u^ EIC RRA Pre PLC M : Y Ses Jt NO B EIU i ^ as nM "no = AASS 3 RTRA SE Be pron ; j Yir f. Eun rm ci zy 2 X eer - Sans Serr hae NIU ate ard x. nC : X (y V ah: Bans t " ^E: aes e ENS d E zt ft iu mE 3 Po DUAE Y Sees ES RS OR : zn ts rohan on. k EONS SA EREN oe PEE aoee EN jia Ey UP T DEUS ene Bs S DECUS Maes, POR vens vg P renee pt Cr MS GALBRAITH & HAUGHTON'S SCIENTIFIC. MANUALS A MANUAL SUB-KINGDOM : C@LENTERATA. BY x ist E REAY GREENE, B.A. Esso or Mahura! HISTORY IN THE QUEEN’S CO S ; i &e. &c. LONDON: E -ONGMAN, GREEN, LONGMAN, AND ROBERTS. 1861. x Price Five Shillings. A MANUAL OF THE SUB-KINGDOM CHLENTERATA. By the same Author. ——— | | ANUAL of PROTOZOA: with a General | | LEE on the Principles of Zoology, p numerous | Woodc p. 8vo. 2s. | aS HIS te first menn of a series of scienti manuals appro- priately dert d sub-kingdom of | explained, and in few par graphs the Enid did opinions of | | fa everal ralists are noticed and animals of the simplest organization, | ANT EA "This part promises well y of which we have been accus- | for the whol = ach vo e will, ome o associate wit l r ^ is anno unced, ontan a con e veget: ingdom. | exposition of the dh ment of science These hitherto obscure be re here upon which it treats,— a the subject- iefly but carefully treated ; and within | matter of these Manuals will be so ar- a compass of less than a hundred pages aiea as t me, pos suitable for a con able amount of information | students of various degr profi- them is conveyed, including the | ciency a l as for self-instruction. recent researches of minute and | The present, as an example, forms a Sentido observers. he Spongide, | good text-book for a wer 25 students.” for example, are clearly and concisely | UM. | London: LONGMAN, GREEN, and CO. Paternoster Row. | $ ET SQUARE LONDON : PRINTED BY SPOTTISWOODE AND CO. NEW-STKE GALBRAITH & HAUGHTON’S SCIENTIFIC MANUALS Evperimental and Natural Science Series. 1 MANUAL OF THE ENIMAL KINGDOM. A. 7 II. CELENTERATA. COT ME mm co I-A M. A BY PROFESSOR J. REAY GREENE. UN ee ae en U4 ii LLECTI ON aii ines LONDON: LONGMAN, GREEN, LONGMAN, AND ROBERTS, 1861. MANUAL OF THE SUB-KINGDOM CŒLENTERATA. BY JOSEPH REAY GREENE, B.A. PROFESSOR OF NATURAL HISTORY IN THE QUEEN’S COLLEGE, CORK, &c. &c. asi Muse / v PENON =AL EN M LL LONDON: LONGMAN, GREEN, LONGMAN, AND ROBERTS. 1861. PREFACE. ‘THE house that is a-building looks not as the house that is built.’ The present Manual, though now issued as complete, is, in truth, but the abridgment of part of a larger work which the Author trusts may yet one day see the light. The general arrangement of the subject-matter here devised does not seem to require any expla- nation. Had the Author sought to evade those delays and difficulties with which, in almost every paragraph, he has found it his duty to contend, another, and far easier, plan might have been chosen. A thoroughly scientific method seemed, however, more likely to prove useful. And, in the discussion of questions hitherto considered unsusceptible of general treatment or, perhaps, insufficiently known to men of science themselves, he has not endeavoured, by the invention of diffi- culties which in nature have no existence, to hide truth beneath the patchwork veil of a meagre quasi-originality. Rather has it been his wish to vil PREFACE. unfold, in the clearest and simplest language at his command, phenomena which, as a student, he has himself earnestly striven to comprehend, Keenly, indeed, does he regret the deficiencies of style and want of artistic combination which, but too frequently, it is feared, will be found to mar his pages; believing, as he does, that for the in- _terpreter of nature there is a standard of literary excellence not less high than that of the poet or historian. In the select bibliographical list appended to the end of the Manual will be found the names of those writers from whose published works has been derived that assistance which the Author would now, gratefully, acknowledge. In particular to Professor Huxley are his best thanks due, for, without access to the original memoirs of that naturalist, the second chapter, on the Class Hy- drozoa, could never have been rightly completed. But the Author must confess himself under deeper and less formal obligations to the same philosophic investigator, whose rich and suggestive seeds of thought could not, from their nature, fail to fall fruitless on the soil of any patient mind. From Professor Allman, also, who has done so much to promote a right knowledge of the Celen- terata, the Author has not been denied kind aid. PREFACE. ix And of foreign naturalists, personally unknown to him, he would especially single out, for courteous thanks, Professors Gegenbaur, R. Leuckart, Milne Edwards, and Agassiz. To Mr. Gosse the Author is indebted for the loan of the beautiful drawings from which two of the woodcuts have been copied. The wood-en- graver, Mr. William Oldham of Dublin, has exe- cuted his share of the following pages in by no means an unsatisfactory manner. Mr. Busk, the Rev. Thomas Hincks, and Dr. Strethill Wright have also supplied the Author with some valuable facts touching the structure of the fixed Hydrozoa. Queen's College, Cork * April, 1861 August, 1861. Professor Max Schultze has just published a memoir on Hyalonema in which he confirms the opinion that the beautiful siliceous fibres of this organism are, in truth, to be regarded as spicules d » Sponge, allied, in some respects, to Hwplec- tella. Very recently, Professor Agassiz (op. cit. (71) p. 256), from personal examination of the living ‘animal of Millepora, has concluded that the x PREFACE. entire division of Tabulata, and, perhaps also, the Rugosa, can no longer be associated with the undoubted Actinoid polypes, but find, rather, their true place in the neighbourhood of the genus Hydractinia. The details of these observations having not yet fully appeared, it seems premature to adopt the important systematic change thereby indicated. CONTENTS. CHAPTER I. THE SUB-KINGDOM CQ@LENTERATA. Page 1. General characters.—2. Classes . 5 : CHAPTER II. THE CLASS HYDROZOA. SECTION I. MORPHOLOGY AND PHYSIOLOGY OF HYDROZOA 1. Type of the Class: Hydr. a,—2. General Morphology.—3. Or- —7. Nervous Be and oe of Sense.— 8. EARN Organ : SECTION II. DEVELOPMENT OF HYDROZOA SECTION III. CLASSIFICATION OF HYDROZOA . Classification. —2. Order 1: Hydride nide. — 3. Order 2: Cory- —4. Order 3: E a Order 4: oin ride.—6. E ue 7. Order 6: Medusidx —8. Order 7: Lucernaride CONTENTS. SECTION IV. DISTRIBUTION OF HYDROZOA. E puerum to Physical Elements. — 2. i Distri- pa bution.—3. Geographical Distribution SECTION V. KELATIONS OF HYDROZOA TO TIME . e LÀ . 130 CHAPTER III. THE CLASS ACTINOZOA. SECTION T. MORPHOLOGY AND PHYSIOLOGY OF ACTINOZOA. 1. Type of the Class : Actini eral bai. ogy. — 3. n.—7. Muscular ion. — 8. Nervous bi sai and Organs of Sense.—9. Reproductive Organs 3 SECTION II. DEVELOPMENT OF ACTINOZOA SECTION III, CLASSIFICATION OF ACTINOZOA. I san? —2. Order 1: Zoantharia.—3. Order 2: Alcyo- ia.—4. Order 3: Rugosa.—5. Order 4: Ctenophora .. 196 SECTION IV. DISTRIBUTION OF ACTINOZOA. I. ea, to Physical Elements. — 2. BH metrical Distri- butio . 251 —3. Geographical Distribution CONTENTS. xlii SECTION V. RELATIONS OF ACTINOZOA TO TIME. ic General History of Actinozoa. — 2. History of Zoantharia. Poi 2: ory of Rugosa.—4. History of Alcyonaria.— - rian Corals Devonian Corals.—7. Carboniferous Corals 8. Permian Corals. — 9. Triassic Corals. — Jurassic Corals. — 11. Cretaceous Corals, — 12. Tertiar y Corals. — 13. Recent Actinozoa . . . + 226 BIBLIOGRAPHY OF THE CXELENTERATA : s - 249 QUESTIONS ON THE C@LENTERATA . : : 2257 Lisr or ILLUSTRATIONS , . . : S2 OT NDEX 4 : . . . . . 25203 THE SUB-KINGDOM CHLENTERATA. Ql LI COQZLENTERATA. CHAPTER I. THE SUB-KINGDOM CQG£LENTERATA, 1. General characters. — 2. Classes, I. General characters.— The animal forms included under the sub-kingdom Celenterata pre- sent modifications of a type of structure better marked than that which is characteristic of the Protozoa. All are furnished with an alimentary canal, freely communicating with the general, or somatic, cavity. The substance of the body consists essentially of two separate layers, an outer, or ‘ectoderm,’ and an inner, or ‘endoderm.’ These two membranes, but especially the former, are in general provided with cilia. Another distinctive characteristic of the Celen- terata is found in the presence of the peculiar urticating organs, or ‘thread-cells,’ which are met with so constantly in the integument of these organisms ( fig. 1). Thread-cells, for which the term ‘cnide’ has been proposed, usually occur as: colourless, trans- parent, elastic, double-walled sacs, rounded or B2 4 THE SUB-KINGDOM CQ@LENTERATA. oval in form, and containing a fluid in their interior. The outer wall of the sac is entire and very delicate ; the inner one is much stronger, having its open extremity produced into a stout, rather fusiform, sheath, which terminates ina long thread, Fig. 1. Sii ( Ae = Urticating organs of Du —a, e, and f, thread- nr í Caryoph, "es Smithii; b, thread-cell of eu ynactis Allma portion of the marginal canal of Willsia stellata, with pei receptacle, containing thread-cells, arising therefrom; d, a single thread-cell of the same ; g, thread-cell of Actinia (or Bunodes) crassicornis. (All magnified. ) or *ecthorzeeum.! A number of barbs or hooks are sometimes disposed spirally around the sheath, the ecthoreum itself being often delicately ser- rated. In the ordinary condition of the thread- te EGG THE SUB-KINGDOM CŒLENTERATA, 5 cell the ecthorzeum lies twisted in many irregular coils round its sheath; the barbs of the latter being closely appressed to its sides, while it com- pletely fills up the open end of the inner sae, into whose interior it projects. Under pressure or irritation, the cnida suddenly breaks, its fluid escapes, and the delicate thread is projected, still remaining attached to the sheath. So quickly is this done that the eye can by no means follow the process, but, in all probability, a complete ever- sion of the cell’s contents takes place. In some cnide the presence of a sheath has not yet been discovered. Thread-cells vary much both in form and size. They are unusually large in the Portuguese Man- of-war (Physalia), where they are spherical in figure and attain a diameter of :003 of an inch. The relative dimensions of the thread and cell also vary. Sometimes the ecthorzum is scarcely longer than the sac; in other cases its length is nearly fifty times as great. The disagreeable stinging sensations experienced when the human skin is brought into contact with the bodies of some Coelenterata is, by most zoólo- gists, attributed to the influence of the thread-cells. tis supposed that the irritation is in part me- chanical, arising from the friction of the filament or its sheath, and in part chemical, from the assumed poisonous nature of the fluid contained within the cell. The ease with which many Colenterate animals seize and, as it were, para- lyze their struggling prey, is also ascribed to the same agency. These stinging propensities were evidently known to Aristotle, who refers to dif- ferent forms of the present group under the name B3 6 THE SUB-KINGDOM C(ELENTERATA. of axadndy, a term understood by some modern naturalists in a more restricted signification. A few of the Coelenterata are microscopic, but by far the majority are of appreciable size, and some attain considerable dimensions. Multiplica- tion by gemmation is of common occurrence among the members of this sub-kingdom, and when, as frequently happens, the growths thus formed re- main permanently in connection with the organ- ism from whieh they originally sprouted, it is evident that this process, repeated several times, may give rise to aggregate masses, the limits of which it is not possible to define. In form the Coelenterata vary considerably, presenting, in many cases, an external resemblance, sufficiently re- markable, to certain members of the vegetable kingdom. The Celenterata possess no proper blooa-vascu- lar apparatus, distinct from the somatic cavity or its processes. The cilia which line the endoderm promote by their motion the circulation of the nutritive, or somatic, fluid occupying the general. cavity of the body, and, in like manner, respiration is effected by the cilia of the ectoderm. Both of these ciliary movements are assisted by the con- tractions of the body walls, within which muscular fibres may, not unfrequently, be observed. In- dications of a nervous system and organs of sense have been met with only in a few instances. Other structures, whose function would seem to be se- cretive, are not, however, wanting. Most of the Coelenterata are provided with prehensile append- ages, or * tentacula,’ and, in many of these animals, special organs, adapted for locomotion, are super- THE SUB-KINGDOM C(ELENTERATA 7 added. Throughout the entire of this department the elements necessary for discharging the function of true reproduction would appear to be present. The power of emitting a phosphorescent light is eminently possessed by several Coelenterata. This is more especially seen among the oceanie species which, together with Noctiluca, and other floating organisms, serve to produce the luminosity of the sea. The Ccelenterate organism, therefore, has not only a plan of structure, or relative position of parts, peculiar to itself, but, viewed also as a mere animal machine, is seen to be, physiologically, in advance of the Protozoón. A comparison o ultimate morphology of the two groups may serve - further to elucidate this proposition. The body of the Protozoón, as elsewhere we have shown, consists chiefly of the elementary tissue known as sarcode, or animal protoplasm; a soft, often transparent, elastic and extensile substance, albuminous in composition, and presenting the faintest traces of organisation. The sarcode body is also remarkable for the manifold diversities of outward form which it may assume, though in many Protozoa there is little which deserves the name of integument, and an inner eavity, whether it exists under the form of contractile vesicle or alimentary track, is rudi- mentary in the highest degree. Some authors consider the Sponges as Coelenterate, but the aquiferous system of these animals, however other- wise it may appear, is, in truth, lined by the outer surface of the organism. B4 8 THE SUB-KINGDOM C(ELENTERATA. Nevertheless, the homogeneity of the primi- tively simple sarcode is liable to become diver- sified by the two processes known as *vacuolation' and ‘fibrillation.’ By vacuolation, clear spaces and granules arise in its substance, of which ex- amples are furnished by lg om eee m o [I] we ct O g ck oct ehis Of ple or rh. pite HYDROZOA. 47 panularia, for example, columnar gonoblastidia arise in the angles between the stem and branches of the ccenosare, or from the sides of the branches _ themselves (figs. 10 and 19). The lower portion . of each gonoblastidium forms a sort of peduncle, above which the cuticular investment of its ec- toderm becomes separated as an urn-shaped cap- gule, the *gonotheca. Such capsules, or “ ovigerous . vesicles," are very variable and beautiful in form. True gonophores, protected by the gonotheca, are borne along the sides of its axial column. In some Calycophoride and Physophoride, particular regions of the hydrosoma may devote TU themselves to the performance of the reproductive ' function, and, becoming separated from the rest of the fabric, subsequently undergo a surprising amount of modification. Finally, in the Lucernaridc, with the exception © of Lucernaria and a few closely-allied genera, the reproductive bodies are produced by fission from ss polypites of almost microscopic minuteness; and, in their detached condition, grow with such ra- ; pidity as ultimately to attain a weight of many . pounds, or even hundreds. A corresponding ad- vance in structure attends this vast increase of , size. Each, at the outset of its free existence, . includes a complete transverse segment of the polypite from which it has separated. This soon forms a lobed swimming organ, or umbrella, with _ the hooded lithocysts before mentioned. From the centre of the umbrella hangs a large polypite, - whose lips, in such genera as Aurelia, Cyanea, and Chrysaora, form lobes of considerable length, on T the folds of which serve as temporary receptacles 48 HYDROZOA. for the ova during the earlier stages of their development (fig. 7,6). The interior of the poly. pite leads to a large central cavity, situate in the substance of the thick gelatinous umbrella, and Fig. 7. Oceanic forms of Lucrrnarmm:—a, Rhizostoma pulmo; b, Chrysaora hysoscella ; c, its lithocyst. (Al reduced.) lined by a layer of endoderm which sends pI” longations into the system of anastomosing canals communicating with a marginal vessel, fringed,” its turn, by a series of tentacular diverticula. The generative products are lodged in saccular Pp!” —e nmn n 00080 HYDROZOA. 49 ne di cesses of the lower portion of the central cavity, EUN immediately above the bases of the radiating | EM canals, and, being usually of some bright colour, orm a conspicuous cross shining through the _ thickness of the disc. But in Rhizostoma, Cephea, and Cassiopeia, a different arrangement prevails, which is best de- à! scribed in the words of Professor Huxley. | “In the Rhizostomide, a complex, tree-like 4l brella, therefore, there is a chamber whose floor J is formed by the quadrate disc, while its roof is | constituted by the under wall of the central cavity _ of the umbrella, and its sides are open. The re- . productive elements are developed within radiat- . ing, folded diverticula of the roof of this genital cavity” (fig. 7, a). nim This is, without doubt, the most complicated ei!) structural product presented by the class, and its description forms a not inappropriate conclusion n to the preceding general survey of their organisa- ich 9" tion. ost; 06 me eh The majority of Hydrozoa are dicecious, the "^ . same hydrosoma not bearing both male and female | E 50 : HYDROZOA. reproductive bodies. Exceptions, however, occur in Hydra itself, in Cordylophora, in Plumularia innata, in many Physophoride and Calyco. phoride, Diphyes being an exception. The re. productive zoóids of the Lucernaride, except in the case of Chrysaora, appear to be unisexual, but it is not yet ascertained whether generative | bodies of dissimilar sexes can be produced by the fission of one primitive hydrosoma. As in other animals, fecundation is effected by the contact of ova and spermatozoa: the sper- maria and ovaria, when fully developed, becoming wholly resolved into these essential elements. The spermatozoa present the form of ovate cor- puscles, from the broad end of which a filament projects. The ova are, in most cases, spherical, destitute of vitelline membrane, with distinct germ-vesicle and germ-spot. Diffusion of the - spermatozoa in the surrounding water seems, in the present class, the usual prelude to the act of fertilisation. But, in Cordylophora, it has been supposed that the male elements can alone obtain access to the ova by reaching them from within along the general cavity of the body. HYDROZOA. ol SECTION II. DEVELOPMENT OF HYDROZOA. Tue fertilised ovum, in all the Hydrozoa, under- goes yolk-division. This process would seem to be determined by the previous division of the germ-vesicle, which, according to Gegenbaur, in some of these animals at least, does not disappear immediately after fecundation. The embryo which results may be developed from the whole, or only a portion, of the vitellus. It usually appears as a minute, free-swimming ciliated body, but, in some instances, presents a different aspect. The ectoderm and endoderm of the adult Hydrozoón correspond with the inner and outer layers into which the blastoderm of the embryo soon separates, the cavity which is at the same time formed representing the somatic cavity of the future animal. Hyprip#.—The modification of one end of the body into a hydrorhiza, the formation of a mouth, and of tentacular processes, are the only changes, save those of growth, which seem needed to bring such an embryo into the condition of a perfect Hydra. But observations are yet wanting on the development of this organism. The re- searches of Laurent point to the conclusion that, in the production of the young Hydra, a part only of the ovum is directly concerned. The polypite thus resulting from a true genera- tive act may subsequently, by gemmation, give E 2 29 HYDROZOA. rise to several others, in all respects similar to the organism from which they were produced. These for a time may remain in connection with each other, but, more usually, they separate, each in its turn, under favourable conditions, to repeat the same budding process The number of inde. pendent beings into which a single Hydra, when well supplied with food, and stimulated by a warm temperature, may resolve itself, is certainly as- tonishing. Not less so are its reparative powers, which seem almost to defy the knife of the ana- tomist. Full details on this subject are given by Trembley, whose researches on the Hydra, pub- lished in 1744, are still well worthy of perusal, Some years ago, Ecker compared the periplastic tissue of the Hydra to aggregate masses of the sarcode, or “ formless contractile substance," com- posing the body of Ameba. Mr. G. H. Lewes has also recognised distinct * contractile masses,’ which he says were so very like Amæbæ, as to make him at first believe that the Hydra had swallowed them. Such ameceboid particles occa- sionally become detached by the method denom- nated “ diffluence,” each usually including one 0 more endoplasts ; but there is good reason to infe that their apparently contractile movements aie for the most part, the result of a process of él dosmose. Jäger, however, has shown that tw budding Hydre, each kept by him in a small | vessel of water, broke up into several isolated particles, which, after the lapse of a month, we still living, performed amoeba-like movements and, in some instances, passed into a peculiar stage, resembling the encysted condition of Inf soria. In this state, Jäger supposes, they maf t t 1 HYDROZOA. 53 remain throughout the winter, and again, on the return of spring, once more assume the aspect of the primitive Hydra. 5 772 a pony e E e X Í V | RI ELIT M x == y Mia ICM HESS deren N e, ur the embryo in its attached condition; f, pe ve polypite, Hes d there- from; g, androphore of the same Cordylophora, its contents es- eaping under pressure ; h, cat cells eee therefrom; 4, spermatozoa. (All magnified.) 54 HYDROZOA. CorYNID&. In Cordylophora, the free swim. ming ciliated embryo, on emerging from the ruptured gonophore (jig. 8, b), is usually of ap elongated oval form, but very contractile, so thai often it assumes a pyriform figure (fig. 8, c and d). Eventually, the embryo loses its cilia, and, fixing itself, developes a hydrorhiza at one extremity and a mouth at the other, thread-cells being at the same time formed in the ectoderm (fig. 8, e and f) Next, a series of about four tentacles make their appearance; these are soon succeeded by others; the somatic cavity becomes fully formed, and the young Cordylophora, increasing in size, is invested with a delicate cuticular layer. The rudimentary coenosare, with its single polypite, formed in this manner, soon commences to sen forth prolongations, and these, by gemmation, develop the polypites and other appendages of the adult organism. A somewhat different series of changes occur in Tubularia (fig. 9). The embryo of this genus is not ciliated, but first makes its appearance às a discoid body, from the circumference of which short thick processes, the rudiments of tentacula, centre of the opposite side. The mouth thet elevates itself on a conical prominence, around which a second series of tentacles arise. In this state the embryo issues from the gonophore (fig. 9 d). Remaining free for a short time, it finally becomes fixed, and developes a ccenosare with its cuticular layer (fig. 9, e and g). à : HYDROZOA. 55 à j iy Fig. 9. b ters consisting of several gonophores, borne on a long branching iy fro’ stalk; c, a single gonophore, containing two young polypites, one jing! ^ of which has commenced to extricate itself; d, the same gono- " : jı phore, in a more advanced condition ; e, a young polypite, thirty- ; ih "ES hours after having escaped fro e gon e; J, the now younger polypite, shown within the gonophores ¢ and d 27 the yee, a polypite e, six weeks after extrication. (a is about thrice the e. natural size: the others are much magnified.) ET Tubularia, like Hydra, and, in all probability, ? ij many other Hydrozoa, possesses well-marke _ parative powers. When living specimens have E 4 56 HYDROZOA. been kept for some days in vessels of sea-water it often happens that the polypites drop from their stalks. Soon, however, new polypites are budded forth, each having usually a smaller number of tentacles than its predecessor. Similar are the results produced by artificial fission. In this manner, by section of a single stalk, Sir J. G. Dalyell obtained, in the course of 550 days, twenty- two successive polypites. SERTULARIDE. In most Corynide, the course of development closely corresponds with that above Development of CAMPANULARIA : —a, Campanularia Loven; b n fit bl tidia fram wh LA - 4. 4 A ifor , m i . . . L L x $ gonophores, one of which is giving exit to a ciliated embryo; 4 cessive stages of the young coenosare developed therefrom; ^ B oO a m E B N [9] o m [er o luc] S "S & 3 & 8 zi & = e o Se Q 3 & 3 le] = ec , . . P JP, hydrotheea ; P, gonoblastidium. (a and f are about twice the natural size; the others are much magnified. ) described as taking place in Cordylophora. Of a similar character, in its more general features at LL ME Cu 1M gu eee ee: zc e S \ Í HYDROZOA. 57 least, is the life history of the Sertularidæ. The young Campanularia or Antennularia, at first free, soon loses its cilia, fixes itself, and contracts into a circular dise, which exhibits a division into four lobes (fig. 10, c and d). In the centre of the dise an opaque spot makes its appearance, and over this the surface becomes gradually elevated, until, finally, a young ccenosarc is the result (fig. IO, €). From this, by gemmation, the branching hydrosoma of the complete organism, with its crowded assemblage of polypites, is subsequently produced. Thus the young condition of a Sertularid would appear to differ from that of a Corynid in having a portion of its ecenosare more or less completely developed before distinct traces of a polypite can be observed. Such a conclusion accords well with the composite structure always assumed by the adult hydrosoma. And in this respect the Sertu- laridee, while departing from the Corynide, seem to agree with the oceanic orders, Calycophoride and Physophoride. CALYCOPHORID4E. Of the earlier embryonic changes in the Calycophoride little is known. In Diphyes, according to Gegenbaur, the blasto- derm at first appears as an elevated protuberance, occupying only a portion of the segmented vitellus. Soon, this blastoderm forms a rudimentary necto- calyx, from which a short canal leads to the ciliated cavity of the yolk below. The nectocalyx then rapidly enlarges, while polypites are seen to arise between it and the appended yolk-mass. PHYSOPHORIDÆ. Our knowledge of the em- bryology of the Physophoride is confessedly scanty. 58 HYDROZOA. - Er e youngest examples of the group seen as yet, ~ Development of Puysarra: —a, young Physalia, with a single polypite and tentacle; 5, the same, more advanced ; c, adult Phy- salia; d, a tentacle, with its basal sac;—a, pneuma ophore ; pneumatocyst; m, polypite; 7, tentacle. (a and b are magnified; c is reduced; d is about the natural size.) exhibit a well-defined pneumatophore, with a single polypite and tentacle (fig. 11, a). 8) Th, 7 "P, HYDROZOA. 59 In a Velella, less than ‘1 of an inch long, ob- served by Mr. Huxley, * the horizontal dise of the adult was represented by a bell-shaped, mem- branous expansion, continued above into a broad crest, half as high as the whole depth of the Wainial. It was “symmetrically disposed, and its superior edge, far from being pointed, was rather concave, and in the tantre presented a curious thickening. The central polypite was already open at is distal extremity, and around -its base were a few short, cæcal processes, the rudiments of the gonoblastidia or of the tentacles. The margin of the dise was occupied by a single series of large, oval vesicles. The somatic cavity was divided by a series of vertical septa, which passed continuously over the pneumatocyst into the crest, near whose free edge they terminated abruptly, and between them other very short septa were interposed. The somatic cavity and its continuation into the crest were thus broken up into a series of parallel [ciliated] canals, united at their ends by two marginal canals at right angles with one another, one in the disc, the other in the crest. The pneumatocyst shone through the dise, and did not extend into the crest at all.” It appeared “as an almost hemispherical body, convex above and flat below. On two of its sides, in a plane perpendicular to that of the crest, there was a double crescentic mark, caused by a depres- sion. The air did not completely distend the pneumatocyst, but appeared to be divided into seven or eight lobes below, so that, at first sight, the organ itself appeared to be lobed, but this was not really the case. It was, in fact, in the smallest specimens a simple vesicle, about ‘05 of 60 HYDROZOA. an inch in diameter, with strong and thin walls, which, when it was burst and the air expelled, fel] into sharp folds.” MEDUSIDXE.—The development of the true Me- duside has yet to be effectively studied. From the observations of J. Müller on Æginopsis, of Gegenbaur on Trachynema and Cunina, and o Fritz Müller on Liriope, it seems highly probable that these genera proceed at once from the con- dition of the embryo to assume the aspect of the organism which gave them birth. Still more con- clusive on this point are the results of some recent researches of Claparéde on a Medusid closely allied (if not belonging) to the genus Liu. Within the substance of the body-wall of the de- Development of Lazzta:—a, adult Lizzza, the walls of whose polypite are seen to bear numerous ova; b, supposed free-swin* ming young of a, viewed from below; c, the same, seen in pl file. (ais slightly, b and ¢ are very much, magnified.) pendent polypite were observed numbers of what seemed to be true ova, some furnished with germ- vesicle and germ-spot, others in a more advance stage of development. These last resembled H HYDROZOA. 61 form and structure certain free floating bodies (fig. 12), each of which, though still enclosed in an outer covering, presented, on a reduced scale, distinct indications of various parts observed in the adult Medusid; four radiating canals, and eight tentacular enlargements, being especially notice- able. The full-grown Lizziæ possessed twelve tentacles, four single, and eight others arranged in four alternating pairs. In the young form four of the rudimentary tentacles were much longer than the others, and it seems not improbable that each of them represented one of the four pairs of tentacles in the perfect Lizzia. No males of this species have been observed. It is worth adding that another form placed by zoólogists in the same genus appears to be only the detached bud of one of the Corynide. Yet, as Professor Huxley has said, “it is within the limits of logical possi- bility that the adult forms anatomically similar, should be genetically different; that they should have arrived at a similar point by different roads. ‘ The observations of M‘Crady on the direct development of another Medusid, Cunina octo- naria, also deserve attention. This creature oc- curs as a parasite within the nectosacof a distantly allied form, Turritopsis nutricula, from whose mouth, by means of a long proboscidiform poly- pite, the young Cunina obtains its food. At an early stage the Cunina appears as a clavate body, presenting a short, rudely globular proxi- mal, and a more attenuate, somewhat cylindrical, distal, region. From the sides of the posterior margin of the former, two long flexible tentacles soon sprout, while, at the same time, a nutrient 62 HYDROZOA. cavity is formed throughout the central portion of the mass. Even at this period the larva produces free buds from its proximal extremity, not more than two appearing to arise at the same time, though the process of gemmation may frequently be repeated. Next, the distal region elongates; the nutrient cavity opens at its free extremity, forming a mouth; and thus a young polypite is produced, while from the proximal margin two new tentacula soon make their appearance. From this region a rudimentary nectocalyx now arises, a fold, in which are developed marginal bodies, appearing, distally, in front of the tentacles, between which four other tubercular lobes are now seen to bud forth. The growth of the nec- tocalyx slowly proceeds; eight marginal bodies distinctly come into view ; the polypite diminishes in size, finally becoming inconspicuous; and the animal attains the adult form characteristic of its family, save only that reproductive organs have not yet been observed. That instances of the above kind should be mul- tiplied and re-observed seems, for many reasons, very desirable, since, as already remarked, not à few of the forms known as Meduside are but the free-swimming gonophores of various other Hy- rozod. Thus, from the ovum of Turris, one of the so-called genera referred to this order, a poly- pite is produced, which sends forth a creeping ccenosarc, giving rise to a hydrosoma, clearly seem to belong to the Corynidw (fig. 13). Dr. T Strethill Wright has further proved that Bougatn- villea Britannica, a common form of Medusoid, is, in truth, the reproductive body of Atractylis ramosa, one of the Corynide. ENS UM cu c ei. ee «. Les LA CN a HYDROZOA. 63 Proh, Fig. 13. al bot: Development of Turris: — a, ovum of the medusiform zoóid (b) iminiè known as Turris neglecta ; c, polypite, with creeping hydrohiza, A developed therefrom.. (All magnified.) i$, » from the bases of the tentacles in Steenstrupia E Owen and Sarsia prolifera, and from the de- cree M. . Hence these medusoids d ought, perhaps, to be regarded as free gonoblas- Boug tidia. Here, also, it may be added, that multi- eit? plication by fission has been observed by Kólliker (jm in a species of Stomobrachium, 64 HYDROZOA. Fig. 14. pen Gemmation of Mupusoms : — a, Diplonema Islandica, showing young Medusoids budding from the tentacles; b, Sarsia gemmifera, with Medusoids arising from the sides of the polypite; c, Sarsia prolifera, in which Medusoids are seen to sprout from the june tion of the tentacles with the marginal canal, (All magnified.) LUCERNARIDÆ. Still more singular phenomena appear in the life-history of Lucernaride. In Aurelia, Cyanea, and Chrysaora, the ova originate within the generative cavities of the gigantic repro- ductive bodies previously described. Thence they are transferred, in some unknown manner, to the peculiar pouches formed along the margins of the dependent lips of the polypite, and on their way to these pouches are, in all probability, fertilised by contact with the diffused spermatozoa. Segmenta- tion of the vitellus, and other primordial change are undergone by the young ovum while ye within the pouch, from which, about the close of the third day, it comes forth, to enjoy, for a brief period, an active, free-swimming existence. first it appears as an oblong, flattened, ciliated body, or * planula, of very minute size, composed DE b a HYDROZOA. 65 of outer and inner layers, enclosing a central cavity (fig. 15, €). Soon it assumes a somewhat pyriform figure, enlarging at one extremity, in the centre of which a depression is observable, Next, the narrower end attaches itself to some gub- tentacula (d). In the interspaces of these four new tentacles arise; others, in quick succession, make their appearance, until a circlet of numerous filiform appendages, containing thread-cells, sur- rounds the distal margin of the * Hydra tuba," as the young organism, at this stage of its career, ; has been termed by Sir J. G. Dalyell (e and f). — The mouth, in the meantime, from being a mere em» quadrilateral orifice, grows and lengthens itself so jg as to constitute a true polypite, occupying the axis orig of the inverted umbrella, or dise, which supports dem: the marginal tentacles. The space between the wall of the polypite and umbrella is divided into y longitudinal canals, whose relations to the rest of " l the organism, and, indeed, the whole structure of M Hydra-tuba, closely resemble what may be seen herr? . . . . ^ 3 Lucernaria. Externally, it presents a delicate, t1 translucent aspect, and in height averages some "3 eg ofan inch. But though dissimilar to Hydra in di! ^ organisation and want of locomotive capacity, the di*! — Hydra-tuba recalls to mind its fresh-water con- ed* gener, first, in its remarkable reparative powers ; gà v and, secondly, in the extent to which it multiplies ne by gemmation. Not merely do buds arise from ,@ the sides of the body, but, in addition, creeping F 66 HYDROZOA. tubes, or stolons, are sent forth, from which fresh — gemme spring up, it may be, to detach themselves, and so one or several large colonies become formed, all the produce of a single fertilised ovum, For years the hydrosoma may continue in this stage, undergoing no further development. But under certain conditions, similar, perhaps, to those which determine the formation of reproductive organs in the Hydra, a new and striking series of changes is inaugurated. ^ First, each Hydra- tuba elongates, increasing somewhat in size Then, from just below the tentacles to within a short distance of the proximal extremity, a succes- sion of transverse markings begin to appear, which quickly take on the aspect of circular con- strictions (g). When the organism was first dis- covered in this condition by Sars, he, thinking it a new animal, called it“ Scyphistoma.” The same naturalist, observing the Scyphistoma at a stil later stage, with the constrictions more strongly marked, and the several segments included between them cleft and lobed around their margins, gave it, from its resemblance to an artichoke, the name of Strobila (A). Still further do the constrictions deepen until the Strobila becomes not unlike à pile of cups or saucers. The marginal tentacles then disappear, but a new row arises in their steal from the summit of the short, undivided, proximal extremity (7). The disc-like segments above the tentacles gradually fall off, and, swimming freely y the contractions of the lobed margin which | each presents, have been described by Eschscholtz as true Medusidæœ, under the generic title o — Ephyra (k). But each Ephyra soon acquires ^ nutritive system, lithocysts, tentacles, and genera pe- HYDROZOA. 