SEASIDE STUDIES IN NATURAL HISTORY. BY ELIZABETH C. AGASSIZ AND ALEXANDER AGASSIZ. MARINE ANIMALS OF MASSACHUSETTS BAY. RADIATES. BOSTON: TICKNOR AND FIELDS. 1865. Entered according to Act of Congress, in the year 1865, by ALEXANDER AGASSIZ, in the Clerk's Office of the District Court for the District of Massachusetts. UNIVERSITY PRESS: WELCH, BIGELOW, AND COMPANY, CAMBRIDGE. THIS LITTLE BOOK IS AFFECTIONATELY DEDICATED BY THE AUTHORS TO PROFESSOR L. AGASSIZ, WHOSE PRINCIPLES OF CLASSIFICATION HAVE BEEN THE MAIN GUIDE IN ITS PREPARATION. PREFACE. THIS volume is published with the hope of supplying a want often expressed for some seaside book of a popular character, describing the marine animals common to our shores. There are many English books of this kind; but they relate chiefly to the animals of Great Britain, and can only have a general bearing on those of our own coast, which are for the most part specifically different from their European relatives. While keeping this object in view, an attempt has also been made to present the facts in such a connection, with reference to principles of science and to classification, as will give it in some sort the character of a manual of Natural History, in the hope of making it useful not only to the general reader, but also to teachers and to persons desirous of obtaining a more intimate knowledge of the subjects discussed in it. With this purpose, although nearly all the illustrations are taken from among the most common inhabitants of our bay, a few have been added from other localities in order to fill out this little sketch of Radiates, and render it, as far as is possible within such limits, a complete picture of the type. vi PREFACE. A few words of explanation are necessary with reference to the joint authorship of the book. The drawings and the investigations, where they are not referred to other observers, have been made by MR. A. AGASSIZ, the illustrations having been taken, with very few exceptions, from nature, in order to represent the animals, as far as possible, in their natural attitudes; and the text has been written by MRS. L. AGASSIZ, with the assistance of MR. AGASSIZ'S notes and explanations. CAMBRIDGE, May, 1865. CO NTENTS. PAGE ON RADIATES IN GENERAL....... 1 GENERAL SKETCH OF THE POLYPS...... 5 ACTINOIDS........ 7 MADREPORIANS........ 16 HALCYONOIDS......... 19 GENERAL SKETCH OF ACALEPHS...... 21 CTENOPHOR......... 26 EMBRYOLOGY OF CTENOPHOR...... 34 DISCOPHORE.......... 37 HYDROIDS.......... 49 MODE OF CATCHING JELLY-FISHES...... 85 ECHINODERMS..... 91 HOLOTHURIANS......95 ECHINOIDS......... 101 STAR-FISHES........ 108 OPHIURANS.......... 115 CRINOIDS..........120 EMBRYOLOGY OF ECHINODERMS...... 123 DISTRIBUTION OF LIFE IN THE OCEAN... 141 SYSTEMATIC TABLE........ 152 INDEX......... 15 MARINE ANIMALS OF MASSACHUSETTS BAY. ON RADIATES IN GENERAL. IT is perhaps not strange that the Radiates, a type of animals whose home is in the sea, many of whom are so diminutive in size, and so light and evanescent in substance, that they are hardly to be distinguished from the element in which they live, should have been among the last to attract the attention of naturalists. Neither is it surprising to those who know something of the history of these animals, that when the investigation of their structure was once begun, when some insight was gained into their complex life, their association in fixed or floating communities, their wonderful processes of development uniting the most dissimilar individuals in one and the same cycle of growth, their study should have become one of the most fascinating pursuits of modern science, and have engaged the attention of some of the most original investigators during the last half century. It is true that from the earliest days of Natural History, the more conspicuous and easily accessible of these animals attracted notice and found their way into the scientific works of the time. Even Aristotle describes some of them under the names of Acalephse and Knidae, and later observers have added something, here and there, to our knowledge on the subject; but it is only within the last fifty years that their complicated history has been unravelled, and the facts concerning them presented in their true connection. Among the earlier writers on this subject we are most indebted to Rondelet, in the sixteenth century, who includes some account of the Radiates, in his work on the marine animals of the Mediterranean. His position as Professor in the University at Mont1 2 MARINE ANIMALS OF MASSACHUSETTS BAY. pelier gave him an admirable opportunity, of which he availed himself to the utmost, for carrying out his investigations in this direction. Seba and Klein, two naturalists in the North of Europe, also published at about this time numerous illustrations of marine animals, including Radiates. But in all these works we find only drawings and descriptions of the animals, without any attempt to classify them according to common structural features. In 1776, 0. F. Muller, in a work on the marine and terrestrial faunae of Denmark, gave some admirable figures of Radiates, several of which are identical with those found on our own coast. Cavolini also in his investigations on the lower marine animals of the Mediterranean, and Ellis in his work upon those of the British coast, did much during the latter half of the past century to enlarge our knowledge of them. It was Cuvier, however, who first gave coherence and precision to all previous investigations upon this subject, by showing that these animals are united on a common plan of structure expressively designated by him under the name Radiata. Although, from a mistaken appreciation of their affinities, he associated some animals with them which do not belong to the type, and have since, upon a more intimate knowledge of their structure, been removed to their true positions; yet the principle introduced by him into their classification, as well as into that of the other types of the animal kingdom, has been all important to science. It was in the early part of this century that the French began to associate scientific objects with their government expeditions. Scarcely any important voyage was undertaken to foreign countries by the French navy which did not include its corps of naturalists, under the patronage of government. Among the most beautiful figures we have of Radiates, are those made by Savigny, one of the French naturalists who accompanied Napoleon to Egypt; and from this time the lower marine animals began to be extensively collected and studied in their living condition. Henceforth the number of investigators in the field became more numerous, and it may not be amiss to give here a slight account of the more prominent among them. Darwin's fascinating book, published after his voyage to the ON RADIATES IN GENERAL. Pacific, and giving an account of the Coral islands, the many memoirs of Milne Edwards and Haime, and the great works of Quoy and Gaimard, and of Dana, are the chief authorities upon Polyps. In the study of the European Acalephs we have a long list of names high in the annals of science. Eschscholtz, Peron and Lesueur, Quoy and Gaimard, Lesson, Mertens, and Huxley, have all added largely to our information respecting these animals, their various voyages having enabled them to extend their investigations over a wide field. No less valuable have been the contributions of Kolliker, Leuckart, Gegenbaur, and Vogt, who in their frequent excursions to the coasts of Italy and France have made a special study of the Acalephs, and whose descriptions have all the vividness and freshness which nothing but familiarity with the living specimens can give. Besides these, we have the admirable works of Von Siebold, of Elrenberg, the great interpreter of the microscopic world, of Steenstrup, Dujardin, Dalyell, Forbes, Allman, and Sars. Of these, the four latter were fortunate in having their home on the sea-shore within reach of the objects of their study, so that they could watch them in their living cdndition, and follow all their changes. The charming books of Forbes, who knew so well how to popularize his instructions, and present scientific results under the most attractive form, are well known to English readers. But a word on the investigations of Sars may not be superfluous. Born near the coast of Norway, and in early life associated with the Church, his