indulges in a minuteness of detail which, though it might be some proof of veracity in a contemporary history, is a palpable indication of want of faith in the case of an antient history so obscure and uncertain as that of Rome. With all his study and research, Dionysius was so imperfectly acquainted with the Roman constitution that he often misrepresents the plainest statements about it. (Niebuhr, Hist. Rome, vol. ii. p. 13, Engl. tr.) For instance, he imagines that the patricians had all the influence in the centuries, and that the plebeians and equites had nothing| to do with the first class. (Antiq. vii. 82-87, x. 17. See Niebuhr, Hist. Rome, ii. p. 178, Engl. tr.) He thought the original constitution of Rome was a monarchical democracy, and calls the curies the demus (oñpoc.) He believed when he wrote his second book that the decrees of the people were enacted by the curies and confirmed by the senate (Antiq. ii. 14), and not, as he afterwards discovered, the converse. (Antiq. vii. 38.) In a word, though the critical historian may be able to extract much that is of great importance for the early history of Rome from the garbled narrative and the dull trifling of Dionysius, he cannot be regarded as a meritorious writer, or recommended to the student of antient history as a faithful guide. Dionysius also wrote a treatise on rhetoric; criticisms on the style of Thucydides, Lysias, Isocrates, Isæus, Dinarchus, Plato, and Demosthenes; a treatise on the arrangement of words, and some other short essays. His critical works are much more valuable than his history, and are indeed written with considerable power. The criticism on Dinarchus [DiNARCHUS] displays good sense and judgment, and shows the great pains which the author took to separate the genuine writings of the Attic orators from the fabrications which passed under their name. The best editions of Dionysius are those of Hudson, Oxon., 1704, 2 vols., in folio; and by Reiske, Lips., 1774-1777, 6 vols., in 8vo. Mai's fragments were first published at Milan in 1816, and reprinted the following year at Frankfort. They also appear in the second volume of Mai's Nova Collectio, Rome, 1827. His rhetoric has been published separately by Schott, Lips., 1804, 8vo.; and his remarks on Thucydides by Krüger, Hal. Sax., 1823, 8vo. There is a German translation of the Roman Antiquities by J. Lr. Benzler, Lemgo, 1771-1772, 2 vols., 8vo. The only English translation of the Antiquities is the following: The Antiquities of Dionysius Halicarnassensis, translated into English, with notes and dissertations, by Edward Spelman, Esq.,' 2 vols., 4to., London, 1748. DIONYSIUS of Byzantium lived before the year A.D. 196. His voyage ('Avárλovg) in the Thracian Bosporus was extant in the 16th century, for Gyllius, who died in 1555, has given extracts in Latin from it in his work on the Thracian Bosporus. A single fragment from this work is printed in Ducange's Constantinopolis Christiana,' and in Hudson's Minor Greek Geographers. Perhaps there is some confusion between this Dionysius and the author of the Periegesis, whom Suidas (Atovvotog) calls a Corinthian. DIONY'SIUS PERIEGETES, the author of a Greek poem in 1186 hexameter verses, intitled Ts Oikovμevne Ilεpinynois, or a description of the habitable world.' 'It is not known where Dionysius was born nor where he lived. Perhaps the most probable opinion is, that he was a native of Byzantium and belonged to the latter part of the third or the beginning of the fourth century A. D. 6 As a poem the Periegesis is of little value, and as a geographical work, not worth the trouble of reading. The commentary of Eustathius on the Periegesis possesses some value for the miscellaneous information which is scattered through it. There are two Latin translations of this poem, one by Rufus Festus Avienus, and the other by Priscianus. There are numerous editions of Dionysius. The last and best edition of the Periegesis is by G. Bernhardy, Leipzig, 1828, 8vo., in the first volume of his Geographi Græci Minores.' DIOPHANTUS, a native of Alexandria, the exact date of whose birth is unknown, some authors asserting that he lived in the reign of Augustus, whilst others place him under Nero, or even the Antonines. The fact is that we do not know when he lived. He lived however, as is well ascertained, to eighty-four years of age. Diophantus left behind him thirteen books of Arithmetical Questions, of which however only six are extant; but from their distinct and peculiar character, in comparison with all the other writings of the Greek mathematicians, these books have given rise to much discussion. It is however scarcely to be conceived that whilst the cumbrous machinery of common language