Cero reece tetet heen peanrenchabmg et eee ETM Ora abalgnteytcnaeesoeek See es otevepeen ee ie re machiotehareh nee ene Ta HtWateieny state poe nets eaenecte ees . ass Ncichburentenes.netgearhagines tase sashes Mee THE my SO Cr ery: INSTITUTED MDCCCXLIV. LONDON: MDCCOLVIII. i ih Y B , Vi Y ty LBL F-L; G na ". s d 2 THE OUR ANC FY DR Oso A DESCRIPTION OF THE CALYCOPHORIDH AND PHYSOPHORID OBSERVED DURING THE VOYAGE OF H.M.S. “RATTLESNAKE,” IN THE YEARS 1846-1850. WITH A GENERAL INTRODUCTION. BY THOMAS HENRY HUXEBY, PRS, 90.8. SHC. Gret: ACAD. IMP. LEOP. CAR. NAT. CUR.; PROFESSOR OF NATURAL HISTORY, GOVERNMENT SCHOOL OF MINES. LONDON : PRINTED FOR THE RAY SOCIETY. MDCCCLIX. MCZ LIBRARY HARVARD UNIVERSITY CAMBRIDGE. MA USA PRINTED BY J, E. ADLARD, BARTHOLOMEW CLOSE, LONDON. TO SIR JOHN RICHARDSON, M.D. F.RB.S., INSPECTOR OF HOSPITALS AND FLEETS, R.N., ETC., ETC. My pear Sir Jonn Ricnarpson, Since the time (now thirteen years ago) when, a subaltern under your orders, I learned to admire your character and to respect your high scientific attainments, we have met but rarely; and the arduous and perilsome service into which your sense of duty has led you in the interval, may well have obliterated from your mind all recollection of the fact that I owe to you those opportunities for scientific observation which I have enjoyed and have endeavoured to use. If I remind you of such a matter, it is only that I may seem less bold in venturing to dedicate to one so justly honoured as a man and so esteemed as a naturalist, these late first- fruits of a beginner in zoology. Tan, My dear Sir Jonn Ricuarpson, Yours very faithfully, THOMAS HENRY HUXLEY. Tae GoveRNMENT Scuoot or Mines, Jermyn STREET ; August 11th, 1859. batt We HATO LT \y i : tt FA, PR TARE in TA Cee * pha naat be Ah tema y rol 91 uh ae : mn re oe rT > cobwebs SEY, Glaitss fetal ak de Coste ui iT! even ) oe Sai omit in ie jet ce - eee Presa i) 0 AOE TU OE OUR tal A txtordyy juin gostei ta) bi! OPTS ead aah Yih i whi, leben ot elvis shoal sey be wingibes ta ort Daye i yom ‘wal - Oat) (AOR ddd iy Wolo Ue DATE (Oe WOT deine key ae Hise die dawiptiie with? aaa “rail Pi hatoute uth b vigelite Wott Oily of. HE PICTON: wr oid HOY. om aves E i Cy ae a a ey aiad Ae sdiatieean h ene i ott Gti aba) MAL nla hy: ky nay mbar Lc Wevcilk Wat's ann? Ya; mara ay hi. Ate) , TH lin i iil if" 1 Py ta ey: Ory: FS ant al is! i“ % Mola in iti pet Hin Ian ) Tere weer ree Ar A ; | te lh eal Cal ly “Tt is the opinion of the Lords Commissioners of the Admiralty that it would be to the honour and advantage of the Navy and conduce to the general interests of Science, if new facilities and encouragement were given to the collection of information upon scientific subjects by the officers, and more particularly by the medical officers, of Her Majesty’s Navy, when upon foreign service. : And it will be for their Lordships to consider whether some pecuniary reward or promotion may not be given to those who succeed in producing eminently useful results.”? \ In the autumn of the year 1846, Her Majesty’s Ship “ Rattlesnake” was commissioned by the late Captain Owen Stanley, who had been charged by the Admiralty with the duty of surveying the intricate passage within the Barrier Reef which skirts the eastern shores of Australia, and of exploring the sea which lies between the northern end of this reef and New Guinea and the Louisiade Archipelago. A very competent naturalist, Mr. J. Macgillivray, was appointed to the vessel, but Captain Stanley, justly appreciating the largeness of the field likely to be opened to students of Natural History by the cruise, desired to increase the strength of his expedition in this department of science. To this end, he applied to Sir John Richardson, at that time the Medical Inspector of Haslar Hospital, to recommend him an assistant-surgeon who should possess some knowledge of Natural History, or who, at any rate, had sufficient zeal and love for it to be likely to convert opportunity into knowledge. Since the spring of 1846, when I joined the medical service of the Navy, I had been doing duty at Haslar, under the orders of Sir John Richardson, who, always thoughtful and kindly in act, though sparing of words, to his subordinates, had, I suppose, noticed my bent; for, in the summer, I found that, without any solicitation on my part, he had endeavoured to obtain for me an appointment to the Haslar Museum. Failing in this, * Extract from a Memorandum by the Lords Commissioners of the Admiralty prefixed to the first edition of the “Manual of Scientific Inquiry prepared for the use of Her Majesty’s Navy,’ edited by Sir J. F. W. Herschel, and published in 1849. vill PREFACE. my chief still kept me in mind, and I shall not easily forget the day when, with Captain Stanley’s letter in his hand, he came to offer me that share in an exploring expedition which had been one of my childish ambitions, and which afforded the largest scope for the faculties, or, at any rate, the tastes, which had grown up with my manhood. I need not say how gladly I accepted the proffered appomtment. The “Rattlesnake” sailed in the winter of 1846; and as a full history of her voyage has been given to the world by Mr. Macgillivray, it is needful only to state that, after safely effecting her circumnavigatory voyage and successfully surveying the regions she was sent to explore, the ship returned to England, and was paid off on the 9th of November of the year 1850. Although occasionally in circumstances which might give rise to anxiety, no serious evil befel the “Rattlesnake,” or her crew, until her last return to Sydney, in the spring of 1850, when her Commander, whose health had been shattered by the trying climate of New Guinea, and by the still more wearing responsibilities of his office, sank with lamentable suddenness. I will not allude to the private circumstances which intensified the sadness of this sudden blow to all who were witnesses of it, but I can truly say that nothing could have been more unfortunate for the scientific interests of the expedition or for the personal welfare of the officers who had performed its duties and shared its fatigues. __ Captain Stanley possessed large means of influence, and as it was an eminent virtue of his to stand by his officers, there can be no doubt that, had he lived, his lieutenants, already men of standing and experience, would not have been left for years without promotion; nor would his and their hydrographic labours have been indistinguishably merged in those of other persons; nor would the official naturalist of the expedition have been refused the means of publishing the narrative of the voyage; nor, in all probability, would the present work be making its appearance so many years after date. In truth it is to the explanation of the circumstance that all the original illustrations in my plates were drawn between the years 1847 and 1850 inclusively, and that all my observations, with the exception of those on Porpita, were made so long ago, that I feel it necessary to devote these prefatory remarks. The facts are these. I made a good many observations during our cruise, and sent home several papers to the Linnean and Royal Societies; but of these doves, or rather ravens, which left my ark, I had heard absolutely nothing up to the time of my return; and, save for the always kind and hearty encouragement of the celebrated William MacLeay, whenever our return to Sydney took me within reach of his hospitality, I know not