentrically or against the cell will, hal
jjfil *he:e folows division of the soft cell body, which is separated from
the firm capsulelike membrane by a wide space (filled with a iellv). Then the
membrane bursts, and around the two halves or four tetrads there is immed atdv
formed a new covering. Considered phylogenetically, the ^.r.aov/rrpear '
very old oceanic Protopkytes of very simple structure!^' Perhaps they ought to 1
regarded as the ancestral form of the diatoms, for the bivalvular shell of ^h latt
could have arisen by a simple halving of the -apsnle of the former

PLANKTONIC STUDIES. 587

4. .DkUomeic— The iucoiiceiviiblc (luaiitities in wliicli the diatoms
populate the whole ocean and the extraordinaiT importance which they
possess as one of the most important constituents of the "fundamental
food supply" {Uniahrimg) in the cycle of matter in the sea has been
considered so many times that it is sufficient here to point to the com-
paratively recent accounts of Murray (o, p. 533; G, p. 737, etc.), Fuchs
(12, p. 49), Castracane (6, p. 1)30), and Ilensen (9, p. 80). Earlier the
chief attention was paid to the benthonic diatoms which everywhere
cover the seacoast and the shallow depths of the sea bottom in aston-
ishing quantities; in part lixed on stalks, in part slowly movhig among
tlie forests of seaweed and the fixed animal banks {festsitzenden Thicr-
hanlcen) of the coast. The importance of the planktonic diatoms was
recognized much later, those abounding in the open ocean as well as in
the coast waters furnishing one of the most important sources of food
for the pelagic animals. The oceanic diatoms, which often cover the sur-
face of the open sea as a thick layer of slime, form another flora, very
insufficiently studied and characterized by many forms of colossal size
(several millimeters in diameter), peculiarly regular in form, and with
extremely thin-walled siliceous shells (species of mhmodiscus, Coscino-
disciis, Bhizosolenia, etc., discovered in such numbers by the Challenger).
The neritic diatoms, on the other hand, which, swimming free in no
small numbers, populate the coast waters, are less in diameter and with
thicker walls, and stand on the whole between the oceanic and littoral
forms. The absolute and relative quantity of the planktonic diatoms
seems to increase gradually from the equator towards both poles.

In the tropical zone the pelagic diatoms are much less developed
than in the temperate zone, and here again much less than in the polar
zone. Wide stretches of the Arctic Ocean are often changed by incon-
ceivable masses of diatoms into a thick dark slime, the "black water,"
which forms the feeding-gr(mnd of whales. The pteropods and crus-
taceans, upon which these cetaceans live, feed upon this diatom slime,
the "black water" of the Arctic voyager. Not less wonderful are the
vast masses of diatoms which fill the Antarctic Ocean south of the
fiftieth degree of latitude, and whose siliceous shells, sinking to the
bottom after the death of the organism, form the diatom ooze. {Ch alien (jer,
stations 152-157). The tow nets here were quickly filled with such
masses of diatoms (for the most part composed of Chcvtoceros) that these
when dried in the oven formed a thick matted felt ((>, p. 920).

5. Xanthelle(V.—A highly important share in the cycle of matter in the
^ea belongs to the remarkable xanthcllecc or "yellow cells," which live
in si/mhiosis in the bodies of many marine animals, in the plankton as
iveli as in the benthos. I first proved that these "yellow cells," which
were observed by Huxley (1851) and by Johannes Mailer (1858) in the
calymma of radiolarians, were "undoubted cells," and also described
their structure and increase by division (3, p. 84), and later (1870)
showed that they constantly contained amyluin (4, § 90). But Cieu-

588 REPOliT OF COMMISSIONER OF FISH AND FISHERIES.

kowski first advanced the view tliat the yellow cells are iudepeudent
unicellular organisms, parasitic algre, which for a time live in the
bodies of the radiolariaus, but after tlie death of the latter come forth
and multiply by division. This supposition was confirmed experiment-
ally by Karl Brandt (24, p. 05) and Patrick Greddes, who explained
further the nature of their symbiosis, and finally showed the wide dis-
tribution of the xanlliellece in the bodies of numerous marine animals,
as well as their production of zoospores {ZoUxanthelht, PhilozoUn).
Whether these are ontogenetically connected with certain "yellow
unicellular algfe" which live free in the plankton, remains to be farther
investigated. Perhaps also in this group belong the Xanthidea which
"were described by Hensen (9, p. 79) and Miibius (10, p. 124) as species
of XantJiidium and as " spiny cystids,"' spherical cells which reach 1
millimeter in diameter, contain yellow diatomin granules, and multiply
by division. Their thick hyaline shell, which seems to consist of
slightly silicified cellulose, armed with simple or star-shaped radial
spines, is characteristic. I find these Xanthidea' very numerous in
the oceanic plankton. Perhaps the siliceous-shelled Xanthidia, which
Ehrenberg has found so abundantly as fossils, also belong here.

6. Bictyoeheie. — The ornamented latticed cases of the Dit'tyochida',
formed of hollow siliceous spicules, are often found in great numbers in
the plankton, pelagic as well as zonary. Although these have long-
been known, both living and as fossils, to microscopists, two very dif-
ferent views as to their true nature are entertained.*

In a preliminary contribution " On the Structure oi Dlstephanus [Die-
iyocha) speculum''' Zool. Anzeiger, No. 334, one of my earlier students,
Adolf Borgert, briefly showed that each single case contains an inde-
pendent ciliated cell. He therefore considered it a new group of Flageh
lata (or MastUjophora), for which he proposed the term SiUcoJiaiieUata.
The "twin parts" described by me (4, p. 1549) lie regarded as a double
case which had arisen through the conjugation of two individual
jiayellaia. To my mind this new interpretation seems to have very
considerable probability, although I do not regard it as settled that
the ciliated cells are the swarm-spores of the Pluvodarium. In case

* Ehrenberg, who in 1838 and 1841 first described the oruaiueuted siliceous skele-
tons of Dictyocha and Mesocena, called them diatoms and distiugnished no less than
50 species of them, some living, some fossil. Later, at Messina (1859), I noticed,
inclosed within the ornamented hat-shaped latticed shell a small cell, and on that
account referred it to the Radiolaria, with reference particularly to the similar
siliceous skeletons of some XasseUaria ( Acan thodesm ida). Twenty years later E. Hert-
wig found a spherical Pha'adarium, the surface of whose calymma was covered with
numerous Dictyocha little hats (Dictyocha-Hutchen), and he therefore believed that
they must belong to this legion. He compares the single siliceous little hats
( Hutchen) with the scattered spicules of the Spha'rozoida. In my ChaUenyer report (4,
p. 1558) I agreed with this interpretation; so much the more when I myself saw nu-
merous similar Fhwcystina (Dictyocha stapedia) living among a similar I'ha'odaria in
Ceylon, and found specimens in several bottles of the ChaUenyer collections, espe-
cially from Station 144, from the Cape of Good Hope (4, p. 1561, pi. 101, Figs. 10-12).

PLANKTONIC STUDIES. 689

the greenish-yellow pigment granules in the protoplasm of the Die-
tyochida' are chlorophyll or phytochrom, they must be placed with
"unicellular alga^." If, as I believe, the supposition of Borgert is cor-
rect, then the masses of DictyocUdw shells found so abundantly in
the calymma of Ph(codaricv can be regarded only as the empty shells
of Silicqfiafiellata, which the skeletonlessP//ft'o^7/?ia has taken in as food.
This supposition is much more probable since these, together with sili-
ceous scales of diatoms and tintinnoids,have been found in great num-
bers in the calymma of other radiolarians. This case would then be
analogous to two similar appearances which I myself have previously
described, My.vobrachia pliiteiis (4, p. 22) and Dalcaromma calcarea (4,
p. 70, § 102).

7. Peridinece {Dinoflaficllata or Binoeytea, earlier Gdioflagellafa).—
This group of Flagellata (or Masfifjophora) earlier placed with the In-
fusoria, has lately, with more certainty, been recognized as a proto-
phytic group with vegetable metabolism. They are represented in the
plankton by numerous and, in part, remarkable and beautiful forms,
a part of which have been lately figured by Stein under the name
Arthrodele flagellata. Many such forms occur in the neritic, fewer in
the oceanic plankton, and often in such masses that they take a great
part in the formation of the fundamental food supply. Henseu cor-
rectly points out the great importance of these Frotista, of whose
quantity he attempted to give a conception by counting (9, p. 73).
Many of these participate in a prominent way in the marine popula-
tion (Ce>v^^^^m, Prorocentrum, etc.). John Murray very often found
chains of Ceratmm tripuH (each composed of eight cells) floating in the
plankton of the open ocean, without ciliary movements, while the
ciliated single cells inhalnted the neritic plankton in vast numbers
close to the shore. Sometimes these crowds of Peridinew, like the
diatoms, appeared so abundantly as to till the tow net with a yellow
slime (G, p. 934).

I?. — METArUYTES OF THE PlANKTOX.

The only class of metaphytes which occurs in the plankton are the
alga^. The great majority of this class, so rich in forms, belong to
the littoral benthos; only a few forms have adopted the pelagic mode
of life, and of these only two, from their great abundance, are of any
considerable importance in the oceanic fundamental food supply, the
Oscillatorkc which live in the depths, and the /Sarfiassa which grow at
the surface. A third group, the Halosphwrea', is much less abundant
and important, but of considerable interest in many relations.*

*The OscUlalorkv must be regarded as true algi«, since their characteristic "jointed
threads" {" Glicdcr-faden") form an actual ThaUm^. and indeed a thread-like thallus,
as iu the Conferva-. But on the same grounds also we must regard as algw the Volvo-
cinea and Halosplurrew with spherical thallus ; they are also multicellular Meiaphytts,
which show the simplest form of tissue (Hhfone.9, 30, p. 420). The foregoing proto-
types, on the other hand, have no tissue, since the entire organism is only a simple
cell (Protista, 30, p. 453),

590 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

1. HaJospha'recv. — Under the name Halosplucra ririilis, Schmitz
(187(() first described a new genus of green algse from the Mediter-
ranean, which appear floating in the plankton of the Gulf of Naples
in great numbers from the middle of January until the middle of April.
They form swimming hollow spheres, from 0.5.") to 0.62 mm. in diameter,
whose thin cellulose wall is covered within by a single layer of chloro-
phyll containing cells analogous to- the blastoderm of the metazoic
egg. Each of tbese epithelial cells divides later into several daughter
cells, each of which forms four cone-shaped swarm-spores with two
ciliated cells. I have known this green ball for thirty years. In Feb-
ruary, 1800, I found them numerous in the plankton of Messina. I
observed a second kind in February, 1807, at Lanzarote, in the Canary
Islands. The hollow spheres found in the Atlantic are twice as large,
and reach a diameter of 1 to 1.2 mm. They have pear-shaped swarm-
spores. I named them Rcdospha-m blastida. Morphologically these
hollow spherical algfe are of great interest, since they are directly com-
parable to the blastula (or blastosphere stage) of the metazoic embryo.
As the latter is to be regarded as the simplest type of the metazoon, so
Halosphcera (like Volvox) can be looked upon as the primitive ancestral
form of the Metaphyta (4, p. 499). Hensen has lately found numerous
living specimens of i7a?os/)//ft'ro r/m7/.y in five hauls from a depth of
1,000 to 2,000 meters (10, p. 521). The light of the bathybic luminifer-
ous animals may possibly be sufficient for their metabolic activity.

2. Oscillator'uv. — Like the diatoms in the cold regions of the ocean,
the oscillatoria? ( THcliodesmium and its allies) are found in the warm
regions in inconceivable quantities. It is very certain that the latter,
as well as the former, belong to the most important source of the
" fundamental food supply." Ehrenberg in 1823 observed in the Ked
Sea, at Tur, such large quantities of Trichodesmium erytlircenm that the
water along the shore was colored blood-red by them. Mobius has re-
cently carefully described the same thing anew, and has (quite cor-
rectly) traced from it the name of the Eed Sea (26, p. 7). Later, I myself
found just as great numbers as these in the Indian Ocean at Maledira
and Ceylon (25, p. 225). In Rabbe's collections are several bottles of
plankton (from the Indian and Pacific oceans) entirely filled with
them.* The Challemjer fo\m(\. great quantities of Trichodesmmminthe
Arafura Sea and Celebes Sea (0, p. 545, 007), and also in the Guinea
stream (0, p. 218) ; and between St. Thomas and the Bermudas (6, p. 130)
wide stretches of the sea were colored by it dark red or yellowish brown.
Murray found it only in the superficial, never in the deeper layers of
tbe ocean.

3. Sargasse(e.— The higher algfe are represented in the planktonic
flora only by a single group, the Sarcjassece, and these again are com-

*In the collection of Eadiolana, which may he purchiised from the famulus Franz
Pohle, at Jena, prejiaration No. 5, from Madagascar, contains many flakes of this
08ciUato)-ia.

PLANKTONIC STUDIES. 591

Dionly only of a siiiiiie .species, iSaygassHm hacciferitm; but tliis lias the
greatest iiiiportauce, since, as is known, it alone forms the lioating
sargasso banks, which, cover such extensive portions of the ocean. Be-
sides this very important species, other fucoids are found floating- in
the ocean, especially species of Fucus {F. vesicnIosii.<i, F. nodoi^us, and
others). Still they never appear in such masses as the familiar "berry
weed." The floating sargasso banks are well known to have their char-
acteristic animal life, which Wyville Thompson accurately described
and fittingly termed nomadic (14, ii, pp. 9, 339).

This remarkable sargasso fauna bears the same character in both the
Atlantic and the Pacific oceans and consists partly of benthonic ani-
mals, which live sessile or creeping on the sargasso weed, partly of plank-
tonic organisms which swim among the weeds; the latter are more
neritic than oceanic. Hensen has lately described this fauna as re-
markably poor, and could only find 10 species of animals in it (9, p.
216). The Challenger found more than five times as many species in
this same Atlantic sargasso, namely, 55 (6, p. 136). It is obvious that
the remarkable negative results of Hensen on this as on other plank-
tonic questions can have no value against the positive results of other
investigators.

C— Protozoa of the Plankton.

The two great chief groui)s of unicellular animals, Rhizopoda and
Infusoria, occur m the ocean in very difterent proportions, in the
reverse condition to that in fresh water.

The Infusoria {Flagellata and Giliata), which chiefly form the pro-
tozoic fauna in the latter, are indeed represented in tlie sea by a great
number of species, but the most belong to the littoral benthos, and
only a few swimming species occur in such quantities that they are of
importance in the plankton, the N'oetilucidw among the Flagellata, the
Tintinnoida' among the Ciliata. Much greater is the wealth of the
ocean in Ehizopoda, calcareous-shelled Thalamophora and siliceous-
shelled JRaf?^o/<lHa. The accumulated masses of these shells form the
most important sediment of the ocean, while their unicellular soft l)odies
constitute the chief food supply for many planktonic animals.

Infusoria. — As is known, the Infusoria do not play so great a role
in the life of the ocean as in that of the fresh water. It is true that a
great number of Flagellata and Ciliata occur in the neritic or littoral
fauna, but neither on account of the number of individuals nor the
richness of forms are they elsewhere of importance, and only a few
small grouj)s extend out into the open sea. It seems as if these tender
and for the most part uncovered Protozoa are not suited for the contest
which the wild " struggle for existence " offers here. The armored
rliizopods take their i)lace. Still two small and very peculiar groups of
Infusoria are found in very great numbers in the plankton, and some-
times in such quantities as to form the chief bulk; the Noctiluca among

592 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

the FJagellata, aud the Tintimia among the Ciliata. Both groups, aud
particularly the NoctilucidcCy beloug to the neritic phxukton. They occur
in the oceanic only where the coast water flows in (0, pp. 679, 750, 933).

The common XoctUuea miUaris aud some rehited species sometimes
cover the surface of the coast waters in such masses as to form a tliick
reddish-yellow slime, often like "tomato soup," and at night are
brightly luminous. The Tintinnoidw ( Tintinnus, Dictyocysta^ CodoneUa)
appear in smaller quantities, but often in great numbers. Some forms
of these elegant Ciliata are oceanic.

Tlialamophora {Foraminifera). — The Thalanio2)hora, often and very
properly called Foraminifera, were once generally regarded as ben-
thonic. Xew observations first showed that a part of these are plank-
tonic, and through the comprehensive series of observations by the
ChaUemjer the abundant occurrence of these pelagic Foraminifera and
their great part in the formation of that most important sediment, the
Olohigerina ooze, was first established. All these Thalamophora of the
plankton belong to the peculiar perforated Polythalamia, to the family
of the Globiyerinidw; only OrhitHna (provided it is independent) to the
Monoihalamia. The number of their genera (8-10) and species (20-25)
is relatively small, but the number of individuals is inconceivably
great. By far the most important and numerous belong to the genera
Glohifierina, Orhulina, and Fulvimdina; after these Splucroidina and
Pullenia. They occur everywhere in the open ocean in nnmberless
myriads. J. Murray could often from a boat scoop up thick masses of
them with a glass, and never fished with the tow net in 200 fathoms
without obtaining some (5, p. 534). A few forms {Hastigerina and
Cymhalopora) show more local increase in numbers, while others are
rare everywhere {ChilostomeUa, Candeina). In the equatorial counter-
currents of the Western Pacific, between the equator and the Caroline
Islands, the Challenger fonnd "great banks of pelagic foraminifera.
On one day an unheard-of quantity of Pulvinulina was taken in the
tow nets; on the following day they were entirely absent, and Ful-
lenia was extraordinarily abundant." These important observations
by Murray I can confirm from my own experience in the Atlantic and
Indian oceans* (comp. 3, pp. 160, 188).

*The important relations of these pelagic Polythalamia to the rest of the fauna of
the phmktou on the one side, as well as its importance in the formation of the "Globi-
gerina ooze" on the other, has been expressly stated by Murray (6, j). 919). I agree
completely with him in the view that these oceanic (ilobit/crinidfc are true pelagic;
rhizopods, which in part are found swimming only at the surface or at slight depths
(autopelagic), in part at zones of dilferent depths (zonary), hut they are not ben-
thonic. The enormous sediment of "Glohigerina ooze" is composed of the sunken
calcareous shells of the dead pelagic animals. On the other hand, the benthonic
thalamophorcs, living partly abyssal, on the bottom of the deep sea, partly littoral,
creeping among the forests of seaweed on the coasts, are of other sj^ecies and genera.
They develop a much greater variety of ibrin. The neritic thalamophorcs found
swimming in the coast waters are in part .again characterized l)y various forms.

PLANKTONIC STUDIES. 593

Badiolaria.—Ti^o class of organisms has remained so long uiiknowu
to us, and by the brilliant discoveries of the last decade has been sud-
denly placed in so clear a light, as the Radiolarla (comp. 4, § 251-2G0),
For half a century we knew next to nothing of these wonderful rhizo-
pods; to-day they appear as one of the most important planktonic
classes.* These, the most varied in form of all the unicellular organ-
isms, forni a purely oceanic class, and live and swim in all seas, especially
in the warmer ones. ^N'umenms species are also found near the coasts,
yet these are not distinguishable from those of the open sea. They
constitute no separate neritic fauna.

