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Cleve 1900b

KONGL. SVENSKA VETENSKAPS-AKADEMIENS HANDLINGAR.

Bandet

32.

N:o 8

THE PLANKTON
OF

THE NOETH

SEA,

THE ENGLISH CHANNEL, AND THE SKAGERAK
IN

1898
BY


P. T.

COMMONICATED TO THE

R.

CLEVE

SWEDISH ACADEMY OF SCIENCES OCTOBER

STOCKHOLM
Kl*IGr..

BOKTRYOKEEIET. P.
1900

A.

NORSTEDT & SOnER

11,

1899


/


F

or

the

hydrographical researches of Pettersson and Ekman,

'

the North Sea was ex-




plored four times during the year 1898, viz.: in March, June, July
August and November.
At the same time samples of water were taken for chemical analysis and of plankton
for microscopical examination.
At the biological stations at Plymouth and Helder samples
were collected almost every week during the whole year and also at S:t Vaast la Hogue
from June onwards. For this valuable assistance I beg to tender the directors of the said
stations, Mr. E. J. Allen, Dr. P. P. C. Hoek and Mr. Eugene Malard my best thanks.

Again,

at

the

expense

of

the

Fishery Association of Gothenburg, samples of plankton

were collected almost every week at M^seskar,
with

regularity,

less

Vinga

west coast of Sweden, and, though

to Vadero.

The North Sea

1.

east

off the

both in the open Skagerak and along the Swedish west coast from

in

March

1898.

The prevailing plankton type is the choeto-plankton, which extends from the British
coast, between the Firth of Tay and Newcastle, to the south-west of Norway and the

west of the Danish Peninsula, to about 55°30'N.,

i.

e.

above the 100 metre plateau.

It

Dogger Bank, above the depression of the bottom at this place.
The chasto-plankton region approximately coincides with the southern part of the
region of the Avater with 35 p. mille salinity, as marked on the hydrographical map of
Pettersson and Ekman.^ The northern part of the North Sea, or above the 200 metre
also occurred south of the

was poor in plankton or almost

plateau,

sterile,

containing Calanus jinmarchicus sparingly.

Above

the great depth between the 200 metre plateau and the west coast of

water

was

number

in

plankton,

containing

however some rare specimens of a

of interesting radiolarians, Ceratium arcticum and Coscinodiscus oculus iridis.

In
plateau,

extremely poor

Norway the

the

the

spring
area

of

of

1897,

this

when

chasto-plankton also prevailed above the 100 metre

plankton type was bordered by a band containing arctic and

northern forms.
This was not the case in 1898. The southern part of the chseto-region
from Newcastle to Skagen, in 1898 contained Coscinodiscus concinnus more or less abundantly; and above the edge of the 50 metre plateau as well as above the Fisher Bank
Rhizosolenia styliformis was met with, more or less sparingly to about 1° 30 E. and also
above the depression south of the Dogger Bank.
1

Bih.

till

K. Sv. Vet.-Akad. Handl.

Vol.

XXV,

II,

N:o

l.

1899.


4

THE PLANKTON OF THE NOETH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

CLEVE.

p. T.

As no samples of plankton have been
is

collected above the 50 metre plateau nothing

known about the plankton of the southei'n North Sea.
The tripos-plankton, prevalent during the past summer, autumn, and winter above the

100 metre plateau, occurred in March 1898 chiefly in the eastern part of the North Sea
and west of the Danish Peninsula, and there more or less intermingled with chseto and
northern neritic plankton: the last-named was present during the winter in the Skagerak.
Origin of the chseto-planlLtoii.
chaito-plankton, and
constitutes

the

it

I

will there be

principal

propose in another paper to treat of the origin of the

shown that the diatom,

mass of the chteto-plankton, belongs

American

Chcetoceros decipiens, which
to the west Atlantic area,

and that it is thence conveyed by under-currents across the Atlantic towards the Azores and the European coast.
In the month of November, when the superficial strata of the Atlantic are driven away
or rather become mixed with those beneath
the species above-mentioned appears at
many points between the Newfoundland Banks, the Azores and the mouth of the English
Channel.
It multiplies during the winter and is conveyed in the spring towards Iceland,
the Faroe Channel and into the North Sea, whence it spreads towards Spitzbergen.
Other species of the west Atlantic area, which accompany Chcetoceros decipiens across the
Atlantic, such as Calanus finmarchicus, Tlialassiothrix longissima and Ceratium arcticum,
die sooner or later in water of so high a salinity as 35 p. m.
or

to

the cold southwards current along the



coast,



Some

species of the temperate Atlantic, such as Oncoea minuta, 0. conifera, Oithona

plumifera, 0. similis,

Collozoum inerme, frequently follow the chteto-plankton on

its

way

towards the north.

accompany the Chaetoceros decipiens into the North Sea. The following species occurred in the North Sea over the whole cha3to area or at least in its
western parts.
Some of them are of southern origin, or belong essentially to the styli
and desmo types, others come from northern regions and from Scotland.
Species

which

Species of southern origin

Species of northern origin

Acartia Clausii,

Calanus finmarchicus,

Microsetella atlantica,

Metridia hibernica,

Oithona

Pseudocalanus elongatus,

similis,

Sagitta bipunctata,

Temora

longicornis,

Globigerina bulloides,

Cyttarocylis denticidata,

Acanthometron quadrifolium,

Gonyaulax spinifera,

Halosphcera

Chcetoceros borealis var. Brightwellii,

viridis.

Coscinodiscus oculus

iridis,

C. polychordus,

Rhizosolenia semispina.

Biddulphia
coasts of Scotland.

mohilensis

and

Streptotheca Thamesis

come

in

all

probability from the


BAND

KOKGL. SV. VET. AKADEMIENS HANDLINGAK.

Among
whole cha'to
as

far

to

the species inontioned above, Halosphcera
area.

is

Norway

north as beyond the 63rd degree of latitude and

the

N:0

5

8.

not equally distributed over the

could be traced from the south west of

It

32.

to

Newcastle and

0° long.; also

from the

south of Norway to Skagen and into Skagerak.

2.

The chfeto-plankton

The North Sea
of

has

spring

the

in

June 1898.

almost completely disappeared, some few
(at 56° N.) and west of Norway (61°N.

remnants lingering west of the Danish Peninsula
2° 30' E.).

Its

place

time of the year.

now occupied by

is
is

It

tripos-plankton, which

more richly represented

is

the ruling type at this

in the eastern than in the western parts

of the area.

To
forms,

the east of the British coast the tripos-plankton

such as Ceratium tripos

north of the

German

longipes,

v.

and

at the

is

mixed with northern

neritic

west of the Danish Peninsula and

coast with Peridinium depressum.

The southern

part of the North Sea contains, north of the continental coast, southern
mixed with styli-plankton.
The hydrographical map for June 1898 by Ekman and Pettersson shows in the
No
north between Norway and Scotland a tongue of 35 p. m. water, temp. 9° to 10°.
sample
from
of
plankton
this
have
been
examined
me.
One
samples
from
area
by
61° 50' N. 2° 30' E., which may be assumed to be from that kind of water, contained triposneritic plankton,

plankton, but not abundantly.

