Papers from Dr. Th. Mortensen’s Pacific Expedition 1914— 16.

XXXIX. Two new Ctenophores hy Dr. Th. Moptensen. . (With Plate HI).

T h e two Ctenophores described in the present paper were obtained by the author some years ago, viz. one, the Beroe, in 1915, during his Pacific Expedition, the other, the Coeloplana, in 1922, during the Danish Expedition to the Kei Islands. When the de­ scription of these forms has been rather unduly delayed, the reason is, partly, that the author has been overwhelmed with other work, partly, some feeling of disappointment about them. The deep-sea Beroe, at a first glance so strikingly different from the usual Beroe cucumis, was found on a closer investigation to offer no morpho­ logical features of special interest. The Coeloplana likewise was found to be comparatively uninteresting in regard to its morphology, while nothing could be learnt about its gonads or its development. Only its selfdivision and its peculiar habitat, on a seastar, are points of special interest. Thus these two new forms do not increase our knowledge of Ctenophoran morphology, while in regard to ecology and biology they may well claim some interest.

I. Beroe abyssicola n, sp. (PI. III. Figs. 1-2). While staying at the Biological Station, Departure Bay (at Na­ naimo) on Vancouver Island in the summer of 1915 I found on the 21st of June in a piankton-haul from ca. 400 meters in the Strait of Georgia just outside Departure Bay a Ctenophore of an intense claret colour. That I had here a hitherto unknown deep- sea Ctenophore before me was at once evident. It was a Beroid, and I expected then naturally to have found a new generic type of that family. It proved, however, to be in all respects a typical Beroe, the main interest attached to it lying in the fact that it was a deep-sea form. Several more specimens were collected in the course of the next month (the last on July 18th), but only in hauls from about ca. 300—400 meters, never in hauls from less than ca. 200 meters. That it is stationary in the deeper strata of the deep basin of the Strait of Georgia seems thus evident; the fact that it was unknown to the then director of the Station, Dr. C. McLean Fraser, as to anybody at the Stat­ ion, also indicates that it does not — at least as a rule — rise to the surface. The largest of the specimens observed was 7 a. I). cm long, 2,5 cm broad. Fig. 1. BeroP abyssicola, n. sp. Natural size. The shape is very much Specimen a. wns narcotized witli ixiagnesium- sulfate, whicli made it rather unnaturally long like that of Beroe cucumis and slender: preserved in formaline. Specimen (PI. Ill Fig. 1; textfigures b, preserved in Chroni-osmic fluid, is sexually ripe. The s«iniming-plates are fallen off. 1— 2), only in general somewhat moje slender; it is not compressed. The pharynx is large and broad, but flat, showing only as a sharp line when seen from the sagittal plane. The edge of the mouth — which may assume any shape, as in the common Beroe — set with the usual captive hairs (PI. Ill Fig. 2); they are arranged in a broad belt, which is not indented along the inner margin. The edge is more or less distinctly furrowed, sometimes so as to be finely serrated, sometimes quite smooth — depending on the muscular contractions. The ribs are of about equal length; they end a good distance from the oral edge, in the largest specimens reaching only about halfway. The fringe of bush- Fig. 2. A series of young specimens of Beroe abyssicola. n. sp. Narcotized with magnesium-sulfate, preserved in formaline. Notiiral si/e. shaped papillae along the edge oF the polar plates as in B. cucumis (Fig. 3); they are smaller in the distal part. On each side of the apical organ the body wall forms a small conical elevation which rises a little above the apical organ; there is a smaller elevation between the other ribs — as may also be found in B. cucumis (see L. Agassiz. Contributions Nat. Hist. U. S. America. PI. I, 2; PI. II, I). The meridian ves­ sels richly proliferating, but no anastomoses are formed. The pharyn­ geal vessels likewise usually richly proliPe- rating, with close set, rather thick branches; there is, however, much Fig. 3. Papill® from the polar plates of Beroe. abyssicola n. sp. x 3.5. variation in the num- ber of the proliferations, as in B. cucumis; in no case the pharyngeal vessels were found to lack proliferations entirely. No anastomoses between pharyngeal and meridional proliferations were observed.^)