passion for Natural History led him to employ all his spare time in the study of the marine animals immediately about him, and his first papers on this subject attracted so much attention, that he was offered the place of Professor at Christiania, and henceforth devoted himself exclusively to scientific pursuits, and especially to the investigation of the Acalephs. He gave us the key to the almost fabulous transformations of these animals, and opened a new path in science by showing the singular phenomenon of the so-called " alternate generations," in which the different phases of the same life may be so distinct and seemingly so disconnected that, until we find the relation between them, we seem to have several animals where we have but one. 4 MARINE ANIMALS OF MASSACHUSETTS BAY. To the works above mentioned, we may add the third and fourth volumes of Professor Agassiz's Contributions to the Natural History of the United States, which are entirely devoted to the American Acalephs. The most important works and memoirs concerning the Echinoderms are those by Klein, Link, Johannes Muller, Jager, Desmoulins, Troschel, Sars, Savigny, Forbes, Agassiz, and Lutken, but excepting those of Forbes and Sars, few of these observations are made upon the living specimens. It may be well to mention here, for the benefit of those who care to know something more of the literature of this subject in our own country, a number of memoirs on the Radiates of our coasts, published by the various scientific societies of the United States, and to be found in their annals. Such are the papers of Gould, Agassiz, Leidy, Stimpson, McCrady, Clark, A. Agassiz, and Verrill. One additional word as to the manner in which the subjects included in the following descriptions are arranged. We have seen that Cuvier recognized the unity of plan in the structure of the whole type of Radiates. All these animals have their parts disposed around a common central axis, and diverging from it toward the periphery. The idea of bilateral symmetry, or the arrangement of parts on either side of a longitudinal axis, on which all the higher animals are built, does not enter into their structure, except in a very subordinate manner, hardly to be perceived by any but the professional naturalist. This radiate structure being then common to the whole type, the animals composing it appear under three distinct structural expressions of the general plan, and according to these differences are divided into three classes, - Polyps, Acalephs, and Echinoderms. With these few preliminary remarks we may now take up in turn these diferent groups, beginning with the lowest, or the Polyps.* * It is to be regretted that on account of the meagre representations of Polyps on our coast, where the coral reefs, which include the most interesting features of Polyp life, are entirely wanting, our account of these animals is necessarily deficient in variety of material. When we reach the Acalephs or Jelly-Fishes, in which the fauna of our shores is especially rich, we shall not have the same apology for dulness; and it will be our own fault if our readers are not attracted by the many graceful forms to which we shall then introduce them. GENERAL SKETCH OF TIE POLYPS. 5 GENERAL SKETCH OF THE POLYPS. BEFORE describing the different kinds of Polyps living on our immediate coast, we will say a few words of Polyps in general and of the mode in which the structural plan common to all Radiates is adapted to this particular class. In all Polyps the body consists of a sac divided by vertical partitions (Fig. 1.) into distinct cavities or chambers. These partiFig. 1. tions are not, however, all formed at once, but are usually limited to six at first, multiplying < indefinitely with the growth of the animal in /'. 4, / some kinds, while in others they never in- - crease beyond a certain definite number. In - the axis of the sac, thus divided, hangs a. " smaller one, forming the digestive cavity, /'hJV. and supported for its whole length by the six primary partitions. The other partitions, though they extend more or less inward in proportion to their age, do not unite with the digestive sac, but leave a free space in the centre between their inner edge and the outer wall of the digestive sac. The genital organs are placed on the inner edges of the partitions, thus hanging as it were at the door of the chambers, so that when hatched, the eggs naturally drop into the main cavity of the body, whence they pass into the secon ssmaller sac through an opening in its bottom or digestive cavity, and thence out through the mouth into the water. In the lower Polyps, as in our common Actinia for instance, these organs occur on all the radiating partitions, while among the higher ones, the IHalcyonoids for example, they are found only on a limited number. This limitation in the repetition of identical parts is always found to be connected with structural superiority. The upper margin of the body is fringed by hollow tentacles, each of which opens into one of the chambers. All parts of the animal thus communicate with each other, whatever is introduced at the mouth circulating through the whole structure, Fig. 1. Transverse section of an Actinia. (yAassiz.) 6 MARINE ANIMALS OF MASSACHUSETTS BAY. passing first into the digestive cavity, thence through the opening in the bottom into the main chambered cavity, where it enters freely into all the chambers, and from the chambers into the tentacles. The rejected portions of the food, after the process of digestion is completed, return by the same road and are thrown out at the mouth. These general features exist in all Polyps, and whether they lead an independent life as the Actinia, or are combined in communities, like most of the corals and the Halcyonoids; whether the tentacles are many or few; whether the partitions extend to a greater or less height in the body; whether they contain limestone deposit, as in the corals, or remain soft throughout life as the seaanemone, - the above description applies to them all, while the minor differences, either in the tentacles or in the form, size, color, and texture of the body, are simply modifications of this structure, introducing an infinite variety into the class, and breaking it up into the lesser groups designated as orders, families, genera, and species. Let us now look at some of the divisions thus established. The class of Polyps is divided into three orders, -the Halcyonoids, the Madreporians, and the Actinoids. Of.the lowest among these orders, the Actinoid Polyps, our Actinia or sea-anemone is a good example. They remain soft through life, having a great number of partitions and consequently a great number of tentacles, since there is a tentacle corresponding to every chamber. Indeed, in this order the multiplication of tentacles and partitions is indefinite, increasing during the whole life of the animal with its growth; while we shall see that in some of the higher orders the constancy and limitation in the number of these parts is an indication of superiority, being accompanied by a more marked individualization of the different functions. Next come the Madreporians, of which our Astrangia, to be described hereafter, may be cited as an example. In this group, although the number of tentacles still continues to be large, they are nevertheless more limited than in the Actinoids; but their characteristic feature is the deposition of limestone walls in the centre of the chambers formed by the soft partitions, so that all the soft partitions alternate with hard ones. The tentacles, al ACTINOIDS. 