Seaside Studies in Natural History. Marine Animals of Massachusetts Bay. Radiates.

SEASIDE STUDIES

IN

NATURAL HISTORY.

BY

ELIZABETH C. AGASSIZ

AND

ALEXANDER AGASSIZ.

MARINE ANIMALS OF MASSACHUSETTS BAY.
RADIATES.

BOSTON:
JAMES R. OSGOOD AND COMPANY,
Late Ticknor & Fields, and Fields, Osgood, & Co.
1871.

Entered according to Act of Congress, in the year 1865, by
A L E X A N D E R A G A S S I Z,
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,

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.

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. A. Agassiz's notes and explanations.

Cambridge, May, 1865.

NOTE.

This second edition is a mere reprint of the first. A few mistakes accidentally overlooked have been corrected; an explanation of the abbreviations of the names of writers used after the scientific names has been added, as well as a list of the wood-cuts. The changes which have taken place in the opinions of scientific men with regard to the distribution of animal life in the ocean have been duly noticed in their appropriate place, but no attempt has been made to incorporate more important additions which the progress of our knowledge of Radiates may require hereafter.

Cambridge, January, 1871.

CONTENTS.

LIST OF THE WOOD-CUTS.

Unless otherwise specified, the illustrations are drawn from nature by Alex. Agassiz.

ABBREVIATIONS OF THE NAMES OF AUTHORS.

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 Acalephæ and Knidæ, 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 Montpelier 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, O. F. Müller, in a work on the marine and terrestrial faunæ 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 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, Péron 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 memoirs of Kölliker, Leuckart, Gegenbaur, Vogt, and Haeckel, 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 Ehrenberg, 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 condition, 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.

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 Müller, Jäger, Desmoulins, Troschel, Sars, Savigny, Forbes, Agassiz, and Lütken, 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, Ayres, 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 different groups, beginning with the lowest, or the Polyps.[1]

[1] 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.

[TOC]

GENERAL SKETCH OF THE POLYPS.

[Fig. 1]

Fig. 1. Transverse section of an Actinia. (Agassiz.)

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 partitions are not, however, all formed at once, but are usually limited to six at first, multiplying indefinitely with the growth of the animal in some kinds, while in others they never increase beyond a certain definite number. In the axis of the sac, thus divided, hangs a smaller one, forming the digestive cavity, 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 second smaller 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 Halcyonoids 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, 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 sea-anemone,—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, always 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 chambers, but have a far more highly complicated structure than in the lower Polyps. Some of these Halcyonoids deposit limestone particles in 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 kinds, 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 freedom of movement as if they had an individual existence, shooting through the water like the Pennatulæ, 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.

ACTINOIDS.

Actinia, or Sea-Anemone. (Metridium 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 internal 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 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 tentacles, though by no means fully spread, yet form a delicate wreath around the mouth; while in [Fig. 5], drawn in life size, the 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.

[Fig_2]

[Fig_3]

[Fig_4]

Figs. 2,3,4. Actinia to different degrees of expansion (Agassiz)

[Fig. 5]

Fig. 5. The same Actinia (Metridium marginatum) fully expanded; natural size.

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.

[Fig. 6]

Fig. 6. Vertical section of an Actinia, showing a primary(g) and a secondary partition of g'; o mouth, t tentacles, s stomach, f f reproductive organs, b main cavity, c openings in partitions, a lower floor, or foot.

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 and slightly spreading around the margin. ([Fig. 2.]) The upper edge of this bag turns in so as to form a sac within a sac. ([Fig. 6.]) This inner sac, s, is the stomach or digestive cavity, forming a simple open space in the centre of the body, with an aperture in the bottom, b, through which the food passes into the larger sac, in which it is enclosed. But this outer and larger sac or main 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 hanging in the centre of the body, but most of them stop a little short of it, leaving thus a small, open space between the chambers and the inner sac. ([Fig. 1.]) The eggs hang on the inner edge of the partitions; when mature they drop into the main cavity, enter the inner digestive cavity through its lower opening, and are passed out through the mouth.

The embryo bears no resemblance to the mature animal. It is a little planula, 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 numerous chambers; but while these internal changes are going on, corresponding external appendages are forming in the shape of the tentacles, which add so much to the beauty of the animal, and play so important a part in its history. The tentacles, at first only few in number, are in fact so many extensions of the inner chambers, gradually narrowing upward 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 the summit, but the upper margin of the body itself thins out to form more or less extensive lobes, through which the partitions and chambers continue their course, and along the edge of which the tentacles arise.

[Fig. 7]

Fig. 7. View from above of an Actinia with all its tentacles expanded; o mouth, b crescent-shaped folds at extremity of mouth, a a folds round mouth, t t t tentacles.

The eggs are not always laid in the condition of the simple planula described above. They may, on the contrary, be dropped from the parent in different stages of development, sometimes even after the tentacles have begun to form, as in Figs.[ 8], [9]. Neither is it by means of eggs alone that these animals reproduce themselves; 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 summit to base, and we have two Actiniæ 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 an 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.