It will be obser\'ed that I have not adopted the designations of the various parts of the gastrovascular system, introduced by Th. Krumbach in his elaborate representation of the Ctenophores in the ’’Handbuch der Zoologie” (Bd. I. p. 905—995) 1925, but am rather keeping the old. familiar designations, used in the whole Ctenophoran literature Of course, the de­ signations, used by Krumbach are very logical and clear— to those who have been educated with the Greek language. But to those who have not learnt Greek — and this holds good of by far the majority of the younger generation of zoologists and no doubt also will for the future — the designa­ tions used by Krumbach must be exceedingly cumbrous: Zentrogaster for the stomach (or Infuadibulum, as it has — unfortunately, I agree — been In the largest specimen (Fig. 1 b) the basal part of the proliferations was found to be enlarged and to contain the gonads. The sexual products were evidently just about to ripen, only few ripe eggs being found, while the spermatozoa were fully ripe. The size of the eggs was ca. 0,o5 mm.^) On making a preparation of the pharyngeal wall, removing the jelly of the body (— which is quite easily done — ) a fairly regular layer of longitudinal and circular muscles was seen to lie on the wall. The colour is the most conspicuous feature of the species. The pharynx wall is in the larger specimens of a deep claret colour, while the body is otherwise clear and transparent. Along the mouth edge the pigment cells often, but by no means constantly, show a radiating arrangement. Scattered pigment cells are found also in the polar branches, and a series of minute dots along both sides of each comb plate. Also along the base of the proliferations from the meridional vessels pigment cells occur. Young specimens may appear almost colourless; but on closer inspection the pharyngeal wall is also here found to be full of pigment cells, only they have designated in Ctenophoran literature), Metagaster for phar>’ngeal vessels, Cla- discus for meridional vessels, Akrotelocladiscus for the excretory channels etc. I think the old designations very much easier to use, even if we got to remember that the ’’infundibulum” means the stomach. But above all, I would object to using the designations Dendrocoela and Rhabdocoela for certain types of the gastrovascular system in Ctenophores, names that have for times immemorial been applied to Planarians and are known as such to every zoologist. And is it really necessary to have a special Greek designa­ tion for any variation in the gastrovascular system — Mesodicladiden, Meso- tricladiden, Metatricladiden, Typhlocoela, Cyclocoela, Crossocoels, Dictyocoela, Mictocoela? (Op. cit. p. 941). I am afraid that this will mainly serve to scare away young biologists from the study of Ctenophores. I) Taku Komai (On Ctenophores of the Neighbourhood of Misaki. Annot. Zool, Japan. IX, 1918, p. 465) calls attention to the Fact that the size of the eggs in B. cucumis and B. ovata is very different; 0 j—0,5 mm in the former, 1 — 1,2 mm in the latter. This difference — which I had not remar­ ked when discussing the question of the specific value ot the two forms in my "lngolf”-Ctenophora (p. 83) — seem s to me so important that, in spite of the fact that the anatomical differences stated to exist between the two said forms do not hold good, I would rather be inclined to think they must be two different species. The development of the two forms most probably will show noteworthy differences. here the shape of small dots, while in the larger specimens they are more expanded. The colouring matter is dissolved by the for­ maline. Clear cells are found scattered, quite disorderly, among the pigment cells of the pharyngeal wall. The specimens were swimming very actively when brought in­ tact to the surface — which was possible only by means of attaching a fairly large glass-jar in the end of the plankton net. In this jar the whole of the plankton-catch gathered, the jar thus being filled by all sorts of plankton organisms, especially Crustaceans. It was then easy enough to isolate the Beroids when brought to the la­ boratory, and they might be kept living for some time, even in the much warmer surface water. If means of cooling the water had been accessible it would no doubt have been possible to keep them alive for a much longer time. But, even under the existing circumstances it was perfectly delightful to observe these splendid organisms of the deep-sea swimming thus actively, in the usual way of the Beroids. As seen from the descriptions and figures here given, there is no doubt that this is a perfectly typical Beroe. In its general features it closely resembles Beroe cucumis. The main characters distinguishing it from Beroe cucumis are the location of the gonads in the basal part of the proliferations from the meridional vessels and the colour. Even though the young specimens may be nearly uncoloured, the larger ones were constantly found intensely claret coloured, as shown in the figure, but B. cucumis, even when taken from deeper water, is, to my knowledge, never thus coloured, always the whole body of a diffuse pink colour. Another character is the shortness of the ribs (Figs. 1 — 2). Finally it differs biologi­ cally from B. cucumis in being confined to the deeper strata, below ca. 300 meters, the latter being mainly a surface form. None of the other species of Beroe known till now (Beroe forskdli and the various species recorded from the Japanese Seas by Moser and Komai) are more closely related to the present species. The existence of this Beroid in the deep basin of the Strait of Georgia is in itself proof that also other Ctenophores must live here, as there must be something that the Beroe can feed on. As a matter of fact I was also able to prove directly that quite a rich fauna of Ctenophores occurs in the deeper strata of this basin. Most oF these Ctenophores were in a poor condition when brought up; still I was able to recognize among them Mertensia sp., Bolinopsis sp. Tinerfe (?) sp. Further unidentifiable pieces (ribs) of a large, brownish Lobate were found, and the pharynx and tentacles of what is probably a new generic type, found in one haul from ca. 400 meters on July 2nd. These tentacles were thick, unbranched, terminating in a knob, as in Aulacoctena. Apparently the tentacle sheath opens aborally, not orally as in Aulacoctena. It is evidently an exceedingly delicate form, judging from the miserable fragments that were observed — whereas Aulacoctena is a rough and resistent form. — The Tinerfe was found on the 19th of July, three specimens, in a haul from ca. 400 meters; they were faintly whitish, otherwise of no special colour. There was, however, no time for a closer study of the living specimens, and as the preservation was not satisfactory, the identification of them as a Tinerfe is not to be regarded as definite. The Mertensia resembles M. ovum in its general shape, only the transversal axis is not much longer than the sagittal. The tentacles are provided with tentilli only in the basal part, the distal part being simple. The infundibular channel is strongly compressed in the sagittal plane, like the pharynx, and is closely set w'ith radiating bush-shaped muscles, so that it has almost the shape of a spruce. No longitudinal muscles were observed (cf. the author’s work on the "Ingolf’-Cfenophores, p. 64, figs, 11 — 12, M. ovum). Also numerous muscle bundles from the pharynx to the body wall. The tentacle basis has the same characteristic shape and size as in M. ovum. The colour is fainter than in M. ovum, the body being colour­ less, only the tentacles and the tentacle bases (not the pharyngeal folds) of a faint pink colour. The largest specimens observed were 1 cm long. It may be emphasized that — as was to be expected — there are no proliferations from the aboral part of the subtransversal vessels, and I have now hardly any doubt that Merten s ’ state­ ment to have ’’deutlich beobachtet, dass von hier sich baumartig verzweigte Gefasse sich gegen den Darmkanal erstrecken” (Be- obacht. u. Unters. iiber die Beroeartigen Acalephen, p. 526) refers to the above mentioned bushshaped muscles, which he has mistaken for proliferations from the vessels. It is very probable that we have here a second species of Mer- tensia. Especially the absence of tentilli on the distal part of the tentacles and of longitudinal muscles on the infundibular channel forbid referring it to M. ovum. However, I shall not definitely establish this Strait of Georgia-Form as a new species, partly be­ cause I have no figures of it, partly because M. ovum itself is still insufficiently known, although having been so often mentioned in literature. I also think it very desirable to have the Strait of Georgia-form studied much more in detail, and especially to have ascertained, whether the absence of the tentilli on the distal part of the tentacles is a constant and normal feature. I may take the opportunity of pointing out here that the figure of Mertensia ovum, given by Vanhoffen in ’’Nordisches Plank­ ton” is turned upside down. The same holds good of the fig. 29 (p. 27) of A. Agassiz’ ’’North American Acalephs”. The observations here recorded show a rich and very interesting fauna of Ctenophores to exist in the deeper layers of the basin of the Strait of Georgia, which would certainly deserve to be made the object of detailed morphological and ecological studies. To me, who could spend only two months at the Biological station at Departure Bay, fully occupied with other problems (— especially studies of Echinoderm development — ), there was no possibility of doing much more than proving the existence of these Ctenophores in the deeper strata of the Strait af Georgia basin. For a closer study it will be necessary to make observations throughout the year, especially to ascertain whether they are constantly confined to the deeper layers, or they do perhaps sometimes rise to the surface. In connection herewith the interesting question arises, whether those forms are found also outside the Strait of Georgia, in the deeper strata of the adjoining parts of the Pacific and perhaps farther away. It would, indeed, be very remarkable, if they should prove to be confined to the small area occupied by the deeper parts of the Strait of Georgia — which would further lead to speculations on the problem^ how they could have passed the Glacial Period here. It is not to me to enter on a discussion of these problems; I must be content to point at them, in the hope that somebody at one of the Biological Stations there will take up the whole matter for a detailed study, which would be sure to yield very interesting results.

