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THE DANISH

INGOLF-EXPEDITION.

VOL. V, PART 5

CONTENTS:

HJALMAR BROCH: STY L ASTERID AE.

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PUBLISHED AT THE COST OE THE GOVERNMENT

BY

THE DIRECTION OF THE ZOOLOGICAL MUSEUM OF THE UNIVERSITY.

•f-^yii^'

COPENHAGEN.

H. HAGERUP.

PRINTED BY BIANCO I. UNO.

rgi4.

THE DANISH INGOLF-EXPEDITION.

VOLUME V.

5.

STYLASTERIDAE

BY

HJALMAR BROCH.

WITH 5 PLATES AND 6 FIGURES IN THE TEXT.

->4K*>«f<-

COPENHAGEN.

PRINTED BY BIANCO LUNO.
1914.

CONTENTS.

Stylasteridae.

Pas

Introduction I

The Stylasteridae of the North Atlantic 3

Pliobothrus Po u r t a 1 es 3

Pliobothrus symmetrica* Pourtales 3

Stylasler G r a y 7

Stylaster gemmascens (Esper) 8

roseiis (Pallas) 12

— norvegicus (Gunnerus) 15

Remarks on the affinities and systematic position of the Hydrocorallines 19

Zoogeographical remarks oil the North Atlantic Stylasteridae 22

Literature

4189G

Introduction.

The close examination of the Hydrocorallines meets perhaps with more difficulties than the
study of the skeleton-bearing Hexacorallia, owing partly to the porous skeleton of the colonies,
partly to the delicate nature of the organisms. The characteristics can be determined roughly by
means of Dr. Koch's detailed method in which thin sections of the colonies are prepared by grinding
with the stained soft parts in situ. The structure of the skeleton can also in part be studied by
breaking the colonies as Hickson (1912 p. 891) seems from the following remark to have done. "The
way in which it is possible to study the shape of the gasteropore styles is to make a vertical fracture
in a plane parallel with the long axis of a branch. In a large percentage of such fractures the whole
length of at least one gasteropore with its style will be exposed". It is evident however, that this
method is not suited to form the base of a more thorough and systematic investigation of the skeletal
parts of the colon)'. Where it is necessary for the observer to make his results free from chance
irregularities he must have recourse to the somewhat slower method of grinding. In the present
studies this latter method has throughout been used in the examination of the skeleton. The soft
parts are first removed by means of Eau-de-Labarraque, and pieces of the colony have then been
ground down on a fine and level whetstone as far as seemed necessary in each single case. For
general systematic work it is usually sufficient to grind down a branch to about its median longi-
tudinal plane; in a Stylastcr, for example, the majority of the gasterostyles will in most cases
appear quite free in the middle of the gasteropore. On the finely polished ground surface it will also
be possible to study the course of the fine canals. Where there is question of examining the finer
structure of the calcareous skeleton, however, this procedure is not sufficient and it is necessary in
addition to have thin sections of the same kind as the geologists use in their studies.

Since Moseley's fundamental work on the Hydrocorallines appeared in 1881 investigators have
mainly directed their attention towards unravelling the features of the skeleton of the colonies. Ex-
cluding a couple of smaller papers on the gonophores of a few species, no observer since that time
has sought to penetrate deeper into the organisation and finer structure of the Hydrocorallines. The
result is, that we cannot yet be said to have full knowledge of their affinities and thus of their syste-
matic position, a matter I shall return to later. — On studying Moseley's work we see at once, that
none of the species hitherto found in the northern seas have been closely investigated; as will
be shown in the following; even their specific characters have been more or less imperfectly

The Jngolf-E.vpedition. V. j. I

STYT.ASTRRIDAK

studied. It was thus of the highest importance to examine the soft parts of the northern Hydro-
corallines more thoroughly; as Pax correctly remarks in a recent work on stony corals (1910 p. 65), "wir
diirfen tins nicht verhehlen, dass jede Art, von der nur das Skelett vorliegt, als unvollstandig bekanut
gelten muss, gleichgiltig, ob ihr anatomischer Bau fur systematische Zwecke verwendbar ist oder nicht."
It appears from the investigations, that the least injurious solution with which to remove the
calcareous constituents is that recommended by Pax (1910 p. 71): 100 parts 70 % alcohol, 10 parts con-
centrated nitric acid and 2 parts concentrated, aqueous phloroglucine solution. In small pieces of the
colony the calcareous parts are usually completely removed during about 12 hours; larger pieces have
sometimes to remain in the liquid up to 48 hours before all the carbonate of lime is removed. The
coarser structure is then studied most easily by means of thick celloidin sections, the finer by means
of thin paraffin sections. The staining methods depend in part on the fixation. In most cases I have
obtained excellent pictures on staining with haematoxylin and counterstaiuing with eosine or picric-
acid-fuchsine (van Giesson's). It is of interest to note, that the structureless organic tissue, which
intersects the skeleton in all directions, is coloured very intensely by the eosine and acid-fuchsine
in the same way as the supporting lamellae of the zooids, whilst the picric acid does not affect it in
van Giesson's staining method. —

I cannot refrain from dwelling a moment here on the mineralogical composition of the skeleton.
Pax has investigated the skeleton of Flabellum inconstans and found, that it consists of aragonite.
He also brings together (1910 p. 70) the results of previous investigations in the same direction. Ac-
cording to his summary calcite has been determined as skeleton in Corallium, Isis, Tubipora, Cysti-
pli v//n in and Anabacia, whilst aragonite has been found in the following genera of Coelenterates:
Hrliopora, Monlipora, Echinopora, Distichopora, Madrepora, Stylopora, Pocilopora, Millepora, Serialopora,
Goniastraca, Podobacea, Galaxea, Fungia, Dciidrophyllia, Porites, Astroidcs, Hydnophora, Sclerohelia,
Cocloria, Ptcrogvra, Merulina, Favia, Stylasler and Trachypyllum. — At my request the assistant at the
Geological Institute of the Polytechnic High School in Trondhjem, Dr. C. W. Carstens, has examined
the skeletons of our four northern Stylasterids. Examination by means of Mei gen's reaction has
shown, that the skeleton in all four is formed of aragonite.

We here face one of the great problems of biology. There can be no doubt, that the power
of animals to produce aragonite in the one or the other manner must stand in connection with their
power to make use of the magnesium of the sea-water; according to the investigations of mineralogists
namely all aragonite contains magnesium. But what makes the matter so puzzling is, that alongside
the animals which have aragonite skeletons live some others, which like Corallium, Tubipora, Cys/i-
pliylliun and Anabacia form calcite skeletons. This shows that it cannot depend on a mere chance
whether the animal builds its skeleton of aragonite or calcite. It seems more than doubtful that
the crystalline system should be of any importance here. Physical characters might probably be
found in aragonite, which for most of the marine animals make it biologically more profitable than
calcite. Unfortunately the differences between aragonite and calcite in physical regards are still
so imperfectly known, that we are unable to form any reasonable supposition as to what part their
occurrence plays in the biology of the marine animals.

STVLASTERIDAE

The Stylasteridae of the North Atlantic.

Pliobothrus Pourtales

The colonies are branched fan-shaped, often with dichotomonsly divided brandies and branchlets.
The gasteropores and dactylopores open irregularly over the surface of the colony and are not collected
into cyclic systems. The dactylopores open out on the top of lower or higher tubular projections.
The gasteropores are of varying depth, sometimes closed below by one or more tabulae; both the
gasteropores and dactylopores sometimes open without distinct ending into the large, irregular, central
longitudinal canals of the colony. The gasteropores and the dactylopores have no styles.

With this diagnosis the genus agrees fairly closely with the Pliobothrus of Moseley (1881 p. 94).
There are a few changes however which require further mention. Moseley included as a generic
character in his diagnosis the absence of tentacles in the gasterozooid, in spite of the fact, that his
own investigations indicated that Pliobothrus tubulatus Pourtales has 5 — 6 tentacles on the gasterozooids.
When we remember the great variation to which the number of tentacles is subject in other genera,
where they have been studied, this character is of extremely problematic value as generic character.
The same applies to the form of the polyps, which more than anything else is dependent on the state
of contraction and preservation. So long as we are unable to demonstrate more constant peculiarities
in the form of the polyps than hitherto, it has no great value even as specific characteristic. The
number of the gonophores in the ampullae must also be referred to the specific characteristics and
may even here be of subordinate importance.

A close study of Pliobothrus symmetricus shows, that the pores of the zooids vary greatly in
length and often stand in open communication with the large central canals which appear irregularly
in the branches. This blots out the boundaries between Pliobothrus and the genus Steganopora recently
described by Hick son and England (1905 p. 26). Open communications between the gasteropores
and the dactylopores may also exceptionally be found in Pliobothrus symmetricus. Steganopora must
therefore be included under Pliobothrus. The species Steganopora spinosa Hickson and England, the
only known species of this genus, stands very near to Pliobothrus tubulatus Pourtales and will possibly
on closer examination prove to be identical with the latter.

Pliobothrus symmetricus Pourtales.

187 1 Pliobothrus symmetricus, Pourtales, Deep-Sea Corals p. 57, Plate IV, figs. 7 and 8.

1874 , P. M. Duncan, Madreporaria .... "Porcupine" p. 336, Plate 49, fig. 7.

1879 — — , Pourtales, Corals .... "Blake" p. 211.

1881 — , Moseley, Stylasteridae "Challenger" pp. 48, 80 and 84, Plate VIII, fig. 2.

The fan-shaped colonies are normally branched in one plane; sometimes a portion of the colony
may develop to a new fan, which forms an angle with the primary plane. There is no distinct or
prominent main stem. The gasteropores are evenly distributed throughout the colony, somewhat more
numerous on the front than on the back. The dactylopores, which open out on low, broadly conical

STYLASTKRIDAE

prominences, are mainly found on the front and lateral sides of the branches and are here irregularly
arranged between the gasteropores. The gasteropores are sometimes provided with one or a few
tabulae; both the gasteropores and dactylopores are sometimes in open communication with the ir-
regular, large, central canals in the colony, exceptionally also with each other directly. The gastero-
zooids have no tentacles. The dactylozooids, which are attached by a narrow base in the pore, have
a central lumen. — The ampullae are deeply placed. The male gonophores are composite and are
developed singly in the ampullae. — The surface of the colony is smooth, not reticulate.

Colour (in alcohol): yellowish dirty gray.

Occurrence: at Florida and in the Northern Atlantic in depths of 190 — 700 m.

Material:

"Ingolf" St. 55 63°33' N, i5°o2' W. depth 594 m. 5.9°. C.

- 57 63°35' - 13W - 658 - 3.40. C.

On the Ingolf Expedition some fragments and a complete colony of this peculiar species, which
at first sight is all too readily regarded as a Bryozoon, were taken. The intact colony (PI. I, figs. 1 and 2)
shows the marked tendency of the species to branch dichotomously. This characteristic is also clearly
seen in Pourtales' and Duncan's drawings. How far this is more than a specific character we are
unable at present to determine with certainty, as only a few quite small fragments have been found
of the other species of the genus Pliobothrus. Pourtales' drawing of Pliobof/irus tubulatus (1871,
PI. 4, fig. 9) suggests however, that we have here a specific character, the fragment figured at any rate
is not branched dichotomously.

There is in general no very marked main stem in Pliobothrus symmetricus, nor do its branches
show any regular difference in thickness. In this regard the intact colony of the "Ingolf differs from
those described earlier; the unbranched, basal part of the colony may best be described as a kind of
main stem, although its dimensions do not in reality differ obviously from those of the branches.
The other, somewhat smaller fragments are not so distinctly and simply fan-shaped. Single branches
show a tendency to new fan formations in planes almost at right angles to the primary plane of the
colony. As no other difference could be detected between the colonies, however, this must be
considered as purely chance variations in the colonial form. — There is a sharply marked difference
between the front and back of the colony. On the front the pores are evenly and densely distributed
over the whole of the surface and here the dactylopores are present in large numbers; on the back,
on the other hand, the dactylopores have practically disappeared and the number of gasteropores is
also somewhat reduced. The difference becomes the more pronounced, the nearer we come to the base
of the colony, the pores on the hind surface becoming more and more reduced both in number and
size. In the above-mentioned, more irregularly branched fragments, all difference between the front
and back disappears on the branches which emerge from the primary plane of the colony; the pores
are evenly and densely distributed on the whole surface of these branches.