'S-'ast crowds of Radiolaria occur at the surface of the ocean, as well
as at different depths. Long ago Johannes Midler remarked:

It is a great plieuomeuon that Araiithomeira can be takeu daily by tlionsaiids in a
calm se.1 and independently of storms; and tiiat of many specits of rolycijatina,
hnndrcds of individnals were seen during my last residence at the seashore (2, p. 25).

I have tried myself, on the hundreds of voyages to different coasts
which I have made since 185(5, to thoroughly study the natural history
of the Radiolaria. The incomparable collections of the Challeru/er
afforded me by far the richest material for observation. The results
obtained therefrom are embodied in the report (18S7). Among other
references to the conditions of the plankton there mentioned, it brought
up the following pro])ositions: (1) Badiolaria occur abundantly in all
seas which contain a medium amount of salt, and which do not (like
the Baltic) receive a sti'ong influx of fresh water. (2) In the colder
seas only a few species occur (chiefly Acantharia), but immense quan-
tities of individuals; towards the equator the variety in form gradu-
ally increases (horizontal distribution, comp. 4, § 220-2.31). (3) The
chief groups of Radiohtria are distributed unequally in the five bathy-
zones or girdles of depth of the open ocean. The subclass Porulosa
(the two legions of S^nmellaria and Acantharia) inhabit especially the
two upper zones. On the other hand, the subclass Oscidosa {Nasselaria

*After Ehreuberg, in 1847, had described the siliceous shells of some hundred
species from the Barbados, we obtained in 1858 the first description of their organ-
ization through Johannes Miiller. In the Avork with which this great master closed
his renowned life he described 50 species which he had observed alive in the Med-
iterranean Sea (2). ^Vhen in continuation of this I devoted a winter's residence
in Messina to their i'urther investigation, I was able in 1862, in the monograph con-
aesiuent thereupon, to distinguish 144 new species, in all 113 genera and 15 families (3).
But this rich Badiolaria fauna of Messina still gave no promise of the immense quan-
tities of these delicately ornamented creatures peopling the open ocean, and
whose variously formed siliceous shells, sinking to the l)ottom after death, formed
that wonderful sediment, the "Badiolaria ooze." This was fust discovered thirteen
years later by the Challenger. The investigation of the fabulous radiolariau treas-
ures (chiefly from the Pacific) which this expedition brought home has led to the
discrimination of 20 orders, 85 families, 739 genera, and 4,318 species (4, v) 256).
Further study of the Badiolaria slime of the deep sea will bring to light many new
forms from this inexhaustibly rich mine.
H. Mis. 113 38

594 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

and Phccodaria) move in tlie three loAver zones (vertical distribution,
4, § 232-239). Tlie dependence of their appearance upon the various
conditions of life has been investigated by Brandt (24, p. 102).

D. — ('(ELENTEKATES OF THE Pl.AXKTOX.

The ancestral group of the coelenterates has important significance
and manifold interest for the natural history of the plankton j still
this applies in very varied degrees to the different principal groups of this
numerous circle (comp. 30, p. 522). The great class of the spojiges,
which belongs exclusively to the benthos, has never acquired a ])elagic
habit of life. The phylum of the 2)latodes also needs no further reference
here. We know, to be sure, a small number of pelagic turbellarians
and trematodes. Arnold Lang, in his monograph on the sea-phiuarians
or polyclads (1884, j). G29), mentions as "purely pelagic" or oceanic
8 species and 4 genera [Flanocera, Stylochns, Leptoplana, Planaria).
Parasitic trematodes are occasionally found as "pelagic parasites" in
medusiie, siphonophores, and ctenophores; but these trematodes and
turbellarians are usually found only individually ; they never appear
in such quantities as are characteristic of the majority of the plankton
animals. Much more important for us is the third type of the coelen-
terates, the diversitied chief group of the nettle animals or Cnidaria
(30, p. 524).

Cnidaria. — With reference to the mode of life and the form condi-
tioned thereby, one may divide the whole group of Cnidaria into two
great principal divisions, polyps and acalephs, which since the time of
Cuvier have lain at the foundation of the older systems. The polyps
(in the sense of the older zoiilogists) eral)race all nettle animals, Avhich
are fixed to the bottom of the sea, hydropolyps as well as scyphopolyps
(Anthozoa). They belong exclusively to the benthos. Only a few forms
have acquired the pelagic mode of life {Minyadoe^ Arachanactis, iarvte
of Actinioe, Cerinthidce, and some otlier corals). The second principal
division of the nettle animals, the Acalcpha, embraces, in the sense of
their first investigator Esclischoltz (1829), the three classes of meduste,
siphonophores, and ctenophores; all swimming marine animals, which,
from their richness in forms, their general distribution in the ocean, and
their abundant occurrence, possess much importance for plankton
study. Since the above-mentioned pelagic polyps {Minyadce, etc.) on
the whole are rare, and never appear in great quantities, we need make
no further reference to them here. Much more important are the Aca-
lejyJis, which offer a fund of interesting problems for plankton study.
Commonly, all these animals are roughly termed "pelagic," but a
new consideration shows us that they are so in a very different sense,
and that the distinction which we have made above in reference to their
chorological terminology here finds its complete Justification. We Avill
first consider the medusae, then the siphonophores and ctenophores.

PLANKTONIC STUDIES. 595

Me(Jusa\ — Tlie great interest wliicb I have felt in this wonderful
class of animals sin<'e my first acquaintance with living medusjc, in
1854, and which has been increased by my nunierous sea voyages, led
me to the monographing of them (1879). I immediately gained thereby
a number of definite chorological and (Ecological ideas, which have
been of permanent influence in the further course of my plankton
studies. By it was definitely fixed the knowledge that the wliole race
of the medusie is polijphi/Jctic, and that on the one side the GraHpcdoia
(or Ili/dromedusa') have arisen independently from the Hyclropolyps, just
as (^n the other side the Aeraspedota (or Scypliomcdnsw) from the kSeyplio-
poJyps. In both analogous cases the transition to the pelagic, free-
swimming mode of life has led to the formation, from a. lower, sessile,
very simply organized benthic animal, of a much higher plauktonic meta-
zociu, with differentiated tissues and organs — a fact which is of great
significance for our general understanding of tlie jjliylogeny of tissues.

I have in that monograph broadly distinguished two principal forms
of ontogeny or individual developmental history among the medusae,
metagenesis and hypogenests. Of these I regard metagenesis, the alter-
nation of generations with polyps, as the primary o\ paUngenetlc form;
on the other hand, hypogenesis, the "direct develoiDment " without alter-
nation of generations, as the secondary abbreviated or cenogcneUc form.
This distinction is of great importance in the chorology, in so far as the
great majority of the oceanic medusjc are hypogenetic; the nentic, on the
other hand, are metagenic. To the oceanic medusae in the widest sense
I refer the TracJiylinw {Trachymedusw jyid Narcomedusa') among the
(Jraspedota; to the neritic, the Leptolincc {Anthomedusw and Leptome-
dusev: comp. 29, p. 233). While the former have lost their relation to
the benthonic polyps, the latter have retained it through heredity. The
same seems to obtain also for the majority of the Aeraspedota, namely
the JHseomedusa\ Among these there are only a few oceanic genera
with hypogenesis, e. g., Pelagia. The development of the smaller but
very important acraspedote orders, which I have distinguished as ISfau-
romedusa\ Peromeditsa^, and Cuhomedusw, is, I am sorry to say, as yet
quite unknown. The first is to be regarded as neritic and metagenic;
the two latter, on the other hand, oceanic and hypogenic. That the
majority of the large Disconiedusce are neritic and not oceanic is shown
from their limited local distribution.

Although ten years ago the Medusw were generally held to be purely
pelagic animals, it has now been found that a certain (j^erhaps consid-
erable) part of them are zonary or bathybic. Among the 18 deep-sea
medusce which I have described in part xii of the Challenger Eeport
(1881) there are, however, some forms which occur also at the sur-
face, and a few which perhaps were accidentally taken in the tow net
while drawing it up. But others are certainly true deep-sea dwellers,
as the Pectyllidev among the Oraspedota, the PeriphylUdw and AioUidw

596 REPORT OF COMMISSIONER OF FISK AND FISHERIES.

amongj tbe Acraspedota. Some Meduscc have j^artly or entirely given
up tbe swimming- mode of life, as Polyclonia^ Cephea, aud other Rhiz-
osfo))ia, which lie with the back towards the sea bottom, the iiiany-
mouthed bunch of tentacles directed upwards. The Lucernaridw have
completely passed over to the benthos. Mnny.l/ert^sft' are spauipelagic,
rise to the surface only during a few mouths (for the purpose of reproduc-
tion!), and pass the greater part of the year in the depths; thus in the
Mediterranean the beautiful Cotylorrhiza tuberenlata, Chdryhdea marsu-
pialis, Timajfavilabris, and OUndias miilleri. These bathybic forms are
sometimes brought up in great numbers with the bottom net (19, p. 122).
Many cling with their tentacles to Alr/fc and other objects (20, p. 341).

The immense swarms in which the MednMv sometimes appear, millions
crowded thickly together, are known to all seafaring naturalists.
Tlius in Arctic waters, Codon'mm princcp^^^ Hippocrene superciliaris; in
tlie North Sea, Tiara pilcata, Aglantha digitalis; in the Mediterraiieau,
Liriantha mncronata, Rliopalonema velatum; in the tro^ncs, Cytms
nigritina; in the Antarctic Ocean, Ilippocrene mocloriana and others.
Hensen (9, p. 05) in the North Sea found a swarm of Aglantha^ the
number of which he estimated at twenty-three and one-half billions.
The extent of the multitude was so great that "the thought of approxi-
mately estimating the animals in this swarm must be given r.p." In
such cases the whole sea for a few days, or even weeks, seems every-
where full of Mediisw; and then again weeks, or even months, may jiass
without finding an individual. The uncertainty of appearance, the
" capriciousness of these brilliant beauties," in other words the depend-
ence upon many different, ancl for the most part unknown causes, is in
this interesting animal group remarkably impressed upon us. I will,
therefore, in another place, referto it orithe ground of my own experience.

Siphonophorcs. — What I have said above concerning the unequal dis-
tribution of the medusa? applies also to their wonderful descendants,
the purely oceanic class of the siphonophores. This highly interest-
ing class was, up to a few years ago, also regarded as purely jjelagic;
but of these, too, it is now known that they are in great part bathy-
pelagic, in part also zonary and bathybic. The new and very peculiar
groui^ of the Ai(ronecfa' {Steplialida' and BJuMlalida'), taken by the Chal-
lenger at a depth of 200 to 000 fathoms, is described in my '^ Report of
the Siphonophores of H. M. S. CMllenger'^ (1888, p. 290). The Batky-
phy.sa taken by Studer, and some of the Rliizopliysidw [Auropkysa^ Lino-
pliy^a) captured by the Gazelle, were taken at a dej)th of 000 to 1,000
fathoms (1. c). But that such deep-sea siphonophores (probably mostly
RhizopJiysida') inhabited the ocean in great masses was first shown by
Chierchia (8, p. 84-80). Previously, in numerous soundings which the
Vettor Pisani had made in the Atlantic and Pacific oceans, the line of
the deep-sea lead when drawn up was found to be wound around with
the torn-off stinging tentacles of great sij)honophores. By means of

PLANKTONIC STUDIES. b97

the new elosible net iji vented by Palumbo, be was enabled to bring up the
entire animals from deliiiite deptlis. From these experiments Cbiercliia
concluded ''that certain characteristic si)ecies of siphonophores live in
great numbers at certain depths, from 1,000 meters above the bottom
n]>wards, the strongest and most resistant in the depths, the vreaker
higlier up" (8, p, 80), Other siphonophores, wliich belong to the forms
most numerous at the surface, extend down to considerable depths, as
Diplujes sieholdii (15, p. 12). The larvai of Hippopodius luteus, which
are very numerous in winter and spring, have quite disap])eared iii
summer, and, according to Chun, live in greater deptlis, even to 1 ,200
meters (15, p. 14). Other forms are spanipelagic and come to the sur-
face only for a short time, only a few weeks in the year, like so many
Physonectw. From these and other grounds the participation of the
sijDhonophores in the plankton, like tiiat of their ancestors, the Hydro-
vieduscc, is extremely irregular, and their appearance at the surface of
the sea is subject to the most remarkable changes.

Ctenopliores. — This Cnidarian class also, like the preceding, is purely
oceanic, not neritic. They also show the same phenomena of jielagic
distribution as the i<iplionopliores and 3h'dvsa\ frequent a])pearance in
great swarms, sudden disappearance for long periods, unaccountable
irregularity in their participation in plankton formation. The tables
which Schmidtlein has given on the basis of three years' observa-
tions, on their periodical appearance in the Gulf of Naples, are very
instructive for all three classes of the plankton ic Cnidaria (19, p. 120).
The ctenophores also, up to a short time ago, were regarded as auto-
pelagic animals; but of them also it has been discovered that they
extend in abundance to various, somewhat definite depths. Chun, in
his monograph of the ctenophores of Naples (1880, p. 236-238) has
pointed out that these most tender of all pelagic animals have just as
definite vertical as horizontal migrations. Many ctenoi}hores, which
in the spring are found as larvse at the surface, later sink, pass the
summer in the cjooler depths, and rise to the surface in the autumn in
crowds, as mature animals. The irregularity of their api)earauce is also
mentioned by Graeffe (20, j). 361).

E. — Helminths of the Plankton.

The race of the helminths or "worms" (the cross of suffering for sys-
tematic zoology) obtains a more natural unity and more logical defini-
tion, if one removes therefrom the platodes and annelids, placing the
former with the coeleuterates, the latter with the articulates. The jus-
tice of this limitation and also the grounds for regarding the worms as
the common ancestral group of the higlier animals, I have set forth
already in the "Gastrea Theory" (1873), and many times at later op-
portunities, last in the eighth edition of my "Natural History of Crea-
tion" (1889, ]). 510). Tliere remain then as helminths, in the narrower
sense, four divisions with about 12 classes, namely, (1) the Rotatoriw

598 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

{Trochospharn, lehthydina, Rotifera) ; (2) the ^Strongt/ktriw {Kenuttoda,
Acanthocrpltala, Chwtognatha); (3) tlie Rhynvhocala {JVcmertina, En-
ter opneusta), and (4) the Prosopygkv {Bryozoa, BracMopoda, Phoronea\
Sijmnculea'). The larviB of iiiaiiy of tliese worms liave acquired the
pehigic mode of life, but most of them are too small aud too scattered
in the plauktou to be of any considerable imi)ortance in its composition.
Chcctoynatha. — In its mature condition only a single class of hel-
minths plays an independent and indeed an important role in the plank-
ton — the small and peculiar class of arrow-worms or CJuctognatka
{Sagitta, Spadella, etc.). These, together with the copepods, salpae,
pteropods, and radiolarians belong to tlie most substantial, most gen-
erally distributed, and usually unfailing constituents of the plankton.
Hensen (9, p. 59) has made some calculations of the immense numbers
in which they ap})ear. He reckons them in the '^ perennial plankton,"
yet does not find " everywhere the regularity which one might expect."
He is astonished at the " highly remarkable variations" in their num-
bers, and finds this very unequal distribution very puzzling (9, p. 60).
Chun has lately shown that the troops of ^Sagitta not only populate the
surface of the sea, but also "in common with the liadiolaria, Tomop-
teridce, Diphyidcv, Crustacea, constitute the most numerous and most
constant inhabitants of the greater depths. In countless multitudes
they are taken in the open as well as in the closible net, from 100
meters down to 1,300 meters " (15, j). 17). It seems that Sagitta, as a
whole purely oceanic, is represen.ted by pelagic as well as zonary and
bathybic species.

F. — MOLLUSKS OP THE Pl.ANKTON.

The race of mollusks play a very important role in the plankton.
Although the great majority of the genera and species belong to the
benthos, yet there are a few families which have become adapted to the
pelagic mode of life, of great importance on account of the great
swarms in which they often appear. The three chief classes which we
distinguish in this race (30, p. r)4:()) live very differently. The Acepliala,
entirely benthonic, can take part only as swarming larva? in the com-
position of the plankton; so also the swimming larva? of many mero-
planktonic Gastropoda. Of these latter only a very few genera have
adopted completely the pelagic mode of life, like lanthina among the
prosobranchs, GJavcns and PhyUirrlm among the opisthobranchs.

Pteropods and Heterojmls.— These two grou])s of snails are holoplank-
tonic, chielly nyctipelagic animals, which come to the surface of the sea,
preferably during the night, in vast numbers (14, pp. 121-125). Chun
has lately discovered that many of them are found at considerable
depths (15, p. 3G). Some kinds of pteropods {e. g., Spirialis) seem to
belong to the zonary and bathybic fauna. The heteropods are on the
whole of less importance. They occur in great swarms less frequently
and only in certain parts of the warmer seas. The pteropods on the

PLANKTONIC STUDIES. 599

other hand surpass the former, not only by a great diversity of genera
and species, but particularly from their enormous development in all
parts of the ocean. Clio and Limacina are known to occur in the
Arctic and Antarctic ocean in schools so vast as to form the chief food
supply of the whales; the swarms of Creseis, Hyalea, and others which
appear in the seas of the warmer a? id temperate zones, are also so con-
siderable that these fluttering "sea butterflies {Farfalle di marey often
play a very important part in the "cycle of matter in the sea" [StoffwecJisel
des Meeres^^). The irregularity of the distribution and phenomena
is also shown by the fact that Hensen, during his plankton expedition
through the iSTorth Sea (July and August, 1887), completely missed the
pteropods (9, p. 50; 10, p. 110). On the other hand, when in August,
1879, I fished at Scoury, on the northwest coast of Scotland, we found
such immense quantities of Limacina (during the forenoon in still
w^eatlier) that these pteropods certainly formed more than nine-tenths
of the entire lilankton, and with a bucket we could scoop up many
thousands. The mass of the swarm had the same density for a deptli of
two fathoms and for more than a square kilometer in horizontal extent.
Cephidopods. — Although entirely swimming animals, these highly
developed mollusks for the most part do not fall under the term plankton,
if with Hensen we limit this to those "animals floating involuntarily
in the sea" (9, p. 1). They must then be included in the "uekton;"
but naturally it depends in some cases entirely on the strength of the
current whether the small cephalopods should be included in the
former or in the latter. In any case this highest developed class of
mollusks is of very great importance in the i)hysiology of the plankton,
the question of the " cycle of matter in the sea." On the one hand
they daily consume vast masses of pteropods, Crustacea, sagitta, medu-
sa?, and other planktonic animals; on the other, they furnish the most
important food for fishes and cetaceans. From recent investigations
it is found that the cephalopods are j)artly pelagic, jiartly zonary or
bathybic {Spirilla, ¥autilus, etc.). Characteristic small, transparent
Deeolenie {LoUgopsidtc) are known as partly pelagic, partly bathybic
species (15, p. 36). The same is true also of some Octolenw {Philonexidw).
Young forms of cephalopods are captured swimming in the plankton at
the surface as well as in the depths.

G. — ECIIIXODEKMS OF THE PLANKTON.

The rayed animals in their significance in the plankton, as also in
many other morphological and physiological relations, show highly
peculiar and varied conditions. Although all echinoderms are without
exception i)urely marine animals, and no single form of this great
group inhabits fresh water, still not a single species has completely
adopted the planktonic life. Not a single echinoderm in its full-grown
and sexually mature condition can be called pelagic. The few forms
\y^hich temporarily swim about {Comatalida;} belong only to the neritic

600 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

fauiui and do uot occur in the ocean. They also are found in such
limited numbers that they are without importance for the plankton.