7 ways corresponding to the cavity of the chambers, may be therefore said to ride this second set of partitions arising just in the centre of the chambers. The third and highest order of Polyps is that of the Halcyonoids. Here the partitions are reduced to eight; the tentacles, according to the invariable rule, agree in number with the chainbers, but have a far more highly complicated structure than in the lower Polyps. Some of these Halcyonoids deposit limestone particles il their frame. But the tendency to solidify is not limited to definite points, as in the Madreporians. It may take place anywhere, the rigidity of the whole structure increasing of course in proportion to the accumulation of limestone. There are many kilds, in which the axis always remains soft or cartilaginous, while others, as the so-called sea-fans for instance, well known among the corals for their beauty of form and color, are stiff and hard throughout. Whatever their character in this respect, however, they are always compound, living in communities, and never found as separate individuals after their early stages of growth. Some of those with soft axis lead a wandering life, enjoying as much fieedom of movement as if they had an individual existence, shooting through the water like the Pennatulae, well known on the California coast, or working their way through the sand like the Renilla, common on the sandy shores of our Southern States. ACTI NOIDS. Actinia, or Sea-Anemone. (IMetridium marginatum EDW.) NOTHING can be more unprepossessing than a sea-anemone when contracted. A mere lump of brown or whitish jelly, it lies like a lifeless thing on the rock to which it clings, and it is difficult to believe that it has an elaborate and exceedingly delicate internaI organization, or will ever expand into such grace and beauty as really to deserve the name of the flower after which it has been called. Figs. 2, 3, 4, and 5, show this animal in its various stages 8 MARINE ANIMALS OF MASSACHUSETTS BAY. of expansion and contraction. Fig. 2 represents it with all its external appendages folded in, and the whole body flattened; in Fig. 3, the tentacles begin to steal out, and the body rises slightly; in Fig. 4, the body has nearly gained its full height, and the tenFig. 2. Fig. 3. Fig. 4. tacles, though by no means fully spread, yet form a delicate wreath around the mouth; while in Fig. 5, drawn in life size, the?'i.. Figs. 2, 3, 4 Actinia in different degrees of expansion. (Agassiz.) Fig. 5. The same Actinia (Metridium marginatum) fully expanded; natural size. METRIDIUM. 9 whole summit of the body seems crowned with soft, plumy fringes. We would say for the benefit of collectors that these animals are by no means difficult to find, and thrive well in confinement, though it will not do to keep them in a small aquarium with other specimens, because they soon render the water foul and unfit for their companions. They should therefore be kept in a separate glass jar or bowl, and under such circumstances will live for a long time with comparatively little care. They may be found in any small pools about the rocks which are flooded by the tide at high water. Their favorite haunts, however, where they occur in greatest quantity are more difficult to reach; but the curious in such matters will be well rewarded, even at the risk of wet feet and a slippery scramble over rocks covered with damp sea-weed, by a glimpse into their more crowded abodes. Such a grotto is to be found on the rocks of East Point at Nahant. It can only be reached at low tide, and then one is obliged to creep on hands and knees to its entrance, in order to see through its entire length; but its whole interior is studded with these animals, and as they are of various hues, pink, brown, orange, purple, or pure white, the effect is like that of brightly colored mosaics set in the roof and walls. When the sun strikes through from the opposite extremity of this grotto, which is open at both ends, lighting up its living mosaic work, and showing the play of the soft fringes wherever the animals are open, it would be difficult to find any artificial grotto to compare with it in beauty. There is another of the same kind on Saunders's Ledge, formed by a large boulder resting on two rocky ledges, leaving a little cave beneath, lined in the same way with variously colored sea-anemones, so closely studded over its walls that the surface of the rock is completely hidden. They are, however, to be found in larger or smaller clusters, or scattered singly in any rocky fissures, overhung by sea-weed, and accessible to the tide at high water. The description of Polyp structure given above includes all the general features of the sea-anemone; but for the better explanation of the figures, it may not be amiss to recapitulate them here in their special application. The body of the sea-anemone may be described as a circular, gelatinous bag, the bottom of which is flat 2 10 MARINE ANIMALS OF MASSACHUSETTS BAY. and slightly spreading around the margin. (Fig. 2.) The upper edge oi" this bag turns in so as to form a sac withi a sac. (Fig' Fig. 6.) This inner sac, s, is the stomach or digestive cavity, forminig a simple open space inl the centre of the body, with an aperture in thle bottom, 6, through which the food passes into the larger sac, in which it is enclosed. But this outer and largoer sac or mail cavity of the body is not, like the inner one, a simple open space. It is, on the contrary, divided by vertical partitions into a number of distinct chambers, converging from the periphery to the centre. These partitions do not all advance so far as actually to join the wall of the digestive cavity hangring in the centre of the body, but most of them stop a little short of it, leaving thils a small, open space between tie chambers anld the inner sac. (Fig. 1) The eggs hang on the inner edge of the partitions; when m ature they drop into the main cavity, enter the inner digestive cavitry through its lower opening, and are passed out through the mouth. The embryo bears no resemblance to the matfure animal. n t is a little planfla, semi-transparent, oblong, entirely covered with vibratile cilia, by means of which it swims freely about in the water till it establishes itself on some rocky surface, the end by which it becomes attached spreading slightly and fitting itself to the inequalities of the rock so as to form a secure basis. The upper end then becomes depressed toward the centre, that depression deepening more and more till it forms the inner sac, or in other words the digestive cavity described above. The open mouth of this inner sac, which may, however, be closed at will, since, the whole substance of the body is exceedingly contractile is the oral opening or so-called mouth of the animal. We have seen how the main cavity becomes divided by radiating partitions into numelrous chambers; but while these internal changes are going on, corresponding external appendages are formilng in the shape of the tentacles, which add so imulch to the boeauty of the anlnlal, and play so important a part in its history. The tenFig. 6.0 ertical section of an Actinia, showing a primary (g) and a secondary partition g' t o mouth, g tentacles, s stomach, ff reproductive organs, b main cavity, c opening in partitions, a lower floor, or foot, METRIDIUMo 11 tacles, at first only few in number, are in fact so many extensions of the inner chambers, gradually narrowing oupward till they form these delicate hollow feelers which make a soft downy fringe all around the mouth. (Fig. 7.) They do not start abruptly from thle summit, but the upper margin Fig 7. of the body itself thins out to';, formi more or less extensive lobes, through which the partitions and l: i:!i'>; lll chambers continlue their course and along the edge of which the tentacles arise. The eggs are not always laid in the condition of the simple planula - described above. They may, on the'. i., contrary, be dropped from the parent in different stages of developmlent, sometimes even after the tentacles have begun to formn as in Figs. 8, 9. Neither is it by mieans of eggs aloln that these Fig. 8. Fig. 9animals reproduce themseles; they may also multiply by a process of self-division. The disk of an Actinia may contract along its centre till the circular outline is changed to that of a figure 8, this constriction deepening gradually till the two halves of the 8 separate, and we have an Actinia with two mouths, each surrounded by an independent set of tentacles. Presently this separation descends vertically till the body is finally divided from Fig. T. View from above of an Actinia with all its tentacles expanded; o mouth, b crescent-shaped folds at extremity of mouth, a a fohls round mouth, t t tentacles. Figs. 8, 9o Young Actiniae int diierent stages of growth. 