ZOOPHYTES.

When the word Zoophyte began to be used by naturalists, it designated a miscellaneous class of beings, which were believed to occupy the space between the animal and vegetable kingdoms, and in which the characteristics of the subjects of each met and were intermingled. They were of a “middle nature,” not because of their outward resemblance to plants, but because they were deficient in the more obvious qualities of animals, and were apparently more influenced by exterior forces than by any volitions springing up within. Almost insensible and immotive, their weak and obscure life was merely regarded as one of vegetation, engendered in them by putrefaction or fermentation, and unsusceptible of the volitions and passions which move and agitate higher entities. Thus the term indicated a mingled life or constitution, and had no reference to figure; but some time after it had been allowed on all hands that the productions in question were “better than mere vege-tives,” another class of objects, hitherto supposed to be altogether vegetable, was ascertained to be of animal origin; and as their similitude to mosses and lichens, to sea-weeds and mushrooms, was undeniable, and indeed so remarkable as to have long veiled their nature from us, so the term Zoophyte was transferred to this newly-discovered order, and has since been applied by the majority of English authors to it alone. With continental naturalists, however, the word has still its widest application, embracing, in their nomenclature, not merely those polypiferous beings which cover the bottom of the ocean with a singularly exact mimickry of vegetation, but also the star-fishes and sea-urchins, the sea-figs and sea-nettles or jelly-fish, and even the intestinal worms. It is in this wide acceptation that the word is employed by Cuvier and Blainville; and we use it here with the same latitude, agreeably to the plan indicated in our article Animal Kingdom .

The Zoophytes, then, as defined by Cuvier, form a sub-kingdom co-equal with the two divisions in the animal kingdom named Radiata and Acrita by Macleay. The classes included in it have less of a common resemblance than the classes of any other sub-kingdom, so that in the great variety of structures which they present to our study, we seek in vain for any one character that shall connect them together. The most general character is that which has conferred upon them the synonyme of “Radiated Animals,” given because the organs of locomotion, and even the internal viscera, are arranged very often in a circular disposition round a centre, so as to give a sort of radiant appearance to the whole body, or to some part of it. The nervous system is at the best only rudimentary, and is demonstrable only in a few genera of three of the classes. Thus its existence has been shewn in several species of intestinal worms, where it consists of one or two ganglions placed near the mouth, and from which diverge a few filaments, and one or two longer chords that follow down the length of the body. In the more normal Zoophytes, the nervous system forms a circle round the oral aperture, whence slender filaments radiate towards the circumference, rarely dividing into a few branchlets, and losing themselves in the parenchyma long before they reach the periphery. But in the larger number of this sub-kingdom no trace of such a system is discoverable, unless, with Macleay, we find it in the “minute granulations” which bespeck their homogeneous, mobile, and irritable pulp, and “which may be considered as the nervous molecules dispersed over, or, as it were, confounded with, the substance of these animals, so as to impregnate the whole with sensibility.” This property of animal life they accordingly enjoy in a high degree of development, while their instincts are reduced almost to a nullity; and in regard to the external senses, it may with truth be said of most of them, that they are “sans teeth, sans eyes, sans taste, sans every thing.”^[1. “Imperfecta veteribus, nec inepte, dicta animantia, destituuntur capite, auribus, naso, oculis, pleraque pedibus; ab insectis itaque diversissima, a quibus dudum removi naturae cryptogama.”—Linnaei Systema Natura, 1069. ] They are almost, without exception, indolent and slow of movement, some advancing by the writhings and contractions of a soft body; some by the play of invisible cilia, which garnish, in set rows, their appendages; and others by the aid of hollow extensible tentacular suckers; while many among them are rooted, and as fixed as the plants whose graceful forms they seem to envy, and strive to emulate.

There is, according to Cuvier, no true system of a circulation in any Zoophyte; but Nordmann has delineated a very beautiful system of vessels, apparently sanguiferous, in some intestinal worms; and a similar one has been shewn to exist in the Planariae, and in some external parasites, as in the genus Phylline. Among the more regular Zoophytes, we find very generally a system of aqueducts, which permeate and ramify through the body, but which are distinguished from any circulatory vessels by having a direct communication with the water in which the animal floats. This system is mainly subservient to locomotion; but to a certain extent it must supply the purposes of a circulation in higher organisms, for the fresh currents of water which it leads within the body will oxygenate, and render fit for assimilation the nutritive materials that come within their reach and influence. The Holothuriae afford a good illustration of this double function, for they have two aquiferous systems; one connected with the intestines, and in correspondency with the organs of respiration; the other subservient only to the turgescency and relaxation of the organs that perform the offices of feet. This latter system only, it is said, can be discovered in the star-fishes and sea-urchins; while the vascular canals that ramify like veins through the clear gelatinous bodies of the sea-jellies, originating in the alimentary cavities, and running in divergent lines to the circumference, seem to constitute a system accessory principally to respiration and nutrition. In many fixed polypiferous Zoophytes, there are also found ducts for introducing water within the body; and in others, where these aquiferous ducts have no existence, the surface or appendages of the little creature are clothed with minute vibratile cilia, that constitute a real breathing apparatus.

Some families, such as the holothuriae, the sea-urchins, and several intestinal worms, as well as some polypiferous Zoophytes, have a mouth, an alimentary canal, and an excrementitious or anal orifice; others have a kind of stomach with only one orifice, which is by turns a mouth and a vent; in a great number there is merely a digestive cavity, excavated in the substance of the body, for the reception of the food, which enters sometimes by one and sometimes by several orifices; and in other Zoophytes of abnormal character there is no mouth, and we suppose that these must imbibe their nutritive matter by pores on the general surface.

The individuals of some species of intestinal worms are male and female, but in general the Zoophytes are hermaphroditical and oviparous. Some are propagated by a sort of gemmation, or by self-division. Many of them are compound animals; a kind of monster, in which often hundreds of individuals consociate, and are organically connected together, so as to make one living mass or commonwealth, that possesses all things in common, and usually shoots up in an arborescent form.
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Having premised these few remarks, we proceed to treat of this sub-kingdom under the following divisions or classes :— I. The Intestinal Worms ; II. The Echinodermata or Sea-stars; III. The Acalephae or Sea-Jellies; IV. The Polypes or Zoophytes properly so called; V. The Sponges ; and VI. The Lithophytes.

I.—INTESTINAL WORMS.^[2. Synonymes: ἕλμινϑες; Entelmintha; Vermes; Intestina; Vermes intestinales; Splanchnelmintha; Entozoa; Vers intestinaux. ]

It affords a striking illustration of the wide diffusion of animal life to have ascertained the fact, that almost every species of the vertebrated orders, and very many of the inferior classes, afford, either within or on the surface of the body, a place of nativity and domicile to one or more living creatures, framed with especial adaptation to the circumstances of their destined abodes. They do not however infest every animal indiscriminately; for, on the contrary, the parasites of almost every species are peculiar to itself, or they are confined to a few of analogous habits and structure. There are some partial exceptions. Thus, the fluke (Distoma hepaticum), so common in the liver and gall-ducts of sheep and other domestic cattle, is found occasionally in the liver of man, but comparatively so small as to have been sometimes looked upon as a distinct species. The Ascaris lumbricodes of man is identical with that found in the horse, the ox, and the sow; his Trichocephalus occurs in the ape; the Cysticercus of the cellular tissue is common to him and the ape and pig; and the Strongylus giganteus has a wide range, not fearing man, and rioting in the kidney of many of the inferior animals. Froelich took from a tropical parrot an Ascaris, which was apparently identical with a worm that Rudolphi found in our domestic pigeon; and similar examples, more especially from among the parasites of fishes, might be instanced.^[3. Of upwards of 200 species examined by Dr Bellingham, several occurred in six, others in ten, and one in fifteen different animals. ] But there is no example of a worm being common to a warm and a cold-blooded animal; nor does the same worm ever occur in the mammalia and in birds, nor in amphibia and in fishes; nor, indeed, in the species of any two well-distinguished classes; and so also it is ascertained that the parasites of the carnivorous animals (with the sole exception of the renal parasites) are in every instance different in kind from those of the vegetable feeders.

It must not however be concluded, that of the animals liable to the attacks of intestinal worms, every individual is vermigerous. On the contrary, the Entozoa in general are comparatively of rare occurrence, and many are so rare that few helminthologists, of however wide research, have ever met with them. Mr Lawrence has seen a female, who from time to time has voided many hundreds of small worms (Spiroptera hominis) from the urinary bladder;^[4. MedicoChirurg. Trans, ii. p. 382. Cyclop. of Anat. and Physiology, ii. p. 124. ] but, so far as is known, no other human being was ever so afflicted. Goeze found in the boar a Trichocephalus, which Rudolphi has sought for in vain both in wild and domestic swine; and he tells us he had dissected innumerable mice in a fruitless search after their Trichocephalus, described also by the first-named naturalist.^[5. Ent. Hist. Nat. ii. part ii. p. 96, 97. ] These are undoubtedly extreme cases, but they place in a strong light the partial and accidental diffusion of these creatures. What circumstances determine them to select one individual in preference to another, are unknown, though reasons enough have been stated, of all which it may be safely said that the facts adverse to their admission are almost as many as those in their favour. There is no denying that worms in general often infest the delicate and sickly; that youth is favourable to the evolution of some, and maturity to that of others; and females may be more verminous than males; but the contraries are numerous, and the lovers of statistics have not yet balanced the proportions. A crude farinaceous diet has been much blamed, and we should suppose justly; yet the poor of Scotland, who subsist much on such a diet, are not more wormy than the better fed poor of England. Rich moist pastures are said to be favourable to the generation of the fluke in our sheep and cattle; but this is only the case with some pastures, which, in every district, have acquired this bad pre-eminence, and on which certainly our herds cannot be fed many days without the certainty of being tainted. Salt pastures are, on the contrary, unfavourable or destructive to the fluke and worms in general; nor in man does any cause apparently more certainly predispose the body to their visitation than an unsalted innutritive diet. “Salt,” says Dr Paris, “when taken in moderate quantities, promotes, while in excessive ones it prevents, digestion: it is therefore tonic and anthelmintic, correcting that disordered state of the bowels which favours the propagation of worms.” And as an instance of the results of its want, Lord Somerville adduces a punishment which formerly existed in Holland. “The ancient laws of that country ordained men to be kept on bread alone, unmixed with salt, as the severest punishment that could be inflicted upon them in their moist climate; the effect was horrible: these wretched criminals are said to have been devoured by worms, engendered in their own stomachs.”^[6. Paris’s Pharmncologia, p. 517. Lond. 1820, 8vo. ]

The extrinsic causes which give a predisposition to worms are as little known as those which act immediately on the body. Very few avertebrated animals are vermiparous, while there is probably no species of vertebrate that is exempted from parasites. Of the latter class, such species as have been reduced to domesticity, or are retained captive, are more subject to worms than the wild and untamed; and fishes appear to be pre-eminently infested with them. It is not yet determined that the same parasites infest the same animals in different and remote countries, although this is probably the case; but a few facts, relating principally to the human species, seem to prove that climate has a certain influence over their generation. The Pilaria medinensis, or Guinea-worm, is only found under the torrid zone, in Asia and Africa; and the Furia infernalis is peculiar to Lapland.^[7. Rudolphi considers the Furia an apocryphal animal, but in favour of its existence we have to add to the testimony of Linnaeus and Solander that of Dr E. D. Clarke. Travels in Scandinavia, part i. p. 208. ] ® Ascarides prevail to such an extent in Abyssinia, as to regulate in some degree the movements of the inhabitants; and in the West India islands, intestinal worms in general are much more common than they are in Europe. We know, on the evidence of Vallisnerius, that Ascarides are very frequent in the calves of Italy; while those born from the cows of Germany, says Rudolphi, are rarely infested with them. Hasselquist tells us that when in Cairo he was told that three fourths of the inhabitants were diseased with Tania solium; and “I have been informed by my friend Dr Knox,” says Dr Hodgkin, “that our troops which were stationed in and near the Cape were generally infested by these animals.”^[8. Lectures on Morbid Anatomy, vol. i. p. 200. ] Egypt and Africa may then perhaps be considered as the lands of choice of this Taenia, which however has spread, though in smaller numbers, over Germany, Holland, England, and France. In the latter country, it occurs, but not simultaneously in the same individual, with the Tania lata, Linn.— a species of extreme rarity in the English, Dutch, and Germans, but very common in the natives of Switzerland and [7:21:992]Russia.^[9. Rudolphi Entoz. Hist. ii. part ii. p. 72, comp. p. 162. ] If any evidence can be drawn from the silence of Otho Fabricius, it would seem that the Greenlanders are not subjected to the tape-worm, but they breed the Ascarides abundantly.

Intestinal worms, as their name implies, are found principally in the alimentary canal, and the viscera subservient to its functions. There are species, however, which have their appropriated seats in the cellular and adipose and serous tissues, and in the parenchyma of the most secret organs. One species peoples in myriads the voluntary muscles, and more than one has penetrated the heart; several develope themselves in the lungs and air-passages, in the liver, the kidneys, and the brain; one or more have entered the blood-vessels or aneurismal tumours connected with them;^[10. “On Animals in the Blood,” sec the Lancet for August 1840, p. 778. ] some float in the humours of the eye; and more than one loathly worm bathes unharmed in the acrid excretion of the urinary organs. If indeed we except the bones, the cartilages, and ligaments, no organ seems exempted from the occasional attacks of worms, unless it be the spleen, in which, according to Rudolphi, no worm has yet been discovered ever to take up its abode. These parasites may in one sense be considered as accidental, since they are found in certain individuals only of the species they infest; and there can be no doubt, although their evil deeds have been frequently much exaggerated, that they become not seldom the cause of serious or fatal disease. And here we may cursorily notice an opinion which has found its advocates in every period of the history of medicine, that most contagious diseases, fevers, and plagues originate from animalcules introduced into the body, and are propagated by their communication to other bodies through the medium of the atmosphere. Linnaeus was a believer in this hypothesis, which has recently been supported, with much ingenuity, by Dr Holland, who however properly remarks, that “though the course of discovery has recently been approaching, in some points, nearer to the hypothesis in question, it still furnishes nothing beyond stronger presumptions and more numerous analogies” in its favour.

If animalcules can be so pernicious, and we admit that no more probable cause of many pestilences, and especially of cholera, has been assigned, their influence is, according to physiologists, more than counterpoised by the share which another class of them has in the continuance and propagation of the species. This class is by naturalists named the Spermatozoa, of constant and invariable presence in the seminal fluid of every animal capable of propagating its kind; but they are absent in that of the mule, and of other animals which may be sterile from age or the season of the year. Like the accidental Entozoa, the Spermatozoa of every animal has its peculiar characteristics, but the differences between them are comparatively slight. “They all agree in having slightly oblong and flattened heads, with lengthened tails, tapering so as to become nearly or quite invisible with the best glasses; they possess active powers of motion, and are evidently endowed with sensation. No trace of organization has yet been discovered in them, probably on account of their extreme minuteness. Whether essential to generation or not, they may be regarded as the parasites of the tubuli semeniferi.”^[11. Hodgkin’s Lectures vol. i. p. 213. On these animated bodies, the reader will find ample information in Blainville’s Manuel d’Actinoloyie, 573, &c. ]

The origin of the Entozoa within animal bodies, and their viscera, has for long been the subject of much debate and curious speculation. It was a hasty disposal of the question to say that they were no other than the worms of stagnant waters, of marshes, and of vegetable roots, intro duced within the body, either in their perfect or egg state, but altered in their appearance and character by the genial heat and other novel circumstances by which they were now surrounded. Though this explanation had the support of Linnaeus, and has lately found a strenuous advocate in one of the most learned men that ever graced the medical profession, it has been long known to be quite untenable; for no fact is better ascertained than that intestinal worms are found solely in animal bodies, where only they can live and propagate. The instances to the contrary which have been alleged, of tape-worms and flukes living in marshes, and of earth-worms in our bowels, are known to rest on fiction or incorrect observation; so that, in the discussion of the question, it must be assumed as a fact, that the worms are born in, and peculiar to, the places where we find them. This assumption presented no difficulty to the earlier naturalists, who were unanimous in the belief that all worms were the results of a putrefactive process; putrefaction into life fermente, And breathes destructive myriads; or of spontaneous generation; the spawn of a superabundant phlegm, vivified by the heat and fermentation of the belly. But to this ancient doctrine the experiments of Redi on the generation of insects gave the death-blow.^[12. Of various hypotheses of the earlier writers, Le Clerc has given an excellent account in his chnpter xiv., "on the origin of Worms in animal bodies.” History of Worms, trans, p. 329, &c. ]

To explain the beginning of these worms within the body on the common doctrine that all created beings proceed from their likes, or a primordial egg, is indeed so difficult, that the moderns have been driven to speculate, as our fathers did, on their spontaneous birth; but they have revived the hypothesis with some modification. Thus it is not from putrefaction or fermentation that the Entozoa are born, for both of these processes are rather fatal to their existence, but from the aggregation and fit apposition of matter which is already organized, or has been thrown from organized surfaces. Thus Buffon applied his doctrine concerning organic molecules to account for their genesis. Milk, he tells us, “consists entirely of organic and prolific matter, which, when not properly digested by the stomach, and applied to the nourishment and growth of the body, assumes, by its natural activity, other forms, and produces animated beings, or worms :” hence their commonness in the bowels of children; and their origin in the most hidden organs has the same source, for the “living organic particles” may, from various causes, be forced too abundantly to any part of the frame, and living creatures in that part are the result of their union. Rudolphi has adopted an opinion very similar to that of Buffon; for it appears to him that the objections which their history furnishes to a belief in their sexual propagation are insurmountable, and that we must of necessity believe in their spontaneous appearance, or rather in their production from the fit apposition of organic particles that have not been assimilated with the parent body, or from the separation from it of organized particles, which, retaining their proper life, become the germs of an entozoan in situations and under circumstances favourable for their development and metamorphosis: Their origin in this manner is not more wonderful, or more inexplicable, than that of many of the inferior animals from sections of themselves. The Nais, the Planaria, and the Hydra, furnish examples of animals of as perfect organization as worms being thus propagated; for if a small portion is cut away from any species of these genera, and placed in a suitable position, it will continue to live and grow, and develope new organs, until it has acquired in every respect the form and structure and habits of the animal from [7:21:993]whence it was separated. Now particles of matter fitted by digestion, and their transmission through a living body, for immediate assimilation with it, or flakes of lymph detached from surfaces already organized, seem neither to exceed nor fall below that simplicity of structure which favours this wonderful development; and the supposition that, like the morsels of a Planaria, they may also, when retained in contact with living parts, and in other favourable circumstances, continue to live and be gradually changed into creatures of analogous conformation, is surely not so absurd as to be brought into comparison with the metamorphoses of Ovid.^[13. See an Essay "on the Equivocal Generation of Entozoa,” by Dr Drummond, in the Annals and Magazine of Natural History, vol. i. p. 101—108; and Dr Good’s Study of Medicine, vol. i. p. 292, &c. The argument, as bandied by Dr Drummond, does not satisfy us; and the analogies adduced to invalidate the doctrine of equivocal generation by Dr Good seem far fetched, and some of his alleged facts are not true. The remarks of Andral in favour of their spontaneous origin are strongly stated. See the article “Hydatids” in Cyclop, Pract. Medicine, vol. ii. p. 4-10. ] It is a speculation fairly open to inquiry; and indeed one main argument in favour of the spontaneous generation of Entozoa, is the admitted inadequacy of all other hypotheses to explain the facts. Is it possible to believe of a worm which has been found, during the nineteen centuries of the world’s age, in one or a few individuals only, that its eggs can have been transmitted from generation to generation, and be thus so very rare in its perfect state? But we have one proof at least that a change of condition in an animal is capable of generating a worm, for a good authority assures us that a parasite found in the flesh of the domestic swine is not to be found in the wild race;^[14. Cyrticercus cellulosa: "The fact of its being found in the swine which man has domesticated, and not in the wild race, appears to furnish an instance of organized bodies which have been formed long after the general creation.” Blumenbach’s Elem. of Nat. History, trans, p. 243. The fact has been contradicted: but the history of insects and infusory animalcules furnishes us with many similar, so that the argument is not invalidated. ] s and Dr Jenner ascertained that he could produce hydatids and fluke-worms at will in rabbits, by feeding them solely on green succulent food.^[15. Cyclop, of Pract. Medicine, vol. ii. p. 438. ] How but from innate workings are we to explain the first origin of worms that have neither sexual organs nor ova, but, like the hydatid, increase from buds that pullulate from the inner surface of the vesicle that contains them? And Rudolphi has even seen what he believed to be young nascent Taeniae germinating from the villous surface of the bowels. We think the hypothesis is supported also in some degree by the fact, that the origin of Entozoa in general is favoured by all causes which tend to disturb the equality between the secerning and absorbent systems. Thus there is great reason to believe that some inflammatory action of the liver, of the eye, and of other wormed viscus, precedes the evolution of parasites in them; and it is well known that a morbid state of the alimentary canal, especially an abundant secretion of unhealthy mucus, is connected with the production and increase of all intestinal worms, so much so that Broussais believes an inflammatory state of the mucus membrane to be even an essential condition to their existence. It is obviously necessary to suppose that there are unknown conditions or laws regulating this, the spontaneous growth of worms within us, so that a certain uniformity in the products is the result; but it seems not more difficult to admit the existence of such laws, overruling the destiny of unappropriated organic matter, than their existence and rule over the shred of a Planaria severed from another’s body. That there are such laws of regulation, we infer from the fact that the detached portions of a Planaria, a Hydra, or a Nais, invariably evolve into their respective species; and from the analogous fact that the worms of the different cavities and textures are usually dissimilar, as might have been expected from the dissimilarity in the structures from which their unformed and unsemi-nated embryos are separated.^[16. The reader will find the subject discussed at great length by Rudolphi in cap. xviii. of his Historia Nat Entozoorum, vol. i. p. 370-416. ]

The variety in the exterior forms of intestinal worms is sufficiently great to form the basis of their classification into subordinate divisions. Thus we have the round or cylindrical worms (Nematoidea); the sacciform with prickly proboscides (Acanthocephala); the flat or fluke worms (Trematoda); the tape-worms (Cesloidea); and the cystic or hydatids (Cystica). In very few of them are there any external appendages, either to diffuse or heighten their sensibilities and perceptions, or to assist in locomotion;^[17. The Phanoglene, which lives in the larvte of some neuropterous insects, has some prolongations like antennae; and Diesiug bas described some genera (Ancyracanthus, Heterochoilus) with heads furnished with filaments of various forms. ] but we can distinguish in all of them a head, a body, and an anal extremity; in some there is a neck; in the Trematodes, one or two ventral suckers; and in some the organs of generation are protruded. The skin is commonly white, smooth, thin, and moist, but coriaceous in many of the Acanthocephala, and sometimes roughened with reverted prickles. Minute black points, suspected to be visual organs, bespeckle the anterior extremity of some non-parasitical genera (Planarias) often classified with the flukes; and similar specks have been discovered on a few true Entozoa at certain stages of their development. Thus they are of a brilliant lustre in the Phanoglene and En-chelidiurn; and traces of them are visible in the Gyrodactylus auriculatus, in several Cercaria, in the Polystoma integerrimum, in the young of many Distoma, Monostoma, and Amphistomae, and in the Scolex polymorphus. ^[18. Lamarck’s Anim. sans Vert. iii. p. 546, note 1, 2d edit. ]

The internal structure of the Entozoa is as various as their outward form, and in some degree of harmony with it, as will be proved when we come to explain the characters of their classification. It ranges from a homogeneous structureless tissue, such as composes the whole of a zoosperm, to that of an animal with organs of defined limits and function, such as we find them in a nematoid worm, where there are distinct muscles, a perfected apparatus of digestion, and a system of generation on male and female individuals. In a very few intestinal worms, anatomists have recently demonstrated the existence of a slightly developed nervous system. In others, there exists a system of vessels, in which an obscure circulation of a colourless fluid has been seen; but in none of the class is there any trace of a distinct respiratory organ,^[19. Respiratory tracheae, similar to those of insects, have been ascribed to some of the nematoid worms, but erroneously. See Rudolphi Entoz. Synopsis, p. 579, &c. ] the functions of which are performed by the skin or surface. The genera whose habitat is the alimentary canal, may have a slightly oxygenated atmosphere to breathe;^[20. Μ. Chevreul, however, found no oxygen in the gas of either the small or great intestines of three different subjects. See Bostock’s Physiology, vol. ii. p. 490. ] but such as live in the muscles, in the humours of the eye, or in the brain, no uncombined air can reach; and we are forced to conclude that all the oxygen they require for existence is communicated to them through the fluids they feed on, or from the blood as it circulates over the surfaces with which they are contiguous, or from the medium in which they float. They doubtless require but a small supply, for the heat that is evolved by respiration in other animals is here furnished [7:21:994]by the warm abodes they live in; and their food, consisting of chyle, lymph, and excretions in a recent state, is already half prepared for assimilation. We know that their food must be of this soft and liquid nature; for many worms, having no oral aperture, seem to imbibe all their nutriment through minute pores in the skin, or by the process of endosmose; and the whole of what they imbibe is probably assimilated. Even in such worms as have a mouth, this is never armed with cutting or triturating instruments, but constitutes a simple pore for the entrance of a soft material upon which suction can operate. As in the nematoid worms there is both a mouth and an anus, we may conclude, that of their food some part is feculent and excrementitious; and the same inference may be made from every species of similar structure. The Trematoda or flukes have no anus, and their mouth is certainly ill defined, but they have an alimentary canal, ramified in a dendritic fashion; and Rudolphi believes it to be proved, by the colour of the matter in these vessels, that their food is also partly excrementitial, for the worm, naturally colourless, is often dusky, or variously tinctured by the nature of its food.^[21. Dr Drummond doubts whether the colour is dependent on the contents of the intestine. "It is certain that in a mass of individuals (of Echinorhynchus acus) found in the same portion of intestine, considerable diversity of colour prevails; and where there has been only a transparent mucus present, I have found specimens of a pure white, and others of a bright orange.” Mag. of Nat. Hist. n. s. ii. p. 519. ] It is singular that this order appears to receive no part of its nourishment from cutaneous absorption, a mode of supply very general in the class, and especially remarkable in the order Acanthocephala. When a specimen of an Echinorhynchus is taken fresh from the bowels, it is small, flattish, and flaccid; but shortly after being immersed in a glass of water, it has become larger, swollen, and distended like a sac; and the most conclusive experiments have proved that the water of distention could only have passed inwards through the skin, the structure of which is peculiarly adapted to the office. If any part of the skin of the Echinorhynchus Gigas is held up opposite to the light, and examined from the internal side with a common lens, we perceive a remarkably elegant net-work of vessels, sprinkled over with minute pearl-like vesicles, which are, as it were, the centres of the anastomosing branchlets, or perhaps merely dilatations of the vessels at their points of coalescence and union.^[22. ' Rudolphi Entoz. Synop. p. 582. See also Owen in Cyclop, of Anat. and Phys. ii. p. 126, and Drummond in Charlesworth’s May. of Nat. Hist. ii. p. 517—8. ]

The nematoid and acanthocephalous worms have distinct sexes; but the Trematoda and many Cestoidea are androgynous, that is, each individual of the species possesses the organs peculiar to both sexes, and may of itself fecundate its ova, although, with regard to some of them, it has been supposed that the union of two individuals is necessary, as is the case with the slug and snail. In other worms, the female or reproductive organs exist alone; and in the cystic Entozoa no generative apparatus has been provided. “They would seem to be gemmiparous, and to have the reproductive power diffused over the whole cyst, at least in the Acephalocysts, in which the young are not developed from any special organ, or limited to any particular part of the cyst.”

The great majority of the higher Entozoa are oviparous; but we have several exceptions among the Nematoids, and one at least among the fluke-worms, which are viviparous. The distinction is however immaterial, for in both kinds the ovaries possess a similar structure, and the eggs accumulate in them in the same fashion. In the oviducts of the viviparous Cucullani, as of the oviparous Echinorhynchi, there are found the same bodies which Rudolphi conjectures to be cotyledons, or little placentae, into which the ovules are fixed, so that even in this respect no difference exists. The ovules of the oviparous species are of two kinds, containing either an unformed and inconspicuous embryo, or one that is fully formed, but motionless. The ovules of the viviparous species, on the other hand, contain a moveable embryo.