Under a low magnification already (PI. I, fig. 3) we notice larger and smaller pores, which,
however, are not arranged in rows or systems. The larger pores — gasteropores — have their opening
plane at the level of the colony surface, whilst the small pores — dactylopores -- are found on the
top of small, conical protuberances. As mentioned above, the number of the dactylopores especially

STYLASTERIDAE

Text-fig. A. Diagram showing
the arched development of the
pores in Pliobothrus symmetri-
cus during the growth of the
colony.

is reduced on the hind surface of the colony; what may be the cause of this our imperfect knowledge
of the biological conditions of the Stylasteridae does not enable us to explain.

If we grind down the branches to about the median longitudinal plane we are able to see the
pores in the whole of their length (PI. Ill, figs. 19 and 20) and it becomes
apparent that these have a typical bend in their course, curving inwards
towards the longitudinal axis of the branch and then downwards towards
its base. The pores — especially the gasteropores — are of varying length;
the terminal pores are, as a rule, quite short and much shorter than those
we find further in on the branches. This indicates a terminal and centrifugal
growth in the branch and gives us the key to the understanding of the bent
course of the pores (Text-fig. A). The pores are first formed at or near the
tip of the branch and approximately in its longitudinal direction; during the
growth of the branch the pore is gradually moved down on its cylindrical
part. The plane of the opening of the pore lies at each place approximately
at right angles to its longitudinal axis and the latter will therefore become
curved during the growth of the branch , as will be seen from the ac-
companying diagram.

A few of the gasteropores open into large, irregular, longitudinal canals, which are formed
secondarily in the central part of the branch; often however their base is formed of one or two tabulae.
In their original form the gasteropores are cylindrical with a slightly expanded basal part in which
the zooid is attached; but during growth the gasteropores often assume a more irregular appearance.
The dactvlopores also are of varying depth; they are cylindrical, more or less curved and have a
slightly constricted opening region; the pore aperture itself, as mentioned, is situated on the top of a
slightly prominent, almost wart-shaped protuberance. — The calcareous substance of the colony is
penetrated longitudinally and transversely by fine canals in which the stolons lie. No regular arrange-
ment could be noticed in these fine canals, neither in Pliobothrus symmetricus nor in our other North
Atlantic Stylasteridae.

The connection of the pores and canal system in Pliobothrus symmetricus is of special interest,
when we compare with the genus Stcganopora established by Hickson and England (1905, p. 26).
The open communication, which is not so very seldom observed between the pores and an irregular
central canal system in Pliobothrus, is said by Hickson and England to be a constant and always
occurring character in Stcganopora and here also results in an open and direct communication
between the gasteropores and the dactylopores. Such a communication also occurs irregularly in Plio-
bothrus symmetricus and we cannot consider this as a fundamental difference between this species and
Steganopora spinosa, as maintained by Hickson and England. In reality there is here only a gradual
difference, which by no means entitles us to make a generic distinction and the last-mentioned species
must therefore be referred to the genus Pliobothrus.

Moseley (1881) has shown, that the structure of the zooids in Pliobothrus symmetricus is very
characteristic. The gasterozooid (Text-fig. B) has a fairly broad basal part, from the circumference of

Tfc

STYLASTERIDAE

which the stolons emerge. Examination of serial sections seems to suggest, that the endoderm in the
basal part itself is strongly vacuolated; but this may also be due to the imperfect state of preserva-
tion. The protoplasm is here strongly granulated and all indicates, that the albumen cells (cf. Schneider
1902 p. 579) form the principal mass of the endoderm in the basal part of the polyp, whilst the

nutriment cells are in majority in the endoderm of the free wall of the
zooid. Apart from this localisation of the cell types the gasterozooid agrees
in the whole of its structure with the Hydroid polyp, as is clearly shown by
m the figures (Text-fig. B, PI. Ill, figs. 28 and 29). Whilst the large cnidocysts
occur in fair numbers in the stolons, the small ones are concentrated in the
walls of the zooids. In the gasterozooids (PI. Ill, fig. 29) the cnidocysts are
Text-fig. B. The contracted accumulated densely in the ectoderm near to the mouth of the polyp and

gasterozooid of Pliohothrm entirely disappear further clown on the polvp wall; in the dactvlozooids they
symmetricus. ec = ectoderm,

cn= endoderm, ?» = mouth, are more uniformly distributed in the ectoderm in the whole length of the
s = stolones, trw = the epi- . . , , , , ... ,_ . , .

thel of the ea t r °b zoolfli but become however less numerous near its basis. — io judge from

= mouth of the gastero- Moseley's drawing (1881 PI. VIII, fig. 2) the gasterozooid should have a wide,
pore. (G0/j).

cruciform mouth in Pliobotlirus symmetricus. The mouth of the polyp is

closed in all the specimens examined from the "Ingolf" Expedition and is neither larger nor shaped

differently from that of the Hydroids generally. The cruciform appearance noted by Moseley is

clearly due to chance, for the protruding parts of the endoderm in the numerous sections examined

vary greatly in form, size and number.

In their discussion of the family characters of the Stylasteridae Hick son and England state
(1905 p. 13): "The solid scalariform endoderm of the dactvlozooids is another very distinctive feature
of the group". This does not hold good for Pliobotlirus symmetricus; the dactylozooids have a distinct
lumen in their centre, as shown in transverse sections (PI. IV, fig. 34). The authors cited maintain,
that "the scalariform tissue is clearly a much more differentiated tissue", — naturally, under the tacit
assumption, that the dactylozooid is a reduced polyp. This would suggest, therefore, that Moseley's
view of Pliobotlirus as a primitive genus of the Stylasteridae is correct.

There is one condition, however, which seems to point in the opposite direction; this is the
male gonophores and their structure. Moseley indicated already, that their appearance differs from
that found elsewhere in the Stylasteridae. But his drawing (1881 PI. VIII, fig. 3) is in so far misleading,
as it gives the impression, that the difference only consists in a denser accumulation of very small,
single gonophores. A series of sections through the male gonophores (PI. IV, figs. 40 — 42) shows ex-
tremely aberrant features. Each ampulla contains a single, fairly large, globular gonophore, which is
composed of a number of follicle-like portions (pseudofollicles); the reproductive cells are in extremely
different stages of development in the various pseudofollicles of the gonophore. The spadix as a rule
is slightly branched between the pseudofollicles and sometimes we find, that slender connecting bridges
lead from the stolons of the ampullar wall over to other parts of the gonophore wall thau those where
its spadix connects with the stolons of the colony. — Hickson (1891) has demonstrated the forma-
tion of a "seminal duct" in Stylasteridae where the male gonophores are of primitive structure. Such
a formation can certainly not be found in Pliobotlirus symmetricus. The apex of the compound gono-

STYLASTERIDAE

phore is prolonged (PI. IV, fig. 42) but seems never to reach the surface of the colony. To
judge from serial sections it opens out into one of the surrounding stolon canals of the calcareous
skeleton at the side of and not in the stolon itself. The available material however is not sufficiently
well-preserved to enable these conditions to be closely studied, nor does it give any clear picture of
the structure or development of the opening of the gonophore.

It would be of great interest to clear up the origin and development of these compound gono-
phores. Probably we have here a secondary coalescence of the whole gonophore complex which we
find collected into the single ampulla in most of the other Stylasteridae. The branched spadix and
the variating stage of development of the reproductive cells in the single pseudofollicles point in this
direction. Investigation of the Stylaster species shows, that the male gonophores in an ampulla are in very
different stages of development and thus function over a long period; the successive maturation, which
obviously must be of great importance for the species, is thus retained in Pliobothrus symmetricus after
the gonophores have become fused into a single complex. Unfortunately the material has not per-
mitted any close study of the development of the gonophore in the present species. — I was unable
to find other developmental stages of the female gonophores than those ahead}- known from the
work of Moseley. Thus nothing was found which differed from his description. —

Pliobothrus symmetricus was first described by Pour tales (1871 ) from the Florida reefs,
where it seems to be common between 180 and 300 m. in depth. The species has only once been
met with in the Northern Atlantic, where P. M. Duncan (1874) mentions it from the cold area of
the Faeroe Channel.

Stylaster Gray.

The usually fan-shaped colonies have the zooids collected into closed cyclosystems, which show
no trace of opercula. Both the gasteropores and the dactylopores are provided with styles; the dactylo-
styles however may be rudimentary.

On the basis of this diagnosis we must also include the genus Allopora Ehrenberg in Stylaster.
Hickson and England (1905 p. 6) rightly point out how small and doubtful the characters are,
which are said to distinguish the two genera. In reality there are quite even transitions between the
genera. None have shown this more clearly than Hickson and England, who following the
proposal of Studer group the species into four divisions: "A. Cyclosystems on lateral sides of branches
only; B. Cyclosystems on lateral sides of branches and a few on the surfaces; C. Cyclosystems evenly
distributed over the surfaces of the branches, and D. Cyclosystems on the anterior surface of the
branches only." The first two groups stand extremely near to each other and should be embraced
within one main group or subgenus Eustylasfcr\ the last group has just the arrangement of the
cyclosystems which is characteristic of Allopora; species like Stylaster divergens Marenzeller and Allo-
pora rosacea Greeff obviously occupy intermediate positions between our northern Allopora species with
its hardly prominent cyclosystems and those Stylaster species which have very prominent, almost
stalked cyclosystems. For group D. the old generic name Allopora should be retained.

The genus Stylaster is represented in the Northern Atlantic by three species, which have been
confounded several times. When the ampullae are strongly developed the colonies in our Eu-

8

STYLASTERIDAE

stylaster species may sometimes become so blown up and deformed that they may easily enough be
confused with the Allopora species. To facilitate the determination in difficult cases I give in the
following table their distinctive features.

gemmascens

norvegica

Cyclosystems

Gasterostyles

Ampullae (9)

with 12— 20, normally 14— iSdactylo-

pores. Wall of gasteropore deeply

incised towards the dactylopores.

conical, twice as high as broad.

near the surface and projecting like a
hemisphere; equipped with blunt spines

with 8 -16, normally 9 — 11 dactylo-
pores. Wall of gasteropore slightly
incised towards the dactylopores.

almost globular with same breadth
as height.

near the surface and projecting like a
hemisphere; without spines.

with 5—9, normally 6—7 dactylo-
pores. Wall of gasteropore slightly
incised towards the dactylopores.

almost globular with same
breadth as height.

deeply embedded, scarcely seen
externally on the colony.

1873

?i874
1879
1881
1882

Subgenus Eustylaster nov.

Stylaster gemmascens (Esper) Milne-Edwards et Haime.
1768 Madrcpora virginea, Gunnerus, Om nogle norske Coraller p. 56, Tab. VIII, figs. 2—4.
nee 1758 Madrcpora virginea, Ljnne, Systema naturae ed. X, vol. I, p. 798.
? 1797 Madrcpora gemmascens, Esper, Fortsetzungen der Pflanzenthiere, T. I, p. 60, Tab. 55.
1857 Stylaster gemmascens, Milne-Edwards, Histoire naturelle des Coralliaires p. 130 ').
— , G. O. Sars, Dyrelivet paa vore Havbanker p. 45.

, pars, P. M. Duncan, Madreporaria .... "Porcupine" p. 332.

, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna p. 24.

, Moseley, Stylasteridae "Challenger" p. 86.

, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna IV, p. 25.
1910 , J. A. Thomson, Note on a Hydrocoralline from Rockall p. 61.

1912 , Nordgaard, Faunistiske og biologiske iagttagelser p. 7.

1912 — , Arndt, Zoologische Ergebnisse, I, p. 122.