whether I should have had the courage to continue labours which might, so far as I knew, be valueless. PREFACE. ix On reaching England, however, I found not only that the Royal Society had thought my Memoir on the Medusze worthy of publication, but helping hands were stretched out to me on all sides; and among the men of science, 1 met with many generous friends whose sympathy and appreciation were bestowed ina measure far beyond my deserts. Among these, the genial and noble-minded Edward Forbes supported me with all that energy which he was wont to throw into his advocacy of the cause of a young man; and now that I have succeeded (though, alas! not replaced) him in the professorial chair he then held, and have some personal experience of an analogous variety of occupations and weight of responsibilities, I cannot reflect without emotion on the patient attention which he bestowed upon me, and the self-sacrificing zeal with which he exerted all his “ power, amity, and authority” in my favour. On reviewing the materials which I had collected with this experienced friend, it seemed that some of my work might fitly be sent in the form of papers to the learned societies; while, on the other hand, the more copious observations upon the MJeduside, Calycophoride, and Physophoride, might better be published in a separate form; and Forbes and other friends of weight were of opinion that the work had sufficient value to justify the Government in aiding its publication. We were the more readily led to hope for this aid, as, in the year 1849, the Lords of the Admiralty had caused a Manual of Scientific Inquiry to be published, and had prefixed to it a Memorandum containing the enlightened and liberal expressions and promises quoted at the head of these pages. And it will be observed that their Lordships’ distinct promise of encouragement to naval officers who should do good work was wholly irrespective and independent of any other aid given by the Government to Science. Clearly, therefore, supposing my work to have any value—and in favour of this suppo- sition I had all sorts of high testimony—I had a claim upon the Admiralty for aid in bringing it out, and a simple person might have imagined that that claim would be strengthened by being the first that had been made (to my knowledge) since the publication of the Minute. I do not know that I can accuse their Lordships of refusing my application, for they took the simpler course of rendering it impossible I should make one. Before my ship was paid off, I applied in due form, through my commanding officer, for a simple permission to publish; and, when one thinks of the Memorandum, there is a touch of humour about the reply which he received: “I have been commanded to convey to you their Lordships’ full sanction to his (my) so doing (¢.e. publishing). . . . . . . But I have to add that their Lordships will not allow any charge to be made upon the public towards the expense.” Nevertheless, the writer hopes that “he will produce a work alike creditable to himself, to his late Captain by whom he was selected for it, and to Her Majesty’s Service.” x PREFACE. , Even could J have flattered myself that I had succeeded in producing “eminently useful results,” I fear this letter would have effectually damped any hopes of “pecuniary reward or promotion,” or other aid, which I might have formed; but my friends were not content that I should make bricks without straw, and, by dint of considerable exertion, they got me a nominal appointment, so that my assistant-surgeon’s pay ran on, while they endeavoured to obtain the £300, required for the publication of my book, from the Government. It would be wearisome were I to narrate the history of their other efforts at length. In vain the Presidents of the Royal Society and of the British Association, separately and con- jointly, officially and unofficially, solicited the Treasury ; in vain did I visit and write to, and I fear, bore, numerous persons in authority about this unfortunate grant. It must be confessed the business was troublesome enough while it lasted; but, in looking back, I would fain only remember with gratitude the zeal of the friends who aided me, and the long-suffering courtesy of the various Government officials, who listened so attentively to the claims of that Natural Science about which, unless I am greatly mistaken, they neither knew nor cared very much. During the three years the contest lasted, I reckon that the Admiralty was good enough to give me, in the form of pay, rather more than fifty pounds over the sum required, although, with steady consistency, their Lordships from the first refused to enable me to publish the work which they paid me for publishmg. I by no means quarrel with an arrangement, which, although very annoying at the time, has been of the utmost service to mie; for when, in 1854, their Lordships, as I suppose, weary of our pertinacity, cut the knot by calling upon me to serve afloat, new prospects had. presented themselves, and, in giving up my commission, I obtained the long-sought funds for publication—the adminis- trators of the Government Grant no longer objecting, that the Admiralty was pledged to supply its officers with funds for the publication of work done in its service. I offer my hearty thanks to the Government Grant Committee for this aid, and, in conclusion, I must apologise to them and to the Ray Society—who two years ago under- took to publish my book—for the delay which has occurred in bringing it out. I can only plead the pressure of new and heavy official duties in palliation of my seeming dilatoriness ; and I may add that, since 1850, so much has been done by the eminent German observers, whose works are incessantly quoted in the following pages, that the literature of the subject, slight enough when my observations were made, has attained considerable dimensions ; and its study has retarded the progress of my book, as much as it has increased my knowledge of the organization of the Oceanic Hydrozoa. As it is, I have been obliged to omit the Meduside, which were included in my original plan, and the illustrations of whose organization are already engraved. I trust that they may yet some day see the light. THE OCEANIC HYDROZOA SECT. I. MORPHOLOGY OF THE HYDROZOA. TuE body of every Hydrozoon is essentially a sac, composed of two membranes, an external and an internal, which have been conveniently denominated by the terms ectoderm and endoderm. The cavity of the sac, which will be called the somatic cavity, contains a fluid, charged with nutritive matter in solution, and sometimes, if not always, with suspended solid particles, which performs the functions of the blood in animals of higher organization, and may be termed the somatic fluid. The ectoderm is commonly ciliated, at any rate while young; the endoderm is also very generally ciliated, though not always, nor in all parts. The cilia of the endoderm, aided by the contractions of the walls of the body, are the sole means provided by nature for the circulation of the nutritive fluid in the Hydrozoa; the cilia of the ectoderm, similarly aided by contractility, constitute the only respiratory mechanism. Notwithstanding the extreme variety of form exhibited by the Zydrozoa, and the multiplicity and complexity of the organs which some of them possess, they never lose the traces of this primitive simplicity of organization; and it is but rarely that it is even disguised to any considerable extent. I know of no Hydrozoon in which the two primary membranes, but little altered, cannot be at once detected in the walls of almost every part of the organism. This important and obvious structural peculiarity could hardly escape notice, and I find it to have been observed by Trembley, Baker, Laurent, Corda, and Ecker, in Hydra; by Rathke, in Coryne; by Frey and Leuckart, in Lucernaria; and it is given as a character of the Hydroid polypes in general (//ydre, Corynide, and Sertulariade) in the second edition of Cuvier’s ‘Lecons.’ I pointed it out as the general law of structure of the Hydroid polypes, Diphyde, and Physophoride, in a paper’ sent to the Linnean Society, from Australia, in 1847, but not read before that body until January, 1849; and I extended the generaliza- tion to the whole of the 4ydrozoa in a ‘ Memoir on the Anatomy and Affinities of the Meduse,’ read before the Royal Society in June, 1849. ' «Observations upon the Anatomy of the Diphyde, and the Unity of Organization of the Diphyde and Physophoride.” Aun abstract of this essay was published in the ‘ Proceedings of the Linnean Society’ for 1849. f I / 2 THE OCEANIC HYDROZOA. Professor Allman, in his valuable ‘Memoir on Cordylophora’ (‘ Philos. Trans.,’ 1853), has adopted and confirmed this morphological law, introducing the convenient terms “ ectoderm and endoderm,” to denote the inner and outer membranes; and Gegenbaur (‘ Beitrage zur niheren Kenntniss der Schwimmpolypen,’ 1854, p. 42), has partially noticed its exemplification in Apolemia and Rhizophysa ; but it seems, singularly enough, to have failed to attract the attention of the other excellent German observers, to whose late important investigations I shall so often have occasion to advert. The peculiarity in the structure of the body-walls of the Hydrozoa, to which I have just referred, possesses a singular interest in its bearing upon the truth (for, with due limitation, it is a great truth) that there is a certain similarity between the adult states of the lower animais and the embryonic conditions of those of higher organization. For it is well known that, in a very early state, the germ, even of the highest animals, is a more or less complete sac, whose thin wall is divisible into two membranes, an inner and an outer; the latter, turned towards the external world; the former, in relation with the nutritive liquid—the yelk. The inner layer, as Remak has more particularly shown, undergoes but little histological change, and, throughout life, remains more particularly devoted to the function of alimentation, while the outer gives rise, by manifold differentiations of its tissue, to those complex structures which we know as integument, bones, muscles, nerves, and sensory: apparatus, and which especially subserve the functions of relation. At the same time the various organs are produced by a process of budding from one, or other, or both, of these primary layers of the germ. Just so in the Hydrozoon: the ectoderm gives rise to the hard tegumentary tissues, to the more important masses of muscular fibre, and to those organs which we have every reason to believe are sensory, while the endoderm undergoes but very little modification. And every organ of a Hydrozoon is produced by budding from one, or other, or both, of these primitive membranes ; the ordinary case being, that the new part commences its existence as a papillary process of both membranes, including, of course, a cecal diverticulum of the somatic cavity. Thus there is a very real and genuine analogy between the adult Hydrozoon and the embryonic vertebrate animal; but I need hardly say that it by no means justifies the assumption that the Mydrozoa are in any sense “arrested developments” of higher organisms. All that can justly be affirmed is, that the Hydrozoon travels for a certain distance along the same great highway of development as the higher animal, before it turns off to follow the road which leads to its special destination. The entire double-walled body of the Hydrozoon, whether it be a minute, simple, oval sac, as in the embryonic condition, or such a vast and complex mass as a tree of Plumularia, an Agalna three feet long, or a Rhizostoma of still more massive proportions, will be termed, in the course of the ensuing pages, a Aydrosoma. The simplest condition of this hydrosoma is that observable in the common fresh-water Hydra, one end of whose body is expanded into a kind of disc, whereby the creature adheres to its support, while the opposite extremity presents a widely-open mouth, opening into a cavity which extends through the whole length of the animal, and surrounded by a circle of long tentacular organs. Here, then, the body exhibits only three distinct morpholo- gical constituents: a disc of attachment—which, with its homologous organs in other Hydrozoa, may be termed the /ydrorkiza; a sac for the digestion and (as there is, in this case, no dis- MORPHOLOGY. 3 tinct somatic cavity) for the distribution of nutriment—the po/ypite ; and, lastly, organs for prehension—the éevfacu/a. Furthermore, at particular seasons, tubercular elevations are developed, which contain either an ovum or spermatozoa, and are the reproductive organs. A polypite and reproductive organs are, in fact, the sole essential constituents of any Hydrozoon, but, so far as I know, no member of this group has yet been discovered of so simple a composition. Organs of prehension and of fixation, or of flotation at least, are always superadded, and, in the majority, there is more than one polypite. But when this is the case it becomes necessary to distinguish between the polypites and the common trunk on which they are supported. To the latter, Professor Allman’s term of ca@zosare is very use- fully applicable ; and it will be found convenient, in treating of these more complex forms, to speak of the hydrosoma as composed of a coenosare and appendages, the latter being those specially modified parts of the hydrosoma which subserve the functions of support, locomo- tion, alimentation, and so forth. I will now proceed to point out the principal modifications which are undergone, first by the coenosarc, and next by the appendages, throughout the //ydrozoa. The Cenosare. The ccenosare of the Corymde and Serfulariade has the form of a branching stem, resembling that of a plant, and presenting almost as many diversities in form and habit. It may be slender and creeping, or twining; or it may simulate a tree, with stout, erect trunk, and multitudinous branches, arranged according to a definite pattern; or its ramifications may run into a sort of fleshy expansion, as in Hydractinia. In these orders, especially in those forms which possess an erect and branching stem, the coenosarc is usually strengthened by the development of a strong cuticular layer upon the exterior of its ectoderm. This structureless, or at most laminated, cuticular substance, may remain in close contiguity with the rest of the ectoderm, or, as in the Campanularia, may become separated by a greater or less interval. In the latter case, it seems at first sight as if the wall of the ccenosare were composed of three membranes instead of two; but the examination of young organs will clearly show that the outermost or cuticular layer is nothing but an excretion from, or metamorphosis of the outermost substance of, the ectoderm. In the Calycophoride, Physophoride, Lucernariade, and Meduside, no such thick and hard cuticular layer is developed, and, consequently, the ceenosare remains, throughout life, soft and flexible. In the two former orders it is never tree-like, and when it gives off branches they are exceedingly short. In some few of the Lucernariade, on the other hand (Rfizos- tomid@), the coenosarc is regularly branched, but, nevertheless, is extremely different from that of the Sertulariade. The coenosare of the Calycophoride is slender‘and filiform; that of the Physophoride varies from extreme slenderness and elongation to a spheroidal or discoidal shape. In both these orders it is excessively contractile, a property which it owes to the abundant muscular fibres developed in its walls, principally in the ectoderm. So far as I have observed, these fibres are always disposed longitudinally (except perhaps in Stephanomia) ; but other investigators describe transverse fibres. 