12 MARINE ANIMALS OF MASSACHUSETTS BAY. summit to base, and we have two Actinie where there was originally but one. Another and a far more common mode of reproduction among these animals is that of budding like corals. A slight swelling arises on the side of the body or at its base; it enlarges gradually, a digestive cavity is formed within it, tentacles arise around its summit, and it finally drops off from the parent and leads al independent existence. As a number of these buds are frequently formed at once, such an Actinia, surrounded by its little family, still attached to the parent, may appear for a time like a compound stock, though their normal mode of existence is individual and distinct. The Actinia is exceedingly sensitive, contracting the body and drawing in the tentacles almost instantaneously at the slightest touch. These sudden movements are produced by two powerful sets of muscles, running at right angles with each other through the thickness of the body wall; the one straight and vertical, extending from the base of the wall to its summit; the other circular and horizontal, stretching concentrically around it. By the contraction of the former, the body is of course shortened; by the contraction of the latter, the body is, on the contrary, lengthened in proportion to the compression of its circumference. Both sets can easily be traced by the vertical and horizontal lines crossing each other on the external wall of the body, as in Fig. 5. Each tentacle is in like manner furnished with a double set of muscles, having an action similar to that described above. In consequence of these violent muscular contractions, the water imbibed by the animal, and by which all its parts are distended to the utmost, is forced, not only out of the mouth, but also through small openings in the body wall scarcely perceptible under ordinary circumstances, but at such times emitting little fountains in every direction. Notwithstanding its extraordinary sensitiveness, the organs of the senses in the Actinia are very inferior, consisting only of a few pigment cells accumulated at the base of the tentacles. The two sets of muscles meet at the base of the body, forming a disk, or kind of foot, by which the animal can fix itself so firmly to the ground, that it is very difficult to remove it without injury. It is nevertheless capable of a very limited degree of RHODACTINIA. 13 motion,'by means of the expansion and contraction of this footlike disk. The Actiniae are extremely voracious; they feed on mussels and cockles, sucking the animals out of their shells. When in confinement they may be fed on raw meat, and seem to relish it; but if compelled to do so, they will live on more meagre fare, and will even thrive for a long time on such food as they may pick up in the water where they are kept. Rlhodactinia, (Rhodactinia Davisii AG.) Very different from this is the bright red Rhodactinia (Fig. 10), quite common in the deeper waters of our bay, while farther north, in Maine, it occurs at low-water mark. Occasionally it may be found thrown up on our sandy beaches after a storm, and. then, if it has not been too long out of its native element, or too severely buffeted by the waves, it will revive on being thrown into a bucket Fig. 10. of fresh sea-water, expand to its full size, and show all the beauty of its natural coloring. It is crowned with a wreath of thick, short tentacles (Fig. 10), and though so vivid and bright in color, it is not so pretty as the more common Actinia marginata, with its soft waving wreath of plume-like feelers, in comparison to which the tentacles of the Rhodactinia are clumsy and slow in their movements. All Actinie are not attached to the soil like those described above, nor do they all terminate in a muscular foot, some being pointed. or rounded at their extremity. Many are nomadic, wandering about at will during their whole lifetime, others live buried in the sand or mud, only extending their tentacles beyond the limits of the hole where they make their home; while others again lead a parasitic life, fastening themselves upon our larger Fig. 10. Rhodactinia Davisii Ag. natural aize, 14 MARINE ANIMALS OF MASSACHUSETTS BAY. jelly-fish, the CyaneT, though one is at a loss to imagine what sustenance they can derive from animals having so little- solidity, and consisting so largely of water. Arachnactis. (A rachnactis brachiolata A. AGo) Fig. 11. Among the nomadic Polyps is a small floating Actinia, called Arac hna.ctis, (Fig. 11,) from its resemblance to a spider, They are found in great plenty floatingl about during the night, feeling p 33_ etheir way in every direction by means of their tentacles, which are large few in 0 numh ber, and tlurned downward B $ IBI \when inl their natural attitude. The partitions and the digestive cavity enw /111 1 1 closed between themE are short, as wtll be seen ill Fig. 11, whel compared to the general cavity of the body floating balloon-like above tllem. Around thae F Fi g 121 YmAouth is at seconid row of shorter tena tacles, better seen in a younger specie men (Fig. 12). This Actinia differs from those described above, in having two of the sides flattened, instead of beillng perfectly circular. Looked at from above (as in Fig. 13) this differFig. 13. ence il the diameters is very perceptible; there is an evident tendency towards establishing a longitudinal axis. In the sea-anemone, this disposition is only hinted at in thei slightly pointed folds or projections on opposite sides of the circle formed by the mouth, which in the Arachinactis are so elongated as to produce a somewhat narrow slit (see Fig. 11. Arachnactis brachiolata A. Ag., greatly magnified. Fig. 12. Young Arachnactiso Fig. 13, Young Arachnactis seen so as to show the mouth. BICIDIUM. 15 Fig. 13), instead of a circular opening. The mouth is also a little out of centre, rather nearer one end of the disk than the other. These facts are interesting, as showing that the tendency towards establishing a balance of parts, as between an anterior and posterior extremity, a right and left side, is not forgotten in these lower animals, though their organization as a whole is based upon an equality of parts, admitting neither of posterior and anterior extremities, nor of right and left, nor of above and below, in a structural sense. This animal also presents a seeming anomaly in the mode of formation of the young tentacles, which always make their appearance at the posterior extremity of the longitudinal axis, the new ones being placed behind the older ones, instead of alternating with them as in other Actinie. Bicidiunm. (Bicidiumn parasiticum AG.) The Bicidium (Fig. 14), our parasitic Actinia, is to be sought for in the mouth-folds of the Cyanea, our common large red Jelly-fish. In any moderate-sized specimen of the latter from twelve to eighteen inches in diameter, we shall be sure to find one or more of these parasites, hidden away among the numerous folds of the mouth. The body is long and tapering, having an aperture in the extremity, the whole animal being ig. 14. like an elongated cone, strongly ribbed from apex to base. At the base, viz. at the mouth end, are a few short, stout tentacles. This Actinia is covered with innumerable little transverse wrinkles (see Fig. 14), by means of which it fastens itself securely among the fluted mem- branes around the mouth of the Jelly-fish. It will live a considerable time in confinement, attaching itself, for its whole length, to the vessel in which it is kept, and cliningg quite firmly if any attempt is made to remove it. The general color of the body is violet or a brownisl red, though the wrinkles give it a somewhat mottled appearance. Fig. 14. Bicidium parasiticuml natural size, 16 MARINE ANIMALS OF MASSACHUSETTS BAY. ]alcaympa, (Ilalcampa albida Ac.) Strange to say, the Actinie, which live in the mud, are among the most beautifully colored of these animals. They frequently prepare their home with some care, lining their hole by means of the same secretions which give their slimy surface to our common Actiniae, and thus forming a sort of tube, into which they retire when alarmed. But if undisturbed, they may be seen at the open door of their house with their many-colored disk and mottled tentacles extending beyond the aperture, and their mouth wide open, waiting for what the tide may bring them. By the play of their tentacles, they can always produce a current of water about the mouth, by means of which food passes into the stomach. We have said, that these animals are very brightly colored, but the little Halcampa (Fig. 15), belonging to our coast, is not one of the brilliant ones. It is on the contrary, a small, insignificant Actinia, resemn bling a worm, as it burrows its way through the sando It is of a pale yellowish color, with whitish warts on the surface. MAD REPO RIA NS$ Astrangia. (Astranga Dance AG.) IN Figure 16, we have the only species of coral growing so far north as our latitude. Indeed, it hardly belongs in this volume, since we have limited ourselves to the Radiates of AMassachusetts Bay, - its northernmost boundary being somewhat to the south of Massachusetts Bay, about the shores of Long Island, and on the islands of Martha's Vineyard Sound. But we introduce it here, though it is not included under our Fig. 156. alcampa albidai natural size, MADREPORIANS. 