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THE DANISH
Mee EP XTE DITION.
VOL. V B.
PUBLISHED AT THE COST OF THE GOVERNMENT
BY
THE DIRECTION OF THE ZOOLOGICAL MUSEUM OF THE UNIVERSITY.
COPENHAGEN.
H. HAGERUP. PRINTED BY BIANCO LUNO AJs.
1914-1919.
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THE DANISH
pee OLS EXPE DITION.
VOL... VooPAR D5
CONTENTS:
HJALMAR BROCH: STYLASTERIDAE.,
PUBLISHED AT THE COST OF THE GOVERNMENT BY
THE DIRECTION OF THE ZOOLOGICAI. MUSEUM OF THE UNIVERSITY.
hare 9 NOY ME D9 — caer
COPENHAGEN. H. HAGERUP.
PRINTED BY BIANCO LUNO.
TQ14.
THE DANISH INGOLF-EXPEDITION.
VOLUME V.
oD.
SEY LAS EPRIDA|
BY
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HJALMAR BROCH.
WITH 5 PLATES AND 6 FIGURES IN THE TEXT.
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COPENHAGEN.
PRINTED BY BIANCO LUNO.
IOI 4.
CONTENTS.
Stylasteridae. Page ESL a i arcs ae art Bs Tl ee a i ae rae I The! Stylasteridae of the. North Atlantic (020. 0. ch eee hae eka Dene vee 3 INRIA” CPTUNE CR Cries erste te Oe SN cee ee et a eha x fF MOPOLREUS: SUMINERFICNS, EC OWEE ALC is ogc isa ais sain nb ale ns hlevidiaeweees 3 ej eal ERC agli rN 25 Stoeee bianca ABU ee un eee a a ald y Styluster: gennawens CE BD EL) Hiei. sats oUF Sek. Vesa orca 8a 8 I 8 a POSCME Cl GERSON case con sap c ciassiaiel asa 's eas 9% os RU ATR eof a ae 12 _ HOP UDCUS (er BOLUS) eee Fo oe ae wiht ey a bas esa we sen 15 Remarks on the affinities and systematic position of the Hydrocorallines ......... 19 Zoogeographical remarks on theNorth Atlantic Stylasteridae ...........00.0.0.4. 22
Literature
arse om se se Le
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 colony. 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 Stylaster, 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 Ingolf-Expedition, V. 5. -
2 STYLASTERIDAE
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 uns nicht verhehlen, dass jede Art, von der nur das Skelett vorliegt, als unvollstandig bekannt gelten muss, gleichgiltig, ob ihr anatomischer Bau fiir 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 counterstaining 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 F/abellwm 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, Cystt- phyllum and Anabacia, whilst aragonite has been found in the following genera of Coelenterates: Heliopora, Montipora, Echinopora, Distichopora, Madrepora, Stylopora, Pocilopora, Millepora, Seriatopora, Goniastraea, Podobacea, Galaxea, Fungia, Dendrophyllia, Porites, Astroides, Hydnophora, Sclerohelia, Coeloria, Pterogyra, Merulina, Favia, Stylaster and Trachypyllum. — At my request the assistant at the Geological Institute of the Polytechnic High School in Trondhjem, Dr. C. W. Catstens, has examined the skeletons of our four northern Stylasterids. Examination by means of Meigen’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, Cysti- phyllum 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.
STYLASTERIDAE 3
The Stylasteridae of the North Atlantic.
Pliobothrus Pourtalés
The colonies are branched fan-shaped, often with dichotomously divided branches 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 Piobothrus 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 Pourtalés 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 Pliodothrus and the genus Steganopora recently described by Hickson 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 Pliodothrus. The species Steganopora spinosa Hickson and England, the only known species of this genus, stands very near to Pliobothrus tubulatus Pourtalés and will possibly on closer examination prove to be identical with the latter.
Pliobothrus symmetricus Pourtalés.
1871 Pliobothrus symmetricus, Pourtalés, Deep-Sea Corals p. 57, Plate IV, figs. 7 and 8.
1874 — = , P. M. Duncan, Madreporaria .... “Porcupine” p. 336, Plate 49, fig. 7. 1879 — — , Pourtalés, 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 1*
4 STYLASTERIDAE
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., 15°02’ W. depth 594m. 5.9°. C.
— - 57 63°35’ - 13°02’ - — 658 - 34°.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. Pourtalés’ drawing of Pliobothrus tubulatus (1871, Pl. 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 Phobothrus 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 5
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 Stylasterfdac 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 (Pl. III, 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 —_‘Text-fig. A. Diagram showing
: . , Z ; Z the arched development of the at right angles to its longitudinal axis and the latter will therefore become pores in Ptiobothrus symmetri-
cus during the growth of the
curved during the growth of the branch, as will be seen from the ac- iret : y:
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 dactylopores 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 Plobothrus 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 Steganopora 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 Phobothrus, is said by Hickson and England to be a constant and always occurring character in Steganofora and here also results in an open and direct communication between the gasteropores and the dactylopores. Such a communication also occurs irregularly in Plzo- 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 Plobothrus.
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
6 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 the figures (Text-fig. B, Pl. III, 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 (Pl. III, 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 Pliobothrus symmetricus, ec = ectoderm, en= endoderm, m=mouth, are more uniformly distributed in the ectoderm in the whole length of the § = stolones, gw =the epi- thel of the gasteropore, pf
= mouth of the gastero- Moseley’s drawing (1881 Pl. VIII, fig. 2) the gasterozooid should have a wide, pore, (°];).
entirely disappear further down on the polyp wall; in the dactylozooids they zooid, but become however less numerous near its basis. — To judge from
cruciform mouth in Pliobothrus 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 Hickson and England state (1905 p. 13): “The solid scalariform endoderm of the ‘dactylozooids is another very distinctive feature of the group”. This does not hold good for Plobothrus symmetricus; the dactylozooids have a distinct lumen in their centre, as shown in transverse sections (Pl. 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 Pliobothrus 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 S¢y/asteridae. 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 (Pl. IV, figs. 4o—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 than 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 Piobothrus symmetricus, The apex of the compound gono-
STYLASTERIDAE 7
phore is prolonged (Pl. 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 Sty/astertdae. The branched spadix and the variating stage of development of the reproductive cells in the single pseudofollicles point in this direction. Investigation of the Sty/aster 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 Phobothrus 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 already known from the work of Moseley. Thus nothing was found which differed from his description. —
Pliobothrus symmetricus was first described by Pourtalés (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 A//opora 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 /ustylaster; the last group has just the arrangement of the cyclosystems which is characteristic of A/lopfora; species like Stylaster divergens Marenzeller and A/dlo- pora rosacea Greeff obviously occupy intermediate positions between our northern AWofora species with its hardly prominent cyclosystems and those S¢ylaster species which have very prominent, almost stalked cyclosystems. For group D. the old generic name A//ofora 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 Zw-
8 STYLASTERIDAE
stylaster 'species may sometimes become so blown up and deformed that they may easily enough be confused with the AJd/ofora species. To facilitate the [determination in difficult cases I give in the
following table their distinctive features.
gemmascens roseus norvegica
Cyclosystems || with r2—20, normally 14—18dactylo- | with 8—16, normally 9—11 dactylo- | with 5—9, normally 6—7 dactylo- pores. Wall of gasteropore deeply | pores. Wall of gasteropore slightly | pores. Wall of gasteropore slightly
incised towards the dactylopores. incised towards the dactylopores. | incised towards the dactylopores. Gasterostyles conical, twice as high as broad. | almost globular with same breadth almost globular with same as height. breadth as height.
Ampullae (9) || near thesurfaceand projecting like a | near thesurfaceand projecting likea | deeply embedded, scarcely seen hemisphere; equipped with bluntspines. hemisphere; without spines. externally on the colony.
Subgenus Eustylaster nov. Stylaster gemmascens (Esper) Milne-Edwards et Haime. r 1768 Madrepora virginea, Gunnerus, Om nogle norske Coraller p. 56, Tab. VIII, figs. 2—4. nec 1758 Madrepora virginea, Linné, Systema naturae ed. X, vol. I, p. 798. ?1797 Madrepora gemmascens, Esper, Fortsetzungen der Pflanzenthiere, T. I, p. 60, Tab. 55. 1857 Stylaster gemmascens, Milne-Edwards, Histoire naturelle des Coralliaires p. 130%).
1873 oe a , G. O. Sars, Dyrelivet paa vore Havbanker p. 45.
21874 — — , pars, P. M. Duncan, Madreporaria .... “Porcupine” p. 332.
187900 — oa , Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna p. 24. 1881 -- — , Moseley, Stylasteridae “Challenger” p. 86.
1882 -= — , Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna IV, p. 25. IgIO - — , J. A. Thomson, Note on a Hydrocoralline from Rockall p. 61.
1912 — — , Nordgaard, Faunistiske og biologiske iagttagelser p. 7.
IQI2 _ — , 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—560 m. depth, Rockall. (Indian Ocean?)
') This work contains a detailed list of the older synonymy.
STYLASTERIDAE 9
Material: “Ingolf” St. 15 66°18’ N. 25°59’ W. 620m +075°C, Hjeltefjord ca. 150m. Gidsk6é (Séndmére) ?
West coast of Norway; _. ‘2 Sondmore ?
Trondhjem Fjord 50—4o00m. 6.5—8.5° C.
The form and appearance of the colonies are subject to such great variations in S¢y/aster gemmascens, that we may often be in doubt as to whether one and the same species is before us. The available material was very large, especially from the Trondhjem Fjord, where the species is fairly common and more luxuriantly developed than from any 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 “facies”. As the most illustrating examples I may mention his treatment of Stylaster eximius Duchassaing et Michelotti (1905) and Zrrina nova-zelandiac 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 laterai 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. 5. 2
10 STVYLASTERIDAE
When the material available only consists of some few fragments of .Stylaster gemmascens, we may often be inclined to divide it up into several species, as already mentioned. Some pieces (Pl. I figs. 5—6) show a regular aspect with uniformly constructed branches; others on the other hand (Pl. I, figs. 4 and 7) 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 (Pl. III fig. 21); in Stylaster gemmascens it is pointed, conical and almost twice as high as broad. A thin section (PI. III 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, Pl. III 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 hydranth with the hydrotheca outside the true, basal line of attach
STYLASTERIDAE 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 “N&ahrzellen” (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 (Pl. 1V fig. 33) have a very thick and muscular sup- Text-fig. GC Diagram- matic median section through the cyclosystem than the gasterozooid. The thick ectoderm of the free wall of the dactylozooid of Stylaster (Zustylaster) gemmascens. The tentac- les are not represented scalariform and compact and thus the dactylozooid has no central lumen. The _ in this section. d= dac-
é . F 3 . tylozooid, g= free por- endoderm is on all sides surrounded by the supporting lamella and is not con- 45... of the bo iy-wall of
nected with the endoderm of the stolons. The nutrition of the dactylozooid from _ the gasterozooid, gs = gasterostyle.
porting lamella and show a more marked power of expansion and contraction
is densely beset with cnidocysts, but the zooid is not capitate. The endoderm is
the stolons must therefore take place througt 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 (Pl. 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 (Pl. 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 2*
om 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 really was this species which Esper (1797 p. 60) described under the name of Madrepora gemmascens and the question cannot be settled from the literature. The reason for nevertheless retaining the specific name gemmascens here is, that our commonest northern S¢y/aster, 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 Pl. 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 S/ylaster gemmascens 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 S¢ylaster 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 gemmascens. Storm (1879 and 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 gemmascens 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 Stylaster roseus, Milne-Edwards, Histoire Naturelle des Coralliaires T. II, p. 130%
1871 _ erubescens, Pourtalés, Deep-Sea Corals p. 34, Pl. IV figs. 10 and 11.
21871 — roseus, Pourtaleés, 1. c. p. 83.
1874 - gemmascens pars, P, M. Dutican, Madreporaria ... “Porcupine” p. 332, Pl. 49, figs. 13—15- 1877 _- roseus, Lindstrém, Contributions to the Actinology of the Atlantic Ocean p. 15.
1878 — erubescens, Pourtalés, Corals ... “Blake” p. 210.
1881 _— roseus -\- S. erubescens, Moseley, Stylasteridae, “Challenger” pp. 86 and 87.
t) This work contains a detailed list of the older synonymy.
STYLASTERIDAE 13
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 45° 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 1400 m.
Material: :
“Ingolf”? St. 7 63°13’ N., 15°41’ W. 128m. 4.5° C. ~~ - 15 66°18’ - 25°59' - 620 - —0O.75° - ~~ 2 17 62°49' - 26°55’ - I400- 3.4° Pr. 8a OS Ag 789. +1, 7-87. eet. 2 64°56’ - 36°19’ - = 204 - — 4.T? -
“Thor” 1904 65°50' - 26°53' - 392 - fs
East Greenland Expedition. Off Angmagsalik 263 - ?
At first glance Sty/aster 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 Pl. 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 S¢ylaster 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. 11) that there is danger of confusing the species with Stydaster (Adlopora) 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 Zwsty/aster. 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 11. Further, the communication of the dactylopores
with the central gasteropore takes place -through a smaller incision in the gasteropore wall than in Stylaster gemmascens.
14 STVLASTERIDAE
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 roseus it is almost transformed to a spherical lattice-work (PI. III, 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 S¢ylaster roseus 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 Sty/asteridae. —. On young developmental stages of the male gonophores (Pl. 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 spermarium of the gonophore in the Stylasferidae. 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 (Pl. 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 Pl. 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 spérmatozoa 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 certainty.
soa a
etree Whe
, > Se a a ee
a —- el
STYLASTERIDAE I5
The female gonophore in its fundamental features is constructed as in Stylaster gemmascens. But its spadix is simpler in structure (Pl. 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 roseus 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. Pourtalés (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 Sty/aster roseus; on the other hand, it is exceedingly doubtful if it is this species which he (l.c p. 83) with doubt refers to Pallas’ species as Stylaster roseus. P.M. Duncan (1874 Pl. 49 figs. 13—15) figures the species from the Faeroe Channel, but refers it erroneously to Stylaster gemmascens. Stylaster roseus 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 norvegica, G. O. Sars, Dyrelivet paa vore Havbanker p. 45.
1874 Stylaster gemmascens pars, P. M. Duncan, Madreporaria ... “Porcupine” p. 332, Pl. 49 figs. 1—3.
1881 Adlopora oculina, Moseley, Stylasteridae, “Challenger” p. 85.
1882 — orvegica, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna, IV, p. 26.
1888 — oculina +- 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.
16 STVLASTERIDAE
Colour: white or faintly rose with strongly yellowish red gasterozooids.
Occurrence: North Atlantic and west coast of Norway at depths from 100 to 1400m.
Material: “Ingolf? St. 15 66°18’ N., 25°59’ W. 620m. 075°C. ay 62°4q' - 26°55 - 1400 - 34° = en Dae 63°57' - 1S gars 790 - 787° - ee ROS 63°33’ - 15°02! - S05 Sigh hie “Thor” 1904 65°50° - 26°53’ - 392 - ? Hardanger Fjord ? ? ne O. Sars leg. 1871) Storeggen (at Aalesund) ? ? Trondhjem Fjord I00—400 - 6.5—7.5°C.
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 Lzstylaster 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. Pl. II, fig. 11). — 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 (PI. 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 (PI. 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 Stylaster 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
ee een ee ee ee ee a ee ee
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 (Eustylaster) gemmas- a
cens. 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 norvegicus 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 pex¢tig. p. Diagrammatic me-
not very well-preserved, the opportunity was taken to obtain fresh material ‘iam section through the cyclo- system of Stylaster (Allopora) nor-
of Stylaster norvegicus from the Trondhjem Fjord, in the outer part of vegicus. d= dactylozooid, gt = tentacle of the gasterozooid, gs = gasterostyle, ew = free part female colonies could be examined and even if most of the questions of the body-wall of the gastero- zooid.
which the species is fairly common in suitable localities. Both male and
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 (Pl. IV fig. 35) so that their origin cannot be settled. The gono- phore shows clearly, that Hickson (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). — Hickson (l.c. p. 390) maintains as a typical difference between the gonophores in Adlofora and Destichopora that the latter genus has no spadix, whilst A//ofora has a strongly developed spadix. In Stylaster (Allopora) norvegicus the spadix is strongly developed in the young gonophores but atrophies during the transformation of the sperm cells (Pl. IV fig. 38) and lastly disappears entirely in the mature gonophore as is the case also in Stylaster roseus.
The present species forms in part the basis for Hickson’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 (Pl. 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 Ingolf-Expedition. V. 5. 3
18 STYLASTERIDAE
fibrillar protoplasmic structure of the inner cells is still more marked at this late stage than before and 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 Hickson’s view were correct, that the spermarium of the gonophore is surrounded by a thin endoderm 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 Pl. 30 fig. 15) of the yong gono- phore in Dzstichopora. ‘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 7 atrophies and the pictures obtained of the condition in Stylaster gemmascens (Pl. V figs. 46. 29 and 50) are fully illustrative of the conditions in Stylaster norvegicus. Were 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 Gunn erus (1768 p. 64), who calls it A@//e- pora norvegica. In an appendix (l. c. p. 67) he states that the species is identical with A/i//epora aspera which Linné described somewhat later in the 11th 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 Pl. I]. — It is doubtful if it really is the same species which is described by Ehrenberg under the name of Adlopora oculina. In Milne-Edwards’ diagnosis of the latter species (1857 p. 132) we find: »Coenenchyme trés-developpé, couvert de points trés-serrés, visible seulement avec des verres grossissants«. This does not agree with the quite smooth surface, which is characteristic of Stylaster (Allopora) norvegicus. On the other hand, the specimens which are sometimes referred to in the literature from the Norwegian west coast under the name of AWofora oculina are undoubtedly identical with Stylaster norvegicus, the only Adlofora 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 A//ofora; he is of opinion that the species is identical with Ehrenberg’s AUofora oculina. CG. O.Sars was the first to describe the conditions
in a living Stylasterid, after studying colonies of S¢ylaster norvegicus out on Storeggen on the west 4 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 (I. c. p. 46): »though I am far from considering this *) as completed, yet I have already learnt this much, that the animal is essentially different from the other corals and probably does not belong at all to the Axthozoa but rather to the AHydrozoac. As is well-known, Moseley a year later (1878)
') i.e, the investigation.