4 THE OCEANIC HYDROZOA. The transverse section of the filiform and tree-like coenosares is usually nearly circular, but in some Physophoride (Forskalia, e.g.) it is said to be reniform, from the presence of a deep longitudinal groove on one side. The coenosarc, as has been stated, always contains a cavity filled with nutritive fluid— the somatic cavity. The endoderm lining this cavity is in many, if not in all, Corynide and Sertulariade, provided with cilia, whose motions are, in many cases, so directed as to give rise to currents in opposite directions on opposite sides of the cavity. The like phenomenon has been observed in his “ Agalma rubra” (LHalistemma, mihi) by Vogt (p. 64); and cilia have been noticed on the endoderm of the ccenosare of many Physophorida. 1 have observed them in Physalia, Velella,and Rhizophysa. Gegenbaur (p. 42) saw them in Rhizophysa and Apolemia. Kolliker, however, denies the existence of cilia on the endoderm of the ceenosare in Morskalia, Agalma, and LTalistemma and is silent with respect to the other species of Physophoride which he describes, except Velella and Porpita, in which the ciliation is distinctly mentioned. Leuckart (Z. U., p.4) agrees with Kolliker in denying cilia to the first- named genera. Will (‘ Hore,’ p. 78) expressly affirms that the inner wall of the ccenosare of Diphyes exhibits as lively ciliary motion as that of the polypites; but I could never verify this state- ment, nor find cilia on the endoderm of the csenosarc (except at its proximal end) in any of the Calycophoride. On the contrary, I have distinctly observed and noted the fact, that solid particles, which, so long as they are in the cavity of the polypite, exhibit a lively rotatory motion, impressed upon them by its cilia, lose that rotation the moment they pass through the pyloric valve into the somatic cavity, and then either remain stationary, or are forced sud- denly along it, backwards or forwards, by the contractions of its walls or of the attached organs. Leuckart and Kélliker have been equally unable to find cilia in any part of the somatic cavity of the Calycophorid@, except its proximal dilated end; but Gegenbaur affirms that it is ciliated throughout in his Diphyes gracilis (= D. Sieboldii of Kolliker, in which, however, that observer distinctly states no cilia exist), and in Praya maxima (‘ Beitriige,’ p. 21). In the Zucernariade and Meduside, the inner surface of the endoderm is, so far as I have seen, everywhere ciliated. The Appendages. Before attempting to describe the structure and relations of the manifold appendages of the Hydrozoa, it will be necessary to determine the corresponding ends of the hydrosoma throughout the series of forms, a task which is not quite so easy as it may at first appear to be. The Hydra is fixed by one end, which is ordinarily lower than the other, and may be regarded as the base; and the end which answers to this is inferior, or basal, in all’ the Corynide and Sertulariade. But the Calycophoride swim with the corresponding end upwards or forwards. The Physophoride float with it upwards. The Lucernariade have it sometimes upwards and sometimes downwards. It would be impossible, therefore, to designate the corresponding ends by the terms “upper and lower” throughout the series without great risk of confusion. Under these circumstances I think it will be best to discard such phraseology, and to employ the terms “ proximal” and “ distal” for the same object. MORPHOLOGY. 5 In fact, the growth of every hydrosoma is, absolutely or relatively, stationary towards one end of its axis, while it takes place with rapidity towards the other. This growing extremity, therefore, is, as it were, constantly moving away from the opposite end, and the open mouths of all the polypites are turned more or less in its direction. Hence, I shall call this the distal end, while the other, comparatively fixed, extremity may be regarded as proximal. The latter is the basal or lower end in Hydride, Corynide, and Sertulariade. It is the anterior end, in the actively swimming Diép/yes, the upper end, in Hippopodius and the Physophoride. It is the upper side of a Medusa, Cyanea, or Rhizostoma ; the lower, or attached, end of a Lucernaria, and of a larval Cyanea or Rhizostoma. The distal extremity of the hydrosoma is always, so far as I am aware, either cecal, or ends in a polypite, but is never modified into any other appendage. The proximal end is variously metamorphosed in the Hydride, Corynide, and Sertulariade ; and becomes a Aydrorhiza, either expanding into a disc, or sending out many radicles, by which it attaches itself to other bodies. In the Calycophoride (Pl. V, figs. 3 and 4), the proximal end of the ccenosarc dilates a little, and becomes ciliated internally, forming a small chamber, which gives off the ducts, by whose intermediation the systems of canals, which embrace the cavities of the organs of loco- motion, are brought into communication with the somatic cavity. At its upper end, this chamber is a little constricted, and so passes, by a more or less narrowed channel, into a variously shaped sac, whose walls are directly continuous with its own, and which will hence- forward be termed the somatocyst. The endoderm of this sac is ciliated, and it is generally so immensely vacuolated as almost to obliterate the internal cavity and give the organ the appearance of a cellular mass. The somatocyst very commonly contains large, strongly refracting globules of an apparently albuminous matter, of precisely the same character as those which may be observed occasionally to pass through the pyloric valves of the polypites, into the somatic cavity ; and I do not doubt that the globules result from the accidental accumulation of such products of digestion. Not unfrequently an air-bubble may be seen in the somatocyst, whither it has travelled, there can be but little question, by the same channel, being either swallowed with the prey or accidentally sucked in by a polypite, whose mouth has been raised above the surface of the water. Such a chance bubble has of course no relation whatever with the air contained within the float of a Physophorid; and it is somewhat surprising that any one acquainted with both structures should have imagined the existence of even an analogy, still less of a homology, between them. The float or pxeumatophore characteristic and diagnostic of the Physophoride is, indeed, a most remarkable and well-defined structure (Pls. VI, VIII, &c.) In these Hydrozoa the proximal end of the ccenosare expands into a variously shaped enlargement, whose walls consist of both the ectoderm and endoderm, and which encloses a wide