[Fig. 8]

[Fig. 9]

Figs. 8, 9. Young Actiniæ in different stages of growth.

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 motion, by means of the expansion and contraction of this foot-like disk.

The Actiniæ 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.

Rhodactinia (Rhodactinia Davisii Ag.)

[Fig. 10]

Fig. 10. Rhodactinia Davisii Ag.; natural size.

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 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 Actiniæ 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 jelly-fish, the Cyaneæ, 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. (Arachnactis brachiolata A. Ag.)

[Fig. 11]

Fig. 11. Arachnactis brachiolata A. Ag., greatly magnified.

[Fig. 12]

[Fig. 13]

Among the nomadic Polyps is a small floating Actinia, called Arachnactis, ([Fig. 11],) from its resemblance to a spider. They are found in great plenty floating about during the night, feeling their way in every direction by means of their tentacles, which are large in proportion to the size of the animal, few in number, and turned downward when in their natural attitude. The partitions and the digestive cavity enclosed between them are short, as will be seen in [Fig. 11], when compared to the general cavity of the body floating balloon-like above them. Around the mouth is a second row of shorter tentacles, better seen in a younger specimen ([Fig. 12]). This Actinia differs from those described above, in having two of the sides flattened, instead of being perfectly circular. Looked at from above (as in [Fig. 13]) this difference in 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 the slightly pointed folds or projections on opposite sides of the circle formed by the mouth, which in the Arachnactis are so elongated as to produce a somewhat narrow slit (see [ 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 Actiniæ.

Bicidium. (Bicidium parasiticum Ag.)

[Fig. 14]

Fig. 14. Bicidium parasiticum; natural size.

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 like an elongated cone, strongly ribbed from apex to base. At the base, viz. at the month 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 membranes 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 clinging quite firmly if any attempt is made to remove it. The general color of the body is violet or a brownish red, though the wrinkles give it a somewhat mottled appearance.

Halcampa. (Halcampa albida Ag.)

[Fig. 15]

Fig. 15. Halcampa albida; natural size.

Strange to say, the Actiniæ, 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 Actiniæ, 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, resembling a worm, as it burrows its way through the sand. It is of a pale yellowish color, with whitish warts on the surface.

MADREPORIANS.

Astrangia. (Astrangia Danæ 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 Massachusetts 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 title, because any account of the Radiates, from which so important a group as that of the corals was excluded, would be very incomplete.

[Fig. 16]

Fig. 16. Astrangia colony; natural size.

This pretty coral of our Northern waters is no reef-builder, and does not extend farther south than the shores of North Carolina. It usually establishes itself upon broken 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 unite 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 not unlike the star-shaped pits on a coral head, formed by Astræans. Unlike the massive compact kinds of coral, however, the individuals multiply by budding from the base chiefly, never rising one above the other, but spreading over the surface on which they have established themselves, a few additional individuals arising between the older ones. In consequence of this mode of growth, such a community, 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, the surface of every such mound 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 may be so unfortunate as to come within its reach.

[fig. 17]

[fig. 18]

[fig. 19]

[fig. 20]

Fig. 17. Magnified individuals of an Astrangia community in different stages of expansion. Fig. 19. Magnified lasso-cell of Astrangia.

Fig. 18. Single individual of Astrangia, fully expanded. Fig. 20. Limestone parts of an individual of Astrangia; magnified.

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 the body. As in all the Polyps, radiating partitions 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 chambers. But the feature which distinguishes them from the soft Actiniæ, 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 one fifth the height of the animal at its greatest extension. This lime deposit does not, however, fill the chamber for its whole width, but rises as a thin wall in its centre. (See [Figs. 13], [17].) Thus between all the soft partitions, in the middle of the chambers which separate them, low limestone walls are gradually built up, uniting in a solid column in the 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 lamellæ, so conspicuous 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 which, this wall is marked by faint vertical ribs.

HALCYONOIDS.

Halcyonium. (Halcyonium carneum Ag.)

[Fig. 21]

Fig. 21. Single individual of Halcyonium seen from above; magnified.

We come now to the Halcyonoids, represented in our waters by the Halcyonium ([Fig. 22]). In the Halcyonoids, 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 structural features, places them at the head of their class. The number of tentacles throughout this group is always eight. They are very complicated ([Fig. 21]), in comparison with the tentacles of the lower orders, being deeply lobed, and fringed around the margin. Our Halcyonium communities ([Fig. 22]) usually live in deep water, attached to dead shells, though they may occasionally be found growing at low-water mark, but this is very rare. They have received a rather lugubrious name from the fishermen, who call them "dead-men's fingers," and indeed, when the animals are contracted, such a community, with its short branches attached to the main stock, looks not unlike the stump of a hand, with short, 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. But when the animals, which are capable of great extension, are fully spread, as in [Fig. 22], such a polyp-stock has a mossy, tufted look, and 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 through the walls of the body; we can then easily distinguish the digestive cavity, supported for its whole length by the eight radiating partitions, as well as the great size of the main digestive cavity surrounding it. Notwithstanding the remarkable power of contraction and dilatation in the animals themselves, the tentacles are but slightly contractile. This kind of community increases altogether by budding, 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 semi-cartilaginous pulp, uniting the whole community. In the neighborhood of Provincetown they are very plentiful, and are found all along the shores of our Bay in deep water.