The fan-shaped colonies have as a rule a concave front surface and show a distinct difference
between stem, main branches and small branches. The cyclosystems are placed laterally and alternately
on the outermost small branches and their main axis forms almost without exception a pointed angle
of less than 45° with the axis of the branch; they are oval, except those just at the tip of the branch
which may be circular, and show from 12 to 20, normally however 14—18 quite separate dactylopores,
each provided with a rudimentary dactylostyle. The wall of the gasteropore shows deep incisions to-
wards the dactylopores. The gasterostyle is conical, twice as high as broad. The gasterozooid
has 4 quite small tentacles. - The female ampullae project like hemispheres above the surface of
the colony and when fully developed are equipped with 1 —7, generally 2 — 4 small, blunt spines. The
surface of the colony is smooth and indistinctly reticulated.

Colour: white or faintly rose-red with darker yellowish red gasterozooids.

Occurrence: west coast of Norway, Denmark Strait in 50—560111. depth, Rockall. (Indian Ocean?)

'J This work contains a detailed list of the older synonymy.

STYLASTERIDAE

."Material:

"Ingolf" St. 15

-0.75° C.

West coast of Norway

66°i8'N. 2.5°59'W. 620111.

Hjeltefjord ca. 150 m.

Gidsko (Sondmore) ?

Sondmore ?

Trondhjeni Fjord 50—400 m. 6.5 — 8.50 C.

The form and appearance of the colonies are snbject to snch great variations in Stylaster
gemmascens, that we may often be in donbt as to whether one and the same species is before us. The
available material was very large, especially from the Trondhjeni Fjord, where the species is fairly common
and more luxuriantly developed than from am- other locality hitherto known; further, I was able to examine
a number of colonies from the west coast of Norway and lastly a couple of small fragments from
"Ingolf" St. 15. Examination of this very large material shows the relationship of all the many
different kinds of variants, partly owing to series of chain-forming variants, partly on account of
apparently quite different growth-types being present in different branches of single colonies. Hickson
in several of his works has divided up some of the species into a series of different "fades". As the
most illustrating examples I may mention his treatment of Stylaster eximius Uuchassaing et Michelotti
(1905) and Errina nova-zelandiae Hickson (1912). The deeper meaning of these "facies" is not apparent from
his method of treatment; they seem only to illustrate the varying growth modifications of the species; nor
do we obtain any information as to the biological conditions under which they appear. In dealing with
the present species, therefore, I discard the subdivision into "facies", which only serves to give the misleading
impression that the species is divided into distinctly separated growth forms or types.

There is always a distinct difference present between the front and hind surfaces of the colony
in Stylaster gemmascens and the more or less composite, fan-shaped colony is almost always bent some-
what inwards, so that the front surface becomes more or less concave. To give any explanation of
the biological significance of these structural features cannot be done with certainty at present, least
of all for our northern species, which only live in great depths. A conclusion by analogy from tropical
species is excluded, since, as Hickson and England (1905 p. 4) point out, we lack all knowledge of
the biology of these animals. - There is a gradual increase in thickness from the outermost small
branches and inwards towards the thick main branches and main stem; the last are almost entirely
free of cyclosystems. The small branches may sometimes show coalescences, but this is seldom.

On the outermost, fine branches we see how the cyclosystems arise alternately on the lateral
sides of the branch; this is the primary condition in the species. The larger cyclosystems however
are not restricted to the lateral part of the branch; they also extend far in over the front surface of
this, as can be seen regularly a few millimetres inside the tip of the branch. The increase in thickness
of the branch proceeds most rapidly on the hind surface; in this we may have one of the causes of
the colony's tendency to bend in towards the front surface. It has the further effect, that the cyclo-
systems are secondarily moved more and more forwards towards the front of the branches, the nearer
we come to their origin; at the same time a few irregularly situated, new cyclosystems arise between
the old. Here and there we also find, that cyclosystems appear quite singly on the back of the colony
but their number here is always very small.

The Ingolf-Expedition. V. \. *

flfl^l

IO STYLASTKRIDAE

When the material available only consists of some few fragments of Stylaster gemmascens, we
may often be inclined to divide it np into several species, as already mentioned. Some pieces
(PI. I figs. 5 — 6) show a regular aspect with uniformly constructed branches; others on the other hand
(PI. I, figs. 4 and y) are irregular in their mode of branching and in the arrangement of the cyclosystems.
A larger material soon shows however, that there is no justification in creating subspecies on the
basis of these variations. Often the appearance of the ampullae may alter the regular structure of the
colony, though not quite so much as in the following species, with which it can easily be confounded.
The most reliable mark of distinction between the two species is found in their cyclosystems and
gasterostyles. But the female ampullae also afford good characters; in Stylaster gemmascens they are
equipped with a varying number of conical, blunt spines; normally we find 3 or 4 of these on the
ampulla, more seldom 2 or 1; often the number may also be larger and once 7 spines were found on
a single ampulla. When the ampullae occur in larger number, these small spines appear in quantities
between the cyclocystems and make the boundaries and arrangement of these indistinct to the naked
eye (PL I fig. 7). Closer examination however shows that the cyclocystems are comparatively little
affected by the ampullae.

The cyclosystems appear as small, oval, stellate elevations except at the very tip of the branches,
where they are still circular in circumference. Even the tops of the septa-like separating walls between
the dactylopores project somewhat strongly above the surface of the colony. The number of the dac-
tylopores in the cyclosystems varies from 12 to 20; in general there are from 14 to 18 dactylopores
round a gasteropore. The wall of the gasteropore shows a deep incision towards the dactylopore.
Any fusion of the dactylopores which lie side by side could not be detected, as is often the case in
some tropical species. — Carefully prepared longitudinal sections made by grinding readily show the
gasterostyle (PI. Ill fig. 21); in Stylaster gemmascens it is pointed, conical and almost twice as high as
broad. A thin section (PI. Ill fig. 24) shows clearly its lattice-work structure. The dactylostyles are reduced
to faint, irregular elevations on the outer wall of the pores; they are very difficult to observe. -
Thin sections of the stem and main branches show very distinctly, that the growth here as in our other
northern Stylaster species proceeds centrifugally and periodically; but it still remains to discover, what
influences in the sea produce this periodic growth in the colonies.

The gasterozooid has the same structure as the hydroid polyp, when we exclude the secondarily
formed gasterostyle (Text-fig. C, PI. Ill fig. 25). Partly near to and partly somewhat below the opening
of the mouth we find four quite small, almost rudimentary tentacles. The small cnidocysts of the
polyp are gathered in these tentacles, though without leading to the formation of a typical, thickened,
distal part such as is found on the capitate tentacles of the Corynidae; their structure agrees fully with
the thread-like tentacles we find in the athecate Hydroids. The ectoderm of the gasterozooid is nor-
mally destitute of stinging cells otherwise. The cell boundaries in the ectoderm are very difficult to
make out; the whole structure here agrees with that of the Hydroids. Often we can observe out-
runners which connect the ectoderm of the polyp wall with the epithelium of the gasteropore wall;
these resemble the irregular outrunners, which are often found in the thecaphore Hydroids and which
here connect the ectoderm of the hydrauth with the hydrotheca outside the true, basal line of attach

STVI,ASTERIDAE II

ment. — The gasterozooid is provided with a strongly developed, supporting lamella. The endoderm
cells are high and show the same cell types that are usually found in the lower Coelenterata; the en-
doderm continues on to the gasterostyle and forms its epithelial covering. Distinct cell boundaries
can in general not be observed in the endoderm of the gasterostyle; the granulated
structure shows, that the albumen cells are decidedly in majority here, whilst
Schneider's "Nahrzellen" (1902 p. 579) compose the main mass of the cells in
the endoderm of the free gasterozooid wall.

A transverse section of the basal part of the gasterozooid gives an extremely
characteristic picture (PL IV fig. 32). The tissues collect into separate columns
which gradually become smaller in diameter and pass over into the stolons. No
lumen could be detected in these columns until they change over into the typical
stolons. Nor do they show any sign of differentiation into ectoderm and en-
doderm like the stolons. The number of columns does not seem to be constant.

The dactylozooids (PI. IV fig. 33) have a very thick and muscular sup- Text-fig. c Diagram-

. , . matic median section

porting lamella and show a more marked power of expansion and contraction through the cvclosvstem

than the gasterozooid. The thick ectoderm of the free wall of the dactylozooid of stylaster (Emtyiaster)

. gemmascens. The tentac-

is densely beset with cnidocysts, but the zoom is not capitate. The endoderm is leg are not represente(1

scalariform and compact and thus the dactylozooid has no central lumen. The in this section. rf = dac-

tylozooid, ^f = free por-
endoderm is on all sides surrounded by the supporting lamella and is not con- tion of the body_wall of

nected with the endoderm of the stolons. The nutrition of the dactylozooid from the gasterozooid, gs =

gasterostyle.
the stolons must therefore take place through its ectodermal wall. —

In spite of the very large material available for investigation I did not succeed in finding
the male colonies and determine their number of gonophores in the ampullae. Nor were young stages
of the female gonophores found in the numerous sections. The fully developed female gonophores
(PI. V figs. 46 and 49) have a complicated spadix. From a narrow base, where the main stolon enters
into the ampullae, the spadix spreads out semispherically; it is formed by numerous, fine, endodermal
blind sacs, the narrow and irregular lumens of which radiate out like the rays of a star from the centre of
the base of the gonophore. As the single blind sacs as a rule have a twisted course and not seldom
branch, the whole picture thus seems very complicated at first sight. The ripe ovum rests on the spadix
like one hemisphere on another and the spherical gonophore, which occupies the ampulla, is surrounded
by a thin endodermal layer. The colonies are not hermaphrodite and it is a puzzle even how fertiliza-
tion takes place in these animals with their closed ampullae. — As the ovum gradually develops to a
planula larva and grows in size, the spadix atrophies, its large cell material being probably used for
the nourishment of the ovum. When the spadix is more reduced (PI. V fig. 50) its structure be-
comes more distinct. — Other stolons of the wall of the ampulla may also secondarily come into
connection with the gonophore and thus increase the amount of nourishment during the embryonal
development.

It has long been an open question whether the larva ruptures the roof of the ampulla when
it escapes. A series of sections through a number of large, empty ampullae points in an opposite
direction; in spite of the fact, that the larva must just have escaped from the ampullae, their roof is

12 STYLASTERIDAE

quite intact. It is probable indeed, that a fairly small opening is simply formed in the roof of the
ampulla, through which the larva escapes. This opening is at once closed again and the ampulla
persists for some time as a large empty space after the larva has escaped. The further fate of the
ampulla has not been observed.

The synonymy of the species offers several difficulties. It is exceedingly doubtful, if it reallv
was this species which Ksper (1797 p. 60) described under the name of Madrepora gemmasccns and
the question cannot be settled from the literature. The reason for nevertheless retaining the specific
name gemmascens here is, that our commonest northern Stylaster, wherever it is mentioned in the
literature, appears under this name. Esper's specimens came from the Indian Ocean but no one
has later found the species there. - The first quite certain and detailed description of the species is
to be found in a treatise of Gunnerus (1768 p. 56), who erroneously identified it with Linne's Madre-
pora virginea; his drawings are the best which have ever been given of the species and the identification
is all the more certain because his specimens are still preserved in the Zoological Museum of Trondhjem.
One of them is reproduced in fig. 4 of PI. I. Gunnerus examined several colonies of this species from
the west coast of Norway, but his work has been passed over by later investigators and thus Esper
has erroneously been taken as the first describer. We thus find, that Milne-Edwards (1857) was still
unacquainted with the fact, that Stylaster gemmasccns lives in northern waters. It was reserved for
G. O. Sars (1872 p. 45) to point out its existence on the Norwegian coasts and he was the first to
refer the northern colonies to Esper's species. In this he is followed by P. M. Duncan, who how-
ever in his work on the material of the "Porcupine" (1874 p. 332) confounds it with Stylaster roseus and
Stylaster (Allopora) norvegicus; on the whole, to judge from his drawings it is extremely doubtful if
Duncan has had any specimens at all of Stylaster gemmasccns. Storm (1879 anc^ 1881) found the
species again in the Trondhjem Fjord and points out that it is fairly frequent in its occurrence there.
Lastly, we find Stylaster gemmasccns mentioned from Rockall; through the kindness of Prof. J. A.
Thomson I have had the opportunity of examining his specimens, which are typical individuals of
the northern species; it is the only certain instance of its occurrence south of the submarine ridge between
Scotland —Iceland and Greenland. Excluding Esper's locality the species has not been found outside
the North Atlantic and even there it lives within a fairly restricted area.