cavity in free communication with that of the ccenosare, and, like it, full of the nutritive fluid. From the distal end or apex of this cavity depends a sac, variously shaped, but always with tough, strong, and elastic walls, composed of a substance which is stated to be similar o to chitin in composition,’ and more or less completely filled with air. 1 At least in Velella, See Leuckart, Z.N.K., p. 114, 6 THE OCEANIC HYDROZOA. In the adult, this sac, which I shall term the preumatocyst, is sometimes open at the apex (Physalia, Rhizophysa), and can communicate with the exterior by a pore which traverses the ectoderm of the pneumatophore. In other cases its apex is shut, but the pneu- matocyst has other external openings (Vedella, Porpita); and, lastly, in Physophora, Forskalia, Agalma, Halistemma, and Athorybia, no external opening at all has hitherto been discovered. In certain of these genera (Lorskalia, Agalna, Halistemma), the pneumatocyst appears to be widely open below. I suspect that more careful examination would show that it only becomes very thin; but however this may be, it is a mistake to suppose that there is any communication between the interior of the pneumatocyst and that of the coenosarc.’ In fact, as I have particularly noted,’ in Physalia, Velella, Rhizophysa, Physophora, and Agalma, the endoderm of the pneumatophore is reflected on to the pneumatocyst, where the latter is in contact with the walls of the pneumatophore, and completely invests it, forming a loose bag over the apparent inferior aperture, in those genera which possess one. The pneumatocyst is thus firmly held in its position by the reflected endoderm, and in some genera (forskalia and Agalma) additional support is afforded by septiform processes, which pass from the lateral walls of the pneumatocyst to those of the pneumatophore. These were first described by Milne Edwards in his admirable Memoir on Stephanomia (Forskalia) contorta,> in which he says, that “the air-vesicle is open below, and retained in a central position by membranous partitions disposed in a radiating manner, and stretched between its parietes and those of the great pyriform cavity (of the upper end of the stem), nearly in the same way as the mesenteries by which the alimentary canal is surrounded in the Alcyonian polypes.” I find no notice of these suspensoria in the works of either Vogt, Gegenbaur, or Kojliker, and Leuckart expressly states (Z. U., p. 6) that he has ‘sought in vain for the suspensoria described by Milne Edwards in Sfephanomia.” I observed them, however, very distinctly in Agalma. (See the description of that genus 7”/rd.) A very peculiar structure is attached to the distal surface of the pneumatocyst of Rhizophysa (P). VIII). A great number of elongated, and more or less branched, processes, in fact, project freely from it into the cavity of the pneumatophore. Each process consists of a cellular axis, invested by the ciliated endoderm. The cells of the axis are clear and very large, measuring as much as jth of an inch in length, and have an opaque, oval ‘‘nucleus’’ xath of an inch in diameter, with an oval or circular nucleolus of ;4,th of an inch in diameter. Quoy and Gaimard would seem to have originally observed these appendages, and they have since been carefully described by Gegenbaur. Nothing of the kind appears to have been seen in other Physophoride, but in Velella and Porpita, the hepatic organ occupies the same position, and hence one is led to suspect a relation between the two structures. It does not appear to me that these ramified processes have any real resemblance to the pueumatic filaments attached to the distal surface of the pneumatocyst in the last-named genera. * See Leuckart, Z. U., p. 6, and Z. N. K., p. 67, who states of the pneumatocyst of Apolemia ; “Die untere Oeffnung derselben die in den Reproductionskanal hineinfuhrt.”’ * Gegenbaur describes the same structure in Rhizophysa, and Leuckart in Apolemia and Forskalia, so that the rule doubtless holds good for all Physophoride. 3« Aunales des Sciences Naturelles,’ t. xvi, 1841. MORPHOLOGY. 7 In form, the pneumatocyst (and the pneumatophore which contains it) varies from that of a spheroid (Riizophysa, Athorybia) or of an elongated oval (Physophora) to that of a cylinder with a narrow inferior neck (Aga/ma), or an irregular, pear-shape (Piysalia), or the figure of a flattened disc (Velella, Porpita). No less does one genus differ from another in the proportional size of this apparatus. In Péysalia, Velella, and Porpita, it occupies almost the whole of the hydrosoma, and constitutes the largest and most conspicuous part of the body, while in such genera as 4yal/ma and Forskalia it attains to only such insignificant proportions as to be readily overlooked.. Its functional importance, of course, depends very nearly on its relative size. When it is large it must necessarily play a very considerable part in determining the habits of its possessor, though we have at present no information as to whether it acts as a permanent buoy or whether it can be voluntarily emptied and filled again.’ When the pneumatic apparatus is so small in proportion to the rest of the organism, as in many Physophoride, on the other hand, its office in the economy ceases to be easily comprehensible, and can hardly be very important. : The last modification of the proximal end of the hydrosoma of which I have to speak is an organ—I mean the disc or wmbrella of Lucernariade—which is commonly confounded under one head, with others—the nectocalyces—of quite distinct structure; apparently, because, like the latter, it acts as an organ of propulsion. Nevertheless, in development, in structure, and in even in mode of action, the umbrella is altogether distinct from any other organ possessed by the Hydrozoa. ’ Iam inclined to think that the rudiments of this structure are visible in the Hydride, and in some Corynide and Sertulariade. Yn examining a Hydra carefully, it is seen that the tentacles do not immediately surround the oral aperture; but they arise in a circle at some distance below it, so that the oral aperture is supported on a kind of conical crater, from whose base they take their origin. In some Campanulariad@, this separation of the polypite into a distal and a proximal portion is still more marked. The latter ends distally in a truncated disc, from whose edges the tentacula spring, while the oral division of the polypite is longer than the basal, and arise from the truncated face of the latter by a narrow neck. The like structure is observable in the “Hydra tuba,” the larval form of the Lucernarian Medusa, and from hence to the structure of Zwcernaria, there is but a step. In the latter genus, in fact, the discoid, proximal portion of the polypite, or proximal end of the hydrosoma, is greatly enlarged, and produced into eight obtuse lobes, each of which gives rise to a few short tentacles; while the short distal division of the animal lies in the middle of the disc. In Zubularia, the buds which give rise to the reproductive organs are developed from the surface of the polypite within the margins of the proximal disc and internal to its 1 There is very little good evidence to be met with on this much disputed question. I have seen part of the contained air to all appearance voluntarily expelled from the pneumatocyst of Rhizophysa, and Forskal appears to have witnessed something of the same kind, for he says of his Physophora filiformis : “ Vivee, vesica aere plena, tamen subsidere possunt ; dum corpus arctando, se reddunt specifice graviores.” Eschscholz found, on irritating a young Physalia five lines long, that it “ suddenly expelled all the air from the bladder, and sank to the bottom of the glass” (p. 159). 