constituted the sole instrument of investigation, the very curious conclusions which we find in this work could have resulted from the researches of one single mind. To suppose that Diophantus was the inventor of the analysis which bears his name, is so contrary to all analogy with experience and the history of mental phenomena, as to be utterly impossible to admit. Still, if we inquire into the history of this branch of analysis, and ask who were the predecessors of Diophantus, or whether they were Greeks or Hindus, no satisfactory answer can be given. Diophantus also wrote a book on Polygon Numbers (πepi woλvywvwv ápidμwv). Holzmann published at Basle, in 1575, folio, a Latin translation of both the works of Diophantus. The first Greck edition was by Meziriac, Paris, 1621, folio: an improved edition of Meziriac's edition was published by S. de Fermat, Toulouse, 1670, folio. A valuable translation of the Arithmetical Questions into German was published by Otto Schulz, Berlin, 1822, 8vo.; to which is added Poselger's translation of the work on Polygon Numbers. DIOPSIDE, a variety of PYROXEne. DIO'PSIS, a genus of Dipterous Insects of the family Sepsida. The insects of this genus are remarkable for the immense prolongation of the sides of the head. The head itself is small, and appears as if it were furnished with two long horns, each having a knob at its apex; these hornlike processes however are not analogous to the parts usually termed antennæ, but are in fact prolongations of the sides of the head, the knob at the apex of each being the eye of the insect. They vary in length according to the species. In some they are almost equal to the whole length of the insect, whereas in others they are only about half that length. The antennæ are situated close to the eyes, and are three-jointed: the basal joint is the smallest and is very short; the terminal joint is the largest, of a globular form (or nearly so), and furnished towards the apex with a simple seta; there is also a short seta on the peduncle or eye-stalk, situated about midway between the base and the apex of that process, and on the anterior part. The thorax is somewhat attenuated anteriorly, but approaches to a spherical form, and is generally furnished with two spines on each side; the scutellum is also furnished with two spines. The body is more or less elongated, sometimes nearly cylindrical, but generally increases in diameter towards the apex. The legs are tolerably long-the anterior femora are generally thick, and furnished beneath with minute denticulations, and the four posterior femora are often furnished with a spine at their apex. For a detailed account of these curious insects we refer our readers to Mr. Westwood's excellent paper in the seventeenth volume of the Transactions of the Linnean Society in which twenty species are described. a Diopsis Sykesii, G. R. Gray. a denotes the natural size. The illustration is copied from one of that gentleman's figures, and represents the Diopsis Sykesii, one of the largest species of the genus, and which has been selected as possessing the longest eye-stalks; these processes in this insect are of a pitchy red colour, and the body is of the same tint. The head and thorax are black and the wings are clouded with brown. But little is known of the habits of these insects. Lieut.Colonel W. H. Sykes, who collected great numbers of the above species during his residence in India, furnished Mr Westwood with the following notice respecting their habitat and habits : 'Habitat. The hill fort of Hurreechunderghur, in the s howmbrous instruwhich arches as the. conTy of dmit. anaus, or yan (περί 2, in western ghauts of the Deccan, at an elevation of 3900 feet In addition to this notice we may add that all the known DIOPTASE or emerald copper, a crystallized silicate of copper, the primary form of which is a rhomboid; its colour varies from emerald to blackish green; its lustre is vitreous; it is translucent, and sometimes transparent; it is sufficiently hard to scratch glass, though but feebly; it is brittle; specific gravity 3.278; the streak is green; fracture uneven; and cross fracture flat conchoidal. It is found in Siberia and the Bannat; and, according to Lowitz, it consists of silica 33, oxide of copper 55, water 12. | ture, particularly interiors, as powerful relief may be ob- The spectatory or saloon for the visitors is a rotunda 40 feet in diameter, with a single opening or proscenium about 20 feet wide; and placed within another rotunda having two openings communicating with the picture-rooms, each of DIOPTRICS. [OPTICS; REFRACTION.] which contains a view. When a change of scene takes place DIORA'MA, from the Greek word dopar, to see