The bulk of tripos-plankton

in

my

samples had come from the northern or eastern

part of the region coloured as containing 34 p. m. water.

The hydrographical map

in

its

south western corner shows an area of 35 p. m.

water, indicating that a flow of Atlantic water enters into the North Sea

from the south.

This fact accounts for the considerable development of the southern neritic plankton above
the 50 metre plateau.

Species

which seem to come into the North Sea round the north of Scotland.

stated above there are
to

Newcastle,

among

the plankton,

such as Ceratium longipes.

some northern

Calanus jinmarchicus,

species east of the Scotch coast

But, on the other hand, there are also in the

western region of the North Sea some southern species.

Northern forms

As

I

name

the following:

Southern forms

Acartia Clausii,

Evadne Nordmannii,

Lahidocera Wollastonii,

Cyttarocylis gigantea.

Evadne

spinifera,

Ceratium macroceros,
Lauderia annulata,
Peridinium divergens.


6

fact

In

THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

CLEVE.

p. T.

the tripos-plankton seems

contain a certain

amount of northern

Two

species,

remarkable

among

the prevailing mass of southern origin to

species.

Halosphcera and Microsetella, have disappeared from the

North Sea since the spring.
Species

English Channel into

becomes

The flow of Atlantic water through the
the North Sea had already taken place before the month of June. This

the southern neritic plankton.

in

apparent

we

if

consider the plankton collected at Helder.

PhcBocystis Pouchetii

was very abundant there in April and the beginning of May. It was seen in the beginning of April at Plymouth. When that species disappeared from Helder (before the 12th
of May) a number of southern forms, such as Noctiluca, Ceratulina Bergonii, Eucampia
zodiacus, Guinardia flaccida and Rhizosolenia Stolterfothii began to develop.
In June we find that the typical Atlantic species Rhizosolenia styliformis had spread
over the whole area from Holland to Skagen, thus indicating that Atlantic water had
arrived from the E. Channel before June and that its plankton had been dispersed through
the water with low salinity off the continental coast. The following species of the southern
normally in the open Atlantic:

neritic plankton occur

Acurtia Clausii,

Diplopsalis lenticula,

Paracalanus parvus,

Rhizosolenia styliformis.

The following

species live, as a rule, above the coast banks, or only occur excep-

tionally in the ocean:

Animals.

Plants.

Acartia longiremis,

Chcetoceros densus,

Centropages hamatus,

C.

Temora longicornis,
Podon Leuckartii,

Eucampia

didymus,

C. Villei,

zodiacus,

Guinardia flaccida,
Lauderia annulata,

Noctiluca miliaris.

Rhizosolenia Shrubsolei,

Rh.

Stolterfothii,

Stephanopyxis turgida.

Of

these species the Noctiluca

the most important.

It seems to be confined to
North Sea. I have not seen a
single specimen in any of the thousand plankton-samples from the Atlantic, which I have

the

English

Channel

and

the

is

continental

coasts of the

examined.

3.

But few
eastern

and

The North Sea

plankton-samples

southern

parts

insight into the state of the

were

in

July— August 1898.

collected

of the North Sea,

North

Sea.

at this period

and those only from the

so that they cannot afford us a complete


BAND

KONGL. SV. VET. AKADEMIENS HANDLINGAR.

The plankton-type which

prevails in the east,

e.

i.

32.

7

N:0 8.

from Skagen

to 4° E.

and 55°

N.,

the tripos-plankton.
is
From the 55th degree to the English Channel southern neritic
plankton is the ruling kind. The areas of the water with 33 to 34 p. m. salinity on the

map by Petteesson and Ekman

hydrographical
least as the
is

55th degree of latitude, but south of

also the case with the area with

Some

contain chiefly tripos-plankton, as far at

34 to 35

p.

there

it

m.

southern neritic plankton, which

is

salinity,

north of the coast of Belgium.

species from the preceding period, such as Oithona similis, Paracalanus parvus,

Pseudocalanus elongatus, Ceratium rtiacruceros and Guinardia flaccida have evidently increased
in abundancy, others, such as
styliformis have decreased.

4.

Evadne Nordmannii, E. spinifera and especially Rhizosolenia
Podon intermedius and Oikopleura dioica begin to develop.

The North

Sea,

The prevailing plankton type

is

November— December

1898.

the tripos-plankton, which extends from the north-

of Scotland to the south west of Norway and to Newcastle.
From there the limit
can be traced to 53° N. 4° E. and from this point to Skagen. The tripos area corresponds
east

p. m. water on the hydrographical map by Ekman
and Pettersson.
As the salinity of the tripos region is higher now than it was in
July August, it is evident that a considerable amount of Atlantic water has entered
the North Sea, which also becomes apparent when the composition of the plankton is

thus on the whole with the area of 35



considered in details.

We
occurs

100

same

note

first

now round

metre

that

the

Atlantic organism Halosphcera, not seen since the spring,

Scotland, across the North Sea to

plateau.

The purely

Another remarkable

distribution.

Norway and Skagen,

i.

e.

above the

Atlantic species Rhizosolenia styliformis has about the

feature

in

the

plankton

is

the abundance of

Coscinodiscus concinnus and Biddulphia mohilensis, which occur in the E. Channel and spread

thence to Skagen,
Species

i.

e.

above the 50 metre plateau.

of the tripos region

in November.

The

tripos plankton contains the usual

forms, such as Ceratium tripos, C. macroceros (which has considerably increased in frequency),

furea and C. fusus; but there are besides a number of other forms, partly from the
southern and partly from the northern Atlantic, as follows:
C.

Northern

Southern species.

Centropages typicus

species.

Parathemisto oblivia,

c,

Microsetella atlantica,

Calanus finmarchicus,

Oithona plumifera

Metridia hibernica

rr,

Paracalanus parvus

Pseudocalanus elongatus,

cc,

Acanthochiasma fusiforme,
Acanthometron quadrifoUurn,
Gazelletta

hexanema

(r

the Orkneys),

Pyrophacus horologium.

r,

south of

Limacina

balea,

Plectophora arachnoides.


8

in

l^ T.

CLEVE.

THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

The Evadne Nordmannii, E. spinifera, Podon intermedius and P. Leuckarti abundant
the preceding periods, have now disappeared.

The southern neritic plankton. As characterizing the plankton above the 50 metre
we note now Coscinodiscus concmnus and Biddulphia mohilensis, but also a
considerable number of other species, most of which have been found from the English
Channel to Skagen. Among these species we note the following:
plateau

Anitaals.

Proto pedata, in the

Acartia

II.

Channel in August,

at

Skagen

in

November.

bifilosa.

Corycceus anglicus.

Euterpe acutifrons, at Plymouth and Helder in September, from the E. Channel to Skagen
in

Temora

November.
longicornis.

Sagitta bipunctata, very

common above

the whole 50 metre plateau.

Tintinnopsis campanula, from the English Channel to Skagen.
Plants.