8 THE OCEANIC HYDROZOA. series of tentacula. In Zucernaria, the reproductive organs are developed in the same way from the surface of the body on the distal side and within the margins of the disc, into which the proximal division of the body is expanded. The mode of origin of the Lucernarian Meduse from their larve is such, that their umbrella is clearly, like that of Zucernaria itself, nothing more than a lobed expansion of the body-walls, and as in Zucernaria, the reproductive organs are developed on the distal surface of this expansion. The peculiar lithocysts of these Zucernariade are developed in the deep notches which mark the ends of the lobes of their umbrella. It will be seen presently, that in the mode of development just described, in its lobed margins, and in the absence of any muscular membranous valve attached to its circum- ference, the umbrella is wholly different from all other organs of natation. Such is the general structure of the axis of the hydrosoma, and of its anterior and posterior terminations, throughout the Mydrozoa. The different orders exhibit many remarkable variations in their number, kind, and mode of attachment. To begin with the last-mentioned point, it is to be observed that no regularity is traceable in the arrangement of the appendages in many Corynide; while in others, and in the Sertulariade in general, the branchings of the ccenosare and the disposition of the appendages upon it, follow a very definite law, to which the regular and symmetrical forms of the organisms are due. The appendages may be developed on one or on both sides of the coenosarc. In such Physophoride as possess a filiform coenosarc (e.7., Agalma, Morskalia, Stephanomta), the appendages appear to be always fixed to only one side of it. And even the strikingly radiate disposition of some of the appendages in Forskalia and Stephanomia, for example, does not result from their forming exceptions to this rule—for their appendages are all really attached to one side of the stem only—but is due partly, perhaps, to a spiral twisting of the ccenosarc, but in a much more important degree, to the manner in which these appendages are forced by their peculiar form, to adapt themselves to one another. Whether the appendages in Physophora, Velella, Porpita, and Physalia follow the same law is not certainly made out. In the Calycophoride 1 am inclined to believe that all the appendages are primarily attached to one side of the ccenosarc, and that the subsequent opposition of the necto- calyces to one another, and of the hydrophyllia to the polypites is a secondary modification. The following distinct kinds of appendages exist in the Mydrozoa, and will now be successively described. 1. Polypites; 2. Tentacula; 3. Hydrocysts; 4. Hydrothece ; 5. Hydrophyllia; 6. Nectocalyces; 7. Reproductive organs, consisting of Gonodlastidea and Gonophores; 8. Lithocysts. 1. Polypites. By this term I understand the principal organ of alimentation of a Hydrozoon. It would be wrong to call it merely a stomach, for it is much more; and the word “ polype ” has been, and is, used in so many senses that it is better avoided. Every polypite is essentially a sac, open at one end, which serves as a mouth, while at the other it communicates with the somatic cavity. The oral end is usually produced into a thin, flexible, and very disténsible lip, whose edges are either quite simple (Hydride, MORPHOLOGY. 9 Corynide, Sertulariade [all?], Calycophoride, Physophoride), or are produced into longer or shorter folds or processes (many J/eduside, Lucernarian and other). I have above referred to the division of the polypite into a distal and a proximal portion in many L/ydrozoa. In the Calycophoride and Physophoride, the polypite presents, in many cases, a further division into a proximal (“basal-stiick”’ of the Germans), a median, and a distal division. There is no distinct line of demarcation between the two latter, but in many cases the median and basal divisions are very sharply separated, not only by their texture, but by a distinct valve (Pl. V). This, in the Calycophoride, is a very well marked structure, though I do not find it noted by any of those writers whose works I have consulted. It isa strong, circular fold of the endoderm, whose lips, when the valve is shut, project into the cavity of the gastric, or median, division of the polypite. As the oily or albuminous globules which result from the digestive process are formed, they usually accumulate close to the valve, and are kept constantly rotating by the cilia which line the gastric chamber. After remaining for a while in this position, the fundus of the gastric chamber contracts, and forces the globule through the valve, which appears to dilate at the same moment. The position and functions of this apparatus, therefore, fully justify the appellation of a pyloric valve. The proximal division of the polypite usually takes on the form of a peduncle, which is sometimes very long, and gives origin to various appendages. Its walls are ordinarily thin and muscular, but the endoderm is sometimes much vacuolated, and partially obliterates its cavity. The median division of the polypite is the widest of the three, and has the thickest walls. In it the process of digestion goes on, and hence it may with propriety be termed the gastric division. The inner surface of the endoderm is richly ciliated, and not only is its general thickness considerable, but in many Calycophoride and Physophoride it is developed into larger or smaller, slender, conical, villous elevations. These villi are larger and more distinct in Physalia (where they attain the length of ;th of an inch or more) than in any other Hydrozoon I have examined (see the description of that genus, zz/rd) ; but they are very well developed in Athoryéia. In both genera they exhibit in their interior one or more clear spaces or vacuoles, sometimes obscured by a quantity of dark pigment, and they contain numerous thread-cells (Pls. IX, X). In Lhizophysa, Physophora, Diphyes, Abyla, and other Calycophoride, the villi are represented by shorter processes of the endoderm, which are sometimes obsolete, all that remains of the villus being the characteristic clear vacuoles, imbedded in the endoderm, and the production of the endoderm into ragged-looking filaments over them. Kolliker and Vogt describe similar organs in Hippopodius and Praya, so that such short villi would seem to obtain universally among the Calycophoride. In the Agalmopsis of Sars, in Agalma, Forskalia, and Apolemia, the villi take on the form of longitudinal ridges, which usually contain much pigment, and thus give a very marked character to the gastric division of the polypite. They have been confounded with reproduc- tive organs. Gegenbaur (p. 28) describes the vacuoles in the villi of Praya maxima as cells. “The contents of these cells differed greatly, sometimes appearing perfectly clear, at others yellowish or brownish, and, in this case, frequently consisting of minute particles. The colour then shines through the walls of the polypite. I corisider these to be hepatic cells, 2 10 THE OCEANIC HYDROZOA. analogous to those cellular elements which coat the gastric cavity and the intestines of ce 7 so many