Much more important for us are the free-swimming echinoderm larvas,
which often ijlay a great part in the neritic plankton. Indeed they are
classical objects in the history of plankton investigation; for to their
study their disco v^erer, Johannes Miiller, forty-five years ago first ap-
plied the method of "pelagic fishery with the fine net," which soon led
to such remarkable and brilliant results. The distribution and number
of the larval rayed animals is naturally dependent upon that of their
benthonic parents; but in addition also partly upon chorological, partly
oecological causes. According to Sir Wyville Thompson (14, ii, pp.
217-245; G, p. ,379), the remarkable metamorphosis, discovered and de-
scribed in a masterly way by Miiller, is the rule only among the littoral
forms, chiefly in the temperate and warm zones; on the other hand, it
is the exception in the case of the majority, for star animals of the
deep sea and cold zones, in the Arctic as well as in the Antarctic,
develop directly. Therefore, great troops of pelagic larvaj of these
animals occur commonly oidy in the neritic jjlanlton of the temperate
and warm zones, uot in the open ocean. They seem to visit the depths
(below 100 meters) very seldom (15,. p. 17). Besides, their appearance
is naturally connected with the time of year of this development; often
oidy during a few months (9, p. 02). The variation in the constitution
of the "periodic plankton" is here very remarkable.

H. — Articulates of the Plankton.

Of the three chief divisions which we distinguish in the group of
articulated animals (30, p. 570) two, the Annelids, and Traeheates, take
no part in the constitution of the plankton. Both are represented only
by a few pelagic genera, and these have a limited distribution. Much
greater in importance is the third chief division, the Crustacea. It is
the only animal class which is never lacking in the tow-net collections
(or only very exceptionally), and which commonly appears in such
numbers that their predominant position in the animal world of the
sea is evident at the first glance. This applies as well to the oceanic
as to the neritic fauna, to the littoral as to the abyssal benthos.

Annelids.— Tha great mass of this group, so rich in forms, belongs to
the benthos, and is represented in the abyssal as well as in the litt(u-al
fauna by numerous creeping and sessile forms. Only very few ringed
animals have acquired the pelagic mode of life and have assumed the
characteristic hyaline condition of the oceanic glasslike animals, the
swimming Tomopteridcc and Alciopidw. Both families are represented
in the plankton only by a few genera and species, and as a rule their
'uimber of individuals is uot very considerable. Chun has lately
shown by means of the closible net that both forms, Tomopteris as well as
Alciopc, are rei)resented in the different depths, from 500 to 1,300 meters,
by peculiar zonary and bathybic species, which are distinguishable

PLANKTONIC STUDIES. 601

from the pelagic species of the surface by cliaracteristic marks. "The
wealth iu such Alciopidw (and Tomopteridce) at all depths of 100 meters
or over is very surprising, and it requires a caveful scrutiny, for the beau-
tiful trauspareut worms ofteu press actively by dozens in serpentine
course through the crowd of other forms in the dishes'' (15, p. 24).

Crustdcea. — In their general <Pcoh)gical importance, in their uni-
versal distribution over all parts of the ocean, and especially in their
incomprehensible fertility and the abundance of their appearance con-
ditioned thereby, the Gnistacea surjDass all other classes of animals. In
the physiology of the plankton the first rank in the animal kingdom be-
longs to them, as to diatoms in the vegetable kingdom. On the whole,
in the organic life of the ocean they have the same predominant impor-
tance as the insects for the fauna and flora of the land. In a similar
way, as the complicated "struggle for existence" has called up for the
latter a quantity of remarkable (ecological relations and morphological
differences conditioned thereby within the insect class, so lias the same
occurred in the ocean within the crustacean class. Meanwhile the
numerous orders and families of this class, so rich in forms, partici[»ate
in very different degrees in the constitution of the plankton. The order
of copepods by far surpasses all other orders. ISText to these follow the
ostracods and schizopods, then the phyllopods, amjdiipods and deca-
pods. The other orders of crustaceans participate in the constitution
of the plankton in a much less degree — part of them very little. It is
to be added that larvic of all orders may appear in great numbers
therein. Thus, for example, the pelagic larvje of the sessile benthonic
cirripeds often appear in the neritic plankton so numerously that they
constitute four-fifths to nine-tenths or even more of the entire mass.

The chorology of the Crustacea offers to the i)lankton investigator one
of the most important and interesting fields of work, the elaboration of
which has yet scarcely been begun. The same applies also to the geog-
raphy and topography of the oceanic and neritic Crustacea,, both in
their horizontal and vertical distribution, to their relations to the ben
thonic Crustacea as well as to the marine fauna and flora in general.
As a very important result of the recent discoveries, particularly of the
Challengerj the fact must here as elsewhere be brought up that in the
different groups of Crustacea (just as in the Eadiolaria) the vertical
divisions of the planMonic fauna can be very plainly distinguished.
Pelagic, zonary, and bathybic forms are found here in quite definite
relations.

Copepoda. — As the Crustacea are on the whole the most important and
influential among the planktonic animals in their cecological relations,
so are the copepods among the Crustacea. Only one who has seen with
his own eyes can gain a conception of the innumerable masses in which
these small crustaceans crowd the surface of the ocean as well as the
zones of different depths. For days the sliip may sail through wide
stretches of ocean whose surface always remains covered with the same

602 REPORT OF COMMISSIONER OF FISII AND FISHERIEB.

yellowish or reddish "animal uiiish/' composed in by far the greater
part of copepods. In the journal which I kept in the winter of 1S0G-G7,
at Lanzarote, in the Canary Islands, of the varying constitution of the
plankton, for many days there is only the remark : " almost pure buck-
ets of copepods," or " the collection consisted almost entirely of Crus-
tacea, by far the greater part of copei)ods." That these small crus-
taceans form the chief food suj^ply for many of the most important
food-fishes {e. g., the herring) has long been known. In the Arctic as well
as the Antarctic Ocean Calanus finniarcMvus and a few related species
form in general the chief bulk of the plankton, and furnish food for
pteropods and cephalopods, for the divers and penguins, for many fishes
and whales. On the voyage from Japan to Honolulu the ChaUemjer
sailed through wide stretches of the :N"orth Pacific Ocean which were
covered with red and white patches, caused by great accumulations of
two species of small copepods, the red being Calanus propinquus (8, p.
758). In many other regions, from the Polar Circle to the Equator, the
ship passed through white bauds many miles wide, composed solely
of copepods (8, p. 843). That their appearance is very irregular and
dependent on many conditions is true of this very important group
of plankton animals as for all others. For two days the Challenger went
through thick shoals of Corycaeus pellucidus. For the next three days
the copepods had entirely disappeared.

Hensen has made statistical statements upon the appearance of the
copepods of the Xorth and Baltic seas (9, p. 45). Chun has lately showu
that this order plays a highly significant role, not only at the surface,
but also at considerable depth? (000 to 1,300 meters), (15, p. 25). " Their
abundance and richness in forms in greater depths is absolutely aston-
ishing. Larval forms of species sessile or living upon the bottom min-
gle in confusion with the young forms and sexually mature stages of
enpelagic species. Many species hitherto regarded as varieties are
numerously represented in the depths." On the other hand, the order
seems to be very poorly represented at very great depths. The Chal-
lenger found only one very characteristic deep-sea species in 2,200
H'diliom^—PontostratioUles ahyssicolla .{S, p. 845). Some genera never
leave the surface and are autopelagic, e.g., Pontellina (15, p. 27).

Ostr acod a. —ThQ ostracods are, next to the copepods, the most impor-
tant Crustacea of the plankton, and are represented at the surface as
well as in ditterent depths by masses of many species. In the (ecology
of the ocean they play a similar role, as do the near-related cladocerans
{I)aj)hni(hv) in the fresh water. The Challenger collected 221 species of
ostracods. Of these 52 were found below 500 fathoms, 19 below 1,5(>0,
and 8 below 2,000 fathoms in depth. Many ostracods, like many cope-
pods and other crustaceans, belong to the most important luminous
animals of the ocean. On my journey to Ceylon (in the beginning of
November, 1881), as well as on the return trip (middle of March, 1882),
I admired as never l)ef()re the oceanic light in its splendor. "The whole
ocean, so far as the eye could reach, was a continuous shimmering sea

PLANKTONIC STUDIES. 603

of light.'' Microscopical investigation of tho water showed that the
luminous animals were for the most part small Crustacea {Ostracoda),
to a less extent Medusa', Salpw, worms," etc. (25, pp. 42, 372). Chierchia,
three years later, in the same region and in the same mouth, saw the
same brilliant pheuomeuou: "The most brilliant emerald-green light
was produced by an infinitude of ostracods*' (S, p, 108).

Schizopoda. — Not less important in the planktonic life than the ostra-
cods (sometimes even more important) are the schizopods. They also
occur in wide stretches in immense swarms at the surface, as well as
in greater and lesser depths. They also play a great role in the cycle of
matter in the sea {Stoffa^echsel des Meeres); on the one side since tiiey
devour great quantities of i^rotozoa and i)lanktonic larv;e, and on the
other because they serve as food for the cephalopods and fishes. Many
schizopods, like many ostracods and copepods, belong to the most bril-
liantly luminous animals, and, like the latter, furnish very interesting
problems for the bathygraphy of the plankton. G. O. Sars, w^ho has
worked up the rich material collected by the (Jhallen(/er, di.stinguished 57
species, and found that 32 of these lived only at the surface, G from 32 to
300 fathoms, and 4 extended down below 2,000 fathoms (as far as 2,740
fathoms), (G, p. 730), Chnn also has discovered in the Mediterranean a
number of new zonary and bathybic schizopods very different from the
pelagic varieties of the surface, Sfylochiron, A rachHomysis, etc. (15, p. 30).

The phyllopods {Daphnida'), the amphipods {Phronimidw, Hyperi-
dw), and the decapods {Miersida', Sergestidw) are indeed represented
in the plankton by a number of interesting forms, partly oceanic,
l^artly neritic; and some of these occasionally appear in considerable
quantities. But as a whole they are of fjir less importance than the
copepods, ostracods, and schizopods. The same applies also to the
other groups of Crustacea, although many of them in their larval state
take a great part in the constitution of the plankton. Also in regard
to these multiformed and often nhujidaiit jjelagic crustacean larva', us
well as for the mature crustacean animals, the advancing plankton
study has still to establish and explain a fund of facts; namely, in
relation to their pelagic, zonary, and bathybic distribution; their migra-
tions, and the relations in which this planktonic fauna stands to the
benthic fauna.

Iiisecta. — That im^jortant branch the Tracheata, the most numerous
in forms of all the principal divisions of the animal kingdom, has in the
sea no representatives whatever. The Protracheata, Myriapoda, and
Arachnidf ai-e exclusively inhabitants of the land and in small part of
the fresh water, except the pycnogonids or pantopods (in case these
really belong to the Arachnida'). Among the Tnsecfa there is only a
single small group of true marine animals, tho family of the Halobatida'.
These small insects, belonging to the Hemiptera, have completely ac-
(piired a ])elagic mode of life, and run about in the tropical ocean just
as our "water-runner" (Hydrometra) on the surface of fresh water.

604 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

Botli of the genera beloDging tliei-e {Ilalohates and Htdohdtodcs, witli
about a clozea species) are limited to the tropical aud subtropical zoue.
The Challenger fouud them iu the Atlantic between 35'^ north latitude
aud 20^ south latitvule; iu the Pacific between 37'^ north latitude aud
23° south latitude. I myself observed Halobates numerously in the
Indian Ocean, and on one day iu crowds in the neighborhood of Belli-
gam. Although they can dive, they never go into the depths.

J. TUXICATKS OF THK PLAXKTOX.

The tribe of mantle animals falls into two chief divisions, according
to their mode of life. The ascidlans belong to the heuthos; all other
tunieates to the plankton. Tlie (Jopelata (or Appendicular l(la')'dve mor-
phologically the oldest branch of the stem, and are to be regarded as
the nearest of the now living relatives of the FrocJiordiniw, the hyr»o-
thetical common ancestor of the tunieates and vertebrates (30, p. ()0."i).
The near relationshi]) of the Gopelata and the ascidiau larva makes it
very probable that the whole class of ascidians has sprung from the
primarily i>elagic (Jopelata^ and has diverged from this through the
acquirement of a sessile mode of life. The Liicidue or Pyrosomidce, on
the other hand, are probably secondarily j)elagic animals, and sprang
from the (Jwlocorniida', a benthouic synascidiau g'roup. The Thalidke
(the DolioUdic as well as the Salpid(v) are to be regarded as primarily
pelagic animals. These conditions are doubly interesting, because the
tunieates in an exemplary manner demonstrate the peculiarities which
the transition on one side to a sessile mode of life iu the benthos (in
case of the ascidians), and on the other to a free-swimming mode of
life in the plankton (in the case of all other tunieates), has bronght
about. All the latter are trans[)arent and luminous fragile animals,
poor iu genera and species, bat rich in numbers of individuals. The
ascidians, on the other hand, fastened to the bottom, in part littoral on
the coast, in part abyssal in the deep sea, are much richer in genera
aud si^ecies, iu many ways adapted to the nmnifold local conditions of
the bottom, and mostly opaque. The few hyaline forms {e. <j., ClavelUna)
may be regarded as the remnant of the old ascidian branch, which
diverged from the pelagic Copelata.

All planktonic tunieates are exquisite oceanic animals and all may
appear in immense swarms of astonishing extent. Murray (G, ])p. 170,
521, 738, etc.) and Chierchia (S, pp. 32, 53, 75, etc.) met with great
swarms of Appendicularia, Pyrosoma, Doliolum, and Salpa in the middle
of the open ocean, both iu the Atlautic and Pacific, i^articularly in the
equatorial zone. I observed the same in the Indian Ocean, between
Ceylim and Aden. Further, I have whole bottles full of closely i)ressed
Thalidia',^y\u(i\l Captain lialibe collected in the middle of the Atlantic,
Pacific, and Indian oceans, far removed from all coasts. In many log
books also these swimming and luminous crowds of iSalpa and Fyro-
soma on the open sea, far from all coasts, are spoken of. On the other

PLANKTONIC STUDIES. 605-

liaiid we know of no neritic tunicates, no other forms of swimming
mantled animals which are found only on the coasts, except the omni-
present ascidian larva.

Lately Chun has established the interesting fact tliat the planktonic
tunicates occur in luimbers not only at the surface and in slight depths,
but also during the summer extend down into greater depths (15, pp.
32, 42). He discovered further in the iMediterrauean new CopeJata,
wl'iich are only /onary or bathybic, never coming to the surface and
characterized by peculiar organization as well as difference in size
[Megalocerens abyssorim, 3 centimeters long, 15, p. 40).

The small, delicate Copelata and Dolioln, from their small size, are
naturally more difficult to see than the large luminous 8alp(c and
Pijrosoma. Whoever lias carefully examined great quantities of oceanic
plankton can readily testify that the former also occur almost every-
where and occasionally take an important part in the constitution of
the mixed plankton. Among the Salpcc there are for example the
smaller species which form extensive swimming shoals. From the
three-year observations of Schmidtlein it is learned tliat the »aipas
belong to the perennial plankton and are numerous throughout the
wholeyear (19, p. 123).

K.— Vertehhates of the Plankton.

The vertebrates of the sea are in their mature condition for the most
part too large and have too powerful voluntary movements to be
reckoned in the true plankton in Hensen's sense, as "animals carried
involuntarily with the water." The sea fishes, as well as the aquatic
birds and mammals of the sea, overcome more or less easi-ly the impetus
of the currents, and thereby prove their independence by voluntary
movements, which is not commonly the case with the floating inver-
tebrate animals of the plankton. Meanwhile I have already shown
above that this limitation of the i)/fmA-fo/i against the neJdon is very
arbitrary and at any moment may be changed in fiivor of the latter
through diminution of the strength of the current. For the chief point
of Hensen's plankton investigation, for the question of the "cycle of
matter in the sea," the vertebrates are of greatest importance, since
they, the largest of the rapacious animals of the sea, daily consume the
greatest quantity of plankton, no matter whether directly or indirectly.
A single sea fish of medium size may daily consume hundreds of
pteropods and thousands of Crustacea, and in case of the giant cetaceans
this (pnintity may be increased ten or a hundred fold. In a compre-
hensive consideration of the plankton conditions, and particularly in
its physiological, ecological, and chorologieal discussion, a thorough
investigation of the vertebrates swimming in the sea, the marine fishes,
the aquatic birds, seals, and cetaceans, is not to be undertaken. We
can then turn from it here, since it has no further relation to the pur-
pose of this plankton study. We can here in Hensen's sense (9, p. 1)

606 REPORT OF COMMISSIONER OF FI^^H AND FISHERIES.

provisionally limit ourselves to the vertebrates of the sea "carried
involuntarily witli the water," and as such (apart from a few small
pelnjiic fishes) only the pelagic eggs, young brood, and larvte of the
marine fishes come into consideration. Some few teleosts {Scojyelidce
Trichiuridw, ct aJ.) occur sometimes in schools in the plankton and
are partly autopelagic, partly bathypelagic. The remarkable Lejyto-
cephaUchv are possibly planktonic larviie (of J\Inr(vnoid(v), which never
become sexually mature (7, p. 502).

Fish cf/f/.s. — The planktonic fish eggs, found in great numbers at the
surface of the sea, as well as the young fish escaped from them, play
without doubt a great role in the natural history of the sea. Hensen,
whose planktonic investigation started from this point, had thereupon
"based the hope to obtain a far more definite conclusion upon the supply
of certain species of fishes than had hitherto seemed to be possible" (9
p. 39). But the assumption from which he starts is wholly untenable.
Hensen says {loc. eit.):

It i8 scarcely to be doubted that an opinion upon the relative wealth of various

kinds of fish in the Baltic or in any other part of theocean whatever can be obtained

through the determination of the quantity of eggs in the area under consideration.

Brandt also characterizes this proposition as very lucid and weighty

(23, p. 517).

This standard proposition of Hensen and Brandt, from which a series
of very important and complicated computations are to be made, was
disposed of in a brilliant manner thirty years ago by Charles Darwin.
In the third chapter of his epoch-making "Origin of Species," treating
of the "Struggle for Existence," Darwin, under the head of Malthus'
theory of population, speaks of the conditions and results of individual
increase, the geometric relation of their increase, and the nature of the
hindrances to increase. He points out that "«? aU cases the average
number of individuals of any species of plant or animal depends only
indirectly on the number of seeds or eggs, but directly on the conditions
of existence under which they develop." Striking examples of these
facts are every Avhere at hand, and I myself have mentioned a number of
them in my "Natural History of Creation" (30, j). 143). Still, to draw
a few examples from the life of the plankton, I recall in this connection
many pelagic animals ; c. g., Crustacea and medusae. Many small medu-
sae, which belong to the most numerous animals of the pelagic fauna
{e. g., Obelia and Lirope) produce relatively few eggsj as also copepods,
the conmionest of all planktonic animals. Incomparably greater is the
number of eggs produced by a single large medusa or decapod, which
belongs to the rarer species. So, from the number of i)elagic fish eggs
not the slif/htest eonelusion can be drawn as to the number of fish which
develop from them and reach maturity. The major portion of the
planktonic fish eggs and young are early consumed as food by other
animals.