Bellerochea malleus.
Chcetoceros anastomosans.

Ditylum Brightwellii, abundant from the E. Channel

to Skagen.

Guinardia flaccida.
Lithodesmium undulatum, observed from the end of September onwards.
RMzosolenia rohusta, from the English Channel to the mouth of the Schelde.
R. Stolterfothii, from the E. Channel to Skagen, where it appeared in the first few days of October.
Streptotheca Thamesis,

from the

E.

Channel to 55° N. 5° 30 E.

The Skagerak
The seasonal changes

in

the

in

1898.

plankton will be examined for certain periods with

reference to the prevailing plankton-types.

Period

The prevailing plankton
neritic plankton,

is

I.

—February.

January

tripos-plankton, but

which disappear, and more or

is

less

mixed with remnants of southern
rarely so with forms which belong to

partly

the northern neritic plankton and increase in frequency in the next period.

Besides the most commom dinofiagellates of the tripos type, we note some more
remarkable species such as Halosphcera, which was more or less common in the whole of the
Skagerak, and Arachnactis alhida, not formerly found in the Skagerak. The last-named species

was seen during the last few days of January and the first few days of February both in the open
Skagerak and along the coast from Vinga to M&seskar. This pelagic actinia is known from


K0K6L. SV. VET. AEADBMIENS HANDLINGAE.
Flora in

Norway

(winter-time), from 56° 35' N.

BAND

32.

9

N:0 8.

20°19'W. (25th of September,

C.

Vogt),

and from 60° N. 7° W. (the 29th of March 1893, Vanhoffen). In the year 1898 it was
found by Ostenfeld in a sample from 60°12'N. 3° 53' W. (21th of August) and from
I
found it in a collection from 60°10'N.
59°59'N 5°56'W. (14th of September).
3° 12'W. (the 6th of September 1898) and from 62°12'N. 0° 37' E. (the 8th of September
The abundancy and sudden appearance of this species over a wide area of the
1899).
Skagerak in 1898 proves better than anything else that the plankton of the Skagerak is
worthy of note that another species, not formerly observed in
the Skagerak, was found at the same time viz. Dictyocysta elegans, a species that is not
rare in the temperate Atlantic nor in the FarOe Channel.
of

foreign

origin.

It

is

Period

II.

February

—March

and April.

and northern species {Si,
They had already appeared in the previous period, but did not reach such a
T, Ns).
In connection with these northern forms Chaitoceros
considerable development as now.
decipiens also appears, a species which, as stated above, was the dominant one in the
North Sea in March.
The organisms which characterize this period are principally diatoms, animals and
dinoflagellates being as a rule rare.
The diatoms belong to the boreal and arctic regions
Most of the southern species, which were abundant in the autumn,
of the Atlantic.
have disappeared or are scarce, among them Halosphcera.
The most decided arctic species, such as Thalassiosira ISfordenshidldii, Chcetoceros socialis, continue during February only and have already disappeared by the middle of March.
Others, such as Chcetoceros debilis, C. diadema, Nitzschia seriata, continue during April. The
most long-lived ones, such as Tlialassiotlirix Frauenfeldii, Leptocylindrus danicus, Rliizosolenia
semispina, Chcetoceros constrictus, C. contortus, C. kiemalis do not disappear before the end
of May or in June, by which time a number of southern species have become frequent.
The most common diatoms during this period are the following:
This

period

is

characterized

by the abundance of

Chcetoceros constrictus,

Chcetoceros socialis,

C. contortus,

Coscinodiscus oculus iridis,

C. debilis,

Thalassiosira gravida,

C. decipiens,

T.

C. diadema,

T. Frauenfeldii.

Period III.
This period

arctic

is

May and

Nordenshioldii,

June.

remarkable for the abundance of euryhaline species, such as the following:
Animals.

Plants.

* Acartia longiremis,
* Centropages hamatus,
K. Sv. Vet. Akad. Handl.

Band

32.

N:o

8.

Cerataulina Bergonii,
* 'Chcetoceros danicus,
3


10

p. T.

CLEVE. THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL,
*

Temora longicornis,
* Evadne Nordmannii,
* Podon Leuckartii.

The

sign * denotes that species

AND THE SKAGEEAK.

Rhizosolenia delicatula,

R. gracillima.

marked thus occur

as far into the Baltic as at least

to Aland.

Whether

these forms are indigenous in the Baltic or enter there from the Cattegatt

means of undercurrents, cannot as yet be decided,
in the Baltic and along the west coast of Sweden.
through the E. Channel, but Rhizosolenia

by

as they usually appear simultaneously

Cerataulina Bergonii comes no doubt

gracillima., although

common

of the Atlantic, does not occur to any extent in the North Sea.

in the styli-plankton

The new

species Rh. deli-

catula occurs in the southern part of the North Sea.
In

the

Skagerak, at some distance from the coast, tripos-plankton occurs from the

middle of May onwards, associated with some more saline or Atlantic species such as Acartia
Clausii,

Calanus finmarchicus and Oithona similis or euryhaline ones such as Pseudocalanus
Evadne spinifera; these become abundant along the coast during the next period.

elongatus and

July to the end of August.

Period IV.

The

prevailing plankton type

remaining from the

Among

last period,

the organisms

is

now

tripos-plankton, but with an admixture of species

and of southern

we note

neritic plankton.

the following:

Animals.

Plants.

Oihopleura dioica,

Ceratium

tripos,

Acartia Clausii,

C. macroceros,

Calanus finmarchicus,
Oithona similis.

Rhizosolenia gracillima.

Paracalanus parvus,

Evadne

spinifera,

Sagitta bipunctata.

Period V.

From

the end of August to the end of October.

The tripos-plankton continues

as before, but

now

the didymus-plankton appears with

didymus and C Schilttii, all at the same time
and abundantly. From the beginning of September Centropages typicus was common and
together with this copepod appeared also Anomalocera Patersonii, Labidoceru Wollastonii,
Acanthometron quadrifolium and Limacina balea, all probably, with the exception perhaps
of Labidocera, from the North of Scotland.
the three species Chcetoceros curvisetus, C.

Period VI.

The

tripos-plankton

From

the end of October to the end of December.

remains

throughout,

but in this period Halosphcera appears.
of northern forms begin to develop, and the southern species, formerly so abundant,
decrease in frequency and die sooner or later.
The currents from the south still continue

A number


BAND

KONGL. 8V. VET. AKADEMIENS HANDLINGAE.

convey into

to

the

forms

Skagerak such

Ditylum Brightwellii,
not rare in December.

Chcetoceros danicus,

as

Guinardia flaccida and Proto pedata, which latter is
The northern forms are principally diatoms, such

Chcetoceros similis,

C. constrictus,

C. teres,

C. contortus,

Coscinodiscus polychordus,

C. dehilis,

Rhizosolenia setigera,

diadema,

C.

laciniosus,

SkeUtonema costatum,
Thalassiosira gelatinosa,
Thalassiothrix Frauenfeldii.