17 title, because any account of the Radiates, from which so important a group as that of the corals -was excluded, would be very incomplete. This pretty coral of Fig. 16 our Northern waters is no reef-builder, and does not extend farther southe lentan the shores of North Carolina. It usually es- tablishes itself upon brokeln angular bits of rock, lying in sheltered creeks and inlets, where the violent action of the open sea is not felt. The presence of one of these little communities on a rock may first be detected by what seems like a delicate white film over the surface. This film is, however, broken up by a number of hard calcareous deposits in very regular form (Fig. 20), circular in outline, but divided by numerous partitions running from the outer wall to the centre of every such circle, where they luite at a little white spot formed by the mouth or oral opening. These circles represent, and indeed are themselves the distinct individuals (Fig. 17) composing the community, and they look ig. 17i not unlike the star-shaped pits on a coral head, formed by Astraans. Unlike the massive compact kinds of viduals multiply by budding friom the base chiefly, never rising one above the | other, but spreading over the surface on which they haveo established themselves, a few addcitional individuals arising between the older ones. In consequence of this mode of growth, such a commuFig. 16. Astrangia colony; natural size. Fig. 17. Magnitied individuals of an Astrangia community in different stages of expansion. 3 18 MARINE ANIMALS OF MASSACHUSETTS BAY. nity, when it has attained any size, forms a little white mound on the rock, higher in the centre, where the older members have attained their whole height and solidity, and thinning out toward the margin, where the younger ones may be just beginning life, and hardly rise above the surface of the rock. These communities rarely grow to be more than two or three inches in diameter, and about quarter of an inch in height at the centre where the individuals have reached their maximum size.'When the animals are fully expanded (Fig. 18), with all their tentacles spread, Pig.:8. tle surface of every such mound _I' becomes covered with downy'white fringes, and what seemed before a hard, calcareous mass upon the rock, changes to a soft fleecy tuft, waving gently to and fro in the water, The tentacles are thickly covered with small wart-like appendages, which, on examination, prove to be clusters of lasso-cells, the terminal cluster of the tentacle being quite prominent. These lasso-cells are very formidable weapons, judging both from their appearance when magnified (Fig. 19), and from the -terrible effect of their bristling lash upon any small crustacean, or worm, that Fig. 19o may be so unfortunate as to come within its reach. The description of the internal arrangement of parts in the Actinia applies in every particular to these corals, with the exception of the hard deposit in the lower part of tlhe body. As in all the Polyps, radiating partitions -g divide the main cavity of the body into distinct separate: chambers, and the tentacles increasing by multiples of six, numbering six in the first set, six in the second, and twelve in the third, are hollow, and open into the chamn bers. But the feature -which distinguishes them from the soft Actinia, and unites them with the corals, requires a somewhat more accurate description. In each individual, a hard deposit is formed (Fig. 20), beginning at the base of every chamber, and rising from its floor to about Fig. 18. Single individual of Astrangia, fully expanded. Fig, 19. 5Magnified lasso-cell of Astrangiao tIALCYO-OIDS. 19 one fifth thle height of the animal at its greatest extension. This lime deposit does not, however, fill Fig. 20 the chamber for its whole width, but rises as a thin wall in its centre. (See Figs. 16, 17.) Thus between all the: soft partitions, in the middle of the ] ehambers which separate them, low...s lime-stone walls are gradually built up, uniting in a solid column in the " tl centre. These walls run parallel'- with the soft partitions, although they do not rise to the same height, and they form the radiating lines like stiff lamella, so conspieu ous when all the soft parts of the body are drawn in. The mouth of the Astrangia is oval, and the partitions spread in a fan-shaped way, being somewhat shorter at one side of the animal than on the other. The partitions extend beyond the solid wall which unites them at the periphery, in consequence of whih, this wall is marked by faint vertical ribs. HIALCYONOIDS. ITalcyoni)um (Healcyonitmo carneum AG.) WE come now to the IHalcyonoids, represented in our waters by the HIalcyonium (Fig. 22) In the HIalcyonoids, the highest group of Polyps, the tentacles reach -their greatest limitation, which, as above mentioned, is found to be a mark of superiority, and, connected with other struc- ig. 21. tural features, places them at the head of their class. The number of tentacles througlhout this group is always eight. They are very complicated (Fig. 21), in comparison with the tentacles of the lower orders, being deeply lobed, Fig. 20. Limestone palrts of an individual of Astrangia; magnified. Fig. 21. Single individual of Halcyonimlu seen from above; magnified, 20 MARINE ANIMALS OF MASSACHUSETTS BAY. and fringed around the margin. Our Halcyonium communities'(Fig. 22) usually live in deep water, l sr, a attached to dead shells, though they ul may oecasionally be found growing at low-watelr mark, but this is very rare. They have received a rather lugubrious name from the fishernmen, who call thlem l dead-men's fingers," and indeedt when the animals are contracted, such a commrun-ity, with its short branches attached to the main stock, looks not unlike the stLump of a hand, with slhort, fat fingers. In such a condition they are very ugly, the whole mass being somewhat gelatinous in texture, and a dull, yellowish pink in color. Buit when the animals, which are capable of great extension, are fillly spread as in Fig. 22, suchl a polyp-stock has a mossy, tufted look, adr is by no means an unsightly object. When the individuals are entirely expanded, as in Fig. 23, they become quite transparent, and their internal structure can readily be seen throug'h the walls of the body; we can then easily distinguish the digestive cavity, sulpported for its whole length by the eight radiating partitionss as well as the great size of -the main digestive cavity surrounding it. Notwithstanding the remarkable power of contraction and dilatation in the animals thlleselves, the tentacles are but slightly contractile. This kind of community increases altogether by bcdding, the individual polyps remaining more or less united, the tissues of the individuals becoming thicker by the deposition of lime nodules: and thus forming a massive senmi-cartilaginous puilp: uniting thle whole community. In the neig'hborhood of Provincetown they are very plentiful, and are found all along the shores of our Bay in deep water. Fig. 22. HIalcyonium community; natural size. _Fig. 23. Individual of lIalcyonium fully expanded; magnified. GENERAL SKETCH OF ACALEPHS. 