Stylaster roseus (Pallas) Gray

1766 Madrepora rosea, Pallas, Elenchus Zoophytorum p. 312.

1857 Sty/aster roseus, Milne-Edwards, Histoire Naturelle des Coralliaires T II, p. 130 '.

1871 erubescens, Pourtales, Deep-Sea Corals p. 34, PI. IV figs. 10 and n.

?i87i — roseus, Pourtales, I.e. p. 83.

1874 gemmascens pars, P. M. Duncan, Madreporaria . . . "Porcupine" p. 332, PL 49, figs. 13 — 15.

1877 roseus, Lindstrom, Contributions to the Actinology of the Atlantic Ocean p. 15.

1878 erubescens, Pourtales, Corals . . . "Blake" p. 210.

1881 roseus -\- S. erubescens, Moseley, Stylasteridae, "Challenger" pp. 86 and 87.

l) This work contains a detailed list of the older synonymy.

STYLASTERIDAE

*3

The fan-shaped colonies are in general branched in one plane and not recurved; they display
a marked difference between small branches, main branches and stem. The cyclosystems are placed
laterally and alternately on the small branches; their main axis forms an angle of 450 or more with
the longitudinal axis of the branch. The cyclosystems are circular except on the thick main branches,
where they have a more oval form. The cyclosystem shows from 8 to 17, in general 9— 11 quite
separate dactylopores, each provided with an almost rudimentary dactylostyle. The wall of the
gasteropore has quite a small incision towards the dactylopores. The gasterostyle is almost spherical
with the same height as breadth. The gasterozooid has four very small tentacles. - The male am-
pullae generally contain 4 to 6 gonophores and are scarcely seen on the surface of the colony. The female
ampullae appear like hemispheres on the surface of the colony; they are smooth, without spines.
The surface of the colony is smooth and faintly reticulate.

Colour: rose with lighter stem and main branches.

Occurrence: Atlantic Ocean in depths from 230 to 1400m.

Material :

"Ingolf" St. 7 63°i3' N., i5°4i' W

- 15 66°i8' - 25°59' -

- 17 62*49' - 26°55' -

- 52 63°57' - i3°32' -

- 94 64°56' - 36°i9' -
"Thor" 1904 65°5o' - 26°53' -
East Greenland Expedition. Off Angmagsalik

At first glance Stylaster roseus is confusingly like the preceding species; it may especially be
easily confounded with such colonies of the latter as are represented in figs. 5 and 6 of PI. I. Closer
examination however shows that there are great and constant differences between the colonies, so that
they must be taken as representatives of different species. The first mark of distinction apparent on com-
paring larger colonies is the form of colony itself. In Stylaster roseus there is a greater difference
between the main branches and the small branchlets than in the preceding species and the colony is
more robust; in addition, the branching of the colony in Stylaster roseus normally proceeds in a single
plane and it seldom shows a slight tendency to curve inwards towards the front surface. When the
colonies are in full process of reproduction they are often so swollen also in the outermost
small branches (PI. II, fig. n) that there is danger of confusing the species with Stylaster (Allopora)
norvegica. The position of the cyclosystems in relation to each other on the outermost small branches
however shows that the species here dealt with belongs to the subgenus Eustylaslcr. The main axis
of a cyclosystem is at right angles to the axes in the inner-lying and the succeeding cyclosystems and
this is more obvious than in Stylaster gemmascens, where the cyclosystems owing to the smaller angle with
the branch axis do not give the small branches such a distinct zigzag form as in Stylaster roseus. In
addition the number of the dactylopores is on the whole less in Stylaster roseus, their number varying
between 8 and 17 but in general lying about 9 to n. Further, the communication of the dactylopores
with the central gasteropore takes place through a smaller incision in the gasteropore wall than in
Stylaster gem mascens.

1 1 28 m.

4-5° C.

620 -

-0.750 -

1400 -

34° -

789 -

7-87° -

204 -

4-i° -

392 -

?

263 -

?

>4

STYLASTERIDAE

The most decisive and constant characters however are found in the condition of the gastero-
styles and ampullae. Whilst the gasterostyle in the preceding species was conical and twice as high
as broad, in Stylaster roseits it is almost transformed to a spherical lattice-work (PI. Ill, fig. 22), which
rests with a broad base on the bottom of the gasteropore. In fertile colonies the female gonophores
especially project like hemispheres above the surface of the colony; whilst the female gonophores in
the preceding species were equipped with spines, in the present species they are quite smooth. These
are important differences, which compel us to consider the colonies as representing quite different species.

Examinition of the structure of the tissues in Stylaster rosciis reveals such small and unessential
differences from Stylaster gemmascens, that we can only ascribe them to the bad preservation of the
specimens of the present species. It is only represented in the material by dried fragments and
colonies, which have been placed directly in 70% alcohol. The only difference which might possibly prove
to have some importance is, that the large stinging cells, which are extremely seldom in Stylaster
gemmascens and Stylaster [Allopora) norvegicus, are fairly numerous in the stolons of Stylaster roseus\
they are not found here either in the zooids.

Most of the colonies are fertile. There is nothing to indicate that they are hermaphrodite and
the largest specimens, which come from the waters off Angmagsalik (Greenland), are male. The condi-
tion of preservation of the material did not permit any exhaustive examination of the gonophores.
I shall therefore only refer here to some few features, which have some interest when compared
with the few and scattered observations hitherto reported regarding the gonophores of the Stylasteridae. — .
On young developmental stages of the male gonophores (PI. IV fig. 36) we see, that the gonophore
has a well-developed central spadix, which however does not reach the apex of the gonophore
No trace could be found of an endodermal cell layer under the ectoderm, which according to Hickson
(1891 p. 392) surrounds the sperinarium of the gonophore in the Stylasteridae. Nor did I succeed in
finding indications of such a cell layer in the later developmental stages. — When the sexual cells ap-
proach maturity we still find a distinct spadix (PI. IV fig. 39) which extends into the spermarium to-
wards the centre of the gonophore. During the transformation of the spermatocytes to spermatozoa
the spadix atrophies and disappears in gonophores with fully developed spermatozoa.

During the last transformation we should expect to find the development of the seminal duct,
which according to Hickson is characteristic of the Stylasteridae. Fig. 43 of PI. V shows the condition
in Stylaster roseus at a spot where the seminal duct should be expected; the picture is of a gono-
phore with the spermatozoa almost fully formed. A slight thickening of the ectodermal epithelium
can be detected both in the gonophore and on the adjacent part of the roof of the ampulla; but a
comparison with other gonophores indicates that this is merely a chance. Even at this place, where
the spermatozoa would very soon escape, we find no trace of the formation of a seminal duct.
The apex of the gonophore points towards a neighbouring stolon canal and at other places also the
conditions suggest, that the gonophores of the ampulla empty their ripe sex cells into adjoining stolon
canals and not directly out through the roof of the ampulla. The conditions seen cannot be explained
by the state of preservation, for they are the same in all the cases, where the course of the cell layers
can be determined with certaintv.

STYLASTERIDAK 15

The female gonophore in its fundamental features is constructed as in Stylaster gemmascens.
But its spadix is simpler in structure (PI. V figs. 47 and 48); it is bowl-shaped. Whilst the spadix
in Stylaster gemmascens develops blind sacs in the direction towards the central parts of the gono-
phore, all the blind sacs in Stylaster roseus lie along the periphery of the gonophore. The structure
may here be said to be more primitive than in Stylaster gemmascens.

The synonymy of the species is not easily determined with certainty from the literature. No
differences between the available colonies and the old descriptions of Stylaster rosetts can be found.
As the species is the commonest Stylasterid in the Atlantic north of the equator, it is probably the
same form that served as a basis for Pallas' description of Madrepora rosea; the name also agrees with
the colour as noted by the collectors of the present material. The only disagreement to be noticed
between these colonies and Milne-Edwards' description (1857 p. 130) is, that the small branches
seldom show coalescences; but this character is of little importance and can scarcely be considered
sufficient as a specific distinction. Pourtales (1871 p. 34) under the name of Stylaster erubescens
describes a species from the deeper layers at Florida; his excellent figures show at once, that it can-
not be specifically distinct from the North Atlantic Stylaster roseus; on the other hand, it is exceeding v
doubtful if it is this species which he (1. c. p. 83) with doubt refers to Pallas' species as Stylaster
roseus. P. M. Duncan {1874 PI. 49 figs. 13—15) figures the species from the Faeroe Channel, but refers
it erroneously to Stylaster gemmascens. Stylaster rose/is is common in the northern Atlantic south of
the submarine ridge between Scotland— Iceland and Greenland.

Subgenus Allopora (Ehrenberg)
Stylaster norvegicus (Gunnerus)
1768 Millepora norvegica, Gunnerus, Om nogle norske Coraller p. 64, Tab. II figs. 20—22.

1873 Allopora norveg/ca, G. O. Sars, Dyrelivet paa vore Havbanker p. 45.

1874 Stylaster gemmascens pars, P. M. Duncan, Madreporaria . . . "Porcupine" p. 332, PI. 49 figs. 1—3.
1881 Allopora oculma, Moseley, Stylasteridae, "Challenger" p. 85.

^82 norvegica, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna, IV, p. 26.

Z888 — oculma + A. norvegica, Hickson, On the maturation of the ovum and Development of
Allopora p. 595.
The fan-shaped colonies are generally branched in one plane; they are not recurved and show
no distinct division into stem and branches. The cyclosystems are arranged irregularly; they are most
numerous on the front surface of the colony. They are circular or more rarely somewhat oval and
have from 5 to 9, in general 6—7 quite separate dactylopores, each with a faintly developed dactylo-
style. By means of a shallow incision the gasteropore stands in communication with the dactylopore.
The gasterostyle is approximately spherical, of the same height as breadth. The gasterozooid has
from 5 to 7, in most cases 6 quite small tentacles. — The ampullae are deeply imbedded and are hardly
seen on the surface of the colony. The male ampullae contain in general 3, seldom 2 or 4 gonophores.
The surface of the colony is smooth, not reticulated.

l6 STYLASTERIDAE

1400 -

3-4^

790 -

7.87

594 -

5-9°

392 -

?

?

?

?

?

100—400 -

6-5-

Colour: white or faintly rose with strongly yellowish red gasterozooids.

Occurrence: North Atlantic and west coast of Norway at depths from 100 to 1400111.

Material:

"Ingolf" St. 15 66°i8'N., 25°59'W. 620111. -0.750 C.

- 17 62°49' - 26°55' -

- 52 63057' ■ 13032' -

- 55 63°33' - I5°°2' -
"Tlior" 1904 65°5o' - 26°53' -

Hardanger Fjord
(G. O. Sars leg. 187 1) Storeggeu (at Aalesund)

Trondhjem Fjord 100— 400 - 6.5 — 7-50C.

Stylaster norvegicus is of coarser make than the preceding species (PI. II figs. 12 — 15) and shows
no distinct main stem. Even the outermost tips of the branches may often be very thick (PI. II fig. 15)
and the cyclosystems show no regular arrangement as in our Eustylaster species. Nevertheless super-
ficial observation may easily confuse the species with colonies of the preceding species which are de-
formed by the numerous ampullae (cf. PI. II, fig. n). — The branches in Stylaster norvegicus are often
flattened in the transverse plane of the colony. There is a marked difference between the front and
back, the number of cyclosystems being very greatly reduced on the back of the colony (PL II
figs. 13 and 14).

