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THE DANISH
INGOLF-EXPEDITION.
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VOL. V, PART 7.
CONTENTS: HJALMAR BROCH: HYDROIDA (PART II).
PUBLISHED AT THE COST OF THE GOVERNMENT
BY
THE DIRECTION OF THE ZOOLOGICAL MUSEUM OF THE UNIVERSITY
■r~iajxii^-
COPENHAGEN.
H. HAGERUP.
PRINTED BY BIANCO LUNO. 1918.
THE DANISH INGOLF-EXPEDITION.
VOLUME V.
7.
HYDROIDA.
(PART II.)
BY
HJALMAR BROCH.
WITH i PLATE AND 95 FIGURES IN TEXT.
-*-j»»:?«f<-
COPENHAGEN.
PRINTED BY BIANCO LUNO. 19 1 8.
CONTE
Page I. Comparative anatomy of the nourishing individuals, and
systematic division of the theeaphore hvdroids i
II. Theeaphore Hvdroids of the Northern Atlantic 6
Family series Hebellina 6
Family Lafteidoe 6
Lafaa (Lamouroux) 7
Lafica dumosa (Fleming) 7
gracillima (Alder) 9
fruticosa M. S a rs 12
Toickopoma Levinsen 15
Toichopoma obliquum (Hi neks I 15
Grammaria (Stimpson) 16
Grammaria serpens ( Hassall ) 16
confer ta ( A 1 1 m a n ) .• 17
— dbietina (M. Sars) iS
immersa Nutting 22
Lictorella ( Allman) 22
Lietorella pinnata ( G. O. Sa rs ) 22
Zygophylax Q u el ch 24
Zygophylax biarmata Billard 24
Familv Campanulinidts 25
Subfamily Cuspidellina 26
Stegopoma Levinsen 26
Stegopoma plicatile ( M. Sars) 26
Cuspidella Hincks 29
Cuspidella humilis Hincks 29
Lafoeina M. Sars 29
Lafoeina maxima Levinsen 30
Campanulina van B e n e d e n 30
Campanuhna turrita Hincks 31
Subfamily Calycellma 32
Calycella (Hincks) 32
Calycella syringa ( L i n n e ) 32
Tetrapoma Levinsen 34
Tetrapama quadridentatum (Hincks) 34
Family series Haleciina 35
Family Haleciida: 35
Halecium O k e n 35
Halecium halecinum ( Linne) 36
Beam/ Johnston 38
scutum Clark 39
curuicaule v. Lorenz 41
NTS
Page
Halecium muricatum Ellis and Solander). . . . 43
labrosum Alder 45
/, nellum Hincks 46
munition Broch 50
Familv Plumulariidcs 51
Kirchenpaueria ( Jick eli ) 52
Kirchenpaueria pinnata (Linne) 53
Plumularia Lamarck) 55
Plumularia setacea (Linne 55
Catharina Johnston 56
Polyplumaria G. O. S a rs 58
Polyplumaria frutescens I Ellis and Solander) . 59
flabellata G. O. Sars 59
profunda (Nutting) 60
Nemertesia Lamouroux 62
Nemertesia antennina (Linne) 64
ramosa Lam ouroux 66
Polynemertesia now gen. 69
Polynemertesia gracillima (G. O. Sars) 70
Family Aglaopheniidce 72
Halicornaria (Busk) 72
Halicornaria campanulata (Ritchie) 72
Nematocarpus nov. gen 74
Xcmatocarpiis ramuliferus (Allman ) 74
Aglaophenopsis ( Fe wkes ) 77
Aglaophenopsis cornuta ( Verrill) 77
(?) pharetra nov. sp So
Cladocarpus Allman 82
Cladocarpus integer G. O. Sars ) S2
formosus Allman S5
Diana nov. sp 87
bicuspis G. O. Sars) S9
Thecocarpus Nutting 91
Thecocarpus myriophyllum (Linne ) 92
Aglaophenia (Lamouroux) 93
Aglaophenia tuhiilifcra H i n cks ; 93
Family series Sertulariina 94
Familv Sertulariidce 94
Sertularella l-rav 96
Sertularetta tamarisca (Linne) 96
! 1 icuspidata (Alder) 9S
amphorifera Allman 100
419nr>
Page
Sertularia polyzonias I Linne I 101
Gayi (Lamourouxl 102
tenella (Alder ) 104
— fusiform is Hill cks 105
rugosa (Linne).. 106
Diphasia Agassiz 107
Diphasia fallax (Johnston) 108
Wandeli Levins en 1 1 1
rosacea ( L i n n e ) 112
attenuate* Hi neks 113
alatti Hi 11 Cks 114
Dynamena (Lamouroux) 114
Dynamena pumila (Linne) 115
Abietinaria (Kirch enpauer) 116
Alictinaria abietina (Linne) 1 17
fihcula (Ellis et Solander) 119
— (l)fusca 1 J o h n s to n I 120
Sertularia (Linne) 1 22
Sertularia cupressina Linne 124
tenera G. 0. Sars 127
Fabricii L e v i 11 s e n 1 30
— (?) tubuliformis (M ark tan 11 er-Tu rneret-
sc her) 132
mirabilis ( V e r r i 1 1 ) 1 33
Hydrattmania H i 11 c k s 1 34
Hydrallmama falcata (Linne) 135
Thujaria (Fleming) 138
Thujana thuja (Linne) 139
sp. aff. hippuris A 11m an T41
laxa Allman 142
alternitheca Levinsen 143
— variabilis now nom 145
— lonchitis (Ellis et Solander) 146
— canca Levinsen 148
t sp. aff. distans Fras er 14S
Page
Family series Proboscoida 149
Family Campanulariidce 149
Campanulana (Lamarck ) 153
Campanularia volubilis (Linne) 153
verticillata | Li n 11 e I 155
groenlandica Levinsen 157
speciosa Clark 158
Integra Mac Gillivray 159
Hincksi Alder 162
Johnstoni Alder 163
Laomcdca Lamouroux 164
Laomedea jiexuosa Alder 165
— geniculata (Linne) 166
longissima (Pallas) 167
hyalina (Hincks) 169
— gracilis M. Sars 170
Bonneviella Broch 172
Bonneviella grandis (All man) 173
III. Addenda to the Athecate Hydroida 174
Corynwrpha nutans M. Sars 174
— groenlandica (Allman) 174
Family Branchiocerianthidtz 174
Branchioccrianthus Mark 174
Branchiocerianthus reniformis now sp 176
IV. Zoogeographical observations on the Hydroid Fauna
of the North Atlantic 1 7S
V. List of the genera treated, and type-species 195
Literature 197
VI. Index 201
Errata 206
I. Comparative anatomy of the nourishing individuals, and systematic division of the thecaphore hydroids.
As with the athecate hydroids, so also in the case of the thecaphores, the comparative anatomy of the nourishing individuals affords us a certain working basis in systematical respects. With regard to this group, however, the investigations are still somewhat incomplete, as will be seen from the following.
The ectoderm of thecaphore hydroids is apparently very uniform in point of development, and the nematocysts, which in the athecates furnished good material for study, seem in the theca- phores to vary but slightly, and should on the whole be referred to the same type as in Athecata filifera. This point is of some considerable interest as further confirmation of the old theory as to a closer relationship between the thecaphores and the mentioned group than between the thecaphores and Athecata capitata. Even among the Grammar/a, where the nematocysts, in one species at any rate, are dimorphously developed, we can find no resemblance to the capsule form in Athecata capitata. The arrangement of the stinging cells also is very uniform in the thecaphores. As a general rule, we may say that the nematocysts in the thecaphores appear in marked transverse zones about the tentacles; the only exception I have found here is that of the gigantic Bonneviella polyps, where the zonate arrangement has become effaced.
A somewhat different organisation of the ectoderm is encountered in one or two families. The grown polyps of SyntheciidcB and Sertulariida have developed adhesive lamella, an exterior ectodermal lamella covering the inner side of the hydrotheca for a greater or lesser extent when the polyp has withdrawn into the same. It is this ectodermal lamella which Nutting (1904 p. 10) considers as one or more "protractors", evidently from more or less accidental breaks in the lamella, this being, in the living polyps, continuous. Nutting even goes so far as to base part of his system upon the number of "protractors", and is here followed by Broch (1905, 1909). These protractors, however, form, as pointed out by Kiihn (1913 p. 66) an unbroken sheath or covering on the inner side of the hydro- theca, attached at its basal margin to the body of the polyp, and at the distal to the opercular appa- ratus. A similar arrangement is also found in Aglaoplieniid(r\ here likewise we encounter lamellous extensions of the ectoderm, attaching the polyp to the inner ribs of the hydrotheca.
We see then, that the ectoderm itself gives us very little to go upon in a systematic classifi- cation. On the other hand, its derivates, i. e. the periderm, will in the thecaphores be found of great importance in this respect. The thecaphores are, as we know, characterised by their stiff, almost
The Ingolf-Expedition. V. 7. I
HYDROIDA II
chitiuous sheath, which is extended to form the hydrotheca. Incipient hydrotheca formation is found once or twice among the athecates, as for instance in Pcrigoniuius, where a folding pseudo-hydrotheca surrounds the polyp below the tentacle whorl. Less attention has perhaps been paid to similar for- mations in a species such as Eudendrium vaginatum Allman, though even here we seem to find trace of an incipient hydrotheca. In the thecaphores, however, the hydrotheca has developed into a permanent component of the colony, and up to now, the systematic arrangement of the thecaphores as a whole has been based mainly upon the hydrotheca and its features. In some few families such as Haleciida; PluvmlariidcB and Siliculariidcr, the hydrotheca is so small that the polyp cannot as a rule be withdrawn entirely into it; often, indeed, the hydrotheca seems merely to furnish a support for the basal part of the polyp. In view of the other structural conditions of the polyp, however, this must not be regarded as a purely primary feature, but should apparently in most cases be con- sidered secondary, as is shown more particularly by the two first-named families. Despite the fact that the hydrotheca in Lafoeidw, for instance, is far more highly developed, we must nevertheless, from the structure of the polyp, consider the last-mentioned family as representing a more primitive stage in the process of development.
A point of more importance is whether the ground plan of the hydrotheca is radial or bilateral. This again is generally connected with the presence or absence of stalk. The stalked, and thus free hydrotheca, will as a rule be constructed on a radial base type, as seen in La/oe/dir, Campanic- linidcr, and Campanulariida. The more or less marked curvings of the hydrotheca, not infrequently found particularly in Lafoeidcr, do not suffice to efface the radial base type, and even in Lafoeida and Campanidimdcr, where the hydrotheca is sessile or even partly fused with the stolons, the radial type is distinctly perceptible. In S/liculari/da; on the other hand, the hydrotheca is assymmetrical or bilateral, the cause of which peculiarity it is by no means easy to comprehend, since the hydrotheca is quite freely set on its stalk, which is as a rule of considerable length. This family is, however, altogether but imperfectly known up to now. The sessile hydrotheca has a greater tendency to devel- op bilaterally. In the Plumulariida', this tendency is not yet quite pronounced; we find, however, that the diaphragm in most of the species takes up an oblique position relatively to the longitudinal axis of the hydrotheca. In Aglaopheniidce, the development has proceeded considerably farther, the diaphragm here being either markedly oblique or else generally falling into two obliquely set portions, whereby the symmetry is arranged about a sagittal plane. This sagittal plane is often also found to be the plane of symmetry for the hydrotheca as a whole, the arrangement of the teeth at the opening being symmetrical according to the mentioned plane, while at the same time, a more or less marked lateral compression is observed in the hydrotheca. A similar bilateral development of the hydrotheca is encountered in Syntheciidce and Seriulariidcr, where the diaphragm is as a rule also oblique, although rarely, if ever, falling so distinctly into two halves as in several of the Aglaopheniidcr. In Serhila- riidcv also, the distal parts of the hydrotheca show a distinct bilateral construction according to the same sagittal plane as in the diaphragm.
A secondary formation in the hydrotheca, the closing apparatus, is likewise of considerable importance in systematic respects. In one genus of the Lafoeidtr, Toichopoma, we find a very primitive type of closing apparatus; the lid here is simply formed by the one side of the distal end of the
HYDROIDA II
hydrotheca, which is somewhat thinner than the wall of the hydrotheca generally, and can be brought in over the aperture of the hydrotheca, so as to close it. Within the family of Campanulinidas, several types of lid have been developed, some consisting of the distal part of the hydrotheca (subfamily Ciispidcllincf) others formed by the primary roof of the hydrotheca (subfamily Calycellintr). The closing apparatus in the first case consists of folding, membranous parts, roof-shaped or conical, covering the opening of the hydrotheca. In the latter case they form a conical roof, consisting partly of folding membrane, partly of triangular plates; in this group, the closing apparatus is always sharply marked off from the hydrotheca, whereas in the Cuspia 'ellince, it passes gradually over into the same. In Ser- tulariidcR also, we find several forms of closing apparatus either consisting of some few separate tri- angular plates, and thus exhibiting the same type as certain Campanulinidce, or reduced to two — sometimes even a single plate -- but they always appear to be formed from the original roof of the hydrotheca, in contrast to Toichopoma and Cuspidellince.
These features have been the subject of general attention in systematic respects; less considera- tion, on the other hand, has been devoted to the different structural conditions in the polyps them- selves, as arising from varying conditions in the endoderm.
In Lafoeidce and CampanulinidcB, the endoderm is, as a whole, but little differentiated; here also, however, we find an oral part above the tentacle whorl, where the indifferent cells with small nuclei are decidedly in the majority, and the structure of the polyps here strikingly resembles that of the Bougainmlliida. In Haleciida, on the other hand, we find practically throughout, a marked distinc- tion below the tentacle whorl between a fore-stomach and the actually digesting, basal part, the sto- mach itself. While the digestive cells in the former are decidedly in the minority, it is they alone which form the endoderm of the stomach. The same differentiation into two stomach sections is still more pronounced in Plumulariida:, and in the polyps of both families we must notice a ring-shaped, external constriction of the polyp, where the boundary between the two endodermal zones must be taken to lie. The same division of the endoderm of the polyp into two regions is likewise found in Agla- opheniidcB, but it is not always so easily distinguishable here on mere external observation of the polyp, being in particular frequently obscured by the ectodermal extensions previously referred to, by which the hydranth is attached to the inner ribs of the hydrotheca.
Even more pronounced is the differentiation of the endoderm in most of the Syntheciida and SertulariidtB. Here, the polyps are as a rule furnished with a single (ventral) blind sack placed abcaulinally to the colony. The endoderm of the stomach parts, otherwise formed by a high cylindric epithelium, forms in the blind sack only a low epithelium, which does not appear to contain digestive elements. This seems to suggest that Kiihn's supposition (1913 p. 68) is correct, and that the abcaul- ine blind sack in these families serves for storage of nutritive matter to be digested subsequently, when the polyp is again in a resting position. The abcauline blind sack must be said to be characteristic of the two families, even though in primitive forms such as for instance Thyroscyphus and Dynamena, only an indication of it may be found.
Finally, there is yet another type of polyp found in Campamdariidcr and Siliculariidm. While all the remaining families of thecaphores are characterised by a conical peristome, this is, in the two mentioned families, clubshaped, situate with a narrow base above the tentacle whorl on the broad
HYDROIDA II
body of the polyp. In external habitus, the polyps of these families thus markedly resemble those of Eudendriidir, and the similarity in point of internal structure is equally remarkable. The eudoderm of the peristome, or the proboscis, is quite predominantly composed of indifferent cells, while the gastral part has a fairly homogeneous endodermal covering of digestive cells. Owing to the devia- tion of the polyps in external habitus, I have in a former work, (1909 p. 133) marked off these two families as a separate sub-order, Proboscoidea. Considering the mentioned features of organisation, however, in the light of what has been stated above, it will hardly be correct to retain this sub- order; but it forms a special family series, ranking with the others, where the thecaphores as a whole must be said to fall, as will be further referred to in the following.
A much disputed group is formed by the genus Bonneviella, which I formerly (1909 a) noted off as a separate family. Kiihn (1913 p. 252) inclines to the view that the genus must be referred to Lafoeidcr, whereas Nutting, in his latest work (1915 p. 94) retains the family of Bonneviellidce. Such description as has been given of the anatomical conditions in this species is as a matter of fact not sufficient fully to elucidate the relationship of the group, and Nutting's explanation, in which he considers that my previous observations may be confirmed, still lacks the essential point required; to wit, the development of the so-called "veloid". A comparison with the remaining genera has led me rather to incline towards Kiihn' s theory, that the formation in question can hardly be regarded as altogether ectodermal, the inner layer being probably rather an extreme development of the indiffe- rent cells- of the endoderm. If this supposition prove correct — a point which can only be determined by study of the development of the polyps — the position of the genus will nevertheless still be doubtful; most of the facts would then seem to lead towards their inclusion as a high form of devel- opment of Campanulariidce ; we may, however, also with good reason suppose the origin to be in Lafoeidce. Having no suitable material for further study of these questions available, I do not pur- pose here to enter upon further theoretical discussion as to the systematic position of the genus. I would merely point out once more, that the interpretation of the peristome as an ectodermal gullet is doubtful in the highest degree.
On summing up the above anatomical data, we find that the thecaphore hydroids fall into four main groups or series of families, which are of great interest from a phylogenetic point of view. The most primitive family series is that of Hebellina, with its conical proboscis and with homogeneous gastral endoderm. This group, which embraces the families Lafoeidce, and Camfianulinida, exhibits a marked affinity with the athecate family of Bougainvilliidcc, and probably originated from the same.
From Hebellina again, two new family series are derived, viz: on the one hand that of Hale- ciina, with the families Halcciidcr, Pliimulariidce, and Aglaop/ieniidcr, and on the other, the series Ser- tulariina) with the families of Syntheciida and Sertulariida;. Haleciina is characterised by its bipartite gastral portion, which is divided into a fore-stomach (probably non-digesting) and a digestive basal part. This division is, especially in certain primitive Halecium species, still but slightly pronounced, thus giving the transition from Hebellina. In Sertulariidae, on the other hand, the basal, one-sided blind sack is developed as a storage chamber; the transition from Hebellina is here represented by forms such as Thyroscyphus, where the partition of the gastral parts into the divisions named is still barely indicated. An exceptional position is that of the Proboscoida series, with club-shaped proboscis. The
IIYDROIDA II
group may be supposed to originate from Hebellina; there is, however, much which would seem to suggest closer relationship with Eudendriidoe. I have in a previous work (1909 p. 132) drawn atten- tion to several features pointing in this direction; Kiihn, (1913 p. 246) endeavours to disprove the close resemblance, while on the other hand Nutting, (1915 p. 20) notes further similarities, and, like Stechow, (1913 p. 22) comes to the conclusion that a close relationship between Proboscoida and Eudendriidoe is not to be denied. I would here merely mention one point, which Kiihn regards as of great importance, but which Nutting has not subjected to closer consideration. Kiihn finds that there is a difference of principle in the gonosomes. In this connection, several of the gonangia of the Canipaiiulanidcr will be found of considerable interest. In the athecates, we repeatedly find that single gonophores, as in Bougainvillea, Hydractinia, and Eudendrium, collect on the stalks of some few hydranths; in several species moreover, we find a reduction of the terminal polyp, so that the whole of the gouophoriferous complex is here transformed into a blastostyle. As a matter of fact, we have in such cases to deal with gonangia aggregates, differing only in gonotheca formation from the gono- some in species such as for instance Laomedea _flexuosa. The development of the gonangia here shows us a reduced terminal polyp, which has now formed an "Endplatte", on the stalks of which gonophores appear. If at the same time we imagine that the gonophores do not penetrate the peri- sarc, but that the latter expands instead into a protecting sheath, we have then the gonotheca in its typical form for Camfanulariidce. It may also be imagined as arising by formation of gonophores on the basal parts of the hydranth, within the hydrotheca, when, on the one hand, the hydranth will thereby be reduced to an "Eudplatte", while on the other hand, hypertrophy of the hydrotheca will set in. Either of these alternatives may be considered as the possible starting point. I do not insist that this explanation of the origin of the gonosome in the group is the correct one; there is, however, nothing to disprove it in the results of investigations made up to date, and it will, if confirmed, alto- gether disprove the existence of a difference of principle in the gonosomes, as maintained by Kiihn. This proof is thus likewise inadmissible as finally disposing of the supposition of a closer relationship between Proboscoida and Eudendriidoe.
If we now endeavour, as in the case of the athecates, to summarise the elucidated features and previous views in a key for determination, we must at the outset point out that in this instance such a method cannot so easily be employed without reserve, as the transitions in the thecaphores are more gradual than in the athecates. An endeavour may nevertheless be made to draw up a scheme of the nature indicated.
I. Polyps with conical, pointed oral part.
A. The gastral endoderm uniformly developed; polyps and hydrotheca: constructed according to a radially symmetric ground plan. (Family series Hebellina). I. Hydrothecse without opercula or with a primitive closing apparatus formed from the thinner
distal part of one side of the hydrotheca. Family Lafoeidcc. II. Hvdrothecse with roof-shaped or conical opercula of composite structure. Family Campaimlinid® B. Gastral endoderm differentiated in heterogeneous parts.
I. Polyps with fore-stomach and digestive basal stomach parts. (Family series Haleciinai
HYDROIDA II
a. Hydrothecse small, radially symmetrical, cannot accommodate the contracted hydranth. Fa- mily Haleciidm.
b. Bilaterally symmetrical hydrothecse, with obliquely set diaphragm.
x. Diaphragm simple. Hydrothecse small, approximately radial structure, generally without teeth ; rudimentary or stalked and mobile, two-chambered sarcotheca. Family Plumulariidce. xx. Diaphragm generally composed of two obliquely set portions; hydrothecse markedly bilateral, large, most frequently toothed. Sarcothecse all or some one-chambered, sessile and immobile. Family Aglaopheniidce. II. Polyps with a basally situate, ventral blind sack with low endoderm cells. Hydrothecse gene- rally bilateral. (Family series Sertulariina).
a. Hydrothecse without opercula. Family Syntheciidce.
b. Hydrothecse with opercular apparatus. Family Sertulariidce.
2. Polyps with club-shaped or trumpet-shaped oral parts. (Family series Proboscoida).
A. Hydrothecse large, radially symmetrical. Family Campanulariidcr.
B. Hydrothecse small, thick-walled, and bilaterally symmetrical. Family SiliculariidcB,
II. Thecaphore Hydroids of the Northern Atlantic.
Family series Hebellina nov. Family Lafoeidae.
Hydrothecse deep bell- to tube-shaped, radially symmetrical after their ground plan, stalked or sessile, at times partly fused with the mother tube; diaphragma rarely present. The hydrothecse without opercula; exceptionally, the distal end of the one wall in the hydrotheca may fold in over the aperture. The colonies are stolonial or sympodial. The polyps are radially symmetrical, with conically pointed oral part; the endoderm is divided into an oral and a gastral part; the gastral endoderm is homogeneous.
The structure of the polyps gives this family a primitive rank among the thecaphores, and among its lowest genera Hebella must be counted as taking a typical position; this genus is, how- ever, especially distributed in the warmer seas. The genus has also been recorded from northern waters, although evidently erroneously; its only northern representative should be Hebella pocillum (Hincks) but as it lacks the diaphragm, it cannot be allowed to remain in this genus, and its identity will be dealt with later on.
In course of time, a whole series has been set up with genera of La/or/da', and on going through the list compiled by Stechow (1913 p. 44) we find that considerable weight is attached to the accumulation of the gonangia in aggregates (scapus, coppinia) or their appearing singly. I have recently (1917) in studying the coppinia of Grammaria abietina, set forth what we know up to the
HYDR01DA II
present concerning this distinguishing feature; our knowledge is, in reality, so insufficient that the greatest care should be exercised in answering for species even where this character has been noted, after superficial study, as the only point of difference in comparison with the nearest related species. It is clear, that in certain species, the gonothecae of the one sex (the female) appear aggregated as scapus or coppinia, while those of the other sex (the male) occur singly. Even though we may not at present possess definite proof, it is nevertheless highly probable that also certain Lafo'eidcr may have unisexual colonies; in such case, however, the occurrence of the gonothecae singly or in aggregates will even fail us as a specific character. Obviously then, in the present imperfect state of our know- ledge as to the gonangia of the different species, the feature in question must be discarded altogether as a generic character. Until we know more about the matter, it will certainly be most correct to disregard the question of gonangia entirely when drawing the limitations of the various genera.
Gen. Lafoea (Lamouroux).
The colony consisting of upright rhizocaulome formations, or creeping, with tubular or narrow bell-shaped hydrothecae. The hydrothecse are without diaphragma or opercular apparatus, stalked or sessile, in the latter case separated from the stolon by a more or less marked constriction; where the hydrotheca lies adjoining the stolons, it is possible to distinguish between the wall of the hydrotheca and that of the stolon.
A whole series of species belonging to this genus have been described from the northern seas, and many of them are based on the distinction as to whether the colonies are creeping or upright, a character which, as we find on closer investigation, can only be applied with the greatest caution. It has long been recognised that Lafoi'a dumosa may either occur as a creeping form, or may form upright rhizocaulome colonies; this fact in itself should be sufficient to point the necessity of careful consideration, and a closer study of the northern species reveals the fact that one and the same spe- cies may at times occur creeping, at others form upright colonies, when some few stolons emancipate themselves from the underlayer and thus form a suitable substratum over which other stolons may creep.