II. Coeloplana astericola. n. sp. (PI. III. Figs. 3-11). While I was staying on Amboina in February 1922 together with my friend Dr. H. Boschma, he one day brought from the reef-flat a seastar Echinaster luzonicus (Gray), on which were found some curious Pianarian-like organisms, mottled red and white. They were creeping slowly about on the arms and body of the seastar assuming often a very irregular shape. The presence of a pair of long tentacles of typical Ctenophoran structure at once proved the organism to be a Coeloplana, and that it was a new species was likewise evident, both from its peculiar coloration and its habitat. In spite of much searching no more specimens of the seastar carrying Coeloplana could be found, but after the arrival to the Kei Islands, it was found {by the end of March 1920) that the same Echinaster occurred here in good numbers, many of them carrying Coeloplana. As a matter of fact this Coeloplana was quite common here and as much material as wanted couid be had without any difficulty, the seastar living in quite shallow water, to be taken with the hands at low tide. Especially on the flats close to the little town Toeal it was quite common. The Coeloplana was found only on the said seastar, Echinaster luzonicus, never on any of the other species of seastars occurring in the littoral region of the Kei Islands {e. g. Archaster iypicus, Culcita novae-guinece, Linckia sp., Nardoa sp., Oreaster sp.). That it is not confined to the strictly littoral region is proved by the fact that it was found also on a specimen of the same Echinaster dredged at a depth of ca. 25 meters N. of the little islands of Doe- Roa (Kei Islands). The seastar being generally of a dark brownish colour, the bright coloured Coeloplana is exceedingly conspicuous on it (Fig. 4).^) It is not localized to any special part of the seastar, but may occur