67 tive organs; thus eventually becoming similar to _ the huge reproductive body, from whose fertilised "s ovum the primitive Hydra-tuba was produced, ®t This, and the stock which it developed, does not, Wi however, perish, but may again, by growth and i — fission, give rise to fresh successions of generative bodies. p s Fig. 15. vest- , young refrom ; pni Similar to the above appears the life-history of bor — Cephea and Cassiopeia, notwithstanding the very yg different structure of the detached reproductive p * zoöids which these genera present. On the de- hsb velopment of Rhizostoma itself accurate observa- gp tions are wanting. qi In the Lucernariadæ proper, no free zoöids are Y produced, but the generative elements are formed F2 68 HYDROZOA. in longitudinal folds, which arise, opposite to each other, along the four inner angles of the polypite’s digestive cavity. In Pelagia, a permanently free form of the same order, the ova are developed directly into the likeness of the organism within which they are evolved. The young Pelagia, according to Krohn, presents a minute, semi-tran t, some- what cylindrical body, invested in a thin, whitish, ciliated, covering. By means of its cilia, the em- bryo swims rapidly, often turning round on its longitudinal axis. At one extremity, which is truncate, a very small mouth appears, leading into a distinct nutrient cavity, or stomach. This cavity quickly enlarges; the mouth, also, becomes protruded, whilst at the same time, the hinder end of the body is developed into an umbrella On the third day, traces of eight lobes indent the margin of the umbrella, an equal number of sacs arising from the sides of the stomach. The mar- ginal lobes lengthen, each becomes further in- dented, and soon rudimentary lithocysts can be distinguished. By this time the oral region is changed into à perceptible polypite, but the or- ganism still moves chiefly by the aid of its cilia, the contractions of the umbrella being at first only occasionally repeated. Afterwards, the ciliated coat disappears; thread-cells are produced; the lips of the polypite enlarge; the umbrella shortens and assumes its proper function; the crystalline contents of the lithocysts make their appearance The stomachal sacs increase in number and take on the aspect which they present in the adult animal. Finally, marginal tentacles are acquired, four of these being equal in length to the diameter aoon ne ———— F HYDROZOA. 69 of the swimming organ, while the four other ten- tacles, and the lips of the polypite, are as yet slightly developed. The development of the various appendages which arise along the coenosare of the composite Hydrozoa now requires to be noticed. The same hydrosoma often exhibits these in different stages of evolution, so that their formation admits of being studied, with more or less hope of success, in specimens which may seem to have reached the adult condition. All the lateral appendages, except the hydro- thecæ, appear first as simple processes of the two layers of the body, and in outward form are won- derfully similar, the characteristic aspect of each manifesting itself as growth advances. In the hydrophyllia and nectocalyces the ectoderm en- larges to a much greater extent than the endoderm ; in most other appendages, the relations of these layers are not so disproportionate. As above remarked, there is but slight differ- ence between hydrocysts and polypites at certain stages of their development. But while the hydrocysts remain closed, an opening is formed at the distal extremity of each polypite, villi and distinct regions soon becoming visible in its endo- dermal lining. The tentacles, as already shown, differ as to the degree of vacuolation undergone by their endo- derm. The lateral threads of branched tentacles * appear successively as close-set buds on one side of the proximal end of the tentacle, the younger buds being always developed on the proximal side of the older ones,” When the structure of the F3 70 HYDROZOA. branch is complex, consisting of two or three distinet portions, these are gradually produced as each of the bud-like processes elongates, “The involucrum is formed as a process of the ectoderm of the distal end of the peduncle.. In Physophora, the distal end of the peduncle itself undergoes a — singular dilatation, and helps to form the envelope — for the sacculus The development of the gonophores has, in the account given of their structure, been sufficiently described. That of the nectocalyces is, at first, precisely similar, but the central mass does not, in these, give rise to a manubrium, while the cen- tral cavity, into which the longitudinal canals open, remains very much larger. The hydrothece of the Sertularide are formed by the gradual separation from the body of each polypite of the outer layer, or polypary, excreted by its ectoderm, which, opening distally, displays the cup-shaped cavity, characteristic of different Species. The relative succession of the appendages also demands attention. In the fixed Hydrozoa the distal polypites are first developed, whereas the proximal appendages are the youngest in the Physophoride and Calycophoride. But this rule does not appear to govern the nectocalyces in the last-mentioned group, their precise order of deve- lopment still remaining involved in some com- plexity. - HYDROZOA. 71 t à th, from their bearing on the subject of animal deve- '* lopment in general. A few words of explanation Cl may therefore, in this place, not appear unneces- Uh sary. ; j tn. The life of every animal species may, from a S certain point of view, be regarded as consisting in ` the alternate performance of two distinct series kp Of acts; the one of reproduction, the other of là development. ; i atg Each act of reproduction consists essentially in. T this, that two dissimilar bodies, an ovum and a Wi spermatozoon, are brought into mutual contact. In " some cases the spermatozoón penetrates the coats E of the ovum, or even enters it by a proper aper- f ture, known as the * micropyle.’ " Thus defined, the process of reproduction is the dia same in all animals, though in some its simplicity a is masked by the occurrence of a variety of other " phenomena, all, however, of secondary i portance. et It must also be borne in mind that the evolu- tion of ova and spermatozoa, obviously necessary 355, asa prelude to the reproductive function, cannot | ovu il 7 be considered as forming a part of it. eis | or spermatozoon is, in truth, nothing more than a ini highly differentiated portion of the parent or- hist ganism, the result of a process of development. int ut no sooner has the act of reproduction been T duly effected, than that of development forthwith T begins. The fertilised ovum gives rise to an embryo, which tends to evolve itself into the like- ness of its parent. This embryo, together with val all the structures subsequently developed there- i , from, is said to constitute, in the zoological sense i of the term, an animal individ al, al Should the resulting organism develop an F4 72 HYDROZOA. ovum in its turn, then, that ovum, if fertilised, forms the basis of a new individual; and so on for every additional ovum concerned in a genera- tive act. So that each performance of the repro- ductive process is, as it were, the natural boundary between two successive individuals, or, in other words, between two distinct cycles of development, Thus, while the individual perishes, the species, by reproduction, is constantly renewed. Much also, might be said on the analogy which exists between the different individuals of the same species, on the one hand, and the constituent parts of each individual, on the other. gain, fission and gemmation are not, as many writers incorrectly state, modifications of the re- productive process, but rather, acts of development. For, as already shown, every ovum is at first a bud, which at length, by fission, becomes separated from the body of the parent. All this takes place quite independently of its fecundation. So that an unfertilised ovum is no more entitled to be considered an individual, than a wart or any other excrescence, The antagonism between development and re- production, or even between development in general and those particular stages of the vital process by which reproduction is preceded, is sometimes shown by the fact that certain external conditions which seem to favour the one exert an opposite influence on the other. Thus, on the approach of cold weather, the Hydra is prone to develop organs of true reproduction, while, if kept in a warm room, it still, as in summer timé continues the formation of ordinary buds. 1 It is, therefore, the object of the reproductive i HYDROZOA. 73 I function to confer individuality upon that which SN previously was but a detached part of the parent te organism. Howsoever complex the body of an nj, adult animal may seem, it was once an ovum, lg whose extreme simplicity of structure might al- Dis most be said to verge upon homogeneity. What Spei inaugurated the wonderful series of changes by y which the ovum fashioned itself into the likeness T i of its parent ? ontact with spermatozoa, or, in A h one word, reproduction. To say, then, that sper- M. matozoa possess a peculiar individualising in- k fluence can scarcely be viewed as a metaphorical | form of expression. How they are capable of | exerting this influence is, however, a problem to te: which, as yet, science has furnished no definite pue solution. Bischoff has compared their action to . that of a ferment, such as the yeast of beer; but pani this hypothesis, as Claparéde truly observes, only s pu removes the present difficulty a single step back- yt wards. | toi The zoological individual being, therefore, de- y ob fined as the entire product of the developmental changes of a single fertilised ovum, we have now NE to consider the principal modifications which the "T cycle of development presents. "T If all the parts of an individual remain mutu- jd ally connected, its development is said to be " ‘continuous’; if any of them separate as inde- " pendent beings, it is *discontinuous'. nb Continuous development may manifest itself s under the three principal modes of ‘growth,’ je ‘ metamorphosis, and ‘gemmation without fis- 3 P sion.” In metamorphosis, growth alternates with certain well-marked changes of form. In gem- mation without fission, a tendency to vegetative 74 HYDROZOA: repetition is more or less distinctly marked. An example of the first of these methods is presented by Pelagia; of the second, by Æginopsis; of the third, by Cordylophora or Sertularia. In discontinuous development the detached portions of the individual are termed “zoöids; that which is first formed being distinguished as the * producing,' that which separates from it, the ‘produced’ zoóid. If there be more than two successive series of zodids, the terms * protozodid, *deuterozoüid, and *tritozoüid, may then be re- spectively applied to them. Thus, the medusoids budded by Sarsia are, probably, tritozoóids. The term zo0id is also extended to the several parts of a connected structure which increases by vegeta- tive repetition; for example, to the polypites, and other appendages of the composite Hydrozoa. The producing zodid may either possess or want generative organs. In the latter case the pro- duced zoóid may take on the performance of the reproductive function, as in so many orders of Hydrozoa. Inthis class we have seen that the produced zooid may resemble the producing zodid, as in Hydra, or be dissimilar to it, as shown by the free-swimming gonophores of the Corynide and Sertularide. The first case affords an illustration of simple * gemmation with fission’; the latter, of the process known as *metagenesis. If the pro- ducing zodid possess sexual organs, and the pro- duced zodid present the morphological, but not the physiological, characters of an ovum, then the process is one of ‘parthenogenesis.’ All these varieties of discontinuous development are col- lectively denominated *agamogenesis, as distin- ——M HYDROZOA. 79 M guished from * gamogenesis, in which the ovum, : to be developed, must first be brought into con- tact with spermatozoa. tay But such modifications are, in nature, less e. distinct from one another than the systematic i definitions just given. might appear to imply. W Furthermore, recent investigations on the de- tg velopment of Insects and Crustaceans have tended Uh alike to confuse our old-established notions of MU animal individuality and of the true nature of bes the generative process. For certain Insect ova lui have been observed to undergo development in 1 the ordinary manner, though no previous contact rt with spermatozoa had taken place. And in un- en impregnated female Vertebrata ovarian tumours esa are said sometimes to occur, which contain traces aq, of hair, teeth, bone, nerves, and other tissues pro- rw per to the adult organism. If, therefore, cases em exist in which the influence of a male element "d seems rather accessory than essentialto the normal eri evolution of the germ; nay, can even be dispensed with, there are others in which, without such dud influence, no proper individuality is manifested, ji though development, to a certain extent, must as- m suredly be considered to have taken place. For a the present we have preferred to advocate the é: views entertained on these disputed points by n Professors Huxley and Carpenter, while, to avoid e needless ambiguity, we have thought it better to La employ the precise terminology which the former ‘naturalist has suggested, < th But other attempts have been made to explain ab the phenomena in question. Steenstrup, followed ii ^ in Britain by the late Professor E. Forbes, and a 0 host of minor investigators, proposed to consider 76 HYDROZOA. both the free zooids of the Hydrozoa and the organisms from which they sprung as alike en. titled to the rank of individual beings, belonging to allied groups, and mutually reproducing each other by a process of “alternate generation." But, in addition to the more general objection which may be raised against this hypothesis, confounding, as it does, true generation with gemmation or fission, the one, an act of reproduction, the other, of development, it is sufficient to show that, in the present instance, its application is based on a very superficial examination of the facts to be explained. The gradual series of transitional homologous forms, so surely connecting the com- plex free gonophores of certain Hydrozoa with the simple reproductive processes of Hydra or Hydractinia, could not have been very familiar to the minds of those who would have hesitated, if called upon, in accordance with Steenstrup’s theory, to impute individuality to the latter. Professor R. Leuckart, however, consistently does this, and would regard as true individuals the independent polymorphic buds of the same com- posite Hydrozoón. And Mr. Lubbock has justly remarked that, “whether we retain the old nomen- clature, or dropping the idea of unity in the term ‘individual, adopt the system proposed by Pro- fessor Huxley, we shall be met by great difficulties and inconsistencies.” It behoves us, therefore, t0 follow that explanation which embodies in the simplest manner all the observed phenomena, and which is, at the same time, least characterised by inconsistency. ecently, Professor Agassiz has proposed 4 modification of Leuckart’s theory, and suggests —— = Sr ] f | : ea E o ae HYDROZOA. 77 T lt; the distinction of four kinds of individuality in lg the animal kingdom. First, hereditary indi- m viduality, when from a single egg a single inde- oh pendent being is produced. Secondly, derivative wi or consecutive individuality, oris that kind | of ug independence resulting from an individualisation tio, of parts of the product of a single egg;” as in Oth many Lucernaride, Corynide, and Campanu- that; lariade. Thirdly, secondary individuality, where sel, the product of one egg multiplies by continuous m gemmation, giving rise to an immoveable com- a munity; as in the Sertulariade. Lastly, there is Sting complex individuality, where a similar but move- "" able community is formed; as seen in the Caly- ^V eophoridc and Physophoride. In this case, he dn. adds, “the individuals of the community are not ni: only connected together, but, under given cir- Sitat cumstances, they act together as if they were one str individual, while at the same time each individual lite may perform acts of its own." y d Others were for regarding the gonophores of the als i fixed Hydrozoa as the perfect or adult stages of ei the forms by which they were produced, the whole je process being viewed as one of ordinary meta- one morphosis. The particular objection just stated elit applies also to the opinion under consideration, vh which has, nevertheless, found its advocates in a val few writers of distinction. There is, no doubt, n some degree of plausibility in a view which consi- 7 ders the fixed Corynid or Campanularid as the young condition of the more complex Medusoid to gil which, by gemmation, it gives rise. It is now " , however, certain not only that the Calycophoride gii and Physophoride agree closely in structure with p the Hydrozoa just named, but likewise, that they 78 HYDROZOA. bear the same morphological relation to their reproductive bodies. Extend the case to these; let Velella, for example, be henceforth the larva of its free medusiform gonophores, and the doc. trine which we have contested is at once seen to become untenable. Another explanation emanated from Professor Owen. Hisingenious theory of * parthenogenesis" supposed that the primitive result of each genera- tive act retains within its body unchanged a cer- tain portion of the germ-mass from which it was first evolved, together “with so much of the spermatic force inherited by the retained germ- cells from the parent-cell or germ-vesicle as suffices to set on foot and maintain the same series of formative actions as those which consti- tuted the individual containing them." So that * every successive generation, or series of sponta- neous fissions, of the primary impregnated germ- cell, must weaken the spermatic force transmitted to such successive generations of cells.” Or, to confine ourselves to the class under consideration, that a Corynid produced, as the resultants of the germ-cells and spermatic force stored up within it, successions of free or fixed gonophores, until the generative force became exhausted. But here, at | HYDROZOA. 79 Section III. CLASSIFICATION OF HYDROZOA. 1. Classification. — 2. Order 1: Hydridz. — 3. Order 2: Corynide. — 4. Order 3: Sertularide.— 5. Order 4: Calycophoride. — 6. Order 5: Physophoridz. — 7. Order 6; Meduside, — 8. Order 7: Lucernaride, I, Classification.—The seven orders intowhich the class Hydrozoa is divided may be defined as follows: | 1. Hydride. — Hydrozoa, whose hydrosoma con- sists of a single locomotive polypite, with tentacles, hydrorhiza, and reproductive organs which appear as simple processes of the body- wall, 2. Corynide. — Hydrozoa, whose hydrosoma is fixed by an hydrorhiza, and consists either of one polypite, or of several connected by a coenosare, which usually developes a firm outer layer. Reproductive organs in the form of gonophores, which vary much in layer. Reproductive organs as gonophores, arising from the ccenosare, or from gonoblas- tidia. 80 HYDROZOA. 4. Calycophoride. — Hydrozoa, whose hydrosoma is free oceanic, consisting of several polypites connected by a flexible, contractile, unbranched coenosarc, the proximal extremity of which is furnished with nectocalyces, and dilated to form a somatocyst. Reproductive . organs as medusiform gonophores, budded from the peduncles of the polypites. 5. Physophoridæ. — Hydrozoa, whose hydrosoma is free and oceanic, consisting of several polypites connected by a flexible, contractile, seldom slightly branched, ecenosare, the proximal extremity of which expands into a pneumatophore, and is sometimes provided with mnectocalyces. Reproductive organs, more or less complex in structure, developed . upon gonoblastidia. 6. Meduside. — Hydrozoa, whose hydrosoma is free and oceanic, consisting of a single poly- pite suspended from the roof of a nectocalyx, furnished with a system of canals. Repro- ductive organs as processes either of the sides of the polypite, or of the nectocalycine nals. 7. Lucernaridæ. — Hydrozoa, whose hydrosoma has its base developed into an umbrella in the walls of which the reproductive organs are produced The characteristics of these orders are indicated more briefly in the subjoined analytical table. 2. Order r: Wydridz. — The order Hydride contains but a single genus, Hydra, distinguished from the few marine Hydrozoa which it approaches in physiognomy by its peculiar habit and locomo: | | j l HYDROZOA. HYDROZOA. | E No umbrella. An hydrorhiza. No hydrorhiza, Oceanic. De Locomotive. Fixed. Inhabiting fresh-water. Order 1. HYDRIDE. aR No hydrothecze. Hydrothecee. Order II. Order III. CORYNIDÆ. SERTULARIDÆ. Polypites free from nectocalyces. No pneumatophore. Nectocalyces. A Somatocyst. Order IV. CALYCOPHORIDA, Polypite sus- pended from the roof of a nectocalyx. MU OT TW A pneumatophore. Nectocalyces present or absent. Order V. PHYSOPHORIDA. Order VI. Mepuspz. Order VII. [el LUCERNARIDR. E An umbrella. 82 HYDROZOA. tive powers. Several species of Hydra have been described under such names as H. viridis, H, rubra, H. vulgaris and H. fusca. These differ in size, colour, the form of the body, or in the relative proportions of the polypite and tentacles, The polypite of H. vulgaris is cylindrical, its colour variable, but usually orange-brown, and its tentacles of moderate length. H. viridis has a polypite of a grass-green tint, furnished with comparatively short tentacula. H. fusca is larger than either of these, its colour is deep brown, and its tentacles very long and extensile; the proximal extremity of the polypite becoming suddenly attenuated for about a third of its length. When living Hydre are removed from the water, they appear to the eye as minute specks of jelly, which quickly, however, recover their true form on re- immersion. In confinement they readily thrive, seeking the light and feeding voraciously. Spe cimens of the Hydra may be kept in glass vessels, and their singular habits observed by the student, with little difficulty. 3. Order 2: Corynid:e. — In Corymorpha, Vorticlava, and Myriothela, the hydrosoma, like that of Hydra, presents only a single polypité but, in the greater number of Corynide, it composite, exhibiting numerous polypites con- nected by a coenosare, which may be either erect and branching, as in Cordylophora, or reduced to a delicate creeping tube, as in Clava and Tr chydra. A hydrosoma of this kind may be com- pared to a Hydra in the act of budding, while 38 yet the young zoóids remain in connection with the primitive polypite, by the hydrorhiza of which — — HYDROZOA. 83 the entire fabric continues to attach itself And, since gemmation may take place in many different ways, so, in like manner, result the great variety of forms due to modifications of what is essentially the same process of growth. In the flower-like Tubularia indivisa, the ccenosare consists of several simple tubes, intertwined one with another near their attached extremities, and sometimes rising to a height of ten or twelve inches ( fig. 16). From the distal ends of these tubes, which are of other genera the colour of the ccenosarc is usually yellowish-brown. All the preceding. forms have the hydrosoma rooted, or attached to other objects, q 2 84 HYDROZOA. and in no Corynid hitherto observed does it appear to be altogether free, unless, indeed, an exception Fig. 16. S» ay SS Se SS = 2 Morphology of TUBULARIADÆ :— 4, Corymorpha nutans; b tuft of gonophores from Corymbogonium capillare; c, Tubularia t divisa ; d, distal extremity of its cænosarc ; e, transverse section of the same. (a and c are of the natural size; 5, d, and 6 arè magnified.) be made in favour of the doubtful genus Ne- Mopsis. | | i | | | = ——— lll zn o mc HYDROZOA. 85 The firm horny layer, or polypary, which the .ecenosare excretes in Tubularia and its allies, remains in a comparatively rudimentary condition among most other Corynide. In few, however, is it absent altogether. In Hydractinia, it be- comes elevated at intervals to form numerous rough processes or spines, while over the general surface of the ectoderm its presence is almost im- perceptible. A very different modification is pre- sented by the genus Bumeria. Here the polypary is not, as in other members of the order, restricted to the eoenosarc, but extends itself so as to clothe the entire body of each polypite, leaving bare only the mouth and tips of the tentacles. The chief differences which prevail among the polypites of the Corynida@ have reference either to size or the disposition of their tentacula. The comparatively gigantic polypite of Corymorpha nutans, which attains a length of 4:5 inches, is described by Forbes and Goodsir as presenting the appearance of a beautiful flower, nodding gracefully upon its stem (fig. 16, à). Another species of the same genus, C. nana, does not exceed *5 of an inch in length, though this, in its turn, is double the size of the tiny Vorticlava humilis (fig. 17, a). Still more minute are the delicate polypites of some species of Hudendrium. In most members of the present group the general form of the polypite is more or less clavate. The tentacles exhibit several distinct modes of arrangement. In Tubularia and Corymorpha a fringe of short appendages immediately surrounds the mouth of the polypite, from the base of which, close to the distal extremity of the ccenosare, arises a second circlet of much longer filiform tentacula, G3 86 HYDROZOA. fewer in number than those of the upper row (fig, 9, a). Vorticlava, also, possesses a twofold series of tentacles, but here, those of the lower circlet are twice as numerous as the upper, which are five in number, short, stout, and capitate (fig. 17,6), In Clava, Cordylophora (fig. 5,c), and Coryne (fig. 17, Various forms of ConyxiAnz : —a and b, Vorticlava humilis ; c, four polypites of Hydractinia echinata, growing on a piece 0 shell; d, portion of Syncoryne Sarsii, with medusiform zoüids (p) budding from between the tentacles (7) of the polypite (0). (All, except a, magnified.) — d), the tentacles appear irregularly scattered along the sides of each polypite, though most abundantly towards its distal extremity. In Coryne the mouth is highly flexible, possessing the power of bending towards that tentacle which has seized the prey; and of converting itself, upon occasion, into à kind HYDROZOA. 87 of sucking dise. The polypites of the allied genus Stauridia are distinguished by the possession of two or more cycles of dissimilar tentacles, separated from one another by a considerable interval, each cycle including four tentacles ; the lower row fili- form, the upper whorl, or whorls, capitate, and placed at right angles to one another and the polypite. In Pennaria, there is a basal circlet like that of Tubularia, between which and the mouth of the polypite lie scattered numbers of shorter tentacles, resembling those of Vorticlava. In Myriothela, multitudes of wart-like tentacles crowd the whole surface of the: club-shaped, soli- tary, polypite. Similar to these are the tentacles of Acaulis, which exhibits, in addition, a basal series of long prehensile appendages. These, how- ever, disappear as the organism approaches ma- turity, so that this form may possibly be but a young condition of Myriothela. A single series of rather long tentacles, inserted as in the fresh- water Hydra, arises at a short distance below the mouth in Trichydra, Clavatella, Perigonimus, Bimeria, and Eudendrium. Some species of these genera seem to foreshadow an arrangement of the tentacles which in Hydractinia becomes sufficiently conspicuous. Around the mouths of the digestive zodids in this genus two rows of al- ternating tentacles are placed, so close to each other that they appear, at first sight, to constitute a single series; the lower tentacula, which are shorter, projecting at right angles to the body of the polypite, from the axis of which the upper tentacles very slightly diverge. "These, however, have no direct connection with the long tentacular appendages, arising directly from the ccenosare, to G 4 88 HYDROZOA. which allusion has already been made. Lastly, in Lar, each polypite supports but two tentacles, above which the mouth is furnished with a pair of wide projecting lobes, capable of being approxi. mated closely to each other, and serving, doubt- less, as efficient organs of prehension. The gonophores of the Corynide vary not a little both in structure and mode of attachment, In Cordylophora, Perigonimus, Garveia, Bimeria, and some forms of Hudendrium and Atractylis, they spring directly from the stem or branches of the ccenosare. In other species of the two last- mentioned genera they are seated either beneath the tentacles of the polypites, or on the summits of special branches, arising from the proximal region of the hydrosoma ( fig. 16, b). In Myrio- thela, Acaulis, and Clavatella, the gonophores have their origin on the polypite, not far from its attached extremity: in Coryne and Stawridia, they are produced between the tentacles (ig. 399 In Corymorpha and some species of Tubularia, they are supported on long branching gonoblas- tidia, inserted immediately within the basal circlet of tentacula (fig. 9, b): in other Tubularic, T. calamaris and T. Dumortierit, as also in the genus Pennaria, these long stalks appear to be absent. The arrangement of the reproductive bodies in Clava and Hydractinia has already been pointed out. In the closely allied genera, Dicoryne and Podocoryne, they originate, in a somewhat simi- lar manner, on proper gonoblastidia, never on the ordinary polypites. But the proliferous stalks of Podocoryne are furnished, each, with a mouth, and differ little from true polypites save in their smaller size and the possession of fewer tentacula. = l dins "n HYDROZOA. 89 B ^^^ Transitional forms of this kind should not, however, i surprise us, when we consider the common bond, Mh community of descent, which connects the two hi kinds of appendages in question. In the genera Perigonimus, Atractylis, Pen- " maria, Corymorpha, Acaulis, Stauridia, and some D forms of Coryne, Tubularia, and Eudendrium, k the gonophores assume the aspect of free-swimming N medusoids. In most other Corynide they are i fixed, exhibiting many remarkable gradations of n structure. An intermediate condition is presented hs, by the curious reproductive zodids of Clavatella, B = which, though locomotive, scarcely merit the ap- n pellation of medusiform. They are described by 7 — Mr. Hincks as free polypoid buds, furnished with fi six forked processes, set round the margin of a » central hemispherical disc, one limb of each fork n being capitate, like the tentacles of the polypite Ë itself, the other terminating in a peculiar sucker- jl like enlargement. By means of these organs the lr zoüid, when detached, moves freely about, until ji finally it proceeds to mature its generative pro- Y ducts. al The gonophores of Trichydra, Vorticlava, and w Lar have hitherto remained unknown. g Two families of Corynidc have been distin- gi guished, though the character employed to sepa- m rate them appears to be somewhat artificial, D i Order CORYNIDJE. yb Family 1. CORYNIADÆ olypary absent, or rudimentary. Family 2. TUBULARIADA. olypary well developed. 90 HYDROZOA. The entire order is sometimes denominated Tubularide, and agrees with the group Tubu- larina of Ehrenberg. 4. Order 5: Sertularidz. — Like the mem- bers of the preceding order, all the Sertularide, after the expiration of their embryonic condition, become permanently fixed by means of the hydro- rhiza which forms the proximal extremity of the coenosarc (fig. 4, c). In this group the tendency to increase by gemmation is even greater than among the Corynide, for no example of a Sertu- larid has yet been recorded in which the hydro- soma exhibits but a single polypite. The ccenosare is plant-like and, frequently, much branched, the main stem either losing itself in its own ramifica- tions or remaining distinct throughout the entire length of the arborescent mass. A good example of the latter mode of growth is afforded by the Sea-Fir, Sertularia cwpressima, the hydrosoma of which may attain a height of two, or even three, feet, and bear on its branches so many as 100,000 distinct polypites. In contrast with this, the largest of our native species, may be mentioned the delicate Sertularia tenella, the length of whose slender creeping hydrosoma scarcely reaches one inch. The waving fronds of Oar-weed on various parts of the coast afford a suitable habitat to the anastomosing thread-like coenosare of another char- acteristic species, Campanularia geniculata, which sends up at intervals its peculiar zig-zag branches, from the angles of which the polypite stalks arise. Other Sertularide attach themselves t? stones or shells, and not a few of the smaller forms occur parasitically on the stems of more conspi- = ———— dicc" eS ae ] Uh, HYDROZOA. 9] uous species. Examples of this habit are afforded Fig. 18. Morphology of SERTULARIADÆ : — a, dried hydrosoma of Sertu- laria tricuspidata ; b, portion of the same; c, fragment of the ccenosare from a dead specimen of Haleciwm halecinum ; d, gono- blastidium of H. Beaniüi; €, three gonoblastidia of Sertularia argentea ;—*', hydrotheca; k, ccenosare; p', gonoblastidium. (All, except a, magnified.) by the genera Coppinia and Reticularia, and by several of the true Sertularie, 92 HYDROZOA. The ccenosare, in all cases, excretes a very firm chitinous polypary, usually of a pale horny colour, which may either remain throughout in close conti- guity with the ectoderm, or become separated from it at regular intervals, so as to impart an elegant ringed appearance to portions of the tree-like structure (jig. 19, b). This semi-transparent, horny, sheath persists long after the destruction of the soft parts of the organism, so that, among the larger species of Sertularide, the peculiar form of the hydrosoma is sufficiently well seen in dried specimens. Here, therefore, the polypary differs from that of the Corynide in its firmer texture, but the most important distinctive feature of the present order is found in the occurrence of the definition of the minor types of structure which occur within the limits of this circumscribed group. In Campanularia fastigiata the distal end of the hydrotheca forms, according to Mr. Alder, a sort of * operculum, which, when closed, slopes down on each side like the roof of a house, the two opposite angles forming the gables. When the operculum is fully open, the folds disappear, and the edges unite into a continuous rim rown the top of the cell." The polypites of the Sertularido, more minute than those of the Corynide, differ little from on? another, either in form or the general arrangement of their tentacles. In Sertulariade proper the polypites are sessile, while in the Campanulariale Se HYDROZOA. 93 yh ; A each is elevated on a conspicuous stalk. An thy intermediate condition is presented by the genus lf, Halecium, the polypites of which are ‘sub-ses- len, sile? each hydrotheca being jointed to a short NA process of the ccenosare (fig. 18, c). 3 The tentacles, though apparently disposed, Hydra-like, in a single row below the mouth, are found, on close examination, to exhibit an indis- ^ tinct alternate arrangement; slight differences in length and position distinguishing those of the two series. The peculiar rough appearance which di each tentacle presents resolves itself under the P» microscope, into rows of minute elevations, or di * palpocils within which numbers of thread-cells fi are lodged. The tentacles are filiform, tapering na gradually towards their free extremities. In Du Campanulina a delicate web-like extension from hi the body of the polypite unites these appendages jg t for about a sixth of their entire length. tot Allusion has elsewhere been made to the nema- ut tophores, or characteristic organs of offence, noticed qti by Mr. Busk in the genus Plumularia, and one it or two of its immediate allies. These singular oI appendages are well deserving of minute investi- she gation. Their offensive nature seems proved by he the abundance of thread-cells in their interior, coupled with the fact that certain species of Plu- " mularia have been observed to sting with some p severity. In Plumularia proper one of these organs arises on either side of each hydrotheca, while in Halicornaria they are situated, between / the polypites, on the general surface of the n" coenosare. f The reproductive organs vary, perhaps, less f than those of the Corynide, and are usually sup- 94 HYDROZOA. ported on the curiously modified gonoblastidia, whose. structure has previously been described, Among the Campanulariade they frequently assume the form of free-swimming medusoids; Y wy 8 y T M ut I: KU 5 CE NU (A LAT M eee eet SSS PLIST uu Morphology of CANPANULARIADUE :—a, Laomedea neglecta ; b, portion of the same; c, gonoblastidium of Campanularia volui- but in the Sertulariadæ seldom, if ever, become detached. In some Plumularic the gonophores appear to be naked. In P, cristata the branch bearing these organs undergoes a curious metamorphosis HYDROZOA. 95 by the development from its opposite sides of Ne alternate leaflets, which eventually arch over, and unite with one another, forming a basket-like receptacle, or ‘corbula, within which the repro- ductive bodies are lodged. In Sertularia polyzonias and some other spe- cies only one gonophore, consisting of a simple closed sac, arises from the gonoblastidial column, and, by the protrusion of this sac beyond the orifice of the urn, an external capsule, or * acro- cyst,’ is formed, into which the ova are trans- ferred at a certain period of their development (fig. 19, e, f, and g). In Campanularia Löveni the ripe gonoblas- tidium displays at its summit the medusa-lik gonophores already alluded to, whose form is, in many respects, so peculiar that Professor Allman has proposed to designate them by a distinct name, ‘meconidia’ (fig. 10). The reproductive elements of this species are developed, as in the m Corynidce, between the ectoderm and endoderm W of the manubrial wall, while in other Sertularide, with medusa-like gonophores, they arise in the course of the calycine canals. The order Sertularide includes two families. " Order SERTULARIDZE. " Family 1. SERTULARIADÆ. Hydrothecæ, and polypites, sessile. Family 2. CAMPANULARIADA. it Hydrothece, and polypites, stalked. l _A more extended acquaintance with the posi- y tion of the nematophores may perhaps afford t grounds for modifying this arrangement. 96 HYDROZOA. 5. Order4: Calycophoridz. — The members | of the next order, Calycophoride, appear, at first sight, very dissimilar in aspect to the fixed Hy. drozoa, which, nevertheless, in all essential cha- racteristics, they closely resemble, Diphyes, the type of the group, presents a delicate filiform ecenosare, to the proximal extremity of which are attached two large, firm, mitrate, nectocalyces (fig. 20, a). To these appendages, which differ slightly in form, the distinctive terms of ‘proxi- mal’ and ‘distal’ have been assigned. The former, as its name imports, precisely terminal in position, is furnished with a conical cavity running parallel with, but distinct from, its nectosac. Into this cavity is fitted the apex of the distal nectocalyx, along the inner surface of which it prolongs itself as a lengthened groove, with its sides arched over in such a manner as to form a more or less per- fectly closed canal. The ccenosare, with its nu- merous appendages, freely glides up and down the peculiar chamber, or * hydroecium,’ thus produced, into which it can, upon occasion, be completely retracted. The ccenosare itself dilates slightly towards its proximal extremity into a small ciliated chamber, which, narrowing above, becomes con- tinuous with a sac of larger size, termed the * soma- tocyst.’ This, too, is ciliated, its cavity appearing in most cases almost obliterated through excessive vacuolation of the endoderm. The somatocyst is firmly embedded in that portion of the prox imal nectocalyx which forms the upper boundary of the hydreecium, while from the smaller ciliated chamber two ducts are given off, one to the distal, the other to the proximal nectocalyx, where each communicates with the small cavity commo? HYDROZOA. 