[Fig. 22]

[Fig. 23]

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 planulæ 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 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 Ctenophoræ, so-called on account of their locomotive organs, consisting of minute flappers arranged in vertical comb-like rows; next to these are the Discophoræ, 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 Ctenophoræ grow from eggs by a direct continuous process of development, without undergoing any striking metamorphosis; the Discophoræ, with some few exceptions, in which they develop like the Ctenophoræ 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 Jelly-fishes; the Hydroids include all those Acalephs which either pass the earlier stages of their existence as little shrub-like communities, or remain in that condition through life. These Hydroid 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 Polyps so much, that it has long been associated with them. The Millepore is a coral, 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], [26]) has recently shown that it belongs with the Acalephs.[2] 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 in the earliest periods of creation, since it refers a large number of fossil corals, whose affinities with the millepores are well understood, to that class, instead of to the class of Polyps with which they had hitherto been associated. But for this we should have no positive evidence of the existence of Acalephs in early geological periods, the gelatinous texture of the ordinary Jelly-fishes making their preservation almost impossible. It is not strange that the true nature of this animal should have remained so long unexplained; for it is only by the soft parts of the body, not of course preserved in the fossil condition, that their relations to the Acalephs may be detected; and they are so shy of approach, 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.

[2] See "Methods of Study," by Prof. Agassiz.

[Fig. 24]

[Fig. 25]

[Fig. 26]

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 Hydræ 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 outer-most 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, Astræans, 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 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 Jelly-fishes, 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, Medusæ, 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. 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 jaw-breaking 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 Linnæa borealis was well named after his famous master, by a disciple of the great Norwegian naturalist; Goethea 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 Linnæus after Buffon, whom he bitterly hated. Indeed, there is a world of meaning hidden under our zoölogical 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.

CTENOPHORÆ.

The Ctenophoræ differ from other Jelly-fishes in their mode of locomotion. All the Discophorous Medusæ, 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 Ctenophoræ there is no such regular expansion and contraction of the disk; they are at once distinguished from the Discophoræ 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 independently 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.[3]

[3] 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.

These locomotive appendages are intimately connected with the circulating tubes, as we shall see when we examine the structural 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 Ctenophoræ 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]). This divergence from the globular form, so slight in Pleurobrachia as to be hardly perceptible to the casual observer, establishing two diameters of different lengths at right angles with each other, is equally true of the other genera. It is interesting and important, as showing the tendency in this highest group of Acalephs to assume a bilateral character. This bilaterality becomes still more marked in the highest class of Radiates, the Echinoderms. Such structural tendencies in the lower animals, hinting at laws to be more fully developed in the higher forms, are always significant, 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.

[Fig. 27]

[Fig. 28]

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 eye-speck 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 matter-of-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 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 the tank in which the animal floating, and one thinks for a moment, so slight is the thread-like attachment, that it has actually fallen from the body; but watch a little longer, and all the filaments spread out along the side of the thread, it expands to its full length and breadth, and resumes all its graceful evolutions.

[Fig. 29]

[Fig. 30]

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 tubes. Toward the opposite end of the body these tubes terminate or unite in a single funnel-like canal, which is a reservoir as it were for the circulating fluid poured into it through an opening in the bottom of the digestive cavity. The food in the digestive cavity becomes liquefied by mingling with the water entering with it at the mouth, 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 tubes, 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, those again ramifying in two directions as they approach the periphery, so that each one of the first main tubes has multiplied to four, before its ramifications reach the surface, thus making in all eight radiating tubes. So far, these eight tubes are horizontal, all diverging on 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 . As in all the Ctenophoræ, 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 (Figs. [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 to pole, 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.

Bolina. (Bolina alata Ag.)

[Fig 31]

[Fig 32]

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 widely, or they may close completely over the mouth so as to hide it from view, and their different aspects under various degrees of expansion or contraction account for the discrepancies in the description of these animals. We have seen that the Pleurobrachia moves with the mouth upward; but the Bolina, on the contrary, usually carries 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 as the larger lobes, though less developed. The rows of locomotive flappers on the Bolina differ in length from each other ([Fig. 31]), instead of being equal, as in the Pleurobrachia. The four longest ones are opposite each other on those sides of the body 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 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.)

[Fig. 33]

Fig. 33. Idyia roseola seen from the broad side, half natural size; a anal opening, b lateral tube, c circular tube, d e f g h rows of locomotive flappers. (Agassiz.)