PLANKTO:VIC STUDIES, 607

v.— COMPOSITION OF THE PLANKTON.

The composition of the planlcton is in quccUtative as well as quantitative
relations very irregular, and the distribution of the same in place and
time in. the ocean also very unequal. These two axioms ap^ily to the
oceanic as well as to the neritic plankton. In both these important
axioms, which in my opinion must form the starting-point anil the
foundation for the cecology and chorology of the plankton , are embodied
the concordant fundamental conceptions of all those naturalists who
have hitherto studied carefully for a long time the natural history of
the pelagic fauna and flora.

The surprise was general when Prof. Ilensen this year advanced an
entirely oi>posite oj)inion, " that in the ocean the plankton was dis-
tributed so equally that from a few hauls a correct estimate could be
made of the condition in a very much greater area of the sea" (22, p.
243). He says himself that the plankton exi)edition of Kiel, directed
by him, started on this '■'• purely theoretical view^'' and that it had '-'■full
results because this hypothesis was proven far more completely than
could have been hoped" (22, p. 24t).*

These highly remarkable opinions of Hensen, contradictory to all
previous conceptions, demand the most thorough investigation; for if
they are true, tlien all naturalists who many years previously, and in
the most extensive compass, have studied the composition and distri-
bution of the plankton are completely in error and have arrived at
entirely false cx)nclusions. If, on the other hand, these propositions of
Plensen are false, then his entire plankton theory based thereon falls,
and all his painstaking computations (on which in the last six years he
has spent 17,000 hours, which he wishes to have number the individ-
uals distributed in the plaidvton) are utterly worthless.

In the first place, the empirical basis upon which Hensen founded his
assumptions must be proved, " starting from a purely theoretical point
of view. " The plankton expedition of Kiel was 9.'> days at sea, and in
the months of late summer (July 15 to November 7) which, as is known,
offer m the northern hemisphere the most unfavorable time of all for
pelagic fishery (28, p. 1(3, 18). Hensen himself says that it bore the
"character of a trial trip" (22, p. 10), and his companion Brandt names
it a "reconnaissance " upon which they had come to investigate rapidly

■^ Heusen speaks of this in the following terms: "Hitherto it was the prevailing
A'iew that the inhabitants of the sea were distributed in schools, and that one, ac-
cordiug to luck and chance, according to wind, current, and season,' sometimes came
upon thick masses, sometimes upon uninhabited parts. Tliis in fact applies only in
a certain degree ior the harbors. For the open sea our knowledge teaches that nor-
mally regular distribution obtainstliere, which changes in thickness and ingredients
only withiu wide zones corresponding to the climatic conditions. I7i any case one
must seek the variation from su<;h condition according to the cause which has pro-
duced it, aud the occurrence of iueiinality is not to be taken as the given starting-
point for relative investigation" (22, p. 244).

608 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

in succession as great areas as possible" (23, p. 525). In a more
remarkable way lie adds: "Thereby has resulted the furnisliing of a
fixed basis for a thorough quantitative and qualitative analysis of
marine organisms." According to my view such "fixed basis" was
obtained long ago, particularly by the widely extended investigations
of the Challenger expedition (from January, 1873, to May, 1876), fitted
out with all appliances. This embraced a period of forty months, and
included " the whole expanse of the ocean." Their experience ought
to lay claim to much greater value than that of .the Ifat ion al, whose
voyage of three months took in only a part of the Atlantic, and was in
addition trammeled by bad weather, accidents to the ship, early loss of
the large vertical nets, and other misfortunes in the carrying out of their
plans. It is hardly conceivable how an "exact investigator," from so
incomplete and fragmentary experience, can derive the "fixed basis"
for new and far-reachiug views, which stand in remarkable contradic-
tion to all previous experience.

It would here lead too ftir, if, from the numerous old and new narra-
tives of voyages, I should collect the observations of seafarers ui)on
the remarkable inequality of the sea population, the different fauna and
flora of the regions of currents, the alternation of immense swimming
swarms of animals and almost uninhabited areas of sea. It is sufficient
to ])<)int out the two works in which the most extensive and thovougli
knowledge up to this time is collected, the " iTarrative of the Cruise of
H. M. S. Challenger,^'' edited by John Murray (6), and the " Collezioni
della E. Corvetta Vetfor PisanP'' (8), published by Chierchia. Since the
general chorological and cecological results in these two principal works
agree fully with my own views gained from thirty years' experience, I
pass immediately to a general exi)osition of these latter, reserving their
proof for a later special work.

A. — POLYMIXIC AND MoNOTONIC PLANKTON.

The constitution of the planMon of swimming plants and animals of
different classes is exceedingly manifold. In this regard I distinguish
first two principal forms, polymixic and monotonic plankton.*

The "mixed tow-stuff (J. w/ifr/ei), or the polymijcic planJdon,''^ is com-
posed of organisms of different species and classes in such a way that
no one form or group of forms comi^oses more than the one-half of the
whole volume. The ^'■simple tow-stuff", on the other hand, or the monotonic
planlton,''^ shows a very homogeneous composition, while a single group
of organisms, a single species or a single genus, or even a single family
or order, forms very predominantly the chief mass of the cai)ture, at
least the greater part of the entire volume of the plankton, often two-
thirds or three-iburths of it, sometimes even more. Under this mon-
otonic plankton one may again distinguish prevalent planlcton, when
the predominant group forms up to three-fourths of the total volume,

* n.o?ivniKToc = mucli mixed, complex; uovurovog = of a single form, simple.

PLANKTONIC STUDIES. 609

and uniform planUon when this exceeds three-fourths and forms ahnost
the whole mass.

In general the mixed plankton is more abundant than the simple,
since as. a rule the circumstances of the "strug-o-le for existence" condi-
tion and vary in many ways the constitution of the planktonic flora and
fauna. Still there are numerous exceptions to this rule, and at many
points in the ocean (especially in the zoocurrents) there occurs locally
a development so numerous, and an accumulation of a single form or
group of forms in such swarms, that these in the haul of the pelagic net
form more than one-half the entire volume. This monotonk' planldon
appears in very different definite forms; for the difterence of climate,
the season, the oceanic currents, the neritic relation, etc., determine
significant differences in the quantitative development of the plankton
organisms, which simultaneously appear in vast numbers in a definite
region. I will next briefly go over the single forms of the monotonic
l^lankton known to me, passing over, however, the consideration of the
extremely manifold composition of the pohjmixic planlcfon, since I am
reserving that as well as a contribution of a number of mixture-tables
for a later work.

1. Monotonic rrotoplnjtic PlanMon.—Oi the seven groups of pelagic
Protophytcs, at least three, the Diatomic, Miwracytes, and Peridinew,
appear in such quantities in the ocean that they alone may constitute
the larger part of the collection of the pelagic nets. The most impor-
tant and most common is the monotonic diatom-planMon, particularly in
brackishand coast waters. Tlie siliceous-shelled unicellular Profophi/fcs
which compose this belong, often predominantly or almost entirely, to
a single species or genus, as Syncdrc in the colder, Chwtoceros in tlie
warmer seas. The colossal masses of Arctic and Antarctic diatoms,
which form the "black- water," the feeding-ground of whales, have been
mentioned above. In the warmer tropical and subtropical parts of
the ocean such accumulations of diatoms seldom or never occur. Here
their place is taken by the monotonio murraciite-planUon, composed of
immense swarms of nyctipelagic Pyrocystidw. Less frequent is the
monotonic pcridinexv-pJanUon. Although these THnofiageJlaia take a
very significant part in the composition, especially of the neritic plank-
ton, yet they do not often occur in such quantities as to form the
greater part of the volume of the capture.

2. Monotonic Mefaphytic-Planlcton.— Among the pelagic Metaphytes
there are only two tbrms, the Oscillatoriw and the Saroassew, which
appear so numerously that they form the greater part of the pelagic
t<jwstuff. The monotonic osciUatonw-planlcton, as a rule formed of
swimming bundles of fibers of a single species of TricJiodesmium, ap-
pears in many regions of the tropical ocean in such masses that the
quantity of the pelagic fauna is diminished on that account. The
monotonic saygassnm-planlcton, formed of "swimming banks" of a single
fucoid, Saryassum baecifernm, is the characteristic massive form of
organic life in the Halistasa of the " Sargasso Sea."
H. Mis. 113 39

610 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

3. Monotonic Protozoic-Flanldon. — Among the miicelliilar Protozoa^
three different groups, the Woctilaca, (Mohigerina, and Eadiolaria, ap-
pear pehigically in such quantities that they form the greater part of
the volume of the plankton. The monotonic noctiluca-planMon is neritic,
and is com])Osed almost exclusively of milliards of the common Nocti-
luca miliaris. It forms the reddish-yellow covering of slime upon the
surface of the coast seas, and in the ocean always points out the litto-
ral currents. On the other hand, the widely distributed monotonic ylo-
Mgerina-planlton is purely oceanic, the point of origin o^ theglobigcrina
ooze of the deep sea. In different regions of the ocean it is composed
of different genera of the above-mentioned pelagic thalamophores.
Much more manifold is the monotonic radiolaria-planMon, also oceanic.
Of these, one can distinguish the three following modifications:*

(1) rolyci/ttnn'a-PlanlctoH, sometimes composed only of Collozoum^
sometimes of Sphwrozoum, sometimes of Collospluvra, most often of a
mixture of these three forms ; in the warmer seas, partly pelagic, partly
zonary; very abuiulant.

(2) Acantharia-PlanMon, commonly formed of milliards of a single or
of a few species of Acanthonietron (iu the colder seas, e. g., on the east
and west coast of South America, south of 4:0^ S. lat. ; also north of
50^ K. lat. on the coast of Shetland, Faroe-Orkney, and jSTorway) ; partly
autopelagic, partly bathypelagic.

(3) Phwodaria-Planldon, zonary and bathybic, mostly composed of the
larger species of Anlosphwridcv and Sagosphwrida', GoeJodendridcv and
CoelograpJiidcr {e. g., Goeloplcgina murndjanum from the Faroe-Orkney
Channel, 4, p. 1757).

4. Monotonic Gnidaria-PlanMon. — In the group of nettle animals
there are numerous forms of medusas siphonophores, ami ctenophores,
which appear in immense schools. The monotone medusa-planlcton is
chiefly neritic, composed of very different local forms on the different
coasts. Of the larger Acraspcdota, in the warmer seas Rhizostoma (Pil-
emidw, Cranihessidw) particularly occur; iu tlie colder, Seniostoma
{AnreUdcc, Cyanida'), which in schools fill the littoral bays and cur-
rents. Of the oceanic Scgphomednscc, Pelagia seems to form similar
schools. Among the Graspedota., monotonic medusa-plankton is espe-
cially formed of neritic Gordonidiv, Jirargelidcc, and Uucopida', of oceanic
u^qnoridce, Liriojridw, and Trachyncmidw. Monotonic siplionopliora-
planldon occurs only in the warmer seas, although Dipliyidea are found
abundantly in all parts of the ocean. The remarkable blue troops of
the pelagic PhysaUdw, Porpididw, and Velellidxv have for a long time

*Radiolariaii-plankton is contained in 13 preparations of the Radiolaria collection,
whicli I have collected (1890) and which can he bought through the famulus Franz
Pohle at Jena; 8 of these preparations contain polycyttaria-plankton, 2 acantharia-
plankton, and 3 plncdodarin-phiuktou. This collection (of 34 microscopical prepa-
rations) cnibraces in addition 17 preparations of the radiolarian-ooze of the deep sea,
and 1 preparations of dee]> sea horny-sponges, whose pseudo-skeleton is composed
of radioiariau slime. (Challenger Report, part Lxxxii.)

PLANKTONIC STUDIES. 611

ill the tropical and subtropical seas attracted the attention of seafarers
I)y their immense numbers as well as by the irregularity of their sudden
appearance and disappearance. Earer is a purely 'physonectic plank-
ton chiefly composed of ForsMUa; I have observed such repeatedly at
Lanzarote. At that same place also occurred frequently a monotonic
cteno2>hora-pl(inkton. These delicate nettle animals also, as is well
known, like the Medusre and Siphonophores, appear in such closely
packed crowds that there is scarcely room between tliem for other
pelagic animals. Not infrequently the great accumulation of a single
species of ctenophore imparts to the planktoii a very reuiarkable char-
acter, and this is true in all oceans, in the cold as well as in the warm
and temperate zones. More often it happens that the monotonic cnid-
aria-plankton is composed of several species of Medusw, Siphonophores,
and Cfenophores, while other classes of animals take only a very limited
share in its constitution.

5. Monotonic Sagittkkv-Phmlion. — Tlie only form of monotonic plank-
ton which the branch of Helminilies furnishes is made up by the class
of the Cha'tognatha, various species of the genera Sagitta and Spadella.
Although purely oceanic according to their mode of life, yet they occur
numerously in the neritic tow-stuff {Auftrieh). Sometimes only a single
species of these genera, sometimes several species close together,
appear in such swarms as to make n[) more tlian half of the entire
plankton. These phenomena have been ol)served in tlie colder as well
as in the warmer seas. In tlie former tlie plankton is composed of the
smaller, in the latter of the larger species. These forms occur also in
the deep sea, and indeed the zonary HagHtUhv-planMon is composed
of different species from the pelagic,

f). Monotonic Pteropoda-Planldon. — /vstonishing masses of oceanic pte-
ropods are very widely distributed in all parts of the ocean, and in part
are formed of characteristic genera and species in the different zones.
The immense schools of Clio horcfdis and Limacina arctica, which
inhabit the northern seas and (as -'whale-food") furnish the chief
food supply for many cetaceans, sea-birds, tishes, and cephalopods,
have long been known. But no less immense are other swarms of
pteropods, composed of different genera and species, which populate
the seas of the temi)erate and tropical zones. These have often escaped
the notice of seatarers, because most species are nyctipelagic. Of the
immense quantities of these floating snails, direct evidence is furnished
by theaccunnilated calcareous shells, which in many stretches of ocean
(especially in the tropical zone) thickly cover the bottom at depths
between 500 and 1,500 fathoms. Often the greater part of this
" pteropod-ooze " is formed solely of them (G, pp. 120, 922). At Messina
as well as at Lanzarote I found the pteropod-plankton often mixed with
considerable numbers of heteropods. Still the latter never form the
greater part of the volume.

612 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

7. Monotonic Crustacea -Phmlcton. — As the crustaceans surpass all
other classes of the animals of the x)lankton in quantitative develop-
ment, so they form monotonic plankton far more often than all other
classes. Most commonly this simple crustaeean-phinkton is composed of
copep'ods, not infrequently entirely of a single species (6, pp. 758, 843).
Next to this I have more frequently found monotonic osiracoda -plank-
ton; next schizopoda-planMon. Sometimes also there are in these two
orders only numberless individuals of a single species, sometimes of
many different species, which compose the monotonic plankton, often
almost exclusively, and at other times nuxed with additions of other
Crustacea, Sagitta, SaJpa, etc. The other above-mentioned orders of
crustaceans, which also- ta-ke a considerable part in the constitution of
the plankton, the decapods, amphipods, and phyllopods, I have never
found in such quantities that they formed more than half of the mass
of tow-stuff. On the contrary, such quantities of crnstace^in-Iarva' of
one species (e, g., of Le^jas and other cirripeds) occasionally appear that
they predominantly determine the character of theplaiditon.

8. Monotonic Tanicata-Flanldon. — Next to the monotonic forms of
plankton, which are comj)Osed of Crustacea and Gnidaria, tliat of the
Tunicata m most numerous. Quite preponderant in quanlity are the
ThalUliw or iSalpacea' (Salpa and ^SaJpeUa), and among these, especially
the smaller species {Salpa dcynocratica-mucronata, S. runcinata-fusi-
formis, and related species). I have often taken such monotonic salpa-
planLion in the Mediterranean, in the Atlantic and Indian oceans, and
have received the same also through Capt. Kabbe from different parts
of the Pacific Ocean. Masses of Doliolum and of Copelata {Appendicu-
laria, VexiUaria^ etc.) are also commonly mixed witli this in greater or
less quantities. Still these planktonic tunicates, on account of their
small size, recede before the Salpa'. I know of no instance where they
have by themselves formed a monotonic plankton. But this is the
case with the nyctipelagic pyrosoma. The (JlialJengcr and tlie Yettor
Fisani in the tropics, on dark nights, met with quantities of monotonic
pyrosoma-planlcton in the middle of the Atlantic and Pacific. By day
not a single one of these "cones of fire" was to be seen, and as soon
as the moon arose they went into the depths (8, pp. 32, 34).

9. Monotonic Fish-PlauMon. — If, with Ilensen, we limit tlie term
plankton to the halohios floating x>assively in the sea, we can desig-
nate as "monotonic fish-plankton" only the schools of very young and
small fishes, which often ai)pear abundantly in the currents, occasion-
ally so compact that very few other pelagic animals can find room
between them. If one wishes to extend the term still farther, and wipe
out the sharp distinction between planMon and neMoUj all those sea
fishes (oceanic as well as neritic) which appear in schools, and which
play so significant an oecological role in tlie cycle of matter in the sea
{e. g., ScopcUda', Clup>eida\ Leptocephalidfe, Scomberoida') will in general
belong here (12, p. 51).

PLANKTONIC STUDIES. 613

B. — Temporal Planktoxic Differences.

The first and most remarkable pheiiomenou, known to every seafaring
plauktologist, is the varying- constitution of tlie plankton and tlie vari-
able mingling of its constituents. The remarkable differences of com-
position apply qualitatively and quanUtaUvely to the oceanic as well as
to the neriUc plankton. They are just as im])<)rtant in the comparison
of different places during the same time as at different times in one
and the same ])lace. We can therefore distinguish h)cal anil temporal
variations, and will first of all consider the latter.

To obtain a complete and more certain survey of the temiDorary vari-
ations of plfinktoii comi)ositiou, there would be needed especially an
unbroken series of observations, which had been carried on at one and
the same place at least for the space of a full year — still better for
several successive years — to obtain from the yearly and monthly oscil-
lations a general average. Such complete series of ohservations, com-
parable to the meteorological (with which they stand in direct causal
connection), have not hitherto been made. Tliey belong to the most im-
portant tasks ofthe zoological stations now everywhere springing up.*

Meanwhile, a general conception of the considerable size of the yearly
and monthly oscillations can be obtained from a comparative summary
based upon the important series of observations extending over three
years, whi(;h Schmidtlein has given u{)on the api)earance of the larger
l^elagic animals in the (iulf of Naples, during 1875-77 (19, p. 120).
The contributions of Graeffe upon the occurrence and time of appear-
ance of marine animals in tlie Gulf of Trieste are also worthy of notice
in this connection (20).