C. scolopendra,

The

seasonal

similar to those in

as:

Chcetoceros horealis,

C.

11

N:0 8.

32.

changes in the plankton of the Skagerak were in 1898 on

the

whole

1895, 1896 and 1897.

January

Tp, Ns,

February— April

Si,

May, June
August

Tp,

Nm a,^
Nm

July,

September, October

November, December

...
.

.

Tp,

Nh,

Ns, (T), C,
cc,

Nm,

Tp, Ns,

Nm.

Seasonal distribution of the plankton-organisms
North Sea and the Skagerak.

in

the

Ascidiacea.
Fritillaria borealis

— January rare in the Skagerak. March rare at M^seskar.
— January: rare in the Skagerak and M&seskar. March:

Lohm.

Oikopleura dioica Fol.

:

:

at

North Sea at 57°18'N. 8° 27' E. and 5.J° 43' N. 7°29'E. June: sparingly in the
Skagerak. July, August: from the E. Channel to west of Skagen, common in the Skagerak
and along the coast, remains more or less abundant to November.
in

the

Amphipoda.
Parathemisto oWivia Keoyeii.

SW.

of
^

Norway
I



Sejjtember: rare in the Skagerak.

November: rare

(58° 12'N. 5° 30' E.).

propose to designate as

Nm a

the plankton in which Rhizosolenia gracillima occurs abundantly.


12

p. T.

CLEVE. THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL,

AND THE SKAGERAK.



January and February (31. 1 and 1. II): rare in the Skagerak.
August: from the E. Channel to Helder. November: north of Holland and west of the
Danish Peninsula, west coast of Sweden, where it was abundant in December.
Proto pedata Leach.

Cladocera.



May: at M&seskar. June: common in the North
from W. Norway to 0° 38' E. and- to Skagen, common in

Evjidne Nordmannii Loven.

between

56° and

Skagerak, where

58° N.,

Along the coast

remains until August.

it

Plymouth from July

it

remains in October.

Sea,

the

Rare

at

to September.



Appears in June abundantly in the region between
Firth of Tay and W. Norway (Stadt) and Skagen, in the Skagerack and along the coast.
In the
In July, August it was found from Skagen to the west of the Danish peninsula.
Skagerak it remains until October and along the coast until the middle of November. At
E.

spinlfera

Plymouth

P.

E.

Muller.

rare in August.

Podon Leuckarti G. 0. Sars.
the Skagerak.

P. intermedius Lilljeb.

Peninsula,



June: rare west of the Danish Peninsula and in

July: rare at the entrance to the Skagerak.

from the

the Skagerak, where

mouth
it



July, August:

more or

abundant west of the Danish
Plymouth, more or less rare in

less

of Elbe to Skagen, rare at

remains until October, or along the coast to the end of that month.

P. pelyphemoides Leach.



Rare

in

August and September

at Helder.

Copepoda.
Acartia bifllosa Giesbr.



November: from the

Channel to Holland and the west

E.

of Skagen.



The whole year in the North Sea, in the Skagerak and at
January to April or May: rare at Plymouth and in the Skagerak. March:
in the North Sea, together with Halosphcera, common between the Shetlands and Norway.
West and south of Norway.
South of the Dogger bank. East of Newcastle. June:
British east coast from Firth of Tay to Newcastle, common. From Holland to Heligoland.
Plymouth (maximum from the middle of May to the beginning of September). St. Vaast
A. Clausii Giesbr.

Plymouth.

la

Hogue not rare. In the Skagerak not rare from
November (maximum from the middle

the end of

May

or beginning of June to

October,

of August to the end of that month).
from the Channel to Skagen and above the Fisher Bank.
November: the
E. Channel, Helder, Skagen to the south of Norway.
South of the Orkneys.

July,

August:

A.

longiremis Lilljeb.

Newcastle,

in

June



abundantly

In the
in

the

North Sea
middle

of

in

March SW.

the

of Norway and E. of
North Sea, 57° N. 3° E, and at


BAND

KONGL. SV. VET. AKADEMIENS HANDLINGAR.
54° N. 5° E.

November: not

mon

Dutch

July:
seen.

In

and along the Danish coast

coast

Skagerak common

— March:

Anomalocera Patersonii Templ.
30.

1

less

at M&seskar;

Stavanger
of

to Skagen, not

more

or

common.
less com-

June, July).

Sparingly west of the Clyde.

— Skagerak:

Along the coast: rare the
the beginning of November, rare to common.

rare in July and in the beginning of October.

from July

to

Calanus flmnarchicus Gunn.

S.

(maximum

13

N:0 8.

in the beginning of June,

in July, along the coast the whole year

more or

32.

and

the



A.

Fisher Bank, Firth

of the Dogger Bank.

June: sparingly

North Sea: ilfarc/i scattered on the space between
of Tay and Newcastle, also above the depression
between Norway and the Shetlands, W. of Firth

Tay and Newcastle, N. of

the Dutch coast, S. of Norway.
July, Arigust: sparingly
November: more or less abundant from the Hebrides and
the south of Norway, in the company of Halosphcera.
Very rare off the

N. of Holland and at Skagen.
the Orkneys to

continental coast.
B.

Plymouth:

rare from the end of

May

to the middle of

July and from the end

of September to the middle of November.
C.

Skagerak: common

in the

November. Along the coast: rare
August to December.
Candace pectiuata Brady.

in



middle oi June, more or less rare
January and February, more or

North Sea:

rare in

March

until the middle of
less

common from

east of Firth of

Tay; very

rare at Skagen in November.

Centropages hamatus Lilljeb,

W.

of Hanstholm.



North Sea: March

sparingly

SW.

of

Norway and

June: not rare on the Dutch coast, together with Noctiluca, not rare

Dogger and Fisher Banks. July: not rare N. of the Dutch coast
Helder: rare in April and from
and above the Fisher Bank. November: the Channel.
Vaast
la
Hogue:
rare
in
June.
Skagerak: from March to
August to October.
St.
November; along the coast from March to November, December, maximum in June and
November.
on

the

north

of the







Kroyer.
61°50'N. 2°30'E.

North Sea: March:



57°21'N. 2°27'E. June:
July: rare at 57°21'N.
9' E. and 57° 40' N. 10° E.
Norare at
southern
NE.
end
of
Scotland
to
Norway,
following
abundant
from
the
Calanus
vember:
/inmarchicus, very rare in the E. Channel, rare at Helder in December.
Plymouth: the whole year, maximum from May to November.
B.
Skagerak: rare in January (30. I), more or less abundant from October to the
C.
of
November. Along the coast: rai^e in January and June, more or less abundant
middle
from the middle of July to December, maximum in September and October.
C. typicus

A.

rare at





North Sea: March: rare
July: very rare W. of the Danish

Corycaeus anglicus Lubbock.

A.

in the E.

Peninsula.
June: not seen.
the
south
coast
of
North
Sea
Skagen.
along
the
to
Channel
from the E.
at

Hanstholm.

Channel and

November:


14

p. T.

THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

CLEVE.

Plymouth:

B.

the whole

almost

year,

maximum from

the end of September to

the middle of December.