The lowest genus of Ctenophoræ 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 to be the almost exclusive function of this animal, for it has a mouth whose ample dimensions correspond with its capacious stomach. Instead of the longitudinal split serving as a mouth, in the Bolina and Pleurobrachia, one end of the body in the Idyia is completely open ([Fig. 33]), so that occasionally some unsuspicious victim of smaller diameter than itself may be seen to swim into this wide portal, when suddenly the door closes behind him with a quick contraction, and he finds himself a prisoner. The Idyia does not always obtain its food after this indolent fashion however, for it often attacks a Bolina or Pleurobrachia as large or even larger than itself, when it extends its mouth to the utmost, slowly overlapping the prey it is trying to swallow by frequent and repeated contractions, and even cutting off by the same process such portions as cannot be forced into the digestive cavity.

The general internal structure of the Idyia corresponds with that of the Bolina and Pleurobrachia; it has the same tubes branching horizontally from the main cavity, then ramifying as they approach the periphery till they are multiplied to eight in all, each of which gives off one of the vertical tubes connected with the eight rows of locomotive flappers. Opposite the mouth is the eye-speck, placed as in the two other genera, at the centre of a small circumscribed area, which in the Idyia is surrounded by delicate fringes, forming a rosette at this end of the body. These animals are exceedingly brilliant in color; bright pink is their prevailing hue, though pink, red, yellow, orange, green, and purple, sometimes chase each other in quick succession along their locomotive fringes. At certain seasons, when most numerous, they even give a rosy tinge to patches on the surface of the sea. Their color is brightest and deepest before the spawning season, but as this advances, and the ovaries and spermaries are emptied, they grow paler, retaining at last only a faint pink tint. They appear early in July, rapidly attain their maximum size, and are most numerous during the first half of August. Toward the end of August they spawn, and the adults are usually destroyed by the early September storms, the young disappearing at the same time, not to be seen again till the next summer. It is an interesting question, not yet solved, to know what becomes of the summer's brood in the following winter. They probably sink into deep waters during this intervening period. The Idyia, like the Pleurobrachia, moves with the mouth upward, but inclined slightly forward also, so as to give an oblique direction to the axis of the body.[4]

[4] Until this summer only the three genera of Ctenophoræ above mentioned were supposed to exist along our coast, but during the present season I have had the good fortune to find two additional ones. One of them, the Lesueuria, resembles a Bolina with the long lobes so cut off, that they have a very stunted appearance in comparison with those of the Bolina. The other, the Mertensia, is closely allied to Pleurobrachia; it is exceedingly flattened and pear-shaped. This species was discovered long ago by Fabricius, but had escaped thus far the attention of other naturalists. (A. Agassiz.)

EMBRYOLOGY OF CTENOPHORÆ.

All the Ctenophoræ are reproduced from eggs, these eggs being so transparent that one may follow with comparative ease the changes undergone by the young while still within the egg envelope. Unfortunately, however, they are so delicate that it is impossible to keep them alive for any length of time, even by supplying them constantly with fresh sea-water, and keeping them continually in motion, both of which are essential conditions to their existence. It is therefore only from eggs accidentally fished up at different stages of growth that we may hope to ascertain any facts respecting the sequence of their development. When hatched, the little Ctenophore is already quite advanced. It is small when compared with the size of the egg envelope, and long before it is set free, it swims about with great velocity within the walls of its diminutive prison ([Fig. 35]). The importance of studying the young stages of animals can hardly find a better illustration than among the Ctenophoræ. Before their extraordinary embryonic changes were understood, many of the younger forms had found their way into our scientific annals as distinct animals, and our nomenclature thus became burdened with long lists of names which will disappear as our knowledge advances.

The great size of their locomotive flappers in proportion to the rest of the body, is characteristic of the young Ctenophoræ. They seem like large paddles on the sides of these tiny transparent spheres, and, owing to their great power as compared with those of the adult, the young move with extraordinary rapidity. The Pleurobrachia alone retains its quickness of motion in after life, and although its long graceful streamers appear only as short stumpy tentacles in the young ([Fig. 34]), yet its active little body would be more easily recognized in the earlier stages of growth than that of the other Ctenophoræ. Figs. [34], [35], and [36] show the Pleurobrachia at various stages of growth; [Fig. 34], with its thick stunted tentacles and short rows of flappers, is the youngest; the flappers themselves are rather long at this age, looking more like stiff hairs than like the minute fringes of the adult. In [Fig. 35] the tentacles are already considerably longer and more delicate; in [Fig. 36] the vertical tubes are already completed, while Figs. [27]-[29] present it in its adult condition.

[fig 34]

[fig 35]

[fig 36]

[fig 37]

[fig 38]

Fig. 38. Young Idyia seen from the anal extremity, magnified; a anal opening, other letters as in [Fig. 36].

The Idyia differs greatly in appearance at different periods of its development, and, indeed, no one would suspect, without some previous knowledge of its transformations, that the young Idyia, with its rapid gyrations, its short ambulacral tubes, like immense pouches ([Fig. 37]), its large pigment spots scattered over the surface ([Fig. 38]), was an earlier stage of the rosy-hued Idyia, which glides through the water with a scarcely perceptible motion. Figs. [37]-[40] represent the various stages of its growth. It will be seen how very short are the locomotive fringes ([Fig. 39]) in comparison with those of the full-grown ones ([Fig. 33]). It is only in the adult Idyia that these rows attain their full height, and the tubes, ramifying throughout the body ([Fig. 40]), are completed.