Another feature in the Lafoea species which renders their limitation exceptionally difficult is
their extrordinary power of variation. Such variation is evidently clue in part to the influence of
physical conditions in their environment, which have led to the formation of gigantic arctic forms, or
heavily built, robust cold-water forms. Critical study of the very extensive material available has thus
ed to considerable reduction in the number of species.
Lafoea dumosa (Fleming) L. Agassiz. 1828 Ca»ipa?uilaria dumosa, Fleming, A History of British Animals, p. 548. i860 Lafoea dumosa, L,. Agassiz, Contributions to the Natural History of the United States, p. 351.
Colonies creeping or upright, irregularly branched and stiffly built rhizocaulome formations. Hydrothecse developed slightly asymmetrically, tubular, with slightly outward curving margin; they
8
HYDROIDA II
are separated by a constriction from the stolons, or may, more rarely, exhibit an indication of stalk, forming half a spiral whorl.
The gonangia are collected in coppinise with tubes much twisted. The coppinise are herma- phroditic, with the male gonothecse wedged in among the female.
Material:
"Ingolf" St. 6, 63°43' N., i4°34' W.; depth 90 fathoms, 7,0°
- 86, 65°03,6' N. 23°47,6' W.; — 76 (West-Iceland)
- 87, 65°02,3' N. 23°56,2' W.; — no (West-Iceland) "Thor" 63°3o N. 2o°i4' W.; — 80 metres
Greenland : Sukkertoppen (on Boltenid) (no further data) Iceland: Vestmanno depth 28 fathoms
Skjalfaudi Bay depth 28 fathoms The Faroe Islands: 62°2o,' N., 7°37' W. ; depth no metres, 8,71° — 62°i6' N., 6°o6' W.; — no —
7 miles N. by E. of Myggenses point; depth 57 fathoms 6 — N. by W. of Store Kalso; — 60 —
— — Deep hole at north point of Nolso; — 100 —
— — Borona;s N. 75 W. — 30 —
... boom.
Fig. I. The Distribution of Lafova dnmosa in the Northern Atlantic. In the hatched regions the literature notes a common occurrence.
HYDROIDA II
Some writers unite this species with the two following; this is, however, as I have previously shown (1908 p. 33) not correct. Both in its creeping form and in the upright colonies it is very typi- cally distinct from the remaining northern Lafoea species, partly by its very slightly asymmetrical hydrothecse, which have practically no real stalk at all, partly by the fact that the hydrothecse, which are set very far apart, form almost a right angle with their corresponding stolon.
The species is widely distributed in the northern seas (Fig. I). It is a distinctly boreal species, which can, however, penetrate far into southern waters, and has been recorded, for instance, from the Mediterranean (Babic 1910 p. 213). On the other hand, purely arctic conditions seem quickly to set a limit to its progress.
Lafoea gracillima (Alder) Hincks. 1856 Campanularia gracillima, Alder, A notice of some new genera and species, p. 361, pi. 14 figs. 5 — 6. 1874 Lafoea gracillima, Hincks, Notes on Norwegian Hydroids from deep-water, p. 132. 1868 Lafoea pygmcra pars, Hincks, A History of the British Hydroid Zoophytes, p. 205, pi. 40 fig. 3. 1887 Lafoea frul icosa pars, Bergh, Goplepolyper (Hydroider) fra Karahavet, p. 334.
The colony is creeping or upright, with irregularly branched rhizocaulome formation. The hydrothecse are narrow, tubular, curved, with the convex side turned upwards; the opening margin is on the concave (lower) side never curved outwards, but may be slightly so on the convex side of the hydrotheca. The hydrotheca passes gradually over into the stalk, which is of varying length, and with a spiral coil closer in some, more open in others. In upright colonies, the stalk axis forms as a rule a very acute angle with that of the mother tube, the basal part of the hydrotheca is often nearly parallel with the latter.
The gonothecse are compressed in hermaphroditic coppiuise, the long tubes of which are as a rule highly curved. The male gonothecae occur wedged in between the female.
Forma typica: finely built colonies, with hydrothecse set wide apart; the hydrotheca? entirely tube-shaped, with loosely spiral stalk, as a rule with two turns.
Forma elcganhila: colonies of coarser build, with closely set hydrothecse; the hydrothecse often with the upper part of the opening margin curved slightly outwards; stalk with a varying number of mostly close spiral windings.
Material:
Forma typica:
"Ingolf" St. 1, 62°3o' N., 8°2i' W., depth 132 fathoms 7,2°
- 5> 63°33' N, i5°o2' W,
- 85, 63*21' N., 25°2I' W, -
- 87, 65°o2,3' N., 23°56,2' W,
- 95, 65°i4' N, 3o°39' W,
- 127, 66°33' N, 20°o5' W, Iceland: Skagestrand
9 miles N.74E. of Hornet, east coast of Iceland, depth 38 fathoms 62°i7' N., 4°57' W., depth 144 fathoms.
The Ingolf-Expedition. V. 7
|
3l6 |
5,9° |
|
170 |
— — |
|
no |
— — |
|
752 |
2,1° |
|
44 |
- 5,6° |
|
44 |
— |
IO HYDROIDA II
Forma elegantula:
"Iugolf" St. 3, 63°35' N., io°24' W., depth 272 fathoms, 0,5°
- 29, 65°34' N, 54°3i' W, - 68 0,2°
- 31, 66°35' N, 55*54' W, 88 1,6°
- 33- 67°57' N, 5503o' W., - 35 0.8°
- 34, 65°i7' N, 54°i7' W, - 55
Greenland: Davis Strait (precise locality not stated) depth 100 fathoms.
Akndlek (no further data)
Egedesminde ( - — )
Mouth of Ameralikfjord ( - — )
Sukkertoppen, on Boltenia ( - — — )
Jakobshavn ( - — — ) Hurry Inlet, depth o — 7 fathoms (East Greenland Expedition)
57 (- )
Harry Land — 20 ( — — — )
Iceland: "Thor" 52 miles E. of Langanes
Skjalfaudi Bay, depth 28 fathoms
9 miles N. 74E. of Hornet, east coast of Iceland, depth 38 fathoms
64°i7,5' N., i4°44' W., depth 40 fathoms. 5,12°
The Faroe Islands: 6i°4o' N., 7°4o' W., - 135 —
6 miles N. by W. of Store Kalso, depth 60 fathoms
Kara Sea "Dijmphna" (labelled Lafoea fruticosa).
The distinguishing features between Lafoea gracillima and Lafoea fruticosa may often appear very insignificant, and in arctic waters especially one may often be in doubt as to whether a specimen is a robustly built colony of L. gracillima forma elegantula or a finely built L. fruticosa forma genuina. The feature emphasised by Bonnevie (1899 p. 61) viz: the number of spiral turns on the stalk, is in particular extremely variable in somewhat larger colonies, and it is likewise found that the angle between stalk and mother stolon, especially among creeping colonies, is little to be relied on. Another feature, however, to which I have long since drawn attention (1907 p. 7) seems to be more constant, and will also according to the present material serve to determine the identity of species. The feature in question consists in the fact that the abcauline concave side of the hydrotheca in -Lafoea gracil- lima lacks the basal convexity found in Lafoea fruticosa, and that the margin of the hydrotheca on this side is never curved outwards in Lafom gracillima, in contrast to Lafoea fruticosa, where the lower (concave) side of the hydrotheca is thus always more or less S-shaped in profile.
Among the synonyms for Lafoea gracillima we have also here included Lafoea pygnnra pars. Jaderholm (1909 p. 80) includes this species as a synonym under Calycella syringa, and he is un- doubtedly right in so doing. According to Hi neks (1868 p. 205) the original drawings by Alder exhibit indications of opercular formation in the hydrotheca here and there, a point which beyond question suggests this species. On the other hand, Hincks's description is entirely in agreement with the
HYDROIDA II
II
creeping colonies of Lafoea gracillima, and a number of colonies which have later been identified as Lafoea pygmcea should doubtless be referred to Lafoea gracillima. Bonne vie, (1899 p. 62) notes in her table as to the hydrothecse that they have "slightly outward-curving margin"; this does not agree with Hincks's expression "hydrothecse . . . cylindrical, elongate and narrow" or with his drawing of the species. In my first report on the hydroids from "Michael Sars" (1903 the table) I recorded Lafoea pygmcea from several localities, giving also a drawing of the coppinia of the species; subsequent revi- sion of the material has shown me that the specimen indicated is, like most of the others, a typical, creeping Lafoea gracillima, while some few colonies are creeping L'afoea duinosa. Lafoea pygmcea must
. boom.
Fig. II. Localities of Lafoea gracillima forma typica • and forma elegantula -\- in the northern Atlantic.
In the hatched regions the literature denotes a common occurrence of the species.
(The dates from British seas are incomplete on account of a general confusion with Lafoea fruticosa).
thus mainly be regarded as synonymous with Lafoea gracillima and Calycella syringa, and can accor- aingly no longer be counted as an independent species.
Lafoea gracillima appears in two forms, affording parallels to those of the following species. The finely built forma typica is quite cosmopolitan in its occurrence, and has been met with in all seas from pole to pole. In arctic — and as far as can be seen also antarctic — waters, there has also developed, in addition to forma typica, a more robust and closely built forma elegantula, the stalk of which generally commences with a single loose winding, continuing then in a varying number of close turns. Forma elegantula is, as mentioned, arctic, but may (text fig. II) also at times penetrate into boreal waters.
2*
I2 HYDROIDA II
Lafoea fruticosa M. Sars. 1851 Campanularia fruticosa, M. Sars, Beretniiig om en i Sommeren 1849 foretagen zoologisk Reise,
p. 131, 138. 1863 Lafoea fruticosa, M. Sars, Bemserkninger over fire norske Hydroider, p. 30. 1868 flociiii/m, Hincks, A History of the British Hydroid Zoophytes, p. 204, pi. 40, fig. 2.
1874 grandis, Hincks, On deep-water Hydroida from Iceland, p. 147, pi. 6, figs. 1 — 2.
1899 symmetrica, Bonnevie, Norske Nordhavs-Expedition, p. 64, pi. V, figs. 2 c and 4.
The colonies are creeping, or form upright, irregular rhizocaulomes. The hydrothecae are cylin- drical or narrowly bell-shaped, more or less asymmetrically developed or slightly curved, the one side as a rule curving somewhat more markedly outwards than the other. The hydrothecae have as a rule a slightly expanded basal part and a more or less outward curving opening margin, they are sharply marked off from the stalk, which is of varying length, spirally turned, or less frequently divided into rings. The stalk itself forms, in the upright colonies, an open angle of 450 — 80° with the mother tube.
The gonothecae are gathered in hermaphroditic coppinise, the tubes of which are as a rule highly curved. The male gonothecse are wedged in among the female.
Forma gennina: finely built colonies, always with asymmetrical, narrow hydrothecae, the stalk forming an acute angle with the mother tube.
Formagrandis: coarsely built colonies with wide cylindrical to narrowly bell-shaped hydrothecae; hy- drothecae often almost or entirely symmetrical, the stalk generally forming a more obtuse angle with the mother tube.
Material:
Forma gennina:
"Ingolf" St. 34 65°i7' N., 54°i7' W., depth 55 fathoms
- 86 65°o3,6' N, 23°47,6' W, 76 -
- 87 65°o2,3' N, 23°56,2' W, - no - "Thor" °5°52' N., 23°58' W., — 62 metres
6i°o7' N„ 9°3o' W, - 835 -
Greenland : Egedesminde (no details noted) Proven ( - — — )
Cape Tobin, depth 57 fathoms (East Greenland Expedition)
Mouth of Hurry Inlet, — 50 — ( — )
Iceland: Skjalfandi Bay, depth 28 fathoms
9 miles N. 74 E. of Hornet, east coast of Iceland, — 38 — The Faroe Islands: 7 miles N. by E. of Myggeuaes, — 57 —
Forma grandis:
"Ingolf St. 2 63°04' N., 9022' W., depth 262 fathoms 5,3°
- 4 64°o7' N., n°i2' W., — 237 - 2,5°
- 34 65°i7' N, 54°i7' W, - 55
- 95 65°i4' N, 3o°39' W, - 752 2,i°
HYDROIDA II
1-5
Greenland: Egedesminde, depth 30—40 fathoms
Sukkertoppen, on Boltenia (no details noted)
Ingmikertok, Angmagsalikfjord (depth not given) (East-Greenland Expedition) Iceland: 33 miles SE. tl2 E. of Stokkesnses near Hornsvig, depth 84 fathoms (labelled Lafoea fruticosa).
We have here a species of highly variable character, especially in the northern waters, where the biophysical factors evidently exercise an important and determinative influence upon the variation of the species. There is consequently also much confusion as to the synonymy of the species. Lafoea fruticosa was established by M. Sars (1849) an(^ m ^s description we find the following with regard to the hydrothecse: "superne latioribus, inferne coarctatis". This certainly gives the impression of a hydrotheca having its lower portion, partly on account of the curvature of the wall, broader than the upper, which again expands nearer the opening. The same is also seen in the drawing subsequently given by G. O. Sars (1873 Tab. IV, figs. 17 — 18) of the species, undoubtedly based upon M. Sars's type specimens. This does not agree with the statements of Bonnevie (1899 p. 65) and we can hardly help feeling that among Bonnevie's Lafoea fruticosa there must also be some colonies of Lafoea gracillima forma eleganfula\ a supposition which is, moreover, confirmed by the study of her material in Christiania. On the other hand, Bonnevie has (I.e.) established an entirely new species, Lafoea symmetrica, which as a matter of fact is based upon variants of Lafoea fruticosa. The principal difference between Lafoea fruticosa and Lafoea symmetrica is, according to Bonnevie, the fact that the latter species has symmetrical hydrotheca;, whereas these are of asymmetrical structure in the former. It will be seen, however, from the drawings of hydrotheca; given (1899 Tab. V, fig. 2 c') that asymmetrical hydrothecte can also occur in Lafoea symmetrica. On the other hand, further examina- tion of the hydrothecae in Lafoea fruticosa (cf. Broch 1908 fig. 4, 1909 textfig. 19) shows that the asymmetry is often but very slightly pronounced, and even disappears altogether in a greater or lesser percen- tage of the hydrothecse in a fairly large colony. We find, in other words, that in this respect, every imaginable transition form may be met with from Lafoea fruticosa to JLafoiia symmetrica; the character in question is therefore not suitable for purposes of specific distinction. There remains then, the size, which is said to differ as between Lafoea fruticosa, L. symmetrica, and L. grandis. It is soon found, however, that this character likewise is here unserviceable. On the one hand, the three species form, according to Bonnevie, a finite series of sizes, Lafoea symmetrica being from the drawings and de- scription, larger than Lafoea fruticosa, but smaller than Lafoea grandis. On the other hand, a large material of the three forms reveals the fact there is no discernible interval throughout the series; all intermediate stages are found, from finely built colonies of Lafoea fruticosa to such extreme cold-water variants as those upon which Hincks's L^afoia grandis is based. We are thus compelled to include the forms under one species, the correct name of which should be Lafoea fruticosa.
The amalgamation of these three species into one. however, involves the further abolition of Lafoea poc ilium Hincks (1868 p. 204, pi. XL, fig. 2). The shape of the hydrotheca; is very correctly described by Hincks as follows: "tumid below, with the sides curved inwards above, and expanding again slightly towards the top". This coincides entirely with M. Sars's "superne latioribus, inferne coarctatis". The length of the stalk in Lafoea species and its spiral winding or division into separate
^
•4*
is v* s »<
14
HYDROIDA II
rings varies even within a single large colony to such a degree that the features in question cannot be taken as distinctive specific characters, unless combined with others more sound. There remains then the creeping form of colony. But Lafoea fruticosa here differs in no wise from the remaining species of the genus; its colonies may be pure upright rhizocaulome formations, but this is very rarely the case. Generally, the somewhat larger colonies consist partly of upright, partly of creeping por- tions, and it is very common to meet with such composite colonies, when they are brought up with the underlayer attached. Exclusively creeping colonies thus merely form the other extreme in the
b oo i
Fig. III. The distribution of Lafoea fruticosa forma genuina • and forma grandis -\- in the northern Atlantic.
The hatched region denotes a common occurrence of Lafoea fruticosa according to literature.
(In British waters the dates are to be revised owing to confusion of the species with Lafoea gracillimd).
same series of variants. Consequently therefore, Lafoea pocillum must be discarded, as being synony- mous with Lafoea fruticosa.
Jaderholm (1909 p. 71) follows, stating no particular reason, the example of Nutting (1901 p. 175) and ascribes Lafoea pocillum to the genus Hebella. Nutting, in his diagnosis of this genus, states as follows: "Hydrotheca? . . . having their cavities separated from those of the stem by a partial septum". Such septum or diaphragm is altogether lacking in the European specimens of Lafoea pocillum.
It must not be forgotten, however, that the former species partly owe their existence to external determining factors. Disregarding the creeping form of colony as opposed to the upright, the differ- ences presented by the colonies in a less extensive material are considerable enough to warrant at any rate temporary distinction of species, and it would in these cases be incorrect not to notice the
HYDROIDA II 15
same. Such "species" will on further investigation often be found to represent regular groups of vari- ants. And this is precisely the case here. In Lafoea fruticosa, the transition forms are not infrequent in boreal waters, and it may often appear doubtful where the limits should be drawn. It is perfectly admissible, in the case of Lafoea fruticosa, to distinguish between a forma genuina as opposed to forma grandis, the first-named comprising that group of variants hitherto indicated as Lafoea fruticosa, and the latter embracing the species Lafoea grandis and Lafoea symmetrica. The two forms also make typical geographical groups.
Forma genuina, which must be regarded as the mother form, is of very wide distribution; it is encountered together with the following form (text fig. Ill) in the arctic region, and alone in boreal and southern waters, both in the Atlantic and the Pacific, where it has been met with so far down as Hawaii. Intermediate forms are, as mentioned, frequently found in boreal and arctic waters, more particularly in the transition zones between the two.
Forma grandis is of strictly arctic occurrence, and must here be regarded as a typical character form. Billard's record (1907 p. 176) of a find at Cape Spartel must, from the measurements and figures given, be due to incorrect diagnosis.
Gen. Toichopoma Levinsen.
The colonies are creeping, or form upright, irregularly branched rhizocaulomes, with stalked, cylindrical hydrothecse. The hydrothecse lack the diaphragm, but have a primitive closing apparatus; the distal integral part of one side of the hydrotheca wall can be closed down over the aperture.
Toichopoma obliquum (Hincks) Levinsen. 1874 Calycella obliqiia, Hincks, On deep-water Hydroida from Iceland, p. 149, pi. 6, figs. 4—5. 1893 Toichopoma obliquum, Levinsen, Meduser, Ctenophorer og Hydroider, p. 178.
191 1 — Kramp, Report on the Hydroids, p. 374, pi. XX, fig. 4, pi. XXIII, figs. 5—8,
pi. XXIV, fig. 1.
The colonies are creeping, or form upright irregularly branched rhizocaulomes. The hydrothecse have a short stalk with a varying number of spiral windings; they are cylindrical, curved, with an adcauline convexity, as a rule somewhat expanded near the base, and slightly broader again near the aperture, which in open hydrothecse is somewhat asymmetrical; the hydrotheca passes gradually over into the stalk. The abcauline distal part of the aperture is thin, and can be closed in towards the opposite wall over the contracted polyp.
The gonothecae are closely packed in a (hermaphroditic?) coppinia on stem or branches; the single gonothecae are pentagonal or hexagonal, with a short, narrow cylindrical neck. Between the gonothecae are inserted long, highly curved tubes, forming a close network over the coppinia.
Material:
Greenland: Jakobshavu (no details noted) Egedesminde ( - — )
Toichopoma obliqzmm is a high arctic species, recorded both from West and East Greenland, as well as from Spitzbergen and the Murman Sea.
j6 hydroida ii
Gen. Grammaria (Stimpson).
Colonies creeping or forming upright, irregularly branched rhizocaulomes with sessile, cylin- drical hydrothecse, which are to a varying extent fused with the tubes, so that in this part it is im- possible to distinguish between the wall of the hydrotheca and tube. The hydrothecse can at times exhibit a basal constriction forming a boundary between them and the mother tube, but such con- striction may also often be wanting. Diaphragm and operculum lacking.
In earlier works, the creeping species have been incorrectly noted as a separate genus, Fiielhim. The type of this genus was Fiielhim serpens (Hassall). I have previously (1912 p. 10) pointed out that this species should be classed under Grammaria, and am supported here by Kramp (1914 p. 1030). Further proof is afforded by Stechow, who describes (1913 p. 118) a species Grammaria scandcns, with both creeping and upright colonies; it would seem doubtful whether this species should properly be maintained beside Grammaria abietina, which may often be found in Throndhjem Fjord in the same manner. Stechow (1. c. p. 121) considers, however, that the genera should be maintained, "da ihre Beibehaltung eine grosse Bequemlichkeit fiir die Bestimmung ist".
Grammaria serpens (Hassall) Broch. 1848 Campanularia serpens, Hassall, Catalogue of Irish Zoophytes, p. 2223. 1868 Fiielhim serpens, Hincks, A History of the British Hydroid Zoophytes, p. 150. 191 2 Grammaria serpens, Broch, Hydroida from the "Michael Sars", p. 10.
Colonies creeping. Hydrothecse cylindrical, bent to an angle, the basal part fused with the stolon. The hydrotheca is tubular, quite cylindrical, or with slightly outward curving opening margin; the transition to the stolon is as a rule marked by a slight constriction.
The gonothecse are collected in close coppinise, with highly curved tubes. They are herma- phroditic, with the male gonothecse wedged in between the female.
Material :
"Ingolf" St. 87 65°o2,3' N., 22°56,2' W., depth no fathoms "Thor" 64°i6' N., 22°I7' W., — 50 metres
64°o2' N, 22°33' W., - 34 - 63°3o' N., 20°i4' W., — 80 — Greenland: Egedesminde (without further details)
Store Hellefiskebanke ( — — — )
Davis Strait ( — — — )
Iceland: Vadlevik, depth 80 fathoms
33 miles SE. of Stokkesuses near Hornvig — 84 — g'/z — S. by W. 7* W. of Iugolfshofdi, depth not given The Faroe Islands: 8 — 10 miles N. of the Faroe Islands (without further details) 7 miles N. by E. of Myggeuses point, depth 57 fathoms
HYDROIDA II
*7
6 miles N. by W. of Store Kalso depth 60 fathoms Deep hole at north point of Nolso — 100 — Boronaes i3/4 miles in N. 75 W., — 30 —
5 miles SSE. of Bispen 50 —
13 — W. by S. of Munken — 150 —
Stokken 2 miles in S. 22 E. — 55 —
This remarkable species was formerly considered as the type of the genus Filellum. Bonne- vie (1899) notes it under Lafoea, but it should, as I have indicated above, be classed under the genus
. 6 0 0 m.
Fig. IV. The occurrence of Grammaria serpens in the Northern Atlantic. In the hatched regions the literature notes a common occurrence.
Grammaria. From the records, the species is of highly cosmopolitan distribution; it is less numerous, however, in the arctic seas, and is likewise not altogether of common occurrence in wanner waters. It is most frequently met with in the mid-littoral parts of the boreal region (fig. IV) and is here but rarely found at greater depths.
Grammaria conferta (Allman) Broch.
1877 Cryplolaria conferta, Allman, Report on the Hydroida of the Gulf Stream, p. 17, pi. 12, figs.
6 — 10. 191 2 Grammaria conferta, Broch, Hydroida from the "Michael Sars". p. 10.
Upright, irregularly branched rhizocaulomes, the outer ramifications monosiphonic, the basal
The Ingolf-Expedition. V. 7. 3
x8 hydroida n
parts polysiphonic. The hydrothecae are arranged on the branches and stem in two opposite rows, alternating, with the mouth turned now to one side, now to the other. The hydrothecae are large, tubular, passing by a slightly marked constriction over into the stolon; the diaphragm is lacking. In its proximal part, the hydrotheca is fused with the stolon; owing to a sharp bend in the hydrotheca, the distal part is almost perpendicular to the proximal. Opening margin slightly everted.
The gonotheese are set close together in a (hermaphroditic?) scapus (without inserted tubes) on the branches or stem. The gouothecas are bottle-shaped, with a short neck.
Material :
|
Ingolf St. ii |
64°34' N, |
3i°i2' W., |
depth |
1300 |
fathoms |
i,6° |
|
- 31 |
66°35' N, |
55°44' W, |
— |
88 |
— |
i,6° |
|
- 32 |
66°35' N, |
56°38' W., |
— |
3i8 |
— |
3,9° |
|
- 78 |
6o°37' N, |
27°52' W, |
— |
799 |
— |
4,5° |
|
- 92 |
64°44' N., |
32°52' W, |
— |
976 |
— |
i,4° |
In a previous work (1912 p. 10) it was pointed out that Cryptolaria conferta is distinguished from the remaining Grammaria species only by differences so slight that they do not by any means warrant generic separation; the bilateral arrangement of the hydrotheca; is not an adequate generic character. — Interesting from a biological point of view is the fact that this typical deep-sea form as a rule developes filiform, root-like basal offshoots, for attachment to the soft bottom; I have, however, once seen a colony which had attached itself to a fragment of the shell of a deep-water mollusc, and had in consequence less highly developed offshoots than most colonies otherwise have.