The number of ova produced by a single worm is sometimes prodigious, and almost incredible. Ascaris lumbricodes contains, when pregnant, many thousands; Ascaris nigrovenosa, according to Goeze, may have 700 living young at a birth; and the Cucullanus as many. But what are these to the calculations of Dujardin,^[23. Ann. des Sciences Nat. n. s. vol. x. p. 34. And so of Filaria nutdinensis Rudolphi writes: “Filariae nostrae prole quasi farctae sunt; quod si harum longitudinem illius vero minutiem spectas, feetuum multa millium millia singulis tribues.” ] who supposes that one Tania serrata, with its 200 articulations, may contain in the united chain not less than twenty-five millions of ova? And it is in fact not uncommon to find eight or ten of these productive monsters in one poor dog. From this fertility we might conclude the numbers within the body of those animals which they infested would be fearfully great; but this is seldom the case, and least of all with those very species that we have instanced as so marvellous in their productive powers. The Taenia or tape-worm is often solitary, and rarely numerous in any individual. It is not difficult to reconcile this apparent contradiction of means and end, when we call to recollection the numerous accidents to which both worms and eggs are exposed, from the nature of their sites; how many undeveloped ova, how many young, how many adults, must daily pass away.

We have already slightly indicated the diseases that may arise from their presence and multiplicity, an injury that some physicotheologists would fain persuade us is countervailed by a series of benefits that animals derive from their parasites. One gravely tells us, that by their motions they cause a gentle irritation in aid of the intestinal functions, which, moreover, may stimulate the other viscera to the discharge of their duties, and prevent their falling into a state of inaction favourable to the commencement and increase of organic diseases. Another insists that the Entozoa drink up the superabundant chyme, chyle, or mucus, in the bowels. Another believes that they were created as a wholesome check on the pride and vanity of man, as trials of his patience and other virtues, and “finally to secure to him an entrance into an immutable and eternal state of felicity when that of probation is at an end, so that the gates of death may be to him the gates of peace and rest !”^[24. Kirby’s Bridgewater Treatise, vol. i. p. 331. ] Now it may be commendable to look for good in every thing; but this, we think, is looking rather too far, looking also into a sort of kaleidoscope, in which we see all beautiful though unstable pictures patterned out of worthless things.

The relationship of the Entozoa with other animals is involved in much obscurity, but we cannot therefore concur with Bäer in his proposal to exclude them from a natural classification of the animal kingdom; nor do we exactly understand Rudolphi’s notion when he says they constitute a peculiar fauna, rather than any order or class parallel with the ordinary divisions of systematists. If the zoosperms are to be reckoned distinct beings, they must probably go to throng the chaos of infusory animalcules; and Dujardin has discovered in the earth-worm and in the slugs a parasite (Albertia) that combines with the structure and habits of an entozoon many of the peculiarities of the rotatory animalcules. The hydatids may represent the hydraform polypes; the tape-worm the cesium Veneris of the gelatinous medusae; the Acanthocephala have some ex [7:21:995]terior resemblance to the sipunculidous genera of the radiated animals; the Nematoids a nearer one to the Annelides; and the Trematoda have, with a very general yet erroneous assent, been made members of a family that embraces the Planariae—leech-like natives of fresh and salt waters—which Mr Swainson errs no less in arranging with the mollusea. Their affinities being thus so remote and uncertain, we are not surprised to find the classification of the intestina unsettled; but from among the many that have been proposed, we only select two for exposition here; that, namely, of Rudolphi, which has been most generally approved; and that of Cuvier, for this, from its wider scope, will afford us an opportunity of noticing some tribes, remotely perhaps allied to the true worms, but which only now come within the plan originally laid down for our guidance.

Rudolphi confines himself to the proper parasites of animal bodies (Entozoa), which, following Zecler and Goeze, he divides into five orders:^[25. Entozoorum Synopsis, &c . Berolini, 1819, 8νο. ] 1. Nematoidea; 2. Acanthocephala; 3. Trematoda; 4. Cestoidea; and, 5. Cystica. In our exposition of their characters and genera, we shall reverse Rudolphi’s plan, and begin with those of simplest organization.

ORDER I .— CYSTICA.

Character .— Body flattened or roundish, continued posteriorly into a vesicle peculiar to one or common to several individuals. Head furnished with two or four bothria,^[26. Bothria are small pits or excavations, with a thickened rim, placed round or near the mouth. ] j or with four suckers, and a circle of hooked prickles, or with four prickly proboscides.^[27. On this order the reader will consult with advantage Dr Hodgkin’s Lectures on Morbid Anatomy, vol. i. p. 184-197. ]

Genus Echinococcus.— An external simple or double vesicle, to the inner surface of which many entozoa adhere, like grains of sand. Of these the body is obovate, and the head armed with a circle of hooked prickles and suckers. The species infest the viscera of man, of apes, and of domestic cattle.

Genus Caenorus.— Vesicle simple, containing many adherent entozoa. Of these the body is elongate and flattish. rugose; the head armed with a prickly beak and with four suckers. The only known species (C. cerebralis, Plate DII. fig. 8) is found in the brain of domestic animals, especially of sheep, and it is the cause of a disease in them known by the name of the sturdy. It is curable by the judicious use of the trephine.

Genus Cysticercus.— Plate DII. fig. 7—External vesicle simple, containing a solitary entozoon, whose roundish or depress, ed body passes insensibly into a caudal vesicle. Head furnished with four suckers and a prickly beak. The species are found in quadrupeds, principally in their abdominal viscera. One occasionally makes good its habitat in the cellular substance between the muscles, and even in the eye and brain, of man; and the same is very common in the muscles of swine, whose flesh is then said to be measled. Blumenbach, as we have before mentioned, asserts that the wild swine are not subject to this disease; but the assertion seems unfounded. “In suis domestici cerebro et omnibus partibus musculosis vulgatissimus occurrit, neque fero deest.” Rud. Ent. Syn. p. 180, c. p. 547.

Genus Anthocephalus.— External vesicle hard and elastic, containing a more delicate one, within which there is a solitary entozoon. Body elongate, depressed, passing into a large caudal vesicle. Head armed with two or four bothria and four prickled rostella. This genus was previously named Floriceps by Cuvier, and naturalists in general have preferred that designation. The species seem to be almost peculiar to the fishes of southern climates, nestling in the abdominal membranes and viscera.^[28. On this genus see some interesting observations by Dr Drummond in the Magazine of Natural History, n. s. vol. ii. p. 655, &c. and vol. ]

The Cystica are all gemmiparous. In the Coenurus, the gemmae pullulate from every part of the inner surface of the vesicle, where heads and their necks have been found at different stages of development, and always united together in groups. They appear at first like minute tubercles, having the limpidness of glass, and gradually evolve from this formless condition into their perfect state. Siebold has also traced the evolution of the young in the Echinococcus. The primary or maternal vesicle is lined with an extremely delicate epithelium, to which there adhere some limpid, mostly oblong, corpuscules, analogous to those primary buds met with in the neck of the Caenuri. The liquid of the vesicle contains some free Echinococci, within whose bodies, when their coronet of hooks and suckers is everted, nothing more is to be distinguished than some scattered limpid corpuscules. These Echinococci evidently derive their origin from the primary vesicle. On examining the inner surface of it, we notice here and there some minute vesicles, enclosing a mass of delicate granulations, whence the heads of the Echinococci pullulate, either solitary or in groups of from two to seven or more. In fact one portion of the granulous mass forms a small roundish body, which is manifestly continuous with the rest of the mass by one of its extremities. This rounded mass soon acquires insensibly a pear-shape, whence it passes to an oval, while at the same time its attachment to the mass whence it issued becomes more slender and frail. We now begin to discern, in the interior of this body, the circlet of hooked prickles and the limpid corpuscules; and now also the heads of the Echinococci commence to protrude and retract these parts, in doing which the entire body is alternately elongated and shortened. Arrived at this stage of development, the thin envelope that enclosed them is torn, but the young Echinococci do not immediately escape, for they are held to its inner surface by a slender cord proceeding from the envelope, and penetrating within their own bodies at a dimple indented in the posterior extremity. This dimple has nearly the appearance of a sphincter muscle grasping this cord of the envelope. After a short period the cords and the Echinococci separate. On being torn up, the envelope of the young Echinococci shrivels upon itself, the Echinococci are ejected, and in this manner they form a rounded mass, in the centre of which the shrivelled envelope is hidden, and upon which the worms repose, as the polypes do upon their stem. These masses sometimes remain for a space hanging from the inner surface of the maternal vesicle, and sometimes they are detached even before the Echinococci have themselves separated. The granulous mass contained in the vesicle is of the nature of a yolk, whence the heads derive the nourishment necessary for their development by means of the slender cords already mentioned. Siebold thinks it doubtful whether all the vesicles, large and small, that contain heads of Echinococci, and which float at freedom in the maternal vesicle among the freed heads, are detached from the inner surface of the vesicle, or whether some of them do not come direct from the freed heads, these having produced germs of Echinococci in their interior, and become distended by them into vesicles. Hanging from the free vesicles containing heads of Echinococci, he has often seen hooked spinules, which were perhaps the remains of a former circle of them; nay, he believes that he has even seen the remains of suckers in these vesicles. Still however there remains much obscurity on this strange transmutation; and even a greater darkness covers the origin and the propagation of the maternal vesicle. Since the Echinococcus hominis frequently presents us with small hydatids enclosed within each other after the manner of a nest of pill-boxes, we are forced to believe that the exterior hydatid is the primordial vesicle, within which the others have been successively evolved; but how? “I can no more answer this question,” says Siebold, “than I can account for the existence of the primordial vesicle itself."^[29. See Burdach’s Traité de Physiologie, vol. iii. p. 32-4. Paris, 1838. ]
[7:21:996]

ORDER II.—CESTOIDEA.

Character .— Body elongate, flattened, soft, continuous, or jointed. Head very rarely simply lipped, usually furnished with two or four bothria or suckers. Androgynous.

Genus Taenia.— Body elongate, flattened, jointed. Head with four suckers. The Taeniae inhabit the alimentary canal, and principally the small intestines, but they have been found very rarely in the liver and gall-bladder. They occur only in vertebrated animals, some of them nourishing two or three species. Of those species which Rudolphi has described without a mark of doubt as to their reality, we find that one infests man, thirty-two the mammalia, sixty-five the birds, six the fishes, and two the reptiles. These numerous species he divides into two sections; first, those with an unarmed, and, secondly, those with a prickled head; but Mehlis has recently shown that many species which are furnished with hooked prickles when young, lose them when they arrive at maturity.

Genus Bothriocephalus.— Body elongate, flattened, jointed.

Head subtetragonal, with two or four opposed bothria. Nearly allied to Taenia. Of twenty-four species described by Rudolphi, one is peculiar to man, three to aquatic birds, and twenty to fishes. The genus has been subdivided into several others by De Blainville. The individuals of one of these subgenera, Di-bothriorhynchus, were affixed by the prickles of their probosces to masses of Ascarides, which again were the parasites of a butterfly.

Genus Triaenophorus.— Body elongate, flattened, subarticulated. Mouth two-lipped, armed on each side with two tricus-pidate spines. There is but one species, a native both of fresh and salt water fishes.

Genus L igula.— In its state before evolution the body is flat tened, continuous, very long, grooved down the middle with a furrow; and neither head nor genital organs are visible. In its developed state the body is also flattened, unjointed, and very long; the head armed on each side with a very simple bothrium; and ovaries are seen on the medial line in a single or double series, with threadlike filaments (lemnisci). The species are principally the intestinal parasites of birds; two or three kinds are found in fish; and one has occurred in the common seal.

Genus Tetrarhynchus.— Plate DII. fig 6,—Body flattened, unjointed. Head furnished with two bipartite bothria, and protruding four retractile prickly proboscides. The species are all piscivorous, although one has been also found in the stomach of a tortoise, and another in some cuttle-fish. They adhere to the abdominal viscera, to the gills and fins, and even infest the muscles. Bremser is of opinion that the species are Bothriocephali in an imperfect stage of development; and Nordmann believes this opinion to be correct, at least in regard to certain species. On the genus see Drummond in Mag. Nat. Hist. n. s. vol. ii. p. 571, &c.; and Leblond in Ann. des Sc. Nat. tom. vi. n. s. p. 293. The latter took a species from the interior of a fluke-worm or Distoma, a true entozoon, the parasite of another of not superior organization and scarcely of greater bulk. Helminthology is indeed full of miracles. Lib. cit. tom. vii. n. s. p. 249-253.

Genus Gymnorhyschus.— Body flattened, unjointed, very long, with a subglobular receptacle for the neck. Head furnished with two bipartite bothria, and emitting four naked retractile proboscides. Found immersed in the flesh of some giltheads (Bramoe) and rays or skates (Haji).

Genus Scolex —Body flattened, unjointed. Head furnished with four bothria. The only species described (S. polymorphus) is common in the intestines of many fish and of the Cephalopods. There exists a suspicion that other Scoleces may be metamorphosed into Bothriocephali.

Genus Caryophyllaeus.— Body flattened, unjoínted. Head enlarged, scalloped, two-lipped, the lips superior and inferior. The species is common in the intestines of the carps (Cyprinorum).

In the preceding order there were no appropriated organs of digestion, which begin now to be developed. In the majority of the Taeniae there are two or four canals which run through all the articulations of the long tape-like body, and which, underneath the cephalic knob, are connected together by numerous anastomoses, forming there a sort of net-work. It is remarkable that no one yet has succeeded in proving any direct communication to exist between these canals and the proboscis. In all the Taeniae, the Bothriocephali, the Schistocephalus, and in the Triaenophorus, the generative apparatus, both fecundating and reproductive, is multi-plicate, while it is simple in Caryophyllaeus. The orifices of both apparatus are, it seems, always separate. In Tetra-hynchus epistocotyle, Nordmann did not find any sexual organs; and the four retractile spinigerous proboscides led by four canals to as many oblong transparent muscular reservoirs, which, he conjectures, ought consequently to be considered stomachs. In the posterior part of the body of these animals, the same distinguished naturalist discovered a vascular system, composed of several longitudinal canals, and ramified by anastomoses; but no movement of any liquid could be perceived in it. On the posterior margin of the body there is a thick fringe of cilia, which is easily detached.

The eggs of the Cestoidea are multiform, and vary remarkably in size. According to Siebold, some have a single envelope, and others not fewer than three. The eggs of Tania stylosa, when found in the intestines of Corvus glandarius, are quite peculiar in their structure; for they have four envelopes, of which the two external ones are round, the inner one oval, and that which lies between the second and the fourth is very narrow and drawn crosswise, having at the same time two very long twisted diverticula. The eggs of Taenia cucumerina deserve also to be particularized, from ten to twenty of them being always placed in a common envelope. The vesicle of Purkinje appears to be wanting in the eggs of the Cestoidea.

The embryo, while yet in the egg, is endowed with certain motions; and Dujardin discovered that the Taeniae have then six hooked spinules, or horny falciform teeth, disposed symmetrically in pairs. These spinules have no relation, as one is at first disposed to conclude, with the spinules that arm the interior of the extrusile proboscis, or the circumference of the oval aperture; for they exist in the embryos of unarmed Taeniae, as well as in those which are so provided; nor are the shape and disposition of the two kinds at all analogous.

The articulations of the body are not formed until some time after the embryo has quitted the envelope of the egg, but the first traces of the suckers surrounding the beak are sooner recognisable. It is probable that the little worm from the tench, described under the name of Gryporhynchus pusillus by Nordmann, is only the young of one of the Cestoidea, perhaps of a Taenia.

ORDER III—TREMATODA.

Character.— Body flattened or roundish, soft, furnished with suctorial pores. Androgynous.

Genus Monostoma —Body soft, roundish, or flattened. The sucker anterior and solitary. The Monostomae live in the abdomen and intestines, and have been found in the muscles, of vertebrated animals. Of the species described in Rudolphi’s Synopsis, one is from a mammal, nine from birds, ten from fishes, and three from reptiles.

Genus Amphistoma.— Body soft, roundish; an anterior and posterior pore or sucker. Of eighteen species, twelve belong to birds, three to the mammalia, and three to reptiles. The genus has been recently subdivided, or its definition will at least embrace the Holostomum of Nitzsch, the Amphistoma and Diplodiscus of Diesing; and the beautiful Diplostomum of Nordmann, found in the eyes of fishes, is nearly related.

Genus Distoma.— Body soft, flattened, or roundish. Suckers solitary, one anterior, the other ventral. A genus better known by the name of Fasciola. The species are the parasites of every order of vertebrated animals, and are exceedingly numerous, nearly 200 having been described. Of these, the most notorious is the Fluke (Plate DII. fig. 9), generally believed to be the cause of the rot in sheep, by which disease numerous flocks are annually destroyed. Another species (Fasciola trachea, Montagu in Wern . Mem. i. p. 197, pl. 7, fig. 4) breeds in the wind-pipe of poultry, and produces the fatal distemper usually termed the gapes.

The three preceding genera are the heads of a large family, extremely variable in the degree of organization, but, amid this diversity, always marked by having from one to three suckers of more or less perfect formation. It is from the number, the form, and the position of these organs that [7:21:997]attempts have anew been made to subdivide the family into groups and genera; for many new and extraordinary forms have been discovered since the publication of Rudolphi’s work. Our space forbids us to characterize these novelties, but we may mention the Gregarina of Dufour, living in groups in the alimentary canal of tardigrade insects; the Diplostomum, which peoples the humours of the eyes of fish; the Cercaria of fluviatile mollusea, so remarkable for its anomalous mode of propagation; and the Diplozoon, the only animal known which is truly double, having two heads and two bodies united at their middle, and in organic connection, and, unlike the Siamese twin, no monstrous production, but a normal species after its kind.^[30. The Syngamus trachealis has been adduced as another example, in which the male is organically blended by its caudal extremity with the female; but Siebold afterwards discovered that he bad been deceived in this description. Lam. Anim. sans Vert. 2de edit. iii. p. 652. ]

Some of the species in the family are without sex, and seem to be composed of granules lying in a fluid gelatinous matrix, held together by a thin skin, which gives the animal form and consistency. On the contrary, in the greater number of the species there is a digestive apparatus, consisting of a mouth, an oesophagus or pharynx, and an intestine forked or sometimes ramified; but there is no anus, for the ascription of this name to the posterior sucker is founded in error. In several genera we find subservient to the digestive organs a double system of vessels, one closed, the other (furnished with a reservoir, named by some helminthologists the cisterna chyli) has a communication with the exterior by means of a caudal aperture, the vent of some secretion. These more complex species are all hermaphrodites, some fecundating themselves, while others copulate after the fashion of the snail. The sexual organs are often very complicated and much interwoven, but they have distinct orifices. The eggs are diversiform, and usually laid anterior to the formation of the embryo. There are some exceptions, however, and at least one species of Monostoma is viviparous. When the embryo is matured, the upper part of the shell of the egg bursts and opens like an operculum, allowing the embryo to pass out; and then it swims about vivaciously in the circumfluent medium by means of cilia that cover the body. We know not what may be the number and the nature of the metamorphoses through which the young passes before assuming the shape of the parent. The young of the Monostoma mutabile, observed by Siebold, contained all of them a worm of a peculiar figure, having no correspondency with the figure of the mother, but resembling the cyst of some Cercariae. Analogy induces Nordmann to believe that this worm within the young is in fact changed into a cyst, from which, under favouring circumstances, the Monostoma is ultimately developed.^[31. Lamarck, Anim. satis Vert. vol. iii. n. 617, 2de edit. ]

Genus Tristoma.— Captain of Bose— Body flattened; two simple suckers in front and a radiated one behind; the mouth emitting a proboscis? between the former. The species infests the gills of various fish. It is occasionally found at freedom in the sea, and has occurred on the British coast.

Genus Pentastoma —Body roundish or flattened; mouth protruding a little hook, placed between the anterior suckers, of which there are two on each side, arranged in a lunated manner. Parasites of the viscera of the quadrupeds. The best-known species is found in the frontal sinus of the dog and of the horse, growing to the length of six inches. The sexes are distinct. The name Linguatula has been preferred for the genus, of which Diesing has published a monograph, with descriptions of eleven species. Because the sexes are separate, Cuvier gives it a place among the Nematoidea, while Diesing thinks its peculiar structure entitles it to be reckoned the type of a separate order, which he names Acanthotheca; and Miram expresses an opinion the same as Diesing’s. Recherches sur l’Anatome du Pentastoma Toenioides, in Ann. det Sc. Nat. n. s. tom. vi. p. 135. (Plate DII. fig. 5.)

Genus Polystoma.— Plate DII. fig. 10, 11—Body roundish or flattened; six suckers in front, a ventral and posterior one solitary. This genus is the type of a family named Polycotyla by Blainville. It contains many genera, and among them the Tristoma, and others which have often been classified with the Leeches. The bulk of the species prefer the exterior of animals, especially the gills of fish, to which they adhere by means of the prehensile organs or suckers on the hinder part of the body. All of them are hermaphrodites. The orifices of the genital organs are in front, not far from the mouth. On each side of this there is an oblong or round sucker; in the oesophagus a body resembling a tongue has been distinguished; the alimentary canal is dendritic, without an anus, and all the body is permeated with a double vascular thread, in which there is obviously a circulation of blood, attended with a vibratile motion. Some species are furnished with eyes, or eye-like specks; and the surface of the body is variegated with spots, or tinctured of a deep colour.

ORDER IV .—A CANTHOCEPHALA.

Character— Body roundish, utricular, elastic; proboscis retractile, armed with spinules arranged in rows; sexes separate.

Genus Echinobhynchus.— The only genus of its order, but a very numerous one, for not less than 100 species have been discriminated. They are found in the intestines and other viscera of vertebrated animals, retaining themselves in their position by means of the prickly proboscis,^[32. Of this organ Dr Drummond has given a good description in Mag. Nat. Hist. n. s. ii. p. 520; and some most interesting observations on their economy in vol. iii. p. 63-71. ] which is not the organ for taking their food, for its extremity is not perforated. The sexual organs are very complex. The ovaries are not attached, but float free in the cavity of the sac-like body. The ova resemble spicula, and appear to be discharged posteriorly through a minute pore.^[33. See Drummond in loc. cit. p. 523. ] It seems that the species undergo a considerable change in figure in their progress from the embryo to the adult state; and some lose the prickles of their proboscis.

ORDER V .— NEMATOIDEA.

Character.— Body cylindrical, elastic, the intestinal tube terminated at one end by the mouth, at the other by an anus; sexes separate.

Genus Liorhyxchus.— Body elastic, round; head evalvular; mouth with a smooth protrusile tube. Of the three species mentioned in Rudolphi, one infests the badger, one the seal, and one the conger eel. Diesing has lately characterised several allied genera.

Genus Ophiostoma. —Body round, elastic, attenuated towards each extremity; head with an inferior and superior lip. The Fistula of Lamarck. The species are intestinal, and occur in quadrupeds and fishes, occupying the swimming bladder of the latter.

It is probably in the neighbourhood of Ophiostoma that we should place the genus Tetrastoma of E. Forbes, a strange parasite, “fixing itself by means of four suckers or mouths to the walls of the stomach, and of the vessels of the Cydippe, after interrupting the circulation of the fluids.” Mr Forbes first described it as a tongue-shaped organ existing in the stomach of the crystalline me. dusans, but its parasitical nature was discovered by Major Playfair of St Andrews. See Athentrum, Sept. 26, 1840, p. 740.

Genus Ascaris.— Body round, elastic, attenuated at both extremities; head trivalvular; spiculum of the male double. The species are numerous, and difficult of discrimination. The most common example of the genus is A. lumbricodes, found in the small intestines of man, of the swine, of the ox, horse, and ass. See Plate DII. fig. 3.

Genus Strongylus.— Body round, elastic, attenuated at both ends; mouth circular or angulated; apex of the tail in the male terminated with a purse-like sheath, whence the penis is protruded.

The S.gigas (Plate DII. fig. 4) may be considered the type of the genus. It attains the length sometimes of two or three feet, and is as thick then as a man’s little finger; and it makes one shudder to think that this monstrous worm is occasionally the cankerous inhabitant of the kidneys of man, where it lies rolled up, battening on their flesh, and producing unspeakable torture. It afflicts other animals, as the dog and wolf, and is not confined to the kidneys. It is often found of a deep red colour, dependent undoubtedly on the blood it has sucked from its victims. Of worms excreted with the urine, see cases very interesting to the “greedy hunters after monsters,” in Le Clerc’s History, p. 264 et seq. Also the Cyclopaedia of Practical Medicine, vol. iv. p. 516.
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Genus Physaloptera.— Body round, elastic, attenuated at both extremities; mouth circular; tail of the male deflexed, winged on each side, ending in an inferior vesicle; penis protruded from a tubercle. The species are few and intestinal.

Genus Spiboptera.— Body round, elastic, attenuated at both extremities; mouth circular; penis emerging from between the wings of the spirally involute tail. The species are numerous. One has been said to occur in the urinary bladder of man.

Genus Cucullanus.— Body round, elastic, attenuated behind; mouth circular, placed under a striated hood; the male organ a double spiculum. The species infest the stomach and intestines of various fish.

Genus Oxyuris.— Body round, elastic, the posterior part of the female subulate; mouth circular; penis sheathed. The species are few, and confined to quadrupeds. One is very troublesome to the horse; and the worm which perhaps annoys man more than any other (Ascaris vermicularis) has lately been removed to this genus.

Genus Tricoephalus.— Body round, elastic, the anterior capillary extremity suddenly succeeded by a thicker portion; mouth circular; male organ simple and sheathed. “The species inhabit the large intestines, particularly the caecum of the mammalia; they do not occur in either birds or fish.”—Bellingham. The T. dispar (Plate DII. fig. 2) is said by Rudolphi to be very common in the large intestines of man. “It is about two inches in length, only one third of which is taken up by the thick part of the animal. This portion has a spiral form in the male, which is furnished with a small penis, protruding from near the tail. In the female, which is oviparous, the thick portion is straighter, and is simply pierced at the extremity. On the continent it would seem that this is the worm which is met with the most frequently in the human intestines. Indeed some of the most distinguished helminthologists state that they scarcely ever fail to find them. The large intestines are their principal seat, but more especially the appendix vermiformis of the caecum. Though I have frequently and carefully sought for this worm, I have only once been able to find it. In this instance it was lodged in the mucus filling the appendix of an emaciated and cachetic girl, who had been much exposed to want and hardship.” Dr Hodgkin’s Lecture·, &c. vol. i. p. 207. Dr Bellingham’s experience is very different; he finds it very commonly in the Irish. See his Catalogue of the Entozoa indigenous to Ireland, in the Mag. of Nat. Hitt. n. s. vol. iv. p 343, &c.

Genus Tbichosoma. —Body round, elastic, very slender, growing insensibly larger to the posterior extremity; mouth a mere point; male organ a simple sheathed thread. Named Capillaria by Zeder. The species are found principally in birds, next in the mammalia, and very rarely in reptiles and fish.

Genus Filaria.— Body round, elastic, linear, elongate; mouth circular; male organ a simple spiculum. The species are numerous, and infest many avertebrated^[34. On the Entozoa of insects consult Léon Dufour, in Ann. des Sc. Nat. n. s. tom. vii. p. 5. ] as well as vertebrated animals. They are principally intestinal, but a species has been found in the eye of the horse, another in the eye of man. and another in the bronchial glands. The most celebrated species (F. medinensis, oτ Guinea-worm, Plate DII. fig. 1) burrows in the cellular tissue under the skin. It was well known to the ancients; and a portion of the history of it given by Paulus Aegineta may be quoted: “In India and the countries above Egypt, there are bred little dragons, animals like worms, in the muscular parts, as the arms, thighs, and legs, and in children they are in the sides, and plainly move under the skin. But after some time a place nigh the end of the worm suppurates, the skin breaks, and the head of the little dragon comes out. While it is drawn out it causes pains, and especially when it is broke. Wherefore some say that a leaden weight should be hung to the dragon, that the falling out should not be in heaps, but in pieces. Others condemning these, because by the weight of the lead the worm is broken, and causes cruel pains, order the part to be put in warm water, by the fomentation of which the worm comes out, and is drawn out piecemeal by the fingers.” I.e Clerc’s Hist, of Wormt, p. 242. Freind’s Hist. of Physick, vol. i. p. 49, &c. Mr Hutcheson gives an account of his having extracted one that measured three yards and a half in length. Good’s Study of Medicine, vol. vi. p. 653.^[35. Its exterior figure might induce us to place after Filaria the genus Trichina of Owen, found in myriads in the voluntary muscles of man, but its simplicity of structure scarcely raises it from among the Infusoria, more especially from above the eels of vinegar and paste. On this interesting worm, see the elaborate essay of Owen in Trans. of the Zoological Society, vol. i. p. 315; and in Cyclop, of Anal, and Phynologg, ii. p. 114; Hodgkin’s Lectures, vol. i. p. 211; and several essays in recent volumes of the Lancet and Medical Gazette. ] i

The eggs of the Nematoidea, with a very few exceptions, are of an oval shape when mature. The changes which they undergo in the process of hatching have been minutely described by Siebold, but we can only mention one or two particulars. The covering or shell is colourless and single, but frequently double. The vitelline mass is whitish, and contains, in unripened eggs, a well-marked proligerous vesicle with a proligerous spot. When these immature eggs have passed into the uterus, remarkable changes begin in the yolk, which at this period is a mass of delicate granulations, set in a uniform manner, and completely filling the envelope of the egg. The proligerous vesicle, deeply hidden in the vitelline mass, is obscurely seen, and soon afterwards disappears. On its disappearance, the physiologist is surprised to observe on the vitelline mass those remarkable grooves, the existence of which he had never suspected in any invertebrated animal, and least of all in the Entozoa, and which had been seen only in the eggs of the Frogs (Bactracians) by Prevost and Dumas, and some other observers.^[36. See Burdach’s Traité de Physiologie, vol. iii. p. 59-64. ]

The Intestinaux constitute the second class of zoophytes in Cuvier’s arrangement.^[37. Règne Animal, iii. p. 245-274. ] He divides them into two orders, so different in their organization, that they seem rather to deserve the rank of classes. The first order, the Intestinaux cavitaires, have an alimentary canal floating in a distinct abdominal cavity, with a mouth and an anus; but the body of the constituents of the second order, the Lit. parenchymateux, contains within its parenchyma only ill-defined viscera, having the resemblance mostly of vascular ramifications; and sometimes even these traces of organism are imperceptible. We shall here present a brief sketch of Baron Cuvier’s system.