1) I am greatly indebted to my friend and companion on the Expedition to the Kei Islands, Mr. Hialmar Jensen, for this excellent photograph. anywhere on it, on the upper or under side, on the arms or on the disk, creeping about with a slow, gliding movement, gradually altering its shape in a perfectly amoeboid manner; the small spines of the seastar thus form no hindrance to its moving about, the less so as these spines are not very close set. The Coeloplana sticks rather tenaciously to the seastar and is by no means easy to remove without damaging it; but by means of a pipette one may succeed in removing it. When then creeping on the bottom

Fig. 4. Ecbinasler luzonicus, with numerous specimens of Coeloplana astericola. From a photograph of a living specimen, taken by Mr. Hjalmar Jensen. Very slightly reduced. of a dish the Coeloplana assumes a more regular shape, transversely elongate, like that of Coeloplana gonoctena, as figured by A. Krempf,^) recalling by its general aspect very much a small Planarian. The largest specimens observed measured, when having thus assumed a more regular shape, ca, 1 cm in the tentacular axis, ca. Va cm in the sagittal axis. The figures 6— 9, PI. Ill give an impression of the various, more or less phantastic outlines which the Coeloplana may assume, fig. 7 giving very nearly the true morphological shape. Besides the tentacles no special structures are observed. When examined