97 to the nectocalycine canals. Along the sides of the ecenosare are placed the several appendages, con- Fig. 20. mI e e TSS aoe es os Os VE Morphology of CALYCOPHORIDÆ : — a, Diphyes appendiculata b, Vogtia pentacantha ; —v, proximal nectocalyx of Diphyes ; , J JE E , ? its posterior contour ; e, its nectosac; »", distal nectocalyx; e", 5 vA € polypite, with its tentacle; v, v, nectocalyces of Vogtia; m, m, its polypites; 7, 7, their tentacles; 0, androphore ; w, gynophore. (Natural size.) sisting chiefly of polypites, tentacles, hydrophyllia, and organs of reproduction. Large specimens of H 98 HYDROZOA. Diphyes attain, when fully extended, a length of several inches, their coenosare giving support to at least fifty distinct polypites. Of the great beauty of these, and other oceanic Hydrozoa, no description can adequately treat. So transparent, in man cases, is the delicate ccenosare, that its course upon distant inspection is revealed only by the bright tints of some of its appendages. A touch is often sufficient to separate it from the nectocalyces, which, from their size and firm consistence, con- stitute the most conspicuous portions of the or- ganism. Hence the origin of the generic name, Diphyes, devised by Cuvier, who regarded the two swimming organs as distinct animals, imperfectly united with one another. An unbranched, filiform, ccenosare occurs in all Calycophoride. In Hippopodius its proximal extremity tolds inwards to form a loop, so that the true position of the nectocalyces is thereby some what confused. Of the many appendages to the ccenosare by far the most remarkable are those just mentioned. In accordance with the relative number, structure, and arrangement of these organs, the few genera of the order hitherto carefully examined may readily be identified and separated from one ano ther; as shown in the accompanying table. ARTIFICIAL ARRANGEMENT or CALYCOPHORIDE. Nectocalyces two in number : pre: ces T sim : E: : A single l, a nectoealyx . phar a eoi ces uk in size and for Nectoca milar Pr aya Proxim: ^i nectoealy equal to, or larger than, 3 the distal on Diphyes. Proximal cae shorter than the distal Ayla HYDROZOA. 99 Nectocalyces horse-shoe shaped , i - Hippopodius. Nectocalyces concave externally, “and pro- 4. duced into five points of which the three upper are much longer and stronger than the two lower.” * - s ogtia, Praya, Hippopodius, and Vogtia have *in- complete’ hydreecia, the nectocalycine groove along which the ccenosare glides not forming, in these genera, a closed canal. In Praya, however, the two, nearly symmetrical, terminal nectocalyces have their open grooves so applied to each other as to form, by their apposition, a short tube ( fig. 4, d). The polypites and tentacles of the several genera of Calycophoride present no very striking differ- ences of structure. Not so, however, the hydrophyllia. Abyla, the genus most closely allied to Diphyes, is distin- guished from that form not merely by its necto- calyces, but also in having thick, facetted, hydro- phyllia, the edges of which do not overlap one another. In Diphyes the hydrophyllia are folia- ceous, smooth externally, slightly convex, and folded so that their edges freely overlap. In Praya, “each hydrophyllium is a thick, gelatinous, and reniform body, bent upon itself, rounded and solid at one extremity, and divided at the other into a median thick and two lateral lamellar lobes, The phyllocyst is prolonged into four ezcal processes.” But in Vogtia, Hippopo- dius, and, perhaps also, Spheromnectes, these or- gans are absent altogether (fig. 20, b). The reproductive bodies of the Calycophoride are always medusiform, and attached to the pe- duncles of their respective polypites. In Vogtia and Hippopodius the manubrium attains a large H 100 HYDROZOA. size, extending far beyond the margin of the short gonocalyx. In other genera the reverse is usually the case, the manubrium being shorter than the swimming cup within which it is suspended. Each gynophore, when fully developed, appears to con- tain several ova. In most Calycophoride, except Diphyes itself, both male and female reproductive appendages appear on the same hydrosoma. our families of Calycophoride have been de- fined by Professor Huxley. Their characters we subjoin. Order CALYCOPHORIDZE. Family 1. Dipyypz. Calycophoride with not more than two, polygonal, nectocalyces. Proximal hydræcium complete. Hydrophyllia. Family 2. SPH#RONECTIDA. Calycophoride with probably not more than two nectocalyces; the proximal one being spheroidal, with a complete hydracium. No hydrophyllia? Family 3. PRrayipz. Calycophoride with only two nectocalyces, whose hydrecia are both incomplete. HY drophyllia. Family 4. HIPPOPODIIDA. Calycophoride with many nectocalycés; whose hydrecia are incomplete. No hydro phyllia. The same naturalist has proposed the distinctive term of ‘Diphyozodids’ for those singular detache reproductive portions of adult Calycophor idw which received the name of ** monogastric Diphy- ner — HYDROZOA. 101 de” from earlier observers. Their true nature was first demonstrated by R. Leuckart, who several times witnessed the separation of these bodies from a well-known species of Abyla. Groups of organs became detached from the cceno- sarc, each group consisting of a hydrophyllium, polypites, tentacles, and gonophores, with a small portion of the ccenosare itself. More frequently, however, the actual detachment of the Diphyozooid has not yet been observed, so that the precise origin of many still presents a subject for inquiry. Pend- ing further investigation, it seems right to designate such forms by provisional generic and specific names, of which not a few have already been con- ferred. Order 5: Physophoride.-— The Physo- phoride differ much more among themselves than do the members of the order just mentioned. All, however, agree in having the proximal end of the ccenosare modified to form the pneumatophore, or float, which presents so characteristic a feature in the physiognomy of these animals. The cavity of this pneumatophore is a simple enlargement of that of the coenosare, the walls of both being directly continuous. To the apex of the cavity is attached a firm, elastic, apparently chitinous sae, known as the *pneumatocyst, containing a greater or less proportion of air. A layer of endoderm, reflected if not always, entire. Its apex, though most fre- quently closed, is open in Physalia and Rhizophysa, H 3 102 HYDROZOA. and, the free extremity of the pneumatophore being likewise perforate, a communication exists, in these genera, between the cavity of the pneuma- tocyst and the surrounding medium. In Rhizo- hysa, moreover, peculiar long branched processes freely depend from the distal surface of the pneu- matocyst. Each process consists of a layer of the investing endoderm containing in its axis clear cel- leeform bodies, ‘o2 of an inch long, each of which includes an opaque oval endoplast, about 4th of these dimensions, and this, in its turn, a more mi- nute particle or nucleolus, oval or circular in form, and ‘ooo8th of an inch in diameter. In Agalma and Forskalia radiating membranous partitions connect the walls of the pneumatophore with those of the pneumatocyst, below which each terminates in a free arcuated edge. In Velella and Porpita the pneumatocyst is furnished with several open- ings, or stigmata, communicating with the exterior, while to its distal surface are attached a number of long slender processes enclosing air, and hence termed the * pneumatic filaments.’ Excepting the presence of the pneumatophore and the absence of a somatocyst, the general plan of structure in these Hydrozoa differs little from that of the Calycophoride. In Apolemia, as m Diphyes, the numerous groups of appendages are supported at intervals along a slender, unbranched, connecting stem. Physophora, the type of the order, has a filiform, but comparatively short, c&- nosare, terminated proximally by a pneumato- phore of moderate size, below which the greater portion of its length is occupied by a double series of nectocalyces, each alternating with its successor on the opposite side, and deeply grooved — — HYDROZOA. 103 on its inner face for attachment to the ccenosare, 22, b). The distal extremity of the latter forms an expanded bulb, above which are disposed, in a spiral or circular manner, the various appen- dages; consisting of polypites, tentacles, hydrocysts, and organs of reproduction. Of these the hydro- cysts are uppermost, or external; next come the polypites, with a tentacle at the base of each, between, or above, which the gonophores, of both sexes, are arranged. The usual length of Physo- phora is about two inches. The typical genus just described may advan- tageously be contrasted, on the one hand, with such forms as Apolemia or Halistemma, on the other, with the widely different, though equally aberrant, genera, Porpita and Velella. In Halistemma rubrum the appendages are attached to a thread-like stem, nearly forty inches in length, having a float of only three or four lines in its longest diameter, close beneath which the swimming-bells, about sixty in number, extend in two parallel rows for a distance of six or seven inches. The remainder of the ccenosare is occupied by the polypites, tentacles, hydrocysts, bracts, and reproductive buds, all associated in one continuous series. Especially conspicuous, from their bright vermilion hue, appear the complex ten- tacular sacculi, while fainter longitudinal bands of the same colour mark the hepatic striz of the polypites, whose size, in this genus, is considerable. The general aspect of this most beautiful, yet withal, extraordinary being, has been compared by Vogt, its discoverer, to that of a delicate, trans- parent garland of flowers, endowed, in a marvel- lous manner, with life and activity. H 4 104 HYDROZOA. Far different is the physiognomy of Velella, whose coenosare appears almost wholly lost in the horizontal, or slightly convex, rhomboidal pneu- matophore, which distinguishes this singular genus, The proximal surface of the pneumatophore is traversed diagonally, from one of its angles to the other, an upright, triangular crest, which, in common with the horizontal dise, consists of a soft Morphology of Vgrsrra :— a, Velella spirans, somewhat en larged ; 0, one of its smaller polypites, much magnified ;—% Test; A, liver; o, mouth of polypite; 8, its digestive cavity ; $, rounded elevations, containing thread-cells; p, medusiform zoóids. marginal membrane, or “ limb," bounding the * firm part," or central portion (fig. 21, a). To the distal surface of the firm part of the disc ae attached the several appendages; including (1) @ HYDROZOA. 105 single large polypite, nearly central in position ; 2), numerous small gonoblastidia, which resemble polypites, and are termed * phyogemmaria'; and, (3), the reproductive bodies to which these last give rise (b). The tentacles are attached, quite independently of the polypites, in a single series along the line where the firm part and limb of the disc unite. There are no hydrocysts, necto- calyces, or hydrophyllia. The average length of Velella may be estimated at two inches, its height at one inch and a half. The entire or- ganism is semi-transparent and tinged with an ultramarine blue, which changes to a deeper shade in the'tentacles and limb of the disc. On closer examination the firm part is seen to enclose a hard, shell-like, pneumatocyst, con- sisting of a horizontal division, included within the disc, and continuous with the simple solid vertical plate, which gives support to the sail or crest. The upper surface of the pneumatocyst is crossed at right angles to the direction of the crest by a linear diagonal groove, indicated on its under surface by a slightly elevated ridge, * while a longitudinal depression, increasing in depth from the margins to the centre, corresponds with the attachment of the crest. The horizontal division of the pneumatocyst consists of two thin laminee, passing into one another at their free edges, and united by a number of concentric vertical septa, between which are corresponding chambers filled with air. All these chambers communicate toge- ther by means of apertures in the septa. Of these each septum presents two, placed at opposite . points of its circumference, and all nearly in the middle line of the pneumatocyst. Kolliker made 106 HYDROZOA. the interesting discovery that many of the cham- bers have an additional opening, by which they communicate directly with the exterior. These apertures are situated in the proximal or upper wall of the chambers, along a line about midway between that of the openings just described and that of the vertical plate of the pneumatocyst. Of the thirteen apertures observed by Kolliker, six lay on one side of the vertical plate and seven on the other; one aperture lies in the wall of the central chamber, the other six at tolerably even intervals between this and the margin. Conse- quently, as there are more than six concentric chambers, some of them must communicate with these stigmata only indirectly." To the under surface of the five or six innermost chambers are attached from ten to fifteen elongated hollow pro- cesses containing air, the pneumatic filaments already mentioned. But complicated as the pneumatocyst of Velella may seem, not less so is its curiously modified s0- matic cavity. On all sides the limb is traversed by an anastomosing system of canals, which are ciliated, and communicate with the cavities of the phyogemmaria and large central polypite. Within the roof of the latter, close beneath the pneuma- tocyst, is lodged a peculiar brownish mass, the 80 called liver. This, also, is furnished with a canal system of its own, which eventually becomes Con- tinuous with the sinuses of the limb. In addition to the preceding organs Velella pos- sesses certain large “ glandular sacs,” for the @* covery of which we are indebted to Vogt. He describes them as presenting a very curious minute structure, and as arranged in a single series around Pe ee is hm a HYDROZOA. 107 the margin of the limb, to open on its dorsal sur- face, where they secrete a clear, viscid, mucus. The true nature of this mucus, whether excretory or lubricative, is still very imperfectly known. Thus the most striking modifications of the common plan of the Physophoride depend on differences in the relative size and shape of the cenosare and pneumatophore. Athorybia and Physalia have, like Velella and Porpita, a dispro- portionately large pneumatophore; but, in these ge- nera, it is globular or pear-shaped, not, as in those, discoidal. In Physalia, the true Portuguese Man- of-war of sailors, often wrongly regarded as the type of the present group, the float sometimes attains a long diameter of eight or nine inches; tentacles, several feet in length, being attached directly to the coenosare along its under surface (fig. 11, €). But, more frequently, the ccenosare is filiform, with a small pneumatophore; and, ex- cept in the case of Rhizophysa, swimming-bells are also present. Nectocalyces and hydrophyllia are alike absent in Porpita, Velella, Physalia, and Rhizophysa. Athorybia has hydrophyllia, without nectocalyces; Physophora nectocalyces, but no hydrophyllia. All other genera possess these two kinds of appendages. The swimming-bells of the Physophoride, when present, are more numerous than in the Calycopho- ridæ, and, among the different genera, vary much In size, shape, and mode of attachment, as also in the relative proportions of the nectosac. Each fre- quently has its surface marked with grooves and ridges, and may send forth processes which serve to embrace the coenosare, and connect it with its fellow of the opposite side. In some genera, more 108 HYDROZOA. particularly Physophora itself, two of the necto. calycine canals, which coincide with what may be termed the medial plane of the ccenosare, remain, as usual, straight, while the two other, or lateral, vessels become convoluted in a most complicated manner before reaching the circular canal. As in the Calycophoride, the common cavity of each nectocalyx is connected with that of the ccenosare by means of a tubular pedicle. The hydrophyllia present variations both in their structure, mode of attachment, and relations to the other appendages. They may be either foliaceous (Athorybia), or clavate (Apolemia), or thick and wedge-like, or even pyramidal (Agal- ma); while their surface is liable to be diversi- the ecenosare by more or less distinct peduz cles. immediately below the pneumatocyst, and above ? much smaller number of polypites (fig. 22; 4 In all other Physophoride with hydrophyllia, nectocalyces also are present; but Athorybits though destitute of the latter appendages, has the HYDROZOA. 109 power of alternately raising and depressing its hydrophyllia, so as to render them agents of pro- pulsion Fig. 22. j b | tus AM ^ d a A Morphology of PHYSOPHORDÆ :—a, Athorybia rosacea; b Physophora Philippii; a, pneuma i mentary nectocalyx; , hyd Bar -N to ) » Hydrocysts; m, polypite; T, tentacles ; B, hydrophyllia, (About the natural Size.) : 110 HYDROZOA. The polypites of the several genera differ chiefly in size and mode of attachment. They may he inserted in continuous series, along one side of ferently on either side, as exemplified y Rhizo- physa. In some cases they are attached directly to the ccenosarc ; in others, supported, with their tentacles and hydrophyllia, upon special stalks, In Apolemia they are arranged in groups of two or three, along with the other appendages, at intervals, as above mentioned; in Physophora and Athorybia they form a spiral or circlet around its distal extremity, while in Physalia, Velella and Porpita, they are restricted to the inferior surface of the much modified hydrosoma, Two kinds of polypites, a larger and a smaller, appear on the same ccenosarc in certain genera Much doubt exists as to the true nature of the inspection, than the true digestive appendage (Jig. 22, b.) HYDROZOA. 111 Attention has, in a previous section, been directed to some of the modifications which the tentacles of the Physophoride present. They appear in Apolemia as simple tubular processes, with numerous large thread-cells on one side: in Velella, they are equally simple, but much shorter, and slightly enlarged at their free ends. In Porpita there is, in addition, a series of longer prehensile appendages, having their distal ex- tremities clavate and beset with stalked knobs, or capitula, containing urticating organs, which are wanting in the smaller marginal “ cirrhi.” In Physalia, as above described, each tentacle con- sists of a broad conical basal sac, and a long simple ribbon-like process, having transverse reni- form enlargements (jig. 11, d). In all other Physophoride the tentacula are furnished with lateral branches, which in izophysa alone appear to be destitute of sacculi. These may want involucra, as in Halistemma or Forskalia, or possess these structures, and become further modified, as in all the remaining genera. The structure of the gonophores, though always medusoidal, is, in other respects, liable to much variation, Among many Physophoride well- marked differences of size, aspect, or relative number, distinguish the male and female reprodue- tive bodies in the same species. Thus in Agalma and Physophora the gynophores are only half the length of the androphores, than which, however, they are more numerous. In Velella and Porpita both androphores and gynophores become com- pletely detached, and the same is probably true of the female organs in Physalia. But the andro- phores of this genus, and the two kinds of gene- 112 HYDROZOA. rative appendages in many other forms, discharge, in all probability, their proper functions, without previous separation from the parent hydrosoma, The gonophore either presents a well-developed swimming-cup, with open margin and conspicuous canals: or the calyx, with its canal system, may m n a very rudimentary condition, so as scarcely to be distinguishable from its contained manubrium; while in the male organs of Stepha- nomia and Athorybia the apex of the latter slightly projects beyond the margin of the bell. In these and many other genera each gynophore gives rise to only a single ovum ; but there is reason to infer that it may be otherwise with the free-swimming gonophores of Physalia or Velella. Most of the Physophoride hitherto examined appear to be monocecious, the androphores and gynophores being borne on the same gonoblastidia, as in Physalia, Agalma, and Athorybia, or, more rarely, on separate stalks, as in Stephanomia. Besides the reproductive bodies, the gonoblastidia may give support to hydrocysts and other appen- dages, as in Physalia or Athorybia. In Halis- temma they are absent or so extremely short, that the gonophores seem attached directly to the coenosare. The phyogemmaria of Velella and Por- pita are obviously homologous with the gonoblas- ‘tidia of Hydractinia or the small polypites of Podocoryne; and just as the former genera differ from other Physophoride, Physalia indeed ex- cepted, in their laterally expanded ccenosare and independent tentacles, so, likewise, may Hydra- tinia be distinguished from all the more typical forms of Corynide. Of Physophoride Mr. Huxley has established HYDROZOA. LIS seven definable families, whose characters may be stated thus : — Order PHYSOPHORIDA. Family 1. APOLEMIADA. Pneumatocyst small. Conosare filiform. Nectocalyces and hydrophyllia present ; the latter united with the other appendages into groups, arranged at distant intervals along the coenosare. Tentacula without lateral branches. Family 2. STEPHANOMIADA. Pnewmatocyst small. Canosare filiform. Nectocalyces and hydrophyllia present ; the latter arranged with the other appendages in continuous series. Tentacula with lateral branches, terminated by sacculi. Family 3. PuysorHoniAD. Pneumatocyst small. Coenosare filiform, but short, and dilated at its distal end. Nectocalyces present, occupying most of the ccenosare below the pneumatophore. No hydrophyllia. Tentacula with branches and involucrate saceuli. Family 4. ATHORYBIADÆ. Pneumatocyst occupying almost the whole of the globular cenosare. — Nectocalyces absent. Hydrophyllia. Tentacula with branches and involucrate sacculi, each having two filaments and a median lobe. I BEL Oo. HYDROZOA. Family 5. RurzoPnuysiAp E. Pneumatocyst small. Ceenosare filiform, Nectocalyces and hydrophyllia absent. Tentacula having branches, without sac- culi. Family 6. PHYSALIADA. Pnewnmatocyst occupying almost the whole of the thick and irregularly fusiform cænosare, Nectocalyces and hydrophyllia absent. Tentacula with basal sacs, but no lateral branches. Family 7. VELELLIDA. Pnewnmatocyst flattened, divided into cham- bers by numerous concentrie partitions, and occupying almost the whole of the discoidal comosac. Nectocalyces and hydrophyllia absent. mou 15431 £ clavate, simple or branched, submarginate. A single central, principal polypite. 7. Order 6: Medusidz.—If the phyogem- maria of Velella and Porpita be regarded as gonoblastidia, the hydrosoma of these genera may then be said to present not more than one true polypite; a character in which they differ from all other Physophoride, but agree with the mem- bers of the next order, Meduside. Cuvier, iN- deed, associated the Velellidw, Meduside, and free zoöids of the Lucernaride in a single group under the name of * Acaléphes Simples "; the re- maining Physophoride, together with the Caly- cophoride, being distinguished as “ Acaléphes Hydrostatiques”. But the Velellide, like all othe! HYDROZOA. 115 Physophoride, differ, as has been shown, from Calycophoride, in possessing a float, and from Meduside in the characteristic mode by which the polypite is connected with the rest of the hydrosoma. In both the Calycophoride and Phy- sophoride, the nectocalyces (when present) and polypites are separately attached to different parts of the ceenosare. In the Meduside, on the other hand, the hydrosoma presents but one nectocalyx, from the roof of which a single polypite is sus- pended (fig. 4, f). The endodermal lining of the polypite passes into the central cavity of the swimming-organ, from which, as in other necto- calyces, canals radiate, to join a circular vessel surrounding the margin of the bell. From this margin depend tentacles, which may be either hollow processes of both layers, in immediate con- nection with the canal system, or, more rarely, prolongations of the gelatinous ectoderm itself. Around the outer margin of the nectocalyx, be- tween the endoderm of the circular vessel and its ectodermal investment, are embedded the mar- ginal bodies, vesicles or pigment-spots, whose peculiar structure has already been described J. 23). The outward form of the polypite varies greatly. It may be long and highly contractile, or stoutly cylindrical, or so short and broad as to be with difficulty discernible on the under surface of the bell (fig. 24). Very often it is curiously con- stricted. In internal structure it is not known to present any peculiar features. The oral margin may be either simple, everted, or produced into lobes, which, most frequently, are four in number, though m some forms it is much divided. In Liriope 116 HYDROZOA. Catharinensis, it is surrounded by a series of little sacs, each well packed with thread-cells. The size and shape of the nectocalyx in relation to the polypite with which it is connected may also vary considerably. The veil which surrounds the open margin of the nectosac in no case appears to Morphology of Mzpuswa :— AE dusid, seen in profile; 2, e same, viewed from below; c, its polypite; d, part of its mar- ginal canal, and other Mibi in connection therewith; — nectocalyx; 7, polypite; x’, marginal canal; M» veil; 7, tentade; x, radiating canal; w, reproductive organ; o', coloured spot; 0, marginal vesicle, be absent. More than four longitudinal canals sometimes occur. In Willsia these canals are seen to bifurcate, each branch again dividing into two others, so that, in this form, pe six canals open by twenty-four ducts into the circular vessel, (fig. 24 c). In Cunina, Ægina, and Æginopsis, both cit- ts thet en iat HYDROZOA. 117 eular and radiating canals disappear, their place being supplied by peculiar pouch-shaped processes, communicating with the digestive cavity of the polypite. The tentacles scarcely require anyspecial mention. Usually the distal extremities of their cavities Various forms of Mupvsrpz :—a, Æquorea formosa, seen in profile; 4, the same, viewed from above; c, upper view of Willsia stellata ; d, Slabberia conica ; e, portion of the marginal canal of Tiaropsis Pattersonii ; f, polypite of Bougainvillea dinema ; g, part of its marginal canal; A, Steenstrupia Owenii. (a, b and d are about the natural size; the others are magnified.) become more or less obliterated through vacuolation of the endodermal lining. In Trachynema and its allies the tentacles are stiff ; not contractile, as in other Meduside, 13 118 HYDROZOA. The reproductive organs have been stated to be. of the simplest kind, consisting of mere expansions, either of the polypite wall, or radiating canals, within which the generative elements are produced, t a time when the free gonophores of the Hydrozoa had been as yet imperfectly studied, it was the custom of naturalists to regard these bodies as independent individuals, worthy of being ar- ranged under definable genera and species. The singular resemblance of such gonophores to the Meduside began, at length, to attract attention. Then it was suspected that many of the Meduside were not individual organisms properly so called, but merely the free reproductive buds of various Hydrozoa. Eventually it was proposed to abolish the whole group of Meduside, and distribute their several forms among the different orders of the class. On the other hand, certain observations of J. Müller, Fritz Müller, Gegenbaur, and Claparéde, to which we have already referred, indicate the probable existence of a group of Medusid forms which appear to be the immediate products of d» generative acts, not of gemmation or fission, g. I In the present state of our knowledge, it seems better to sum up the several aspects of this doubt- ful question in the following series of conclusions I. That several of the organisms formerly de- scribed as Meduside are the free gonophores 0 other orders of Hydrozoa. 2. That the homology of these free gonophores with those simple expansions of the body-wall Which in Hydra, and some other genera are known to be reproductive organs by their contents alone ————M HYDROZOA. 119 is proved alike by the existence of numerous tran- sitional forms, and an appeal to the phenomena of their development. 3. That many other so-called Meduside may, from analogy, be regarded as, in like manner, me- dusiform gonophores. But that there may exist, nevertheless, a group of Medusid forms, which may give rise, by true reproduction, to organisms directly resembling their parents, and, therefore, worthy of being placed in a separate order under the name of Me- dusidc. All the Trachynemide and Æginidæ belong, according to Gegenbaur, to the order in question. And to the same group may be referred, provision- ally, that large assemblage of forms anatomically similar to true Meduside, but whose development is unknown; just in the same manner as genera and species are established for those Diphyozooids which, there is every reason to believe, are but the detached fragments of other Calycophoride. Pending the study of the life-history of these am- biguous Medusoids, their true nature must, also, remain undetermined. Such are the forms brought together by Gegen- baur in the systematic table here annexed, which, at the same time, concisely displays their most striking anatomical peculiarities. Order MEDUSIDE. With radiating canals. Benrodnoeti I gans in the poly- pite-wall. Ocelli at bases of the tentacles — . ; Family 1, OcEANIDZE. r4 120 HYDROZOA. Reproductive organs in the course of the radiating canals. Radiating canals arising from he base of the polypite. Ocelli. : . ; .. Family 2. TuavwANTIADA, Radiating canals arising from utermargin of the poly- pite. Vesicles. . ; Reproduetive organs as rounded protuberances of the radiating s. Family 3. ZEqvonipz, canals. Vesicle Tentacles contractile. . . Family 4. Evcorrpx. Tentacles stiff. Family 5. TRAOHYNENIDA, Reproductive organs as flattened expansions of the radiating ‘ canals. Vesicles. . : . Family 6. GERYONIDE. With pouch-shaped prolongations of the polypite, in which the re- productive products are formed, Vesi 3 : : . Family 7. Aeriwa. The Meduside were termed by Eschscholtz, Cryptocarpze; by E. Forbes, Gymnophthalmata ; and by Gegenbaur, Craspedota. These words contrast, respectively, with the names Phanero- carpe, Steganophthalmata, and Acraspedota ap- plied by the same naturalists to a large section of the Lucernaride. In this group the family Lwcernariado is not usually included, many na- turalists, from a mistaken view of its organisation, referring it to the class Actinozoa, of which Professor Milne Edwards has recently made it à distinct sub-class, under the title of Podactinaria. . Order 7: Lucernaridz,— In these Lucel” nariade the body is more or less cup-shaped, an requently about an inch in height, terminating proximally in a stalk of variable length, an furnished with a hydrorhiza, which, like that HYDROZOA. 121 Hydra, is not permanently attached. Round the distal margin of the cup arise a number of short tentacles which, in Lucernaria itself, are disposed in eight or nine tufts, but in Carduella form one continuous series. Their free extremities appear sucker-like or capitate; in Depastrum, however, they are simply clavate. The whole organism is semi-transparent, variously coloured, and of a gelatinous consistence (jig. 25). Th viewed from above, presents in its centre a four-lobed mouth, which is easily seen to form the free extremity of a distinct polypite, occupying the axis of the entire hydrosoma. The oral margin of this polypite is simple and slightly everted. Its gastric region exhibits a number of tubular filaments, arranged in vertical rows, and projecting freely into the digestive cavity. In transverse section the polypite may be described as somewhat quadrilateral, with a sinuous outline, ` which expands at its four angles to form as many deep longitudinal folds, within which the simple generative bands are lodged. The space between the polypite-wall and the inner surface of the cup is divided in the following manner. From each pro- jecting angle of the gastric region run a pair of ver- tical septa, which diverge widely from one another so as to reach the wall of the cup at points precisely opposite the two sinuosities on either side of the generative band. Thus four of the equidistant canals, outside of which are four other spaces, bounded, within, by two septa of the same pair, 122 HYDROZOA. and, externally, by the cup itself. The outer canals are closed superiorly by a roof, consistin of four inflected lobes from the summit of the Fig. 25. o, Rp o o oS60o ocho 2020009 Oo Qo? 9595500 ove sea. coo We 9o. 0920, 2.09 0090900 LOC Soo" 2080 05290 Se TX 9509 5959 ‘0302 oops LUCERNARIA: T 1 : pecimens of Lucernaria auricula, attached piece of sea-weed. That figured to the right is somewhat abnormal, having a ninth tuft of marginal tentacles, (Natural size.) By means of a band of muscular tissue which traverses its margin, and another set of fibres which radiate towards the polypite, the distal ex- tremity of the cup can fold inwards and contract itself at the pleasure of the animal. Some Lucer- nariado have been observed to detach themselves, HYDROZOA. 123 The swimming organ of Pelagia is sub-globose, about three inches in diameter, divided at its margin into sixteen lobes. Under eight of these lobes are seen notches, each lodging a hooded lithocyst, while from the remaining lobes depend an equal number of long, contractile tentacula. A polypite, short and broad, is attached, proxi- mally, to the concave centre of the umbrella; distally, it terminates in four furbelowed lips, which extend to a length of nearly four inches. A number of cecal sacs, corresponding with the lobes of the umbrella, are prolonged from the digestive cavity. In other characters Pelagia resembles the free zooids of Aurelia and its allies (fig. 7, b). The Lucernaride admit of being arranged under two principal sections, in one of which the development is continuous, in the other, discon- tinuous. The first section includes Pelagia and the Lucernariade, in which reproductive elements 124 HYDROZOA. ture; so that the relation between the producing and produced zoóid is here by no means the same as in the other orders of Hydrozoa. The true import of this fact should not escape attention, All the Lucernaride may be at once distin- guished by their umbrella. The cup or dise in the Lucernariade and Hydra-tube, the swimming organ of Pelagia and of the free zodids, are alike included under this designation. A free umbrella differs from a nectocalyx, with which it is often confounded, (1), in the absence of a veil; (2), in its mode of development; and (3), in the nature of its canal system and marginal bodies. The ra- diating canals, never less than eight in number, send off numerous anastomosing branches, which form a very intricate net-work. The peculiar structure of the lithocysts has been previously explained. Each is supported on the end of a short double-walled stalk, the cavity of which runs into one of the radiating canals. Protection is given to this apparatus by a hood-like, cres- centic fold of the ectoderm, at the base of which, and on the convex surface of the umbrella, a funnel- shaped orifice has been observed, whereby the ra- diating canal communicates with the exterior feature in their gastric filaments, the presence 0 which appears to be universal throughout the HYDROZOA. 125 order. They may, without difficulty, be oad in the common species of Lucernaria. The usually solid, perhaps through vacuolation ; Benes thread-cells, and, even when detached, exboute a peculiar writhing Ind of movement. In Chrysaora, "idee » Fritz Müller, they attain a length ae several in Three Eus of Lucernaride may be defined as follows: — Order LUCERNARID. Family 1. LUCERNARIAD E. Reproductive elements developed in the primitive hydrosoma, without intervention of free zooids Umbrella with short marginal tentacles and a proximal hydrorhiza. Polypite single. Family 2. PELAGIDz. Reproductive elements developed in a free umbrella, which either constitutes the primi- tive hydrosoma or is produced by fission from an attached Lucernaroid. Umbrella, with marginal tentacles. Polypite single. Family 3. RHIZOSTOMIDÆ. Reproductive elements developed in free zooids produced by fission from attached Lucernaroids. Umbrella, without marginal tentacles. Polypites numerous, modified, forming with the genitalia a dendriform mass depending from the umbrella. 126 HYDROZOA. Not far from Pelagia, but in a family by itself, Gegenbaur has placed the genus Charybde. Fritz Miller, however, shows, that in the close] allied Tamoya, a distinct veil is certainly present, while Charybdea itself is furnished with marginal processes, which seem to represent the same ap- paratus. SECTION IV. DISTRIBUTION OF HYDROZOA. 1. Relations to Physical Elements, — 2. Bathymetrical Distribution. — 3. Geographical Distribution. I. Relations to Physical Elements, — The Hydrozoa, asa class, are almost exclusively marine; Hydra and Cordylophora being the only fresh- water genera hitherto described. 2, Bathymetrical Distribution, — The ma- rine Hydrozoa, with reference to their distribution, may conveniently be divided into two groups, the fixed and the oceanic. The fixed Hydrozoa, Cory- nidæ and Sertularidæ, are less abundant between tide marks than at depths of a few fathoms, some forms extending their range to very deep water. The Corynidc are, perhaps, on the whole, more partial to shallow waters than the Sertularide, certain species of the latter order, especially of the genus Campanularia, being found at considerable depths. But the vertical distribution of severa forms is more limited than that of others. Thus Clava and Coryne appear usually not to wander HYDROZOA. 127 far from low-water mark, while Tubularia occurs at depths varying from less than one to more than fifty fathoms. The oceanic Hydrozoa in fine weather swim near the surface of the water, the approach of rain or wind compelling them to retire for safety to the more tranquil depths below. The large “ jelly- fishes " which, during summer and autumn, occur so abundantly in our seas, are, with few exceptions, the reproductive zoóids of Aurelia, Cyanea, and Chrysaora. Equally numerous with these, but less conspicuous from their extreme transparency, appear hosts of minute medusoids, while Diphyo- zoüids, Velella, Physalia, and one or two other Physophoride may, at rarer intervals, be de- tected. 3. Geographical Distribution.