Grammaria. confertds northern limit of occurrence is moved a considerable distance farther north by the latest finds; otherwise, its distribution is that of a typically abyssal form, and the record of its occurrence in only 88 fathoms' depth far up in Danmark Strait thus comes as a surprise; the more so since the species should generally be noted as a character form for the warmer and deeper waters of the Atlantic. It does not penetrate in over the submarine ridges which form the southern boundary of the Norwegian Sea.
Grammaria abietina (M. Sars) Stimpson. 1851 Campaiutlaria abietina, M. Sars, Beretniug om en i Sommeren 1849 foretagen Zoologisk Reise, p. 131. 1854 Grammaria robusta, Stimpson, Synopsis of the Marine Invertebrata of Grand Manau, p. 9, pi. 1,
% 3-
The colonies form coarsely built, stiff, irregularly branched rhizocaulomes, in exceptional cases with creeping portions. The hydrothecae lack the diaphragm, and pass over without constriction into the mother tube; their lower limit is formed by the ring of small chitinous bodies to which the base of the hydrauth is attached. The hydrothecae are tubular, bent to an angle, and have as a rule a slightly everted opening margin. The plane of the aperture itself is normally parallel with the axis of the branch; in forms with particularly short hydrothecae, the aperture is slightly turned upwards. The hydrothecae project in most cases far beyond the secondary tubes.
The gonothecas are closely collected in hermaphroditic coppinite with highly curved tubes. The
HYDROIDA II ig
|
depth 55 |
fathoms |
|
— 68 |
7,32° |
|
— no |
— |
|
976 |
14° |
|
- 752 |
2,1° |
|
138 |
5,9° |
|
48 |
— |
female gonothecse are much compressed, sessile; the male are stalked, with the stalks pressed in among the female gonothecse. There are only a small number of almost spherical male gonothecac in the coppinia; they are freely placed between the surface of the female aggregate and the outer coils of the tubes. The female gonophores are heteromedusoids; the male reduced cryptomedusoids; the fertile- colony has nematocysts dimorphously developed.
Forma fypica: The upper (adcauline) wall of the hydrotheca proiects 1,5—3 times the diameter of the aperture beyond the tubes; the plane of the aperture is parallel with the axis of the branch.
Forma brevicyatha: the free portion of the adcauline wall is 0,5 — 1 times the diameter of the aperture; the aperture itself is turned obliquely upward.
Material:
Forma typica:
"Iugolf" St. 34 65°i7' N, 54°i7' W,
- 51 64° t5' N, I4°22' W,
- 87 65°02,3'N., 23056,2'W,
- 92 64°44' N, 32°52' W,
- 95 65°i4' N., 30=39' W,
- 98 65°38' N., 26°27' W., "Thor" 66°43' N., i5°03' W., Greenland: Davis Strait, depth 66 fathoms (without further details)
Sukkertoppen, on Boltoiia ( — — )
Godthaab, depth 50—60 fathoms Hunde-Eiland (without further details)
Cape Tobiu, depth 57 fathoms (East-Greenland Expedition) Jan Mayen: /0°32' N., 8°io' W., depth 470 fathoms Iceland: 4 — 5 miles E. of Bakkefjord, 70 —
5 miles E. of Seydisfjord, — 135 —
64°27' N., i3°27' W., — 150 metres
The Faroe Islands: 6i°40' N., 7°4o' W., — 135 fathoms
6 miles N. by W. of Kalso, — 60 — Forma brevicyatha:
The Faroe Islands: 7 miles N. by E. of Myggenses point, depth 57 fathoms 6 - N. by W. of Kalso 60
A rich and well-preserved material of Grammaria abietina from the Trondhjem Fjord afforded an opportunity for further study of the species. Its polyps have an oral part with mainly indifferent endoderm cells above the tentacle whorl; the true gastral endoderm exhibits an altogether uniform development. The base of the hydranth is fastened to the wall of the hydrotheca far in between the tubes of the rhizocaulome, by a wreath of small chitinous bodies; this is the only discernible limit between the hydrotheca and its mother stolon, which are otherwise practically of equal breadth. A study of the coppinia (Broch 1917) brought to light several peculiarities. In fertile colonies we find,
20
HYDROIDA II
in the defensive polyps and elsewhere, large, practically cylindrical nematocysts in addition to the small capsule form which is found in all thecaphores; the nematocysts are thus dimorphous. A remarkable feature about the coppinia is the position of the male gonothecse, which here appear as stalked, oval to spherical formations between the closely packed female gonothecse and the outer protective network of the tubes. Grammaria abietina thus presents an intermediate stage between types with uniform, hermaphroditic coppinia;, where the male gonothecse are wedged in among the female, and those where the male gonothecse appear singly outside the coppinia or scapus, which has become an alto- gether female aggregate. The gonophores in Grammaria abietina exhibit distinct sexual dimorphism ; the female gonophores are heteromedusoids, the male cryptomedusoids. The cryptomedusoid gono- phore is, however, here highly reduced, and distinctly presents a transition stage which would, on
slight further reduction, become a styloid gonophore.
From two places at the Faroe Islands we have in the material some very richly developed colonies which, owing to the somewhat divergent character of the hydrotheca, are here noted as representatives of a particular form, forma bremcyatha nov. In point of habitus, the mentioned colonies differ but little from forma typica, they are of equally robust build, and with the same rich ramification; on closer examination, however, one cannot fail to observe the remarkable short hydrothecse (fig-. V). In forma tvpiea, the hydrotheca protrudes its distal parts out in front of the stolons so far that the free portion of its upper (adcauline) wall reaches a length of 1,5 to 3 times the diameter of the aperture; in forma brevicyatha,cm the other hand, the corresponding part is only one-half to one diameter in length. This might perhaps by some be regarded as a good specific character. We find however, here and there among the colonies, hydrothecse presenting the same features as forma fypica, and, in slightly greater numbers, intermediate forms with lengths filling the interval between the dimensions named. On
Fig. V. Grammaria abietina
forma brevkyatha. Terminal the other hand, these intermediate forms, and "typica" hydrothecse occur
°, a»r f311^1'™0 °ny only in so slight a percentage among- the colonies that thev exert no influ- fromymiles N. by E. of Mygge- J ° r & tt
nses point, the Faroe islands, ence upon the general character of the colony as a whole. How far we have
57 fathoms. (X 4°-) , ......... , , ....
here to deal with a local variant group, cannot be determined with certainty;
that the form can hardly be very common in the northern seas is evident from its rare occurrence in the extensive material now being dealt with, even when this is supplemented by the large collect- ions from Trondhjem Fjord. Still, the form in question cannot be summarily disposed of by noting it under the head of casual single variants, since it occurs in a single colony from one place, but in four remarkably luxuriant ones from the other.
Forma brevicyatha exhibits certain resemblances to Grammaria immcrsa Nutting; there are, however, so considerable differences observable that the two cannot be confused. The latter species is immediately recognisable from its finer structure, whereas Grammaria abietina is a species of very coarse build. The splitting of the tops of the branches (fig. V) in forma brevicyatha also agrees with Grammaria abietina, as distinct from Grammaria immersa. A certain likeness to the latter species
HYDROIDA II
21
again, we find in the shape of the hydrotheca; according to Kramp, (1911 p. 376) the margin of the hydrotheca in Grammaria abietina - in contrast to Grammaria immersa — always curves outwards slightly; in forma brevicyatka, on the other hand, this is only quite exceptionally the case, and by far the greater number of hydrothecse show no indication of outward curvature in the margin. Kramp has (1. c.) pointed out another feature which is here of more importance. In forma brevicyatha, the hvdrotheca aperture is almost invariably turned somewhat obliquely upwards, not as in forma typica, where the plane of the aperture is parallel with the axis of the branch, or in Grammaria immersa,
200 m.
Fig. VI. Localities of Grammaria abietina (forma hrevicyatha +) in the Northern Atlantic. In the hatched region the literature notes a common, although scattered occurrence.
where the opening is even turned slightly downwards. In forma hrevicyatha, only the few large hydro- thecse have a plane of aperture parallel with the axis of the branch.
Grammaria abietina is a typical arctic-boreal species, recorded also in a single instance (Bil- lard, 1904 p. 164) from the north of France. It may at times penetrate down to great depths, as for instance at the "Iugolf" St. 92, where it reached 976 fathoms, the greatest depth hitherto recorded for this species. Otherwise it is chiefly found (see fig. VI) in the deeper parts of the littoral regions of the boreal and arctic area. Grammaria abietina is also apparently an Atlantic species; it is known from the east coast of North America, to Taimur, but has not hitherto been recorded from about Bering Strait or the Pacific. If, however, it should prove correct that Grammaria scandens Stechow is a synonym for Grammaria abietina, then it must be classed among the circumpolar species.
22 HYDROIDA 11
Grammaria immersa Nutting. 1901 Grammaria immersa, Nutting, Papers from the Harrhnan Alaska Expedition, p. 178, pi. XXI,
figs. 5, 6.
The colonies form stiff, but finely built, irregularly ramified rhizocaulomes. The hydrothecse pass over into the stolon without marked constriction, their basal limit is formed by the series of small chitiuous bodies to which the base of the hydranth is attached. Diaphragm lacking. The hydrothecse are tubular, highly curved in the distal part, and with no outward curvature of the opening margin. The aperture is normally turned somewhat obliquely down; more rarely, we may find the plane of the aperture parallel with the branch axis. The short freely projecting part has an upper (adcauline) wall in front of the stolons, its length being almost invariably less than half the diameter of the aperture.
The gonothecae are collected in close (hermaphroditic?) coppinise, the tubes of which are highly curved, making a close network outside the gonothecae.
Material :
Iceland: 8 miles E. of Seydisfjord, depth 60 fathoms (labelled Grammaria abietina).
Grammaria immersa is an arctic character species; only quite exceptionally does it seem to penetrate into the boreal regions. It is circumpolar, and belongs to the littoral region.
Gen. Lictorella (Allman).
Upright colonies with sympodial growth. The hydrothecse deep bell-shaped to tubular, often exhibiting a slight asymmetrical development; they have a low yet strong diaphragm, but lack opercular apparatus. Nematothecse and nematophores lacking. Gastral endoderm of the polyps uniformly developed.
Lictorella pinnata (G. O. Sars) Allman. 1874 Lafoea pinnata, G. O. Sars, Bidrag til Kundskaben om Norges Hydroider, p. 94, tab. 4, figs. 25 — 28. 1874 Iialecioides, Allman, Report on the Hydroida .... Porcupine, p. 471, pi. 66, figs. 1, 1 a.
1888 Lictorella Iialecioides pars, Allman, Challenger Report vol. XIII, p. 35. nee 1907 Lafoea pinnata, Browne, Hydroids collected by the "Huxley", p. 25.
Upright, single or double pinnate colonies, generally in one main plane, with polysiphonie main stem. The hydrothecse alternating in two rows along the branches, with a tendency to unilateral arrangement; the hydrothecse all turned obliquely forward towards the one side (front) of the colony. The hydrothecse are narrowly bell-shaped, with slightly everted opening margin; transition to stalk gradual. The hydrotheca has a low but strongly developed diaphragm. Stalk generally short, with an oblique furrow on the upper side, at times also a furrow running right round the stalk lower down. The latter furrow runs transversely to the stalk. Polyps with uniform gastral endoderm.
The gonothecse are collected in an openly constructed scapus on the stem or main branches.
HYDROIDA II
23
The single gonothecse are reversed, narrowly conical to almost cylindrical, fastened to the hydrocanlns by a rudimentary stalk at the narrow end; distally, they are furnished with three, more rarely with four or two, round lateral openings, each with a short neck.
Material:
depth 600 fathoms 4,5°
- 582 - 3,3°
- 485 6,i°
- 872 metres
Levin sen (1913 p. 287) believes to have found a blind sack in Lictorella pinnata; this must doubtless be due to an accidental S-shaped curvature of the polyp, which woidd not, however, produce
"Ingolf" St. 7 63° 13' N., i5°4i' W.,
- 25 63°3o' N, 54025' W,
- Si 61 "44' N, 27°oo' W, "Thor" 6i°i5' N., 9°33' \\\,
_ _ 600 m
Fig. VII. Finds of Lictorella pinnata in the Northern Atlantic.
a blind sack of any real anatomical importance. Microtome sections reveal an entirely uniform gastral endoderm, and I have not been able to find any portion of the endoderm histologically corresponding to the epithelium in the blind sack of Sertulariidce. The "blind sack" observed must thus be due to accident. Lictorella pinnata exhibits a highly remarkable distribution (fig. VII). It belongs to the upper part of the abyssal region, but penetrates as far down as 1300 metres; on the other hand, the species can at times occur right up in the littoral region, and has been met with in the Hardanger Fjord even up at a depth of only 90 metres. Horizontally, the species seems to be quite widely distri- buted, but the few records from southern seas are unreliable, as the species has here been confused with Lictorella antipathes (Lamarck). Pictet and Bedot (1900 p. 16) record it from the Bay of Gas-
24 HYDROIDA II
cogne. Browne's specimens from the Bay of Biscay (1907 p. 25) on the other hand, should not be included here; from the uematothecae, they shonld be ascribed to Zygophylax, and are plainly identical with the following species. In the northern Atlantic regions, the species appears to follow the warmer water-masses in their progress through the boreal regions; it has exceptionally been found right up in the Barents Sea.
Gen. Zygophylax Quelch.
Upright colonies with sympodial growth. The hydrothecae are narrowly bell-shaped to tubular, not infrequently somewhat asymmetrical in structure, with a low, bnt strongly developed radially symmetrical diaphragm. The colonies are furnished with small nematothecse. The polyps have a uni- formly developed gastral endoderm.
Zygophylax biarmata Billard.
1906 Zygophylax biarmata, Billard, "Travailleur" et '-Talisman", p. 180.
1907 Lafoea pinnata, Browne, Hydroids collected by the "Huxley", p. 25.
1911 Lictorella Levinseni, Ssemundsson, Bidrag til Kundskaben om de islandske Hydroider II, p. 86. nee 1913 Zygophylax biarmata, Stechow, Hydroidpolypen der Japauischen Ostkiiste, p. 114.
Colonies upright, in a plane singly or doubly pinnately branched with polysiphonic main stem; the branches nearly regularly alternating. The hydrothecae are alternately placed, turning obliquely- forward towards the one side (front) of the colony; i. e. with a tendency to unilateral arrangement. The hydrothecae are mainly tubular, with slightly outward curving margin, narrowing evenly down- wards to a stalk of varying length, which has one or two more or less distinctly marked segmenta- tions. The hydrotheca has a well developed low diaphragm. At the base of the hydro theca stalk, and occasionally elsewhere on the tubes, there are small, cylindrical nematothecse, attached to the tube or apophyse by a short and often indistinct stalk, generally in one piece. The apophyse has normally a couple of nematothecse.
The gonothecse are collected in a primitive, open coppinia (hermaphroditic?) on the stem or main branches; the nematothecse are more richly developed in the gonotheca aggregate than elsewhere, and appear there in large numbers. The gonothecse are flattened ovate, with an outward and down- ward curving neck distally on either side in the transversal plane.
Material :
Iceland, near Vestmanno, depth 510 metres. (Type specimen of Lictorella Levinseni).
The first description of this remarkable species is that given by Billard (1906 p. 180) who had, however, only sterile colonies to go upon. It is undoubtedly the same species which Browne records (1907 p. 25) from the Bay of Biscay, though he ascribes it incorrectly to Lafoea piiuuita G. O. Sars; the nematothecse show that it must be a Zygophylax, and the exhaustive description very di- stinctly suggests Zygophylax biarmata. Ssemuudsson (191 1 p. 86) describes the species anew under
HYDROIDA II
25
the name of Lictorella Levinseni, and notes the nematothecse as among its characteristic features; his colonies, which I have had an opportunity of examining, are fertile, wherefore he was also able to describe the gonosome. This is of a highly peculiar character, and at once demonstrates the incorrect- ness of Stechow's supposition (1912 p. 114) that the species should be identical with Zygophylax armata (Ritchie). Ritchie's species (1907 p. 533) has a typical coppinia, the tubes of which are each furnished with several nematothecse.
The single gonothecee in Zygophylax biarmata resemble not a little those of Lictorella pinnata, the number of opening tubes, however, being apparently in Zygophylax biarmata constantly reduced to two, the tubes being at the same time somewhat longer. The single gonotheca stands out freely, but the gouothecse are closely packed in clusters on the stem or main branches, and between them we find numerous long nematothecae, remarkably well developed, so that the whole aggregate must be regarded as a primitive coppinia, or rather as something between the open scapus and the coppinia.
There are one or two points which seem to count against the identity of Lictorella Levinseni and Zygophylax biarmata. Sasmundsson's description rather gives the impression that there are not, normally, a pair of nematothecse on the apophysis; on closer investigation, however, we are led to the conviction that there are, as a rule, a couple of holes in the periderm showing that nemato- thecse have been there, but have fallen off. The colony investigated is the same which Ssemunds- sou shows in fig. 2 a. — A further difference would seem to exist in the hydrotheca stalks, which in Ssemuudsson's specimens are somewhat longer in proportion than stated by Billard. The length of stalk, however, varies considerably in hydroid species, and cannot thus be used as a specific char- acter. And finally, the hydrothecae in the colony here concerned exhibit a tendency to unilateral arrangement Ssemundsson does not mention this feature, nor does Billard make any reference to the same in his exposition. It would nevertheless seem, from Bil lard's figure (1. c. text fig. 8) that the hydrothecse point obliquely forward towards the one side, the hydrothecse shown being indic- ated in oblique projection, with the aperture directed slightly forward towards the observer. Here again then, there is nothing which can be taken as evidence of distinction in species.
The find here recorded extends the known distribution of this deep-sea form considerably towards the north, the species having hitherto been known only from the Bay of Biscay and south of the same. It appears to belong to the abyssal region.
Family Campanulinidae.
The hvdrothecse are tubular to bell-shaped, sessile or stalked, of the radially-symmetrical type, more rarely with diaphragm. The hydrothecse are furnished with highly organised closing apparatus, falling in the shape of a roof or a pyramid over the indrawn polyp. The colonies are stolonial or sympodial. The polyps have a conically pointed oral part, and gastral endoderm of uniform organisation.
The generic division of this family has given rise to much dispute, and we even find, that certain writers, such as Schneider (1897) and Bonne vie (1899) regard it as a single genus. The
The Ingolf-Expedition. V. 7. 4
26
HVDROIDA II
best exposition of the family is that given by Kramp, who has in two works (1911 and 1913) given a close description, which as regards its main features, is adhered to in the present work. Kramp (1913 p. 14) inclines to the view that the family should be divided into two, a primitive family, Cus- pidcllidiC, where the closing apparatus is formed by the upper part of the hydrotheca wall, and a more highly developed family, Campanulinida, where the closing apparatus consists of the original roof of the hydrotheca. Kr amp's point of view is doubtless highly correct, but as my material is not suited to serve as basis for more detailed exposition, I have merely noted the two mentioned groups as sub- families, otherwise following mainly the generic division established by Kramp (1911 p. 383).
The gouothecae in several members of the family are of considerable interest, differing only in their greater dimensions from the hydrothecse — doubtless a primitive feature. This peculiarity is known among the genera of Stcgopoma, Cuspidella, and Lafo'iina. Unfortunately, very little is known as to the gouophores, but we know that the family comprises the polyp-generation of a number of highly heterogeneous Leptomedusae, which are distributed by systematists throughout a whole series of families. As, however, the polyps, save for the mentioned characters in the sub-families, exhibit very considerable uniformity, we can hardly, from what we know at present, consent to a further sub- division of the family. We have evidently here to deal with a series of biological divergencies in the medusa generation, particularly calculated to demonstrate the impossibility of establishing, in the pre- sent state of our knowledge, any common system for the two generations. The hydroid system cannot here be adapted to the medusa system, which evidently demands thorough investigation of the biolog- ical adaptation phenomena in order to give a system which can claim to be considered as fairly satisfactory from a phylogenetic point of view.
Sub-family Cuspidellinae.
Campanuliiiidcp with closing apparatus formed by the integrating distal part of the hydro- theca wall.
Gen. Stegopoma Levinsen.
Colony creeping or developed to an upright rhizocaulome. The hydrothecae tubular to narrow bell-shaped, without diaphragm; the closing apparatus consists of two folding membranous parts of the distal hydrotheca wall, which shuts down in a roof-shaped lid over the aperture, between two diame- trally opposite teeth. The polyps have uniform gastral endoderm.
Stegopoma plicatile (M. Sars) Levinsen. 1863 Lafoiia plicatilis, M. Sars, Bema:rkuinger over fire norske Hydroider, p. 31. 1874 Calycella plicatilis, G. O. Sars, Bidrag til Kuudskaben om Norges Hydroider, p. 95. 1893 Slegopoma plicatile, Levinsen, Meduser, Cteuophorer og Hydroider, p. 37. 1893 caricum, Levinsen, — - p. 37.
HYDROIDA II 27
|
:pth 420 |
ra thorns, |
3-5" |
|
68 |
— |
0,2° |
|
3i8 |
— |
3,9° |
|
— 55 |
— |
|
|
— 362 |
— |
3,6° |
|
— 293 |
— |
-0,5° |
Colonies form upright, irregularly pinnate, polysiphonic rhizocaulomes, sometimes with creeping parts. Hydrothecse long, tubular, some quite free and short-stalked, others with the one side for part of its extent fused with the stolons; more or less curved, exceptionally with the distal part almost perpendicular to the proximal. Diaphragm lacking. Closing apparatus formed by two folding thin distal portions of the hydrotheca, shutting in a roof over the indrawn polyp between two strong, tooth- like, diametrically opposite parts of the distal portion of the hydrotheca.
The gonothecse are situated on the branches or on the stalk. They present the appearance of gigantic hydrothecse, with the same structure of the closing apparatus. The gonothecse are entirely free, short-stalked, or to a greater or lesser extent attached to the tubes.
Material:
"Ingolf" St. 28, 65°i4' N, 55°42' W.;
- 29, 65°34' N, 54°3i' W.;
- 32, 66°35' N, 56°38' W.;
- 34, 65O17' N, 54°i7' W.;
- 35, 65°i6' N, 55005' W.;
- 126, 67°i9' N, 15*52' W.; Greenland: Davis Strait (without further details) depth 80 fathoms
Umanak ( — — — )
Ritenbenk ( — — — ) on sEga crenulata
Godhavn ( — — — )
Kara Sea, "Dijmphna" (Type specimen of Stegopoma carie/ii/i.)
This remarkable species shows an astonishing power of altering its appearance. One variant is described by Levinsen U893 p. 37) as a distinct species, Stegopoma earn/////, from the fact that it has, at the points of the branches, only three hydrotheca-bearing stolons. This feature, however, as I have previously pointed out (1912 p. n), cannot be maintained as a specific character, since it may occur in certain branches, while others of the same colony have four or five such tubes near the point; very rarely, again, we may find the number of hydrotheca-bearing tubes reduced to two. It was also pointed out, on the same occasion, that the hydrothecse can vary, being at times entirely free, at others fused with the tubes. Free hydrothecse on creeping stolons assume entirely the same appear- ance as in Stegopoma fastig/atu/>/ (Alder).
The gonothecse are mentioned several times in the literature, and have been described by Bonnevie (1899 p. 73) as follows: "Gonangia large, cylindrical with circular opening at the distal end". Kramp, (1913 p. 16) on the other hand, describes them in the same manner as noted in the diagnosis, and gives excellent drawings. In the very extensive material at my disposal from Trond- hjem Fjord, where the species is extremely frequent, I have often had occasion to observe the gono- thecse, which in all cases agreed with Kramp's description. It might be imagined that the gono- thecse would exhibit sexual dimorphism; up to the present, however, I have not been able to find anything in support of this idea, and it must thus be presumed that the earlier descriptions were based upon inadequate observation of the gonothecse.
4*
28
HYDROIDA II
Stegopoma plicatile is an arctic species, which can nevertheless penetrate into the boreal region (fig. VIII); its occurrence is, however, somewhat of a mystery. The species must be described as circumpolar, having been recorded from Davis Strait through the Norwegian Sea, the Barents Sea, the Kara Sea, and the Siberian Frozen Sea to the Bering Sea and the Sea of Okhotsk. Bathymetri- cally it is mostly found in the lower part of the littoral region. From this, then, the species should be noted as arctic; as a matter of fact, however, this would not agree with the data from the northern Atlantic regions. There are a couple of isolated finds from the cold area, but the species has not yet been noted either from the east coast of Greenland or from the eastern side of Davis Strait, and
Fig. VIII. The occurrence of Strgopoma plicatile in the Northern Atlantic. In the hatched parts the literature notes a scattered, although common occurrence.
also appears to be entirely lacking in Iceland waters. On the other hand, we find that it is very common along the eastern side of Davis Strait, and — according to the records — along the west coast of Norway ; i. e. just in those places where the warmer water layers predominate in the bathy- metrical area of its distribution. It may also be noted, in this connection, that the species occurs on the LophoJiclia reefs in the Troudhjem Fjord, in quantities unknown elsewhere. This occurrence is altogether mysterious in the case of a species otherwise only met with in high arctic waters; one would naturally expect that any extension of its distribution would follow the colder eastern shores, not the boreal western coasts of the continents. It is difficult at present to give any satisfactory explanation of this peculiarity.