[fig 39]

[fig 40]

The Bolina, in its early condition, recalls the young Pleurobrachia. At this period it has the same rapid motion, and when somewhat more advanced, long tentacles, resembling those of the Pleurobrachia, make their appearance ([Fig. 41]); it is only at a later period that the tentacles become contracted, while the large lobes ([Fig. 42]), so characteristic of Bolina, are formed by the elongation of the oral end of the body, the auricles becoming more conspicuous at the same time ([Fig. 43]). A little later the lobes enlarge, the movements become more lazy; it assumes both in form and habits the character of the adult Bolina.

[fig 41]

[fig 42]

[fig 43]

The series of changes through which the Ctenophoræ pass are as remarkable as any we shall have occasion to describe, though not accompanied with such absolutely different conditions of existence. The comparison of the earlier stages of life in these animals with their adult condition is important, not only with reference to their mode of development, but also because it gives us some insight into the relative standing of the different groups, since it shows us that certain features, permanent in the lower groups, are transient in the higher ones. A striking instance of this occurs in the fact mentioned above, that though the long tentacles so characteristic of the adult Pleurobrachia exist in the young Bolina, they yield in importance at a later period to the lobes which eventually become the predominant and characteristic feature of the latter.

DISCOPHORÆ.

The disk of the Discophoræ is by no means so delicate as that of the other Jelly-fishes. It seems indeed quite solid, and somewhat like cartilage to the touch, and yet so large a part of its bulk consists of water, that a Cyanea, weighing when alive about thirty-four pounds, being left to dry in the sun for some days, was found to have lost about 99/100 of its original weight,—only the merest film remaining on the paper upon which it had been laid. The prominence of the disk in this group of Jelly-fishes is well characterized by their German name, "Scheiben quallen," viz. disk-medusæ. We shall see hereafter that the disk, so large and seemingly solid in the Discophoræ, thins out in many of the other Jelly-fishes, and becomes exceedingly concave. This is especially the case in many of the Hydroid Medusæ, where it assumes a bell-shaped form, and is constantly spoken of as the bell. It should be remembered, however, in reading descriptions of these animals, that the so-called bell is only a modified disk, and perfectly homologous with that organ in the Discophoræ.

The Discophorous Medusæ are distinguished from all others by the peculiar nature of the reproductive organs. They are contained in pouches ([Fig. 50], o, o, o, o), the contents of which are first discharged into the main cavity, and then pass out through the mouth. Pillars support the four angles of the digestive cavity, thus separating the lower from the upper floor of the disk, while the chymiferous tubes ([Fig. 50]) branch and run into each other near the periphery, forming a more or less complicated anastomosing network, instead of a simple circular tube, as is the case with the Hydroid Medusæ. ([Fig. 74.])

Cyanea. (Cyanea arctica Pér. et Les.)

In our descriptions of the Discophoræ, we may give the precedence to the Cyanea on account of its size. This giant among Jelly-fishes is represented in [Fig. 44]. It is much to be regretted that these animals, when they are not so small as to escape attention altogether, are usually seen out of their native element, thrown dead or dying on the shore, a mass of decaying gelatinous matter. All persons who have lived near the sea are familiar with the so-called Sea-blubbers, sometimes strewing the sandy beaches after the autumn storms in such numbers that it is difficult to avoid them in walking or driving. In such a condition the Cyanea is far from being an attractive object; to form an idea of his true appearance, one must meet him as he swims along at midday, rather lazily withal, his huge semi-transparent disk, with its flexible lobed margin, glittering in the sun, and his tentacles floating to a distance of many yards behind him. Encountering one of those huge Jelly-fishes, when out in a row-boat one day, we attempted to make a rough measurement of his dimensions upon the spot. He was lying quietly near the surface, and did not seem in the least disturbed by the proceeding, but allowed the oar, eight feet in length, to be laid across the disk, which proved to be about seven feet in diameter. Backing the boat slowly along the line of the tentacles, which were floating at their utmost extension behind him, we then measured these in the same manner, and found them to be rather more than fourteen times the length of the oar, thus covering a space of some hundred and twelve feet. This sounds so marvellous that it may be taken as an exaggeration; but though such an estimate could not of course be absolutely accurate, yet the facts are rather understated than overstated in the dimensions here given. And, indeed, the observation was more careful and precise than the circumstances would lead one to suppose, for the creature lay as quietly, while his measure was taken, as if he had intended to give every facility for the operation. This specimen was, however, of unusual size; they more commonly measure from three to five feet across the disk, while the tentacles may be thirty or forty feet long. The tentacles are exceedingly numerous (see [Fig. 44]), arising in eight distinct bunches, from the margin of the disk, and hanging down in a complete labyrinth.