ORDER I.—THE CAVITAIRES, Cuv.

This nearly corresponds with the order Nematoidea of Rudolphi, embracing also the genus Linguatula or Pentastoma, and the Prionoderma, which Rudolphi has placed among his fictitious or obscure species. Cuvier believes that at the end of this order we ought to classify, as a distinct family, the Lernaeae of Linnaeus, or Epizoaires of Lamarck; but it is now proved that these are really crustaceans, which, in their infancy, do not differ from the new-born Cyclopes, and are equally capable of swimming about; but assuming the character of adhesive parasites, they suffer a deformity that increases with their growth, and conceals their nobler alliances,^[38. The males however retain their freedom and powers of locomotion at all ages. See Cuvier, Règ . Anim. iii. p. 255, note 2; and Burdach’s Traité de Physiologie, tom. iii. p. 130. ] for they never acquire all the members with which the more normal crustaceans are provided. Of all the paradoxical creatures which the naturalist meets with in his researches, there is none that surpasses or equals these in eccentricity, none more at variance with our notions of animal conformation, and exhibiting less of that decent proportion between a body and its members, which constitutes what we choose to call symmetry or beauty. Of these monsters we shall attempt no description; but the figures of a few of them, given in Plate DII. figs. 13-17, will convey some idea of their shapes and variety. They are all external parasites, living on the skin and on the gills of fish, to which they adhere by hooked grasps or claws; and it is presumed that they injure the fish by sucking out their blood. Burmeister, who places them among the Siphonostomous Crustacea of Latreille, gives the following synopsis of their genera.

I. Family Penellina. body without tentacula or articulated members.

*Body more or less twisted in an angular manner, unequally thick, and furnished anteriorly with bifurcated arms.

† Three long corneous arms placed around the mouth; the two anterior, or all the three, forked: the oviferous sac resembling a spirally twisted cord. Leb-naea, Oken.

†† Four soft and fleshy appendages placed around the mouth; the anterior forked; oviferous sac cylindrical. Lerneocera, Blainv.
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Body straight and of equal thickness; four pairs of cutaneous prominences toward the anterior part, which is prolonged into the form of a neck.

† Without arms; nor is the tail penniform. Pennicula, Nordm.

†† With arms, and a penniform tail. Penella, Oken.

II. Family Lernaeoda.

BODY WITH TWO PINCERS, OB PREHENSILE APPENDAGES, SITUATED BEHIND TΠE PROBOSCIS, AND WITHOUT SWIMMING FEET, WHICH AHE SOMETIMES REPRESENTED BY SIMPLE CUTANEOUS PROLONGATIONS.

* Prehensile apparatus simple, situated at the point of union between the trunk and the neck. Anchorella. Nordm.

** Prehensile apparatus elongated, composed of appendages which have the shape of arms, and which are united together near their extremity.

† Cephalothorax prolonged into a neck.

§ Pincers with hooklets placed on the lower part of the neck, between the arms. Tracheliaste, Nordm. Lernantoma, Blainv.

§§ Pincers with hooklets placed at the upper part of the neck, almost behind the head. Branchiella, Nordm.

†† Cephalothorax short, rounded or heart-shaped; pincers, with hooklets, placed immediately in front of the arms.

§ Arms very long and thin: the abdomen elongated, and not jointed. Lerneopoda, Blainv.

§§ Arms very long and thin: the abdomen circular and jointed. Achthere, Nordm.

§§§ Arms short and thick: abdomen not jointed, and verrucose. Basaniste, Nordm.

*** No prehensile organs in the shape of arms.

† Tentacula of two or three joints not formed of articulated feet, armed with hooklets; a pair of jaws and two palpi. Chondrocahthus, Cuv.

†† Tentacula with six joints; an eye on the top of the head; three pairs of jointed pincers behind the mouth, which is conical. L erenanthrope, Blainv.

After this family there follow, in the system of Cuvier, some genera of marine worms, which are not parasitical, and are undoubtedly members of the family Planariae. The Nemertes had been previously characterized by Sowerby, and by him named Lineus. It is remarkable for the extraordinary length to which it grows. We have been informed that specimens of thirty feet long have been seen, and have had some in our possession which, when extended, could not be less than fifteen or twenty. It is to be found under stones, coiled up in an intricate mass of a purplish-brown or claret colour, smooth and glossy, of nearly uniform calibre throughout, and free of wrinkles or joints. The head is distinct enough; and underneath it there is a long slit, which is the mouth. The intestine runs the entire length of the body; and, what is very curious, we have a specimen which has swallowed a periwinkle, the shell forming a knob near the middle of the body, reminding us of the appearance of a gorged snake. After the Nemertes, says Cuvier, we ought probably to place the Tubula-hiae of Renieri, which are equally large and very much elongated, but which have a small mouth pierced under the anterior extremity; and the Ophiocephales of Quoy and Gaimard, distinguished by having the apex of the snout cleft; and the Cerebratules of Renieri, which differ from these merely in the comparative shortness of the body.

ORDER II .— THE PARENCHYMATEUX, Cuv.

This order is divided into four families. The first is co-equal with the Acamnocephala of Rudolphi; the second embraces the Trematoda of the same author, with some additions. One of the most extraordinary is the Hectocotyles of Cuvier, a long worm, compressed and enlarged at the anterior extremity, upon which is the mouth, whose inferior surface is garnished with numerous suckers, arranged in pairs; and at the posterior extremity there is a sac, filled with folds of the oviduct. One species, which hides itself in the flesh of the sea-polypus (Octopus), is four or five inches long, and has 104 suckers; another of smaller size, and with seventy suckers, is the parasite of the Argonauta. The Aspido-gaster of Baer is a minute parasite of the mussel, distinguished by having under the belly a lamina, hollowed with four rows of littlepits. In this family also Cuvier arranged a multitude of animals which were formerly comprised in the genus Planaria of Müller.^[39. The best history of the Planariae is entitled Observations on some interesting Phenomena in Animal Physiology, exhibited by several species of Planaria:. By John Graham Dalyell, Esq. Edinb. 1814, 8vo. Judging from the infrequency with which thia interesting volume is quoted, we presume it to be much less known than it deserves to be. ] They are little worm or leech-like animals, with a soft, compressed, or foliaceous body, found both in the sea and in fresh waters. There is no abdominal cavity. The mouth, placed in the belly near its middle, is furnished, in many, with a protrusile proboscis, which leads into an intestine of a dendritic character, and whose ramifications permeate the whole body. A vascular network occupies the sides; and there is, posterior to the oral aperture, a double system of generative organs. The species are androgynous like the snails, and oviparous. The head is ornamented in most with black specks, which are probably eyes. They are voracious creatures, feeding on animal matter; but, above all, they are remarkable for the facility with which they reproduce any part of the body that may have been lost by accident, or cut away by the curious experimenter. In this wonderful power they equal the Hydra. The species and races are extremely numerous, and admit of much complicated classification.^[40. They constitute the class Turbellaria of Ehrenberg, and a synopsis of his arrangement is given in Lam. Anita, sans Vert. 2de edit vol. iii. p. 609. ] Dugés distinguishes them into the typical Planariae, with a ventral aperture: the Prostomae, which have one orifice at the anterior, and another at the posterior extremity; and the Derostomes, in which the oral aperture is beneath, but placed considerably forwards.^[41. See a description of some British species by Dr Johnston in the Magazine of Zoology and Botany , vol. i. p. 529. ]

The third family of the intestinal Parenchymateux is named the Taenioides It conjoins the orders Cestoidea and Cystica of Rudolphi. The fourth family is the Cestoides, and embraces only the genus Ligula of Bloch, parasitical worms found in the intestines of some birds, and of various fresh-water fish. They appear the simplest of all the Entozoa. The body is like a long ribbon, obtuse in front, marked with a longitudinal stria, and finely scored crosswise. There is apparently no external organ; and in the interior we see nothing but the ova scattered in the parenchyma. The species which infests the bream grows to five feet in length; and Cuvier says that the worms are considered in some parts of Italy an agreeable food.

In the bowels of some seals, and birds which live upon fish, there are found certain worms very like the Ligulae, but in which genital organs have been developed, and even a head similar to that of the Bothryocephalus or tape-worm. Rudolphi hazards the conjecture that these worms of birds are identical with the Ligulae of the fish, which have acquired their fuller organization by passing from the intestines of the cold-blooded animal into those of a warm-blooded one. There are some facts in the history of other tape-worms which give a colour to this conjecture: and we may just call attention to its bearing upon the question of their equivocal generation.^[42. Entoz. Syn, p. 596. ]

II .— ECHINODERMATA.^[43. From ιχινος, a hedgehog, and έϑμα , the skin. Synonymes: Echinoderma; Les Echinodermes; Cirrhodermaires; Crustacea of Blumenbach. ]

The Echinodermata have been defined to be radiated animals, with a coriaceous or crustaceous skin, commonly tuberculated, or even spiny, and perforated with holes arranged in regular series, whence issue contractile tentacular suckers. The mouth is either inferior or lateral, and mostly armed with certain osseous pieces that form a circle of teeth within the lip; the stomach is a loose bag, with distinct parietes, and with an intestine or caecal appendages; the respiratory apparatus is vascular; and the species are oviparous. This definition however must not be too nicely examined, otherwise several animals, which offer but a feeble and partial adumbration of its characters, might be excluded from a class to which they properly belong. The stellated disposition of the organs is generally so remarkable, that fancy will dream the Echinodermata to be the children of night, which have drawn their figures from the stars that presided over their birth; but there are among [7:21:1000]them some vermiform families which have resisted the planetary influence, excepting only in certain parts around the mouth. Their next most general character is derived from the tentacular tubes which the animals push out from pores drilled in rows between the vertical segments of the thick integument of the body, and withdraw again in part at pleasure: but the character becomes abnormal in some Holothuridae, which have these suckers pullulating irregularly from the surface; and it fails us altogether in Sipunculus and its allies. The organs in question much resemble the tentacula of the snail, but they are really very dissimilar both in the use and mechanism of their movements: they may be compared to the glass of a thermometer, for they are closed tubes, with a vesicular bulb placed within the body, and they are protruded by forcing the fluid, with which the bulb is filled, up the cylindrical portion. It is not through them, as Lamarck imagined, that the circumfluent water gains access within the body, although it is very true that almost all the Echinodermata contain a large but variable quantity of it, partly flowing through a special apparatus, and partly effused, if we may so speak, into the visceral cavity, bathing the surface of every viscus which may be said to float in it; and since the quantity of this water can be increased or lessened at pleasure, so we find that the contour of all the flexible species is liable to alteration of figure, according to circumstances. When

Batt'ning in ease, and slumb ’ ring life away, the skin is rotund and swollen, and the organs are distended and displayed; but if alarmed or removed from their sites, the fluid escapes from them, and collapsion and retraction follows. Other purposes which this water must serve, are its aid in rendering the crude nutritive fluids of digestion fit for assimilation, and its purifying influence over the blood; for we learn from Delle Chiaje, that in all the Echinodermata there is a blood of a yellowish or orange colour, composed of a large proportion of lymph, and a certain number of globules endowed with a self-rotatory motion.^[44. Blainville’s Man. d’Actinologie, p. 65. ] In what course this blood circulates, has not been determined. Tiedemann, who may be regarded as our best authority on such a point, says that it “moves in a circle, but which is confined to the alimentary sac and ovaria alone. In the Asterias, numerous thin-coated veins, coming from the stomach, the coecal appendages, and ovaries, unite into a single trunk. This produces a dilatation analogous to a heart, and then ramifies like an artery. In sea-hedgehogs are found, on both sides of the circumvolutions of the intestinal canal, two vascular trunks, the external of which seems to be a vein, and the internal an artery. These two trunks communicate by a dilatation similar to a heart, or by their minutest ramifications. The intestinal canal of Holothuria likewise exhibits an arterial and venous trunk, connected with each other by their smallest ramifications, as well as by a large vascular net-work spread over one branch of the respiratory organ.”^[45. Treat, on Comp. Physiology, trans, i. p. 160. ] Delle Chiaje’s description of the same system differs considerably;^[46. The differences are fully pointed out by Dr Sharpey in his excellent article “Echinodermata,” in the Cyclop, of Anat. and Physiology, it p. 41. ] and it is difficult to define the limits between it and the system of vessels for conveying currents of water through the body. Blainville, of distinguished excellence as a comparative anatomist, felt this difficulty. He has concluded that there is no real circulation, and that the sanguineous system of the Asterias, and perhaps even of the Echinides, is nothing else than a system of ramose aqueducts, like the tracheae of insects; and indeed it appears certain that these vessels communicate with the exterior by orifices more or less conspicuous. But, he adds, it is difficult to say as much of the vessels which we find in the Holothuridae, for no anatomist has suspected their direct communication either with the arbuscular tentacula, or with the real aquiferous vessels, or with the desi-droidal branchiae; so that in these animals there may be an oscillatory movement of the blood in its special system, but certainly no circulation of it, returning and going to and from a font of pulsion.^[47. Man. d’Actinologie, p. 86. ]

The aquiferous system alluded to must not be confounded with the aquiferous cutaneous tubes that jut out from between the tubercles on the dorsal surface of the star-fishes, but is an internal ramose set of vessels for leading water from the general cavity of the viscera, more especially into the locomotive organs of the animal, and its buccal tentacula. “It is composed of vessels,” says Tiedemann, “which commence from a canal placed around the mouth, and spread in rays over the internal surface of the skin, as in Holothuria, or proceed to the chalky covering, as in seahedgehogs and asterias. These vessels open in the hollow tentacula,^[48. The feet or suckers are here meant. ] and their vesicular dilatations. They contain a limpid fluid, which is shed over the tentacula during the animal’s motions, and causes their increase or shrinking. When the animal draws in his tentacula, the contraction of their muscular coats forces the liquid again into the vessels. The fluid contained in this vascular system is not therefore agitated by a circular movement, but only flows outwards from within, and vice versa. This liquid, which is probably derived from the blood, seems at the same time to serve for the nutrition of the skin, of the chalky covering, and the locomotive organs.”^[49. Comp. Physiology, trans, vol. i. p. 161. Dr Sharpey doubts their being nutritious vessels, as is here asserted, for their liquid is not san-gu neous, or even a secretion, “but agrees almost entirely in composition with sea-water.” Cyclop, of Anat. and Phys. ii. p. 41. ]

With this system, that of respiration is most intimately associated; nor indeed are there any separated branchiae, either in the star-fish or sea-eggs, whose fluids are aerated by a flow of pure water over their surfaces, and around and within their viscera, driven over them in currents determined by the regulated action of vibratile cilia, which clothe them almost everywhere, as the researches of Dr Sharpey have more especially proved.^[50. Cyclop, of Anat. and Phys. art. "Cilia,” i. p. 615. ] In the Holothuridae, anatomists have generally considered as pulmonic certain organs which lie between the long curves of the intestine, and closely connected with it. They are very much branched in a dendroidal fashion in some species, their branches reuniting successively backwards, until they form at last two trunks, or one only, that opens with the intestine into the cloacum; but it seems to shew how readily their presumed function can be transferred to the general cavities, when we find other species of the family in which these organs are slightly sketched, and some in which their existence is not to be demonstrated.

With Lamarck, we shall further pursue the history of this class under its three sections or orders, which are named and defined as follows.

I. Fistulides. Body elongate, cylindraceous; the skin leathery, soft, and irritable; intestine with an oral and anal orifice, the former encircled with retractile tentacula.

II. Echinides. Body more or less rotund or angular, covered with a shell of immoveable testaceous pieces without projecting arms; anus distinct from the mouth.

III. Stellerides. Body depressed, circular or angulated, and divided into arms or rays; the skin creto-coriaceous, tubercular; intestine in some families only, with an orifice distinct from the mouth.
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ORDER I .— FISTULIDES,^[51. Synonymes: Fistulida; Fistulidans; Holothurida; Holothuridea; Holothurina; Holothuries. ] , Lamarck.

The radiant character of the class is faintly impressed upon this family, being marked with decision only in those parts which encircle the mouth. The form of the body is in general that of an elongated cylinder or pentagon, rather unseemly, and invested with a thick coriaceous tunic, which is sometimes scaly, like the skin of a fish, more frequently of a uniform earthy colour, or white painted with bright red or orange spots. If placed in a vessel of sea-water, we soon observe, issuing from perforations in the skin, a number of papillary tubes, which the animal has the power of extending at will. These are scattered over the body, or more usually arranged in rows, limited sometimes in extent, at other times running uninterruptedly from one extremity to the other. The creature gives perhaps little other evidence of life than what we infer from the protrusion of these organs, and from continual changes in the figure of its body. A species of Holothuria, which we watched for some time, was as changeable in this particular as its native ocean. From a long vermiform cylinder, it would become gradually shortened, and swollen in the centre; then it would relax itself, and again become cylindrical; next one part would be blown out, and another drawn in, with a deep stricture, as if a thread had been tied round; or the contraction would begin near the head, which is then made very narrow, and would spread backwards, the anterior portion recovering its original diameter as the wave of constriction passed away; and sometimes the contraction will spread in the opposite direction. This mutability in form is dependent on the action of the muscles which enter into the composition of the skin, and which are of two kinds: one set forms a series of transverse parallel fibres, lining its inner surface completely with an even muscular coat, while the other set is collected into five or ten strong cord-like tendinous bands, which stretch from the oral to the anal aperture, usually in pairs, but where five only, they are at equal distances.

In this state, it is not always easy to say which is the anterior and which the posterior extremity, for the tentacula and foreskin containing the oral apparatus are retractile, and then wholly concealed. When displayed, the tentacula form a circle, in which all the beauty of the creature centres. They are all alike in some species; in others two of them are smaller and less divided than the rest, which for the most part are sufficiently branched to be called plumose or arborescent. Whether their functions are the same, has not been questioned; but we may observe, that the less are often alternately pushed out and in when the larger are kept steadily extended. They fringe, and are the continuation of a ligamentous neck; and in their middle we find the mouth, a round aperture, often limited by an interior ring of bony pieces, bound together by a strong muscular ligament, and giving insertion to one half of the longitudinal muscles. The pieces of the ring are ten in number, a large one placed in regular alternation with a smaller, all of them of a fibro-cretaceous consistence, so that, acted upon by the muscles attached to them, they must prove bruising instruments of considerable power.^[52. "Quaeque lanternae in Echinis quasi analoga est, nisi quod amplior sit, et dentes deficiant, quibus ea in Echinis armnta reperitur.” Pallas, Misc. Zool. p. 156. ] Exterior to, and between them, there is a circle of five or more vesicular glands of a linear oblong shape and fleshy nature, the use of which is undetermined; for while Bo-hadsch and Cuvier regard them in the light of salivary glands, Blainville is tempted to refer them rather to the aquiferous system. The intestine is very long. The superior portion, or that immediately under the osseous ring, from being thicker in texture and a little wider, may be considered the proper stomach, for the remainder is of a cylindrical form and nearly equal calibre throughout. It is tied to the side by a vascular mesentery; and after making a large bend upon itself within the belly, terminates in a cloacum or passage common to it and the respiratory apparatus, and which leads outwards by an aperture opposite the mouth. The only chylopoetic organ attached to the intestine, the salivary glands excepted, is what is presumed to be a liver, under the guise of some penicillate structures, which occupy the space formed by the sinous bend just mentioned. From this structure, and from the great length of the alimentary canal, we may infer with probability that the food of the Fistulides is of sparingly nutritious quality, while their organization otherwise fits them to be little better than the recipients of that chance fare which currents or accident may bring almost within contact. Bohadsch found the intestine of a large Holothuria, of which he has written an excellent description, filled with sea-sand and the fragments of corallines and fuci;^[53. De Anim. Marin, p. 86. ] and from matter like this, and the water gulped with it, the necessary nourishment is extracted during its long and lingering course.

The ovaries consist of a bundle of filaments attached to a determinate spot on the side near the middle of the visceral cavity, and notwithstanding their numbers, they have only a single exterior orifice placed in the median line near the head, which it is often difficult to discover from its minuteness. Each ovary contains many ova, of a roundish figure, and apparently immotive, being unclothed with the cilia which move about the eggs of polypes. At the period of their maturation, there occurs a simultaneous development of certain very extensible filaments, which originate from near the anus, and are supposed by some anatomists to be the male organs. How and under what form the ova escape, is not known. They are occasionally retained in the abdomen and developed there, which has given rise to a belief in their viviparous generation. Thus Bose affirms, on the evidence of personal observation, that the common species of Holothuria are viviparous;^[54. Hist. Nat. des Vers, ii. p. 150. ] and the same assertion had been made long before by Otho Fabricius in regard to his H. pentactes.^[55. Faun. Groenlandica, p. 353. ] But the most singular notion has been broached, that these animals do, at their full time, evacuate the entire mass of pregnant ovaries, with the other viscera, through the month or anus; do, in fact, voluntarily, and from a law of their nature, eviscerate themselves.^[56. Bohadsch de Anim. Mar. p. 88. ] The fact on which this seemingly absurd conjecture is based is most singular, perhaps unexampled in any other animals. When a Holothuria is placed in a basin of sea-water, it has been seen to emit jets of water from the posterior aperture at regular intervals, the jets succeeding each other at not more than about a minute’s interval. This water is undoubtedly what has been rendered injurious by its stay and use in respiration, mixed probably with a considerable proportion from the intestine. But when the water in the basin has become impure, these jets become also less regular; and after evidence of uneasiness, and some unusual motions, the worm will at length vomit up its tentacula, its oral apparatus, its intestine entire and with its appendages, and a large cluster, if not the whole, of the ovaries. And after this complete embowelling, the animal lives for at least six or seven hours; for the empty skin shews, by its motions, that nearly all its irritability remains, and even its power of locomotion is not lost. “Denique, quod magis mirum est, omnia Hydroe individua, postquam intestina sua dejecere, septem et ultra horas su-pervivunt, [7:21:1002] motu non duntaxat elastico sed progressivo gaudentia.^[57. Bobadsch ut supra cit. p. 86. Also Edin. New Phil. Journ. viii. p. 47. ]” Sir John G. Dalyell has even proved, by actual experiment, that if this poor embowelled worm is supplied with fresh sea-water at proper intervals, it will live to replace all its viscera with new growths, reproduce new tentacule, new teeth, a new stomach and intestine, and all its complicated aquiferous system, so as to be in every respect as it was previous to its wonderful evomition. It is by such miracles that we are brought to exclaim with Pliny, “mihi contuenti sese persuasit rerum natura, nihil incredibile existimare de ea.”

The Fistulides are natives of every sea. Blainville believes them to be more numerous on the coasts of cold or temperate countries, than under or within the tropics; but the data for such an opinion are unsatisfactory.^[58. Man. d’Actinologie, p. 189. ] They abound in the Mediterranean, and are scattered over the German Ocean. The more remarkable species live at considerable depths, and come rarely under the notice of the zoologist; but some are littoral, lurking among sea-weed and in the crevices of rocks, while others burrow in the sand. They appear to be gregarious, and are evidently by their organization very limited in their powers of locomotion. When they reluctantly remove from their sites, it is by the aid of their tentacular suckers; thrusting these forward to the utmost, they fix them to the ground, and drag the body on at a pace slower than the shadow on the dial. By the same organs they retain themselves in their natural positions, and effect a safe anchorage when the sea is agitated to the bottom. Otho Fabricius says of Holothuria pentacles, that it can swim,^[59. “Alias etiam in libero mari trans littora nature conspicitur, tentacula sua extendendo et complectendo.” Faun. Groenl. p. 353. ] a sort of exercise which the structure of the creature would not lead us to predicate; but the fact appears to be confirmed by Bosc, who tells us that the Holothuriae swim slowly, as much by a kind of vermicular motion as by that of their tentacula, and the faculty which they possess of inflating the body at will.^[60. Hint. Mat. dee Vers, ii. p. 148. ]

We learn from Delle Chiaje, that some of the Holothuriae are eaten by the poor inhabitants of the rich shores of Naples; and the Sipunculus edulis (Lumbricus edulis, Pallas) serves as food for the Chinese who inhabit Java, and who search for it in the sand, with little bamboo sticks prepared for the purpose.^[61. Griffith’s Cuvier, Moll, and Rad. p. 455, pl. 12, fig. 3. ] Their appearance is to us loathly, and they breathe no Sabaean odour; yet the celebrity of the Trepang, a species of Holothuria,^[62. The species does not seem to have been ascertained. Mr Collier and Professor Jameson refer it to Holothuria tubulosa; Professor Grant says that it is the H. ananas (Outh. of Comp. Anat. p. 332); while Lesson calls it H. edulis, which is the type of a new genus named Trepang. From Collier’s figure, it appears to be apodous, and also destitute of tentacula, so as much to resemble an Ascidia (See Edin. New Phil. Journ. viii. p. 47, pl. 1, fig. 1); but his description corrects these iconographical defects. ] must rescue the family from contempt in the eye of every liberal epicure, who, rising above national prejudices, allows his Chinese brothers to extol unchecked their treasures of the stormy seas. “This animal,” says Professor Jameson, “is used very extensively by the Chinese for culinary purposes. They make of it a very rich and palatable soup, and dress it in different kinds of stews. There are various modes of curing it. It is first gutted and the water pressed out of it, and then laid in dry lime, called by the natives chunam; afterwards, according to the circumstances of the fishing station, dried in the sun, or on stages by means of fires of wood under them. It is a most important article of commerce, and is the most considerable article of the exports of the Indian islands to China, unless perhaps pepper. There are fisheries, as they are called, of trepang, in every country of the Indian Archipelago, from Sumatra to New Guinea. It has also within these last few years been discovered abundantly on the coasts of Ceylon and the Isle of

France, and is no doubt general throughout those seas. It has, as we are informed, already been sent from thence to China, where it finds a ready market, although, from its being unskilfully prepared, it is classed with the lowest qualities of the archipelago. When the Chinese can be employed in fishing and preparing it, there is little doubt that it will form an important article in the commerce of those countries with China, as it can be got in any quantities.” After some farther details relative to the mode of fishing and curing it, the professor adds, “the whole quantity sent to China from Macassar, and other parts of India, may be estimated at 14,000 piculs. Taking this quantity at the low average of forty dollars a picul, and valuing the dollar at 4s. 3d., its entire value, in a commercial view, is L.119,000. Notwithstanding this enormous export to China, we do not understand that its value in the market has ever been materially affected by the quantity imported; an evident proof that the demand of the market still exceeds the supply. When we reflect that the opium, pepper, birds’ nests, sharks’ fins, trepang, and various other articles, the products of the countries under our control, which are fully as indispensable to the Chinese as the teas of China are to Europe, the fear so much entertained of the Chinese interdicting our trade with that empire is quite preposterous. In short, these few articles of luxury give us the command of the Chinese tea market. The celestial empire cannot exist without its trepang and birds’ nests.”^[63. Edin. New Phil. Journ. viii. pp. 50-2. ]

The systematic arrangement of the order has kept increasing in complexity with the discovery of new species, and their minuter examination. Linnaeus found two genera sufficient in his time, viz. “Siponculus —corpus teres, rostro cylindricoangustato and “Holothuria —corpus ore antico tentaculis camosis antice cinctum.”^[64. Sgst. Nat. edit. 12, p. 1072. ] Pallas referred the latter to Actinia, of which they formed a section, distinguished by having two apertures to the alimentary canal; for it was the opinion of this great naturalist, that differences of structure, which, in higher grades of animals, were justly reckoned to be of generic value, were in worms to be deemed not more than specific.^[65. Miscell. Zoolog. p. 72. ] The family, nearly as we view it, was first defined by Lamarck, who made it embrace five genera, that stood in three separate sections, thus:

* 1. Actinia:

* * 2. Holothuria;

3. Fistularia:

* * * 4. Priapulus;

5. Sipunculus.^[66. Anim. sans Vertèbres, ii. p. 528. ]

In the Règne Animal, the Echinodermata form two orders, the pedaneous and the apodous. The Holothuries are one of the families of the first, while the species which Lamarck would have referred to his third section constitute the entire second order. Cuvier throws the Holothuries into unnamed groups, from peculiarities in the distribution of the tentacular suckers; and his apodous genera are Molpadia, Minyas, Priapulus, Litho-dermes. Siponculus, Bonellia, and Thalassema.^[67. Règne Anim, iii. p. 238 and p. 241 ] " The latter is now generally allowed to belong of right to the class Vermes.