The cyclosystems are very regular in their formation in Stylaster norvegicus. They are almost
circular and surrounded by a slightly raised ridge, which continues out into the septa between the
dactylopores. As the ampullae are very deeply immersed, their development causes no disturbance of
the regular form of the cyclosystems. In general there are 6 or 7, more rarely 8 quite separate dactylo-
pores round the open and deep gasteropore. The wall of the gasteropore shows an incision not specially
deep towards the dactylopore. The short and broad gasterostyle is very characteristic; it is

approximately spherical and has almost the same breadth as height (PL II fig. 23). The dactylostyles are
a little more prominent than in the two previous species, but they are also rather difficult to ob-
serve in Stylaster norvegicus.

The ampullae are deeply imbedded in the branches and in general cannot be seen externally
on the colony; but branches with ampullae are on the whole thicker than sterile branches. - The
growth of the colony proceeds after the same type as in the Sty taster species already dealt with;
the concentric layers, which indicate a periodic growth in the colony, are also distinct here on thin
transverse sections of branches of the colony and are also readily seen in transverse series of sections
of branches which are freed from their calcareous substance.

Whilst in the two preceding species we constantly find four tentacles on the gasterozooids
the number varies in Stylaster norvegicus. As a rule the gasterozooid has 6 quite small tentacles, but
sometimes their number is reduced to 5 or increased to 7. The tentacles (Text-fig. D, PL III figs. 27 and 31)
are also very small here; we might be inclined to call them rudimentary. They are also here the seat
of the small cnidocysts, which the gasterozooid is on the whole provided with. There is no reason

STYLASTERIDAE

17

whatever here or anywhere else to call the tentacles capitate; they are formed quite like the thread-
like tentacles in the athecate hydroids. - Further, the gasterozooid shows in its finer structure no
difference from what has been described in Stylaster (Ewtylaster) gemmas- a

ecus. In the present species it is also broken up at the base into a circle
of columns, the number of which seems mostly to be about 6. — The
structure of the dactylozooid also agrees with that in the other northern
species of Stylaster; but the dactylozooids are somewhat larger in Stylaster
norvegicits than in the previous species. The large cnidocysts are found
in extremely small numbers in the stolons.

Whilst the preceding species was only represented by specimens Text-fig. D. Diagrammatic me-
not very well-preserved, the opportunity was taken to obtain fresh material dian section trough the cycle-

system of Stylaster {Allopora) nor-

of Stylaster norvegicits from the Trondhjem Fjord, in the outer part of vegktis. d = dactylozooid, gt =

which the species is fairly common in suitable localities. Both male and . . gas

1 J = gasterostyle, gw = free part

female colonies could be examined and even if most of the questions of the body-wall of the gastero-

• -ii zooid.

concerning the development of the gonophores must still remain un-
answered, yet the investigation contributes a good deal to the understanding of the nature of the
gonophore in Stylaster.

The sexual cells are already present in the youngest developmental stage of the male gono-
phore which was found (PI. IV fig. 35) so that their origin cannot be settled. The gono-
phore shows clearly, that Hicksou (1891 p. 384) was wrong in maintaining, that "the spermarium is
covered by a double sheath of very thin etcoderm and endoderm". Neither at this stage or later can
anything be seen in the numerous gonophores examined (PI. IV, fig. 37), which could be taken for an
endodermal layer between the ectoderm and the generative cells. -- Hick son (1. c. p. 390) maintains
as a typical difference between the gonophores in Allopora and Distichopora that the latter genus has
no spadix, whilst Allopora has a strongly developed spadix. In Stylaster [Allopora) norvegicits the
spadix is strongly developed in the young gonophores but atrophies during the transformation of the
sperm cells (PI. IV fig. 38) and lastly disappears entirely in the mature gonophore as is the case also
in Stylaster roscus.

The present species forms in part the basis for Hick sou's studies on the seminal duct.
Unfortunately I did not succeed in finding all the developmental stages of it and it is remarkable
that it is not always to be found in almost or quite ripe gonophores in spite of the fact, that the preserva-
tion of the material is excellent. It seems doubtful, if under all conditions it comes to development
even in all gonophores within the same colony; its importance therefore must be reduced in the
general considerations on the group. — The youngest developmental stage found (PI. V fig. 44) appears
as a collection of somewhat higher and lighter-coloured cells at the apex of the gonophore. The rudi-
ment is distinctly double, for under the thickened ectoderm cells there is a collection of inner cells (I), which
have a characteristic, almost fibrillar protoplasmic structure; these fairly large and light-coloured cells
are separated from the outer ectodermal layer by a very fine lamella. At a more advanced stage,
when the seminal duct is almost fully formed (PL V fig. 45) the inner cells push the thin lamella in
front of them into a conical point, which is surrounded by the more deformed ectodermal cells. The

The IngoH'-Expedition. V. 5. 3

!8 vSTYI.ASTRRIDAE

fibrillar protoplasmic structure of the inner cells is still more marked at this late stage than before
aud is most distinctly seen in the distal part of the developing organ. — I did not succeed in finding
a fully formed seminal duct.

We have now the question: from which cell layer arise the inner cells of the duct, are they
ectodermal or endodermal? The question cannot be answered on the basis of the present investigations
If Hick son's view were correct, that the spermarium of the gouophore is surrounded by a thin eudoderm
layer, their origin from the endoderm would be a consequence. But the investigations give no support
to this view and it is contradicted by Hickson's own figure (1891 PI. 30 fig. 15) of the yong gono-
phore in Dislichopora. The endodermal layer round the spermarium might be a later formation, but
this theory does not find any support either in the present investigation. Provisionally therefore the
question of the origin of the inner cells in the seminal duct must remain unanswered.

The female gonophores agree down to the smallest detail with those of Stylaster gemmascens.
The mature egg is surrounded by an ectodermal layer and in Stylaster norvegicus no indication can
be found either of an endodermal layer between the egg-cell and the ectoderm, as Hickson (1891
p. 390) has found to be the case in Distichopora. During the development of the egg the spadix
atrophies and the pictures obtained of the condition in Stylaster gemmascens (PI. V figs. 46. 29 and 50)
are fully illustrative of the conditions in Stylaster uorvcgicus. Here also I did not succeed in finding
the young developmental stages of the female gonophore.

The first description of the species is found in a paper of Gunnerus (1768 p. 64), who calls it Mille-
pora norvegjea. In an appendix (1. c. p. 67) he states that the species is identical with Millepora aspera
which Liune described somewhat later in the nth edition of the Systema naturae. The original
specimens of Gunnerus are preserved in the Zoological Museum of Trondhjem; one of them is
represented in fig. 12 PI. II. - - It is doubtful if it really is the same species which is described by
Eh 1 en berg under the name of Allopora oculina. In Milne-Edwards' diagnosis of the latter
species (1857 p. 132) we find: Coenenchyme tres-developpe, couvert de points tres-serres, visible seulement
avec des verres grossissants . This does not agree with the quite smooth surface, which is characteristic
of Stylaster {Allopora) norvegicus. Oil the other hand, the specimens which are sometimes referred to
in the literature from the Norwegian west coast under the name of Allopora oculina are undoubtedly
identical with Stylaster uorvcgicus, the only Allopora met with in the northern Atlantic. It is this
species which formed the basis of G. O. Sars' classical investigations (1873 p. 45), in which he restores
the specific name of Gunnerus but refers it to the genus Allopora; he is of opinion that the species
is identical with Ehr en berg's Allopora oculina. G. O. Sars was the first to describe the conditions
in a living Stylasterid, after studying colonies of Stylaster norvegicus out on Storeggeu on the west
coast of Norway. He was in doubt as to the coralline nature of the animal, as he never succeeded
in observing the extended polyps, when the colonies were at rest in sea-water, as is the case in our
northern corals otherwise, and when he later studied the preserved animal somewhat more closely he ex-
pressed his opinion (1. c. p. 46): though I am far from considering this *) as completed, yet I have already-
learnt this much, that the animal is essentiall}- different from the other corals and probably does not belong
at all to the Anthozoa but rather to the ffydrozoa-. As is well-known, Moseley a year later (1878)

') i. e. the investigation.

STYLASTERIDAK 19

confirmed the correctness of Sars' supposition. — Since Storm (1882 p. 169) some years later mentioned
the occurrence of the species in the Trondhjem Fjord, we find little or nothing in the literature regarding
its occurrence on the west coast of Norway.

The species has been figured however by P. M. Duncan 11874 PI. 49 figs. 1—3) from material
from the Porcupine:; the identity of the colony from the figures given cannot be doubted, though
the author refers it erroneously to Stylaster gemmascens. Moseley (1881 p. 85) notes the species under
the name of Allopora oculina; Hickson (1888 p. 594) mentions the species from the Hardanger Fjord
as Allopora oculina and from the Tritons Expedition as Allopora norvegica. Apart from the doubt
whether the two species belong together, the present species must in any case under the international
rules of nomenclature retain the specific name which was given it already by Gun n er us in the year 1768.

Remarks on the affinities and systematic position

of the Hydrocorallines.

After L. Agassiz in 1859 had pointed out the Hydroid nature of the Millepora and Moseley
in 1878 had indicated, that the organisation of the Stylasterids also characterised them as Hydrozoa,
no one has doubted that the Hydrocorallines are most nearly related to the Hydroids and in reality
must be regarded as highly specialised Hydroids, whose main characters are the power of the colony
to form a skeleton of calcium carbonate and the polymorphic development of their polyps.
These are thus the main characters which mark off Moseley's order Hydrocorallinac.

Closer consideration of these characters entitles us to doubt, however, whether on such a basis
we are justified in raising the Hydrocorallines to the rank of a special order. If we compare them
for example with the large order of corals, we see how the greater or less ability of the colonies to
separate out carbonate of lime — as for example in the Umbellula species — is only regarded as a specific
character and is not even sufficient for a generic separation of the species, unless the lime-excreting function
is combined with distinct morphological changes in the individuals or colonies. It is thus a question, whether
the latter is the case or not when we compare the Hydrocorallines with the Hydroids. We must therefore in
the first place endeavour to ascertain, to which of the Hydroids the Hydrocorallines are most closely related.

The first hint is obtained from the tectonic structure of the colony itself. The fine anastomosing
canals of the decalcified Hydrocoralline are quite homologous with the stolons of the Hydroid colony;
we thus remark a conspicuous resemblance between the Stylasteridac and the Hydroceratinidae ').
Even the structure of the colony agrees exactly in Clathrozoon Wilsoui Spencer and the primitive
Stylasteridae, only the chitin of the skeleton being replaced in the Stylasteridac by a thick layer of
calcium carbonate. Another Hydroid group also, Solanderiinae (family of Cory//idae, cf. Kiihn 1913)
shows the same structure of the colony and can be imagined as standing near the parent stem of the
Hydrocorallines.

The structure of the polyp will perhaps show the further line of connection. Most Hydroid
investigators lay great stress systematically on the form of the tentacles and consider them one of the
principal phylogenetic characters. Moseley (1881 p. 46) maintains, that the tentacles of the Hydro-

■) By Kiihn (1913 p. 22S) the Hydroceratinidac are considered a subfamily of Bougainvilliidae.