HVDROIDA II
29
Gen. Cuspidella Hincks.
Stolonial colonies, with stalkless, sessile tubular hydrothecte. The closing apparatus is formed by an integrating distal portion of the hydrothecae, which folds conically over the indrawn polyp; there is no distinct limitation between the closing apparatus and the remainder of the hydrotheca. Nematothecse lacking.
Cuspidella humilis Hincks. 1863 Campanularia humilis, Hincks, M. S., Alder, Supplement to a Catalogue of the Zoophytes, p. 239. 1866 Cuspidella humilis, Hincks, On new British Hydroida, p. 298.
Creeping colonies with cylindrical or slightly downward tapering hydrothecse, passing over without stalk into the stolons. The hydrothecse are set perpendicularly on the stolons, and are short, with a closing apparatus in which 10—12 segments can be distinguished.
The gonothecse are set on the stolons, and are of the same shape and appearance as the hydro- thecse, but much larger. The gonophores develope into free medusae.
Material :
"Thor" 64°i6' N., 22°i7' W., depth 50 metres Reykjavik, from the bottom of a well-boat
This unpretending little species seems to have a fairly wide distribution, and has been met with from the Siberian Frozen Sea down to the Cape Verde Islands. Nevertheless, the few finds lie very wide apart, probably owing to the fact that the species, from its insignificant size, easily escapes observation. Its principal bathymetrical occurrence lies in the middle portion of the littoral region.
Gen. Lafoeina M. Sars.
Stolonial colonies with stalkless, sessile hydrothecse and nematothecse. The closing apparatus of the hydrotheca is formed by the integrating folding part of the hydrotheca, and passes over without distinct limitation into the same; it closes conically over the indrawn polyp. The nematotheca has a distal laterally situated aperture.
Hadzi points out in a letter that there are possibly two genera concealed under this definition. According to the drawing given by G. O. Sars, of Lafoeina tenuis (1874, tab. V, fig. 3), there seems to be a diaphragm occurring in this species at the junction of the hydrotheca and stolon. Levin sen (1893 p. 40) was not able to find any diaphragm in Lafoeina maxima, and I have likewise been unable to find any such here; my material, however, is of such a nature that a negative result cannot be considered as of decisive importance. Should it be found that certain species have a diaphragm, while others lack the same, it will then doubtless be most correct to divide the genus, and a further investig- ation of Lafoeina tenuis must then decide which of the two groups is to retain the name Lafoeina.
j0 HYDROIDA II
Lafoeina maxima Levinsen. 1893 Lafoeina maxima, Levinsen, Meduser, Ctenophorer og Hydroider, p. 182, tab. IV, figs. 9—12.
The colonies form upright, robust rhizocaulomes, often combined with creeping parts, which spread out in plates over the underlayer. The closely set hydrothecse are cylindrical, somewhat irregul- arly bent, with their outer portion nearly perpendicular to the branch axis. The hydrotheca has a conically closing distal portion, exhibiting 110 distinct limitation from the remaining part of the same. Between the hydrothecse are the nematothecae, which are very numerous, and closely packed; they are slender, cylindrical, somewhat irregularly curved, with a distal, laterally situated oval aperture, in which are some few large nematocysts.
The gonothecse are wedged in between the nematothecae and the hydrothecse; they differ neither in form nor in size from the hydrothecse, and their nature can thus as a rule only be determined from section preparations.
Material :
"Ingolf" St. 29 65°34' N., 54°3i' W.; depth 68 fathoms 0,2° - 34 65°i7' N, 54°i7' W.; - 55
Holstensborg Harbour — 30
Greenland: Egedesminde (without further details)
Store Hellefiskebauke, depth 24 fathoms
north of Holstensborg ( — — )
Holstensborg ( — — — )
Godthaab, depth 60—70 fathoms Davis Strait — 100 —
Iceland: Hrutafjord, depth 45 metres.
L e v i 11 s e n ' s type- specimens
Lafoeina maxima is a typical arctic species, belonging to the upper half of the littoral region (fig. IX). The most southerly records of its occurrence are from Godthaab in Greenland, and Hruta- fjord in Iceland; in the Norwegian waters it has hitherto only been met with in Ramfjorden, near Tromso (about 69°3o' N.)
Gen. Campanulina van Beneden.
Colonies with sympodial growth and stalked, radially symmetrical hydrothecse. The closing apparatus of the hydrotheca is formed by the distal folding portion of the hydrotheca wall, and goes over into the same without sharp limitation. When folded down, the closing apparatus covers the hydrotheca with a conical lid. The gonothecse differ in appearance from the hydrothecse.
Kramp, in his exposition (1911 p. 383) merely draws attention to the stalked hydrothecse of the genus as opposed to the sessile in Cuspidella and Lafoeina. Further, secondary characters are, it would seem, here also to be found in the growth types of the colony, whether stolonial or sympodial.
HYDROIDA II
31
Thus the two last-named genera have, as far as we know, always stolouial colonies, whereas in Campanulina they are invariably sympodial.
Campanulina turrita Hincks. 1868 Campanulina turrita. Hincks, A History of the British Hydroid Zoophytes, p. 190, pi. 36, fig. 2. Upright sympodial colonies with monosiphonic hydrocaulns, ringed throughout. The stem slightly zigzag. Stem and branches are divided into slightly pronounced internodia, bearing distally
Zooo m.
Fig. IX. Finds of Lafoeina maxima in the Northern Atlantic.
an apophysis and one or two short-stalked hydrothecse; from the apophysis the next internodium projects. At irregular intervals, one of the hydrothecse is replaced by a branch, so that the colonies assume an irregularly bushy appearance. The hydrothecas are fairly large, and when closed, about twice as long as broad; they are practically cylindrical, with evenly curved proximal part. Diaphragm lacking. Closing apparatus passes over without distinct limitation into the lower portion of the hydro- theca wall; it closes conically over the indrawn polyp.
The gonothecse are set upon short, ringed stalks, projecting from the stem or branches beside the hydrotheca stalks. The gonothecse are small, slender, reversed conical or cylindrical with gradu- ally tapering basal part; they are cut off transversely at the distal end. The gonophores develope (according to Hincks) into free medusse.
,2 HYDROIDA II
Material :
"IngolP, Holstensborg Harbour, on algae. Greenland: Smallesund near Egedesminde, on algse.
In one of the colonies from Smallesund, a distinct renovation is discernible; unfortunately, it cannot be determined with certainty whether the primary individual has been a hydrotheca or a gono- theca, but the size would seem to suggest a primary hydrotheca. We have in this case not a hetero- morphotic renovate, as the renovate is a fully developed, stalked hydranth. The instance in question calls to mind L,ev in sen's description (1892) of renewal of individuals in certain Campanulariidce.
The new find of Campanulina turrita from Greenland is highly interesting. Since Hi neks found the species in Ireland it has only been recorded by Levinsen (1893 p. 181) at Egedesminde; from Holstensborg Harbour, the "IngolP brought home a whole series of finely developed colonies.
Sub-family Calycellinae.1
Campanulinida with closing apparatus formed by the original roof of the hydrotheca.
Gen. Calycella (Hincks).
Creeping colonies with tubular hydrothecae, the closing apparatus sharply marked off from the hydrotheca itself, and easily falling off. The closing apparatus is formed by the peripheral parts of the original hydrotheca roof, the central portion of which is discarded; the closing apparatus is a folding membrane folding conically over the indrawn polyp. The hydrotheca lacks diaphragm.
Calycella syringa (I/inne) Alder. 1767 Sertularia syringa, L,inne, Systema Naturae, ed. 12, vol. 1, p. 1311. i860 Calicclla syringa, Alder, Descriptions of a Zoophyte . . ., p. 73. 1868 Lafoea pygmma, Alder, pars, Hincks, A History of the British Hydroid Zoophytes, p. 205.
Colonies creeping. Hydrothecae tubular, often somewhat bent, with slightly outward curving opening margin; they are borne upon stalks, short or long, furnished with a varying number of rings. The closing apparatus is sharply marked off from the thicker wall of the hydrotheca, and easily falls off; it consists of an entire membrane, which folds down on definite lines, forming a conical roof over the indrawn polyp.
The gonothecae are attached by short, ringed stalks to the stolons. They are oval, smooth. Gonophores heteromedusoid.
Material :
"IngolP St. 95 65°i4' N., 30°39' W.; depth 752 fathoms, 2,1°
"Thor" 64°i6' N., 22°i7' W.; — 50 metres
64°02' N., 22°33' W.; - 34 -
1 As the genus Campanulina belongs to the preceding subfamily, the present subfamily should not be called Campa- nulinina but better Calycellin<e.
HYDROIDA II
33
Greenland: Godhavn (without further details)
Egedesminde ( — — )
Store Hellefiskebanke off Holsteusborg, depth 18—20 fathoms
Sukkertoppen, on Boltenia and on algse (without further details)
Davis Strait, depth 80 — 100 fathoms ( — — _ )
Iceland: Seydisfjord 6 —
— 80 - 95 metres
8 fathoms 10—15
— 40 metres 46 - 30 fathoms 10 —
— 28 —
Vadlavik
Rodefjord
Djupivogur
Vestmano
Skagi
Hvalfjord
Stykkisholm
Onundarfjord
Skjalfandibugt
Bredebugt 65°i7,5' N., 23°32' W., depth 7—12 fathoms 6 miles W. of Iceland (without further details) The Faroe Islands: 6 miles N. by W. of Kalso, depth 60 fathoms
Deep hole at north point of Nolso, depth 100 fathoms.
_ . _ boom.
._ tooo m.
Fig. X. The distribution of Calycella syringa in the northern Atlantic. In the hatched regions the literature denotes a common occurrence.
The Ingolf-Expeduion Y. 7,
34
HYDROIDA II
It is evidently this species which is partly mentioned under the term Lafoea pyg/// tea; according to Hi neks (1868 p. 205) some of Alder's original drawings show a conical lid in this species, which at once shows that Alder's specimens, or at any rate some of them, must have been Calycella syringa. That Lafoea pygmaa is here only partly noted as synonymous with this species, is, as indicated under Lafoea gracilli?/ia, owing to the fact that several writers at any rate have recorded creeping colonies of the latter species under the same name.
Calycella syringa appears to be a wholly cosmopolitan species, which has been met with in all seas. Its bathymetrical area is very extensive, ranging from about 6 metres down to nearly 1500; it should nevertheless be observed that its occurrence in the abyssal region is exceptional, its chief area of distribution being restricted to the middle and upper parts of the littoral waters. Within the area investigated (fig. X) we find that it is apparently lacking along the greater part of the east coast of Greenland, where it is first met with far to the north, about 760 N. Its occurrence under high arctic conditions is altogether scattered, save where an intermixture of warmer water is discernible.
Gen. Tetrapoma Levinsen.
Stolonial colonies with tubular or narrowly bell-shaped hydrothecse without diaphragm. Closing apparatus formed by the original roof of the hydrotheca, and separated by a marked limitation from the thicker hydrotheca wall; it consists of (four) separate triangular plates, each attached in a sinus, between as many hydrotheca teeth. The polyps have a uniformly developed gastral endoderm, and lack outer ectoderm lamellae.
In a previous work (1909 p. 165) I united this genus with Lovenella. Kramp (1911 p. 383) separates them again as two genera, chiefly, it would seem, on account of the number of plates in the lid. This feature can hardly be called important as a generic character; there is, however, another distinguishing feature of greater significance, which renders it necessary to separate the two genera. Hincks (1868 p. 178) especially mentions in Lovenella clausa (Loven) the presence of a diaphragm, a formation which does not appear to be found in Tetrapoma quadridentatum, and which warrants generic distinction. Secondarily, this separation is supported by the fact that Tetrapoma has stolonial colonies, while those of Lovenella are sympodial.1
Levinsen (1913 p. 283) observes in a footnote, regarding Tetrapoma, "This genus must, no doubt, be united with Thyroscyphits". In this I am for several reasons unable to concur. In the first place, Thyroscyphus has a distinct diaphragm, and hydrothecse of bilateral structure; in the second, the structure of the polyp also is entirely different. Tttyroscyphus, with its ectoderm lamellae and inci- pient blind sack formation, as also the differentiated gastral endoderm, exhibits closer relationship with Scrhthtriidcr, and should probably far rather be considered as a primitive genus of this family.
Tetrapoma quadridentatum (Hincks) Levinsen. 1874 Callycella qttadridentata, Hincks, On deep-water Hydroida from Iceland, p. 149, pi. 8, figs. 17 — 20. 1893 Tetrapoma quadridentatum, Levinsen, Meduser, Ctenophorer og Hydroider, p. 180. 1 Cump. also Lovenella corrugata Thornely (Broch 1914 p. 32).
HYDROIDA II
35
Creeping colonies with tnbular hydrothecse. The hydrotlieca stalk is irregularly, but distinctly ringed or spirally coiled. The hydrothecse pass over evenly into the stalk, they are somewhat expanded at the base, then tapering slightly upwards, to expand again a little towards the open- ing margin, which curves somewhat outwards. The opening margin itself has four low, but distinctly discernible teeth, and has four triangular opercular plates fastened between them.
The gonothecse are unknown.
Material:
Greenland: Egedesminde, depth 30-50 fathoms.
Scattered specimens of this high-arctic species have been found at West Greenland, Spitzbergen, in the Murman Sea, the Barents Sea, the White Sea, the Siberian frozen Sea and the Sea of Okhotsk, and must thus doubtless be referred to the circumpolar species. It belongs to the middle parts of the littoral region.
Family series Haleciina nov. Family Haleciidae.
The hydrothecse are radially symmetrical and very small, at times practically altogether dis- appearing; they have as a rule a basal cavity, often marked off from the hydrotlieca itself by a dia- phragm. The hydranths are large, and cannot be drawn quite into the hydrothecse. They have a conical proboscis, and their gastral endoderm falls into two divisions, answering to the fore-stomach and stomach of the polyp, which as a rule are separated by a limit indicated by a more or less marked ring furrow round the body of the polyp. The basal part, the stomach, forms the digestive portion. The polyps are radially symmetrical in structure. The colonies are stolonial or sympodial, with simple or derived growth of the tips.
Gen. Halecium Oken.
Creeping stolonial, or upright sympodial colonies with small radially symmetrical hydrothecse with basal cavitv. The diaphragm can be present or lacking. Nematotheeae and nematophores lacking. The gouophores are developed in gonothecse.
The Halecium colony, in species with polysiphonic stem, often presents a peculiar appearance, differing greatly from that of other hydroid colonies, as the polysiphonic main stem, which is gener- allv verv strongly developed, most frequently presents the same impression as an altogether irregularly branched rhizocaulome, while the outer parts of the branches almost always exhibit regular ramifica- tion. Halecium in in it turn Broch especially, seems in some respects to take up a remarkable and exceptional position; according to Kramp's observations (1913 p. 5) it can at times exhibit large colon- ies of composite structure with rhizocaulome-like polysiphonic main stem and main branches, while otherwise, the species normally presents small, monosiphonic colonies proceeding from a network of
0
36 HYDROIDA II
creeping stolons. This thus confirms, as Kramp points out, the doubts which have been expressed by certain previous writers as to the fundamental importance of the structure of the colony for hydroid s\ stematics, and partly effaces the limit between creeping species and species with upright, composite colonies.
The genus Halecium is characterised by the lively renovation of its hydranths. This should, it would seem, be explained as due partly to the lack of special defensive individuals, partly to the minimal size of the hydrotheeae, and finally also to the large dimensions of the polyps, which probably render them particularly attractive to creatures preying upon hydroids generally. The marked reno- vation activity often leads to the formation of whole piles of hydrothecae, or apparently small branches, for which Schydlowski (1901) has introduced the term "psel|dohydrocauli".
Not infrequently also, heteromorphotic renovates may be observed; I have previously (1909 p. 151) noticed that the formation of gonothecae as heterorenovates is characteristic of the male in Hale- cium ornatum Nutting. Heteromorphotic renovates of a more accidental nature will be noted later on in several species; these are of great interest, since renovates of this kind have, according to Hadzi (1915) only been met with in nature among Halecium and Symtheciidir. The question has, however, been too little studied as yet to permit of our drawing further conclusions from this, but the point should be kept in mind, until it has been fully cleared up.
Halecium halecinum (Linne) Oken. 1758 Sertularia halecina, Linne, Systema Naturae, Ed. 10, p. 809. 1815 Halecium halecinum, Oken, Lehrbuch der Naturgeschichte, vol. 1, p. 91.
Stiffly built, as a rule doubly pinnate colonies with polysiphonic main stem. The branches are as a rule pinnately ramified in the same plane as the main stem, or the colonies may, more rarely, assume an irregular bushy shape. The minor branches are divided up into regular internodia, the length of which is about twice the distal breadth. The primary hydrothecae are low, often almost like a mere opening in the branch apophysis at the distal end of the iuternodium. The secondary hydrothecae are small, with a large basal cavity, generally somewhat asymmetrically developed, and having the basal part of its adcauline wall highly concave. The hydrothecse are somewhat broader at the aperture than at the well-developed, fairly strong diaphragm; the opening margin is not curved outward.
The gonothecae are large, and proceed from the apophysis at the base of the primary hydro- thecae. The males are narrowly cylindrical to elongated oval, tapering below, distally cut off trans- versely, or more often broadly rounded. The female gonothecae have a distal laterally placed aperture with a pair of hydranths; the aperture is furnished with a short cylindrical neck, and situate normally at the distal end of the hydrothecas; more rarely, the distal part of the gonotheca may be domed somewhat forward, so that the opening is a little below the point. The gonotheca is slender, almost entirely straight or slightly convex on the side opposite the pair of hydranths, and tapering evenly downwards.
HVDROIDA II 37
Material :
"Ingolf" St. 7, 63° 13' N., i5°4i' W., depth 600 fathoms, 4,5°
- 9( 64°i8' N, 27°oo' W., - 295 5,8°
- 54, 63"o8' N, i5°4o' W., - 691 3,9°
"Thor" 63°30' N., 20°i4' W., — 80 metres — [labelled Halecium halecinum, H.
Beanii and H. labrosuni]. Greenland: Cape Tobin, depth 57 fathoms (East Greenland Expedition). Iceland : Vadlavik (depth not stated)
Vestmano, depth 30—40 fathoms |labelled Halecium halecinum and H. Beanii] 10 miles W. of Akranes (depth not stated) [labelled Halecium Beanii]. Between Iceland and The Faroe Islands, depth 192 fathoms (without further details) The Faroe Islands: 6 miles N. by W. of Kalso, depth 60 fathoms Stokken 2 miles in S.22E., — 55 — Deep hole at north point of Nolso, depth 100 fathoms. Glyversnses near Thorshavn, on red algae. Borouaes 13 miles in N.75W., depth 30 fathoms.
Halecium halecinum is generally of somewhat coarser build than Halecium Beanii, but a good deal finer than Halecium scutum; it is often extremely difficult to distinguish these species one from another, especially when the colonies assume an altogether irregular form, which the males in particular are inclined to do. The female gonothecse in Halecium halecinum will, in their normal shape, with the quite terminal lateral opening, hardly be confused with normal individuals of the other species, but when, as not infrequently occurs, the distal portion of the gonotheca is domed forward, so that the aperture is found somewhat below the point on one side of the gonotheca, the identity is by no means easy to determine. True, Halecium scutum is in most instances of far coarser build than the two others, but the variation in dim- ensions is within each of the three too great to permit the fixing of proper size
Fig. XI. Halecium hale- limits; they would be found to overlap considerably. A useful general character ,,„,„„. internode with
for Halecium halecinum is the asymmetrical development of the basal cavity in ? ro re^'E' ,
J r Faroe Islands at north
the secondary hydrotheca (fig. XI); the basal part of the adcauliue wall is more point of Nolso. (y 60). strongly developed, and highly curved, so that the hydrotheca axis thus diverges widely from the branch. On the other hand it must be remarked that the hydrotheca aperture is perpendicular to the longitudinal axis, a feature whereby the species is distinguished from Halecium Beanii.
Halecium halecinum has an extremely wide area of distribution, and is very common right up in the Mediterranean; it has also been recorded from waters south of the Equator. In the northern waters, the species appears as a boreal character form, with warmer tendency (fig. XII) and is mostly met with in the middle part of the littoral region; at times, however, it may penetrate right down into the abyssal, as at the "Ingolf St. 54, where it was taken in a depth of over 1300 metres. In purely arctic waters, it is very rare, and records of its occurrence there must be treated as doubtful, as it
38
HYDROIDA II
has evidently on several occasions been confused with Halecium scutum. The same applies in part to certain of the records from southern waters, where the species has undoubtedly often been mixed up with Halecium Bcanii.
Halecium Beanii Johnston. 1847 Halecium Beanii, Johnston, A history of the British Zoophytes p. 59, pi. 9, figs. 1-2.
Upright denselv built colonies with polysiphonic, fairly robust main stem, and monosiphonic, piunately ramified outer branches; the ramification of the colony presents as a rule a main plane. The
200 m. 60001. ._ 1000 m. 2000m
Fig. XII. The distribution of Halecium halecinum in the northern Atlantic. In the hatched regions the literature denotes a common occurrence.
minor branches are divided into slender regular internodia; the distally situate, hydrotheca-bearing apophyse is almost of the same breadth as the branch itself, and sharply defined; the length of the internodium is about 2 — 2.5 times the distal breadth (including apophyse). The hydrothecae small, bounded on the lower side by a slight diaphragm. The primary hydrothecse are hardly more than an aperture in the apophyse, and the hydranth is evidently very soon renewed; the basal chamber of the secondary hydrotheca is symmetrical, with a distinctly marked basal expansion; above this the hydrotheca stalk is narrowest, its breadth increasing slightly from there until it passes over into the somewhat obliquely set hydrotheca; the latter is a little broader at the aperture than at the diaphragm; opening margin not outward curved.
Gonothecse of medium size, proceeding from the apophyse of the primary hydrotheca;. The
HVDROIDA II
39
males are very elongated oval, the females elongated oval to sausage-shaped, highly curved, with a short cylindrical neck in the middle or on the basal half of the gonotheca, and on the concave side of the same. Opening margin level; in the opening itself a pair of hydranths.
Material :
"Thor" 63=30' N., 20°i4' W., depth 80 metres.
The Faroe Islands: Boronses 13 miles in N75W., depth 30 fathoms.
On a previous occassion (1913 p. 13) I stated that Halecium Beanii should be regarded as a variant of Halecium halecinum; further investigations have, however, shown that this is not correct, even though the two species, more particularly in a sterile state, may often enough be difficult to distinguish. Fertile female colonies are not easily confused, the form of the gonotheca; being typically different; in comparison with the follow- ing species it should be noted that the aperture in Halecium Bc<i>/ii lies roughly in a line with the basal and distal end of the gonotheca, and that the neck axis closely approaches, if not entirely coinciding with, this line. (Fig. XIII). The bran- ches are, in Halecium Beanii, often slenderer than in Halecium halecinum and Halecium scutum^ and the apophyse is somewhat more marked; in addit- ion, the basal chamber of the secondary hydro- theca is symmetrically developed, and not asym- metrical as in Halecium halecinum; finally also, the oblique position of the hydrotheca aperture as towards the axis serves to distinguish Halecium Beanii from the two related species mentioned.
The geographical data for Halecium Beanii are extremely unreliable as regards the northern waters; the species is, as I have frequently been able to perceive, often confused with Halecium scutum in arctic, with Halecium halecinum in boreal areas. In all probability, it is a heat-loving form, which exceptionally penetrates into the northern waters.
a b
Fig. XIII. Halecium Beanii. a. Internode with hydrothecae. i. Gonotheca 5. From the Faroe Islands. Boronaes 13 miles in N.75W. X 60.
Halecium scutum Clark.
1876 Halecium scutum, Clark, Report on the Hydroids Alaska and the Aleutian Islands, p. 210,
pi. 10, figs. 13—14.
Robust colonies with polysiphouic main stem. The outermost small branches exhibit an almost regular pinnate ramification in the same principal plane as that in which the branching of the colony falls; more rarely, the colonies may be quite irregularly bushy. The minor branches are divided up into internodia, the length of which is about twice the distal breadth (apophyse included). The primary
4o
HYDROIDA II
hydrothecae are low, often hardly more than an opening in the apophyse, which is distally placed, and distinctly marked. The secondary hydrothecae are likewise small, with a fairly large basal chamber, which is almost always symmetrically developed. The hydrothecae have a thin, bnt well-developed diaphragm; they expand towards the aperture, but have no outward curving margin.
The gonothecae are small, and attached to the apophyse at the base of the primary hydrothecae The males are cylindrical to elongated oval, tapering downwards, broadly rounded distally. or cut off transversely. The female gonothecae have a laterally placed opening with a pair of hydranths; the opening margin has on its inner (adthecal) side a short, broadly lingueform protuberance. The gouo- theca openings are situated between the middle and the distal end of the gonotheca, rarely quite distally. The gonotheca is often somewhat irregularly bent.