Latreille’s arrangement is little other than the reduction of Cuvier’s to named divisions, as will appear from the following outline of it.

Class— HOLOTHURIDA.

Order I .—Apoda.

Fam. 1. Lombriciformia. Mouth unarmed. Genera—Boncilia, Siponculus, Miniada.

2. Veretriformia. Mouth armed with osseous pieces.—Priapulus, Molpadia.
[7:21:1003]

Order II— Polyfoda.

Fam. 1. Vagipedes. Feet scattered over the whole body. Genera —Holothuria, Actinopoda, Fistularia.

2. Inferipedes. Feet ventral only.—Phantapus, Phalloide.^[68. Fam. Nat. du Eigne Anim. p. 529. Pari«, 1825. ] '

Blainville’s method of classifying the proper or pedaneous Holothuridae is exhibited in this neat synoptical table:
[table]

But the host of species discovered within these few years, during the voyages undertaken for the promotion of the natural sciences, has proved the inadequacy of these systems; and although the researches of Joeger and Brandt, with ample materials at their disposal, have brought into operation characters of a higher value on which to found a better arrangement, that good work has not yet been satisfactorily accomplished. The characters on which the naturalists mentioned have proposed to proceed, are derived from the absence or presence of the tentacular suckers, their homologous structure or dissimilarity, the existence or not of the aquiferous branchial apparatus, the pattern after which the suckers are disposed, the floating character or adhesion of the respiratory organ, and, lastly, the variations in the tentacule which guard the mouth. Guided by these characters, whose importance is in the order stated, Brandt has worked out a genealogy of the family, perplexing from its numerous subdivisions; but it is confessedly the basis of that lately offered to us by Blalnville, and which we now analyse; for, however dry and barren such tables may seem to be, it is really from their careful study that the student obtains his clearest view of the forms and general structure of the species. “The use of synoptical tables in every branch of science,” says Mr Duncan, “is obvious. They afford great aid to memory; but also, on frequent review, they suggest continually to the inquiring mind new traces of undiscovered relations."^[70. Ann. da Sc. Nat. n. s. vii. p. 272. ] Blainville’s new method of distributing the species, then, is as follows:^[71. Man. d’Actinologie, p. 191. ]

A. H: VERMIFOBMES.

Body elongate, soft, vermiform; the feel small or none. No suckers; tentacula pinnate 1. Synapta, Eschecholtz.

No suckers; tentacula pinnatiful 2. Chirodota, Eschscholtz.

Suckers small, in five bands 3. Oncinolabes, Brandt.

These species are closely connected with the apodous Entomozoa by the Siponculus, the Priapulus, and perhaps even the Molpadia. The first species, instead of feet or suckers, have the body covered with small crotchets, by which they anchor themselves to submarine rocks, &c. Their tentacula are continually in motion, moving towards the mouth. There is no cloacum, the anus being strictly terminal; and there is no aquiferous respiratory dendroidal apparatus.

B. H: ASC1D1FORMES.

Body short, coriaceous, convex above, flattened below, with the orifices superior rather than terminal.

The skin sealy4. Cuvieria, Perou.

The skin rugose but soft 5. Psolus, Oken.

C. H: VERETILLIFOBMES.

Body considerably elongated, softish, subcylindrical, covered throughout with tentacular suckers, of which the inferior are the longest.

The anus widely patulous 6. Holothuria.

The anus plaited 7. Bohadschia, Jager.

The anus closed, with five teeth or scales...8. Mullebia, Jager. d. h: Body more or less elongated; the inferior s uetorial feet longer than the superior, and disposed in a determinate number of longitudinal rows.

The suckers in three rows 5. Stichopus, Brandt.

The suckers in five rows. 10. Diplopebidebis, Brandt.

E. H: CUCUMIFORMES.

Body but little elongated, more or less fusiform, pentagonal, with the tentacular feet forming five ambulacra, one along each angle.

The feet small or obsolete 11. Liosoma, Brandt.

The feet very obvious, and tentacula pinnate. 12. Cladodactylus, Brandt. and tentacula pinnatiful 13. Dactylota, Brandt.

The species in this section connect the family with the Echinides.

F. H: siγonculiformes. Body more or less Suddenly narrowed behind, the pentagonal figure indistinct, without ambulacra, and perhaps without tentacular feet: tentacula simple, short, and cylindrical, as in Actinia. Embraces only the genus 14. Molpadia, Cuvier.

Still more recently the order has been reviewed by Agassiz, and because of the influence which his views will probably nave with naturalists, we deem it necessary to give the names of his genera, to which we shall add their synonymes, and the number of species he enumerates as belonging to each. Agassiz rejects from the order all echinoderms which are not strictly referable to the Linnaean genus Holothuria, a genus of family rank, and divisible into,^[72. Man. d’Actinol. Supp. p. 650, ]
[table]
[table]

ORDER II—ECHINIDES,^[74. Synonymes: Echinida; Echinina; Echinidans. ] Lamarck.

The Echinides are popularly known by the name of sea-urchins or sea-hedgehogs, given to them from their shells being covered with moveable prickles like the skin of those quadrupeds; “Horret capillis ut marinus asperis Echinus but when the prickles have fallen off, the shells are more commonly called sea-eggs, partly from a conformity in the figure between the objects compared, and more so from a similarity in their calcareous composition and texture. From their forms, certain genera have been also called turbans, diadems, mermaids’ skulls or hearts, or fairy-stones; a nomenclature more pleasing to us than the Greek compounds of science, and not more poetical than useful, since it aptly conveys a portraiture of those varieties in which nature has, with her usual sportiveness, moulded these productions. It is from this variety that a general description of the shell becomes impossible; and to form a correct idea of its beautiful and complicated mechanism, it is necessary to select one as a type or standard for comparison and further description. For this purpose we shall take the shell of the common Echinus (E. esculentus).

The shell is of a globular figure, with a flattened base, formed of ten conformable plates, alternately broad and narrow, and ten annectant ones dissimilar in character. All of them proceed from the rim of the oral aperture in the base, and rise upwards, bellying in the middle, whence they again converge, and are united in a circle opposite the mouth by a series of small pieces to be afterwards described. The first series of plates is called arece by Linnaeus; and those by which they are joined together, and which are all narrow and of the same size, he named the [7:21:1004] ambulacra, from a resemblance his rich fancy traced in them to the walks between the parterres of a garden laid out after the olden fashion. The arete are thickly studded with tubercles of different sizes; and when more narrowly examined, it will be seen that each area is divided down the middle, by a zigzag line, into two equal halves, composed of numerous small pentagons set in cross rows, and dove-tailed into each other with the most perfect adaptation, the projecting angle of one series being fitted into the concave angles of the other. Their tubercles support the spines, which move on a pearly globular pivot that sinks into a corresponding cup in the base of the spine, and where they are retained by the soft epidermis or skin that covers the entire shell in its fresh condition. The spines are calcareous, columnar, very often large in proportion to the shell; but with these primary spines smaller ones of three kinds are numerously intermixed, viz. one of the same form, differing only in size; another slender as a hair, but dilated into a club at each end; and another on a flexible stalk supporting three moveable prongs placed in a triangle, not very unlike the trident of Neptune. These Müller mistook for parasitical polypes; and we still find them in many systems forming the genus Pedicellaria among these animals. Their function is unknown; for Monro’s conjecture that they supply the place of the organs of the senses in the more perfect animals, is a very loose one, and improbable.^[75. It has been recently stated, that the animal uses them as grapnels to attach itself to sea-weeds. Our native species covers itself, when residing between tide-marks, with fragments of sea-weeds, evidently as a means of concealment; and we believe they are held on the shell by means of these organs, which are a sort of self-acting forceps. ] The ambulacra are joined to the areae by a plain or even suture, and instead of being tu-bercled, they are perforated from top to bottom with holes, always disposed after a regular pattern, which probably varies in every species. These holes give exit to numerous fleshy tubular pedicles, whose apex forms a circular testaceous shield, serrulated round the rim, concave and perforated in the centre, and formed of six distinct pieces, united by a plain elevated suture. If we now examine the top of the shell, we find it occupied by a small circular tuberculated plate, with a hole in its centre (the vent ) , and the plate surrounded by five triangular scales, and five less ones of a lunate figure placed exterior to and between them. The triangular scales, called the ovarial by Mr Gray, are each of them perforated with a hole leading to the ovaries, and they stand opposite the large areae, into an emargination of which the point of the triangle dips, while the lunate scales, the interovarial pieces of Mr Gray, embrace the points of the small areae and the ambulacra, and are likewise perforated with a hole scarcely visible to the unaided eye, and the use of which is quite unknown. “One of the ovarial plates is considerably larger than the rest, convex externally, and perforated like a sieve with numerous minute foramina, and internally thick and rugose. This plate is somewhat similar, both in form and perhaps in use, to the orbicular spot on the back of the Stellerida, called corpus spongiosum by Spix.”^[76. Gray in Annals of Philosophy, n. s. X. p. 425. On the structure of the shell, see also Grant’s Outh. of Comp. Anatomy, p. 18-21. ]

This description of the crust or shell of the Echinides, it will be remembered, is in a great degree specifical, and will not apply universally even to the globose species, from which it is especially drawn; and it must less accurately apply to those which are greatly depressed, or oval, or heart-shaped, or cranial, or which rise up in the form of a conical pentagon. In all these the ambulacra are often only half of the typical number, and often only partial in their extent; while the areae become coalescent, amalgamating more or less completely, with a consequent loss in the distinctness of their radiation. In many of these, also, the oral aperture loses its central position, and gradually, through a succession of genera, approaches the margin, which in some it occupies; the vent being subjected in its position to the like variations, and drawing with these, alterations of equal extent in the other exterior apertures. Nor in shape and armature does the mouth vary less. It is circular in the true Echinus, and armed within with a most complex apparatus of calcareous jaws, arches, and teeth, consisting of twenty-five separate pieces; while other genera, nearly allied, present the strange contrast of having no trace of these parts, being wholly toothless, with the outer aperture transformed into a narrow transverse labiated slit. To fill up the interval between these extremes, there are genera which have an oral apparatus less complicated than that of the Echinus; for in natural orders or families there are no abrupt transitions in structural organization. Amid all their varieties there reigns an evident connection and harmony, indicating a design or plan after which they have been called into existence; and in contemplating that unity of purpose, and the beauty and intricacy of the workmanship bestowed on the individuals created to fulfil that purpose, we endow them with our superior intelligence, and give utterance to their evidence of the existence and attributes of the Deity.

From the differences just indicated in the structure of the mouth, we naturally and correctly infer that there will be a corresponding diversity of the food on which the Echinides subsist. The jawless Spatangi burrow in the sand, and, swallowing the earth around them, extract a hard nutriment from the decayed animal and vegetable matter intermixed; but the Echini live amid rocks near low water, trace their crevices, and there seek the small crustaceous and testaceous Mollusea, whose shells they are enabled to break by the power and hardness of their teeth. Cavolini indeed asserts that the Echini live upon sea-weed; but the testimony of Dr Monro to the contrary is equally positive, and more consistent with the anatomical structure. That great anatomist tells us that they prey upon living Buccini, “as I had found particles of shells in their alimentary canal ;” and they seize and secure their prey by means of the suctorial tubes which garnish the ambulacra. “I therefore directed the fishermen to bring me, along with the Echini, some living Buccina; to which, as I had supposed they would do, they attached themselves so effectually, that when I lifted the Echinus out of the water, I found it could support with ease a Buccinum which weighed nearly a quarter of a pound.”^[77. The Struct. and. Physiol, of Fishes, p. 71. ] “The Echinidans,” says Mr Kirby, “whose station appears to be often near the shore, upon submerged ledges of rocks, feed upon whatever animal they can seize. We have seen that they sometimes turn upon their back and sides, as well as move horizontally. This enables them more readily to secure their food, with the aid of the numerous suckers in the vicinity of their mouth, which, when once they are fixed, never let go their hold till the animal is brought within the action of their powerful jaws. Lamarck thinks they do not masticate, but only lacerate their food; but as two faces of each of their pyramidal organs answer those of the two adjoining ones, and these faces are finely and transversely furrowed, this looks like masticating surfaces. Bosc, who appears to have seen them take their food, says it consists principally of young shell-fish and small crustaceous animals. As the latter are very alert in their motions, it is difficult for the sea-urchins to lay hold of them; but when once one of these animals suffers itself to be touched by one or two of the tentacles of its enemy, it is [7:21:1005]soon seized by a great number of others, and immediately carried towards the mouth, the apparatus of which developing itself, soon reduces it to a pulp.”^[78. Bridgew. Treatise, i. p. 210. ]

The intestinal canal which this food has to traverse is, like that of the Fistulides, long, cylindrical, and tortuous, with a vent separate from the mouth. There is no chylopoetic viscus; but Blainville deems to be hepatic some glandular spots which he has detected in the parietes of that portion which may be regarded as stomach.^[79. Man. d’Actinologie, p. 72. ] The intestine is fringed throughout with a mesentery, on the under edge of which Monro found two vessels without valves, nearly equal in size and parallel to each other, which he injected with quicksilver, and from them filled a beautiful net-work of vessels, not only on the intestines, but dispersed on fine membranes, which tie the intestine to the inner side of the shell. “I could not however,” he continues, “observe that these two vessels communicated with each other directly, nor by the medium of any organ like to our heart; nor could I observe in the living animal any beating organ like to the heart; yet near to the anus, and connected to the rectum, which is the place of the heart in many other worms, I found a small organ, which seems to be hollow. It appears to be highly probable that one of these vessels is the principal artery or aorta, and the other analogous to our vena cava; and that they communicate by invisible branches, and circulate the blood by the muscular action of their coats, without the intervention of a heart, nearly in the way the vessels in fishes carry the blood from the gills back to their heart.”^[80. The Struct, and Phys, of Fishes, p. 67. ] Blainville however, with a full knowledge of Monro’s opinions, and of subsequent discoveries, aided too by his own dissections, acknowledges that he cannot tell which vessels are arterial and which venous, and thinks it very possible that there is no such distinction in animals so low in organization as the Echinides, the vessels being at one and the same time both arteries and veins.^[81. Man. d’Actinolugie, p. 76. ] How the blood circulates is therefore a subject of conjecture; but we know more precisely the manner in which it is aerated. Lying along the inner surface of each of the ambulacra, there is a branchial leaf or doubled membrane, “not unlike the processes or subdivisions of the gills of a skate,” and having a direct communication with the external tubular suckers, already described as pullulating from the ambulacral pores. The water sucked in by these tubes gains access within the shell by two of the pores (for there is a pair to each sucker), and by their divergence is carried into the opposite folds of the branchiae. Here one portion of the sea-water is supposed to be exuded into the general cavity of the shell, between its inner covering and the intestine; while another portion is again collected, by anastomosing vessels, into five large ducts, that terminate, each by two branches, in large sacs or receptacles over the sockets of the teeth, communicating with each other; and from these the liquor passes down the sockets of the teeth, and is discharged into the sea, on each side of the tooth, between the socket of the tooth and beginning of the oesophagus.^[82. Monro’s Struct. and Phys. of Fishes, p. 69. ] Such is the course of the fluid as described by Monro; but later anatomists maintain that the current has in fact exactly the reverse direction; and they inform us that the sea-water which fills the interior cavity is introduced through certain membranous tubes, arranged in ten small groups round the oral aperture in the base of the shell. Be the fact as it may, there remains a provision of aqueducts most curiously contrived for conducting the medium of respiration and assimilation through the body; and very probably the current is propelled and directed in its way by the action of vibratile cilia, which, in these animals, as in most others, clothe all the serous surfaces of the internal viscera, keeping the fluid in contact with them in perpetual change and renewal, and not allowing it to stagnate even on the outer shell.^[83. See Sharpey in Cyclop, of Anat. and Phys. i. p. 617. Ehrenberg says that the prickles of Echinus saxatilis are covered with these cilia. Ann. des Sc. Nat. n. s. iv. p. 304. ]

The ovary or roe occupies much space within the shell, being very large in proportion to the animal and its other viscera, it is divided into five or four lobes, disposed radiantly, each lobe having a distinct exterior aperture, as well as a communication with each other. The apertures are placed round the anal when this is central, but otherwise their relationship is not so regular and constant. It is probable the ova, after their extrusion, undergo no change analogous to a metamorphosis.^[84. It has been usually believed that the Echinides were hermaphrodites, but Μ. Edwards and Dr Peters are said to have discovered that they are of separate sexes. Ann. and Mag. of Nat. Hist, vol. i. p. 156. ] We have examined the young of Echinus esculentus when it did not exceed one-eighth of an inch in diameter, and then it had the form and armature of adultness; but the prickles were toothed along their sides, and the forcipated organs appeared to have only two prongs. The pieces of which the shell was built were few in number, and the spines round its base were most developed, but the globular form was as perfect as when full grown. It is enlarged in its growth, partly by the deposition of new matter on the edges of the pentagons of which the areae are constructed, and partly by the formation of additional pieces intercalated among the others. These new pentagons are formed principally near the dorsal summit, where the connection between the areae and ambulacra remains loosest. “If, carrying the examination still farther, we remove the spines, we shall then observe that amongst the oviducal and interoviducal plates, and the inter-ambulacral plates that bear spines, there are some less fully developed, irregular in form, wanting even the mammellae and the spines, and taking their place among the mammellated plates only in proportion as they gradually attain to a larger size. The new plates are at first very small, and may be compared to points of ossification, which at first grow simultaneously in all directions, though their lower side completes its formation sooner than the upper, and the upper side is sometimes yet incomplete, even when an incipient mammella is observable in the middle of it. In the region of the body where this increase takes place, the membrane which unites all the plates, and spreads itself over their surface, forming an articular capsule about the base of the spines, is softer and more spongy than it is in the inferior part, where the plates are consolidated and immoveable. It is in fact this spongy mass that deposits the calcareous matter of which the plates are composed; and the spines shoot out in the centre almost in the same manner as the horns of a stag. They do not become moveable until they have attained a certain stage of development; and there is a period in their growth after which their size does not increase. Those however which drop off accidentally are replaced by others, formed, as those had been, by the tumefaction of the membrane which covers the plates. We may always observe, in a single specimen of the Cidaris, all the gradations of increase, from that of the plates which have completed their growth, and bear spines several inches long, down to the smallest points of ossification of the plates yet unfurnished with spines. These facts I have ascertained by examining several individual specimens, which exhibited all the intermediate stages of development through which the pieces in question must pass; and indeed, when we have no direct means of observing the growth of an animal in one individual, the only resource left us is to compare a great number of individuals, representing a [7:21:1006]complete series of all the stages through which the species to which they belong has to pass before their growth is completed. The only difference between this process and the direct observation of any development is, that in the one case we observe in one and the same individual that succession of changes which, in the other, we trace through a series, as complete as possible, of several individuals. Such is the course that I have taken with respect to the Echinodermata. The young Echini have a small number of plates in each of their vertical series; they appear to be slowly increased in size by the deposition of calcareous matter at their circumference, until those which surround the mouth have completed their growth, and are entirely consolidated. The superior plates continuing to grow, increase, from the top downwards, the periphery of the body, which remains depressed so long as the inferior are the only plates consolidated; but in proportion as a greater number of plates becomes immoveable, and as there is formed, in the upper region, a greater number of plates reaching down to the circumference of the spheroid, the testa becomes rounded, and finally assumes a spherical form. It is to this cause that we are to ascribe the differences of contour exhibited by the Echini at different ages. In some species there are found individuals presenting even a pyramidal shape, and this takes place when there is still formed a great number of plates subsequently to the consolidation of those occupying the greater diameter of the animal’s body. These facts sufficiently explain the gradual growth of beings which approximate more or less nearly to the spherical form; and shew how carefully we should guard against the introduction of nominal species in consequence of a mere difference of form resulting from age only.

“It would be interesting to trace the development of these animals ab ovo. But no naturalist has yet observed the state of the Echini on their first issuing from the egg. As to the spines, it is evident, especially in the Cidarites, that those surrounding the mouth are the first that attain their full growth, while the largest are those in the upper tier of the disc; and those which have not yet completed their growth are found around the oviducal plates on the outside. The correctness of these observations will be demonstrated by comparing the differences of development exhibited in this region by the spines that stand nearest to each other. We should be mistaken however as to the growth of the Echinodermata, did we think that there is a generic connection between the plates, on account of their forming vertical series from the mouth to the summit of the disc. It has been already remarked, that the plates of each space are alternately a little more elevated than each other; but no attention has been paid to the manner in which the plates of all the spaces succeed each other in the same Echinus; and yet, if we consider it closely, we shall see that the new plates are developed in spiral lines, passing without interruption from one series to another, through all the spaces from the circumference of the mouth to the dorsal summit, so that those which rest on each other in a vertical line do not make their appearance in immediate succession. It appears to me well worthy of remark, that in these animals, holding so low a rank among organized beings, we should find the succession of the solid parts composing the integument so strikingly analogous to the arrangement of the leaves around the stems of plants; an arrangement the laws of which have been recently discovered by Μ. Schimper, and explained, so far as regards the Coniferce, in a memoir of Μ. Braun on the arrangement of the scales of their cones.

“The small plates surrounding the mouth, and those around the anus, are arranged in a peculiar manner. They are easily moved, and thus facilitate the deglutition of the food, and the voiding of the excrements. In general the testa of the Echini is not so immoveable as one who had not observed them in a fresh state might be led to suppose. All the plates forming the upper part of the disc are often set in motion; sometimes they sink, sometimes they rise, and, in the oblong species, the longitudinal diameter is often extended beyond its ordinary length.”^[85. Agassiz in Annals of Nat. Hist. i. p. 40-42. ]

The Echinides are in general littoral animals. The species with a thin brittle shell, covered with small hairs like bristles, as the Spatangi, burrow in the sand, covering themselves up by the aid of their spines; but those with a stronger prickly crust hide themselves in rocky places. Looking at their rotund limbless forms, we might imagine that they must constantly be fixed to one spot, or, if moveable, that, from the difficulty in bringing members so numerous and opposite to co-operate, or from hesitation in what tract to move, seeing that they are all alike and look to all sides, still a perpetual sedentariness would be their choice. But it is not so, and their motions are neither less regulated nor slower than those of the majority of avertebrated animals. They usually advance on their flat basis, but when an individual chooses, it can move forward by turning on itself like the wheel of a coach. From the nature of their localities, they are much exposed to bruises, and worse foes in the shape of fish and worm. The latter they repel by their spinous panoply, which they can erect and stiffen, presenting a thousand spears on every side, and no point unguarded;^[86. The following epigram of Martial (xiii. 86) is very descriptive:— Iste licet digitos testudine pungat acuta, Cortice deposito mollis echinus erit. ] the bruises they bear with impunity, and it must be a wound only short of total disorganization from which they cannot recover. Monro has even seen the pieces of a broken shell walk off in different directions. By what organs the Echinides exercise their locomotive powers has been disputed. Most authors assign this duty to the spines of the areae and the ambulacral suckers conjointly. Baster tells us, that the latter are the principal organs;^[87. * Opusc. Subs. i. iii. p. 110-4. Also Fleming, British Animals, p. 476. ] and, according to Blumenbach, they are the only ones,^[88. * Introd. to Nat. Hist. trans. p. 267. ] the prickles being merely organs of offence and defence. Now, says Μ. Agassiz, this is a very erroneous opinion,—vox et praeterea nihil,—for it owes its birth and continuance to a mere verbal influence, the term ambulacra being first translated into alleys or walks, and then the organe which grow in them were subsequently supposed to be the walkers. Without questioning this very questionable transition, we know that Agassiz is wrong in denying the tentacula their pedestrious function. “How, in fact,” he asks, “could these small tentacula, with all their softness of texture, situated, as they generally are, in that part of the body which is never brought into contact with the ground when the animal moves, and overhung by calcareous solid spines; how, I ask, could those flexible tubes be used as organs of motion? It is an undeniable fact, and I have often observed it myself, that it is with their spines the Echini move themselves, seize their prey, and bring it to their mouths, by turning the rays of their lower edge in different directions.”^[89. Annals of Nat. Hist. i. 36 ] Our own observations, on the contrary, have satisfied us that the common Echinus moves from place to place solely by the aid of the tentacular suckers; the spines, as Mr Couch correctly states, acting as levers or crutches. Agassiz exaggerates the littleness and weakness of the suckers: in the common Echinus, whose spines are not above half an inch in length, the suckers can be extended one inch and a half, so as greatly to overreach the spines; and they can at the same time be rendered firm and rigid [7:21:1007]by distention, from water, and the contraction of their own muscular parietes. The spines are moved principally, we think, by means of the exterior irritable skin which covers the shell and envelopes their bases; but when these spines are very large, the tubercle to which they are articulated is perforated for the transmission of muscular fibres from within, and which appear to be inserted into their roots by a coronet of fibres.^[90. See Kirby’s Bridgew. Treatise, p. 207. the largest spine of an Echinus on record is that noticed by Mr Gray, “nearly an inch and half in circumference, and more than eight inches long.” Ann. of Nat. Hist. i. p. 414. ] The number of spines and suckers,— and let it be remembered that there are several muscles to every spine and every sucker,—on a single individual, is indeed wonderful. A specimen of Echinus esculentus, of moderate size, will have at least 160 primary prickles on each of the large, and 80 on each of the small areae; that is, 1200 in all; but reckoning the lesser bristles, there will not be fewer than 3000: and there cannot be less than 100 suctorial tubes in each ambulacrum, making the number of exterior appendages in this creature 4000. We join in the conclusion of Baster: “Quod si jam musculorum, ad aculeorum et proboscidum motum necessariorum copiam animo concipiamus, Omnipotentem, quae haec animalia creavit, sapientiam attoniti et venerabundi adoremus, necesse est.”^[91. Opusc. Subt. i. iii. p. 113. Professor Grant says, “there are more than 10,000 pieces in the shell of the Echinus esculentus, without counting the complicated dental apparatus of the mouth, or the respiratory and ovarial plates, or the very minute calcareous pieces disposed irregularly on the coriaceous membrane around the oral and the anal orifices.”— Outh. of Comp. Anat. p. 20. ]

The seas of warm and tropical countries are the most productive in Echinides; but the living species are few compared with the fossil, which are found principally in the chalk and oolite formations, in such abundance, and in so fine a state of preservation, that they are common and favourite objects in collections. Desmoulins has, in the following table, which, although incomplete, is interesting, exhibited the proportions which the extinct bear to the still existing species.
[table]

The direct uses of the Echinides to man are few and trivial. As its name indicates, the Echinus esculentus is eaten in some parts of the south of Europe; Pennant says, “by the poor in many parts of England, and by the better sort abroad.” They are in season in spring, when the ova are most developed, and nearly fill the shell. They are recorded as among the favourite dishes of the Greeks and Romans. “They were dressed with vinegar, honied wine or mead, parsley, and mint; and esteemed to agree with the stomach. They are the first dish in the famous supper of Lentullus, when he was made Flamen Martialis, priest of Mars. By some of the concomitant dishes, they seemed designed as a whet for the second course, to the holy personages, priests, and vestals invited on the occasion.” Epicharmus describes them as used likewise at the marriage feast of Hebe: “Thither came crabs and urchins, unable to swim in the sea, but travelling only on the ground.” In the Wasps of Aristophanes, the old dicast, who is the hero of the piece, repeats a fable respecting an urchin, who, when his shell had been cracked by a woman, summoned witnesses to prove the assault. He is interrupted by the remark, that it would have been much wiser for the creature to buy a bandage. Ennius, in his Phagetica, mentions “dulces echini,” and “calvaria pinguia,” the latter evidently a species of Spatangus, which, we also know from Aristophanes, was considered a very dainty morsel. The Echinus is several times mentioned in Horace as good eating. The shells, cleaned and bleached, are pretty ornaments, with which finical idlers dress up their moss or summer houses, and naturalists their museums. Some fossil species are called fairy-stones, their spines elves’ spurs; and with these names were once associated, as we learn from Sir Thomas Browne, suitable and terrible apprehensions, as well as medicinal virtues; “common opinion commendeth them for the stone, but are most practically used against films in horses’ eyes.”^[93. Vulgar Errors, p. 71. ] Once only has an Echinus been truly beneficial to our race. Some species of the genus Cidaris, we may observe, have very large prickles. The heathen children of the island of Rarotonga, in the South Seas, converted to Christianity by English missionaries, were in want of pencils with which they might be taught to write on slates; for these "they went into the sea, and procured a number of the Echinus, or sea-egg, which is armed with twenty or thirty spines. These they burnt slightly to render them soft, that they might not scratch; and with these flakes of stone for a slate, and the spine of the sea-egg for a pencil, they wrote exceedingly well; and hundreds of them took down the principal portions of every discourse they heard.”^[94. Williams’s Missionary Enterprises, p, 409. ]

We now proceed to give an analysis of a few of the modern methods of classification proposed for the Echinides. Linnaeus, keeping his eye fixed on the recent species only, of which he knew no more than seventeen, reduced them all under one genus, believing, probably, that all previous attempts were premature; for he could scarcely regard the differences on which certain groups were previously grounded, as unimportant, or uninfluential over the habits of the animals. Müller did no more than give a name to the Linnaean sections, which were two, founded on the central or eccentric position of the anus;^[95. Echinus.—“ * Regulares: ano verticali. ** Irregulares: apertura ani subtus uti os.” Syst. Nat. p. 1102 and 1104. ] and the Linnaean simplicity was praised and followed until the views of Cuvier, and the system of Lamarck, freed us from the thraldom of the great Swede, and generated a new spirit, too little regardless, perhaps, of authority, and too prompt to invent and promulgate novel plans, which have had however one good result, in bringing before us prominently and distinctly, structural peculiarities which were previously hid or disregarded amid the vagueness of the Linnaean generalities. The system of Lamarck is exhibited in the following table:
[table]
[7:21:1008]

Of Mr J. E. Gray’s arrangement, published in 1825, we can only give a bare outline, remarking that it is the only attempt which has been made to classify the Echinides after the views of Macleay. We have then, first, the Typical Group— Body globular; mouth central, below; jaw; conical, projectile, with five acute teeth; anus vertical, dorsal; ambulacra complete, forming bands extending from the mouth to the anus.