— The genera of Hydrozoa, are very widely distributed, renewed investigations tending rapidly to diminish the number of those supposed to be peculiar to certain regions of the globe. The limits of the area inhabited by Hydra have not yet been definitely ascertained. The other fresh-water genus, Cordylophora, has been met with only in Denmark, Great Britain, Ireland and North America. Not much is known accurately of the geographi- cal range of the Corynide; the Sertularide, from the ready preservability of their polypary, having been far more extensively studied. Sertu- laria, Plumularia, Antennularia, and Campa- nularia are truly cosmopolitan, and the same may, likewise, be said of some species of these genera, for example, S. operculata. Many South African 128 HYDROZOA. Sertularide are identical with European forms, both being, in a large number of cases, sufficiently distinct from the Australian, Phillipine, and New Zealand species. Several British species cannot, however, be distinguished from those of the Atlan- tic coasts of America, while on the other hand, greater differences prevail between these last and the North Pacific forms. ^ Among purely exotic genera may be mentioned Cryptolaria, one species of which has been found in Madeira and another in New Zealand, and Lineolaria, a remarkable Australian Sertularid, having gonophores"with two longitudinal rows of strong spines elevated in ridges, between which a few smaller spines are scattered over a flattened, transversely furrowed area. The Calycophoride and Physophoride have hitherto been most successfully studied in the Mediterranean and Southern seas; some genera, such as Diphyes and Agalma, having been obtained by Sars at a latitude of 614° N. off the shores of Norway. It were premature to describe any of these forms as peculiar to certain regions, many of the species and genera ranging over areas of consi- derable magnitude. Precise information is much wanting on the dis- tribution of the Meduside and Lucernaride. The free zodids of some species are very extensively diffused, and are occasionally met with by sailors in numbers so immense as almost to impede navi- gation. Our common Aurelia aurita has been obtained in the Red Sea, off the east coast of North America, and in various parts of the southem hemisphere. A few words on the phosphorescence of the HYDROZOA, 129 Hydrozoa may here be inserted. This property has been observed in most orders of the class, though, among the Physophoridæ, Stephanomia, and, of the Lucernaridæ, Pelagia are most re- markable for its manifestation. Some, however, of our more common jelly-fishes are also luminous. It does not appear that, in any of these, special light-giving organs exist. In the Medusida, the phosphorescence chiefly arises from around the marginal bodies, but, in some instances, it is emitted by the reproductive swellings, and, occa- sionally, by the walls of the central polypite. Our own Thaumantias lucifera, a species by no means rare, displays this phenomenon in a very beautiful manner. The little creature, when ir- ritated by contact of fresh-water, marks its position by a vivid circlet of tiny stars, each shining from the base of a tentacle. Such small Meduside are, doubtless, more efficient in promoting the luminosity of the ocean than their larger and, at times, more brilliantly conspicuous congeners. But the fixed Hydrozoa, which, obviously, can take no share in this display, are, also, eminently phosphorescent. A remark- able greenish light, like that of burning silver, may be seen to glow from many of our native Sertularide, becoming much brighter under various modes of excitation. It is an error to suppose, however, that thus alone do these cold, oily, flames emanate. «If (writes Professor E. active and alive imto fresh-water or Spirits, a gorgeous display of living stars is instantaneously produced," K 130 HYDROZOA. SECTION V. RELATIONS OF HYDROZOA TO TIME. Well-preserved remains of extinct Hydrozoa are wanting. Obscure indications of fossil Sertu- laridee and, perhaps, also of Lucernaride, have on a few occasions been met with, but of too fragmentary a character to permit of definition. Professor Agassiz, indeed, states that, many years ago his “ attention was attracted by two slabs of limestone slate from Solenhofen, the counterparts of one another, upon which a perfect impression of a Discophorous Acaleph was distinctly visible.” The Graptolites and Oldhamiz have, by some naturalists, been referred to the present group. Both, however, may, with more propriety, find a place in the Molluscan class of Polyzoa. CHAPTER III. THE CLASS ACTINOZOA. Section I. MORPHOLOGY AND PHYSIOLOGY OF ACTINOZOA. 1. Type of the Class: LE kei. General Morphology. — 3. Or- gan E m "a hensile apparatus. — 5. Tegumentary Organ 6. Corallum or tg ure — 7. Muscular System an Organs of of Locom otio E Nervous System and Organs of Sense. I. Type of the Class: Actinia. — The Ac- tiniq, or E us is the type of the class Actinozoa (fig. 2 The body of ees presents a soft, fleshy, or leathery consistence, and varies much both in mens attain, when expanded, a diameter of one to three inches, their height being vati less; but these dimensions are often exceeded. The expanded Actinia is somewhat cylindrical in figure, ae itself by one of its flattened ends, nown as the * base,’ a mouth being placed in the centre of » * disc,’ or opposite extremity. Nu- merous tentacles, disposed in alternate series, surround the disc's outer margin, between which and the mouth a region destitute of any append- K 2 132 ACTINOZOA. ages, the ‘peristomial space,’ is usually observ- able. is a short, distensible tube, open at both ends, and extending about half-way towards the base of the animal; in diameter scarcely exceeding the mouth itself, with which its form, when viewed from above, is seen to correspond. The folds, or grooves, between the oral tubercles are continued, in the form of semi-canals, along the inner surface of this stomach, until, finally, they reach the wide aperture by which it communicates with the so- matic cavity. A transverse section of the body of Actinia exhibits two concentric tubes, the outer being constituted by the body-wall, the inner by the digestive sac. The wide space which intervenes between these tubes is divided by a number of radiating partitions, or ‘mesenteries,’ arising at definite intervals from the inner surface of the body-wal. The ‘primary,’ or first-formed and widest, mesenteries serve to fix the stomach in its place, their inner edges being inserted throughout the entire length of its outer surface. From the base of the stomach, the inner edge of each me- sentery, becoming free, arches, at first, abruptly outwards, and then, more gradually, downwards and inwards, until at length it reaches the centre of the base, from which all the primary mesen- teries appear to radiate. Other partitions, de veloped in successive cycles between those just ACTINOZOA. 133 mentioned, and having no connection with the stomach wall, are distinguished, in accordance with their relative narrowness, as ‘ secondary me- senteries,’ ‘ tertiary mesenteries,’ and so on. Fig. 26. D ( i jd ^in As fil UU Morphology of AcrrNozoA : —a, polype of Alcyonium; b, ideal transverse section of the same; c, longitudinal section of Actinia ; — M, somatic cavity; c, mesentery; 3’, digestive cavity; 5, wall of digestive cavity; o, mouth; 7, tentacles; ex, ectoderm; ev, endo- e p, muscular layer; B’, base; p, reproductive organs; ¢’, eonvoluted filaments, containing thread-cells. («æ and bare en- larged; c is of the natural size.) The mesenteries of each cycle are arranged in alternate pairs, while those belonging to opposite sides of the body correspond and are similar to 134 ACTINOZOA. in radii, along the base and dise. Their arrange- ment is best seen in living, semi-transparent species, without any recourse to dissection. the disc. They are most constant in the primary partitions ; the secondary mesenteries being fre- quently imperforate. The tentacles, which are hollow, and, in many Actiniæ, perforate at their free extremities, open directly into the somatic chambers. To the faces of the mesenteries are attached contents. Most Actiniæ are dicecious, but, by no external character can the individuals of both sexes, which seem to be about equally numerous, be distinguished from each other. Accurate obser- vations are yet wanting on the reproduction of Actinia. It is probable that the spermatozoa, first diffused in sea-water, find their way through the mouth to the ova contained in the general cavity of the body. ; long convoluted cord, or * eraspedum,' arises in front of the reproductive apparatus, along the free edge of each mesentery. In addition to the - craspeda, other organs of similar structure, terme ACTINOZOA. 135 ‘acontia, are occasionally met with. Both cras- peda and acontia are richly furnished with thread- cells, for the emission of which special apertures along the wall of the somatic cavity have, in some species, been observed. Mr. Gosse, who gives the name of ‘cinclides’ to these apertures, describes them as varying considerably in size and opening directly into the somatic chambers. “ Each is an oval depression, with a transverse slit across the middle.” The sides of the cinclis can be opened or closed at the animal's pleasure, yet, when sepa- rated to their utmost extent, the front of the orifice is seen to be protected by a very thin superficial film. In the common Sea-anemone the margin of the dise is furnished with a series of white or bright blue specks, which some writers describe as a rudimentary apparatus of vision. The structure of these organs is not yet fully understood. Like the body-warts, mentioned elsewhere, they are probably to be regarded as sac-shaped prolonga- tions of the outer layer. Good evidence has not yet been brought forward of the existence of a nervous system in Actinia. A muscular apparatus is, however, well developed, and has been described in detail by M. Hollard. In the inner layer of the body-wall are two sets of flattened muscular fibres; a superficial circular, and a deeper longitudinal. Each mesentery has four muscles, two for each of its faces. The stomach wall is also provided with its own mus- cular fibres, these being so arranged in the vicinity of the inferior aperture as to permit the latter to be closed at pleasure. The existence of this sphincter is denied by some observers. A similar K 4 136 ACTINOZOA. arrangement has been noticed in the delicate muscles which surround the tps of the tenta. ula. Though, histologically, the several Structures of Actinia admit of being resolved into two founda- tion membranes, an ectoderm and an endoderm, yet each of these, more especially the former, manifests a tendency to differentiate into other secondary layers, so that several apparently dis- tinct tissues are recognizable in the body of the adult animal. This is well seen in the column wall, the principal thickness of which is composed of the two sets of muscular fibres mentioned abore. That portion of the ectoderm which serves as an external investment to this muscular wall appears to consist, in some Actiniz at least, of two separ- able, transparent membranes ; an outer, or epithe- lial, forming the general surface of the body, and an inner or dermal layer in immediate contact with the muscular substance. The dermal mem- brane is almost wholly made up of a structureless periplast containing very few endoplasts ; in the epithelium, however, endoplasts are more abundant. Between these two membranes thread-cells are sometimes found embedded in such numbers as almost to form a true layer, while close beneath the epithelium occur masses of the pigment gran- ACTINOZOA. 137 digestivesac does not differ, in any essential respect, from that of the column, than which it is much thinner and more delicate, its endoderm being richly furnished with cilia. Ordinary pigment ranules are here absent, but in their stead occurs, within the upper portion of the stomach wall, a thin layer of a red or yellowish brown tint, to which some writers have ascribed the function of a liver. The mesenteries are to be regarded as processes of the column wall. The thin layers of endoderm which invest the two sides of each mesentery are produced beyond its free edge to form the sac-like covering, within which the repro- ductive elements are lodged. Having enclosed these, the two layers are brought into mutual con- tact, a narrow band being thus produced, to which the cord-like craspedum is attached. The flower-like appearance of the fully expanded Actinia is sufficiently familiar to every sea-side ob- server. While the animal is in this condition any passing object likely to serve as food is firmly grasped by one or more of the tentacula, which, aided by the muscular contractions of the body wall, soon force it into the interior of the digestive sac. The morsel thus swallowed is usually, after atime, rejected by the mouth; while the nutritive matters withdrawn from its substance by the action of the stomach secretions are transferred to the somatic cavity, within which, as in the Hydrozoa, the process of nutrition is completed. Of the voracity of the Actinia many amusing accounts have been made known. It may, nevertheless, be kept in eaptivity for several months, if supplied with water containing minute particles of organic matter. 138 ACTINOZOA. mouth and tentacles being more or less completely concealed by the folded margin of the disc. In the act of expanding, this is gradually rolled backwards, displaying the tentacles, which, as the margin con- tinues to unfold itself, are soon distended to their full extent by the pressure of the fluid contained in the somatic cavity. The Actinia has the power of effecting con- siderable alterations in the general form of its body by the alternate contraction and expansion of the muscular fibres mentioned above. It can also, like the Hydra, shift its position at pleasure, though some species, under ordinary circumstances, attach themselves so firmly as not to be removed without laceration of the base. 2. General Morphology.— In no essential respect does any Actinozoón depart from the typi- cal structure above described, nor do the members of the present group present such varied modifi- cations of a common plan as have been shown to appear in the Hydrozoa. In all Actinozoa the digestive apparatus, though communicating freely with the somatic cavity, is furnished with a wall of its own, between which and the outer boundary of the body the generative elements are produced. By these characters they may readily be distin- guished from the Hydrozoa, with which, in the more minute details of their structure, they closely agree; the body of an Actinozoón, like that 0 ACTINOZOA. 139 a Hydrozoón, wholly consisting of ectoderm and endoderm. The entire class is divided into four orders. In the first of these, Zoantharia, represented by Activia and its immediate allies, the number of mesenteries, tentacles, and other parts in connec- tion therewith is, in general, some multiple of five orsix. In the three remaining orders some mul- tiple of the number four appears to prevail. Thus in the Alcyonaria there are eight somatic cham- bers, eight mesenteries, and eight tentacles, not simple, as in Actinia, but furnished with pinnate margins (fig. 26, a and b). The members of the third order, Rugosa, known only through its fossil representatives, seem to have possessed a structure in some respects intermediate between that of the two preceding sections. Lastly, the Ctenophora are free-swimming, gelatinous animals, in physiog- nomy widely different from the other Actinozoa, though evidently akin to these in their leading anatomical features. They are the most highly or- ganized of Coelenterate animals, a common repre- sentative of the order, Plewrobrachia, possessing à complex nutritive apparatus, together with well-defined organs for prehension, reproduction, locomotion, and, in addition, unmistakeable indi- cations of a nervous system ( figs. 27 and 39). Like the members of the preceding class, many of the Actinozoa multiply freely by gemmation, complex plant-like individuals being thus formed which consist of numerous zoóids united by a ccnosare (figs. 34, d and 35). In such instances, each nutritive zooid, or that portion of the organism Which answers to the polypite of a Hydrozoón, is distinguished by the name of « polype When 140 ACTINOZOA. gemmation does not occur, as in several Species of Actinia, the name polype is often employed to denote the entire animal. Though the soft parts of the Actinozoa have only of late years received proper attention from zoólogists, yet the hard structures to which these animals give rise have, under the general name of “ Corals,” been objects of interest from a very remote period. The outward aspect of Corals, as preserved in our museums, is familiar to most persons. Their true nature, in relation to the living organisms by which they are produced, is known only to the student of the Actinozoa, The limits in size presented by the several forms of Actinozoa are not very readily defined. The polypes of this group are usually much larger than the polypites of the Hydrozoa, and, in a few cases, attain a diameter of even eighteen inches, The gigantic dimensions of some of the coral structures, produced by a combined process of growth and gemmation, are well known. Though the separate polypes of such a mass may, in certain instances, be little larger than pin’s heads, yet, very often, they are half-an-inch in diameter, and not unfrequently, their size is much more consider- able. It can scarcely be said that any Actinozoa are of microscopic dimensions. All the Ctenophora are conspicuous animals; Pleurobrachia, already alluded to, one of the smaller members of the group, being often about the size of an ordinary The various structures of the Actinozoa may be described under the general heads of a. Organs of Nutrition, 6. Prehensile apparatus, ACTINOZOA. 141 c. Tegumentary organs, d. Corallum or Skeleton, e. Muscular system and organs of Locomotion, f. Nervous system and organs of Sense, g. Reproductive organs. . Organs of Nutrition.—The whole interior of the polypes and, in the budding species, that of the ecenosare by which they are connected, con- stitutes the nutritive apparatus of the Actinozoa. In most Zoantharia the structure and functions of the polypes are best illustrated by reference to the account of Actinia, above given. But in some members of this order the digestive sac is rela- tively much shorter than the somatic cavity, being, according to Dana, little more than ‘2 of its length in the genus Palythoa. So, likewise, among the Alcyonaria, the somatic cavity of each polype usually appears as a long, somewhat slender, tube, in the upper portion of which the comparatively short stomach is, as it were, suspended ; the proximal, or post-stomachal, region of the body cavity becoming gradually much narrowed. In the Gorgonide, however the somatie cavity is shorter and slightly dilated towards its basal extremity. There are two apertures to the digestive cavity of every Actinozoon ; first, the mouth, and secondly, the proximal or inferior outlet, which opens freely into the somatic cavity. In many, though not all, Alcyonaria, the somatic cavities of the separate polypes which make up the compound mass are prolonged into canals, freely communicating with one another, inoscu- lating, and forming a sort of aquiferous system, 142 ACTINOZOA. within which the nutritive products circulate. In Meandrina and certain other oantharia, the general cavities of the polypes open by wide aper- tures into each other; but in very many forms of coralligenous Actinozoa it is erroneous to suppose that any connection, available for nutrient pur- poses, is maintained between the different polypes presents peculiar features which render it necessary that some account of Pleurobrachia (= Cydippe) ACTINOZOA. 143 as a typical example of the group, should in this place be given (jig. 39, e). The body, or * actinosome,’ of Pleurobrachia is sub-spherical or melon-shaped, colourless, gela- tinous, and perfectly transparent, bnt displaying, in sunlight, tints of a beautiful iridescence. Two poles, an oral and an apical, mark the opposite extremities of the axis of the animal. The slightly protuberant mouth appears, when closed, as an elliptical fissure, presenting two flattened sides and two opposing edges. Eight meridional bands, or * ctenophores,’ bear- ing the comb-like fringes, or characteristic organs of locomotion, traverse, at definite intervals, the interpolar region, which they divide into an equal number of lune-like lobes, termed the *actino- meres. But this division of the body does not extend into the immediate vicinity of the poles, before reaching which the ctenophores gradually diminish in diameter, each terminating in a point. Around the apical pole, in particular, may be noticed a somewhat oblong, depressed, area, dis- tinctly circumscribed by the adjacent converging actinomeres. he eight actinomeres are by no means equal in size, and, to understand their relations aright, it seems desirable to distinguish three principal kinds of these parts as the antero- posterior, the lateral, and the accessory actino- The two antero-posterior actinomeres, wider than their fellows, are opposite to each other and the edges of the elliptical mouth. At right angles to these, but in like manner opposite one another, lie the two lateral actinomeres, which, therefore, 144 ACTINOZOA. face the flattened sides of the mouth. The acces- sory actinomeres, slightly narrower than either of the preceding, serve to occupy the four inte. spaces which occur between the lateral and an- tero-posterior pairs. The lateral actinomeres are further distinguished by the presence in each of a large sac, which opens obliquely, outwards and downwards, about mid. way between the equatorial region and the apical ments. The structure of these parts, as also of the prehensile, locomotive, and reproductive appa- ratuses are described in their appropriate para- graphs. At present let us chiefly notice, in con- nection with the form of the body, the arrange- ment of its somewhat complex nutrient system. (fig. 2 just above the ctenocyst and nervous mass. From the funnel three pairs of canals are given off ACTINOZOA. 145 Two of these, the ‘apical canals,’ very short and narrow, run directly downwards and outwards on either side of the ctenocyst, and soon open exter- nally as the ‘apical pores,’ situate immediately beyond the margin of the ‘apical area) Some writers describe the apical canals as lateral, others as antero-posterior in their direction. oth opinions are partially correct, the apical pores Fig. 27. X: OS i on A 1 NS 2 2 / we M 4 4 sg MAIS — IG proe l--77L4/ à c NEA Morphology of PLEUROBRACHIA :— 4, diagrammatic longitu- dinal section of Pleurobrachia; b, the same in transverse section ; o, mouth; ò, digestive cavity; K’, funnel; o' ganglion and etenocyst; 7’, sac of the tentacle; 7, tentacle, with one of its branches ; x, radial canal; x’, one of the ctenophoral canals; x”, apical canal ; x, paragastrie canal. The numerals 1 and 2 indicate the first and second bifurcations of the radial canals. being obliquely opposite one another, though placed on different sides of the body. Two other canals, the * paragastric canals,’ assume an upward course, parallel to and not far from the flattened sides of the digestive sac, but terminate cæcally before quite reaching its oral extremity. A third pair of canals, much wider and shorter than those Just mentioned, radiate from the funnel in a L 146 ACTINOZOA. horizontal or slightly oblique direction, proceeding towards the bases of the pits in which the tentacles are lodged. Before gaining these, however, each ‘radial canal’ divides into two branches, the secondary radial canals; each of these again into two others, and, thus, eight tertiary radial canals are formed, which run towards the equatorial region of the body, where they open at right angles into an equal number of longitudinal vessels, the ‘ctenophoral canals, whose course coincides with that of the eight locomotive bands. These canals end cæcally both at their oral and apical extremities. If, now, a comparison be made between this nutrient system and that of Actinia, the digestive sacs of the two organisms are clearly seen to cor- respond; in form, in relative size, and mode of communication with the somatie cavity. The funnel and apical canals of Pleurobrachia, though — more distinctly marked out, are the homologues of those parts of the general cavity which in Actinia are central in position and underlie the free end of the digestive sac. So, also, the para- gastric and radial canals may be likened to those lateral portions of the somatic cavity of Actinia which are not included between the mesenteries. Lastly, the ctenophoral canals of Plewrobrachiaand the somatic chambers of Actinia appear to be truly homologous, the chief difference between the two forms being that while in the latter the body chambers are wide and separated by very thin partitions, they are in Plewrobrachia reduced to the condition of tubes; the mesenteries which intervene becoming very thick and gelatinous, 8? as to constitute, indeed, the principal bulk of the ACTINOZOA. 147 body. In both, the nutrient system is lined by a ciliated endoderm, the vibratory action of which serves to maintain a circulatory motion of the included fluid. The contractile tissues of the ectoderm may further assist such movements. And in Pleurobrachia, whose bilateral symmetry is more strongly marked than that of Actinia, the nutrient fluid, as Agassiz has shown, is at times alternately impelled between the right and left sides of the somatic cavity. Very many curious modifications are presented by the canal system among the different genera of Ctenophora, to some of which reference will be made in the more particular account to be given of that order. No manducatory apparatus exists in the Acti- nozod. The oral margin may, however, be some- what thicker and firmer than the surrounding parts, or otherwise become altered in appearance ; and the cilia of the digestive sac may also differ from those which occur on other regions of the bod As in Actinia, one part of the digestive cavity may undergo someamount of modification, coloured granular masses appearing in its walls which have been supposed to indicate a liver. Such coloured cells in the Ctenophora usually arrange themselves as vertical ridges which surround the innermost, or stomachal, division of the otherwise transparent digestive sac. Milne Edwards has also shown the existence in Cestum of another structure whose function is probably secretive. Between certain of the cili- ated bands and their corresponding ctenophoral canals; parallel to, and in close connection with L2 148 ACTINOZOA. the latter, runs a tube occupied by a number of granular bodies, and giving off, at right angles to itself, a series of short vertical branches, which open along the line of the locomotive fringes to communicate with the surrounding medium, 4. Prehensile apparatus, — The tentacles of the Actinozoa, like those of the Hydrozoa, appear usually, if not always, as hollow appendages, in immediate connection with the somatic cavity, their walls being richly provided with thread-cells and consisting throughout of two layers, an ecto- derm and an endoderm. Among the Zoantharia, the tentacles vary ex- ceedingly in size and external form. Viewed from without, they are seen to arise, save in Humenides, disc (figs. 33—35). Dissection shows them to be hollow processes in free communication with the somatic chambers, each of which is furnished with one or more of these appendages. Their most usual form is that of a slightly curved, more or less tapering, cone, as in many species of the genus Actinia itself. But from this typical aspect there are very many aberrant modifications. Among the Alcyonaria, the tentacles are com- paratively short, closely arranged in a single cycle of eight around the mouth of each polype, their margins being produced into a number of lateral pinne (fig. 26, a). These last, according to Dana, are perforate at their free ends, the extremity of the tentacle itself being cecal; but this statement is denied by Milne Edwards and others, who more correctly view the pinnz, in some genera at least, ACTINOZOA. 149 as destitute of distal orifices. The pinnz are very contractile, so as to vary in form from mere lobes or tubercles to long filiform fringes. But little diversity is exhibited by the tentacles of this order. Except in the distinctive characters just mentioned, they agree essentially with those of Actinia. The tentacles of the Ctenophora are best des- cribed in connection with the general survey of the characters of that order. 5. Tegumentary Organs.— In but few Acti- nozoa do the tentacles appear to be processes of the ectoderm only. This layer, as we have seen in Actinia, exhibits a tendency to differentiate into two diverse planes of growth, which, with Professor Huxley, we may designate the *ecderon' and the ‘enderon’, respectively. Sometimes, however, this distinction is not observable. The ectoderm is usually ciliated, and in the Ctenophora becomes very thick and gelatinous, presenting a structure somewhat similar to that which occurs in the oceanic Hydrozoa. Gegenbaur describes the re- ticulating threads which traverse the periplastic mass as tubular in young Ctenophora, but, as growth advances, tending to become solid. Other minor histological modifications have been ob- served. The general surface of the body, smooth in most Ctenophora, is in Chiajea and a few other genera diversified at intervals by the elevation of numer- ous simple papilla. And, in some Sea-anemones, it exhibits a number of clear warts or vesicles, each of which, according to M. Hollard, possesses a muscu- lar arrangement of its own, in connection with a sort of two-lipped mouth; so that a needle, or L3 150 ACTINOZOA. other small foreign body, introduced into the vesicle, is quickly and tenaciously secured. In their natural situations these creatures are often completely covered by fragments of shell, gravel, or sand, attached to their bodies by a peculiar viscid secretion, in the production of which these warts are, perhaps, concerned. Or, the epidermic secretion may give rise to a distinct membranoid coat, protecting the integu- ment of the animal, from which it is at times cast off by what may be termed a process of sloughing, Such a membrane in Cerianthus Mr. Gosse states to be “ wholly composed” of altered cnidz, which intertwine one with another to form a wide tube, investing the entire surface of the column. Here the connection of the tube is so loose that it canat any time be removed without much inconvenience to the animal, but, in other genera, a more adherent covering may be found. In Adamsia the base excretes a delicate, somewhat chitinous membrane, which, upon occasion, may continue its growth beyond the attached outline of its possessor, and even form an artificial extension of the peculiar surface which this genus is wont to choose for its abode. The thread-cells of the Zoantharia have been studied with great care by Mr. Gosse, who dis- tinguishes four principal kinds of these bodies by the titles of ‘chambered,’ * spiral,’ * tangled’ and ‘globate cnide.’ The chambered cnide (which are the most common) are of a long oval form, the ecthoreum, which varies greatly in length, presenting in all cases, thecomplex armature characteristic of these minute weapons ; a number of delicate barbs, or * pterygia’, being attached to ACTINOZOA. 151 a thickened band, the *strebla', twisted in a screw-like manner around the basal portion of the thread. The tangled cnide are relatively broader then the preceding, having a very long ecthorzeum, loosely rolled up into a confused bundle. The spiral cnide present a much elongated, fusiform chamber, within which the thread lies coiled in a close regular spiral. Lastly, the so-called globate cnide have been seen to push out at each end a cy- lindrical protuberance, sometimes equal in length to the enida itself, which does not contain any thread. On the urticating organs of the Alcyonaria less attention has been bestowed. In general, they are of minute size and seem to resemble the tangled enide of the Zoantharia. In Sarco- dictyon they are aggregated on the tentacular pinne in minute rounded swellings, homologous with the palpocils of the fixed Hydrozoa. The thread-cells of the Ctenophora present a peculiar structure. Each, in Plewrobrachia, ac- cording to Professor H. J. Clark, appears of a rounded or slightly napiform figure, and is covered externally by a single, dense, layer of very minute granules. From the summit of a broad conical projection on the inner surface of its otherwise uniformly thick, but rather delicate, wall, arises, in a very oblique direction, the simple thread, which, after making not more than seven or eight, equi-distant, spiral turns, set very far apart, ter- minates suddenly in what seems to be a free ending, precisely opposite its point of attachment. The thread is cylindrical, smooth, apparently solid, of firm consistence, and about eight or nine times the length of its envelope, from which it is set 152 ACTINOZOA. free by the gaping of the cell itself, around the thread’s distal extremity. On the whole it seems safe to say that among the Actinozoa the thread-cells exhibit a greater ten- dency to become collected in particular organs than has been shown to be the case with the Hydrozoa; though we by no means wish to forget the tentacles or nematophores of the latter. The mesenteric cords of the Sea-anemones strikingly illustrate this, and, in the Ctenophora, the urticating organs form a well marked layer on the outer surface of the tentacles and their lateral fringes. Parallel to, and agreeing in position with, these last, the two tentacles in Hormiphora are furnished, as Gegen- baur has proved, with a number of very peculiar, bright yellow, appendages, one between from about every ten to fifteen of the ordinary side filaments, Each of these bodies, which serve as special recep- tacles for the thread-cells, is hollow, of a flattened fusiform, or lancet-shaped, form, with a short stalk of attachment, above which it is prolonged later- ally into several pairs of tubular processes, which gradually diminish in length, and finally vanish altogether, before reaching its free, simply taper- ing, extremity. igment-masses, irregularly scattered in some Actinozoa, are in others combined so as to form be examined in the commoner species of Sea- anemones. In the substance of the body-wall and tentacles, outside the muscles of the mesen- teries, or even in the digestive tube itself, such interrupted layers of colouring-matter have been bserved. The exquisite roseate tint of some Ctenophora ACTINOZOA. 153 is due to the presence of pigment-streaks or less regular stellate masses, in various parts of the ectoderm. rallum or Skeleton.—Intimately con- nected with the tegumentary organs of these animals, under which head, indeed, it might with- out impropriety be described, is the so-called skeleton, or ‘corallum’, with which so many of them are furnished. The term coral, or corallum, is properly re- stricted, in zoólogy, to the hard structures deposited in the tissues, or by the tissues, of the Actinozoa. Any form of this class which possesses such a framework is called a ‘Coral’. All Actinozoa are not coralligenous. The Cteno- hora and several species of Zoantharia deposit no corallum. On the other hand, the order Rugosa is known only from the remains of extinct Corals. Of coral structures there are two principal kinds, which must be carefully distinguished from one dudihér. jecur the ‘sclerobasic’ corallum, a true tegumentary excretion, formed by the conversion of successive growths from the outer of skeleton, deposited, as it is, within the tissues of the animal, and, in all probability, by the en- deron. The sclerobasie corallum is by Mr. Dana termed “foot secretion”; the sclerodermic, «tissue se- cretion ”. Let us first notice the sclerobasie corallum, Which is found only in certain budding composite 154 ACTINOZOA. Actinozoa. Most frequently its texture is simply corneous, but in Corallium proper and a few other forms, it becomes calcareous by deposition; and in Hyalonema and Hyalopathes, if these be true Actinozoa, it is siliceous. In Isis and Mopsea it consists of alternately disposed calca- reous and horny segments, thus, as it were, com- bining strength with a yielding plianey. In Isis branches are developed from the calcareous, in Mopsea from the horny segments of the sclero- basis. Melitea presents a like structure, save that, in it, the corneous segments are replaced by others which assume a porous and suberous as- pect. Section of a sclerobasis shows it to be, in some cases, solid or nearly so; in others, distinctly resolvable into concentrie layers, which serve, also, to illustrate the manner in which it has been produced; while, more rarely, it is composed of an aggregation of separate fibres. Two principal modifications of form distinguish the sclerobasis. In some Actinozoa it constitutes varying much in composition and thickness. In others it is attached, simple or branched, and often singularly plant-like in physiognomy, as m those Gorgonidc to which the name of Sea-shrubs has been applied. The relations of such structures to the soft parts of the animal are, with little difficulty, ‘discerned. The sclerobasie corallum is, in fact, outside the bases of the polypes and their con- necting coenosarc, which, at the same time, receive support from the hard axis which they serve t? conceal Thus the coenosare of these corals ap- ACTINOZOA. 155 pears as a soft, fleshy covering, from which the several polypes arise, their somatic cavities freely communicating one with another. Far different in its nature is the sclerodermic corallum, deposited, as above stated, within the bodies of polypes, which, in some cases, remain separate, but, in others, multiply by continuous gemmation. And, just as the whole body of an Actinozoün is made up either of one polype or of several united by a coenosare, so, too, may the fully developed sclerodermic corallum consist of a single ‘corallite’ or of several connected by a * cenenchyma ’. The parts of a typical corallite are these ( fig. 28). First, an outer wall, or ‘theca’, somewhat cylindrical in form, terminating distally in a cup-like excavation, or *calice', and having its central axis traversed by a ‘columella’. The space between this and the theca is divided into ‘loculi’, or chambers, by a number of radiating vertical partitions, the ‘septa’. These do not, in certain instances, quite reach the columella, but are broken up into upright pillars, or ‘pali’, arranped in one, two, or three circular rows, termed ‘coronets’. All the preceding parts are best brought into view by transverse section. Longitudinal division of a corallite shows, fre- quently, the existence of imperfect transverse partitions, or *dissepiments', which, growing from the sides of the septa, interfere, to a greater or less extent, with the perfect continuity of the loculi. Sometimes the septa have their “sides covered with styliform or echinulate processes, which, in general, meet so as to constitute nume- Tous * synapticule ’, or transverse props, extending 156 ACTINOZOA. ` across the loculi like the bars of a grate.” Tn other cases, the dissepiments are replaced by the development of successive horizontal floors, or ‘tabulz ’, which do not grow from the septa, but Fig. 28. , tabulee; P, coenenchyma. (The septa should be seen between the dissepiments, but are left out for distinctness’ sake.) le; extend, without interruption, across the entire space bounded by the theca. On the We surface of the latter may occur ‘coste’, or ver lines, corresponding in position to the septa Wee” ‘exothecee’, which arise from the sides of the a ACTINOZOA. 