of the lower animals.” In his Diphyes gracilis, Gegenbaur states that the “cells possess a distinct double contour and a nucleus, neither of which have I ever observed. “There can be no question,” he adds, “that these elements must be regarded as glandular cells; and their ultimate fate is in favour of this view. For we find between them empty depressions, with sharply defined edges, which correspond exactly in form and size with those in which the cells in question are imbedded. These depressions can be hardly anything else than the spaces formerly occupied by such glandular cells, which have burst and emptied their secretion.” Kolliker (p. 26) gives a still more definite account and figure of the structure of the villi and vacuoles in 4thorybia. He considers them to be “glandular sacs of the simplest kind,” also that they are “open sacs, lined with cells,” and inclines to the opinion that their function is hepatic. Leuckart takes the same view of the cavities in the villi of the ph iuscg as myself, regarding them not as cells, but as vacuoles (Z. N. K., p. 68). Vogt (p. 102) appears also to consider the cavities of the villi in Praya to be vacuoles and not cells; and he gives an account of an experiment, which would be well worth repeating. “Having mixed indigo in the water of a vessel containing a lively Praya, I saw after some time that the digestive cavities were streaked with blue, the colouring matter being detained by the villi (Zowrrelets); and I convinced myself by microscopic examination that the colouring granules existed only in the cellceform spaces, which are nothing else than shallow depressions or widely open glandular sacs.” Without by any means denying the posstbility that the vacuoles (for such mere excavations full of fluid I must confess they always appeared to me to be) contain a special secretion, I am inclined to think that the villous emmences in which they are imbedded have other functions. I once observed a half-digested mass in the stomach of an Athorybia, all the villi in the neighbourhood of which were much elongated, and thrust into it. The ends of these villi contained fewer thread-cells than usual, while many thread-cells were scattered through the mass of food. Is it not possible that when the living prey is introduced into the gastric cavity, its struggles may be restrained and cut short, not only by the mechanical application of the elongated villi, but by the shooting out of the threads of the numerous thread-cells with which they are provided : Allman’ has described structures corresponding very closely with these vacuolated villi in Cordylophora, and it is therefore probable that something of the same kind will be found in other Hydrozoa. But, so far as I know at present, the only structures in the Lucernariade to be compared with the villi are those solid tentacular filaments, with vacuolated axes, which project from the endoderm into the stomach or into the somatic cavity. They are, like the villi, covered at their extremities with abundant thread-cells. The villi and vacuoles are confined to the gastric division of the polypite. The walls of the distal or buccal division are thin and smooth, but richly ciliated internally. 1 «Anat. et Phys. of Cordylophora,” ‘ Phil. Trans.,’ 1853, MORPHOLOGY. 11 2. Tentacula. All the //ydrozoa possess more or less numerous filiform appendages, abundantly provided with thread-cells, and subserving purposes of offence or defence, which receive the general name of tentacula, though they differ very widely in structure and place of attachment. In the Hydride, Corynide, and Sertulariade, numerous tentacula are always attached to the body of the polypite itself, and they usually form a circle not very far below the mouth, though sometimes they are scattered irregularly (Coryne, Cordylophora), and sometimes form a double circlet (Zwbularia). The Calycophoride and most Physophoride have single tentacula springing from the base of the gastric division of the polypite, or from the peduncle just on the proximal side of that base. But in the Pdysaliade and Velellide, the tentacles are wholly distinct from the polypite, arismg by themselves from the coenosarc. In the Lucernariade and Meduside, finally, the tentacles are developed from the margins of the umbrella and from its under surface. The tentacles of the Hydride, Corynide, Sertulariade, Lucernariade, and Meduside, are always extremely simple in structure, consisting, at any rate primarily, of tubular processes of the endoderm and ectoderm, enclosing a diverticulum of the somatic cavity, and sometimes clavate at the ends, or presenting little papillary elevations, but hardly ever branched. The internal cavity is sometimes persistent, but it very commonly becomes almost obliterated by the vacuolar thickening of the endoderm; and when this has occurred, the tentacles usually appear as if they had a solid cellular axis. Besides these ordinary tentacles, certain Sertulariade possess organs which must be ranged in the same category, though they differ greatly from them in position and in external appearance. These xemafophores, as they have been termed by Mr. Busk, are cecal processes of the ccenosarc, invested by a continuation of its hard cuticular layer, so as to be quite firm and inflexible. The cuticular investment, however, is open at the end, and in the soft substance beneath the opening le a number of large thread-cells. These bodies are particularly characteristic of the Plumulariade. The tentacles of the various genera of the Physophoride and Calycophoride differ very widely in structure, gradually increasing in complexity as we advance along a series, the lowest term of which is Ve/el/a, and the highest Physophora. The tentacles of Vele/la, in fact, differ in no essential respect from those of the Hydride and Sertulariade ; they are simple cecal processes of the wall of the ccenosarc, with a greatly vacuolated endoderm (Pl. XI). Those of Porpita have the same fundamenta. structure, but they are branched at the ends. The tentacles of Apolemia are described by Leuckart and Gegenbaur’ as simple, tapering, unbranched filaments, which are beset with large thread-cells on one side, and are traversed by a narrow, ciliated canal. One of these tentacles is said to arise from the base of each polypite. The tentacles of Physalia (Pl. X) exhibit an advance on this structure. They arise inde- pendently from the ccenosarc, and each is provided at its base with a large, pyriform, saccular ' ZN. K., p. 69; Gegenbaur, p. 40, 12 THE OCEANIC HYDROZOA. dilatation—the basal sac. The tentacle itself is a filament which in a large specimen attains the length of many feet when fully extended. It has no lateral branches, but itis beset along one side, at regular intervals, with reniform enlargements, full of large thread-cells, which are disposed transversely to the axis of the tentacle, and look like so many beads threaded upon it. On the opposite side, the tentacle widens out into a ribbon-like muscular band, which, attached above to one edge of the basal sac, is the agent of its rapid and extensive contrac- tions. A canal traverses the whole length of the tentacle, and sends cecal diverticula into the reniform enlargements, while above, it communicates with the cavity of the basal sac. It has been supposed that the latter organ, by its contraction, drives the liquid which it contains into the canal of the tentacle, and thus effects its elongation. Without denying that such may