Skagerak:

C.

common

March;

Labidocera

Skagerak:

in

WoUastonii

57°21'N. 2°27'E.

Skagerak:

holm.



Lubb.

December.

to

Plymouth

E.

Channel:

at

Plymouth, St Vaast and Helder.

rare at

in

January to

Rare in the North Sea, June, at 56° N, 2° E.

rare in June; along the coast not rare in September,



Brady & Robts.

Metridia hibernica
to



The
September— December

acutifrons Giesbr.

Euterpe

from June

rare in January, February,

October.

from Firth of Tay
iVoum^er; not rare SW. of Hanst-

North Sea: March:

June: rare at 56°26'N. 4°13'E.

rare

in January, June,

Along the coast rare

rare in January and in July.

not rare in November, December.
Microsetella atlantica

Firth of Tay,

above

more or

depression

the

less
S.

Plymouth

W.

rare in February.

at

Skagerak:



56°irN. 2°31'E.

0. similis

Glaus.



east of

A.

Also

August: rare SW. of Norway and W. of

of the Danish Peninsula to Skagen.

Oithona plumifera Baird.

November:

North Sea: March: abundant

sparingly scattered through the chaito-region to Skagen.

of the Dogger Bank.

November: rare

Jutland.



Brady & Robts.

of Newcastle.

E.



rare in July and in October.

March: rare N. of the Shetlands.

Skagerak: very

At 61°32'N. 2°31'E.

rare in January.

North Sea: March: abundant between

the Shetlands and

Norway, E. of Firth of Tay, more or less sparingly scattered in the whole chseto-region.
Not rare W. of Denmark at 55° N. June: common between the Shetlands and Norway,
more or less common from the Firth of Tay to Skagen. Common at 54° 25' N. 5° 37' E.
July, August: more or less abundant above the Fisher Bank and from the E. Channel to
Skagen. November: the same distribution, but rarer.
B. The E. Channel: Plymouth the
whole year. St Vaast in November.
Helder from August to November.
C. Skagerak:
the whole year, rare June, very common from July to December.





Paracalamis parvus

Claus.





North Sea: March:

A.

June: rare from
the E. Channel to the north of Holland. July, August: abundant from the E. Channel along
the south coast to the Fisher Bank and Skagen. November: as before, but also from the
north of Scotland to the south of Norway.
B. Plymouth: the whole year, maximum
from August to December. C. Skagerak: very rare in January, February, abundant from
not seen.



July to October, November.
Pseudocalanus elongatus Boeck.

through

the

depression

common

S.

chceto-region,

from

S.

A.

of

North Sea: March: more

Tay and Newcastle

or less abundant

to Skagen, also

above the
June: decidedly rarer, chiefly on the 50 metre plateau,
July, August: above the Fisher Bank, common above the

of the Dogger Bank.

near the E. Channel.

depression

Firth



of the

Dogger Bank.

November: continues above the 50 metre plateau.

From




BAND

KONGL. SV. VET. AKADEMIENS HANDLINGAR.
Scotland to the south of

Norway and Skagen,

company

in the

32.

oi Halosphcera.

Channel: at Plymouth from January to August, as a rule rare,
C. Skagerak: the whole year, maximum from June to October.
Temora



longicornis 0. F. Mull.

North

A.

— B.

The

E.

at St Vaast in June.

March; more or

Sea.

15

N:0 8.

less

abundant

from Scotland to the Skagerak, above the Fisher Bank and the
57° to
June, July, August: from 0°38'E. along 56°
Skagerak.
South part of the North Sea to the E. Channel. November: abundant from the
B. The E. Channel: at Plymouth
S. of Norway to the Fisher Bank. Southern North Sea.
from February to November, maximum from April to the middle of May. St. Vaast in
through the

depression

S.

chceto-region,



of the Dogger Bank.



June and rare in November,
from June to October.
Temorella

affinis

Poppe.

December.





Skagerak: the whole

C.

At Maseskar

rare

at

tho

end

of

year,

maximum

May, common

in

November.

Chaetognata.

&



North Sea.

March: through the chcetoregion, between Firth of Tay, Newcastle and the Fisher Bank.
June: rare above the
Fisher Bank. July: rare above the Fisher Bank and in the E. Channel.
November: very
abundant above the Fisher Bank, on the edge of which it seems to have its optimum;
thence to the south of Norway. Above the whole 50 metre plateau. B. The E. Channel:
more or less common at Plymouth from September to November.
C. The Skagerak: the
whole year, abundant from June to November, or, along the coast, to the end of the year.
bipunctata

Sagitta

Quoi

Gaim.

A.



Pteropoda.



November

B.



North Sea: November: W.
The Skagerak: very common in September, rare

Limacina balea Mollee.
3° E.

(30.

A.

of Hanstholm to 57° N.
in October,

common

in

XL).

Zoantharia.
Arachnachtis albida M. Saks.



See page

8.

Ciliata.

L

— The

between the new,
induced
me to retain the old name.
nearly related, species of Brandt and Ostenfeld has
All the new species are nearly connected and have the same distribution, or belong exCyttarocylis

denticulata Ehb.

s.

difficulty of distinguishing

and northern Atlantic and to the Arctic Sea.
rare on some spots in the chgeto-region. June: common between
The Skagerak: rare from January to May; rare in December.
the Shetlands and Norway.
clusively to the western

North Sea: March:




16

CLEVE. THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

p. T.

Daday.
September



Cyttarocylis Claparedii v.

given in

1.

fig.



Rare in



Dictyocysta elegans Ehb.

at

Rare

in

As constituting this species
Plymouth and Helder.
March

at

I

consider the form

6r32'N. 2°13'E. and

the 31.1. in

the Skagerak.



North Sea: March:
Brandt (or Tintinnus urnula Auct.).
E. of Newcastle.
rare
November:
rare.
Skagen,
between the south of Norway and
Skagerak: rare from January to March, not rare in November and December.
acuta

Ptychocylis

Pig.

Cyttarocylis Claparkdii

1.

225

&

P. Ehrenbergii Cl.

by the published

figures.

Tintinnus Ehrenbergii, but
In

serratus.
species.

to

It

all

cases

Dad.

v.

Fig. 2.

'225

Lachm.?
I
it

what



I

am

I

t.

m.

unable to decide what form

believe the annexed

may

& Lachm.

Ptychocylis Ehrenbergii Clap.

m.

t.



fig.

2 represents what

is

is

represented

understood as

perhaps also represent what some authors name Tint,
name P. Ehrenbergii is an easily recognized neritic

here

occurs abundantly in August and September at Plymouth, and from September

December sparingly

at Helder.



Daday.
North Sea: rare in March at 55° N. 6°W.
Helder: rare in June, more or less scarce from September to December. The E. Channel:
Plymouth: rare in February to April, less rare in November, December. S:t Vaast: not
rare in August, rare in December.
The Skagerak: rare in January, April and May,
November and December.
T. beroidea var. acuminata v.