Family I. Cidaridae ; of which the genera are, 1. Cidaris; 2. Diadema; 3. Astropyga.

Family II. Echinidae : the genera, 4. Echinus; 5. Echino-metra.

Annectant Group.— Body not globular, variously shaped; jaws not projecting; anus lateral or below; anus and mouth covered with imbricate irregular scales.

Family III. Scutellidae : the genera, 1. Echinanthus; 2. La-gana; 3. Echinarachnius; 4. Eehinodiscus; 5. Echinocyamus; 6. Cassidulus.

Family IV. Galehitidae; with the genera, 7. Galerites; 8. Discoidea; 9. Echinanaus; 10. Echinocorys; 11. Echinolampas; 12. Echinobrissus.

Family V. Sfatangidae; embracing, 13. Spatangus; 14. Echi noeardium; 15. Brissus; 16. Ova.^[97. Annals of Philosophy, x. p. 424-431. ]

Blainville’s views of this order are shewn in the following synopsis of his method.
[table]

From the researches of Μ. Desmoulins, it appears that Blainville would now unite Echinoclypeus with Nucleolites, Laganus with Clypeaster, Echinodiscus with Scutella; and Echinocya-mus is probably not distinct from Fibularia, for although they stand in the table in different sections or families, Desmoulins finds that Fibularia ought to be transferred to that which is distinguished by its possession of teeth; and this also is the case with Cassidula.^[99. Ibid. sup. p. 654. ]

The arrangement of Agassiz may be thus epitomized.

ORDER ECHINIDES.

FAMILY I.—SPATANGIDAE.

Body more or less elongated, gibbous; mouth with jaws, sub-anterior; anus posterior, sometimes on the upper surface of the disc, sometimes on the lower; shell thin, granulous, the spines setaceous, often compressed and unequal. The anterior ambulacrum is generally less developed than the rest. They form round the mouth grooves, where the holes are larger, and whence proceed ramified tentacula, like those of the Holothuriae. There are only four oviducal plates, which are very distinct.

1. Disaster, Ag.=Spatangus , Ananchytes, et Nucleolites, Auct.

2. Holaster, Ag. = Spatangus, Auct.

3. Ananchytes, Lam. = Echinocorys, Breyn. Galea et Galeola, Klein.

4. Hemipneustes, Ag = Spatangus, Auct.

5. Micraster, Ag. = Spatangus, Auct. Brissoides, Klein. Amygdala et Ovum, V. Ph.

6. Spatangus, Klein. = Echinospatangus, Breyn.

7. Amphidetus, Ag . = F.chinocardium, V. Ph. Spatangus, a. Bl.

8. Brissus , Klein. = Echinobrissus, Breyn. Nuces, F. Ph. Spatangus, d. Blainv.

9. Scihzaster , Ag. = Echinocardium, V.Ph. Spatangus, b. Bl. family ii.—clypeastres.

Body generally circular; mouth central or sub-central; anus more or less approximated to the periphery, found sometimes at the upper, sometimes at the under surface of the disc.

1. Catopygus, Ag. = Nucleolites, Auct.

2. Pygaster, Ag. = Nucleolites et Clypeus, Auct.

3. Galerites, Lam. = Conulus, Klein. Echinochonus, Blainu.

4. Discoidea, Klein. = Conulus, Leske. Echinodiscites, V. Ph. Galerites, Lam.

5 . Clypeus, Klein. = Echinoclypeus, Blainv. Echinosimus, V. Ph. Galerites, Lam. Nucleolites, de Fr.

6. Nucleolites, Lam. = Echinobrissus, Breyn. Clypeus, Phil.

7. Cassidulus, Lam. = Nucleolites, Auct.

8. Fibularia, Lam. = Echinocyamus, Leske. Echinoneus, Goldf.

9. Echinoneus, F. Phels. = Echinanaus, Koen. Echinoconus, Breyn.

10. Echinolampas, Gray. = Echinanthus, Lcske. Clypeaster et Galerites, Lam .

11. Clyγeaster, Lam. = Echinanthus, Breyn. Echinodorum et Echinodiscus, F. Ph. Lagana, Gray.

12. Echinarachnius, Leske. = Arachnoides, Kl. Echinodiscus et Lagana, Bl. Scutella, Lam.
13.
Scutella, Lam. = Echinodiscus, Lcske. Mellita et Rotula, Kl. Lagana, Bl. family iii.—cidarites.

Shell spheroidal, with two kinds of spines, the first larger on large mammillae, the others smaller, surrounding the base of the first, or covering the ambulacra. Mouth central, inferior; anus opposite, on the summit, opening between the small laminae surrounding it, opposite and sometimes very near to the posterior ambulacral space.

1. Cidaris, Lam.

2. Diadema, Gray, part of Cidarites, Lam.

3. Astropyga, Gray,— Cidarites, Lam.

4. Salenta, Gray,— Cidarites, Auct.

5. Echinometra, Breyn. Echinus, Auct.

6. Ariiacia, Gray,— Echinus, duct.

7. Echinus, Linn. ^[100. Ann. des Sc. Nat. n. s. vii. p. 257, &c.; and Annals of Nat. Hist. i. p. 300, &c. ]

ORDER III—STELLERIDES,^[101. Synonymes: Asterina; Asteroida; Stellerida; Stellendes; Stelleridans; Les Astéries; Astéroides. ] Lamarck.

The “seas have stars,” sings Du Bartas; and if challenged, he would probably have appealed to the members of this family in proof that his fancy was in this instance not more licentious than his verses.^[102. Linckius begins his work "De Stellis Marinis” thus: "Non coelo tantum, sed et mari suae stellae sunt, opera quidem unius Dei artifìcis, sed dieversae prorsus fabriere et naturae " In his “Enquiries into Vulgar and Common Errors,” Sir Thomas Browne has a chapter entitled “That all animals of the Land are in their kind in the Sea ;” which, he rightly says, “although received as a principle, is a tenet very questionable, and will admit of restraint" After some good remarks, the chapter concludes with the following passage, and such passages abounding in the works of this learned physician, render them delectable reading.” Lastly, by this assertion we restrain the hand of God, and abridge the variety of the creation; making the creatures of one element but an acting over those of another, and conjoyning, as it were, the species of things which stood at distance in the intellect of God; and though united in the chaos, had several seeds of their creation. For although in that indistinguisht mass, all things seemed one; yet separated by the voice of God, according to their species, they came out in incommunicated varieties, and irrelative seminalities, as well as divided places; and so, although we say the world was made in six days, yet was there, as it were, a world in every one; that is, a distinct creation of distinguisht creatures; a distinction in time of creatures divided in nature, and a several approbation and survey in every one.” Book iii. chap. 24 ] But it is only some species which have felt the skyey influence over their forms; for even certain of the Asterias are merely pentagonal, and some square, while the total forms of other genera rather imitate a wheel in their facies, with spokes radiating from a central navel: and others again have sought no impress from any object in the heavens or in earth; for though they have been called “lily-shaped animals,” yet is the semblance but postulatory, and he must have a more [7:21:1009]assimilating fancy than our own who perceives it in these objects. Amid this diversity of forms, we may nevertheless remark, that a line drawn so as to connect the species of the rays together would give a circular outline to the body, which is very rarely protuberant, and never globular. It consists of two parts, the disc and the rays; the latter either continuous and homologous, or dissimilar and articulated to the other by the medium of peculiar scales. There is always a distinct dorsal and ventral surface; the former in general vividly coloured, and covered with spongeous tubercles or scales, whose office is defensive; the latter colourless, and furnished with the organs of locomotion and of touch. The colour resides in the mucous coat that occupies the place of the epidermis of higher animals, but the scales and tubercles are essentially parts of the thick creto-coriaceous skin which gives figure and consistency to the whole. In this skin there is deposited a considerable proportion of carbonate of lime, with some phosphate of the same earth, sometimes in the form of scales, either imbricated or scattered; more usually in grains or short pieces, so joined as to make a sort of knotted thread, that, by its divarications and anastomoses, is woven into a netted frame-work, the interstices of which are filled up by the mucous tissue. On the calcareous frame-work the spines and tubercles are placed, and these vary in size and structure according to their position. When dorsal, they are mostly short and obtuse, unordered and immoveable, excepting in so far as their degree of erection and relative position may be effected by the more or less turgid condition of the body; but on the sides of the rays, while their size is greater, they are also dressed in regular lines, and appear to be capable of being moved backwards or forwards by peculiar muscles. In the Asterias, the under surface of the rays is deeply furrowed from their origin to their extremity; and the furrow, analogous to the ambulacra of the Echinides, is occupied with two or four series of tentacular feet, which are also guarded by moveable spines, different in their structure, however, either from those of the back or sides, and forming a protective hedge on each side. There is nothing similar in the Ophiuridae or Crinoidea, whose rays are not grooved, nor possess tentacular feet, but consist of a succession of similar pieces soldered to each other, so that they resemble the vertebral column of some slender anima), or, more exactly, from the squamous nature of the pieces, the tail of a lizard; and, like that tail, they are tapered and flexible to a certain extent, and equally brittle. It is interesting to remark, that this ray, apparently very dissimilar from that of the Asterias, really finds in that genus its type and original; for the roof, if we may so speak, of the ambulacral groove, is made up of a series of pieces catenated exactly like those of the Ophiurae, with compressed processes arching up from each side after the manner of ribs, between whose intervals the tentacular feet are extended.

The mouth is situated in the centre of the ventral surface. It is a circular orifice, with a membranous lip, capable of great dilatation, but bounded by spinigerous and tuberculated angular projections, formed by the convergence of the bases of the rays, that may be useful in capturing and bruising the prey. A short oesophagus leads to the stomach, a large membranous sac occupying the centre or nave of the body; and though connected to the parietes by several ligaments, yet sufficiently loose and dilatable to permit of its frequent eversion and extrusion in the shape of bladdery lobes. It has no intestine, excepting in the Crinoid family, where there is a distinct vent opening on the inferior surface, near the mouth.^[103. Gray in Annals of Philosophy, n. s. xii. p. 392. ] But the nutritive parts of the food pass from the stomach either into sacculated reservoirs, as in Ophiura, or through narrow vascular passages into large complicated caecal appendages, which lie along the floor of the rays, two in each ray, consisting of a regular series of pectinations or overlying lobules, and having no unapt resemblance to some beautiful compound leaf or fern. Such organs we find in the Asterias; and as it circulates through them, the chyle is largely subjected to the influence of the oxygenating medium, and prepared for its assimilation. Such at least is the opinion of Tiedemann; but it may be necessary to mention, that Cuvier, Blainville, and Meckel regard these caeca as secreting organs, analogous to the biliary organs of many invertebrate animals, with which, says Dr Sharpey, it must be allowed they agree in several respects. In the living animal they are bathed, or rather float, in sea-water, which is presumed to be introduced within the body by means of numerous small tubular filaments that rise up on the back between the tubercles, penetrating the soft parts of the skin; and it is ascertained that the water, after a time, may be expelled through the same conduits,^[104. Reaumur in Linck. de Sidi. Mar., App. p. 93. Ehrenberg has discovered that these filaments are inwardly clothed with vibratile cilia, and he believes there is within them a circulation, not of water, but of a fluid analogous to blood; for he says we see in it globules altogether like the blood-globules of other animals. Ann. des Sc. Nat. n. s. iv. p. 304. ] ® for there is no doubt of the animal’s ability both to fill and empty its body. The animal, observes Dr Sharpey, slowly distends itself with the water, “and again, but at no stated interval, gives out a portion of it: this is obvious from the fact, that the same animal may be seen distended at one time and flaccid at another. Naturalists are generally of opinion that the water enters and issues by the respiratory tubes (or dorsal filaments), and indeed no other orifices have been discovered; we must however freely own that we have never been able actually to observe its passage through these tubes.” In the Ophiuridae, in whom these tubes are not to be found, there must certainly be other entrances for the fluid; and these are probably certain orifices situated on the ventral surface, near the base of the rays. The water, however introduced, is there for the purpose of respiration, the principal seat of which seems to be the peritoneal membrane. “Spread over the viscera and the parietes of their containing cavity, and lining the respiratory tubes, it presents a great extent of surface, continually in contact with the surrounding medium; and we have found that a beautiful provision exists for maintaining currents of water along the membrane, and thus effecting that constant renovation of the fluid in contact with its surface which is required in the respiratory process. These currents are produced by means of cilia.”...“Ciliary currents take place also on the external surface of the body, which probably partakes in the process of respiration; we have moreover observed them within the tubular feet, and on the internal surface of the stomach and caeca: in this last situation they are probably subservient to digestion.”^[105. Sharpey in Cyclop, of Anal, and Phys. ii. p. 40. ]

The mode of progression of the Stellendes is probably limited to a sort of creeping;^[106. Baster ( Opusc. Subs. i. p. 119) and Bosc say that the Asterias can also swim. “In this act they suspend themselves obliquely in the water, and with their rays produce slight undulations, which suffice to direct their course. When they wish to descend, they cease these motions, and immediately sink to the bottom.” Hist. Nat, des Vers, ii. p. 125. Blainville has seen certain species of Asterias swim swiftly. Man. d’Actinologie, p. 241. ] but their walk is not so slow as the language of most authors would induce us to believe; nor have we been able to ascertain, from many observations, that any one or two rays have a preference for the van, as has been insinuated, but whatever ray happens to point toward the object or place in view, is made the leader for the time being. The organs of locomotion are very dif-feront[7:21:1010] in the different families. The rays of the Asterias, as already mentioned, are broadly furrowed underneath, the furrows planted with soft tentacula, which are flexible in every direction, being moved by circular and longitudinal muscular fibres, which enter copiously into their structure. In form, these tentacula may be compared to a retort or florence-flask with a long neck: the swollen vesicular bulb is placed within the cavity of the rays on each side of their mesial vertebrated column, while the neck issues from between the interstices of its side-pieces, and protrudes outwardly. They are hollow, being filled to a certain degree with water, introduced by a set of ramified internal vessels, which constitute an aquiferous system, similar to that which we found in the Holothurae.^[107. For a description of this apparatus, and of the interior anatomy in general, see the excellent article “Echinodermata.” in the Cyclop. of Anat. and Physiology. ] When the star-fish wishes to elongate any particular tentaculum, it contracts the vesicular bulb, and the water in it is consequently forced up the neck, distending and stretching it, and putting it in a fit condition to be applied against the ground or any object within reach. To this the extremity is affixed by the action of the muscular fibres, some contracting the centre of the point into a dimple, and others firmly appressing the edge, so as to give it the form as well as the virtues of a sucker. Now, by shortening the tubes which have been so fixed, the body is drawn towards their insertion; and by a curious succession of these actions, the creature goes whither it has willed.^[108. Reaumur in lib . s. cit. p. 92. Linck argues logically against this pedestrious property of the tentacula, which he wishes us to believe are solely organs of touch and taste, little tonguelets. De Stell. Mar. pp. 13, 14. But logic may prove other things than facts. ] It is impossible to follow the exact succession of the retraction and elongation of the suckers, nor indeed do they seem to be called into action after any regulated plan. Some are employed as stilts merely, on which the body is raised up buoyant in the circumfluent medium, while others are pulled in and stretched out to act as legs or feet; and others again seem to be used, more especially for the time, as seekers and feelers, that no prey may pass unawares, while the main object in view is apparently only a change of place. But the Ophiurae progress by a very different apparatus. “The diverging rays are firm and hard, have few spines, and no channel with suckers; they are used by the animal as legs, and as they are regularly placed, it can move in any direction that suits it. To go towards any particular spot, it uses the two rays that are nearest to it, and another that is most distant from it; the two first curve at their extremity, so as to form two hooks, which, being applied to the sand, drag the body forwards, while the posterior is curved vertically, and performs the part of a repelling lever.”^[109. Kirby’s Bridgew. Treatise, i. p. 202. The passage is translated from Reaumur. See Linck. sup. cit. p. 95. ] This action of the rays is assisted by some subsidiary organs, which have been hitherto unnoticed. On examining the rays of a living Ophiura, we have noticed that every one of their articulations is furnished with a pair of strong sharp moveable claws, similar to those of many insects and crustaceans; and from their position under the lateral spines on the ventral aspect, not more conveniently placed for taking hold of a plain surface than their form has an obvious adaptation to that act. They are unquestionably organs belonging to locomotion, which seems to us to be further aided by some filamentous tentacula that issue from pores in the ventral disc, whose function, though mainly respiratory, may be in a secondary degree locomotive, by serving as stayers to support the body, and elevate it above the unevenness and friction of the surface traversed.

The nature and number of the senses bestowed upon the Stellendes is a subject of doubtful inquiry; for the organs of these senses are either so far removed from ours that analogy offers no clue to their function, or the resemblance is so forced and superficial that it may possibly lead us to very erroneous conclusions. There is no reason to doubt that the species are richly endowed with the sense of touch; but it is doubtful whether any part or organ possesses that modification of the senses on whose discrimination the luxury of taste depends. It is equally doubtful to us, whether any have visual organs, for that blindness is the lot of most of them is granted. Ehrenberg, however, when examining living specimens of the Asterias violacea, discovered a point of a bright red colour, precisely defined, and situated beneath and towards the apices of each of the five rays. This point he believes to be ocular; and to give scope and direction to the organ, the star-fish curls back the tip of the ray when in the act of progression. Ehrenberg succeeded in tracing some nervous filaments to the apex of the rays, where he also found a small ganglion placed near the eye. In front of this ganglion, towards the mouth, there are some jointed nervous fibres; but similar articulations are not visible in the nerves situated near the mouth itself, whence this illustrious naturalist concludes, that the noblest part of the nervous system is found towards the apices of the rays.^[110. Ann. des Sc. Nat., n. s. iv. p. 306. Mr E. Forbes also considers these scarlet dots to be ocular (see his paper on the “Asteriadae of the Irish Sea,” in the eighth volume of the Wernerian Memoirs') ; but Dujardin retains his doubts. ] But what office are we to assign to those anomalous organs, which, in the Echinides, Monro has compared to insect antennae? They exist in the Stellendes, principally on the sides of the rays hid among the spines. “Each consists of a soft stem, bearing at its summit, or (when branched) at the point of each branch, a sort of forceps of calcareous matter, not unlike a crab’s claw, except that the two blades arc equal and similar. When the point of a fine needle is introduced between the blades, which are for the most part open in a fresh and vigorous specimen, they instantly close, and grasp it with considerable force. The particular use of these prehensile organs is not apparent; their stem, it may be remarked, is quite impervious.”^[111. Sharpey in Cyclop, of Anat. and Phys. ii. p. 32. ]

The Stellendes are oviparous, the ovary forming a grape-like cluster, placed near the origin and at the sides of the caeca, for there are two ovaries to each ray. The eggs lie numerously imbedded in a colourless jelly, covered with a thin pellicle, and are at first equally colourless; but during their progress to complete development, they pass through a great variety of colours, and when fully formed, assume invariably the distinguishing shade observed in the adult animal.^[112. Knox on the Nat. Hist. of the Salmon, p. 52∙ ] They escape from the body by certain apertures, observable at the side of the mouth in the angle of separation of the rays; and the greater number of the species are said to deposit their spawn in spring. When excluded from the egg, they are, according to Soars, very unlike the parent, for they are then binary, and do not become radiated until after some weeks.^[113. Ann. des Sc. Nat. n. s. vii. p. 248; and Lam. Anim. sans Vert. 2de edit, iii. p. 257. ]

The Stellerides are richly endowed with the wonderful property of reproducing parts which they may have lost from accident. In summer, it is asserted by Bosc, the parts pullulate and attain their original size in the course of a few days, while in winter some months are required for such production; but this is one of those loose assertions in which the works of Bosc abound. The time really required is much longer, though not exactly ascertained, and seasons probably influence it in no great degree. One ray lopt off, or two or three, all grow again; nay, a single arm.
[7:21:1011]

provided any portion of the disc remain attached, will live and become cinquefoil, as it was previously to its miserable mutilation. There was a time when these phenomena gave rise to expressions of the greatest wonder,^[114. Reaumur, Hist. des Insect. vi. pref lx. &c. ] and to speculations more curious than edifying, touching the possible divisibility of the soul, and other metaphysical subtilties. We may safely from them infer, that the susceptibility to pain in these animals must be very considerably, and almost infinitely, less than in animals of a more perfect kind, since in these the pain consequent on such injuries, and the sympathetic fever which follows as its necessary result, would be sufficient to kill them, independently of any other cause.^[115. Good’s Book of Nature, i. 429. ] ®

In relation to habitat, the Stellendes may be enumerated among the denizens of the shores of every sea, living generally at a depth of several fathoms, where they congregate in incalculable herds. There are beds of some species on our own coasts, that spread over an extent of some hundreds of yards, lying, in some spots, one upon another, to the thickness of a foot or more. The species are more various, if not more productive, in tropical than in temperate or cold seas. They prey upon small testaceous mollusea, which they catch with their suctorial feet, and retain opposite the mouth by means of the spinous projections surrounding it. We have found in their stomachs various univalved species, but the conchifera are supposed to be more especial favourites. Μ. Eudes Deslongchamps has observed five or six individuals of Asterias rubens clustered together in the form of a ball, the nucleus of which was a Mactra. The star-fish had retroverted their vesicular stomachs, and were found endeavouring to suck out the fish from between the valves of the shell; but it is impossible to believe, with this naturalist, that the Asterias had separated, or were capable of separating them, so as to inject within a fluid capable of benumbing the mollusc and placing it beyond resistance, the more especially as this fluid has no other than imaginary existence. There can be no doubt that the valves had partially opened, from the feebleness or death of the molluscum, before it was set upon by the star-fish.^[116. • Edin. New Phil. Journ., ii. p. 394. ] We have seen similar clusters around a Turbo or whelk. Deslongchamps’s opinion is indeed only worth notice as coinciding with that of the fishermen, who, regardless of the certain inefficiency of the agent, are fond of telling of the exterminating war waged by the Asterias against the oysters; a tale which has its invention at a far-distant date, being found in Aristotle, paraphrased by Aelian, and versified by Oppian, and hence copied without question by every subsequent popular compiler.

In their turn the Stellendes are greedily preyed upon by fish of almost every sort; for they who assert that the acridity of their flesh, or the spines and prickles of their skin, render them distasteful or formidable,^[117. Blumenbach’s Man. of Nat. Hist., trans. p. 267. ] know nothing of the voracity and power of their foes. We have very often found the stomach of cods and haddocks crammed with the remains of star-fish, more especially of the prickly Ophiurae, and that at a season when the fish were in high perfection. Dr Knox has attempted to prove that the ova of the Echinodermata are the proper food of the salmon, which is only fit for the table of the epicure when he has been feeding on them: "from the richness of the food on which the true salmon solely subsists, arises, at least to a certain extent, the excellent qualities of the fish as an article of food.”^[118. “On the Nat. Hist, of the Salmon,” &c. p. 8, a pamphlet from the Trans. of the Boy. Soc. of Edin. vol. xii. The same food is said to communicate poisonous qualities to the mussel. “C’est ce frai qui, dit-on, rend les moules dangereuses à manger.” Blainv. Actinolog. p. 234. ] Vast numbers are more certainly destroyed by the fisherman, who finds they materially injure the produce of his art, by clinging to and clustering round his baits, and who therefore wreaks his vengeance on them by throwing them in heaps on the dunghill. In some places the common species have even been used as manure; but otherwise man has not found them adapted to his use, for the medicinal virtues which the early physicians and astrologers ascribed to them, have disappeared in their modern generations.

To remedy that looseness of description which of necessity belongs to such general views as we have been giving, we proceed to notice the systematic arrangements of the order, whose only common characters seem to be, us Linck long ago observed, a depressed multiful coriaceous body, with rays or lobes radiating from the margin of the disc, and an inferior central mouth. Linck’s primary division of it into the fissured and entire (fissae et intégra) indicates his perception of those differences in structure on which modern naturalists found their principal families; but his want of knowledge of system becomes very obvious in the subor. dinate details, when he exclusively drew the character of his secondary divisions from the number of the rays; a character of such trivial importance as not even to be specifical, but subversive of every natural affinity. Linnaeus arranged the whole under one genus (Asterias); which Lamarck divided into four, whose essential characters may be shortly stated thus:

• Rays articulate, distinct from the disc.

1. Comatula. Rays of two kinds, dorsal and marginal; the dorsal simple, short and filiform; the marginal larger, and pinnate.

2. Eubyale. Rays marginal, alike, dichotomous, and much divided.

3. Ophiura. Rays alike, marginal and simple.

* * Rays continuous with the disc.

4. Astebias. Rays furrowed underneath, and tentaculiferous.

Cuvier adopted the genera of Lamarck, but, with a proper regard for the rights of priority, for Comatula he substituted the name Alecto, and for Euryale that of Gorgonocephalus, which had been previously bestowed on the same groups by our celebrated countryman Dr Leach. The genus Ophiura, Cuvier further proposed to divide into two; the one embracing those species whose rays are furnished with mobile lateral spines, and between whose articulations small fleshy tentacular filaments (pieds) issue on each side; the other those in which the rays, having no lateral spines, resemble the tails of lizards. In these “the central disc has, in each interval of the rays, on the side where the mouth is, four holes, which penetrate into the interior, and serve perhaps for respiration, or, according to others, for the issue of the eggs. There are no feet, except in five short furrows, which form a star around the mouth.” The genus Encrinus, which Lamarck had referred to the Zoophytes, Cuvier properly placed near the Comatula, adopting the views of Miller implicitly in regard to its structure and further subdivisions.