157 cost, thus representing the dissepiments; and a continuous layer, or * epitheca ’; consisting of the coalesced, external, indications of tabule. It needs scarcely to be stated that an organism producing such a structure as the foregoing must elosely have resembled, in every essential respect, the Actua, or typical polype, previously de- scribed. The relations of the septa and pali to the mesenteries, of the theca to the column wall, of the columella to that part of the enderon which forms the floor of the somatie cavity below the digestive sac, are, indeed, sufficiently obvious. The septa, too, like the mesenteries, are primary, secondary, and tertiary, according to their degree ofapproximation to the columella; the primary septa alone being in direct contact therewith. All these parts are, in the living animal, completely concealed by the soft integuments: the digestive sac, and much of the somatic cavity, especially its upper portion, performing, as in the soft-bodied species, their proper nutrient and reproductive functions ( fig. 33). In a similar manner is the coonenchyma de- posited within the coenosare (fig. 28). It may be united with the corallites at their bases only, thus forming a creeping expansion or stalk, or become connected with them throughout the greater por- tion of their height. There are even cases in Which the corallites appear sunk amid a very abundant ecenenchyma, while, in others, the same structure is but sparingly developed. The relative distance of the corallites from one another is also subject to much variation. But the typical structure of the corallite above described does not admit of being studied in any 158 ACTINOZOA. single species. Its nearest approach, as Milne Edwards has stated, is found in the genus Aceryy. laria, which wants, however, synapticule and columella, the pali, also, being rudimentary. This genus is a member of the extinct order Rugosa, in which the sclerodermie corallum may, per- haps, be said to attain its most remarkable deve- lopment. Both septa and tabuls here occur in the same corallite, the former being always ar- ranged in multiples of four. 9 See a EZ $2 Ey T cg Portion of corallum, of the natural size. Among the sclerodermic Zoantharia tabule and septa are scarcely known to co-exist, a specia section of this group, Tabulata, being distin- guished by the nearly exclusive possession of the former (jig. 29). In two other large divisions, the Aporosa and Perforata, including several families, septa, in sets of five or six, normally occur in some are associated with dissepiments more rarely with synaptieule. Ina fourth section; ACTINOZOA. 159 Tubulosa, the septa are indicated by mere streaks g. 36, €) And in the Tubiporide, a famil of Aleyonaria, septa are absent; each corallite be- ing a simple tube, connected with the thecæ around it by horizontal plates, which represent the inner transverse floors of the Tabulata (fig.30). S Tuprpora Music Fragment of corallum, of the natural size, From the Tubiporide to other Alcyonaria in which the corallum, though sclerodermic, soon ceases to present traces of theca, a transition, not very abrupt, may be effected. Such intermediate stages, though not of much value to the sys- tematic zodlogist, are of great interest in a mor- Phological point of view, since they show well the Manner in which the complete sclerodermic co- tallum has been formed ; thus at once illustrating its minute structure and the several stages of its development. In Telestho, the corallum is made 160 ACTINOZOA. up of a number of branching tubes, which are not, as in all the preceding forms, perfectly calcareous, In Cornularia and its allies a corallum, never wholly tubular or of a firm calcareous consistence, has yet been detected ; and in Sarcodictyon masses of spicules only can be observed. In some species of Aleyonide proper, the spicules attain a com- paratively large size, and become aggregated into definite nodular masses. These * dermosclerites’, as Milne Edwards has shown, are of two principal kinds, the fusiform, and the irregular. e for- mer are somewhat cartilaginous in consistence, and have their surface studded with slight asperi- ties. The irregular nodules are stronger and more decidedly calcareous, presenting six faces, each, in general, furnished with a tubercular enlargement, which sometimes prolongs itself into a number of spines, bearing on their sides other secondary tubercles. By the coalescence of such masses and the deposition of more minute particles among their interstices, a thecal corallum, in other Ach- mozod, at length comes to be formed. In Alay- onium itself the spicules, though numerous, are not of large size, and are most conspicuous in the column wall below the margin of the dise. Re- turning to the Zoantharia we find, in the genus Zoanthus, a spicular corallum still more feebly developed than that of Alcyonium. In many? the Sea-anemones no spicules have been observed, though traces of a corallum are not, even in these absolutely lost. Finally among the Ctenophora we in vain search for the faintest indications of its existence. From what has been said it were easy to infer that but little minute structure would be presented ACTINOZOA. 16] by the perfect sclerodermic corallum. Its decalcifi- cation, however, reveals delicate shreds of the periplastic substance by which it had been de- posited, usually exhibiting an irregular reticulating arrangement. The ‘sclerenchyma,’ or coral tissue, presents every gradation between this nearly solid condition and the spicular stage permanently ex- emplified in Alcyonium. Thus, in the Aporosa, it is frm and compact; in the Perforata, porous and granular, or even spongy and reticulate. In the accompanying table the chief modifica- tions of the corallum, from an artificial point of view, are systematically exhibited. It must not, however, be supposed that the presence of a sclerobasis renders the deposition of tissue secretions wholly impossible, for, among the Gorgonide it is certain that, in addition to the basal corallum, true sclerodermic spicules appear, within the substance of the investing mass. When such a Gorgonia is dried, and the soft parts washed away, a thin layer of calcareous spicules will be found gently adhering to the brown, horny sclerobasis below. M. Valenciennes has proposed to distinguish five kinds of these spicules, or 'sclerites by the names of capitate, fusiform, massive, stellate, and squamous, respectively. KEY TO MODIFICATIONS OF CORALLUM. Corallum wholly sclerodermic, Corallum thecal, calcareous. abul present Septa in x of 4. ; ; . . Rvcosa. ` Septain x of 5 or 6, rudimentary or absent. . TABULATA. Tabulæ absent. Septa well marked, in x of 5 or 6. Sclerenchyma porous. : . PERFORATA. 162 ACTINOZOA. Sclerenchyma imperforate. APOROSA, by a basal, creeping ccenenchyma. . TUBULOSA. Septa absent. Thee ded, drical, united at various heights by distinct, horizontal epithecze. . TusnrPORIDE, Corallum spicular or, if thecal, corneous or sub-calcareous. Spieules numerous, in some replaced, either wholly or in part, by an imper- evlin- J fect, tubular corallum. : 3 . ALCYONIDX, Spicules scanty, or replaced by particles ofsand. . : — . ZOANTHIDE. Corallum sclerobasic. Sclerobasis spinulous or smooth. . . Z. ScrEROBAsICA. Sclerobasis sulcate. Sclerobasis attached proximally. . GoncoNipz, Selerobasis free. ; : : . PENNATULIDE, 7. Muscular System and Organs of Loco- motion.—Reference has already been made to the muscular system of Actinia. A like apparatus, presenting, however, some differences of detail, appears to become differen- tiated from the general periplastie substance in most other Zoantharia and Alcyonaria. But the power of altering the position of the body by the slow alternate contractions of a normally attached base is possessed only by those Zoantharia to which the name of Sea-anemones is usually applied. Their non-adherent allies, such as Edwardsia and Cerianthus, have a highly contractile column- wall, capable of greatly varying its length, and of executing movements, for the most part, of à feeble worm-like character. The Alcyonidw and ! ACTINOZOA. 163 Gorgonide are permanently fixed, as are also many of the higher coralligenous Actinozoa, es- pecially those which multiply by continuous gem- mation. Others, however, and these chiefly the simpler forms, are free, but, like the unattached Pennatulide, not truly locomotive. Yet in the greater number of the Actinozoa each polype, though fixed, is contractile to some extent, shrink- ing down under irritation, and again unfolding itself at pleasure, while, among the Alcyonaria, with a few exceptions, it is also retractile into the fleshy substance of the ccenosare. Even this, too, has its own share of contractility, most evident in those species which possess an elastic sclerobasis. Thus, on the South American coast, Mr. Darwin observed a Sea-pen which, on being touched, forcibly drew back into the sand some inches of its compound, polype-covered, mass. All the Ctenophora are free-swimming animals, but doubt yet hangs over the nature of certain exceptional Zoantharia, reputed to be of similar habit. The apical extremity of the genus Minyas and its allies is represented by Lesueur and Lesson as dilated into a large air-sac, excavated beneath the floor of the somatic cavity, and furnished be- low with an opening into the surrounding medium. By means of this sac the creature is said to float without effort, its oral disc being turned down- wards; but further observations on its structure aremuch wanting. Again, the Arachnactis albida of Sars, possesses, according to Professor E. Forbes, not merely the power of swimming like a Medusid, ut “it can convert its posterior extremity into a Suctorial disc, and fix itself to bodies in the man- her of an Actinia.” But the aspect of the tentacles M 2 ^" 164 ACTINOZOA. in this organism strongly suggests the possibility s of its being an immature form, nor is the suspicion j weakened by the discovery of Haime, that the g oung of Cerianthus, while resembling Arach- a nactis in physiognomy, enjoys a similar oceanic à mode of life. p The muscular fibres of the Actinozoa are in- | teresting to the histologist, as wanting, among 0 many forms, those distinct transverse striæ, which, | elsewhere, they so frequently present. Such strie 6 are not, however, always absent. In the body- ( substance of this class we have, in truth, obvious transitions from a simple contractile periplast to f muscular fibres, which in no essential respect l differ from those of various invertebrate animals. ! In the typical Ctenophora, the contractile tissues l appear to be disposed in two principal sets; a i transverse or circular, and a longitudinal. | Some Zoantharia employ their tentacles as | aids to locomotion, though neither in these nor in the Alcyonaria can it rightly be said that special motile organs exist. this nature, however, are the ‘ctenophores; or ciliated bands, which constitute so obvious à feature in the physiognomy of the OCtenophora. | The normal number of these bands would seem to | be eight, though in Cestum, and one or two other | forms, their typical structure and arrangement i$ i somewhat modified. Each ctenophore is of à | much elongated ovate form, widest at the equa- | torial region of the body, and tapering gradually | to end in a point at some distance from the oral | and apical poles; slight differences in degree of | approximation to these parts, and such-like minor | characters, distinguishing the ctenophores of the ACTINOZOA. 165 several genera. The surface of the ctenophore is transversely elevated at intervals throughout the greater portion of its length into a number of successive ridges, to each of which a row of strong cilia is attached in such a manner as to form a paddle-like plate, or comb, the free extremities of the cilia remaining separate. The cilia are not all of equal length, those of the middle portion of the comb usually having the advantage in this re- spect, while the cilia on either side symmetrically correspond ; their degree of elongation varying so as to impart to the edge of the entire comb a gently curved outline, when seen at rest. This is, indeed, seldom the case during the life of the animal, throughout which the combs manifest an astonishing amount both of simultaneous and successive activity. Nay, even after death, de- tached portions of these creatures, bearing frag- ments of the ctenophores, exhibit for many hours no apparent diminution of their ordinary vibratile efficiency. 8. Nervous System and Organs of Sense. —In no Actinozoa, save the Ctenophora, has good evidence of the presence of a nervous system or organs of sense yet been obtained. Nor should this appear surprising, for the sensitivity which, in more highly differentiated organisms, has its course restricted to definite tracks, is here diffused, na less appreciable manner, through the more general and comparatively ill-developed tissues of the body. The white or blue marginal sacs of Some Actiniz, and the body-warts in allied species, have, it is true, been regarded as sensitive in function, and the former have even been dignified M3 166 ACTINOZOA. by the title of rudimentary eyes. The radiating system of ganglia and nerve-fibres which Spix described as existing within the base of Actinia has not come under the notice of other observers, But in the Ctenophora occurs a well-marked sense-organ, the ‘ctenocyst,’ upon whose precise function, whether oculiform or auditory, naturalists are far from being agreed. Such differences of opinion are in truth based on the prejudices which most anatomists acquire from a too exclusive attention to the structural peculiarities which the higher animals present. The ctenocyst, in all probability, neither sees nor hears, but would seem to be the localised recipient of those obscure - general impressions to which its lowly-organised possessor is capable of responding. . The ctenocyst occupies a central position amid the soft substance of the ectoderm, immediately within the apical pole of the body. In form it is ovate or spherical, smooth externally, but, in some cases, invested with an adventitious layer of pig- ment granules. Its wall appears to be very firm and elastic, so as quickly to recover its proper figure, should this be changed in accordance with the ordinary contractions of the body. Within, the ctenocyst is hollow, and apparently distended with a fluid. In the midst of this fluid lie a number of rounded or polyhedral concretions, semitransparent, colourless or somewhat tinted, occasionally coa- lesced into a single mass, and composed, probably; of carbonate of lime. Each granule is little more than ‘0003 of an inch in diameter. The concre- tions appear subject to a peculiar vibratory move ment, but some observers have disputed the fact of its occurrence, ACTINOZOA. 167 The nervous system of the Ctenophora consists either of a single ganglion or of a pair of ganglia closely approximated, giving origin to a number of delicate nerve-like cords. The ganglion lies deeply seated within the pyramidal mass of ecto- derm included between the apical canals, towards the narrow extremity of which its apex is directed, while its base rests upon the surface of the cteno- cyst. In form it is sub-pyriform or bluntly conical: anatomically, it seems resolvable into a thin tran- sparent wall, enclosing granular contents; in colour, it is most frequently pale yellow. From this central mass issue two principal series of nervous cords, one of which arches inwards towards the walls of the digestive cavity, and, in some cases, separates into four sets or bundles to supply the principal regions of the body. The nerves of the second series, usually eight in number, are distributed along the rows of swimming combs so as to lie between the latter and their corresponding canals. These cords appear dilated at intervals istence of a nervous system in any of the Cteno- phora which he had himself investigated. Agassiz M4 168 ACTINOZOA. is equally sceptical. On the other hand, the careful observations of Will, Milne Edwards and, more recently, of Gegenbaur, point to an opposite con- clusion. Somewhat similar are the views of Frey and Leuckart. All the preceding writers are un- animous in rejecting the prior account of the nervous system of Pleurobrachia given by Grant, who describes a double nervous ring surrounding the mouth, in the course of which he thought he could detect eight ganglia, each giving off on either side two fibres and a fifth larger filament, traceable onwards beyond the middle of the body. Yet this description, when carefully considered, is less irreconcileable with the views expressed on the same subject by other observers than seems to be usually supposed. Certain curious appendages, which possess, per- haps, a tactile function, have been observed b R. Wagener in two genera of Ctenophora, Beroe and Plewrobrachia. These organs appear as long hair-like threads, which arise from either side of the ctenophores along their whole length, and form around each pole of the body a sort of wreath, composed of several concentrie rings. The threads have not been seen to exhibit any inde- pendent movements, Each swells once or twice in the course of its length into a smooth or angular, rounded or flattened, expansion, the entire surface of which is abundantly beset with minute stalked knobs. In some threads smaller swellings, want- ing the capitate stalks, take the place of those just noticed. Occasionally the threads branch and, instead of ending in points, terminate in dilatations of a like nature to those which inter- rupt their filiform axes, da ACTINOZOA, 169 9. Reproductive Organs.— The reproduc- tive organs, in most Alcyonaria and Zoantharia, agree, both as to position and structure, with the same parts in Actinia; each spermarium or ova- rium consisting of a prolongation of the peritoneal membrane which clothes the sides of the mesen- teries, and forms along their free edges a double band, within which true generative elements are produced (fig. 26, c). Each band usually con- tains only ova or spermatozoa, but ovaria and spermaria may occur either in the same or in different polypes. Cerianthus and some other forms are moncecious, but more frequently, as in the majority of Sea-anemones, the sexes appear to be distinct. Not so, however, the Ctenophora, in which group bisexuality may certainly be said to prevail, An ovarium and spermarium occur as thickened folds along the opposite sides of each etenophoral eanal, beneath its endodermal lining. But the same mesentery gives rise on both of its free sides to only one kind of generative element. Here, as in other Actinozoa, the male and female organs differ in their contents alone. The ova of the Actinozoa are, in general, of a rounded form, smooth or dilated, and often bril- liantly coloured. Their structure is typical, pre- senting the parts common to ova in general. The spermatozoa are caudate, with a broadly conical or even heart-shaped body, to the apex of which the tail is usually attached. Reproduction does not, as in so many Hydrozoa, devolve upon specially modified zodids. Some Actinozow have been known to become everted and die shortly after the maturation of their genital products. But in. others, no such exhaustion 170 ACTINOZOA. seems to occur. Fertilisation is probably effected while yet the ova remain within the somatic cavity of the parent. Here, in many cases, the early stages of development also take place. Section II. DEVELOPMENT OF ACTINOZOA. Tue life-history of the Actinozoa presents a series of phenomena by no means so diversified as those which have been shown to characterise the developmental cycle in most of the Hydrozoa. For here the embryo, by an easy and gradual suc- cession of changes, tends finally to assume the condition of an organism similar to that which brought it forth. In the evolution of the embryo the whole or a greater part of the fertilised ovum seems to be concerned. The product of the reproductive act usually soon appears as a ciliated body, while yolk- cleavage, division into layers, and formation, by liquefaction, of an internal nutrient cavity, take place in the ordinary manner. ZOANTHARIA and ALCYONARIA.— Among the Zoantharia and Alcyonaria the further develop- ment of the primitive polype into which the embryo is resolved would seem to be, in most cases, a8 follows. ACTINOZOA. ITI tegumentary system is gradually becoming dis- tinct, thread-cells accumulating to form a super- ficial layer, beneath which pigment globules may also be observed. Soon the muscular substance begins to be differentiated, its longitudinal fibres and the first rudiments of the mesenteries being, at an early period, discoverable. Next, small pro- tuberances arise round the mouth, each of which gradually elongates to form a tentacle. The initial number of tentacles in the embryonic polype always bears some relation to that observable among the adult forms of the group of which it is a member. Thus, in most Zoantharia either five or six tentacles first sprout forth, but this number is rapidly doubled, an increase in size of the older tentacles being simultaneously effected. But, in very young Alcyonaria eight tentacles appear, as in the mature polype. Within the body-substance transverse contractile tissues may now, at length, be detected. Minor changes of external form also take place; the cilia disappear, or are replaced by others of smaller size; and the proximal extremity modifies itself in accordance with the habits of the adult animal. But before the formation of its tentacles, the young polype undergoes that important structural change which distinguishes it from the rudimen- tary polypite of the Hydrozoa. A circular fold of the body-substance surrounds the oral extremity and grows inwards in such a manner as to produce the wide digestive sac, open above and below, and freely communicating with the somatic cavity, from which it, nevertheless, remains distinct. The histological composition of the wall of this sac 172 ACTINOZOA. differs, in no essential respect, from that of the outer boundary of the body. The polype, while yet immature, presents a well- marked bilateral symmetry. The oral fissure is produced more in one direction than in another, its form being by no means, as some have wrongly stated, circular. At its opposite angles, gonidial grooves, in certain cases one only, arise. Two of the mesenteries in Actinia, as Haime has pointed out, are developed opposite to each other before the rest make their appearance, and these in direc- tion correspond with the two mouth-angles. The mesenteries grow from above downwards and, in some long-bodied polypes, do not extend much farther than the level of the free end of the digestive sac, or, becoming narrowed and much convoluted, are finally lost in the proximal portion of the wall of the somatic cavity. In Cerianthus two of the mesenteries descend, far below the others, almost to the orifice at the base of the general cavity. The remaining mesenteries, much shorter than the preceding, gradually diminish in length till they reach two points at either side of the larger mesenteries and, like them, opposite to one another. The rudimentary tentacles, also, afford proofs of the symmetry just noticed. In those young Zoan- tharia which possess five of these appendages, four, as Agassiz has stated, are arranged in pairs on either side of the mouth, while the fifth lies opposite one of the oral angles. The subsequent development of the tentacles has been well illustrated by Haime from the case of the common Sea-anemone. The succession of these organs is effected from within outwards in @ E — ACTINOZOA. 173 series of concentric circlets, each of which, save the second, includes twice the number of tentacles proper to its predecessor. Thus, the first circlet contains 6 tentacles, the second 6, the third r2, the fourth 24, the fifth 48, and the sixth 96. In Antipathes and some other polypes never more than the first six tentacles arise. Among certain other Zoantharia, one or more tentacles are occa- sionally aborted, and hence the somewhat puzzling numerical proportion of these organs noticed in slightly abnormal forms of this group. Should the young polype give rise to a calcareous corallum, the early stages of its deposition consist chiefly in the formation of spicules which, at first small and detached, gradually increase in size and coalesce in a greater or less degree to form the various structures whose nature has elsewhere been explained. Where a septal apparatus occurs, the develop- ment of its several elements follows the same definite law by which the number of the mesen- teries and tentacles is determined. The young Zoantharian has at first six septa, another, and separating similar loculi. In a few genera only can a smaller number of initial septa be detected. But among the great majority of Zoantharia, the typical grouping of the septa is hexameral; among the Rugosa, tetrameral. In some Zoantharia the number of the septa never exceeds six, but, more frequently, new septa appear midway between those first formed, at the lower portion of the theca. "These gradually grow inwards, at the same time increasing in height. hus the primary loculi become divided into 174 ACTINOZOA. secondary chambers; these, by the formation of other intermediate septa, into tertiary chambers, and so on till the development of the corallite has been accomplished. The primary loculi alone are complete, for the septa limiting the other chambers neither extend so high, nor so closely approach the columella, as do those which are afterwards formed; the size of all succeeding series of septa being in direct ratio to the order of their development. So that the latter may be almost as clearly pronounced in an adult corallite as in a collection of specimens of different ages belonging to the same species. In like manner those stages of the septal apparatus which are transitional among the more complex corallites are well illustrated by an appeal to the various permanent conditions of the same system among less developed representatives of the group. Thus in some species of Stylophora we can count but six septa, and an equal number of primary cham- bers. In a much larger number of Zoantharia twelve septa may be observed, of which six are primary and six secondary. In others, there are twenty-four septa; six primary, six secondary, and twelve tertiary. The septal formula in all these types admits, therefore, of being, respectively, stated thus: i. 2 E =. 6, IL . eee uc ae IL . . 646+12=8. 24. in S. 12 one, and in S. 24 three additional septa being developed between each of the primary pairs. And, since the normal number of primary septa is 6 among the Zoantharia, it might be — 422 f> c m> ^f e et- et- ur- eS Ch c a vr CO c Co. — <=, = at text och = _ ACTINOZOA. 175 expected that for all corallites of this order having a higher formula than S. 24, the number of new septa produced within each of the first formed chambers would be represented by the successive terms of the series 7, 15, 31, 63, &c., in which each number is double plus unity of its antecedent. Practically, however, we find that, as soon as the formula S. 24 has been reached, only two septa arise at the same time in each primary chamber, or, in other words, the corallite developes simul- taneously not more than twelve additional septa. So that the simple expression n x6+6 at once determines the normal septal formula for all Zoantharian corallites having twenty-four or more septa. Here n is = the number of septa between each primary pair, and corresponds to the succes- sive terms of the arithmetical progression 5, 7, 9, In. 13, &c. Since, therefore, the number of septa in process of formation is often less than the number of loculi, it becomes necessary to determine those chambers in which the new septa first appear, and the precise order of succession which they observe. But first let us explain the few technical terms by which the facts to be announced have been ren- dered susceptible of definition. ll septa which commence their growth simul- taneously are said to be of the same order, while those which divide chambers of equal size belong to the same cycle. It is evident that septa of the first three cycles must correspond to those of the first, second, and third orders, respectively. But the fourth cycle includes septa of the fourth and fifth orders ; the fifth, of the sixth, seventh, eighth, and ninth; and the sixth of the roth, 11th, 12th, 176 ACTINOZOA; 13th, 14th, rsth, 16th, and 17th orders. In but few corallites does a seventh cycle occur. The lines in the subjoined diagram are supposed to represent the septa of part of a corallite having the formula S. 48,each septum being indicated by the numeral proper to its order. I 4 3 5 2 5 i. + The same numerals also enable us readily to point out any one of the loculi included between the primary septa. In the present case the chambers, from left to right, would be denoted as I1+4, 4+ 3, and so on, respectively. Again, chambers of equal size are said to be similar, and those represented by corresponding numerals are of the same expression. Thus, in the diagram, the chambers 1+ 4 and 44-1 have the same eX pression. So, also, just before the development of septa of the fifth order, the chambers then separated from one'another by the septa marked 3 could not have been denominated similar. : ACTINOZOA. 177 We are now in a position to understand the five rules of septal development laid down by Milne Edwards and Haime, to whom science is indebted for most of what we yet know on the subject under consideration. Rule 1. The formation of new septa takes place simultaneously in all loculi having the same expression. Rule 2. The formation of septa takes place suc- cessively in loculi having a different ex- pression. Rule 3. The order of succession of the septa is determined in the first place by the age of the cycle to which they belong, and those f a new cycle do not commence to be formed till the development of the pre- eding cycle is complete. Rule 4. Among loculi of the same cycle having different expressions precedence in the for- mation of new septa is determined by the inferiority of the sum of the two terms of this expression. Thus, if septa of the 6th order were to be de- veloped in the corallite indicated by the above diagram, we should expect them to appear in the chambers 1 +4 and 4+1. Rule 5. Among loculi of the same cycle having different expressions, but which yield the same sum by the addition of the two terms of each expression, the order of appearance of the septa is determined by the relations which exist between the lowest terms of these expressions, the new septa being formed first where the lowest term occurs. N 178 ACTINOZOA. Or, recurring to our diagram, we might look for the appearance of new septa in the chambers 5+2 and 2+ 5 sooner than in 4 +3 and 3+4, As might be expected, from abortion and other causes, variations from the above arrangements now and then occur, the careful investigation of which is far from exciting that attention which it so well deserves. It is to be remarked that some coralligenous polypes, when in confinement, appear to attain a considerable bulk before any traces of their skeleton can be observed. í Except in its minute size, and the comparative paucity of its tentacula, the young polype, when first excluded, closely resembles its parent, through whose mouth it usually makes its entrance into the surrounding world. The student will ex- perience little difficulty in obtaining Actiniæ containing young in several stages of development for detailed anatomical examination. It is to be wished that the embryology of the composite Alcyonaria and Zoantharia were more efficiently worked out, since it is just possible that, apart from other modifications of the de- velopmental process, a rudimentary coenosare may, under certain circumstances, be produced before the formation of a distinct polype. CTENOPHORA. The development of the Cteno- phora, while presenting some peculiar features, resembles that of other Actinozoa in the compara- tive rapidity with which its early stages progress so that the product of the reproductive act, while yet of small size, attains a form and structure similar to the parent. | -a aio cC — — — C c c ee ee c p co — LH — HE ct ACTINOZOA. 179 The young Bolina, according to Mc Crady, is not very unlike an adult Plewrobrachia in shape, but the oral extremity appears somewhat truncate, and smaller than the more rounded apical region. From around the latter radiate eight short cteno- phores, each containing from five to seven combs. The mouth leads into a very large digestive sac, tapering rapidly as it proceeds inwards to meet the narrow funnel, from which are given off two broad lateral sinuses, opening by eight “ short pointed projections” into the embryonic indica- tions of the ctenophoral canals. The extremity of each horizontal sinus also connects itself with a wide excavation, or pit, at the side of the body, from which freely issues a short tentacle, furnished with three or four fringing threads. Apical canals, also, may be observed to the right and left of the large rudiment of the ctenocyst. At a later stage are developed the paragastric canals, while as yet the ctenophoral tubes remain short and incomplete. These last are seen to approach the apical region, before lengthening so as to come near the oral pole of the body. Their development would seem to besomewhat in advance of that of the ctenophores themselves. From the wide horizontal sinuses out. The mouth gradually becomes depressed, while the large antero-posterior lobes of the adult animal are making their appearance. Meanwhile, the tentacular pits shift, as it were, rather closer to the oral extremity, until at length they arrange appearance as their development proceeds, ecoming more numerous, but simple and less N 2 180 ACTINOZOA. contractile, so as no longer to resemble those of Pleurobrachia. Short branches are given off from the extremities of the paragastric canals, and from these the two canals which run by the sides of the mouth are probably produced. Not until the large lobes have become very distinctly recognizable do the earlets, four small appendages in connection with the lateral ctenophores, render themselves visible. The observations of Semper on Chiajea multi- cornis, another lobed representative of the same order, indicate a still more rapid evolution of the embryo, which before quitting its egg-covering has the outward form of the adult animal, the canal system and ctenophores being as yet rudi- mentary. Asin Bolina, the digestive tube appears the first formed part of that system, and is, indeed, developed earlier than any other internal organ. At no period of its career is the young Chiajea provided with a uniform covering of cilia. In Beroe, a genus destitute of tentacles, the funnel of the embryo is comparatively large, before the ctenophoral canals are fully developed. The circular oral vessel is formed from two lateral tubes, whose extremities anastomose with four of the ctenophoral canals, while as yet the four others have not approached more than half way the oral pole of the body, towards which, as in the pre- ceding, they are gradually developed. We have here an interesting proof of the bilateral symmetry of the Ctenophora, for in the adult Beroe, as from its want of tentacles might have been expected, this symmetry is, on a hasty inspection, less obvious than in most other members of the order Like Chiajea, Pleurobrachia is developed within ACTINOZOA. 181 an egg-covering, and with an equal degree of rapidity. After yolk-cleavage the embryo appears rudely cylindrical in form, a belt of cilia passing round the middle of its body (fig. 31). This soon Fig. 31. Development of PLEUROBRACHIA :— 4, newly extruded ovum, showing the yolk with its external covering ; b, the same, after segmentation; c, d, and e, successive stages of the embryo. (All ified.) breaks up into two lateral groups which eventually disappear altogether; the ctenophores, at first very broad and few in number, at an early period taking on the performance of their special function. The tentacles are at first destitute of lateral fringes, traces of which appear while the rest of the canal System is but imperfectly indicated.. The form of the adult animal is, according to Agassiz, fully “sumed before the young organism attains a length of -o4 of an inch. N3 182 ACTINOZOA. Of the duration of life among the Actinozoa, as among Celenterata in general, we are still Very ignorant. Some Ctenophora appear to last but a single season, yet this statement can by no means be regarded as true of the entire group. The Alcyonaria and Zoantharia seem long-lived and hardy animals, a specimen of the common Sea- anemone, kept in confinement for forty years, showing no visible signs of decrepitude or old age. In reparative power the members of this class, notwithstanding their increased differentiation of tissue, appear fully to rival the Hydrozoa. Many experiments show how complete may be the healing of wounds and regeneration of lost parts among a large number of Actinozoa. Occasionally the pro- cess of reparation displays itself in a curiously abnormal manner. Thus, a section having been made below the disc of a Sea-anemone, tentacles were developed from both of the fresh surfaces thus exposed. A common British Zoantharian, Anthea cereus, adapts itself well to the conditions of such experi- ments. Artificial fission of this species, if per- formed with care, does not always result in death of the parts so divided. The same animal may also illustrate the mode in which spontaneous fission occurs among many other forms of Actinozoa. A longitudinal cleavage of the polype commences, in most cases, across the region of the disc, and thence proceeds down- wards towards its proximal extremity. Less frequently is fission effected by the separa- tion of small portions from the attached base 0 the primitive organism, whose form and structure a ACTINOZOA. 183 they subsequently, by gradual development, tend io assume. Further observations are wanting on the occur- rence of fission and gemmation among the Cteno- hora. In none of these animals do we find colonies of zodids resulting, as in the Hydrozoa, from a process of continuous budding. But in other Actinozoa continuous gemmation abundantly takes place, and in this manner are formed those composite structures, consisting of numerous polypes, met with among so many genera of Zoantharia, Alcyonaria and Rugosa. In a few of these organisms, discontinuous gem- mation may also be noticed. Young polypes may be budded either (1) from the base of the primitive structure, or (2) from the sides of the polypes, or (3) from their oral discs. Since these surfaces are but parts of a common integument it might be anticipated that intermediate positions of buds would now and then occur. Nevertheless, it has been found con- venient to distinguish three principal modes in which gemmation of polypes may be effected, as the ah the parietal, and the calicular, respec- ively. In basal gemmation the polype sends forth a rudimentary ccenosare, from which, after a time, the young polype-bud is produced, and so on for all the zodid forms subsequently evolved. The extent to which a coenosare may be deve- loped varies, however, considerably. It must not be inferred that in every composite Actinozoón such a structure is present; for the mass may exhibit nought else save a congeries of polypes mM immediate mutual connection. In this case 184 ACTINOZOA. multiplication by fission or by parietal gemma- tion has probably occurred (fig. 32). If parietal gemmation be repeated several times during the growth of the budding organism, it is said to be indefinite; if once only, definite. Indefinite gemmation is termed regular when — the young polypes arise at points which are deter- - minate for the same species; irregular, when budsare produced indifferently from different parts. The results of definite gemmation vary accord- ing as the producing and produced zodids are turned towards the same side, or in opposite direc- tions. Calicular gemmation is only known among cer- tain extinct coralligenous Actinozoa. In Cyatho- phyllum and its allies, members of the order Rugosa, the primitive polype sends up from its oral dise two or more similar buds, these, in their turn, produce other young polypes, and thus, the Milne Edwards has carefully insisted on the necessity of distinguishing between fission and gemmation among the Actinozoa. The oral disc of the budding polype always remains entire, and the bud, when it first appears, wants not only a mouth, but most of the other structures which subsequently it acquires; whereas the polypes produced by fission resemble each other in organ- isation and, not unfrequently, in size, as soon as they become distinct. Here, it need hardly be said, oral fission is referred to ; basal fission, à mere variety of discontinuous gemmation, being, ACTINOZOA. 