Tintinnopsis

and T. cinctus Cl.
nella

Hkl.

is

campanula

&

Ehb.,

in

which species

Lachm., which seem to

perhaps another species.

me

I

include T. campanella v.

to be the

young

states only.

T.

Daday
campa-


K0X6L. SV. VET. AKADEMIKNS HANDLINGAR.

North

Sea.

BAND

17

N:0 8.

32.

November: not rare on the
Plymouth: more or less scarce

July: rare west of the Danish Peninsula.

Germany. — The

Holland and
E. Channel.
August and September.
S:t Vaast: rare in August, common in September, rare in
November.
Helder: rare in July, not rare in September, rare in October and November.
The Skagerak: from July increasing in abundancy until November.

coast, north of

in





{=

T. fistularis Moebius
I

consider the annexed

rings

and

(fig.

T. Helix Clap.

The membrane

3).

variable in height and

&

number.

It

Lachm.?),

is

— As representing

this species

and irregularly punctate and the
the end of October in the Skagerak

finely

occurs at

at M3,seskar.

&

T. ventricosa Clap.

January
tember.
rare in

and March.



Helder:
January and

Fig,

3.

— The

E. Channel in November. Plymouth: rare in
Hogue from August to December, maximum in SepNovember, maximum in September.
The Skagerak:

Lachm.
Vaast

S:t

August

to

in March,

la



maximum

Tintinnopsis fistularis Moeb.
226 t. m.

T. Lobiancoi v. Dad.



in October,

Fig.

4.

Tintinnopsis Lobiancoi
225

suppose the annexed

I

November.

fig. (4)

may

t.

have some doubts whether it may not be T.
Helder in August and September, both in 1897 and 1898.



Dab.

represent this species, but

Karajacensis Brandt.

Tintinnus minutus Brandt.

v.

m.

It

was found rarely at

This arctic form was seen sparingly in June, east of

Stadt in Norway.
T.

The Skagerak: very

secatus Brandt.

rare in January and in

November,

December.
T. Steenstrupii Cl.

& Lachm.

T. subulatus Ehrb.



K. Sv.

Vet.

Akad. Handl.

Baud



The Skagerak from October

The Skagerak from August
32.

N:r

8.

to

to December.

November.


18

p. T.

GLEVE. THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

Radlolaria.

— Rare November: NE. of Scotland and of
— Plymouth: rare January, common in August,

Acanthochiasma fusiforme Hkl.
Newcastle.

In the



rare in October.

Acanthoma



Hkl.

Miilleri

E.

in

SW. of Norway.
The Skagerak: very

in

rare in December.

Sea very rare in November between Scotland

North

and the Orkneys.
Acanthometron fuscum
February (1st).
A. elasticum Hkl.



E.

of Scotland

rare in

rare in the Skagerak,

June W. of Stadt

in

January (31st) and

Norway.



to the

W.

(incl.

of"

from the

Halosphsera,

The Skagerak: rare

(63°

1'

N. 1°36'E.) and in the chasto region to the

N.



The Skagerak: rare

Gazelletta

Scotland to the

of

November: rare, together
Norway and the Skagerak.



Plymouth: rare in August.
In November rare
January and in November, December.

W.

of

in

hexanema Hkl.



Litholophus ligurinus Hkl.

November very

In



rare S. of the Orknej-s.

Very rare W. of Stadt (Norway)

Plectophora arachnoides (Clap
rare N. of Scotland

of

S.

in September, October.

Dictyocha fibula Ehb.
Jutland.

Norway

Also above the depression south of Dogger bank.

Skagerak.
with

Very

Very

North
A. catervatum and Acanthostauros pallidus).
March: in the company of Halosphcera not rare in several spots from the N. and
A. quadrifolium Hkl.

Sea:



Mull.

&

— March: rare
Bank. — The Skagerak,

Lachm.).

and above the Fisher

in June.

at Skagen.

November:

very rare in January,

February.

Rliizopoda.
Globigerina

buUoides

d'Orb.



Rare' in

March

at

58° 21' N.

1° 40' E.

and

at

58°40'N. 4°18'E.

Cystoflagellata.



The E. Channel: at Plymouth common from the end of
end of July, rare in September, common from October to December. Southern
North Sea: abundant in June from the E. Channel to the NW. of Heligoland. July to
September: common from the E. Channel to the coast of Holland, rare from September to
Noctihica miliaris Surir.

June

to the

November.

The Skagerak,

rare in December.


KONGL. SV. VET. AKADEMIENS HANDLINGAU.

BAND

19

N:0 8.

32.

Silicoflagellata.



specnlnm (Ehb).
Rare in March at the Fisher Bank, in August at
November in the E. Channel, at Helder and Avest of the Danish Peninsula.
Rare in the Skagerak in October and November.
Distephanus

Plymouth and

in

Chlorophyllaceae.



The North Sea: abundant in March from
from Stavanger to Skagen and to Newcastle.
November: at the Hebrides. Between the N. of Scotland, Newcastle and Skagen.
B. The E. Channel: rare in August and September at Plymouth.
C. The Skagerak:
in January, February and November, December.
Halosphaera viridis

63° N. 1° 30' E.

to

Schmitz.

A.

sparingly

Stavanger,





DinoflagellataB.
Ceratium furca Duj.

Skagerak: common



North Sea:

in .January,

more or

follows as a rule
less rare the

C. tripos,

but

rarer.

The

whole year.



fusus Duj.
North Sea: follows C. tripos but rarer. The Skagerak: the whole
seems to be more abundant from August to the end of the year.
Plymouth:
the whole year, maximum in April.
C.



year,

C.

C.

The Skagerak:

lineatum Ehb.

from August

to

rare almost the whole year,

maximum

probably

November.

macroceros Ehb.



A.

The North Sea. March: more or

less rare in the chaBto

region from Scotland to Norway and Skagen.
June: common W. of Skagen to half way
between Skagen and Newcastle. Not rare E. of Firth of Tay. July, August: very common W. of Skagen and the Danish Peninsula. November: very rare W. of Scotland,

common from
Skagen

common
C.

and

S.

the

S.

of

Norway.

until the

the



Orkneys towards Newcastle and to 53° N. 4' E., thence to
B. The Skagerak: more or less rare until July, later

end of the year.

tripos NiTZSCH.



A.

.

The North Sea.

March: common

in

the eastern part,

of Norway, W. of Skagen and
Common also
53°26'N. 3°57'E. June: from Skagen to TE., between 56° 30' and 57°30'N. July,
August: from Skagen to 57° N. 4°E. and to 55°30'N. 7°30'E. (no observations from the
western North Sea).
November: the whole North Sea from Scotland to Norway, Skagen

and to 53° N.
E.
B. The E. Channel: the whole year at Plymouth, maximum from
C. The Skagerak: common in January, then r-are to June, common
July to December.
from July to the end of the year.

SW.

the Danish Peninsula towards 55° N.

at





20

p. T.

CLEVE. THE PLANKTON OF THE N01{TH SEA, THE ENGLISH CHANNEL,



AND THE SKAGBRAK.

The North Sea.