through, the inner rotunda is turned by means of machinery beneath a mode of painting and scenic exhibition invented of late the floor, till the proscenium is gently shifted from the openyears by two French artists, Daguerre and Bouton, which, ing into one picture-room to that of the other, the two being although it does not possess some of the advantages of the quite contiguous. At the next change it is shifted back panorama, produces a far greater degree of optical illusion. again, so that the whole space passed over backwards and It has also one advantage over the panorama, in being forwards is about one-third of the entire circumference, or equally suitable for architectural and interior views as for double that portion of the circle forming the proscenium. landscape; nay even more so, because the positive degree of The diorama at Berlin, executed by Carl Gropius, an emilight is more natural, and the relief of the objects becomes nent scene-painter, is somewhat on the same plan, yet with more deceptive. The peculiar and almost magical effect of some slight differences. The peculiar mode just described, of the diorama arises, in a considerable measure, from the con- turning the spectatory from one painting to the other, is trivance employed in exhibiting the painting, which is viewed adopted, as the scenes are much larger than the opening through a large aperture or proscenium. Beyond this open-through which they are viewed, and require to be stretched ing the picture is placed at such distance that the light is on a framing, so that they cannot be either rolled up, or thrown upon it, at a proper angle, from the roof, which is drawn aside in two halves, as is done with scenes of a theaglazed with ground glass, and cannot be seen by the spec- tre. Nevertheless, it would perhaps be found practicable to tator. Besides the light being thus concentrated upon the exhibit a succession of three or four views, in a single 'picpicture, the effect is materially increased by the spectator ture-room,' by making that part of the building sufliciently being in comparative darkness, receiving no other light spacious to allow each scene to be slided backwards or forthan what is reflected from the surface of the painting it- wards, so as to be entirely out of view when drawn aside. self. Another circumstance greatly favouring illusion is the DIOSCO'REA, the genus of plants which furnish the intervening distance; and also the circumstance that the tropical esculents called yams. They are perennial fleshysides of the proscenium or opening are continued inwards to- rooted or tuberous dioecious plants, with annual twining wards the picture, so as to screen its extremities, and at the stems, broad alternate leaves having a somewhat netted arsame time assist in confining the light to the scene itself. rangement of their veins, and loose clusters of small green The contrast thus occasioned, and the exclusion of all other flowers. The corolla and the calyx taken together consist objects of vision save those represented in the painting, so of six small equal segments, which, in the females, stand that the eye has no immediate standard of comparison be- upon the top of the ovary. The male flowers have six statween them and real ones, give to this species of exhibition mens; the females three styles. The seed vessel is a thin such extraordinary force that a very moderate degree of compressed three-winged capsule, containing one or two light will suffice to show the painting. Hence the light membranous seeds. may be diminished or increased at pleasure, and that either gradually or suddenly, so as to represent the change from ordinary daylight to sunshine, and from sunshine to cloudy weather, or to the obscurity of twilight; also the difference of atmospheric tone attending them: all which variations give to the diorama a character of nature and reality beyond that of any other mode of painting. These transitions, in regard to light and atmospheric effects, are produced by means of different folds or shutters attached to the glazed ceiling, which are so contrived that they may be immediately opened or closed to any extent, thereby increasing or diminishing the light just as required, and otherwise modifying it. Further than this, some parts of the painting itself are transparent, and on them the light can occasionally be admitted from behind, thereby producing a brilliancy far exceeding that of the highest lights of a picture upon an opaque ground, which can be made to appear vivid and sparkling only by contrast, not by any positive increase of light on those parts of the surface. Here, on the contrary, such augmented light is admitted through it, in addition to that which