The considerable temporal variations which underlie the appearance
of the i^elagic organisms and which determine such great differences in
the plankton composition, relative to quality and quantity, may be
divided into four groups: (1) yearly, (2) monthly, (3) weekly, (4) hourly
variations. Their causes are manifold, partly meteorological, partly
biological. They are comparable to corresiionding temporal oscillations
of the terrestrial flora and fauna, on one side depending upon climatic
conditions and meteorological processes, and on the other upon the
changing mode of life, especially upon the conditions of reproduction
and development. As the annual development of most terrestrial
plants is connected with definite time conditions, as the period of bud-
ding and leaf development, of their blossoming and fructification, has

* My own extensive experience, I am sorry to say, is in this regard very Insufficient,
since I have never worked at a zoological station, and since usually I was only so
fortunate as to go to the seacoast for a few months (or even only for a few weelis)
during the academic vacation. Only once have I had the opportunity to extend my
plankton studies at one and the same place to a half year (from October, 1859, to
April, 1860, at Messina, 3, p. v, 166), and three times have I carried them on for
three months at the same place — in the summer of 1859 at Naples, in the winter of
1866-67 at Lanzarote, and in the winter of 1881-82 in Ceylon.

614 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

become adai)te(l to the meteorological coiKlitions, the time of year and
otlier conditions of life in tlie " struggle for existence, " so also tlie
annual development of most marine aninmls is governed by definite,
inherited habits. With them also the intiuence of meteorological vari-
ations on the one side, of oscological relations on the other, are of the
greatest importance for the periodical appearance. Most organisms
aijpear in the plankton only periodically, and only very few can be
reckoned as belonging to the " perennial plankton" in Hensen's sense
(9, p. 1). This investigator also attaches great importance to the tem-
poral "highly remarkal)le variations'' in the plankton composition (9,
pp. 29, 59); he explains it in part by " periods of famine" (p. 53).

Yearly oscillations. — The i)lankton literature has hitherto contained
only a few reliable statements upon the yearly variations, which underlie
the appearance of the pelagic animals and plants. Still there are a few
contributions of liigh merit, extending over a series of years, namely
those of Schmidtlein irom Naples (19) and of Graeffe from Trieste
(20), Even the first glance at the tables, those of the former relating
to the ai)pearance of the i^elagic animals in the Gulf of ISrai)les, shows
us how remarkably different was the action of the majority of these
in several successive years. As there are good and bad wine and fruit
years, so there are rich and barren plankton years. But Schmidtlein
correctly remarks that extensi\e observations extending through a
long series of years are demanded to gain a deeper insight into the
meaning of these yearly and monthly variations shown in the tables.
The same view is also held by Chun, Avho, in his monograph of the
ctenophores of the Gulf of Naples (p. 236), points out how very differ-
ent was the number of these in five successive years.

Graeffe, resting on the basis of his observations for many years, says
of CotylorMza tuberenlata, that this beautiful acaleph has not for many
years been found in the Adriatic, in other years only individually, but
not at all rarely (yet always only in the three months of July, August,
and September). Just as variable is the occurrence — ^^ according to the
year'''' — of Umhrosa lohafa and other medusa^ Of the six species of
ctenophores of the Gulf of Trieste, only one a^ipears every year, the five
others only noAv_ and then. Not only do the qnantities of individuals,
but also the " time of appearance of pelagic animals change according to
the meteorological conditions of tlie time of year" (20, v, p, 361). I
myself can fully establish this proposition on the ground of observa-
tions which 1 have made in the course of many years of medusa
studies. Many of these "capricious beauties" occur in one and the
same place on the Mediterranean coast {e. g., in Portofino, in Viila-
franca), numerously in the first year, rarely in the second, and not at
all in the third. When, in April, 1873, 1 fished in the Gulf of Smyrna,
it was full of swarms of the great i)elagic Chrysaora hyoscella. In
April, 1887, when for the second time I sought the same gulf, I could
not find a single individual of that beautiful medusa, but instead the

PLANKTONIC STUDIES. 615

g-ulf was tilled by crowds of a new, hitherto uudescribed, large medusa,
Drymonema eordelia. Thousaiid.s of these Cijaneidw lay cast upon the
beach at Cordelio.*

MoHthUj oscillations. — The time of year is of Just as great imi^ortauce
for the appearance of very many i>elagic animals as for tlie liowering
and fruit formation of laud j)lauts. Many of the larger planktonic ani-
mals, Medusw, Siphonophores, Gtenophores, Heteropods, Fi/rosoma, etc.,
appear only in one month or during a few montlis of the year. They
form Hensen's "periodic plankton." In the Mediterranean many
pelagic animals are numerous in the winter, while in the summer they
are entirely wanting'. This "periodical ai)pearance of pelagic animals"
has long been known and often mentioned; but not so tl^e important
fact that these ethoral periods themselves show considerable variations.
For tliis the tables of Schmidtlein (19) and the notes of Graeffe (20)
give important points of support. Especially the DisconecUv and other
Siphonophores\ behave very irregularly. The cause of the monthly
variation lies on the one side in the conditions of reproduction and
develoi>ment; on the other in the varying temperatTU-e of the season,
as Chun has lately Shown (15, 16).

Daily oscillations. — Every naturalist wh.) has observed and fished
pelagic aninuils and plants in the sea fov a long time, knows how uidike
their appearance is on different days in the same period of the year or
in the same mouth, when one may daily hope to find them. As a rule,
the weather, and particularly the wind, conditions tlie remarkable
<liflerence of appearance. In long-continuing calms the surface of the
sea becomes covered with swarms of various pelagic creatures. In
long bands, smooth as oil, the most wonderful zoorurrents appear.
Bat as soon as a fresh wind stirs up lively waves, the majority sink
into the quiet depths, and if a more violent storm churns u^) the deeper
layers, all life vanishes from the surface for days. Many aninmls of
the plankton (especially oceanic) are very suscejitible to the infiuence
of fresh Avater, and therefore disappear during violent rains. Warm
sunshine entices the one to the surface, while it drives the other into
tiie depths. This influence of the weather upon the quality and quantity
of the planktonic composition is so well known that it is not necessary
to give examples. Hensen (9) has even gone over his work many times,
without thinking how the above endangers his "exact methods" and
nmde their results illusionary,

* Driihionema eordeVm, whose milk-white iiml)rella. reache.s halfii meter in diameter,
I will describe liereafter. It differs! in the formation of tlie gonads and oval tenta-
cles, as in several other points, Irorn the Adriatic species, which I have described as
Drtjmonema victoria {^= (lalmaiinum) (ii, 29).

f Of the Disconectce (Poiyita and VcJella) Chun during a 7 months' residence at
tlie Canary Islands (1887-88) conld find not a single specimen. According to him
they should appear first in midsummer (July to September). On the other hand
I saw at Lanzarote an isolated swarm of these Diseonectw in midwinter, in Feb-
ruary, 1867.

61 G REPORT (5F commissioner OF FISH AND FISHERIES.

Hourly osciUailons. — Manj' pelagic auiuials appear at the surface
of tlie sea only at a definite hour of the day, some in the morning,
others at noon, still others towards evening. During the remainder
of the day uot a single individual of the species is to be found,
Agassiz, thirty years ago, brouglit forward noticeable examj^les of
this from the class of Medime, and I can from my own experience adduce
a number of other examples. But many other pelagic animals also
{e. g., Sq)honophorc.s', Reteropods) come to the surface only for a few hours.
We have long known that the swarms of the nyctipelagic Fteropods,
Pyrosoma and many Crustacea, come, to the surface only during the night
and flee the light of day. Other groups act Just reversely. But the
late extensiye observations, especially of Murray (0), Ohierchia (8),
and Chun (15) have taught us how great is the (extent and importance
of those hourly variaticms. That these are of great influence upon
the composition of the plankton, and that this accordingly is very
different at different times of day, needs n > repetition. But we must
allude once more to liow all these tiimporal oscillations must be taken
into consideration, if the equality of planlton distrlhution is to be
proved by observation and estimation. In point of fact they all seem
to tend to very remarkable Inequality.

C. — Climatic Plankton Differences.

The mimerous contributions which earlier and later observers have
made upon the appearance of the swarms of the pelagic aniuuils in
different regions of the ocean, agree in pointing out the differences
among them, corresponding to tlse climatic zones. Thus the Arctic
oceans are characterized by masses of monotonic plankton of Diatom,
.Beroidw, Gopepod, and Fteropod groups, swarms which are often com-
l)osed of milliards of single species. In the oceanic regions of the
temperate zone we meet monotonic plankton of the Facoid, Kovtiluca,
Medusa, Ctenophore, Salpa, Scliizopod, etc., classes, sometimes com-
posed of one, sometimes of several species. In the tropical ocean im-
mense banks of monotonic plankton appear, in which the Murracytes,
OsciUatoriic, FhysaUa, Fyrosoma, Ostracoda, determine the character of
the swimming oceanic population. Although these facts have long
been known, up to this time no attempt has been made to arrange
them chorologically or to define more closely the characteristic features
of the plankton in the climatic zones. Yet I believe, partly ui)on the
ground of the ac( ounts referred to above (particularly of the Challenger
and of the Vetf or Fisani), imrtly on the ground of my own comparative
investigations (of the Challenger as well as of the Rabbe collections),
that even now an important proposition can be formulated.

The quantity of the planldonis little dependent upon the climatic differ-
ences of the zones, the quality very dependent; especially in this tcay, that
the number of component species diminishes from the equator towards
both poles. This i)ropositiou corresponds, on the whole, with the con-
ditions which the climatic differences show in the terrestrial fauna and

PLANKTONIC STUDIES. 617

tiora. Here as there the explanation of the facts is above all to be
sought in the intluence of the sua, that -'all-powerful creator," which
in the tr()i)ical zone conditions a much more lively interaction of the
natural forces than in the pcdar zones. The ''cycle of matter in the
sea" {Stoffwechsel cles Meeres) is no less influenced by the perpendicular
rays of the sun than is the terrestrial f\iuna and flora; and as in the
tropics the quantity and the complexity of the terrestrial organic living
forms is by far most highly developed, so is it also the case Avith the
marine forms.

Hensen places himself in remarkable opposition to this hitherto
accepted view when in his account of the results of the Xafional expe-
dition he suri)rises us^with the following statement:

Altliongli \Ye have found plankton everywhore, the amount of it under and near
the tropics Avas relatively small, namely on an average 8 times less than in the
north near the Banks of Newfoundland. Each one of these hauls contained
upwai'ds of a hundred different forms; hut the poverty of the (juantity is still a
remarkably ajiparent established fact (22, \). 245).

In the notable account which E. du Bois-Reymond (on January 23,
1890) laid before the Berlin Academy \\-pon the results of the National
expedition, it was said concerning its scientitic results that a complete
account could not be given for three years, but then he added:

Only one chief result may here be assumed beforehand. Contrary to all expecta-
tions, established upon a theoretical basis, the quantity of plankton in the tropical
Avaters is shown to be surprisingly small (21, p. 87).

Since Hensen with this "chief result" of the National expedition
stands in strong opposition to the familiar experience of the Challenger,
of the Vettoi' Phnnl^ix^d of many other exi^editions, we must first of
all again examine the empirical foundations upon w^hich his assertions
rest. For these he admits that he regards as such only the results of
his '■'■trial trip^'' through a part of the Atlantic ocean, in which the resi-
dence in the tropics embraced scarcely two months. The results which
he here draws from his plankton fisheries, which obviously turned out
remarkably poorly as a result of accidental conditions, may contradict
the results which were set up by the Challenger and the Vettor Fisani
during a residence in the tropics of altogether four years, in different
parts of three great oceans. It is not indeed saying too much, if we
declare this kind of conclusion by Hensen as hasty, and the "exact
method" which he wishes to establish by computation as useless.

My own comparative study of the rich planktonic collections which
Murray and Rabbe have brought in from the different parts of the three
great oceans, has convinced me that the tropical ocean is not only qual-
itatively much richer (by the variety and number of planktonic spe-
cies and genera) than the oceans of the temperate and cold zones, but
that it also does not fall behind the latter quantitatively (in the abun-
dant distribution and vast accumulations of individuals). To be sure,
one ought not to take into consideration merely the surface of the trop-
ical ocean (although this also is often extremely densely populated), but

618 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

also the deeper zonary regions. For in tlie tropical zone tliere are
numerous nyctipelagic organisms, whicli by day sliun the glow of the
I)erpendicular rays of the sun and betake themselves into the cooler,
more or less deep layers of water; but at night these bathypelagic ani-
mals and plants jippear at the surface in such immense crowds tliat
they are not surpassed in quantity by the "immeasurable swarms" of
pelagic organisms in the temperate and cold zones.

During' my trip through the tropical region of the Indian Ocean, as
well on the way to Ceylon (from Bombay) as on the return (from Soco-
tora), I daily wondered at the great richness of pelagic life on the mir-
rored surface. At night the ''Avhole ocean, as far as the eye could see,
was a continuous shimmering sea of light" (25, p. 52). The luminous
water, which at night we scooped up directly from the surface with
buckets, showed a confused mass of nyctipelagic luminous animals {On-
tracods, tSaljia, Pyrosoma, Medusw, Fyrocystcc), so closely packed that
in a dark night we could plainly read the print in a book by the bright-
ness of their pelagic light. The crowded mass of individuals was not less
considerable than I have so often found in the Mediterranean in the
currents of Messina. What quantities of food the plankton must here
furnish to the larger aniuials was shown by the vast schools of great
medusre and flying-fish, which for days accompanied our vessel; and
this mass covered large areas of the open Indian Ocean, midway
between Aden and Ceylon. Just such i>lanktou masses I have received
through the kindness of Capt. llabbe from other tropical parts of the
Indian Ocean, between Madagascar and the Cocos Islands, and be-
tween these and the Sunda Archipelago, I encountered a wonderfully
rich and thick planktonic mass in a iielagic current of the southwest
monsoon drift, 50 nautical miles south of Dondra Head, the southern
point of Ceylon.* I have referred to the richness of this in my " Indian
Journal" (25, p. 275).

That the tropical zone of the Atlantic Ocean also possesses a vast
wealth of plankton is shown by many older accounts, but especially
from the experience of the Challenger. In the middle of the Atlantic,
between Cape Verde and Brazil, Murray observed colossal masses of
pelagic animals; and if by day they were scarce at the surface, he con-
tinually found them below the surface, in depths of 50 to 100 fathoms
and more (0, pp. 195, 218, 27G, etc.); at night they ascended to the sur-
face and filled the sea far and wide with a brilliant glow (pp. 170, 105,
etc.). '' On the ichole cruise along the Guinea and equatorial currents, the
pelagic life teas exceedingly rich and varied, in the quantities of individ-
uals as well as of vspecies, onueh more than anywhere else in the northern
or soutliern part of the Atlantic Ocean. The greatest quantities were
seen in the Guinea current during calms, when the sea literally sicarmed

*A part of the new species of pelagic animals wliich I found in this astonishingly
rich oceanic current arc described in my '■ Keports on the Siphonophora and Kadio-
laria of H. M. S. Challenger."

PLANKTONIC STUDIES. 619

with life'" (p. 2iS). This astonisliing wealth of i)laukton was observed
in the wliole breadth of the Atlantic tropical zone in Angiist and Sep-
tember, 1873; bnt it was not less than that passed by the Gltnllenger
on her return in March and April, 187G, in the eastern part of the same
region, between Tristan d'Aonnha and Cape Yerde. "When the water
was calm, an extraordinary siiperabnudance of pelagic life appeared at
the snrface. O.^clllatorice covered the sea for miles, and vast quantities
of Badiolaria [Gollosoun) filled the nets" (p. 930). With those and
other accounts by the Challenger, those of tiie Vettor Flsani quite agree.
" T'nc zone of eiimitorial calms is out ofaUjjrojjorlion rich in organic life.
Sometimes the' water seems coagulated, jelly like, even to the touch.
It is impossible to describe the quantities of variously colored forms"
(8, p. 31). Chiercliia enthusiastically describes the wonderful spectacle
which the luminous ocean furnishes at night — "a sea of light which ex-
tends to the whole horizon" (pp. 32, 53, etc.). The iiumerous plankton
samples wiiich I myself have investigated from the Atlantic tropical
zone show for the most part an extraordinarily rich composition, par-
ticularly those between Asceusion and the Ganarj? Islands {Challenger
stations 315 to 353), above all the two equatorial stations 317 and 318,
which, like the Canary currents, which I studied for three months at
Lanzarote, whose fabulous wealth I have already mentioned, also belong
to the region of the iroplcal trades-drift.

Tiie quantity and wealtli of forms of the plankton in the tropical
zone of the Pacific Ocean is not less than in the tropical region of the
Atlantic and Indian oceans. In the most diverse parts of this region
the Challenger sailed tlirough "thick banks of pelagic animals,"
Between the iSTew Hebridiis a id ]S"ew Guinea "the surface of the water
and its deeper levels swarmed with life. All the common tropical
forms were found in great abundance. The list of genera of animals
was about the same as in the Atlantic tropical region (i)p.218, 219), but
it showed consideraMe diiference in the relative abundance of species''^
(0, p. 521). Among the Philippines the water showed "a quite uncom-
mon quantity and variety of oceanic surface animals" (p. CC2). On
the voyage from the Admiralty Islands to Japan the oceanic "fauna
and flora of the surface was everywliere especially rich and varied.
In the neighborhood of the equatorial countercurrents, between the
equator and the Carolines, pelagic foraminifera and mollusks were
taken iii such quantities in the surface net that they surpassed all
earlier observations," etc. (p. 73S). On the voyage through the ce«f>v(i
part of the tropical Pacific, from Honolulu to Tahiti, between 20° ]Sr.
hit., and 2i)'^ S. lat., "the catch of the tow net was everywhere very
rich. The superahundance of organic life in the equatorial current and
countercurrent is very noticeable, as well with reference to the number of
species as of individuals''' (p. 776), From this wonderfully rich region,
which of all parts of the tropical ocean is farthest removed from all
continents, came the absolutely richest plankton samples which I have

620 REPORT OF COMMrsSIONER OF FISH AI7D FISHERIES.

ever studied, those which the Challenge)- brought from her stations
262-280, My astDiiishiuent was great when I first saw these planktonic
masses, in the autumn of 1876; but it grew boundless when a year
later I studied iireparatious talcen from them aud found in them hun-
dreds of new species of pelagic animals.

The wonderfully rich Badiolaria ooze which the ChaUenger brouglit
up at the central Pacific stations 263-274 (from depths of 2,000 to 3,000
fathoms) is only the siliceous remains of that planktonic mass, from which
all organic constituents have vanished and the calcareous shells for the
most part dissolved by the carbonic acid of the deep currents.* The
numerous surface preparations which Murray finished npon the spot
on this remarkable voyage of planktonic discovery through the central
Pacific, and mounted in Canada balsam, are ahsolutely the richest planJc-
ton preparations which I have ever studied, especially those of stations
266-274, between 11° N. lat. aud 7° S. lat. The richest of all stations
is 271, lying almost under the e(pmtor (0o33'S. lat., 152o 56' W. long.).
I have since shown these pre^jarations for microscopical studies to many
colleagues aiul friemls, and they have always expressed the liveliest
astonishment over the new " wonder- world " concealed in them. They
are jokingly called tlie "mira-preparatious" (comp. 4, §§228-235).