STYLASTERIDAE 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 (1874 Pl. 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 AW/opora oculina; Hickson (1888 p. 594) mentions the species from the Hardanger Fjord as Allopora oculina and from the »Triton« Expedition as Allopora norvegica. Apart from the doubt whether the two species belong together, the present species must in any case under the irternational rules of nomenclature retain the specific name which was given it already by Gunnerus 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 Mil/epora and Moseley in 1878 had indicated, that the organisation of the Stylasterids also characterised them as ydrozoa, 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 Aydrocorallinae.
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 Umdellula 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 Stylasteridae and the Hydroceratinidac '). Even the structure of the colony agrees exactly in Clathrozoon Wéilsoni Spencer and the primitive Stylasteridae, only the chitin of the skeleton being replaced in the Sty/asteridae by a thick layer of calcium carbonate. Another Hydroid group also, Solanderiinae (family of Corynidae, 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 ptincipal phylogenetic characters. Moseley (1881 p. 46) maintains, that the tentacles of the Hydro-
1) By Kiihn (1913 p. 228) the Hydroceratinidae are considered a subfamily of Bougainvilliidae. hg
20 STYLASTERIDAE
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 S¢y/asteridae do not have capitate tentacles like the Corynidac, 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 S¢ylasteridae fully agree in their structure with the thread-shaped tentacles of the Bougainvilliidae. On the other hand, the A/ileforidae 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 Hickson and England (1905 p. r.). 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 MZilleporidae as Hydroids, whilst they regard the Stylasteridae as most nearly related to the Trachomedusae; 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 Sforadopora and still more Errima 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 Stylasterddae 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 »feelersc 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 Stylasteridac, 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 Coelenterates. — Hickson (1891) through his evidence of a medusa generation in A#il/epora 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 gonophores. Moseley (1881 p. 93) maintains that the -gonophores of the Stylasteridae are »adelocodonic«; but he regards the spadix of the female gonophores as an organ (»the trophodisc«) special to the Stylasteridac. 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 Stylasteridae becomes extremely doubtful. In his excellent studies on the hydroid gonophores (gro) Kiihn has
shown, that the medusa reduction may be so complete, that even the endocodon may disappear; thus
STYLASTERIDAE 21
only the manubrium remains as spadix. In his figures (1888 Pl. 38 figs. 4 and 6) Hickson has shown cases of such reduced gonophores in Dzstichopora and the northern Sty/aster species also have similar gonophores. Even though such a gonophore structure has not yet been shown in the Bougainvilliidae, yet it is not without a parallel in the athecate Hydroids. In Zudendrium racemosum (Cavolini) the spadix is bifurcated into two or often three 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 step from this to the condition in .S¢ylas/er gemmascens and Stylaster norvegicus is also
short. There is thus no fundamental difference ‘ext-fig. I: Female Gonophore of Eudendrium racemosum (Cavolini) from the Adriatic (95/;)'). II: semidiagrammatic figure of the female gonophore of Stylaster roseus. o = ovum, stk = stalk of
steridae to a special order. the gonophore, sfo, = main stolon of the gonophore, sto, =secon- dary stolon of the gonophore, sf = blind sacs of the spadix.
present, which justifies the raising of the Sty/a-
There is one condition however to which Hickson ascribes even greater weight. In his work on the gonophores in Déstichopora 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 ata 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 Sty/asteridac, his argumentation is hardly maintainable in the light of later
_ studies on the gonophores of the Hydroids. In a species such as Coryne fruticosa Kiihn (1910 p. 65, Taf. 6 figs. 25—27) has shown, that the gonophores have just the structure which Hickson gives as characteristic of Destichopora and Allopfora. 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 Gymmnogonos 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 Jhighly organised gonophore type of all.
1) After specimens from Triest kindly sent me by Hr. Dr. C. Lehnhofer (Innsbruck).
22 STYLASTERIDAE
In its structure Plobothrus shows several features which indicate, that it stands nearer to the origin of the S¢ylasteridae 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. P/obothrus 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 mostimportant phylogeneticinterest. 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 Szy/as¢eridae in relation to the other Coelenterata. 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, they can by no means be used as evidence for the view, that the S?/ylasteridae are more distantly related to the Hydroids than the MM7lleporidae.
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 A/dleporzdae traces its origin to that of the Corynidae, whilst the Stylasteridae is a highly specialised branch which has been derived from the Bougainvillitdae. Just as the Corynidae are distinguished from the Lougainvillidae by their capitate tentacles, the A/dleporidae with their capitate tentacles are distinct from the Stylasteridac, 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 Lofhohela reefs and form here a complete and extremely interesting parallel
to the numerous Stylasterid species of the tropical coral reefs.
STYLASTERIDAE . 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 Sty/asteridae are those given by Gunnerus in his work »Om _ 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 Trondhjem. — 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 Pourtalés’ 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. Pourtalés described here for the first time Pliobothrus symmetricus and also mentions a second of the North Atlantic species, Stylaster roseus, under the name of Stylaster erubescens. In addition, we have still two other, old records from the North Atlantic. G. O. Sars (1871) has given a classic description of the living A/lopora 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 Sty/asteridae of the »Challenger«.
Later information regarding the northern Stylasterids is very meagre. Storm (1882) mentions Stylaster gemmascens and Allopora norvegica from the Trondhjem Fjord; there is a casual remark by Hickson (1891), that he has had material of AJ/opfora oculina from the Hardanger Fjord and of Allopora norvegica from the »Triton« Expedition; lastly, J. A. Thomson (1910) informs us, that he has examined colonies of Stylaster 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 oui 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 Sty/asteridae in the Norwegian Sea are typical coral reef dwellers. Yet at places in the Trondhjem Fjord Stylaster 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
Stylaster (Allopora) norvegicus is bound to the Lephohelia 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 Sty/as¢er 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.
SAGE 200 m. depth A Pliobothrus symmetricus
A _ — incompl. geograph. data. Ses SiS ibects GOOFS PES @ Stylaster gemmascens Les 1300 8S O62 bate
+ — (Allopora) norvegicus
Text-fig. F. Map showing the localities of the Stylasteridae in the North Atlantic and the Norwegian Sea.
The study of the occurrence of the North Atlantic Stylasterids shows several biogeographical features of interest (cf. Chart Text-fig. F). — Pliobothrus 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 »Porcupine« 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.
STYLASTERIDAE 25
Stylaster roseus forms a parallel to Pliobothrus symmetricus. It is fairly common between 230 and 620 metres at Florida and on the whole has probably a greater bathymetric distribution than Pliobothrus symmetricus. Stylaster roseus is much more frequent in its occurrence than the latter form, but 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 Sty/aster 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 Wyville-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 Trondhjem 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. : 4
CeoRTs
12.
LITERATURE
Arndt, W., 1912: Zoologische Ergebnisse der ersten Lehr-Expedition der Dr. P,. Schottlénderschen Jubildums Stiftung. (Jahresber. Schles. Gesellch. vaterl. Cultur 1912) Breslau. : Duncan, P. M. (1874): A description of the Madreporaria dredged up during the Expeditions of H. M. S. “Porcupine” in 1869 and 1870, (Transact. Zool. Soc. London Vol. VIII) London. Esper, E. J. C. (1797): Fortsetzungen der Pflanzenthiere, Theil 1. Niirnberg. Greeff, R. (1886): Ueber westafrikanische Stylasteriden. (Sitzungsber. Ges. Beférd. gesamt. Naturwiss. Marburg, Jahrg. 1886) Marburg. Gunnerus, J. E. (1767): Om nogle norske Coraller. (Det kgl. norske Videnskabers Selskabs Skrifter, 4de Deel) Kiébenhayn. Hickson Sydney, J. (1888): On the Maturation of the Ovum and the Early Stages in ths Development of Allopora. (Quarterly Journ. Micr. Sci. Vol. XXIX) London. — (1891): The Medusze of Millepora murrayi and the Gonophores of Allopora and Distichopora. (Quarterly Journal Micr. Sci. Vol. XXXII) London. > — (1906): Coelenterata & Ctenophora. (The Cambridge Natural History Vol. I) London. — (1912): On the Hydrocoralline Genus, Zrrina. (Proc. Zool. Soc. London 1912) London. — and England, Helen M. (1905): The Stylasterina of the Siboga Expedition. (Siboga-Expeditie, Monogr. VIII) Leiden. -— and England, Helen M. (1909): The Stylasterina of the Indian Ocean, in: The Percy Sladen Trust Expedition. (Transact. Linnean Soc. London Ser. Zoology vol. XII) London. Kiihn, Alfred (1910): Die Entwickelung der Geschlechtsindividuen der Hydromedusen. (Zool. Jahrb. Abt. Anatomie, Bd. 30) Jena. — (1913): Entwickelungsgeschichte und Verwandtschaftsbeziehungen der Hydrozoen. I. Die Hydroiden. (Ergebn. u. Fortschr. der Zool. Bd. IV) Jena. Lindstrom, G. (1876): Contributions to the Actinology of the Atlantic Ocean. (Kongl. svenska Vetenskaps-Akademiens Handlingar, Ny Féljd. Bd. 14) Stockholm. Marenzeller, Emil v. (1904): Stein- und Hydro-Korallen. (Bull. Mus. Comp. Zool. vol. XLIII) Cambridge, Mass. — (1903): Madreporaria und Hydrocorallia. (Expéd. Antarct. Belge) Anvers. Milne-Edwards (1857): Histoire naturelle des Coralliaires, Tome II. Paris. Moseley, H.N. (1878): On the structure of the Stylasteride. (Phil. Trans. Roy. Soc. 1878) London. — (1881): Report on certain Hydroid, Alcyonarian, and Madreporarian Corals. (Rep. Sci. Res. “Challenger”, Zoology Vol. II) London. Nordgaard, O..(1912): Faunistiske og biologiske iakttagelser. (Det kgl. norske Vidensk. Selsk. Skrifter 1911) Trondhjem.
. Pallas, P. S. (1766): Elenchus Zoophytorum. Hagee-Comitum.
Parker, T. Jeffery and Haswell, William, A. (1897): A Textbook of Zoology Vol. I. London. Pax, Ferdinand (1910): Die Steinkorallen. (Deutsche Siidpolar-Expedition 1901—1903 Bd. XII, Zool. IV) Berlin. Pourtalés, L. F. de (1871): Deep-Sea Corals. (Illustr. Catalogue Mus. Comp. Zool. No. IV) Cambridge, Mass. — (1878): Corals and Crinoids in: Reports on the Dredging Operations of the U. S. Coast Survey Str. “Blake”. (Bull. . Mus. Comp. Zool. Vol. V) Cambridge, Mass. Sars, G. O. (1873): Bidrag til Kundskaben om Dyrelivet paa vore Havbanker. (Vidensk.-Selsk. Forhandlinger for 1872) Christiania. Schneider, K. C. (1902): Lehrbuch der vergleichenden Histologie der Tiere. Jena. Storm, V. (1879): Bidrag til Kundskab om Throndhjemsfjordens Fauna. (Det kgl. norske Vidensk. Selsk. Skrifter 1878)
: Throndhjem. — (1882): Bidrag til Kundskab om Throndhjemsfjordens Fauna IV. (Det kgl. norske Vidensk. Selsk. Skrifter 1881) Throndhjem. Thomson, J. Arthur (1910): Note on a Hydrocoralline from Rockall. (Proceed. Roy. Phys. Soc. Edinburgh vol. XVIII) Edinburgh.
4*
EXPLANATION OF THE PLATES The following letters indicate the same parts in all Plates is
Ae Ectodermal epithelium oftheampulla. Gp Gasteropore.
Cn Cnidocysts. Gs Gasterostyle. Dp Dactylopore. _ I The inner cells of the seminal duct. Ds Dactylostyle. O egg cell. j Ec Ectoderm. } Sp Spadix. En Endoderm. s Stolon. e Ectodermal epithelium of the gastero. TT Tentacle | | pore wall. t tabula. othe Wee
Ge Ectoderm of the gonophore. WwW Free wall of the gener
Fig. 1. Pliobothrus symmetricus; front surface of an intact colony from the “Ingolf” St. 55 ‘Na
Plate I. ae
o: — _ hind surface of the same colony. Nat. size. 3. = — two ends of branches from “Ingolf” St. 55. 4/;. gee 4. Stylaster gemmascens; one of the type eo of Gunnerus’ Madrepora virginea |
west coast of Norway. Nat. size. —
Nat. size. 6. Stylaster gemmascens; hind surface of same colony. Nat. size. = — front surface of the compact branch of a fertile ony @.
Nat. size. ak oe 9. Stylaster roseus; hind surface of the same fragment. Nat. size.
ngoy Expeaiiion, V, o. Broch: Stylasteride. Tab. 1.
S .! ’ ~ ty : 4 ‘ 4“e y ' i ¥ Ss i F, . j ‘ £ 4 t 5. * oo , : . t = Ne eee > GS a Sch Se ie ae Cee Re Mla RSD Nini cig lS aed gent LE aed St lores Snel La Somat =a Set Ghd ae
4 ; % 2 j iz = ce > are “ mi
Il. 12. 13.
14. 15.
16.
17; 18.
Plate Il.
Stylaster roseus; front surface of a fragment of a colony with — oe iy
Nat. size. ; Stylaster roseus; fragment of a colony which i is entirely deformed oe to the ¢ of numerous female ampullae; “Ingolf” St. 7. Nat. size. Stylaster norvegicus; one of the type Se a ta of Gunnerus’ Milepora , west coast of Norway. Nat. size. : Stylaster norvegicus; front surface of a narrow-branched colony from T eiudvacest EH — — hind surface of the same colony. Nat. size. _
— roseus; end of a branch of a colony from “Ingolf” St. 15. ae 3 Gog eo ee — norvegicus; ends of two branches of a colony from Trondhjem Ford Wes ae
es
ee eee ee er meee mg
yh etal ee
t , :
SPORES iA Des td BE tte
- , “7
Plate ILL.
Pliobothrus symmetricus; median longitudinal section of a branch point. '°/;. _ — median section through a gasteropore with tabula. */;. Stylaster gemmascens; median longitudinal section of a branch. */;. _ voseus; median longitudinal section of a branch. *°/;. — norvegicus; longitudinal section through two cyclosystems. '/;. Median, longitudinal, thin section of the gasterostyle in Stylaster gemmascens. %/;.
Longitudinal section of the gasterozooid in Stylaster gemmascens. %3°/;.
Transverse section of the gasterozooid at the base of the tentacles in Stylaster gemmascens Oblique transverse section of the gasterozooid at the base of the tentacles in S norvegicus. 3°],,
Transverse section of the gasterozooid in Pliobothrus symmetricus. 3°°/. i Longitudinal section through the oral part of the gasterozooid wall in Pliobothrus s tricus, 45°]. Longitudinal section through the oral part of the gasterozooid wall and tentacle in Sty gemmascens. 45°/;. Longitudinal section through oral part of the gasterozooid wall and tentacle in Styl
norvegicus. 45°/;.
‘The Ingolf Expedition, V, 5. Broch: Stylasteride. Tab. III.
Dp
Nordenfjeldske Klicheanstalt. Waldemar Janssens Boktrykkeri.
‘
. Transverse section of the gasterozooid at its base near its transition into the stolons in Stylaster 3 . Longitudinal section of the dactylozooid in Stylaster gemmascens. 3°/;.
. Median longitudinal section of a very young gonophore (¢) in Stylaster norvegicus. 45°/;. . Median longitudinal section of a young gonophore (#) in Stylaster roseus, 45°/;.
. Median longitudinal section of an unripe gonophore (¢') in Sty/aster norvegicus. 3°°/;.
. Median longitudinal section of two gonophores (#) in Stylaster norvegicus. ‘The larger wi
- tozoa. 139/;,
. Median longitudinal section of a gonophore (#) in Pliobothrus symmetricus. 3°/;. . Median longitudinal section through apex of the fully developed gonophore in (#) Pliobothrus
Plate IV.
‘gemmascens, 3°],
Transverse section of a dactylozooid in Pliobothrus symmetricus, 3°/;.
spadix partially atrophied contains spermatocytes in process of transformation to sperma-_ Median longitudinal section of a gonophore (3) in Stylaster roseus; the spermatocytes in process
of transformation to spermatozoa. 13°/;.
Transverse section of a young gonophore (3) in Pliobothrus symmetricus, 3°°/;.
symmetricus, 3°°/;.
Stylasteride. Tab. IV.
Broch
The Ingolf Expedition, V, 5.
Nordenfjeldske Klicheanstalt. Waldemar Janssens Boktrykkeri.
1 « Fe atsid eal ; . - . t : ae ie aoe SE, ee PSE Sa ok So | eae Fe age ee sei - CaS ; 4 > " p= eer Zi. 4 : ; ¢ se tne. i i ey a r i ee ead Wee Gt Fe ; { hae Vety > alee ad ~ = we is Bh : ; fi
Plate V.
Apex of a gonophore (#) in Stylaster roseus, containing spermatocytes in process of formation. 45°/,.