Material :
"Ingolf" vSt. 31, 66°35' N., 55°54' W., depth 88 fathoms i,6°
- 34, 65°i7' N, 54°i7' W, - 55 Greenland: Sukkertoppen (without further details)
Davis Strait, depth ioo fathoms (without further details) [labelled Halecium Beanii] Iceland : Vadlavik, (depth not stated) [labelled Halecium Beanii]
Between Iceland and The Faroe Islands: 63°i5' N., 9°35' W., depth 270 fathoms [labelled Hale- cium Beanii] The Faroe Islands: Deep hole at north point of Nolso, depth 100 fathoms
6i°4o' N., 7°4o' W., depth 135 fathoms Kara Sea: "Dijmphna" [labelled Halecium Beanii].
It is not without a certain doubt that we can admit Halecium scutum as a distinct species and not as an arctic form of Halecium halecinum. From a geographical point of view, as also with regard to most of the variational features, it stands in almost exactly the same relation to the last- named species as the arctic forms of several other more or less cosmopolitan hydroids. And it is also Halecium scutum which has formerly (Broch 1909 p. 144) been noted as forma gigantea of Halecium halecinum.
A comparison of the two species reveals various points of resemblance. Bonnevie's state- ment (1899 p. 57) "ramification in all planes" as a characteristic feature cannot be admitted; it applies as a matter of fact far more to the exceptions, the great majority of the colonies exhibiting a decided main plane in which the ramification takes place. On the other hand, the short and broad internodia (fig. XIV a) are typical, and differ not a little from Halecium Beanii, with which the species has espe- cially been confused. The secondary hydrothecae differ normally from Halecium halecinum in having a symmetrical and proportionately lower basal cavity, and from Halecium Beanii in having the plane of the aperture perpendicular to the longitudinal axis. — The frequent confusion of Halecium scutum with Halecium Beanii is due to the great variability of the female gonothecae (figs. XIV b — h) which not infrequently (e—f) resemble strongly those of the latter species. We should, however, note that in Halecium scutum the aperture and its short neck are as a rule obliquely placed, diverging widely from the line between the stalk of the gonotheca and its top; in addition, the gonotheca has an
HYDROIDA II
41
adthecal lingueform protuberance which is lacking in Halecium Beanii. The extreme variants in the other direction, {b and c; h) are markedly suggestive of broadly built gonothecce in Halecium haleci- num, so that fertile colonies likewise may here often be confused. The illustration c shows a gono- theca which has arisen as a heteromorphotic renovate.
Fig. XIV a — //. Halecium scutum. a. Internodium and secondary hydrotheca. Davis Strait
100 fathoms (X 60).
b—e. Gonothecse from a colony (9) in Kara sea (X 30).
f—h. Gonothecae from a colony (9) in Davis Strait
depth 100 fathoms (X 3°).
Every gonotheca contains fully developed
planula larvae.
The material includes several specim- ens of Halecium scutum which had previ- ously been determined as Halecium Beanii; this shows, that extreme caution should be observed in dealing with records in literature of the last-named species, the occurrence of which under arctic conditions is, as above s
mentioned, doubtful. Halecium scutum, on the other hand, is an arctic character form, with circuin- polar distribution. In the waters investigated (fig. XV) it is found in the lower part of the littoral region, but quite exceptionally, as at the Faroe Islands, does it penetrate to any considerable extent into the warmer boreal waters.
Halecium curvicaule v. Lorenz. 1886 Halecium curvicaule, v. Loreuz, Polypomedusen von Jan Mayen, p. 25, pi. 2, figs. 1 — 2.
Colonies creeping or upright, with irregular, more rarely almost dichotomic ramification, mono- siphonic hydrocaulus. Hydrothecse terminal: the next hydrotheca stalk or branch internodium proceeds
The Ingolf-Expedition. V. 7. 6
42
HYDROIDA II
from an almost spherical apophyse situate close under the terminal hydrotheca. The hydrotheca itself is low, somewhat broader at the aperture than at the faint diaphragm, more rarely with margin slightly bent over. Secondary hydrothecse occur in smaller numbers. The hydrotheca stalks are as a rule fairly long, as a rule with a couple of rings below.
The gonothecse proceed from the hydrotheca stalks close under the polyp, and are attached by a short, often almost quite rudimentary stalk, or are exceptionally formed as heterorenovates in the hydrothecse. The males are elongated oval or narrowly egg-shaped, attached to the colony by their narrower end. The female gonothecse are practically pear-shaped, laterally compressed, and with a pair of hydranths in the distal, asymmetrically placed opening; on the side opposite this aperture, the
200 m.
Fig. XV. Finds of Halecmm scutum in the Northern Atlantic, o Localities of Halecium Beanii after Kramp (1914), referring to Halecinm scutum.
gonotheca has 2—9 transverse furrows, more or less pronounced, at times almost imperceptible; they never reach right round the gonotheca.
"Ingolf" St. 29, 65°34' N., 54°3i' W., depth 68 fathoms, 0,2° Greenland: Egedesminde (without further details) Iceland: Bakkefjord, depth 10 fathoms Hvalfjord, — 46 metres.
A detailed description of Halecium curvicaule has been given by Dons (1912 p. 61) who shows, that Haleciitm mirabile Schydlowsky and Halecium repens Jaderholm are synonyms to this species.
HYDROIDA II
43
Examination of a large amount of material leaves no doubt as to the correctness of this. The species is enormously multifarious in its power of variation, and has a remarkable capability of changing its appearance; an examination of the branches, however, will always reveal the characteristic, almost spherical apophyse typical of the species, and the distinguishing characters established are seen to be founded on growth stages.
Dons does not appear to have noticed that his figure D. 5 shows how the male gonotheca can be formed in hydrotheca as a heteromorphotic renovate. This is particularly interesting in the case of the present species, since other heteromorphotic renovates likewise appear in the same in nature, as tendril-like stolon formations in place of hydranths. Dons mentions such renovates, with illustra-
2 CO IB. - 600 m. ._ _,_ 1000 m. 2 000 m.
Fig. XVI. Localities of Halecium curvicaule in the Northern Atlantic.
tions, and points out that these very features have served as the basis on which the species Halecium mirabile was established. The species is thus characterised by a less lively hvdranth renewal, but has on the other hand a more marked tendency to form heteromorphotic renovates than most other forms of Halecium.
Halecium curvicaule is a markedly high-arctic species, belonging to the littoral region. Only quite exceptionally does it penetrate into boreal waters (fig. XVI) as for instance at Iceland. Off the coast of Norway it has not yet been met with south of Bjarkoy.
Halecium muricatum (Ellis and Solander) Johnston. 1786 Sertularia muricata, Ellis and Solander, The natural history of many curious an uncommon Zoo- phytes, p. 59, pi. 7, figs. 3—4.
1847 Halecium muricatum, Johnston, A history of the British Zoophytes, p. 60, pi. 9, figs. 3—4.
6*
HYDROIDA II
Upright colonies with polysiphonie, irregularly ramified main stem, and regular singly or doubly pinnate branches; the outer, minor branchlets regularly alternating. The hydrothecae small, with exjDanded margin, especially on the adcauline side; the basal cavity is large, somewhat asymmetrically developed, with a markedly convex adcauline wall and a straight or slightly concave abcauline wall, inserted asymmetrically on a laterally placed apophyse at the distal end of the inter nodium. The branches are divided into internodia, which often exhibit one or two basal constrictions.
The gonothecse proceed from the tubes of the stem. They are large, somewhat flattened, and furnished with spiny longitudinal ribs on the flat side.
Material:
"Ingolf" St. 29 65°34' N., 54^ 1' W., depth 68 fathoms 0,2°
- 34 65°i7' N, 540i7' W, - 55
- 84 62°58' N, 25°24' W, - 633 4,8° "Thor" 65°52' N., 23°58' W., — 62 metres
64°i6' N.. 22°i7' W., - 50 — 64*16' N„ ii°i5' W, - 378 - Greenland: Egedesminde (without further details)
Store Hellefiskebanke ( — — )
Store Hellefiskebanke depth 24 fathoms
Davis Strait ( — — — ) — 100 —
Ingmikertok, Augmagsalikfjord (East Greenland Expedition) Iceland: Mouth of Hornafjord (depth not stated) Rodefjord, depth 80 fathoms Djupivogr — 8 — Vestmano — 10—15 — 10 miles W. of Akranes (depth not stated) Stykkisholm, depth 30 fathoms
Bredebugt 65°i7' N., 23°32' W., depth 7 — 12 fathoms Adelvik (depth not stated). The Faroe Islands: 7 miles N. by E. of Myggenaes point, depth 57 fathoms 6 miles N. by W. of Store Kalso, — 60 —
Deep hole at north point of Nolso — 100 —
5 miles SSE. of Bispen — 50 —
Forma abyssalis:
"Ingolf" St. 125, 68°o8' N., i6°02' W.; depth 729 fathoms, —0,8°
HaLecium muricdtum, with its asymmetrically developed hvdrotheca stalks or basal cavities and its slenderer form, stands out distinctly from the remainder of the northern Halecium species, and is not easily confused. It is as a rule finely built, but may occur in large colonies with highly rami- fied polysiphonie main stem; the ramification then mostly proceeds in a main plane, but can also be altogether irregular, so that the colonies assume a quite bushy appearance. The margin of the hydro-
HYDROIDA II
45
theca can vary with regard to curvature, and may in extreme cases somewhat resemble Halecium labrosum; in Halecium muricatum however, we always find that the adcauline margin of the hydro- theca is more markedly curved, the abcauline less so.
Normally, the length of the interuodium is about three times its distal breadth (including the apophyse); we have, however, from the "Ingolf" St 125, a colony which, from its extremely long inter- nodia, must be regarded as a deep-sea variant (fig. XVII b\ forma abyssalis nov. It is not unusual among hydroids to find that the colonies from greater depths exhibit an extension of the single branch parts; in this case, however, the tendency is pushed to an extreme, and at a first glance, the colony presents an altogether alien appearance. It is probably clue to the fact that the species here occurs in the cold area, at the considerable depth of 729 fathoms. The colonies are very slender, about 10 cm high, with polysiphonic stems. The internodia of the minor branches are 3—4 mm long, about five times the distal breadth incl. apophyse. The apophyse itself is very distinctly mar- ked and bears a slender hydrotheca. The hydrotheca has close under the diaphragm the typical adcauline thick- ening of the wall, the "pseudodia- phragm" which as a rule is also found in the typical form. The hvdrothecae Fig XVII a_b
exhibit the form typical for the spe- Halecium muricatum.
,, , , , ., a. Internodium and hvdrothecae
cies; the secondary hvdrothecae are
from a typical colony from Store
comparatively short-stalked, but other- Hellefiskebanke, depth 32 fath.
wise of the same shape as the pri- j. Internodium with hydrothecaa
mary. The colonies are sterile. From of forma «*?««** from "ingolf
St. 125. (X 401. *
the features mentioned it follows that
the colonies cannot be taken as representatives of a distinct species; they should, however, be distin- guished as the type of a particular forma abyssalis of the original species.
Halecium muricatum is a circumpolar arctic species, able to penetrate into the boreal region and out to the limits between this and warmer layers (fig. XVIII). Its principal occurrence is restricted to the upper part of the littoral region, but it may, as seen from the foregoing, penetrate far down into the abyssal. It was met with already by the Norwegian North-Atlantic Expedition at a depth of 1350 metres.
Halecium labrosum Alder. 1859 Halecium labrosum, Alder, Descriptions of three new species of Sertularian Zoophytes, p. 351, pi. 13.
Robust, upright, and irregularly branched colonies with polysiphonic main stem. The hvdrothecae are short, symmetrical, with markedly recurvate aperture margin. The basal cavity is very large, and bounded above by the base of the; hydranth; the diaphragm rudimentary or entirely lacking. The
46
HYDROIDA II
branches are divided into fairly short internodia, having a hydrotheca on the distal apophyse; the' latter is often, though not always, separated from the basal cavity of the hydrotheca by a joint.
The gonothecse are very large, and proceed from the tubes of the stem and branches, or from the apophyse. They are irregularly oval, flattened, without spines or ribs, the females are much larger than the males, often more flattened in proportion, but otherwise of the same shape.
Material :
"Ingolf" St. 33 67°57' N., 55°3o' W., depth 35 fathoms o,8° Greenland: Egedesminde (without further details)
Store Hellefiskebanke ( — )
Davis Strait, depth 100 fathoms ( — — — )
67°34' N., 55°2o' W., (depth not stated) Iceland : Vadlavig, depth 46 fathoms Vestmano, — 28 —
Halecium labrosum is an arctic species capable of penetrating into the boreal areas (fig. XIX). In strictly arctic waters it is of very robust build, perhaps the coarsest of all arctic Halecium species, and can hardly be confused with others. In warmer parts, it assumes a somewhat finer structure, but should even here be reckoned among the robust forms. Bathymetrically, the species belongs to the upper part of the littoral region, and has very rarely been observed below this. The few records of its occurrence in the Mediterranean and Atlantic south of the boreal region demand renewed investi- gation, as much would seem to suggest that confusion has taken place.
Halecium tenellum Hincks. 1861 Halecium tenellum, Hincks, A catalogue of the Zoophytes of South Devon, p. 252, pi. 6, figs. 1 — 4.
Picjii Halecium textum, Kramp, Report on the Hydroids the Danmark Expedition, p. 368, pi.
XXI, figs. 5-6.
Colonies upright, with monosiphonic hydrocaulus, and typical, somewhat irregularly sympodial growth. The branches — the new hydrotheca stalks -- proceed from close beneath the basis of the terminal primary hydrotheca, not infrequently in pairs, so that dichotomic ramification takes place; more rarely several branches from the same point. Pseudohydrocauli are of minor importance in the colonies, the renewal of hydrotheca; is not particularly active. The hydrothecse are of medium size, broadening upward from the slight diaphragm and terminating in an often recurvate opening margin. The stalk of the secondary hydrothecse is ringed, the branches are often ringed throughout their entire length, and exhibit at any rate distinct rings above their origin.
The gonothecse proceed from the base of the primary hydrothecse, or more rarely, they may be formed as heteromorphotic renovates in the hydrothecse themselves. The gouotheca is somewhat flattened; viewed from the broad side they are elongated oval, with the distal part cut off transversely or broadly rounded; seen laterally, they are more egg-shaped, with a pointed distal part. They lack hydranth pairs.
Material:
"Ingolf" St. 87 65°02,3' N., 23°56,2' W., depth no fathoms
HYDROIDA II
47
2 00 m. 6 oo m. looorn. 2C00 m
Fig. XVIII. The distribution of HaUcium muricatum (forma abyssalis -+ ) in the Northern Atlantic. In the hatched regions the literature notes a common, although scattered occurrence.
. boom
Fig. XIX. The occurrence of Halecium labrosum in the Northern Atlantic. In the hatched parts the occurrence according to literature is scattered, no accurate details as to localities are given.
48
HYDROIDA II
Greenland: Sukkertoppen, on Boltenia (without further details). Iceland: Brunnes, depth 4 fathoms Seydisfjord — 6 — Hvalfjord — 46 metres Stykkisholm — 30 fathoms. The Faroe Islands: 6 miles N. by W. of Store Kalso, depth 60 fathoms Deep hole at north point of Nolso — 100 — Glyversnses near Thorshavn, on red algse.
There may be some possibility that the colony here shown (fig. XX) from the "Ingolf" St. 87 does not altogether agree with Halecium tenellum. On comparing with the des- criptions given by Hincks (1868 p. 226, pi. 45, fig. lc), Rit- chie (1907 p. 525), and Jaderholm (1909 p. 14) the gono- thecse do not agree with those shown. Hincks describes them as follows: "the capsules vary in form, being broadly ovate, or slender and somewhat pointed above; they contain a single, large gonophore". His figure shows us a slenderly oval or more pear-shaped gonotheca broadly rounded at the distal end. Ritchie's description is as follows: "The gon- angia are ovate, broad in the proximal region, obtusely pointed in the distal. They are supported on short stalks, which arise from the sides of the hydrotheea, and always from the lowest segment in any hydrotheea tier". Jaderholm writes: "Go- notheken eirund, unter den Hydrotheken ausgehend nnd (nach T homely) auch von der Hydrorhiza uud aus der Hydro- thekenmiindung. Distale Zahne fehlen". From the statements here quoted, it is not easy to gain a clear impression of the gonangia, and none of them will altogether cover the present fertile colonies, of which there are not a few in my material, and which agree with the specimen shown.
The gonotheca^ are here set on short stalks, close under the primary hydrothecae, or may exceptionally arise from the interior of the same; this agrees with the statements given above, as also with a later observation by Ritchie (1911 p. 30) where however, nothing new is stated as to their shape. The gonotheca contains, as Hincks points out, a single large gonophore, but the state of preservation of the material did not permit further investigation of this. On the other hand, the shape of the gonotheca agrees but ill with Hincks's drawing, and forms rather a cross between the description given by Ritchie and that of Jaderholm, not improbably because the gonothecae are somewhat flattened. In lateral view, they are egg-shaped, with a broad basal part, and pointed distal end; viewed from the flat, on the other hand, they are more elongated oval, more or less trans- versely cut off at the distal end. On comparing this with the passage from Hincks's description quoted above, we find that his expression "broadly ovate, or somewhat pointed above" agrees after
Fig. XX. Halecium tenellum.
9 from "Ingolf St. 87.
By * a gonotheca formed as heterorenovate.
(X 20).
HYDROIDA II
49
all, as long as we bear in mind that the two statements refer to the gonotheca as viewed in the one ease from the flat, in the other from the side. Consequently, all things considered, I regard the col- onies in question as representatives of Halecium tenellum.
Jaderholm (1909 p. 55) notes Halecium Schneider i (Bonnevie) (1898 p. 10) as synonymous with Halecium tenellum; this, however, requires further justification. The shape of the colony, and the lively formation of pseudohydrocauli in Halecium Schneideri, agree rather with Halecium minutum, but the identity of the species is altogether doubtful, from the data we possess. Should the female gonothecse prove to correspond with Schneider's Halecium nanum (1898 p. 481) then we have here a species entirely distinct from Halecium tenellum and^Halecium minutum. Similarly, it may be doubtful
200 rn. 6 co m. looom. .._. 2000 m.
Fig. XXI. Finds of Halecium tenellum in the Northern Atlantic.
whether the species noted by me (1913 p. 17) as Halecium tenellum, from the Adriatic, really belongs here; the method of growth of the colony, and its dimensions, differ to such a degree from what is found in northern specimens of Halecium tenellum, that we must await demonstration of the gonothecas in the Adriatic form before we can determine with certainty whether it belongs to this species.
The colonies agree on the other hand very well with the Halecium textum described by Kramp (1911 p. 368); the marked curvature of the hydrotheca margin in this species is not more pronounced than is frequently met with in Halecium tenellum; here, however, we must also await the finding of gonangia. It would also seem likely, as Kramp (1914 p. 1003) points out, that the Hale- cium crinis described by Stechow (1913 p. 79) belongs under Halecium tenellum; Stechow's inter- pretation of the manner of ramification in the colony is based upon an entirely erroneous appreciation
The IngolfExpcdition. V. 7. 7
5°
HYDROIDA II
of the actual conditions; a point which has likewise been demonstrated by Kramp. Stechow's drawings in the mentioned work are sadly schematic, and thus afford but poor support.
Halecium tenellum belongs to. the littoral region, and appears to occur but rarely deeper down in northern waters. From records in the literature, the species is altogether cosmopolitan, penetrating far into the Arctic waters, albeit it must here evidently have been frequently confused with the related Halecium minutum. Despite the fact that it is cosmopolitan, its occurrence in the boreal waters (fig. XXI) is remarkably scattered, and apparently irregular. It is probably considerably more common than appears from the chart, but occurs often in insignificant little colonies which may easily escape notice.
Halecium minutum Broch. 1903 Halecium minutum, Broch, Die von . . . "Michael Sars" . . . gesammelten Hydroiden, p. 4, Taf. I,
figs. 1—4.
Colonies upright, generally with small, monosiphonic hydrocaulus, with regular, zigzag shaped sympodial growth; these small colonies arise as a rule from creeping stolons, but at times the stolons may collect together into well developed, branched and polysiphonic rhizocaulome-like formations, from which small branches with sympodial ramification proceed. New branchlets arise from under the base of the primary hydrothecae, normally only one branch at the hydrotheca. The renewal of the hydrothecae is lively, and gives rise to pseudohydrocauli, which may more rarely serve as the base for secondary sympodial formations. The hydrothecae are fairly large, expanding considerably upwards from the slightly developed diaphragm, and have as a rule a highly curved margin ; the stalks of the secondary hydrothecse are ringed; the branches have distinct rings under the uppermost hydrothecae, rarely elsewhere.
The gonothecae arise from the creeping stolons or from the tubes of the polysiphonic parts of the colony. The females are very large, up to 3 mm. long, broad oval to round, and may not infre- quently even be broader than long; they are highly flattened, with spines along the edge, especially in the distal part. The male gonothecae are smaller, elliptical, and smooth; they may also proceed from beneath the base of the primary hydrothecae.
Material:
"Thor" 66°ic/ N. 23°i4' W.; depth 115 -120 metres Greenland: Egedesminde (without further details) Iceland: 9 miles N.74°E. of Hornet, depth 38 fathoms
Vadlavik, — 80 — [labelled Halecium lenellum\
Djupivogr 8 — |
64°i7' N., i4°44' W. — 75 metres | — |
Skagi — 40 —
Hvalfjord — 46 — | — Schneidrri\
Skjalfandi Bay — 28 fathoms.
Kramp's studies (1913 p. 5) of Halecium minutum are highly interesting. He has succeeded in finding fertile female colonies, the identitv of which is thus placed beyond doubt, but where the
HYDROIDA II
51
200 tn. . boom. ._ _ ._ gooom. 'room.
Fig. XXII. Finds of Halecium minutum in the Northern Atlantic.
small sympodial parts, normal in appearance, arise from enormous rhizocaulome formations instead of from creeping stolons. This, as Kramp also points out, places the question of growth conditions as generic character in a remarkable light; and what is worse, it shows us that the shape of the colony can even in specific limitation only be applied with great discretion, a point which has also been noted here under the heading of Lafoeidce. Kramp thus supports my supposition (1909 p. 153) that the colonies which Jaderholm (1907) mentions from the Bering Sea under the name of Halecium telescopicum should more probably be ascribed to Halecium minutum..
Halecium minutum is an arctic species which has doubtless a considerable distribution in the Polar Sea, but which is often confused with others, and especially with Halecium tcuc/lum, as is also clearly evident from the list of investigation material given above. Apart from the Bering Sea, the species has been recorded at Spitzbergen, the Murmau coast, east and north coasts of Iceland, northern east coast of Greenland, and several places along the west coast; finally also Fraser (1913 p. 168) has met with it at Nova Scotia, on the Canso Bank. The species penetrates but very slightly into the boreal region, as far as can be seen from the finds made up to now.
Family Plumulariidae.
The hydrothecse are small, sessile, approximately radially symmetrical, one side partly or en- tirely fused with the branches (tubes); the diaphragm is somewhat asymmetrical. The large polyps can practically speaking never be drawn entirely into the hydrothecae. The sarcothecse are two-chambered,
7*
52
HYDROIDA II
stalked and mobile, or small, rudimentary or entirely effaced, being represented merely by holes in the periderm, at times with slightly raised, asymmetrical edges. The margin of the hydrotheca is almost always without teeth. The colonies are monopodial with terminal growth point. The gastral endo- derm of the polyp is divided into a fore stomach and a digestive stomach part, the limit between them appearing as a constriction round the body of the polyp.
As thus defined, the family covers the group Eleutheroplea auctt. but it also further includes such primitive forms as Kirchenpaueria, which lacks true sarcothecse. What have been taken for such are in reality merely low, as a rule somewhat asymmetrically developed margins round the aperture in the periderm through which the sarcostyle passes out. This formation cannot be altogether regarded as a parallel to the sarcotheca, which forms the fixed point of support for the sarcostyle, and is as a rule furnished with a diaphragm in Phtmulariidce.
On the other hand, it must be admitted that there are certain transition forms which render the limit between Plumulariidae and Aglaopheniidce somewhat indistinct at times, as we find species with both stalked mobile, and immobile, sessile sarcotheca;; these forms must be regarded as primitive AglaopheniidcB. Such transition forms are also met with as against Haleciidcr, though it has not in this case been found advisable to unite the two families. We find, as a matter of fact, in almost every hydroid family such intermediate forms, the position of which is more or less a matter of doubt. If entirely definite boundary lines had to be drawn, it would very possibly involve the reduction of the entire group of hydroids to one or two families. But the heterogeneity would then be too great. In the same way, the Plumulariidcv, as viewed by Nutting (1900) and Stechow (1913) make a too heterogeneous group, which as both writers also admit, really comprises two very well defined main groups. As these two main groups differ in principle, as much as any two families in the other family series of thecaphore hydroids, and as, moreover, the intermediate forms here are neither more numerous nor more marked than elsewhere, it will be correct to keep the two groups apart as sepa- rate families.