The wonderful planktoa v/ealth of the tropical Pacific is as well
established by the mauifold observations of Chierchia: " The quantity
and quality of the organisms tchich inhabit the tropical regions of the sea
surpass all conceptions^ (8, p. 75). Inconceivable quantities of pelagic
animals of all groups were seen in the middle of the tropical Pacific,
between Callao aud Hawaii, between HonoluUi and Hongkong, not
only at the surface, but in the most various depths up to 4,000 meters.
The quantity of deep-sea siphouopliores was here so enormous that the
sounding lead was never drawn up without its being surrounded with
torn-off tentacles (p. 85). During the forty days' voyage from Peru to
Hawaii the pelagic fishery at tlie surface as well as in tlie depths
brought to light *'suc]i a quantity of different organisms that it must
seem almost impossible to one who did not follow the work witli his own
eyes" (8, p. 88). Similarly, in the Chinese sea and in the Suuda Archi-
pelago immense masses of plankton were encountered.

It is my intention here to bring together the most general impres-
sions of the relative planktonic wealth of the various oceanic regions,
which I have gained from a comparative study of many thousand
planktonic preparations. The iselagic fauna aud flora of the tropical
zone is richer in different forms of life than that of the temperate zone,
and this again is richer than that of the cold zone of the ocean. This
is true of the oceanic as well as of the neritic plankton. Everywhere
the neritic plankton is more varied than the oceanic. The wealth of

*0f this Badiolaria ooze there are 16 saniijles (embracing about 1,000 dilfereut
species) coutaiued in the " Radiolariau collection " (1890) above mentioued. The 8
richest of these (Nos. 20-27) belong to the tropical central Pacific (stations 265-274).

PLANKTONIC STUDIES. 621

individuals can in none of these regions bo ciiUed absolutely greater
than in the others, since the quantitative development is very depen-
dent upon local and temporal conditions and, according to time and
place, is on the whole extremely irregular. Estimation of individuals
can in this relation prove nothing.

U. — CrUHEXTIC PlANKTONIC DiKl r>KKNCES.

By far the most important of all the causes which determine thfe
changing- and irregular distribution of the plankton in the sea are the
marine currents. The fundamental imi)ortance of these currents for all
planktonic wStudies is generally recognized and has lately been men-
tioned many times and explained by Murray (0) and Chierchia (8). Even
the zo()logists of the plankton expedition of Kiel have not been able to
close themselves to this intelligence. Brandt calls special attention
to "the importance of the marine currents as a means of, and limit to,
the distribution of the planktonic organisms," so that in the various
Atlantic currents numerous forms continually appear which were want-
ing in the regions previously traveled" (23, p. 518). Thus, Heuseu
mentions the "extraordinarily large i)lankton catches, which were
transported by various currents."

I learned thirty years ago to recognize the great importance of the
marine currents and their direct influence upon the composition of the
plankton, when at Messina I went out almost daily in the boat for
six months to secure the rich i^elagic treasures of the strait (3, p. 172).
The i)eriodical strong marine current, which there is known to the
Messinese under the name of the current or the Eema, enters the harbor
twice daily and brings to it inexhaustible treasures of pelagic animals
which since the time of Johannes Miiller have aroused the wonder
and desire for investigation of all naturalists tarrying there. Not
less important did I find later the planktonic importance of the local
marine currents (at Lanzarote), when the "Zain" current of the Canary
Sea in like manner brought with it an extraordinary wealth of pelagic
animals. My companion on the trip, Richard Greefr', has very vividly
described these marine currents as "animal roads" (IS, p. 307). Dur-
ing my numerous pelagic journeys on the Mediterranean it was always
my first care to investigate the conditions of the currents, and on the
most different parts of its coast (from Gibraltar to the Bosporus, from
Corfu to Rhodos, from Nizza to Tunis, I have always been convinced
of the determining influence which they exerted upon the composition
and distribution of the plankton.

Although the fundamental importance of the marine currents for the
diverse questions of oceanography are now generally recognized, still
very little has been done to follow out in detail their significance for
planktology. It seems to me, we must here, with reference to our theme,
particularly distinguish {1) Judicurrcnts (the great oceanic currents) ;
(2) the hathycurrents (the manifold deep cuiTents or undercurrents);

622 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

(3) the veroGHrrents (the littoral ciirreiits or local coast currents); aud

(4) the zoocurrents (the local phmktoiiic streams or very crowded animal
roads).

Ralicur rents or ocean streams. — The unequal distribution of plank-.
ton in tiio ocean is in great part the direct result of the oceanic
currents. In general the proposition is recognized as true that tlie
great ocean streams, which we briefly designate as halicur rents, effect
a greater accunuilation of swimming organisms and thereby are
richer in i:)lankton than the /m^/.stesa or "still streams,'' the extensive
regions which are inclosed by them and relatively free from currents.
For a long time (lie richness in i)lankton which characterizes the Giilf
Stream on the east coast of Xorth America, the Falkland Stream on
the east coast of South America, and the Guinea Stream on the west
coast of Central Africa, has been known. Less understood and investi-
gated thaji these Atlantic streams, but also very rich in varied plankton,
are the great streams of the Indian and Pacific oceans, the Monsoon
Stream on the south coast of Asia, the Moziunbique Stream on the east
coast of South Africa, the Black Stream of Japan, the Peru Stream on
the west coast of South America, etc.

It is very difficult, from the numerous scattered accounts of the
pelagic fauna and flora of these great ocean currents, to form a general
picture of them, but it is now possible to draw Irom them the conclu-
sion that generally the i)lanktou of the halicurrents, qualitatively as
well as quantitatively, is richer than the plankton of the haUstasa, or
the great oceanic sea basins around which flow the great streams and
counter streams, and which meet the first glance on every recent map
of the marine currents.*

In defending this proposition I rely especially upon the rich experi-
ence of the two most iraportaut plankton expeditions, of the (JhaUcnfjer
(6) and of the Vettor Pisani (8), and also upon my own comparative
study of several hundred plankton samples, which were collected in
part by Murray, iu part by Capt. Rabbe, in the most diverse parts of
three great oceans. The planktonic wealth of the great halicurrents is
most remarkable at the place where they are narrowest, when the
masses of swimming animals and plants are most closely pressed
together. Highly remarkable here is the opposition which the rich
pelagic fauna and flora of the stream forms iu qualitative and quanti-
tative relation to the sparse population of the immediately adjacent
halistase. As the temperature and often even the color of the sea

* The systeni.itic biologioal investigation of the hnJisinsa seems to uie to form one
of the nearest and most pressing problems of planlitology, and also of oceanography.
Apart from the smaller and little investigated Arctic and Antarctic regions, iu all
five great areas of quiet water ought to ho distinguished, namely: (1) the North
Atlantic licdisiasc (with the Sargasso Soa) ; (2) the South Atlantic (between Benguela
and Brazil streams); (3) the Indian (between Madagascar and Australia); (4) the
North Pacific (between California and China), and (5) the South Pacific halistasq
(between Chili and Tahiti).

PLANKTONIC STUDIES. 623

water in two adjacent regions is remarkably different and often sliarj)ly
contrasted, so also is tlie constitution of th\^ir animal and vegetable
world. Thus Murray observed a strong contrast between the cool green
coast streams and the warmer deep-blue ocean water when the Challen-
ger neared the coast of Chili, between Juan Fernandez and Valparaiso,
and correspondingly there occurred a sudden change of pelagic fauna,
for the oceanic globigerina disappeared and the neritic diatoms, infu-
soria, and liydromedusa^. appeared in greater abundance (0, i^. 833).

This change was very remarkable when the Chcdlenger (at station
240, June 21, 1875) h'ft the warm 'Hjlack stream" of Japan and entered
the cold area of quiet water adjacent on the soutli (about 35° IST. hit.,
153° E. long".). Great i)olymixic masses of plankton, dwellers in the
tirst area, were here killed by the sudden change of temperature and
rei)laced by the monotonic copepodan fauna of the cold halistase (10, p.
758). Also, later, on the voyage through the Japan stream, the plank-
tonic contents of the tow net plainly showed the proximity of two dif^
ferent currents. ''In the cold streams there appeared a greater mass
of small diatoms, noctiluca, and hydromednsa:' than in the warmer
streams where the richer pelagic animal world {Bafliolaria, Olobif/erina)
remained the same which the Challenger observed from the Admiralty
Islands to Japan." Many similar cases occurred during the voyage,
when proximity to the coast or the presence of coast currents was indi-
cated by the contents of the tow net (0, p. 750).

Observations upon the plankton richness of the oceanic currents,
similar to those of Wyville Thompson and Murray on the Challenger
(6) were made by Palumbo and Chierchia on the Vettor Pisani. The
latter calls attenti<m especially to the great importance of these and the
great accumulation of pelagic animals in limited regions of currents.

It is a fact, that f^onorally ou a voyage tlircngli the ocean great quantifies of indi-
vidiiah of one sjiccies are found pressed fof/ethcr in relative! ij small sjiaees, r.ucl this is
true of orgnuisms Avhich, on account of their small size, are not capable of extensive
movements. In addition, it is also a fact that Avhen the ship is in the midst of the
great oceanic currents, the pelagic fishery gives the nio^.t brilliant results (8, p. 109).
It is quite certain that the investigation of the distribution of the pelagic organisms can not
progress unless aeeompanied hy aj)arallel study of the currents, the temperature, and the
density of the tvater (8, pp. 109, 110).

Even the participators in the Xational expedition of Kiel could not
avoid noticing the great irregularity of planktonic distribution in the
ocean and the importance of the oceanic currents in this respect.
During the voyage it was noticed that in different Atlantic currents
numerous forms appeared continually which were absent in the regions
previously traversed :

The conditions are much more complicated ( !) than we had hitherto supposed (23,
p. .518).

But it is worthy of notice how Hensen, the leader of this plankton
expedition, has noticed this abundant accumulation of pelagic organ-

624 REPOKT OF COMMISSIONER OF FISH AND FISHERIES.

isms iu single regions of currents, and lias twisted it in favor of bis
theory of the regular distribution of the ])lanMon:

The tests of the volume of the plankton show that, five times in the north, once
north of Ascensiou, extraordinarily laryv catches ( !) were made. These must have been
caused by various currents in this regiou, and can therefore be left out of consider-
ation (9, p. 249).

It seems to me that Hensen would have done better to take into
consideration these Jind other facts observed by him relative to the
unequal plankton distribution before he built up his fundamental,
certainly adequate, theory of the equality of the same. This was to be
expected, since he himself in his first oceanic plankton studies (1S87)
observed mauy 'h'emarliahle inequalities,'^ mid his own tables furnish
l)roof of this. While he many times mentions the immense swarms of
Medusw and declares this " quite superabundant accumulation to be
mysterious," he adds: "such j)lacesmust be avoided in this fishery" (9,
pp. 27, 65). When Hensen later, in comparing the different catches of
copepods (one of the most important planktoiiic constituents), finds
that the distribution of the plankton' in tlic ocean is very irregular
and that the constitution of this seems to very strongly contradict
his general conceptions of natural life (9, p. 52), he holds it to be best
that these catches, which are of "such a different kind, should be
excluded from consideration" (pp. 51, 53). Also, in the case of Sagitta,
which Hensen reckons with the copepods as belonging to the uniform
perennial plankton, he finds "throughout not the equality which one
might exx^ect, but much more remarkable variations" {]}. 59).

These "surprising inequalities," "variations even to tenfold," he finds
iu case of the Dax)hnid(v (pp. 54, 56) and Hyi^eridw (p. 57), the pelugic
larvpe of snails and mussels (pp. 57, 58), Appendicularia and Salpa
(pj). 63, 64), the Medusm and Ctenophores (64, 65), the Tintimioids (p.
68), the Peridinia^ (!>. 71), and even in the Diatoms (p. 82) — in brief,
in all groups of pelagic organisms which by the numerous production
of individuals are of importance for the plankton and upon which
Hensen employs his painstaking method of calculation by quantitative
planktonic analysis. If one freely "sets apart from consideration"
all these cases of remarkable inequality (because they do not fall in
with the theoretically X)i"econceived ideas of the equality of planktonic
composition), then finally the latter must be proved by counting.

Bathycurrents or deep streams. — Through recent investigations, par-
ticularly of Englishmen (Carpenter, Wyville Thompson, John Murray,
et al.), we have become acquainted with the great importance of the
submarine currents or deep streams. It has been demonstrated that
the epicurrents, or the surface streams, furnish us no evidence rela-
tive to the understreams to be found below them, which we name bathy-
currents. These undercurrents may in different depths of the ocean
have a quite different constitution, direction, and force from the over-
currents. This is as true of the great oceanic as of the local coast cur-
rents. If the more accurate study of marine currents is a very difficult

PLANKTONIC STUDIES. 625

subject and great liiudraiices lie, as they do, in the way of exact deter-
minations, the same applies especially to the deep currents. New ways
and means must first be found for pressing into the dark labyrinth of
very complicated physical transactions. Kow we can only say that
the bathycurreuts are of great importance for the irregular constitution
(lud distribution of the planliton. Since the time when, through the
discoveries of Murray (1375), Chierchia (1885), and Chun (1887), we
learned to recognize tlie existence and importance of the zonary and
bathybic fiiuna, aiul particularly, through Chun, the vertical migration
of the batliypelagic animals, tlie complicated conditions of the sub-
marine currents must evidently have exerted an extraordinary signifi-
cance for planktology. Although we have liitlierto known so little
about this subject, yet two points stand out clearly: First, that these
are of great influence up(Ui tlie local and temporal oscillations of plank-
tonic composition ; second, that it is an untenable illusion if Hensen
and Brandt believe that, by means of tlieir perfect-working vertical
plankton net, " a column of water whose height and base area can be
accurately determined h;is been completely filtered" (23, p. 515); for
one can never certainly know what considerable changes in tlie plank-
ton of this colunm of water one or more undercurrents have caused
during the drawing up of the vertical net.

Nerocurrents or coast streams. — .While the halicurrents or the great
ocean streams are influenced in the first place by the Avinds and stand
in immediate connection witli the air currents of our atmosi)here, it is
only partly the case with the local coast currents, for here a number of
local causes, which are to be sought in the climatic and geographical
condition of the neighboring coast, work together. In the case of coasts
which are much indented, in archiijelagos with numerous islands, etc.,
the study of the littoral currents ])ecomes a very complicated problem.
The physical and geological natural condition of the coast mountains
and of the beach, the number and force of the incoming rivers, the quality
and quantity of the coast flora, etc., are here important factors. The
fishermen, pilots, etc., are very well acquainted with these local coast
currents,, which we will briefly call nerocurrents^ and are usually to be
trusted in the details. Scientifically these currents sliould be studied
more closely in smaller part and less quantity. For planktology they are
of very high interest and not less important than the oceanic currents.

Next, the above-intimated reciprocal relations of the ncritic and oceanic
planlcton are to be taken into consideration. He who for a long time
has carried on the pelagic fishery at a definite point on the coast
knows how very much the result of this is influenced by the natural
condition of the coast, by the course and the extent of the coast cur-
rents. Straits like those of Messina and Gibraltar, harbors like those
of Villafranca and Portofino, furnish uncommonly rich plankton results,
because in consequence of the littoral currents a mass of swimming
animals and plants are collected together in a limited space. The vol-
H. Mis. 113 10

626 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

uine of this planktouic mass thus lieapcd up is often ten or many times
greater than that in the immediately adjacent parts of the sea. On
the contrary, the i)hiiiktoni(; mass is extraoidinaiily poor in pelagic ani-
mals and plants, where by the emptying of great floods a rpiautity of
fresh water is brought into the sea and its saltness diminished. Johan-
nes Miiller pointed out how very much the result of pelagic fishery
was influenced therei)y. Again, on the other hand, the rivers day by
day bring into the sea a quantity of organic substances which serve as
food for the benthonic organisms, and since the benthos again stands in
manifold reciprocal relation to tlie plankton, since the meroplanktonic
animals (like the medusre, the pelagic larva) of worms," echinoderras,
etc.) are the means of a considerable interchiiiige between the two, so
is it easily understood how the distribution of the holoplanktonic ani-
mals is also influenced thereby and how irregular becomes the com-
position of the plankton.

Zoocurrents, or planMonie streams. — Among the most noteworthy and
important phenomena of marine biology is the great accumulation of
swimming bodies which form long and narrow bands of thickened
plankton. All naturalists who have Avorked at the seashore for a long
period and have followed the irregular appearance of the pelagic organ-
isms know these j)eculiar streams, which the Italian fishermen call by
the name " correnti." Carl Vogt, in 184S, pointed out their great impor-
tance for pelagic fishery (17, p. 303). For their scientific designation
and their distinction from the other marine currents I propose the term
Zoocurrents or Zoorema*

The pelagic animals and plants are so luimerous and so closely packed
in these zoiicurreuts as to resemble somewhat the human popuhition in
the busieststreet of a great commercial city. But millions and millions
of small creatures from all the above-mentioned groups of planktonic
organisms are crowded confusedly together, and furnish a spectacle of
whose charm a conception can be formed only by seeing it. If one
directly scoops up a portion of this motley crowd with a tumbler, not
infrequently "the greater part of the contents of the glass (an actual
living animal broth) is composed of the volume of animals, the smaller
of the volume of water" (3, p. 171). From a distance these "crowded
sea-animal streets'' are usually discernible from the smoothness which
the surface of the sea presents, while close beside it the surface is more
or less rippled. Often one can follow such an " oil-like animal stream,"
which usually has a breadth of 5 to 10 meters, for more than a kilometer
without finding any diminution of the thick crowd of animals in it, while
on both sides of it, right and left, the sea is almost vacant, or shows
only a few scattered stragglers. At Messina, as at Lanzarote, the phe-
nomena of the zoocurrents were especially x)ronounced. My companion

*Rema (used hi Messiua) is from the Greek pn'ua = current; comp. 3, n. 172 note.

PLANKTONIC STUDIES. 627

on the trip, Eicliard Greeff, has described the Canary animal streams
so vividly that I will here give his description verbatim :

Our gaze was directed to the highly peculiar long and narrovs' currents, which
are of very especial importance for pelagic fishery with fine nets. If one looks at
the calm sea, especially from an elevation over a wide exjjanse of water, here and
there are seen strongly marked shining streaks, which intersect the surface as long
narrow bands. Their course and place of appearance seem to be continually chang-
ing and irregular. Sometimes they are numerous, sometimes only few or entirely
absent; to-day they appear here, to-morrow there; some have one direction, others
the opposite or crossing the first. Occasionally they run along close to one another
and unite in a single stream. If one approaches this streak it becomes evident
that here in fact a current prevails different from the movements of the surrounding
water, and that thereby is brought about the smooth band-like api^earauce. They
give the impression of streams cutting through the rest of the ocean, with their own
channel and banks, which, notwithstanding the great variations in the time and
place of their appearance, yet 'during their existence, which is often brief, show a
certain independence.