Early eee in the See of a seminal duct in ecb sya ose pan see)
Median longitudinal section hark a gonophiore (9) vidi ripe ovum in syilitoper geminiascens, Median longitiemaes section of a gonophore (¢) with ripe ovum in Splenic roseus.
Median longitudinal section through a gonophore with advancot planula eee in 8 gemmascens, 13°/;, .
1899.
1913.
1903.
1907.
1914.
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IgI2.
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IgI0.
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.VOLUME V.
6.
HYDKOUge
ony (PART I)
HJALMAR BROCH.
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WITH 2 PLATES AND 20 FIGURES IN THE TEXT.
COPENHAGEN. PRINTED BY BIANCO LUNO.
1916,
Page
The comparative anatomy of the nourishing individ-
= uals and the system of the athecate hydroids ..... a E Athecate Hydroids of the northern Atlantic .......... a Capitata LEE NET AR Wot pee ret Rae pve EN
RI EUIGOPYNIAGE ool as cir vals cv e's <b stabs again ee <e ORE CES) 1) pe app terete err aries as Ba Coryne Sarsii (WOvEN)..... 6... 0c eee n eee en eees 14
Pa LOUENE (Mi SATB) ci. bo05e ge are deaestet 15
Ser usta GASTEME oye ce wise tines Saniv'e 16
— sp. aff. Hincks? Bonnevie.............. 18 Family Myriothelidae AN ee tea ae ore ot 18 | Myriothela RPT LOINC cates sca sie: ss Dele wd oh A 19
| Myriothela phrygia (Fabricius) eustarcaee rae 19 MINS A MUSLAP HAGE. Soiai0 5 viele ibd os een pe etme 2I
| Tubularia BS RINOU Heimat s sek sees okay oe eet 22 ‘Tubularia pulcher (Semundsson)............ 22 — CUSED TTA Ee he ee Bee 24
— he ae OTS CRS store ior perry 25
_ larynx Ellis et Solander.......... 27
_ SEG e Ss ras diate. Aes Ae Gs tirnst es 28 Cmpmrpra- Mi Sate os. ccs cee ote ts eet’ 29 Corymorpha nutans M. Sars ........062000 eee 3r — wlacials Mu Sarees esse ccs ere. 32
— groenlandica (Allman)............. 33
CONTENTS
Page
Corsmor bla Bp. INGE cos ii)s Saas Vek ek esse 37 ECHO: MURSEPA she oS dade hain weenie wen ewe ch vas vers 38 PARE CAUMMIE: ei OL aOR node eh cthelp ee ge NS 38 CRNA AD CITE A Sic ok Dik GA i cin Weide Fir eo ieretite 38 Clava multicornis (ForskAl) ............+.0.0.. 38 Meromae NOV ihe Soke Goh Fane 40 Merona cornucopiae Norman .........000.e eee 40 Monobrachium Mereschkowsky ................ 42 Monobrachium parasitum Mereschkowsky..... 42 Family Bongestegiliiidae........ 0.0.0. cece nee enees 43 Hydractinia van Bemeden................ eae 44 Hydractinia Sarsit St eenstrup..... 5 hol he nu a 45
_ echinata (Fleming)......... ach hes 46
—_ COPE BOP BW oie al dasa oe utolens 48 Bougainolha TEC ORs. oF. nic Ge venvycwticeo dm tix riers 49 Bougainvillia conferta (Alder).............0.00% 50 Perigontnus: Mie Sars) x. os37.." ove toniniaasd vend oboe eres 51 Perigonimus repens (Wright)........... Re Rmeie 52
— 80988 Gy OS RIS AY gods Se ees 53
_ FOES (MS ate) 2.5 suawiep eseels 54
Bamily- Radendpndae oj 2:0. seca ve Fa ted ee ORIOLE 56 Eudendrium Ehrenberg ....... cc cc cesses veeeees 57 Eudendrium rameum (Pallas).........-.0+00005 57
_— ramosum (Tinné)...........00..005 59
= Wright? Hartlaub................- 60
— . annulatum Norman......... «2+... 62
— Capitlare BICEP Ces ec ee cen 62
ey
ee ee
ee eae a IL me
yitt
Preface.
The investigation of the large Danish collections of hydroids from the Faroe Islands, Iceland, and Greenland, and the researches into the interesting material brought home from the Ingolf Expedition, have realised great results. In fact, several points of dispute as to the classification of northern species have been settled. In the first place, the Danish collections contain original specimens of some species which have been described as new several times after being originally recorded. In other cases, the large number of specimens tend to bridge the division between species which have hitherto been looked upon as “good” ones. It is, indeed, a matter of regret that deficiencies of diagnosis and inaccuracy of design have frequently put obstacles to the recognition of species previously recorded, and that the literature has, consequently, been encumbered with synonyms which we should rather have done without. This inconvenience, in fact, enforces the necessity of giving full and exhaustive accounts of every single species. The American investigators, indeed, on the pattern of Nutting have iong tried to give brief diagnoses and drawings of all American species. But it must be observed that, because of the impressionist way of drawing, the illustrations are, as a general rule, somewhat wanting in accuracy, and to the brief diagnoses there is the objection that they are often too summary to give exhaustive account of the distinguishing features. On the whole such weak points as appear in the last works of Allman, have gone down to his epigones. Great difficulties, indeed, are in this way given to students of the geographical distribution of the hydroids. No doubt, more species than those which are at present pointed out by literature, are common to the European and the American
seas. But in general it proves impossible to form, on the ground of the brief diagnoses, a well-founded
_ Opinion as to the virtual qualities of many species. As far as the European species are concerned, we
are fortunate in possessing the classic work of Hincks, A History of the British Zoophytes. However, since the appearance of that work, plenty of fresh subjects have been added by descriptions of several species and genera which can hardly all be maintained, and publications have of late appeared in such abundance that it proves difficult to students of this group of animals to find their way through the crowded matter.
These are the reasons why I have tried to give new and detailed diagnoses of every single species in question. The diagnoses are essentially founded on the copious material occurring in the Danish collections. Of synonyms I have only selected those of absolute necessity. Detailed accounts
of synonymy are found — as far as earlier literature is concerned — in the excellent treatises of Bedot,
The Ingolf-Expedition. V. 6. :
2 HYDROIDA
Matériaux pour servir 4 Vhistoire des Hydroides, and — regarding recent literature on northern q hydroids — in the groupings framed by Jaderholm (1909), Broch (1909), and Kramp (1914). As far al as possible, the various species are accompanied by maps illustrative of the geographical data in the a northern Atlantic. Besides the collections the recent literature has served as basis. In this respect a the groupings occurring in the works of Bonnevie (1899), Jaderholm (1909), Broch (1909), Se- 4 mundsson (1911), and Kramp (1914), have proved particularly available. a
I have made it a point to define precisely the limits of genera and families by full diagnoses, : and at the same time I have tried to account for the ee oasti aas I hold to for the purpose of .
principles of . many of them have disregarded phylogeny and allowed biological considera- _
tions to play a predominant part; consequently the circumscription of genera has been practised in — most various ways. To leave no opening for misunderstanding I have thought it necessary to give
lections will tell better and to fuller advantage than otherwise. aon
Trondhjem the 22nd August 1915.
Hh
I. Introductory Notes.
Scarcely in any other part of the animal world greater difficulties are thrown in the way of the systematist than those occasioned by the lowest Coelenterata, impeding the attempts to establish a natural grouping of the hydroids and their attendants, the hydromedusz. This is due not only to the actual deficiencies of our knowledge of these low organisms, but also to the fact — as pointed out by Kiihn in his excellent summary (1913) — that the groups present partly a confused series of adaptations and phenomena of convergency, partly the occurrence of meduse of widely divergent development as companions of closely allied hydroids or, vice versa, closely allied medusee accompanying hydroid polyps divergently developed. It is a striking fact that in certain species, for instance the Codonide, the phylogenetic development and differentiation of form of the medusze have been com- paratively stunted, whereas the polyps (Corynide, Pennariide, Tubularitde) have developed hetero- geneously so as to present a large series of various forms. The exact reverse is represented by the homogeneous polyps of the family Bougainviliiide forming the nurse generation of the hetero- geneously developed hydromeduseze of the families Margelide and Tiaride. The possibility of construct- ing a safe system common to medusz and hydroid polyps, indeed, appears remote. For in the first place the two “generations”, on account of their excessive abundance of species; have had to be treated separately, each generation by specialists of its own, and moreover, we are in fact still in the dark as to which of the two generations is to be regarded as the primitive or the phylogenetically older.
When looked upon as a whole the group of Zoophytes must be characterized as a very low
group of animals. In the nurse generation as well as in the free-swimming meduse the structure
- of the individual is very simple, though the meduse after all must be said to be a little higher
organised than the polyps. In addition to the two primary layers of cells, the endoderm and the ecto- derm, occurs in the medusz a “mesogloea”, whose descent from one or the other of the primary layers is not yet definitely ascertained as far as all species are concerned. However, a mesoglcea also occurs with some hydroids, for instance the “parenchyma” of the Z7udwlariide, which is a typical endodermal formation.
To students of the hydroids it very soon becomes obvious that the leading systematic characters have been derived from such criteria as urge themselves on a superficial view of the animals, while, contrarily to the method practised in investigating most other groups of animals, the inner
anatomy is all but entirely left out of account. This is due to the generally accepted view that the tog
4 HYDROIDA
structure of the hydropolyps is throughout quite homogeneous and accordingly affords no holds of use to the systematist. A careful study, however, of the slight information occurring in the literature as to the structure of the polyps, will show that the old view is wrong. In this connection it will be sufficient to refer to the excellent passage written by K iihn (1913), Die Ausbildung des Polypenk6rpers, in which are mentioned several examples of the heterogeneous structure of the polyps in the various groups of hydroids.
Nevertheless Kitihn himself (1913), in constructing his system of the hydroids, has, according to the old practice, left this fact almost wholly out of account. I will afterwards come back to the subject and point out how unreasonable it is to set aside this part of systematics even though a thorough investigation of the anatomy of the polyps may seem almost impracticable because of the state of preservation in which the hydroids generally occur in the materials of the great expeditions and collections. In fact, it is confirmed that Levinsen (1893) is right, emphasizing that the systematist in treating of hydroids should rather lay stress on all about the nourishing individuals than on the
varying development and organisation of the generative individuals.
a. The Hydroid Gonophores bearing on classification.
Our knowledge of the hydroids has advanced a vast stride ahead owing to the thorough researches of Kiihn into the development and the organisation of the gonophores (1910). As to the importance of the gonophores to systematics, it has lately (1913) been asserted by the same author that no weight whatever can be given to the various gonophoral development, but that particular stress should be laid on the structure of the full-grown gonophores. On account of difference of structure he distinguishes between four types of sessile gonophores: eumedusoids, cryptomedusoids, heteromedusoids, and, finally, the simple gonophores, called styloids (Bonnevie 1898). The eumedusoid gonophores, indeed, retain the structure of the medusa throughout, and occasionally breaking away (Campanularia integra Me. Gillivr. — Agastra mira Hartlaub) occur like defective meduse. The structure of the crypto- medusoid gonophores is more reduced. Certainly they keep their endocodon and their umbrellary cavity, but have a single-layered umbrellary endoderm; however, also of cryptomedusoids occur exceptional instances breaking away, as in Pachycordyle Weismannt Hargitt. The heteromedusoids are entirely wanting the umbrellary endoderm, and the inner umbrellary ectoderm is formed by delamination, not by invagination of the outer ectoderm (endocodon). The simplest gonophores, finally, are without any trace of medusoid organisation. These four types of sessil gonophores Kiihn (1913) regards as char- acters important to the systematist for the division of hydroids into genera.
Stechow (1913) in his important work on Japanese hydroids occupies another standpoint, attaching more importance to the conditions of the gonophores. Thus he draws nearer to earlier principles of classification, but at the same time he tries to make his systematic division more manage- able by drawing out characters from the outward morphology of the colonies, thus effecting the transition to the American school. The Americans, headed by Nutting, look on classification only as “a matter of convenience”, and accordingly in their groupings, as a matter of fact, relinquish the idea of constructing a natural system aiming at summing up and drawing by critical sifting of the char- acters a skeletonlike picture of the phylogenetic affinities of the group of animals in question. Con-
HYDROIDA 5
sequently the system brought about by the American investigators, picking up heterogeneous char- acters, is indeed, as I have shown in an earlier treatise (1909), to a great extent one of arbitrariness, placing the species now in one, now in another genus, according to the character it is thought desir- able to emphasize at the moment. The system has, in this way, become a matter of chance.
Before proceeding to the special explanation of the several species of hydroids and their occur- rence in the seas of the northern Atlantic, we, therefore, must try to realize, from a systematic and phylogenetic point of view, the value of each single character. In the first instance the question must be answered what part the gonophores play as to the phylogeny of the hydroids or, in other words, what importance has to be attached to the gonophores and their conditions for the purpose of classification.
The application of the characters of the gonophores as distinguishing marks of higher system- atic unities, of families, or of subfamilies, has been abandoned by all modern investigators of the hydroids. On the other hand, it is held by several investigators that they are of importance as to the limitation of genera. The last significant publications maintaining this view, are those of Kiihn (1913) and Stechow (1913). Kiihn, however, applies the characters of the gonophores with much caution and discretion, while Stechow, as a giance at his tables (1913, p. 36 and the following pages) suffices to show, undiscerningly recurs to the principle of laying the main stress on the “medusa” as contrasted with the “sporosac”. In fact, as long as the limits between these designations are not more precisely defined, they will be subject to much arbitrariness. An interesting instance is afforded by the point in dispute, where the limits are to be drawn between the genera Coryne and Syncoryne. The old criterion, accepted by Allman and other investigators, was the free medusa as contrasted with the fixed gonophore or sporosac, and, to all appearance, it is the same limitation Stechow tries to maintain in his table. Indeed, this principle of limitation was only supportable on the ground of the deficient knowledge of the organisation and development of the hydroid gonophores attained to in Allman’s days. Kiihn, therefore, (1913, p. 229) is seen to take quite another departure, defining the Syncoryne as including all species having “meduse”, while the Coryne is distinguished by styloid gonophores. It is evident from Kiihn’s previous argument (l.c. p. 174) that under “meduse” he also includes the eumedusoids which normally do not break loose, and that accordingly Coryme, in his opinion, exclusively embraces species having styloid gonophores.
Parallel to these genera Stechow also treats of Podocoryne (with meduse) and of Hydractinia (with “sporosacs”). Kiihn (1913, p. 227) groups them in the following vague way:
ges a Medusen (Margelinen), Eumedusoide, Cryptomedusoide, Styloide. Hydractinia
From his premises (1. c. p. 226) it appears that he agrees with most modern investigators, think- ing it right that the two old genera should be merged into one, Hydractinia; for he states that in fact we have here before us a series of closely allied forms, in which “zwischen Arten mit Vollmedusen und einfachen Medusoiden die verschiedensten Ubergange bestehen”. Thus K iihn, elsewhere considering the characters of the gonophores as significant generic criteria, in this place actually reduces them to mere specific characters.
In another connection Kiihn (1913 p. 197) gives an instance of the fact that the sexes in
6 HYDROIDA
one and the same species can be distinguished by different types of gonophores; thus the female gonophore of Laomedea flexuosa Hincks is heteromedusoid, while the male gonophore is _ styloid. This strongly defined sexual dimorphism is most interesting, and the question is obvious whether the case is a solitary one, or if in other species other types of gonophores, of those stated by Kiihn, might perhaps be found united in one and the same species. On that account I have (1915) more closely examined the development of the gonophores of, among others, the Zudwlaria indivisa Lin. and the Zubularia regalis Boeck, two species in which a marked sexual dimorphism is found pro- nounced in the external characters of the gonophores. The examinations resulted in the startling result that the female gonophores of both species are eumedusoid, though not equally high in medusoid organisation, whereas the male gonophores of both species are heteromedusoid and of entirely the same organisation and development as the gonophores of the genus Zampra Bonnevie (1898) (comp. Broch 1915). It is owing to the gonophores that Lamfra is separated from Corymorpha, the latter genus producing free meduse or having gonophores eumedusoid. Acting on this principle of division, as far as the species of the genus Zudbularia are concerned, we should have to separate the male Tubularia indivisa and Tubularia regalis as a new genus, while the female individuals belonging to the same species would retain their places'.
The outcome of the searching studies of the last years shows, indeed, that in proportion as a greater number of species have been examined, the more evidently the characters of the gonophores appear as criteria of species. The increasing knowledge of the gonophores makes ever clearer that the gonophores alone cannot form the base of any division of genera, but at most serve as second- arily corroborative.
The free medusz show throughout a greater abundance of forms developed than the polyps, which are more conservative. No doubt, the medusz present a series of phenomena of adaptation and, accordingly, display several characters of convergency, to which the systematists are inclined to attach a greater phylogenetic value than is their virtual due.» Nowhere, I dare say, the adaptations to habits of life and the accommodations to varying physical conditions play such a part as with the pelagic organisms, to which the slightest variation of salinity and of temperature causes great changes of viscosity of the surrounding water, decisive of the adaptation of their suspension organs. Therefore, the hydroid systematist should not lay too much stress on the statements of the medusoid specialist as to the systematic grouping of the free-swimming generation; phylogenetically the char- acters of the nurse generation are of the greatest interest. A similar state of things urges itself with the sessile gonophores. It is a circumstance of vital importance to the maintainance of the species, that the generative individuals are able to accommodate themselves quickly to the peculiar conditions of life to which the species is subjected. What I observed in my treatise on the Sty/astertde (1914), is fully applicable (or even more so) to the case under consideration: “Owing to their conservatism in development the polyps are of the most important phylogenetic interest. The gonophores, the genera- tive individuals, on the other hand, might almost be said to be a playball in the hands of chance biological conditions and thus phylogenetically have much less interest”.