These animals are not so harmless as it would seem, from their soft, gelatinous consistency; it is no pleasant thing when swimming or bathing to become entangled in this forest of fine feelers, for they have a stinging property like nettles, and may render a person almost insensible, partly from pain, and partly from a numbness produced by their contact, before he is able to free himself from the network in which he is caught. The weapons by which they produce these results seem so insignificant, that one cannot but wonder at their power. The tentacles are covered by minute cells, lasso-cells as they are called, (similar to those of Astrangia, [Fig. 19],) each one of which contains a whip finer than the finest thread, coiled in a spiral within it.

[fig 44]

These myriad whips can be thrown out at the will of the animal, and really form an efficient galvanic battery. Behind the veil of tentacles, and partly hidden by it, four curtains, with lobed or ruffled margins, dimly seen in [Fig. 44], hang down from the under surface of the disk. The ovaries are formed by four pendent pouches, placed near the sides of the mouth, and attached to four cavities within the disk. Around the circumference of the disk are eight eye-specks, each formed by a small tube protected under a little lappet or hood rising from the upper surface of the disk. The prevailing color of this huge Jelly-fish is a dark brownish-red, with a light, milk-white margin, tinged with blue, the tentacles and other pendent appendages having a somewhat different hue from the disk. The ovaries are flesh-colored, the curtain formed by the expansion of the lobes of the mouth is dark brown, while the tentacles are of different colors, some being yellow, others purple, and others reddish brown or pink.

[fig 45]

[fig 46]

[fig 47]

Fig. 45. Scyphistoma of a Discophore; Aurelia flavidula. (Agassiz.)		Fig. 47. Strobila of a Discophore; Aurelia flavidula. (Agassiz.)		Fig. 46. Scyphistoma, older than Fig. 45. (Agassiz.)

[fig 48]

Fig. 48. Ephyra of a Discophore; Aurelia flavidula. (Agassiz.)

Strange to say, this gigantic Discophore is produced by a Hydroid measuring not more than half an inch in height when full grown; could we follow the history of any egg laid by one of these Discophoræ in the autumn, and this has indeed been partially done, we should see that, like any other planula, the young hatched from the egg is at first spherical, but presently becomes pear-shaped, and attaches itself to the ground. From the upper end tentacles project (see [Fig. 45]), growing more numerous, as in [Fig. 46], though they never exceed sixteen in number. As it increases in height constrictions take place at different distances along its length, every such constriction being lobed around its margin, till at last it looks like a pile of scalloped saucers or disks strung together (see [Fig. 47]). The topmost of these disks falls off and dies; but all the others separate by the deepening of the constrictions, and swim off as little free disks ([Fig. 48]), which eventually grow into the enormous Jelly-fish described above. These three phases of growth, before the relation between them was understood, have been mistaken for distinct animals, and described as such under the names of Scyphistoma, Strobila, and Ephyra.

Aurelia. (Aurelia flavidula Pér. et Les.)

[fig 49]

Fig. 49. Aurelia seen in profile, reduced. (Agassiz.)

Another large Discophore, though by no means to be compared to the Cyanea in size, is our common Aurelia ([Figs. 49],[ 50]) Its bluish-white disk measures from twelve to fifteen inches in diameter, but its dimensions are not increased by the tentacles, which have no great power of contraction and expansion, and form a short fringe around its margin, widening and narrowing slightly as the tentacles are stretched or drawn in. It is quite transparent, as may be seen in [Fig 49], where all the fine ramifications of the chymiferous tubes as well as the ovaries, are seen through the vault of the disk. [Fig. 50] represents the upper surface, with the ovaries around the mouth, occupying the same position as those of the Cyanea, though they differ from the latter in their greater rigidity, and do not hang down in the form of pouches. The males and females in this kind of Jelly-fish may be distinguished by the difference of color in the reproductive organs, which are rose-colored in the males, and of a dull yellow in the females. The process of development is exactly the same in the Aurelia as in the Cyanea, though there is a very slight difference in their respective Hydroids. They are, however, so much alike, that one is here made to serve for both, the above figures being taken from the Hydroid of the Aurelia. It is curious, that while, as in the case of the Aurelia and Cyanea, very dissimilar Jelly-fishes may arise from almost identical Hydroids, we have the reverse of the proposition, in the fact that Hydroids of an entirely distinct character may produce similar Jelly-fishes.

[fig 50]

Fig. 50. Aurelia flavidula, seen from above; o mouth, e e e e eyes, m m m m lobes of the mouth, o o o o ovaries, t t t t tentacles, w w ramified tubes.(Agassiz.)

The embryos or little planulæ, hatched from the Cyanea and Aurelia in the fall, seem to be gregarious in their mode of life, swimming about together in great numbers till they find a suitable point of attachment, and assume their fixed Hydroid existence. The Cyaneæ, however, when adult, are usually found singly, while the Aureliæ, on the contrary, seek each other, and commonly herd together.

The Campanella. (Campanella pachyderma A. Ag.)

[fig 51]

Fig. 51. Campanella seen in profile; greatly magnified.