If one conies upon such streams, which are not too far distant from the coast, he
sees that all the smaller, lighter objects which formerly scattered over the surface,
floated about or cast upon the shore, were drawn into it. Pieces of wood and cork,
straw, alga', and tangle tornloose from the bottom, all in motley procession are carried
along in this current. But in addition (and this is for us the most important
phenomenon) all the animals belonging in the region of these currents arc drawn in
and fill it, often in such great quantities that one is tempted to believe it is not
merely the mechanical influence of the narrow stream which has brought about such
an accumulation of animals, but that the latter voluntarily seek out these smooth,
quiet streams, perhaps in (Connection with certain vital -expressions. A trip ujion
such a pelagic animal road furnishes a fund of very interesting observations. We
can lean over the edge of the boat and review the countless brightly colored sea-
dwellers, sometimes passing by singly, so that we can iusjiect them in their unique
peculiarities, sometimes in such thickly massed hordes that they seem to form an
unbroken layer of animals for a few feet below the surface. Yet these animal roads,
where one meets them in the sea, will always form the most certain and richest
mine for the so-called pelagic fauna, although naturally, from their changeableness
and their dependence upon a calm sea, they can never be definitely counted upon.
Likewise, the origin of these noticeable streams and their significance in the natural
history of the sea is still almost completely dark, in spite of the fact that they can
be observed in almost all seas and under favorable circumstances daily,- and also are
known to the fishermen of Arrecife under the name Za'ni (18, p. 307).

Although the zoocurrents seem to occur in the most diverse parts of
the ocean, and have often aroused the astonishment of observers, yet a
recent investigation of them is wanting. What I know al)out them
from my own exi)erience and from the contributions of others is
essentially the following:

The zoocurrents occur in the open ocean as well as in the coast
regions, particularly in the region of those nerocurrents which run in
straits between islands or along indented coasts. They are dependent
upon the weatlier, especially the wind, and appear as a rule only dur-
ing calms. Although in the case of the neritic zoiJcurrents the local
course is more or less constant, still it is subject to daily (or even
hourly) variations. Their breadth is usually between 5 and 10 meters,
but sometimes 20 to 30 meters or more; their length is sometimes only a

G28 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

few hundred meters, and at others several kilometers. Oceanic animal
streams reach much greater extension. Their constitution is some-
times polymixic, sometimes monotouic, often changing from day to
day. Highly remarkable is the sharp boundary of the smooth, thickly
populated animal roads, especially if the less inhabited and plankton-
poor wateron both sides is rippled by the wind. What combination
;0f causes produces this vast accumulation is still quite unknown;
(certainly wind and weather play a role in it; often, also, the ebb and
flow of the tide and other local conditions of the regions, especially
local currents. As whirlwinds on laud drive together the scattered
masses of dust and smaller objects and raise a column of dust upwards,
so may the submarine whirlwind press closely together the l)athy[)clagic
l^lanktonic masses and carry them upward to the surface. But xirob-
ably, also, in the same connection, complicated <Ec<dogical conditions
come into play, e. .(/., sudden simultaneous develoi)ment of quantities of
eggs of one species of animal. A new study of the zoocurrents is one
of the most urgent problems of planktology.

VI.— METHODS OF PLANKTOLOGY.

The new aspects and methods which three years ago were introduced
by Prof. Heusen into planktology, and of which I have already spoken,
have for their main jiurpose the qHantitative anah/sis of the planlion,
i. e., the most exact determination possible of the quantity of organic
substance which the swimming organisms of the sea produce. To
solve this subject and come nearer to the question connected with
it of the '^ cycle of inatter in the sea," Hensen devised a new mathe-
matical method which aims chiefly at the counting of the individuals of
animals and plants which populate the ocean. This uew method we
can briefly term the ocean'i e j)(>pnlat ion statistics of Hensen. The high
value which this indefatigable physiologist attributes to his new arith-
metical method is shown by the special mention which he makes of it
in his first contribution (9, pp. 2-33), from the wonderful i)atience with
which he counted for months the single Biatoms, Fcridinea', Infusoria,
Crustacea, and other pelagic individuals in a single haul of the Miiller
net, and from the long tables of numbers, the numerical j)rotocols, and
records of captures which he has appended to his first plankton volume
which appeared in 1887.

Any ordinary pelagic haul with the Miiller net or tow net brings up
thousands of living beings from the sea; under most favoral)le circum-
stances hundreds of thousands and millions of individuals.* How much
labor and time was involved in the counting of these organisms (for the
greater part microscopic) is shown from the fact that "even the count-
ing of one Baltic Sea catch, which is pretty uniform in its composi-
tion, required eight full days, reckoning eight working hours to the

*In a small catch, which filtered scarcely 2 cubic meters of Baltic Sea water, were
found 5,700,000 organisms, including 5.000,000 mici-oscopic peridiuete, 630,000 diatoms,
80,000 copepods and 70,000 other animals (23, p. 516).

PLANKTONIC STUDIES. 629

daj'" (23, p. 516). Meoinvliile Brandt, explaininfi' tlie ''highly original
procedure" of Hensen (''turning attention to attacking a problem, the
solution of which no one had ever thought of"), remarks, with refer-
ence to the foregoing quantitative analysis of the Atlantic i)laidcton
expedition of the Xational (1889), ''that the very much more manifold
ocean catches will consume presumably twice as much time, and since
on the plankton voyage at least 120 such catches were made, then the
working out of these (quite apart from the preliminary preparations)
will fully occupy an investigator for 120 x 14: days, or about 6 years"
(23, p. sio).*

Opinions respecting the significance and the value of the oceanic
po]»ulation statistics of Hensen are very different. E. du Bois-Key-
mond, in his paper before the Berlin Academy (21, p, 83), t attributes
to it extraordinary importance, "wherefore the uncommon sacrifice
made for it was justified." According to his opinion, the plankton
expedition of the Kational, arranged for this purpose, within its defi-
nite limits, from the novelty and beauty of its well-described task,
assumes a unique i)la(;e, and the Humboldt fund ought to be proud at
having been among the first to contribute to its execution" (21, p. 87).
On the ground of this honorable recognition, as well as of the great
hopes which the naturalist of Kiel himself based upon the results of
the National expedition, numerous notices have appeared in German
newspapers, disseminating the view that an entirely new field of
scientific investigation had been thereby actually' entered upon, and
that a further extension of it was of great importance. I am sorry to
say that I can not agi'ce with tin's very favorable conception,

DISTEIBI TION OF THE PLANKTON.

The foundation upon which the entire planktonic conception and
computation of Hensen rests is the view "that in the ocean the plank-
ton must be regularly distributed; that from a few catches very safe
estimates can be made upon the condition of Very great areas of the
sea" (22, p. 243). As Hensen himself says, he started with this '■'■purely
theoretical view,"^ and he believes that a completely successful result is
to be had, because these theoretical premises have been more fully

^According to this; the unfortunate plankton counter would in these 120 catches
have to count for over 17,000 hours. How such an arithmetical Danaida? work can
he carried through without ruin of mind and body I can not conceive.

tin the introduction to this noteworthy paper Du Bois-Reymond says that since
1882 Hensen ''had been mindful that, especially on the surface of the sea, there was
found a more unequally numerous population of uunutest liviug forms than had
previously been supposed" (21, p. 83). This remark needs correction, because many
times in the celebrated log l)ook of the Naiiondl plankton expedition this has been
overlooked, and therefore it lias wroiiyly been inferred that Hensen eight years ago
was the first to discover the existence and ahunduuee of the pelagic fauna and flora. In
fact, for forty-five years they have been the object of wonder and study for numerous
naturalists.

630 REPORT OF COMMISSIONER OF FisH AND FISHERIES.

established than could have been hoped. 1 have already shown that
this fundamental premise is entirely wrong. The mass of i}lanldon in
the ocean is not perennial and constant, hut of highly variable and oscil-
lating size. The biological coniiiositiou is very diverse, dependent ui)on
temporal variations — year, season, weather, time of day, upon climatic
conditions and especially upon the complicated currentic conditions of
the streams of the sea, of the oceanic and littoral currents, the deep
currents, and the local zoocurrents.

A comprehensive and fail- estimation of all these O'cological condi-
tions must a priori lead to the couvictiou that the distribution of the
2)lanMon in the ocean must be extremely irregular, and Ave find this
"purely theoretical view comi)letely established" a posteriori by the
comparative consideration and comparison of all the earlier above-
mentioned observations. These can not lie regardetl as refuted by the
opposing view of Henseii; for the empirical basis of the latter is, in
regard to its time and place, much too scanty and incomplete.

One might perhaps object that the technical methods of plankton
capture which Hensen employed gave more complete results than the
methods hitherto used; but this is not the case. The recent descrip-
tion v> hich Hensen gives of his technical methods for obtaining plankton
(or pelagic fishery) is very praiseworthy (0, pp. 3 to 14). The construc-
tion of the net (material, structure of the net, size of filtration), the
management of the catch and of the craft, are there carefully described.
The advance of the new technique there realized may indeed serve to
carry on the pelagic fishery or plankton ca])ture more productively and
more completely than was possible with the previous simpler technical
apparatus of planktology; but 1 can not find that one of the projiosed
improvements of this pelagic technique shows a great advance in prin-
ciple and is at all comjiaiable to the great advance which Palumbo
and Chierchia made in 1884 by the invention of the closible net.
Besides, I can not understand how the new "plankton net" constructed
by Hensen could give more accurate results than the simple "Miiller
net" hitherto employed, and the "tow net" used by the Challenger.
Such a vertical net Mill always bring up only a part of the plankton
contained in the volume of water going through it, and by no means,
as Hensen and Brandt believe, is a column of water whose height and
base area can be measured with sufficient accuracy perfectly filtered.
In this supposition the incalculable disturbances by conditions of cur-
rents, especially of concealed deep streams, are left out of account, as
already mentioned. Besides, Chierchia has lately shown how unreliable
and little productive is the fishery with the vertical net on account of
the considerable horizontal swimming movements of the pelagic animals
(8, J). 79). At any rate, the improvements Hensen has introduced into
the technical methods of plankton capture are not so important that
the remarkable difference between his and the earlier results can
thereby be explained.

PLANKTONIC STUDIES. 631

OCEANIC POPT'LATION — STATISTICS.

Statistics ia general is kuowti to be a very danoeroiis science, be-
canse it is commonly employed to lind from a number of incomplete
observations the approximate average of a great many. Since the
results are given in numbers, they arouse the deceptive api^earauee
of mathematical accuracy. This is especially true of the comi^licated
biological and sociological conditions, whose total x)henonu!non is con-
ditioned by the cooperation of numerous different factors, and is,
therefore, very variable according to time and phice. Such a highly
complicated condition, as 1 believe I have shown, is the composition of
the plankton. If, as Hensen actually wishes, this were to be sufiliciently
analyzed by countiug the individuals, and oceanic population statistics
were thereby to be made, then this would only be possible by the forma-
tion of numerous statistical tables, which should give results in figures
of the plankton fishery quantitatively in at least a hundred different
parts of the ocean, and in each of these at least during ten different
periods of the year.

A single "reconnoiteriug voyage" on the ocean, a single "trial
trip," limited in time and place, like the three-months Atlantic voyage
of the National expedition, can furnish only a single contribution to
this subject. But it can in no way, as Brandt thinks, offer " firm foun-
dations" for the solution of this and that "thorough analysis" (23, p.
525). If, also, after six years the 120 catches should actually be counted
through (after a labor of more than 17,000 hours), if by statistical
arrangement of this numerical protocol, by rational reckoning of their
results, a serviceable conce|)tion of the quantity of individuals of the
oceanic region investigated should be obtained, then at best this one
computation would give us an approximate coiiception of the conditions
of population of a very small part of the ocean ; but from it by no means
can we, as the investigator of Kiel wishes, arrive at conclusions bear-
ing upon the whole ocean; for that purpose hundreds of similar com-
putations must be made, including the most diverse regions and based
ui)on continuous series of observations during whole years. The zoolog-
ical stations would be the best observatories to carry out complete series
of observations of this character, not such trial trips as the three-months
voyage of the National. *

* In my opinion tlie results of the National expedition of Kiel would bave been
quite difterent if it had been carried out in the three months from January to March,
inster.d of from July to October. On the whole, the volume of jjlanlvtouic catch, at
least in the North Atlantic Ocean, would have more than doubled; in some places it
would have been increased many fold. Its constitution would have been entirely
different. If the expedition had l)y accident fallen in with a zoocurrent, and its
voyage had continued in it for a few miles, the contents of the nets would have
certainly been a hundredfold, possibly a thousandffdd, greater.

632 REPORT OF COMMISSIONER OF FI8H AND FISHERIES.
COUNTING OF INDIVIDUALS.

Since the new method of oceanic population statistics introduced by
Heusen seeks its peculiar basis in the counting of the Individuals
which compose the plankton, and since it finds in this '' counting the
only basis upon which a judgment can rest" (9, p. 26), then we must
examine more critically this cardinal point of his method, upon which
he lays the greatest stress. The counting of the single organic indi-
viduals, which compose the mass of the i^lankton, is in itself, quite apart
from its eventual value, an extremely difficult and doubtful task. Hen-
sen himself has not concealed a part of this great difficulty, and attempts
to partly allay the doubts which arise against his whole method.* But
in fact these are much greater and more dangerous than he is inclined
to admit.

WHAT IS AN ORGANIC INDIVIDUAL?

This simple question, as is known, is extremely difficult to answer.
If one does not accept all the grades of physiological and morpho-
logical individuality, which I have distinguished in the third book of
my " GenereJIe Morphologic, "' 1800, there are at least three distinct chief
grades to be kept apart: (1) The cell (or jilastid); (2) the person (or
bud); (3) the cormus (or colony). t Only among the Protista {Pro-
tophi/ta and Protozoa) is the actual individual represented by a single
cell; on the other hand, among the Histouti {Mrtaphyta and 3Ietazoa), by

* The fourth part of the "Methodik" in the plankton volnme of Hensen, which
treats of "the work on land," (a) Determination of the volnme, (&) the conntin<^
(9, pp. 15-30), is especially worthy of reading, not only hecanse it gives the deeiiest
insight into the error ofliis method, but also into his very peculiar conception of
a general biological problem.

tThe swimming animals and plants whicli com]>os(^ the plankton should in this
respect be arranged under the following heads: (r/) Protojihi/ia — among the Vhro-
viacecB, Calcocyletv, Mnrracyiew, XaniheUexv, TJiciiiocltw, and Peridiueo', all single cells
are to be counted; among the diatoms partly the latter, partly the cenobia or cell
aggregates, (b) MeUtpln/ia — among the /frt?os^)/(fl')Y( are to be coTiuted the spherical
Thalli; among the OsciUalorHV the single, thread-like ThaUi ; among tbe Sarr/assa
the cormus as well as its buds; but the cells which constitute each thallus and bud
are also peculiar, (c) Protozoa — the TnfuHorta {NoeiUuca and Tintinua) as well as
the rhizopods {Thalamoplwra and Padiolarta), are all to be counted as unicellular
individuals, but among the Pohjcuttaria:, besides the C'ocnohia (colonies of Collozoidw,
Sphairozoidiv, and (■ollosphwridw). (d) CoeJentcrata — among the Medusa', and Cteno-
phorcs, as also among the i>elagic Antkozoa and Tiirhellaria the single persons are to be
counted ; among the Sipho^iojihores these as well as the single colonies ; for each person
(or each medusom) of a cormus is here equivalent to a medusa, (e) Tunlcata — among
the CopeJala, Doliohon, and the generations of solitary tSalpas, the single persons are
to be counted; on the other hand, among the Pijrosoma and the Salpa chains, the
single cormi as well as the persons which compose them, (/-/i) In all the remaining
groups of planktonic animals, in the case of sagitta, mollusks, echiuoderm larv;e,
articulates, and iishes, not merely the persons are to be counted, but also the cells
which make up eai<-h of these metazoa.

PLANKTONIC STUDIES. 633

tlio higher unit of the person or of the colony, which is composed of
many cells. If we actually wish to cany out exactly the method, held
by Henseu as indispensable, of counting the individuals, and wish to
obtain useful results for his statistical work, then nothing remains ex-
cept a counting of all single cells which live in the sea. For only the
single cells, as the '' organic elementary individual," can form the
natural arithmetical unit of such statistical calculations and the com-
putations based thereon. If Henseu in his long " numerical protocols
and comparisons of captures" (9, pp. xi-xxxiii) places close to one
another as counted individuals — as coordinated categories — the uni-
cellular radiolaria, the cormi of siphonophores and tunicates, the per-
sons of medusae, ctenophores, echiuoderms, and Crustacea, the eggs
and persons of fishes, then he places together vastly incommensurable
bulks of quite different individual value. These can only be compar-
able for his purpose if all single cells are counted. But since each fish
and each whale in the ocean daily destroj^s milliards of these planktonic
organisms, so, in order to gain an ''exact" insight into the "cycle of
matter in the sea," the cell milliards which compose the bodies of these
gigantic animals must be counted and placed in the reckoning.

ECONOMIC YIELD OF THE OCEAN.

Hansen holds the quantitative determinations of the plankton not
only as of the highest importance in theoretical interest to science, but
also in practical interest to national economy. He thinks " that we
Avill be able to invent correct modes of action in the interest of the
fisheries,* only if we are in position to/orm a judgment upon the iiro-
ductive possibilities of the sea" (9, p. 2). Accordingly he regards it as
the most pressing problem to determine the economic yield of the
o(teaii in the same way as the farmer determines the useful yield of his
fields and meadows, tlie yearly production of grass and grain. By the
counting of the i)lanktonic individuals which Henseu has carried on for
a long time for a small part of the Baltic Sea, he thinks he has become
convinced that the "entire production of the Baltic in organic sub-
stance is only a little inferior to the yield of grass upon an equally
large area of meadow land."

The farmer determines the yield of his meadows, garden, and field
by quantity and Aveight, not by counting the individuals. If instead
of this he wished to introduce Hensen's new exact method of deter-

* How the practical interests of the fisheries can be advanced hy quantitative
plankton analysis I am not able to understand. The most important modes of
action which we can employ for the increase of the lish production of the ocean —
artificial propagation, increase and xirotection of the fry, increase of their food
supply, destruction of the predaceous fishes, etc. — are entirely independent of the
numerical tables which Hensen's enumeration of individuals gives. That the number
of swimming fish eggs furnishes no safe conclusion upon the nuiaber of mature fish
has been pointed out above.

634 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

«
miuatiou, lie must count all the potatoes, kernels of grain, graiDes,
clierries, etc., and not only that, Le must also count the blades of grass
of his meadow, even every individual weed which grows among the
grain of his field and the useful plants of his garden; for these also,
regarded from the physiological point of view, belong to the "total
production" of the ground. And what would be gained by all these
immense countings? Just as little as with the "desolate figures" in
Henseu's long numerical protocols. *

VOLUME AND WEIGHT OF THE PLANKTON.

If one actually regards the determination of the planktonic yield as a
highly important subject, and believes that this can be solved by a
certain number of quantitative plankton analyses, then this goal can
be reached in the simplest way by determination of the volume and
weight of each planktonic catch. Heusen himself naturally first trod
this nearest way; but he thinks that it is not accurate enough and
encounters difiiculties (9, p. 15). In his opinion, "an accurate analysis
of the plankton, on account of the great variety of its parts, can only
be obtained by counting; he quite forgets that such a counting of
individuals also possesses only an approximate and relative value,
not a complete and absolute one; farther, that from the counting of the
difierent individuals no more certain measure for the economic value
of the whole diversely constituted i)lanktonic catch is furnished ;
finally that the counting of one catch is of highest value as a single
factor of a great computation, which is made from thousands of dif-
ferent factors.