1 The possibility of a fusion of four species is precluded, as in 7ubularia indivisa and in Tubularia regalis 3 and Q occur in the same colony.
HYDROIDA 7
On account of their dependence on outward conditions and their power of plastic accommodation to biological influences, the gonophores are unsuitable for basis of division into genera. On the other hand, the genera, owing to the conditions of the gonophores, often fall into a series of biological groups (or subgenera). The systematists who lay the main stress on the gonophores in establishing the system, in fact apply biological conditions as fundamentum divisionis, and let phylogeny, the pro- perly governing principle of systematic inquiry, recede into the shade.
b. The comparative anatomy of the nourishing individuals, and the system of the athecate hydroids.
An exact review of the researches of the last years makes ever clearer, as also appears from the statements above, the correctness of Levinsen’s view (1893), maintaining that in the great classifica- tion of the hydroids the main stress must be laid on the peculiar conditions of the nourishing polyps, and reducing at the same time the modifications of growth and the conditions of the gonophores as characters of subordinate importance. Later investigators' have, indeed, attached ever more importance to the conditions of the polyps. But in so doing they have almost exclusively taken into considera- tion such morphologic criteria as urge themselves on a superficial view of the polyps. The inner anatomy, on the contrary, has been disregarded. Kiihn (1913) certainly by the way points out that the inner anatomy can be different in the different groups. He treats (l.c p. 50) at some length of the peculiar structure of the polyps of the 7udulariide, and points out the multifarious development of the ¢hecaphores. But in drawing the bases of his system he makes no attempt to turn these features to further account.
As a result of searching inquiries, the structure of the polyps in the different genera and families has turned out not to be quite so homogeneous as it has been generally held. Both in the construction of the ectoderm and in that of the endoderm differentiations occur, which may be char- acteristic of greater or smaller groups of species and give us several holds for judging the systems drawn up for hydroids in the course of time.
Therefore, it will here be appropriate to give a brief synopsis of the more important peculiarities of anatomy distinguishing the various groups of athecate hydroids, in order to apply them afterwards to drawing up the system of the group.
The ectoderm, deciding by the disposition of its elements whether the tentacles have to be claviform or not, has, to some extent, been turned to account as fundamentum divisionis. The clavi- form shape is particularly due to the accumulation of the stinging cells on the tips of the tentacles, while the tentacles are filiform when the nematocysts are more equably distributed. A third type of tentacles, which, as far as is known, is found with all thecaphore hydroids, occurs in the Zudendride;
t Works like that of Poche (1914) I leave out of account. That sort of “zoology” which is based not on study of the organisms themselves, but only on what may be beaten up from books, here debouches in the construction of airy castles of complicated systematics, which does not advance zoological science by a hairbreadth, but only contributes to increasing the systematic confusion. Between “regnum” and “family” are inserted 34 — thirty four — degrees. It is a matter of regret that we do not learn how many osculant categories must be placed between “family” and “individual” to give a “full” picture
of nature. But this will suffice to illustrate the scientific value of the work.
8 HYDROIDA
here the stinging cells are arranged in dense transverse belts round the tentacles so as to give these, when distended, a peculiar transversely striped appearance.
On the ground of filiform and claviform tentacles Kiihn (1913) divides the athecate hydroids into the two principal groups of /7i#fera and Cafitata. However, we find in the latter group also instances of filiform tentacles; in the Pexnaritde filiform tentacles occur together with claviform ones; in the Zubulariide, on the contrary, the claviform tentacles have disappeared, at any rate in the polyps fully developed. Kiihn (l.c. p. 228), therefore, also makes the reservation that the tentacles are “dauernd oder in der Jugend gekn6pft”. Embryological studies on Corymorpha have, in fact, shown that the actinula has claviform tentacles (Torrey 1907, Hartlaub 1907). However, this state of things cannot be generalized as a matter of course to embrace the Zudularia; on the contrary the figures of Allman (1872) show quite distinctly that the actinula in Zubularia larynx and Tubularia indivisa have filiform tentacles, and inquiries into the Zwbdularia regalis in the Trondhjem Fjord have shown no trace of capitate tentacles during the development of the actinula. Nor do here claviform tentacles occur in full-grown polyps.
But even though the definition of Kiihn must be characterized as erroneous so far, there is another criterion showing that his division of groups is correct. A searching study of the very nemato- cysts, shows, as a matter of fact, that the athecate hydroids fall into two large principal groups, cor- responding to the Cafitata and the /ilfera stated by Kithn.
In the hydroids occur two characteristic principal forms of nematocysts (Pl. I, figs 1—7). In all the Cagztata we find large oviform or almost wholly spherical nematocysts of the same principal type as is often mentioned in the Hydra. These large nematocysts are always accumulated on the tips of the claviform tentacles, as in the Coryne, while on the filiform tentacles of the Zwbularia they are more equably distributed all over the ectoderm of the tentacles. However, these stinging capsules are also found elsewhere in the ectoderm of polyps, as is the case with Monocoryne and Myriothela. In the last mentioned form the nematocysts, like those of A@dlepora, have developed dimorphicly; besides the typical oviform nematocysts we find here a larger and more slender oval form; in general the latter nematocysts are outnumbered by the oviform ones, but still they amount to a large percentage — of the total stock of stinging capsules occurring in the animal. In the A@//efora this type of nemato- cysts, judging from the figures in hand, is rather broad.
The rest of the hydroids are distinguished by quite a different type of nematocysts. The pre- dominant type is a very small, all but rod-shaped nematocyst, particularly occurring in the tentacles, generally accumulated in belts, vertically on the tentacle axis, giving the tentacles, when wholly stretched out, a peculiar transversely striped appearance, like that of the tentacles of the Audendrium recorded. Concurrently with this typical small nematocyst distinguishing all /7i/era sometimes occurs, finally, a somewhat larger form, as in the Hudendrium and the Stylasteride. In the Eudendrium Wrightt we find in the tentacles only small rod-shaped stinging capsules; on the contrary in the basal whorl of stinging cells of the polyp body of the species in question the capsules are much larger, though keeping a slenderly oval appearance. It is strange that this large type of the Hudendrium and the Styasteride should appear almost entirely consistent with the aberrant slenderly oval nemato-
cyst with the Alyriothela. The simultaneous occurrence of the type in so different and so highly
HYDROIDA 9
organised forms suggests, indeed, that we have before us phenomena of convergency, the cause of which is at the moment quite inexplicable.
However, not only the ectoderm itself and its elements are of interest to comparative anatomy. The derivates of the ectoderm are of great importance. In the same way as the ectoderm of the stem secretes a periderm, we find that with all thecaphore hydroids a chitinous hydrotheca is secerned by the ectoderm of the polyp. Remarkably enough, a parallel is found also in a single genus of the athecate hydroids, the Perigonimus. In this genus the ectoderm of the polyp secretes a “pseudohydrotheca”, a hydrotheca-like, folding periderm case of a jellied substance surrounding the basal portion of the polyp up to the tentacle whorl. The first inquiries as to the pseudohydrotheca have been made by HadZi (1913 and 1914). The pseudohydrotheca is distinguished from the real hydrotheca in having no free margin, but being distally firmly connected with the ectoderm of the polyp so as to be indistinguishable, on a superficial view, when the polyp is wholly distended. On the contrary, when the polyp is contracted, the pseudohydrotheca is, in general, easily discerned, forming a richly folded cover round the basal portion. The pseudohydrotheca bears some resemblance to the genuine hydrotheca by the way in which the polyp is attached to it, the supporting lammella of the polyp being basally connected with the pseudohydrotheca by a whorl of small chitinous pro- minences. Similar chitinous prominences are also seen, for instance in Hudendrium, connecting the soft parts of the stem with the periderm cover; systematically, however, no ‘particular interest can be attached to them.
Also in the endoderm diversities of great interest are found. The simplest, most homogeneous shape is represented by the gastric endoderm of Clava (Broch 1911), forming a homogeneous epithel- ium for absorbing the nourishment, from the orifice of the mouth to the passage of the polyp into the stem; almost all of the cells of the gastric endoderm are filled with larger or smaller grains showing a strong affinity to Delafield’s hematoxyline (“nutritive cells” and “albumen cells”, comp. Schneider 1902). As to Coryne, the state of things is quite different; here the endoderm in the portion nearest to the mouth is extremely rich in mucous gland cells, while the digestive cells are comparatively few in number. In Coryne we must consequently distinguish between the oral portion secerning mucus and the part of the endoderm of the polyp which is the proper gastric or digestive portion. The difference between these two endodermal zones appears still more distinctly in Myriothela; the glandular cells are here densely concentrated on a small portion near to the mouth, strongly conspicuous by its clear blueing after being treated with Delafield’s heematoxyline; the other endodermal cellular forms have almost wholly disappeared in the glandular zone with Myriothela. In Tubularia, on the contrary, the glandular zone has disappeared, so that the endoderm here by its homogeneous appearance all over the polyp strongly recalls the case of C/ava.
A rather different state of things is found in the Bougainvilliide. Here, indeed, mucous cells, occur in the oral endoderm of the polyp. But the bulk of the cellular elements in the oral portion as far as the whorl of the tentacles, is constituted by cells which appear indifferent to the nutritive elements. All the cells here have small nuclei strongly concentrated, while in the gastric endoderm taking the nourishment, from the whorl of tentacles and downwards, the nuclei are large, with open chromatine
net-work. This condition of things is still more pronounced in Hudendrium, the mucous cells of
The Ingolf-Expedition. V. 6. =
Io HYDROIDA
which, however, are most frequently concentrated in the proboscis, closely to the basis of the tentacles, where the entrance to the proper gastric cave is found.
Thus there is throughout a typical difference between the Cagitata and the Filifera as to endodermal matters, though the C/ava apparently presents an intermediate form or a form of depar- ture from which the other types are derivable. Simultaneously the /7ij/era, as far as can be judged from the data in hand, bear a typical resemblance to the thecaphore hydroids, and here the parallel between the Eudendrium and the Campanulariide is particularly obvious. Whether this is owing to a closer affinity or it must be explained only as a phenomenon of convergency, we must at present leave unanswered, because of our deficient knowledge of the group.
A single family, the Zwbudariide, shows an anatomic peculiarity, as with the species of this family there occurs a peculiar m’esogloeal formation, At the basis of the large tentacles the endoderm has developed a thick supporting cushion formed as a ring of mesoglceal tissue of large cells round the polyp. This leans inwardly on the supporting lamella, and is bounded against the axial endoderm of the tentacles by a delicate membrane, which in some cases it is rather difficult to point out.
Hollow tentacles occur in two ways. In their original shape they are, as is the case with Hydra, openly communicating with the gastric cave of the polyp. This state of things, however, has ceased with most hydroids and cannot be found in any of our northern species. In these, on the other hand, occasionally occurs, as in Clava multicornis and in Myriothela a central cavity in the tentacles, at any rate in their basal part. This cavity, however, does not communicate with the gastric cave of the polyp, but is basally bounded by the unbroken supporting lamella. This central cavity of the tentacles, as it is represented by well-developed Clava mu(ticornis, might be looked upon as a primitive condition of things. However, in forms so highly organised as AZyriothela, it must sooner be considered as a secondary phenomenon, which cannot have any direct correspondence with the primitive condition of things in Hydra, ’
In Myriothela the tentacles show a peculiar structure, elsewhere unknown in the hydroids. The matter is more precisely described by Jaderholm (1905). The supporting lamella is in the thickened distal part of the tentacle transformed into a cushion constructed by delicate radially — placed fibres, showing no cellular structure and densely crowded. They seem to be intended for strongly stiffening the distal portion of the tentacles and for making the armed outmost portion of the tentacles larger and more powerful of resistance.
On the ground of the anatomical features stated, and of morphological characters hitherto turned to account in systematics, is brought about a system which, as far as the athecate hydroid families
are concerned, can be summed up in the following key of determination:
A. No formation of gonophores. Eggs and sperms, developed in the wall of the polyp. The tentacles — if such ones occur — hollow, openly communicating with the gastri¢ cave (Sectio Simplicia nov.) Fam. Hydride.
B. The generative cells developed in special gonophores. I. The polyps with large, broadly oval or spherical nematocysts (Sectio Capitata K ihn).
a. The tentacles of the polyp wholly or in part claviform.
HYDROIDA II
1) The polyp having only one kind of nematocysts. The claviform tentacles of simple struc- ture, having no central cavity and no particularly developed supporting lamella.
a. All tentacles claviform. Fam. Corynide.
8. The distal tentacles claviform; proximally a whorl of filiform tentacles. Fam. Pennariide.
2) The polyps, besides having oviform or spherical nematocysts, also provided with slenderly oval or nearly cylindrical stinging capsules.
a. Without calcareous skeleton. The claviform tentacles having a central cavity, greatly widened distally, but not openly communicating with the gastric cavity of the polyp. The supporting lamella, in the outer portion of the tentacles, developed into a thick radial fibrous supporting tissue. Fam. Myriothelide.
f. Colonies with calcareous skeleton. The tentacles of simple structure, having no central cavity. Fam. Jlleporide.
b. All the tentacles of the polyp filiform, arranged in two main circles:
1) The proximal (basal) whorl of tentacles leaning against a well-developed mesogloeal cushion. The polyps of radial symmetrical structure. Fam. Zudbulariide.
2) The mesogloeal formation at the basis of the proximal whorl of tentacles almost wanting, owing to radial canals. The structure of the polyps bilaterally symmetric. Fam. Branch- tocertanthide.
Il. The nematocysts always only slender, the small ones quite rod-shaped. (Sectio Filifera K itihn). a. Colonies without calcareous skeleton.
1) The tentacles irregularly spread all over the polyp, or reducible to a single large tentacle. The endoderm not differentiated into oral endoderm and gastric endoderm. Fam. Clavide.
2) The tentacles forming a main circle round the polyp. The endoderm differentiated into an oral endoderm and a gastric endoderm.
a. The polyps fusiform with conically pointed proboscis. Fam. Bougainvilliide.
f. The broad body of the polyp well defined from the stem, and provided with a clavi- form proboscis placed with a narrow basis on the whorl of the tentacles. Often two kinds of nematocysts, large ones and small ones. Fam. Hudendride.
b. Colonies with calcareous skeleton and with two kinds of nematocysts, the large ones being
slenderly oval or nearly cylindric, frequently slightly curved. Fam. Stylasteride,
Il. Athecate Hydroids of the Northern Atlantic.
Section Capitata Kiihn. Family Corynidae.
“Hydroids with fusiform or more cylindric polypes, whose oral portion is conically pointed.
The stinging capsules are large, oviform, or almost globular. All the tentacles of the polype are
capitate with the stinging cells mainly concentrated on the thickened distal portion. The structure 2*
12 HYDROIDA
of the tentacles is simple, with no central cavity, and with a thin supporting lamella without any particular thickening. In the endoderm we must distinguish between an oral portion, abounding
in mucous gland cells, and the gastral portion proper. The colonies develop no calcareous skeleton”.
It is questionable, as is also pointed out by Kiihn (1913), whether it is justifiable to maintain the Corynidae and the Pennariidae as two distinct families. Stechow (1913) states that “das gleich- zeitige Vorkommen gekndépfter und fadenformiger Tentakel ein vorziigliches Merkmal fiir das Bestim- men ist”; simultaneously, however, he ranks the genera Acaulis and Clavatella with the Corynidae, though, having tentacles both capitate and filiform, they should, from this main characteristic, be reckoned among the Pennariidae. Also as compared with the Zudbularitdae, the limitation of the Pennari- dae makes some difficulty. Thus Bonnevie (1899) e. g. classes Heterostephanus among the TZu- bulariidae in spite of the fact that the species is provided with capitate distal tentacles. Stechow (1913), on the other hand, as well as Broch (1911), ranks this genus with the Pennaridae. I regret that I am in lack of material for a more thorough inquiry into the Pennariidac; it is not unlikely that the anatomical structure of the polypes might afford safer holds for the judging of this group of hydroids than the merely outward morphological characters.
The Corynidae form a very central group, with which all the other groups of the section of Capitata, stated by Kiihn, are likely to have originated. — At the first glance it may appear as if one of the genera Aonocoryne has_got nematocysts heterogeneously developed, so as to show, be- sides oviform or globular capsules, partly also long, narrowly oval ones. That this is not the case, is ascer- tained by a careful study of material of Monocoryne gigantea (Bonnevie) collected in the Trondhjemsfjord. Partly all the nematocysts of this shape are discharged, and partly developmental stages of other nematocysts than oviform ones are not traceable. It is, therefore, obvious that, in being discharged, the oviform nematocysts assume a narrowly oval shape. The apparent dimorphism of the nematocysts would otherwise have been greatly interesting as a connecting link with AZyrzo- thela, and would have been likely to support the supposition of Bonnevie (1899) of the derivation of the last-mentioned genus from the Corynidae through Monocoryne. But as a matter of fact, the large Monocoryne gigantea shows the anatomical structure of the true Corynidae. Swenander (1903) mentions - that its tentacles are coalesced at the basis; this statement, however, only holds good for the ectoderm, which in several places appears to be stratified; the endoderm, as far as the single tentacles are con- cerned, continues, wholly surrounded by the ectoderm, to the supporting lamella. Monocoryne gigantea presents another peculiarity which the inquirers have hitherto obviously failed to notice; the indivi- duals are hermaphrodite, in a most peculiar way. Not only we find in a single individual sheer female and sheer male gonophores; but among these also occur several gonophores containing, besides large ova, also sperms and spermatocytes of all stages. The gonophores of this species are reduced to cryptomedusoids.