Gen. Kirchenpaueria (Jickeli).
Upright pinnate colonies, the stem bearing on its apophyses only undivided branches (hydro- cladia) with several hydrothecse, these being unilaterally arranged, and fused with the branch. Beside the nutritive polyps appear the sarcostyles, which proceed from holes in the periderm; these holes are often surrounded by a slightly raised, as a rule somewhat asymmetrically developed periderm collar. Paired sarcostyles lacking.
Bedot (1916) reintroduces this genus, and defines it further in such a manner that the old Sertularia pinnata Linne appears as its typical species.
In the list published in 1915, "Nomina conservanda. Unter Mitwirkung zahlreicher Spezialisten herausgegeben von Prof. C Apsteiu" (Sitzungsberichte der Gesellschaft naturforschender Freunde, Berlin, Mai 1915) we find under polyps (p. 126 — 127) as type for Plumularia the Plumularia pinnata L. This is well calculated to show that a list such as the one mentioned may easily manage to defeat its own ends. Within the verv large number of species which are referred to the genus Plu- mularia, the Plumularia pinnata takes up a quite exceptional position, owing to its reduced sarcothecse,
HYDROIDA II 53
which are partly or entirely lacking. If we were to follow the list, we should then be obliged, as Pro- fessor M. Bedot writes me in a letter on this matter, to alter the generic name for all the over 200 species which have hitherto been noted under genus Plumularia. There is, as Professor Bedot further writes, nothing to suggest that Lamarck, the founder of the genus, ever regarded Plumularia pin- nata as the type species in preference to any other then known species of the genus. There would seem much more reason to establish Plumularia setacea as type species. That a generic distinction should be made between Plumularia pinnata and the remaining species, where the sarcothecae are far more highly developed, and generally appear partly paired, is beyond all doubt; this Stechow (1913 p. 25) also points out, and suggests Kirchenpaueria as generic name for the group, but without going further into the matter.
There are indeed several objections to be made to the mentioned list as regards the hydroids. That the authors note the genera Clytia, Gonothyraea, Pasythea, Podocoryne, and Schizotricha, may be taken for a party contribution to the dispute as to leading fundamental principles in systematics, which has no place in such a list, given without justification or explanation; the effect here is merely to create confusion, not to form a basis for firm and tenable conditions. Here again there is no question of names rendered so familiar through the medium of the handbooks as to have any claim to acknow- ledgement on that count. Furthermore, the revival of a name such as Monocaulus is more confusing than the retention of the later, generally employed appellation Branchiocerianthiis. The authors have here evidently failed to realise that the type species given, imperator, does not as a matter of fact occur at all in Allman's original Monocaulus genus, which was founded on northern Corymorpha species with sessile gonophores, while the mentioned species was not found until later, by the "Chal- lenger", and incorrectly placed in the genus Monocaulus, with the original diagnosis of which the spe- cies does not agree at all. We may further note the question as to whether Antennularia or Nemer- tesia should be retained. The latter name is generally adopted in later works by Stechow, Broch and Billard, and is likewise recognised in Bedot's eminent historical nomenclature studies, and neither of the names can be said to be of over frequent occurrence in the handbooks; the retention of Antennularia is here less due to sound defensible reasons than it is a matter of taste. — But we can- not here go farther into details with regard to this list; the foregoing will be sufficient to show that in its present form it is far from attaining the end proposed by discussion as to the retention of names whose alteration would bring about confusion in zoological handbooks and teaching works.
As regards the generic name Kirchenpaueria, there may be some little hesitation. The name in question first appears as a synonym in Kir chen pa tier's paper Neue Bryozoen, Catalog IV des Museum Godeffroy, Hamburg 1869, where we find Kirchenpaueria elegans Greeff in litt. = Reichornia Greeffei Kirchenpauer. In the Bryozoa literature it occurs again only in E. C. Jelly, Synonymic catalogue of the recent Bryozoa, London 1889, as Kirchenpaueria elegans Graeffe, Kirch, in litt. — Jickeli introduces the name in 1883 for a hydroid which, as Bedot points out (1916 p. 641) is identical with Plumular/a pinnata. Strictly speaking then, we should according to the precise rules of nomenclature perhaps rather have taken another name, but I regard it nevertheless as most correct for the present to follow Bedot, as there can hardly be any risk of confusion thereby. The generic name Kirchenpaueria is therefore here maintained for the genus whose type is Sertularia pinnata Linne.
Kirchenpaueria pinnata (Linne) Bedot. 1758 Sertularia pinnata, Linne, Systema naturae, ed. 10, p. 813. 1916 Kirchenpaueria pinnata, Bedot, Sur le genre Kirchenpaueria, p. 645.
Upright, singly pinnate colonies with monosiphonic or more rarely, in the basal part polysi- phonic stem. Hydrocaulus divided into internodia with one or several apophyses alternating to either
54
HYDROIDA II
side. The apophyses have each an unbranched hydrocladium, divided by transverse joints into segments with numerous hydrothecae. Each, or more rarely, every alternate internodium on the hydrocladium has on its distal half a hydrotheca entirely fused down its one side with the inter- nodium, or more rarely having a low free adcauline edge. The hydrotheca-bearing internodia are also distally furnished with a median pore, proximally with a median pore having raised edges, through which the naked sarcostyles pass. The length of the hydrotheca varies between L/2 and '/s of that of the internodium.
The gonothecae are situated on the stem or on the basal parts of the hydrocladia, without
2 00 m. 6oo»> ,1000m. looom.
Fig. XXIII. The distribution of Kirchenpaueria pinnata in the Northern Atlantic. In the hatched regions a common occurrence is stated by the literature.
special protective organs. They are oval to pear-shaped, smooth or spiny, often much flattened from the side.
Forma typica. Short internodia with hydrothecae in length from '/, to 72 the internodium.
Forma elegantula (G. O. Sars) slender internodia with small hydrotheca;, length as a rule from J/s to 78 of the internodium.
Material (forma typica):
Greenland? (without further details).
The Faroe Islands: (without further details) [= Plumularia echinulata Winther|.
The synonymy of the species has recently been worked out by Bedot(ic.i6). It gives us an interesting insight into the variability of a species, and throws a sharp light upon several of the
HYDROIDA II 55
distinguishing features which have hitherto been regarded as good specific characters in PlumulariidtB. There are undoubtedly, among the numerous recorded species of Plumularia, synonyms in abundance, and the new species and varieties which are constantly being described do not make matters better. New forms demand not only morphological but also other justification, as is the case with the forms here noted. The variant group indicated as forma typica penetrates exceptionally {Plumularia Helleri) right into the Mediterranean, but has otherwise its main distribution in the boreal waters and in sub- antarctic regions, thus exhibiting a tendency to bipolar occurrence (cf. Broch 1914). Forma elegantula on the other hand, which is remarkable for its fine slender build, predominates under tropical-subtro- pical conditions, and is only on rare occasions met with in the temperate seas.
The area of distribution for Kirchenpaueria pimiala forma typica in northern waters coincides in the main with the fields on the chart (fig. XXIII); it is likely, however, that new finds will be made off the coast of Iceland, and we must wait until the species has been further localised in Green- laud waters, before the query on the label can be erased. Kirchenpaueria pinnata appears in the northern waters as less susceptible to diminished salinity, and thus penetrates far up into the fjords; lower temperature, however, soon sets a limit to its progress. In the northern seas, it belongs to the littoral region, especially the upper half of the same, and only exceptionally occurs down in the abyssal.
Gen. Plumularia (Lamarck).
Upright, single or double pinnate colonies, the stem bearing on its apophyses undivided bran- ches (hydrocladia) with hydrothecas unilaterally arranged, and partly or entirely fused with the branch. The apophyse lacks sessile large sarcothecse; the sarcostyles are situated in two-chambered mobile sarcothecae, generally a pair at the mouth of each hydrotheca.
Plumularia setacea (Linne) Lamarck. 1758 Sertularia setacea, Linne, Systema naturae, ed. 10, p. 813. 1816 Plumularia setacea, Lamarck, Histoire naturelle, vol. 2, p. 129.
Single pinnate colonies with monosiphonic main stem. The stem is divided into short inter- nodia, each with a distal apophyse, turned alternately to either side. Each apophyse has a hydrocla- dinm divided by transverse joints into internodia, of which latter every alternate one bears a hydro- theca and three sarcothecae, and every other one or exceptionally two sarcothecse in the median line; the hvdrotheca-bearing internodium has a proximal, median sarcotheca, and a supracalycine pair at the opening of the hydrotheca. The length of the hydrotheca varies between I/2 and l/s the length of the internodium. The hydrotheca is fused throughout its whole length with the hydrocladium.
The gonotheese arise from the branch apophyse on the stem. The}- are elongated oval, with a cylindrical, narrow, often somewhat curved neck; the males are smaller than the females. The colon- ies are as a rule hermaphroditic, with the male gonangia on the basal part.
Forma typica: length of hydrotheca I/2—I/z the length of the internodium; the internodia com- paratively coarsely built.
56
HYDROIDA II
Forma microtheca: length of hydrotheca '/4 — I/s the length of the internodintn; the internodia of slender build.
Material (forma typica):
"Thor" 35°57' N., 5°35' VV., depth 740 metres Iceland: Vestmano, depth 50 fathoms.
Plumularia setacea divides in the same manner as the foregoing into a widely distributed warm water variety, forma microtheca, and a temperate forma typica, occurring both in subantarctic and boreal waters. Plumularia setacea is in northern waters a denizen of the middle and upper parts of the lit-
200 m. , boom. _ 1000 m. _. j ooo m.
Fig. XXIV. The occurrence of Plumularia setacea in the Northern Atlantic. In the hatched parts the occurrence according to the literature is common, although scattered.
toral region, whereas in warmer seas it goes fairly deep down into the abyssal region. The species is altogether somewhat rare in the boreal area (fig. XXIV) and penetrates in considerable numbers only into the southern and warmest parts of the same.
Plumularia Catharina Johnston. 1833 Plumularia Catliarina, Johnston, Illustrations in british Zoology, p. 497, figs. 61 — 62.
Upright, pinnate colonies with simple or branched, monosiphonic, little pronounced stem. The branches proceed from the base of the hydrothecse on the stem, and are as a rule placed oppositely, more rarely alternating. Stem and hydrocladia are divided into internodia by alternating transverse
HYDROIDA II
57
and oblique nodes; above a transverse joint there is an internodiuin bearing one or two unpaired sarcothecae in the median line, then the highly oblique joint, and an internodiuin furnished with a proximal, unpaired median sarcotheca, a large hydrotheca, and two supraealyeine pairs of sarco- thecae. Of the supraealyeine pairs of nematothecae, the outermost is placed on small projecting apo- physes, the inner pair arises from the internodiuin on the inner side of these sarcotheca apophyses. All the sarcothecae are mobile. The hydrotheca is very slightly fused with the interuodium, the adcladial side has a free portion, in length equal to the hydrotheca opening or a little less, between r/2 and 3/4 the length of the hydrotheca. The hydrotheca is somewhat expanded towards the opening, and is able to accomodate the contracted polyp almost entirely. The gonotheeae arise from the stem or the hydrocladia close beneath the hydrotheca;. The gonotheca is oval to pear- shaped, as a rule somewhat curved, the males a little more slender than the females. The female gonothecae have basally two sarcothecae, which, (according to Hi neks) are lacking in the males. ,
Material :
The Faroe Islands: 6 miles N. by W. of Store Kalso
depth 60 fathoms Deep hole at the north point of Nolso, — 100 — Boronaes 13 miles in N. 75 W. — 30 a
Fig. XXV. Plumularia Catharina
The inner pair of supraealyeine sarcothecae in Plumu- from 6 miles N. by w. of store Kalso.
,„„, , , , a. hydrothecate internode seen from
larta Catharina (fig. XXV) appears to have escaped the atten- behind _ b two successive inter_
tion of most investigators; it is probably this pair of sarcothecae nodes in side view. - / inner pair
of supraealyeine sarcothecse. (X 80). which has eiven rise to the distal median sarcotheca so often
ascribed to the species. Such median (unpaired) distal sarcothecae I have been unable to find in the colonies at my disposal; not infrequently, however, one or both of the sypracalycine may have fallen away, rendering it difficult even to trace where they had been. It is remarkable that it should be the inner pair which exhibits such a marked tendency to fall off, exceeding that of the other sarcothecae; the ones in question are, how- ever, also the smallest. In view of the abundance of the present material, and the fact that I found occasion also to investigate material from other parts of the Atlantic, we must regard the statements as to occurrence of an unpaired distal sarcotheca on the hydrotheca-bearing internodiuin in Plumu- laria Catharina as based on incorrect interpretation of the inner pair of supraealyeine sarcothecae. There can be no doubt that the species Plumularia geminata Allman, Plumularia alternata Nutting and Plumularia Clarkei Nutting should be included under Plumularia Catharina, as I have already pointed out in a previous work (1912 p. 4); it is impossible to attach any weight to the characters given for specific distinction when once a larger material has been closely investigated.
Plumularia Catharina is a southern visitor to the boreal waters (fig. XXVI); round the British Isles it still seems to be of fairly frequent occurrence, but off the coast of Norway it is but little met with, and has only once been recorded from the south coast of Iceland. At the Faroe Islands, the
Tlie Ingolf-Expedition. V. 7. 8
^m,
58
HYDROIDA II
_ boom.
Fig. XXVI. The distribution of Plumularia Cathariua in the Northern Atlantic. In the hatched parts the literature notes a common, although scattered occurrence.
species seems to be somewhat more common than would appear from earlier records; at the two loca- lities noted here, it was present in great numbers. In Greenland waters, Plumularia Catharina has not yet been found. It belongs especially to the upper half of the littoral region.
Gen. Polyplumaria1 G. 0. Sars.
Upright, composite pinnate colonies with polysiphonic branched stem. The apophyses of the stem (the primary tube) bear hydrocladia from which secondary hydrocladia proceed, as a rule from the first hydrotheca-bearing internodium. The apophyse lacks sessile sarcotheca. All the sarcothecae are mobile and two-chambered.
It is not without hesitation that I retain this genus beside Plumularia, with which it is closely related; it may be a question whether we should here, more than in other cases, base the generic division upon the form of ramification. That I have retained it for the present as a separate genus is due to the fact that its species, from their peculiar appearance, form a well-defined group, sharply distinguished from the remaining ones which have been included in the genus Plumularia. My material is not so extensive as to suffice for a revision of the entire family, a task which becomes more and more imperative as further species continue to appear in the literature. A work such as
1 Nutting has (1900 p. 83) by a slip of the pen called the genus Polyplumularia.
HYDROIDA II
59
that of Nutting (1900) shows more than most how absolutely indispensable such critical revision really is. It is therefore most correct here for the present to retain a genus such as Poly plum aria.
Polyplumaria frutescens (Ellis et Solander). 1786 Scrtularia frutescens, Ellis and Solander, The natural history of many curious and uncommon
Zoophytes, p. 55, pi. 6, fig. a, Ay pi. 9, fig. 1.
The colonies are upright and singly or doubly pinnate, with polysiphonic hydrocaulus. The primary stem tube bears on its front a series of hydrothecse, one to three on each internodium; at the base of each hydrotheca, the tube has an apophyse, which is directed obliquely forward and to the side, alternating to either edge. The apophyse bears a hydrocladium, as a rule secondarily branched, which is at first directed obliquely upward and forward, but gradually turns into the broad plane of the colony. The hydrocladium is divided by transverse nodes into internodia, bearing one to several hydrothecse, and around this a pair of supracalycine sarcothecse, and one median, unpaired, under the base of the hydrotheca. The hydrotheca is fairly large, slender, and fused throughout the whole of one side with the internodium. The secondary hydrocladia proceed from under the base of the basal hydrotheca of the primary hydrocladia, and assume the same appearance as the primary hydrocladia.
The gonothecae are set on the branches without special protective organs. They are pear- shaped, cut off obliquely distally, with a large lid-bearing opening.
Material :
"Ingolf" St. 54 63°o8' N., isV' W., depth 691 fathoms 3,9°
- 55 63°33' N., i5°o2' W., - 316 5,9°
The Faroe Islands: 6i°4o' N., f^o' W., — 135
16 miles E. by S. of the south point of Nolso, depth 80 fathoms.
Polyplu vmaria frutescens has its chief occurrence in the lower parts of the littoral region, and in the upper portion of the abyssal. It is a southern visitor to the boreal seas, having only on a single occasion been encountered in colder water layers, viz. east of Iceland (fig. XXVII). In Green- laud waters, the species has not yet been found, and its occurrence at the Faroe Islands is here recorded for the first time.
Polyplumaria flabellata G. O. Sars.
1874 Polyplumaria flabellata, G. O. Sars, Bidrag til Kundskaben om Norges Hydroider, p. 93, pi. 2,
figs. 16—22. Upright, doubly pinnate colonies with polysiphonic branched main stem. The primary tube bears on its internodia alternating apophyses, directed obliquely forward and upward. From the apo- physe proceed the primary hydrocladia, which soon curve into the broad plane. The hydrocladia are divided by almost transverse nodes into internodia, each bearing a large hydrotheca, a pair of supra- calycine sarcothecse, a larger, unpaired proximal, and a smaller unpaired distal sarcotheca in the median line. The hydrothecse are fairly large, about half as long as the internodium; the adcauline wall has
a free portion in length about equal to the opening diameter, between one and two thirds of the length
8*
6o
HYDROIDA II
200 m.
. _ » b 0 0 m.
2000 m.
Fig. XXVII. Localities of Polyplumaria frutescens in the Northern Atlantic. In the hatched parts the literature notes a scattered occurence without further data.
of the hydrotheca. The secondary hydrocladium proceeds from beside the basal hydrotheca of the primary hydrocladium, and is of the same appearance as this.
The gonothecae are fastened to the stem or the branch apophyses by a very short stalk. They are oval, with a large, somewhat asymmetrical distal opening, and with four sarcothecce at the base. Material:
"Thor" 35°57' N, 5°35' W, depth 740 metres
Iceland: Vestmano, — 510 —
According to Ritchie (191 1 p. 223) the number of unpaired small distal sarcothecae on the internodium should vary from one to three. No such variation could be discerned in the colonies investigated by me.
Polyplumaria flabellata is a very rare visitor in the northern waters (fig. XXVIII) and occurs here only in the deeper water layers. The species has altogether its main distribution in the upper parts of the abyssal region. The Vestmanna Islands mark the most northerly point where it has been found up to now; in Greenland waters it would seem to be entirely lacking.
Polyplumaria profunda (Nutting). 1900 Plumularia profunda, Nutting, Plumularidae, p. 66, pi. 8, figs. 2 — 3.
Upright, composite pinnate colonies with branched polysiphonic main stem. The primary tube which is seen in the outer parts of the colony is divided by transverse nodes into internodia, bearing
HYDROIDA II
61
Fig. XXVIII. Finds of Polyplumaria flabellata in the Northern Atlantic.
one or two alternating apophyses. The apophyse proceeds asymmetrically from the base of a cauline hvdrotheca; this is surrounded by a pair of supracalycine sarcothecae, and a third sareotheca situate proximally and a little to the side of the median line, somewhat removed from the base of the hvdro- theca, on the side of the median line opposite to the apophyse. The hydrocladia are divided by trans- verse nodes into internodia, which have about the middle a hvdrotheca with a supracalycine pair of sarcothecae, on low apophyses near the opening of the hydrotheca, and a proximal, unpaired sareotheca in the median line near the proximal end of the internodium. The basal internodium on the primary hydrocladium has two proximal unpaired sarcothecae in the median line; at the base of this inter- nodium's hydrotheca there appear, in fertile colonies, apophyses to the secondary hydrocladium, which is of the same structure as the primary. The hydrotheca; are on the hydrocladium about twice as long as broad; on the stem somewhat shorter; they have a somewhat outward curving opening margin, and are fused throughout their whole length with the internodium.
The gouothecae are situate on the stem or close under the base of the proximal hydrothecas on the primary and secondary hydrocladia; they have a short, often rudimentary stalk. The gouothecae are pear-shaped, often curved, rounded off somewhat asymmetrically distally, with a broad opening; thev have two sarcothecae basally.
Material :
"Ingolf" St. 24 63°o6' N., 56°oo' W., depth 1199 fathoms 2,4°
- 55 63°33' N., 15W W, 316 5.9°
- 98 65=38' N, 26°27' W., 138 5,9°
62
HYUROIDA II
That Nutting (1900 p. 66) should refer this species to Plumularia must be due to his having had small or poorly developed colonies to deal with. From the "Ingolf" St. 55 we have a couple of splendid colonies showing the typical secondary hydrocladia of Polyplumaria in practically every branch, and richly furnished with gonangia. These are situated on the basal part of the hydrocladia — both primary and secondary, and partly also on the tubes of the stem.
It might be imagined that the present specimens, with their typical Polyplumaria colonies, were specifically different from Nutting's Plumularia profunda. We found, however, besides the two
mentioned, extremely luxuriant colonies, also a smaller, single pinnate colony, where only the basal hydrocladia were furnished with secondary hydrocladia, all the remaining hydrocladia being simple. Nevertheless, this colony is likewise fertile, and a fur- ther investigation of the larger colonies shows that here also the secondary hydrocladia are lacking on several branches. In all these colonies, the stem is polysiphonic. But from the "In- golf" St. 24 we have a quite young, sterile colony, where the whole stem is mouosiphonic; only at the bottom of the basal part is a secondary tube developed. Here then, we have the complete transition from Nutting's description to the typical yy Polyplumaria which the species represents in its fully developed form. The resemblance in detail will furthermore be seen from a comparison of the illustrations here given (fig. XXIX).
The finding of Polyplumaria profunda in the northern Atlantic is highly interesting. The species is a typical deep sea „ , , lg" " . ' ,„, _,. form, previously known only from West Indian waters. We now
Polyplumaria profunda "lngolf St. 24. ' r J J
a. Hydrocladial internodium. b. internodium find, that it penetrates in deep water right up into Davis Strait of the primary stem tube, with apophyse. ( X 60).
and Danmark Strait, and to the southern slope of the Iceland
region, where the warm and salt Atlantic water predominates. It is evidently not able to pass over
the submarine ridg-es or into strictly boreal waters.
Nemertesia Lamouroux. Upright colonies with as a rule pronounced main stem, which may be branched or 1111- branched, generally articulated and furnished with strong apophyses bearing finely built hydro- cladia. The hydrocladia are single, unbranched. The colonies are furnished with stalked, two-chamb- ered and mobile sarcothecse, and have in addition, on each apophyse at its upper side where it pro- ceeds from the stem, a large sessile sarcotheca ("mamelon"). The hydrocladia are segmented, and have several hydrothecae, which as a rule are fused throughout their entire length with the branch. The hydrocladia are generally situated in several rows in fully developed colonies.
Formerly, in drawing the limits for this genus, the principal stress was laid on the fact that the hydrocladia are in multiserial arrangement, not merely in two rows as in Plumularia. This cannot
HYDROIDA II 63
however, be admitted as a particularly important feature in generic distinction, as will be seen from a closer study of the Nemertesia species and their development. A species such as Nemertesia tetrasticha (Meneghini) differs in reality but little from the pure Phimularia type, its four-rowed appearance being due to a slight alternating displacement of the apophyses on the two sides; we have here then, as a matter of fact, two-rowed colonies, which have probably when younger been of the pure Phimularia form. In Nemertesia ramosa (Lamarck) I have in a previous work (1912 p. 5) pointed out that the distal parts of the colony not infrequently exhibit a purely biserial arrangement of the hydrocladia; the present material shows that small colonies both of this species and of Nemertesia antennina (kiune) are altogether biserial. Here, as a matter of fact, it is quite another character which warrants the generic identity, to wit, the large sessile sarcotheca ("mamelon") of the apophyse, which occurs in the colonies from the earliest stages onwards.
The development of the colonies, and the grown colonies themselves, clearly show that the multiserial arrangement of the hydrocladia is a secondary adaptation which is, moreover, in many species, subject to great variation within one and the same colony. The number of branch series is even variable in the single species, as in Nemertesia ramosa, where it varies from two to eight, or Nemertesia antennina, where we find from four to twelve. It is not easy to see why it should be more reasonable and effective to draw the limit between biserial and multiserial than for instance be- tween quadriserial and multiserial. On the other hand, there is one constant feature in all the species hitherto noted under this genus; to wit, a peculiar large sessile sarcotheca on the apophyse. A com- parison with other species (see for instance more particularly Aglaophenopsis cornuta) suggests that this formation should in reality be regarded as an abortive hydrotheca. In most cases, it forms a rounded raised portion, with circular opening, happily described by the French writers as a "mamelon". This sarcotheca occurs in colonies from the smallest to the largest in the same manner, whether the species is biserial or multiserial. It must thus be regarded as of generic importance. Consequently, we must reject from Phimularia those species which are furnished with a "mamelon" on the apophyse and have unbranched hydrocladia, placing them instead under Nemertesia.