Miller names the family of which the Encrinus may be considered the type, Crinoidea or lily-shaped animals, a family rendered interesting, as Mr Parkinson^[119. Introd. Foss, Org. Remains, p. 95. ] remarks, not only by their curious forms and extraordinary structure, but also by their being among the earliest inhabitants of this planet. Hence they are so far aliens of this world, that whilst immense tracks of rocks are literally formed of the entombed remains of different species in a mineralized condition, only five or six species have yet been discovered in a recent state.^[120. Kirby is led by his speculations to believe that the extinct forms stiil exist in the deepest abysses of the world of waters. Bridgew. Treat. ii. p. 15. ] “An idea of their structure may be obtained if we imagine an Asterias placed with its mouth upwards on a columnar jointed stem, one end of which is connected to the dorsal surface of the animal, and the other most probably fixed at the bottom of the sea. The rays or arms extending from the circumference of the body are much branched, and at last pinnated; other jointed processes, named auxiliary arms, surround the stem in whorls placed at short intervals. The column is perforated in its centre with a narrow canal, down which a prolongation of the stomach extends, and lateral canals proceed from the central one through the verticillate auxiliary arms The Comatula has rays spreading from the circumference of the body, branched and pinnated like those of the Pentacrinite. It is not fixed on a column, but the dorsal surface of the body is elevated in the middle, and bears a number of smaller rays or arms; and this dorsal eminence, with its rays, has been sometimes compared [7:21:1012]to a rudiment of the column of the Pentacrinite with its auxiliary arms. Besides the mouth, there is an anal opening on the ventral surface, situated on an eminence near the margin.”^[121. Sharpey in Cyclop, sup. cit. p. 32. ] The exactness of the comparison here drawn between the Comatula and Pentacrinus, first detected by the acuteness of Miller and Gray, has been singularly illustrated by the discovery of Mr J. V. Thompson, that Pentacrinus is only Comatula in its first stage of existence; the head, in the progress of development, separating from the stem, to become, instead of a fixed pedicellated floriform zoophyte, a nomade star-fish in the bosom of the ocean. In their fixed condition, the Crinoidea appear to have had a considerable range for the seizure of their prey, without possessing absolute locomotion,

Still moving, yet immoved from their sted; for the peculiar mode of the articulation of their vertebrae probably afforded them a great degree of mobility, with considerable security against dislocation.^[122. Parkinson in lib. cit. p. 95. ] They grow erect, the stem being in general sufficiently stiff and strong to support the heavier head; but when it is not so, as in the Umbellularia, we find that, just under what has been called the pelvis, “a hollow bladder-like membrane” embraces the upper part of the stalk for about two or three inches, and, performing the office of a buoy or swimming-bladder, keeps the head in an upright position.^[123. Ellis’s Corallines, p. 97. ]

In 1826, Mr J. E. Gray proposed to divide the Stellendes into three families. I. Asteriadoe, distinguished by having tentacular feet in the ambulacra of its rays, and by a calcareous wart (the corpus spongiosum of Spix) on the dorsal surface of the disc: II. Ophiuridcae with solid articulated rays, and no wart: III. Encrinida, co-equal with the Crinoidea of Miller, and distinguished from the two preceding by possessing a double aperture to the digestive organs, a peculiarity which he was the first to discover in Comatula.^[124. Annals of Philosophy, n. s. xii. p. 394. The Rev. Mr Guilding’s arrangement so much resembles Mr Gray’s, that its quotation here is unnecessary. See Mag. Nat. Hist, viii. p. 70. ]

Our limits will permit us to give no more than a mere outline of Blainville’s arrangement, which rests on the same basis, but is more elaborately framed, and embraces the crinoidean genera, which the industry and sagacity of Miller had enabled him to detect and define.
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Agassiz has not introduced any essential novelty in the distribution of this family, but, to compensate the brevity of our notices of previous attempts, we find it necessary to give the definitions of such of his genera as contain recent species, at length.

FAMILY 1.—ASTERIADAE.

The Asteriadae answer to the limits which Lamarck has assigned to the genus Asterias. What distinguishes them is their possessing a single orifice of the intestinal canal, surrounded by suckers, but void of teeth; while deep grooves, containing several series of pedicles, extend from the mouth to the extremity of the rays. On the dorsal surface we remark, between the two posterior rays, a calcareous wart, convex externally, and grooved like a madrepore, which has therefore been denominated the madreporiform tubercle. It covers a singular organ, named the stone-canal by Tiedemann, who believed its office to be the secretion of the earthy matter required for the growth of the calcareous skeleton. The accuracy of his description of its structure has however been called in question; and the opinions relative to its function are various and contradictory.^[127. The subject is ably stated by Dr Sharpey in Cyclop, of Anat. and Physiology. ] Blainville considers it to be in some way connected with generation; and from its variations he asserts we may draw our most permanent characteristics of the species.^[128. Man. d’Actinologie, p. 237. ] It is almost certain, he also tells us, that there is a distinction of sexes among them, and consequently a sexual union; and indeed Otho Fabricius says that in the month of May in Greenland they are to be found in pairs united face to face.^[129. ’ Man. d’Actinologie, p. 236. ]

Genus Asterias, Linn.— Body star-like; superior surface tesse-

lated; rays flattened, edged with two series of large laminae bearing small spines.

Genus Caelaster, Ag.—“ Differs from the preceding genus in having the interior cavity circumscribed by laminae arranged like those of the Echini, and at whose summits we observe a star of ambulacra. This genus approaches therefore by its organization to the family of the Crinoidea, while its form is that of the true Asteriae.” There is only one fossil species.

Genus Goniasteb, Ag.— u Body pentagonal, bordered by a double series of laminae, bearing small spines; upper surface nodose.”

Genus Opindiaster, Ag.— “Body star-like, finely tesselated on its whole surface; inferior grooves very narrow.”

Genus Cribella, Ag.— “Body star-like, rays tuberculous and elongated; epidermis porous in the intervals.”

Genus Uraster, Ag.— “Body star-like, entirely covered with more or less prominent spines.”

Genus Astebina, Nardo.— “Body pentagonal, covered with pectinated scales; upper surface inflated; grooves of the under surface deep.”

Genus Palmipes, Linck.— Body pentagonal, very flat, thin, but membranaceous at its edges.

Genus Calcita, Ag.— Body pentagonal, slit at the angles; teguments granular.

FAMILY II.—OPHIUB1DAE.

The Ophiuridae are distinguished by the central part of their body forming a distinct and flattened disc, to which are annexed more or less elongated and even ramified rays, with no grooves on their surface. "They are spinigrade animals, and have no true suckers by which to walk, their progression being effected (and with great facility) by means of five long flexible jointed processes, placed at regular distances round the body, and furnished with spines on the sides and membranous tentacula. These processes are very different from the arms of the true star-fishes, which are lobes of the animal’s body; whereas the arms of the Ophiuridae are superadded to the body, and there is no excavation in them for any prolongation of the digestive organs. The stomach is a sac with one aperture, its walls externally covered with vibratile cilia. The ovaries are not branched; they are placed near the arms, and open by orifices near the mouth, between the origin of the arms. Their investing membrane is also ciliated; but on the rest of the body and arms no cilia exist, hence we may conclude there is no separate respiratory system.”— Edward Forbes.

Genus Ophiura, Lam.— Disc much flattened; rays simple, squamose, bearing very short spines adhering to the rays.

Genus Ophiocoma, Ag.— This genus differs from the preceding in having very long moveable spines attached to the rays.

FAMILY III .— CRINOÏDEA.

The Crinoidea, notwithstanding their star-like form and their great external resemblance to the Ophiuridae, constitute however a distinct family, characterized by the presence of two separate orifices to the intestinal canal, although very near to each other. These orifices are by no means easily distinguished among the rays which surround them, especially in the fossil species. The greatest part of the species are pediculate, i. e. carried on a foot-stalk adhering to the centre of the region, which, in the star-fish, we considered as the middle of the dorsal surface.

Genus Comatula, Lam.— Disc pentagonal, arched at its upper surface, which bears several series of simple and articulated rays; rays of the disc bifurcate, beginning however with two simple pieces. The edges of the rays are pinnate; mouth central, sunk; anus between the mouth and the border of the disc, obliquely prominent. Animal free when mature, but fixed and pedicellate when young.

Mr J. V. Thompson has discovered that “the body of the Comatula, when the animal is kept in a small quantity of sea-water, is soon detached, entire and perfect, from the cavity in which it is lodged, and in this state it might be mistaken for an animal of a very different tribe.” He suspects that the genus Mammaria of Müller may have no better foundation. The same naturalist has [7:21:1013]made the still more singular discovery that the Pentacrinite of the Irish seas, which he first described under the name of Pentacrinus Europatu, and which has since been made the type of the genus Phytocrinus by De Blainville and Agassiz, is a Comatula in its earlier states of development. When not more than one eighth of an inch in height, this Pentacrinus “resembles a little club, fixed by an expanded basis, and giving exit at its apex to a few pellucid tentacula; no other part of the solid fabric is observable, but an indistinct appearance of the perisome. In those specimens which have made a little more progress, together with the elongation of the pedicle or stem, its joints begin to make their appearance; the body acquires a larger size and brownish tint, from a grosser food; the tentacula of the mouth protrude in a greater degree, and move slowly in various directions. In others still more advanced, the joints of the stem become quite obvious, from their opacity and white colour, and the base of the future arms, as well as the auxiliary side-arms, are rendered palpable. The arms from this period lengthen apace from their bifurcation, and have superadded to them a double range of transparent jointed tentacula; so that the animal begins to put on a more perfect appearance, and now for some time merely acquires a somewhat greater size and an extension of its arms, which, although they solidify from their origin upwards, remain pellucid and thick at their apices, where elongation, evolution, and the secretion of calcareous matter is gradually going on.” Subsequently the arms again bifurcate at or near to their extremities, a second and even a third time, and having reached the full development entitling it to the name of a Pentacrinite, the head appears to be cast off, that it may become a nomade Comatula. How just then the conclusion of Mr Thompson from these interesting discoveries. “From these observations connected with the growth of this animal, and by which it appears to present itself at various stages of its progress under considerable diversity of form, naturalists may learn to avoid the unnecessary multiplication of the genera and species of the Crinoidea, by giving undue weight and consideration to characters originating in the progressive evolution of individual species, and which are consequently of a transitory and delusive nature.”^[130. See J. V. Thompson’s Memoir on the Pentacrinus Europoeus, Cork, 1827, 4to; the Edin. New Phil Journal for 1836; and Mr Edward Forbes’s History of British Star-fishes. ] '

Genus Comaster, Ag.— This genus has the same organization as the preceding, but the arms are ramified instead of being simply furcate.

Genus Ganymeda, Gray.— The genus which Mr Gray described under this name in the Proc. Zool. Soc. of London for 1834, p. 15, he has ascertained to be founded on what is evidently only the basal joint of the body of the English species of Comatula.— Annals and Mag. of Nat. Hilt. i. p. 158.

Genus Pentacrinus, Miller— Pedicle more or less pentagonal, bearing at intervals simple verticillate rays; rays of the disc fixed to the pedicle, each by a cuneiform piece, followed by two simple pieces, after which the rays bifurcate, and at a little farther distance divide into two, which then branch out into numerous appendices, pinnate at their edges. The space between the base of the rays, occupied by the visceral cavity, is formed by numerous small laminae. The only living species (P. caput Medusa) is a native of the Carribbean seas.

III .— ACALEPHAE.^[131. Synonymes: Radiares mollasses; Orties de mer libres; Arachnodermes; Gelatines; Jelly-Fish; Sea-Blubbers. ]. 3 —SEA-JELLIES.

The Acalephae have been named by Blainville the Arachnodermata, to mark in a stronger manner how remarkably they contrast with the Echinodermata in the structure of the skin, which is a soft serous pellucid cuticle, containing sometimes miliary granules, but always smooth and even, and as thin as the gossamer’s web. They are radiated animals of a gelatinous consistency, with an unarmed mouth in the centre of the ventral surface, the entrance into a stomachal cavity without proper parietes, but furnished with vasculiform canals ramified through the body; their respiratory apparatus is ciliary, and their mode of generation oviparous; they are all nomade and marine, and move through the water by alternate contractions and dilatations of their periphery, or by the aid of vibratile cilia. The constituents of the class are divisible into two orders, viz., 1. The Medusides, with a body almost always circular, convex dorsally and concave below, supported in a few genera by an internal cartilaginous plate; the rim, as well as the oral aperture, mostly fringed with tentacular ciliated appendages: 2. The Acalephes properly speaking, whose body is irregular and multiform, bilateral, and sometimes orbicular, with brachial or filamentous appendages, and ciliary fringes.

ORDER I—MEDUSIDES.^[132. Synonymes: Radiares medusaires: Acalephes simples; A. Discopbores; Acalepha Cyclomorpha; Medusida. ]

Among animate creations, there is none that excels the Medusides in beauty and ornament, or in the variety and eccentricity of their forms;
— there’s not a gem
Wrought by man’s art to be compared to them;
Soft, brilliant, tender, through the wave they glow,
And make the moonbeam brighter where they flow.

When floating in the ocean, most of them appear like crystal bowls of the purest transparency, veined and patterned with the most brilliant colours, and their rims ornamented with fringes, furbelows, and arbuscles of such delicacy and intricacy of workmanship, that even the most experienced in nature’s works marvel how it is that such textures, too frail to bear the lightest handling, are kept entire amid the restless element of their nativity.^[133. See Kirby’s Bridgew. Treat. i. p. 199. ] We have often watched with intense interest some of the least complicated, and, it may be, some of the least beautiful, as they floated by us on the surface of a summer’s sea. On a hasty examination, they may seem to be supported there by their own inherent buoyancy, and to be carried onwards with the tide or current, which they have apparently no power to resist; but watched a while, they are seen alternately to contract and expand the whole periphery of the body at regularly-timed intervals, in a manner which Dr Roget has aptly illustrated by comparing it to the opening and shutting of a parasol, and with a quickness and force which we have felt to be considerable. By these motions the Medusides can swim against a gentle current, though they more commonly yield themselves up to its persuasive violence; and when alarmed they can also sink deep into the bosom of the sea with considerable velocity, so as frequently to elude an attempt to secure them. They can stop and maintain themselves at any depth, and rise again with equal ease to enjoy a nearer intercourse with light and air. Lamarck’s speculations rendering it necessary to deny to them either nerves or muscles, he has persuaded himself that these motions of the body are entirely mechanical, produced by the influx and efflux of imponderable fluids, such as electricity, permeating and flowing through its gelatinous texture;^[134. Anim. Vert. ii. p. 444, 446, and 452-5. ] but we are very sure that he will summarily reject this theory who has once observed the phenomena, which are certainly in some degree under the control of the animal, and regulated by its will and sensations. It seems indeed to be now proved, more especially by the anatomies of Ehrenberg,^[135. Ann. des Sciences Nat. n. s. iv. p. 290, &c. ] that they are the effects of the contraction of muscular fibres, radiating from near the centre of the body to the circumference, running alongside the vein-like nutritious canals, and by others in the rim, which have a circular direction. We know also that the Medusides do possess a nervous system, formed after the same plan, and rather more complete than it is in other radiated beings.

The figure of the Medusides is regular and almost always circular (for the Velella alone are ovaD, sometimes discoid or spheroidical, but generally hemispherical, so as to allow of a comparison between them and the mushrooms, which they are presumed to represent in the animal kingdom; and the [7:21:1014] same fancy may see in them the living models on which our umbrellas have been made. The margin is usually fringed with tentacular filaments; and in many species we also observe, placed at wide intervals, a circle of coloured warts, which, from their organization, are evidently organs of importance in the animal’s economy. Ehrenberg believes them to be branchial, for connected with each of them he has discovered a partial circulation of a fluid analogous to blood; and, what is still more singular, he has detected in their near vicinity an organ retractile, within a sheath, and containing a mineral crystal, to which he assigns the office of an eye, because it is similar in structure to the eye of several infusory animalcules, and is more amply provided with nerves than any organ other than one of sense ought to be.

The under surface of the umbrella is sometimes entirely naked, sometimes furnished with numerous scattered tentacular suckers, as in Porpita and Velella, or with greatly diversified brachial appendages, which depend usually from the lips of the mouth. These are either free from each other and separate to the base, or they coalesce so as to form a kind of stalk previous to their ramification into lobes or filaments, each division having at its extremity pores for the absorption of the thin nutriment on which such species must necessarily subsist. The Medusae with this structure resemble a bulbous root with its radical fibres, and were therefore called Rhiznslomous by Cuvier.^[136. Règne Animal, iii. p. 278. Figures illustrative of the structure are given in the Bridgew. Treatise of Dr Roget, ii. p. 888-9. ] The greater number of the Medusides, however, have a distinct mouth, placed always centrally, either sessile or at the end of a species of proboscis more or less prolonged. It has no hard parts, nor teeth, nor jaws, and leads by a very short oesophagus into the stomach, consisting frequently of four separate cavities excavated in the gelatinous parenchyma, without any peculiar lining. From the stomach proceed numerous vessels, which all bend to the circumference. Some of these vessels are simple and undivided, others ramify dichotomously like veins, and form anastomoses among their ultimate divisions. Injections from the stomach pass more readily into the simple than into the ramose vessels; but both kinds serve for the conveyance of the digested food, whose unassimilated remains pass from the body through their extremities, which open by apertures on the rim. The portion intended for nutrition and growth probably transudes in part into the parenchyma, while it flows along the vessels; and a part seems to enter a peculiar vessel which runs round the periphery that it may pass into the partial circulations at the marginal tubercles, and be submitted to the action of the air. It must, however, be admitted that these tubercles exist in comparatively few species;^[137. We may here warn the student that be should guard against the too great extension of these general remarks; for the truth is, few species have been examined anatomically, and even the most general detail will be found to have many individual exceptions. ] s and there can be little doubt that the principal airing of the nutritive fluids is effected by the action of the circumfluent water on the exterior surface, as well as in the internal cavities and vessels. To effect this great purpose the more completely, we find that the oral and marginal filaments are clothed with vibratile cilia, which drive currents of water over them in determinate directions; and these cilia are said likewise to line some of the interior cavities. It is from their action that portions cut off from the appendages continue to move like independent and perfect beings; a circumstance apparently so demonstrative of their completeness, as to have given origin to several spurious species.

The Rhizostomes, as we have already mentioned, feed only on fluid matters, and such also is the condition of those genera which Peron and Le Sueur named agastric, from a belief that they had neither mouth nor alimentary sacs; for although this latter statement has been shewn to be erroneous, yet the absorption of the aliment appears to be through pores. But the bulk of the Medusides love a grosser fare, and there is some slight evidence in favour of their having a discrimination in the matter; for Gaede remarks that he has never found fishes in the stomach of Medusa capillata, but often worms; while in that of Medusa aurita there are frequently fishes, rarely worms. The latter species, according to our observation, feeds more frequently on pelagic Gammari; and minute Crustacea and entomostraca constitute the principal food of most of them. Digestion is extremely rapid. We remember once observing in the stomachs of Medusa aurita, several specimens of a Gammarus unknown to us,^[138. Probably the Oniscus medusarum of O. Fabricius. Faun. Groenl. p. 257. ] and which we were anxious to examine: they were living when first seen, and when we left the Medusa in a basin of sea-water for half an hour, we little dreamed of the disappointment awaiting our return, for not a trace of the Crustacea was then visible.

All the species are propagated by ova generated in appropriate organs situated generally in the immediate vicinity of the stomach, but very variable in appearance and general structure. Previously to the deposition of the spawn, the ovaries swell in a very remarkable manner, and the young Medusae, according to Blainville, are cast out through the mouth, sometimes after a certain degree of development in the appendages. In the Medusa aurita, according to Ehrenberg, the ova, previously to their maturation, escape through the peculiar aperture of the ovarial sac into the water, where they are laid hold on by the tentacula and the two layers of the brachial appendages, and received into little sacs which are formed on these layers, and which have a direction from the interior outwards. It is in these sacs that the ova are metamorphosed and matured. While in the ovary they have a thin smooth membranous envelope, are of a roundish figure, and filled with a dark-violet granulous fluid; but in the faetal sacs they have no shell, and present themselves under three distinct forms. Some resemble bramble-berries, and their colour is a pale violet; others, also of a pale violet, are disciform, in shape like a miniature Medusa, without arms, and without nutritive canals; and the third, which is the most numerous, has a cylindrical form, truncated at both ends, and of a yellowish-brown tint. The last two are densely covered with cilia, and swim freely. The largest among them attain a diameter equal to the one eighth of a line; and they are about one third of this size when they lose their shell. From being unable to discover male organs in this Medusa, Ehrenberg has hazarded the conjecture that the smaller ova may become, as we understand him, males, which remain always of a microscopical size, while the females only grow Urge;^[139. Ann. dee Sc. Nat. n. s. iv. p. 297. Rathke apparently borrows his account of the development of the Medusae principally from Ehrenberg, but he omits their escape into the sea previously to their introduction into the brachial sacs, which is really incredible; and he says that when lodged in these sacs they have no longer a chorion, as Ehrenberg pretends, and are consequently already young Medusae. See Burdach’s Traité de Physiologie, tom. iii. p. 67, &c. ] but the conjecture is a bold one. We are scarcely able to reconcile these interesting facts with one observed by Μ. Saars. In a small volume published some years ago, this Swedish naturalist described a new genus of Medusides under the name of Strobila, from its great similitude to a fir cone; but he now assures us that the Strobila is the young of Μ. aurita. In its strobiline state, it is composed of a series of circular pieces, with numerous tentacula, and the cone is surmounted by a cylindrical shaft: in its development the pieces separate successively into disciform ra [7:21:1015] diated fragments, each of which becomes a perfect individual.^[140. Ann. des Sc. Nat. n. s. vii. p. 248. ]

The growth of the Medusides is as rapid as their life appears to be short and transitory. There are many which never reach the magnitude of a pin’s head; and thence they graduate upwards to a size, even in our northern seas, of fully two feet across the disc, with labial appendages not less than six feet in length. The bulk to which they occasionally grow in the Indian Ocean is immense; and were a like hugeness attainable by them in the northern seas, we might lend an easy belief to those naturalists who tell us that the Kraken was truly a Medusa.^[141. See Bester, Opusc. Subs. i. p. 26. ] Mr Telfair saw a Medusa cast on shore in the Bombay territory in 1819, which must have weighed many tons. “I went to see it when the gale had subsided, which was not for three days after its being cast upon the sand; but it had already become offensive, and I could not distinguish any shape. The sea had thrown it high above the reach of the tide, and I instructed the fishermen who lived in the immediate neighbourhood to watch its decay, that if any osseous or cartilaginous part remained, it might be preserved; it rotted however entirely, and left no remains. It could not be less than nine months before it entirely disappeared, and the travellers were obliged to change the direction of the road for nearly a quarter of a mile to avoid the offensive and sickening stench which proceeded from it.”^[142. Edin. New Phil. Joum. iv. p. 406. ]

The Medusides abound in our seas during the summer and autumn, and are thrown ashore in heaps after every storm.^[143. “They are sometimes thrown in great quantity upon the shores of our climate, where endeavours have been made to turn them to some advantage. It has been attempted, but without much success, to extract ammonia from them. They have been more beneficially employed in the way of manure upon arable land.” Griffith’s Guoier, xii. p. 567. The Medusides are all pelagic; but Professor Schwencke is said to have kept a species for six days alive in a basin of fresh water,—“ex 8para fluvio hausta.”—a very wonderful fact, when we remember how instantaneously poisonous fresh water is to marine animals in general. Bester, Opusc. Subs. ii. p. 58. ] Before the winter has set in, they have disappeared, most of them being doubtless destroyed; but during the cold season some surely inhabit the deep recesses of the ocean, to re-appear in another season; and it is probable that the spawn of one summer’s generations lies hidden in the ooze until revived and evolved by the heat of the coming summer. In tropical seas they are still more profuse, as well as more sportive in their configurations. Voyagers tell us of sailing through flocks so dense as to check the ship’s progress, and expanding for miles over the surface; nor are they weary of speaking of their beauty and their phosphorescent and stinging properties. In the arctic seas these creatures are equally abundant, furnishing the giant whale with the material of his growth, and swarming so thick, when of microscopic minuteness, as to communicate their colour to the water. After his description of a globular semi-transparent species, from 1-20th to 1-30th of an inch in diameter, Dr Scoresby proceeds to say, “I afterwards examined the different qualities of sea-water, and found these substances very abundant in that of an olive-green colour; and also occurring, but in less quantity, in the bluish-green water. The number of Medusae in the olive-green sea was found to be immense. They were about one fourth of an inch asunder. In this proportion, a cubic inch of water must contain 64; a cubic foot 110,592; a cubic fathom 23,887,872; and a cubical mile about 23,888,000,000,000,000. From soundings made in the situation where these animals were found, it is probable the sea is upwards of a mile in depth; but whether these substances occupy the whole depth, is uncertain. Provided, however, the depth to which they extend be but 250 fathoms, the above immense number of one species may occur in a space of two miles square. It may give a little conception of the amount of Medusae in this extent, if we calculate the length of time that would be requisite, with a certain number of persons, for counting this number. Allowing that one person could count a million in seven days, which is barely possible, it would have required that 80,600 persons should have started at the creation of the world, to complete the enumeration at the present time.”^[144. Edin. Phil. Journ. ii. p. 12. ]

Great numbers, for all of them are not so, as has been asserted, of the Medusides, are phosphorescent animals, emitting their lights at irregular intervals; and the flame generally passes away after a short glow. The large species appear, when luminous, like globes of living fire floating on the surface, or shining at a great depth through the water; but when the species are small and crowded, the luminousness is diffused all round, or it is broken into innumerable spots of light, “rising to the surface, and again disappearing, like a host of small stars dancing and sparkling on the bosom of the sea.”^[145. Baird in Mag. of Nat. Hist. iii, p. 309, and vol. ix. p. 502. See also Thompson’s Zoological Researches, p. 38, &c. ] The first kind of light is at least sometimes emitted at the pleasure of the creature, without the intervention of any foreign irritation;^[146. Some naturalists deny the luminous property of the Medusides ex toto, maintaining that the light is merely elicited by friction. &c., from some matter or fluid with which the water is impregnated at the time. This opinion is ably supported by Mr Westwood in the Mag. of Nat. Hist. iv. p. 505, &c.; and for some observations confirmatory of this view, we refer to the same work, vol. v. p. 1, &c. The opinion however appears to us to be untenable, and is apparently disproved by the fact that Medusae have been noticed giving out their light at many fathoms depth, where they were beyond disturbance. "While sailing in the more shallow parts of the Carribbean Sea,” says the Rev. Mr Guilding, "and looking over the vessel’s side when becalmed in these dangerous waters, in the midst of reefs, I have seen at the bottom huge molluscous or radiate animals emitting the splendour of a lamp, but could never ascertain the species.” Mag. of Nat. Hist. vii. p. 581. It were easy to quote similar facts, but a more conclusive one is this. We had a luminous Dianea in a glass of sea-water, and in a vessel of the same water we had, at the same lime, a small specimen of Medusa aurita. The light was readily evoked from the Dianea, but we could obtain no light from the other vessel. It must therefore have proceeded from something else than the water. See in relation to this question the observations of Mr Bennett in Proceedings of the Zool. Soc. of London for January 1837; and those of his brother in the same work for June 13, 1837. ] but the other two seem always to require for its elicitation some outward stimulus, such as is given by their mutual contact and friction when a fresh breeze curls the waves, or when an oar-driven boat or a ship passes through the teeming waters, when “a long train of lambent coruscations are perpetually bursting upon the sides of the vessel, or pursuing her wake through the darkness.”