In the internal structure of the polype of the Corynzdae our attention is fixed on a great ac- cumulation of mucous gland cells in the endoderm next to the orifice. Here are densely accumulated a lot of cells, whose affinity with Delafield’s haematoxyline make them very conspicuous on material
well preserved. This concentrated glandular zone is found still more strongly marked in the Myrio-
HYDROIDA 13
thelidae, whereas in the 7ubularitdae it has disappeared. It forms a striking contrast to the proboscis of the Ludendriidae, the outer oral portion of which is more abounding in indifferent endodermal cells and more nearly approaching the state of things in the Bougainvillitdac, in which, however, also the indifferent endodermal cells appear in larger numbers. As is mentioned before, this oral zone is wanting both in the Clavidae and the Stylasteridae.
The Corynidae, like their near relations the M/yriothelidac, are distinguished by a vigorously developed polype musculation, and in connection with this show an astonishing power of changing appearance and volume. It is easy for them to swallow a comparatively large copepode, and in my material I have found several shapeless-looking Corynze-polypes which were digesting rather large crustaceans. Thus they are very greedy animals, frequently feeding on organisms larger than the polype of normal size. Series of sections show how the food half dissolved also is led direct into the gonophores and is absorbed by their endodermal spadix. The endodermal cells of the spadix then are filled with some granulous contents, which are greedily absorbing and tenaciously keeping the haema- toxyline of Delafield, while they are rather indifferent to both the haematoxyline of Bohmer and
to eosine. However, the cells also contain several eosinophile grains.
Gen. Coryne Gaertner.
“Corynidae forming colonies, with solitary capitate tentacles spread all over the hydranth. The colony is formed by the ramification of an upright hydrocaulus, whose tubes do not communicate
through secondary canals. The gonophores are developed on the proximal portion of the polypes”. .
Many investigators place the species productive of medusae in a separate genus, Syncoryne. This criterion, however, is of merely biological nature, and thus of less importance to systematists. And apart from this, it is evident that some species of Coryne produce more strongly reduced eume- dusoids which are only quite exceptionally detached from the mother colony. The species have not yet been sufficiently examined. Therefore, it is obvious that, for instance, the species Coryne Loveni (M. Sars) must have been several times confounded with Coryne Sarsi (Lovén). In the medusoid -gonophores of the former species the tentacles are wholly reduced, while Coryne Sars? has complete medusoid gonophores with tentacles. The opinion maintained by L. Agassiz (1860) and Hincks (1868), based on the observations of L. Agassiz (lc) and Clark (1865), that some species of Coryne at one time of their lives produce free-swimming medusae, at other times, on the contrary, sessile eumedusoids, has not yet been refuted, but, quite the contrary, been strengthened by the observation of a parallel condition of things in species of Campanularia (Giard 1899, Behner 1914). It is not impossible that Coryne Sarsi should be one of these species of Coryne. In Coryne Lovenit the eumedusoid gonophore has lost its tentacles, and at the same time the development of the generative cells shows us that the gonophores are not here normally disengaged from the colony. Other species, such as Coryne Hincksi Bonnevie and Coryne brevicornis Bonnevie, seem to have gonophores somewhat more reduced, still, however, keeping the medusoid structure strongly defined. These
species, then, exhibit stages forming the transition to Coryne pusilla Gartner with its strongly
reduced styloid gonophores.
14 HYDROIDA
If we, therefore, like Kiihn (1913) and Stechow (1913), separate Syucoryne as a genus of its own, there will be insurmountable difficulties about drawing the limits. If, as is done by Stechow, the limit is drawn by the production of free-swimming medusae, Coryne Loveni must normally be omitted from the genus Syzcoryne, and a species such as Coryne Sarsi will probably have to be reck- oned sometimes among the Syxcoryne, at other times, on the contrary, among the Coryne. If, on the other hand, we follow Kiihn and draw the limits of genera between species with eumedusoid gonophores and species having gonophores more strongly reduced, it may be greatly questionable where, for instance, Coryne Hincksi and Coryne brevicornis ought in fact to be placed. In this case as in others, the more species we learn to know more exactly, the more impossible it proves to draw the limits of genera on the ground of gonophoral conditions. To this must be added that in all the species of Coryne or Syucoryne the colonies and the polypes are so uniform as to their appearance, that they cannot with certainty be identified to species or included under one or the other of the two “genera”, if the gonophores are wanting or only little developed. It is, therefore, absurd to insist on drawing an artificial and arbitrary line of distinction, founding on merely biological phenomena of adaption.
Coryne Sarsii (Lovén) Johnston.
1835 Syucoryna Sarsi, lovén, Bidrag til Kannedomen af Slagterna Campanularia och Syncoryna p. 275, pl. 8, fig. 1—6.
1847 Coryne Sarsii, Johnston. A History of the British Zoophytes, p. 43.
?r911 Syncoryne Sars, Semundsson, Bidrag til Kundskaben om de islandske Hydroider II, p. 72.
“The delicately constructed colonies attain to a height of up to 30 mm. The hydrocaulus is wholly irregularly ramified with no distinct main stem; the branches form acute angles with the stem or the main branch whence they proceed; both the stems and the branches are almost entirely smooth with no rings nor wrinkles. The strongly contractile polype, when extended, attains to a length of up to 1.5 mm., and is then almost wholly filiform; when contracted, it is oviform or nearly globular. The numerous capitate tentacles are irregularly distributed over the polype.
The gonophores develop into medusae, which are likely to break away during the greater part of the generative period of the polype; the medusa bud developes four tentacles. One or two,
more rarely three, gonophores occur simultaneously on the polype”.
Material:
Iceland, Reykjavik. Shallow water (associated with small dZytilus),
In all probability, Semundsson (1902, 1911) is right in including these very delicately con- structed colonies under Coryne Sarsiz. The occurrence of the species is boreal. But the possibility that the species is frequently confused with forms nearly related, as yet precludes certain decision as to its distribution. Coryne Sarsii is recorded from the coasts of Norway, Bohuslén, Denmark, Helgoland, Great Britain, Iceland, and Northern France. Hartlaub (1905 a) and Jaderholm (1903), though with
some doubt, refer some colonies from Tierra del Fuego and from Patagonia to the same species.
HYDROIDA 15
Coryne Loveni (M. Sars) Bonnevie.
1835 Syncoryna ramosa, Lovén, Bidrag til Kannedomen af Sligterna Campanularia och Syncoryna, p. 275, pl. 8, figs. 7—10.
1846 — Lovent, M. Sars, Fauna littoralis Norvegiae, p. 2, footnote.
1899 Coryne Lovent, Bonnevie, Norske Nordhavs-Expedition, p. 14.
“The colonies are rather coarsely constructed and attain a height of up to 30 mm. The hydro- caulus is wholly irregularly ramified and shows no distinct main stem. The branches proceed almost rectangularly from the stem or the mother branch, but at once curve upwards, forming a very acute angle or even a parallel with it. The hydrocaulus and the branches are almost entirely smooth, having
only here and there wrinkles slightly indicated. The strongly contractile polype, when extended,
60
40
teeeeeee « 200% ~~ Swe'cone b600m. Cri ast RESO OO ME | FO aes estonenies 2000m. Text-fig. A. The occurence of Coryne Loven? in the Northern Atlantic (the hatched coastal Region denotes a scattered occurence, the totally black parts indicate a common occurence)
attains to a length of nearly 2 mm., and then is slenderly fusiform or nearly cylindric; when contracted it is oviform, oval, or almost globular. The numerous capitate tentacles are irregularly distributed all over the polype.
The gonophores develop into eumedusoids, 1.5 mm. long, with no tentacles, normally not break- ing away; they have four well-developed radial canals and a circular canal. Up to three gonophores
occur on the polype near its base”.
Material: Greenland, Godthaab litoral (on Ascophyllum)
Norway, Bjark6éi, Lofoten litoral (on /cotdeae)
16 HYDROIDA
Hartlaub (1907) informs us that in his aquaria he has observed a Syncoryne, whose gono- phores are not set free, though being full-grown medusae with four tentacles well developed; the generative products are developed in the sessile medusa, which is reduced after having performed her generative task. Hartlaub refers this form to Coryne (Syncoryne) Lovent M. Sars. This identifica- tion however, cannot be right; most likely we have here rather in hand individuals of the Coryne Sars during the part of the generative period when the medusae are not detached. Through Mr. C. Dons, conservator at Tromsé, I received a very copious material of Coryne Loveni from Bjarkdi, where the species occurs in abundance on the Fucozdea in the tidal water region. The large number of individuals examined have most frequently two, more rarely three gonophores, which are developed into a complete medusa without any tentacles. The four radial canals end in a small enlargement, which is the only indication of tentacles traceable. The species, accordingly, cannot be identical with the form recorded by Hartlaub, but agrees very well with the description and the illustration given — by Lovén.
Coryne Lovent is earlier known only from the west coast of Scandinavia. Jaiderholm (r1g09, taf. 1, fig. 7) gives an excellent drawing of the species collected from Bohuslan; elsewhere it is recorded from the coast of Norway from Bergen as far as Lofoten, where its occurrence in the northern part of its habitat is most numerous. Some colonies from Godthaab show us that Coryne Lovent must also be added to the fauna of Greenland. The species is native to the boreal tidal water zone and
attains to its most luxuriant development in the passage to the regions of the Artic Ocean.
Coryne pusilla Gartner. 1774 Coryne pusilla, Gartner, in Pallas: Spicilegia zoologica vol. 1, fase. 10, pag. 40; pl. 4, fig. 8. 1893 Syncoryne mirabilis Levinsen, Meduser, Ctenophorer og Hydroider fra Grénlands Vestkyst, p. 150. 1902 Coryne vermicularis, C.fruticosa, Syncoryne eximia, Seemundsson, Bidrag til Kundskaben om de
islandske Hydroider,; p. 50.
“The colonies are coarsely constructed, attaining a height of up to 4o mm. The hydrocaulus is wholly irregularly branched, showing no distinct main stem; the irregularly curved branches are everywhere densely wrinkled and form almost right angles with the hydrocaulus or with the mother branch. The strongly contractile polyp, when extended, attains to a length of 2.5 mm., and is then slender and narrowly fusiform or almost wholly cylindrical; when contracted, it is oviform or oval. The numerous capitate tentacles are irregularly distributed over the polyp.
The gonophores are globose, showing a styloid structure. There occur 4—8 gonophores, irregu-
larly distributed over the proximal (basal) half of the polyp”.
Material: The Faroe Islands. Iceland: Grindavik. On littoral algae (labelled Coryne pusilla and C. fruticosa). Reykjavik. On littoral algae (labelled Syucoryne eximia and Coryne vermicularis). Greenland (labelled Syncoryne mirabilis),
t Dr. P. L. Kramp kindly informs me, that Coryne Loven? is abundant in the Little Belt.
HYDROIDA 17
A closer investigation of the living polyps and of their conditions very soon shows us that the appearance of the polyp is varying very strongly according to its state of contraction. Now it is stretched at length, assuming approximately the shape of a thin worm, now it is again contracted to a short, thick lump, very ‘nearly approaching the globular shape. Sometimes the polyp is at the widest at the base; sometimes it is contracted in this part, so that the largest width appears farther out. The study of the live polyps thus, in this case as in many others, shows us that many characters which have been turned to account as criteria of species with the Coelenterata, may be of most doubt- ful value or even of no importance whatever to classification. In the first place, of course, this is appli- cable to the various states of contraction, which, in Coryne pusilla, have even led to subdivision into several species. J&derholm (1909) thus, on account of difference of shape of the polyp, still
distinguishes Coryne pusilla and Coryne vermicularis Hincks; as, however, all other characters wholly
0 40 20 ; 0
~ 200M j = waeewece 600M = —=§«_—_ tees ctv eee - tooom. te motenssm cams. 2000 M.
Text-fig. B. The distribution of Coryne pusilla in the Northern Atlantic.
agree, and the differences put to account as specific characters fall far within the limits of the polyp movements described above from observation of living individuals, the separation into species cannot be recognized; Coryne vermicularis forms a synonym of Coryne pusilla and, in fact, only represents a “ phase of the movement of the polyps. Coryne pusilla has previously been recorded from the north of France, from Great Britain and Ireland, from Helgoland, from Denmark, from Bohuslan, from the west coast of Norway, from the Faroe Islands, and from Iceland (Reykjavik). In my material there also occurs a colony marked “Greenland?”, wrongly determined as Syncoryne mirabilis Agass; the species thus seems to belong to the fauna of Greenland, but particulars are still missing. The rather numerous Icelandic colonies of
the species are all derived from the south-western point of the island. The species, accordingly, must The Ingolf-Expedition. V. 6. 3
8 HYDROIDA
be characterized as southern boreal; it mainly occurs along the coasts of the North Sea and round the British Isles; how far it advances to the north on the coast of Norway, we do not as yet know
with certainty; but a any rate it does not push forward as far as into the Arctic seas.
Coryne sp. aff. Hincksi Bonnevie. Material:
“Ingolf St. 44. 61°42’ Lat. N., 9°36’ Long. W., 545 met. 4.8°.
A small colony of young individuals of a species of Coryne is attached to the stalk of a Zz bularia sp. The hydrocaulus is irregularly wrinkled and attains a height of up to 6 mm. with polyps I—2 mm. long. There occur 4—8 small, apparently medusoid, gonophores at the base of the polyp closely below the tentacles. The tentacles are short. The stolon of the colony is reptant, the stalks of the polyp are unbranched. On account of the bad state of preservation it is impossible to furnish a proper design of the individuals.
It is possible that the individuals belong to the species Coryne Hinckst Bonnevie, which
has previously been recorded only from a depth of 100 fathoms near Hammerfest (Bonnevie 1899).
Family Myriothelidae.
“Large solitary hydroid polyps with stratified ectoderm, in which occur two kinds of nemato- cysts, Besides the typical oviform nematocysts of Cafztafa are found in somewhat smaller numbers narrowly oval or nearly cylindrical, rather large nematocysts which are especially frequently occur- ring in the ectoderm of the gonophores. The tentacles are capitate with a central cavity which does not communicate with the gastral cavity of the polyp, and which is distally broader. The vigorously developed distal portion of the tentacles is shored up by a particularly developed portion of the supp- orting lamella, here showing a fibrillary structure with fibres radiarily arranged. The supporting lamella is vigorously developed in the wall of the polyp and provided with bilamellae. The endoderm — exhibits a dense circle of mucous glands at the mouth of the animal. No calcareous skeleton is
developed”.
The Myriothelidae seem to be nearly related to the Corynidac, and also to the Adlleporidae, which latter form calcareous skeletons. The last mentioned family presents in its dimorphically developed nematocysts a strong resemblance to the AZyriothelidae. However, only a character as the peculiarly developed supporting lamella in the thickened distal portion of the tentacles, as well as” the dimorphic development of the nematocysts, justifies the distinction of the A/yriothelidae as a parti- cular family beside the Corynidae, Already Bonnevie (1899) has pointed out the near rela- tion between Myriothelidae and Corynidae and the bridge between them suggested by the species J/o- nocoryne gigantea (Bonnevie). The arrangement by groups of the tentacles and the attachment of the gonophores to these groups are very likely to form the base of the development of the blasto- styles of Myriothela, But on account of the peculiar direction in which the structure of the tentacles
HYDROIDA 19
of the Myriothelidae has developed, we cannot subscribe to the view of Kiihn (1913), reducing the two families into one. The anatomical structure of the polyps of the two groups differs too much, and to this difference must be attached a greater importance than the investigators have hitherto been inclined to do; anatomically the difference between the groups is too great to allow their amalgamation, in spite of the agreement of the two families as to the endodermal mucous gland portion near the ori- fice of the polyp.
Hitherto only one genus has been recorded of Myrtothelidae.
Gen. Myriothela M. Sars.
“The large solitary polyps have only exceptionally slight indications of hydrocaiilus; in general the base of the polyp is truncate or pointed and provided with rhizoids or filaments of adhesion, which are in fact transformed tentacles. Both the ectoderm and the endoderm are stratified. The tentacles are capitate and are irregularly distributed over the polyp and the blastostyles. The gono- phores are developed on small polyp-like blastostyles attached to the inferior half of the polyp; the blastostyles bear tentacles on their distal portion”.
The genus Myriothela is recorded from the northern seas and from the Antarctic Ocean. The spread and rare occurrence of the individuals prevents us from deciding whether the genus is in fact
bipolar, as the finds hitherto recorded seem to indicate.
Myriothela phrygia (Fabricius) M. Sars. 1780 Lucernaria phrygia Fabricius, Fauna Groenlandica, Nr. 333, p. 343: 1851 Myriothela arctica M. Sars, Beretning om en zoologisk Reise, p. 134. 1873 _ phrygia G. O. Sars, Bidrag til Kundskab om Norges Hydroider, p. 130.
“The capitate or almost cylindrical polyp extended reaches a length of about 400 mm. The inferior termination of the polyp is truncate, and it is attached to the substratum by tentacle-like fila- ments of adhesion. Above the portion wearing blastostyles it is studded with strong capitate tentacles; on the other hand tentacles are wanting on the surface of the polyp between the blastostyles.
The cryptomedusoid gonophores are developed on small polyp-like blastostyles, attached to the inferior portion of the polyp and wearing capitate tentacles on their outward parts. The female blasto- style has only one or two fully-developed gonophores at the same time, while the male blastostyles
wear numerous gonophores”.