21 GENERAL SKETCH OF ACALEPHS. IN the whole history of metamorphosis, that wonderful chapter in the life of animals, there is nothing more strange or more interesting than the transformations of the Acalephs. First, as little floating planulne or transparent spheres, covered with fine vibratile cilia, by means of which they move with great rapidity, then as communities fixed to the ground and increasing by budding like the corals, or multiplying by self-division, and later as free-swimming Jelly-fishes, many of them pass through phases which have long baffled the investigations of naturalists, and have only recently been understood in their true connection. Great progress has, however, been made during this century in our knowledge of this class. Thanks to the investigations of Sars, Dujardin, Steenstrup, Van Beneden, and many others, we now have the key to their true relations, and transient phases of growth, long believed to be the adult condition of distinct animals, are now recognized as parts in a cycle of development belonging to one and the same life. As the class now stands, it includes three orders, highest among which are the CTENOPHORE, SO called on account of their locomotive organs, consisting of minute flappers arranged in vertical comb-like rows; next to these are the DIS COPHOR2, with their large gelatinous umbrella-like disks, commonly called Jelly-fishes, Sun-fishes, or Sea-blubbers, and below these come the HYDROIDS, embracing the most minute and most diversified of all these animals. These orders are distinguished not only by their striking external differences, but by their mode of development also. The Ctenophora grow from eggs by a direct continuous process of development, without undergoing any striking metamorphosis; the Discophorae, with some few exceptions, in which they develop like the Ctenophorae from eggs, begin life as a Hydra-like animal, the subsequent self-division of which gives rise, by a singular process, presently to be described, to a number of distinct Jellyfishes; the Hydroids include all those Acalephs which either pass the earlier stages of their existence as little shrub-like com 22 MARINE ANIMALS OF MASSACHUSETTS BAY. munities, or remain in that condition through life. These iydroid stocks, as they are sometimes called, give rise to buds; these buds are transformed into Jelly-fishes, which in some instances break off when mature and swim away as free animals, while in others they remain permanent members of the Hydroid stock, never assuming a free mode of life. All these buds when mature, whether free or fixed, lay eggs in their turn, from which a fresh stock arises to renew this singular cycle of growth, known among naturalists as " alternate generations." The Hydroids are not all attached to the ground, - some like the Physalia (Portuguese man-of-war), or the Nanomia, that pretty floating Hydroid of our own waters, move about with as much freedom as if they enjoyed an individual independent existence. As all these orders have their representatives on our coast, to be described hereafter in detail, we need only allude here to their characteristic features. But we must not leave unnoticed one very remarkable Hydroid Acaleph (Fig. 24), not found in our waters, and resembling the Fig. 2'. Polyps so much, that it has long been asso-,< — ciated with them. The Millepore is a coral,:~-j ^. and was therefore the more easily confounded with the Polyps, so large a proportion of which build coral stocks; but a more minute investigation of its structure (Figs. 25, Fig. 25. 26) has recently shown that it belongs with / the Acalephs.* This discovery is the more ^.- important, not only as explaining the true position of this animal in the Animal Kingdom, but as proving also the presence of Acalephs ('x \ \ ~; } in the earliest periods of creation, since it re(Q ^^1^ fers a large number of fossil corals, whose za:~-^^ a., affinities with the millepores are well understood, to that class, instead of to the claes of Polyps with which they had hitherto been associated. But for this we should have no positive evidence of the existence of Fig. 24. Branch of Millepora alcicornis; natural size. (Agassiz.) Fig. 25. Animals of M. alcicornis expanded; magnified. a a a small Hydroid, b larger Hydroid, I tentacles, m mouth. (Agassiz.) * See " Methods of Study," by Prof. Agassiz. GENERAL SKETCH OF ACALEPHS. 23 Acalephs in early geological periods, the gelatinous texture of the ordinary Jelly-fishes making their preserva- Fig. 26. tion almost impossible. It is not strange that the a1.7 true nature of this animal should have remained l \t so long unexplained; for it is only by the soft gi parts of the body, not of course preserved in the 1i'fossil condition, that their relations to the Acalephs i.''i2 may be detected; and they are so shy of approach, E n 9. drawing their tentacles and the upper part of the " - body into their limestone frame if disturbed, that it is not easy to examine the living animal. The Millepore is very abundant on the Florida reefs. From the solid base of the coral stock arise broad ridges, branching more or less along the edges, the whole surface being covered by innumerable pores, from which the diminutive animals project when expanded. (Fig. 25.) The whole mass of the coral is porous, and the cavities occupied by the Hydrae are sunk perpendicularly to the surface within the stock. Seen in a transverse cut these tubular cavities are divided at intervals by horizontal partitions (Fig. 26), extending straight across the cavity from wall to wall, and closing it up entirely, the animal occupying only the outermost open space, and building a new partition behind it as it rises in the process of growth. This structure is totally different from that of the Madrepores, Astraeans, Porites, and indeed, from all the polyp corals which, like all Polyps, have the vertical partitions running through the whole length of the body, and more or less open from top to bottom. The life of the Jelly-fishes, with the exception of the Millepores and the like, is short in comparison to that of other Radiates. While Polyps live for many years, and Star-fishes and Sea-urchins require ten or fifteen years to attain their full size, the short existence of the Acaleph, with all its changes, is accomplished in one year. The breeding season being in the autumn, the egg grows into a Hydroid during the winter; in the spring the Jelly-fish is freed from the Hydroid stock, or developed upon it as the case may be; it attains its full size in the fall, lays its eggs Fig. 26. Transverse section of a branch, showing pits, a a a a, of the large Hydroids with the horizontal floors. (,yassiz.) 24 MARINE ANIMALS OF MASSACHUSETTS BAY. and dies, and the cycle is complete. The autumn storms make fearful havoc among them, swarms of them being killed by the fall rains, after which they may be found thrown up on the beaches in great numbers. When we consider the size of these Jellyfishes, their rapidity of growth seems very remarkable. Our common Aurelia measures some twelve to eighteen inches in diameter when full grown, and yet in the winter it is a Hydra so small as almost to escape notice. Still more striking is the rapid increase of our Cyanea, that giant among Jelly-fishes, which, were it not for the soft, gelatinous consistency of its body, would be one of the most formidable among our marine animals. Before entering upon the descriptions of the special kinds of Jelly-fishes, we would remind our readers that the radiate plan of structure is reproduced in this class of animals as distinctly as in the Polyps, though under a different aspect. Here also we find that there is a central digestive cavity from which all the radiating cavities, whether simple or ramified, diverge toward the periphery. It is true that the open chambers of the Polyps are here transformed into narrow tubes, by the thickening of the dividing partitions, or in other words, the open spaces of the Polyps correspond to tubes in the Acalephs, while the partitions in the Polyps correspond to the thick masses of the body dividing the tubes in the Acalephs; but the principle of radiation on which the whole branch of Radiates is constructed controls the organization of Acalephs no less than that of the other classes, so that a transverse section across any Polyp (Fig. 1), or across any Acaleph (Fig. 50), or across any Echinoderm (Fig. 140), shows their internal structure to be based upon a radiation of all parts from the centre to the periphery. That there may be no vagueness as to the terms used hereafter, we would add one word respecting the nomenclature of this class, whose aliases might baffle the sagacity of a police detective. The names Acalephs, Medusae, or the more common appellation of Jelly-fishes, cover the same ground, and are applied indiscriminately to the animals they represent. The name Jelly-fish is an inappropriate one, though the gelatinous consistency of these animals is accurately enough expressed by it; but they have no more structural relation to a fish than to a bird or an insect. GENERAL SKETCH OF ACALEPHS. 