illuminates the picture generally, an artifice which secures the advantages of painting in transparency without its defects; the objects looking more solid, and the effect being altogether more natural than when the whole of the light passes through the picture. The combination of transparent, semi-transparent, and opaque colouring, still further assisted by the power of varying both the effects and the degree of light and shade, renders the diorama the most perfect scenic representation of nature, and adapts it peculiarly for moonlight subjects, or for showing such accidents' in landscape as sudden gleams of sunshine and their D. rubella, the guranya-aloo, is another Indian sort with disappearance. It is also unrivalled for showing architec-large tubers stained with red immediately below the cuticle; 4 The only general account of the species, which at all deserves to be consulted, is that of Dr. Roxburgh, who cultivated seventeen sorts in the Botanic Garden, Calcutta ; others are known to botanists, but far from perfectly. Be The common West India yam, which is often sold in the shops of London, is produced by Dioscorea alata. It is met with in the East Indies also, but only in a cultivated state. A figure of it is given in Rheede's 'Hortus Malabaricus,' vol. vii. t. 38, under the name of katsji-kelengu. Its tubers are oblong, brown externally, white internally, and often of great size, weighing sometimes as much as 30lbs.; they perish after the first year, if left in the ground, having first produced the young ones that are to replace them. sides the tubers the proper roots of all these plants are fibrous, springing from and chiefly about the union of the stems with the tubers, and spreading in every direction.' The stems are furnished with four crested leafy wings, and spread to a great extent twining round trees and bushes; they often bear prickles near the ground. The first leaves that appear on the stem are alternate, the succeeding are opposite, seated on long stalks, deeply heart-shaped at the base, sharp-pointed, smooth, with from five to seven ribs. The flowers are small and green, and appear in compound pani cles. The remainder of the species are very similar to this in general characters; a few short notes will sufficiently in dicate their differences. D. globosa, cultivated in Bengal under the name of choo puree aloo, is most esteemed of the Indian yams. Its flowers are highly fragrant; the tubers are white internally; the leaves arrow-headed. B 2 it is much esteemed; its tubers are sometimes three feet long; its flowers are fragrant. Another valuable kind is D. purpurea, called lal-guranyaaloo in Bengal, whose tubers are permanently stained purple throughout. At Malacca is cultivated another purple-rooted sort, the D. atropurpurea, whose tubers are large and irregular, and grow so near the surface of the ground as to appear in dry weather through the cracks that they make in the soil by raising the earth over them. Other eatable sorts are numerous, but are less valuable, and therefore not cultivated. In Otaheite the D. bulbifera, which bears small fleshy angular tubers along the stem in the axils of the leaves, is the favourite species. It is not a little remarkable that while so many species are nutritious in this genus, some should be highly dangerous; but such is unquestionably the fact. Dioscorea Dæmonum and triphylla, both ternate leaved species, have dreadfully nauseous and dangerous tubers. No genus is more in want of revision than this. DIOSCOREA'CEA, a natural order of endogenous plants, referred to the Retose group, and having the last genus for their type. They are particularly distinguished by the following character. Flowers dicecious; calyx and corolla superior; stamens six; ovary three-celled, with one or two-seeded cells; style deeply trifid; fruit leafy, compressed, occasionally succulent; embryo small, near the hilum, in a large cavity of cartilaginous albumen. All the species are twining shrubs, with alternate or spuriously opposite leaves. They consist, with the exception of Tamus, or Black Bryony, of tropical plants, or at least of such as require a mild frostless climate. Some of them produce eatable farinaceous tubers, or yams, as the various species of Dioscorea and Testudinaria; but there is a dangerous acrid principle prevalent among them, which renders the order upon the whole suspicious. It exists in a perceptible degree in Tamus, and is still more manifest in the three-leaved Dioscorea. 