[fig 52]

Fig. 52. Same, seen from below.

The Campanella ([Fig. 51]) is a pretty little Jelly-fish, not larger than a pin's head, reproduced directly from eggs, without passing through the Hydroid stage. During its early stages of growth it probably remains attached to floating animals, thus leading a kind of parasitic existence; but as its habits are not accurately known, this cannot be asserted as a constant fact respecting them. The veil in this Jelly-fish is very large, forming pendent pouches hanging from the circular canal (see [Fig. 51]), and leaving but just room enough for the passage of the proboscis between the folds. It may not be amiss to introduce here a general account of this organ, which occurs in many of the Medusæ, though it has very different proportions in the various kinds. It is a delicate membrane, hanging from the circular tube, so as partially to close the mouth of the bell, leaving a larger or smaller opening for the passage of the water, which is taken in and forced out again by the alternate expansions and contractions of the bell.

There are but four chymiferous tubes in the Campanella, and four stiff tentacles, which in consequence of the peculiar character of the veil appear, when the animal is seen in profile, to start from the middle of the disk. The ovaries consist of eight pouches, placed near the point of junction of the four chymiferous tubes. ([Fig. 52.]) This little Medusa is of a dark yellowish color with brownish ocellated spots, scattered profusely over the upper part of the disk.

Circe. (Trachynema digitale A. Ag.)

[fig 53]

Fig. 53. Trachynema digitale; about twice the natural size.

Among the Jelly-fishes, the position of which is somewhat doubtful, is the Circe ([Fig. 53]), differing greatly in outline from the ordinary Jelly-fishes. As may be seen in [Figure 53], the bell forms but a small portion of the animal; it rises in a sharp cone on the summit, thinning out at the lower edge, to form the large cavity in which hangs the long proboscis and the eight ovaries, four of which may be seen in [Fig. 53] crowded with eggs. The Circe differs in consistency, as well as in form, from other Jelly-fishes. It is hard and horny to the touch, and the veil, usually so light and filmy, is here a thick folded membrane, which at every stroke of the animal forces the water in and out of the cavity. It is very active, moving by powerful jerks, each one of which throws it far on its way. It advances usually in straight lines; or, if it wishes to change its direction, it drives the water out of the veil suddenly on one side or the other, so as to shoot off, sometimes at right angles with its former path. Four large pedunculated eyes, hidden in the figure by the tentacles, stand out prominently from the circular tube. When the animal is in motion, the tentacles are carried closely curled around the edge of the disk, as in [Fig. 53], where the Circe is represented under a magnifying power of two and a half diameters. This Jelly-fish is of a delicate rose color, the tentacles assuming, however, a dark-purple tint at their extremities when contracted.

Lucernaria. (Haliclystus auricula Clark.)

[fig 54]

[fig 55]

One of the prettiest and most graceful, as well as one of the most common of our Jelly-fishes, is the Lucernaria ([Fig. 54]). It has such an extraordinary contractility of all its parts, that it is not easy to describe it under any definite form or position, since both are constantly changing; but perhaps of all its various attitudes and outlines none are more normal to it than those given in [Fig. 54]. It frequently raises itself in the upright position represented here by the individual highest on the stem, spreading itself in the form of a perfectly symmetrical cup or vase, the margin of which is indented by a succession of inverted scallops, the point of junction between every two scallops being crowned by a tuft of tentacles. But watch it for a while, and the sides of this vase turn backward, spreading completely open, till they present the whole inner surface, with the edges even curved a little downward, drooping slightly, and the proboscis rising in the centre. In such an attitude one may trace with ease the shape of the mouth, the lobes surrounding it, as well as the tubes and cavities radiating from it toward the margin. A touch is, however, sufficient to make it close upon itself, shrinking together in the attitude of the third individual in [Fig. 54], or even drawing its tentacles completely in, and contracting all its parts till it looks like a little ball hanging on the stem. These are but a few of its manifold changes, for it may be seen in every phase of expansion and contraction. Let us now look for a moment at the details of its structure. The resemblance to a cup or vase, as in the upper figure of the wood-cut ([Fig. 54]), is deceptive; for a vase is hollow, whereas the Lucernaria, though so delicate and transparent that its upper surface, when thus stretched, seems like a mere film, is nevertheless a solid gelatinous mass, traversed by certain channels, cavities, and partitions, but otherwise continuous throughout. The peduncle by which it is attached is but an extension of the floor of a gelatinous disk, corresponding to that of any Jelly-fish. Four tubes pass through the whole length of this peduncle, and open into four chambers, dividing the digestive cavity above into as many equal spaces. ([Fig. 55.]) These spaces are produced by folds in the upper floor of the disk, uniting it to the lower floor at given distances, and forming so many partition-walls, dividing the digestive sac into four distinct cavities. These lines of juncture between the two floors, where the partitions occur, produce the four radiating lines, running from the proboscis to the margin of the disk, on the upper surface. ([Fig. 55.]) The triangular figures, running from the mouth to each cluster of tentacles, are produced by the ovaries, which consist of distinct pouches or bags attached to the upper surface of the disk, and hanging down into the cavities below; every little dot within these triangular spaces represents such a bag. Each bag is crowded with eggs, which drop into the digestive cavity at the spawning season, and are passed out at the mouth. The tentacles always grow in clusters, but are nevertheless arranged according to a regular order. They are club-shaped at their extremities, but are hollow throughout, opening into the chambers of the digestive cavity, two of the clusters thus being connected with each chamber. Their chief office seems to be to catch the food and convey it to the mouth, though they may also be used as a kind of suckers, and the animal not unfrequently attaches itself by means of these appendages. Between every two clusters of tentacles will be observed a short, single appendage, of an entirely different appearance. These are the so-called auricles, and though so unlike tentacles in the adult animal, when in their earlier stages ([Fig. 56]) they resemble each other closely. But as their development goes on, the tentacles stretch out into longer, more delicate flexible organs, while the auricles remain short and compact throughout life. They contain a slight pigment spot representing an eye, though how far it serves the purpose of vision remains doubtful. They are chiefly used by the animal as a means of adhering to any surface upon which it may wish to fasten itself; for the Lucernaria, though usually found attached to eel-grass in shoal water, has the power of independent motion, and frequently separates from its resting-place, floating about freely in the water for a while, or attaching itself anew by means of the auricles and tentacles upon some other object. The color of this pretty Acaleph varies from a greenish hue to green, with a faint tinge of red, or to a reddish brown. One of its commonest and most exquisite tints is that of a pale aqua-marine. It may be found along our shores wherever the eel-grass grows, and as far out as this plant extends. It thrives admirably in confinement, and for this reason is especially adapted to the aquarium.