Material: “Ingolf? St, 117. 69°13'N., 8°23’ W., depth 1003 fathoms, + 1° C. — St. 125, 68°08’ N., 16°08’ W, — 729 — + 08°C Myriothela phrygia has an enormous faculty for extension and contraction, and it is likely to share this faculty with its nearest relatives. A specimen I had the opportunity of observing when it was brought up by the trawl in the Trondhjemfjord, had stretched its distal portion wearing tentacles
so strongly that the animal was as thin as a thread and measured up to 30 cm. in length; but as vs
20 HYDROIDA
soon as it was irritated by the preservation fluid, it contracted to a length of only 9 cm., and simultan- ously the diameter of the distal portion of the polyp increased to the measure of 2—3 mm. This observation shows how little importance is, in fact, to be attached to the absolute measures of the polyp in the limitation of the species of M/yriothela. While the individuals from st. 117 wholly agree with the earlier descriptions and drawings of the species, the defective specimen from st. 125 (tab. I, fig. 8) at the first glance differs greatly. The broad, longitudinally strongly contracted basal portion is studded with blastostyles in a narrow belt, above which the polyp tapers rapidly so as to assume a conical appearance fairly reminding of the drawing by Bonnevie of AMyriothela mitra (1899, tab. IV, fig. 3). However, a closer examination shows that the distal portion of the polyp has been torn off,
onsets encses eonsess 200 m. oe sewn 600M. teeter mere 1000 M. eerste eee, 2000 M.
Text-fig. C. Localities of Myriothela phrygia in the Northern Atlantic.
and as its trunk above the blastostyles is studded with capitate tentacles, while the polyps of the species mentioned have no tentacles at all, a mistake of identity is out of the question.
Myriothela phrygia is an arctic deep-sea form, mainly occurring in the icy water at the bottom of the northern seas. It is recorded from Taimyr (J4derholm 1908), from the north of Norway, and from the depths of the ocean between Spitzbergen and Greenland (Bonnevie 1899), besides from the localities laid down in the map subjoined (Text-fig. C). The original description has been given on specimens from Greenland, from where, however, we still lack particulars as to localities. “Ingolf” now adds two new finds in the waters of the Arctic Sea between Iceland and Jan Mayen. On the whole, the occurrence of the species is scattered; most of the finds are situated in high-arctic regions, and here the species is seen to occur even at so small a depth as between 12.8 and 14.6 m (J ader-
holm 1908). Therefore, two localities are, indeed, apt to give surprise. One of these localities is recorded
HYDROIDA 21
from the “Michael Sars” 1902, when the species was found in the warm Atlantic waters to the south of the Wyville-Thomson-Ridge (Broch 1903). There is in this case a possibility that the animal has been carried with Arctic currents from northern regions; if so, the currents have conveyed the animal at an early period of life to the new locality, where it has been able to subsist and develop further. The other locality, in the Trondhjemfjord was previously recorded, and the Trondhjem Museum was in possession of a defective specimen which was said to have been taken in the fjord; but particulars were wanting till the researches of the fjord in 1911 brought to light, from the depth of 200 m. near Tautra, and thus in the midst of the Atlantic water layers of the fjord, a well developed female polyp. This find gives the more surprise, because there is left no opening for the possibility that the specimen should have been carried to this place from Arctic water layers. Like other Arctic hydroids, such as Tubularia regalis Boeck, Corymorpha groenlandica (Allman), and Stegopoma plicatile (G. O. Sars), Myriothela phrygia thus thrives very well in the region of the Trondhjemfjord which is otherwise characterized by Atlantic ZLofhohelia-reefs. This cannot, however, be turned to account as a proof against the Arctic character of the species; in the Trondhjemfjord all these species must be looked on as Arctic relicts.
Family Tubulariidae.
“Hydroids forming colonies, or solitary, with large oviform or globose nematocysts in the ecto- derm. The tentacles of the full-grown polyp are filiform and simply constructed with no central cavity; they are arranged in two main circles, a proximal whorl round the broad basal portion of the polyp and a distal whorl round the mouth. The basal whorl of tentacles is supported by a ring-shaped mesogloeal cushion round the basal portion of the polyp. The polyps are radially symmetrical. The supporting lamella shows a very simple structure”.
Most authors refer to this family also Branchiocerianthus, which I reckon as the type of a family of its own, the Branchiocerianthidae. This family is distinguished from the 7ududariidae partly by bilaterally symmetrical polyps, partly by the peculiar anatomical structure of the polyps. In fact, the structure of the polyps of the Branchiocerianthidae differs greatly from that of all other hydroids (comp. Stech o w 1909). There occurs a supporting lamella of complicated structure, and the polyp is provided with numerous, prominent radial canals. They are distinguished from the Zudu/ariidae also in their inner anatomy by almost lacking any trace of mesogloeal tissue at the base of the proximal whorl of tentacles, owing to the radial canals. These points of difference are, indeed, of such importance that they fully justify the sepa- ration of Branchiocerianthus into a family of its own, the Branchiocerianthidae beside the Tubularidae.
Kiihn (1913) divides the Zudulariidae into two subfamilies, Zubelariinae and Corymorphinae. The former he defines by the characters “Koloniebildend, Periderm gut entwickelt”, while the latter is defined as “Solitir, Periderm hautig oder riickgebildet, Wurzelhaare”. To this is to be observed that a species as Zubularia cornucopia Bonnevie is a typical Tubularia in spite of its forming no colonies. The filamentary appendages of Corymorpha must be compared with similar phenomena in /yriothela, some species of which have rhizoids, while others such as Myriothela Cockst (Vigurs), attach thems-
elves by a plateformed perisarc; when this is considered as nothing else or no more than a criterion
22 HYDROIDA
of species with JZyriothela, there tells indeed little in favour of raising it to a distinguishing mark between two subfamilies of the Zzbzlariidae. As far as finally the development of the periderm is concerned, this is a gradual character showing many transitions, to which no importance can be
attached as a distinguishing mark between two subfamilies.
Gen. Tubularia Linné.
“Hydroids most frequently forming colonies, the hydrocaulus being surrounded by a stiff and chitinous perisarc. The polyps are radially symmetrical, having two main circles of tentacles, a proximal (basal) whorl of long tentacles leaning on a mesogloeal ring in the trunk of the polyp, and a distal whorl with short tentacles round the mouth. The tentacles are also in the actinula filiform.! The gono- phores are generally borne on blastostyles; the gonangia spring from the trunk of the polyp between the two whorls of the tentacles”.
The gonophores are, in this genus as in most other genera, sometimes medusoid, sometimes more or less reduced. The species producing free medusae have been grouped by many authors as a genus of their own, Hydocodon. In this case as in others, the question then arises where the line is to be drawn. While in species as 7ubularia pulcher (Seemundsson) the medusa breaks away, the fully developed medusoid gonophore in Zudbularia regalis Boeck, as far as is known to us, never voluntar- ily relinquishes its sessile existence. If we follow Kiihn (1913), as might seem right, we get into a dilemma, having to refer the female of Zudularia regalis to Hybocodon, while the male, having crypto- medusoid gonophores (Broch 1915), must remain in the genus Zwébularia. Only this should be suffi- cient to show the error of turning the organisation of the gonophores to account as fundamentum divisionis. No doubt, it is wrong to set up AHydocodon as a particular genus of hydroids, and the same is certainly the case with the genus Aw/iscus set up by Semundsson (1899), the medusae of which as we are going to see, are scarcely particularly distinguished as compared to the other ybocodon- medusae,
Tubularia pulcher (Semundsson).
1899 Auliscus pulcher Seemundsson, Zoologiske Meddelelser fra Island, p. 425, Tab. IV.
“Colonies, the hydrocauli of which are up to 50 mm. long, unbranched, and separated down to the reptant hydrorhiza. The stalk is covered with a brown perisarc, which is thick at the base, but upwards against the polyp narrowing periodically and at distinct intervals, so that the stalk gets an appearance approximately articulate; the spaces between the transverse striae, brought about in this way, attain their greatest length in the middle part of the stalk, being here 13 mm. long. The upper portion of the stalk is provided with a thin perisarc, widening funnel-shapedly into a thin collar under the polyp. The polyp is fitted ott with a basal circle of 24—30 tentacles, about 5 mm. long; the distal tentacles, about 30, are placed, densely crowded, in a narrow belt, consisting of several rows, round the orifice, and attain a length of a little more than 1 mm.
The gonophores develop into free Hysocodon-medusae with gemmation on the bulb of the
t The tentacles of the actinula may be swollen at their tips (comp. Allman 1872) but never show the dense accumula- tion of stinging cells here. which is so characteristic in the truly capitate tentacles of the section Caf/tata.
HYDROIDA 23
large tentacle; there are four radial canals. The bell exhibits five exumbrellary stinging cell stripes. The gonophores are developed on eight blastostyles faintly branched, a little more than 1 mm. long”.
Material: Iceland, Reykjavik. Near the shore (1 specimen).
The specimen in hand is one of the original specimens investigated by Semundsson (1899). It is an individual with hydrocaulus 30 mm. high. The polyp is fitted out with 25 proximal tentacles, 5 mm. long, and 8 blastostyles a little branched, about 1 mm. long. A closer inquiry of the gonophores gives a picture somewhat different from that drawn from the explanation of Semundsson. In the first place the umbrella of the medusa is not quite symmetrical, but somewhat oblique, as in /Zyboco- don prolifer 1. Agassiz. At first only one tentacle, not two, is developed on the large tentacle bulb (Tab. Il, fig. 16); the “corpora acuminata et duo ovata”, mentioned by Semundsson as springing from the tentacle bulb, are all gems of medusae; none of them can be made out as “initium tentacu- lorum novorum” belonging to the original medusa. Wherever at the first glance two tentacles seem to occur on the bulb, a closer research will show that one of them in fact belongs to the bud of a new medusa on the bulb of the gonophore. Therefore, we have to concur in the opinion of Hart- laub (1907) and subscribe to his explanation of the apparent occurrence of two tentacles with Aydo- codon prolifer as satisfactory for the species in hand, that “bei der Knospung von Hybocodon der Ten- takel in der Entwickelung stark voraneilt und schon fertig sein kann, wenn der dazu gehdrige Me- dusenkérper noch nicht deutlich in die Erscheinung getreten ist”.
The conditions of gonophores described show a much nearer relationship to 7udularia (Hybo- codon) Christinae Hartlaub (= Zudularia prolifer Bonnevie 1899). Hartlaub’s drawing of Hybo- codon Christinae (1907, fig. 98) is, according to the statements cited, easily reconcilable to the figure a little more skeletonlike given by Semundsson (1899, tab. IV, fig. 3). Nor is the difference between the polyps very great; Bonnevie (1899) states for her specimen 14 proximal tentacles, about 10 mm. long, while the species stated by Semundsson is said to have 24—30. It is a matter of regret that we only know the length of the proximal tentacles of the specimen in hand. But on account of the great contractility of the tentacles, no particular systematical importance can be attached to their length, and as far as the difference of numbers of the proximal tentacles is concerned, we see in other Tubulariidae within easy reach such a variety that the difference quoted by itself cannot justify any se- paration of species. When Zbularia Christinae is nevertheless maintained as a separate species beside Tubularia pulcher, it is in the first place owing to the express declaration of Bonnevie (1899) that her specimen has no collar under the hydranth; such a collar is, on the other hand, strongly developed in Tubularia pulcher, though at the first glance it may seem very little distinctive on material preserved."
Hartlaub (1907) holds that the medusa is identical with the medusa drawn by Steenstrup (1842), Coryne fritillaria, and much is speaking in favour of the correctness of this supposition. On the other hand, the polyp described by Steenstrup, in the same place and by the same name, cannot be identified. It may be that it really is a Coryne; some features are even suggestive of Coryne Lo- ' veni M. Sars; but the only thing the drawing shows us with full certainty; is that the polyp is no
t The original specimen of Bonnevies Zubularia prolifer was wanting in the museum of the Kristiania university.
a M7 \BRARE SN » ‘ \ a a
VA OF THY
24 HYDROIDA
Tubularia, and that its medusoid gonophores, if they are rightly perceived, cannot develop into medusae of the Hybocodon type. The only locality from which Zubularia pulcher is recorded with certainty, is the shore near
Reykjavik, Iceland, where it has been found only once.
Tubularia indivisa Linné. 1758 Tubularia indivisa Linné, Systema Naturae, Ed. ro, p. 803. 1899 i obliqua + T.indivisa Bonnevie, Norske Nordhavs-Expedition, p. 24.
“Colonies, whose long dark brown-coloured hydrocauli are, in the lower part, twisted together. The stems are covered with a vigorous perisarc, but show no rings nor wrinkles. No collar is formed below the polyp. The polyp has a basal whorl of 20 to 30 tentacles up to 20 mm. long; the distal _ tentacles are up to 3 mm. long and densely crowded round the orifice in a whorl consisting of several rows.
The female gonophores are eumedusoid with four rudimentary radial canals, one of which (the shortest) is often slightly indicated even in the gonophore fully developed. The gonophore has, near the apex, a tentacle-like bulging, obliquely situated. The male gonophores are crypto- medusoid and almost wholly globular, not oval. The gonophores are born upon up to 10 blasto- styles, which attain a length of 10 mm. ‘The actinula-larvae, when set free, wear filiform
tentacles”.
Material: “Ingolf? St. 31, 66°35’ N., 55°54’ W.; depth 88 metres 1,6° C. (Davis’s Straits). — St. 87, 65°02’, N., 23°56, W.; depth 110 metres (West-Iceland). Greenland: Davis’s Strait (without further data).
— Egede’s Minde( — _ —). Iceland: Brede Bugt 65°12’ N., 23°28! W, depth 36 fathoms. — Grindavik littoral. — Skagestrand depth 60 fathoms. — Vestmannd littoral.
The Faroe Islands (without further data). The North Sea: the West side of large Fishing bank 57°7’N., 2°40’ E., depth 37 fathoms.
_ Swenander (1903) has pointed out that Tubularia obliqua Bonne vie (1899) is based on female individuals of 7uébularia indivisa; thus in the very external characters of the gonophores this species presents a peculiar sexual dimorphism, and inquiries into the conditions of the gonophores (Broch 1915) have made good that this sexual dimorphism is a radical one, the female gonophores being eumedusoid, the male ones on the contrary cryptomedusoid. — Tuédularia indivisa is very easily con- founded with the following species, Zwbularia regalis, particularly when only male individuals are in hand for examination. In this case only the somewhat different shape of the gonophores makes it~ possible to refer with certainty the individuals to one species or the other, the male gonophore of
HYDROIDA 25
Tubularia indivisa being globular, and accordingly broadly rounded in the distal part, while that of Tubularia regalis is oval and showing au attempt to be pointed in the distal part.
Tubularia indivisa has a very wide distribution. Its main occurrence in the boreal seas is bound to the middle and deeper parts of the littoral region and to the upper part of the deep sea region. From the cold area we find the species but once recorded, by Grieg (1914). After the examination of his specimens I cannot confirm this record; the specimens consisting only of hydrocauli without polyps, more probably belong to another species of Zwdu/aria inhabiting the deep sea.
To judge from literature, 7udularia indivisa penetrates rather far into the shallower parts of the Arctic regions, where it is recorded even from the New Siberia Islands (J iderholm 1908). How-
ever, as appears from what is stated above, there is a possibility that some of the Arctic individuals
40
steven sneees nae enee 200m .... . waaewcoe 600m. cape dev ens es IOOO My vere, 2000m. Text-fig. D. The distribution of Zxdularia indivisa in the Northern Atlantic.
are in fact to be referred to 7udbularia regalis. — The species also penetrates far towards the south. It is recorded by Fewkes (1881) even from the Caribbean Sea, by Allman (1877) from between Cuba and Florida, and by Billard (1906) from the west coast of Africa. As Zubularia indivisa is recorded at the same time both from the East and the West coast of North America, it must be characterized
as a circumpolar or rather “circumboreal” (Nordgaard 1912) species.
Tubularia regalis Boeck. 1860 Tubularia regalis Boeck, Videnskabsselskabets Forhandlinger for 1859. 1899 — — + TZvariabilis Bonnevie, Norske Nordhavs-Expedition, p. 24. Colonies whose long, dark-brown-coloured hydrocauli are in the lower parts twisted together.
The stem is covered with a vigorous periderm, but shows no rings nor wrinkles. No collar is formed
The Ingolf-Expedition. V. 6. 4
26 ° HYDROIDA
below the polyp. The polyp wears a basal whorl of 20—35 tentacles up to 4o mm. long; the distal tentacles, up to 3 mm. long, are densely crowded round the orifice in a whorl consisting of several rows.
The female gonophores are eumedusoid with 3—6 external longitudinal ribs and as many corresponding radial canals. The male gonophores are cryptomedusoid and oval, often with an attempt to be pointed in the distal part. The gonophores are born upon up to 20 blastostyles, which attain a
length of 35 mm. The actinula larvae, when deliberated, wear filiform tentacles.
Material: Between the Faroe Islands and the Shetlands, depth 505 fathoms.
Tubularia regalis presents so many points of resemblance to 7udularia indivisa that the risk of
confounding the two species is very easily incurred. As a general rule, the jfull-grown polyps of 7z-
teescecesees eocece 200 m. was ose a 600M. tare F000 M, so ants axes enstaiess £ OOO MH,
Text-fig. E. The occurence of Zubularia regalis in the Northern Atlantic.
bularia regalis are larger than those of Zudularia indivisa. But this is not the case in younger individuals of Zubularia regalis, in which consequently the only certain distinguishing marks are pre- sented by the gonophores. The gonophores, indeed, are typical enough in the female individuals, but are not very conspicuous in the male ones, especially at earlier stages. The male gonophores of 7w- bularia regalis are oval, while those of Zudbularta indivisa are globular. It is evident from the diag- nosis of the species, that also 7ubularia regalis presents a strong sexual dimorphism. The first who got aware of this fact, was Swenander (1903), who accordingly pointed out that the female had been described as a different species Zubularia variabilis Bonnevie.