1, a shoot of Rajania cordata; 2, a male flower; 3, a female:flower; 4, a portion of a ripe fruit with the seed exposed; 5, a section of the seed. DIOSCO'RIDES, PEDA'CIUS, or PEDA'NIUS, a Greek writer on Materia Medica, was born at Anazarbus, in Cilicia, and flourished in the reign of Nero, as appears from the dedication of his books to Areus Asclepiadeus, who was a friend of the consul Licinius or Lecanius Bassus. In early life he seems to have been attached to the army; and either at that time or subsequently he travelled through Greece, Italy, Asia Minor, and some parts of Gaul, collect ing plants with diligence and acquainting himself with their properties, real or reputed. He also gathered toge her the opinions current in his day concerning the medical plants brought from countries not visited by himself, especially from India, which at that time furnished many drugs to the western markets. From such materials he compiled his celebrated work on Materia Medica, in five books, wherein between 500 and 600 medicinal plants are named and briefly described. He is moreover reputed the author of some additional books on therapeutics, &c.; but in the judgment of Sprengel the latter are spurious, and from the mixture of Latin and Greek names of plants, are probably some monkish forgery. Few books have ever enjoyed such long and universal celebrity as the Materia Medica of Dioscorides. For sixteen centuries and more, to use the words of one of his biographers, this work was referred to as the fountain-head of all authority by everybody who studied either botany or the mere virtues of plants. Up to the commencement of the seventeenth century the whole of academical or private study in such subjects was begun and ended with the works of Dioscorides; and it was only when the rapidly increasing numbers of new plants and the general advance in all branches of physical knowledge compelled people to admit that the vegetable kingdom might contain more things than were dreamt of by the Anazarbian philosopher, that his authority ceased to be acknowledged. This is the more surprising, considering the real nature of these famous books. The author introduced no order into the arrangement of his matter, unless by consulting a similarity of sound in the names he gave his plants Thus, medium was placed with epimedium, althæa can nabina with cannabis, hippophæstum (cnicus stellatus) with hippophae, and so on; the mere separation of aromatic and gum-bearing trees, esculents and corn-plants, hardly forms an exception to this statement. Of many of his plants no description is given, but they are merely designated by a name. In others the descriptions are comparative, contradictory, or unintelligible. He employs the same word in different senses, and evidently attached no exactness to the terms he made use of. He described the same plant twice under the same name or different names; he was often notoriously careless, and he appears to have been ready to state too much upon the authority of others. Nevertheless, his writings are extremely interesting as showing the amount of Materia Medica knowledge in the author's day, and his descriptions are in many cases far from bad: but we must be careful not to look upon them as evidence of the state of botany at the same period; for Dioscorides has no pretension to be ranked among the botanists of antiquity, considering that the writings of Theophrastus, four centuries earlier, show that botany had even at that time begun to be cultivated as a science distinct from the art of the herbalist. The most celebrated MS. of Dioscorides is one at Vienna, illuminated with rude figures. It was sent by Busbequius, the Austrian Ambassador at Constantinople, to Mathiolus, who quotes it under the name of the Cantacuzene Codex, and is believed to have been written in the sixth century. Copies of some of the figures were inserted by Dodoens in his Historia Stirpium, and others were engraved in the reign of the empress Maria Theresa under the inspection of Jacquin. Two impressions only of these plates, as far as we can learn, have ever been taken off, as the work was not prosecuted.' One of them is now in the Library of the Linnæan Society; the other is, we believe, with Sibthorp's collection at Oxford. They are of little importance, as the figures are of the rudest imaginable description. Another manuscript of the 9th century exists at Paris and was used by Salmasius; this also is illustrated with figures, and has both Arabic and Coptic names introduced, on which account it is supposed to have been written in Egypt. Besides these, there is at Vienna a manuscript believed to be still more antient than that first mentioned, and three others are preserved at Leyden. The first edition of the Greek text of Dioscorides, was published by Aldus at Venice, in 1499, fol. A far better one is that of Paris, 1549, in 8vo. by J. Goupyl; but a better still is the folio