[fig 56]

Fig. 56. Young Lucernaria; magnified.

HYDROIDS.

Under this order, the general character of which has already been explained in the introductory chapter on Acalephs, are included a number of groups which, whether as Hydroid communities in their earlier phases of existence, or as free swimming Medusæ in their farther development, challenge our admiration, both for their beauty of form and color, and their grace of motion. Some of them are so minute that they escape the observation of all but those who are laboriously seeking for the hidden treasures of the microscopic world, but the greater number are large enough to be readily found by the most inexperienced collector, when his attention is once drawn to them; and he may easily stock his aquarium with these pretty little communities, and even trace the development of the Jelly-fishes upon them.

To the Hydroids belong the Campanularians, the Sertularians, and the Tubularians. Some examples of each, as represented on our shores, will be found under their different heads, accompanied with full descriptions. There is another group usually considered as distinct from Hydroids, and known as a separate order among Acalephs, under the name of Siphonophoræ, but included with them here in accordance with the views of Vogt, Agassiz, and others, in whose opinion they differ from the ordinary Hydroid communities only in being free and floating, instead of fixed to the ground. Some new facts, published here for the first time, tend to sustain the accuracy of this classification.[5] With these few preliminary remarks to show the connection of the order, let us now look at some of the animals belonging to it more in detail.

[5] See Chapter on Nanomia.

Campanularians.

All the Campanularians, of which Oceania ([Fig. 68]), Clytia (Fig. 73), and Eucope ([Fig. 61]) form a part, belong among those little shrub-like communities of animals called Hydroids, from which most of our Jelly-fishes are developed. They differ in one essential feature from the Tubularians. ([Fig. 93.]) The whole stem, from summit to base, is enveloped in a horny sheath, extending around both the fertile and sterile individuals of the community, and forming a network at the base of the stem, which serves as a kind of foundation for the whole stock. To the naked eye such a community looks like a tiny shrub (see [Fig. 57]), with the branches growing in regular alternation on either side of the stems. The reproductive calycles, i.e. the protecting envelopes covering the young Medusæ, usually arise in the angles of the branches formed by a prolongation of the sheath. These calycles or bells, as they are called, assume a great variety of shapes,—elliptical, round, pear-shaped, or ringed like the Clytia. ([Fig. 72.]) In one such bell there may be no less than twenty or thirty Medusæ developed one below the other; when ready to hatch, the calycle bursts and allows them to escape.

Eucope. (Eucope diaphana Ag.)

In Figs. [60] and [61] we have a representation of our little Eucope, one of the prettiest of the Jelly-fishes belonging to this group; [Fig. 57] represents the Hydroid from which it arises; a single branch with the reproductive bell being magnified in [Fig.58]. In [Fig. 59] is seen a portion of the Jelly-fish disk, with the fringe of tentacles highly magnified. The disk of the Eucope ([Fig. 60]) looks like a shallow bell, of which the proboscis often seems to form the handle; for the disk has such an extraordinary thinness that it turns inside out with the greatest ease, so that the inner surface may become at any moment the outer one, with the proboscis projecting from it, as in [Fig. 60], while the next movement of the animal may reverse its whole position, and the proboscis then hangs down from the inside, as in other Jelly-fishes. (See [Fig. 61].)

[fig 57]

[fig 58]

[fig 58]

[fig 60]

[fig 61]

[fig 62]