In such species as we have observed, the luminosity could not be detected issuing from any particular point or organ: it seemed that the whole body was impregnated with the light, which was given out involuntarily, if we may so speak; for some exterior irritation was necessary to produce the appearance of it, though the Medusae do not distinguish whether the annoyance proceeds from an animate or inanimate object. The species which possess the property are diffused through all seas, and the phenomenon is little less beautiful and interesting in the Hebrides than it is under the line, or in Australian seas.^[147. This is contrary to the assertion of voyagers, and it may be that our opinion is biassed by our partiality to all that is native. Humboldt says, “The sea is phosphorescent in all latitudes; but he who has not witnessed this phenomenon in the torrid zone, and especially in the Pacific Ocean, can form but an imperfect idea of the magnificence of such a spectacle.” See Edin. New Phil. Jours., v. p. 329.—Dr Maccul-Joch, during a voyage to the Shetland and Orkney Isles, discovered upwards of 190 luminous animals, of which the most conspicuous were about twenty small Medusae. Edin. Phil. Journ. v. p. 389. ] "The phosphorescence takes place, particularly around the tentacula, during [7:21:1016]the movements of the animal. Macartney saw it increased in the Medusa lucida when he warmed the water. The light also became more vivid in alcohol; the animals, however, quickly perished in it, and their light was extinguished. Spallanzani remarked the trickling of a viscous fluid from the surface of Medusae, which had a burning taste, and produced an itching sensation on the skin. This liquid, mixed with water or milk, renders them phosphorescent for some hours, particularly when they are warmed and agitated. Dead animals, whose light was extinguished, again became phosphorescent by the addition of a quantity of spring water, and by movement at a heat of 26° to 37°. Humboldt observed his fingers to shine for some time after he had touched Medusae: he also saw the light become stronger when the animals were galvanized. The light of Medusae to which Macartney applied an electric shock, was extinguished for an instant, but afterwards appeared more vividly than previously."^[148. Tiedemann’s Comp. Physiology, i. p. 259. See also a summary of Spallanzani’s experiments in Griffith’s Cuoier, xii. p. 567. ] In reference to the immediate cause of the phenomenon, the opinions which have been divulged are numerous and contradictory: here it must suffice to give Tiedemann’s, as the most probable. “Weighing well all the circumstances,” says he, “phosphorescence would seem to depend on a matter, the product of the changes of composition accompanying life, and, to all appearance, secreted from the mass of humours by particular organs. This liquid probably contains phosphorus, or an analogous combustible substance, which combines with the oxygen of the air, or of aerated water, at a medium temperature, and thus produces the disengagement of light. The preparation and secretion of this substance are acts of life, which change, augment, or decrease by the influence of external stimulants, whose action on the animals modifies their manifestations of life. But the phosphorescence itself depends on the composition of the secreted matter, and cannot be regarded as a vital act, because on certain occasions it continues for whole days, even after the death of the animal.”^[149. - Comp. Physiology, p. 269. ] ® As for its use, opinions are equally various; but perhaps we err least when we conjecture it may serve to protect those gifted with it from the aggressions of their enemies.

Many Medusides possess likewise a stinging property sufficiently strong to blister the skin and inflict acute suffering.^[150. Hence they were named Urticae marina: by the older naturalists, and sea-nettles by the common people. What Aristotle and Pliny meant by their stinging acalephes is very doubtful, as is shewn by Kirby in Bridgeur. Treatise, p. 402, &c . ] Bosc describes the consequences thus. When a venomous Medusa touches the skin, there results a considerable redness, with buttons of the same hue, which have a little white spot in their centres, attended with a piercing pain, which, after it has somewhat subsided, may be compared to often-repeated pricks. This lasts generally a half hour, and may be appeased by the application of linen steeped in oil, or even in fresh water. The redness will often re-appear after the lapse of several days, when the part is exposed to a temperature higher than that of the atmosphere.^[151. Hist. Nat. des Vers, p. ii. 163-4. Also Griffith’s Cuvier, xii. p. 568. ] He imagined that it was occasioned by the application of numerous microscopical suctorial papillae, which issue from the surface of the tentacular arms, to the skin; but this is disproved by the fact of the dead animal being not less vesicatory than the one yet living. It probably resides, as Dicquemare believed, in some caustic exudation of the exterior membranes; but it is not identical with the phosphorescent secretion, for some vesicating Medusae are not luminous, and we know from our own experience that our native luminous species are not all endowed with the power of vesication.

The distinction of the species is difficult, because of the changes which they suffer in their growth; and the difficulty is increased by their frequent minuteness and transparency, which render them scarcely visible in the water; by their soft fragility and tendency to dissolution, which prevents them being handled without injury, and opposes an almost insurmountable obstacle to their preservation in museums. From these inherent difficulties, the classification of the Medusides is believed to be still in an imperfect and artificial state; yet a comparison between its Linnaean barrenness, when one small genus embraced all the known species, and its present richness, when many genera are necessary to exhibit all its variety and fulness, affords a pleasing argument in behalf of the zeal and inquisitiveness of modern naturalists. Peron and Le Sueur, with a good knowledge of what had been done by others, and with much new information acquired in their voyages, were the first to attempt the orderly arrangement of the Medusides;^[152. Annales du Museum, tom. sir. ] but it was found to be too artificially constructed, and has not been adopted by subsequent systematists. Lamarck’s method, which was based on Peron and Le Sueur’s, has the recommendation of greater simplicity. It is as follows:

RADIARES MEDUSAIRES.

* One mouth only in the inferior disc of the umbrella.

1. Umbrella without pedicle, or arms, or tentacula.

[ a ] No lobes or appendages on the margin of the umbrella.

Eudora. Phorcynia.

[ b ] With lobes or appendages on the margin.

Carybdea.

2. Umbrella without a pedicle, and armless, but furnished with tentacula.

Equorea.

3. Umbrella without a pedicle, but with arms^[153. Under the name of arms, Lamarck embraces the labial appendages of every kind. ] below, and generally with tentacula on the margin.

Callirhoe.

4. Umbrella with a pedicle, with or without arms. No tentacula at the margin.

Orythia.

5. Umbrella with a pedicle, with or without arms: tentacula on the margin.

Diane·.

** Several mouths in the inferior disk of the umbrella.

1. Umbrella without pedicle, arms, or tentacula.

Ephyra.

2. Umbrella without a pedicle or arms, but with marginal tenta cula.

Obelia.

3. Umbrella without a pedicle, but furnished with arms under neath. No marginal tentacula.

Cassiopea.

4. Umbrella without a pedicle, but with arms underneath, and marginal tentacula.

Aurelia.

5. Umbrella having a pedicle and arms, but no marginal tentacula. Cephea.

6. Umbrella having a pedicle and arms, and marginal tentacula. Cyanea.^[154. Anim. sans Vertèbres, ii. p. 491. ]

The following table gives a synoptical view of the system adopted by Eschscholtz in his work on this order,^[155. System der Acalephen. Berlin, 1829, 4to. ] which has a high reputation, and is founded on much personal observation.

1. Μ. Discophorae.

Medusae with a large central digestive cavity, and for their only locomotive organ a gelatinous disc in form of an umbrella, constituting the greater part of the body.

Section 1.— Phanerocarpae. The ovaries are visible.
[table]
[7:21:1017]

Section II Cryptocarpae. The ovaries are concealed.
[table]

Blainville divides the class into two very unequal sections, from the presence or absence of a solid plate of support to the soft gelatinous umbrella or body of the animal,—the Cirrhogrades having such a support, and the Pulmogrades being destitute of it; and they are further distinguished by considerable differences in the nature of the appendages which garnish the oral surface. The Pulmogrades, by far the most numerous in its constituency, and embracing the proper Medusides, might be divided into perhaps natural subsections by the character of their digestive organs; some having no mouth or stomach, as has been alleged, and others having a distinct stomachical cavity, with one or more oral apertures. But Blainville prefers drawing the distinctive peculiarities of the families from the form and appendages of the mouth, or central part of the disc; for he thinks it very doubtful whether any among them are really unfurnished with a stomach, a fact which is anomalous in the animal kingdom, and which every subsequent observation tends to disprove. He gives the following synopsis of his system, which embraces all the genera of Peron and Le Sueur, and of Eschscholtz; but he tells us at the same time that he doubts the existence of several of them, for they seem to be founded on imperfect figures, perhaps representing parts only of some mutilated species.

Sub-order I— Pulmogrades.

Section i. Simple.— Eudore: Ephyre: Phorsynie: Eulymene: Carybdee: Euryale.

Section ii. Tentaculated— Berenice: Equoree: Mesoneme: Polixene: Aegine: Cunine: Foveolie: Eurybie: Pegasie: Obelie.

Section iii. Subprobosridiform— Oceanie: Aglaure: Melicerte: Cytacis: Thaumantias: Tima: Campanella.

Section iv. Proboscided.— Orythic: Geyronie: Saphenie: Diance: Linuche: Favonie: Lymnoree: Sthenonie.

Section v. Brachiated and pedunculated— Ocyrae: Cassiopee: Aurelie: Melitee: Evagore: Cephee: Rhizostome: Chrysaore: Pelagie.

Sub-order II Cirrhogrades.

The genera are, Velelle: Rataire: Porpite.^[156. Manuel d’Actinologie, p. 270. ]

Of these genera our limits do not permit us to give the characters at length. Of their British representatives the number is most imperfectly ascertained, and no department of our native zoology has been so greatly neglected. We need not painfully search the “dark unfathomed caves” for novelties, so long as the surface of our heaving ocean teems with varieties undescribed and unknown. Of such as are known, the student will find the fullest account in Dr Fleming’s History of British Animals ; and of several species not specified in that excellent work there are notices and figures in Loudon’s Magazine of Natural History, more particularly in the ninth volume, where Mr Templeton describes the Irish species.

ORDER II—ACALEPHES.^[157. Synonymes: Les Acalèpbes hydrostatiques: Radiares anomales; Acalepha Paecilomorpha. ]

After the example of Macleay, we restrict the application of this term to some families of Arachnodermata, which, by their fantastic forms, are estranged from the typical tribes, and exhibit in their organization such a variableness among themselves, and such a mixture of the elements of more than one class, that their true position among animals is rendered doubtful; and we are fain, in order to preserve distinctness and precision to our definitions of the various classes, to set them aside as anomalous, or annectant, or osculant groups, which, like corner-stones in a building, are adapted, by their very irregularity, to cement and gird the whole together. Most naturalists have believed them to bear the closest alliances with the Medusides, more particularly with the Cirrhogrades; but Blainville deems them to have superior claims to a connection with the Mollusea.^[158. Man. d Actinologie, p. 112. This view has been adopted by Quoy and Gaymard, and by Lesson. Ann. des Sc. Nat. n. s v. p. 235-6. ] A common character can scarcely be assigned to the order. They are gelatinous, nomade, sometimes globular and radiated, more usually without any radiation, and deviating widely from familiar objects, so that we might compare them to the beautiful but misshapen orchideous and cryptogamous plants which blossom in the shades of the tropics, rather than to any animals which even the fancy of the herald-at-arms has yet pictured. Hence we shall distribute the little we have here to say of them under the two families which the order embraces.

The first family is named by Blainville Physogrades, an air-bladder being their principal organ of locomotion. Its general character is defined to be a regular symmetrical, bilateral, fleshy, contractile body, often greatly elongated, constructed with an air-bladder of greater or less size, which Blainville supposes, in the spirit of a transcendental anatomist, to be formed by a partial inflation of the intestinal canal, that has always a mouth and anus distinct from each other, and placed at the opposite extremities. The respiratory organs, according to the same-author, reside in the lengthened irritable cirri attached to the body, and with which the ovaries are intermixed. The animals appear to have the power of secreting air, by which means the bladder can be filled more or less completely, and their buoyancy and position regulated according to their instincts. Whether the air is again absorbed when the floating Acalephes wish to descend, or whether it is ejected by compression from certain appropriate orifices, has been disputed. The latter is the common, and, as we believe, the correct opinion. A different opinion is however entertained by Dr Grant; for after a storm of three days endurance, he found many Velellae cast on the shores of Cornwall, which should, on our hypothesis, have sunk to the bottom, and thus, in its stillness, have avoided the wreck which they suffered.^[159. Proc. Zool. Soc. Lond. iii. pt. i. p. 14. ] But a fact which concerns the Velellae alone, cannot be legitimately applied to the Physales, since the discrepancy in their structures manifestly prohibits such an application. With relation to the Physales, Mr Peacock says, “on compression, air escapes from the sac by small orifices at each extremity.”^[160. Mag. of Nat. Hist. n. s. i. p. 598. ] Mr Baird, who had many opportunities of making examinations of them, says of the same animals, “They have the power of contracting and dilating their membranous (air) bag at pleasure, and no doubt, by trimming it to the wind, make it act the part of a sail to propel themselves through the water. ‘ They are very often to be met with at sea,’ says Sir Hans Sloane; ‘ and seamen do affirm that they have very great skill in sailing, and managing their bladder or sail with judgment for this purpose, according to the different winds and courses.’ Upon attentively examining the narrow or free extremity of the bladder, a small round aperture is perceptible, surrounded by a circular zone of fibres, of a beautiful red colour, like the muscular fibres of the iris of the eye. Out of this small hole, which is not larger than would be sufficient to admit the passage of a very fine bristle, I squeezed the air out of the bladder.” ^[161. Mag. of Nat. Hist. iv. p. 476. Knowing Mr Baird’s accuracy, we are disposed to receive his statement as correct; but it is opposed by Mr George Bennett, who states that he could never discover the orifice in question, nor expel air from the bladder without a puncture being previously made; and, moreover, that the partial escape of air from the bladder has no influence on the creature’s buoyancy. See Proc. Zool. Soc. Lond, for April 1837, p. 43. j ]
[7:21:1018]

The genera enumerated by Blainville as appertaining to the family are,

1. Physalus,

2. Physsophora,

3. Diphysa,

4. Rhizophysa,

5. Apolemia,

6. Stephanomia,

7. Protomedea,

8. Rhodophysa,

9. Cucubalus,

10. Cucullus,

11. Cymba,

12. Cuboides,

13. Enneagona,

14. Amphiroa,

15. Calpe,

16. Abyla,

17. Diphyes,

18. Pyramis,

19. Praia,

20. Tetragona,

21. Subculeolaria,

22. Galeolaria,

23. Rosacea,

24. Noctiluca,

25. Doliolum.

Of these the Physalus is the most celebrated. It is known to sailors as the Portuguese man-of-war, and almost every book of voyages into distant lands contains some account of its habits, mixed, as we may notice in the above extract from Sir Hans Sloane, with a little fable. One of the earliest descriptions of it is given by Clayton in his account of a voyage to Virginia, which we extract, because it is sufficiently descriptive, and gives the notions of the period regarding its nature. “In the sea I saw many little things which the seamen call Carvels. They are like a jelly, or starch that is made with a cast of blue in it. They swim like a small sheep’s bladder above the water. Downwards there are long fibrous strings, some whereof I have found near half a yard long. This I take to be a sort of sea-plant, and the strings its roots growing in the sea, as duck-weed does in ponds. It may be reckoned among the potential cauteries; for when we were one day becalmed, getting some to make observations thereof, the sportful people rubb’d it on one another’s hands and faces, and where it touch’d, it would make it look very red, and make it smart worse than a nettle.”^[162. Phil. Trans, an. 1688, v. xvii. p. 783. ] Of the tentacula which hang from the lower edge there are two kinds; the longest being used by the Physalus for the capture of its prey, and capable of being coiled up within half an inch of the air-bladder, and then darted out with astonishing rapidity to the distance of twelve or eighteen feet, twining round and paralyzing, by means of an acrid secretion, any small fish within that distance. The food thus seized is rapidly conveyed to the short appendages or tubes, which are furnished with mouths for its reception.^[163. G. Bennett ut sup. cit. p. 43. ] The creature is not only vesicatory, but luminous in a high degree; and we may here remark, that these properties are probably common to every species of the family.

Of the other genera all are remarkable for singularity of form. We might single out as among the most curious, the Rhizophysa, from its likeness to a bulbous root, with long radicular fibres, and the Physsophora, which imitates a root partly bulbous and partly tuberous; the bulbs represented by the air-vesicles which are clustered above on a common stalk, and support the animal^[164. “Mr Milne-Edwards believes that these (Physsopbores) are not single animals, but the aggregation of a great number of individuals growing by buds, and living united together like the compound polypes.” Ann. and Mag. of Nat. Bist. i. p. 156. ] in an upright position, while under them the stalk parts into many unequal tubers, whence depend the fibrilose radicles, which are the organs of respiration. The Apolemia and Slepha-nomia, if possible, surpass this eccentricity of form; they are living clusters of sea-grapes or currants, with tentacula of curious structure pullulating from amidst the berries.^[165. The Stephanomiae are, according to Lamarck, compound animals, consisting of a cluster of individuals which enjoy a common life and mutual communications through the medium of the central tube to which they hang. Anim. sans Vert. ii. p. 462. ] The Diphyes, although less attractive, yet deserve notice from the view Cuvier takes of their organization. He believes that each animal, as it is usually taken, consiste of two different individuals, one being emboxed in a cavity of the other; an arrangement which permits them to separate without destruction to individual life. The Noctiluca is pre-eminent for its luminosity. It is a minute gelatinous spherical body, with a depression on one side, whence protrudes a sort of contractile stalk or proboscis; and we strongly suspect it is the same with the Medusa scintillans of our shores, better or more amply described and delineated. Mons. Surivay, to whom we owe our fullest knowledge of the Noctiluca, mentions that it seemed to have disappeared entirely from its ordinary habitats in the Channel during the period of the prevalence of the cholera at Havre, which was in the months of May, June, and July 1834.^[166. Mag. of Zool. and Botany, i. p. 492. ] The fact is too remarkable not to be recorded, and seems to point to an atmospherical poison as the cause of that plague.

De Blainville gives to the second family the name of Ciliogrades, The Vibrastes of Chamisso; Beroides of Lesson. 6 because they move about in the ocean by means of certain rows of vibratile cilia which garnish the body. They are gelatinous, translucid, fragile, very irritable and contractile animals, of multiform aspects, but always evidently binary or bilateral, although there are not unfrequently some signs of a tendency to radiation in their structure. Thus the genuine Beroës are egg-shaped or globular, girded longitudinally with eight ciliated bands, equidistant or in pairs, so as to force a comparison between them and the Echinus with its ambulacral grooves.^[168. The boatmen of Sheerness are familiar with the Beroë pileus “ under the name of the spawn of the sea-egg (Echinus), which it somewhat resembles in its globular and ribbed form.” Grant in Trans. Zool. Soc. i. p. 9. ] The alimentary canal is usually described as traversing the body from pole to pole, with an orifice to each, the inferior and larger being the mouth, while the vent opens opposite in the centre of the apex. Near the middle of the body the canal is dilated into a stomachal cavity, at the sides of which the ovaries are usually to be distinguished by their vivid coloration;^[169. “I have generally observed that the lively hues presented by the Acalepba depend on the bright opaque colours of their reproductive gemmules, which are often red, sometimes yellow, or brown, or purple.” Grant in loc. cit. ] and from the same cavity there run two or more canals, which tend towards the tentacula, on the lower surface, and carry water to them; for their elongation and various movements are dependent on the propulsion of water into them from behind, or its reflux back within the stomach.^[170. This description has been lately pronounced by Mr Forbes and Mr Goodsir to be inaccurate. They believe the supposed anus to be imperforate, and a great portion of the supposed intestinal canal to belong to the circulating system. ] The bands on which the cilia are placed run from the inferior or oral extremity, to the opposite one, always in straight lines; they are of firmer consistency than the rest of the body, and are apparently formed by a duplicature of the thin skin, so inserted as to leave a fine canal between their base and the surface. Through these canals there is probably a constant flow of water, and it has been suggested by Professor Grant that the play of the cilia may be maintained by this current, for muscular action for such a purpose seems to be inadequate.^[171. Grant ut sup. cit. p. 12. Dr Fleming observed in Beroë ovatus water moving in vessels along the middle of the bands to which the cilia are attached. The animals can change the direction of the currents in the vessels, and also the direction of the motions of the cilia. ] Our knowledge of their generation is very imperfect. Eschscholtz has seen minute Beroës, which even then had a close resemblance to their adult parents, but they were destitute of the eight rows of natatory lamellae. He could perceive in them only four opaque longitudinal bands, which were probably the rudiments of as many rows of lamellae. These lamellae then are developed not until after the body has assumed the figure [7:21:1019]characteristic of the species; and of the eight rows which these all possess, it appears that at first there are only four, between which the others are afterwards produced.

The Ciliogrades abound in all seas, but many of them are rendered invisible to our dim vision by their pellucidity and small size. They move about with great alacrity, sometimes whirling on their own axis, or advancing forward obliquely, or rising to the surface and again quickly descending. As already mentioned, their principal organs of locomotion (and they are at the same time the organs of respiration) are the banded cilia, aided however by the contractility of the body itself, perhaps also by currents of water flowing through them, and in some genera (Ocyroes) by the undulatory movements of certain fin-like expansions peculiar to them. When they wish to repose, they poise themselves in mid water by the aid of their tentacula, or by ceasing the play of the cilia; but motion, constant motion, is their joy and occupation. Their vivacity, their extreme delicacy and fragility, the purity of the tints which colour their internal organs, and their varying iridescence reflected from the surface by the changes and motility of their cilia, have made them the objects of admiration to every one who has seen them. The Beroë ovum is, in the estimation of Otho Fabricius, the most beautiful of the class, but so frail as to be injured and broken by the gentlest handling; and when we remember that their life is probably as transitory as that of the Ephemera, it does indeed require from their admirers all the philosophy of the poet to bid him say, unrepining,

Oh I mourn not, that in nature, transitory Are all her fairest and her loveliest things.

The family is coequal with the order Ctenophores of Eschscholtz, whose arrangement of the genera, though not the latest, is considered the most satisfactory. He divides the order into families and genera thus:

1° Callianihides, which have a small stomachal cavity and tentacula.

A. Tentacula simple, furnished with delicate filaments.

(a ) Body extended laterally in the form of a ribbon. Cettum.

(b ) Body globular or ovoid. Cydippe.

B. Tentacula ramified. Callianira.

2°. Mnemiides, which have a small stomachal cavity without tentacula.

A. With straight prolongations near the mouth.

* With rows of vibratile cilia on the body.

(a ) Surface of the body furnished with papillae, without large lobes at the mouth. Eucharis.

(b ) Surface of the body even, with large lobes at the mouth. Mnemia.

** No rows of vibratile cilia on the body. Calymna.

B. Without straight prolongations at the mouth. Axiotima. 3°. Beroides, which have a large central cavity in the place of the digestive cavity.

A. The rows of vibratile cilia exposed.

(a ) Cilia shorter than the interspaces. Beroë.

(b ) Cilia one half longer than their interspaces. Medeae.

B. The rows of cilia in furrows, in which they can be hidden.

Pandora.

Mr Edward Forbes has kindly furnished us with the following synopsis of the British Ciliograda.

I. Cydippe. Eschscholtz. Filamentary appendages.

1. C. pileus, Linn.—Rows of cilia nineteen or twenty, on the summits of the lobes; filamentary appendages white. Hab. East coast of Scotland and England: Irish Sea: Isle of Man.

2. C . Flemingii, Forbes—(Beroë ovatus, Firm.) Rows of cilia thirty-six, on the summits of the lobes; filamentary appendages white. Hab. St Andrews Bay.

3. C . lagena, Forbes—Rows of cilia about twenty-five, placed in the furrows of the lobes; filaments white. Hab. North coast of Ireland.

4. C. pomiformis, Patterson.—Rows of cilia about twenty; filaments rufous. Hab. Coast of Ireland and Firth of Forth. (Mr Patterson has given us a history of this species, written in a peculiarly interesting and pleasing style, in the Trans, of the Royal Irish Academy, V. xix., part 1st.)

Obe— Mr Forbes and Mr Goodsir have made many observations on the cilia of this genus, which lead to important conclusions on the nature of these organs in general. They found, as Mr Garner had previously ascertained, cilia on the walls of the stomach and vessels, and a row of minute ones surrounding the mouth; but none was seen on the filamentary tentacula, or on the walls of the filamentary cavities. The cilia which are placed on the longitudinal ridges are linear-lanceolate, flat, and not hollow. They are not webbed together, and have no communication with the vessels which run beneath the ciliary ridges. Each row of cilia is mounted on a transverse base of a more solid texture, and less transparent than the rest of the body. The substance of this base consists of globules irregularly imbedded in a homogeneous substance. When one of the cilia of a Cydippe is cut off, it has of itself no power of motion; but if the smallest portion of the substance of its base remains attached, it moves with great vivacity. Hence the observers conclude that the ciliary motion is effected by the undulatory movements of this peculiar tissue; which explanation will also account for the rotatory appearance of the circles of cilia on certain animalcules. Athenaum, Sept. 26, 1840, p. 746.

II. Alcyöe, Rang. Tentacula round the mouth.

1. Al. rotunda, Forbes and Goodsir.—Ovate, rounded, crystalline; tentacula rounded at their extremities; natatory lobes forming half the animal. Hab. Kirkwall Bay, Orkney.

2. Al. Smithii, Forbes.—Elongate-pyriform, sub-compressed, crystalline; natatory lobes about a third of the length of the animal; tentacula acute lanceolate. Hab. Sea near Ailsa Craig.

3. Al. [Botina] Hibernica, Patterson—Ovate, crystalline; tentacula acute; natatory lobes nearly one half the length of the animal. An Mnemia Norvegica, Sars.? Hab. Irish coast, Mr Patterson, who has described it excellently in the work above quoted.

III. Beroe, Linn. Neither tentacula nor appendages.

1. B. cucumis, Otho Fabricius. No spots on the external surface; internal dotted with red points; ciliaferous ridges red Hab. Isle of May, in the Firth of Forth.

2. B. fulgent, Macartney. Hab. Hearne Bay.

Obs. The “Eulimena quadrangularis” of Fleming appears to have been a ciliograde. The name Eulimena is pre-occupied for another genus of Medusa.

IV.—POLYPES.

The constituents of this class are in general animals of minute size, and of almost gelatinous consistency, characterized by having the oral aperture in the superior disc or extremity of the body encircled with a row, or sometimes with several rows, of tentacular filaments. The aperture always leads into a cavity appropriated to the digestion of the nutrient matter, but in all other particulars the Polypes differ so widely in their organization, that to give a view of it which shall have any distinctness or use, there is a necessity to separate the class into groups, founding their distinctions on that knowledge of their anatomy which has been recently obtained through the labours of Cuvier, Blainville, Savigny, Rapp, Grant, Thompson, Ehrenberg, Milne-Edwards, Dujardin, Farre, Lister, and others.

It is an axiom, that no class of animals stands isolated, but every one has its kindred claims on those around it, proving, not that each has been evoked from the pre-existent class by innate or external influences, but that the Creator has perhaps called his creatures into existence by a fiat worded in one spirit, and which matter has obeyed with one uniform intelligence. And thus it happens, that while Polypes have mostly felt the force of radiation in their development, they are not without their families that connect them with the unsymmetrical molluscans; and since it seems to us to be of importance that these relations should be remembered (for what study is more interesting to the zoologist than the mutual harmonies of two apparently remote classes?) we shall in the first instance divide the class into two sections, distinguished in a manner that brings this relationship into prominent view. The mollus-can Polypes have both an oral and an anal aperture to the alimentary canal, and the tentacula that surround the former[7:21:1020] are filiform and ciliated; but the radiated Polypes have only one aperture to their digestive sac, serving by turns the purposes of a mouth and a vent, and the tentacula that guard it are not ciliated, but very contractile.

I.—MOLLUSCAN POLYPES.^[172. This order corresponds with the Polyzoa of Thompson, the Bryozoa of Ehrenberg, the Ciliobrachiata of Ferre, and with the Zoophyta Ascidioida of Dr Johnston. ] «

The molluscan Polype is always a very small, almost a microscopic animal, with an elongated, slender, subcylindrical body, which is bent upon itself like a syphon, so that the two extremities approximate each other. The mouth is a wide edentulous aperture, situated in the centre of the circle of tentacula, which rise from its rim, and constitute a funnel-shaped coronet of extreme delicacy. The number of filaments of which the coronet consists is very variable, but each of them forms a long slender filiform tube, clothed on one side with vibratile cilia, by whose active and well-regulated movements a current of water is incessantly driven along them in one determinate direction. These currents not only supply a succession of unbreathed water to the animal for the purpose of respiration, but they carry in their stream the animalcular prey that the polype feeds upon. Under the tentacular coronet the alimentary canal forms a kind of pouch analogous to the branchial sac of the ascidian mollusea, and, like it, plaited usually in a longitudinal direction. From this pouch or pharynx the gullet descends a short space previously to its dilatation into the stomach,—an organ usually of an oblong shape, with its wells studded with spots of a rich brown colour,—apparently hepatic follicles, that secrete a fluid which often tinges the whole organ, as well as its contents, of a similar hue. The intestine, on departing from the stomach, makes a sudden bend, to which is suspended a large short caecal appendage; and afterwards the intestine proceeds upwards in a course parallel with the gullet to its termination, which is a little below the mouth, behind the pharynx, and on the side of the membranous sheath containing the tentacula.^[173. See Ferre in Philosophical Transactions, an. 1837, p. 406, &c.; Μ. Edwards in Lamarck’s Anim. sans Vert. 2de edit. vol. ii. p. 214; and Johnston’s British Zoophytes, p. 240, &c. ]

This kind of polype is never found isolated and naked. It dwells enclosed in a calcareous or horny cell, of which a great number is placed in juxtaposition, usually after a quincunx pattern; and the entire congeries forms sometimes a leprous crust, sometimes a stony branched coral, sometimes a fleshy unformed mass, and at other times a horny flexible sea-weed like polypidom, or one that more nearly resembles some fine capillary moss or shrubby lichen. The numerous tenantry of these aggregations are besides all connected together, so as to form what has been named a “compound animal every individual capable of self-support and of continuing its kind, yet so connected with the rest as necessarily to participate in every good and every evil that affects the community. The polypes are so connected with their cells that they cannot leave them, for indeed the cell and polype are merely parts of the same body. This, such as it has been described above, is enclosed in a thin membranous sac; and the cell is formed by a continuation of this tunic reflected over the inner layer, and hardened by the deposition in it of calcareous or albuminous matter to fit it to endure with impunity the contact and friction of the circumfluent waters, or to protect the soft viscera from accident and from the access of their enemies. Milne-Edwards compares the cell to the lopt finger of a glove, which has had its open truncate extremity ornamented with a thready fringe, capable of being withdrawn by an act of involution within the finger-stool. The point of junction between the retractile portion and that which is not so, constitutes, when the finger or polype is withdrawn, an opening usually called the mouth of the cell, which is very often overhung with a sort of moveable lip or valvular fold named the operculum. Two muscular bands are attached to the inner surface of this valve, and their office is to draw it down and shut close the cell when the tenant has retired for rest or from danger.