1) A. K rem pf. Coeloplana gonoctena. Biologie. Organisation, Develop- pement. Bull. Biologique de la France et de la Belgique. LIV. 1921. under the binocular microscope (12 times magnification) the statocyst is seen, and four more or less regular series of knobshaped warts, principally in an arch of four, along each side of each tentacle base (PL III. Fig. 4). The warts are hollow, their cavity being in direct communication with the gastrovascular system, from which they are simple diverticles. They are retractile and often retract quite suddenly and so completely as to disappear entirely; there are no regular intervals between these retractions. Of the gastro­ vascular system only the outer ramifications along the margin of the body are discernible. — Colloblasts of the tentacles small, but of the normal structure. The statocyst (PI. III. Fig. 5) lies in an oval depression, resting on a uniform ciliation, not on specialized balancers. There is a strong, circular muscle along the edge of the depression. When it contracts, the cavity is closed and covered by six conical prominences, two pairs formed by the polar fields and one small at the transverse (tentacular) end by a thickening in the wall of the cavity itself (PI. III. Fig. 6). The clear, halfmoon shaped spaces seen to each side of the statocyst cavity in the sagittal axis are the excretory canals. — The polar fields are oval, with a restriction in the middle; they are quite simple, with no papillae whatever (Pi. III. Fig. 5). Outside each polar field is seen a distinctly ciliated canal, which opens on the dorsal side through the excretory pore; the pore was, however, never seen quite di­ stinctly, and the two canals were never distinct at the same time, the figure being thus far a composition. — Genital organs were not observed, only in one of the preserved specimens traces of what appears to be the testes are discernible, apparently arranged like those of Coeloplana gonoctena. — The oral surface is strongly ciliated, the aboral surface non-ciliated. The colour as seen in PI. ill Fig. 3, Is very striking, a deep red or claret ground colour with large, irregular spots of creamy- yellow (or the inverse). Unfortunately the colour conceals the internal structures to a great extent, the animal being, therefore, a poor object for studying the morphology on living specimens. As it could not be satisfactorily preserved by any of the reagents at my disposal (I had no osmic or Fleming’s fluid), I am thus unable to give a full account of its anatomy; but what could be discovered on the living animals leaves no doubt that its anatomical structure is essentially like that of Coeloplana bocki and C. gonoctena as described so excellently by Taku Komai^) and Krempf. The said difficulty of studying the anatomical structure of this Coeloplana on the living specimens, on account of the strong colora­ tion, is to some extent compensated by the easily observable fact that it propagates by autotomy. Very often its body is drawn out to such an extent that it seems quite lacerated (PI. Ill Fig. 9). 1 have not directly observed such drawn out parts to separate off from the main part of the body. But judging from the many very small, incomplete specimens that are found on the seastars together with fully sized specimens and such of all various sizes, and at a time of the year when ripe sexual products are not, or at most only exceptionally, found, it seems beyond doubt that it does propagate in this way that small parts of the body are detached and regenerate into the new individuals. It is not so that the animal divides into two equal halves, each of which regenerates the rest of the body; but evidently small parts from anywhere of the body are detached. That such minute parts are able to regenerate into complete animals has been shown by Krempf for Coeloplana gonoctena, the only condition being that both entoderm and ectoderm must be repre­ sented in the fragment. - - Of course, mutilations may account for some of the small specimens; but that all these small specimens should have originated from parts being removed by mutilation due to other organisms seems hardly possible, and it is, therefore, scarcely to be doubted that it is indeed autotomy that takes place. That these small pieces do really develop into complete specimens is sure enough. I have kept such small specimens in dishes for some days and seen them develop the tentacles and statocyst. The smallest specimens observed were 2— 3 mm in diameter; but Krempf has found that in Coeloplana gonoctena pieces of only Vs mm cut off from the body would regenerate into complete specimens, and there is every reason to expect that the same will be the case with the present species. On the other hand, it is worth mentioning that an experiment which I made in cutting a large specimen into two equal parts, through the sagittal midline, failed, the two pieces dying after a few days. Whether this was

Taku Komai. Studies on two aberrant Ctenophores, Coeloplana and Gastrodes. Kyoto 1922. due to accidental circumstances or perhaps to the animal not being able to stand such a cutting through its main axis, cannot be. decided, of course, from one single experiment. The facts other­ wise known with regard to the regenerative ability of Ctenophores (cf. the author’s paper ”On regeneration in Ctenophores”. Vid. Medd. Dansk Naturh. Foren. Bd. 66. 1913) decidedly lead to expect that also Coeloplana would stand any sort of cutting, and the pieces be able to regenerate, howsoever the division had been made. What the Coeloplana astericola feeds on I have not been able to ascertain. It may not be improbable that it feeds on small or­ ganisms found on the skin of the seastar, besides on what it may catch by means of its tentacles. That it also attacks the skin of the seastar may not seem improbable in the light of the fact observed by Krempf that Coeloplana gonoctena at times attacks the skin of the Alcyonarian on which that species lives. — But future researches must decide this and the many other problems connected with this new species of that in so many regards intensely interesting genus Coeloplana.

Explanation of Plate 111. Figs. 1—2. Beroe abyssicola n. sp. Fig. 1. Specimen showing natural coloration; drawn from life. About na­ tural size. - 2. Captive hairs from mouth edge of Beroe abyssicola. X 400. Figs. 3 — 12. Coeloplana astericola n. sp. Fig. 3. Specimen showing natural coloration; drawn from life. X 6. - 4. Specimen drawn from life, showing the statocvst and the four series of dorsai papillae. The specimen had only one tentacle, the other having been lost, by autotomy or mutilation. X 12.' - 5. The statocyst, polar fields and the openings of the excretory canals; these latter were never seen so distinct both at the same time; the figure being in this regard a construction, x 200. - 6. The same after the contraction of the circular muscle, showing six papillte covering up the cavity of the statocyst. The haifmoon-shaped spaces are the excretory vessels. X 200. Figs. 7— 12. Various specimens, of different sizes, from small, just detached pieces about to regenerate, to the fully developed form, with ex­ panded tentacles. X 5.

3.VI1I.27.

Andelsbogir>'kkeriet i Udense fMimy "

Th. M. del.