March: more or less scattered
over the chceto region, from Scotland to Norway, Skagen and the W. of the Danish Peninsula.
June: abundant W. of the Hebrides, E. of Firth of Tay (56°30'N. 0°38'E.) and
55°
25'
at
N. 0° 8' E., less abundant W. of Skagen and above the Fisher Bank.
July,
August: sparingly W. of the Danish Peninsula (observations incomplete).
November:
almost absent from the North Sea, but common at Helder in November and December.
B. In the E. Channel: at Plymouth rare in March, April, not rare in June, July and in
December.
In the Skagerak: as a rule rare from January to June and from
C.
September to the end of the year.
C. tripos var. longipes

Bail.

A.





Mcephala Cl. A. In the North Sea: rare in March on some spots
(at
6°E., 56° N. 1°E. and 55° N. 1°E.), not seen in June and August.
In November not rare, sometimes common, round Scotland and between Scotland, Norway and
Skagen, rare at 53° N. 4°E. and 55° N. 5° 30' E.
In the Skagerak rare in January
and from August to December.
tripos V.

C.

57° N.



platycorne v.

C.

Plymouth

Daday (=



Dinophysis acuta Ehrb.
at

some spots

and Skagen.

C.

trip.

aurita

v.

Cl.).



Very rare

in

November

at

from the region of the Azores).

(drifted

North Sea

the

In

as a rule rare, in

March and June

November at several points between Newcastle
from January to March, in June and July and from

the eastern region, in

in

In the

Skagerak

rare

October to the end of the year.



Diplopsalis lenticula Bergh.

Scotland.

In

At Plymouth rare from January

June rare N. of Holland, in November E. of
to August. In the Skagerak rare in July and

in October.



Gronyaulax spinifera Clap. & Lachm.
Rare in March in the North Sea (at
56° N. 0° and 55° N. 1°W.).
In the Skagerak common in January, not rare in No-

vember, December.
Peridinium depressum Bail.
the eastern part,
less

common

more or

A.

North Sea more
and W. of Skagen.

In the

common NW.fof Heligoland

N. of Holland and on the Fisher Bank.

points

several



between

less rare

the

N.

of Scotland,

from January to June,

P. divergens Ehb.



In the

In the Skagerak rare in January,
P. Michaelis Ehb.



Rare

S.

less rare

in

April

from July

In the

more or

less rare at

Skagerak

October, December.

as a rule rare

among

the tripos-plankton.

to October.

Plymouth,

at

In July, August,

November more or

Norway and Skagen.

less rare in

North Sea

In

or less rare in June in

in

June W. of Schleswig, in

October at M&seskar.
P.

Rare

in

oMongum Auriv. (=

June

in the E.

Channel

P. diverg.

v. obi.

at S:t Vaast, in

Aur. and

July

;it

P. div. v. oceanica

Vanh. Ostenf.).

Helder, in the Skagerak and at MSseskSr.


BAND

KONGL. SV. VET. AKADEMIENS HANDLINGAli.
P. ovatum PoucHET.



Rare in January
Cape Stadt and in the E. Channel, in July
September to November at Helder.

off the

32.

Swedish west

in the Skagerak, in

21

MIO 8.
coast, in

August

at

June W. of
Plymouth,



Pyrophacus horologium Stein.
In March at 53° N. 4°E., in April very rare at
Plymouth, in June NW. of Hanstholm, in November S. of the Orkneys, ENE. of New(55°35'N. 0°34'E.) and at 56° N. 9°E.

castle

Pyrophacus horologium belongs to the tropical Atlantic (also the Indian Ocean) or
to the desmo- and styli-plankton, where it has considerably greater size than in the
North Sea, when among the tripos-plankton.

FlagellatsB.

in June,

mon

common

in

in June, also in



At Helder very abundant in April and May, rare
August and not rare in October.
At S:t Vaast la Hogue comDecember.
At Plymouth common from the beginning of April

PhjBocystis Pouclietii Lagerh.





to the beginning of June, rare in September.

Cystae.

Xauthidinm Hystrix Cl.

By
seems

to

the above

be

nearly

name

I

akin

usually not divided, spines.



Rare in the Skagerak in March, October and November.

denote an organism, which belongs to the tripos-plankton and
to

X. brachiolatum Moebius, from which it differs by longer,
Probably a stage in the development of some dinoflagellate.

\

'

/

mmMt^
Fig.

5.

X. multispinosum Moebius.
at M&sesktlr, September, October

Xanthidium hystrix


in

Cl.

500

t

m.

In April at M^seskar, in

the Skagerak, always rare.

June

at

Plymouth,

in

July


22

p. T.

CLEVE. THE PLANKTON OF THE NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

Hexasterias proWematica Cl.
alga,

with
of

which
six,

the

have

I

found

in



By

several

this

name

collections.

I

denote provisionally a unicellular

It is

a

flat

diameter

disc,

0,o4

mm.,

ends truncate and denticulate empty processes, twice as long as the radius
Having seen only specimens preserved in spirit I am unable to decide

at the

disc.

whether the chromatophores are yellow or green.

Fig.

6.

Hexasterias problematica Cl.

Habitat: Helder, rare in December.

500

t.

m.

Outside the North Sea at the following points:

(Westmannao 26. X. 98), the Faroes (23. VII. 98), at 51° N.
66°30'N. 22°30'W. (29. V. 99) and at 61°37'N. 6°40'W. (20. V.

Iceland



at

99).

5'

W.

(14. XI. 98),

DlatomaceaB.
Asterionella japonica Cl. (in Cl.

Very

Moll. Diat. N:o 307, 1882.

rare in

Cl.).

— Very rare
— Very rare

Asteromphalus heptactis Ralfs.
IJactei'iastrum delicatulnm Cl.

B. varians Lauder.



in August, September, rare in

November, December.

Bellerochea malleus Btw.

and

at S:t

Vaast

la

at



In

April, rather

63°1'N. 1°36'E.

June W. of Stadt in Norway.

In March at Plymouth, in July, August

At Helder common

November

March

in

in

or less sparingly in

In

A. glacialis Ostenf.



At Plymouth in March and
the Skagerak on the 31st of January.

probably Castrac. 1886 A. spathulifera
rare in September.

&

October.

At

S:t

NW.

Vaast

March very rare W. of Jutland (55°

Hogue, from the Channel

of Heligoland.
la

Hogue more

43' N. 7°29'E.).

to the coasts of Holland, at

Helder

in the Skagerak.



aurita Lyngb.
In March on] the whole sparingly round the south
Norway, at Skagen, on the Fisher Bank and above the depression S. of the Dogger
Bank.
At Helder rare in February. In the Skagerak from January to March. In
November common at Helder, rarer in the Skagerak and at S:t Vaast la Hogue.

Biddulphia

coast of




KONGL.

VET. AKADEMIENS HANDLINGAU.

SV.

BAND. 32.

23

N:0 8.