Frankfort edition, of 1598, by Sarracenus. Sprengel laments, 'nullum rei herbariæ peritum virum utilissimo huic scriptori operam impendisse. Nevertheless, there have been many commentators, of whom some, such as Fuchsius, Amatus Lusitanus, Ruellius, Ta thartin. The volatile oil and the extractive appear to be the active ingredients. They are usually administered in the form of infusion. Buchu leaves have been long known to the Hottentots as a remedy against rheumatism, cramps, and above all in affections of the urinary organs. They have of late years been introduced into European practice. In their action they resemble those of the arctostaphylos uva ursi, but from their containing volatile oil, buchu leaves are in many cases preferable. [BEAR's WhortleBERRY.] DIP, in magnetism, the angle which the magnetic needle, freely poised on its centre of gravity and symmetrically formed in both its arms, makes with the plane of the hori zon. It is more scientifically termed the inclination of the needle, or the magnetic inclination. [INCLINATION and MAGNETISM.] DIPHILUS. [ATHENS, vol. ii., p. 18.] DIPHTHONG (dipoyyos) is the sound of two vowels pronounced in rapid succession, as the German au in maus, pronounced precisely like the English word mouse, the vowel sound consisting of the broad a of father, followed quickly by the sound of u or oo. Again, the i in the English word mind, though represented by a single character, is virtually a diphthongal sound, consisting of the broad a of father, followed by the vowel sound which is heard in mean. The name diphthong however is commonly given to any vowel sound represented by the junction of two vowels, as in dream, though the sound produced is not compounded. bernæmontanus, Tragus, and Dalechampius, are of no sort DIOSMA, a genus of Rutaceous shrubs inhabiting the -: An erect shrub, smooth in every part, and growing a foot or so high; branches tapering, purplish, long, lax; branch lets somewhat whorled, ternate, or scattered, angular, purple, twiggy, incurved, loose. Leaves alternate, on short stalks, ovate-oblong, blunt, flat, smooth, deep green above, paler beneath, dotted with sunken glands, the midrib somewhat keeled, the margin scolloped, glandular-dotted, and shining. Flowers solitary, white, middle sized. Peduncles filiform, shorter than the leaves. By most modern botanists the old genus Diosma is broken up into eight, namely, Adenandra, Coleonema, Diosma proper, Euchatis, Acmadenia, Baryosma, to which the Buckus belong, Agathosma, and Macrostylis. Diosma crenata (Linn.) and Diosma serratifolia (Vent.) yield leaves which at the Cape of Good Hope are termed buchu, or bucco, and which are sometimes used alone, but more frequently mixed. When bruised they emit a strong peculiar odour, resembling rosemary or rue. The taste is aromatic, but not bitter or disagreeable Cadet de Gassecourt analysed the leaves, and found no alkaloid, but 6.65 of volatile oil; 21.17 extractive; 2.15 resin; 63 lignin ; 1.10 chlorophylle. Brandes considers the extrac tive to be peculiar, and terms it Diosmin, analogous to ca All diphthongs are said to be long syllables; and this would be true if they were only employed to mark the union of two vowel sounds. This probably was originally their sole office; for in many English words now written with diphthongs, but pronounced as if they had single vowels, an earlier pronunciation contained the double sound; and indeed this view is often supported by the provincial pronunciation of a word. For example, such words as meat, dream, are pronounced in many parts of England as dissyllables, meat, dream. In practice however a diphthong is often used where the vowel sound is not only uncompounded but short, as in friend, breadth. Again, diphthongs are occasionally used to represent simple sounds intermediate between the vowels, as in the English word cough, and the German sounds represented by ae, oe, ue, commonly written ä, ö, ü, where the dots placed over the vowels are merely a corruption of the letter e. DIPHUCEPHALA, a genus of coleopterous insects belonging to the Lamellicornes, section Phyllophagi. This genus appears to be confined to Australia, and the species of which it is composed are distinguished from those of allied genera chiefly by their having the clypeus deeply emarginated; they are of an oblong form; the thorax is attenuated anteriorly, the elytra are somewhat depressed, and the abdomen is very convex. The antennæ are eightjointed, and the club is composed of three joints; the anterior tibiæ are generally dentated externally; the anterior tarsi of the males have the four basal joints dilated, and furnished with a velvet-like substance beneath, and all the claws are bifid. A