20 STVLASTHRIDAE

corallines, where they occur, are capitate or rather knobbed at their tips . Closer comparison of his
drawings and of the figures later authors have given indicates, however, that the Stylasteridac do not
have capitate tentacles like the Corynidae, even though the cnidocysts are accumulated more densely
in the distal part of the tentacles. It has been pointed out several times in the foregoing, that the
tentacles in the northern Stylasteridae fully agree in their structure with the thread-shaped tentacles
of the Bougaiwvilliidae. On the other hand, the Milleporidae have typical, capitate Corynid tentacles.
This suggests that the Hydrocorallines have a diphyletic origin and that the excretion of a calcareous
skeleton in the two groups is purely a character of convergence. This witnesses further to the
correctness of the separation of the Hydrocorallines into two families, as is done by Hicks on and
England (1905 p. 1.). On the other hand, we are not entitled to regard the two groups as sub-orders
we should rather consider them as two highly specialised Hydroid families. Hickson and England
take the Milleporidae as Hydroids, whilst the}- regard the Stylasteridac as most nearly related to the
Trac/wmcdusae; what support they may have for this last view, does not appear anywhere in their
works; the consequence is, that Hickson in his contribution to The Cambrigde Natural History
(1906) discusses the two families at widely separated places. — The structure of the gasterozooid in
the Stylasterid genera as in Sporadopora and still more Errina agrees fully with the polyp of the
Bougainvilliidae\ excluding the gasterostyle, which phylogenetically must be of fairly recent origin and
which does not occur either in all Stylasterids, the gasterozooids of the Stylasteridae fully agree with
the polyps of Clathrozoon. This indicates, that the latter genus contains the nearest allies of the
Stylasteridae among the Hydroids.

The second main character, the polymorphic development of the polyps in the Stylasteridae,
we find already indicated in such Bougainvilliidae as Hydractinia; in several species of these we find
tentacle-less »feelers« and tentacle-bearing nutritive individuals. In the Hydractinia species this
distinction is not considered a useful mark of generic separation, nor can it be considered so important
a feature in the Stylasteridae, that it can form the basis for a separation of the group into a special
order, even if the dimorphic development of the somatic individuals has become a constant character.

We have hitherto directed attention exclusively to the somatic individuals, assuming that they
give the most important supports in judging of the phylogenetic conditions of the Coeleuterates. —
Hickson (1891) through his evidence of a medusa generation in Millepora has produced the last
incontrovertible proof of the Hydroid nature of this genus; the medusa seems to be an undoubted
Anthomedusa and thus shows clearly the close relationship with the Corynidae. On the other hand
the Stylasteridae have sessile gouophores. Moseley (1881 p. 93) maintains that the gonophores
of the Stylasteridac are .adelocodonic* ; but he regards the spadix of the female gonophores as an
organ (the trophodisc ) special to the Stylasteridae. Hickson later (1888 and 1891) has examined
the gonophores more closely and supports Moseley's view, that the trophodisc is a special formation
in the Stylasteridae which is no direct parallel to the spadix of the hydroid gonophores.

If we consider the manifold nature of the development and organisation shown by the gono-
phores of the Hydroids, the special character of the trophodisc and gonophores of the Stylasteridac
becomes extremely doubtful. In his excellent studies on the hydroid gonophores (1910) Kiihn has
shown, that the medusa reduction may be so complete, that even the endocodou may disappear; thus

STYI.ASTERIDAE

21

\

"V

only the manubrium remains as spadix. In his figures (1888 PI. 38 figs. 4 and 6) Hickson has shown
cases of such reduced gonophores in Distichopora and the northern Stylastcr species also have similar
gonophores. Even though such a gonophore structure has not yet been shown in the Bougainvilludac,
yet it is not without a parallel in the athecate

Hydroids. In Eudendrium racemosum (Cavolini) J stk

the spadix is bifurcated into two or often three *p;
branches, which claw-like embrace the egg-cell
(Text fig. E). This is in fact a simplified tropho-
disc; an increase in the number of the spadix
branchings would very soon lead to the condi-
tion we have found in Stylaster roseus and the s,„,
step from this to the condition in Stylaster ^~~~-su<
gemrnascens and Stylastcr iiorvegicus is also 1 11

short. There is thus no fundamental difference Text-fig. I: Female Gonophore of Eudendrium racemosum (Cavolini)
.... .... ,, . . r ^. .,. , from the Adriatic (95/,)'). II: semidiagrammatic figure of the

present, which justifies the raising of the Stylo- female gonophore of Sly/astr.,. roseus. 0 = OVUII1| ,«=Btalk cf

stertdae to a special order. tne gonophore, stol== main stolon of the gonophore, rfo2 = secon-

dary stolon of the gonophore. sp = blind sacs of the spadix.
There is one condition however to which

Hickson ascribes even greater weight. In his work on the gonophores in Distichopora and Allopora

he states (1891 p. 392): Comparing the adelocodonic gonophores (fig. 4) with the male gonophores of

Allopora (fig. 5), two points of difference may be observed. In the first place the endoderm completely

surrounds the gonad in the latter, excepting at a small aperture at the distal pole, where it forms the

inner wall of a seminal duct. Secondly, there is no layer of ectoderm between this endoderm and the

gonad of Distichopora. In the adelocodonic gonophore there are two layers of ectoderm between the

gonad and the wall of the gonangium-.

Quite apart from the disagreements between Hickson's results and the present studies on the
gonophore structure in the Stylasteridae, his argumentation is hardly maintainable in the light of later
studies on the gonophores of the Hydroids. In a species such as Corync fruticosa Kithn (1910 p. 65,
Taf. 6 figs. 25 — 27) has shown, that the gonophores have just the structure which Hickson gives as
characteristic of Distichopora and Allopora. It is thus not without a parallel in the Hydroids. Much
more rare then is the still simpler gonophore type in the Hydroids, where the endodermal cell-layer
has also disappeared; nor is this without a parallel however; according to Kiihn (1912 p. 199) it has
been found in Gymnogonos crassicornis and in Eudendrium simplex.

The only gonophore type in the Stylasteridae, which in reality differs greatly from the known
conditions in the Hydroids, is the male gonophore in Pliobothrus symmetricus. With its follicular
structure this shows a higher stage in the gonophore structure than any other gonophore we as yet
know from the lower Coelenterata. In reality we have here striking evidence of the fact, that the
gonophore structure has been greatly overestimated in judging of the phylogeny of the Hydrozoa ;
one of the most primitively organised Stylasterids has the most | highly organised gonophore
type of all.

') After specimens from Triest kindly sent me by Hr. Dr. C. I.ehuhofer (Innsbruck).

rc

*»l

22 STYLASTERIDAE

In its structure Pliobothrus shows several features which indicate, that it stands nearer to the
origin of the Stylasteridae than most of the other Stylasterid genera. In the first place, the
zooids are not yet collected into distinct cyclosystems but are irregularly scattered over the colony;
no regularity in the occurrence of the gasterozooids and dactylozooids can be detected. In the second
place, the dactylozooids are less reduced than in the other Stylasteridae, as they still retain their inner
cavity; nor do they show the marked division between an expanded basal part attached to the skeleton
and a distal tentacle-like part, which is inserted obliquely on the basal part, as in most of the other
Stylasteridae. Lastly, the gasterozooids lack a gasterostyle. These features show, when taken together,
that Pliobothrus occupies a primitive position. Pliobothrus shows further, that the conservative, somatic
parts of the colony are less exposed to the influence of the surroundings, to adaptive tendencies, than the
generative parts, the power of which to change plastically in relation to the special biological demands
is of vital importance for the existence of the species. In this therefore we also see the reason for
the great variety displayed by the hydroid gonophores and in this we have the reason, why the
gonophores of nearly allied species may be quite different. Owing to their conservatism in develop-
ment the polyps are of the most important phylogenetic in terest. The gonophores, the
generative individuals, on the other hand, might almost be said to be a play-ball in
the hands of chance biological conditions and thus phylogenetically have much less
interest; they are suited to display the subdivision of the genera into biological adaptive groups
and are thus more exposed to the influence of convergence than the other parts of the colonies.

We must therefore not ascribe too great importance to the condition of the gonophores in
judging of the affinities of the Stylasteridae in relation to the other Coeleuterata. Their organisation
according to the results of all investigations may well be compared with that of the Hydroid gonophores
and even if a single genus shows somewhat special features, the}' can by no means be used as evidence
for the view, that the Stylasteridae are more distantly related to the Hydroids than the Milleporidae.

Bringing together the main points of the above discussion the result is, that we in reality
cannot consider the Hydrocorallines as anything else but two convergent Hydroid families, which are
characterised by their power to develop a skeleton of calcium carbonate and by the dimorphic development
of their somatic individuals. The family Milleporidae traces its origin to that of the Corynidae, whilst
the Stylasteridae is a highly specialised branch which has been derived from the Bougainvilliidae. Just as
the Coryuidae are distinguished from the Bougainvillidae by their capitate tentacles, the Milleporidae
with their capitate tentacles are distinct from the Stylasteridae, in which the tentacles are constructed
like the thread-shaped tentacle type of the Bougainvilliidae.

Zoogeographical remarks on the North Atlantic Stylasteridae.

Few animal groups have been so little investigated in our northern waters as the Hydro-
corallines. They do not form any prominent faunistic element, it is true, as they are only represented
by four species in the northern Atlantic and of these, as known, only two penetrate into the Norwegian
Sea. But by contrast these two species at several places form a very characteristic element in the
large biocoenosis of the Lophohelia reefs and form here a complete and extremely interesting parallel
to the numerous Stylasterid species of the tropical coral reefs.

STYLASTKRIDAE 23

A very speaking example of how little attention has been paid to the Atlantic Stylasteridae
on reference being made to the faunistic conditions of this ocean is found in a statement in Parker
and Haswell's Textbook of Zoology (1897 p. 147): The Hydrocorallinae occur only in the tropical
portions of the Pacific and Indian Oceans, where they are found on the coral reefs : partly or entirely
surrounding many of the islands in those seas.. Nevertheless, some of the oldest, quite identifiable
descriptions of Stylasteridae are those given by Gunnerus in his work Ora nogle norske
Coraller (1768). His figures leave no doubt as to the identity of the species and his originals, which
all came from the west coast of Norway, are preserved in the Zoological Museum of Troudhjem. —
The work of Gunnerus has been little known owing to the humble and little distributed journal
in which the paper was published. But several papers have also been published later in which the
Atlantic Stylasteridae are mentioned and here we must place in the first rank Pour tales' excellent
work on the deep-sea corals (1871), in which he describes quite a number of Stylasterids from the
American side of the Atlantic, especially from the waters round Florida. Pourtales described here
for the first time Pliobothrus symmetricus and also mentions a second of the North Atlantic species,
Sfylaster roseits, under the name of Sfylasfer erubescens. In addition, we have still two other, old
records from the North Atlantic. G O. Sars (187 1) has given a classic description of the living Allopora
norvegica and P. M. Duncan (1874) mentions Stylasterids from the Faeroe Channel. With exception
of the work of Gunnerus all these papers are cited in detail by Moseley (1881) in his great work
on the Stylasteridae of the >- Challenger .

Later information regarding the northern Stylasterids is very meagre. Storm (1882) mentions
Sfylaster gemmascens and Allopora norvegica from the Troudhjem Fjord; there is a casual remark by
Hickson (1891), that he has had material of Allopora oculina from the Hardanger Fjord and of
Allopora norvegica from the ;»Tritou;: Expedition; lastly, J.A.Thomson (1910) informs us, that he
has examined colonies of Sfylaster from Rockall.

On the basis of the literature, therefore, we cannot penetrate very far into the biogeographical
conditions of the northern Stylasterids. In this respect the comparatively large material collected by
the Ingolf , »Thor- and the East Greenland Expedition of 1900 fills up a large gap in out knowledge.
Supplementing this material with that preserved in the museums of Christiania and Trondhjem and
further with observations from the Trondhjem Fjord we are able to throw a fairly good light on the
biogeographical conditions of this enigmatical group in our northern waters.

As already noted, the Stylasteridae in the Norwegian Sea are typical coral reef dwellers.
Yet at places in the Trondhjem Fjord Sfylasfer gemmascens is able to live in somewhat shallower
water, sometimes even in towards a depth of 50 metres. This must depend on the special biophysical
conditions of the fjord and it is of interest to note in this connection, that according to the investigations
the species is only able to live in the shallower parts at places where projecting, submarine cliffs or
barriers force the masses of water upwards which are brought in by the tidal wave. The shallowest
occurrence of the species lies near its innermost boundary in the fjord. In the outer parts of the fjord,
on the other hand, where the sides of the fjord are steeper and more regular, the species as also
Sty taster [Allopora) norvegiciis is bound to the Lophohelia reefs and both species here as elsewhere

24

STYLASTERIDAE

must be regarded as characteristic forms of the large biocoenosis of the coral reefs. This is also
strengthened by the single discovery of Stylaster gemmascens made in the Hjelte Fjord in the
neighbourhood of Bergen, where Dr. O. Nordgaard has obtained two small fragments of colonies
from the coral reef there.