185 as above stated, of comparatively rare occur- rence. Every polype-bud is, therefore, at first, no more than a protuberance from the two parent layers, enclosing a cecal diverticulum of the somatic cavity. Thus, the nutrition of the young zoóid is provided for, till it developes for itself a mouth ; after which it may either still continue its primi- tive connection with the common mass or, as already stated, by deposition of tissue secretions, become, physiologically, a separate organism, though morphologically associated with other zoöids of the same composite fabric. The growth, gemmation, and fission of the composite coralligenous Actinozow require, in addition to what has been said, the following more particular explanations. The whole compound structure in the sclero- basic species may be regarded as the result of a peculiar modification of the process of basal gemmation; the rudimentary ccenosare developed around the base of the primitive polype, instead of spreading only at its circumference, shaping itself into a slender and, at first, slightly elevated stem which, gradually increasing in height, con- tinues, at the same time, to excrete a succession of epidermic layers. Thus the young coenosare enlarges in diameter, and soon a number of buds 186 ACTINOZOA. These branches may be apparently quite irregular in their arrangement, or they may arise in the same vertical plane from opposite sides of the stem, sometimes uniting one with another by the formation of an intricate network, as in the well- nown and beautiful Fan-Corals. Such is the growth of the corallum in the fixed Gorgonide and Antipathide. Among the Penna- tulide, which are free forms, the proximal end of the coenosare usually becomes produced into a gently swelling or tapering mass, supported by a comparatively slender, elongated sclerobasis. More varied are the modifications of the com- posite sclerodermic corallum, the increase of which may be the result of fission alone, or of gemmation alone, or of gemmation and fission combined. produced either supply by reparation those parts which were wanting to render them complete, or, it may be, continue through life in a more or less imperfect condition. The coral structures which result from a repe- tition of the fissiparous process are of two principal forms, according as they tend most to increase in a vertical or horizontal direction. In the first of these cases the corallum is cwspitose, or tufted, convex on its distal aspect, and resolvable into a succession of short diverging pairs of branches, each resulting from the division of a single coral- lite. In some parts of the mass the walls of the corallites blend, so that a few of them may even ecome compacted with one another. ACTINOZOA. 187 When growth takes place chiefly in a horizontal direction, the so-called lamellar form of corallum results. Here, the secondary corallites are united throughout their whole height, and disposed in a linear series, the entire mass presenting one con- tinuous theca. Sometimes it is possible to count the number of corallites, but often their several calices merge, as it were, into a single groove, traversed, perhaps, by a columella running parallel to its sides, towards which two opposite rows of septa are seen to converge. Both the lamellar and ccespitose forms of coral- lum are liable to become massive by the union of several rows or tufts of corallites throughout the whole or a portion of their height. An illustration of this is afforded by the large gyrate corallum of Meandrina, over the surface of whose spheroidal mass the calicine region of the combined corallites winds in so complex a manner as at once to suggest that resemblance to the convolutions of the brain which its popular name of Brain-stone Coral has been devised to indicate. Basal gemmation, among sclerodermic Corals, affords very different products, according as the ecnosare remains soft, or deposits a coenenchyma; appears under the form of stolons, or of stouter connecting stems; or even spreads out in several directions as a continuous horizontal expansion. In this case it is evident that the latest formed Parts of the mass are those which are situated nearest to its circumference. and, perhaps, confused by reason of the scanty development of an intervening coenenchyma. 188 ACTINOZOA. In some cases the basal deposit encroaches but little on the sides of the corallites; in others it rises upwards till on a level with their calices, or even above them. Again, instead of remaining horizontal, it may become folded in such a manner Ky GN E er e CÓ Su Y (S G TURBINARIA PALIFERA. Corallum, of the natural size. that one part of its distal surface is brought into more or less close contact with the other; the corallites, which previously seemed to arise from the same plane, having now their calices turned in opposite directions. The resulting corallum will be dense or foliaceous, according to the degree of de- velopment of the included ccenenchyma, and the greater or less elongation of its projecting corallites. Budding from the sides of the corallites takes place, however, more commonly than basal gem- mation, not that the latter must be considered of infrequent occurrence. The aspect of the corallum to which parietal gemmation gives rise varies in accordance with a per pap TN — i ee L ACTINOZOA. 189 1, The number of buds which each corallite pro- duces : 2. The frequency with which the budding process is repeated; whether once only or several times during the life of the corallite, but at different stages of its growth: DENDROPHYLLIA NIGRESCENS:— Part of a branch, in outline, of the natural size. A single polype.is shown separately, mag- fied. 3. The height which each corallite attains: 4 The angle at which the growing buds diverge rom the parent corallite: 5. The degree of rapidity with which such diver- gence takes place: 6. The position of the buds produced ; from one side only of the budding corallite, or indif- ferently from any part of its circumference ; at a short distance from its base, or relatively nearer to the edge of the calice: — 190 ACTINOZOA. 7. The degree and nature of the union between the several corallites; whether this be pro- duced by the close contact and blending of their walls, or by the development, both in à horizontal and vertical direction, of am epitheca, ccenenchyma, and other similar structures (jig. : and several less essential modifications of the same process, manifested either separately or in com- bination. It is, therefore, not surprising to find among budding Corals forms analogous in every respect to those produced by fission and, in addition, many others whose physiognomy, copious as is the list of descriptive terms, it is scarcely possible to define. Nor does each Coral always restrict itself to a single mode of growth, but, on the contrary, several kinds of gemmation, or of gemmation and fission in unison, have been observed to take place in the same species. So that, even with the aid of figures, and extensive suites of museum specimens, the development of the composite Corals can receive illustration in but a limited Se he gG. — .—R. 2. M OU D VU Sia D. qQ A ws Dm r --4-- id £o Es e E» © — PR ey de E Et, 4 er (a SO oR © t =] 2» © ar} vn eR eo } £ B = un ct c [19] ! — xd studied amid “the elorious variety of Nature" 8 itself, *living and multiplying in their destined homes and habitats." Mr. Dana, who devoted much time to the exami- i nation of the Corals of the Pacific, thus endeavours tl to describe some of their general diversities of form: |—4 not emulating in size the oaks of our forests,— E : 1 * Trees of coral are well known; and although à t for they do not exceed six or eight feet in height, d ACTINOZOA. 191 leaves or folia, and resemble some large-leaved plant just unfolding; when alive, the surface of each leaf is covered with polyp flowers. The cactus, the lichen clinging to the rock, and the fungus in all its varieties, have their numerous representatives. Besides these forms imitating vegetation, there are gracefully modelled vases, some of which are three or four feet in diameter, made up of a net-work of branches and branchlets and sprigs of flowers. There are also solid coral hemispheres like domes among the vases and shrubbery, occasionally ten or even twenty feet in diameter, whose symmetrical surface is gor- geously decked with polyp-stars of purple and emerald green.” Under such aspects appear the living organisms whose combined efforts have mainly constructed those reefs and islands of Coral origin which now lie scattered far and wide over the surface of the tropical ocean. Three principal forms under which such reefs occur have been distinguished by the names of Fringing-reefs, Barrier-reefs, and Atolls. Fringing-reefs skirt the shores of favourably situated lands, towards which, at a gentle slope, they incline, ending abruptly seawards, where soundings reveal a depth of from 20 to 30 fathoms. The surface of the reef is covered at high water, and forms a nearly level platform, from a few feet to more than a mile in breadth, according to the degree of inclination which the land presents. Its 192 ACTINOZOA. outer margin may be rendered sinuous by bays, or the continuity of the whole reef completely interrupted by one or more irregular inlets, : From such reefs to Atolls we may trace every possible transition. An Atoll differs from an encircling Barrier-reef in enclosing, instead of a central island with its intervening channel, an uninterrupted surface of calm water, or lagoon. The low-lying strip of land separating this lagoon from the line of white breakers which marks the outer boundary of the Atoll is seldom more than half-a-mile in breadth, and presents an imper- fectly circular or prolonged crescentic form, though occasionally, as in Whitsunday Island, the circle is complete. eefs, in general, grow only along their outer edge and, when upraised above the sea-level, always appear highest to the windward side. Clear sea-water, well aérated, at a certain tem- perature, and a depth of not more than 25 or 30 fathoms, are among the most important of those TOU, OOMMEEU ee, ACTINOZOA. 193 external eonditions which seem favourable, if not essential, to the growth of reef-building Corals. But to what other influences do the above three classes of reefs, which present so much in common, owe their occurrence? It has been said that they are of Coral origin; yet how is it that some of them rise from depths so considerable, seeing that those living Corals, by which they have been constructed, build only in seas comparatively shallow ? It is not our business here to discuss the various speculative views which have from time to time been put forward on the subject of Coral-forma- tions. Let it suffice to say that Mr. Darwin’s theory of elevation and subsidence offers the only consistent explanation of most of their known phenomena which science is prepared to receive. If we suppose a Fringing reef, together with the area which it surrounds, to sink at a rate not more rapid than the upward growth of its consti- tuent: Corals, the reef itself will undergo little apparent alteration, while a channel of water, gradually increasing in width, will appear between it and the more elevated regions of the slowly submerging land. Thus a Barrier-reef is formed. Depression still going on, the land encircled by the reef is reduced to one or more projecting peaks, as in those islands of the Pacific to which allusion has been made. Further subsidence causes these peaks to disappear beneath the E and the Barrier-reef changes into an toll. Fringing-reefs, therefore, show that the shores which they skirt are stationary or rising, while o 194 ACTINOZOA. Atolls and Barrier-reefs attest that subsidence has taken place. That such slow subsidence does occur over many parts of the extensive area occupied by Coral-reefs is proved by a number of considera- tions; some of which were forcibly suggested by Sir Charles Lyell, several years before Mr. Darwin's theory was promulgated. Observations and experiments made with a view to ascertain the rate of growth of the reef- building Corals have not hitherto yielded a suffi- cient number of accurately recorded results. That, in certain instances, their growth is rapid, varying, however, with the species, may be re- garded as proven; but it is also far from impro- bable that there are many species which have the same average rate of increase. It may likewise be conceded that the growth of the same species varies at different periods and under different external conditions. In future investigations on this subject the particular form of the corallum, and its mode of fission or budding, should in eac case receive attention. For it is obvious that the same amount of calcareous deposit, if appropriated respectively by a massive and by a dendroid species, would give rise to apparently dissimilar quantitative products. The Coral-polypes are, however, powerless to raise their structures higher than the line of low- water. To effect this, various agencies, but chiefly the forees of wind and ocean, acting upon masses detached from the reef and other marine débris, are brought into play. But the mode of operation of these agencies, the general theory of elevation and subsidence, the conversion of the irregular pne ee ea ee ek So e te ee ee Wa RT c DN ME 1 4. ^5 ne A cU au hec. ee ee e ae O ` jgations ACTINOZOA. 195 surface of the reef into one continuous level, and the alterations to which its dead and deeply-sub- merged portions become exposed in the lapse of time ; these, and other kindred subjects of inquiry, fall rightly within the province of the geologist. As monuments of past change, Coral-reefs form the basis of some of the most “ splendid general- ” which his science has deduced. For him an island occupied each region where now without interruption flow the quiet waters of a lagoon. And seas must have once rolled over those existing continents amid whose mountain- chains remains of ancient Coral-reefs abound. Yet the zodlogist, in taking leave of his own department of this subject, cannot, without satis- faction, contemplate how large a portion of the earth’s substance must, during the long lapse of geological time, have formed part of the organised structures of a group of beings who still continue to fulfil, with no impairment of efficiency, the great task for ages allotted them in the scheme of universal nature. Not matter only, but force, he sees made subject to their sway. The physical agencies, which seemed at first to threaten destruc- tion to the growing Coral, are soon successfully overcome, and then pressed into itsservice. Nay, without their aid, so much of the reef as rises above the ocean level, forming the abode of plants and animals, and finally of man, could not even have existed. But had Coral-polypes not pre- viously laboured, the same forces would have been potent only to destroy. o 2 196 ACTINOZOA. Section III. CLASSIFICATION OF ACTINOZOA. 1, Classification. — 2. Order 1: Zoantharia.— 3. Order 2: Alcyon- aria. — 4. Order 3: Rugosa. — 5. Order 4: Ctenophora. ' I. Classification.—The class Actinozoa may be divided into the four orders here defined : 1. Zoantharia.—Actinozoa,in which the tentacles are simple or variously modified, in general numerous and, together with the mesenteries, disposed in multiples of five or six. Corallum absent or sclerobasie, in most sclerodermie, the septa of each corallite following the numerical law of the soft parts. 2. Aleyonaria.—Actinozoa, in which each polype is furnished with eight pinnately fringed tentacles. Mesenteries and somatic chambers in number some multiple of four. Corallum sclerobasic or spicular, rarely thecal, and never presenting traces of septa. 3. Rugosa.—Actinozoa, presentinga sclerodermic corallum, with tabule and well developed septa arranged in multiples of four. Soft parts unknown. 4. Ctenophora.—Transparent, oceanic, delicate gelatinous Actinozoa, swimming b means of ctenophores, or parallel rows of cilia dis- posed in comb-like plates. No corallum. 2. Order 1: Zoantharia.—The chief modi- fications of the plan of structure proper to the J bs xd L ê ACTINOZOA. 197 jui ANTHARIA MALACODERMATA : — d. N Actinia (or Sagartia) rosea; b, Ilyanthus Scoticus ; c, Arachnactis albida ; d, Zoanthus Couchii. (Natural size.) , form and structure of the polype has been died in the soft-bodied Zoantharians, more The best stu 198 ACTINOZOA. familiarly known as Sea-anemones. A typical Sea-anemone, when contracted, may be compared widening somewhat towards its extremities (fig. 34, a). The base is scarcely broader than the column in some species; in Adamsia, on the other hand, it is ovate in form, sending forth two lateral lobes, which extend so far as to surround the aperture of the univalve shell on which this curious animal-flower is found, the lobes at length uniting by a zigzag suture along the outer lip of the shell. As in the case of Hydractinia, the shells which Adamsia selects appear always to be tenanted by a species of Hermit-crab. The column may have its surface marked by a variety of epidermie growths, or pierced by sundry apertures. In Actinoloba its summit rises into a conspicuous ridge, separated from the outer series of tentacles by a deep depression or furrow. Oc- casionally, as in the same genus, the margin of the disc is waved or thrown into sinuous folds, so that the arrangement of the tentacles appears thereby somewhat confused. The peristomial space may also vary in size, and relative depression or elevation. The lips of the mouth undergo their own modifications, and, in some genera, a groove with mouth-tubercles occurs at but one of the oral angles. In Actinopsis these tubercles are produced upwards to form a pair of long, rigid, semi- cylinders, the lateral margins of which again bend downwards to terminate in cleft extremities. In the non-adherent Sea-anemones, such as Ilyanthus and its allies, the column is propor- ACTINOZOA. 199 tionally larger than in most of the Actinide roper. The base is either rounded or bluntly tapering, and, in certain genera, becomes at times much distended, as in Saccanthus or Edwardsia. In some the base is furnished with a central perforation : in others this appears to be wanting. In Peachia the oral region is singularly modified ; the tubercles of its single groove uniting to form a tube, the expanded summit of which, * conchula’ of Mr. Gosse, presents a more or less thickened, everted edge, cleft into a variable number of lobes. The polypes of the Zoanthide and true coral- ligenous Zoantharia, save in characters merely generic, resemble those of the Actinidæ. Their average size is, perhaps, smaller, though the Ac- tinia Paumotensis of the Pacific, whose expanded dise measures a full foot in diameter, is, in this respect, certainly exceeded by large specimens of Fungia. This genus presents a widely extended, éreular or elliptic disc, destitute of the usual folding margin, and blending, by insensible de- grees, with the shallow, ill-defined column, over the radiating septa of which the tensely stretched soft parts converge towards the prominent, central mouth. Such a simple form contrasts strikingly with Meandrina and those allied genera in which the several polypes produced by fission fuse to- gether into a convoluted linear track, with tentacles arising from its opposite sides. Of these appendages and their variations, a brief notice seems here required. In Anthea (=Anemonia) they are long and slender; in Fungia and Discosoma, reduced to mere warts or papille; in Capnea, very short, resembling oblong tubercles ; while in Arachnactis, the outer 04 200 ACTINOZOA. extremities are often perforate, the animal having the power of opening or closing the orifice at pleasure. Dana describes the inner tentacles of his Actinia flagellifera as terminating in a re- tractile pencil of hairs, but it is possible that these hairs may have been, in reality, large everted thread-cells. Although in most Zoantharia the tentacles are simple, yet in Thalassianthus and its allies they are branched, and have their surface studded with tubercles or papille. In a few genera, two kinds of tentacles appear on the same polype; the one simple, the other lobed or branched, as in Phyllactis. The number of the tentacles, though in general some multiple of five or six, is, in other respects, liable to considerable variation. Their arrange- ment, also, is correspondingly diversified. They may dispose themselves in one, two, or more con- centric series, and in some species they appear irregularly scattered. ^ Amtipathes exhibits six tentacles in a single circlet ; Peachia twelve, simi- larly disposed ; while in the common Sea-anemone species, as in most other Zoantharia, the tentacles of contiguous rows alternate. Cerianthus and Saccanthus, however, possess two distinct circlets of tentacles, the one oral, arising close round the mouth, the other marginal, not far from the edge of the disc, the tentacles of the inner row being eae ae Se CEN ww Ko S ACTINOZOA. 201 equal in number and opposite to those of the uter. ° The tentacles of most Zoantharia are retractile, put in Cerianthus, Anthea, and a few other forms, this power is either absent, or imperfectly exercised. The numerous families of the present order have been conveniently arranged by Milne Ed- wards under three sub-orders: Malacodermata ; Sclerobasica ; and Sclerodermata. In the Z. Malacodermata, the corallum is either absent or represented by scattered spicules. The actinosoma, in most of these animals, presents but a single polype. Exceptions to this rule oc- cur, however, among the Zoanthide, the budded polypes of which remain permanently united by a ecnosare, in some linear, in others carpet-like or incrusting. In certain Actinide also, for example, the Corynactis mediterranea of Sars, a similar connection is maintained (fig. 34, d). Within the soft parts of the Z. sclerobasica spicular tissue secretions seem wanting (fig. 35). All the members of this sub-order are composite structures. Antuypathes, the type of the group, presents a stem-like, simple or branched ccenosarc, which in one species tapers to a length of more than nine feet, with a basal diameter of scarcely 'j of an inch. In this genus the sclerobasis is horny, and each polype, according to Dana, has but six tentacles; but in the allied family of Hyalochætidæ, the tentacles are twenty in num- ber, while the basal excretion resolves itself into humerous siliceous threads, transparent, twisted Into an erect axis. Doubts, however, are yet entertained of the true nature of these so-called 202 ACTINOZOA. * Glass-plants,” whose siliceous stem may be the product, not of the polype-mass, but of the sponge on which it is parasitic. Fig. 35. ZOANTHARIA SCLEROBASICA:— Part of a living stem of Anti- pathes anguina, of the natural size. Two polypes are shown separately, magnified. Of the Madrepores, or Z. Sclerodermata, want of space forbids us to say much. A short sketch of the several] families into which the sub-order is divided appears to be the best form into which this part of our subject may be condensed. Among the Tute iie the corallum is usually simple, never enting a ccenenchyma. In Cenocyathus sie pes lateral “ah A takes place, the corallites so form ed r maining con- nected in a close irregular tuft. In B gemmation also occurs, but here it is discon- tinuous. The septa are very perfectly developed, not giving Hee to either dissepiments or synap- ticule (fig. 3 In the Obi ida: there is a very abundant coenenchyma, which blends gradually with the ACTINOZOA. 203 thece through their entire height. Each corallite has its chambers slightly interrupted by a few dissepiments. The members of another family, Astrwida, are either simple or composite, but there is no proper coonenchyma, as in the Oculinide. The epithecze or costze form the chief substance of the mass by which, sometimes, the corallites are separated. Many Astræidæ present that rapid fissive develop- ment of the corallum, whose curious results have been already indicated in the case of Meandrina. Dissepiments, in most, are numerous. In number of genera and species, perhaps, also, of indi- viduals, and, apparently, in general importance, the Astræidæ seem to surpass all other families of the class Actinozoa. The Fungide are at once distinguished from the three families just noticed by the possession of synaptieule. Dissepiments are absent, nor can it be said in many cases that a proper theca exists ; the septa passing, without interruption, into the coste, save at the base of each corallite. Both simple and composite Fungide occur, the latter multiplying by lateral gemmation. In the somewhat porous condition of their ill- developed theca the Fungide may be said to differ from other Aporose Zoantharia, and ap- proaeh the two next families, collectively distin- guished by the title of Perforata. These, like the Aporosa, have a well-marked septal appa- ratus, and present no traces of tabule. , Among the Madreporide the sclerenchyma is simply porous, the septa are distinct, and but very slightly perforate. Save in Éwpsammia and some of its allies, the corallum is composite, but 204 ACTINOZOA. less definite series of trabicule. The entire corallum, in like manner, appears to be made up of a spongy, reticulate sclerenchyma. The next division, Tubulosa, contains only a single family, Auloporide; and this but two Fig. 36. ZOANTHARIA SCLERODERMATA : — a, corallum of Turbinolia costata ; b, the same, in transverse section, showing the columella, septa, theca, and costz ; c, part of corallum of Aulopora tubefor- 5, (All, except c, magnified), genera, Pyrgia and Aulopora, in both of which the corallite, while destitute of tabule, has its septal system indicated by faint markings along the inner surface of a comparatively smooth tube. Pyrgia is simple, though having a distinct epi- theca. In Aulopora the somewhat remote coral- lites are connected by means of a basal creeping conenchyma. (fig. 36, c. The four last families of Zoantharia constitute ACTINOZOA. 205 the great division of Tabulata, in which the rudi- mentary condition of the septa is made amends for by the extensive development of the transverse floors, referred to in the name this group bears. (fig. 29-) ; The corallum of the Tabulata is mostly, if not always, composite. Among the Milleporide an abundant coenenchyma occurs, and the resulting compound structure assumes a massive or folia- ceous aspect. ‘The substance of the corallum is traversed by interspaces which give to its section a somewhat tubular or cellular appearance. In the Seriatoporide it is more compact, but here, likewise, the coenenchyma is abundant, present- ing, externally, a tufted or arborescent form. In the Favositide the corallites have their lamel- lar walls brought into very close apposition, little or no true ceenenchyma being observable; while in the Thecide the septa form by their lateral union the greater portion of the dense spurious eenenchyma, of which their massive corallum is composed. The following may be given as definitions of the families of Zoantharia. Those of the Madre- porie forms, founded wholly on characters derived from the corallum, admit readily of being ex- hibited under the guise of an analytical table. Order ZOANTHARIA. Sub-order 1. Z. Malacodermata. Family 1. ACTINIDÆA. orallum not evident. Polypes rarely con- nected by a coenosare; in general, locomo- 206 ACTINOZOA. tive, the flattened base of each adhering at pleasure. Family 2. ILYANTHIDÆ. r not evident. Polypes unat- tached, with rounded or tapering base; no connecting cœnosarc Family 3. ZOANTHIDÆ olypes attached, united by a coenosare, and furnished with a spicular corallwm. Sub-order 2. Z. Sclerobasica. Family 4. ANTIPATHIDA. rallum — sclerobasic, horny, smooth or spinulous. Folypes with six tentacles. Family s. HYALOCHÆTID Corallum elerni composed of twisted siliceous fibres. Polypes with twenty ten- tacles. Sub-order 3. Z. Sclerodermata. Tabule present. Septa rudi- ae (Tabulata). . x : 5 é : 02 Tabule absent, : : . : aes a endive wanting, or ill- . Ww 3 sive coe a. Family 6. Tusc Septa and. Wie distinct. . Family 7. T Selerenchyma tubular or cel- Family 9. MirrEPoRIDE. e indicated by faint striæ 5 Family 10. AULOPORIDZ. Ba ipie velo oped : $ , . . 6 ws ehem, porous (Perfo- slay imperforate Jis ymacompact. Coral- scent. Family 8. SEnIATOPORIDX. — P —— —L- — — A LIE a a 2 EE UNE a ACTINOZOA. 207 arm reticulate. The- d distinct from the sur- g cenenehyma . Family 11. Porrrmz, sind simply porous. net. . Family 12. Mapreporm. = sei No dis- g iments : . . Family 13. Fuxarpx. or imme o only Dot the deve- e of the costae or epi- wo Family 14. Asrz IDE. Diseepiments fow or r absent. ? $ i E : .IO chyma ssas abun- Family 15. OCULINIDÆ.. No COEM : ; . Family 16. TURBNOLDÆ. In addition to those heredefined, Milne Edwards has distinguished four other families of Aporosa, which inosculate, so to speak, between the primary groups just mentioned. The first family, Das- mide, includes but a single genus, closely related to the Turbinolide, from which it differs in the peculiar modifications of its septa. Each of these is represented by three vertical laminz, united only along their external margin. A second family, Stylophoride, appears as a transitional group between the Oculinidw and Astrwide. As in the former, there is a well-developed coenen- chyma and few dissepiments; but, on the other hand, the surface of the coenenchyma is echinu- late, while it is smooth in the Oculnidc, and the thec of the corallites do not, as in that family, increase endogenously, so as almost to obliterate the loculi. Another osculant family, Echino- poridee, still more closely resemblesthe Astraida, differing therefrom chiefly in the possession of a foliaceous, basal coenenchyma. But one genus 208 ACTINOZOA., presenting this combination of characters has been observed. The family Merulinide has, lastly, been constituted for the reception of an equally aberrant Astreoid genus, Merulina, which clearly points in the direction of the Fungide, resembling these corals in the perforate condition of its coral- lum, though, as in the true Astrwide, no synap- ticule occur. . Order 2: Aleyonaria. — The Alcyonaria, with the exception of one genus, Haimeia, which may, however, yet prove to be an immature form, are composite in structure; their polypes being mutually connected by a ccenosare, through which permeate prolongations of the somatic cavity of each, forming a sort of canal system, whose several parts freely communicate and are, therefore, rea- dily distensible. Throughout the whole order the polypes exhibi a very close agreement in structure, howsoever much the ecnosare may vary. Each, when ex- panded, displays a cylindrical, or somewhat octa- gonal, tube, with delicate transparent walls, and eight pinnate tentacula, whose form offers slight though characteristic variations among the several genera of the group. In some the polypes are retractile into excavations which occur in the sub- stance of the conosare, while in others such excavations seem to be wanting. Alcyonium, the typical genus, presents, when first dredged up, a sufficiently repulsive aspect, suggestive of the vulgar names, * Cow's paps " and * Dead-man's hand," sometimes conferred on it. But, when placed in sea-water, the lobate fleshy mass, distending its aquiferous system, is gradu- ACTINOZOA. 209 ` ally seen to become exquisitely pellucid, while from all parts of its surface numbers of tiny polypes, emerging, expand to the utmost their star-shaped crowns of delicately fringed tentacula. Within the somatic chambers circulating currents may now be observed. These find their way up one side of the tentacles, following the course of would not, perhaps, be too much to say that the tentacles, by reason of the delicacy of their ciliated walls, fulfil the proper function of a respiratory system. In Sarcodictyon, as in Alcyonium, a spicular corallum occurs, but the ccenosare is scanty and creeping, resembling that of the Zoanthidw. So also in Cornularia, the corallum of which is, however, more consolidated. But of all the Al- eyonide proper Telestho, with its tufted, sub-cal- careous, tubular corallum, makes the nearest approach to the allied family of Tubiporide. The beautiful Organ-pipe Corals, forming the several species of the genus T'ubipora, appear to be the sole representatives of this group. Allusion has already been made to the exceptional structure of their corallum, the colour of which, in all cases, is of a bright crimson-red. The polypes are either violet or grass-green in tint, and, according to the dissections of Dana, present this anatomical peculiarity, that two only of the mesenteric edges are furnished with ova, the remaining six sup- porting spermaria. The oral extremity of each polype can be inverted for protection into the summit of its calcareous tube, but it is wrong to P 210° > ACTINOZOA. abulata, nor are traces of internal tabulæ wholly wanting. The characteristic form of Tubipora seems due to the periodic budding of zoóids from the distal surface of the plates, while at the same time certain of the older corallites continue to increase in height. But neither the minute struc- ture nor development of this interesting genus have yet received proper attention. The Gorgonidee differ from all other Alcyonaria in having an erect branching ccenosare, firmly The modifications which this structure displays in Corallium, Isis, M opsea,and Melitæa have already received a brief notice. It may suffice to add that very exaggerated conceptions seem to prevail as to the height which the horny Gorgonidæ are capable of attaining. It is doubtful whether their largest trees ever rise to more than five or six feet, yet some have been reputed to rival oaks in size, an assumption which, however incredible, is, nevertheless, not inconsistent with theoretical con- siderations. The Alcyonaria, as a group, seem destitute of locomotive power, though one family of this order, the Pennatulide, have been often regarded as ACTINOZOA. 211 oceanic, £ and described by such names as “ Polypes eurs.” It is more probable, however, that, under ordinary circumstances, these creatures ie with their proximal extremity plunged firmly into the sand or mud of the sea-bottom; the distal Fig. 37. Pennatutipz and Gorconipm: — a, dried stem of Virgularia mirabilis ; b, portion of another stem, in the living condition; e, corallum of Mopsea costata; d, fragment of the same. (a is reduced one-third; b and c are of the natural size; d is magni- fied.) end of the ccenosare, which bears the numerous polypes, freely exposing itself to the influence of the pe water ab ecnosare of the Pennatulide may be ee and simply sinpanite, with very short 212 ACTINOZOA. pinnules, or lateral lobes, bearing the polypes, as in Virgularia, the sclerobasis of which is rigid, tapering towards its extremities, and densely cal- careous (fig. 37, &). In the true Sea-pens, forming the genus Pennatula and its near allies, the pin- nules are very conspicuous, and so modified as to arrangement and comparative size that the whole mass presents a striking resemblance to a bird's feather. The proximal end of the ccenosare, often for nearly half its length, is bare of pinnules or polypes, appearing swollen and fleshy. In other Pennatulide the entire ccenosare is club-shaped, without any pinnules, the polypes being irregularly scattered, as in Veretillum, or arranged in longi- tudinal rows on part only of the surface, as in Kophobelemnon. In Renilla a comparatively short ccenosare expands distally to support a smooth, symmetrical, kidney-shaped disc, from the free surface and edge of which the scattered polypes arise. This aberrant genus appears to want a sclerobasis, the interior of the stalk and disc being hollow, and in free communication with the cavities of the polypes, so that the animal possesses the power of largely increasing its dimensions by allowing itself to become expanded by the ingress of the surrounding sea-water. Like the members of the preceding families, many Pennatulide are liable to have their soft entire group. “Tt shines at night with a golden green light of a most wonderful softness. When — ACTINOZOA. 213 excited, it flashes up more intensely, and when suddenly immersed into alcohol, throws out the most brilliant light.” Experiments performed on our own British Pennatula phosphorea led Professor E. Forbes to the conclusion that this species is “phosphorescent only when irritated by touch”; but it seems safer to infer that the light, itself the index of an energetic display of vital power, is only evoked in answer to proper stimuli, which may very well be expected to occur more appropriately in nature, though, doubtless, under a form less clumsy, than in the exaggerated con- ditions of an experiment. Forbes also showed that the phosphorescence, when thus excited by shock, sparkles onward from the portion struck in an upward or distal direction, still, however, con- ünuing to be emitted from the point of prime contact. The vividness of the luminosity appears to bear a direct ratio to the living energy of the animal. Such are the chief conditions of its manifestation, but the true cause of this pheno- menon, as of vital phosphorescence in general, still remains almost wholly unknown. Four families of Alcyonaria may be defined: Order ALCYONARIA. . Family 1. Arovoxip. orallum sclerodermic, in general spicular, without true calcareous thecæ. Coenosarcfixed. Family 2. Tuprrorrp x. orallum consisting of a number of distinct - corallites, destitute of septa, their theca: united externally by horizontal plates, arranged at distant intervals. Ccnosare fixed. 12 214 ACTINOZOA. Family 3. PENNATULID AE. Corallum sclerobasie, tissue secretions also being sometimes present. Comosawc free. Family 4. GORGONIDA. Corallum sclerobasie, sulcate, with or with- out additional tissue secretions. Canosare shrub-like, attached by its expanded proximal extremity. 4. Order 3: Rugosa.