25 They have, however, received this name before the structure of animals was understood, when all animals inhabiting the waters were indiscriminately called fishes, and it is now in such general use that it would be difficult to change it. The name Medusa is derived from their long tentacular appendages, sometimes wound up in a close coil, sometimes thrown out to a great distance, sometimes but half unfolded, and aptly enough compared to the snaky locks of Medusa. Their third and oldest appellation, that of Acalephs, - alluding to their stinging or nettling property, and given to them and like animals by Aristotle, in the first instance, but afterwards applied by Cuvier in a more limited sense to Jelly-fishes, - is the most generally accepted, and perhaps the most appropriate of all. The subject of nomenclature is not altogether so dry and arid as it seems to many who do not fully understand the significance of scientific names. Not only do they often express with terse precision the character of the animal or plant they signify, but there is also no little sentiment concealed under these jawbreaking appellations. As seafaring men call their vessels after friends or sweethearts, or commemorate in this way some impressive event, or some object of their reverence, so have naturalists, under their fabrication of appropriate names, veiled many a graceful allusion, either to the great leaders of our science, or to some more intimate personal affection. The Linncea borealis was well named after his famous master, by a disciple of the great Norwegian naturalist; Goetlea semperflorens, the ever-blooming, is another tribute of the same kind, while the pretty, graceful little Lizzia, named by Forbes, is one instance among many of a more affectionate reference to nearer friends. The allusions of this kind are not always of so amiable a character, however, - witness the " Buffonia," a low, noxious weed, growing in marshy places, and named by Linnaeus after Buffon, whom he bitterly hated. Indeed, there is a world of meaning hidden under our zoological and botanical nomenclature, known only to those who are intimately acquainted with the annals of scientific life in its social as well as its professional aspect. 4 26 MARINE ANIMALS OF MASSACHUSETTS BAY. C T E N O P 1 O RE. THE Ctenophorae differ from other Jelly-fishes in their mode of locomotion. All the Discophorous Medusae, as well as Hydroids, move by a rhythmical rise and fall of the disk, contracting and expanding with alternations so regular, that it reminds one of the action of the lungs, and seems at first sight to be a kind of respiration in which water takes the place of air. The Greeks recognized this peculiar character in their name, for they called them Sea-lungs. Indeed, locomotion, respiration, and circulation are so intimately connected in all these lower animals, that whatever promotes one of these functions affects the other also, and though the immediate result of the contraction and expansion of the disk seems to be to impel them through the water, yet it is also connected with the introduction of water into the body, which there becomes assimilated with the food in the process of digestion, and is circulated throughout all its parts by means of ramifying tubes. In the Ctenophorae there is no such regular expansion and contraction of the disk; they are at once distinguished from the Discophorae by the presence of external locomotive appendages of a very peculiar character. They move by the rapid flapping of countless little oars or paddles, arranged in vertical rows along the surface of the disk, acting indepen dently of each other; one row, or even one paddle, moving singly, or all of them together, at the will of the animal; thus enabling it to accelerate or slacken its movements, to dart through the water rapidly, or to diminish its speed by partly furling its little sails, or, spreading them slightly, to poise itself with a faint, quivering movement that reminds one of the pause of the humming-bird in the air, - something that is neither positive motion, nor actual rest.* These locomotive appendages are intimately connected with the circulating tubes, as we shall see when we examine the struc* The flappers of one side are sometimes in full activity, while those of the other side are perfectly quiet or nearly so, thus producing rotatory movements in every direction. PLEUROBRACHIA. 27 tural details of these animals, so that in them also breathing and moving are in direct relation to each other. To those unaccustomed to the comparison of functions in animals, the use of the word breathing, as applied to the introduction of water into the body, may seem inappropriate, but it is by the absorption of aerated water that these lower animals receive that amount of oxygen into the system, as necessary to the maintenance of life in them, as a greater supply is to the higher animals. The name of Ctenophoroe or comb-bearers, is derived from these rows of tiny paddles which have been called combs by some naturalists, because they are set upon horizontal bands of muscles, see Fig. 29, reminding one of the base of a comb, while the fringes are compared to its teeth. These flappers add greatly to the beauty of these animals, for a variety of brilliant hues is produced along each row by the decomposition of the rays of light upon them when in motion. They give off all the prismatic colors, and as the combs are exceedingly small, so that at first sight one hardly distinguishes them from the disk itself, the exquisite play of color, rippling in regular lines over the surface of the animal, seems at first to have no external cause. Pleurobrachia. (Pleurobrachia rhododactyla AG.) Among the most graceful and attractive of these animals are the Pleurobrachia (Fig. 29), and, though not first in order, we will give it the precedence in our description, because it will serve to illustrate some features of the other two groups. The body of the Pleurobrachia consists of a transparent sphere, varying, however, from the perfect sphere in being somewhat oblong, and also by a slight compression on two opposite sides (Figs. 27 and 28), so as to render its horizontal diameter longer in one direction than in the other (Fig. 30). Fi. 27. This divergence from the globular form, so slight 7 in Pleurobrachia as to be hardly perceptible to / i1 \ the casual observer, establishing two diameters of different lengths at right angles with each other, -. is equally true of the other genera. It is inter- -:____ esting and important, as showing the tendency in ) I Fig. 27. Pleurobrachia seen at right angles to the plane in which the tentacles are placed. (Ayassiz.) 28 MARINE ANIMALS OF MASSACHUSETTS BAY. this highest group of Acalephs to assume a biFig.28. lateral character. This bilaterality becomes still i more marked in the highest class of Radiates, the (1 1 J11 Echinoderms. Such structural tendencies in the lower animals, hinting at laws to be more fully developed in the higher forms, are always signifi~ \ cant, as showing the intimate relation between all parts of the plan of creation. This inequality of the diameters is connected with the disposition of parts in the whole structure, the locomotive fringes and the vertical tubes connected with them being arranged in sets of four on either side of a plane passing through the longer diameter, showing thus a tendency toward the establishment of a right and left side of the body, instead of the perfectly equal disposition of parts around a common centre, as in the lower Radiates. The Pleurobrachia are so transparent, that, with some preparatory explanation of their structure, the most unscientific observer may trace the relation of parts in them. At one end of the sphere is the transverse split (Fig. 27), that serves them as a mouth; at the opposite pole is a small circumscribed area, in the centre of which is a dark eye-speck. The eight rows of locomotive fringes run from pole to pole, dividing the whole surface of the body like the ribs on a melon. (Figs. 27, 28.) Hanging from either side of the body, a little above the area in which the eyespeck is placed, are two most extraordinary appendages in the shape of long tentacles, possessing such wonderful power of extension and contraction that, while at one moment they may be knotted into a little compact mass no bigger than a pin's head, drawn up close against the side of the body, or hidden within it, the next instant they may be floating behind it in various positions to a distance of half a yard and more, putting out at the same time soft plumy fringes (Fig. 29) along one side, like the beard of a feather. One who has never seen these animals may well be pardoned for doubting even the most literal and matterof-fact account of these singular tentacles. There is no variety of curve or spiral that does not seem to be represented in their evolutions. Sometimes they unfold gradually, creeping out softly Fig. 28. Pleurobrachia seen in plane of tentacles. (dgassiz.) PLEUROBRACHIA. 