We thus see that the two Stylaster species which occur on the coast of Norway, form interesting
parallels in the animal community of the northern coral reefs to the Stylasterids of the tropical coral
reefs. They are thus, like the Lophohelia reefs as a whole, bound in their occurrence to those localities
with hard bottom, where the Atlantic current makes its influence most felt in the Norwegian Sea.

o

200 111. depth
600 - —

A Pliobothrus symmetricus

A — ineotiipl. geograph. data.

• Stylaster gemmascens

O — roseiis

+ (Allopora) norvegicus

Text-fig. F. Map showing the localities of the Stylasteridae in the North Atlantic and the Norwegian Sea,

- I3°°

The study of the occurrence of the North Atlantic Stylasterids shows several biogeographical
features of interest (cf. Chart Text-fig. F). — PliobotJirus symmetricus was first described from the waters
round about Florida and must be fairly common there between 190 and 300 metres. It has been found
by the »Ingolf« on the steep slope off the south coast of Iceland towards the depths of the Atlantic
in 594 and 658 metres. According to Duncan (1874 p. 336) the .< > Porcupines obtained a single specimen
in the cold area of the Faeroe Channel; unfortunately he does not state the exact locality. We thus
have a species here which belongs to the warm Atlantic waters and normally is not able to penetrate
in over the submarine ridge, which towards the south separates the Norwegian Sea from the depths
of the Atlantic. The one find in the cold area must be a pure chance and forms a parallel to the
single and scattered finds which have been made here and there in the Norwegian Sea of other
typical warm water forms among the Hydroids.

STYLASTKRIDAE 25

Stylaster roseus forms a parallel to Pliobothrus symmetrzcus. It is fairly common between 230
and 620 metres at Florida and on the whole has probably a greater bathymetric distribution than
Pliobothrus symuietricus. Stylaster roseus is much more frequent in its occurrence than the latter form,
bnt is restricted in the Atlantic to the south of the submarine ridges and has not yet been found in
the Norwegian Sea. The Ingolf« has taken the species at a single place in the Denmark Strait in
water of negative temperature; this occurrence is due probably to a submarine wave making the
conditions inhabitable for the species when it became attached as larva or that the station at the time of
observation was covered by a wave of the cold polar water -- In the Norwegian Sea the species is
replaced by the nearly allied Stylaster gemmascens^ which in reality must be ranged with the extremely
few animals, which are entirely bound to the warmer layers of the Norwegian Sea. We may feel tempted
to consider it a biologically defined, local species, which has divided off from Stylaster roseus. The
two species have only been found side by side with certainty at the above-mentioned boundary station
in the Denmark Strait, where the line of separation must be drawn between the Atlantic deep-water
region and the boreal water-layers. This is the only time that Stylaster gemmascens has also been
found in water of negative temperature. Once the species has been identified with certainty south of
the Wy ville-Thomson ridge, a couples of colonies being found at Rockall ; the fauna at Rockall however
has a strong mixture of species, whose chief occurrence is bound to the Norwegian Sea.

Finally, the last species Stylaster norvegicus is an Atlantic species which belongs to the North
Atlantic and has been able to penetrate into the Norwegian Sea, where it has found a new home in
the warmer water-layers there. Its occurrence shows a secondary centre in the Troudhjem Fjord,
where along with Stylaster gemmascens it is more abundant than anywhere else in the northern parts
of the Atlantic. The occurrence of the species in more southern waters cannot be accepted as certain,
for its systematic characters have hitherto been too little unravelled; but it can hardly be very
common there.

Trondhjem, November 1913.

The Ingolf-Expedition. V. 5.

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2S. Storm, V. (1879): Bidrag til Kundskab om Throndhjemsfjordens Fauna. (Det kgl. norske Vidensk. Selsk. Skrifter 1S7S)
Throudhjem.

29. — (1882): Bidrag til Kundskab om Throndhjemsfjordens Fauna IV. (Det kgl. norske Vidensk. Selsk. Skrifter 1881)

Throndhjem.

30. Thomson, J. Arthur (1910): Note on a Hydrocoralline from Rockall. (Proceed. Roy. Phys. Soc. Edinburgh vol. XVIII)

Edinburgh.

x

.".

EXPLANATION OF THE PLATES

The following letters indicate the same parts in all Plates.
Ae Ectodermal epithelium of the ampulla. Gp Gasteropore.

Cn Cnidocysts.
Dp Dactylopore.
Ds Dactylostyle.
Ec Ectoderm.
En Endoderm.
e Ectodermal epithelium of the gastero-
pore wall.
Ge Ectoderm of the gouophore.

Gs Gasterostyle.
I The inner cells of the seminal duct.
O egg cell.
Sp Spadix.
s Stolon.
T Tentacle,
t tabula.
W Free wall of the gasterozooid.

Plate I.

Plate I.

Fig. i. Pliobothms symmetricw, front surface of an intact colon)- from the "Ingolf ' St. 55. Natural size.

— 2. — — hind surface of the same colon)-. Nat. size.

— 3. — — two ends of branches from "Ingolf St. 55. 4/,.

— 4. Sty last rr gcmmascens; one of the type specimens of Gunner us' Madrepora virgin ca from the

west coast of Norway. Nat. size.

— 5. Stylastcr gcmmascens\ front surface of an openly built colony from the Trondhjem Fjord.

Nat. size.

— 6. Stylastcr gemmascais; hind surface of same colony. Nat. size.

— 7. — front surface of the compact branch of a fertile colony ($) from the

Trondhjem Fjord. Nat. size.

— 8. Stylastcr rosct/s; front surface of a fragment of a colony from Angmagsalik with male ampullae

Nat. size.
— 9. Stylastcr roseus; hind surface of the same fragment. Nat. size.

The Inoolf Expedition, V, 5.

Broch: Stylasteridce. Tab. I.

Hj. Broch'iphot.

Nordenfjeldske Klicheanstalt.
Waldemar Janssens Boktrykkeri.

Plate II.

Plate II.

Fig. 10. Stylaster rose-us; front surface of a fragment of a colony with female ampullae; "Ingolf" St. 15.
Nat. size,
n. Stylaster rose/is; fragment of a colony which is entirely deformed owing to the development
of numerous female ampullae; "Ingolf" St. 7. Nat. size.

— 12. Stylaster norvegicus; one of the type specimens of Gunner us' Millcpora norvegica from

west coast of Norway. Nat. size.

— 13. Stylaster norvegicus; front surface of a narrow-branched colony from Trondhjem Fjord. Nat. size.

— 14. — hind surface of the same colon}'. Nat. size.

— 15. front surface of a broad-branched colony from Trondhjem Fjord. Nat. size.

— 16. geinniasccns; ends of two branches of a colony from Trondhjem Fjord. 4/t.

— 17. roseus\ end of a branch of a colony from "Ingolf" St. 15. */z.

— 18. norvegicus; ends of two branches of a colony from Trondhjem Fjord. 4 ,.

<■ **<

2 1"

The Ingolf Expedition, V, 5.

Broch : Stylasterida : Tab. II.

Hj. Broch phot.

Nonlenfjeldske Klicheanstalt.
Walilemar Janssens Boktrykkeri.

Plate III.

Plate III.

F"ig. 19. Pliobothrus symmetricus; median longitudinal section of a branch point. l6/.,.

— 20. median section through a gasteropore with tabula. l6/j.

— 21. Stylaster getnmascens\ median longitudinal section of a branch. i6/l

— 22. rose/is; median longitudinal section of a branch. l6/r.

— 23. norvegicus; longitudinal section through two cyclosystems. l6/\.

24. Median, longitudinal, thin section of the gasterostyle in Stylaster gemmascens. 9°/..

— 25. Longitudinal section of the gasterozooid in Stylaster gemmascens. Ii°/1.

— 26. Transverse section of the gasterozooid at the base of the tentacles in Stylaster gemmascens. 3°°/,
27. Oblique transverse section of the gasterozooid at the base of the tentacles in Stylaster

norvegicus. 3°°/lP

— 28. Transverse section of the gasterozooid in Pliobothrus symmetricus. 30o/t.

29. Longitudinal section through the oral part of the gasterozooid wall in Pliobotlirits syiiune-

tricus. 450/j.

30. Longitudinal section through the oral part of the gasterozooid wall and tentacle in Stylaster

gemmascens. 45<yT.

31. Longitudinal section through oral part of the gasterozooid wall and tentacle in Stylaster

norvegicus. 45°/,.

Dp

The Ingolf Expedition, V, 5.
Go

C 1 1 x

Dp

op

m

19.

Ds

23 a

23 b

En

Gs

....

**. -

• • •

■ ♦

ft

•'.*..

26.

En

24.

Broch: Stylasteridce. Tab. III.

W

h

■■&

21.

22.

Gs

■

In

Ec

25.

28.

• .

En

— en

en

■
■

> *\* •
*• . *

en

29.

Hj. Broch del.

30.

31.

Nordenffeldske KUcheanstalt .
W'aldemar Janssens Eoktrykkeri,

Plate IV.

Plate IV.

Fig. 32. Transverse section of the gasterozooid at its base near its transition into the stolons in Sty luster
gemmascens. 3°%.

33

34
35
36
37
38.

Longitudinal section of the dactylozooid in Stylastcr gemmascens. $°°/t.

Transverse section of a dactylozooid in Pliobothrus symmetricus. 3°%.

Median longitudinal section of a very young gonophore (J1) in Sty/aster norvegicus. 45°/j.

Median longitudinal section of a young gonophore (J1) in Stylastcr roseus. 45°/^

Median longitudinal section of an unripe gonophore (c?) in Stylastcr norvegiciis. 3°°^.

Median longitudinal section of two gonophores (c?) in Stylastcr norvegicus. The larger with
spadix partially atrophied contains spermatocytes in process of transformation to sperma-
tozoa. lT>°U.

39. Median longitudinal section of a gonophore (<?) in Stylastcr roseus; the spermatocytes in process
of transformation to spermatozoa. 1i°/1.

— 40. Transverse section of a young gonophore (J1) in Pliobothrus symmetricus. i°°/s.

— 41. Median longitudinal section of a gonophore (0*) in Pliobothrus symmetricus. 3°°/^

— 42. Median longitudinal section through apex of the fully developed gonophore in (<$) Pliobothrus

symmetricus. i00/^

The Ingolf Expedition, V, 5.

Broch: Stylasteridce. Tab. IV.

i-\

En

Fn

34.

ir

33.

Ai

■■:

38.

Sp — m

Ge

35.

Gt

Sp

36.

37.

39.

Sp

/##&
X&&}?.

40.

Hj. Broch del.

Ge-

Sp

"•9M - JSP .••.•/.•.«.

4/.

S/;

s

«

Ae

•$*&

Nordenfjeldske KUcheanstalt.
Waldemar Janssens Boktrykkeii.

Plate V.

Plate V.

Fig. 43. Apex of a gonophore (cT) in Stylaster roseus, containing spermatocytes in process of trans-
formation. +so 1.

— 44. Early stage in the development of a seminal duct in Stylaster norvegicus. 4S°/t.

— 45. Longitudinal section through an almost full-grown seminal duct in Stylaster norvegicus. i;" ,.
46. Median longitudinal section through a gonophore (°j with ripe ovum in Stylaster gemmascens. 3°° x.

— 47. Median longitudinal section of a gonophore |C) with ripe ovum in Stylaster roseus. 1;" ,.

48. Transverse section of a gonophore ($) near the distal end of the spadix in Stylaster roseus. '3° ,.

— 49. Transverse section of the spadix close beneath the ovum in Stylaster gemmascens. l3f/I.

— ^o. Median longitudinal section through a gonophore with advanced planula larva in Stylaster

gemmascens. 1i°l'1.