— Among the Rugosa a highly developed sclerodermie skeleton occurs, each corallite being very distinct, and presenting, in many cases, both septa and tabulæ. Some Rugosa are simple, the corallite often attaining a considerable size; others are composite, increasing either by lateral or calicular gemmation, these two processes, but especially the latter, checking to a greater or less extent the growth of the primitive corallite. A true cænenchyma is ab- sent. In Stauria, Holocystis, and Polycælia four of the septa admit readily of being distinguished, by their greater development, from the others, but in Cyathaxonia only one primary septum or chamber remains conspicuous. So, also, of Za- NN TRU CI ien ae te a hE a m - = ES c > = iv) 9 B Qu. Ld ct mR B o a] [t] [n E (a) Qu [2] = [t 2 m Ei. iq?) mR S S W oo w. a In other genera the septa radiate, in about an l ia) de [er] D — £5 B B [0] dd E S ct Ey? [e] fede B =) (D A n S zh e^ c [t9] D kh — E [t] c E [19] © © uu In many Rugosa they are incomplete, that is, ‘do not extend from the bottom to the top ofthe i corallite, in the form of uninterrupted lamine.” The tabule exhibit various grades of develop- ment, and, in some species, are wanting altogether. In a few Rugosa the columella is cylindrical, and of large size ; in others, styliform or lamellar: AmATRÁTSZ A ——————Á —nrQS € ACTINOZOA. ALO often, it is wanting. In Cyathophyllum and certain allied forms there is a spurious columella formed by the “ twisting together” of the inner edges of the septa. In Cystiphyllum neither columella, septa, nor tabula can be distinguished. The whole interior of the corallite, save its shallow calice, is here, as Fig. 38. “ i aA i ZR Gi if AAN ZAPHRENTIS CYLINDRICA. (Part of a corallite, of the natural size.) it were, broken up by the numerous laminæ of a sclerenchymatous deposit resembling the vesicular substance of its epitheca and wall. Most Rugosa belong to the large group of Cyathophyllide. The remaining families include ut a few generic forms. Order RUGOSA. Family 1. STAURIDA. Corallum simple or composite. Septa complete, united by lamellar dissepiments. 4 216 ACTINOZOA. Family 2. CyATHAXONID. Corallum simple. Septa complete. No dissepiments or tabulee. Family 3. CYATHOPHYLLIDE. Corallum simple or composite. Septa in- complete. Tabulz, in general, present. Family 4. CYSTIPHYLLIDA. Corallum simple; composed chiefly of a vesicular mass, with but slight traces of septa. 5. Order 4: Ctenophora.— The leading characters of the Ctenophora, or oceanic Acti- nozod, have been already, to some extent, sketched out in the account given of Plewrobrachia, se- lected as the type of the group, and in the com- parative survey which has been taken of the prin- cipal organie systems of the present class. The more striking modifications which appear within the limits of the order have reference chiefly to size, the general form of the body, the several parts of the canal system, and the struc- ture and arrangement of the tentacles. The ordinary dimensions of Plewrobrachia are by many other Ctenophora frequently exceeded, a common British species of Bolina often attaining a long diameter of two or three inches, while Beroe sometimes reaches the size of a large lemon. In Pleurobrachia alone does the form of the body approach the spheroidal (fig. 39, e). Its axis is somewhat lengthened in the Beroide, so that the animal, when seen in profile, appears more or less ovate (c). In Cestum, on the other hand, elongation takes place to an extraordinary extent, at right angles to the direction of the P DU X D | ! 0 ]- ACTINOZOA. 917 digestive track, a flat ribbon-shaped body, three or "four feet in ‘length, being the result (a). Calli- Fig. 39. Various forms of CTENOPHORA : — a, Cestum Veneris ; b, Eu- rhamphea vexilligera ; c, Beroe rufescens ; ; d, Callianira triplo- piera; e, 3s iai piens, (a is considerably reduced; : slightly 80; c and e are about the natural size: the size of d i uncertai n.) amira, a genus of which very little is known, is remarkable for having its ctenophores elevated on 218 ACTINOZOA. prominent wing-like appendages, and may possibly yet prove to be but an imperfectly developed member of the group (d). In one large division of the order two wide diverging lobes project from the antero-posterior regions of the body, far beyond the level of the mouth, which, by their approximation, they some- times wholly conceal. Between these lobes, in Bolina and its allies, occur on either side two small lateral appendages, or earlets. Four of the ctenophores, much shorter than their fellows, run to the bases of these, along which they are con- tinued as simple ciliated fringes. The earlets, therefore, may be regarded as specially modified prolongations of the lateral ctenophores. - Lurhamphea, one of these lobed Ctenophora, is remarkable for the general elongation of the axis of the body, which is, moreover, much compressed from side to side (b). The two lateral actinomeres terminate in long tapering appendages, which project for some distance beyond the apical extre- mity of the animal, and then curve gently upwards and outwards. Of a similar nature, but much shorter and wider, are the apical appendages, or lappets, of some Beroide. The mouth of the Ctenophora varies as to size, degree of prominence, and the relative develop- ment of distinct lips. Even in the same indivi- dual its form, at different periods, presents many diversities of aspect. It attains a very large size in Beroe and its allies, extending right across almost the entire oral extremity, in its usual antero-posterior direction. Hence Leuckart has proposed to divide the Ctenophora into two sepa- rate groups; the Hurystomata, corresponding to aC cS. ee ee ee OU ure ACTINOZOA. 219 the Beroide, and the Stenostomata, including all remaining members of the order. The apical area, also, presents its own peculiar variations. In general it appears as a somewhat oblong flattened space, bounded by a distinct ridge, its long diameter coinciding with that of the mouth. The ridge is usually smooth, and the general surface of the included region covered with very fine cilia. But in the Beroide a num- ber of conspicuous, though short, arborescent fila- ments fringe the margin of the area, which, in this family, appears divided into a pair of shallow, ovate lobes, converging to a point at the apical pole of the body. The modifications of the nutrient system now require our attention. ‘The whole of this appa- ratus may, for purposes of description, be resolved into the following minor systems or groups of parts : — 1. An axial system ; including the digestive tube, the funnel, and the apical canals. 2. A paraxial system. To this belong the para- gastric canals arising from the funnel, and an oral vessel, or vessels, into which, in some genera, their distal extremities open. 3. À ctenophoral system; the eight canals of which may be variously prolonged to supply the lobes or other appendages of the body ; and — n 4. A radial system; or those channels whereby the several elements of the preceding system become connected with the funnel. I. The parts of the axial system vary but little throughout the order. In Pleurobrachia the di- |] * 220 ACTINOZOA. gestive sac is relatively shorter than in other Ctenophora. In the Beroide the funnel is very short and wide. Not more than one pair of apical canals ever appears to have been noticed. 2. Of paragastric canals, one or two pairs may be present. The single pair of these canals are cecal in Pleurobrachia; in Beroe they open into an oral tube. In most of the lobed Ctenophora two pairs of paragastric canals occur, of which one lies close to the sides of the digestive sac, the position of the second pair being more superficial. The inner pair may be cecal, while the outer pair open into the oral tube; or the latter may anas- tomose with both pairs of paragastric canals, as described by Milne Edwards in Chiajea Paler- mitana. The oral vessel may be circular, as in the Beroidæ, or consist of two straight canals run- ning by the sides of the mouth, as in many of the lobed Ctenophora ; though in one of these, Eurhamphea, this vessel is complete. e eight ctenophoral canals may conve- niently be divided into four lateral, and four antero-posterior. The oral extremities of all these canals may be cecal, as in Pleurobrachia, or open into the cir- ctenophore, winds round the edge of one of the smaller lobes or earlets, and having again reached " " —_ = mm. ys ACTINOZOA. 991 the general surface of the body, soon joins the extremity of the oral tube of that side, before gaining which it sends off a branch, destined, after having pursued a long and devious track, to anastomose with its fellow from the opposite side of the body, and the complex system formed by the much convoluted and prolonged extremities of the intervening pair of antero-posterior canals. These last, after quitting their ctenophores, which are relatively much longer than those of the sides of the body, are produced to supply the two large lobes, in front of and behind the mouth, within the substance of which, after many sinuous turns, they finally blend and become lost. The course of the ctenophoral canals is usually simple. In Chiajea Palermitana each gives off on either side a number of very short straight branches, which in the Beroide are replaced by somewhat larger, arborescent tufts. 4. Lastly, the apical extremities of the cteno- phoral canals, and the manner of their communi- eation with the axial system, or, in other words, the disposition of the radial vessels, remain to be noticed. In Pleurobrachia, as has been shown, the primary, secondary, and tertiary radial canals are very well marked, meeting the ctenophoral vessels at right angles to, and about midway in, their course. The apical extremities of the latter are distinctly prolonged, to end cæcally around the oblong, flattened area. In the Beroide a radial system can scarcely be said to occur, the apical ends of the cteno- phoral canals curving gently round, to open into 222 ACTINOZOA. the funnel, which is placed very close to its own extremity of the body. rrangements intermediate between the two extreme conditions just noticed may be traced among the several genera of the lobed Cteno- phora. Thus, in Le Sueuria, the apical extremities of the eight canals curve inwards to empty them- selves into the four short radiating vessels which issue from the funnel. Somewhat similar is the radial system in Bolina and, perhaps, in some species of Chiajea. But in C. Palermitana, while the four longer or antero-posterior canals comport themselves much as in LeSueuria, each lateral canal, near the middle of its course, is connected by a short transverse branch with the extremity of one of the four short radial vessels, just where it receives the .curved inward prolon- gation of the adjacent antero-posterior vessel. In this form the apical extremities of the shorter ctenophoral canals are czecal, but in Eurhamphea, whose radial system resembles that just noticed, the lateral canals of each side open at an acute angle into one another, at the bases of the two curved appendages of the apical lobes peculiar to this genus. Comparing the preceding account with the little yet known of the development of the nutrient apparatus in the Ctenophora, the following con- clusions seem deducible. The first formed part of this apparatus seems to be that large rudiment of its axial system from which, at an early period, the digestive sac and funnel become differentiated. From the funnel, or central portion of the whole nutrient cavity, the apical canals soon branch off. ad; ACTINOZOA. 293 Thus the axial system is completed. Next, radial and paragastric canals appear, the former quickly reaching the surface of the body, where they branch and give origin to the ctenophoral canals, the apical ends of which are well developed, while their opposite extremities are still on their way towards the oral region, in striving to gain which they are outstripped by the paragastric vessels. The extremities of these either remain ceca (Pleurobrachia), or, by branching, give origin to the two lateral rudiments of the oral canal. These may still continue distinct (Bolina, Chia- jea, Le Sueuria), becoming connected with the extremities of the lateral ctenophoral canals; or unite to form a complete circular tube, which receives, as before, only the four lateral canals (Eurhamphæa), or both these and the vessels of the antero-posterior ctenophores (Beroe). Thus, the oral tube bears to the paragastric canals a relation comparable, perhaps, with that between the etenophoral vessels and the radial system : and the gradual development of the entire canal sys- tem may be described as tending in a peripheral direction, while its several elements bifurcate; the branches so formed, to a greater or less ex- tent, again uniting, and prolonging their course beneath the surface of the body. In the above survey the canal systems of Cestum and Callianira have not been included. Of the latter nothing whatever is known. In Cestum the axial system resembles that of Bolina and the Ctenophora in general. Each half of the cteno- phoral system is represented by four very long canals, two of which run side by side along one of the fringed margins of the ribbon-shaped body, 224 ACTINOZOA. the other pair, parallel to these, being situate midway between them and the opposite, or oral, margin. For,in this strangely aberrant form, the course of the axial system corresponds with the short mid-axis of the ribbon, the apparent width of which represents, therefore, the true height of the animal, whose breadth answers to the length of the ribbon, and antero-posterior diameter to its thickness. On this account, it will be convenient tospeak of two of the ctenophoral canals as mar- ginal, the two others being medial. There are four radial vessels, two on either side, each of- which divides into a single pair of branches, com- municating with the ctenophoral canals. The two branches of each radial canal are very unequal in length, and run in opposite directions, the shorter branch soon becoming continuous with a marginal canal, while the longer branch trends parallel to the sides of the digestive cavity, turning round abruptly to open at right angles into one of the medial canals, as soon as it has reached its level. At each extremity of the ribbon the marginal and medial canals anastomose with one another and a long vessel running parallel to their course along the oral margin of the body. At its opposite - extremity, near the mouth, this canal unites with its fellow of the other side, where both are joined y a pair of paragastric canals, which Milne Edwards has figured as running in an antero- posterior direction, parallel to the digestive sac. A second, or inner, pair of these canals has not yet been observed. There can be little doubt that the paired medial and marginal canals of Cestum represent the eight ctenophoral vessels of other genera of the order, ACTINOZOA. 225 and that each half of the long unpaired marginal canal is homologous with one of the lateral oral vessels in such genera as Bolina or LeSueuria. Two principal kinds of tentacles occur in the Ctenophora: long, highly contractile cords, capable of being retracted into special pits; and shorter, isolated threads, which may, in some species, become aggregated to form tufts or bunches. Among the Beroide, tentacles are absent. In Pleurobrachia a large tentacular pit excavates obliquely upwards the substance of the two lateral actinomeres. The base of this pit is brought into lose connection with the distal extremity of the short primary radial canal, which opens directly into a wide heart-shaped sac, from between the two deeply-cleft lobes of which, at the upper portion of the fissure formed by their junction, the tentacle itself makesits appearance. Proximally, it is some- what compressed, but for the greater part of its length becomes truly cylindrical, giving off on that side which is turned away from the body a number of secondary lateral filaments. Both these and the tentacle itself are hollow, communicating with the canal system through the medium of the basal sac, their walls also, like those of the body canals, being lined by an investment of endoderm. n the secondary branches them- selves still more minute threads are said to have been observed. Of the grace and beauty which the entire apparatus presents in the living animal, or the marvellous ease and rapidity with which it can be alternately contracted, extended, and bent àt an infinite variety of angles, no verbal descrip- tion can sufficiently treat. These movements seem partly caused by the action of the contractile fibres Q 226 ACTINOZOA. which occur in the tentacular walls, and partly by the distensive pressure of the fluid forced into the interior of the tentacle, by means of the elastic basal sac. An account somewhat different to the above has recently been given by Professor Agassiz, both of the precise structure of the tentacle itself, and the mode of its connection with the canal-system. * Nearly two-thirds of the length and breadth of the proximate side of the actinal or closed end of the tentacular socket is occupied by an oblong dise, from the mid-length of which the tentacle arises, The distal side of the disc, or that which: faces towards the periphery of the body, is convex, with a shallow furrow extending from the base of the tentacle to the actinal end of the disc; and the proximate side, or that which faces towards - the axis of the body, is a plane, immediately beneath whose surface and next to the edge, two chymiferous tubes run parallel; leaving between them, along the median line, a thick ridge, which is nearly as broad as the diameter of the tubes." —“ Only imagine the socket to be removed or reverted, as oftentimes does ha pen in a great measure, and the whole apparatus will appear like a peripherie ridge, which, at one point, is drawn out into a slender thread, the tentacle. The base of the tentacle has the form of a high, narrow ridge or keel, more or less plicated or distorted, according to whether the apparatus is extended or retracted; but we have never seen it projecting beyond the aperture of the socket. At the basal end of the keel it is as broad as the dise from which it arises, but it suddenly narrows to a uniform thickness, which it retains to the other end, where * $2. Áo 3 = No Lye. — a Ae Ems y coU SU ES. o ME S M CIENT, VET TR ee me wes SS ACTINOZOA. 297 it merges into the cylindrical part of the tentacle.” Professor Agassiz describes the latter not as hollow put solid, though he recognizes the two layers of which it is composed. In Callianira two long tentacles, relatively situate as in Pleurobrachia, but destitute of lateral threads, divide, at their free extremities, into two or three lengthened branches (jig. 39, d). In Cestum, also, a pair of symmetrical tentacles appear to be usually present, but these do not, as in the preceding forms, issue from the equatorial region, thence turning away from the mouth; but, rather, take their position in front of and behind the latter, towards which they are seen to incline. Milne Edwards figures the tentacles of C. Veneris as simple ; by other writers, and perhaps in other species, they are described as variously branched. Among the lobed Ctenophora the particular In Chiajea, occur two tentacles, one on each side of the body, but similar in other respects to those of Cestum. Tentacles of the second type are, however, more frequently to be met with in this section of the order, and these may be either lateral, and arranged in groups, as in most genera, or disposed in a ring round the mouth, as in Lurhamphea. In Bolina a tuft or brush of very short tentacles is seen to arise on either side of the mouth, where the oral vessels appear to meet, about midway in their course, the superficial paragastric canals. The extremity of each of these canals ends in a simple socket, within which the tuft of tentacles may be withdrawn. But there is no proper sac, Q 2 228 ACTINOZOA. as in Pleurobrachia. Agassiz states that, in this genus, only the innermost pair of paragastrie canals open into the oral vessels, the outer pair, notwithstanding their close approximation to the sides of the mouth, being destined solely for the supply of the tentacular bulbs. In LeSueuria two tufts of tentacles, similar in position to those of Bolina, but prolonged to form a pair of lateral fringes, were first observed by Milne Edwards, and in addition four simple conical appendages, of moderate length, arise, one between each of the four pairs of smaller lobes character- istic of this genus. The outer paragastric canals are seen distinctly to open into the canals repre- senting the oral vessels, but Milne Edwards does not notice the existence of any communication between them and the lateral tentacular fringes, which are, perhaps, nothing more than filamentous extensions of the ectoderm. i LeSueuria, according to the same writer, is. furnished, however, with a pair ofcurious appen- dages by means of which the oral extremities of - the paraxial canal system communicate directly with the exterior. Each appendage is cylindrical, short, and tubular, arising from the midst of one of the principal tentacular tufts, and terminating distally in four small lobes, surrounding the orifice of the canal, which seems to perforate its axis. Agassiz denies the existence of this opening, and considers the two appendages homologous with the tentacular bulbs of Bolina. In Leucothea a very complicated tentacular apparatus occurs; short threads like those of Eurhamphæa and LeSueuria being here present, in addition to three long tentacular organs, arising ! ACTINOZOA. 229 on each side of the mouth. Of these, one is simple, while the others display a number or lateral ramifications. But all these structures from the sea-water and exposed to the rays of the sun, an almost imperceptible film remaining the only trace of what was erewhile an active and beautiful organism. Yet are the Ctenophora very voracious, feeding on a number of floating marine animals, among which their own kindred seem especially to be preferred. The prey, once swal- lowed, is assimilated with a rapidity which to some may seem strange, when the simple structure of the digestive apparatus is considered. All the Ctenophora are not equally fragile. Pleuro- brachia, in spite of its tender gelatinous aspect, may be preserved in captivity for weeks, or even months, if properly supplied with food. The Ctenophora swim in various positions, and some may often be noticed with their apical ex- tremity turned downwards or forwards. Hence many writers term this the dorsal aspect; the digestive sae, by a strange perversion of language, being deseribed as situate below the funnel; and 80 with the relative positions of the remaining organs, This practice is not only objectionable in itself, but has tended much to confuse almost every published account of the structure of a Broup of beings, than which few anatomical sub- Jécts are at once so easy and so accessible. Not Q3 230 ACTINOZOA. in learning, but in unlearning, is the student of the Ctenophora compelled to waste his time and ingenuity. ‘Some nino are phosphorescent. In a species of Bolina common around our shores this beautiful property may very readily be observed. Specially distinguished for its luminosity is the much larger Cestum Veneris of the Mediterranean, which is said to gleam at night like a brilliant band of flame, moving beneath the surface of the water. By Gegenbaur the Ctenophora have been di- vided into five families, which may be defined as follows : — Order CTENOPHORA. Sub-order 1. Stenostomata. Family r. CALLYMMIDA. Body furnished with a pair of antero-pos- terior oral lobes, and other smaller lateral appendages. Tentacles various, turned to- wards the mou Family 2. CESTIDÆ. ody ribbon-shaped, extended in a lateral direction, without oral lobes. Tentacles two in number, antero-posterior, turned towards the mouth Family 3. CALLIANIRIDA. ody produced into a pair of wing-like, lateral lobes, bearing the ctenophores. Ten- tacles two in number, lateral, turned from the mouth. Family 4. PLEUROBRACHIADA. Body oval or spheroidal, without oral ACTINOZOA. 231 lobes. Tentacles two in number, lateral, turned from the mou Sub-order 2. Hurystomata. Family 5. BERO Body Si DT without oral lobes. Tentacles absent. Here we have slightly modified the definitions of Gegenbaur, at the same time indicating what appears to be the most natural sequence of the several families. The group Callianiride must for the present be considered as merely provisional. The four other divisions of Ctenophora have been recently elevated by Agassiz to the rank of sub- orders, and the entire number of families increased toten. This arrangement, however, presents no advantage over the more simple and natural one adopted by Gegenbaur, which, in its turn, must be regarded as an improved modification of the prior classification of Eschscholtz. Section IV. DISTRIBUTION OF ACTINOZOA. I. Relations to Physical Elements. — 2. RUBRI Distribution. — 3. Geographical Distributio I Relations to Physical Elements, — All the Actinozow are marine. . Bathymetrical Distribution. — Upon the whole it may be said that the Alcyonaria are less abundant between tide-marks, and occur in deeper Q4 232 ACTINOZOA. waters, than the Zoantharia. Alcyonium has been met with at seventy fathoms, but, like Pennatula, is common in much shallower seas. From so great a depth as 240 fathoms a species of Virgu- laria, V. Fimmarchica, was dredged at Oxfjord by M. Sars, who also obtained, in the same locality, the widely different Briareum grandiflorum, a low creeping Alcyonid, allied to Sarcodictyon. The Gorgonide, in like manner, seem to prefer deep seas, Corallium having been found at 120, and Gorgonia itself at nearly 200 fathoms. Though depths equal to or even exceeding those just mentioned have yielded many species of Zoantharia, Ulocyathus, for example, frequenting water of 200 fathoms, yet, in general, the members of this order are most abundant in seas of not more than 50 to 100 fathoms deep. The Actinide and Madreporide include those species which are most prone to descend below this limit. Many of the Actinidæ, it is well known, are numerous between tide-marks, the common Sea-anemone tending to encroach upon the line of high water. The shallow vertical range of the reef-building Actinozoa has already been sufficiently explained. Certain species are chiefly restricted to particular parts of the reef; Astræidæ and Seriatoporide choosing its more submerged portions, below the outer exposed edge, upon which Porites and its allies flourish. On the surface of the reef both Astreide and Fungide may readily be distin- guished, the labyrinthic form of Meandrina, among other genera, being here especially con- spicuous. The soft-bodied non-adherent Zoantharia usually oceur on muddy or sandy banks, at or ACTINOZOA. 233 near the level of low water. A few appear to be oceanic. Philomedusa, a minute form, from the Brazilian seas, habitually seeks shelter beneath the swimming-organ of various Meduside and Lucernaride. The bathymetrical distribution of the Cteno- phora, by reason of their oceanic habit, is scarcely amenable to observation. Some species, during the storms of winter, appear to seek considerable depths, on the return of spring again approaching to the surface. 3. Geographical Distribution. — The Cte- nophora, Alcyonaria, and soft-bodied Zoantharia appear to be about equally abundant in tropical and temperate seas, many forms extending their range to high latitudes. Of coralligenous Zoan- tharia two families, Turbinolide and Madrepo- . mide, are not without northern and even arctic representatives, yet by far the majority of other selerodermie species are seldom found to occur beyond the limits of the tropics. The reef-build- ing Corals, according to Dana, will not flourish in water wherein the mean winter temperature is lower than 66? F. So that on either side of the equator a zone of water sufficiently heated for the growth of these Corals extends, the boundary lines of which have of necessity a somewhat contorted, irregular course, by reason of the varied com- binations of circumstances influencing the local distribution of heat. Even within these limits other external conditions, not less essential than à high temperature to the welfare of reef-build- ing Corals, are often absent. But when once the nature of these conditions has been carefully " 234 ACTINOZOA. understood, the many apparent anomalies in the distribution of Coral-reefs, far from being, as some have stated, unaccountable, become in each case susceptible of their appropriate physical explanation. In the British seas about ten species of sclero- dermic Zoantharia occur. The number of Medi- terranean Corals is much greater, though these, with few exceptions, are specifically distinct from those observed by Ehrenberg in the Red Sea. The Mediterranean also yields two or three forms of sclerobasic Zoantharia, a group. apparently unknown in more northern seas. Corallium rubrum, the Red Coral of commerce, would seem to be restricted to the same region, though other species of its genus have from time to time been dredged off Madeira and the Sandwich Isles. Of Actimozoa, which oecur beyond the limits of the Méditerranean and North Atlantie Seas, our knowledge still remains very imperfect, save only in the case of the reef-building Corals and the more conspicuous forms of Ctenophora. The genera Cestum, Calliamira, Calymma, Chiajea, and Leu- cothea, may be cited as examples of this order cha- racteristic of the tropical and warmer temperate zones. Ocyroe, an obscure but interesting Cteno- phorid, distinguished by the possession of two antero-posterior lobes, prolonged outwards at right angles to the true axis of the body, and which, when better known, may prove to be the imma- ture condition of some apparently dissimilar form, has a range not wider than the equatorial regions of the Atlantic. In high latitudes several Actinide, a few Tur- binolide and Madreporide, together with various ACTINOZOA. 235 Alcyonaria and Ctenophora, of which one genus, Mertensia, is said to be exclusively arctic, chiefly represent the class. The Pennatulide appear more numerous than other Alcyonaria around the northern colder temperate shores, seven spe- cies being named in the Norwegian fauna of Sars, while but three have yet been recorded as British. , | . Umbellularia, a very aberrant member of this 1 | family, which presents a rod-like ccenosare six feet in length, crowned with a spreading tuft of polypes at its summit, is only known from the published i deseriptions of two specimens, dredged from a ) depth of 236 fathoms, off the coast of Greenland, | about the middle of the last century. ; | WOW TUM wx ww" Among genera of Actinozoa which enjoy a wide distribution, Actinia, Alcyonium, Zoanthus, and Gorgonia are perhaps best worthy of men- f tion. To this list should be added the names of r | several forms of Ctenophora, than which few ma- rine animals appeared so well adapted to thrive under every variety of climatal conditions. Two genera in particular, Beroe and Plewrobrachia, are remarkable for their unbounded geographical area. XN With less confidence can the names of such Actinozoa as are restricted in their range be, at ) | present, insisted on. Renewed observations show that the number of extra-tropical genera, once thought to be peculiar to certain regions, must undergo considerable diminution. Of specific forms, however, not a few seem to characterise the "m various seas and shores to which they are confined. The existence of natural barriers, whether of ! land or deep water, exercises a marked influence E on the distribution of the Actinozoa. The differ- 236 ACTINOZOA. ences between the East and West Indian species of Corals, or between the several Atlantic and bling one another under similar conditions of depth and temperature, but, in a large number of cases, specifically distinct, may thus be easily accounted for. Many genera of fixed Actinozoa, abundant in one hemisphere, are found wholly wanting in the other. To a less extent is this observation true of the soft-bodied or free-swim- ming species. Section V. RELATIONS OF ACTINOZOA TO TIME. 1. General History io Actinozoa. — 2. History of Zoantharia. —35 History of Rug —4. Hi story of es ei — SI s EX ora. ^ —6. D arbonifer rals. Per- Corals. — 9. Tri assic "Corals, — 10. Jurassic Co ora IIL. Cae “orale — 12. Tertiary Corals. — 13. Recent fe I. General History of Actinozoa. — Acti- nozow appear to have been numerous during each of the greater artificial geologic epochs. The hard parts of the coralligenous species only have been preserved. Hence the expressions * fossil Corals” and “fossil Actinozoa" may be used as syno- nymous. One order, Ctenophora, has no fossil represen- tatives. The Rugosa, on the other hand, are wholly extinct. The accompanying table exhibits, from a general point of view, the relations to time of the prin- cipal groups of Actinozoa. Lists are appended of those genera of Corals which range through more than one geological period. ACTINOZOA. CHRONOLOGICAL ARRANGEMENT or ACTINOZOA. OO 4 Names of Groups. | Names of Periods. Silurian Devonian. | Carboniferous. Permian. Triassic. Jurassic. Cretaceous. Tertiary. Recent. Actinozoa . ` eaS Meo e ies Im : RES An ee See ES por 5 aes E Tarbinolides = Ka] £5 a FREE M. 8 E £u DESC A 1 Seriatoporide ; —|— — Mille poride . MA : ` I—|— Antipathi de . —|— Rugosa .l|— —|—|— — Cystiphyllidee .l—/— ee eng = oa E RE PE E 8 R33 El Gorgonidee Ctenophora : 238 ACTINOZOA. PALEOZOIC CORALS, WHICH OCCUR IN MORE THAN ONE GEOLOGICAL PERIOD. fG d in order of their appearance, Silurian. Names of Periods. Devonian. Carboniferous. Cystiphyllu Ptychophyllum Aulacophyllum Heliolit ites opium yathophy Ilum aphre Cy ( Pr A Ciel ] i 4 (t : Philippsast: Lithostrotion X y. I I n F "istulipora We We Tp | kdob5p id REIFE A FS EE E EI Permian. ACTINOZOA. 239 MESOZOIC, CAINOZOIO, Aw» RECENT CORALS, WHICH OCCUR IN MORE THAN ONE GEOLOGICAL PERIOD. Names of Periods. Names of Gene need | in order oft their appearance. Triassic. Jurassic Cretaceous. Tertiary. Recent. Hybocenia ^ A — Goniocora . ^ aoe - | T-151 ed m Isa Montliveultia Eurymeandra E jm zr id 3 - ETE EN es Se Astroecenia : Stephanocenia . Thee osmilia : p Wa PM PPLIÍI [T dd bl EET set (ie ale GB to Oe 240 ACTINOZOA. MESOZOIC, CAINOZOIC, Ax» RECENT CORALS, waicu OCCUR IN MORE THAN ONE GEOLOGICAL PERIOD — continued. Names of Periods. T Names of Genera arranged in order of their appearance. Triassic. Jurassic. Cretaceous. Tertiary. Recent. pu Phyloceenia a ee DI Caryophyllia Mycetophyllia Hydnophora Cladocora . Cycloseris . Corallium . | 3 Nm m E NE NS MIS Acan thocy athus are ; "e T Acid j t TUS al culin ee ia : ; T M. NN : : = id Eu anne ; : = sank Ge 1 L alax : : mede å : — — Dasyphylia . ` = TEES ACTINOZOA. 241 MESOZOIC, CAINOZOIC, aw» RECENT CORALS, wzuicu OCCUR IN MORE THAN ONE GEOLOGICAL PERIOD — continued. Names of Genera _ arranged in order of their appearance. Names of Periods. Triassic Jurassic Cretaceous. Tertiary Recent Symphyllia Plesiastrea Solenastrea opseà . Hyalopathes Paha te ee C Te Lee | Chætetes passes up into the Trias. With this exception no genus of Corals survives the Paleozoic epoch except, perhaps, Tsis, of which doubtful in- dications have been met with in rocks of very ancient date. No Triassic genus of Corals has recent represen- tatives. Of genera which occur in the Jurassic Series seven still survive. Fourteen recent genera R 242 ACTINOZOA. first appear in the Chalk, while very many are common to the Tertiary and Recent periods. But few Recent species of Corals occur in a fossil state, It appears also from the preceding tables that six genera of Corals range through four periods, thirty-four through three, and sixty-eight through two. Some genera, however, arise in one forma- tion, are apparently absent from the next, but again present themselves at a subsequent period. Of this seeming anomaly Millepora furnishes an ex- ample. Such instances must always be received with suspicion, since they are probably due to defective observation, 2. History of Zoantharia.— All extinct Zoantharia belong to the group of Sclerodermata, with the exception of a few slight indications of Antipathide which appear in the Tertiary period. The Malacodermata axe wholly recent. On the other hand, the small group of Tubulosa does not survive the Paleozoic epoch. But two families of Zoantharia, Thecide and Auloporide, have altogether disappeared. On the whole it may be said that Tabulata prevail in the Paleozoic deposits, Aporosa and Perforata in those which succeed. — Tabulata are comparatively scarce in strata anterior to the Carboniferous, though no geological period is without some representative of this division, and in modern seas four genera have been observed. A single genus, Paleocyclus, which occurs in the Silurian period, is the only known representative of Aporosa in strata older than the Trias. The Perforata are represented in the Paleozoic rocks by two genera, but, excepting these, no other forms of the group T — + occ ase s > gor © ct c Y =< M» B. os cS Ea Eu “SA PrP Pes oO «e ve C FL CD ACTINOZOA. 243 have been met with in deposits of earlier date than the Jurassic. a History of Rugosa.— All Rugosa are confined to the Paleozoic epoch, with the exception of the genus Holocystis, which is peculiar to the Lower Greensand, where it is represented by a single species, H. elegans. "The Rugosa first appear in the Lower Silurian. They are especially abundant in the Upper Silu- rian, Devonian, and Carboniferous deposits. In the Permian rocks they are represented by only one generic form. 4. History of Aleyonaria.— Few genera of Alcyonaria have hitherto been found in a fossil condition, and scarcely three of these are wholly extinct. The existence of this order during the Paleozoic epoch must be regarded as doubtful, though the genus Protovirgularia has been constituted for the reception of a Silurian fossil, supposed to belong to the family Pennatu- ide. The genus Isis, also, has been stated to occur in some of the Paleozoic formations. With these rocks more ancient than the Chalk. The family Aleyonide is without an extinct representative. 5. Silurian Corals.— The Silurian Corals consist chiefly of Rugosa and Tabulata. The Aporosa are represented by the genus Palwocyclus; the Perforata by Protarca. Doubtful indications of Tubulosa and Alcyonaria also occur. At least nine families of Corals first make their appearance in this period, and one, R 2 244 ACTINOZOA, Thecidc, does not survive it. The following genera are peculiar to the Silurian series: Funew. Goniophyllum. Paleocyclus. Strombodes PORITIDÆ FAvOoSITDÆ. Protarea ente. THECIDE. Halysites "cia. Fletscheria Columnaria naia MiLLEPORDÆ Dekaia Lyellia. CYATHOPHYLLID&. Constellaria Streptelasma. Sr Omphyma. Stauria, 6. Devonian Corals. Excepting the genus ,. Aulopora, and the am- biguous form Plewrodictywm, the Devonian Corals . bu ‘consist wholly of Rugosa and Tabulata. One family, Seriatoporide, first makes its appearance in this formation, and one, Cystiphyllide, does not survive it. The following genera are exclusively Devonian : Por CYATHOPHYLLIDE. Pleurodi ictum. Smithia. AULOPORIDJE, Spongophyllum. Aulopo Acervularia SERIATOPORIDJE. Endophyllum endropora. Pachyphyllum rk udo Heliophyllum Favos Chonophyllum Thecosteqi tes. Anisophyllum. Ape gi ites. Baryphyllum. Romer Hadrophyllum. We aan: allia. Battersbyia. A atrio um. 7. Carboniferous Coral In addition to the genus Pott the Coral fauna of the Carboniferous rocks seems to be wholly e—a SS Se Se aid ACTINOZOA. 245 made up of Rugosa and Tabulata. Three families, Auloporide, Cyathophyllide, and Cyathaxonide, do not outlive this period. The following genera are restricted to the Carboniferous deposits: AULOPORIDAE. | CYATHOPHYLLID2 : Pyrgia. | Lonsdaleia, SERIATOPORIDZE. Stylaxis Chonaxis. CYATHOPHYLLID A, Aulophyllum. Axophyllum. Menophyllum. | Trochophyllum. 9. Permian Cora The few Permian ‘ome hitherto found belong to the Rugosa and Tabulata. The genus Poly- celia, of the family Stawrido, is peculiar to this period. 9. Triassic Corals.