We thus obtain, in this genus, biserial and multiserial forms. It is impossible to determine, from the data available, whether a species like Nemertesia caulitheca (Fewkes) (= Phimularia cauli- tl/eea, Nutting 1900 p. 63) is a young stage or not; its gonaugia have not yet been discovered, and it may possibly be found to go through a development similar to that of our northern species, passing 0-radually from a biserial type over into the multiserial form. If not, then it must be regarded as a primitive species. The next stage is represented by Nemertesia tetrasticha (Meneghini), with its alter- nately displaced apophyses in the two branch rows; Nemertesia ramosa undergoes this stage, and probably also Nemertesia antennina, the former, however, at any rate soon proceeding further with a marked twist of the internodia, so that the apophyses in one internodium are perpendicular to those of the previous and subsequent ones. Not until later do further apophyses appear at the same level as the first, and from now onwards we regularly find, owing to the revolved position, a number of branch series divisible by two.
The nature of the stem has also served as basis for a division of the genus; here again, how- ever, there is no real difference of principle to work on. The younger stages of Nemertesia ramosa
64
HYDROIDA II
4
have monosiphonic stem; not until later does it become canaliculate, and finally, in fullv developed colonies, we find purely polysiphonic basal parts of the stem, where secondary tubes cover the canali- culate central tube. Thus the limits between Nemertesia and Antennopsis become effaced, and these genera must in consequence, as I have previously maintained (1912 p. 28), and as Stechow also points out (1913 p. 25) be united into one. Similarly it follows, that Stechow is correct in placing Sibogella under Nemertesia.
Bedot, in a work which has just appeared (1917) treats of the genus Nemertesia at length, unfortunately, however, without giving any synopsis of the generic characters. It is nevertheless clear that Bedot inclines to regard the canaliculate ("pluricanaliculee") stem as a family trait. The char- acter is developed, as mentioned above, only in somewhat larger colonies — generally at least 5 cm high — it is moreover often lacking in large distal parts of the colony in the northern species, where the stem fre- quently retains its primary ("unicanaliculee") character. And finally, the primary "pluricanaliculee" stem tube is secondarily covered, as in Nemertesia ramosa, by tubes "unicanaliculees" to a greater or lesser extent. This in itself detracts from the value of the character in question. But in addition, it is also found to stand in a certain relation to the dimensions of the stem tube; thick, single stems are "pluricanaliculees" in spe- cies within the same genus, where the thin ones are constantly "unicanaliculees" (cf. for instance Tubularia). As a matter of fact, the two types "fasciculee" (poly- siphonic) and "pluricanaliculee" (canaliculate) represent
Fig. xxx a — c. Nemertesia antennina, juv. "Ingolf" St. 98. parallel processes of development towards the same
a. The entire colonv (nat. size). — b. Internodium of the , , , , , , , ., r
, , .... ./ , , . ,. , , , .. end. And as we are unable to take the former
hvdrocaulus with the hydrocladial apophyse, showing the
sessile sarcotheca. — c. Two successive internodes of a as basis for generic distinction, so also the latter hydrocladium (4 and c X So).
character must be considered quite inadequate as a
means of distinguishing between genera (or families).
Nemertesia antennina (Linne) Lamouroux. 1758 Ser tularin antennina, Linne, Systema naturae, ed. 10, p. 8ti.
1812 Nemertesia antennina, Lamouroux, Extrait d'un memoire sur la classification des polypes coralli-
genes, p. 184. Colonies with unbranched or quite exceptionally slightlv branched canaliculate and segmented stems. The apophyses are set in circles on the internodium, each circle containing three to six or even more apophyses; the internodia are revolved, so that the stem has twice the number of longitu- dinal rows of apophyses. Near its point of origin, the apophyse has on its upper side a comparatively small, sessile sarcotheca ("mamelon") and two or three irregularly arranged, stalked and two-chambered
HYDROIDA II
65
mobile sarcothecse. The hydrocladia are divided by transverse nodes into internodia of which normally every second one bears one or two unpaired sarcothecse in the median line, the alternate ones having a small hydrotheca with a snpracalycine pair of sarcothecse at the month, and an unpaired median sar- cotheca on the proximal part of the internodium. The hydrotheca is about \!$ to ' /- the length of the iuternodium, and is on one side entirely fused therewith.
The gonotheca; are attached by an almost rudimentary stalk to the apophyses; they are oval to pear-shaped, with a distally laterally placed asymmetrical opening.
200 rn. _. - 600 m looo m. 2000 m.
Fig. XXXI. The distribution of Nemertesia anUnnina ill the Northern Atlantic. In the hatched parts the literature notes a scattered although common occurrence.
Material :
"Ingolf" St. 87, 65°02,3' N., 23°56,2' W.; depth no fathoms
- 92, 64°44' N., 32052' W.; 976
- 98, 65°38' N., 26°27' W.; - 138 Greenland: Davis Strait, — 80
65027'N, 54°45'W.; • 67 Iceland: 5 miles E. of Seydisfjord, 135
i,4"
5,9° (without further details)
The Faroe Islands: Deep hole at the north point of Nolso, depth 100 fathoms.
Some luxuriant colonies from Davis Strait exhibit interesting variations in the number of hydrocladia. The nodes of the stem are slightly marked, and each iuternodium bears but three apo- physes; owing to the revolution of the internodia therefore, these colonies or parts of colonies are six- rowed; among these colonies again there are others, or in the single colony, other parts, which in a
The Ingolf-Expedition. V. -. 9
66 HYDROIDA II
similar manner appear eight-rowed, with four apophyses in the circle. The same octoserial type was met with at the "Ingolf" St. 87, and from St. 92, we have for the first time specimens with six apo- physes in each circle, giving a twelve-rowed colony. The revolution of the segments is thus charact- eristic of grown colonies, and calls to mind the features noted in Nemertesia ramosa (cf. Broch 1912 p. 5).
From St. 98, the "Ingolf brought a young specimen of Nemertesia antennina which is of con- siderable interest (fig. XXX). The colony is still quite biserial, and can only be distinguished from Plumularia by the sessile "mamelon" of the apophyses. As however, the arrangement of the sarco- thecse and hydrothecse entirely agrees with Nemertesia antennina, I have no hesitation in referring the colony to this species, the more so since altogether parallel stages occur in the following species together with later phases of development.
Nemertesia antennina is a southern form with wide distribution in the boreal region (fig. XXXI). Towards the south, it goes at any rate as far as Madeira, and is common in the Mediterranean; it belongs to the middle and lower parts of the littoral region, but may exceptionally, as shown by the finds from the "Ingolf" St. 92, go deep down into the abyssal. It has not yet been met with in purely arctic waters, unless the one find from the east coast of Iceland should be so described.
Nemertesia ramosa Lamouroux.
1816 Nemertesia ramosa, Lamouroux, Histoire des Polypiers coralligenes, p. 164.
1903 Antennularia. variabilis, Broch, Die von dem norwegischen Fischereidampfer "Michael Sars"
gesammelten Hydroiden, p. 10, Taf. IV, figs. 22^25.
Colonies with branched main stems, polysiphonic in their lower parts, canaliculate in the upper. Apophyses form circles about the internodia of the stem, two to four in each circle, and the internodia are revolved, giving twice the number of longitudinal rows. In the lower parts of the colonies, where secondary tubes cover the primary stem, the circular arrangement of the branches is less distinctly marked. The apophyse has on its upper side a strong, narrow, but high sessile sarcotheca ("mamelon") and 3—4 irregularly placed, mobile sarcothecae. The hydrocladia are divided by transverse nodes into internodia, each of which has a median hydrotheca with a supracalycine pair of sarcothecse at the opening, and one proximal and one distal unpaired sarcotheca in the median line; exceptionally, the distal part with its sarcotheca may be divided by a slight joint from the main internodium. The hy- drotheca is entirely fused with the hydrocladium, and is l/(, to r/3 the length of the internodium.
The gonothecce are attached to the apophyse by a short, almost rudimentary stalk. They are oval to pear-shaped, with a distally lateral asymmetrical opening.
Material :
"Ingolf" St. 55 63°33' N., i5°o2' W.; depth 316 fathoms, 5,9
- 85 63°2i' N., 25°2i' W., — 170
"Thor" 6i°i5' N., 9°35' W.; — 872 metres
Iceland : Vestmano, — 50 fathoms
The Faroe Islands: 62°i6' N., 6°o6' W.; — no metres
6o°55' N, 8°56' W.; - 840 -
HVDROIDA II
6?
6 miles N. by W. of Store Kalso. depth 60 fathoms
Deep hole at the north point of Nolso, — 100 1,5 — 2 miles off the month of Borovig, — 20—30 Provences 13 miles in N.75°W., — 30
Boronses in N.75°\V., — 30
The Faroe Islands, — 30
(without further details).
Nemertesia ramosa is extremely variable as regards arrangement and number of the hydrocladia, as I have previously (1912 p. 5) had occasion to explain. In the revolution of the internodia, however, it follows the same regular principles as Nemertesia antennina. The structure of the stem presents
Fig. XXXII. Nrmertesia ramosa juv. a. Young colony from "Ingolf" St. 55
(nat. size), b. hydrocladial internode from the same colony (X So), c. apophyse from the same colony (X 80). d. colony from "Ingolf St. 85 (nat. size', c. apo- b physe from the colony from St. 85 (X 80).
features of considerable interest. The distal part of its ramifications exhibits the same structure as Nemertesia antennina, having, inside the homogeneous peridermal chitinous^ sheath, coenosarc strings; these parts of the stem are thus canaliculate. Farther down, however, we find secondary tubes closely arranged about the primary stem tube, and the nearer we come to the base, the closer is the network and the thicker the stem. Where these secondary tubes occur, they cover the apophyses more and more, finally burying them altogether, while the hydrocladia here also fall away. Consequently, the basal part of well-developed colonies of Nemertesia ramosa lacks hydrocladia, whereby the colony assumes a highly peculiar appearance.
At a couple of the "Ingolf" stations, some quite small colonies of Nemertesia ramosa were found; these serve well to show the difficulty of distinguishing the young stages from Plumularia (fig. XXXII). The smallest colony (a) is altogether pinnate; the thin stem is divided into irregular internodia with a varying number of apophyses, but closer investigation shows that the apophyses do not form two regular longitudinal rows, being as a matter of fact alternately somewhat displaced to one side or the other, so that we have here a slight approach to quadriserial arrangement. A some- what larger colony (</), where the stem is slightly thicker, reveals more clearly the displacement of
9*
68
HYDROIDA II
the apophyses, which is here evident at the first glance. In this case, it would scarcely be possible for anyone to doubt that the specimen is a young Nemertesia, the more so since the stem is strikingly thick. Further confirmation is in both instances afforded by the branch apophyses [c and e)\ in both colonies we find the characteristic "mamelon" on the upper side of the apophyse, close to the stem, which proves that they belong to the Nemertesia. The entire arrangement of the hydrothecae and sarcothecse also shows that the species is Nemertesia ramosa.
The stages found already show that the younger Nemertesia are throughout constructed after the Plumularia type, with biserial apophyses, and that Nemertesia must be derived from Plumularia. It would further seem to suggest that Plumularia caulitheca Fewkes is probably a young stage of a
2 00 m. 6oom. looom. 2ooom.
Fig. XXXIII. Occurence of Nemertesia ramosa in the Northern Atlantic. In the hatched region the literature notes a common occurrence.
Nemertesia. And it is likely that also other Plumularia species in reality cover young Nemertesia species, and should, from the presence of a "mamelon", be transferred to that genus.
Among the synonyms of Nemertesia ramosa should also be reckoned Antennularia variabilis Broch. The defective srjecimens, where only the chitinous parts are preserved, have lost all their sarcothecse, so that only a hole in the periderm, or a slightly raised part here and there, shows where the sarcothecse have been. The difficulty of discerning these remains has led to their being regarded as variable in number, and the remains or traces of supracalycine sarcothecse had altogether escaped attention. Otherwise the colonies agree entirely with Nemertesia ramosa, and must thus be referred to that species.
Nemertesia ramosa has its chief occurrence in the littoral region, especially in the middle and
HYDROIDA II 69
lower parts of the same; it has been met with once or twice quite deep down in the abyssal region, as for instance on the "Thor" expedition, when it was taken near the Faroe Islands at 872 metres, probably the greatest depth from which the species has hitherto been recorded. Nemertesia ramosa belongs to the warmer parts of the Atlantic, and penetrates thence (fig. XXXIII) in great numbers into the southern part of the boreal region. The species has not hitherto been found in Greenland waters, but is recorded fiom one or two places on the south coast of Iceland. Round the Faroe Is- lands, it is seen to be of very frequent occurrence, and is said by Hincks (1868 p. 283) to be more numerous even than Nemertesia antennina on the coasts of Scotland. The species has not yet been located with certainty on the Norwegian coasts, but its occurrence in the Skagerak (Broch 1905 p. 241 and Bohuslan (Jaderholm 1909 p. 105) suggests that it will probably be found to occur there.1
Polynemertesia nov. gen. Upright colonies with distinct, branched main stem, exhibiting segmentation in its monosipho- nic parts; the stem is furnished with alternating strong apophyses which bear finely built hydrocladia. The hydrocladia are secondarily branched. The apophyses — both those of the primary and those of the secondary hydrocladia — are furnished on their upper side, near the point of origin, with a short sessile sarcotheca, "mamelon"; all the remaining sarcothecse are mobile. The primary and se- condary hydrocladia are segmented, and bear several hydrotheca;, which are as a rule fused through- out their entire length with the branch.
It is with considerable hesitation that I have established this new genus for Plumularia gra- cillima G O. Sars. Previous investigators have overlooked the presence of a "mamelon" on the apo- physes, in virtue of which the species must be separated from the Plumularia. With its secondary ramification of the hydrocladia, however, the species stands in the same relation to Nemertesia as Polyplumaria to Plumularia. A separation of the two latter genera therefore logically demands a like separation between the parallel groups of Nemertesia and Polynemertesia. The fact that the prim- ary apophyses in the only known species are biserially arranged on the hydrocaulus must be regarded as of minor importance.
It might be thought more reasonable here to revive an older name for the genus in question ; it should then be Diplopteron or Schizotricha. The former, however, has already been withdrawn by Allmann himself (1883 p. 30) as synonymous with Polyplumaria; Nutting's attempt to revive it (1900 p. 81) can onlv be explained as due to his having taken as basis for the generic division a character which should otherwise be used only with caution even in distinction between species, as in all pro- babilitv, it would seem that the type species for Polyplumaria and Diplopteron are very nearly identi- cal. And with regard to Scliizotricha it should be borne in mind that both the two species originally placed by A 11m an (1883 p. 28) in this genus must be referred to Polyplumaria. It would thus be incorrect to take as the type a species which has not from the first been ascribed to this genus; Plu- mularia gracillima G. O. Sars is first placed under this head by Nutting (1900 p. 80). Of the remain- ing species which have been referred to this genus, Schizotricha bifurea Hartlaub and Schizotricha
' After the close of the manuscript a find of the species in the Trondhjem fjord has proved the correctnes of this supposition.
HYDROIDA II
antarctica Jaderholm must doubtless be removed to a genus of their own, more closely related to Kirchenpaueria. It would thus not be advisable to introduce a new diagnosis for Schizotricha\ the genus should rather be allowed to disappear definitely as synonymous with Polyplumaria, which latter generic appellation is older, and originally better defined. For Plumularia gracillima G. O. Sars there- fore, it will be best to take an entirely new generic name.
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Polynemertesia gracillima (G. O. Sars).
1873 Plumularia gracillima, G. O. Sars, Bidrag til Kuudskaben 0111 Dyrelivet paa vore Havbanker, p. 86.
1893 Plumularia groenlandica, Levinsen, Meduser, Cteuophorer og Hydroider, p. 63, tab. VIII, figs. 10 — 12.
Single pinnate colonies with monosiphonic or in the basal parts polysiphouic main stem. The mono- siphonic stem is divided by trans- verse nodes into iuternodia, which bear distally a short apophyse, di- rected obliquely forward, turning alternately to either side of the me- dian line. The stem has no hydro- theae, but bears mobile sarcothecse, two unpaired, somewhat asymme- trically arranged on the basal part of each iuternodium. The apophyse has a "mamelon" on its upper side near the stem; beside this on the
rear side a mobile sarcotheca, and * c Fig. XXXIV. Polynemertesia gracillima from the Davis Strait als0 an Unpaired mobile Sarcotheca [type specimen of Plumularia groenlandica\ a. Internodium of the distallv ill the median line The stem with primary apophyse. b. Second internode of a prim- ary hydrocladium with secondary apophyse, showing a distinct apophyse bears a secondarily brail- "mamelon". c. Hypothecate internode. (X So). ched hydrocladium; the hydrocla-
dium is divided by transverse nodes into irregular internodia, of which every alternate one bears two unpaired sarcothecte in the median line, every other a median hydrotheca, a supracalycine pair of sar- cotheca^ at the opening of the same, and an unpaired proximal, and as a rule an unpaired distal sarco- theca in the median Hue; on the distal parts of the hydrocladia the hydrothecaless internodiuin often melts into the hydrotheca-bearing internodium. The basal internodium of the hydrocladium is hydro- theca-bearing; the following small internodium is furnished at the middle with an apophyse directed obliquely forward and bearing the secondary hydrocladium; from the second segment of the latter there proceeds as a rule a further hydrocladium in the same manner; these secondary (tertiary) apophyses also are provided with a "mamelon" and two mobile sarcotheca;, as in the case of the primary apo- physe. The secondary hydrocladia are of the same structure as the primary. The hydrothecse are small, with slightly outward curving opening margin, and are throughout their entire length fused with the internodium.
(,:(!<
HYDROIDA II
71
The gonothecse are attached to the apophyse beside the sessile sareotheca. Fully grown gon- angia have not yet been found.
Material:
"Ingolf" St. 27 64°54' N., 55°io' W., depth 393 fathoms 3,8°
- 34, 65°i7' N, 540i7' W.. - 55 Greenland: Davis Strait (without further details) [type specimens of Plumularia groenlandica\. Iceland : Ingolfshofdi g1/2 miles in N. by E. 1j2 E., depth 53 fathoms.
L,ev ins en (1893 P- 63) gives a very detailed description of this species, which he incorrectly regards as different from Sars's Plumularia grin-Mima. He has however, in common with others who
200 m. _ _ _ _ 600m. ._ looom. 2000m.
Fig. XXXV. The localities of Polynemertesia gracillima in the Northern Atlantic. In the hatched region the occurrence according to the literature is common, although scattered.
have investigated the species, overlooked its typical sessile sareotheca on the apophyses (fig. XXXIV) It is noticeable that a mamelon occurs not only on the primary but on all the apophyses in the colony. The idea that it should, as Nutting (1900) believes to be the case with other species, form the point of origin of the gonothecse, is due to inadequate investigation; the gonothecse have their point of attachment by the side of this sareotheca. Levinsen's description incorrectly gives the impression that he has had grown gonothecse before him at the time; they are, however, only quite young stages, and grown gonangia have thus not been described for this species.
Polynemertesia gracillima is plainly a southern visitor to the northern waters, and has strangely enough not yet been recorded in the British waters (fig. XXXV). The "Ingolf" was able to furnish
-,2 HYDROIDA II
further data as to the occurrence of the species at West Greenland, where it penetrates right into the Lille Hellefiskebanke. On a single occasion it has been found in Iceland waters. On the coast of Norway it has been met with now and then between Lofoten and Stavanger. It has also been found off Bohuslan (Jaderholm 1909 p. 108). The species belongs to the lower part of the littoral region, and the upper parts of the abyssal.
Family Aglaopheniidae.
The hydrotheca; are large, with distinctly bilateral structure, sessile, and with the one side wholly or partly fused with the branches. The diaphragma is assymmetrical or bipartite. The polyps can retire altogether into the hydrothecse. The sarcothecoe are sessile, immobile and well developed; exceptionally we may find, in addition, also mobile, stalked supracalycine sarcothecse. The hydrotheca margin is as a ride furnished with teeth. The colonies are monopodial with terminal growth point. The endoderm of the polyps is divided into a fore-stomach and a digestive part; the ectoderm often gives off an ectoderm lamella which fastens the polyp to the ribs of the hydrotheca.
The division of this family is based chiefly upon the nature of the gonangia and the protective formations which are richly and variously developed in the different genera. Primitive in this respect is Halicornaria, from which the remainder are derived. On the one side, there is a development to- wards Nematocarpus, where the hydrocladia are secondarily branched, though without discernible relation to the gonangia. On the other arise, in all probability separately, the phylaetogonia-bearing genera Aglaophenopsis and Cladocarpus, typical deep sea genera, of which the former has hydrotheca- bearing phylactogonia, the latter, on the other hand, only sarcotheca-bearing phylactogonia. Possibly also, the corbula-bearing genera Thecocarpus and Aglaophenia should be derived from these, but their origin is not yet certain.
Gen. Halicornaria (Busk).
Upright colonies with branched or unbranched main stem, the apophyses of which bear 1111- branched hydrocladia with several hydrothecse. All sarcothecee are immobile. The gonangia are situate on the stem or branches without protective organs of any kind.
Halicornaria campanulata (Ritchie). 1912 Cladocarpus (?) campanulatus, Ritchie, Some Northern Hydroid Zoophytes, p. 226.
The colony is doubly pinnate, with polysiphonic branched main stem, which consists in its extreme portions of the primary segmented tube alone. This has mternodia of medium length, which bear about the middle a short, but quite broad apophyse ; the internodium is further provided with a pair of sarcothecae at the upper side of the apophyse, and an unpaired median sarcotheca in front at its lower side; the sarcothecae are almost tubulous, adcaulinally split. The hydrocladia have on each internodium a broad, and not particularly large hydrotheca and three sarcotheca;; a supracalycine pair at the opening, and a median proximallv, which with its opening margin reaches up to the bottom
HYDROIDA II
73
of the hydrotheca. All the sarcothecae are adeaulinallv split, and have a slightly dentate margin. The hydrotheca is broad, and has a very slightly curved opening margin; its basal part has a somewhat thicker wall than the distal two-thirds, and the boundary between the two portions is apparent as a fine line abcladially directed obliquely forward towards the opening; hydrothecal ribs or septa lacking. The internodium shows two to four inner ribs at the adcladial side of the hydrotheca; one such, which is three-branched, and markedly prominent, forms a boundary between the proximal sarcotheca and the internodium.
The gonotheeae are situate on the stem at the apophyses. The young gonotheca shows distallv a peculiar oblique termination, the one side of which gradually projects further forward, suggesting that the fully developed gonotheca would be furnished with a roof-like upper lip. Phylactogonia lacking:.
Material:
"Ingolf" St. 127
66°33' N., 20°05' W., depth 44 fathoms, 5,6°
Iceland: Tistil fjord, 66°43' N., i4°53' W., — 78 —
Ritchie (1912 p. 226) refers this species to Cladocarpus, but with a query, as he did not find gonangia in his specimens. These agree entirely with the present colonies (fig. XXXVI) which, from the comparatively short, broad hydrothecse, can hardly be confused with other species from northern waters. The col- onies in question show that the species should be placed under Halicornaria. The gonangia occur in several stages of development, but none fully developed. The series of phases represented in the colonies investigated are entirely parallel to what we find in Cladocarpus integer ( G. O. Sars); the oldest stage also seems to show that it developes, as does the species mentioned, an "upper lip" which will dome out more or less over the opening; further investigations must determine, how far the development proceeds.
Phylactogonia are altogether lacking in the colonies here concerned, and the species must consequently be regarded as a Halicornaria; there is, however, the possibility that it may later prove to be a primitive Cladocarpus. The otherwise close resemblance of the species to Cladocarpus integer would also seem to point in the same direction; the last-named species has hitherto likewise been regarded as a Halicornaria^ but, as is further explained below, it is as a matter of fact a primitive Cladocarpus, whose phylactogonia do not always or everywhere attain development. We cannot therefore altogether disregard the possibility that Halicornaria campanulata may also under normal conditions develope more or less regularly- occurring phylactogonia. But as long as this has not been shown to be the case, the species must remain in the genus Halicornaria.
Ritchie {1912 p. 227) could not state the locality of origin of the species nearer than "from the neighbourhood of Iceland", which from a bio-geographical point of view is very meagre inform- ation indeed. The localities now recorded are the more surprising, since we should a priori suppose
The Ingolf Expedition. V. 7. IO
Fig XXXVI. Halicornaria campanulata from "In- golf' St. 127. Hydrothecate internodium from a hvdrocladium in side and front view. (X 60).
HYDROIDA II
that we have to deal with a form from the warmer Atlantic regions; both the finds are in fact from near the north coast of Iceland. At the same time, however, it should be noted that both are situate in water of positive temperature; at the "Ingolf" St. 127 no less than 5. 6°; it is thus not impossible that the occurrence of the species here is due to larval transportation from the Danmark Strait. Arctic the species certainly cannot be; even the one Aglaoplicniid hitherto found in any number in arctic water lavers, Thecocarpus myriophyllum (Linne) is not indigenous there. We must therefore regard the Aglaopheniidce on the whole as southern visitors in the colder northern seas. Halicornaria cam- panula fa must likewise be placed in this category; its true home, however, has yet to be discovered.
Nematocarpus nov. gen.
Singly or doubly pinnate colonies, the apophyses of the primary stem tubes bearing hydrocladia, which in fully developed colonies are secondarily branched. All' sarcothecse immobile. The secondary hydrocladium is formed from the proximal sarcotheca branch on the primary, and stands in no relation to the gonangia. The latter are not surrounded by any protective organs.