The Ingolf Expedition, V, 5.

Broch: Stylasteridce. Tab. V.

43.

Ge

46.

Ae

O

Ge

,1,

44.

(i,

Sp

Ge

49.

45.

O

Ge

Sp

47.

(je

Sp

/

Ge

48.

Hj. Broch del.

50.

Sp

Nordenjjeldske Kticheansialt.
Waldemar Janssens Boktrykkeri.

THE INGOLF-EXPEDITION

1895 — 1896.

THE LOCALITIES, DEPTHS, AND BOTTOMTEMPERATURES OF THE STATIONS

Depth

Depth

Depth

Station

Nr.

Lat. N.

Long. W.

in
Danish
fathoms

Bottom-
temp.

Station

Nr.

Lat. N.

Long. \Y.

in
Danish
fathoms

Bottom-
temp.

Station
Nr.

Lat. N.

Long.W.

in
Danish
fathoms

Bottom-
temp.

I

620 30'

8° 21'

132

7°2

24

63° 06'

56°oo'

1 199

2°4

45

6i°32

9° 43'

643

4°i7

2

63° 04'

9° 22'

262

5°3

25

63° 3°'

54° 25'

5S2

3°3

46

6i°32'

n° 36'

720

2°40

3

63° 35'

io° 24'

272

o°5

63°5i'

53° 03'

136

47

61 ° 32'

13° 40'

95o

3°23

4

64° 07'

ii° 12'

237

2°5

26

63° 57'

52° 41'

34

o°6

48

6i°32'

15° «'

1 150

3°i7

5

640 40'

12° 09'

155

64° 37'

54° 24'

109

49

62° 07'

15° 07'

1 1 20

2°9I

6

63° 43'

14° 34'

90

7°o

27

64° 54'

55° lO-

393

3°8

50

62° 43'

15° 07'

1020

3°i3

7

63° 13'

15° 41'

600

4°5

28

65° 14'

SS0 42'

420

3°5

5i

64° 15'

14° 22'

68

7°32

8

63° 56'

24° 40'

136

6°o

29

65° 34'

54° 31'

6S

0°2

52

63° 57'

13° 32'

420

7°87

9

64° 18'

270 00'

295

5°8

3°

66° 50'

54° 28'

22

i°05

53

630 15'

15° 07'

795

3°o8

IO

64° 24'

280 so-

788

3°5

31

66° 35'

55° 54'

88

i°6

54

63° 08'

15° 40'

691

3°9

II

64° 34'

Si0 12'

1300

i°6

32

66° 35'

56° 38'

318

3°9

55

63° 33'

15° 02'

3i6

5°9

12

64° 38'

32° 37'

1040

o°3

33

67° 57'

55° 3°'

35

o°8

56

64° 00'

15° 09'

68

7°57

'3

64° 47'

34° 33'

622

3°o

34

65° 17'

54° 17'

55

57

63° 37'

13° 02'

35°

3°4

14

64° 45'

35° 05'

176

4°4

35

65° 16'

55° 05'

362

3°6

58

64° 25'

12° 09'

211

o°8

15

66° 18'

25° 59'

330

-o°75

36

61° 50'

56° 21'

1435

i°5

59

65° 00'

11° 16'

3io

-o°i

16

65° 43'

26° 58'

250

6° 1

37

60° 17'

54° 05'

1715

i°4

60

65° 09'

12° 27'

124

o°9

17

62° 49'

26^ 55'

745

3°4

38

59° I2'

5i° 05'

1870

i°3

61

65° 03'

13° 06'

55

o°4

18

61° 44'

3°° 29'

"35

3°°

39

62° 00'

22° 38'

865

2°9

62

63° 18'

19° 12'

72

7°92

19

60° 29'

34° 14'

1566

2°4

40

62° 00'

210 36'

845

3°3

63

62° 40'

I9° 05'

800

4°o

20

580 20'

400 48'

1695

i°5

4i

61° 39-

17° 10

1245

2°0

64

62° 06'

I90 OO'

1041

3°i

21

58° 01-

44° 45'

1330

2°4

42

61° 41'

io° 17'

625

o°4

65

61° 33'

19° 00'

1089

3°°

22

580 10'

48° 25'

1845

1-4

43

61° 42'

10° ti'

645

o°o5

66

6i°33'

20° 43'

1128

3°3

23

60° 43'

560 00'

Only toe

Plankton Net

used

44

6i°42'

9° 36'

545

4°8

67

61° 30'

22° 30'

975

3°°

Depth

Depth

Depth

Station
Nr.

Lat. N.

Long. W.

in
Danish
fathoms

Bottom-
temp.

Station

Nr.

Lat. N.

Long. W.

in
Danish
fathoms

Bottom-
temp.

Station

Nr.

Lat. N.

Long.W.

in
Danish
fathoms

Bottom-
temp.

68

62° 06'

22° 30'

843

3°4

92

640 44'

32° 52'

976

i°4

118

68° 27'

8° 20'

1060

i°o

69

620 40'

22° 17'

589

3°9

93

64° 24'

35° 14'

767

i°46

119

67°53'

10° 19'

1010

— 1°0

7°

63° 09'

22° 05'

134

7°o

94

64° 56'

36° 19'

204

4°r

1 20

67° 29'

II°32'

885

i°o

7i

63° 46'

22° 03'

46

65°3i'

30° 45'

213

121

66° 59'

13° "'

529

— o°7

72

63° 12'

23° °4'

197

6°7

95

65° H'

3°° 39'

752

2°I

122

66° 42'

14° 44'

"5

i°8

73

62° 58'

230 28'

486

5°5

96

65° 24'

29° 00'

735

I°2

123

66° 52'

15° 40'

145

2°o

74

620 17'

240 36'

695

4°2

97

65° 28'

27° 39'

45o

5°5

124

67° 40'

15° 40'

495

-o°6

61° 57'

25° 35'

761

98

65° 38'

26° 27'

138

5°9

125

68° 08'

16° 02'

729

— o°S

61° 28'

250 06'

829

99

66° 13'

25° 53'

187

6°i

126

67° 19'

15° 52'

293

-o°5

75

61° 28'

260 25'

780

4°3

100

66° 23'

14° 02'

59

o°4

127

66° 33'

20° 05'

44

5°6

76

6o° 50'

26° 50'

806

4°i

101

66° 23'

12° 05'

537

— o°7

12S

66° 50'

20° 02'

194

o°6

77

6o° 10'

26° 59'

95i

3°6

102

66° 23'

io° 26'

75°

— o°9

129

66° 35'

23° 47'

117

6°5

78

6o° 37'

27° 52'

799

4°5

i°3

66° 23'

8° 52'

579

-o°6

130

63° 00'

20° 40'

338

6°55

79

60° 52'

280 58'

653

4°4

104

66° 23'

7° 25'

957

— i°i

13"

63° 00'

I90 09'

698

4°7

80

61° 02'

29° 32'

935

4°o

i°5

65° 34'

7° 3i'

762

— o°8

132

63° 00'

I 7° 04'

747

4°6

81

61° 44'

27° 00'

485

6°i

106

65° 34'

S°54'

447

-oc6

133

63° 14'

11° 24'

230

2°2

82

61 ° 55'

270 2S'

824

4° 1

65° 29'

8° 40'

466

134

62° 34'

io° 26'

299

4° 1

33

62° 25'

2S0 30'

912

3°5

107

65° 33'

10° 2S'

492

-o°3

135

62° 4S'

9° 48'

270

o°4

62° 36'

26°Ol'

472

108

65° 3o'

12° 00'

97

i°i

136

63° 01'

9° 11'

256

4°8

620 36'

25° 30'

401

109

65° 29'

13° 25'

38

i°5

137

630 14'

8° 31'

297

— o°6

84

620 58'

250 24'

633

4°8

no

66° 44'

ii° 33'

781

— o°8

138

63° 26'

7° 56'

47i

-o°6

85

63° 2l'

25° 21'

170

in

67° 14'

8° 48'

S60

— o°9

139

63° 36'

7° 30'

702

-o°6

86

65 ° 03'6

230 47'6

76

112

67°57'

6° 44'

1267

— I°T

140

63° 29'

6° 57'

780

—o°9

87

65° 02'3

230 56',

no

113

69° 31'

7° 06'

1309

— i°o

141

63° 22'

6° 58'

679

-o°6

88

64° 53'

240 25'

76

6°9

114

70° 36'

7° 29'

773

— i°o

142

63° 07'

7° 05'

587

-o°6

89

64° 45'

27° 20'

310

8°4

"5

70° 50'

8° 29'

86

o°i

143

62° 58'

7° 09'

388

-o°4

90

64° 45'

290 06'

568

4°4

116

70° 05'

8° 26'

37i

-o°4

144

62° 49'

7° 12'

276

i°6

91

64° 44'

31° 00'

1236

3°i

117

69° LV

8° 23

1003

— 1°0

■■&mi-

THE DANISH INGOLF-EXPEDITION.

HITHERTO PUBLISHED:

1899.

1900.

1899.
1899.

1900.
1904.

1912.

1899.

1908.

1903.
1907.
1914.
1904.
1912.

1912.

I9I3-
1914.

1902.

!9°5-
1910.

Vol. I, Part I. 1. Report of the Voyage by C. F. Wandel (1 plate) j

2. Hydrography by Martin Knudsen (34 plates) )

Part II. 3. The deposits of the sea-bottom by O. B. Bocggild

(7 charts)

4. Current-bottles by C. F. Wandel (1 plate)

Vol. II, Part I. The ichthyological results by Chr. Liitken (4 plates) ...
Part II. On the Appendices genitales (Gaspers) in the Greenland-
Shark, Somniosus mierocephalus (Bl. Sehu.), and other Sela-
chians by Hector F. E.Jungersen (6 plates)

Part III. Nudibranchiate Gasteropoda by R. Bergh (5 plates)...

— Part IV. The North-European and Greenland Lycodiua? by
Adolf Sever in Jensen (10 plates)

Part V. Lamellibranchiata, Part I, by Ad. S. Jensen. (4 plates

and 5 figures in the text)

Vol. Ill, Part I. Pyenogonidse by Fr. Meinert (5 plates)

Part II. Crustacea Malacostraca, I: Decapoda, Euphausiacea,

Mysidacea by H. J. Hansen (5 plates)

Part III. Crustacea Malacostraca, II: Tanaidacea by H.J. Hansen

(12 plates; -

Vol. IV, Part I. Echinoidea, Part I, by Th. Mortensen (21 plates)

Part II. Echinoidea, Part II, by Th. Mortensen (19 plates)

Part III. Chaetognaths by R. von Ritier-Zahony

Vol. V, Part I. Pennatulida by Hector F. E.Jungersen (3 plates)

Part II. Ctenophora by Tli. Mortensen (10 plates and 15 figures

in the text)

Part III. Ceriantharia by Oskar Carlgren (5 plates and 16 figures

in the text)

Part IV. Zoantharia by Oskar Carlgren (7 plates and 6 figures
in the text)

— Part V. Stylasteridae by Hjahnar Brocli (5 plates and 7 figures
in the text)

Vol. VI, Part I. Porifera (Parti), Homorrhaphidae and Heterorrhaphidre

by Will. Lundbcck (19 plates)

Part II. Porifera (Part 2), Desrnacidonidse (Pars) by Will. Luudbeck

(20 plates)

Part III. Porifera (Part 3), Desmaeidonidae (Pars) by Will. Lundbcck
( 1 1 plates)

C\v'

Kr.

25,00 (Sh. 30)
8,00 ( - 11)

13,00 ( - 18)

4,75 ( -

7)

9,75 I -

13)

8,00 ( -

")

6,00 ( -

9)

8,00 ( - II)

13,00 ( -

18)

20,00 ( -

24)

19,00 ( -

23)

0,50 ( -

1)

6,50 ( -

9)

10,50 ( -

14)

6,00 ( -

9)

7,00 ( -

10)

4-75 ( -

7)

•

17,00 ( -

22)

20,50 1 -

25)

12,00 ( -

16,