— Fossil remains of Corals are scarce in the Trias. The family Astrwide, so abundantly represented in all subsequent formations, now first makes its appearance. To this group most of the Triassic Corals have been referred. The Favositide are represented by the old genus Chetetes. It can scarcely be said that any genera of Corals are characteristic of this formation. Io, Jurassic Cora!s.— There are no Rugosa in Jurassic rocks, and Millepora, a recent genus, is the sole representa- tive of the Tabulata. The greater number of Jurassic Corals belong to the Aporosa, and cer- tain beds of this series have received the name of Coral-Rag from the great abundance of Astraide Which they contain. The genera Stylina and 246 ACTINOZOA. Montlivawltia are especially rich in species. appear for the first time. The following genera are exclusively Jurassic: 'TURBINOLIDZE. ASTREIDE .: Discocyathus. Placosphyllia. Thecocyathus, Angeastrea Ocurr Funct Euhelia Protoseris. A ID Comoseris Axosmilia. Porrrip Haplosmilia. Micro Phytogyra. peer. II. Cretaceous Corals.— The Corals of the Chalk are very numerous, belonging chiefly to the Aporosa and Perforata. Here also undoubted indications of Alcyonaria present themselves. The Tabulata are repre- sented by two genera. For the last time the order Rugosa makes its appearance, a single genus, Holocystis, being its representative. The families Madreporide, Pennatulide (?), and Gor- gonide (?) now first appear. The following genera are peculiar to this period : TURBINOLIDE. ASTRJEIDJE rachycyathu Ho Cyclocyathus. Acanthocenia Stylocyathus. Placocent Smilotrochus. Elasmocwnia. CULINIDÆ, Pentac Synhelia. erocami Baryhelia Leptop hyllia. ASTRJEIDE, Dactylosmilia. Placosmilia. Hymeiophyllia, ee Aspidcus. Parasmilia. Stellornisa. Peplosmilia. Meandrastrea. DID c " = zm = aux == ONES Gum a GEO ACTINOZOA 247 ASTRJEIDJE ? MADREPORIDZ, Dimorphastrea. Actinacis. Pleurocora. FAVOSITIDZE. FuxcrIDAE. Koninckia. Micrabacia. MILLEPORIDA, bacia. Polytremacis. Genabacia. STAURID ZA. Holocystis. 12. Tertiary Corals. — The Tertiary formations are abundantly sup- plied with Corals, chiefly belonging to the Apo- rosa and Perforata. The Tabulata are repre- sented by a single genus. There are distinct traces of Alcyonaria. The Sclerobasic Zoan- tharia now first present themselves. Here, too, appear for the first time the Dasmidc and Stylo- phoride, whose claim to the rank of distinct families is somewhat doubtful. The Dasmide do not survive the period. The following genera are restricted to the Tertiary deposits : TURBINOLIDZE. Haplocenia. Conocyathus. Circophyllia. Deltocyathus. Tichastrea. Leptocyathus Metastrea. Cmesus. Cryptangia Turbinolia? Cladangia atytrochus, Ceratotrochus. T'rochoseris Discotrochus. Cyathoseris. MADREPORID Dasmia Lobopsamnia. OcuLInip Stereopsamnia Diplohelia Dendracis Astrohelia. PontrrpzE STYLOPHORIDJE. Litharea. ræacis. MirrEPORIDZE, Cyclosmilia. PENNATULIDAE. Dendrosmilia. Graphularia, R4 248 ACTINOZOA. I3. Recent Actinozoa.— Except the Rugosa, Tubulosa and Thecide, all the orders and families of the sub-kingdom Coelenterata have living representatives. The names of the recent genera are too numerous to be here mentioned. Many of them have already been indicated in those parts of the work devoted to the study of their classification. The systematic form under which we have sought to exhibit the above selection of facts touching the general relations to time of the several groups of Corals must not lead the student forms does not really exist. The entire subject, like many others discussed in the preceding pages, still offers a wide and richly promising field for future inquiry. “ee O ee Nee 249 BIBLIOGRAPHY OF THE C(GLENTERATA. (1.) FREY und ei p — er zur Kenntniss Wirbelloser Thiere,' 1847. (pp. (2.) LEUCKART.—* Ueber die Mor phologie der Wirbellosen Thiere, 1848. ( 31.) (3.) LEyp1G.—* CARP der Histologie,’ 1857. (passim.) (4.) Carus, J. V.— Icones Zoótomicz, 1857. (Taf. IL—IV. (5.) GEGENBAUR. — * Grundzüge der as RNE Anatomie,” 18 plates, by his pupils); Lamarck, Ae Nat. des Minauk s. Vertebres (2nd ed. by Deshayes and Milne Edwards) ; E Bu LLE, Manuel d'Actinologie, 1834; JOHNSTON, History of British Zoóphytes, 1847, B. LOZNVA Memorie per servire alla storia de' Polipi marini, 1785; Bosc, Hist. Nat. des Vers, 1802; EsrEm, Die Pflanzen- Thiere, 1806; Parras, Elenchus Zoüphytorum, 1766, “Seige der Thierpflanzen, sete and the following, mg (7.) - HERR De quibusdam Animalibus marinis,’ 1761. (8.) Buscu.—* Beobachtungen über Anatomie und Entwickelung einiger p Seethiere,’ 1851. (9. DarvELL.— Rare and Remarkable Animals of Scotland,’ -8. 1847- (10.) Dette Curase.— Descrizione e Notomia degli Animali inver- tebrati della Sicilia citeriore osservati vivi negli anni 1822 (11.) Forges and Goopstr.—‘ On some remarkable Marine Inver- tebrata new to the British Seas, Trans. Roy. Soc. Edin. 1851 250 BIBLIOGRAPHY > ) FORSKAL.— oe Animalium, 1775. ————.—‘ Icones Rerum naturalium," 1776. o GossE.—* A Naturalist’s Rambles on the D hire Coast,’ VUdsl, 1053: (15.) LAURENT.— Zodphytologie’ (in Vaillant’s Voyage de la Bonite), 18 (16.) Lesson.— Condes Zoülogique, 1 (17.) Leuckart.— Ueber den Pelos a der Individuen, 1851 (18.) Mitis , O. F.—* Zoólogia pc 1788-1806, (19.) Quoy dt GAIMARD. — * Zoó > (in Voyage de lUranie, sous Freycinet), 1824. (20.) * Zoölogie’ (in Voyage de l'Astrolabe, sous Dumont d’ Urville , 1830- (21.) Sars.—‘ Beskrivelser og J Maripat &c.’ 1835. (22.) ——.—‘ Bidrag til Kundskaben om Middlehavets Littoral- Fauna,’ 1857. (23.) ——, Koren et Danretssen.— Fauna littoralis Norvegiæ, 184 6 and 18 (24.) STEENSTRUP. — ios the Alternation of Generations? (Eng. rans. by Busk), 1845. (25.) Strmpson.—‘ Synopsis of the Marine Invertebrata of Grand Manan’ (sep. and in Smith. ee ies History Review ’ (London, 1861 et seq.), cannot of this catalogue will from time to time appear. The Reports fur- nished each year by Leuckart to dies s Archiv. für Na- turgeschichte may also be consulted with advantage. Of the more select memoirs which. "Ps of particular groups of Coelenterata we have here attempted to subjoin the names: HYDROZOA. a. HYDRIDÆ. (26.) TREMBLEY. — * Mémoires dis seryit à Fbletoipo d'un genre de olypes d'eau douce, à bras i (27.) Hancock. —* Notes on a species of it Hy dra found i in the North- umberland Lakes,’ A. N. H. 1850. i OF THE CŒLENTERATA. 251 (28.) THOMSON, ALLEN. —‘On the Co-existence of Ovigerous and Spermatic ese - the same individuals of the Hydra viridis, Phil. Jou (29.) ECKER. — Zur Leh re von Bau und Leben der contractilen Sub- stanz der niedersten Thiere, Z. W. Z. 1849 (or Trans. by Busk S. 1854). (30.) JÄGER.— Ueber das spontane Zerfallen der Sü nebst einigen Bemerkungen über Generationswechsel,’ Vien. Sitz. 1860: and other memoirs cited in Bib. Zool, especially nd Rou ET The British species of ees are described by JoHNSTON cop: s. cit.), and Lewes, A. N. H. 1860. b. CoRYNIDZ AND SERTULARID. (31.) Loven.—‘ Beitrag zur Kenntniss der Gattungen Campanu- laria und Syncoryne,’ Wiegm. Arch. 1837. (Abstract in STEEN- STRUP) (24). (32.) BENEDEN, VAN.—* Mémoire sur les Campanulaires dela cóte d'Ostende, considérés sous le rapport physiologique, embryo- génique et pouce Bruss. Mém. 1843. (443) ————, — Recherches sur l'embry es ks iE et l'histoire oe des différents genres habitent la cóte d’Ostende,’ Bruss. Mém. 1844. (34-) E Max.—‘ Ueber die agiiiriflichen Geschlechtstheile panularia geniculata, Arch. Anat. 1850 (or Trans. in à 1 M. S. 1855). (35: Mummery.—‘ On the Development of Tubularia indivisa, J. M. S. 1 . J. M. S. 1855. (36.) Attman.—‘ On the Anatomy and Physiology of Cordylophora,’ Phil. Trans. 1853. ) .— On the Structure of the 2d peg Organs in certain Hydroid Polypes,’ R. S. E. Proc. 1857-8; and ‘ Ad- ditional Observations on the Mo E of the Reproduc- tive Organs in ich Hydroid Polypes,’ ibid. 1858. (38.) ———— .—* Notes on the Hydroid Zoophytes, A. N. H. 1859 et seq. Other memoirs on the reproductive organs and PE of these orders are those of DUJARDIN, Ann. S. N. 1843 and 45; D cH W. KROHN, Arch, nee 1843 and 53, Wiegm. Arch. 1851. Also, the 252 BIBLIOGRAPHY works of Sars (21), ae G3; STEENSTRUP Eb GEGENBAUR (47). N 1ograph of the es Corynide and Seriularidas ba as yet appeared. For Mose and figures of the British d see the works of DALYELL 9» GossE (14), and Linn. Trans. 1857; ELLIS, wards a Natural History of Corallines,’ 1755, and JOHNSTON (op. s. cit.); together with the papers of ALLMAN ; ALDER, . H. 1856 et seq. ; Hinoxs, A. N. H. 1 1851 et seq. ; STRET- HILL WRIGHT, Phil. Journ. 1857-8-9; and WYVILLE THomp- 8 UR Es TRUE (tae Soils pus. by Busx, B. Ass. Rep. 1850, in Q: J. M; S. passim, and in supplement to Vol. I. of Voyage of * Rattlesnake;? and Hincxs, A. N. H. 1861. c. CALYCOPHORIDE AND PHYSOPHORID&. (39.) Beast The P qus: Hy Ace a Description of the pl ved during the voyage of H MSs M " in the years 1846-50. With a General Introduction, 1859: and the writings of MILNE E hvson memoirs by GEGENBAUR, Nov. Act. 18 ; CLAvs, Z. We Z. 860; and KErERsTEIN und EHLERS pince in Wiegm. Arch. 1860), have since appeared. d. MEDUSIDÆ AND LUCERNARID E. (40.) Escuscnorrz.—-* System D Acalephen,’ 1829. (41.) EHRENBERG.— Die Aka ephen des rothen Meeres und der 836. rgani S (42.) WAGNER.— Ueber den Bau der r Pelagia noctiluca, und die Organisation der Medu usen,’ 1841. (43.) Lesson.— Acale hes,’ Nouvelles Suites à Buffon, 1 1843. (44.) FORBES.— A Monograph of the British Naked- -eyed Medusz,’ 1848. (45.) AGassrz.—'On the Naked- eyed Meduse of the Shores of Tous in their Perfect State of Development,’ Trans. ai ca (46.) Hos UXLEY.—' On the Anatomy and Affinities of the ui of the Medusze Phil. : ans. 1849. OF THE C(GLENTERATA. 253 (47) GEGENBAUR.—'Zur Lehre vom Generationswechsel und der (4$) — (49. Fortpflanzung bei Medusen und Polypen,’ 1 ——— —-.— Versuch eines Systemes der Medusen, mit comu neuer oder wenig gekannter Formen, Z. W. Z 1057 ) M‘Crapy.— Gymnophthalmata of Charleston Harbor,’ Ell. Soc. Proc. 1857: and the systematic papers of PERON et LESUEUR, Ann. d. Mus. 1809-10; BRANDT, Petersb. Mem. 1833 and 38; d : E e Z. W. Z. 1858; Eysennarpt (Rhizostoma) N ct. 1821; and Trtesius (Cassiopeia), Nov. Act. On Structure of Marginal Bodies see especially GEGENBAUR, Arch, Anat. 1856 (or English abstract in Q. J. M. S. 1 On Minute Structure of Medusidæ and Lucernaridæ, vid. BUSK, Mic. Trans. 1852; SCHULTZE, Arch. Anat. 1856; and Hux- LEY (46 (46). On pee of Charybdeidæ: MirxE Epwarps (Charybdea), n. S. N. 1833; and Frirz MÜLLER (Tamoya), Halle Abh. a On Bp of Meduside:; J. MÜLLER (JEginopsis), Arch. Anat. 1851; GEGENBAUR (Cunina and Trachynema), (47); Fritz MÜLLER (Liriope), Wiegm. Arch. 1859; M‘Crapy Bn Ell. Soc. Proc. 1856; and CLAPAREDE, Z. W. Z. ^N ssi of Lucernaride: Sars (21), Isis, 1833, and Wiegm. Arch. 1837-41 and 1857; SIEBOLD, Beitrage zur Naturgeschichte der Wirbellosen Thiere, 1839; STEENSTRUP 24); DALYELL (9); DEsoR, Ann. S.N. 1849; and REID, GEGENBAUR (Cassiopeia), (47); FRANTZiUS (Cephea), W and Kroun (Pelagia), Arch. Anat. 1855 (or English abstract in A. N. H. 1856). 254 BIBLIOGRAPHY The viduas pn of pipers (and ioe are opes by FoRBES (44), and Zoül. Proc. 1851; FonBEs and Goo SIR (y Gosse npe GREENE, Nat. Hist, Rev. 1857-8; CosBoLp, Q.J. M.S. 1858; PATTERSON, D.U. Z.B. À, 1859; and STrRETHILL Wrieut, Phil. Journ. 1859. The s. cit. and A. N. H. 1860. Brief descriptions, without d of the pelagic Lucernaride are given by FORBES (44), b most of the species are figured in the other works dm above, ACTINOZOA. a. ZOANTHARIA, (50.) [AR deca — Essay towards elucidating the history of the Sea-Ane ' Phil. Trans. 1773. * A second essay on the natural TR of the Sea-Anemones,’ ibid. 1775, and a third essay in ditto, 1777 (51.) ELLIS and Sor e — b Natural History of many curious and uncommon Zoiphytes,’ 1786. (52.) Rapp. Ueber die Palypeci im Allgemeinen und die Actinien 29; (53.) EnRENBERG.—' Beit rage zur physiologischen Kenntniss der orallenthiere im Allgemeinen, und besonders des rothen i pret 5 “ Synopsis ” of the Report itself has since appear (56.) EDWARDs et Harme.— ‘Recherches sur les Polypian Ann, S. N. 1848— —52. (57-) —— ——— — Histoire Naturelle des Coralliaires ou Polypes proprement dits, 1857—60. (58.) HorrAnp.—- Mono ographie anatomique du genre Actinia de inné, considéré comme type du groupe général des Polypes Zoanthaires, Ann. S. N. 1851. ———————— P ÓOÓÉÓÉÁ— | | | © 2 OF THE CGLENTERATA. 255 (59.) HAIME.—' Mémoire sur le Cérianthe,’ Ann. S. N. 1 1854. (60.) GossE.—* Actinologia Britannica: A History of the British 1860, See also various memoirs by Mirx E EDWARDS, HorrARp, and GossE, cited in Bib. Zoól, in addition to don of Sprx KOLLIKER ; LEWES, * sty th Studies ;? LACAZE pu Taine. ; RaTHKE; ERDL; and oth On the strsture of aliua see especially Aged (58); Gosse (60); Harmer, C. rend. 1854; Frey und LEUCKART (1); TEALE, Trans. Leeds Soc. 1837, and B. ye Rep. 1858; and ConBBorp, A. N. H. On the Sclerobasic cp Ded vid. BRANDT, Symbolæ ad ga Hyalochetides spectantes, 1859;" and Scnurrzz, C. B DANA (55) describes the polypes of Antipathes. (57) is plet 1 of the orders Zoantharia, Alcy- onaria, us Rugosa, For collections of figures n Works d Esper, ELLIS, DANA, and the French voyagers m consulted. The British Zoantharia are ‘described and figured by Gosse (60). On Coral reefs and islands see peus ‘The Structure and Distribution of Coral Reefs,’ 1842 (now forming part of the same author's “Geological Observations”); and Dana, ‘On Coral Reefs and Islands, 1853. b, ALCYONARIA. (61.) Rapp.—‘ Untersuchungen über den Bau einiger Poly pen des Mittelandischen Meeres,’ Nov. Act. 182 (62.) EpwARDs, MILNE.— Mémoire sur un nouveau genre de la famille des Alcyoniens,’ and ‘Observations sur les Alcyons proprement dits, in Recherches sur les Polypes, 1838, or Ann. S. N. 18 (63.) Ans — *On the Structure of the Halcyonoid Polypes, Am. s. Rep. 1850. Also: MinxE Epwanps, in Règne Ani- JOHNSTON, op. s. cit., describes and figures the British Aleyo- naria, c. Rucosa and Fossrn CORALS. (64.) Epwarps et HAIME.—'A Monograph of the British Fossil Corals’ (published by the Paleontographical Society), 1850 =o 256 BIBLIOGRAPHY OF THE C(ELENTERATA. (65) Epwarps et HArwE.—' Monographie des Polypiers Fossiles d. Mus. 1851 des Terrains peers Arch. 51. And many other paleontological works, d of which are E (57). (66.) quoted by dida et Hamm d. CTENOPHORA. MERTENS.—' ethane tiber die Beroéartigen Acale- phen,’ Petersb. Mem. (67.) Epwarps, MILNE. — Olevia sur divers Acaléphes,’ Ann. S.N. 1841. (68.) (69.) WILL.— de (70.) — Note sur l'appareil Gastrovasculaire de quelques mem Cténophores, Ann. ss N. 1857: ‘Hore Tergestine, oder Beschreibung und Anatomie er im Herbste 1843, bei Triest pobici pea 1044. AGASSIZ.—. On the Beroid. Meduse of the Shores of Massa- chusetts, in their Perfect State of Development,’ Amer. Acad Trans. eda ontributions to the Natural History of the United TS ‘of America,—Part II. of Second Monograph, 8 1860. (72.) GEGENBAUR.—‘ Studien über eer he: Systematik r 856 +The dr Arch. 1856: and the papers o Grant, Z. Trans. 1833; Karas Z. W. Z. 1853; LESSON, S. N. SiN. ite hi of M‘Crapy, (Beroe and Bolina), Ell. Soc, Proc. 1859; PRICE (Pleurobrachia), B. Ass. Rep. 1846; — (Eucharis), Z. W. 1858; and STRETHILL GHT nike ctae. eg nett 1856. The British s Cre are described by FORBES and GoopsiR, B. Ass , 1840-1; and cristina R. I. A. Trans. 1839-40. abbreviations above used to indicate the titles of periodi- cal journal are dune i in the Dibliography of * Natural History Review,’ 1861. 257 QUESTIONS ON THE C(ELENTERATA. 1. By p. D. features are Ccelenterata separated from other ary divisions of the animal kingdom ? 2 m the two mibi kingdoms, Protozoa and Ceelenterata. 3. Describe the typical structure of a thread-cell. Compare the classes, Hydrozoa and Actinozoa. 5. Describe the structure of Hydra. How does the * polypite of his genus differ from that of the non-budding forms of the Corynide ? 6. Define the terms, a. *hydrotheca? 7. In what order of Hydrozoa do ‘nematophores’ occur? Describe the structure and position of these appendages. 8. E the structure of a ‘nectocalyx.’ How does this organ om an ‘umbrella’? 9. Dine the structure and relations of the ipee in Diphyes, and state how the same parts are modified raya. Io. In what Physophoride are nectocalyces absen 11. Briefly describe the modifications of the coenosarc, and relative attachment of its appendages, in the following genera of Physophoridze a. Physophora b. E hanni c. Apolemia; d. Athorybia; e. Velella. S 258 QUESTIONS ON THE C(ELENTERATA. 12. Compare the structure of the tentacles in ysalia; b. For skalia; ; olem Apo 13. What is ae d E the idet in the following genera of Hydro a. Tubularia; b. Hydractinia; 14. Describe a pneumatocyst’ of any of the Physophoride, and the ix cipal METUO wt it presents among other ene of the same order. I5. Describes as to structure and posi a. the marginal * zu a Geryonia ; . the ‘lithocyst’ of a free Lucernari 16. How are NP gonophores’ situated in is tallow genera of Corynidæ : 5 Vatella ; d. Cordylophora? 17. Compare the structural relations of the reproductive organs in urelia ; . Rhizostoma. 18. W Ki are EN ? Explain the WC. which structures present among the Sertular 19. In = pram of Lucernaridæ do free p zoöids occur ? ace the development of any of s ese forms. 20. Describe the CEP ey of a medusiform gonophore . Give some account of the early stages of tordopnat i in Cordylophora Pac stri MD ur Lov . Cunina octonaria. 22. What me seems to Res successive development of the endages vam Bs Phy sophoridae? 29: Define-the order. a. Sertularide ; b. Calycophoride ; c. Lucernaride. QUESTIONS ON THE C(ELENTERATA. 259 24. What genera of Coelenterata are known to inhabit fresh water? 25. Give some account of the geographical distribution of the Sertu- laridee. 26. Describe the minute structure of the body-wall in Actinia. 27. What law appears to determine the number of parts among the several orders of Actinozoa? 28. What is the number and structure of the tentacles in the Alcyonaria? 29. Describe the structure s a typical ‘corallite.’ 30. Define the o 31. Explain the Lancia. of the gyrate corallum of ee hc 32. How does a * sclerobasis ’ differ from a true corallum 33. Compare the nutrient system a. Actinia and a cond 6. Pleurobrachia and Beroe 34. Describe the structural relations of the tentacles in a. Actinia; b. Cestum ; c. Pleurobrachia. 35. What cite distinguish the thread-cells of the Cteno- pho 36. iom. the structure and position of the * ctenocyst.’ 37. Give some account of the nervous system of the Ctenophora. 38. What peculiarity of position distinguishes the NEXT organs of Tubipora? 39. dei wed = position of the male and female organs in e Cte 40. E. rra a Haime, is the number and succession of the tentacles in the common Sea-anemone ? 4I. E Some account of the E ka of the canal system in roe. 42. Wha numerical law viue the development of the * septa’ in oantharian cora 43. ae three ina modes of gemmation among the co- alligenous Actin 44. od the PA of a Fringing-r 45. How has Mr. Darwin explained the ne nature of Barrier-reefs and bs lls? 260 QUESTIONS ON THE C(ELENTERATA. 46. Define the characters of the family Beroidz, with reference to the subjoined categories i. mou c. canal system ; d. tentacles a. form of body ; ti; 47. Give some account of the distribution, bathymetrical and geo- phical, of the reef-building Corals 43. What families of Zoantharia seem wholly ex 49. In what deposits does the family of eae p make its ap- pearance? 50. Name those groups of Corals which are most abundantly repre- sented in the Paleozoic series. 261 LIST OF ILLUSTRATIONS. 1, Urticating organs of Celenterata, after Gosse Development of Celenterata . Morphology of pes after MINCE J Johnston, and ‘Allen omson. ; . Morphology of dro Morphology of co MN ifti its Reproductive processes of Hydrozoa, is Gog Oceanic forms of Lucernaride, after E Development of rors, after yw Development of T after Mummery . Development of Campanularia, after Lov : - Development of Physalia, after Huxley 12, Development of Lizzia, after Claparede 13. Development of Turris, after Gosse 14, Gemmation of Medusoids, after Forbes and the Auer 15. Development of Chrysaora, after Dal 16. E uo E Tubulariade, after Alder, PRSE a Stret- ill Wri 2p SP om ans LU -] T i 17. Various i of dcs, fier Sider. Toros sihi Sars 18, ape E oe” after Alder, Dalyell, Forbes, Johns 19, eem 5 E eurais ate Alder a Bus : 20. Morphology of Calycophoride, after Kéllike 21. Morphology of Velella, after Kölliker 22. Morphology of aa after Kölliker dus 23. Morphology of Me arious forms of Eu : . 25. Lucernaria, after Johnston . ? : : : : s 3 262 LIST OF ILLUSTRATIONS, . Morphology of Actinozoa, after Gosse and Holla Morphology of Pleurobrachia, altered from n am Huxle ey; . Morphology of Zoanthari ia Selerodermatas after ‘Huse nklinii . Development of Pleurobrachia aftór Strethill Wright . Turbinaria palifera, after Dan . Dendrophyllia nigrescens, afte xr na . Zoantharia Malacodermata, after Couch, Fates and Gis - Zoantharia Sclerobasica, after Dana 36. Zoantharia Geb nadeemuta: after Milne Tavani aaa Hale me o3 N : reer and d e after A RO Milne Edwards and Hai . : : k : Zaph rentis ‘cylindric 39. Marais forms of nx after De Blainville Gegen- r, Lesson, Patterson, and the Auth 263 INDEX. Abyia, 98, 99, Y Acaléphes Ei 14. Acaléphes Hydrostatiques, 114, canthoceenta, 246. B oaths 240. Acaulis, 87, 88, 89. "one ia, 158, 244. m ER I20. era OCyst, 95. M inae cis, 247. m om 346, 166, 172, 199, 235. Actin A me, 143. Actinozoa, type of, 131; general cha- racters of, 19, z to Dor p en 1705 pua ssification of, 196; dis bution of, 231; relations of, to tim 236. Adamsia, 150, 198. ae 239. 4Egina, 116. Es gaim 2, 2, 108, IIO, TIT, 112. Agamogenesis, 74. Air-vesicle, of Physophor — IOI. Alcyonaria, general characters of, 139, o£ 208 ; nutritive cav he of, 141 ; tentacles of, 148; thread-cells of, 151; corallum of, 154, 159, 162 ; de- velopment of, 170; families of, 213; 231, 233 ; relations of, to time, 237, 2 Alcyonide, 213.5 corallum of, 160, 162, Aleyont nium, 161, 208, 232, 235. Alimentary canal, of Ceelenterata, 3, 29, I41. Alternate generation, 76. meas S, 238. ES condition of Hydra, 11, 52. d dle , 238. Anabacia, 247. Androphore, 45. el- dnisophalvo, 244- An D LM een development Bes 72. Antipathes, 201 Antipathide, 206. aps rtures, of somatic cavity in Acti- NOZOQ, 142. Apical area, of Ctenophora, 143, 145, A canals, 145. Apical pores, 142, 145. olemia, 102, I p acie miade, 113 Aporosa, 158, i 162, 203, 206, 237, 42. Appendages, of Hydrozoa, 27, 69; o ue miphora, 152; of Cierra, actor, 163, 199. 47. €, ZAI. tr@ide, 20 Ur e RS "COS 5 E stroceenia, 239. str $i 1 207 232, 237 245—7» str@opora, 241. strohelia, 247. thorybia, 107, 1 shes IIO, 112. thorybiade RE: d 94, 2. ue. 204, 2 kA 237, 244, 245. a, 47, EE La 127, 128. opora, A xosmilia, 246. 4 E A A Atoll I 4 » Au A AX A 264 Balanophyllia, 241. Barrier- id P og Baryhelia Bari Barysmi 3. al membrane, of Adamsia, 150, 198. se, of Actinia and its allies, 131, 8. hycyathus, 240. Batt ymetrical distribution, of Hy- droxoa, 126 ; of Actinozoa, 231. Batter sb; yia, 244. Beaumoniia, 238. poat tactile Mr of, 168 ; develop- ent of, 180 of, 216; adim of, 28 canals 73 220- I. Ber oide, form of body in, 216; lappets of, 218 ; apical filaments of, wd cana, system of, 220— ; defin itior » 231. NR 7a, 85, 87, 88. Blastoderm, s Blastotrochus O2. Body-layers, of Celenterata, 3, 10, ree substance, of Protoxoa, 7; of Coelenterata, 10. Soy in of Hydroxoa, 25; of 4c- tinoxoa, 136, 149. ena, ports lopment of, 179; size of, 2 16; lob bes and earlets ipie print » 220—3 ; y; tacles of, 227 ; phos- phoresc cence of. 230. id ite dud 6. Bra AIS 246. Brachyphy yllia, "240. rain MINE Coral, 187. Briareur 232 Calamophyllia, 239. Calice, 155. alicular EUM OR of Actinozoa, oride, p eral characters of, gane velopment of, 57; soma t x yst oh 96; ceenosarc of, 98 ; nec- alyces of, 98 ; polypites of, 29 3 Hp Pa He 32—4; hy "e phyllja of, 993 gonophores. e ds s of, Tour erem : Calymmide, 4 Campanula id, 4 47, 57, 90 —5, 126. Companular adc, 94, 95. Campanulina am Cekap; 238. Canal syst of Medus idæ and Lu- cer nae. 48, II 15, I121—4; of Cte- nophora, 144—7, 219—24. Capnea, 199. INDEX. Carboniferous Corals, 244. Carduella, 121. stidee estum, ee and size of, 216; canals of, 223 ; tentacles of, > ale secretive orga n of, 147; ee orescence of, 2355 distribution o gr Chaiabered e nidæ, ho Char Chishea Tego. of, 149; development 180 ; canals of, 220—3; tentacles Cona axis Chonophyitus N, 244. Chonostegites, 244. CMM jd 64, 123, 125, 127. Cilia, of Celenterata, 35 ot Cteno. Mus 165. AE esl ot A its alli haa po 241, 245. VH 3^33? x Ci rcophyllia, 247. Circulation, in Celenterata, 6, sh 142, I Cladangia, 24:7. Cladocora, eee 5 Cladophyllia ; Ta of Sertu zo D @, 1 S s pa o s, ae of ir aee 230, 6, 82, 86, E, ara, 41, 46, 82, Clavatella, 87, 88, 89. listophyllu 8 ynide, Geine eia general characters of, 3, 6,13, 19; classes of, 14, I9; thread- ceils of, 5 iy uute struc ture of, 10 ; developm of, 14— 244. seii Coenosarc, an P ‘orynide, 82—3; Se —— ride, 9o; ot Cal a nes 98; of Physophoridee 1 zb 07; of _ Acti INOZOA, 139, 157, 2 fi eec 155. yeas of Hor 7a, 198, 199. Columnaria, Combophylium, 2 244- Combs, of Ctenophora, 165. INDEX. e moseris, 246. Conocyathus, 247. [gesund id, 244. ntinuous development, 73: rsio n, chemical, of tissues, 9. 3: commerce, 234. Pa reefs, E —$. 140, 153. oral, I5 Coral of a Corallite. i. Cor allium, pores of, 142; corallum of, 4 154, Corallum, structure of, mri de- velopment of, 173—8, 185— 903 of Zoantharia, 201—5 ; of Alcyonaria, 159, ; of Ru gosa, 214. bula, 0 Cya se agi 184, 215, 238. Cyathoseris, 247. smilia, 247. Cydi ppe i I iam Cypha Custodie, pr 237, 244- Cystiphyllum, 215, 238. ps ape 246. Don ps Dasmtdce. 207, 237, 247 Dasyphyili, 240. or 5. Cordylophora, gonophores x no. $8; deve opment OR SAs pod of, $2; tentacles of, 86; distribution of, 126, 127. Cornularia, 160, 209. Coronets, 5 Corynactis, 2. Coryne, E ohoros of, 41, 88, 89; tentacles of, 86; distribution of, 126. Corynia ae, 8 Corynid E. CR al characters of, 79, E; tenta cles OG 2h esa p sarc of, 82; polypary of, 35, 85; polypites of, 22 85 5 : LS CM of 88, development of, ES familles ot, /89; distribution of, 126, m eda, De Cretaceous Oris: 246. = m ry f, Of, 139, 142, es. 216; fin E d size of, 140, 216— 9; cen system a 144 44, 219 ; tentacles of, ta organs of, 225; teg 149, 152; lend -tclla of, 151 ; cte- id res of, 164; nervous ot a [ uctive organs of, 1 neit of, 60, 61; pouches of ; 116. Dekai 244. Deltocyathus, 247. Dendracis, 247., Dendrophyllia, ^d 121. Dona. chemical, in tissues, 9 Dermos clerites, 160. De. Ooko Uar 2 240. Development, of animals, 14, 18, 70; of b iege p 17, u$; a Hy- ay » 5I Ide, varia and b auo. 170, 85; of € (Sis p 178. S, 244» Devonian eute Ae Dicoryne, 88. 74 Digestive sac, of Actinozoa, 132, 141, 144, 22 Dimorphastr a, 247. Diphyd Dd. ; e , 128. SO se Diploria Dise, gelatinous, of Meduside and Lucernaride, 34; of Actinia and its allies, 131, 198. Discocyathus, 246. : Pp » 73+ oo I oohug; 7 Dissepim 155. Distal NAR of NE ZB of polypite, 29. Distal nectocalyx, of Diphyes and 8. Distribution; of Celenterata, 13; of , 126 ; of Actinoxoa, 231. Hydroxoa 266 Earlets, of Ctenophora, 218. Ecderon, 1 Echinopor ide, 207, 237. Ecmesus, 2. écthoreum, Ectoderm, 3, 10, 17. Edwardsia, 162, 199 ceris ta, 246. Embryo, of Hydrozoa, 51 ; of Actino- z 170, Emmonsia, 238. nalloheelia, 239 Enderon, 1 Endo End Ephyra, Epithec Epithe ial He er, of disc in Meduside and Lucernaride, 35; of body-wall in Actinozoa, 136 Eridophyllum, 238 ucopide, 120. Euden ium, 83, 87—9 Euhelia, 246. Tienie 148, 200. oe phy li a, 240. 03, 241. hea, 218, 220, 223, 2277, 228. UM a, 239. Eu NONE: 218, 231. ec 156. Eye- -specks, 38, 166. Families, of kid tyve 89; of Sertu- laride, 95 ; of Cal sita +A, 100 ; B Physiploride, i ud Meduside, of Lucernaride, ; of Zoa Weeks, 205 "of jaar hc ot nay ne NEC of Ctenophora, 230. Fan-Cor 186. tea A n. avo Fa Mis cs 237, 244, 245. Fecundation, in Hydrozoa, 50 ; in Ac- tinoxoa, 17 Feelers, of Phy Pops "d 40. Fibrillat ft Filament, o f ten ter in \ Hydrozoa, 335 Firm part, “of Velella, 1 Fission, d of Hydra Uu 2; of Medu- soids, 63; of Simands salem: 63; of Hydra-tuba, 66; of Act tinoxoa, 182, 185. Fistulipora, Fletscheria 244. Float, of Physophor td@, 27, 10%. Foot secretion, 153. Form of Do dy, 1 Coelenterata, 6 ; Hydrog RS ard in Actinozoa, ba 208, A Formles Heys Fo We ui 102, d nr Fossil Corals, 236. INDEX. Fossil forms, of Hydroxoa, 130; of ctinoxoa, 236—47. Fresh-water forms of Ccelenterata, 13, Fringing- NN I91—4. A éd, I Fungide, 203, 207, 232, 237, 244, 246, 247. Funnel, of Ctenophora, 144, 220. Gala 240. dudo S, 75. Gan mets a, of Actinia, 1663; of Cteno- ph hora, 167. Garveia, 88. Gastric filaments, of Lucernaride, Gastric reion; of polypit e, 29. G of Celenterata, 6; of Hydr an ih 54, 57, 63, 65, 69; of Acti oa , 182— 9o. Genabac 247- Genera hae of ydo 17, 293 of Actinozoa, 17, 1 General morphology, of peus p 1, 6, 10; of Hydrozoa, 25 ; of Act oer distribution, of Hydro- a, 127; of Actinoxoa, 233. Germinal ‘dot Germinal vesicle, 15. Ger Seat , marginal vesicle of, 38. Ger Bais Gla ies er sacs, ‘of Velella, 106. poe ce cnida, 150. Gon vy 240 nio saat jl elg 244. emat. 45; of Corynide, 46, 8; Ere 46, 94; of Phy- sophori Gonocalyx E aa Gor photon vues "e eres f, 40—5 ; » 45—73 of Co orynide, am 44, 88 ; t$ pu os 44, 46, ot Calycophor en 45, 99; of Lh Mee horidæ, 45, 1 Aa, vie Gorgonia, 161, 2 232, 235. Gorg onda general characters of, 163, 210, 214; somatic cavity of, 1413 sclerobasis ‘of 154, 162 ; Richie ee 161; development of, 185 dist 232; T to tion of, 2 relations o "s 237,240. phulari Graptolites, 130. Gymnophthalmata, 120. Gynophore, 45. Hadr. MN 244. Hai aimeia Halec a petia 7a, 93. Halistemma, 103, 108, 111, 112. d T 45, 98, 99. History, of Hydrozoa, 130; of Ac » nozo 2 Rugosa, 243; of Alcyonaria, 243. Hoemal region, 17. 'ydnophora, 240. Hy pe morphology and physiolog: y .20—5; development of, 51; boid condition of, 11, 52; species cipes 82; distribution of, 126, 1 b. Cœ- nosarc of, Ag pos ryo De gono ida! 1 25. Boden, of Sertularide, 27, 70, Hydrozoa , type of, 20; general. cha 19, 20 me D» E Aon of, 795 Den dt ! of, 126,; relations of, to time, 130. Hymenophyll. ia, 246. Ilyanthus ES Indefinite gem 184. Jndividuality, of eat: Se Involucrum E rregular gemmation, 184. Isastrea, 239. Isis, 154, 210, 240, 241. Jelly-fishes, 13, 127. Jurassic Corals, 245. Koninckia, 247. Ko Eln, 212. 1 — 244. Lagoon, 192. Lamellár corallum, 187. Lappets, of Beroide, 218. : T, E Jayers, of Caelenterata, 3, 10. eptocyathus, 247 eptophyllia 46. Leptoria, s eSueuria, canals of, 222, 223; tenta- cles of, 228. Lew cothea, t tentacles of, 228. Life, duration of, in EI eed 182. Life- "history, of Hydr rozoa, 51; of Ac- TH dX. of "de lla, 104. Lineolaria, gonophores of, 128. Liriope, II5. Li ra aen 247. Lithocysts, of ‘Lucernar ide, 38, 124. ci de ba DE 240. rem strotion, 238. Liver, of Hydroxoa, 31, 106; of Acti- nozoa 137, 147. Liz RVI, development of, 60, 63 Lobopsamnia, 2 gans, of Hydroxoa, 36; of Actinozoa, 164. 155. s 3 45 ca : of, 48, 124; gastric Brewer of, 1245 EM NOUS rice s of. di develop- ent of, 64, ; familie of; 1255 distribution ET 127,1 128. Lucernaroids, 123. Lyellia, 244. Madrepora, 241. Madreporide, 203, 207, 232—4, 237, Malacodermata, 201, 205, 237. Man m, 43. Mea biis, of Meduside, 37 ; of Lucernaride, 38,124; of Actinia, Massive corallum, 187. Meconidia, of Campanulari. ia Lovent, S. eu. general characters of, 80, Annie alyx of, 36, organs of, 118; lopment of, 60, 2 ilies of, 119; distribution v dune horescence of m gonophores, Me 43; 45, 62, 118. 268 Melitea. 154, 2 Membrana incermedia, 16. lum, 245. Merulinide, 2 08, 237. Mesenteries, of Actinoxoa, 132—4, 137, tlc a, 247. cropyle, of animal ovum, 71. Micros olen, 246. Millepor 239. pe ae ide, 205, 206, 237, 244, 2476 Meandras S iuri ina, 142 s 187. > 203,232, 239. Monee "2 us forms, of Hydroxoa, 50, 69, 209. Mop 54 210. Mouth, È Hydrozoa, 29, 86, 88; of A a, 131,141; of Ctenophora, 21 Move s, of Hydroxoa, 23, 27, 36; ye Pd 138, 162, 210; of Cte- nophora, 229. Mucous tayor: id blastoderm, 16. Mul 16. uet of Hydrozoa, 36; of etin NOZOA, 162. Mycetophyllia, 240. Mau 82, 87. . Nectocalyces, 27, 36, 70; phoride, am xh 7; of Me Sees 1e ge f Calyco e) fios ide, > 30. es, of Sertularide, 34, 93. gy m 84. Nerv stem, of Medu. usidæ, 39 ; of ctinia, 1 d 2 of Ctenophora, 167. egion, 17. Nutritive organs, of Hydrozoa, 28 ; of Actinoxoa, 141. Ocana turrita, marginal bodies of, ulin na, 240. Oculinidae, 203, 207, 237, 246, 247. c Old dhamis 130 Omphyma, 244. Opremo, of Campanularia fasti- iata, 92. Oral canals, of UM à, 220. Order, of septa Orders, i Run atis, 79; of Actino- INDEX. "39. T aye, E blastoderm, 16. of dep o ; of Hydrozoa, zoa, 1 Ovigerous vesicles, of Sertularide, 47. Pachygyra, 239. Pachyp oyun. 244» Pali, 1 alythoa, 141. Paracyathus, 240. Paragastric ‘canals, of Ctenophora, 145, 220. Parasitic forms, of po 61,83; Actinozoa, "198, 2 Poa a, 246. Parietal Madden io of Actinoxoa, 183. Part FOROR 74 ; theory of, 78. avonaria, 2 Peachia, 142, Mo edicle, of ten idee d in Hydrozoa, 33. Peduncle, of polypite, 29, 31. Pelagia, structure of, 40, 123; de- VU ONE of, 68; phosphorescence f, 12 Pelagi 2 Pennari a, 87 me Pennans, 212— Pennatulide, um 18. 210—3, 214, 235, , PLANTE so P POS ji Perfora um p 203, 206, 237, 242. Perigonimus OD. Periplas Pontem space, 132, 198. Permian Cora 245. Pha i : Phillipsastrea, 238. Philomedusa, 142 , 233- hosphorescence, of oed Js pa Hun xod, 128 ; s natulide, : es poca "d dw pe Phy ogemmaria, of Velelia, 105. Physalia, thread-cells of, EL villi of, a5 tenta spe 91,32, 33, ITI; dev velop- nt of, 5 preumatophore of, 1073 onophores of, YII, Tig disteibation of, 127. Us AW dc, 11 Physical elements, relations to, Hydrozo oa, 126; Physop O2. D Phy iphoto d Pbhysophoride, benal characters of, of of = d nox0d, 231. INDEX. 269 80, 101; development of, 57; pneu- | Prot s, 246. matoph IOI, : éceorare Bode 243. of, 107 ; nectocalyces of, 107 ; hy Protozoa, their minute structure phyllia of, 108 ; pol aay of, 29, ied compared ii Meu f Celenter ata, hydrocy O, GA «d : do evelopment of, 14, 18. 32—4, III ; gonophore of, 47, 1 Protozoüids, "a families of, 1125 distribution of Proximal extremity, of hydrosoma, , 128. 255 of eic ne Phylosyra a, 246. HRosonoRius core masses, of Hydroxoa, 36,38; | Pterygia, 1 e Act (à. 152. Da M Man Pla enia, 246. Pylo rx ve, of *Caiycophoride, 29. Placosmilia, 246. Pyrgia Ficophylis 246. n of structure, of Celenterata, 3, ew anal system, of Ctenophora, a ; of Hydrog es i 19, 25 ; of Ac- tinoxoa, 17, R ca satin e lanula, 6. Regular gem 184. Platytrochus, 247. egg enlargements of tentacle Plerastrea, 239 a 335 æa Ple urobrachia, S PEE and structure of, 216 zs thread-cells of, m of, 168 ; tactile development of, 235. Pieuratractiade, 230, Pleu nA » 44, 50, 93, 94- T Se Pieta and 2, 106. Pneum cien 5 "of Physophoride, 101; of Velelia, 105. Pneumatophore, of Physophoride, IOI, 107. Podactinaria, 120. Podocoryne, 88, 112. Polycolia, 245. par, of ^an and Sertula- 35, $5, 92. Riles, 13 of Zoantharia, 197; of Alcyona d / 4, 208. d Polypite, 25, 29 ; lydrid@, 20, 823 ory, 5.951 a ce d. 92; of Calycophor 29, 99 ; of Piysophoride, sable 3 p Meduside, TE of Lucernaride, 47, 65, 121, a Mr Porites, 232, Poritide, 204, a 244. 246, 247. Porpita, 32, 45, 102, As rail Pouches, of Aiginide, 116, 1 Praya, 98, 99: Prayide Prehensile or > organs, of Hydrozoa, 32; of Actin Th po. Protoplasi, animal, ve Renilla: 212. Reparative power 55 ; of Actinozoa, 1 Reproductive or fidus gt Hydroxoa, 40; of 4 caper da T Ies ; of Hy- dride, 23; ide, 88; s, of Be th pt 52, [s] = rid ks 118; of L æ Zoantharia ane opm se aria, Des 209; of Ctenophora, 240. Rhizophysa, 101—2, 107, 110—1. Rhixophysiad@, 114. Rhizostoma, 49, 67. "ia, 244. "ils corallum 01,7159, 17230 214. families $A ide relations of, to time, 237, 2. Sac 199, 2 eleg of gaa in Hydrozoa, 33. f Gorgoni mide, 161. Selerobasie corallum, 153; men 85. Sclerobasie Zoantharia, 154, 162, 201, develop- Seleroderiie corallum, 155, 173; 186. Scler mic Zoantharia, 158, 161, 173, 234. 237+ Se litori 66. Sea-Anemones, 131 162, 198. Sea-Fir , 90 270 Sea-Pens, 1635 212; Sea-Shrubs, 154. Secretive organ, of Cestum, 147. Segmentation, of ovum, 15. Sense-organs, of Hy Ac inaro, 166, 16 Septa, 155; dev elopment of, 173. So al formulæ, 174- Seri atoporide, 205, 206, 232, 237, 244, n us la ayer, of blastoderm, 16. 127: ertu Ser Ser pho 74455035 veu ak pene B lisributian n 126— Siluri: an Cor 43. Size Cele nt ae 6; of Hydrozoa, 28 ; of Actin pin 140. ^ wv = ~ Se EI SE c ES E z an s d a, 241. So matic e cavity or Ceelenterata, 3; 10, of Hydr > 17, 29. 31 ; of Ac- ees i7; ed ; pras Somatic c chambers, of Actinoxoa, 134, 140. Soma uid, 6. Ceu of Fat ok dlp 96. Spermaria, o Dm a, 40, 50; of Actinoxoa, 1 Spermatozoa, i5: of Hydroxoa, 50; of Actinozoa, 169. d ane corallum 160, 162, 209. 2 picul m Spi pi A yonidæand Zoanthidz, 160; gonide, 161. al Ba ben 150, 151. " Spongophyllum. Sporosac, 40, 45. » 205 Stauria 1, 214, 2. Stauride, 215, As: 244. 245. etie maa EN gs of, 87; gono- es 8,8 Sci u hi ^ Steganophthalmata, 120. Stelloria, 246. d tenostomata, 219, 230. Stephanoceenia, 239. Stephanomia, 108, IIO, 112. ephanomiade, 11 Stephanophyllia, 240, ereopsamnia, 247. Stinging powers, of Caclenterata, 5. Stomach, of Actino OZUQ, 132, 141, 144 Of Lucernaride , 124 INDEX. Stomatodendra, of Rhixostomide, pi eae chi ium, fission of, 63. tabla ISI. 49. of m in Ac Besse of septa in cora 173 Pe lr bh bells, of Hydroxo wie 36; of Calycophoride, 96 LY s0~ phoride, ert of LABEL. —6. ium hyllia, Synapticulz, p 203. Synde vires. of Rhixostomide, 49. Synhee 246. S PPAR 238. Syringopora, 238. Tabulata, "i 161, 205, 237, 242. Tabula, 1 actile itd las of Hydroxoa, 40; of nd s 168. a, A Tad nidae, 150, X51. Tegumentary organs, of Hydrozoa, ; of Actinozoa, 149. Télestho, 159, 2d 9. Tentacles, xoa, 325 tin ok Ctenophora, 225. Tertiary Cor. n 247. Taasan m ‘tentacles of, 200. træ Thamnasir Thaumantiade, l4 Thaumant ey 63, 129. Theca, 155. hecia, 244. Thecide, see 237. 242, 244. Thecocyathus, 246. Thecosmilia pes Thecostegites, 2. 244. Thread-cells, of Cælenterata, 3; of hysalia, 53 of Hydra, 20; of Ac- Trachynema, 60, 1 Trachynemide, 119, 120. — INDEX. Trachypora, 244. Tria iassi ic : Cor als, ubu jari ite, P4 Tubula Tlosa. Es fw 204, 206, 237, 242, 243. Turbinaria, 241. A binolia, 247. urbi D 202, 207, 233, 234, 237, Turr di Boiss, 61. ja, n of Hydrozoa, 20; of Actinozoa, Uloc n ahus, 232. Uloph 239. Unbeliularies 235. Umbrella, of Lucernaride, 27, 37, 47, Urticating organs, of Celenterata, 3. Vacuolation, of tissues, 8, 32. eil, of nectocalyx, 36, 1 16. Take form and ero of, 104; 271 evelopment of, 59: Pee eae of, 102, 105 ; tentacles of, 32, 11 Se LA of, 1 105, I II4; go e pees : 45, 112 — oat pee. sacs IO o6; distribution of, 1 127. Velie v eretillum, 2 Vesicles, of Meauside, 37: Villi, of polypi Virgula aria, | song a Vital endowments, of lower animals, 10. Vitelline membrane, 15. Vogtia, 45, 99. Vorticlava, $2, 85— —7, 89. Warts, of Sea-anemones, 149. Willsia, canals of, 116. Yolk, 14. Yolk. division, 15, 51, 170. Yolk-sac, 15. Zaphrentis, 214, 238. Zoantharia, gene va characters of, SUM 162, Na 201, 206. PEARSA 160, 2 Zoöids, 74. THE END. LONDON PRINTED BY SPOTTISWOODE AND CO. NEW-STREET SQUARE of Elementary Works cale reader with ¢ clear Ro of the “and deu n Mes rsen ‘ The e ‘Manual oft e Vertebrata. By J. B.1 : m M.D © Motalloids. Manual of Sys tematic Bot Re rt I. PHÆNOGAMIA H E , Professor of. VS in “the Un \ v i D P» LP BETA V td a : RAO] d: dea Wr ise i di e e à Xi E ies eer tnd DE Ty a UT. T p Sate d M ved ME ACA Ay seh Foe SERA Mele e Nee RAE a pad = CS Gh E š EMR Den eode SR A DEN ed SA SEED Baws ATi s^ M ^ x at "t E EE. sn SPEC MARIA. z ae XT er «ci e elt ~ Ws