The polypidom, formed frequently of a congeries of many thousand cells, invariably begins with one only. This original or seminal cell has no sooner been completed (or even in many instances previously to its perfection) than another begins to shoot out from a fixed point of its parietes, the bud gradually enlarging and developing itself until the form and size of the primary one has been attained. This process can most easily be traced in the common sea-matts (Flustra) and Lepraliae, where, round the margin of the crust, cells can at all seasons be observed in every stage of their evolution; one just budding, another half formed, and others again nearly complete. They never begin their original in the body of the polype, but always from the parietes, or from the connecting medium of the cells; and it is not until these have made considerable advances to maturity that the polype becomes distinguishable within them.

From this mode of increase there would seem to be no natural limits set to the magnitude and duration of the polypidom, except what arise from accident or exterior causes. The original polype and its immediate successors may grow old, languish, and die; but the solid cells remain in their connection as a root and fixture, while the newer races, which have sprung up towards the outskirts, continue their work, generation following generation in rapid and ever-multiplying successions. The polypidom in this respect resembles a tree in its growth: the trunk and main branches have stood years and centuries, but the increase has been made by annual shoots and renewals, and the last only know vigour and juvenescence. And as the form of the tree depends on the fashion of its ramifications, so that of the polypidom on the mode of evolution of its cells, for every part of the axis is not equally organized to produce buds, nor the same parts in all. Hence, if the primitive cell has only one point fitted for this generation, the polypidom will be built up in a catenated chain; if the cell has two points, two series of cells are formed, and in several the multiplication goes on in a regular arithmetical progression; but in others the cells are heaped together without apparent regularity, as in Alcyonella and Alcyonidium, where the softness of all the parts seems to allow of an irregular succession of buds. In this order, however, the general disposition of the cells is certainly after the quincunx, affording examples which the learned Sir Thomas Browne would have gladly adduced in proof that “Nature geometrizeth and observeth order in all things, and of the generality of this mystic figure.”

The molluscan Polypes are all hermaphroditical and oviparous. The ova, which originate in the organized medium connecting the individuals together, are lodged and matured within the cell in some families; but in others their matrix is a little pearly globe that is placed over the mouths of the cells, and often constitutes the principal beauty of the specimen. When ripe for expulsion, the ova are of a vivid orange or yellow colour, of a roundish shape, and clothed with vibratile cilia, by means of which they swim about to and fro in the water like beings endowed with volition, and scatter themselves abroad.

The structure and form of the polypes seem to be very much alike throughout the entire class, so that it becomes [7:21:1021]necesssary to resort to the more varied polypidom for the basis of a method to arrange it into families and genera. Many such methods have been proposed, but in general so little are they in harmony with the structure of the animated tenants that they are of little value. Of the more recent ones none appears to us so good, as no one is so comprehensive, as that of the celebrated Ehrenberg, an outline of which is exhibited in the following table. We have only to remark, that the microscopic polythalamous shells which Ehrenberg arranges in the class for the first time, have been usually referred to the cephalopodous mollusea, where evidently they had no claim to be placed; and very lately Dujardin has contended, in opposition to Ehrenberg, that the animalcules inhabiting them are not of higher organization than the homogeneous and gelatinous Infusoria.^[174. “Recherches sur les Organismes inférieurs, par F. Dujardin,” in the 4th and following volumes of the Annales des Sciences Naturelles, seconde série. ] Bryozoa.

Animalia asphvcta, tubo cibario simplici, sacciformi aut tubuliformi, vera corporis articulatione nulla aut sensim numerosinre, corporis forma gemmis aut novis articulis accedentibus sensim aucta, hinc indefinita, nunquam sponte dividua, omnia et singula verisimiliter periodice ovipara, ideoque hermaphrodita.

Ordo I.—P olthalamia .

Libere vagantia et loricata. Monosomatia.

Familia I. Miliolina.

Genera 2.? Miliola,? Gromia.

Familia II. Nodosarina.

Gen. 11. Glandulina, Mucronina, Nodosaria, Orthocerina, Dentalina, Lingulina, Frondicularia, Rimulina, Vaginulina, Planularia, Marginulina.

Familia III. Textularina.

Gen. 6. Bigenerina, Dimorphina, Textularia, Grammostomum (Vulvularia), Polymorphina, Virgulina.

Familia IV. Uvellina.

Gen. 11. Guttulina (et Globulina), Uvigerina, Bulimina, Valvulina, Rosalina, Clavulina, Globigerina, Pyrulina, Sphaeroidina. Familia V. Rotalina.

Gen. 22. Operculina, Soldania, Planorbulina, Rotalia, Trochu-lina,? Spirulina, Calcarina, Pleurotrema, Planulina, Discorbis, Omphalophacus,? Gyroidina, Truncatulina, Lenticulina, Nonioniua, Cristellaria, Siderolina, Dendritina, Robulina, Anomalina, Saracenaria, Cassidulina.

Familia VI. Plicatilia.

Gen. 6. Biloculina, Spiroloculina, Triloculina, Articulina, Quinqueloculina, Adelosina.

Polysomatia.

Familia VII. Asterodiscina.

Gen. 6. Asterodiscus, Lunulites, Orbitulites, Cupularia, Flustrella.

Familia VIII. Soritina.

Gen. 2. Sorites, Amphisorus.

Familia IX. Frumentarina.

Gen. 3.? Dactylopora,? Ovulites,? Polytripe. Familia X. Helicosorina.

Gen. 5. Peneroplis, Pavonine, Vertebralina, Orbiculina,? Heterostegina.

Familia XI. Helicotrochina.

Gen. 3. Polystomella,? Amphistegina,? Geoponus.

Familia XII. Alveolinea.

Gen. 2. Melonia, Alveolina. Familia XIII. Fabularixa.

Gen. 2. Fabularia, Coscinospira.

Onno II Gymnocorae.

Libere vagantes, nudae.

Familia I. Cristatellina.

Gen. 2. Cristatella, Zoobotryon.

Ordo III— Thallofodia.

Stolonibus thallove membranaceo affixa, incrustantia nec adnata, sed loricata.

Familia I. Halcyoxellea.

Gen. 8. Halcyonella, Vesicularia, Bowerbankia, Farrella (= Lagenella), Valkeria, Stephanidium, n. G. Dynamene, Halodactylus (= Alcyonidium).

Familia II. Cornularina. Gen. 1.? Cornularia.

Familia III. Escharina.

Gen. 5. Eschara, Melicertina (= Afelicerita), Crisis, Acamarchis, Notamia.

Familia IV. Celleporina.

Gen. 5. Cellepora, Flustra, Membranipora, Briolophus, n. G. Apsendesia.

Familia V. Auloforina.

Gen. 1. Tubulipora. Ordo IV.— Scleropodia.

Stolonibus destitute, excreto fulcro axique anorganicis firmiter affixa eisque fruticulosa.

Familia I. Myrioforina.

Gen. 9. Hornera, Idmonea, Retipora, Distichopora, Myriopora, Tilesia, Cricoora, Ceriopora, Spiropora.

Familia II. ? Antipathina.

Gen. 1. Antipathes.

This extensive class contains few or perhaps no species that contribute directly to the use of man, or interest him by their applications to the arts on which he prides himself. Their instincts and habits are obscure; and although the beauty and variety of their polypidoms is singularly great, the pattern is on too minute a scale to have ever engaged vulgar attention. Their influence on the earth’s surface is however not inferior to that of any class of animals whatever. Large formations of limestone, of chalk and chalk-marl, and extensive banks of sand, have been the result of their active life, and prodigious multiplications, continued over untold ages. “Many, and probably all, white-chalk rocks,” says Ehrenberg, “are the produce of microscopic coral-animalcules, which are mostly quite invisible to the naked eye, possessing calcareous shells of 1 / 24 to 1 / 288 line in magnitude, and of which much more than one million are well preserved in each cubic inch; that is, much more than ten millions in one pound of chalk.”^[175. Annals of Natural History for June 1841. ]

The Radiated Polypes, or Anthozoa of Ehrenberg, present us with a greater diversity of structures than the molluscans. In all, the body is perforated superiorly with the larger circular opening into the digestive cavity, and surmounted with a coronet of tentacula; but the structure of the stomach, and the disposition of the tentacula, vary so much, that if our classification would follow and reflect a representation of the principal modifications of this variety, we are constrained to subdivide the class into three sections as follows:

I. Helianthoida. Polypes single or aggregate, free or permanently attached, fleshy, naked, or encrusted with a calcareous polypidom, the upper surface of which is crossed with radiating lamellae; mouth encircled with tubulous tentacula; stomach membranous, plaited; intestine 0, anus 0; oviparous, the ovaries internal.

II. Asteroida. Polypes compound, the mouth encircled with eight fringed tentacula; stomach membranous, with dependent vasculiform appendages; intestine 0, anus 0; reproductive gemmules produced interiorly. Polype-mass variable in form, free or permanently attached, carnose, generally strengthened with a horny or calcareous axis, enveloped with the gelatinous or creto-gelatinous crust in which the polype-cells are immersed, and which open on the surface in a starred fashion with eight rays.

III. Hydroida. Polypes compound, rarely single and naked, the mouth encircled with roughish filiform tentacula; stomach without proper parietes; intestine 0, anus 0; reproductive gemmules pullulating from the body, and naked, or contained in external vesicles. Polypidoms homy, fistular, more or less phytoidal, fixed, external.
[7:21:1022]

I.—HELIANTHOIDA.^[176. Synonymes: Zoantharia, Blainrille; Zoantaires, Milne-Edwards. ]

The typical representatives of this order are the Actinia or sea-anemonies. which abound on every European shore between tide-marks, rivalling in beauty and vividness of colouring their floral namesakes. It is now well ascertained that the animals of the madrepores, sea-mushrooms, and brainstones of tropical seas, differ from the Actiniae no otherwise in essence than in their power of excreting, from the inferior portion of the body, a large quantity of calcareous matter, the deposition of which under and around the body, and in the tissue of the folds formed by the tunics of the abdominal cavity, constitutes the cell or polypidom, into whose hollows the tenant can partially or wholly retire. “The stony substances so formed are called corals, and their mode of formation causes them exactly to represent the animal which secretes them: the upper surface is always furnished with radiating plates, the remains of the calcareous particles which were deposited in the longitudinal folds of the stomach, before referred to; and as these plates do not usually reach to the centre, there is almost always a vacant space in the middle between them.” The cells are either single and cupped, or they are branched like a tree, or they are aggregated together so as to resemble a cauliflower, or even to imitate the human brains; all these variations resulting from the manner in which the animal emits from the whole surface, or from a particular part of the sides of the body, the bud by which the new individuals of the general mass or society are produced.

The Helianthoida are all oviparous, the ova being produced in appropriate ovaries situated between the compartments formed by the septa that radiate from the outer parietes of the stomach to the skin. The ova are contractile and motive, being carried about from the action of the cilia that clothe the surface. “Under the microscope they prove of diversified form, many resembling flattened peas, some elongated or exhibiting irregular prominences, some almost spherical, and some which cannot be referred to any particular figure.” After moving about for several days, during which their forms suffer some slight change, they insensibly relax in their motility, the cilia disappear, and having become stationary, each ovum rapidly runs through the stages of development that lead it up to the similitude of its parent.

The productiveness of the species and the rapidity of their growth are very great. The calcareous species often form enormous masses of coral, of the size of which we cannot judge by the specimens usually shown in collections, which are small individuals taken in the sheltered places among the rocks, where they are not exposed to the action of the waves, and collected before they have reached their proper magnitude. “The form of the masses appears to be greatly influenced by the positions in which they have grown, and the size of the individuals greatly depends on the quantity of nourishment they are able to procure. This is proved by the fact, that if all the individuals of the same mass are equally exposed, they are of an equal size, but if the surface of the coral is waved, as in the Explana∙ ria, the individuals on the convex part of the mass, which could procure the most food, are large, while those in the concave or sunken parts are small.”— J. E. Gray.

It is to the polypes of this order that the origin of the coral islands in the Pacific and other tropical seas are principally ascribed. The quickness of their growth, and the depths from which they rise, have been undoubtedly exaggerated; yet this, with every deduction, is so great that the coral-bearing Helianthoida are justly reckoned the principal operators in the mutations of the bed of every tropical sea, as they were in the seas of the primeval world. They roughen the bottom and fill up hollows in every shallow sea; they occupy the tops of reefs in deeper ones, and bar up the entrance to harbours and lagoons; they cap submarine mountains, and bring them to the surface; and they lay up everywhere the materials for the formation of future quarries of limestone.

The families and genera into which the Helianthoida have been distributed are as follows:

Fam. I. Acliniadoc.— Actinia; Anthea; Adamsia; Iluantho."; Metridium; Megalactis; Actinodendron; Epicladia; Heterodactyla; Lucernaria.

Fam. II. Zoanthida— Isaura; Hugbea; Zoanthus; Mammillifera; Corlicifera.

Fam. III. Madreporida.— Fungia; Turbinolia; Diplocterium;

Cyclolithes; Desmophyllum; Cyathina; Caryophyllia; Manicina; Oculina; Stephanocora; Cladocora; Columnaria; Strombodes; Cyatbophyllum; Pterorrhiza; Anthophyllum; Stylina; Favia; Astraea; Dictyophyllia; Favosites; Monticularia; Meandra; Dendrogyra; Turbinaria; Explanaria; Alerulina; Pavonia; Agaricia; Polyastra; Haliglossa; Polyphyllia.

Fam. IV. Poritida.— Madrepora; Porites; Alloporina.

Fam. V. Paocilloporidae.— Seriatopora; Anthopora; Paecillopora;

Heliopora.

Fam. VI. Milleporidae.— Millepora.

Fam. VII. Distichoporidae.— Distichopora.^[177. ’ Synopsis of the British Museum, by J. E. Gray, p. 75. Lond. 1840. ]-

II— ASTEROIDA.^[178. Synonymes: Zoophytaria or Ctenocera of Blainville; Alcyoniens, Μ. Edwards. ]

The name of this order is derived from the starred marks that stud the surface when the polypes have contracted and hid themselves under the skin of the common mass or polypidom. These marks are produced by the incisures whence the tentacula are evolved; and hence the number of rays in each mark is mostly eight, but sometimes only six in number, corresponding with the number of tentacula. These organs are, in this order, comparatively short, thick, and fringed or pectinated on the margins, and they radiate from a flat disc, in the centre of which the mouth is situated. This aperture is always circular, and leads by a gullet into a long cylindrical stomach, which is as it were suspended in a thin membranous sac or vesicle, and kept in its central position by eight or six septa or ligaments stretched between it and the vesicle, dividing the intermediate space into as many distinct compartments. From the inferior extremity of the stomach there hang eight or six twisted, intestine-like, but probably biliary, appendages, into a wide cavity, that communicates freely with the fleshy parenchyma by which the polypes are connected together, for the Asteroida are all compound Zoophytes; that is, each species is a collection of numerous individuals participating in a common life, while each individual at the same time enjoys an independent vitality for every part of its body. The connection is effected partly through the medium of the skin, which is formed by the confluence of the outer thickened tunic of the polypes, and partly by aquiferous ducts that depart from the infra-abdominal cavity just mentioned, and permeate the entire mass in every direction.

The forms of the polypiferous masses are very various. Some are fleshy amorphous productions, covered with a coriaceous skin loaded with variously-shaped calcareous grains or crystals; others resemble a quill, and are called Sea-pens; others are like a rush or rod; while many, like the Gorgonia and Coral, are eminently imitative of marine vegetations. The internal part of the amorphous species is [7:21:1023]fibro-gelatinous; “but when the axis assumes an erect or a branched tree-like form, the animals excrete in the centre of their body a more or less rigid support, which has been called their axis, and which has sometimes, though erroneously (from its being commonly seen in collections without the remains of the investing animaD, been considered the entire coral. This axis is thickened by depositions of fresh layers of horny matter on its surface as the mass increases in size and requires more support, the increase of the thickness and length of the axis being always simultaneous with the growth of the mass.”—(J. E. Gray.) In some genera the axis is bony, in a greater number it is of a horny nature, and very compact, in a few it is formed by the aggregation of siliceous needle-shaped spicula, and in others it is calcareous and stony; of which we have a familiar example in the red and black coral of the Zoophyte that furnishes the coral of commerce, so highly valued for ornamental purposes. In the genus Isis , “the axis has been considered as jointed, because the stony and the horny parts easily separate from each other when the mass of the animal has been removed and the axis is dried; but a larger and larger quantity of stony matter is gradually deposited as the mass increases in size, and in the large masses the axis of the lower part is almost entirely stony, like the axis of Corallium.”—(J. E. Gray.)

The Helianthoida are all oviparous, and it has been recently affirmed that the sexes are distinct and separate. Dr Erdl of Munich says that he found in Veretillum only female individuals in one polypary, and in another only males; and he has convinced himself of a similar distinction existing in the genus Alcyonium or Lobularia. Plate DVI. fig. 9.

According to J. E. Gray, this order arranges itself under the following families and genera:

Fam. I. Cornularidoe.— Cornularia.

Fam. II. Clavulariadae.— Actinantha; Clavularia; Telesto.

Fam. III. Tubiporida.— Tubipora.

Fam. IV. Coradliada.— Corallium, Plate DVI. fig. 3; Isis; Mopsea; Melitaea; Prymnoa; Muricea; Scirpearia; Eunicea; Plexaura; Gorgonia; Pterogorgia.

Fam. V. Antipathidae.— Antipathes; Leiopathes.

Fam. VI. Briareidae.— Briareum.

Fam. VII. Lobulariadae.— Lobularia; Ammothaea; Anthelia; Sympodium; I<hizoxenia.

Fam. VIII. Zeniadae.— Zenia; Nephthya; Nidalia.

Fam. IX. Hyalonemidae— Hyalonema.

Fam. X. Bennatulidae.— Pennatula, Plate DVΓ. fig. 8; Virgularia; Renifla, Plate DVI. fig. 11; Pavonaria; Veretillum.

Fam. XI. Umbellariada—Umbellaria.

III.—HYDROIDA.^[179. Synonymes: Sertulariens, Μ. Edwards: Polypiaria, J. E. Gray. ]

The Hydra, or fresh-water Polypus (Plate DVI. fig. 10and 14), of which more has been written than of any other Zoophyte, is the type of this order, very remarkable for the extreme simplicity of organization of its members, and for their wonderful powers of redintegration and reproduction. The polype, considered independently of its polypidom, possesses no defined organs whatever; but when highly magnified, the whole body is seen to consist of a granular substance, the granules being loosely connected by a semi-fluid albuminous matter. On the upper pole of this gelatinous and very contractile body there is an aperture encircled with a variable number of tentacula, roughened with nodules, and extremely extensible, so that the creature can spread and stretch them far and wide in search of prey, which consists of very active crustaceous animalcules and small worms. These are no sooner seized upon than they appear to be paralysed by some poisonous secretion of the polype, for their struggles and resistance are stopt as it were by magic, and they are carried unresisting to the mouth, and forced into the central digestive sac.

The Hydroida are reproduced by gemmules or buds, which are developed from the common substance of the body. In the Hydra they spring from no particular part, but in other genera they have a determinate origin, and in many others they are contained, like ova, in ovarian capsules, whence they are not discharged until ripe for evolution. But perhaps the most remarkable feature in the history of these Zoophytes, is their power of being multiplied by mechanical division. If a snip be made with a fine pair of scissors in the side of a Hydra, not only does the wound soon heal, but a young polype sprouts from the wounded part; if it be cut into two portions by a transverse incision, each soon developes the wanting parts of its structure; if longitudinally divided, both portions soon become complete animals; if it even be cut into several parts, every one of them will rapidly assume the form and functions of the original. The inversion of its body, by turning it inside out, does not destroy it; on the contrary, the exterior surface assumes the office of a stomachical cavity, and that which was originally internal will give birth to buds, and take upon itself all the properties of the skin. See R. Jones’s Outline of the Animal Kingdom, p. 26.

The Hydra is locomotive and naked, but the majority of its order are permanently affixed to their sites, and are invested with a horny sheath or polypidom, which in many instances excels all other zoophytical productions in the delicacy and gracefulness of its form. These polypidoms are converfoid and more or less divided, the ramifications being divided in a variety of elegant plant-like forms. The stem and branches are alike in texture, slender, fistular, and almost always jointed at short and regular intervals, the joint being a mere break in the continuity of the sheath, without any character of a proper hinge, and evidently formed by regular periodical interruptions in the growth of the polypidoms. Along their sides, or at the extremities, we find the denticles or cup-like cells, within which the polypes are contained, arranged in a determinate order, and either sessile or elevated on a stalk. Plate DVI. fig. 12. Though of the same substance, the cell is something more than a simple expansion of the stem or branch; for near its base there is a distinct partition or diaphragm, on which the body of the polype rests, with a plain or tubulous perforation in the centre, through which the connection between the individual polype and the common medullary pulp is retained.

According to Mr J. E. Gray, this order embraces five families, viz.

Fam. I. Hydraidae— Hydra. Plate DVI. fig. 10 and 14.

Fam. II. Tubulariada— Tubularia; Eudendrium; Corymorpba. Fam. III. Corynaidae— Coryne; Syncoryna.

Fam. IV . Sertulariadae— Thoa; Sertularia; Dynamena; Thuiaria; Pasythea; Epistomea; Lirizoa; Plumularia; Antennularia; Cymodoce; Salacia; Idia.

Fam. V. Campanulariadae— Laomedea; Campanularia; Peripyxis.

V.—SPONGES^[180. S Synonymes: Spongiae; Spongiadae; Spongiaires; Porifera; Amorphozoa. ]?

The Sponges differ so much from all other Zoophytes, that De Blainville has constituted with them a separate [7:21:1024]class, under the denomination of Amorphozoa , to mark that want of a definite and constant form in their species for which they are remarkable in the animal kingdom. Their general appearance and structure must be familiar to every one. They are soft, elastic, porous or cellular bodies, of a uniform structure in every part, without any organs or vessels, and capable of absorbing large quantities of liquid, which they again yield up on pressure, without injury to their textures. They are quite insensible to every sort of irritation, and can contract neither the body as a whole, nor any portion of it; nor can they remove in any way from the site on which they have grown.

In a recent state the sponge is filled with a colourless animal jelly, the quantity of which varies much in different species. This jelly is apparently homogeneous; but, with the assistance of the microscope, it has been discovered to be full of numerous transparent spherical granules. It is diffused through every part of the sponge, filling the intercellular spaces, and it lines also the canals which permeate the mass, and often covers the surface with a slimy coat.

The sponges used in domestic economy are composed of a horny fibre, netted together so as to form small irregular meshes, with larger canals and holes interspersed. The fibre is solid and transparent, generally smooth, but sometimes closely invested with a fine branched vascular tissue. These sponges are soft, compressible, and eminently bibulous; but there is a gradual passage from them into others of a more rigid and compact texture; and on examining into the cause of this change, we find that the fibre has become loaded with crystalline needle-shaped spicula, which, chemical tests assure us, are formed of pure silex or flint. There are many sponges in which these spicula predominate so far that the horny matter has become of secondary importance; and such sponges, after being dried, resemble crumbs of bread, and are easily rubbed down into a powder merely by friction between the fingers. Mr Bowerbank has shewn that the transition from the fibro-horny to these siliceous sponges is insensibly made, and that many species which were believed to be purely fibrous, contain in fact numerous minute imbedded spicula.^[181. ’ Microscopic Journal, i. p. 8, 4c. ]

There is another class of sponges, rather of a felted than reticular structure, and containing a very scanty proportion of organic fluid. They are usually of a grayish-white colour, and are loaded with spicula, but the spicula are composed of carbonate of lime. These spicula are more variable both in form and size than the siliceous kinds; for in the same sponge we often find some which are needle-shaped, others that are club-shaped, and others that are formed of three or four divergent prongs. There has not been discovered any sponge in which the calcareous and siliceous spicula naturally co-exist; but some species of a compact fleshy texture have been described, in which, while the central parts are crammed with spicula of flint, the surface is covered with a layer of calcareous earth.^[182. S Lam. Anim. sans Vert. 2de edit ii. p. 606. ]

In all sponges the surface is porous, and of a finer and closer texture than the interior, which is also permeated with some irregular sinuous canals, that open on the surface in the form of circular orifices, which have been called their oscula, but which are properly their vents. When living and in health, the sponge is continually imbibing by the pores the water which surrounds it. This water, penetrating to every part, fills the cells and distends the body equally; it is then forced into the canals, and driven, in an agitated current, from the body, through the oscula. By this circulation the air and food of the sponge is supplied, and its effete excretions removed; but by what agency it is originated and kept up, is not positively ascertained. Dr Grant thinks it probable that minute vibratile cilia planted in the canals and pores are the moving power; while Dutrochet ascribes the phenomena to that law of endosmose which he has discovered to regulate the transmission of liquids of unequal densities through all organic membranes.

Sponges are propagated by gemmules, which originate in the organic mucus, and are carried out of the body by the effluent currents just described. In some sponges these gemmules are ciliated and locomotive when mature; but it seems probable that the majority of the species produce only unciliated gelatinous grains, which are nevertheless endowed with a very active motility, like the ultimate particles of even inorganic matter.

With one or two exceptions, sponges are natives of the sea, ranging from tide-marks to a very considerable depth. They are scarce and small in cold latitudes, and gradually increase in size and numbers as we trace their course towards the tropics, but perhaps they abound most of all in the genial seas of the Australasian islands. The sponges of commerce are chiefly procured from the Mediterranean, and from the Bahama islands in the West Indies.

The classification of sponges is in a state of the utmost uncertainty, and most of the genera rest on very insufficient characters. The names of such as have been proposed are as follows:

Alcyoncellum. Hallirhoa. Siphonia.

Achilleum. Hippalimus. Scyphia.

Caeloptycium. Halichondria. Spongia.

Choanitea. Geodia. Tethia.

Cnemidium. Lvmnorea. Tragos.

Chenendopora. Manon. Ventriculites.^[183. For the fullest and most accurate account of the structure and physiology of the sponges, the reader is referred to Dr Grant’s papers in the 13th and subsequent volumes of the Edinburgh Philosophical Journal; and for a description of the genera and species, to the 2d vol. of Lamarck’s Animaux sans Vertèbres. ]

Grantia. Myrmecium.

VI.—LITHOPHYTES.^[184. Synonymes: Coraliinae; Calciphytae. ]

The Lithophytes, in the restricted sense in which we use the term, are plant-like marine organized bodies, which adhere to other substances by a crustaceous base, and are composed of an internal fibrous axis encrusted over with a chalky porous bark, either continuous, or divided by septa into numerous equal articulations. From the time of Ellis, who was a strenuous advocate of their animality, they have been always described as members of the animal kingdom; but the observations of Blainville and Schweigger leave no doubt of their being truly vegetables, differing little from many algae.

There are two families of lithophytes. In the first the calcareous crust is rather thick, compact or minutely porous, and jointed. The family corresponds exactly with the genus Corallina of Linnaeus, subdivided by Lamarck and Lamouroux into the following genera: Cymopolia, Corallina, Jania, Flabellaria, Amphizoa, Penicillus, Galax-aura, Acetabulum, and Polyphysa. Many of the species are very pretty, and the Acetabulum is a parasol in miniature. Plate DVI. fig. 13. One species (Corallina officinalis) has been much celebrated as a powerful vermifuge.

The second family, from being more decidedly vegetable in its aspect, is named by Blainville Fucoideae. In it the cretaceous crust which covers the stem and branches is very thin and continuous, and it offers to observation no trace of pores. The organic substance is also more gelatinous, and consequently approaches nearer to that of the true sea-weeds. The genera are, Udotea, Dichotomaria, Liagora, and Neomeris. (d. μ.) [7:21:1025]