Tubularia regalis is a form of true Arctic character, particularly occurring in the deeper
parts of the cold area. In the seas far towards the north it rises to shallower parts, and it is, for instance,
HYDROIDA 27
recorded from Spitzbergen at the depth of only 38 m. (Broch 1909). Evidence of its occurrence in the Kara Sea is still wanting. From this locality a specimen is in hand, determined by Bergh (1887) as Zubularia regal’s. As a matter of fact, the specimen is a Corymorpha, probably a Cory- morpha glacialis M. Sars. — A remarkable exception to the habitat stated is formed by the frequent occurrence of the species in the Trondhjem Fjord, where it is found in abundance on the Lophohelia- reefs. In spite of the luxuriant development which it attains in the Trondhjem Fjord, it must probably, like Corymorpha groenlandica (Allman), Myriothela phrygia (Fabricius), and Stegopoma plicatile (G. O. Sars), be accounted for as an arctic relict in this locality.
Tubularia larynx Ellis et Solander. 1786 Tubularia larynx, Ellis et Solander, The Natural History of Many Curious and Uncommon Zoophytes, p. 31. 1864 “= humilis, Allman, Notes on Hydroida, p. 57 and 60.
Colonies whose long polyp stems, generally unbranched and irregularly curved, are separated quite down to the tangled network of basal tubes. The stems are covered with a fairly vigorous, but colourless perisarc, which is irregularly wrinkled or more rarely quite smooth. The polyp wears a basal whorl of up to 25 tentacles, attaining a length of 8 mm.; the numerous distal tentacles, 2 or 3 mm. long, are densely crowded round the orifice in a whorl consisting of several rows.
The gonophores are eumedusoid, without radial canals, but with a rudimentary circular canal; they are most frequently provided with three rudimentary tentacles. The gonophores are supported by 6—12 short blastostyles, which may be erect or hanging. The actinula larvae, when deliberated, show
filiform tentacles.
Material:
Iceland: Reykjavik. tO) Rare hed ee ROE yo er oe depth 4 fath. SS TES 5 aaa ee Pe PPO ER eB aoe ory eee one Ce eS — 15-16 — Faxebugt three miles N 37 E Keflavik.................e. sees sees — 195 — OF Havnnefjord 20. suis oc bees ne eee Soe wae ene cea en ven» - 25 — CVE IBN ON oii 5 60 ad PCs Sev eee Geen cena SEE ee ae — 20-30 — ET SER PEW eae ok, wal Ree Cre ae eae cy eb cee = 40 +m Wesbirian SISIANOS yc. ruties «cco obese ei sewinclble wou wale oars eeuctine — 28 fath
The Faroe Islands: Andefjord...........e.e cece cece tec cece eee tebe eecees — 16-23 —
The North Sea 60°35’ N., 1°50’ W... 1. eee e eee ene e cere ence renee eeeees — 5Se°0.C«‘
The synonymy of the varying species has been thoroughly accounted for by Fenchel (1905). ‘He points out that, as is also maintained by Bounevie (1899) and by Swenander (1903), Tubularia coronata Abildgaard must be subsumed under 7wdelaria larynx. On the other hand, it is not plainly seen whether he regards 7ubularia humilis Allman to be a peculiar species. On a closer exami- nation, indeed, the characters pointed out by Bonnevie (1899) as distinguishing marks, prove to
be of no particular systematic importance. The wrinkling of the stem is strongly varying from 4*
28 HYDROIDA
one individual to another in a larger colony, and individuals with quite smooth stems are not seldom observed in colonies which are otherwise typical Zxdbalaria larynx. The dimensions of Tubalaria humilis wholly agree with those of young colonies of Zxbularia larynx, and the numbers stated as characteristics stand far within the range of variability known in this species. Then only remains the condition of the blastostyles, which should be erect in Zubularia humilis, but hanging in Zubularia larynx. An examination, however, of living material will show that only in rare cases the blastostyles of 7wdzlaria larynx can be described as hanging (comp. Broch 1911); on the contrary they are generally borne in a rather erect position, particularly when not yet very large. Thus also this criterion proves to fail, and consequently we are forced to consider 7udbularia humilis as a synonyme of Zubularia larynx.
Tubularia larynx is an entirely boreal species, which has its main occurrence in the zone of the
60 40 20 Y)
OOM I aes ater boom. Come aos eo atoee. t000 a1. ermnecbeaccadiy e OOO WN
Text-fig. F. The distribution of Zuébularia larynx in the Northern Atlantic. laminaria and the red algae. Towards the south it enters into the Mediterranean, and towards the north it penetrates as far as Nova Zembla, and seems still to occur at Spitzbergen. On the south-
western coasts of Iceland it is very frequent, and it is also found on the east coast of North America.
It is to be wondered that the species has not yet been met with at Greenland.
Tubularia sp. indet. Stems of Zuédularia of the type imdivisa-regalis are in hand from the following localities: “Ingolf? St. 8 63°56' N., 24°40’ W., depth 136 fathoms, + 6° C. bebe cope IBS i OGREO: ) 2g 5°05) «+! crs NOGGM Ti iee ce ceetern ge + — - 36. 61°50’ - 56°2ar' - 3 — 91435 9 =<» 4 :1°5 -
HYDROIDA 29
“Ingolf” St. 40. 62°0o' N., 21°36’ W., depth 845 fathoms, + 3°3 C.
—_ - 86. 65°03'6- 23°476- — 76 — ? - - 87. 65°03'2 - 23°56'2 - —- m0 — ? — = 106, 65°34’ - 8°54’ - — 447 = 0S C. — - 127. 66°33’ - 20°05’ - reas Y Weta 4+ 5° - — = 143 62°58’ - 7°%09' - — 388 — + 0% -
Of a type like that of Zubularia cornucopia Bonnevie from the localities: “Ingolf St. 11. 64°34’ N., 31°12’ W., depth 1300 fathoms, + 1°6 C. — - 18 61°44’ - 30°29' - — 1135 pad +: 3°O.'-
Gen. Corymorpha M. Sars.
Solitary hydroids, whose contractile hydrocaulus is surrounded by a flexible, thin, and membran- aceous perisarc. The hydrocaulus is attached to the substratum by numerous rhizoids. The structure of the polyp is radially symmetrical with two main whorls of tentacles, a proximal or basal whorl of long tentacles supported by a mesogloeal ring in the polyp body, and a distal whorl of short ten- tacles round the orifice. In the full-grown polyp all the tentacles are filiform; in the actinula larva at any rate the distal (oral) tentacles may be capitate. The gonophores are generally supported by blastostyles; the gonangia arise from the body of the polyp between the tentacle whorls.
As early as 1909 I stated this limitation of the genus, grouping at the same time the species, on the ground of gonophoral matters, in four subgenera. However, I suggested that, as to the rela- tions between the two subgenera Monocaulus and Lampra, a closer inquiry was wanting. As a matter of fact, one of the species stated by Allman (1876) Monocaulus groenlandica really proves to be identical with two of the species of Lampra stated by Bonnevie (1899). Also the other northern spe- cies of Monocaulus has met a peculiar fate, being first ranked by Allman (1872) within his genus as Monocaulus glacialis (M. Sars), and afterwards (1876), after the examination of some specimens from the museum of Copenhagen, described as a new species, Amalthaea tslandica Allman. | These matters, indeed, throw a glaring light on the unmaintainability of the subdivision into so-called “genera” to which Corymorpha has been the subject. At the first glance it is a matter of sur- ptise that Stechow (1913) still tries to maintain the old genera. Indeed, in zoology more considera- tion must be given to the observations made on living individuals than has hitherto been done. Thus the two main criteria turned to account by Stechow (1912) for the purpose of distinguishing Cory- morpha Sarsii Steenstrup (1854) and Corymorpha vardéensis Loman (1889) testify to the fact that matters of contraction are still allowed to play a prominent part as to the limitation of species. By the observation of a living Corymorpha it will soon be ascertained that, by extension and contraction of the lower parts of the polyp and of the upper sections of the stem, the same polyp will show now amore emphatic distinction from its stem, now a smoother transition into it. The points of difference de- lineated by Stechow (1912, Taf. 12, Fig. 2 and 3) are, in this respect, not so great as those which may be observed in a single individual while alive. The other main character, that the spadix of the
30 HYDROIDA
gonophore of Corymorpha Sarsii is “fast immer” projecting from the umbrellar cavity, while this is “fast nie” the case with Corymorpha vardéensts, is in the first place very vague, and secondly depend- ent partly on the various contraction of the umbrella, partly on the sex and the degree of maturity of the gonophore. On the whole there can be no doubt that the description of Corymorpha vardéensis is based on an individual of Corymorpha Sarsut.
I have entered on this subject because Stechow (1912, 1913) puts together the species menti- oned into a genus of their own, Amadthaca. The genus was first established by O. Sch midt (1854) for the species Amalthaca uvifera O. Schmidt, which is likely to be identical with Corymorpha Sarsi. It em-
braces the species of Corymorpha whose gonophores develop into complete medusae, but, after all, not
breaking away, whereas the species whose medusae are normally breaking away, are gathered in the 4
genus more narrowly limited, Corymorpha. It is evident,however, that the medusa of Amalthaea excep-
tionally breaks away and then leads a wretched life, unfit as it is for free existence on account of |
possessing a too small umbrella, the greater part of which is, into the bargain, occupied by the enormous -
spadix with mature generative cells. The medusa strongly reduced, further, shows so near a rela~ tionship to the medusa of Corymorpha nutans M. Sars that a systematist of medusae so skilful and
discerning as Hartlaub (1907) decides on only placing it in a subgenus of the medusoid genus — ;
Corymorpha. "The classification afterwards maintained by Mayer (1910), who distinguishes the two a
groups of medusae as peculiar genera and even places them in quite different places in his syn- | i opsis, as Amalthaca and Steenstrupia, only proves that he has failed to notice the excellent drawing B by M. Sars (1877), which shows us in fact, that the female gonophore, when fully developed, is often an entirely typical Steenstrupia, though one of the main tentacles is not quite so large as in Cory- a morpha nutans. ‘The figures delineated by Sars wholly agree with the facts observed in living 7 individuals, and make good the correctness of Hartlaub’s view of division, giving the right place to affinity and biology. But where is then the fundamentum divisionis adaptable for the purpose of = classifying the Corymorpha-like species of polyps into separate genera? ;
From Amalthaca to Monocaulus glacialis there is, indeed, a very short step; all the difference, as a matter of fact, is to be found in the gonophore, also here eumedusoid, being even somewhat more
reduced, as the tentacles, the special organs of the umbrellar margin, are entirely wanting. The con- =
formity of the polyps is obvious; the gonophores of both species are eumedusoid and normally sessile; Be the difference is accordingly too little for a separation of genera.
Then only remains the group of Zampra, whose gonophores are cryptomedusoid. A generic ‘a separation between, for instance, the species of Lampra and Corymorpha (Monocaulus) glacialis, will,
as I have recently pointed out (1915), correspond to a generic separation between ¢ and 2 in Zabu- a
laria indivisa jinné or Tubularia regalis Boeck. A particular argumentation of the unnaturalness a
of this limitation is hardly required. But then it is obvious, as a matter of course, that a generic separation of the species of Zampra and the other species of Corymorpha cannot be maintained. Also the species of Lampra must be ranked within the genus Corymorpha.
HYDROIDA 31
Corymorpha nutans M. Sars. 1835 Corymorpha nutans, M. Sars, Beskrivelser og Iagttagelser ...... p. 7, Pl. 1, Fig. 3.
The hydrocaulus, when extended, attains a height of 100 mm. It is broad at the basis, attached to the substratum by numerous rhizoids, and tapering upwards till it reaches its least breadth closely below the polyp. The basis of the polyp is broad and surrounded by a proximal whorl consisting of up to 50 tentacles, which, when extended, attain a length of 30 mm. The distal tentacles are small and placed round the orifice in a main whorl composed of several irregular circles quite closely set.
The gonophores are developed into free medusae with four radial canals, one well-developed
tentacle and three rudimentary ones. The gonophores are developed on 15—20 blastostyles, arising
40
40
seesse cesses seseees 200 m. woe wun o.600M, sme 1000 M, cceoeyaccvesscumes £ OOO Wie
Text-fig. G. The habitat of Corymorpha nutans in the Northern Atlantic. (In the hatched regions the litterature denotes a scattered, allthough common occurence).
closely above the proximal whorl of tentacles. The blastostyles bear small alternating branches, each
provided with a large number of gonophores.
Material: Iceland, 16 minutes N. W. Akranes, depth 26—30 fathoms (a couple of young polyps).
The occurrence of the species is typically boreal. It is indigenous to the middle parts of the littoral region. Towards the north it goes along the coast of Norway as far as Lofoten and towards the south it penetrates to the northern parts of France. The species is recorded by J iderholm (1909) from Matotschkin Schar (Nova Zembla) at the depth of between 2 and 5 fathoms. This find is most peculiar and mysterious. Corymorpha nutans occurs not rarely in the North Sea, and I think Hart- laub (1907) is right in supposing the specimen from the North Sea recorded by me (1905) as a Cory-
32 HYDROIDA
morpha, to be in fact a young colony of Corymorpha nutans. Remarkably enough, the species has not yet been met with at the Faroe Islands; but it has been found several times on the west side of 4 Iceland. At Greenland it is not likely to occur; nor has the species as yet been recorded from this .
locality.
Corymorpha glacialis M. Sars. 1859 Corymorpha glacialis, M. Sars, Om Ammeslegten Corymorpha. . 1872 Monocaulus giacialis, Allman, A Monograph of the Gymnoblastic or Tubularian Hydroids, —
Pp. 396. q 1876 Amalthea islandica, Allman, Diagnoses of new Genera and Species of Hydroida, p. 256, Pl. IX Pig. 5—6
?1887 Zubularia regalis, Bergh, Goplepolyper fra Kara-Havet.
Nec 1893 Amalthea islandica, Levinsen, Meduser, Ctenophorer og Hydroider fra Gronlands Vestieyaia
ie 4
The hydrocaulus, when extended, attains a height of 100 mm. It is wide at the base, where |
it is attached to the substratum by numerous rhizoids, and is gradually tapering upwards till closely ~
below the polyp where its width reaches its minimum. The polyp has a broad base, surrounded by a
whorl of up to 50 tentacles, which, when extended, attain a length of 30 mm. The distal tentacles are
small arid numerous, placed round the orifice in a main whorl formed by several irregular and closel
set circles.
The gonophores are eumedusoid, with four radial canals, but without rudiments of tentacle a
They are sessile. The gonophores are scattered all over the surface of 30—35 unbranched blastostyl the oldest and most developed ones at the apex of the blastostyle.
Material: Iceland, @fjord (without particular data). Original specimen of Amalthaca tslandica. ? The Kara Sea (“Dijmphna”. Particular data are wanting). Labelled Zubularia regalis.
The original specimen in hand of Amalthaea islandica Allman (1876) proves as clearly as de- — sirable that this species is wholly identical with Corymorpha glacialis. Allman, certainly, states that the gonophores of the species are provided with four short tentacles, which are also, in his rather skeletonlike drawings, delineated as rather considerable formations. But in the original specimen can only in some straggling gonophores be pointed out some accidental wrinkles, which, when acting in good will, we may consider as the origin of the rudimentary tentacles stated. Other divergencies from the typical Corymorpha glacialis are, on the whole, not traceable. zi 4
A specimen from the Kara Sea has been identified by Bergh (1887) as Zubularia regalis Boeck. q The specimen is an unquestionable Corymorpha and no Tubularia; indeed, everything suggests that it is a Corymorpha glacialis, but the state of preservation impedes a safe identification. 4
According to the particulars in hand Corymorpha gilacialis is indigenous mainly to Arctic wa- q ters. It has been recorded from the Varanger fjord (M. Sars 1859), from Nova Zembla (Maren-
zeller 1877), and from Spitzbergen (Broch 1909). But the species also penetrates into warmer water
HYDROIDA 33
layers, as is seen (Text-fig..H) from the finds to the north east of the Faroe Islands and on the south east coast of Iceland (Broch 1903). As new localities must be added Northern Iceland (@fjord). On the other hand, the specimens from Davis Strait, recorded by Levinsen (1893) as Amalthaea tslandica,
prove to belong to Corymorpha groenlandica (Allman).
Corymorpha groenlandica (Allman) Broch. 1876. Monocaulus groenlandica, Allman, Diagnoses of new Genera and Species of Hydroida, p. 257, Pl. IX, Fig. 7—8. 1893. Amalthea islandica +- Monocaulus groenlandica, Levinsen, Meduser, Ctenophorer og Hydroider
fra Gronlands Vestkyst, p. 151.
40
Sbeeseee poes'ses o6e - 200 m, pase aie oi O OOM tate ere 000M. smeee eee ireees 2000 M.
Text-fig. H. Finds of Corymorpha glacialis in the Northern Atlantic.
1899 Lampra atlantica +- Lampra purpurea, Bonnevie, Norske Nordhavs-Expedition, p. 20, Tab. II Fig. 4, Tab. III Fig. tr.
1903 —- socia, Swenander, Uber die athecaten Hydroiden des Drontheimsfjordes, p. 6, Taf. Fig. 1—3. 1909 — arctica, Jaderholm, Hydroiden, p. 41, Taf. I Fig. 9—10.
1909 Corymorpha spitzbergensis, Broch, Die Hydroiden der arktischen Meere, p. 140. IQI5 -- groenlandica, Broch, Hydroiduntersuchungen IV, p. 11.