rich golden green appears to be the prevailing colour of these insects, and we understand that they are found on flowers. Diphucephala sericea (Kirby) is nearly half an inch in length, of a golden green hue, and has a silk-like gloss on the upper parts; the legs are red; the anterior tibiæ have an obtuse tooth-like process on the outer side, near the apex; the head and thorax are very thickly and delicately punctured; the elytra are covered with confluent punctures which are arranged in longitudinal rows, and each elytron has two smooth elevated striæ; the under parts of the body are covered with white scale-like hairs. This is the largest species known; there are however many which are nearly equal to it in size. The genus Diphucephala forms the subject of a monograph in the first volume of the Transactions of the Entomological Society of London,' where sixteen species are described. DI'PHYDES, DI'PHYDE, a family of zoophytes, thus characterized by M. de Blainville, and placed by him between the Physograda and the Ciliograda. Body, bilateral and symmetrical, composed of a very small, nucleiform, visceral mass, and two natatory organs, which are contractile, subcartilaginous, and serial; one anterior, in more or less immediate connexion with the nucleus, | by an examination of certain species of Physsophora. M. de Head, at the extremity of a more or less proboscidiform stomach. Vent, unknown; a long cirrhiform and ovigerous production, proceeding from the root of the nucleus, and prolonging itself more or less backwards. M. Bory de St. Vincent, in his voyage to the African coasts, appears to be the first who noticed these animals, which abound in all the seas of warm latitudes, with any degree of certainty. He considered them to be Biphores (Salpa). Tilesius also said something of them in the zoological part of Krusenstern's voyage. Blainville then states that the body of a Diphyes, at first sight, and especially as it appears during life, seems to be composed of two polygonal, subcartilaginous, transparent parts, placed one after the other, the posterior portion penetrating more or less into an excavation of the anterior por tion. These two parts, constantly more or less dissimilar, have this in common: viz., that they are ordinarily more or less profoundly hollowed out by a blind cavity opening externally by a very large and regular, though diversiform aperture. Adding to this a production regarded as the ovary by Cuvier, and which comes out of the superior cavity of the anterior cartilaginous part, we have the whole that had been remarked about the Diphyde before the memoir of Quoy and Gaimard, who have described numerous species which they have observed, very nearly like Cuvier; with this modification, however, that they have considered the two parts as belonging to the same animal: but the study of the differences of form necessary for the establishment of the new genera which they have proposed, and above all, the good figures which they have given, have enabled them to go further, and to see in the Diphyde something beyond the two subcartilaginous parts. In fact, taking for example the Calpes, and especially the Cucubali and the Cuculli, it is seen that the bodies of the Diphyda form true nuclei, situated at the anterior part of the entire mass, and that the nucleus is composed of a proboscidian œsophagus, with a mouth having a cupping-glass-like termination (en ven touse), continuing itself into a stomach surrounded with green hepatic granules, and sometimes into a second, filled with air. There is, moreover, to be remarked, at the lower part, a glandular mass, which is probably the ovary, and is in more or less immediate relation with the cirrhigerous and perhaps oviferous production, which is prolonged back wards. This nucleus would seem to be more or less en veloped by the anterior cartilage, which offers to it, in fact, a cavity sometimes distinct from the second (which has been mentioned above), serving for locomotion, and at other times confounded with it; it is, besides, in intimate connexion with its tissue by filaments, which M. de Blainville believes to be vascular. It has been already remarked that the posterior part of the body is hollowed out by a great cavity, which is continued nearly throughout its length, and it is from the bottom of this cavity that a prolongation, perhaps equally vascular, proceeds, which goes above the root of the oviferous production, and unites itself, without doubt, with the nucleus. Thus,' continues M. de Blain ville, it would appear to me certain that this part really belongs to the Diphyes; but it is easy to conceive how it may be detached by the slightest effort, because the union is only