B. mobileusis Bail.
A. In the North Sea, in March more or less abundant
round Scotland, between the Shetlands and Cape Stadt, above the Fisher Bank. Common
above the depression S. of Dogger Bank. In November common from the E. Channel to the
W. of Jutland.
B. In the E. Channel at Plymouth more or less abundant from January
to April, rarer in October
December, at S:t Vaast la Hogue rare in November.
C. In the Skagerak in January and in October
December.











Cerataulina Bergonii H. Per.

In the

A.

North Sea

rare in



March about 57° N.

June at about 62° N. 2°30'E. and 57° N. 9°E.
B. In the E. Channel
rare at Plymouth in March, less rare in April and June, rare in November at; S:t Vaast
la Hogue rare from June to August.
C. At Haider more or less common from the
end of April to the beginning of June, rare in November.
D. In the Skagerak rare
in January, more or less common from June to the end of the year, maximum in June
and in October.
6°E.,

rare

in



Chaetoceros anastomosans Geun.
in







Very rare

in

August

at Helder, in the

Skagerak

October.
C.

of

atlanticus

Jutland,

in

Cl.

June


rare

March

In

W.

of

rare

Cape

at

Stadt

some
and

spots SW. of Norway and W.
mid-way between Scotland and

Norway.

— A.
region, maximum
W. of Jutland. — B.

North Sea

rare and scattered in March through
June E. of Firth of Tay abundant; less
common
In the Skagerak more or less rare from January to June,
more abundant from October to December.
C.

the

Iborealis

Btw.

Tar. Brightwellii Cl.

from
November.

chaeto region

and

in

In

the

at 57° N.

chffito



In

6° E.

In

North Sea

the

56° N. 4° E. to Skagen.

March

some spots in the
In the Skagerak rare from January to March
rare

in

at




Gran.
In March common at Skagen and on some points S. of
In the Skagerak from January to June, maximum in
Norway, rare at Plymouth.
March, at M§,seskar from March to the middle of June. More or less common in
October, November.
C.

constrictus

C.

contortus

Schutt.



More or

less

sparingly in July, August at S:t Vaast la

Skagerak from the end
June, maximum in March and June.

Hogue, in September at Helder, in the
and from January to
C.

coronatus

Gran.



Rare

Caste.



Rare

in

August

of August to December,

at Helder, in the

Skagerak

in October

and November.
C.

criophilus

in the Skagerak.

in

March on some spots SW. of Norway,

in

January


24

p. T.

C.

Norway,
E.

CLBVE. THE PLANKTON OF THK NORTH SEA, THE ENGLISH CHANNEL, AND THE SKAGERAK.

at

September, at
September.



from August

Bank.

S:t

In

In the

North Sea: more

or less sparingly in

March SW. of



In the
W. of Jutland, in November rare W. of Jutland.
Plymouth more or less common in March, very abundant in August,
Vaast la Hogue very abundant in October, November, at Helder rare in
the Skagerak more or less rare from January to April, very common

Skagen

at

Channel

C.



curvisetus Cl.

and

November.

to

(==

Cl.

densiis

borealis v.

C.

densa Cl.).

In

March

not rare on the Fisher

or less abundant from the

Tay and more

In June E. of Firth of



mouth of

the Schelde

At Helder rare in June and not rare from August to December. In the
E. Channel at Plymouth more or less abundant from the end of March to the end of April,
common in July, August, rarer in September. S:t Vaast la Hogue in June and from

to Schleswig.

October to December.
danicus

C.

Skagerak

In the



Cl.

the

In

rare in the beginning of October.

Channel at
At Helder

E.

Plymouth not rare in September.
Skagerak from March to June, maximum

in

Vaast

S:t

la

Hogue

rare in July, at

November and December.

in

June, and

In the

from the end of October

to

December.
C.



deWlis Cl.

In the



Skagen, in June E. of Firth of Tay.

from October

to

December.

rarer in October,
C.



common at
At Plymouth rare in April, at Helder common
Skagerak in January io June (maximum m March),

North Sea
In the

March SW. and

in

decipiens Cl.



A.

In the

North

Sea.

55°— 56°

Tay and Newcastle. At
tween Norway and the Shetlands.

West

of



the spot

March from Skagen

In

June (very abundant

of



Rare

Helder

rare

diadema Ehb.

September,

at

more or

in March),

(abundant in March) and very



in

in

to the

W. of

N. from the Danish Peninsula to the E. of
53° 30' N. 3° 40' E.
In June at one spot be-

of Jutland 66° N., in

November very sparingly
Plymouth more or less sparingly
later rare. At S:t Vaast la Hogue
In the Skagerak January to
October, November.

B. In the E. Channel
from the E. Channel to Jutland.
from January to March, common in October, November,
very abundant in June, rare in October and December.

C.

of Norway,

November.

Stavanger and 58° N. 1°30'E., along
Firth

S.

less rare in

at



March SW. of Norway. At Plymouth rare at the end
December.
In the Skagerak from January to May

common

in

November.

North Sea

March

SW. and S.
Skagen and W. of Jutland. In June NW. of Heligoland. In November very rare from the E. Channel to the W. of Jutland. At Helder rare from August
to the end of November.
B. In the E. Channel: at Plymouth rare in March and in
C.

coast

of

didymus Ehb.

Norway,

A.

In the

in

rare along the

at



At S:t Vaast la Hogue common in June and July,
rare in August, more or less sparingly from the end of October to the end of December.
In the Skagerak rare from January to March, more or less abundant from the end
of August to December, maximum September, October.
October,



common

in

November.


BAND

KONGL, SV. VET. AKADEMIENS HANDLINGAR.
[C.

in

my

Granii Cl., mentioned in

rectangular, thin- walled cellules (longit.: sagittal axis

Awns

hexagonal, smaller than the cellules.

and

obliquely

Their

transverse.

25

N:0 8.

paper »Plankt,on Researches in 1897», was not seen

This species, represented in the annexed figg. 7 and

1898.

32.

basal

\'s

1:2).

8, forms loose chains of
Foramina large, elongate

from the angles of the

arising

part

=

as

cellules, sagittal

The

as the longitudinal axis.

long

seem to contain one parietal plate. Endocysts biconvex, in transverse sagittal
numerous simple spines. Sagittal axis 0,oi3 to 0,oi5 mm.
M^seskar in March 1897.]

cellcontents



section elliptical, covered with

ChcBtoceros Granii Cl.

Fig. 7, 8.

C.

In the



hiemalis Cl.

Skagerak from

June rare

In

1000

E. of Firth of

t.

m.

Tay and common W.

of Skagen.

the end of March to June more or less abundant, and in October,

November.

The annexed

fig.

9 represents the endocysts

500

t.

magnified.

They

resemble those of C. laciniosus.
C.

Rare

laciniosus Schutt.

in the Skagerak,

January

—March,

less
Fig.

rare in November.
C.

ScMttii Cl.

North Sea

rare

in

follows

March

K. Sv. Vet. Akad. Handl.

as

a

rule

C.

curvisetus

at the Fisher Ban^, in

Band 32.

N.o

8.

and

C.

didymus.



A.

9.

In the

June W. of Cape Stadt, in November
4


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