This peculiar genus is known only in a single species, originally described as a Halicornaria by Allman (1874 p. 477). In Nutting's diagnosis of this genus (1900 p. 126) we find "Hydrocladia not branched; hydrocladial iuternodes without septa". The latter point is of minor importance even in distinction of species, but the first-mentioned character is also adopted by Stechow (1913 p. 43) "Hydrocladien einfach".
On the other hand, we may with some justification maintain that the genus Aglaophcnopsis (Fewkes) is based on forms with branched hydrocladia. We must, however, here note a great differ- ence in comparison with Halicornaria ramulifera Allman; the secondary branches in Aglaopkenopsis are hydrotheca-bearing phylactogonia, and stand thus in definite relation to the gonangia; in this case, however, they have nothing to do with the gonangia, and do not develope into minor branches, as in . Iglaophenopsis, but into secondary hydrocladia of the same structure and appearance as the primary. This difference is important, inasmuch as we should, as Bale already (1887) pointed out, establish a new genus on the basis of the same. The nearest related genera are Halicornaria, Aglaopkenopsis, and Clailocarpus, where we often, especially in the two last, find the same structure of the gonotheca as in the known Nematocarpus species.
Nematocarpus ramuliferus (Allman).
1S74 Halicornaria ramulifera, Allman, Report on the Hydroida .... Porcupine, p. 477, pi. 67, fig. 3. 1903 Halicornaria pin ma, Broch, Die von dem norwegischen Fischereidampfer "Michael Sars" .... ge-
sammelten Hydroiden, p. 8, Taf. IV, figs. 15—21.
Doubly pinnate colonies, with somewhat irregularly branched, polysiphonic main stem. The
primary tube is segmented, and has on the middle of each internodium a strong apophyse, directed
alternately to each side, and a pair of sarcothecse at the upper side of the apophyse; the sarcothecse
are adcaulinally split. From the apophyse proceeds a hvdrocladium, bearing a hydrotheca on each
IIVDROIDA II
75
internodium, surrounded by a pair of supracalycine sarcothecee on the distal part of the internodium and an unpaired median proximally; between this and the base of the hydrotheca arises a sarcotheca- bearing branch, which bends forward over the hydrotheca, and has on its convex (outer) side a row of sarcothecae. The sarcotheca-bearing branch of the basal hydrotheca developes into a secondary hydrocladium of the same appearance as the primary, but somewhat finer. Also in the exterior sarcothecal branches hydrotheca; may be developed. The hydrothecae are fused throughout their basal half with the branch; the distal portion forms an angle with the basal, and widens some- what towards the aperture. The margin is furnished with 9 or n teeth; a large median proximal (abcladial), beside this as a rule a couple of smaller ones, then two well marked, and finally there are distally (adcladially) a pair of large teeth of the same size as the proximal, and between them a couple of quite small ones.
The gonothecse are attached by a short, often almost rudimentary stalk to the stem; viewed laterally, the gonotheca is asymmetrically egg-shaped or oval, with a distal lateral opening; seen from the front, they are oval, distally often broadly rounded; the aperture is round. At times there may be some approach to formation of an "upper lip" above the mouth.
Material :
"Ingolf" St. 44 6i°42' N., 9°36' W., depth 545 fathoms 4,8° - 98 65*38' N, 26*27' W, - 138 5,9°
The new colonies brought home by the "Ingolf" show that the Halicornaria pliinin Broch (1903 p. 8) described as distinct species is really only a somewhat older stage of Nematocarpus rannt- liferus (Allman); we have now colonies showing the next stages through which they pass over to the possession of secondarily branched hydrocladia (fig. XXXVII a). Here also the species retains its peculiar nude posterior side, whereas the front appears even more furry than in young colonies. There are certain signs which seem to indicate that a primary hydrocladium may bear several secondary ones. Halicornaria pliima was established chiefly on the strength of the fact that the basal sarcotheca- bearing branch of the hydrocladium has a hydrotheca, whereas the remaining sarcothecal branches lack hydrothecse. The present colonies nowf show that this was merely the forerunner of the second- ary hydrocladium, which gradually developes new hydrothecae with sarcotheca-bearing branches out- side the first1. At the same time, however, we find a hydrotheca with its corresponding sarcothecal branch developed at the second, often also at the third hydrotheca, and it is therefore highly possible that in still larger colonies we may also here find developed secondary hydrocladia, showing that a primary hydrocladium can bear several secondary ones.
The gonothecce are incompletely described both by Allman (1874 p. 477) and Broch (1903 p. 8) probably from imperfectly developed specimens. They are of very peculiar form (fig. XXXVII b). Thev are attached by a stalk which is not infrequently very short, almost rudimentary. The one (adcauline) side is somewdiat flattened and short, the other however, highly curved and a good deal longer, so that the plane of the aperture is almost or entirely parallel with the longitudinal axis of
1 In fig. XXXVII a, the secondary hydrocladium shows only one complete sarcothecal branch (the basal); this is due to the fact that the two next are broken off. Ordinarily, they appear in fully normal development at every single hydrotheca.
76
HYDROIDA II
z
Fig. XXXVII. Nematocarpus ramuliferus. a basal part of a hydrocladium 'showing the development of the secondary hydro-
cladium [p primary, s secondary hydrocladium; the proximal, sarcothecal branch is a little abnormally developed]. "Ingolf" St.
44. b internodium of the primary tube of the stem of a young colony from "Ingolf St. 98. c Hydrotheca, "Ingolf" St. 44.
d Gonotheca in side view and front view, "Ingolf" St. 9S. (a X 45, * — <* X 90).
the gonotheca itself. The aperture is round or often somewhat broader, oval, and we thus find here a distinct approach to the remarkable form of gonotheca which occurs in all known forms of Aglao- ■phenopsis and Cladocarpus species, save that a distinct upper lip is less often clearly discernible.
Nematocarpus ramuliferus was formerly only found in the cold area (fig. XXXVIII), but the two finds fall just in the zone where otherwise warmer atlantic, deeper-living visitors occur sporadi-
boom ._. .1000 rn.
Fig. XXXVIII. Finds of Nematocarpus ramuliferus.
HVDROIDA II
77
cally in the Norwegian Sea, and lie also comparatively near the submarine ridges. It was therefore most likely that the species should be reckoned, bio-geographically, as belonging to the class of such visitors, and the two new finds appear to confirm this supposition, both being situate in the warmer atlantic region; one on the slope down towards the Atlantic Deep, west of the Faroe plateau, and the other on the east side of the threshold in Danmark Strait, where several other warm-water species also come in. The last-named locality, with a depth of 138 fathoms, is the shallowest of the finds made; the others lie deeper down in the true abyssal region. We are therefore justified in concluding that the species belongs to the warmer and deeper atlantic communities.
Aglaophenopsis (Fewkes).
Upright colonies with branched or unbranched main stem, the apophyses bearing unbranched hydrocladia with several hvdrotheca;. All the sarcothecse are immobile. The gonothecse are protected by minor branches forming a basal appendix to the hydrocladia, and with both hydrotheese and sar- cothecse; the gonothecse are situate on the stem or on the minor branches.
Practically speaking, this definition coincides with Nutting's limitation of the genus (1900 p. 118). Nutting also lays most stress upon the occurrence of the protective branchlets, but does not seem quite to have realised that the principal character for these lies in the fact that they bear hydrothecse, not, as in the case of Cladocarpus, sarcothecse only. Aglaophenopsis differs from Nemato- carpus in principle by the fact that the minor branches do not develope into secondary hydrocladia of normal appearance, but merely appear as protective appendices in fertile colonies.
Aglaophenopsis- Cladocarpus form a pair of genera parallel with Thecocarpus-Aglaophenia. As a matter of fact, we cannot determine which of the two in each case is the more primitive; having regard, however, to the development of a species such as Nematocarpus ramuliferus, which appears to be more primitive than the others in the state of its gonangia, we must probably incline to the theory that Cladocarpus and Aglaophenia are the more primitive, rather than the more highly developed. Still, we can hardlv in either case regard the one genus as derived from the other; it would seem more likely that each has arisen independently.
Aglaophenopsis cornuta (Verrill) Nutting. 1879 Cladocarpus cornutus, Verrill, Notice on recent additions to the marine fauna, p. 310. 1900 Aglaophenopsis cornuta, Nutting, Plumularidse, p. 120, pi. 30, figs. 6—9.
Colonies doublv pinnate, with branched polysiphonic main stem, monosiphonic in its extreme portions. The primary stem tube is divided into short internodia, bearing in the middle an apophyse directed obliquely forward and sideways, and three sarcothecse, one pair nearest the upper side of the apophyse, and an unpaired one medially on the lower part of the internodium; all are split along the upper side, and project far forward, especially the paired ones. At the base of the apophyse, between it and the unpaired sarcotheca, there appears a pattern which must be interpreted as an abortive hvdrotheca. The hydrocladia have on the rear side a markedly prominent keel; they are divided into short internodia, each bearing a large hvdrotheca and three sarcotheca^, a supracalycine pair at the
78
HYDROIDA II
opening, and a median proximal sarcotheea, the opening margin of which hardly reaches up to the middle of the hydrotheca; the sarcothecae have a dentate margin, and project far forward; they are adcaulinally split. The hydrotheca is laterally compressed; seen from the side, it is egg-shaped and pointed at the lower end. The hydrotheca has abcaulinally a median keel, running out into a large, hollow, generally sharply horn-shaped tooth, the free projecting part of which may reach a length of
up to 2/3 that of the hydrotheca; the cavity forms a continuation of the lumen of the hydrotheca. The hydrotheca margin has at the base of the mentioned projection a median abeauliue tooth, and on either side four teeth, which become broader and less pro- nounced nearer the hydrocladium. The internodium has four to six inner ribs at the hydrotheca wall; an inner rib also bounds the lumen of the proximal sarcotheea on its lower end. The hydrotheca
Fig. XXXIX. Aglaophenofsis cortuta. lacks imler ribs 0r SePta-
"Ingolf St. 25. — a. Cauline intemo- Tne gonothecas are set on the stem, or more often on short,
dium of the primary tube, showing
both sarcotheea; of the upper pair. — once dichotomically divided branchlets proceeding from the basal
i. Front view of the internode, showing internodium of the hydrocladium beside its proximal sarcotheea ; the
the abortive hydrotheca at the base
of the apophyse above the proximal small branches bear as a rule a hydrotheca on each branchlet; more
sarcotheea. (X 40). , , , , ., . , ,, m,
rarely the one may have two hydrothecae, the other one. I he gono-
theca is broad oval to pear-shaped; seen from the side it is somewhat more slender, with subterminal
opening on the adcladial side and with a short upper lip, formed by the abcladial wall, which is
domed forward roofwise over the opening.
Material:
"Ingolf" St. 15, 66°i8' N., 25°59' W., depth 330 fathoms
- 25, 63°3o' N, 54°25' W, - 582
- 98, 65°38' N, 26027' W, - 138 Greenland: Davis Strait, — 100 — (without further details)
65>' N, 55036' W, - 289
In Nutting's description of Aglaopheiiopsis cornuta (1900 p. 120) there is a misunderstanding as to the cauline sarcothecae, which he describes as follows: "cauline nematophores very large, one just at the base of each hydrocladium, another immediately below this, and a third, long and spur- like opposite the base of each hydrocladium". As regards the last sarcotheea (fig. XXXIX a) this is as a matter of fact one of a pair situate nearer the upper side of the base of the apophyse; both of them project far out from the stem, but on viewing the colony from the front (fig. XXXIX b) the one is hidden by the basal part of the hydrocladium. The lower, proximal sarcotheea is very broad, and does not project quite as much. The sarcotheea which Nutting mentions as just at the base of the hydrocladium, i. e. practically on the apophyse itself, must on the other hand be regarded as an abort- ive hydrotheca which has been checked in its development by the growth of the apophyse and hydro- cladium ; it bears no resemblance to the remaining sarcothecae, and does not seem to be provided with any sarcostyle or nematophore. A point of great importance in this explanation is also the fact that the basal portion of large pinnate parts may be formed of internodia with hydrothecae, but without
o,75 3,3° 5,9°
HYDROIDA II
79
apophyses and hydrocladia; here again we fmd the supracalycine sarcothecse particularl) well devel- oped, in the same manner as over the apophyse, and more than on the normal cladial internodia; at the same time there is not the slightest indication of any such pattern as that which Nutting has taken for a sarcotheca. The abortive hydrotheca probably forms a parallel to the apophysal "mamelon" in Nemertesia and Polynemertesia, and would seem to throw some light on its origin.
There is considerable variation in the appearance of the hydrotheca.* (fig. XL) especially owing to the fact that the abcauline keel and its prolongation vary very greatly both in length and breadth ; the outgrowth may be broad and blunt, or more slender, and running out to a point. It forms an incurvation in the wall of the hydrotheca; at its base, the hydrotheca is furnished with a sharply cut tooth, directed obliquely inward and forward, and between this and the internodium the edge shows
Fig. XL. Aglaopliowpsii cornuta, a Basal part of a hydrocladium with the phylactogonium and a gonotheca in side view from "Ingolf" St. 98 (X 40). -- b Front view of a hydrotheca from the same colonv (X 60). — c Side view of a hydrotheca from the same colony (X 60). — d Hydro- theca from a colonv from "lnoolf" St. 25, side view I'X 601.
as a rule four teeth on either side, which become broader and lower nearer the hydrocladium. The innermost tooth on either side, and at times the one next to it, can even now and again be entirely effaced, so that only two abcauline teeth can be distinguished on either side. - The proximal sarco- theca also varies considerably, diverging now more, now less widely from the hydrotheca, and having a free portion of varying length.
The basal internodium of the hydrocladium has a different structure owing to the position of its proximal sarcotheca. This is shifted to the obliquely upward trending hydrocladium, — the side away from the stem — and is also somewhat smaller than on the following internodia. The cause of this must be sought in the growth of the phylactogonium.
The phylactogonium (fig. XL a) is segmented and has only hydrothecse on two of its branches; on one of them at times two, but as a rule only one on each; they are surrounded by the usual three
So
HYDROIDA II
2 00 m. 6 co m. ._.-_. §ooo m. 2 ooo m.
Fig. XLI. Finds of Aglaophenopsts cornuta in the Northern Atlantic.
sarcothecce, which, however, are here generally somewhat smaller than on the hydrocladia. The gono- theca has a well developed upper lip, which does not appear clearly from Nutting's illustration and description. It is domed strongly forward, so that the aperture becomes turned down towards the base. Aglaophcnopsis cornuta is a typical deep-sea species which has only in Davis Strait been observed at ioo, and in Danmark Strait at 138 fathoms depth; it can thus also penetrate up into the lower part of the littoral region. The species probably belongs strictly speaking to the warm, deep northern part of the Atlantic; it moves up into Davis Strait, where it appears to be of not infrequent occurrence (fig. XLI) and has now, as we see, also been recorded from Danmark Strait. As it is not known from other localities than those mentioned and the waters off Nova Scotia, we are justified in characterising it for the present as a west atlantic species.
Aglaophenopsis (?) pharetra n. sp. The colony pinnate with polysiphonic stem, monosiphonic in the extreme portions, and having the primary tube indistinctly segmented. Each of the internodia of the stem bears at two thirds of its height a well defined, fairly short apophyse, and three unpaired sarcotheese, two in the median line below the apophyse, and the third in the corner between the stem and the apophyse above the origin of the latter. The alternately placed hydrocladia form almost a right angle with the stem; they are divided into long internodia, each of which bears a hydrotheca, and three sarcothecce, a supracalycine pair at the opening of the hydrotheca and an unpaired proximal about midway between the base of the hydrotheca and the proximal end of the internodium; the opening margin of the
HYDROIDA II
8l
proximal sarcotheca does not reach up to the base of the hydrotheca; all the sarcotheca; have a smooth margin and are adeanlinally split. The length of the hydrotheca is about three-fifths that of the inter- nodium. The hydrotheca is of extremely slender build, not laterally compressed, somewhat expanded towards the opening; the opening margin is quite smooth. Numerous small inner ribs are found in the internodia along the hydrotheca wall; a rib also forms the lower boundary of the proximal sarcotheca.
f\
f\
J
Material :
"Ingolf" St. 81 6i°44' N., 27°oo' W., depth 485 fathoms, 6,i°.
Of this remarkable species we have only a single quite small colony, the height of which amounts to only about 2 cm. above the close rootlike net- work by which it was attached. The upper 6 mm. bear the hydrocladia, two fairly long on each side, and there is also, at the top of the colony on the left side, a third hydrocladium where the hydrotheca no 2 is still only indicated. On the lower part of the stem there is a secondary tube, which creeps upward along the lower 7 mm. of the primary, show- ing that the fully grown colony will exhibit a poly- siphonic stem. The primary tube differs from that of most other species in the arrangement of the sar- cothecae (fig. XLII «); paired cauline sarcotheca; are lacking, but each internodium has three unpaired sarcothecse; the two lower in the median line one above the other, and the third in the corner at the upper side of the apophyse.
The hydrotheca; are very characteristic (fig. XLII 6, c), in appearance not unlike a slender quiver, whence the species has been named pharetra. The opening margin is quite smooth, without indication of teeth or irregularities. The supracalycine sar- cotheca; project somewhat up beyond the hydrotheca opening. The proximal sarcotheca is separated by a quite considerable interval from the hydrotheca.
As no indications of gonangia have yet been found, the systematic position of the species cannot yet be determined with certainty. It presents, however, a so considerable resemblance to Aglaophenopsis Verrilli Nutting that it should, for the present at any rate, be placed near this; the differences consist in the somewhat shorter and broader hydrotheca; of the latter species, where the opening is furnished with teeth, as also in the much shorter distance from the hydrotheca to the proximal sarcotheca. The species is therefore placed with a query in the same genus, under the name of Aglaophenopsis (?) pharetra. On the other hand, it also resembles not a little certain Cladocarpus
The Ingolf-E\pedition. V. 7. II
Fig. XLII. Aglaophenopsis (?) pharetra from "Ingolf ' St. Si.
a. Internodium of the primary eauline tube with the apophyse.
b. Internodium of the hydrocladium with hydrotheca in side view. c. Frontal view of hydrotheca and internodium. ( X 60).
g2 HYDROIDA II
species such as Cladocarpus tenuis Clarke and Cladocarpus flexuosus Nutting. There is therefore the possibility that the species may have to be referred to this genus, and the query affixed to the generic name must remain for the present.
Only the one specimen was found, in the deep south west of Iceland. The locality suggests that we have here to deal with a warm-water form from the deep water of the Atlantic.
Cladocarpus Allman
Upright colonies with branched or unbrauched main stem, the apophyses with unbranched hydrocladia with several hydrothecse. All the sarcothecae are immobile. The gonothecse are protected by small branches, phylactogonia, which form a basal appendix to the hydrocladia, and are furnished with sarcothecae, but lack hydrothecse. The gonothecse are set on the stem or on the phylactogonia.
Cladocarpus integer (G. O. Sars). 1874 Aglaophenia Integra, G. O. Sars, Bidrag til Kundskaben 0111 Norges Hydroider, p. 100, pi. 2, figs
11— 15.
1879 Cladocarpus Pourtalesi, Verrill, Notice on recent additions to the marine fauna, p. 309.
1893 Cladocarpus Holwi, L-evinsen, Meduser, Ctenophorer og Hydroider, p, 67, tab. VIII, figs. 15—18.
The colonies are doubly pinnate with branched polysiphonic main stem, exhibiting only in its very outermost parts the primary segmented tube alone; this has fairly short internodia, bearing on the basal third a strong but short apophyse; the internodium is also furnished with three adcaulinally split sarcothecse, an unpaired median at the bottom, and a pair at the upper side of the apophyse. The internodium of the hydrocladium has a fairly large hydrotheca and three sarcothecse, a supra- calycine pair at the opening, and a median proximal sarcotheca, which with its opening margin hardly reaches up to the basal fourth of the hydrotheca; all the sarcothecae approach the tubulous form, but are adcladially split. The hydrothecse are laterally somewhat compressed, and slightly expanded at the opening; the opening margin, in the hydrothecse as in the sarcothecoe, is quite smooth. The inter- nodium exhibits one or two inner ribs at the hydrotheca wall, and two below the proximal sarcotheca.
The gonothecae are fastened as a rule by a rudimentary stalk to the stem or to the phylac- togonia, which are almost invariably unbranched, and have two irregular rows of sarcothecae; the phylactogonium proceeds from the basal internodium of the hydrocladium, beside the proximal sarco- theca. The gonotheca is somewhat flattened; seen from the flat side it is broadly pear-shaped, broadly rounded distally; viewed laterally, it is a slender oval, with a distal lateral adcauline opening over which the abcauline wall domes out like an upper lip.
Material:
"Iugolf" St. 25 63°3o' N., 54°25' W., depth 582 fathoms, 3,3°
- 27 64*54' N, 55°io' W, 393 3,8°
- 94 64°56' N., 36°i9 W., — 204 — 4,1°
- 98 65°38' N, 26*27' W, - 138 5,9°
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83
Greenland: Davis Strait, depth 80 fathoms (without further details) |type specimen of Clado-
carpus Hoi in i\ Iceland: 5 miles E. of Seydisfjord, depth 135 fathoms [labelled Cladocarpus Holmi\.
Cladocarpus 111 tiger has led a somewhat unsettled existence in various genera. G. O. Sars (1874 p. 100) regarded it as an Aglaophenia, and is followed by Bonne vie (1899 p. 93) who places all northern Aglaopheniida in this one genus. Jaderholm (1909 p. 109 and no) refers to it either as Halicornaria Integra or as Cladocarpus IFolini and Cladocarpus Pourtalesi] while Ritchie (1912 p. 228) classes the species under Halicornaria. A very rich material from the Trondhjem Fjord, where the species is found in great numbers, enabled me to study it further, and determine its systematic position. And it now turns out that the species must be regarded as a primitive Cladocarpus. The
Fig. XLIII. Cladocarpus integer. a. Basal parts of a hydrocladiurn and its phylactogoniutn with an entire gouotheca, from the Trondhjem fjord (X 4°)- — *• Hydrotheca of the same colony (X 60). — c. Hydrotheca of a colony from "Ingolf" St. 98
(X 60).
gonothecse are very often fixed to the stem or more correctly, to the apophyses; Ritchie's descrip- tions show that this may often occur on the whole for an entire colony, and that the phylactogonia may in consequence be altogether lacking, which is also exceptionally found to be the case in some of the colonies from Trondhjem Fjord. The great majority of the colonies have, however, at any rate in considerable parts of each, developed primitive but typical phylactogonia (fig. XLIII a). These pro- ceed from the basal internodium of the hvdrocladium beside the proximal sarcotheca. The phylacto- gonia are practically always unbranched, and furnished with two somewhat onesidedly arranged rows of sarcothecse, set either in pairs or irregularly placed; only once or twice have I found phylactogonia which had, by dichotomic division, developed a short lateral branch of the same structure. The phylac- togonium also exhibits irregular segmentation. It has as a rule two or three gonothecce on the same side as the sarcothecse. The gonotheca is of the typical Cladocarpus form, with upper lip; this is, however, shorter than in most other species, so the opening is not yet directed downwards.
Ritchie's specimen (1912 p. 228) should, it would seem, be taken as the representative of a special variety Ritcliici nov. differing from the typical form in having the hydrotheca margin slightly
84
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sinuous. The hiternodial ribs of this variety are also somewhat more strongly marked than in the common form, and it likewise shows a more pronounced indication of intrathecal septum.
The features mentioned, that the species can at times lack phylaetogonia, show that Clado- ttirpits Pdurtalesi must be considered as a synonym. The difference between this species and Clado- carpus Holmi is not apparent from Levinsen's description of the latter (1893 p. 67) and an investig- ation of the type specimens shows that the species has been founded on typical colonies of Clado- carpits integer.
2 000 m.
Fig. XL,IV. The distribution of Cladocarpus integer in the northern Atlantic. In the hatched regions the literature denotes a scattered occurrence.
The species is a typical warm atlantic form, which appears to have its chief occurrence in the western Atlantic, in the lower part of the littoral region and the upper part of the abyssal. In northern waters, it has long been known from the west coast of Norway, and is also found to be a not alto- gether infrequent visitor to Greenland, both in Davis Strait and up towards Danmark Strait (fig. XLIV). On one occasion, it was met with off the east coast of Iceland, at the boundary of the arctic deep region. That it has not yet been located with certainty between the British Isles and Iceland must be due to accident. Ritchie (1912 p. 228) had before him a specimen brought home by Hull trawlers, and we may doubtless presume that it would then have originated from the northern slope of the North Sea plateau or from the Faroe Islands Banks.
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85
Cladocarpus formosus All man.
1874 Cladocarpus formosus, Alhnan, Report on the Hydroida Porcupine, p. 478, pi. 68, fig. 1.
1893 Cladocarpus crci/u/afus, Levinsen, Meduser, Ctenophorer og Hydroider, p. 68, pi. VIII, figs. 13 — 14. The colonies have an unbranched or branched polysiphonic stem. The primary, foremost tube is divided into short internodia with a short apophyse directed obliquely forward and sideways,