The only thorough method of determining the yield, in plauktology
as in economy, is the determination of the useful substance according
to mass and weight and subsequent chemical analysis. In fact, the
determination of the planktonic volume, as of the weight, just as the
qualitative and (piantitative chemical analysis of the plankton, is pos-
sible up to a certain degree. The difficulties are less than Hensen
believes. It seems odd that the latter has not mentioned tbese two
simplest methods in a single place in his comprehensive volume (9, p.
15), but hastily casts them aside and replaces them with the quite use-
less " counting of individuals," a Danaid^e task of many years.

*'\\niile Hensen is going over the connting of the single constituent parts of the
plankton, he calls special attention to the fact ''that iii spite of the apparently"
desolate figures, in almost every single case certain results of general interest have
come out, though the opportunity is not offered to show thena in a comparison.

PLANKTONIC STUDIES. 635

CYCLE OF MATTER IN THE OCEAN {Stoffwcchscl des Meeres.)

The many and great questions which the mighty cycle of matter in
the ocean furnishes to biology, the questions of the source of the fun-
damental food supply, of the reciprocal trophic relations of the marine
flora and fauna, of the conditions of support of tlie bentbonic and
planktonic organisms, etc., have, within the last twenty years, since
the beginning of the epoch-making deep-sea investigation (13), been
much discussed and have received very different answers (11). Hen-
sen has also devoted considerable attention to this, and particularly
emphasizes the physiological importance of the fundamental food sup-
ply ( Urnahrung). He believes this complicated question can be solved
esi)ecially by quant it at ice determination of the fiin(Jamcntal food stippli/.

I have already shown why this method of quantitative plankton
analysis must be regarded as useless. Even assuming that it were
possible and practicable, I can not understand how it could lead to a
definite solution of this question. On the other hand, I might here
point to one side of the oceanic cycle of matter whose further pursuit
seems very profitable. The two chief sources of the "oceanic fun-
damental food supply" have already been correctly recognized by
Mobius (11), Wyville Thompson (13, 14), Murray (6), and others: First,
the vast terrigenous masses of organic and particularly vegetable
substances, which are daily brought by the rivers to the sea; sec-
ondly, the immense quantities of plant food which the marine flora
itself furnishes. Of the latter we previously had in mind chiefly the
benthonic littoral flora, the mighty forests of alga', meadows of Zostera,
etc., which grow in the coast waters. ;Only in recent times have we
learned to value the astonishing quantity of vegetable food which the
planktonic flora i^roduces, the Fiicoids of the Sargasso Sea on the one
side, the Oscillatoriw and the microscopic Diatoms and Peridinew on
the other. But the smaller groups of i^elagic Protophytes^ which I have
mentioned above, the Ghromacete^ Murracytecc, Xantliellece, Divtyochece,
etc., also play an importantTole. Tlie great importance which devolves
upon the small symbiotic XantJieUea\ has been especially emphasized
by Brandt (24), Moseley (7), and Geddes. Evidently their multiplica-
tion is extremely rapid, and if each second milliard of such Protophytes
were eaten by small animals, new milliards would take their places.
\Yli6ther or not the number of these milliards is shown to us by the
quantitative planktonic analysis seems to me wholly indifferent. More
important for the understanding of their j)hysiological importance
■would be the ascertainment of the rapidity of the increase.

The importance of these Protophytes and of the Protozoa living ujion
thein has lately been particularly described by Chun (28, pp. 10, 13). He
has also rightly emphasized the extraordinary importance which the
vertical m igration of the bathy])elagic animals has for the support of the
deep-sea animals. They are to a great extent the under workmen, who

636 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

constantly bring- the provision transports into the deep sea (15, pp. 49,
57). Thither, in addition, come the immense quantities of marine plant
and animal corpses, which daily sink into the depths and are borne
away by currents. Thither comes the constant "rain" of the corpses
of zonary Protozoa (especially Glohigerina and RafUoIaria), which
uninterruptedly pour down through all the zones of depth into the
deepest abysses, and whose shells form the most abundant sediment of
the deep sea, the calcareous Glohigerina ooze and the siliceous Radiolaria
ooze. In general, it seems to me that the daily supply of food materials
which the decaying corpses of numberless marine organisms furnish to
the others, is much more important than is commonly supposed.* How
much food would a single dead whale alone furnish?

But especially important and not sufficiently valued in this regard
it seems to me, is the trophic importance of the benthos for the plankton.
Immense quantities of littoral benthos are daily carried out into the
ocean by the currents. Here they soon disappear, since they serve as
food for the organisms of the phmkton. If one weighs all these com-
plicated reciprocal relations, he obtains without counting- a sufficient
general conception of the "cycle of the organic material in the marine
world."

COMPARATIVE AND EXACT METHODS.

The farther the two great branches of biology, namely, morphology
and physiology, have developed into higher planes during the last
decade, so much tiirther have the methods of investigation in both
sciences diverged from one anothei-. In morphology the high worth of
comparative or declarant methods has always been justly more recog-
nized, since the general phenomena of structure {e. g., in ontogeny and
system ization) have been in great part removed from exact investi-
gation, and comprise historical problems, the solution of which we can
strive for only indirectly (by way of comparative anatomy and phylo-
genetic speculation). In physiology, on the -other hand, we constantly
strive to employ the exact or mathematical methods, Avhich have the
advantage of relative accuracy and which enable us to trace back the
general phenomena, of vital activity directly to physical (particularly
to chemical) processes. Plainly it must be the endeavor of all sciences
(of morphology also) to find and retain as much as possible this exact
mode of investigation. But it is to be regretted that among most
branches of science (and particularly the biological ones) thisls not
possible, because the empirical foundations are much too incomplete and

*Heu8en values this source of food very slightly, because "only a very few aui-
malslive upon dead matter," and explains it iu this way, "that material in a state
of foul putrefaction requires a stronger digestive power than the organization of the
lower animals can produce " (9, p. 2). I must contradict both ideas. The sponges live
chiefly upon decaying organisms, as do also many Protozoa, Helminths, Crustacea, etc.

PLANKTONIC STUDIES. 637

tUe problems in hand iiiiu-U too coinplicated. >ratliematical treatment
of these does more liarm tlian good, betuiuse it tjives a deceptive sem-
l)lauce of accuracy, which in fact is not attainable.* A part of physi-
ology also embraces such subjects as are with difficulty, or even not at
all, accessible to exact definition, and to these also belong the chorology
and (ecology of the plankton.

The funda mental fault of Tlenseii^^ plankton tJieori/ in my opinion lies
in the fact that he regards a highly complicated i)roblem of biology as
a relatively simple one, that he regards its many oscillating- parts as
pro])ortlonally constant bulks, and that he believes that a knowledge
of these can be reached by the exact method of mathematical counting
and computation. This error is partly excusable from the circum-
stance that the i»hysiology of to-day, in its one-sided pursuit of exact
research, has lost sight of many general problems which are not suited
for exact special investigation. This is shown esi)ecially in the case
of the most important question of our i)resent theory of develop-
ment, the species jjroblem. The discussions which Ilensen gives
upon the nature of tlie species, u})on systemization, Darwinism, and
the descent theory, in many places in his plankton volume (pp. 19, 41,
7o, etc) are among the most peculiar v/hich the volume contains. They
deserve the special attention of the systematist. The "actual species"
is for him a physiological conception, while, as is known, all distinction
of species has hitherto been reached by morphological means.t

In my Report on the Badiolaria of H, M. S. Challenger I have at-
tempted to point out how the extremely manifold forms of this most
numerous class (739 genera and 4,.'U8 species) are on the one hand dis-
tinguished as species by morphological characters, and yet on the other
hand may be regarded as modifications of 85 family types, or as de-
scendants of 20 ancestral orders, and these again as derived from one
common simple ancestral form {Actis.saj 4, § loS). Hensen on the other
hand is of the opinion that therein is to be found "a strong opposing
proof against the independence of the species" (9, j). 100). He hopes
"to lighten the systematic difiiculties by the help of computation" (p.
75). Through his systematic plankton investigations he has reached

* A familiar and very iustrtictive t'xauii)l(i of this perverted employment of exact
methods in morphblogy is furnislied by the familiar "Mechanical theory of develop-
ment" of His, which I have examined in my anthropogeny (3d edition, p. 53, 655) as
well as in my paper upon Ziclc and Wege dcr Entwickehingsgeschichte (Jena, 1875).

t Since of late the physiological importance of the "species" concci)tiou has often
been emphasized and the " system of the futnre " by the way of '•' comparative physi-
ology " has been pointed out, it must here be considered that np to this time not
one of these systematic physiologists has given even a hint how this new system of
description of species can be practically carried out. What Hensen has said about
it (i», pp. 41, 73, 100) is just as worthless as the earlier discussions by Pol^jaeff, which
have been critically considered in my Report on the Deep-Sea Kerafcosa {Challenger,
Zoology, vol. XXXII, part 82, pp. 82-85.)

G38 EEPORT OP COMMISSIONER OF FISH AND FISHERIES.

the conviction tluit '' the more accurately tlie investigation lias been
made, so much tlie more plain becomes the distinction of species" (9,
p. 100), On the other side I, like Charles Darwin, through many years
of comparative and systematic work, have arrived at the opposite con-
clusion: " The more accurately the systematic incestUjations are made, the
greater the number of individ^tals of a S2)fcies compared^ the intenser the
study of individual variation, hy so much more impossible becomes the
distinction of actual species, so much more arbitrary the subjective Uuiits
of their extent, so much stronger the conviction of the truth of the Theory
of Descent.'^*

PLANKTOLOGICAL PROBLEMS.

The wonderful world of organic life, which fills the vast oceans, offers
a fund of very interesting subjects. Without question, it is one of the
most attractive and profitable fields of bioh)gy. If we consider that
the greater part of this field has been open to us scarcely fifty years,
and if we wonder at the new discoveries which the Challenger expedition
alone has brought to light, then we ought to count iipon a brilliant
future for planktology.

Above all we ought to cherish the hope that our German National
expedition, the first great German undertaking in the field, may
promote many x>lanktonic problems, and that the six naturalists who,
under such favorable conditions and with such important instruments,
studied the oceanic plankton for ninety-three days and in 400 hauls of
the net were able to ol)tain a rich collection of pelagic organisms, will
by their careful working up of these enrich our knowledge many fold.
However, the preliminary contributions of Hensen (22) and Brandt (23)
give us no means of passing judgment ni^on the matter now. Among
the results which the former has briefly given to the Bejlin Academy
few require consideration; but for this the difference of our general
])oint of view is to blame. Thus, for exami)le, I have attempted to
explain the remarkable "similarity to water of the pelagic fauna," the
transparency of the colorless glassy animals, in 1860, in iny General
Morphology (ii, p. 242), according to Darwin's Theory of Selection, by
natural selection of like colors (30, p. 248). Hensen, on the other hand,

* F. Heincke lias briefly, in his careful "Investigations npon' the Stickleback,"
given expression to the same conviction in the following words : " All the conclu-
sions here deduced by me are simply and solely I'ounded upon the comparison of
very many individuals of living species, or, in other words, upon the study of indi-
vidual variation. I am convinced that in essentials the study of embryology will
conlirm my theory. It will be a proof of this, that he who wishes accurately to
describe related species, and races of a species, and to study their genealogical rela-
tion to one another, must begin by comparing a very {ircat number of ifidividuals from
different, localities accurately and methodically. He will then soon see thai proofs of
the theory of descent by tliis means are found in great nmnbers at all times, if only one
docs not spare the pains to trace them out." (Ofversigt af K. V. Akad. Forh. Stock-
holm, 1889, No. 6, p. 410.) This view of Heincke is shared by every experienced ami
unbiased svetcmatist.

PLANKTONIC STUDIES. 639

regards Imiiger as the cause of this, uud the "teiuleucy to explore a
rehitively great bulk of water." In general, according to his view,
" many larger pelagic aninuils bear the outsi)oken character of unfavor-
able conditions of life, of a life of hunger."

Eegarding the appearance of many i^elagic animals in swarms, Hensen
explains " that the young do not float, but swim freely. In conse(iuence
of this, the mother animals drive tirem away, and if the larva', linally
rise to the surface the former can not enter into competition with
them" (23, p. 252). The accumulation of numbers of FlujsaHa in great
swarms stands, according to his view, in correlation with the mode ot
movement. The animals which are capable of no independent move-
ment of progression must renmiu rather closely crowded together, in
order to be able to reproduce hisexnaJUj ; those carried too far away
must perish." On the other hand it is to be noted that the Physalia is
not, as Hensen assumes, go)iochoristic, but always hermaphroditic*

The above-mentioned phenomena, the similarity to water of the pe-
lagic fauna, the periodic appearance of many pelagic organisms in
swarms, their abundant accumulation in the zoi (currents (p. 85), particu-
larly their relation to the currents, are only a few of the greater prob-
lems which planktology furnishes for human investigative energy. For
these, as for so many other fields of biology, Charles Darwin, by the
establishment of the descent theory, has opened to us the way to
a knowledge of causes. We must study the complicated reciprocal
relations of the organisms crowded together in the struggle for exist-
ence, the interaction of heredity and variation, in order to learn to
understand the life of the plankton. But in these plankton studies, as
well in physiological as in morphological questions, we nuist use that
method Avhich Johannes Miiller, the discoverer of this field, always
employed in a manner worthy of imitation: simultaneous "observation
and reflection."

* The cormi of all Physalida; are moua-cions, their cormidia monoclinic. ICach
siu"-le brancli of the racemose gonodcudron is niunostylic, and hears one female and
several male medusoids. The facts were brought out thirty -five years ago by Huxley.
(Compare my Keport ou the SiphouophoriC : Zoology of the Challenger, vol. xxviii,
pp. 347, 356.)

640 REPORT OF COMMISSIONER OF FISH AND FISHERIES.

LITERATURE.

1. Johannes ^Mullek. 1845-1855. Ucher die Larven nnd die Metamorpho.se der Echi-

noderuieii. A))liandluugen der Berliner Akadeaiie der Wis.senschaften.

2. , 1858. Ueber dieThassicollen, I'olycystiiien uud Acautboiiietreii des Mit-

telmeeres. Idem.

3. Ernst H.eckel, 1862. Monographie der Kadiolarieu. Uebersicht der Verbrei-

tung, i)p. 166-193.

4. , 1887. Report ou the Radiolaria collected by II. M. S. Challeuger dtiriug

the year.s 1873-187G. Chronological .section. §iji 226-240. (Deutsch' in der
"Allgemeineu Naturgeschichte der Radiolarieu." 1887, jip. 123-137.)

5. John Murray, 1876. Preliminary report ou some surface organisms examined

on board II. M. S. Challenger, and their relation to ocean deposits.
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6. , 1885. Narrativeof crui.se of H. M. S. Challenger, with a general account

of the scientific i-esults of the expedition (1873-1876), vol. i, li.

7. H. N. MOSELEY, 1882. Pelagic Life. Address at the Southampton Meet. Brit.

Assoc, Nature, vol. xxvi, No. 675, p. 559.

8. Gaetano Chiercuia, 1885. C(dlezi(mi per Stud i di Scienze Natural i, fa tteuel

Viaggio intorno al moudo dalla R. corvetta Vettor Pisani. Anni 1882-
1885.

9. Victor Hensex, 1887. Ueber die Bestimmung des Planktons, oder des im Meere

treibendcn Materials an Pflanzeu und Thieren. Y. Bericht der Commis-
sion zur wissensch. Unters. der Deutschen Meere in Kiel.

10. K. MoBius, 1887. Systematische Darstellung der Thiere des Plankton in der

westl. Ostsee uud auf einer Fahrfc von Kiel in den Atlantischeu Ocean
bis jenseit der Hebriden. (V. Idem).

11. , 1871. Wo kommt die Nahrung fiir die Tiefseethiere her? Zeitsch. fiir

■wissensch. ZooL, 21. Bd., p. 294.

12. Th. Fuchs, 1882. Ueber die pelagische Flora uud Fauna. Verhaudl. d. k. k.

Geolog. Reichsanstalt iu Wien, 4. Febr., 1882, pp. 49-.55.

13. Wyville Thoaipson, 1873. The Depths of the Sea. An account of the general

results of the dredging cruises of H. M. S. S. Porcupine and Lightniug.

14. , 1877. The Atlantic. A preliminary account of the general results of the

exploring voyage of H. M. S. Challenger.

15. Carl Chi'X, 1888. Die pelagische Thierwelt in grosseren Meerestiefen uud ihre

Beziehungeu zu der Oljerfliichen-Fauna. Bibliotheca zoologica. Heft i.

16. , 1889. Bericht iiber eiue nach den Canarischen Inseln im Winter 1887-88

ausgefiihrte Reise. Sitzungsberichte der Berliner Akadeniie der Wiss.,
p. 519.

17. Carl Vogt, 1848. Ocean uud Mittelmeer, p. 303.

18. Richard Greeff, 1868. Reise nach deu Canarischen luselu. " Die Meeresstro-

mungen als Thierstrassen," pp. 307-309.

19. R. ScriiMiDTLEiN, 1879. Vergleichende Uebersicht iiber das Ersclieineu grosserer

pelagischer Thiere wiihreud der Jahre 1875-1877. Mittheil der zoolog.
Station Neapel, Bd i, p. 119.

20. Edward Gkaekee, 1881-88. Uebersicht der Seethier-Fauna des Golfes von

Triest, nebst Notizeu iiber Vorkommen, Lebensweise, Erscheinungs- und
Fortpflauzungs-Zeit. Arbeiten d. zool. Station Triest.

21. E. i>u Bo*s-Reymond, 1890. Bericht iiber die Huraboldt-Stiftung und die

Kieler Plankton-Expedition des National. Sitzungslierichte der Berliner
Akademie d. Wissensch. vom 23. Januar 1890, pp. 83-87.

I'LANKTONIC STUDIES. 641

22. Victor Hensex, 18il0. P^inige Ergelinisse der Plankton-Expeditiou der Hiim-

boldt-Stiftiing. Sitzniigsberichte der Berliner Akaderaie der Wisseu-
schaffcen voin 13. Miirz 1890, pp. 243-253.

23. K.\RL Bkandt, 1889. Ueber die biologischen irntersuchungen der Plankton-Ex-

jieditiou. Verhandl. der GeselLschaft fiir Erdkimde zu Berlin, vom 7.
Dec. 1889, p. 515.

24. , 1885. Die coloniebilden<leii Radiolarien (Sphaerotsen) des (4olfes vou

Neapel.

25. Ernst H.eckel, 1882. Indische Reisebriefe. II. Aufl.

26. Karl Mobius, 1880. Beitriige znr Meeres-Fauna der Insel Mauritius iin<l der

Seychellen, 1880.

27. Carl Chun, 1886. Ueber die geographiscbe Verbreituug der pelagiscblebeuden

Seethiere. Zoolog. Auzeiger, Nr. 214, 215.

28. ,1890. DiepelagischoThiecwelt ingrosseiiTiefen. Verbandl. d. Gesellsch.

deutscli. Naturf. u. Aerzte, Bremen, 1890.

29. Ernst H^CKEL, 1879. Monogrnphie derMednsen. I. Bd. Das System der Medu-

sen, II. Bd. Der Orgauismus der Meduseu.

30. , 1889. Natiirlicbe Schopfimgsgescbichte. Aclite AuJiage.

H. Mis. 113 41

New York Botanica) Garden Library

Haeckel Ernst Hein/Planktonic studies:

gen

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