effected by a single filament. But it was Cuvier who first formed these creatures into a separate genus, under the name of Diphyes, and he placed them at the end of his Hydrostatic Acalephans, immediately after Stephanomia of Peron. Cuvier describes the genus as very singular, consisting of two individuals, which are always together, one including itself in a hollow of the other (l'un s'emboîtant dans un creux de l'autre), an arrangement which nevertheless permits their separation without the destruction of life. They are, he observes, gelatinous, transparent, and move very nearly like the Medusa. The including individual (l'emboîtant) produces from the bottom of its hollow a chaplet (chapelet), which traverses a demi-canal of the included individual (l'emboîté), and would seem to be composed of ovaries and of tentacula and suckers like those of the preceding genera. Cuvier then goes on to state the divisions established by MM. Quoy and Gaimard, according to the relative forms and proportions of the two individuals. Thus, in the Diphyes, properly so called, the two individuals are nearly alike, pyramidal, and with some points round their opening, which is at the base of the pyramid. In the Calpes, the included individual has still the pyramidal form, but the including individual is very small and square. In the Abyles, the included individual is oblong or oval, and the including rather smaller and bell-shaped. In the Cuboides, it is the included individual which is small and bell-shaped; the including individual is much larger and square. In the Navicules, the included individual is bell-shaped; the including individual large also, but slipper-shaped (en forme de sabot). Cuvier concludes by remarking that there are many other combinations, and refers to the memoir of MM. Quoy and Gaimard, in the Annales des Sciences Naturelles,' tome x. This, then, is the account given by Cuvier in his last edition of the Règne Animal;' but it was in the first that he established the genus, and in that edition he evidently knew of only one species from the Atlantic, for which he refers to M. Bory's Voyage,' and places the genus among his free Acalephans, between Cestum of Lesueur and Porpita of Lamarck. It is to the first edition that M. de Blainville refers in his Actinologie,' and he there says that in fact M. Lesueur, more than a year previously, had sent him the drawing of a genus of the same family, to which Lesueur had given the name of Amphiora (Amphiroa ?), and which M. de Blainville observes was, from what he now knows of the Diphyes, very nearly approximated to them, to say the least; but the want of information as to the characters of the genus prevented him (De Blainville) from publishing it. He remarks, that he ought to add that Lesueur was more fortunate than Cuvier, inasmuch as the former had at his disposal a complete and living animal; while the latter characterized as one Diphyes an animal composed of two individuals, giving as the type the anterior moiety only, to which he attributes two apertures, one for the mouth and the other for the exit of the cirrhigerous production which he regards as the ovary. M. de Blainville then, after some further observations as to the place assigned to the animal by Cuvier, refers to the Memoir of MM. Quoy et Gaimard,' above mentioned, and states that during the rest of their Voyage those zoologists had met with more Diphyde, of which they had formed distinct genera, and had submitted them to his examination; that he had also obtained some beautiful drawings of these animals, made by Lesueur in the Gulf of Bahama; and that M. Paul-Emile Botta, placed by his recommendation on board a merchant ship about to make a voyage round the world, had also communicated to him the observations which he (Botta) had been able to make on the genus; so that, difficult as the study of these singular animals may be, he thinks that he has been able to arrive at their true natural relations, aided, above all, After this statement of the organization of Diphyes, one may see that the part which M. Cuvier regarded as by itself constituting the animal, is only an organ of minor importance; that there must be added to it the posterior part, which was regarded as a distinct individual; but above all, that it is necessary to take into the account the visceral nucleus, which, with the oviferous production, forms the essential part of the animal. From this analysis of a Diphyes, it is evident that it cannot be an animal of the type of the Actinozoaria; but in order to establish its natural relationship, let us see what the observers above named have recorded of its manners and habits. 'The Diphyes are very transparent animals, so that it |