The hydrocaulus, when extended, attains a height of 100 mm; it is widest at the base, where it is attached to the substratum by numerous rhizoids, and is gradually tapering upwards till close
below the polyp where the width reaches its minimum. The polyp has a wide base, surrounded by
The Ingolf-Expedition. V. 6. 5
34 HYDROIDA
a basal whorl of up to 37 tentacles, which, when extended, attain a length of 4omm. The distal ten- — tacles, when extended, attain a length of 9 mm; they are placed in large numbers round the mouth j in a main whorl formed by two or more irregular and closely set circles.
The gonophores are cryptomedusoid and globular (?) or sub-oval (3), often somewhat taperin distally, but without any rudiments of tentacles. The gonophores are supported by unbranched a strongly contractile blastostyles, which, when extended, attain a length of 4o mm. The gonopho: es first ripen at the apex of the blastostyle. As many as 32 blastostyles may occur, but, in general, number is much smaller; the blastostyles arise close above the basal whorl of tentacles.
Material: “Ingolf” St. 102. 66°23’ N., 10°26’ W., depth 750 fathoms, + 0°9 C. - 107. 65°33’ - 10°28’ - —..492. = + 0° - - 139. 63°36’ - 7°30’ - — 7Oo2 — + 0% -
Greenland: Godthaab (no particulars) [Allman’s original specimen of Monocaulus groenland Davis Strait, depth 100 fathoms [labelled Amalthaca tslandica). : Iceland: 66°02’ N., 11°05’ W. 5 miles east of Seydisfjord; depth 435 fathoms.
racters (all the measurements are given in mm).
Height of) Blastostyles || Proximal Tentacles Distal Tentacles Nr. Finds Hydro- Observations caulus |} Number| Length Number Length Arrangement Length & I | “Ingolf’ St. 139 go 14 5 ? ? in several close circles 2 Hydrocaulus stron : extended q 2 || “Ingolf” St. 139 60 15 | I—3 ? ? in several close circles 2 Blastostyles very s ly contracted 3 || “Ingolf” St. 107 57 13 3.5 26 25 in a double circle formed by | 1.5 alternating displacement 4 || “Ingolf” St. 102 45 10 5 23 up to 24 | in several close circles 1.5 5 | “Ingolf” St. 102 41 8 5 25 24 in a double row formed by 2 alternating displacement 6) Davis Strait 4o 20 7 24 25 in several close circles Sa r 7 || “Ingolf’ St. 107 ? Io |6—13 21 30 in three irregular rows formed | 1.5 || Hydrocaulus morethan _ by alternating displacement 50 mm high : 8 || ‘“‘Ingolf” St. 102 ? 9 4 28 up to 23 || in several close circles 2 9 || “Ingolf’ St. 107 ? 16 | 3—4 24 22 in a double row formed by | 2.5
alternating displacement
10 |66°2'N.11°05’ W. ? 28 |5—18 22 25-30 ? ? Blastostyles. placed alt- — ernatingly; attempt at forming two rows
I
i)
“Ingolf” St. 107 ? 14 4 18 18 in three irregular rows formed 2 by alternating displacement
HYDROIDA 35
The species, which is widely distributed in the deeper parts of the cold area, has been found by several expeditions, and has formed the base of the genus Lamfra stated by Bonnevie (1898, 1899). I have already in works earlier published pointed out that, for several reasons, this genus cannot be maintained. In the first place, the name of Lampra had already been applied to a subgenus of the beetle family Buprestidae, and should, therefore, disappear among the hydroids, according to the rules of nomenclature internationally adopted. Secondly the characters distinguishing Zamfra from Cory- morpha are not sufficient to justify a separation of genera.
A closer examination of the numerous northern species of Zampra described will show their un- maintainability. A survey of the figures forming distinguishing characters is obtained by grouping the criteria stated as follows:
Height of Blastostyles : Tentacles _ Nomenclature Hydro- Proximal Distal } Gonophores caulus Number} Length Number} Length Arrangement Length Monocaulus groenlandica Allman 1876.) 1inch || 7—8 2 |1ca. 20 |"Modera- “numerous” | short no tentacles tely long” Lampra arctica Jiderholm tgog ..... 45 mm 22 |5—8mm| 25 25mm || 5-6 close circles ? =| globular,broadly oval with rounded apex Corymorpha spitabergensis Broch 1909..| 60 mm 12 5mm 25 20mm _ || 4-5 close circles | 2 mm| oviform or globular aa) : ___|| without tentacles Lampra atlantica Bonnevie 1899 .... 80 mm 10 |4—6mm | Io |10-20 mm) several close- ? without tentacles set circle ee Lampra purpurea Bonnevie 1899..... roo mm 10 30-40 = 30 | 30-40 mml||_ two circles ? without tentacles Lampra socia Swenander 1903....... 45mm |18—32\till 25 mm|29—-37) 35mm numerous | up to|| Q more rounded, close-set circles) 9 mm 3 sub-oval, without tentacles
The original discription given by Allman (1876) is founded on a series of young individuals from Godthaab, in which it may be observed how the number of proximal tentacles increases by new tentacles being established and growing out among the old ones. How far the number of tentacles may increase in this way, cannot be settled. But no definite rule of the increase being trace- able, we here face one of the reasons of the great varying of the numbers of tentacles. In these young individuals it is also interesting to observe that the distal tentacles are established quite irregularly Tab. Il Fig. 14), and that the blastostyles arise as simple fingerformed bulges of the polyp wall. The gonophores only appear at a rather late stage of development. j
The skeletonlike figures and rather deficient diagnosis of the species given by Allman long impeded its recognition, and, therefore, only a couple of specimens occurring in the museum of Copen- hagen have later on been correctly referred to his species Monocaulus groenlandica. Bonne vie (1899) accordingly describes two new, closely related species, Lampra atlantica and Lampra purpurea, ‘The former species is distinguished from the latter mainly by its small number of tentacles, having only ten proximal ones. However, even though this difference must be regarded as very large, as far as in ‘the single specimen of Lampra purpurea as many as thirty proximal tentacles have been observed, we cannot acknowledge it as a sufficient specifical distinguishing character after the examination of a
larger material of the species. The rather numerous specimens found in the Trondhjem fjord present By
36 HYDROIDA
so great a range of variability that the number stated in ZLampra atlantica must only be considered as an extreme variation. The variation of the individuals found in the Trondhjem fjord is even larger than stated by Swenander (1903); individuals have been found with only 15 tentacles in the proximal whorl. The difference in the shape of the gonophores, being either subglobular or oval with attempts at tapering, is of little importance. Swenander points out that the female gonophores are more globose, the male more oval. In a specimen picked up north east of the Seydisfjord (Iceland) the gono- phores are partly globular, partly oval, with the same attempt at tapering towards the distal end as is shown in the figure of Bonnevie (1899, Tab. III, Fig. ra). However, one criterion is still left, the distal tentacles of Lampra purpurea being arranged in two separate circles, while in other spe-
cies they are placed in several irregular and close-set circles. From the comments of Bonnevie it
appears that the description has mainly been based on the drawings of G. O. Sars, which were exe- .
cuted on board ship. In these drawings the double whorl is not peculiarly clearly rendered; nor can, -
from the remnants of the original specimen kept, the character be ascertained any longer. From the table set up of the specimens from the Danish collections, however, it appears that, from individuals with a distal whorl consisting of two rows to individuals with a distal tentacle whorl of several rows, every transition may be pointed out. Thus neither this table nor the criteria stated in the other table may be turned to account for the purpose of attaching any peculiar systematical importance to this character. Lampra atlantica and Lampra purpurea, therefore, cannot be recognized as two separate species, and are moreover identical with Corymorpha groenlandica.
For a thorough examination of the species we are indebted to Swenander (1903), who considered — the Lampra of the Trondhjem fjord as a peculiar species, Lampra socia. From what I have stated 4 above, the shape of the gonophores, applied by Swenander as a main character distinguishing the 4
species from Lampra purpurea Bonnevie, cannot be maintained as a criterion. The number of the —
blastostyles then remains; Bonnevie, for both the species mentioned, states 10 blastostyles; Swen-
ander, for Lampra socia, 183—32. Still Swenander has not found the minimum for the individuals 4 of the Trondhjem fjord; as a matter of fact, specimens with only 15 blastostyles are now in hand.
In the Danish material collected from the northern Atlantic the number is throughout lower, varying
from 10 to 28, thus bridging the difference between Zampra socia and the species stated by Bonne- 4
vie. Also the other distinguishing characters, the emphatic demarkation of the hydrocaulus from the
polyp, or its gradual transition into the latter, and the colour of the animals, are varying from one =
individual to the other, forming no strongly defined limits. The demarkation of the stem from the
polyp more or less emphatic, is, in living individuals, varying according to the state of contraction, as a
in other species of Corymorpha. Therefore, also Lampra socia must be considered as a synonym of Corymorpha groenlandica.
Jaderholm (1909) and Broch (1909) describe two new species, respectively Lampra arctica and Corymorpha spitzbergensis. The table at once shows that they come within the range of variation of Corymorpha groenlandica. As to Lampra arctica the short and thick blastostyles, maintained by Jaderholm (1909) as a good criterion, are in fact to be looked upon as a mere phenomenon of con- traction which may be partly observed even in preserved material, where in the same individual some
blastostyles may be short and thick, while others are thin and strongly extended. Illustrative in this
HYDROIDA 37
respect is the individual nr. 10 of the first table, the length of the blastostyles varying from 5 to 18 mm., and the thickness being inversely proportional to the length. ‘The rest of the distinguishing characters fall under what has been earlier stated.
Corymorpha groenlandica is a typical form characteristic of the great deep of the cold area. It proves to be widely distributed, from Spitzbergen to the Faroe Islands, and from Norway to Green- land. It has also been recorded from Davis Strait. In the seas far to the north it rises to more shallow waters. Thus it has been recorded near Spitzbergen at the depth of ‘only 45 metres (Broch 1909). A remarkable geographical exception is formed by the occurrence of the species in the deeper Atlantic
[ ; o 40 nal ote D
%0 20
seeererseseeeeee ZOOM = =—§ mmm enna 600m. me morans ances. fooom. comsce tess scanss £000 M7.
Text-fig. I. Localities of Corymorpha groenlandica in the Northern Atlantic. strata of the Trondhjem fjord. At present the occurrence of the species in this locality cannot be accounted for. But a great deal may be said in favour of the notion that we have here in hand a relict form, which has been able to accommodate itself to the altered circumstances in the same way as Tubularia regalis Boeck and Stegopoma pilicatile (M. Sars) which are rather frequently occurring on or at the Lophohelia reefs of the fjord.
Corymorpha sp. indet. Indeterminable remnants of species of Corymorpha occur from the following localities: “Ingolf” St. 28, 65°14’ N., 55°42’ W., depth 420 fath., + 3°5 C, attached to the tube of a Pectinaria.
pee = 124, 67°40' = “15°40 - 495 OO
38 HYDROIDA
Section Filifera Kiihn.
Family Clavidae.
Hydroids forming colonies, with polyps fusiform or capitate, the distal part of which is coni- cally tapering. The stinging cells are small and rodformed. The tentacles are filiform, irregularly dis- tributed over the body of the polyp, now and then showing a heterogeneous development or even reduced to a single large tentacle. The endoderm forms a homogeneous gastral cell-layer through
the whole of the polyp. The colonies have no calcareous skeleton.
The family Clavidae, as it is here defined, includes the genus much in dispute Monobrachium, which has been distinguished by most investigators as the representative of a family of its own, MZ- nobrachiidae. This family is maintained even by Kiihn (1913), who has obviously failed to notice the significant pointing out by Vanhdffen (1909) of the heterogeneous development of the tentacles of Campaniclava clonis V anh 6ffen, forming an obvious link between Monobrachium and the other Cla- vidae. VanhOffen, therefore, does away with the family onobrachitdae and refers Monobrachium
to Clavidae. In this he is rightly followed by Stecliow (1913).
Gen. Clava Gmelin.
The reptant colonies have polyps capitate or subfusiform with filiform tentacles irregularly distributed over the polyp. The proboscis is conically pointed. The hydrocauli are not surrounded by any distinct stiff perisarc. The gonophores are clustered on the polyp below the portion bearing tentacles, or seated on the reptant stolons either solitary or in clusters.
According to this diagnosis also the genus Rhizogeton must be included under Clava. The two 4 genera have hitherto generally been distinguished on the ground that in Rhzzogeton the gonophores are seated on the stolons, while in Clava they are borne by the polyp itself. This criterion, however, : is too insignificant to justify a division of genera, and it is also suggested by Stechow (1913) that very likely the two genera have to be united. In his key of genera, indeed, Stechow puts down
Rhizogeton in a parenthesis under Clava.
Clava multicornis (Forskal) Gmelin. 1775 Hydra muilticornis, Forskal, Descriptiones animalium, p. 131. 1776 — squamata, Miller, Zoologia Danicze Prodromus, p. 230. 1788 Clava parasitica, Gmelin, in Linné: Systema natura Ed. 13, vol. I, p. 3131.
On the reptant stolons the capitate or almost fusiform polyps are placed in close or opener clusters. The stem of the polyp is without perisare. The filiform tentacles are irregularly distributed q over the distal parts of the polyp. ;
The gonophores are cryptomedusoid, and placed in larger or smaller groups like clusters of grapes closely below the portion of the polyp bearing the tentacles.
HYDROIDA 39
The species may be divided into two forms:
Forma genuina, growing, in colonies more openly constructed, on stones and shells (Mytilus); it is delicately built and bluish or rose-coloured.
Forma sguamada forming clusters of polyps more brick-coloured or yellowish-red on the leaves of Fucotdeae; its polyps are large and robustly built.
Material: Iceland: Reykjavik depth 3—4 fathoms. Vestmatney on the shore (on /zcordeae) The Faroe Islands: Sundelaget north of Kvalvik on the shore (on Fucotdeae)
(There also occur specimens marked “Faeré” without particular data). Pp P
Clava multicornis and Clava squamata ate recorded by most investigators of hydroids as two separate species; the distinguishing characters, however, are rather vague, being made out by the closer or opener occurrence of the polyps in the colony or by the colour of the colonies. A copious material from various localities, in fact, presents all transitions possible, and it is virtually impossible to draw any certain limit between the species. A closer inquiry soon makes clear to us that the points of difference must be of biological nature, and the two species, therefore, have to be regarded only as biologically determined “forms” of a single species, which I, accordingly, denominate forma
genuina and forma sgumata. The occurrence of typical colonies of the forma gewuina, which are, in
oO %0 __28. o
. 200m, Ramin aa = OOO caremcene ee SY Se we ee 2000m.
Text-fig. K. The distribution of Clava multicornis in the Northern Atlantic.
(In the hatched part of the Norwegian coastal region the occurrence is rather scarce).
40 HYDROIDA
fact, rather rare and scattered, is bound to substrata of stones, which may be, at a pinch, replaced by the shell of a AMy¢z/us, while the colonies luxuriantly developed of the forma sgwamata are resident on the leaves of the /ucotdeae, where certainly the supply of food is much more copious.
The description of Forskal (1775) being older than that of O. F. Miiller (1876), we have according to the rules of nomenclature in force, to drop the specific name employed by the latter, Clava squamata and to maintain the denomination bestowed on the species by Forskal, Clava multi cornis. Its limitation from the American species Clava leptostyla ,. Agassiz, has not as yet been ascertained, and it seems on the whole questionable if the two species are really to be distinguished.
Clava muiticornis is a boreal species, which seems, nevertheless, to be able to penetrate far into the Mediterranean (Babi¢ 1904). It is a littoral form, and forma sgwamata has been found only in the tidal zone; forma gexuina, on the other hand, at rare intervals, has been met with a little ben- eath the tidal zone in places with rather small salinity. Fabricius (1780) records the occurrence of the species at Greenland without particular statement of locality; however, it has not afterwards been observed in this place. On the other hand, the species seems to occur not unfrequently on the south west coast of Iceland. It is frequently met with at the Faroe Islands, and is found everywhere round the British Isles and on all coasts round the North Sea. Its occurrence at the northern parts
of the coast of Norway is not sufficiently accounted for, but does not seem to be particularly frequent.
Gen. Merona Normann.
From the reptant stolons arise unbranched, chitinous polyp stems. In the upper part of the stem the perisare is so wide that the polyp can be retracted into it, though developement of a hydro- theca is not indicated. The filiform tentacles are irregularly spread over the polyp. The gonophores
are borne upon reduced polyps (blastostyles) arising from the reptant stolons.
With great hesitation I set up Merona as a genus of its own. It is distinguished from Cory- dendrium van Beneden (1844) only in mere trifles of no great importance. Thus its polyp stems — are unbranched, while the hydrocaulus of Corydendrium is richly branched. Another distinguishing =
character may perhaps be sought in the quality presented by Merona in its wide perisarc, into which
the polyps are retractile. But none of these criteria can be said to be of properly generic value. When, nevertheless, A/ervona is provisionally maintained, it is due to the fact that only an exceedingly scarce material of a single species is in hand, and that the state of preservation of this material allows of
no closer inquiry into the polyps.
Merona cornucopiae Norman. 1864 Tubiclava cornucopiae, Norman, On undescribed British Hydrozoa, Actinozoa and Polyzoa, p. 357. 1865 Merona — Norman, On Merona, an undescribed genus of British Hydrozoa, p. 262.
The hydrocauli are unbranched and attain a height of about 5 mm.; the stems are narrowest at the base and increase gradually in diameter till they attain their greatest width closely below the
oe a el
HYDROIDA 41
extended polyp; they are without rings; at most there is some faint and irregular wrinkling here and there, The polyp is fusiform with the tentacles irregularly distributed all over the surface; the