29 and slowly from a state of contraction, or again the little ball, hardly perceptible against the side of the body, drops suddenly to the bottom of Fi 290 the tank in which the a animal is efoatl ing, and one thinks for a mo entl i so slight is the threadlike attachmenct, that it ohas actualnte ly fallen forom the body; but watch a little longer, and all tuhe filaments spread outs allong the sid e of the thread, it expands, tt to its full length a:hid breadth, and esumes all its graceful evolutions. One word of the internal structure of these animals, to explain its relation to the external appendages. The mouth opens into a wide digestive cavity (Figs. 27, 28), enclosed between two vertical tb est. Toward the opposite en of the body these tubes terminate or unite in a single funney ike canal, which is a resero vo as it e ere for the circlatin fluid poraed into itpl through an opening i 2n the bo ttom of the digestive cavity The food in othe digestive cavity becomes liquefied by minglinig with the water entering with it at the mounth, and, thus prepared, it passes into this canal, from which, as we shall presently see, all the circulating tubes ramifying throughout the body are fed. Two of these circulating t-ubes, or, as they are called from the nature of the liquid they contain, chymiferous tubes, are very large, starting horizontally and at right angles with the digestive cavity from the point of junction between the vertical tubes (Fig. 30) and the canal. Presently they give off two branches, these again ramifying in two directions as they approach the periphery, so that each one of the first main tubes has rmultiplied to four, Fig. 29. Natural attitude of Pleurobrachia when in motion. 30 MARINE ANIMALS OF MASSACHUSETTS BAY. before its ramifications reach the surface, thus making in all eight radiating tubes. So far. these _i. 30. eight tubes are horizontal, all diverging onL the same level; but as they reach the periphery each one gives rise to a vertical -tube, running along the surface of the body from pole to pole, just within the rows of locomotive fringes on the outer surface and immediately connected with them (Figs. 27. 28), As in all the Ctenophora, these fringes keep up a constant play of color by their rapid vibrations. In Pleurobrachia the prevailing tint is a yellowish pink, though it varies to green, red, and purple, with the changing motions of the animal. We have seen that the vertical tubes between which the digestive cavity is enclosed, start like the cavity itself from that pole of the body where the mouth is placed, and that, as they approach the opposite pole, at a distance from the mouth of about two thirds the whole length of the body, they unite in the canal, which then extends to the other pole where the eye-speck is placed As it is just at this point of juncture between the tubes and the canal that the two main horizontal tubes arise from which all the others branch on the same plane (Figsf 27, 28), it follows that they reach the periphery, not on a level with the pole opposite the mouth, but removed from it by about one third the height of the body. In consequence of this the eight vertical tubes arising from the horizontal ones, in order to run the entire length of the body from pole polepoe extend in opposite directions, sending a branch to each pole, though the branch running toward the mouth is of course the longer of the two. The tentacles have their roots in two sacs within the body, placed at right angles with the split of the mouth. (Figs. 27, 30.) They open at the surface on the opposite side from the mouth, though not immediately within the area at which -the eye-speck is placed, but somewhat above it, and at a little distance on either side of it. The tentacles may be drawn completely within these sacs, or be extended outside, as we have seen, to a greater or less degree, and in every variety of curve or spiral. Fig. 30. Pleurobrachia seen from the extremity opposite the mouth. BOLINA. 31 Bolina. (Bolina alata AG.) THE Bolina (Fig 32), like the Pleurobrachia, is slightly oval in form, with a longitudinal split at one end of the body, forming a mouth which opens into a capacious sac or digestive cavity. But it differs from the Pleurobrachia in having the oral end of the body split into two larger lobes (Fig. 31), hanging down from the mouth. These lobes may gape Fig. 31. widely, or they may close completely over the mouth so as to hide it from /' view, and their different aspects under.. I various degrees of expansion or contrac- 7. I, tion account for the discrepancies in the \ description of these animals. We have t seen that the Pleurobrachia moves x'\\ Aly with the mouth upward; but the Bo-. lina, on the contrary, usually carries i/ the mouth downward, though it occasionally reverses its position, and in this attitude, with the lobes spread open, it is exceedingly graceful in form, and looks like a white flower with the crown fully expanded. These broad lobes are balanced on the other sides of the body by four smaller appendages, divided in pairs, two on each side (Fig. 32), called auricles. These so-called auricles are in fact organs of the same kind Fig. 32. as the larger lobes, though less developed. b_ 9 The rows of locomotive flappers on the Bo-'' lina differ in length from each other (Fig.' 71 ii 7 31), instead of being equal, as in the Pleu-; K robrachia. The four longest ones are op- Xi posite each other on those sides of the body 1 (l 2I,D where the larger lobes are developed, the.\\ -^'" four short ones being in pairs on the sides where the auricles are placed. At first sight they all seem to terminate at the margin of the body, but a closer Fig. 31. Bolina seen from the broad side; o eye-speck, m mouth, r auricles, v digestive cavity, g h short rows of flappers, af long rows of flappers, n x t z tubes winding in the larger lobes; about half natural size. (Agassiz.) Iig. 32. Bolina seen from the narrow side; c h short rows of flappers, ab long rows of flappers; other letters as in Fig. 31. (Ayassiz.) 32 MARINE ANIMALS OF MASSACHUSETTS BAY. examination shows that the circulating tubes connected with the longer row extend into the lobes, where they wind about in a variety of complicated involutions. (Fig. 32.) The movements of the Bolina are more sluggish than those of the Pleurobrachia, and the long tentacles, so graceful an ornament to the latter, are wanting in the former. With these exceptions the description given above of the Pleurobrachia will serve equally well for the Bolina. The structure is the same in all essential points, though it differs in the size and proportion of certain external features, and its play of color is less brilliant than that of the Pleurobrachia. The Bolina, with its slow, undulating motion, its broad lobes sometimes spreading widely, at other times folded over the mouth, its delicacy of tint and texture, and its rows of vibrating fringes along the surface, is nevertheless a very beautiful object, and well rewards the extreme care without which it dies at once in confinement. Idyia. (Idyia roseola AG.) The lowest genus of Ctenophorae found on our coast, the Idyia (Fig. 33), has neither the tentacles of the Pleurobrachia, nor the lobes of the Bolina. It is a simple ovate sphere, the interior of which is almost entirely occupied by an immense digestive cavity. It would seem that the reception and digestion of food is intended Fig 33. to be the almost exclusive function of this ^.~.a animal, for it has a mouth whose ample dimensions correspond with its capacious stomach. Instead of the longitudinal split serving b- >.: as a mouth, in the Bolina and Pleurobrachia, 1K_ i 1. one end of the body in the Idyia is completely d1!1 1 -:i open (Fig. 33), so that occasionally some un71XL~:- l