be its office, I would remark, that the tentacles of other species which are not provided with basal sacs are just as capable of rapid elongation. The reniform enlargements to which I have referred may be regarded as rudimentary latera) branches. If they be supposed to elongate and become filamentary, the result will be a tentacle very similar to that possessed by Rhizophysa, except that in this genus there is no basal sac, nor muscular band, and that each tentacle is attached to a polypite. The lateral branches of the tentacles of RAzzophysa have one wall much thicker than the other, but it contains only spheroidal thread-cells, and the branches are not divided into distinctly characterised regions. In Forskalia, however, while the tentacles have essentially the same structure, each lateral branch is divided into three distinct portions: a proximal slender part; a median division, with one wall much thicker than the other, containing numerous elongated thread-cells, arranged in transverse rows perpendicularly to the wall, and flanked on each side by a longi- tudinal series of larger oval thread-cells; and, finally, a terminal cylindrical thread, full of small, rounded thread-cells. I shall term the first of these regions the pedicle, the second the sacculus, and the third the filament. The muscular band of Physalia is partially represented by two pairs of muscular cords, which, according to Leuckart (Z. N. K., p. 99), lie in the thin wall of the sacculus. In the contracted state, the sacculus and the filaments are thrown into spiral coils. The structure of the tentacles of Halistemma is essentially the same, except that they are provided with a more complex muscular apparatus, fora description of which I must refer to the works of Vogt and Leuckart. The tentacula of the Calycophoride (Pl. V) resemble those just described, and arise either from the base of the gastric division of the polypite, close to the pedicle, or from the latter itself. The larger, oval thread-cells are confined to the distal end of the sacculus, which is usually bent so as to have a half-moon shape, the thick wall forming the convexity. The filament is coiled up into a close spire, folded against the straight, thin wall; and, where it joins the sacculus, the points of five or six oval thread-cells commonly project, like those of the rowel of a spur. Where the peduncle joins the sacculus it exhibits a small dilatation, which I conceive to be a rudiment of a part to be described presently as the involucrum. Leuckart has particularly described a structure in the sacculus of the Calycophoride, where it has also been noticed by Vogt and Kolliker, which he terms the “ angelband.” It is “a simple, but strong and sharply defined, muscular cord, which is folded in zigzags, and lies in the posterior (thin) wall of the canal of the sacculus, partly covers it at the MORPHOLOGY. 13 sides, and then appears to be coiled almost spirally around it. The upper end passes gradually into the pedicle, while the lower extends as far as the beginning of the filament. In Praya and /7ippopodius, this cord has a diameter of about ;’,th of an inch, and differs in no essential respect from the muscles in other parts of the body, especially in the stem, although at times a slight transverse striation can be detected in it. In Diphyes, and still more in Abyla, however, this muscular cord becomes gradually thicker during its course, so as even to attain as much as ;,th of an inch in 4dy/a, and therewith assumes a very distinct transverse striation, so that, especially in Aéy/a, it might be compared to the most beautiful transversely striped muscular fibres. No nuclei can be observed in this cord, nor can its sheath be distinguished from its contents. It appears as if the transverse striation were caused by a regular jointing, for the edges of the cord are completely incurved at intervals, corresponding with the constrictions between the joints. In ddy/a, furthermore, this muscular filament is but little flattened, and becomes triangular in many places by the mutual pressure of the superimposed folds. If one of the thin edges be accidentally turned directly towards the microscope, the transverse striation readily leads one to suppose that two series of transverse rods are imbedded in the cord, as I indeed previously supposed to be the case.” (ZN. K., p. 19.) I confess I entertain great doubts as to the real nature of this structure, which is particularly worthy of the attention of future observers. In the tentacles of Stephanomia (Pl. VII), which, in many respects, resemble those of Halistemma, a new part makes its appearance, in the shape of a sort of hood, which is developed at the junction of the pedicle with the sacculus, and encloses the latter like a cup. I term this the czvolucrum. It is a solid, lamellar process of the ectoderm, containing no internal cavity. The sacculus is very long and spirally coiled, terminates in a single filament, and has a well-developed muscular band in its thin wall. In the genera Agalma and Athorybia, the involucrum has become much larger in proportion to the sacculus, and the latter is terminated, not by a single filament, but by two filaments, between which the sacculus ends in a clear, thin-walled, median lobe, devoid of thread-cells, and said to be contractile by Leuckart and Kolliker, though in the species I observed it exhibited no such faculty (Pls. VI, IX). Finally, the tentacular branches attain their utmost complexity in Physophora, the spheroidal involucrum here completely investing the sacculus, which lies coiled up within it, and having undergone other changes, which will be particularly described under the head of that genus (PI. VIII). 3. Hydrocysts. I apply this name to certain singular organs which are found more particularly in the Physophoride, and which resemble nothing so much as the imperfectly developed polypites of the species to which they belong. As such, indeed, I always considered them, until the perusal of the works of Philippi, Leuckart, and Kélliker, led me to modify my opinion. These investigators term the organs in question “fihler” and “taster,” and are 14 THE OCEANIC HYDROZOA. inclined, not without a great show of reason,’ to regard them as organs of prehension and touch, to which may perhaps be added excretory and respiratory functions. The hydrocysts are always pyriform sacs, composed of the ectoderm and endoderm, shut at their apical or distal ends, where they are commonly provided with large thread-cells, but, at their proximal ends, in free communication with the somatic cavity. Like the polypites, they usually give origin to a tentacular appendage. But this is always simple and filiform, and the hydrocysts further differ from the mere polypites in their closed apices and in the general absence of villi. The latter, however, exist in a rudimentary state in the hydrocysts of Apolemia, according to Leuckart (Z. N. K., 70), and I have seen them in the closed sacs, which appear to be hydrocysts, of Physalia (Pl. X). These bodies are not found in Velella or Porpita, and 1 must confess I am very doubtful, whether the structures to which Ihave just referred in Péysalia are other than young polypites. In the Stephanomiade they are attached to the ccenosarc, between the polypites, and are usually in more or less close relation with the reproductive organs. In Physophora (Pl. VIII) a circlet of large hydrocysts is interposed between the nectocalyces and the polypites, and in